RICHARD FREEMAN: RESEARCH INTO ALIEN ANIMALS

A new publication coordinated by the Global Invasive Species Programe has found that New Zealand is the country most under threat from invasive foreign species with no less than 222. The least effected country was Equatorial Guinea with 9. They looked at 57 countries and found that, on average, there are 50 non-indigenous species per country which have a negative impact on biodiversity. 542 species were documented as invasive. But Professor Melodie McGeoch, lead author on the publication and member of the Centre for Invasion Biology this there are actually far more.

"We showed that regions with low development status and little investment in research have lower than expected numbers of invasive aliens." She said. The rise in international trade has helped species to colonize countries that they could never have reached naturally.

The pathogenic chytrid fungus, which was unknown until 1998, is thought to be the cause of the decline and extinction of many amphibian populations around the globe. The disease, caused by the fungus, can be spread by humans and a host of other species, ranging from exotic fish to African Clawed Frogs.

The yellowhead, a bird endemic to New Zealand, has suffered considerably in recent years due to a surge in the number of rats. Two populations of the Yellowhead are now extinct and three more are significantly falling in number.

But the impact of invasive alien species can be successfully controlled. The black-vented Shearwater, a seabird native to Natividad Island off the Pacific coast of Mexico, was under threat from cats, goats and sheep. But since they've been eradicated, the status of the bird has been reduced from Vulnerable to Near Threatened on the IUCN Red List. Similarly, the control of the Red Fox in south-western Australia in the last decade allowed the population of the endemic Western Brush Wallaby to recover sufficiently for it to be downlisted on the IUCN Red List to Least Concern.