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Alien invaders get a bad press

10 June 2013, by Alex Peel

Some invasive species could be unjustly maligned.

Zebra mussels

A new study, published in Acta Oecologia, says many of the most damning claims about invaders are not backed up with hard evidence. This might be skewing priorities when it comes to dealing with them.

'Some invasive species are possibly getting a harder time than they deserve,' says Claire McLaughlan, a NERC-funded PhD student at the University of Cambridge, who led the study.

'It's an emotive subject but it needs to be looked at in a balanced way. For many of the species in the list of Europe's top ten worst invaders, we could find little evidence of their reported effects in the literature.'

'If this is the literature behind the worst species, then what is the evidence like for others?'

There are thought to be more than 12,000 non-native species in Europe. Having evolved under different competitive pressures, some can quickly overwhelm their new ecosystems and become invasive.

If this is the literature behind the worst species, then what is the evidence like for others?
Claire McLaughlan,
University of Cambridge

These invaders can wreak havoc, out-competing their native neighbours and damaging the many economic, cultural and health benefits of nature, known as ecosystem services.

Several projects have been launched to tackle invasive species and protect those services, but there is only so much money available. To help prioritise spending, a group of European scientists put together a list of the 10 most damaging invasive species in Europe.

Sika deer, Canada geese and zebra mussels all made the list, but McLaughlan and her team wanted to examine the evidence behind it.

They found that the damaging effects of invaders are often assumed, rather than based on hard evidence. Some invasions, particularly those in environments which are already severely damaged, could even enhance ecosystem services.

'It's context-dependant,' explains McLaughlan. 'For example, with the zebra mussel, if they were to invade a stream full of rare, native species, they would obviously be very damaging.'

Zebra mussels

'But if they were to become established in a large man-made reservoir with very few species and an algae problem, they could help to process the algae and improve some ecosystem services.'

'We're not for a moment suggesting that you should introduce invasive species anywhere; prevention is always better than cure.'

'But with the species that are already there, there's only limited money available and we need new ways to prioritise which species we tackle. That has to be based on the evidence of their effects.'

McLaughlan's PhD research focusses on the invasive zebra mussel and its effects on the ecosystem services of UK reservoirs.

McLaughlan C, Gallardo B, Aldridge DC, 'How complete is our knowledge of ecosystem services impacts of Europe's top 10 invasive species?,' Acta Oecologia, 2013, DOI: 10.1016/j.actao.2013.03.005

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Your comments

Having just been stung by the B.hypnorum and seeing that it can steal nests from our native birds, not only is it successfully colonising the UK, it is now doing the same in Iceland. Will it become an invasive species.... will it endanger our wildlife, humans or outcompete some species....
You may find this article re above interesting....

George Pilkington, Warrington
Monday, 10 June 2013 - 15:09

In response to George above; That species has naturally expanded its range into the UK. This means it is generally not regarded as an invasive species, which are artificially introduced by humans. I understand that they use bird nest boxes to create their nest, but I have never heard of them stealing actively used nest boxes. It is likely that as the bird species' ranges and bumblebee's ranges overlap in Europe that there will be some form of behavioural adaption to this.

Tom K, Manchester
Wednesday, 19 June 2013 - 11:34


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