How pests affect our biodiversity and pest control initiatives

For 60 million years after New Zealand split from Gondwanaland there were no mammal predators or browsers of plants. This meant flightless birds (eg, kiwi and moa), unusual creatures (eg, tuatara and giant weta) and unusual plants were able to evolve.

People have had major impacts on New Zealand’s native fauna and flora. Many native species are now extinct due to having been either hunted for food, killed by introduced predators or because their habitat was destroyed when land was cleared.

There is now a huge amount of effort that goes into protecting and restoring habitats to stop the decline of our native plants and animals.

Possums, stoats and rats are the main predators of our indigenous plants and animals.

Possums eat large quantities of indigenous vegetation and prey on invertebrates and birds. They are the major cause of loss of forest canopy health and can cause major changes in the species present in native forests.

Rats and stoats prey on indigenous birds, reptiles and invertebrates. They have caused the decline or extinction of many of our native insects and lizards. Along with mice they affect the regeneration of some plants by eating seeds and seedlings.

In freshwater systems, pest fish (eg, gambusia and koi carp) are a major threat to both native ecosystems and freshwater ecosystems. Most freshwater pest species are found only in a small number of waterbodies or parts of the country.

A key element in most biodiversity programmes is the reduction and, where possible, eradication of predators and browsers of plants.

There are now 100 predator-free offshore islands around New Zealand. Together they provide homes to tuatara, numerous species of lizards including Duvaucel’s gecko, and large invertebrates such as wetapunga and Mercury Island tusked weta.

Preventing the spread of new pest fish populations is a focus of pest fish programmes.

Possum control is a focus of New Zealand’s National Pest Management Plan for Bovine TB. This is operated by OSPRI New Zealand.

See TB management areas [OSPRI]

Pests and threats [Department of Conservation website]

Surveillance programmes [Ministry for Primary Industries website]