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the ouline of a weta in red but no weta is there it is just empty
Insects are among the most threatened native species (Image: Tina Tiller)

ScienceApril 10, 2023

Why the latest report on extinction in New Zealand should make all of us worried

the ouline of a weta in red but no weta is there it is just empty
Insects are among the most threatened native species (Image: Tina Tiller)

A new indicator highlights how many of Aotearoa’s native species are treading the precarious path towards extinction. It’s all the more reason to value and protect the interconnected relationships within ecosystems.

The idea of extinction is a scary one – particularly in New Zealand, where high-profile conservation efforts place the demise of beloved species like tuatara and kiwi in constant view. There’s a myth-making in extinction too, like the near loss of takahe, rescued through a chance encounter in the Murchison Mountains, the devoted egg laying of black robin Old Blue, the song of a hoped-for South Island kōkako

A Statistics New Zealand indicator released last week might evoke some of that extinction pathos. The indicator, based on information gathered by the Department of Conservation, shows that more than 75% of indigenous reptile, bird, bat, and freshwater fish species in New Zealand are at risk of extinction. The decline of each of these species is worrying, notjust for the loss of biodiversity alone, but because this jeopardises the thousands of ecological interactions species are involved in.

A majority of indigenous species are categorised as “threatened” and “at risk of being threatened”, the two highest risk categories in the system. The threat classification is an ongoing project, and is intended to capture the current risk for species. This latest dataset highlights in particular risks to 47 marine and freshwater taonga species that have an important role for ecosystem resilience. Assessing taonga species is crucial, as the wellbeing of these species informs mātauranga Māori and tikanga – and provides kai. 

two very cool and beautiful kea on a roof with a shadowy forest behind them
Kea, the world’s only alpine parrot, are endangered (Image: Finnbar Lee)

“This data shows just how widespread a threat extinction is – when you look across species groups, you see that this is a systemic problem,” says Michele Lloyd, a senior manager for environmental and agricultural statistics (although she also notes that Stats NZ’s role is to analyse and present data, rather than act on it). The extinction threat indicator encompasses the population of the species and its distribution across the country, as well as threats like ecosystem decline, climate change, predators and pest species, and overall population trends.

Scientist Finnbar Lee, a freshwater ecologist at the Cawthron Institute, has studied how species decline threatens entire ecosystems. New Zealand seabirds, for example, tend to nest on the ground or on burrows. Those seabirds eat fish, then return to land to feed their young – and also poo on the ground, moving nutrients from the sea to the land. “We know from the fossil record that we had huge numbers of seabird colonies,” Lee says. That’s no longer the case – those nests on the ground are a perfect target for predators like rats, stoats and possums. While seabird species have survived thanks to offshore islands and trapping measures, the declining numbers have drastically reduced this vital nutrient cycling. 

Lee particularly focuses on freshwater fish, including the five species whose larva are known as whitebait. Īnanga, the most common whitebait species, “grows fast and reproduces quickly”, he says. It’s also categorised as being at risk of becoming extinct. While whitebait are delicious kai for humans, declining numbers, caused by overfishing and damaged habitats, reverberate through the ecosystem too. “Those fish are food for tuna, shag, herons – if [the fish] aren’t there, all those other species will be impacted, but it’s hard to quantify exactly how.”

light reflecting off a tank and small fish lurking at the bottom
Īnganga, a whitebait species, are declining. (Image: Finnbar Lee)

The risk of extinction is an easy one to understand: one day a species is there, and the next, it is not – and the microbes that live inside it, or the plants that rely on it for pollination and seed dispersal, and the species that eat it have lost a node in their ecological web. New Zealand’s Threat Classification System, which carries out regular surveys of different species, is useful for understanding which species are at risk of extinction – but learning to see a damaged ecosystem has to encompass all of the ecological relationships species are entangled in, not just whether or not they continue to exist. 

Lee says that it’s not always clear why a species is declining, but there are a few obvious causes. The four main ones are loss of habitat, meaning species have nowhere appropriate to live; loss of connectivity, so species have no way to get between locations like dams in the rivers traversed by migrating fish; climate change, making existing habits hard to live in; and predation, which is particularly prominent in New Zealand due to the many voracious introduced mammals, which indigenous species haven’t evolved to avoid. 

While some species, like birds, can move to areas with a better climate or less predation, that isn’t an option for others. “Slow-growing trees can’t move around the land following the climate,” Lee points out. 

The Stats NZ indicator examines extinction threat at a national level. Before something goes entirely extinct, however, its numbers decline or disappear in local areas. A fern can no longer grow in a gully where it once flourished when changing weather systems make it too dry for it to live there. A fish disappears from a stream because its offspring can’t migrate through a drain under a road to return to mating grounds. Even if that species still exists elsewhere, that loss impacts ecosystems at the local scale.

misty mountains and a stream with slippery rocks and steep bushy hills rising into the sky
Mt Tarawera stream, whose cold water might be an important refuge for water species as the climate warms (Image: Finnbar Lee)

While species can successfully repopulate areas where they used to live, restoration efforts often focus on large animal species, not the lichens, insects and microbes that might dwell with them. If a tree species has disappeared from an area, then the insects that nestled in its bark and the moss that grew on its branches might be gone forever, even if the tree is introduced. “Those lichens might be able to come back if they could grow on another tree nearby and their spores are close enough to be dispersed,” Lee says.

There’s definitely hope, especially if reintroductions are done in tandem with habitat restoration and trapping to prevent predation. “You can start getting an ecosystem back to what it was previously, and with that comes other benefits, like pollination.” Increasing kererū populations, for instance, has also been good news for karaka trees, whose large berries and seeds can only be dispersed by big birds like the native pigeon. 

There can be a temptation, when confronted with the cold hard data of extinction, to fall simply into hopelessness and despair, yet more evidence that humans and the natural world are inimical. But Lee says that’s all the more reason to care, because humans are part of ecosystems, not separate from them. The food we eat is grown in soil enriched by other species, and it’s pollinated by them too. The carbon we produce is absorbed by trees and the ocean. The waste we throw away is decomposed by microbes and invertebrates, ready to begin the cycle all over again. 

Beyond the services that ecosystems offer humans – a transactional way to see the species we depend on – the risk of extinction is worrying if you think that other living beings have an inherent right to exist, Lee says. “We know what the problems are, and we should do our bit to fix them. If we let species decline, the world will be a less vibrant and rich place.”

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