Harakeke, New Zealand’s native flax, had been planted there, probably around 25 years ago. It had grown to form a formidable fortress of foliage, sheltering the wetland behind from the southerly gales which howl up the wind tunnel created by the steep sides of the gully. Then, when the weather warmed, it would send up its flower spikes, more than two metres tall. The gully would fill with the songs of tūī, each one wearing an orange cap of pollen from plunging its head into the harakeke flowers to drink the nectar.

Late last spring, though, I noticed an ominous sign. Harakeke often has a yellowish leaf or two as the old leaves die off. But some of the plants had a little too much yellow. I wondered whether I was seeing the first signs of disease.

A few months previously, I’d noticed sick harakeke plants in a park a couple of suburbs away. Those plants were obviously yellow, and I suspected a disease known as Phormium yellow-leaf (Phormium is part of the scientific name of harakeke). I discussed the sick plants with some of the staff from the local council. They confirmed that there were periodic outbreaks of the disease in Wellington.

Yellow-leaf disease is caused by the same kind of bacteria which killed off many of our large tī kōuka (cabbage trees) in the 1980s and 1990s. Precisely when the disease was first noticed in harakeke is unclear, but both the bacteria and the insects which spread them are considered to be native. If that is the case, then the disease must have been known to Māori, long before Europeans arrived. I haven’t found anything about it online, but that doesn’t mean the information doesn’t exist. However, the first scientific publications about yellow-leaf were in the late 1910s, when the disease was seen spreading rapidly in the lower North Island. It received considerable attention in the following decades, as it contributed to the demise of harakeke as a commercial fibre crop. Its cause, though, was not known until the late 1960s.

Once a plant is infected with the bacteria which cause yellow-leaf, there is nothing which can be done for it. Many plants die, although some do recover. That’s exactly what I’ve seen over the last year. By the start of winter, around half of the plants were dead and others were obviously sick. When the wind whipped up the gully, it was no longer deflected by the sturdy harakeke. It blasted half of the leaves off the sapling pukatea trees. One pūkio, which has long, grass-like leaves cascading from the top of its trunk, lost all the leaves growing on its southern side.

Now, the edge of the wetland is a mass of dead harakeke leaves and there are several other holes in the wetland where plants have died. Dead plants seem to rot from their centre, although the tough leaves last much longer. Some plants are alive but stunted, a common result of infection with these bacteria, and are now swamped by weeds. Some plants still seem to be slowly dying. A few, though, seem to be in good health, with robust fans of grey-green leaves and barely a trace of yellow. It will take some years to restore the wind-break to its former strength, but I’m hopeful that some of the harakeke in the wetland will survive.

It’s particularly shocking to see harakeke plants die like this because it’s such a famously tough plant. It’s a plant of coastal slopes and cliffs, an environment battered by salt winds, where the combined effects of salt burn and thin soil subject plants to constant drought. It’s a plant of estuary margins and dune slacks, which are wetlands that form among or behind sand dunes. In these environments, harakeke must still cope with salt, but also too much, rather than too little, water. It’s also a plant of lake margins and freshwater wetlands. And it grows perfectly well in a garden, too, often a little too well.

What makes it so versatile? That’s a hard question to answer, it seems. I’ve found some relatively recent work studying its drought tolerance, which indicates that it has a number of genes associated with drought tolerant traits. But why it should also grow in wetlands is not clear. I went down a research rabbit hole trying to determine whether it has the same kind of mechanism for making food which I wrote about last week, thinking perhaps I might find an answer there. This is a trait which allows many succulents and some aquatic plants to absorb and store carbon dioxide at night, to use during the day. While some of its desert-dwelling cousins do have this trait, I haven’t found evidence that harakeke does. That wouldn’t explain why it grows in wetlands anyway, because the trait is reported in aquatic plants with submerged leaves.

So I can’t answer this question. All I can say is that harakeke is a tenacious plant. In fact, the second part of its scientific name, tenax, makes this explicit. In Latin, tenax means holding fast, persistent or stubborn and is the root of the English word tenacious.

So far I’ve talked only of harakeke, but it has an equally hardy cousin, commonly known by the name wharariki. In English, it’s usually known as mountain flax, but this name is so confusing that I try to avoid it – more on that in a moment. Botanists consider that there are two different kinds of wharariki, one which grows in subalpine and alpine areas of the South Island and lower North Island, and one which is predominantly coastal (making mountain flax an obvious misnomer). The coastal form of wharariki is found in different areas from harakeke; it’s the predominant species on the coast of the South Island and is sometimes found on cliffs inland.

Although the Māori names harakeke and wharariki are widely used, there are many other Māori names associated with the plants. The flower stem of harakeke is known as kōrari, while the central leaf at its heart is known as rito. There are dozens of named cultivars of harakeke and wharariki, each with different properties when used for weaving, fibre extraction or medicine. The plants are steeped in lore and tradition, and gave rise to one of the most famous whakataukī (Māori proverbs), although also perhaps the most misused. I’m not the one to tell the story, but if you’d like to learn more, there’s a great essay from Khylee Quince of the law school at Auckland University of Technology which addresses this proverb in the context of the enquiry into the law firm Russell McVeigh. The essay is linked here.

The English name for both harakeke and wharariki is flax, a name which surely leaves those from the Northern Hemisphere scratching their heads. For thousands of years, the people of Europe, western Asia and North Africa have been extracting the fibre from a dainty, blue-flowered herb and weaving it into fabric. The use of the word flax for the plant goes back to early Germanic languages and had entered the English language before 1100.

Harakeke and wharariki don’t have the remotest resemblance to flax plants. However, when Europeans were first shown the fibre, they considered it similar to flax fibre, and so the plant was given the same name. Ropes made from harakeke became New Zealand’s first export, as visiting sailors began buying it for rigging their ships at the end of the 18^th century. It waxed and waned in importance as a crop during the 19^th and 20^th centuries, partly in response to changing demand, partly in relation to the availability of other fibres and partly because of outbreaks of yellow-leaf disease. It continues to be the subject of research for its fibre and medicinal properties.

While it’s clear that harakeke and wharariki are not botanically related to flax, it has long been unclear what they are actually related to. Early botanists classified them with the lilies. By the 1970s, they were grouped with tī kōuka (cabbage trees) in the agave family. Now, they sit alongside the day lilies (which are not related to the true lilies), either in the day lily family, or part of a larger family which also includes plants such as aloe vera. Their closest native relatives are a group of yellow-flowered, onion-like plants found mainly in alpine areas.

There has also been debate about where, precisely, harakeke comes from. There’s no dispute that wharariki is unique to New Zealand, growing naturally nowhere else. But harakeke is usually considered by botanists to be also native to Norfolk Island, since it was present when Europeans first visited there. In fact, the availability of harakeke on Norfolk Island was part of the British motivation for attempting to establish colonies there. However, this view has been challenged over the last 25 years, since there’s evidence that Polynesian people visited and once lived on Norfolk Island. Although the question isn’t settled, recent genetic research has given results which are consistent with harakeke being a Polynesian introduction, although recent natural dispersal can’t be ruled out.

Whatever the original range, both species, but especially harakeke, have been introduced to many other countries, whether for fibre or as garden and landscaping plants. I’ve been looking at records on iNaturalist, and the two species are planted all over Britain and Ireland, scattered around Europe, on the US west coast, in Mexico, and in cooler parts of South America, South Africa and Australia. They have also been introduced to many islands, including the Azores, the Canary Islands, the Scilly Islands, Jersey, Guernsey, Hawai’i, St Helena, Tristan da Cunha and the Falklands. Most of these records are for harakeke, and it’s clearly thriving.

What’s not clear from iNaturalist photographs is how many records are of wild plants. In some cases, such as the records from the Azores, it’s clear that many of the iNaturalist records are of wild plants. One image shows a large plant hanging off the side of a cliff among other invasive weeds. For other places, though, I’ve had to use other sources. It was noted more than 200 years ago that harakeke thrived in Ireland. Since then, it has spread and is considered a potential invasive species, but is not of great concern. It’s causing more concern in Hawai’i, particularly in Volcanoes National Park and on the island of Moloka’i. It has spread on Tristan da Cunha and a couple of its outlying islands, and has been the subject of an eradication programme on these outlying islands.

But it’s on the island of St Helena where harakeke has had its greatest impact. Long before its introduction, the unique native plants of St Helena were already in trouble. The problems began when goats were introduced in the 16^th century. They soon formed massive flocks and stripped the native plants in many areas, resulting in severe erosion. In the 17^th century, settlers destroyed most of the remaining forest. When harakeke was introduced in the 19^th century, its fibre became the mainstay of the island’s economy. It was planted extensively, but it spread well beyond the areas where it was cultivated and invaded some of the last remaining areas where native plants still grew.

While we can’t be sure exactly how many unique plant species once lived on St Helena, more than 50 are known. Of these, six are already extinct and two more survive only in cultivation. Many of the surviving species are endangered. The contribution harakeke has made to the perilous situation of St Helena’s plants is small in comparison to the impact of goats and land clearance by settlers. Nonetheless, it has played a part. In the future, it will be perceived as an increasing problem. Large-scale land clearances have ended and feral goats have been eradicated. This tenacious plant, though, will prove much more difficult to control.

On a fine day, the views are stunning and the air is full of birdsong. There’s a gorgeous old ngaio tree which stands tall above the regenerating forest which surrounds it. For families, there’s a recently rebuilt playground. But for someone who yearns to be deep in the forest or high in the mountains, it’s uninspiring.

Perhaps that’s why I failed to notice a plant growing there which I really shouldn’t have missed. Until a publication in 2023 reported it growing wild around Wellington, I’d never heard of it. But it’s a member of a plant group I’m interested in, so I should have seen it. Once I heard about it, I started noticing it growing on banks up and down my street, as well as on the track to Homebush Park.

The plant I should have spotted sooner is a kind of succulent native to the Canary Islands. Its common name is rather unhelpful: tree of love. It’s not a tree, nor even close to a tree, in fact I’ve never seen it growing any taller than 20 centimetres. And I’ve no idea what it has to do with love. But what I can see, when I look at it, is that it’s a member of a large group of succulent plants known as the stonecrop family. This group has fascinated me since childhood, and I became even more interested when I worked with legendary botanist Bill Sykes. He had dozens of plants in this family, probably well over 100, growing in pots on his deck at his home in Christchurch.

The stonecrop family is one of the most important families of succulent plants. It’s among the largest, with around 1500 species, and it’s also the most widespread. Members of the stonecrop family can be found growing from the coast of Greenland to remote subantarctic islands. Certain locations, however, have larger numbers of species, such as southern Africa, Mexico, the Mediterranean and the islands to the west of southern Europe and northern Africa, such as the Canary Islands. But so, too, do the Himalayan mountains. While we typically think of succulents as plants of hot, dry conditions, species in the stonecrop family can be found from deserts to swamps. Typically, though, they are not found in the driest of deserts, as succulent plants do require semi-regular rainfall.

Succulents are plants which store water in living cells. Usually these cells are concentrated in specific part of the plant. In a typical cactus, these cells are in the stem, and in members of the stonecrop family, the water-storing cells are mainly in the leaves. Members of the stonecrop family have many different kinds of leaves: tiny and scale-like, broad and flattened, clustered in tight rosettes, long and narrow, or round and fat. All, though, are succulent to some extent.

The advantages of storing water are obvious for plants growing in dry conditions. But why are members of the stonecrop family found growing in places such as Greenland and the Himalayas? This seems counter-intuitive, because most succulent plants are very sensitive to damage from frost and being frozen. The main reason seems to be that the water held in their leaves provides some protection against freezing. A tight rosette of thick leaves will freeze more slowly than thin leaves, just as water in a square container freezes more slowly than the same volume of water spread as a thin film. Nonetheless, a relatively small proportion of the plants which grow in extremely cold environments are succulent. There are other strategies which protect against cold, such as having densely hairy leaves and growing as tight cushions, which are more common.

But there’s something else which contributes to the success of plants in the stonecrop family. They have an unusual ability which is common to succulent plants, many rainforest orchids and bromeliads, and certain aquatic plants. This is something which cannot be seen just by looking at the plants, because it takes place inside the cells.

When plants make food from sunlight in the process known as photosynthesis, they need a supply of carbon, which comes from carbon dioxide in the atmosphere. Carbon dioxide gets into leaves through tiny pores, but these pores also allow water to escape. Brighter sunlight and warmer temperatures increase the rate of photosynthesis, but also increase water loss. A plant can close the pores in its leaves to conserve water, but then it begins to run out of carbon dioxide.

Certain plants have developed the ability to absorb their carbon dioxide at night, when temperatures are cooler and there is less water loss. But photosynthesis requires sunlight and is impossible at night. So, the plants hold onto the carbon dioxide until the sun comes out. Then they can make their food using the stored carbon dioxide, keeping their pores closed so they don’t dry out.

It’s obvious why breathing at night would be an advantage to plants in hot, dry climates. But they aren’t the only plants which face a lack of water. Soil is essential for most plants in part because it holds moisture which can be absorbed through a plant’s roots. Environments which lack soil dry out much more rapidly. So, plants which grow where soil is limited, such as orchids growing in the canopy of trees and alpine plants growing in rock crevices, also experience frequent droughts. The ability to continue photosynthesis while keeping leaf pores closed is an advantage in these environments too. Many of these plants don’t do this all the time, but it’s a good strategy under difficult conditions.

Perhaps surprisingly, this strategy can give an advantage to aquatic plants too. While water is clearly not limited in a pond or lake, carbon dioxide often is, at least during the day. At night, though, carbon dioxide builds up, as it’s released by both animals and plants. So a plant with the ability to absorb carbon dioxide at night and save it until morning might have an edge.

In New Zealand, we have relatively few native succulents, since we don’t have the kinds of conditions which typically favour that growth form. We have rather more which have been introduced from elsewhere and gone wild, although these are only a tiny proportion of the species which are grown in cultivation and have never spread.

Almost all of the succulents which have gone wild in New Zealand are members of the stonecrop family. They range from plants which persist where they were once cultivated or dumped to some significant weeds. Wellington has close to thirty species growing wild to some extent, which may seem surprising for an area with such high rainfall. But all the steep banks and road cuttings make ideal habitats. Among the most invasive, around Wellington and elsewhere, is a plant usually known as fairy crassula. I was unpleasantly surprised to find it growing among the filmy ferns close to the summit of Rangitoto Island the last time I was there.

Our native succulents, too, are mostly members of the stonecrop family. We have eleven species, all tiny and obscure, at least in New Zealand. Like many of our tiniest native plants, a number of our native stonecrops are in serious trouble. Some grow in ephemeral wetlands, areas which may be submerged in winter, damp in spring or autumn and baked dry in summer. Others grow in coastal turfs, which are dense mats of low-growing vegetation in areas exposed to constant salt-laden winds and sometimes to inundation with brackish or salt water. These environments are often heavily invaded by weeds, which are the main threat to these plants.

One of these tiny succulents, though, has proven anything but vulnerable. In fact, it may be New Zealand’s most notorious plant. It has a couple of different common names, but I’m going to avoid the one which may be considered a derogatory ethnic name and refer to it as swamp stonecrop. It’s native to the South Island West Coast and a few places in Canterbury, and perhaps parts of Australia. However, the Australian plants aren’t quite the same as ours, and there’s debate about whether the Australian plants are a different species.

