A group of tree-sitters who were protesting expansion plans at the University of California at Santa Cruz came down over the weekend, ending a 13-month standoff, the Santa Cruz Sentinel reported.

On Saturday morning, university officials arrived with 90 police officers to try to persuade the protesters to leave the trees after months of failed negotiations. But the officials were surprised to find the trees already vacated, according to a spokesman for the university.

“We really are gratified this ended voluntarily and completely peacefully,” the spokesman, Barry Shiller, told the Sentinel. “Had there been occupants in the trees, we were still going to give them ample opportunity to come down voluntarily, without the need for any kind of extraction.”

The protesters were trying to prevent the construction of a biomedical-research facility on the campus, a project that would involve cutting down about 60 redwood and oak trees. But a spokesman for the protesters said they wanted to avoid the confrontation seen in September at the university’s Berkeley campus, where officials ended a similar protest only after building a giant metal staircase around a disputed tree to usher the tree-sitters down. —Josh Keller