Environmental advocates have won a preliminary injunction against livestock grazing across 22,000 federal acres in Oregon slated for sage grouse research a decade ago.

A federal judge issued the order after finding the Oregon Natural Desert Association is likely to prevail in a lawsuit accusing the U.S. Bureau of Land Management of unlawfully scaling back research sites where grazing is prohibited.

U.S District Judge Michael Simon has determined the nonprofit would likely suffer irreparable harm if BLM reduced the number of “research natural areas,” or RNAs, by more than 30% and decreased their total acreage by 83%, thus hindering sage grouse studies.

“In the absence of a preliminary injunction, any research that scientists could conduct using ungrazed land would be statistically insignificant and therefore of little to no probative value in the sage-grouse conservation efforts for which the RNAs were created in the first place,” the judge said.

The BLM originally set aside 22,000 acres of federal land in 2015 as part of a broader effort to prevent the Greater sage grouse from becoming threatened or endangered across the West.

The agency was later sued by environmental advocates who claimed it was dragging its feet on shutting down grazing within 13 RNAs, prompting an earlier court order that required BLM to follow through with the plan.

Earlier this year, however, the BLM decided to formally revise the sage grouse land management plan for Oregon, cutting the number of RNAs to 8 and their total size to 3,700 acres, which the Oregon Natural Desert Association is opposing in its federal complaint.

The environmental plaintiff sought a preliminary injunction to prevent livestock from being turned out onto the RNAs, which the judge has now granted because it’s likely that BLM violated federal environmental and land management laws by shrinking the number and acreage of sites.

Though the BLM argued that its updated plan was owed deference, the judge disagreed, ruling the agency’s decision was probably “arbitrary and capricious” because it “failed to provide an explanation, supported by expertise, for reversing course on its earlier factual finding about minimum amounts of land necessary to do research.”

The agency didn’t sufficiently account for why the reduced RNAs would be adequate after initially claiming in 2015 that it had allotted the minimum number and size of sites to achieve research objectives, the ruling said.

The judge likewise discounted BLM’s arguments that it could still conduct sage grouse studies in areas that have been “lightly grazed” and “relatively unaltered,” finding the agency didn’t adequately support why this “change in direction” regarding baseline conditions was justified.

“The problem with BLM’s analysis is that although it makes statements about the limited effects of grazing on the land, BLM does not explain how opening the key RNAs is consistent with its previous position that it needed the 2015 key RNAs to conduct meaningful science,” he said.

Shutting out livestock from the RNAs shortly before the upcoming grazing season will be disruptive to ranchers, who “will now have to make last-minute alternative plans,” such as selling cattle or buying additional feed, the judge said.

Even so, it doesn’t appear likely that ranchers “will lose their business altogether” or that the injunction will affect their “livelihood for years to come,” the ruling said. Meanwhile, the economic harm would likely be outweighed by the damage to “restoring sagebrush communities for scientific purposes” if grazing were allowed.