Governments seek strategies to battling invasive alien species, estimated to be the second main cause of extinction of native life.

Officials from the 180 member governments of the Convention met in Montreal, Canada, from 12 – 16 March to consider a problem which is second only to habitat destruction for threatening the extinction of native species across the globe.

The meeting considered 17 draft principles for guiding action against invasive alien species relating to such matters as the precautionary approach, the ecosystem approach, border controls and quarantine measures, intentional and unintentional introductions, eradication, control, and containment. The species’ effects on ecosystems mentioned at the conference include changing light levels, decreasing dissolved oxygen in water, changing soil chemistry and its structure, and increasing surface run-off and soil erosion. Most importantly, alien species can affect ecosystem processes such as nutrient cycling, pollination, regeneration of soils, and energy flows.

Invasive species also compete with native ones, displacing or consuming them, acting as parasites or transmitting diseases, and reducing growth and survival rates. In some cases they cause the decline or extinction of local populations or even entire species.

Estimates of the economic costs of invasive alien species vary widely, with the costs to the US economy an estimated $123 billion per year.

Pertinent examples of the devastation caused by invasive species discussed at the conference include:

• invasive plant species covering an estimated 156,000 square miles (400,000 sq km) in the US, spreading annually across 4,700 sq miles (12,000 sq km), an area almost the size of Northern Ireland;
• the invasive sea lamprey has caused trout and other fish stocks in the Great Lakes to collapse causing Canada and the US to spend $13 million a year attempting to control it;
• the Weed Science Society of America recognises about 1,200 plant species as weeds in Canada and the US, of which about 65% in the US are non-natives;
• Prosopis (Mesquite) in the Thar desert of India has displaced other flora of the area and in Sri Lanka seriously threatens the biodiversity of the only Ramsar-listed wetland of the country;
• in the Galapagos Islands, a World Heritage Site that is renowned as a natural showcase of evolution, the number of introduced plants is almost as high as the number of natives due to introduced mammalian predators and herbivores as well as insects and plants;
• the corn rootworm, accidentally introduced into the Balkans in the late 1990s during the conflict there, now threatens the region’s maize production;
• in the Eurasian part of the Arctic, the alien Racoon dog is multiplying and consuming large numbers of various small mammals as well as spreading rabies and;
• the Hibiscus mealybug has invaded the Caribbean and is attacking a range of plants, including fruit and forestry trees.

“Over the past few centuries, invasive alien species have caused untold damage to natural ecosystems and human economies alike,” said Klaus Toepfer, Executive Director of the UNEP. “In today’s highly integrated world, where tourism and trade offer more and more opportunities for unwanted species to hitchhike to new homes, we urgently need a more effective international system for turning back the tide of harmful non-native species.”

The meeting will forward its results and recommendations to the Conference of the Parties when it holds its sixth meeting in April 2002 in The Hague.