Chapter 12: Biodiversity

At a glance

Biodiversity in New Zealand

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 comparatively large proportion of these are endemic – they do not occur naturally anywhere else on earth.

Pressures on biodiversity

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. Today, almost 2,500 native land-based and freshwater species are listed as threatened. The effects of climate change may further exacerbate pressures on our most endangered species.

Freshwater biodiversity is affected by surrounding land use and water quality. Invasive freshwater species such as the alga didymo (Didymosphenia geminata) pose risks for freshwater biodiversity.

Native land cover

About 44 per cent of New Zealand’s land area is covered by native vegetation, most of which is in hill country and alpine areas. Less native vegetation remains in lowland areas; this has implications for species that need this type of habitat to survive.

Between 1997 and 2002, it is estimated that native land cover decreased by 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.

It is estimated that wetland areas have reduced by 90 per cent from their original area. New Zealand has designated six wetlands as having global importance under the Ramsar Convention on Wetlands (an inter-governmental treaty signed in 1971). Together, these Ramsar wetlands cover a surface area of 39,068 hectares.

Legally protected areas

By international comparison, a large proportion (just over 32 per cent) of New Zealand’s land area is legally protected for conservation purposes, either as public conservation land (8.43 million hectares) or through conservation initiatives on private land (221,473 hectares). The area of public conservation land has increased by 4.56 per cent between 2004 and October 2007. Private land under legal protection has increased by just over 51 per cent between 2004 and 2006.

However, some of our land environments and the ecosystems they contain, for example wetland and lowland ecosystems, are not well represented among the legally protected areas.

Distribution of selected native species

The distribution of the selected native species discussed in this chapter (the lesser short-tailed bat, kiwi, kōkako, kākā, mōhua, wrybill, and dactylanthus) has decreased over time on a national scale.

Some of our more common native birds have shown an increase in distribution in recent years (27 out of 96 observed species). The same percentage (28 per cent) reduced in distribution between 1985 and 2004. Ninety-three per cent of these were endemic species.

Decreases in distribution since the 1970s are largely due to the impacts of introduced pest species, rather than habitat loss.

Present and future pest management

Pest management efforts have intensified over the last decade, and areas receiving ongoing management have increased for all major targeted pests. For instance, between 2000 and 2006, areas targeted for possum management by the Department of Conservation increased by 60 per cent. Areas targeted by the Animal Health Board have increased by 40 per cent since 2001. Together, areas targeted by the Department of Conservation and the Animal Health Board for possum management equate to around 37 per cent of New Zealand’s land area.

Introduced animal pest and weed species remain a serious threat to New Zealand’s endangered native plants and animals. Over the last decade, increasing priority has been given to controlling pests in the habitats of the most threatened native species, and to stopping unwanted species coming into the country.

While offshore island reserves continue to protect many of our rarest species, sanctuaries on the mainland are increasingly aiming to match that level of protection. Attention has also turned to the protection of endangered native species and ecosystems on private land.

In the future, conservation priorities are likely to continue to focus on improved pest control and biosecurity, and on increasing legal protection for the land environments and ecosystems that are currently under-represented.