Sheep and cattle in particular eat most of the native grasses, creating perfect conditions for invasive species such as leafy spurge to move in, explained Mark Salvo, director of the Chandler, Arizona-based Sagebrush Sea Campaign.
The campaign works to restore and preserve the 150 million acres (61 million hectares) of sagebrush steppe that covers the U.S. West.
Strategic Grazing
Seefeldt acknowledges that some public lands are overgrazed. But he says research is showing how domesticated sheep can be used to benefit the sagebrush ecosystem by ridding it of invasive weeds.
He and his colleagues have hand-picked a flock at the Sheep Experiment Station that shows a high preference for leafy spurge. The researchers use the flock in tests to determine the best time of year to set them loose on leafy spurge-infested rangelands, stopping the spread.
Salvo said such initiatives work in theory but they make little economic sense to livestock ranchers who rely on public lands to graze their sheep and cattle.
While sheep strategically graze leafy spurge on one section of land, ranchers would continue to graze the rest of the land as they have in the past, creating the conditions ripe for leafy spurge's spread, he said.
"So while we're in agreement with the suggestion that precision grazing in limited areas may help to check the spread, it's not doing anything long term if we don't remove the grazing pressure," Salvo said.
As an alternative, a coalition of environmental groups proposes that the federal government pay livestock ranchers to retire their allotments of public grazing land.
Private ranchers could then be paid to strategically graze their sheep on degraded land as part of the restoration process.
According to Seefeldt, putting strategic grazing programs to work effectively will require changes in how public lands are managed for grazing.
However, he said, some shepherds are already reaping the rewards of their sheep's rediscovered appetite for weeds.
"There are some people now who have flocks of sheep and all they do is graze weeds," he said. "They take them from one place to another, and they are actually paid to control weeds."
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