More than a century ago, swamp stonecrop arrived in Britain, although it’s not clear whether it was introduced intentionally or by accident. It was sold as a plant for growing in and around ponds from the 1920s onwards, and seems to have behaved itself for the first fifty years or so. This is typical of many (but not all) weeds. They may appear innocuous for decades after their first introduction, then suddenly be noticed as a problem. Swamp stonecrop was first noticed growing wild in 1956 and began to cause concern during the 1980s. It had originally grown mainly as small, low-growing mats on pond margins and shallow water, but by the 1980s it had been found growing up to three metres deep and with trailing stems well over a metre long.

Since then, swamp stonecrop has spread throughout England and into Wales, Scotland and Ireland. It was first found in Europe in the early 1980s and has spread through northern Germany, the Netherlands, Belgium and northern France. There are also a few records from other European countries. In places, particularly in England, it grows as dense mats of stems which grow both under and on the surface of the water. The mats can break apart, floating away to create new patches. The tiniest fragment of stem can grow a new plant, but seeds are seldom, if ever, seen.

Over the last forty years, swamp stonecrop has caused considerable concern. While it does die back over winter, it regrows in the spring. If it’s growing in a pond or drain which dries out, it also survives and regrows when conditions are more favourable. It competes with and can exclude native plants, in part because it uses the unusual form of photosynthesis which allows it to absorb and store carbon dioxide at night. Once established, it is difficult to eradicate.

Why has it become such a problem in Europe when it doesn’t cause problems in Australia and New Zealand? This is a perennial question when it comes to invasive species, and there’s no simple answer. Firstly, there’s some evidence it can behave like a weed in New Zealand. Although considered native only in the South Island, since 2021 it has been found in a few North Island locations. These are all in environments modified by human activity rather than more natural environments, where it grows with other weeds. Secondly, it may have escaped from the animals which feed on it where it grows naturally. In Australia, there’s a weevil, a fly and a mite which all eat it, and the mite is now being assessed for introduction to Europe as a biological control agent. Thirdly, it’s possible that either the plant originally introduced to England was particularly vigorous, or that it has undergone some genetic change to become more vigorous since. There is evidence that the plants growing in Britain have some genetic differences from both the Australian and New Zealand plants which have been analysed. There may be other possibilities as well. I haven’t found a definitive answer.

As I’ve read about the invasion of swamp stonecrop in Europe, I’ve noticed that different sources use different common names. Some have New Zealand in the name, while others have Australia. But do we know where the European plants actually came from? The first source I looked at indicated that the plants were thought to originate in New Zealand. However, subsequent sources have indicated the origin is more likely Australia. Records from the plant nursery where swamp stonecrop was first seen in England give the plant’s origin as Australia. In the 1990s, genetic analysis suggested its origin was the Murray-Darling River Basin in Australia. One publication noted that this didn’t narrow the origin down much, as the Murray-Darling drains approximately half of the Australian continent, which is only a slight exaggeration. Genetic analysis techniques have advanced considerably since the original studies, but I haven’t found any further research. It seems, though, that New Zealand may not bear responsibility for this particular invasive species.

Read more

Although the NZ Plant Conservation Network conference is focused on endangered plants, this year there was also a focus on an endangered laboratory. The Lions Ōtari Plant Conservation Laboratory was established in 2018, after the arrival of myrtle rust in New Zealand exposed major gaps in our knowledge of how to propagate many endangered plants. Since then, the lab has contributed to our knowledge of many native plants, a point highlighted in a number of talks at the conference.

Now, though, the lab itself is under threat. While it was established with funds from the Lions Club of Karori and various private donations, its ongoing activities have been funded by the Wellington City Council, because it is part of the Ōtari-Wilton’s Bush native plant garden. Earlier this year, the council planned to cut the lab’s entire budget of $211,000 per year, which would have seen the lab closed and the stored seeds lost at the end of June 2026. The lab has had a reprieve, with enough money to keep the experienced technician employed and the facility running. However, the funding has been cut by more than half and it is unclear whether even this reduced funding will continue beyond June 2027.

Many of us will have grown plants from seed at some point in our lives, but those plants have almost certainly been vegetables. Our cultivated vegetables have been bred for many hundreds, if not thousands, of years. Brassicas such as cabbage and kale were first domesticated more than 5000 years ago. We know the best conditions for storing their seeds and the length of time they can be stored for. We know whether they germinate better on the soil surface or buried, whether they need to be exposed to cold temperatures and whether it’s better to sow directly in the ground or in pots for later transplanting.

But growing vegetables gives us an oversimplified picture of plant propagation. We didn’t breed vegetables solely for taste and nutrition. The process of domestication, where people selected and sowed seed from the best plants over many generations, helped ensure that our vegetables were easy to propagate.

We don’t have that history and knowledge for our native plants. Māori propagated and cultivated some species from seed, most notably the karaka tree. But we have a much shorter history of propagation for our native plants than many plants from overseas.

Of course, we propagate many more plants than just the ones we use for food and fibre. The range of plants grown as ornamentals is vast, including many native plants. This doesn’t mean that they are grown from seed, though. Many plants are easy to grow from cuttings, and cutting-growing plants are usually fine for gardens. However, one important point raised at the conference is that sometimes cutting-grown plants are less suitable for restoration projects. They may not grow such a robust root system, which is crucial for long-term survival in the wild.

Even if we can grow plants from seed in a nursery, planting these in the wild may be difficult. Not every site is accessible. Some may be remote, while others are too steep or unstable to carry in seedlings then dig holes to plant them. It might be easier to sow seed directly, perhaps in the form of seed balls or seed “bombs”. But some of our native plants have seeds which are particularly tricky to germinate. Miro and hīnau tree seeds, for example, can remain dormant for years before germination. Research conducted in the lab at Ōtari has begun to uncover the secrets of seed dormancy and germination for a number of our native plants.

But coaxing dormant seeds to germinate is only part of the challenge. There’s no difficulty, for example, with germinating kauri seed, as long as seed is collected fresh. After a few months on the forest floor, though, seed is no longer viable. Careful storage can extend the seed’s life, but we don’t know how to store seed for long periods. Even when fresh, only a small proportion of kauri seed is viable. With our kauri forests under threat from a disease attacking kauri roots, we don’t just need to know how to grow the seed, we need to understand how to keep it.

Storing seed for long periods in conditions which ensure the seed stays viable is known as seed banking. It’s a crucial backstop for preserving rare plants, because it achieves much more than just keeping a few plants in a botanic garden. We can store large amounts of seed from many different plants and locations, ensuring that we retain the diversity within each plant species. Facilities such as the Millennium Seed Bank in England have stored seeds of tens of thousands of plant species.

Seed banking is possible because, in the 1950s and 1960s, scientists worked out that the seeds of most plants can be dried and then stored at low temperatures for many years. However, the seeds of some plant species don’t survive being dried. We aren’t sure exactly how many species have seeds which don’t survive drying, but it’s estimated to be from 7-20% and it varies between different environments. Rainforest trees, for example, often have large seeds which don’t survive drying.

In New Zealand, we have data for less than a quarter of our plant species. It’s likely, though, that up to 20% of our trees have seeds which cannot be dried, including many important forest trees, such as kauri, kahikatea, rimu and tawa. The lab at Ōtari has been at the centre of research on seed storage for a number of endangered plants, including several of our native myrtle species, as well as more common species such as kahikatea and tōtara.

But the challenge of storing and germinating seed of our native trees seems insignificant when compared to the challenges we face with the extraordinary pua o te rēinga and orchids. The pua o te rēinga lives attached to the roots of native hardwood trees, depending on the trees for all its nutrients. It only appears above the ground when it produces flowers and fruit, and seed can take years to germinate. It’s a species which has suffered a precipitous decline, resulting from forest destruction, and trampling and browsing by introduced mammals. Many plants have been destroyed by over-collection of the distorted roots the host tree produces where the pua o te rēinga is attached, which are known as wood roses. Its main pollinators are native bats, which have also declined in many areas, meaning that even if plants survive, they may not produce seed.

Pua o te rēinga was one of the first species to benefit from research at the Ōtari lab. The research has looked both at seed and pollen, because a lack of pollination by bats is one of the problems this species faces. There are now plants established at Ōtari and this mysterious plant is slowly revealing some of its secrets.

While pua o te rēinga is able to survive only when attached to a host tree, at least we can easily see and identify these trees. Orchids, however, depend on specific fungi to help their tiny seeds germinate. Most seeds carry reserves of food which allow a young plant to grow to a certain size before it must make its own food from sunlight. However, this takes a lot energy from the adult plant.

Orchids, as one conference speaker explained, favour quantity over quality. They produce massive numbers of tiny seeds which can be blown long distances on the wind. But to germinate, they must come into contact with the right fungus, because the fungus supplies the seed with food.

To germinate orchid seed, the first step is to figure out the right fungus. This involves taking samples from the orchid’s roots then growing the fungi found inside. Even that doesn’t give an answer, because there can be more than one type of fungus in an orchid’s roots. Only by testing different fungi with orchid seeds can these complex partnerships be understood. Thanks to research conducted at the Ōtari lab, we now know the correct fungi for a number of native orchids and have successfully germinated them from seed. Among the orchids successfully grown because of research at the lab are the critically endangered swamp greenhood, two species of fleshy tree orchid, the swamp helmet orchid, black potato orchid and at least one sun orchid.

Ideally, we want to save our endangered species by protecting them in the wild. Sometimes, though, they need extra help, and the only way to save them is to bring them into cultivation. Sometimes, we need to restore the places these species grow. That, too, means we need to know how to propagate and cultivate native plants. For the last eight years, the Ōtari Lions Plant Conservation Laboratory has sowed seeds of hope for the recovery of our precious plants. We have to hope that this work is able to continue.

Ngaio trees aren’t showy and you probably won’t find one at your local garden centre. But their hardiness has made them an essential tree for restoring native coastal forest, particularly in more exposed sites such as Cashmere Reserve. They are ubiquitous around Wellington and I walk past them every day, either at Cashmere Reserve or the nearby Homebush Park, the places where I walk my dog before I start work for the day.

New Zealand’s ngaio belongs to a group of trees and shrubs which is found in Australia, many Pacific islands, part of east Asia and Mauritius. There’s a species unique to the Chatham Islands and another found on the Kermadec Islands. I remember being delighted to encounter the Mauritian species when I was there in 2002, and earlier this year I was equally delighted to see the Hawai’ian species and learn that it’s traditionally known as naio.

Although the cousins of ngaio are spread far and wide, around two thirds of the species are native to Australia. Some are coastal, like our ngaio, while others grow inland. Some are widespread while others are native to small areas only. Some are trees while others are sprawling or creeping. Among these species are several which are known by the name boobialla. Yes, really, that’s the name of a plant, not a scantily-clad alien in a 1960s movie. Apparently it’s a mangled version of an indigenous Tasmanian word for a completely different plant. The plant known as common boobialla is native to coastal parts of southern Australia and Tasmania, and looks very similar to our ngaio.

At some point, for reasons which are not clear to me, someone decided that one species of ngaio wasn’t enough for New Zealand and introduced the common boobialla here1. It’s more shrubby and sprawling than ngaio, making it useful as a windbreak. As a result, by the 1970s it had been planted in many coastal areas and was sometimes growing wild. Because the two species were similar, many people struggled to distinguish them, and boobialla was sometimes planted on sites where native forest was being re-established, including some remote offshore islands.

I have some experience of this issue myself, because when I was working on weeds in the late 1990s, boobialla instead of ngaio was accidentally planted at a Department of Conservation reserve in Marlborough. I spent a couple of hours removing the boobialla plants, and learned to distinguish the two species properly.

The problem with boobialla, though, wasn’t really that a non-native species was being planted where native forest was being re-established. Nor did boobialla establish in the wild to any great extent. However, when closely related species from different locations are grown together, they sometimes interbreed, creating hybrids. In many areas where boobialla was planted, this is exactly what has happened. There are now hybrids growing around most of our coastal cities, as well as in more remote areas, and they are spreading. While ngaio is not a threatened plant, the true species is becoming less common in some regions.

Ngaio isn’t the only New Zealand native species to cross with a related introduced plant. The example I’m most familiar with is our native iceplant, a dainty little succulent which grows in some of the most inhospitable coastal areas, on the seashore just above the high tide mark, on eroding coastal cliffs, among the burrows of nesting seabirds. It forms hybrids with a species of South African ice plant, a fast-growing invasive species many times the size of the New Zealand plant, which grows in similar environments. The hybrids are sterile, so they never produce seed. But they are still larger than the New Zealand species and capable of displacing it.

Another surprising example can be found among our ferns. Our native hen and chicken fern earned its name because it sprouts tiny new fern plants along its fronds. However, many plants cultivated under that name, both in New Zealand and overseas, are hybrids between the native species and a related plant from Norfolk Island. In some cases these hybrids have been planted in native forest as part of restoration projects. Like the hybrid iceplant, they are sterile, but can spread to a limited extent from the new ferns which sprout on their fronds.

There are also examples among birds, but these deserve their own article, so I won’t look at them today. But hybridisation of this kind, between a native species and an introduced species, is relatively rare. We have many native plants which are closely related to introduced species but haven’t been reported to form hybrids. In some cases, the native plants may never grow near their introduced cousins, as is the case with most of our native buttercups. Or it may be that they aren’t closely enough related, which is likely the case with New Zealand’s relatives of the weedy blackberry. While there is a risk that native plants will be hybridised out of existence by a related introduced species, there’s often a much more compelling reason to keep our native plants away from their relatives. Ngaio is a perfect illustration.

Although some in New Zealand decided our native ngaio wasn’t good enough and planted an Australian species, overseas our ngaio’s hardiness has been much admired. It has been introduced around the world, to Europe, South Africa and both North and South America2. There are even a few plants in some rather unlikely locations, such as the coast of Egypt. I found the Egyptian plant while hunting around on the iNaturalist website, and it was only when I zoomed in on the area that I discovered a possible reason for its presence. It’s growing in the town of El Alamein, where New Zealand soldiers were involved with two major World War Two battles. Perhaps ngaio was taken there by New Zealanders commemorating those battles.

As might be expected of such an indomitable species, ngaio has grown well, sometimes too well, in many of the places where it has been introduced. In South Africa, it was first found growing wild in 1934. It is now wild in a number of areas, but mainly in the Western Cape, the same region where pōhutukawa is invasive. Unlike pōhutukawa, though, it is largely confined to highly disturbed areas and it’s unclear whether ngaio is having any significant impact. The same cannot be said for boobialla. It was also introduced to South Africa, perhaps later than ngaio. It was widely promoted as an ornamental plant in the 1950s and was considered to be an invasive species by the 1980s. Hybrids with ngaio have not been reported, though, at least not in any of the sources I could access.

In the case of South Africa, I am reasonably confident that the information about the invasiveness of ngaio and boobialla is accurate. There’s a recent paper by scientists from a reputable research group on the subject. The paper notes that distinguishing the species is not always easy, especially as there is at least one other Australian relative of ngaio present there. The paper also records how the scientists determined which records were of ngaio, which were boobialla and which were the third species.

