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Threatened species

by  Gerard Hutching and Carl Walrond

New Zealand’s lizard-like tuatara once lived throughout New Zealand, but became extinct on the mainland after humans arrived. The species survived on some nearshore islands, but people, dogs, cats and rats soon took their toll. Fortunately, people can also do good: raising tuatara in captivity, and removing predators from the islands. The fate of many threatened species lies in our hands.


What is a threatened species?

Low populations

Threatened species are native plants and animals that are under threat of extinction. Their numbers in the wild have dropped to low levels. There may not be enough individuals of a species to breed and naturally increase the population to a level that is self-sustaining, or they may have such a limited range that a natural disaster could wipe out them out. Without human intervention it is likely such species will become extinct.

Causes

While a low rate of extinctions is natural, the current rate of human-induced extinctions is much higher.

The main human activities to blame are:

  • over-harvesting species
  • destroying habitats
  • introducing weeds and pests.

Vulnerable species

New Zealand’s plants and animals evolved in isolation for millions of years. Many are found nowhere else, and have unique features. Free of predatory land mammals, a number of birds became flightless and ground-dwelling.

When humans arrived they made major changes to the environment of native species – changes that continue today. Many native species had no evolved defences against the predators introduced by humans (for example rats, which ate the eggs and chicks of flightless birds).

Saving birds

Birds are the most significant vertebrate life in New Zealand. It was only natural that in the early days of conservation, they were the focus – many species had become extinct and others were declining. In the 1970s, saving the Chatham Island robin, reduced to seven individual birds (and just two females), paved the way for rescuing other threatened birds.

…and other animals

Since the late 1990s there has been a move to save species that are less visible, such as freshwater fish. The remaining habitats of many animals (for example, the Canterbury mudfish) are on private land, and it is only through the goodwill of landowners that they are not destroyed.

There has also been a shift from saving single species to restoring entire habitats. Poisoning introduced predators such as possums and rats on islands gives protection to many life forms. Birds, plants and insects all benefit when predators and browsers are removed.

Saving plants

Some of New Zealand’s threatened native plants may always have been quite rare, or their habitats may not have been large. Many grow in open sites such as bush fringes, coastal cliffs, terraces, dunelands and wetlands. Often these habitats are on private land, much of which has been developed into farmland.

The wild one

Red-flowering kākā beak (Clianthus puniceus) is cultivated in many gardens, but is nearly extinct in the wild. A 2006 survey found just 154 wild plants growing in fewer than 20 sites.

Saving seeds and propagating

Saving threatened plant species has largely been the domain of enthusiastic botanists and plant breeders who have collected seeds and cuttings, and propagated plants in nurseries. In the 1990s, regional councils started collecting seed from local plants, rearing seedlings and encouraging people to grow them in their gardens.

‘Zombie species’

While some species may be saved in the short term, they risk becoming ‘zombie species’ – plants that are extinct in their natural habitats, and live on only in gardens where they are cultivated. It is important that viable wild populations are also saved.

Plants historically a lower priority

Threatened plants have not been top of the conservation list, and since 1840, six species have become extinct. It can be hard to attract funding for a low-growing herb, but easy for more attractive plants – Project Crimson raises private funding to help protect the large, scarlet-flowering rātā and pōhutukawa trees.

In 2003 the New Zealand Plant Conservation Network was set up to stop further loss of native plants.


Which species are threatened?

Rating systems

The International Union for the Conservation of Nature has a ranking system for threatened species. Many countries also have their own systems.

New Zealand’s system

In 2002, conservationists created a New Zealand-specific system for classifying threatened species. It can be used for all New Zealand life forms, including marine species. The ranking depends on conservation status, threats to survival, whether they are endemic, vulnerability and cultural importance. There are eight rankings, from the most to the least threatened:

  • nationally critical
  • nationally endangered
  • nationally vulnerable
  • serious decline
  • gradual decline
  • sparse
  • range restricted
  • data deficient.

High rates

New Zealand has one of the highest rates of threatened native species in the world. For example, 34% of plants are considered to be at some level of risk, and 37% of the 215 native birds are listed as threatened by the International Union for the Conservation of Nature.

