Human impacts put a quarter of all species under threat


Global mapping analysis reveals many animals are affected across 90% of their range. Nick Carne reports.


For hundreds of species, increasing urbanisation means decreasing range.

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Detailed mapping of the accumulated human impact on birds, mammals and amphibians across the globe paints a disturbing picture.

Nearly a quarter of the 5457 threatened species studied by an Australian team are affected by threats covering more than 90% of their habitat, with 395 – including many “charismatic large mammals” – affected across their entire range.

The assessed threats comprise a range of destructive human activities, such as hunting and the conversion of natural habitats for agriculture, urbanisation and other industrial land-uses. Infectious diseases were not included, however.

"We only mapped threats within a species' location if those threats are known to specifically endanger the species,” says lead author James Allan from the University of Queensland.

“This means species will decline, and possibly die out, in the impacted parts of their habitat without conservation action. Completely impacted species will almost certainly face extinction."

The findings are reported in the journal PLOS Biology. They show that impacts on species occur across 84% of Earth's surface, with particular hotspots in South East Asia and South America, where tropical forests contain Earth's richest diversity of life.

The authors also mapped global "cool spots" where species had not been impacted, identifying the world's last threat-free refuges.

“Almost the entire Earth’s surface (97%) hosts at least one unimpacted threatened species, acting as a potential refugium for that species; however, impacted and unimpacted species co-occur across 80% of Earth’s surface, identifying places where species with divergent sensitivities to threatening processes are present,” they write.

Allan and colleagues obtained spatial data on threats from the World Wildlife Fund’s recently updated Human Footprint project, which considers eight human pressures globally: built environments, crop lands, pasture lands, human population density, night lights, railways, major roadways, and navigable waterways.

They then developed a unique methodology they say represents “the first global assessment of the spatial distribution of human impacts”.

As such, they suggest, the results provide essential information for conservation and development planning, and can help guide future national and global conservation agendas.

And while their findings are concerning, they believe there is “room for hope”.

“The threats we map can be mitigated by in situ conservation actions, but diverse approaches are required,” they write.

“To ensure the survival of highly impacted species with little or no threat refugia, active threat management, restoration, and rewilding efforts are needed to open up enough viable habitat for species to persist.

“Conservation action in the hotspots of human impact we identify will have high benefits since they are areas with exceptionally high threatened species richness and species-specific threats.”

  1. https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000158
  2. https://www.worldwildlife.org/threats/the-human-footprint
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