An international group of scientists and conservationists is calling for tougher action to stop the spread of alien species - the animals and plants which can cause massive damage when they are transported into habitats other than their own.
Invasive species are one of the main factors behind large-scale extinctions.
The measures include tighter controls at borders to check that potentially harmful species are not being carried in freight, and fines for those who are found to have brought animals or plants into an area which is later damaged as a result. Recent examples of the havoc caused by invasive species include the arrival on the Pacific island of Guam of the brown tree snake from south-east Asia. Its introduction led to 10 of the island's 13 bird species becoming extinct. Hard fight In Africa, the introduction of the South American water hyacinth to Lake Victoria led to large areas of water being covered and starved of oxygen, severely damaging marine life. Professor Harold Mooney, from Stanford University in the United States, presented the GISP plan to the annual meeting of the American Association for the Advancement of Science.