June 8 (UPI) -- Protected areas are helping preserve biodiversity by providing a buffer against invasive species, but new research suggests many wildlife preserves and national parks are vulnerable to invasion by non-native plants and animals.
Much attention is paid to the habitat destruction and pollution caused by humans, but people have also severely damaged global ecosystems through the introduction of invasive species.
"These species may kill or compete with native species, or destroy habitats, amongst other impacts," Tim Blackburn, professor of invasion biology at the University College London, said in a news release. "Invasions by alien species are regarded as one of the top five direct drivers of global biodiversity loss, and aliens are establishing themselves in new areas at ever increasing rates."
"Protected areas are a cornerstone of biodiversity conservation, but aliens don't know where their boundaries lie," Blackburn said. "It's important to know whether these areas might protect against the spread of invasive species."
For the new study, scientists analyzed the territorial conquests of nearly 900 terrestrial animal species, including mammals, birds, reptiles and invertebrates, that have successfully colonized regions outside of their native ranges.
Next, researchers looked at how many alien populations were established inside or near protected areas, such as wilderness areas and national parks.
While only 10 percent of the planet's 200,000 protected areas are currently home to invasive species, researchers found alien species living within a few dozen miles of 99 percent of the surveyed areas.
What's more, their analysis -- published Monday in the journal Nature Communications -- showed most protected areas across the globe feature habitat and ecological conditions suitable to nearby invaders.
The protected areas most likely to host invasive species were those with a larger human footprint index -- parks and preserves with large human populations nearby and where humans frequently come and go. Parks that were newer and bigger were also more likely to host non-native species.
"At the moment most protected areas are still free of most animal invaders, but this might not last," said study co-author Li Yiming, research ecologist with the Chinese Academy of Sciences. "Areas readily accessible to large numbers of people are the most vulnerable. We need to increase efforts to monitor and record invasive alien species that people may bring into protected areas, deliberately or by accident, especially damaging species like the American bullfrog, brown rat and wild boar."
Scientists found new evidence that high concentrations of biodiversity rendered protected areas immune to invasion by non-native species.
"If alien species continue to spread -- and we would expect many to do that -- many more protected areas will have their boundaries reached, and potentially breached, by these alien species," Blackburn said.