POINT REYES NATIONAL SEASHORE, Calif.—Cows have grazed the slopes of this Pacific peninsula for more than a century, sharing the space with hikers, elk and sunbathing elephant seals. But their days of seaside munching may be numbered.

Environmentalists are suing the federal government in a case that could get the cattle kicked out of the park, about 60 miles north of San Francisco, arguing that the herds are harmful to wildlife and not a natural part of the landscape.

“This is a very sad use of a very special place,” said Karen Klitz, a Berkeley, Calif.-based board member of the Hailey, Idaho-based Western Watersheds Project, one of three environmental groups suing the National Park Service, the federal agency that administers the park.

The suit, also brought by the Center for Biological Diversity in Tucson, Ariz., and the Resource Renewal Institute in Mill Valley, Calif., demands the park service assess whether ranchers can graze cattle there.

According to the lawsuit, the ranching at Point Reyes detracts from its national park status. The suit said “many ranches typically reflect large commercial operations with substantially developed footprints, sprawling residential quarters for ranchers, trailers or other housing for employees, waste disposal pits and hundreds of cattle.”