The bad news is that although New Zealand was one of the first countries to provide legal protection for its wildlife, 40 percent of its terrestrial birds are extinct and more than 40 percent of the remaining birds are threatened. Likewise, many endemic reptiles, invertebrates, and plants are threatened. New Zealand’s plants and animals are particularly vulnerable to introduced mammals because the country has almost no native land mammals.
The good news is that “the scale and urgency of these threats seem to have fueled the innovation and determination of New Zealand conservationists,” says Mick Clout of the University of Auckland, New Zealand, who in the August 2001 issue of Trends in Ecology & Evolution summarizes a May 2001 nine-paper special issue of Biological Conservation on how introduced animals are affecting New Zealand’s ecology. Rats are one of the greatest threats to New Zealand’s reptiles. Only two species of tuatara (Sphenodon sp. ) remain, and about 60 endemic lizard species (a fourth of the geckoes and half of the skinks) are imperiled.
Twenty-five years ago, biologists thought it would be impossible to eradicate rats from islands larger than one hectare. Recently, however, conservationists have used bait laced with anticoagulant poisons to eradicate rats from New Zealand islands as large as 2,000 ha. Now tuataras and 12 species of lizards are being reestablished on 25 newly rodent-free islands, and the Dept. of Conservation is planning to eradicate rats from the 11,400-ha Campbell Island.
Similarly, predatory mammals (rats, cats, and stoats) almost wiped out the kakapo (Stigops haprobtilus), an endemic flightless, nocturnal parrot. The 62 remaining kakapo have been translocated to mammal-free islands. This innovative conservation program also includes captive raising, supplementary feeding, and nest protection. Since 1996, the number of kakapo has increased by one fifth.
Restoring New Zealand’s ecosystems may take more than reestablishing threatened species. Many extinct endemic species served critical ecological functions, and restoring some ecosystems might require replacing these species with similar or related species. “This is controversial,” says Clout. “We don’t really know what specific ecological functions most extinct species served, and the concept of ‘ecological equivalence’ is debatable.”
While conservationists are making progress in restoring New Zealand’s islands, the challenge remains severe on the mainland. However, the island restoration approaches are also being applied to sites on the North and South Islands. Called “mainland islands,” these sites have ecosystem-focused restoration goals. Notably, biologists used traps and poison bait to remove possums, cats, and rats from the Karori Sanctuary in Wellington; surrounded the 250-ha forest with a virtually mammal-proof wire mesh fence; and then released threatened birds, including the little spotted kiwi and flightless rails called weka.
“Conservationists in other biologically invaded islands should take note and take heart from this set of papers,” says Clout. “Biological invasion is a serious threat to biodiversity, but all is not lost and sometimes it is even possible to turn the tide.”
For more Information
Clout, M. 2001. Where protection is not enough: Active conservation in New Zealand. Trends in Ecology and Evolution 16:415-416.
Atkinson, I.A.E. and D.A. Norton. 2001. Introduced pest species and biodiversity conservation in New Zealand. Biological Conservation 99:1-133.