Aquatic invasive species threat to UK rivers

'Dirty dozen' invasive species threaten UK

April 2013. Parts of the UK are at greater risk of invasion by non-native aquatic species than previously thought, according to new research. The first to include human factors in models used to predict where invasive species will arrive and spread, the study shows the Thames, Anglian and Humber river basins are most vulnerable. The findings, published in the Journal of Applied Ecology, should help improve control of invasive species in the UK.

The researchers, Dr Bellinda Gallardo and Dr David Aldridge from the University of Cambridge, focussed on the 'dirty dozen' - a group of high-risk invasive aquatic plants and animals. Some, like the killer shrimp (Dikerogammarus villosus) and the bloody red mysid (Hemimysis anomala) are already in UK but have yet to spread. Others, such as the Asian clam (Corbicula fluminalis) and the marmokrebs, a crayfish (Procambarus fallax) may not yet have arrived.

Species Distribution Models

Working with Species Distribution Models, which are routinely used to predict which regions most suit invasive species, the Cambridge pair made the models more accurate by including human factors such as population density, land-use and proximity to ports. Traditionally, the models are based on environmental conditions such as temperature and rainfall.

According to Dr Gallardo: "Invasive species need to be in the right place at the right time; they need the right environmental conditions, but they also need a helping hand from humans. This can happen intentionally, for example through introduction of commercial fish, or accidentally via hulls of boats, fishing equipment, or ballast water."

Thames, Anglian and Humber river basins at highest risk

The role of humans, plus invasive species' great adaptability, make predicting their spread challenging. By including both human and environmental factors in the models, the researchers found the risk of invasion in the UK was increased by 20% in coastal, densely populated areas and places near transport routes, with the Thames, Anglian and Humber river basins at highest risk.

‘Invasional meltdown'

"These river basins already host many aquatic invaders. This is particularly worrying because invasive species often modify their habitat, making it more favourable to other invaders. This can eventually lead to a process known as invasional meltdown," she says.

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