Alien invaders threaten Europe's native plants

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http://www.guardian.co.uk/environment/2012/nov/02/alien-invaders-native-plants


An ash sapling in Warwickshire. Ash dieback has surprised some of Britain’s most experienced tree experts. Photograph: David Jones/PA

More than 30 alien insects and mites, fungi, bacteria, viruses, diseases, pathogens and invasive plants, many with the potential to devastate native populations, are expected to reach Britain and other European countries in the next few years, according to the European plant protection organisation's alert list.

Some could arrive on imported trees and shrubs from Brazil or in soil from China or Africa, others via wooden ornaments and even packaging crates. But plant scientists say no one can predict exactly what ecological impact they will have because they are likely to behave differently in new environments than they do in the places where they have evolved over millennia.

When and if they come, they will join at least 10 new organisms that have arrived in the last few years and now threaten swaths of forest and woodland. Some could die out in months and do no damage but others could spread rapidly, as Dutch elm disease did in the 1960s or as ash dieback may do in the next decade, said Joan Webber, principal pathologist and head of the tree health research group at the Forestry Commission. "There's been a massive jump in the number of pathogens in the last 10 years. It's a combination of climate change , trade and other factors."