Numbers of threatened species

A 2002 survey classified a total of 2,372 species (including 312 subspecies) as threatened. This included bats, birds, bryophytes (mosses, liverworts and hornworts), freshwater fish and invertebrates, frogs, fungi, macro algae, marine fish, marine mammals, reptiles, land invertebrates and vascular plants.

Kea culled

Between 1860 and 1970, at least 150,000 kea (alpine parrots) were killed. This figure is based on a bounty offered to kill the birds, which were believed to attack sheep, causing blood poisoning, and drive flocks over cliffs. There may be as few as 1,000–5,000 kea left.

By 2007 the total number of threatened species had increased to 2,788. This was mostly due to better information on many that were once classed as ‘data deficient’.

Visible species

Scientists know a lot about the more charismatic species – those that are large, attractive, odd, or rare. Little is known about less visible species. Only bats, birds, and frogs have been described and understood well enough to be assigned a status with some confidence.

Less understood species

Many species fall into the ‘data deficient’ category. Scientists may suspect they are in danger, but have little information – 1,455 species and subspecies of fungi belong in this group.

Although 30,000 native New Zealand species have so far been identified and named, there are possibly a further 50,000 that are as yet unidentified. Most of these are insects, worms, fungi, or micro-organisms such as algae. Some of these may be threatened, and some may have already been lost without ever being scientifically described.

Setting priorities

It is difficult for the Department of Conservation to decide where to spend its limited funds. Many questions arise. Which species are actually at risk of extinction? Can the risk be measured? Even if enough information exists to answer these questions, trade-offs have to be made.

Private funding

In 1990 the Department of Conservation and other groups set up the Threatened Species Trust Programme to attract commercial sponsorship. This has generated more funds for saving threatened species. For example, between 1990 and 2004 the aluminium smelting company Comalco donated $1.6 million towards saving the kākāpō. The Bank of New Zealand has been a multi-million-dollar sponsor of saving the kiwi since 1991.


Land management and conservation

Conservation lands

The most intensive efforts to save species at risk focus on small areas within the conservation estate, which comprises about 30% of New Zealand. Many such areas are nearshore and offshore islands. Because these have been protected from habitat destruction, predators or weeds, remnant populations of threatened species are still found.

Recovery plans

Once a species is recognised as threatened, the next step is not always simple – for example, a bird’s ecology and reproduction may be poorly understood. It often takes years to develop effective recovery plans.

The Department of Conservation has recovery plans for many individual species on the brink of extinction. Methods developed in New Zealand during the 1980s and 1990s are now being used worldwide. Common solutions are:

  • island sanctuaries
  • controlling or eradicating pests
  • captive breeding programmes.

Island sanctuaries

Early conservationists, such as Richard Henry of Resolution Island in Fiordland, realised that many small, nearshore islands still had native species that on the mainland were nearing extinction. Animals were free from predatory mammals, and plants from browsing mammals.

Conservationists began moving birds to islands such as Kapiti, north of Wellington. Today these sanctuaries form a network that is a key component of New Zealand’s efforts to save threatened native species.

Pest control and eradication

On small islands, pests such as rats, pigs and goats have been eradicated by poisoning and hunting programmes. Helicopters drop poison bait in a grid pattern, using global positioning systems to ensure an even coverage.

‘Mainland islands’ are especially chosen areas on mainland conservation land that are intensively managed with poisoning and trapping programmes. They are not fenced. Some small sanctuaries have predator-proof fences.

Captive breeding

Captive breeding programmes have helped raise the numbers of some species.

One success story is the takahē. Once thought to be extinct, it was rediscovered in 1948 in the Murchison Mountains, Fiordland. In the early 1980s, efforts were made to understand the breeding requirements of this dwindling species, and to reduce chick mortality. Eggs were incubated, and the chicks were raised and held in enclosures near Te Anau.

Secondary, captive populations can be started up, often on island sanctuaries. These then form a back-up in case the original population dies out.

