Tiger numbers in Nepal have doubled since 2009, mainly due to targeted antipoaching efforts. Picture: VINCENT VAN ZALINGE/UPSPLASH
Tiger numbers in Nepal have doubled since 2009, mainly due to targeted antipoaching efforts. Picture: VINCENT VAN ZALINGE/UPSPLASH

The biggest killers of wildlife globally are unsustainable hunting and harvesting, and the conversion of huge swathes of natural habitat into farms, housing estates, roads and other industrial activities. There is little doubt that these threats are driving the current mass-extinction crisis.

Yet the understanding of where these threats overlap with the locations of sensitive species has been poor. This limits the ability to target conservation efforts to the most important places.

In a new study, published earlier in March in Plos Biology, 15 of the most harmful human threats were mapped — including hunting and land clearing — within the locations of 5,457 threatened mammals, birds and amphibians globally.

It was found that 1,237 species — a quarter of those assessed — are affected by threats that cover more than 90% of their distributions. These species include many large, charismatic mammals such as lions and elephants. Most concerningly of all, 395 species were identified that are affected by threats across 100% of their range.

Researchers only mapped threats within a species location if those threats are known to specifically endanger that species. For example, the African lion is threatened by urbanisation, hunting and trapping, so only the overlap of those specific hazards was quantified for this species.

This allowed researchers to determine the parts of a species’ home range that are affected by threats and, conversely, the parts that are free of threats and therefore serve as refuges.

Global hot spots of human impacts on threatened species, as well as “cool spots” where species are largely threat-free, could then be identified.

The fact that so many species face threats across almost all of their range has grave consequences. These species are likely to continue to decline and possibly die out in the affected parts of their ranges. Without targeted conservation action, completely affected species certainly face extinction.

More than 1,000 species were found that were not affected by human threats at all. As the researchers did however not map every possible threat, the results likely underestimate the true impact. For example, they didn’t account for diseases, which are a major threat to amphibians, or climate change, which is a major threat to virtually all species.

The researchers produced the first global map of human impacts on threatened species by combining the parts of each species range that are exposed to threats. The overwhelmingly dominant global hot spot for human impacts on threatened species is Southeast Asia.

This region contains the top five countries with the most threats to species: Malaysia, Brunei, Singapore, Indonesia and Myanmar.

The most affected ecosystems include mangroves and tropical forests, which concerningly are home to the greatest diversity of life on Earth.

A global map of cool spots was also produced by combining the parts of species ranges that are free from human threats. This map identifies the last vestiges of wild places where threatened species have shelter from the ravages of guns, snares and bulldozers. As such, these are crucial conservation strongholds.

Cool spots include parts of the Amazon rainforest, the Andes, the eastern Himalayas, and the forests of Liberia in West Africa.

In many places, cool spots are located near hot spots. This makes sense because in species-rich areas it is likely that many animals are affected whereas many others are not, due to their varying sensitivity to different threats.

There is room for optimism because all the threats mapped can be stopped by conservation action. But this action should be directed to priority areas, and it should have enough financial and political support.

An obvious first step is to secure threat-free refuges for particular species through actions such as protected areas, which are paramount for their survival.

To ensure the survival of highly affected species with little or no access to refuges, active threat management is needed to open enough viable habitat for them to survive. For example, tiger numbers in Nepal have doubled since 2009, mainly due to targeted antipoaching efforts.

Tackling threats and protecting refuges are complementary approaches that will be most effective if carried out simultaneously. The study provides information that can help guide these efforts and help to make national and global conservation plans as successful as possible.

• Allan, O’Bryan and Watson are academics at the University of Queensland. Their article was first published by The Conversation Africa and can be accessed here.