It hasn’t been so easy to determine whether or not ngaio and boobialla are wild or invasive in other countries. The South African paper suggests that ngaio is considered to be an invasive species in Argentina, Bolivia, Gibraltar, Morocco, Portugal, Spain (including the Canary Islands), the USA and Uruguay. However, this hasn’t been easy to verify. Many of the publications, such the one mentioning Portugal, are plant checklists. These checklists simply list the plants growing wild or considered invasive in an area, without details about how they identified the different species. When I looked at photographs on the iNaturalist website, some of the records labelled as ngaio did not look like ngaio to me, particularly those from Europe. Some resembled boobialla, but there may also be hybrids growing in some areas.

One area where the evidence is clear is in California, because researchers have had good reason to try and tell the species apart. Ngaio, as well as some Australian relatives, were planted beside thousands of kilometres of road, favoured for their tolerance of drought and other harsh conditions, and because of their low flammability. By the late 1960s, ngaio was reported growing wild, and by the 2000s it was considered an invasive species in at least some areas.

But then some of the trees began to die, or at least show severe damage to their leaves. Instead of growing normally, the new leaves grow twisted and distorted. The damage to the trees prompted more careful study, and scientists determined that the most severely damaged trees were ngaio, while boobialla and other Australian species showed little to no damage. The culprit was a tiny insect known as a thrips3. It was closely related to a kind of thrips found on boobialla in Australia, but the thrips on ngaio in California were a species never before described by scientists.

The scientists who first described the thrips on ngaio in California suggested that since ngaio was the most favoured host plant, perhaps the thrips was native to New Zealand. This is unlikely. If the thrips came from New Zealand, nobody had ever noticed them. It’s true that thrips are tiny and difficult to see, but the damage they were causing in California was not. How could a thrips capable of severe damage to ngaio trees go unnoticed for so long?

It is possible that the environmental conditions in New Zealand differ from California, and perhaps the thrips is more damaging in the hot, dry environment. But possible doesn’t mean it’s likely. There’s a simpler explanation, one which we have observed time and again: when a pest or disease jumps from the host it evolved on to a new, related host, sometimes it proves more dangerous to the new host. The most likely explanation is that the ngaio thrips comes from Australia, where most of ngaio’s relatives are found. It may not have been noticed because it’s found in only a limited area, or because it causes minimal damage. But once the thrips arrived in California and encountered our ngaio, it became obvious.

Pests and diseases causing havoc by jumping from their original host to a related species are a much greater threat than native and introduced species forming hybrids4. This doesn’t mean that hybrids aren’t a problem when they happen though. Ngaio is a little unlucky to be at risk from both. But perhaps it’s also lucky, because if ngaio hadn’t been a problem in California, we may have remained unaware that this thrips was a threat.

So far there’s been no sign that the ngaio thrips has reached New Zealand. Thrips are usually transported on living plant material and this species seems to be confined to ngaio and its immediate relatives. Unless we import live material of ngaio’s relatives from overseas, something it’s not currently legal to do, our ngaio trees are likely to remain safe from this pest.

In order to learn more about New Zealand plants behaving badly overseas, I have set up a project on iNaturalist to help me keep an eye on where these plants are growing and where they are wild. I’ve also added in a couple of animals that I’m aware of.

If you are interested, you can see the records at the link below. It is clear that a number of the records are incorrectly identified. I am attempting to correct those I notice.

https://www.inaturalist.org/projects/endemic-new-zealand-species-overseas

This is where I feel most alive: alone in nature. I experience each moment, alert to what I can see, smell and hear. My hand brushes against a fern growing on a bank or the trunk of a tree. I notice the shades of green, the shapes and textures of the foliage, familiar and unexpected.

I’ve come here because this area of forest is known to be one of the best places in Wellington to see native orchids. It’s further than I usually take Donna, but she’s so much better in the car that I decided to make the trip. We were richly rewarded for the effort. She was delighted with the large number of people who were willing to stop and pat her. I spotted some lovely orchids in flower, as well as one of the native sundews.

Here are a few images of the treasures we found.

Pixie cap (Acianthus sinclairii)

This is a common orchid, but it’s so tiny that it’s often overlooked. We found lots of this orchid, but they had finished flowering and had already shed their powdery seeds.

The rest of this article is for my paying subscribers. Thank you so much for your support.

Read more

We’re in no hurry, so I stop to show her a coast banksia growing in the park which runs the length of the beach. At first glance, it may not look like a tree to interest a five-year old, but I know my audience. Coast banksias bear their flowers clustered around a woody stalk, like a bottle brush, and these flower clusters contain a secret treasure. I look for a fallen cluster under the tree and rub away the withered flowers. Then I hand the stalk to my niece and watch as she strokes the brown velvet which coats the stalk.

I discovered banksia velvet when I was a child. I would often place a stalk in my pocket and occasionally pull it out and pat it as if it were a pet. I still do, sometimes, although not today. I’ll be returning to New Zealand soon, and I don’t want to enter New Zealand with a piece of unauthorised plant material in my pocket.

Australia’s coast banksia has been widely planted in New Zealand, which is how I was able to collect banksia velvet as a child. Since the 1990s, it has been going wild in New Zealand, mainly in coastal areas but also inland. In many areas, it’s now considered a significant weed. Here at Coogee, though, it’s growing where it belongs. When the beach was backed by natural dunes, coast banksia would have been here. It still thrives, even though the original landscape is buried under concrete and manicured lawn.

My niece and I are continuing our leisurely walk towards the sand when I spot something which makes me stop and look again. It’s a plant sprouting from a crack in the stone wall above the beach. It’s a couple of metres above me, but I recognise it immediately because I’ve seen the same species hundreds of times growing in similar situations. The location, though, makes me question my judgement. This is no Australian species. It’s a pōhutukawa, New Zealand’s iconic Christmas tree.

I take a few photos with my phone, then continue on to the sand with my niece. Later, I will use iNaturalist to see whether pōhutukawa has been reported in the area before. Sure enough, there’s a mature plant in one of the garden beds not far away. It’s really no surprise that a seedling is sprouting from the wall, because that’s exactly how pōhutukawa grows naturally. And it’s a species which has already shown a tendency to spread when planted in new areas.

In New Zealand, pōhutukawa is native to coastal areas around the northern half of the North Island , and perhaps inland, around the central North Island lakes. Different sources give slightly different accounts of where it originally grew, because it has long been planted by both Māori and Pākehā. Where I live in Wellington, it’s well outside its original range, but there are numerous large trees in gardens. Seedlings constantly sprout in my plant pots and on roadside banks. It’s one of a number of northern species which are now wild a long way south of where they were originally found, but that’s a topic for another week.

Pōhutukawa is a member of the myrtle family, cousin to Australia’s gum trees, among others. It belongs to a group of myrtles known by the scientific name Metrosideros. I’ve seen many sources suggest that this means iron heart, but I’ve been unable to verify this1. Nonetheless, it has dense, hard wood. For me, it has always been an emblem of resilience, thriving where few other plants grow, clinging to coastal cliffs, blasted by salt and wind. The trees may be gnarled and the sparse leaves a dull grey, but when a pōhutukawa bursts into bloom it is glorious.

The ability of pōhutukawa to establish in harsh conditions, including the absence of soil, makes it an important pioneer plant following disturbance. It’s often the first plant to grow after the most extreme of disturbances, such as volcanic eruptions. Pōhutukawa (as well as its hybrids) makes up much of the forest on Rangitoto, which erupted into existence 600-700 years ago. It is also the dominant plant on the highly active Whakaari (White Island).

Despite its resilience, pōhutukawa has suffered a major decline over the past 200 years. When Europeans first arrived, pōhutukawa forest formed an almost continuous belt around the northern coastline, from northern Taranaki in the west to around Gisborne in the east. Now, only a few remnants of forest remain, and pōhutukawa is usually found as isolated trees or clumps of trees in the most inhospitable locations. Forests have been cleared for farmland or coastal development, and remaining stands of forest have been degraded by introduced animals and plants. Australian possums can kill mature trees, while feral goats and livestock prevent new plants from establishing. Coastal areas around northern New Zealand are also heavily invaded by weeds.

To New Zealanders who have long been concerned about the plight of a beloved tree, the idea that pōhutukawa could be a problem elsewhere might seem improbable. Yet, that is exactly what has happened in South Africa. There, it’s not simply a case of a few seedlings in a wall near where a pōhutukawa has been planted. The South Africans are facing a serious invasion of their native shrublands.

To botanists, the south-western part of South Africa, running from Gqeberha (Port Elizabeth) in the east to around Vredendal, 250 km north of Cape Town, is known as the Cape Floristic Region. It’s a true botanical marvel, because in an area a little smaller than Northland in New Zealand, there are around 8,700 native flowering plants, conifers and ferns. More than two thirds of these are found nowhere else.

Most of the Cape Floristic Region is made up of a type of shrubland known as fynbos. The soils are usually infertile and the climate Mediterranean, with hot, dry summers and cool, wet winters. Fires are frequent. Similar areas in other regions, such as south-western Australia and the chaparral of California and northern Mexico, are also highly diverse. Exactly why isn’t entirely clear, but these are typically landscapes which are old and have been buffered to some extent against past climate fluctuations.

Some fynbos plants will be familiar to many gardeners in New Zealand and elsewhere. One of the most important plant groups is the protea family, with more than 300 different species. This is nowhere the number of species Australia has, over 1000. But the proteas are more prominent in the fynbos than they are in Australia, where plants of the myrtle family dominate the landscape. Also prominent in the fynbos are members of the heath family and wiry, grass-like plants known as Cape reeds. Grasses, though, are comparatively uncommon, and fynbos has never supported the large grazing mammals we associate with African grasslands. However, there are many birds, mammals and amphibians unique to the fynbos.

There’s something else the fynbos has in common with other areas of Mediterranean climate: it’s highly vulnerable to weed invasion. The low-growing plants are easily over-topped by larger shrubs or trees. In the fynbos the most serious invaders are trees: pines from Europe and North America, and gums and wattles from Australia. As well as shading out the native plants, these trees take up more groundwater than the low-growing fynbos plants, affecting streams and rivers, and therefore water supplies. And there are many other introduced plants causing problems in the fynbos as well, including our pōhutukawa.

The first signs that pōhutukawa might prove a problem came in the 1980s, when seedlings began popping up in fynbos around Betty’s Bay, south-east of Cape Town. Pōhutukawa had first been planted in the area in the 1940s, and for many years, pōhutukawa trees had produced abundant seed, but not spread. They had even been promoted in an attempt to discourage people from growing the Australian coastal tea tree, which was another invasive species.

Researchers began investigating in the 1990s, and found some areas downwind of mature trees had thousands of seedlings per square metre. While not all the seedlings survived, in one four by four metre plot, they counted 130 sapling trees. Pōhutukawa wasn’t invading everywhere, though. It had a specific preference for areas of peaty soil which were very damp during the winter. Even so, the high diversity of fynbos, with many species found only in very small areas, meant that pōhutukawa was recognised as a serious threat.

Although pōhutukawa first went wild in Betty’s Bay, it was soon seen spreading in other coastal towns in the region. It is also now growing wild around Cape Town, particularly the peninsula to the south of the city, which includes Table Mountain National Park. I’ve even found some iNaturalist records showing it growing wild in other parts of South Africa.

So far, the view on pōhutukawa in South Africa is that it’s a significant problem and could get much worse, but it’s unlikely to be as serious as the pines, wattles and gums which have been so devastating in the fynbos. One reason may be that pōhutukawa is not well-adapted to survive or regenerate after fires, while many pines, wattles and gums are. The most seriously-invaded area near Betty’s Bay was burned (unintentionally) in 2019. Following the fire, there were few seedlings, as seeds still held on the trees didn’t survive and pōhutukawa seeds don’t survive for long in the soil. Although half of the mature trees resprouted following the fire, local conservationists took the opportunity to treat the survivors with herbicide. The accidental experiment suggests that South Africa’s pōhutukawa problem may be manageable.

Nonetheless, given the chance, pōhutukawa is clearly capable of becoming a weed. As well as South Africa and parts of Australia, it has gone wild in California, the Açores, Madeira, Portugal, Spain and even the Scilly Islands. It’s also cultivated in many areas, including Italy, France, Tunisia, Greece and Cyprus, so may have further opportunities to become a problem.

This does raise a question, though. How can a species which has been struggling in New Zealand become a problem in other places? In the case of pōhutukawa, the answer is relatively clear. It’s a tree capable of dominating areas where it grows naturally, as long as its canopy is not browsed by animals such as possums and its seedlings aren’t prevented from regenerating by goats, sheep and cattle. It’s capable of rapidly establishing in areas which have been disturbed, something we consider a good thing where a plant is native but isn’t so desirable in an introduced species. It can also grow in environments many trees find hostile, such as coastal cliffs. And where pōhutukawa is growing overseas, it may have the extra advantage of escaping the many native insects which eat it in New Zealand. Whether that’s the case with the other New Zealand species which have become invasive overseas, and there are a number of them, is another matter. I’ll return to more of these species next week.

In New Zealand, and in many other parts of the world, we face a continuing struggle to restore our natural environments following the invasion of introduced plants and animals. When we see a forest smothered by old man’s beard, a wetland choked with willows, or pines spreading across native grassland, it’s tempting to demonise the invasive species. But pōhutukawa reminds us that species are not good or bad. Sometimes they simply end up, through no fault of their own, in a place where they shouldn’t be. I’m glad that South Africa’s worst infestation of pōhutukawa is now largely under control, but it doesn’t make me love this glorious tree any less.

When a flowering plant grows from a seed, it first grows a root, which heads downwards. Then it sends a shoot upwards, which becomes the aboveground parts of the plant, the stem and leaves. At this stage, the emerging plant isn’t yet making its own food from sunlight. It may still be under the ground or buried under a layer of fallen leaves. Instead, it’s relying on food stored in the seed itself, in a part of the seed known as the cotyledon. The term is a bit of a mouthful, but it’s relevant to classification, which is why I’ve mentioned it.

The majority of plant species, around three quarters of them, have two cotyledons. When the first leaves develop, there are two of them as well, growing from the same point on the stem. In some plants, the cotyledons emerge from the soil as the plant grows and become like leaves. If you’ve ever planted radishes or another plant in the brassica family, you’ve probably seen the two cotyledons. They are also obvious in beans.

Around a quarter of plant species, though, have a single cotyledon. As the plant grows from the seed, it produces a single first leaf, then another and so on.

It’s such an obvious distinction, that plants have long been classified based on whether they have one or two cotyledons. Those with one are known as monocotyledons, shortened to monocots. Those with two are known as dicotyledons, or dicots. Because botanists name plant groups after a plant species which represents the group, the monocots were named after lilies (they were sometimes known as Liliopsida), and the dicots were named after magnolia trees (for example, Magnoliopsida).

