For many years, ranchers have grazed livestock on public rangelands. But, intensive, extended grazing in some areas has taken a toll. Cattle favor some plants over others and have grazed some areas so heavily that some species of their favorite plants no long grow there. These are but the first moves in a complex game that appears to pit the cattle and cattle ranchers against the environment, environmentalists, and against people who enjoy the environment for recreation.
Wayne Leininger and Joe Trlica are looking for a new set of rules that will make everyone a winner. The two are rangeland ecosystem science researchers for the Colorado Agricultural Experiment Station. Since 1985, they've been finding ways to turn livestock grazing on rangelands from a problem into a tool to help manage forests.
The game takes place in riparian areas — the area around streams, rivers, and lakes.
"Riparian areas comprise only about 1 percent of the land area," says Trlica. "That's a small percentage for such an important part of the ecosystem. It's where everyone wants to picnic, camp, fish, and hike. When you add wildlife and livestock to the cluster on that small area of land, you have conflicts."
The Colorado State Forest Service and United States Forest Service have grazing regulations for forests, but those regulations aren't entirely based on research. They called on Leininger and Trlica to take a scientific look at how livestock affect riparian areas.
The two started their research by looking at the number of willows in riparian areas. The number and health of willows in a riparian area are a good yardstick for assessing grazing impacts for the simple reason that animals like to eat them. But Leninger and Trlica stress that willows are more than just food. Willows stabilize stream banks, filter sediments from runoff, provide habitat, and keep water cool by shading streams from the sun. By finding a way to help promote the growth of willows, they would be helping promote the entire ecosystem. The trick was to find a way to help the willows without detriment to the cattle, which gain the most nutritional value from grazing the abundant vegetation found in riparian areas during the spring.
Leininger and Trlica found that cattle eat willows only during certain seasons because of taste preferences and availability of other forage. They much prefer willows in late summer and early fall — just when willows are most easily damaged by heavy grazing.
The discovery allows ranchers and range managers to work together using grazing to enhance forests and rangelands. Encouraging grazing in riparian areas in spring or early summer, rather than late summer and early fall, gives willows more time to recover, preserving natural habitat.
In addition, the project shows that proper grazing does not affect water quality or vegetation on riparian areas. Previously, it was believed that because livestock kept native riparian grasses short near a stream, more sediment washed into the water, affecting its quality. However, Leininger and Trlica found that it isn't the height of riparian vegetation that affects the amount of sediment that reaches streams. Rather, it's the type of plants and the density of vegetation close to the ground that affects water quality.
Leininger and Trlica have shown that grazing can be used as a tool for controlling wildlife diversity because it helps determine the type of habitat in a riparian area, and habitat determines shade, food, and nesting resources for a variety of wildlife. For example, robins like areas that are mostly grass — ideal areas for livestock grazing. Other birds prefer to nest in willows, so they congregate in riparian areas with woody plants. The type of birds in an area affects both the birds' prey and animals that prey on them. By using cattle to create a balance of wooded and grassy riparian areas, range managers can balance wildlife diversity as well as livestock grazing.