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Environment New Zealand 2007 – Summary

Message from the Minister

Preface

Section one: Setting the context

Section two: Pressures on the environment

Section three: State of the environment

References

Glossary

Section three: State of the environment

Biodiversity

New Zealand’s varied landscapes and unique native plants and animals have helped shape our national character and cultural identity. Biodiversity helps sustain the ecosystems that support the country’s primary production and tourism sectors.

Internationally, New Zealand is regarded as a significant contributor to global biodiversity, with an estimated 80,000 species of native animals, plants, and fungi. A large proportion of these species do not occur naturally anywhere else on earth. All our frogs and reptiles, more than 90 per cent of our insects, about 80 per cent of our vascular plants (plants other than mosses, liverworts, and hornworts), and a quarter of our bird species are found only in New Zealand.

Run by a charitable community trust, the Karori Wildlife Sanctuary is a 252 hectare safe haven for endangered native birds and other wildlife located 2 kilometres from Wellington city. A unique predator-proof fence, specifically designed to exclude 14 species of non-native mammals, ranging from possums to mice, encircles the 8.6 kilometre perimeter.

Many threatened species of native wildlife are expected to be reintroduced to the sanctuary as appropriate habitats recover. The little spotted kiwi, stitchbird (hihi), weka, saddleback (tīeke), kākā, bellbird (korimako), whitehead (pōpokatea), and tuatara have already been released there.

Bellbird/Korimako (Anthornis Melanura).

Source: Courtesy of the Department of Conservation.

Protecting native habitat and vegetation

By international comparison, a large proportion (just over 32 per cent) of New Zealand’s land area is legally protected for conservation purposes. The area of public conservation land increased by 4.56 per cent between 2004 and 2007, bringing the total to 9.27 million hectares.

The area of private land protected under the Queen Elizabeth II National Trust (QEII Trust) and the Ngā Whenua Rāhui covenants, combined, increased by more than 51 per cent between 2004 and 2006 to a total of 221,473 hectares. By 30 June 2007, over 82,933 hectares were legally protected through more than 2,600 QEII Trust covenants. However, some of our land environments, for example, wetland and lowland ecosystems, are not well represented among the legally protected areas.

About 44 per cent of New Zealand’s land area is covered by native vegetation, of which almost two-thirds is protected. This is mostly found in hill country and alpine areas. The vegetation types that have experienced the greatest loss are broadleaved native hardwoods, mānuka and/or kānuka, tall tussock grassland, and native forest. There is less native vegetation remaining in lowland areas and this has implications for species that need this type of habitat to survive.

Table 3.1 in the Land section shows that, in total, between 1997 and 2002, native land cover decreased by an estimated 16,500 hectares (0.12 per cent). This total decrease included an increase of 700 hectares of non-vegetative native cover, such as sand and gravel, and a decrease of 17,200 hectares of native vegetative cover. These changes either occurred through conversion of land to other uses, or as a result of natural processes.

Since humans arrived in New Zealand, the country has experienced one of the highest species extinction rates in the world, due to the loss of habitats and the introduction of pest plants and animals. Table 3.4 shows that almost 2,500 of our native land-based and freshwater species are listed as threatened. Decreases in population sizes since the 1970s are largely caused by the impacts of introduced pest species, rather than habitat loss.

A changing climate may further exacerbate pressures on our most endangered species.

Table 3.4: Distribution of threat ranking by native species group according to the Department of Conservation’s Threat Classification System, 2005

View distribution of threat ranking by native species group according to the Department of Conservation’s Threat Classification System, 2005 (large table).

In some species groups, a large proportion of native species are threatened. For example, all native frog species are threatened because of habitat loss and predation. Diseases, such as the chytrid fungus and a ranavirus recently detected in some native frogs, are probably also responsible for declines in some species. Five out of six New Zealand bat species are endangered because of predation and loss of large trees required as roosts. Table 3.4 indicates that not enough is known about some groups to reliably determine their threat status. For example, many fungi and plants are listed as data-deficient.

Monitoring the extent of suitable native habitats for a selection of ‘indicator species’ is a practical way of assessing changes in New Zealand’s native biodiversity. Changes in the distribution of a small number of indicator species over specific periods are used to illustrate the changing extent of native habitats over time. The three periods used are: before human settlement; during the 1970s and 1980s; and the present.

Seven indicator species have been selected from the national biodiversity indicator programme currently under development by the Department of Conservation. These species are all managed by the Department under recovery plans, and were selected for their usefulness as indicators, their habitat requirements, the availability of data for them, and their level of threat. Table 3.5 shows the selection of indicator species and their descriptions.

Table 3.5: Selection of native species used to illustrate changes in New Zealand’s native biodiversity

Source: Ministry for the Environment.

Readers will find extensive information about the seven indicator species in the full Environment New Zealand 2007 report. In this summary, Figure 3.11 on page 66 presents an example of distribution information for the kākā.

In the 19th century, kākā were abundant throughout forests of both islands, but by 1930 had become more localised. North Island kākā are now almost absent from many large forested areas with high predator levels. They remain common in some central North Island forests, but even within these strongholds they are thought to be declining. They are still common on some larger offshore islands.

Although low in number, the South Island subspecies is still widespread and has become progressively more common down the West Coast of the South Island to Fiordland and on Stewart Island.

Kākā currently occupy less than 20 per cent of their original range, and recent evidence suggests that most populations without predator control are declining and remaining populations may consist predominately of males. Since the 1970s, the kākā’s range has contracted a further 6 per cent.

Getting better at protecting biodiversity

In 2007, biodiversity in New Zealand faces the same pressures – notably introduced animal pest and weed species – as it did 10 years ago. Native plants and animals that survived the initial habitat modification caused by human settlement continue to be threatened by predators and competitors.

What has changed in the past ten years, however, is the greater area under pest control on both public and private land, much of it especially targeted at the habitats of the most threatened species. For instance, between 2000 and 2006, areas targeted for possum management by the Department of Conservation increased by 60 per cent. Those targeted by the Animal Health Board have increased by 40 per cent since 2001. Together, areas targeted by the Department of Conservation and Animal Health Board for possum management equate to around 37 per cent of New Zealand's land area.

Since 1997, pest control has become more effective as technology and knowledge have improved. The recent introduction of new Department of Conservation traps for stoats, as well as enhanced control regimes on Department of Conservation offshore and mainland island projects, demonstrate how pest control is evolving in New Zealand.

Increased biosecurity is now recognised as a key measure to protect New Zealand from new pest plants and animals (see box 'New Zealand's biosecurity system'). This is important not only for native biodiversity, but also for the introduced species on which much of our economy depends.

In the future, conservation priorities are likely to continue to focus on improved pest control and biosecurity protection, and on increasing the legal protection for those land environments and ecosystems that are not well represented in areas legally protected for conservation purposes. Attention is also likely to focus on the impacts of climate change on our native biodiversity.

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