Ranchers often argue that cattle grazing is the best way to combat cheatgrass, an aggressive invader that has taken over vast areas of the Great Basin, destroying the native sagebrush ecosystem and fueling huge wildfires.
But a study published today in the Journal of Applied Ecology arrives at the opposite conclusion. Reseachers who studied 75 Great Basin sites invaded by cheatgrass found that greater grazing intensity promoted the alien’s spread.
“Our findings raise serious concerns regarding proposals to use cattle grazing to control [cheatgrass] in these systems where remnant bunchgrass communities persist,” wrote scientists from Augustana College, the U.S. Geological Survey and Oregon State University.
It’s long been known that livestock played a role in speading cheatgrass, an annual grass from Eurasia that is thought to have been accidentally introduced to the West by settlers in the late 1800s. The study attempts to develop a better understanding of the various factors that favor cheatgrass dominance in the Great Basin, which encompasses most of Nevada and parts of nearby states.
Using field observations and computer modeling, the researchers looked at grazing intensity, soil conditions, spatial gaps between native plants and biological soil crusts. The results indicated that grazing and trampling by cattle can reduce native bunchgrass cover as well as the beneficial biological crust, clearing the way for more cheatgrass.
The alien grass, on the other hand, is “extremely tolerant of even highly intensive grazing,” the scientists wrote.
Management of cheatgrass-invaded land, most of which is owned by the federal government, is an ongoing point of contention. Ranchers who lease public land for livestock grazing complain about grazing restrictions, while conservationists argue the U.S. Bureau of Land Management has allowed too much grazing.
The study suggests that land managers should watch for widening gaps in native vegetation and reduce grazing levels to prevent a cheatgrass take-over.
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