The differences don’t end with the cotyledons, though. There are many differences between the two groups. While not all these differences are universal, they can be seen often enough to be a useful identification tool. If you look closely at the leaves of monocots, they have lines, known as veins, which run parallel. In dicots, the veins typically branch. If you count the petals of a monocot, they are usually in threes or multiples of three, while dicots are in fours and fives. The differences could be seen inside the plants too. If you cut through a stem, dicots have cells which transport food and water arranged in a ring towards the outside of the stem. Monocots have these cells throughout the stem. Monocots never produce true wood and don’t grow the massive trunks which can be seen in dicots.

I’m sure that there are more differences, but these are the ones that I remember. They are memorable because they are easy to see. If you look at the leaves of a corn plant, iris, or lily, all monocots, you will see the parallel veins. If you look at the leaves of a rose, cabbage or daisy, you’ll see the branching veins. It can be tricky with cultivated flowers, but if you look at wild roses, you’ll see five petals, while brassicas have four. A lily, in contrast, appears to have six petals (botanists call these tepals, but the point is that they are in multiples of three).

Usually, I don’t write articles based on what I remember. I look everything up and I provide links to my sources. But there’s a specific reason I’m working from memory today. During the 1990s, there was a revolution in botany. The classifications changed, because it turned out that this obvious distinction wasn’t entirely correct. I had to discard the simple classification I had learned and accept that there were actually eight, not two, groups. The monocots were still the monocots, but the dicots were divided.

This might sound like a minor change, but it wasn’t. New information had shown that some plants formerly considered dicots, including magnolias, were much less closely related to other dicots than had been previously thought. In fact, monocots were more closely related to other dicots than magnolias were.

My previous knowledge wasn’t entirely useless. The majority of the old dicot group fitted into a new group known as the eudicots. I could still separate the monocots and eudicots with the same set of characters, such as the veins in the leaves. But I had to learn that a number of plants I knew belonged to other groups.

The magnolias still gave their name to a group of plants, but it was much smaller, only around 2% of flowering plants. Botanists had long considered this group, comprising magnolias and some of their cousins to be “primitive”, representing some kind of ancestral plant. Monocots, in contrast, were thought to be an advanced group which had evolved from the dicots. However, this is a slightly misleading way to describe them. Modern daisies and roses didn’t evolve from modern magnolias any more than humans evolved from chimpanzees or lemurs. However, we do share common ancestors with these animals.

Scientists use classifications based on common ancestry for animals, plants and all other living things, as well as for viruses, which aren’t quite living but do evolve as living things do (for an explanation of viruses, I wrote an article linked here). Humans, chimpanzees and lemurs, all classed as primates, shared a common ancestor around 80-90 million years ago, before the extinction of the dinosaurs. From that point on, the ancestor of lemurs followed a different path, evolving into a group with around 140 species of small primate. The ancestor of humans and chimpanzees continued along with other apes and monkeys. Around 6-7 million years ago, humans and chimpanzees split, following different evolutionary paths, but millions more years would pass before recognisable humans and chimpanzees appeared.

The new understanding of magnolias rewrote the order in which the different groups of plants had split from one another. One of the earliest splits in flowering plants was between the ancestors of water lilies and all other flowering plants. This group had long been recognised as unusual, not just because they grew only in fresh water. They were sometimes classified with magnolias and sometimes classified with buttercups, but under the microscope they also had features which closely resembled monocots. Recognising them as a group which split from other flowering plants long before the traditional dicots and monocots began to diverge made much more sense. Another few groups of plants split relatively early as well, but most of these are much less well known.

The magnolia group split from other flowering plants a little later. From the sources I’ve read, there doesn’t seem to be complete agreement on exactly when this split happened, or the precise order. A 2014 paper suggests that the magnolia group split from other dicots around 160-165 million years ago, after the monocots had already split. Another paper, from 2015, suggests that the magnolia group split from other flowering plants at around the same time as the monocots split from the eudicots, around 130-134 million years ago. Another 2015 paper gave a date range of 127-179 million years ago. Looking that far back in time can be an imprecise process, and the method used to measure the time makes a difference to the result.

Most of what we now know about the evolution of the different plant groups comes from complex analyses of their genes. Modern genetic analysis has led to numerous name changes in plants and a great deal of confusion to those, like me, who are interested in being able to identify plants on sight. I assumed that the abandonment of the traditional dicot–monocot split also resulted from genetic analysis. However, when I looked into the history of classification, I realised that this change was prompted by a different kind of study, one which used a much older approach.

Scientists first learned that pollen had different shapes when they began using microscopes as tools for studying biology in the late 17^th century. By the late 19^th century, they had begun to use the different shapes to help in classifying plants. But these tiny grains aren’t useful only for studying existing plants. They have a rigid and durable outer coat which means they are well-preserved in deposits of ancient plant material such as coal. We can learn a lot about the past climate and vegetation of an area by studying the fossil pollen. We can also learn about plant evolution.

As far as I can tell from looking back through the literature, the reclassification of the dicots and monocots was prompted by studies on fossil pollen which were conducted prior to the widespread use of genetic analysis. The researchers drew their conclusions simply by observing the similarities and differences between different types of pollen using extremely powerful microscopes. Their insight was to identify which of the features were important indicators that plants were related, and which were not. The conclusions based on pollen were supported by later genetic analysis. It’s another example of the way that science which appears arcane may lead to significant advances in our knowledge.

I was prompted to look into this classification because I’ve been thinking about some of our native plants which fall into the magnolia group. We don’t have any native magnolia species, but there are a number of native trees and shrubs which are classified in the same broad group which split from other flowering plants so long ago. Among them are a couple of important forest trees, as well as some smaller trees and shrubs, some of which will be familiar to many people who spend time in our native forests.

Around Wellington, one of the most common trees in our remnant forests is tawa. Although its timber is considered useful and many trees were logged in the 19^th and 20^th centuries, many of the trees remaining around Wellington are ones which appear to have suffered some damage in their early growth. They branch low, growing gnarled and twisted, and would have been useless for timber. And so they survived. Tawa belongs to one of the subgroups of the magnolias, cousin to the bay laurel, with its aromatic leaves, and the avocado.

Another tree which survives in some remnants around Wellington is the pukatea. It’s a stunning tree, with glossy leaves and reddish stems, and with massive buttresses at the base of large trees. There aren’t many of them, because they mainly grow in damp areas and most of these areas were cleared and drained. There are about a dozen which have been planted in Cashmere Park, the reserve where I’ve been doing restoration work. Pukatea is related to tawa, but more distantly. Its closest relatives grow mainly in Australia, although it’s also related to another common tree in forest remnants around Wellington, porokaiwhiri or pigeonwood.

I intended to write about some of the other plants in this group, including the familiar kawakawa, which is instantly recognisable by the ubiquitous holes in its heart-shaped leaves. However, I allowed myself to be diverted by fossil pollen grains and the story they told us about plant evolution. I will return to kawakawa another day.

I wanted to share a little garden joy …

Read more

Ōtari, in contrast, still has some of these forest giants. The oldest of these is a rimu, named Moko, which is thought to be more than 800 years old. There are other giants as well, kahikatea, tōtara, miro and mataī. Although the original area protected in Ōtari was smaller, around 7 hectares compared with 12 in Khandallah, Ōtari was protected earlier and never logged.

We will have to wait a long time before there are forest giants in Khandallah Park, hundreds of years. But it isn’t simply a matter of time. Among the many thousands of seedlings sprouting among the ferns, there are few which could grow to be one of the forest giants I can see in Ōtari. The settlers so thoroughly stripped the forest of these trees that, in all of Khandallah Park, there is only a single large tree of any of these species remaining, a mataī. There are a few miro which would have been small when the forest was logged but are now large enough to produce fruit, but it’s a tiny number of trees for regrowing a forest.

We have around a dozen tree species which grow to be so massive and tall that they emerge from the surrounding forest canopy: what we call emergent trees. From the Waikato region northwards, these emergent trees are often kauri. South of the Waikato, there are no kauri trees, but others take their place. The majority of these are, like kauri, conifers, or cone-bearing trees. But while kauri cones are recognisable as cones to anyone familiar with pine cones, the cones of our other conifers such as rimu, are something quite different.

The conifers are an ancient group of plants, with fossils recognised as conifers dating back 300 million years. They are part of a larger group known as the gymnosperms, which were the most important land plants during the Jurassic era, when dinosaurs were becoming the dominant animals. Over the last 150 million years gymnosperms were gradually replaced by flowering plants in most parts of the world. Conifers, however, remained important, particularly in cooler regions. More than half of the surviving gymnosperm species are conifers. The remainder are mainly cycads, which superficially resemble palms and are found in tropical regions. Then there are a few unusual plants, such as the ginkgo tree of China and the Welwitschia plant of the Namib desert, which have no close living relatives. The Welwitschia is one of the strangest plants known, since it has only two leaves which continue growing from the base throughout its long life, which can be 1500 years or more.

Apart from extremely unusual plants such as Welwitschia, the difference between gymnosperms such as conifers and flowering plants isn’t immediately obvious. It’s only by looking closely at the structure of the seed and how the plants breed that it’s clear how they differ. Flowering plants protect their seeds within a complex structure, the ovary, which is inside a flower. The flowers also produce pollen and assist with the dispersal of pollen, for example by attracting insects. Sometimes, the flowers which produce pollen and the flowers which produce seeds are separate, and sometimes the flowers do little to assist dispersal, such as the flowers of wind-pollinated grasses. But the seed is always inside an ovary which is inside a flower.

Gymnosperms don’t have the same kind of structure around their seeds. Instead, pollen and unfertilised seeds (known as ovules) are produced on the surfaces of modified leaves. Typically, these modified leaves are formed into cones, although not in all species. More than half of gymnosperms produce pollen and seed on separate plants, while the remainder produce them in separate structures on the same plant. Almost all are wind pollinated, which means they produce vast amounts of pollen to ensure that a small amount ends up where it’s needed. Those of us who live near pine trees are familiar with the way that everything is covered with yellow dust when the trees release their pollen, and conifers are a curse for those with hay fever because of the quantity of pollen and its indiscriminate spread.

Until humans began moving them around, pine trees were almost entirely confined to the Northern Hemisphere, as were their cousins, trees such as Douglas fir and larch. In cooler parts of North America, Asia and Europe, they dominate the landscape. In the Southern Hemisphere, similar environments are more likely to be dominated by species of southern beech, which are flowering plants. However, conifers are also present. Sometimes these are members of the cedar family, which is a group of plants found all around the world. Members of the cedar family include the largest of all trees, the giant redwoods of California, as well as the coast redwoods which dominate the rainforests on the west coast of the USA. In New Zealand, though, these are most often members of the podocarp group (which translates to foot-fruit, a name I’ll explain in a moment).

The podocarps are unusual among conifers for a number of reasons. Most conifers are unable to compete with flowering plants in more favourable environments, such as tropical rainforest. But podocarps continue to hold their own in environments where flowering plants dominate, including tropical rainforest and the temperate rainforests of New Zealand. One reason they can do this is because they are usually more shade tolerant than most other conifers. They are able to regenerate in canopy gaps, such as those formed when a single tree falls, rather than depending on larger disturbances such as fire, which many other conifers require.

Podocarps also have unusual “cones”. The pollen cones are similar to the pollen cones of other conifers, but the seed cones have a single seed. Before pollination, the ovule (unfertilised seed) excretes a drop of liquid which catches the pollen and is then reabsorbed into the ovule, taking the pollen with it. While many conifers use this method to catch pollen, podocarps often have their cones arranged so that the drop of liquid spreads further, even catching pollen which landed before the drop was excreted. As the seed matures, some of the surrounding tissue develops into colourful, juicy flesh which attracts animals which then disperse the seeds. Most are dispersed by birds, but mammals, such as fruit bats and baboons, disperse the seeds of some podocarps.

Around half of New Zealand’s podocarps have their seed and pollen cones on separate plants, including kahikatea, all four species of tōtara, miro and, crucially for Khandallah Park, mataī. There’s no chance of the lonely mataī in Khandallah Park being able to reproduce until it has other mataī trees nearby. Even once it does, we wouldn’t want all of the mataī in Khandallah Park to be descended from a single tree.

The situation is even worse for areas of regenerating forest, such as the reserve I’ve been helping to regenerate. There were no surviving podocarps at all, and it’s many kilometres from other remnants, meaning that there’s not much chance of seed being carried there by birds. In fact, the failure of podocarps to regenerate following logging and other disturbances is a major issue for forest restoration around New Zealand.

If we want our forest giants to return, we have to help them. But this is not as simple as it might appear. Podocarps are more difficult to propagate than many flowering plants, especially to produce the large numbers of plants needed for forest restoration. Like many conifers, they can be tricky to grow from cuttings. They can be equally tricky to grow from seed. I’ve spoken to those involved with growing native plants for use in restoration, and they’ve told me that one option can be to collect seedlings from the wild. When this is done carefully, by people who understand the forest, it causes no harm, because in some places close to existing trees many more seedlings grow than can possibly survive.

But collecting seedlings only solves part of the problem. Many areas are too steep and inaccessible to dig holes and plant young plants. We could scatter seed, perhaps using drones to access difficult areas, but we don’t know enough about the best ways to harvest and store seed to ensure that we aren’t wasting our efforts.

In the last few years, there has been some progress in understanding seed germination in New Zealand’s podocarps, thanks in part to research supported by the Lions Plant Conservation Laboratory at Ōtari. Working with the laboratory, Sarah Goldberg recently completed her PhD, which showed that kahikatea has seeds which don’t tolerate storage, so need to be sown fresh. Tōtara, miro and mataī seeds survive better and can potentially be stored, but are difficult to germinate once removed from storage.

The Lions Plant Conservation Laboratory was set up in 2018 with funding from the Lions Club. Since then, it has made an important contribution to our understanding of how to propagate a number of endangered plants, including members of the myrtle family at risk from myrtle rust, orchids, kauri, wood rose and a buttercup. Unfortunately, we may not have the Lions Plant Conservation Laboratory for much longer. In April, the Wellington City Council, which supports its ongoing work, decided to cut all of the funding. There’s since been something of a reprieve, and the lab will keep running for another year or two, at reduced capacity, but beyond that its future is uncertain. It’s still very much needed though. We have a lot to learn about many plants, including our podocarps.

Despite the difficulties, in the last 20-30 years many thousands of young podocarps have been planted around New Zealand to replace our fallen giants. It’s only the start, though, of a process to reverse more than a century of forest destruction. Podocarps are not pine trees, which reach astounding sizes within a few decades. They are, comparatively speaking, slow growing. The people who are planting podocarps today will be long gone before the trees are mature. And even their grandchildren will be long gone before a few of those trees grow to become forest giants.

I live in a suburb on the western side of Wellington Harbour. Most of the nearby forest is dominated by large-leaved trees, such as kohekohe, māhoe, karaka1 and rewarewa. Another dominant tree, tawa, has smaller leaves, but they are still much larger than the leaves I was observing in the eastern forest. A few forests in Wellington’s west still have trees such as rimu and kahikatea, which have tiny leaves, but these too are different from the trees in the east.

Wellington’s eastern and western forests are fundamentally different. The western forests are dark and gloomy under the large-leaved canopy. The trees are draped with vines and their branches heavy with perching lilies and ferns. To me, they feel like tropical rainforest, even if they are bitterly cold at times. There’s a reason for this. Trees such as kohekohe, māhoe, tawa and karaka, as well as the vines and perching lilies, are close cousins of tropical species.

