Invasive species threat growing globally
Threat to native species from alien invaders is growing and posing one of the greatest threats to wildlife around the world, conservationists say 
By Press Association
www.guardian.co.uk, Friday 22 January 2010 11.14 GMT Hundreds of invasive species – from rats to diseases – are posing one of the greatest threats to wildlife around the world, conservationists warned today. A study of 57 countries coordinated by the Global Invasive Species programme (pdf) found 542 types of animals and plants were putting native wildlife at risk in places where they are not naturally found. On average, around 50 non-native species are having a negative impact on existing plants and animals in each country, ranging from nine in Equatorial Guinea to a massive 222 in New Zealand. On the list of invasive aliens are 316 plants, 101 marine species, 44 freshwater fish, 43 mammals, 23 birds and 15 types of amphibian. And the threat to native species from alien invaders is growing, the experts warned. Invasive plants and animals are those which threaten native wildlife, by eating native species, laying eggs, damaging their habitat, spreading disease or by competing with them for the same “niche” in an ecosystem. Many invasive species are successful because they have no natural predators in their new environment. Examples of non-native species causing problems in the UK include grey squirrels, whose spread has led to widespread declines in red squirrels, the rampant plant Japanese knotweed, American signal crayfish and water primroses. The study said that, globally, the increase and spread of invasive species is the result of a substantial rise in international trade in the past 25 years. …
