Space invaders!

Collaborative study suggests nature reserves enable greater resilience for ecosystems against foreign invaders.  

Grey squirrel (Sciurus carolinensis)
The invasive grey squirrel displaced red squirrels in the UK

Nature reserves, national parks and marine protected areas have been proven to effectively shield native wildlife from the impacts of invasive species, in a new study published this week in the journal Global Change Biology.

Led by the Pyrenean Institute of Ecology (IPE) alongside co-authors from institutions including international conservation charity ZSL (Zoological Society of London), the University of Cambridge and CABI, the international research shows that despite their effectiveness, these areas could be compromised in future, as climate change impacts the range of increasing numbers of species. 

Invasive species – non-native organisms that are introduced to an ecosystem and can often thrive at the expense of native wildlife, such as the invasive grey squirrel (Sciurus carolinensis) which displaced red squirrels (Sciurus vulgaris) in the UK – have been implicated in 58 per cent of recent extinctions worldwide and are unanimously recognised by conservationists as posing a serious threat to global ecosystems. 

Until now, however, conservationists have lacked evidence of how effective protected areas are in mitigating against the threats and challenges these species cause, such as competition for food and territory, inter-species predation and invasive diseases. 

Evaluating the current and future distributions of 100 of the most invasive terrestrial, freshwater and marine species in Europe – from the brown rat (Rattus norvegicus) to the red-swamp crayfish (Procambarus clarkia) – the team assessed the combined threat these animals pose to existing protected areas, when combined with the overarching issue of climate change. 

Encouragingly, they found that only a quarter of the protected areas set up over the last century have so far been colonised by invaders, even in cases where the conditions inside the protected area appear to be favourable for them.  

Fewer invasive species were found in more well-established protected areas with low levels of human activity – underlining the role played by humans in either deliberately or unintentionally facilitating the movement of invasives.  

However, this could all change in future. The team’s findings also suggest that climate change has potential not only to drive vulnerable species out of the current boundaries of their protected areas, but also to allow invasive species to colonise these areas more effectively, further increasing the pressure on native wildlife.

Co-author Dr Chris Yesson, from ZSL’s Institute of Zoology, said: “As climate change increases the pressure on vulnerable species worldwide, in many cases heightening the extinction risk, it is vital that we develop a more sophisticated understanding of the impacts of our current conservation methods and how these could potentially help mitigate against these threats.  

“It’s already been shown that climate change, with the changes in land-use and human movement this often entails, may facilitate the spread of invasive species. Our latest findings suggest just how significant this threat could be, but also highlight the potential role of effectively-managed protected areas in pointing towards a brighter future for all wildlife worldwide.” 

Dr David Aldridge from the University of Cambridge’s Department of Zoology, a co-author of the study, said:  “Our study shows that protected areas are providing an important refuge for species that are threatened by biological invasions. However, in the future we must also consider the effect of a changing climate in continuing to select the very best regions of land, sea and freshwater to conserve.”

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