The eastern forests, however, are dominated by a mix of New Zealand’s native beech species. These belong to a group of trees known as southern beeches, which have relatives in Tasmania, south-eastern Australia and temperate South America. They were once considered to be close relatives of European beech species. While they are no longer considered such close relatives, they are still closer to European beeches than they are to tropical-looking species such as kohekohe.

New Zealand has five beech species, two of which are common in forests on the eastern side of Wellington Harbour. The trees with the velvet-black trunks are black beech or tāwhairauriki. The bark is black because tiny insects known as scale insects feed on the bark. They suck sugary sap from plants and excrete excess sugar, which supports the growth of black sooty mould. Black beech and the closely related mountain beech have the smallest leaves among our native beeches, no more than 1.5 cm long.

The other common beech in Wellington’s eastern hills is the hard beech. Along with red beech, hard beech has larger leaves, but they are still no longer than 4cm at the most, usually smaller. Further afield, there are also silver beech trees, which have leaves of intermediate size, although they are closer to black and mountain beech in size. The silvery bark of young silver beech trees make its name obvious, as does the black bark of black beech and the habitat of mountain beech. The common names of red beech and hard beech, however, appear less obvious. They are named for their timber, reddish in colour in red beech and particularly durable in hard beech.

The small leaves of beech trees give their forests a distinctive character. There’s a softness to the light under a beech forest canopy, as the sun’s rays are filtered and scattered by the tiny leaves. The proportion of leaf to twig makes the canopy more brown and less green. The leaf litter is thick and spongy. The colours are different too. While New Zealand’s beech species are not deciduous, fallen leaves are often bright yellow. The flowers, while tiny, are red.

Because I’ve spent so much time in Wellington’s western hills in the last 20 years, beech forest feels more exotic and unfamiliar to me. My impression, however, is false. New Zealand has around 6.4 million hectares of native forest remaining and around 4 million hectares contain one or more species of beech. Around half of that forest is like the beech forest I was walking in, with a mixture of beech and other trees such as kohekohe and rimu. The other half is pure beech, frequently a single beech species. As a general rule, beech trees tend to grow in cooler, wetter and less fertile conditions than our other tree species.

Each beech species prefers a slightly different environment. Mountain beech, as the name suggests, dominates at higher altitudes. It’s usually the species which demarcates the treeline, a line of altitude below which grows dark green forest and above which grows lighter green grassland with low-growing shrubs. The trees are often stunted by the harsh mountain environment, creating a forest which appears to be drawn straight from the pages of a fantasy novel, often referred to as goblin forest. Silver beech is also tolerant of colder conditions and dominates in places such as Fiordland which are cold and wet. In high-altitude areas which are also very wet, it can replace mountain beech at the treeline. Red beech also tolerates cool conditions, but it dominates on the fertile soils of inland river valleys.

Hard beech and black beech are a little different. They are more often trees of lowland areas, although they do sometimes grow at higher altitudes. They tend to be trees of less fertile and drier areas, so their presence on the eastern side of Wellington Harbour, and absence from the west, indicates a difference in climate and soil conditions on opposite sides of the harbour.

The presence or absence of beech trees helps us to read the environment in other ways as well. There’s a band across the lower North Island, and another across the middle of the South Island, where they are absent. Beech trees are also absent from Rakiura (Stewart Island) and Taranaki. These gaps have long fascinated botanists, because in many of these areas the environment is ideal for beech trees. Their absence cannot be explained by our current environmental conditions. Instead, they draw a picture of the past. They give us clues to the history of New Zealand’s climate, in particular, where trees grew during the last ice age. However, it’s not a clear picture, and has been the subject of much debate among scientists.

In the frozen depths of the last ice age, around 20,000 years ago, luxuriant forest made up of large-leaved trees such as kohekohe was confined to the northern parts of New Zealand. Beech forest was more widespread, but was still very limited. In the lower North Island and throughout the South Island, it was found mostly in small patches where micro-climates were just warm enough for it to hold on. Why, then, are there gaps in beech, but not in trees such as kohekohe or our native conifers such as rimu and kahikatea?

The answer lies with the fruit. Most species of forest tree have fleshy fruit which is eaten by birds; this is the case for conifers such as rimu and kahikatea as well as large-leaved species such as kohekohe, karaka and māhoe. Beech, however, has small, dry fruit with no specialised way of dispersing. They can be carried by the wind, but not as far as the fluffy seeds of daisies. They can be carried downhill by flowing water. But they don’t fly far and wide in the bellies of birds. The seeds of beech, therefore, disperse more slowly than the seeds of many other trees. However, because they can tolerate cold, small patches of beech trees, particularly silver beech, survived even in the far south of the South Island.

The distribution of beech trees reminds us that species can take a long time to respond to environmental changes. Our forests still bear the imprint of the last ice age. How might they respond to the rapid warming we are now experiencing? How long will they bear the scars of the large-scale destruction caused by logging during the late 19^th and 20^th century? That’s hard to know.

Our forests are ancient in relation to the time humans have been present in New Zealand. But they are not as old as they feel to us when we stand among the gnarled branches of a goblin forest in the mountains. I think back to a memory from when I lived in Nelson, of walking along a ridge above the Cobb Valley on a cold, misty morning. The twisted limbs of the trees were swathed in hanging mosses and our footfalls were muffled by the deep leaf litter. It was a magical forest which felt as if it had emerged from the dawn of time. But the area was probably covered by permanent snow during the last ice age. I find something hopeful in the thought, even as I worry what might happen to our forests in the future. These trees are survivors.

Read more

It’s the opposite of what I learned to do in the public service. There, I wrote documents to advise busy decision-makers. I kept to the point. Conclusions up front. No wasted words. But the goal was the same: understanding without effort.

Over the last few weeks, I’ve looked at different aspects of bird flu in depth. I’m going to step away from bird flu for a while and write about more joyful topics, including some lovely walks I’ve done recently and, of course, Bird of the Year. But I’ve decided to apply a little of my public service style before I do.

Here’s my bird flu wrap-up. What do we know about bird flu in Australia and New Zealand right now? What can we expect in the coming months? What do we need to know?

In Australia, bird flu has now been reported in 27 wild bird species and 4 wild mammals

A report from the Australian Department of Agriculture, updated on the 3rd of September, reported that bird flu has been detected in 31 wild animal species in Australia, with most records from South Australia and Victoria. Although it’s not clearly stated, as far as I can tell all of the records are from dead or very sick animals. Two thirds of the records were from the greater crested tern, a large and widespread tern found around the coastlines of Australia, South-East Asia, India, the Arabian Peninsula and Africa as far west as Namibia. While the greater crested tern is occasionally spotted in New Zealand, records are typically single birds.

Almost all the birds infected have been seabirds, but there are a small number of records from land birds. So far, all of these are predators or scavengers, which means they’ve probably become infected from eating sick or dead seabirds. This is also the case of one of the four mammals affected, the fox, which is invasive in Australia. There are a few records from fur seals, which could be expected based on what bird flu has done overseas, and two records from different dolphin species. As I mentioned in my article on bird flu and mammals, dolphins aren’t typically susceptible to the flu in the way many seals are. So finding bird flu in two different species of dolphin, just a few months into Australia’s outbreak, is particularly worrying.

There are still only three reports from New Zealand

So far, there have been three reported bird flu cases in New Zealand, one in a skua, one in a giant petrel and one in a kāhu (swamp harrier). All three species are commonly predators and scavengers, with skuas and giant petrels often preying on other seabirds and scavenging dead seals, making them particularly vulnerable. Both skuas and giant petrels fly long distances, including to subantarctic islands where bird flu has been spreading for the last year or so. The kāhu, although not a seabird, is also quite capable of flying to subantarctic islands. Whether bird flu is spreading here yet is therefore uncertain.

Bird flu in Australia is increasing and we can expect it to get much worse

It’s difficult to tell the numbers of birds affected in Australia from the official sources and media coverage. The government is reporting detection events, which can be one animal or a group. The largest number of sick or dead birds I’ve seen reported on an official site so far is 80. However, a media report from the 21^st of August suggested that more than 1000 greater crested terns had been killed in three separate events in South Australia. Media reports also state that bird flu has killed more than 100 little penguins on an island off Tasmania’s coast.

The experience from overseas suggests that the numbers are likely to get much worse. Single die-off events in other parts of the world have involved thousands or tens of thousands of birds. In the first year after bird flu reached South America, it is estimated that it killed at least 667,000 wild birds and 52,000 wild mammals (mainly seals). Some species have suffered major declines, including the great skua (a Northern Hemisphere skua species), common tern, sandwich tern and northern gannet. Those most affected are typically species which either nest in dense colonies or are predators and scavengers of dying and dead birds. In Australia, this is likely to include native mammals, some already endangered.

The number of species affected will also increase as the virus spreads. Between the time when I began writing this article and when I finished, an update had already added two new species to the list in Australia.

We can also expect it to get much worse in New Zealand

Although we don’t have confirmation that bird flu is spreading here yet, there’s no reason to think it won’t be soon. But exactly what else will be infected, and which species will bear the brunt, is still uncertain. Overseas, terns have often been among the worst-affected species, but these are not the species we usually see in New Zealand. We just don’t know.

Australia, however, has given us some clues. Around half of their bird flu records are from birds also found in New Zealand. These birds are likely to be affected here as well. After the greater crested tern, the bird with the largest number of records is the silver gull (called tarāpunga or red-billed gull in New Zealand)1. We can also expect our little penguins (kororā, also known as the little blue penguin) to suffer. The fur seals killed by bird flu in Australia are the same species as New Zealand’s fur seals, so we will also probably have significant numbers of deaths, especially as related species were also hit hard in South America. It’s likely, too, that many birds and seals are now, or will soon be, dying on our subantarctic islands, since similar Southern Ocean islands have also seen large losses.

Other birds infected in Australia include the black-faced cormorant (māpunga in New Zealand), the great pied cormorant (kāruhiruhi), both species of giant petrel (pāngurunguru), brown skua (hākoakoa), white-fronted tern (tara), Australasian gannet (takapū), fluttering shearwater (pakahā), and Hutton’s shearwater (Kaikōura tītī)2. With these species, though, it’s not clear how many have been killed by bird flu in Australia, or to what extent they might be affected in New Zealand.

There’s one small glimmer of hope. Our rarest bird is the tara iti or fairy tern, with fewer than 50 birds in 2025. It’s a subspecies of a tern which is also found in Australia and New Caledonia, but their fairy terns belong to two different subspecies. Ours is unique to New Zealand. So far, fairy terns are not one of the birds reported to be infected in Australia. Nor have its closest relatives been severely affected elsewhere, possibly because they don’t breed in such dense colonies as some other seabirds. I’ve been worrying about tara iti for months, fearing it will be gone for good before the year is over. This may still happen. But perhaps it stands a chance.

People, poultry and pets are at risk too, but probably not cattle

In other regions, outbreaks of bird flu in wild birds and outbreaks in domestic poultry are linked. Typically, it is chickens and their relatives (such as turkeys) which suffer severe disease, while ducks are more likely to have a milder illness. Cats and dogs have been affected as well, although this is relatively uncommon. Most of the records from cats are either associated with raw meat from infected poultry, or raw milk from infected cattle. However, contact with infected wild birds is likely to be a risk as well. There appear to be fewer records from dogs, but dogs scavenging dead birds are likely to be at risk.

Both Australia and New Zealand have released official advice on how to protect birds for those keeping poultry either in commercial operations or backyard flocks, as well as advice to pet owners. The advice is centred around minimising contact between domestic animals and wild birds. For example, don’t let dogs sniff dead animals at the beach, and try to prevent wild birds from accessing the food and water used by domestic animals.

Humans are also at risk of bird flu, but again cases are uncommon. Typically, infection in a human involves close contact with an infected animal, because the type of cells which bird flu infects are found deep in our lungs, not in our nose and throat. Human-to-human transmission has not been reported. To keep ourselves and our families safe, we should avoid contact with sick or dead birds.

In the USA, bird flu jumped into dairy cattle and spread rapidly. Bird flu hasn’t often been seen in cattle, and genetic research suggested the US outbreak resulted from a rare variant which crossed into cattle in late 2023 or early 2024. It’s relatively unlikely, then, that this will happen in Australia or New Zealand.

As bird flu proliferates, so too will misinformation and conspiracy theories

If you’ve been keeping an eye on social media, you may have noticed that some of the conspiracy language used to describe COVID-19 is now being used to describe bird flu. Some of the media commentary has framed this as a New Zealand issue, but it’s part of a pattern seen elsewhere. Canadian researchers documented very similar conversations on Facebook and Instagram related to the spread of bird flu in North America. A similar pattern can be seen on YouTube. People are convinced that bird flu is a hoax, that viruses aren’t real and that tens of thousands of scientists are conspiring with various authority figures to achieve some nefarious goal.

I don’t have any answer for this, except that trying to argue with those spreading these conspiracist beliefs over social media is unlikely to help. At some stage soon, I’ll pull together some resources for those who have friends and family members caught up in these beliefs, as I did when COVID-19 was at its height.

It’s hard to know what will happen next

This particular type of bird flu, which first emerged in 1996, has already behaved like no other bird flu. Even among influenza viruses, which are known for evolving rapidly, it stands out for the range of species infected and the scale of its spread. Twice, it has subsided, but each time it has come back it has affected more species over a wider area. The variant which re-emerged in 2021 has spread further and killed more wild birds than bird flu ever has before. The outbreaks are described as unprecedented. It jumped into mammals, including some which weren’t considered particularly susceptible to bird flu. It has reached some of the most remote locations on earth.

Some birds in the Northern Hemisphere are showing signs of increased immunity. We can expect some species to recover from seemingly devastating losses, but others may not. While there haven’t yet been any extinctions attributed to bird flu, this may still happen. So far, though, the situation doesn’t seem quite as dire as chytrid in frogs, which I wrote about last week.

That’s small comfort, I know. It’s going to get worse, and it’s immensely sad. I’ll keep an eye on the situation and will write an update when I think that there’s enough new information.

In the meantime, please go and do something joyful. Voting is now open for Bird of the Year 2026. You don’t need to be a New Zealander or live in New Zealand to vote. We love foreign interference in Bird of the Year. But please, vote for a seabird. Or a shorebird, since in this election, terns are in the shorebird category.

Vote now for Bird of the Year 2026

The first disease which came to mind was rinderpest, the devastating cattle disease which also killed many wild relatives of cattle when it reached Africa in the 1890s. But when I ran a couple of simple searches of the academic literature, another disease came up. It hadn’t immediately occurred to me, but it ticked the boxes. Global spread? Yes. Deadly wildlife disease jumping from species to species? Yes. Lessons which might help us understand bird flu better? Almost certainly.

Those lessons might be hard to hear, though. As I write these early paragraphs, I’m not yet familiar with the details, but I do know that this disease has caused hundreds of species to decline and has driven some to extinction. As far as I can tell, we haven’t found a solution. But because many of the species affected are easily overlooked, it’s a disease which has seldom made headlines.

