The difference in the results of that study and the new one by CI lies in the way that wilderness was measured. The CI study considered population density and plant cover, while the October study also took into account the ways in which people use wilderness and other land.
Although the two studies took different tacks, the results are surprisingly similar, said Eric Sanderson, a landscape ecologist with the Wildlife Conservation Society and co-author of the human footprint study.
"The amazing thing is that if you compare the two maps using different data sets and different criteria, they are really more similar than they are different," he said.
North America's Wilderness Hot Spots
The CI study identified nine wilderness areas within U.S. boundaries. The major hot spots are North American deserts, which include the Sonoran and Baja Californian deserts, the Colorado Plateau, the Greater Chihuahuan Desert, and the Mojave Desert.
Although deserts and diversity may not seem to be a good match, many of these relatively arid areas harbor a wealth of plant and animal life.
"People get the impression that deserts are empty, void places, and they're not," said Tom Van Devender, a senior research scientist at the Arizona-Sonora Desert Museum in Tucson. "Once you live here, you get fascinated by them," he said.
The Sonoran Desert is one of the richest spots for desert life. "It's not like the Sahara or the Gobi," said Karen Krebbs, a conservation biologist at the museum. "It's really diverse."
The Sonora Desert covers about 100,000 square miles (259,000 square kilometers) across Arizona, California, and Mexico. Its range of habitats shelters approximately 2,000 plant species, such as columnar cacti and legume trees.
Protecting North American deserts and other wilderness areas is important not only because they're home for many species, but also because they help keep Earth running, said Gustavo Fonseca, executive director of CI's Center for Applied Biodiversity Science.
"They provide critical ecosystem services to the planet," he said. Such services include natural cleaning of water supplies and absorbing carbon dioxidefunctions that people, even wilderness lovers, might take for granted. Sanderson of the Wilderness Conservation Society said studies like the two recent ones are important in helping people make choices about the protection of remaining wild lands. "Organizations like WCS and CI hope that we all will make better decisions that allow wildlife and wild places, however defined, to co-exist with us," he said.
The CI study will appear in a new book, Wilderness: Earth's Last Wild Places. It is the third in a series of books that began with "Megadiversity" and "Hotspots."
SOURCES AND RELATED WEB SITES