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Biodiversity
Introduced species
Introduced pests, coupled with the loss of native habitats and ecosystems have caused a substantial decline in New Zealand’s native plant and animal species.
More than 25,000 plant species, 54 mammal species and about 2000 invertebrate species have been introduced to New Zealand since it was settled. Nearly 2000 exotic plant species are now established in the wild. Of the mammals introduced to New Zealand, a group of 31 species now dominates many of our landscapes.
While some of these introduced species, such as sheep and cattle, are cornerstones of New Zealand’s agricultural industry, others pose a threat to our native biodiversity. Browsing pests such as goats, deer and Australian brushtail possums change the structure and composition of our forests and grasslands. Predators like rats, stoats and cats hunt some of our rarest native animals. Introduced weeds can smother or overshadow native plants.
Without sustained control of such pests, many of New Zealand’s protected ecosystems are at risk of continued biodiversity loss.
Pest management
New Zealand’s biosecurity system is a multi-agency programme that aims to exclude unwanted organisms at the border and to control incursions and growth of pest populations within the country. It aims to exclude and control the invasive species that threaten our natural species and ecosystems and those species that underpin our primary production sector.
Biosecurity efforts include pest management for conservation and animal health purposes. Because bovine tuberculosis (Tb) – a disease affecting livestock and humans – is transmitted by possums, the control of possum numbers has benefits for both conservation and New Zealand’s farming industry.
Possum control or surveillance is carried out by the Animal Health Board (the organisation responsible for managing and implementing the National Pest Management Strategy for bovine Tb) and the Department of Conservation (DoC). Other pest groups such as rodents, mustelids (primarily stoats), cats, hedgehogs, pest grazers (including rabbits), and weeds are also managed in some of these areas.
In the past decade, animal pest and weed control efforts have significantly increased in their extent and intensity. As an example, since 2000 the area of DoC-land under sustained management for possums has increased by 60 per cent, from 669,000 to 1,069,000 hectares in 2006. Within sustained pest control areas, targeted pest treatment also increased from 40,000 hectares in 1991 to 302,000 hectares in 2006.
Land area under sustained management of pest species by the Department of Conservation, 2000–2006
Data (text description) for above graph
The area controlled for possums by the Animal Health Board has also increased by 40 per cent, from 6,153,200 hectares in 2001 to 8,870,000 hectares in 2006.
This results in a total of 9,939,000 hectares under sustained possum management in 2006, which constitutes about 37 per cent of New Zealand’s total land area (this excludes all council and private management activities).
This information has come from the latest national state of the environment report Environment New Zealand 2007.
Last updated: December 2008
