ASU Research E-Magazine: Grazing Habitats to Death

New Mexico’s Aldo Leopold Wilderness Area is named after the father of American conservation biology. Nevertheless, Arizona State University ecologist Robert Ohmart describes the riparian areas in the Aldo Leopold Wilderness as “beat to hell by domestic livestock grazing. It looks like a stockyard in there.”

The situation is much the same for streamside habitats throughout Arizona’s public lands, according to the Arizona Comparative Environmental Risk Project (ACERP). Other major stresses on riparian areas: water management through dams and reservoirs, and groundwater pumping.

The state’s only river not affected by water management is the San Pedro in southeastern Arizona. And now it is threatened by groundwater pumping from the town of Sierra Vista and the U.S. Army base at Fort Huachuca.

Healthy riparian habitats are vital to humans, says Ohmart, who served as a member of ACERP’s ecosystems committee. “The more we degrade them, the more we’re going to spend on water-treatment plants and buying bottled water. It’s costing us, one way or the other.”

Arizona Gov. Fife Symington established ACERP in February 1993. The project appointed technical committees on human health, ecosystems and quality of life to examine and rank Arizona’s environmental risks. ASU Botany Professor Emeritus Duncan Patten chaired the eco-systems committee. He and Ohmart wrote the section on riparian ecosystems.

“What I’m seeing is not just in Arizona. Public lands throughout the West are in very poor condition,” Ohmart says.

Ohmart grew up on a ranch in eastern New Mexico. Even today, he keeps five cows and a bull in his Chandler backyard.

“I’m not a big rancher by any stretch of the imagination, but cow pie doesn’t bother me.”

Many ranchers are concerned about grazing’s ecological risks but don’t know what to do about it. Other ranchers, however, dispute the notion that grazing degrades riparian habitats. But Ohmart has documented his findings with time-repeat photography.

“Show me where it’s not true,” he says. “Show me a stream that’s in proper functioning condition in Arizona. You can count them on one hand.”

Arizona contains about 260,000 dwindling acres capable of supporting riparian habitat along 5,000 miles of flowing streams. The entire state contains 73 million acres. One-tenth of 1 percent of the land thus supports 60 to 80 percent of Arizona’s wildlife.

“In general, I don’t have any problem with domestic livestock grazing public lands, but we’ve got to do a better job,” Ohmart explains. “Future generations are going to be left with one hell of a mess unless we start changing things today.”

Domestic livestock grazing eliminates riparian areas in two ways. Weighing between 1,000 to 2,000 pounds, full-grown cattle create erosion by trampling stream banks with their hooves. They also eat vegetation. This promotes more erosion, which prevents young trees and shrubs from taking root.

Fortunately, a grazed area can recover in a few years if protected from cattle. The White Mountain Apache Tribe removed the cattle from its riparian areas years ago.

Today, streams about 6 inches wide and 2 feet deep snake through the meadows of the White Mountains. The tribe has discovered that outdoor enthusiasts will pay good money to flyfish those streams for the endangered Apache trout.

Nearby, domestic livestock has devastated the streams of the Apache Sitgreaves National Forest, Ohmart says “People wonder why the Apache trout or the Gila trout is in trouble. You don’t have to be a rocket scientist to understand. I can show it to you in pictures why trout are in trouble.”

ASU law Professor Joseph Feller, a member of the ACERP Steering Committee, says that the ecosystems committee findings regarding grazing are likely to be politically controversial.

“If you talk to scientists, I don’t think you would find much surprise at the conclusion that grazing is a very major problem when it comes to eco-systems in the desert Southwest,” says Feller, who specializes in environmental law.

“That’s been documented over and over. But the livestock industry is a segment of the economy that is very sensitive to criticism.”

Feller said public debate on Arizona’s environmental issues make the ecosystems report important, even though it contained no scientific surprises.

Feller pointed out that ecosystems committee members did not call for the elimination of grazing on Arizona’s public lands. “They are identifying risks. They are not prescribing solutions. That wasn’t the role of the technical committee. Nor was it even the role of the project as a whole.”

The next step belongs to the steering committee, which will recommend an action agenda that will go to the governor and the Arizona Legislature. —Conrad J. Storad