From the Glenwood Springs Post Independent (Julie Sutor):
By the mid 1800s, American beavers were on the brink of being wiped out, and their salvation and eventual recovery hinged on the whims of fashion: In the 1840s, silk top hats replaced beaver-felt hat as the must-have headwear. By the 1870s, beaver populations began to slowly rebound in Colorado. However, their return was slowed by mining and agriculture, which infringed on their habitat and diverted and polluted their waters. “Beavers have always had a tough time in Colorado, whether from trapping for their pelts or from development,” said Randy Hampton of the Colorado Division of Wildlife. In the last 50 years, as environmental regulations improved water quality and habitat, beavers at last staged their comeback in the Rockies. “Beavers have responded fairly well, and now they’re found pretty much everywhere around the state where there’s water,” Hampton said.
Beavers are a keystone species, meaning that their presence will dictate the overall health of their ecosystem. Their incessant activity in creating dams along streams and rivers fundamentally alters riparian areas, leading to the formation of pools, ponds, wetlands and meadows, which all serve as habitat for other species, including fish, plantlife, amphibians, deer and other wildlife on up the food chain. Without beavers, fish lose important breeding and spawning areas, as waters run too cold and fast for reproductive activity. That impact to fish then cascades throughout the entire ecosystem. “Beavers do more to shape their landscape than any other mammal except for human beings,” [Alice Outwater] wrote.
More conservation coverage here.