Pest purge for Hauraki islands

Prime Minister Helen Clark and Conservation Minister Chris Carter at Home Bay on Motutapu Island yesterday. Picture / Dean Purcell.

Rangitoto and Motutapu Islands are to be restored to their natural state in an unprecedented pest eradication project.

Prime Minister Helen Clark and Minister of Conservation Chris Carter visited the Hauraki Gulf yesterday after the Department of Conservation (DoC) was allocated $595,000 over the next three years to make the islands pest free.

The initiative follows DoC's successful two-year eradication of kiore - the indigenous rat - from Little Barrier Island, which has allowed tuatara, giant weta, skinks and Cook's petrel to thrive again.

Rangitoto and Motutapu have a combined area of 3800ha and are thick with mice, two species of rats, stoats, cats, hedgehogs and rabbits. Their eradication would make the islands the largest pest-free habitat in the Hauraki Gulf.

The complex project is expected to take up to seven years to complete with feasibility studies for the next two years and operational planning starting in 2008, but Helen Clark is confident of success.

"The scale of this operation is several times larger than that of Little Barrier Island and just continuing to keep it pest-free is a challenge particularly with the number of visitors both islands see each year," she said.

"The fact that Motuihe [Island] has been rat-free indicates this can be done."

Ecosystem threatened

New Zealand's indigenous flora and fauna developed in isolation making it vulnerable to introduced species against which its defence mechanisms are insufficient.

Two species of rat, stoats, cats, hedgehogs and rabbits are targeted under the Department of Conservation's eradication project on Rangitoto and Motutapu Islands. All of these pests threaten the islands' ecosystems. Rangitoto has flourished since the removal of possums and wallabies in the 1990s but the island's full regeneration has been constrained by the remaining pests.

Eradicating rats is a necessary step in restoring habitat for threatened species and flora. They are omnivorous, eating seeds, fruits, insects, lizards, eggs and chicks.

Stoats were introduced to New Zealand in the 19th century to control rabbits but have since become a threat to fauna, eating birds when rats, rabbits and mice are not available.