University of Auckland, New Zealand
New Zealand may be the place on Earth that has had the greatest impact from alien species. This pervasive influence is evidenced by the fact that 43% of all New Zealandıs flora are now alien to the country. Of all the land mammals currently living in New Zealand, 34 species are aliens and only 2 are natives. Through browsing (grazing) and predation, these invading mammals have made huge changes to natural ecosystems. Faced with this dire situation, New Zealand has undertaken an aggressive set of responses for dealing with invaders.
One distinctive New Zealand native animal which is endangered by exotic invaders is the flightless takahe. There are only about 150 individuals left. Other native species of flightless birds have also been decimated by cats, rats, and other exotic land mammals. A particularly troublesome invader in New Zealand is the possum which kills native trees, changing the composition of forests. Methods of controlling possums include trapping and dropping poison pellets containing the chemical "1080" from aircraft.
The Polynesian rat has had massive effects on small fauna and has traditionally been very hard to control. Recently, however, it has proven possible to eradicate this and other rats on islands. Several New Zealand islands have been cleared of rats through aerial distribution of anti-coagulant poison baits. This has been proven effective on islands up to 250 hectares and is scheduled for trials on islands up to 3000 hectares.
A new organization, the Invasive Species Specialist Group (ISSG), is being set up by the Species Survival Commission of IUCN to identify appropriate actions to deal with invasive species worldwide. Their mission is to reduce threats posed by invasive species to natural ecosystems and native species. Sub-groups are planned to focus on terrestrial weeds, water weeds, fish, invertebrates, marine invaders, microorganisms, etc. Proposed ISSG projects include a newsletter- style publication to promote current awareness, a global database of invasive species, workshops and conferences, technical reports, and information pamphlets for local use.