Invasive animals in protected areas by humans pose native species risk

Invasive animals brought into protected areas by humans are competing with native species and destroying natural habitats worldwide, study warns

  • Invasive species introduced by humans are putting pressure on protected sites
  • These species out compete local animals for food or even kill native creatures 
  • Dozens of species were found within as little as 6 miles of protected locations 

Non-native ‘alien’ species introduced by humans to an area near to a protected wildlife site are destroying natural habitats and killing local species, study warns.

Researchers from the Chinese Academy of Science and University College London found that protected areas across the globe were at risk from these ‘alien’ species.

The team say the majority of protected sites are currently keeping invasive animals at bay, but it was an ongoing battle with invasive species often just a few miles away. 

These ‘alien species’ may kill or out compete native species and destroy habitats – creating one of the top drivers of global biodiversity loss, researchers claim.

These alien species are as little as 6 miles from a protected site, such as the American mink found near the Cairngorms National Park in Scotland. 

American mink (Neovison vison) was found in 1,251 protected areas such as Cairngorms National Park in the UK, where this photo was taken


Researchers discovered dozens of ‘alien species’ commonly found near protected areas. Including:

  • Rock dove (Columbia livia): in 6,450 places such as Yosemite National Park
  • Ring-necked pheasant (Phasianus colchicus): in 4,822 places including UK sites such as Minsmere
  • House sparrow (Passer domesticus): in 3,972 places such as Kruger National Park, South Africa
  • Wild rabbit (Oryctolagus cuniculus) in 1,673 ares including much of Australia and UK
  • American mink (Neovison vison) in 1,251 protected areas such as Cairngorms National Park
  • Brown rat, such as in Fiordland National Park, New Zealand 
  • Red-eared Slider (Trachemys scripta) in 164 public areas such as Singapore nature reserves
  • Cane toad (Rhinella marina) in 265 areas such as Kakadu National Park   

The Chinese and UK team say these invasive species don’t know that an area has been designated ‘protected’ to safeguard endangered or at risk local species and are just doing what comes naturally – the humans that introduced them are at fault.

Co-author Professor Tim Blackburn from UCL said one of the most harmful ways people are impacting the natural environment is through the introduction of species.

These ‘alien’ species are animals that ‘do not occur naturally in an area, but have been taken there by human activities.’

‘These species may kill or compete with native species, or destroy habitats, amongst other impacts,’ said Blackburn.

‘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. It’s important to know whether these areas might protect against the spread of invasive species.’

The researchers investigated 894 animal species – including mammals, birds, reptiles and invertebrates – known to have established alien populations.

They then assessed whether these species occurred within, or near, the boundaries of the 199,957 protected areas across the globe.

These sites are defined by the International Union for Conservation of Nature (IUCN), including wilderness areas, national parks, and natural monuments or features.

The team found that less than 10 per cent of the protected areas are currently home to any of the invasive species surveyed, suggesting that protected areas are generally effective in protecting against invasive species.

Almost all of those areas may be at risk of invasion, as an invasive species was found within 62 miles of the boundaries of 99 per cent of the protected areas. 

For 89 per cent of the protected areas, there was an alien species resident within just six miles of the boundaries.

More than 95 per cent of the protected areas were deemed to be environmentally suitable for the establishment of at least some of the alien species being studied.

The researchers also investigated common factors among the protected areas that are already home to alien species. 

They found that protected areas tend to have more alien animal species if they have a larger human footprint index, due to factors such as transport links and large human populations nearby.

The researchers also found that larger, and more recently established protected areas, tend to have more alien species compared to older sites.

Red-eared slider (Trachemys scripta), a semiaquatic turtle, was found in 164 protected areas such as Singapore nature reserves (as depicted in photo)

Ring-necked pheasant (Phasianus colchicus) found in 4,822 protected areas including UK sites such as Minsmere (where this photo was taken)

They found that the older protected areas tend to be in more remote areas, so they are less exposed to human impacts.

Senior author Dr Li Yiming  from the Institute of Zoology, Chinese Academy of Sciences said right now most protected sites are free of alien invaders. 

‘But this might not last,’ Yimming added. ‘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.’

The findings do not suggest that the rich existing biodiversity in protected areas acts as a barrier to invasions, as they found mixed evidence on the relationships between existing native biodiversity and presence of invasive 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,’ Professor Blackburn said.

The most invaded parks were all found in Hawaii: Volcanoes National Park (80 species), Hakalau Forest National Wildlife Refuge (63 species) and Kipuka Ainahou (62 species).

The research has been published in the journal Nature Communications. 


Nature is in more trouble now than at any time in human history with extinction looming over one million species of plants and animals, experts say.

That’s the key finding of the United Nations’ (UN) first comprehensive report on biodiversity – the variety of plant and animal life in the world or in a particular habitat.

The report – published on May 6, 2019 – says species are being lost at a rate tens or hundreds of times faster than in the past. 

Many of the worst effects can be prevented by changing the way we grow food, produce energy, deal with climate change and dispose of waste, the report said.

The report’s 39-page summary highlighted five ways people are reducing biodiversity:

– Turning forests, grasslands and other areas into farms, cities and other developments. The habitat loss leaves plants and animals homeless. About three-quarters of Earth’s land, two-thirds of its oceans and 85% of crucial wetlands have been severely altered or lost, making it harder for species to survive, the report said.

– Overfishing the world’s oceans. A third of the world’s fish stocks are overfished.

– Permitting climate change from the burning of fossil fuels to make it too hot, wet or dry for some species to survive. Almost half of the world’s land mammals – not including bats – and nearly a quarter of the birds have already had their habitats hit hard by global warming.

– Polluting land and water. Every year, 300 to 400 million tons of heavy metals, solvents and toxic sludge are dumped into the world’s waters.

– Allowing invasive species to crowd out native plants and animals. The number of invasive alien species per country has risen 70 per cent since 1970, with one species of bacteria threatening nearly 400 amphibian species.

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