Impact of nature’s invading aliens measured for first time

IUCN 22 Jan 10;

Invasive Alien Species, ranging from disease and plants, to rats and goats, are one of the top three threats to life on this planet, according to a new publication coordinated by the Global Invasive Species Programme (GISP), of which IUCN is a partner. Most countries have made international commitments to tackle this threat, but only half have introduced relevant legislation and even fewer are taking adequate action on the ground.

The publication, “Global indicators of biological invasion: species numbers, biodiversity impact and policy responses”, looked at 57 countries and found that, on average, there are 50 non-indigenous species per country which have a negative impact on biodiversity. The number of invasive alien species ranged from nine in Equatorial Guinea to 222 in New Zealand.

A total of 542 species were documented as invasive aliens, including 316 plants, 101 marine organisms, 44 freshwater fish, 43 mammal, 23 bird and 15 amphibian species. According to Prof. Melodie McGeoch, lead author on the publication and member of the Centre for Invasion Biology, these numbers are a significant underestimate. “We showed that regions with low development status and little investment in research have lower than expected numbers of invasive aliens”. An increase in the number and spread of alien species, which adversely affect the habitats they invade, is nonetheless attributed to a substantial rise in international trade over the past 25 years.

“While some threatened species on the IUCN Red List have improved in status as a result of successful control or eradication of invasive alien species, a growing number are more threatened owing to increasing spread and threats from non-indigenous species,” says Dr Stuart Butchart from BirdLife International. “This shows that although we are winning some battles in the fight against invasive species, current evidence suggests that we are losing the war.”

If left uncontrolled, invasive alien species can have a serious impact on native species. 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, leading to the species to move up from Vulnerable to Endangered on the IUCN Red List of Threatened Species™.

Similarly, the pathogenic chytrid fungus, which was entirely 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.

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.

“It’s likely to be more cost effective to prevent the spread of invasive species in the first place than to tackle the biodiversity crisis once they have become established,” says Dr Bill Jackson, IUCN’s Deputy Director General and Chairman of GISP. “With sufficient funds and political will, invasive species can be controlled or eradicated. This will allow native species to be saved from extinction, but countries need to dramatically improve the way they deal with the problem.”

Editor’s notes:

The publication was produced by scientists from the Centre for Invasion Biology (Stellenbosch University), BirdLife International and IUCN.

Full publication available at: http://www3.interscience.wiley.com/cgi-bin/fulltext/123243506/PDFSTART?CRETRY=1&SRETRY=0

Invasive species threat growing globally, experts warn
Threat to native species from alien invaders is growing and posing one of the greatest threats to wildlife around the world, conservationists say
Press Association, guardian.co.uk 22 Jan 10;

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.

In some places invasive species are driving native wildlife towards extinction, for example in New Zealand where the yellowhead bird is now endangered because of a surge in the number of rats, while the chytrid fungus is spreading around the world causing massive declines in amphibians.

There are examples of success stories, in which threatened wildlife has bounced back after control measures were taken against the invasive species.

On Mexico's Natividad Island, the black-vented shearwater was at risk from the introduction of cats, goats and sheep, but its numbers are now recovering following an eradication programme.

And control of the red fox in south Western Australia has allowed the western brush wallaby to recover sufficiently for it to be downgraded on the "red list" of endangered species compiled by the International Union for Conservation of Nature (IUCN).

But while most countries have made commitments to tackle the threat of invasive species, only half have introduced legislation and even fewer are taking enough action on the ground, according to the IUCN.

Dr Stuart Butchart, from Birdlife International and one of the authors of the study, said: "While some threatened species on the IUCN red list have improved in status as a result of successful control or eradication of invasive alien species, 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 in the fight against invasive species, current evidence suggests that we are losing the war."