More than a hundred sites contain more than one at-risk species. The Massif de la Hotte region of Haiti, for example, is home to 13 species of endangered or critically endangered amphibian.
The researchers limited their study to mammals, birds, selected reptiles, amphibians, and conifer trees, because these were the creatures for which sufficient information was available.
"Known species in these groups form less than one percent of all species we are pretty sure exist in the world," Ricketts said. "The vast majority [of species] we've not named, and of ones we have names for, for most we have no good information on where they live."
Pimm, who is a member of the National Geographic Society's Committee for Research and Exploration, said the creatures identified in the study represent only about 1/1000 of all species on the planet.
Steps taken to protect these 794 known species in imminent danger of extinction will therefore protect a thousand times more species of fungi, plants, and insects that likely live in the same places.
"That adds bang for the buck," Ricketts said. He added that the research is intended to "put a face on the extinction crisis. These are the places where extinction will most likely strike next for the [groups of life-forms] we know."
The research also highlights a shift from historic extinction trends, Ricketts said.
A majority of recently recorded extinctions were birds that went kaput on islands. For example, the dodo, a large, flightless bird, famously went extinct in the late 17th century on the island of Mauritius in the Indian Ocean.
Modern day Mauritius shows up in the study as home to two endangered bird speciesthe Rodrigues warbler and the Pink pigeonand a critically endangered mammalthe Rodrigues flying fox.
Today the so-called extinction crisis has expanded to mainland areas rich in biodiversity, where a host of amphibians, reptiles, mammals, and plants are now threatened.
Only 39 percent of the species identified in the study are island dwellers, down from 80 percent of recent extinctions.
And only a third of the identified sites have legal protection. Most are surrounded by intense human developmentchopped forests, drained wetlands, crisscrossing roads, introduced diseases, and suburban sprawl.
According to Pimm, the extinction shift reflects the European pattern of colonization: Islands were settled first and thus first faced the ravages of humankind. Now that the mainland interiors are becoming settled, species there are feeling the impact.
Ensuring the long-term survival of these species will often take more than protecting their habitats. But Ricketts says doing so complements broader efforts to combat global warming and loss of species diversity.
And steps taken to protect species "dangling on the edge" will also protect untold others and conserve habitats, such as mountain forests, that capture and supply water to lowland farms and cities.
Beyond the bonus benefits, Ricketts said, "There are many people who thinkI'm one of themthat preventing extinctions is simply the right thing to do."
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