Mass American mink removal in Scotland
1 February 2011 Last updated at 09:35 GMT
Invasive species - animals and plants introduced into a country from overseas - are a major threat to global biodiversity.
But now time may be running out for one animal in the UK. A project led by the University of Aberdeen has carried out one of the world's biggest eradications of an alien invader - the American mink.
Our science reporter Rebecca Morelle has been to Aberdeenshire to find out more.