A national report by REPUBLIC is naming the Boundary Waters Canoe Area Wilderness the most endangered public land in the United States.

The report was written by National Geographic Explorer Stephanie Pearson and warns that more than 640 million acres of public lands across the country are now, quote, “under siege.”

Despite its pristine, one-million-acre boreal forest and its status as the most visited wilderness area in the U.S., the Boundary Waters is facing growing pressure.

At the center of the concern are federal efforts to open parts of the region’s watershed to sulfide copper mining — a process widely considered one of the nation’s most toxic forms of mining.

Conservation groups have said these plans could threaten critical wildlife habitat, indigenous cultural homelands, and roughly 20 percent of the freshwater within the U.S. National Forest system.