The disease I’m talking about is commonly known as chytrid, pronounced kit-rid for those who use British pronunciation and kite-rid for those who use US pronunciation. It is caused by certain kinds of fungus and it affects frogs and their relatives. The story of chytrid is disturbing and sad, so I seriously considered whether I wanted to look into it right now. But I think it’s a story worth understanding.

Frogs belong to a group of animals known as amphibians. While amphibians, reptiles, birds and mammals all evolved from an ancient, four-limbed fish, the amphibians were the first to branch off this family tree. The first amphibians appeared around 340 million years ago, around 150 million years before New Zealand began separating from the ancient continent of Gondwana. As well as frogs, the amphibian group includes toads, newts, salamanders and a fascinating group of worm-like animals which live underground in the tropics, called caecilians.

Amphibians are remarkably diverse in the ways that they live and breed, but many spend the early part of their life in the water then the later part mainly on land. The typical frog life cycle, for example, involves eggs laid in the water, tadpoles which develop in the water and adult frogs which live on land, as do some salamanders and newts. However, there are many variations in life cycle. New Zealand’s native frogs, for example, lay eggs in damp places on land. Their eggs are large in proportion to the size of the frogs, with lots of yolk, meaning that the young are well-developed by the time the eggs hatch. The tadpole stage has well and truly passed and the young froglets already have four legs and breath air. Two of our native frog species watch over their eggs then care for their young for a month or so after they hatch, or rather one parent does. The female lays her eggs and is done with parenting. From then on, the male frog does all the work.

There are many more variations in life cycle. For a start, not all amphibians lay eggs. Some frogs, salamanders and caecilians give birth to live young. Some salamanders, such as the axolotl and mudpuppy, spend all their life underwater and never develop into an air-breathing adult form. A numbers of caecilians, both those which lay eggs and those which give birth to live young, produce milk-like secretions to feed their young.

What is consistent, though, is that amphibians need water. They don’t always need a pond or a stream, but they need moisture around them. There’s a crucial reason for that. Breathing requires moist surfaces for the process of gas exchange, where oxygen is taken into the body and carbon dioxide released. This is no problem for aquatic animals such as fish, which simply need a flow of water across their gills. Land animals, though, need to keep their breathing surfaces moist in environments which are often dry. They do this by having the breathing surfaces deep inside their lungs, which protects them from drying out.

Amphibians do have lungs, unless they are entirely aquatic, like the axolotl. But their lungs aren’t the only way they breathe. They also breathe through their skin. Some species depend more on their skin than their lungs, while others depend more on their lungs. Frogs and toads which hibernate bury themselves in mud and breathe entirely through their skin during this time. But even species with well-developed lungs need to be able to breathe through their skin. This makes them sensitive to environmental conditions in a way that thicker-skinned species are not.

Despite this limitation, until very recently amphibians had been remarkably successful. There are 8000-9000 known species, more than there are species of mammal, although fewer than there are birds or reptiles. They are found almost everywhere, with the exception of Antarctica, Greenland, a few remote oceanic islands and some areas of desert. But even most deserts have frogs. There are, for example, nineteen frogs native to the deserts of Western Australia and seven species native to the Sonoran desert in the USA. But even these frogs can’t tolerate conditions which are too dry. They survive either in permanently wet areas within deserts, or they bury themselves somewhere cool and enter a state of dormancy until the rains come. They face the same problem as all amphibians: the drier the environment they are in, the faster their skin dries out and leaves them unable to breathe.

Despite their astounding adaptability, amphibians are now in serious trouble. More than 40% are considered endangered, a figure exceeded only by reef corals and a group of ancient plants known as cycads2. Historically, the main threat to amphibians has been the destruction or degradation of the places where they live. In New Zealand, our frogs also proved vulnerable to introduced predators such as rats. More recently, though, something else has been happening.

Since the 1970s, there had been unexplained disappearances of frogs in a number of areas, including tropical Australia, Central America and parts of California. In 1989, a major conference brought together amphibian experts from different regions, and they joined the dots; the local disappearances they had seen were part of a global amphibian decline. A few years of research and debate followed. Many amphibians naturally experienced fluctuations in their numbers. Had they really disappeared? Was it pollution? Was it increased ultra-violet radiation as a result of the ozone hole? Was it climate change?

The most troubling aspect of the declines and disappearances was that they weren’t necessarily happening in areas which were disturbed by human activities. Some were happening in remote, protected areas, which were thought to be largely safe.

In Australia, a senior wildlife ranger and a disease researcher worked together, largely in their spare time, to try and understand the problem. By looking at the pattern of disappearances, they worked out that it was likely to be a disease and even predicted its rate of spread. As a result, they and other researchers were able to document, in meticulous detail, the disappearance of the sharp-snouted day frog. Dead and dying frogs were collected in the early 1990s, and their skin proved to be infected with a fungus. In some areas where adult frogs had disappeared there were still tadpoles, so some of the tadpoles were collected and kept in captivity. When they matured into adult frogs, they too died, infected with the same fungus. In tadpoles, they found that the fungus could infect only the skin around the mouth, but on adult frogs, the whole of the skin could be infected.

The fungus turned out to be something entirely unexpected. It belonged to an ancient and poorly-known group of fungi found in wet environments. This group is so poorly-known, in fact, that most of them are classified as dark matter fungi or dark fungi. We know that many of them exist only because we can detect their DNA in the environment. They can be found in soils, in fresh water and in marine environments. Fungi belonging to this group are commonly known as chytrid fungi or chytrids. Most known chytrids live on decomposing plant and animal matter, with some parasites. There had never been a chytrid which infected vertebrates (that is, mammals, birds, reptiles, amphibians and fish).

At the same time as Australian researchers were finding chytrid in their frogs, it was found killing captive frogs in the USA. Soon after that, it was also detected in Panama. Although there was still some uncertainty about how much chytrid was contributing to the global declines, it became increasingly clear that it was a major part of the problem.

The chytrid I’ve been discussing so far has been reported only from some frogs and toads, but it’s not the only chytrid infecting amphibians. In 2013, another chytrid was found infecting European salamanders. It has caused a precipitous decline in fire salamanders in Europe. It has also proved lethal to a number of other newt and salamander species in laboratory tests. So far, this chytrid hasn’t reached North America, home to around half of the world’s salamanders.

For some years, there was considerable debate about where chytrid came from. How had the frog chytrid appeared on three continents at around the same time? Genetic studies suggested that the chytrid fungus infecting frogs in different continents was fairly uniform, suggesting a recent, common origin. In 2018, this was narrowed down to most likely the Korean Peninsula in the early 20^th century.

Frogs don’t fly thousands of kilometres when foraging for food or migrating to breeding areas, so chytrid hasn’t spread like bird flu. Instead, we are squarely to blame, by moving amphibians around the world as exotic pets, food and for medical uses3. And we are still doing it. Countries such as New Zealand and Australia have strict rules preventing most imports of amphibians, but most places, including the USA and Europe, have few, if any, restrictions. It’s unlikely that North America’s salamanders will stay free from chytrid for long. Even with our strict rules, chytrid reached New Zealand and has contributed to the decline of our native frogs.

So far, New Zealand’s frogs are still hanging on, despite chytrid. But many frogs around the world haven’t been so lucky. An assessment of amphibians which suffered significant declines from 1980-2004 found that chytrid was the major cause for more than half. During that time, 120 species were either confirmed or suspected to have become extinct due to chytrid. Since 2004, chytrid has remained a major problem, with a further 26 likely extinctions. The Chiriquí harlequin frog, from Costa Rica, is gone. The splendid poison frog, from Panama, is gone. Australia’s mountain mist frog and Mount Glorious torrent frog are gone. The Corquin robber frog, from Honduras, is gone. The Malvasa stubfoot toad, from Colombia, is probably gone. So, too, are the Nombre de Dios streamside frog, the Haitian streamside frog, the green poison frog and the Pacific marsupial frog. All of these species were either last seen in the early 1990s, before chytrid was detected in their area, or suffered a major decline linked with the arrival of chytrid and then died out a few years later. And I haven’t listed them all.

Before the emergence of chytrid, the accepted wisdom was that diseases didn’t cause extinctions. Sadly, the first lesson we can take from chytrid is that diseases can and do. So far, I’ve found no species of bird or mammal thought to have become extinct as a result of bird flu, but the world is only five years into this disastrous outbreak. We will be very lucky to avoid any extinctions, particularly somewhere like New Zealand, where there are so many seabirds and shore birds already in desperate trouble.

Another painful lesson of chytrid is that we aren’t good at learning from our mistakes. We had a good idea that the global trade in amphibians was responsible for spreading chytrid within a decade or so of its discovery, yet that trade continues. The form of chytrid infecting salamanders hasn’t been found in North America yet, despite extensive surveillance, but there are still no restrictions on importing amphibians as pets.

We haven’t spread bird flu in quite the same way as we spread chytrid, although we do bear some responsibility, since the disease emerged in part because of the ways we keep poultry. But whether anything will change is debatable.

I feel such sadness at the losses of all these frogs and what we are facing with our birds. I don’t want to know but I can’t look away. If you feel the same way, I’m not going to try and convince you otherwise. Sometimes, the world is horrible. Sometimes, all we can do is to recognise that, and be as kind to each other and the planet as we can be.

I can’t leave without one last lesson, though. There are always moments of hope. An American biologist who moved to Australia for his PhD has found a way to help one of Australia’s frogs fight chytrid. The green and golden bell frog, once common in south-eastern Australia, has suffered a severe decline as a result of chytrid. The fungus is sensitive to temperature, and these frogs suffer more severely in winter than summer. He has found that providing shelters which keep the frogs warmer over winter improves their survival and resistance to chytrid. He’s also one of a number of researchers looking at vaccines.

It took more than a decade before we were able to connect the decline of frogs in different regions with a single cause. That cause was something entirely unexpected, a species of fungus we had never seen before, belonging to a group we knew little about. We do, at least, have a running start with bird flu. We understand flu. We know it’s dangerous. We have some ability to protect domestic and captive birds with vaccines. We’re getting better at developing vaccines quickly.

Australia is now starting to see the mass die-offs of seabirds which have been seen in other parts of the world. New Zealand won’t avoid this either. But many species overseas have begun to recover following the initial die-offs. And so I keep watching and hoping.

The first is one of my favourite nat…

Read more

Antarctica’s massive Weddell seals, then, came as a shock. They can weigh more than half a tonne and haul themselves out of the water through holes in the sea ice, barely a dozen metres from Scott Base. Although I was never close enough to truly appreciate their size, adults are around 3 metres long. Their bloated, blubberous bodies seem far too large for their tiny heads and their front flippers absurdly small. Seeing them flop about on the ice it’s hard to imagine that they’re a predator. Even seeing them swimming underwater (video linked here), it’s hard to imagine them catching anything. But they are superlative swimmers, reaching depths of up to 600 metres and able to stay underwater for more than an hour.

There are six species of seal found around Antarctica, but the Weddell seal breeds further south than any of the others. It is usually found on fast ice, which is sea ice attached to the Antarctic coastline. Because of tidal movement, there are often cracks in the fast ice. Weddell seals swim long distances underwater to emerge through these cracks, allowing them to breed far from predators such as leopard seals, which will happily eat their pups if they can reach them.

Leopard seals are one of the three seal species which breed in the pack ice, which is drifting sea ice amalgamated into a large mass. Unlike Weddell seals, which breed in colonies, leopard seals are solitary. They are an important predator in the Antarctic environment, eating penguins, the pups of other seals and fish. However, they also filter krill, which are tiny, abundant, shrimp-like animals. Their teeth indicate this dichotomous diet, with the fearsome canines of an apex predator and branched molars adapted to filtering.

The crabeater seal is another species with teeth adapted to filtering krill. While the molars of a leopard seal have at most three branches, the crabeater seal’s molars have at least four, often more. Despite the name, it doesn’t eat crabs, only krill. It is the most abundant seal in and around the Antarctic. It lives and breeds among the pack ice, and pups are particularly vulnerable to attack by leopard seals. A third species of seal lives among the pack ice, known as the Ross seal. It’s smaller and more rarely seen than the other pack ice species, and there’s great uncertainty about how many there actually are.

All four of these seals are ice specialists, usually spending their entire lives in Antarctic waters. A further two species, southern elephant seals and Antarctic fur seals, are found around Antarctica but not among the pack ice. They breed in dense colonies on beaches further north, mainly on subantarctic islands such as South Georgia and Macquarie Island. Elephant seals are the largest of the Antarctic seals, with adult males weighing up to 3 tonnes. Antarctic fur seals, which are not true seals but related to sea lions, are the smallest, with males weighing around 200 kilos.

As I write this article, the Antarctic seals are coming to the end of their long, dark winter. Perhaps a few of them have strayed into areas where people are also overwintering, but winter is not a time when people are often out and about in Antarctica. So, nobody knows what is happening I find myself wondering what is happening with these seals. Are they surviving as they have for tens, if not hundreds, of thousands of years? Or is something terrible happening?

Long before the current, devastating bird flu strain emerged in 2021, seals were known to be at risk from influenza viruses. The first outbreak, in 1979, killed hundreds of seals on the US East Coast. The virus which killed them was closely related to influenza viruses from birds, that is, bird flu. There were subsequent outbreaks as well, also linked to birds, although none was as large as the 1979 outbreak. At least in part, seals are vulnerable because their natural habitats overlap with the main types of birds which carry bird flu, such as ducks and gulls.

Before I go further, I need to step back and clarify what I mean by bird flu, because there are different ways to define it. There are at least four different types of influenza or flu viruses, but only one, Influenza A, jumps from species to species, including seals and humans, and causes pandemics. The natural hosts of Influenza A are wild birds, particularly aquatic birds, including ducks, geese, gulls and other wading birds (yes, including turnstones). Strictly speaking, then, all Influenza A could be called bird flu, but this isn’t what the term usually means.

Influenza A is highly variable, with many different sub-types and variants. These vary in which animals they infect, which animals they are transmitted by and how severe they are. Influenza A viruses which are transmitted between mammals aren’t usually termed bird flu, even though they originated from birds at some point in the past. Those which are transmitted between birds but only occasionally infect mammals are generally called bird flu or avian influenza. Typically, when bird flu infects a mammal, it is not passed on to other mammals, that is, a mammal catches bird flu because they’ve had contact with an infected bird.

There are a couple of other distinctions made between Influenza A viruses which it’s useful to understand. The sub-types are categorised by variations in two different proteins on the surface of the virus. This is why we hear flu described by names such as H3N2 (one of the flu viruses currently infecting people around New Zealand) and H5N1 (the current pandemic bird flu). There’s also a distinction between forms of bird flu which cause severe disease in poultry such as chickens, termed highly pathogenic, and those which cause only mild disease in poultry. Until the bird flu detection in a skua last month, New Zealand has never had H5N1 bird flu, but we do have other sub-types and we did have an outbreak of highly pathogenic bird flu in an Otago poultry farm a couple of years ago. We know that this was unrelated to the current pandemic because it was a different sub-type.