Non-conservation land

Managing the 70% of New Zealand that is not conservation land has major implications for threatened species. Until the 1980s this land was mainly developed for farming and other production. But in 1991 the Resource Management Act changed the focus to the sustainable management of resources. However, this only addresses the negative environmental impact of new developments, rather than restoring already degraded habitats. Still, city councils and regional councils are required to consider conservation values, and many have begun to restore certain habitats.

Biodiversity strategy

The New Zealand Biodiversity Strategy, launched in 2000, aimed to conserve New Zealand’s diversity of species, and to include the whole community in the effort. For example, throughout New Zealand there are local schemes to control predators in areas of native bush.

The strategy also recognised that these projects must cut across map boundaries, and should not be the sole responsibility of the Department of Conservation. For example, the black-billed gull, considered to be in serious decline, nests on South Island riverbeds which are not conservation lands. The regional council, Environment Canterbury, is now involved in saving the gull, among other species.


Case histories

Mahoenui giant wētā

Wētā are insects unique to New Zealand. Related to crickets and grasshoppers, they have remained relatively unchanged over millions of years. There are around 100 species, including the giant wētā.

The Mahoenui giant wētā (Deinacrida mahoenui) is a ‘nationally endangered’ species discovered in 1962 in a patch of spiny gorse at Mahoenui in the North Island’s King Country. The gorse may have protected it from rats, and therefore extinction. Since the late 1980s, there have been attempts to start new populations elsewhere. Hopes centred on islands off the Coromandel coast, but by 2007 the only success was in another gorse-ridden patch near Te Kūiti.

In 2000, 124 wētā were released into the gorse patch, and another 60 in 2001. A follow-up survey found insects that were all under a year old – offspring of the transferred wētā. In 2003 the Department of Conservation noted that although there were thousands of wētā, they were on just one paddock and therefore vulnerable to fire, which would spell tragedy for the species.

Mistletoe

Like the canaries sent into a coal mine to test for dangerous gases, New Zealand’s showy Peraxilla mistletoes are key indicators of the health of the forest. As mistletoe depends on birds, lizards and insects for pollination, good numbers of it suggest a sizeable population of native animals, and an absence of plant-eating browsers such as possums.

The mistletoe flower remains closed until a bird, lizard or insect twists the top, at which point it bursts open. These plants are among the few in the world that are ‘explosive’ pollinators.

Two species of the scarlet Peraxilla mistletoes attach themselves to beech trees – P. colensoi and P. tetrapetala. These are considered to be in ‘gradual decline’. Possums eat them, and predators have reduced the native birds and insects that pollinate them.

Five that survive

The Codfish Island fernbird, Campbell Island mollymawk, crested grebe, black petrel, and a snail of the Chatham Islands are five of New Zealand’s native species whose conservation status improved in 2005.

Conservation groups are working to maintain mistletoes by trapping rats and possums, and planting host trees for these beautiful plants.

Tuatara

New Zealand’s tuatara (Sphenodon punctatus) is a species of ancient, lizard-like reptile. There are reasonably good numbers on the stronghold of Stephens Island, in Cook Strait. Its ‘range restricted’ conservation rating reflects the fact it occurs on only a few islands, even though there may be up to 100,000 individuals.

The tuatara has been moved to islands from the Coromandel northwards. After kiore (Pacific rats) were finally wiped out on Little Barrier Island (Hauturu) in 2004, progeny of tuatara originally rescued from that island were returned. As Little Barrier is six times larger than the next biggest tuatara island (Hen Island), there is huge potential for re-establishing the species.

The Brothers islands tuatara

It was not until the late 1980s that the tuatara Sphenodon guntheri, which had somehow survived on a tiny island of The Brothers group in Cook Strait, was described as a separate species. They are considered ‘nationally endangered’ because in 2005 there were fewer than 1,000.

Scientists at Victoria University of Wellington began a captive rearing programme, and in 1995 released the first juveniles onto Tītī Island in the Marlborough Sounds. A second group was moved to Matiu (Somes Island) in Wellington Harbour in 1998.


External links and sources

More suggestions and sources


How to cite this page: Gerard Hutching and Carl Walrond, 'Threatened species', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/threatened-species/print (accessed 22 November 2019)

Story by Gerard Hutching and Carl Walrond, published 24 Sep 2007