Invaders' threat to world wildlife

HUNDREDS of invasive species – from rats to diseases – are posing one of the greatest threats to wildlife across the world.

A study of 57 countries co-ordinated by the Global Invasive Species Programme found 542 types of animals and plants had invaded places where they were not naturally found and were putting native wildlife at risk.

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 Japanese knotweed, American signal crayfish and water primroses. On average, there were about 50 non-native species having a negative impact on existing plants and animals in each country, ranging from nine in Equatorial Guinea up to 222 in New Zealand.

On the list of invasive aliens are 316 plants, 101 marine species, 44 freshwater fish, 43 mammals including rats and goats, 23 birds and 15 types of amphibian.

Invasive plants and animals are those that threaten native wildlife, by eating them or their eggs, damaging their habitat, spreading disease, or competing with them for the same "niche".

Dr Stuart Butchart, of Birdlife International and one of the study authors, said: "While some threatened species on the (endangered] red list have improved, a growing number are more threatened owing to increasing spread and threats from non-indigenous species.

"This shows that, although we are winning some battles, we are losing the war."

Dr Bill Jackson, deputy director general of the International Union for Conservation of Nature and chairman of the Global Invasive Species Programme, said: "It's more likely to be more cost-effective to prevent the spread of invasive species than to tackle the crisis once they are established."