Most people are aware of invasive species such as grey squirrels and Japanese knotweed and the problems they cause – the former have almost entirely displaced native red squirrels from England and Wales, while the latter can cause extensive damage to concrete, walls and drains and sewers.
These two non-native species have been in Britain many decades, but there are others – such as the Asian hornet – that are more recent arrivals, and then there are those that scientists fear could establish themselves in the future.
With the aim of preventing this, experts at the UK Centre for Ecology & Hydrology (CEH) have carried out what they call a horizon-scanning exercise in order to identify which exotic animals and plants we should be most worried about.
Top of their list of concerns are a number of insects, various marine invertebrates, a species of salmon that is normally found in the North Pacific, and the North American carnivore, the raccoon.
Helen Roy, who led the exercise, says it involves screening hundreds of species that have become invasive elsewhere. “We look at their potential to arrive in Britain and the probability they could establish themselves in the next 10 years,” she says. “And then we look at their potential impact – for example, are they going to cause major disruptions to ecosystems and local extinctions?”
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Pink salmon, which are now breeding in parts of Scandinavia and the Baltic after escaping from fish farms, could have devastating impacts on our native Atlantic salmon, which have declined by 70 per cent in the past 25 years as a result of declining water quality, the spread of pathogens from salmon farming and some other factors.
CEH freshwater molecular ecologist Lori Lawson Handley says there is evidence that pink salmon are successfully breeding in two rivers in Scotland. They could have a negative impact on our native salmon by competing for the same resources, transmitting pathogens and by altering the ecology of the freshwater rivers where they both breed.
“There’s also a parasite, a liver fluke, that is absolutely decimating farmed and wild Atlantic salmon in Norway,” she adds. “There’s a chance of accidental introduction of this through trading of live salmon stocks.”
Helen Roy says many marine species arrive in the ballast water of large ships, and that once established, it is very hard to take any effective action. “Horizon scanning is all about how to stop them arriving in the first place and ensuring there’s really effective biosecurity,” she adds.
Main image: Raccoon (Procyon lotor). Credit: Getty
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