The analysis by American, African and British researchers -- which suggests that the continent's lion population has declined from 100,000 to roughly 32,000 over 50 years -- provides a clear picture of where the animals now live and how major land-use changes and population growth have put them in jeopardy.
"It's a shock," said Stuart Pimm, a professor for conservation ecology at Duke University and one of the paper's authors. "Savannah Africa has been massively reduced. ... As people moved in, lions have been hunted out."
The findings come just one week after the U.S. Fish and Wildlife Service announced that it will study whether African lions should be listed under the Endangered Species Act, a move that would end the importation of trophies into the United States. Several groups petitioned the agency last year to list the species, though some conservationists argue that trophy hunting provides a source of revenue to local communities, which helps keep savannah habitat intact.
Thomas Lovejoy, a professor in science and public policy at George Mason University, said the paper's authors "have made a historical contribution" by showing how dramatically Africa's viable terrain for lions has declined in recent decades. Lions used to roam much of Africa and Eurasia but are now limited to sub-Saharan Africa. A small population of a separate species inhabits the Gir Forest National Park of India.
Mr. Lovejoy said the fact that savannah habitat loss is outpacing the decline of the world's tropical rain forests "is terrifying when combined with the prospects of population growth and land-use change in Africa."
To reach their assessment, the paper's lead author, Jason Riggio, who received his master's degree from Duke, assembled a team of graduate students to examine high-resolution satellite imagery of Africa from Google Earth to determine what could qualify as suitable lion habitat. They then compared that information with existing lion population data, concluding that there are only 67 isolated areas in Africa where lions might survive.
Part of the challenge lions face is that when they venture outside national parks, they may kill livestock and come into conflict with humans, Mr. Pimm said.
Mr. Lovejoy said he was optimistic that sufficient public pressure will build for U.S. officials to take action. The officials will decide within a year whether to list African lions as endangered.
"This is something the public can easily get," he said, adding that lions are the kind of "animal cracker animals" everyone has revered since childhood.
The study does not, however, answer one of the central questions federal officials must answer: whether trophy hunting helps or undermines the species' ultimate survival.
Jeff Flocken, Washington office director of the International Fund for Animal Welfare, said Americans are responsible for importing 64 percent of the lions hunted for sport in Africa and that the practice destabilizes prides.
But hunting groups such as Safari Club International and some environmental organizations say a trophy ban could have unintended consequences.
Luke Hunter, president of the wild cat conservation group Panthera, said that even though he finds lion hunting "ridiculous and abhorrent, as a scientist, I have to ask myself whether it can be a tool for conservation."
While current studies suggest African lion hunting "is unsustainable," Mr. Hunter added, ending it could accelerate the large-scale land conservation that poses the greatest threat to lions. "The danger is you stop that revenue stream, all those areas are up for grabs."
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