Article by Mike Gaworecki.
Mankind poses a number of threats to the survival of large carnivores, from hunting, trapping, and habitat loss to outright persecution by humans, especially in conflicts around livestock.
Many of these threats have been the subject of considerable scrutiny, but according to the authors of new research published in the Royal Society Open Science last week, no study has focused exclusively on range contractions for all large, terrestrial carnivores alive today around the world.
The authors — Christopher Wolf and William Ripple, both researchers at Oregon State University in the United States — set out to fill that knowledge gap by comparing current range maps for 25 large carnivores, which they defined as species of 15 kilograms (33 pounds) or more in body mass, with historic range maps for those same species. Their analysis, the researchers write in the study, “provides several key insights into how best to conserve threatened large carnivore populations.”
Wolf and Ripple found significant range contractions are common for the world’s large carnivore species, with 22 of the 25, or 80 percent of the studied species, having seen their range contract 20 percent or more. The red wolf’s (Canis rufus) global range, in particular, has shrunk almost entirely, with Wolf and Ripple quantifying the loss as 99.7 percent. The Ethiopian wolf’s (Canis simensis) range has declined by 99.3 percent. The range for four other species has also decreased by more than 90 percent: tiger (Panthera tigris, 95 percent), lion (Panthera leo, 94 percent), African wild dog (Lycaon pictus, 93 percent) and cheetah (Acinonyx jubatus, 92 percent).
“With the exception of the red wolf, all 13 of the large carnivore species that experienced the greatest percentage range contraction are currently both threatened with extinction (IUCN Red List status ‘Vulnerable’, ‘Endangered’ or ‘Critically endangered’) and have decreasing population trends according to the IUCN Red List,” Wolf and Ripple note in the study.
The six carnivores identified as having experienced the smallest contractions of their range were the Eurasian lynx (Lynx lynx, 12 percent), dingo (Canis lupus dingo, 12 percent), striped hyena (Hyaena hyaena, 15 percent), spotted hyena (Crocuta crocuta, 24 percent), grey wolf (Canis lupus, 26 percent), and brown hyena (Parahyaena brunnea, 27 percent).
The researchers did not include otters (Lutrinae) or polar bears (Ursus maritimus) in their analysis, as both are primarily aquatic species, not terrestrial. They also excluded the maned wolf (Chrysocyon brachyurus) because they could not find a sufficiently accurate historical range map for the species.
Wolf said that, based on their study of historical range maps, he and Ripple had determined that 96 percent of Earth’s landmass (not including Antarctica) once contained one or more large carnivores. Today, just 34 percent of the world’s land area contains all members of its historical large carnivore guilds.
Considering the fate of carnivores at the guild level — in other words, as a group of species reliant on similar resources — might be the key to crafting successful conservation strategies, Wolf told Mongabay. “Recent carnivore recoveries in Europe and the United States suggest a possible reversal of the long-term patterns of range contraction that we observed,” he said. “As major range contractions are common to most carnivores, conservation of entire guilds is critical to maintaining ecosystem function and preventing further extinctions.”
Historical large carnivore richness was highest in South and Southeast Asia, where as many as nine large carnivore species once coexisted in some ecosystems, and in Africa, which once had up to six co-occurring species. So it’s no surprise that the greatest declines in large carnivore richness were in Southeast Asia and Africa, which both lost 2.9 species, on average, and the rest of Asia, which lost an average of 2.8 species. Oceania, Europe, and the Americas have all lost an average of one or less large carnivore species (though it’s worth noting that 100 percent of historic large carnivores have been lost in some parts of Europe and the Eastern United States, in addition to Southeast Asia).
“We were surprised to see the extreme contractions for some of the large carnivore ranges,” Ripple told Mongabay. He and Wolf found that proximity to higher densities of rural humans, livestock, and cropland area made the decline of large carnivore ranges far more likely — a finding that would seem to contradict previous research showing that larger-bodied carnivore species are at greater extinction risk due to their need for larger prey and extensive habitat.
“Increasing human tolerance of large carnivores may be the best way to save these species from extinction,” Ripple added. “Also, more large protected areas are urgently needed for large carnivore conservation. We are not only losing the large carnivore species, but we are also losing their important ecological effects.”
A 2014 study for which Ripple was the lead author found that maintaining “ecologically effective” numbers of large predators is crucial to the health of a diverse array of ecosystems. “Large carnivores deliver economic and ecosystem services via direct and indirect pathways that help maintain mammal, avian, invertebrate, and herpetofauna abundance or richness,” Ripple and his co-authors wrote in that paper. “Further, they affect other ecosystem processes and conditions, such as scavenger subsidies, disease dynamics, carbon storage, stream morphology, and crop production.”
Wolf and Ripple stress in the Royal Society Open Science study that conserving what’s left of the world’s large carnivore guilds “can be accomplished… by expanding and strengthening protected area networks or by increasing human tolerance of predators.” Though growing rural human populations are driving range contractions, and further rural population increases are projected in the future, “many large carnivores are resilient, particularly when human attitudes and policy favour their conservation. This helps to explain the large carnivore recoveries observed in Europe and elsewhere (e.g. grey wolves in the continental United States).”
Likewise, there might be ways to mitigate the impacts of expanding pastureland and agricultural land, they write: “[A]lthough our results associate increasing cropland and cattle density with range contractions, this relationship may be limited when predator-friendly agriculture methods are employed — an area where more research and practice is needed.”
Ripple, W. J., Estes, J. A., Beschta, R. L., Wilmers, C. C., Ritchie, E. G., Hebblewhite, M., … & Schmitz, O. J. (2014). Status and ecological effects of the world’s largest carnivores. Science, 343(6167), 1241484. doi:10.1126/science.1241484
Wolf, C., & Ripple, W. J. (2017). Range contractions of the world9s large carnivores. Royal Society Open Science, 4(7), 170052. doi:10.1098/rsos.170052
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