The current bird flu pandemic can be traced back to a sub-type which was first detected in the late 1990s and has been spreading since 2003. From the start, this sub-type was known to infect humans, but only rarely. In order for a flu virus to infect a cell, proteins on the surface of the virus must bind to molecules on the surface of the cell. The specific proteins on the surface of the H5N1 virus won’t bind to the surface of cells in the human nose and throat. They will, however, bind with cells deeper into our lungs, which is why close contact with infected animals can result in human infection. While infection is rare, the resulting disease is often severe, with around half of the known human cases resulting in death.

I’ve found few references to other mammals being infected with this sub-type, apart from ferrets. However, these were in laboratories, where they are commonly used to study flu viruses. There was an outbreak of flu which killed more than 160 seals on the US East Coast in 2011, but this was caused by a different sub-type of bird flu. Apart from the occasional human infection, bird flu was living up to its name.

When the new variant of bird flu emerged in 2021, everything changed. Within a couple of years, numerous species of wild mammal were reported with the virus. Many were carnivores such as bears, bobcats, foxes and raccoons, which preyed on sick birds, or scavenged carcasses of infected birds. These reported infections didn’t necessarily indicate a change in the ability of the virus to infect mammals, it may simply have been because there were more sick and dead birds around. Pet cats and dogs became infected too, in some cases probably from being near infected birds, in others probably from pet food.

Before long, however, it became clear that this form of bird flu was being transmitted from one mammal to another. The first outbreak suspected to involve mammal transmission was seen on a mink farm in Spain. The following year, similar outbreaks were seen on a number of fur farms in Finland, affecting foxes, raccoon dogs and mink. Mammal to mammal transmission wasn’t confirmed, largely because priority was placed on preventing further spread rather than studying the outbreak, and all the animals on affected farms were killed.

By late 2022, deaths were being seen among South American sea lions on the coasts of Peru, Chile, Argentina, Uruguay and Brazil. In Peru and Chile alone, more than 15,000 sea lions died between November 2022 and June 2023. Genetic studies indicated that the bird flu infecting these sea lions had mutations which made them more able to infect, and be transmitted by, mammals. These studies also showed that other marine mammals, such as dolphins, sea otters and elephant seals, had been infected with the same mammal-adapted virus. So, too, were South American terns, a case of bird flu being transmitted from mammals to birds.

In late 2023, bird flu jumped to a species nobody expected: cattle. It took some time to notice and then identify the cause of the illness which was affecting dairy cattle in the south-western USA, because cattle aren’t considered particularly susceptible to Influenza A. While the cows recovered from their illness after a couple of weeks, they also infected other animals. Cats given raw milk died. Although a relatively small number of dairy herds were reported to be infected, fragments of the virus were detectable in a third of retail milk samples tested in April and early May 2024. Although these detections were in pasteurised milk, and the fragments were not capable of causing infection, it was a disturbing discovery. Increased testing, stricter controls on cattle movement and immunity among cattle which had recovered meant that the virus was much less prevalent by the end of 2024. However, the outbreak in US dairy cattle continues, with cases continuing to be reported throughout 2026.

Somehow, though, when bird flu jumped into dairy cattle and began to spread, it didn’t acquire an increased ability to infect humans. In fact, it seems the opposite has happened. By March 2026, there had been 41 reported human cases resulting from contact with infected dairy cows. These cases, however, mostly looked like seasonal flu, a potentially serious illness but not the frequently deadly disease typically seen with bird flu. Given the large number of cows infected and the amount of contact these cows have with people, either the form of bird flu associated with cattle seldom infects people, or infection is often so mild it isn’t noticed.

Humanity may have somehow avoided disaster, so far, but other species have not been so fortunate, which brings me back to the seals of the Antarctic. Seals around the world have been affected by the current bird flu outbreak, but in most places relatively small numbers have been reported dead. In the Northern Hemisphere, only the northern fur seal and the Caspian seal have suffered outbreaks which killed thousands of seals. The Caspian seal is already endangered, having declined from around a million at the end of the 19^th century to around 50,000 at the end of the 20^th. The loss of many thousands due to bird flu is a huge blow.

There are other endangered seals in the Northern Hemisphere, but so far they appear to have avoided major bird flu outbreaks. In the Southern Hemisphere, though, it has been much worse. By the end of 2024, tens of thousands of South American sea lions and southern elephant seals had been killed around South America, as well as thousands of South American fur seals. Then, from South America, bird flu reached the subantarctic islands and the Antarctic Peninsula. I’ve mentioned some of these outbreaks previously, but they deserve a closer look.

South Georgia is one of the largest subantarctic islands and one of the most important for both birds and marine mammals. Around 95% of Antarctic fur seals breed there, as well as half of the world’s population of southern elephant seals. Hundreds of each species were found dead, but of more concern was the number missing. The three main breeding colonies of elephant seal had nearly 50% fewer females in 2024, following the arrival of bird flu, in comparison to 2022.

Losses of elephant seals haven’t been confined to South Georgia. Even on the extraordinarily remote Kerguelen and Crozet Islands, in the southern Indian Ocean, there have been dozens of reported deaths. Last summer, scientists visiting Heard and McDonald Islands, which are 4000 kilometres south-west of Australia, found thousands of dead baby elephant seals. They estimated that around three quarters of the pups born on the islands that summer had died from bird flu.

Elephant seals were not considered endangered before the outbreaks caused by bird flu, but now they are. Antarctic fur seals are also now considered endangered, although that is largely due to the impacts of climate change on krill, their main food. Still, losing hundreds of animals, perhaps more, to bird flu can’t be helping.

So far, reports of losses among the ice-specialist Antarctic seals are limited. Hundreds of crabeater seals have been reported dead, which doesn’t sound like much since they have a total population in the millions. I have found no reports of infected Weddell, leopard or Ross seals. But the Antarctic coastline and pack ice cover vast areas, and there are few people to observe if there are dead seals. It may be some years before we can be sure whether these species are being affected by bird flu.

There are a couple of other worrying possibilities as well. Both Australia and New Zealand have endangered species of sea lion, with only a few thousand of each remaining. Australia’s breed mainly on the coast of South Australia and southern Western Australia, but New Zealand’s mainly breed on subantarctic islands, particularly the Auckland Islands. These islands are uninhabited and largely inaccessible, and it could take some time for us to notice if the sea lions there were affected.

There are also other mammals around the Antarctic and Subantarctic which are potentially vulnerable to bird flu, and they are even more difficult for us to monitor. In the Northern Hemisphere, there have been a few records of bird flu fatalities in dolphins and porpoises. So far, there are no records in whales, but killer whales, in particular, may prey on infected birds and seals around Antarctica and subantarctic islands. While whales, dolphins and porpoises aren’t usually considered susceptible to flu viruses in the way that seals are, the fact that there have been reported fatalities shows that this virus is different.

With bird flu now moving around the Southern Ocean and Antarctica, carried by birds such as the skua, it’s only a matter of time before more species of marine mammal come into contact with the virus. It’s quite possible that some will suffer losses large enough to threaten the survival of the species. But because these habitats are so difficult for us to access, we may remain in the dark for some time about bird flu’s real impact.

So, to launch the tītī campaign, I’ve decided to write about the remarkable travels of the tītī and some of our other seabirds. Usually, these journeys are something to celebrate, but this year they are also cause for concern. We’ve already had a couple of bird flu detections in New Zealand, but when our wandering seabirds come home to roost in the spring, we can expect to see many more cases. That’s if they return at all.

Many of you will have heard about the extraordinary flights made by the 2015 Bird of the Year, the kuaka or bar-tailed godwit. The birds which arrive on our shores in the spring of each year have made a non-stop 8-9 day flight from western Alaska. The spend the spring and summer feeding in harbours and estuaries, then those which are ready to breed depart for Alaska in March. One way, it’s over 11,000 kilometres, and the first time the kuaka makes this journey, it’s only four months old.

The journeys made by seabirds such as the tītī are different. When tītī depart from New Zealand in the autumn, they are not heading for land, but the vast expanse of the Pacific Ocean. They spend most of their time in flight, and rest only on the water. The next time they touch the ground, it will be when they return in the spring. Some will have been feeding off the coast of California and Mexico, where an upwelling of cool water carries nutrients from the sea floor and supports abundant squid (their main food) and other marine life. Others will have been feeding off the coast of Peru and Chile, where a similar upwelling creates another rich bounty of food for seabirds. While tītī don’t travel quite as far as the kuaka, they still make a round trip of more than 20,000 kilometres.

The name tītī refers to more than one type of seabird. The best-known is probably the species known in English as the muttonbird or sooty shearwater, a large, dark seabird which is still found in the millions on some of our southern offshore islands. Another species of tītī is also known as the grey-faced petrel, which mainly breeds on northern offshore islands, but does still breed on the mainland in a few areas. The third common species to bear the name tītī is the tītī wainui or fairy prion. In the north, it breeds only on the Tawhiti Rahi or Poor Knights Islands, but breeds on many islands and rock stacks from Marlborough southwards, as well as Rēkohu (the Chatham Islands) and the Subantarctic Islands.

Cook’s petrel is one of two much rarer tītī species. It breeds only on Aotea (Great Barrier Island) and Te-Hauturu-a-Toi (Hauturu or Little Barrier Island), to the north-east of Auckland, and Whenua Hou, near Raikura (Stewart Island). The birds which breed north of Auckland are different from the birds which breed on Whenua Hou, and they are considered to be two separate subspecies.

The other rare tītī is the Kaikōura tītī, or Hutton’s shearwater, which breeds high in the Kaikōura Ranges. It’s an extraordinary bird, with adults foraging up to 250 kilometres offshore to feed their chicks which are in burrows around 1200 metres above sea level. It’s also in trouble, classed as Nationally Vulnerable and with only two colonies remaining. A small backup colony has been established on the Kaikōura Peninsula, safely behind a predator-proof fence. Establishing seabirds in new locations is extremely difficult and from the many hundreds of birds moved to the site, there’s now an average of 30 eggs laid and 22 chicks fledged each year. It doesn’t sound like much, but it’s huge progress1.

The birds which fall under the name tītī all belong to a family of birds known in English as petrels, shearwaters, prions or fulmars . They are cousins to albatrosses, mollymawks and storm petrels, but are not closely related to gulls, terns and skuas. Cook’s petrel is one of the gadfly petrels, so called because their flight is rapid, weaving and erratic, much like that of gadflies, which are large, biting flies. It’s a close relative of one of my favourite seabirds, although not a Bird of the Year candidate this year, the Chatham Island tāiko, which was thought to be extinct for over a century before its rediscovery in 1978.

In the past, all of our tītī species, as well as the other petrels and related species, would have bred in massive colonies on New Zealand’s two main islands. These birds, however, all nest on the ground. They lay a single egg, large in relation to their body size, usually in a burrow. It isn’t only the eggs and chicks which are vulnerable on the ground. Apart from the giant petrel, which can strut around and squabble over carrion as well as any seagull or skua, petrels and their relatives are largely unable to walk. On land, they shuffle and stumble, and sometimes assist themselves with their wings, as you can see in this entertaining encounter between a kākākpō on her nest and a kōrure which blundered into her burrow (click the link to see the short video).

Kākāpō vs. petrel (Department of Conservation YouTube channel)

It doesn’t take much to imagine what happened when introduced mammal predators arrived. A bird which comes off second-best in a fight with a kākāpō doesn’t stand a chance against a stoat or a cat. And eggs and chicks lying on the ground were defenceless against rats, pigs and all manner of other mammals. Almost all of our mainland tītī and other petrel colonies have been wiped out. Even those not classed as threatened now confine their breeding to a tiny remnant of their former range. Some ended up in desperate trouble, and we came close to losing Cook’s petrel forever.

Although it clung to survival on three islands, none of these islands was free of introduced predators. On Aotea, it had to contend with two species of rat, cats, dogs and feral pigs. On Hauturu there were feral cats and Pacific rats. On Whenua Hou, there were possums and Pacific rats as well as weka, a feisty, flightless bird native to New Zealand but not Whenua Hou. Although weka are a much-loved native bird, they can also be predators. On islands which are crucial for the survival of endangered species and where weka aren’t native, they can be a problem.

By the 1970s, the southern subspecies of Cook’s petrel was close to extinction. On Whenua Hou, where there had been around 20,000 burrows in the 1930s, there were perhaps as few as 100 breeding pairs remaining. There were more birds of the northern subspecies, with tens of thousands of birds breeding on Hauturu, although only a dozen burrows had ever been found on Aotea, despite extensive searching. However, even the birds on Hauturu were far from secure. Hundreds of birds killed by cats were found during studies on Cook’s petrel in the 1970s and taking into account the areas not searched, it’s likely that many thousands of adult birds were being killed every year. Fewer than half of the eggs laid survived to the point where the chicks fledged in any of the colonies. For bird which lay clutches of several eggs, that might not be a disaster, but petrels and their relatives lay a single egg each year.

Cook’s petrels go to extraordinary lengths to care for their single egg. For around 50 days, they take turns incubating it. Once the chick hatches, one or other parent will initially stay to guard it, while the other forages. Soon, however, the chick is left alone in its burrow while the parents gather food. Their foraging trips last 2-12 days, covering hundreds of kilometres, and they are in flight for around three quarters of that time.

These extraordinary efforts, however, often came to nothing in the presence of mammal predators and weka. And Cook’s petrels were far from the only species in serious trouble on islands such as Hauturu and Whenua Hou2. So, from the 1970s on, serious efforts began to control the predators. Cats were eradicated from Hauturu in the late 1970s and possums eradicated from Whenua Hou in the 1980s. Weka were also recognised as a threat on Whenua Hou, and removed in the early 1980s, a decision which almost certainly saved the Whenua Hou birds from extinction.

But the birds on these islands, including Cook’s petrel, were not out of trouble. On Whenua Hou, the number of breeding birds increased steadily following the removal of weka, but breeding success fluctuated considerably from year to year. In those years with a strong El Niño, there were much greater losses, while rats continued to kill eggs and chicks. On Hauturu, Cook’s petrel first showed signs of recovery following cat eradication, but within a couple of years their situation had worsened. Prior to the eradication of cats, 25-40% of chicks survived to leave the nest. Once the cats were gone, the rats increased and began to kill more eggs and chicks. At best around 20% of Cook’s petrel chicks on Hauturu survived following cat eradication.

Rats were eradicated from Whenua Hou in 1998 and Hauturu in 2004. A survey in 2007 found that there were around 5000 pairs of Cook’s petrel on Whenua Hou. It may take some time for the birds to reach their former numbers on the island, but they are certainly recovering.

The picture is less clear for Hauturu, simply because Cook’s petrel is a difficult bird to monitor. Breeding success has improved, but I haven’t found precise numbers. A study published in 2007 estimated that there were more than 280,000 pairs on Hauturu. This number is sometimes compared with the estimated numbers in the early 1980s, around 50,000, to indicate that the species is recovering. However, it’s not that simple.

A close look at the 2007 paper shows that most of the field work was done from November 2004 to March 2005. This work began less than 6 months after the rat eradication took place. That’s far too soon for a slow-breeding bird which was losing most of its nests to rats to have recovered. There are two possible explanations for the numbers. The first is that despite the losses attributed to rats, Cook’s petrel recovered strongly following the cat eradication. It’s certainly plausible that the losses to cats exceeded the increased losses to rats, especially as cats were killing adult birds. However, the authors of the 2007 paper suggest another reason. It’s difficult to count a bird which, during the breeding season, spends its days at sea and returns to land only at night, to nests which are underground in steep areas of dense forest, then, once breeding has finished, disappears to the far corners of the Pacific Ocean. The authors state that the difference in bird numbers is likely to be because they used a better method for counting them.

