Two Views, Same Waterway
It's not hard to see the difference cattle can make to a streamside ecosystem
From where the San Pedro River splashes across the Mexico border in southern Arizona to where it empties into the Gila River 125 miles to the north, the waterway runs much of its course as a wide, shallow trickle framed by eroded banks with scant vegetation. But cross a fence at the river not far from the town of Sierra Vista, and suddenly reeds, sedges and willows crowd the banks. The waterway is narrow and cool, and bird song fills the air. "In this area, the San Pedro has gone from a wide, beat-out stream to a luxuriant, cottonwood-willow gallery forest replete with songbirds," says Arizona State University ecologist Bob Ohmart.
The scene is not unlike descriptions of the region recorded three centuries ago by spanish explorers who wrote camping in lush forests next to cold, clear creeks, where cottonwoods and willows grew so thick they blotted out sky.
In today's Southwest, bird song and lush forests both are rare along streams and their banks, known as riparian zones. According to a 1995 National Biological Service (NBS) report, 85 to 98 percent of southwestern riparian forests have vanished since colonial times. The report lists these areas among the most endangered ecosystems in the country. "Virtually every serious study that's ever been conducted by independent scientists and by government agencies has come to similar conclusions that these systems are terribly degraded and need restoration," says Reed Noss, a coauthor of the NBS study and editor of the professional journal Conservation Biology.
Seventy-five percent of all endangered species that live in or move through this region depend upon the remnant streamside habitat. In New Mexico alone, the Bureau of Land Management has identified 111 "special status" species--drawn from various federal and state lists of animals at risk--that visit what's left of the riparian zones.
The cause of the deterioration? While dams, irrigation and invasive exotic plants have all contributed, experts pin much of the blame on grazing cattle, which trample vegetation and mow down ground cover, putting soils at risk of erosion. Every flood widens channels. "If we had vegetation in there to create blockage and slow the floodwater, it wouldn't come down like a shot out of a cannon," says Ohmart. Cattle also prevent new growth by dining on young shoots. And without shade, streams get too warm for fish.
To demonstrate what happens without cattle, the BLM started fencing off sections of some waterways in the mid-1980s, including a 40-mile stretch of the San Pedro. The protected area now boasts one of the highest densities of breeding birds in the world, including many rare species.
Six years ago, the agency set a goal of restoring 75 percent of western riparian areas to proper functioning condition by 1997. As of January, only 38 percent of those zones functioned as they should. "When that goal was first set, it was kind of a shot in the dark," says BLM biologist Andy Dimas. "We really didn't know what it might take to reestablish these areas."
Land managers do know that one key is costly fencing. Also critical is management of cattle to allow riparian areas to thrive. That requires the cooperation of ranchers--who as a group exercise considerable political muscle. According to Arizona Cattle Growers Association spokesman C.B. Lane, cattle have been unfairly blamed for damaged riparian areas. "Cattle have no more of an impact than any other factors," he says, "like highways or too much paving in the uplands."
Says NWF public-lands specialist Cathy Carlson, "We aren't advocating cattle-free public lands. But we have to recognize the exceptional values of riparian areas and not allow cattle grazing to wreck these areas and their value for recreation and for fish and wildlife." If the lands' owners--the nation's citizens--agree, perhaps streamside visitors in the next century will see the same sights Spanish explorers recorded so long ago.
NWF is working to ensure the health of streamside wildlife habitat on public lands in the West. To help protect public lands and stay informed about threats to them, write: NWF Land Stewardship Team, 2260 Baseline Road, Suite 100, Boulder, Colorado 80302. Or call and leave your name and address at 1-303-786-8001, ext. 50.