Leslie Landrum stands atop Coon Bluff in the Tonto National Forest and surveys the fertile banks of the Salt River below.
Grasses grow between the gnarled trunks of mesquite trees and tall salt cedar bushes with reddish bark crowd the edges of the riverbank. Eighty years ago, though, many of these plants weren't here, says Dr. Landrum, an Arizona State University botanist. And now they're choking native plants such as willows and cottonwoods.
The loss of native plants across America - either from invasion of nonnative species or from land development - is of increasing concern to US scientists. In fact, the International Union for the Conservation of Nature says as many as 1 in 4 of the nation's native species is in danger of becoming extinct.
The problem is particularly acute in California and Hawaii, but it's also becoming more troublesome here in the Southwest, where the area's rapid growth is disturbing natural habitats. At stake, say biologists, is the future health of local ecosystems, as well as benefits that some plants may provide when studied further.
THE jojoba, for example, is emerging as an important species. A plant with leathery bluish-green leaves that grows only in the Southwest's Sonoran Desert, it produces an oil that is used in cosmetics, in cooking, and as car wax. The pulp can be used for animal feed.
For Landrum, along with three other scientists from ASU and the University of Arizona in Tucson, the race is on to document certain Arizona plants before it's too late. It's one of many similar projects under way across the country.
Yet even with 100 specialists contributing to the Arizona project, it will take another 30 years to complete at the current rate.
One problem is that botanists themselves are an increasingly rare breed. In an age of genetic tinkering and telescopes that can peer billions of light years into space, the work of cataloging plants is not considered glamorous enough to attract younger scientists, says Landrum.
For her part, Nancy Morin, executive director of the American Association of Botanical Gardens and Arboreta, says she sees signs that some younger scientists may begin to abandon the laboratory for the field. But she worries that by then there will be no one left to train them. "There won't be anyone to bridge the gap," she says.
Experts say the Southwest is one of the most diverse and least botanically understood areas in the US. The terrain is rugged and topologically diverse, ranging from scorching Sonoran Desert landscapes to snowy mountain forests. Many of the species that grow in isolated mountain ranges in Arizona and New Mexico are found nowhere else on earth.
Of about 3,600 species in Arizona, about 3,000 are native, Landrum estimates. According to Nature Conservancy data, somewhere between 10 and 20 percent of those are at risk. "It's getting harder and harder to find native species," he says.