With two of the three populations of Cook’s petrel now on islands free from introduced predators, the species is no longer in serious trouble, although the colony on Aotea remains in a precarious situation. But bird flu brings a new threat. So far, there have been only two New Zealand detections. However, many of the seabirds which breed around New Zealand are currently far away from here. So, too, are shorebirds such as the kuaka which breed overseas but spend their summers feeding here. In a month or so, they will begin returning. I don’t know for certain, but I suspect that it will be spring and summer when bird flu becomes more apparent here. That’s been the pattern overseas.

As our wanderers return and congregate in the few locations which are safe for them, they are extraordinarily vulnerable. Whenua Hou is home not only to the southern form of Cook’s petrel and a large proportion of our kākāpō, it’s also the only place where the Whenua Hou diving petrel breeds, and a backup site for Subantarctic birds such as the Snares Island snipe and Campbell Island teal. The picture is similar on Hauturu and other offshore islands.

Conservationists have long understood the vulnerability of these islands to the arrival of a single pregnant rat or stoat, or even a determined wildlife smuggler. We’ve learned to manage these risks and brought a number of species, including Cook’s petrel, back from the brink. But whether we can do anything about such an intangible, elusive threat as a virus carried by birds which fly thousands of kilometres is another matter.

I know that the Bird of the Year competition is supposed to be fun, but I’ve decided that it’s also a great opportunity to highlight the threat of bird flu to our sea and shore birds. I’ll be sharing images and information here and on social media over the next few weeks and will share the voting link when the polls open on the 4^th of September.

By the way, there are still a few birds who don’t have campaign managers, so if you’d like to help out one of our under-appreciated species, here is the link: Apply to be a Bird of the Year 2026 campaign manager | Forest and Bird.

Every bird on the list of candidates gets a campaign manager. This year, they have also been assigned to partie…

Read more

The first obstacle is crossing the stream at the end of the track down to the beach. I walk across a low bridge, made from a metal mesh. It’s adequate for human feet, but the holes are too large to allow a dog to walk across. Donna jumps in the stream, but the water has cut a deep, steep-sided channel and she’s not as agile as she used to be. She makes a couple of unsuccessful attempts to jump upon the other side before I can grab the back of her harness to help her out.

We then have to scramble over football-sized stones at the outlet of the stream, before we reach an area where the stones are smaller and easier to walk on, although it’s still hard work. Donna wants to run around sniffing everything, but I can see how much harder it is for her this year. It’s a tricky balance, because she’s overjoyed to be on the beach, but she doesn’t always realise what she can no longer do. If I let her, she’ll exhaust herself or give herself hypothermia.

Donna and I first visited this beach in autumn last year, on our previous trip to Taranaki. It’s just outside the town of Hāwera, facing to the south-west, a sliver of black sand and mostly grey stones between the relentless sea and lethally unstable cliffs. Signs warn against both swimming and standing too close to the cliffs. I was struck, then, that this was a place we could visit, but not occupy. There was nothing humans could do to tame this beach and make it ours. It would always shift and fluctuate, with each wave and tide, with the weather and seasons, over years, centuries and millennia. Having such a rare and precious place to ourselves was both uplifting and humbling.

This year, it’s a different experience. We don’t have the beach to ourselves, the sky is moody and grey, and I’m aware that I need to stop Donna from pushing her body beyond its limit. But this beach is still stunning. I head south, where there’s more sand and it’s easier to walk. Donna trots past me, following her nose, her stride easier on the sand.

I’m frustrated that I can’t read the stones here in the same way I can read the plants when I walk in the forest. I can see the action of water, how it has shaped this forbidding landscape by carving through the soft stone of the cliffs to create ravines, or tumbled the stones over one another until they are worn smooth. But I don’t understand the stones themselves.

I originally intended to write about the geology of this area, to explore the interplay between the stone laid down by ancient oceans and the stone deposited by the region’s explosive volcanoes. I wanted to tell you about the fossils discovered here, too, because there are many more than the shells I’ve seen. But I’m also aware that I’m tired, there’s nowhere comfortable for me to work where I’m staying, and I have a long drive home tomorrow.

So I’m not going to write that article today. For now, I will share a few of my pictures of Waihi Beach. And I will recognise that I need to do for myself what I’m trying to do for Donna.

Nobody’s told the terns, though. Just off the beach there’s a tiny flock, four birds soaring and circling above the water. Sometimes, one will suddenly plummet head first into the water, emerging a few seconds later with a fish, or without one, if it’s unlucky. The water might be polluted and the surrounding land altered beyond recognition, but I’m delighted that there are still enough fish left in the harbour to attract these elegant birds.

Terns have been on my mind lately, because they’ve been particularly hard hit by bird flu. The terns I was watching last Christmas were white-fronted terns, or tara, which are mainly found around New Zealand but are also seen around Tasmania and Australia’s east coast, so until very recently they wouldn’t have come into contact with bird flu. But they are a close relative of one of the most affected species in the Northern Hemisphere, the common tern. This suggested to me that the white-fronted terns may also be at risk, but this was just my assumption. I decided to see whether there had been any work which would clarify what was likely to happen in New Zealand, whether my assumption was likely to be correct and whether I could apply any of my own risk assessment experience to the issue.

Predicting how a species will behave when it reaches a new area has been part of my work, in one way or the other, for nearly 30 years now. Actually, it might be more accurate to say I’ve been attempting to predict how species will behave, because such predictions are frustratingly inexact. I have learned that it’s usually possible to determine that some scenarios are unlikely. But among the realistic possibilities, it can be difficult to narrow down which are likely.

Many diseases of both animals and plants are shared among related species but rarely, if ever, infect unrelated species. For example, foot and mouth disease, the livestock disease which New Zealand hopes will never reach here, almost exclusively infects cloven-hooved animals like cattle, sheep, goats, deer and pigs2. Another example is myrtle rust, a fungus which infects only plants belonging to the myrtle family. However, within the myrtle family, different strains of the fungus affect different plants to different degrees. Prior to its arrival in New Zealand, we couldn’t say exactly which of our native plants in the myrtle family would be infected and which would suffer the most damage. However, we could be pretty confident that it wasn’t going to infect any plants outside the myrtle family.

When I started looking at bird flu, I wondered whether there were any patterns of this kind in the birds which were being infected. I particularly wanted to see whether the birds which were being killed in large numbers were related to one another. This is relatively simple, because the classifications which scientists use for living things reflect these relationships. Species are grouped together if they share common ancestors.

I started with the highest level grouping of birds, known as the order. There are around 40 orders of birds, and around half of all bird species, well over 6000, belong to a single order commonly known as perching birds. This order includes most of the familiar small birds such as sparrows, blackbirds, robins and swallows, as well as a few larger birds such as crows and magpies. However, in New Zealand we have only 22 native perching birds which still survive, including our robins and tomtits, tūī, riroriro (grey warbler), tīeke (saddleback) and kōkako.

Before I continue: I encountered something of a problem in trying to make this article clear. I realise that I need to pause and explain my approach, so please bear with me.

Most orders of bird, apart from the perching birds, don’t have a clear common name, because these classifications aren’t widely used by non-scientists. The scientific terms, however, can be a real mouthful. Phoenicopteriformes doesn’t roll easily off the tongue, for example. The usual way to refer to the orders is by the common names of some of the birds in that order. This works perfectly for some orders, such as the flamingos, which are the only bird in the order Phoenicopteriformes. But other orders contain a number of well-known bird groups.

For clarity, when I first mention an order, I will name some of the birds in that order, but I will write one of the names in italics. When I next mention the order, I will use only the italicised name. So, when I later refer to the order which contains pigeons and doves, I will refer to it as ‘pigeons’.

Aside from the perching birds, no other order of birds contains more than a few hundred species. Among the orders with a few hundred birds are pigeons; parrots and parakeets; and eagles, hawks and vultures (but not falcons, which belong to another order). Chickens belong to another moderately large order, along with quail, pheasants, turkeys and peacocks. The birds we usually consider seabirds belong to several different orders. Penguins are in an order of their own, another order contains albatrosses and petrels, another gannets and cormorants, and then there’s a single order which includes the birds we commonly call shorebirds, such as plovers, stilts, godwits, knots and snipe, as well as gulls, terns and skuas. Ducks, teals, geese and swans are another order, but these are separate from grebes such as the pūteketeke (the bird made famous during the Bird of the Year competition, thanks to some election interference from John Oliver). Pelicans, herons and ibises are another order, which is separate from flamingos and also separate from cranes and rails (such as the weka).

These orders become important when we start to look at which birds are infected with bird flu. As I’ve mentioned in previous articles, mild forms of the virus are found in birds around the world, including New Zealand. Some are restricted in the species of bird they infect, such as two which are known only from shorebirds. But the pandemic bird flu we are worrying about at the moment is a descendant of a severe form which arose in the early 2000s and has been spreading and evolving ever since. It also belongs to a subgroup of bird flu viruses, first found in domestic geese in 1996, with a known tendency to jump from one species to another. Bird flu viruses in this subgroup didn’t move just between related species, such as geese and ducks. They also moved between species in different orders, such as ducks and chickens.

Because there are different forms of bird flu, estimates of how many bird species can be infected vary. One recent list of birds known to be infected with bird flu names under 400 species, from 26 different orders. This list uses records from 1973-2023, so some records pre-date the bird flu pandemic. It also uses only one source of data and is missing some records, such as the African penguin. However, it was still useful as it came with a spreadsheet of all the data, so I sorted through it until I found only the type associated with the pandemic bird flu. There were around 250 different bird species listed where there was at least one record of the pandemic bird flu type. The two orders which are most important for bird flu, the ducks and the shorebirds, comprised around 40% of the species listed, and the perching birds and eagles each comprised about 10% of the species. There were 20 other orders where at least one species was recorded with bird flu.

The perching birds and eagles on this list are interesting for two different reasons. Although 32 species of perching bird have been recorded with bird flu, this is a tiny proportion of the whole order, less than 1%. The order includes species such as the starling and sparrow, which are found in large numbers in cities, suburbs and agricultural landscapes. One of the first serious bird flu outbreaks in wild birds, in Hong Kong in 2002, included one sparrow. But it’s still not clear how important perching birds are in spreading bird flu, and there don’t appear to be records of any species suffering severe impacts.

In comparison to the perching birds, eagles are over-represented as bird flu hosts, for one obvious reason. Eagles and their relatives are mainly birds of prey, with a few species which are mostly scavengers. If they eat an infected bird, they can be infected and killed by the virus. As the pandemic has spread, more and more eagle species have been affected, and there have been significant numbers killed. There have also been a number of deaths among other predatory birds such as falcons and owls.

The birds of prey are an important indicator of a pattern with bird flu: relatedness doesn’t tell us which species will be infected or killed. This pattern becomes even more apparent when we look at the outbreaks where large numbers of wild birds have been killed. In one of the first outbreaks, in Hong Kong in 2002, the birds which died in the greatest numbers were ducks and geese, which belong to the same order, and flamingos, which have their own order. Another early outbreak, at Qinghai Lake in China in 2005, mainly affected four species: one goose, one cormorant and two gulls. These birds belong to three different orders. The 2017 and 2018 outbreaks in southern Africa mainly killed terns, but also killed more than 1000 gannets and hundreds of African penguins; again three different orders were affected.

The new strain of bird flu which emerged in 2021 caused larger and more frequent outbreaks in wild birds. Sometimes, it affected the same kinds of birds as previous outbreaks, particularly ducks, shorebirds (especially terns) and gannets. Sometimes, though, it killed large numbers of other birds, such as cranes, pelicans and sooty shearwaters. These belong to three different orders, and while there were occasional cases of bird flu reported from birds in these orders in the past, they had not previously suffered severe outbreaks.

The pattern to these outbreaks, if there is one, doesn’t have much to do with relatedness between different bird species. What matters is the opportunity for transmission. Birds of prey become infected when they feed on infected birds. Some outbreaks are associated with areas where large numbers of migratory birds are found together. Other outbreaks are associated with birds which breed in dense colonies, creating ideal conditions for the spread of bird flu.

What’s less clear is whether all these different bird species are able to spread bird flu, as opposed to catching it but not passing it on. Nor is it clear why some bird species seem to escape the outbreaks. In the South American outbreaks of 2022 and 2023, some abundant seabirds had only a few deaths recorded due to bird flu. Were these species not particularly susceptible, and the few dead birds already weakened by something else? Did few birds of those species come into contact with the virus? I’m still wading through the numerous papers on the subject, trying to see whether anyone’s worked that out.

So what does this mean for our ability to predict what might happen in Australia and New Zealand? It’s not good news. A 2024 risk assessment concluded that many species have overlapping habitats, which will allow migratory birds carrying bird flu to pass on the virus to birds which don’t migrate, including those which live mainly on land, rather than on the coast. But there’s no clear indication of which species will be affected. This is not an orderly virus, behaving in a predictable way.

But there’s something the risk assessment doesn’t mention and which I haven’t seen discussed elsewhere. One factor may make some of New Zealand’s rarest birds even more vulnerable. Many are concentrated on small islands which also have many seabirds. This may increase the chances of bird flu being spread to our rare birds.

One potentially vulnerable bird is the kākāpō. Almost all live on three predator-free islands, and on one of these, Whenua Hou, they come into contact with seabirds which may carry bird flu. If you watched the live video of a kākāpō on her nest last summer, you may remember when a petrel entered the burrow and was chased off by the kākāpō. While there are very few records of parrots infected with bird flu, it’s difficult to predict what will happen when parrots come into close contact with seabirds. Many of the kākāpō on Whenua Hou have been vaccinated against bird flu for this reason.

Some of our other rare birds have been vaccinated as well, but this is really only worthwhile where birds can be given two doses of the vaccine. In reality, this means that it’s mostly birds which are being bred in captivity or are under intensive management, such as kakī (black stilt) and tuturuatu (shore plover). Other birds will have to fend for themselves.

Some of our rare birds are extremely vulnerable. There are fewer than 100 tara iti (fairy terns), fewer than 200 tchaik (Chatham Island tāiko) and around 200 Whenua Hou diving petrels. Two of our three surviving snipe species have fewer than 2000 birds and there are no more than 3000 hoiho (yellow eyed penguins), with numbers already falling dramatically in the mainland population. All of these birds belong to orders where some species have experienced large outbreaks and live in habitats where they may encounter infected birds from other species. Maybe they will be lucky and maybe they won’t. I’m not sure that we can do more than hope.

While I’ve been looking at birds, I’m also aware of an elephant in the room, or rather an elephant seal. Bird flu is not a disease which is confined to birds. As I mentioned in last week’s article, it has spread to marine mammals, including elephant seals. These are far from the only mammals affected. Next week I will be away in Taranaki, so I’ll write an article related to my trip, but I will return to bird flu and its spread to mammals, including humans, in a couple of weeks.