A helicopter with a shooter will fly over a portion of the vast Gila Wilderness in southwestern New Mexico next week, searching for feral cows to kill.

U.S. Forest Service managers approved the plan Thursday to protect sensitive spots in the nation’s first designated wilderness area. The move sets the stage for legal challenges over how to handle unbranded livestock and other stray cows as drought deepens in the West.

The Gila National Forest issued the decision amid pressure from environmental groups who raised concerns about nearly 150 cattle whose hooves and mouths are damaging streams and rivers. Ranchers, meanwhile, have criticized the plan to shoot cows from a helicopter as animal cruelty. They said the action violates federal regulations and will be problematic when carcasses are left to rot.