A new study maps out how disruptive human changes to the environment affect the individual ranges of more than 5,400 mammal, bird and amphibian species around the world.

Almost a quarter of the species are threatened by human impacts in more than 90 percent of their range, and at least one human impact occurred in an average of 38 percent of the range of a given species.

The study also identified “cool” spots, where concentrations of species aren’t negatively impacted by humans.

The researchers say these “refugia” are good targets for conservation efforts.

Animals around the globe are losing ground to farming and ranching, and their numbers are dwindling at the hands of human hunters. But the question of where to direct precious resources to protect that biodiversity remains vexing.

This week, a team of researchers published a new study with the potential to aid that calculus, for the first time mapping out how disruptive human changes to the environment affect the individual ranges of more than 5,400 mammal, bird and amphibian species around the world.

“We’ve provided a framework that conservationists can now use to work out what specific actions they need to be doing in each place,” James Allan, the study’s lead author and a conservation scientist at the University of Queensland in Australia, said in an interview.

Allan and his colleagues began with related research that mapped the “human footprint” around the globe that used a set of eight of “the most harmful pressures humans exert on nature,” they write. These pressures encompassed human population density, ranches and farmland, and roads and railways.

The team then plotted out these threats in places where they’re known to diminish the ability of a species to survive in 30-by-30-kilometer (18.6-by-18.6-mile) grids. In all, the scientists looked at 5,457 animal species classified as near threatened, vulnerable, endangered, or critically endangered by the IUCN.

The analysis, published March 12 in the journal PLoS Biology, reveals that 84 percent of the land on Earth has at least one of these threats. For 23 percent of species — more than 1,200 types of animals — these threats occur in more than 90 percent of their range. And for 7 percent of the species, deleterious human impacts are present throughout the entire area they inhabit. If we don’t move to protect these species, the authors caution, they’re likely to disappear completely.

The study flags key “hotspots” where conditions for many resident species are dire, as well as “cool spots” where lots of species live unencumbered by human impact.

Nearly two decades ago, research published in Nature first identified “biodiversity hotspots” in places where wide ranges of species were losing substantial chunks of their habitat. Building on that “incredibly important piece of work,” this new study allows scientists and conservationists to probe more deeply into a broader range of threats, such as “the insidious hunting that occurs below the canopy,” Allan said.

The results showed at least one human impact occurred in an average of 38 percent of the range of a given species. In general, the most threatened animals — those tagged as critically endangered by the IUCN — faced threats across higher proportions of their ranges.

Piero Visconti, an ecologist at the International Institute for Applied Systems Analysis in Vienna, who was not part of the study team, said it was “remarkable” that the current paper matched the 2000 Nature study in identifying critical hotspots where lots of species face threats, including the rainforests of Southeast Asia and parts of the Brazilian Amazon.

“It means that all the conservation interventions that have been going on — it was well-invested money,” Visconti told Mongabay. “But clearly there is need for more because if they’re still ‘hot,’ it means that we haven’t done the job.”

He called the new analysis by Allan and his colleagues that identified these hotspots “valuable” and “insightful,” and added, “In terms of informing conservation interventions, this is probably a first step to identify which places just have a lot of species that are impacted.”

The researchers also found that the ranges of more than one-third of the species in the study were not impacted by the eight threats, though the scientists caution that that they may still be affected by other human activities. In certain “cool” spots, high concentrations of these unaffected species turned up.

Several of these cool locations made sense: the temperate forests of North America, for example, or the Arctic tundra. But much of the island of Borneo, as well as other parts of Indonesia and peninsular Malaysia — areas that are also home to many species that are impacted by humans — show up somewhat perplexingly as cool.

The authors explain that these places are packed with high numbers of species in general, and threats affect different species differently. A fence might be “catastrophic” for a small mammal or an amphibian, Allan said, but that alone wouldn’t likely affect a migrating bird.

Visconti voiced concerns — shared by other scientists, if Twitter is any indication — about how cool locations might be interpreted by decision-makers working out where to direct conservation efforts or looking to place new infrastructure developments. Would they make the assumption that the cool locations are also places with intact habitat? That might be the case in some spots, but not in others.

“It’s not clear to me exactly what you do, especially in places that are both at the same time a cold spot and a hot spot,” Visconti said.

To Allan, the cool spots are a reason for “optimism.” They act as refuges from human impacts (at least for some species), making them promising targets to proactively protect from human impacts, he said.

“That’s the simplest, most effective way to do conservation,” Allan said. “We know it works.”

The places where hot and cool overlap, he added, are prime places for both reactive and proactive conservation to simultaneously address the threats already having an impact on species as well as staving off the incursion of new threats.

The analysis also revealed that none of the threats is a “game breaker,” Allan said, a sentiment echoed by co-author and University of Queensland ecologist James Watson.

“All the threats we mapped can be stopped by conservation action,” Watson, also director of science and research for the Wildlife Conservation Society, said in a statement. “[W]e just need the political will and funding to do it.”

Conservationists also need to focus on improving the available data on threats and species, said Lucas Joppa, a computational ecologist and chief environmental officer at Microsoft, who was not involved in the research.

“Overall, this study represents an important step forward in understanding threats to species,” Joppa said in an email, adding that it brought “more clarity to this issue.”

“There’s still so much work to be done, though, because we have such limited data on both species and threats,” he added. “[E]ven the best global datasets on threats represent only a small fraction of known threats.”

Allan said that, as new research becomes available detailing the problems that species face, the team’s research can be updated and applied in new ways.

“We’re really open to talking to anyone about it,” he said, “so hopefully others take it in weird directions I can’t even imagine.”

Banner image of an African bush elephant in Rwanda by John C. Cannon.

John Cannon is a Mongabay staff writer based in the Middle East. Find him on Twitter: @johnccannon

Citations

Allan, J. R., Watson, J. E. M., Di Marco, M., O’Bryan, C. J., Possingham, H. P., Atkinson, S. C., & Venter, O. (2019). Hotspots of human impact on threatened terrestrial vertebrates. PLoS Biology, 17(3), e3000158. doi: 10.1371/journal.pbio.3000158

Myers, N., Mittermeier, R. A., Mittermeier, C. G., Da Fonseca, G. A., & Kent, J. (2000). Biodiversity hotspots for conservation priorities. Nature, 403(6772), 853.

Venter, O., Sanderson, E. W., Magrach, A., Allan, J. R., Beher, J., Jones, K. R., … & Levy, M. A. (2016). Sixteen years of change in the global terrestrial human footprint and implications for biodiversity conservation. Nature Communications, 7, 12558.

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