Conservationists have been working to restore the population since as early as 1928, when Grey Owl (né Archibald Belaney), the original beaver believer, established his first colony with two baby beavers he found in the backwoods of Canada. In the 1940s, Idaho’s Department of Fish and Game embarked on an effort both larger in scale and kookier in method. Finding long, dusty overland trips too hard on the beavers, the department instead packed pairs of the animals into crates, loaded them onto airplanes bound for drought-stricken corners of the state, and dropped them by parachute. (The crates were rigged to open on impact.) The endeavor was apparently a success: a 1950 report notes that of the 76 beavers airdropped in the fall of 1948, only one fell to its death; the others began building dams and homes and founding colonies, which can grow as large as a dozen or so beavers.

Idaho’s strategy has since been validated by dozens of scientific studies illustrating the vital role beavers play in ecosystems. Their dams create ponds and wetlands that retain rainwater and snowmelt, and while beaver ponds themselves are shallow little affairs, research has shown that they help preserve groundwater, allowing vegetation and trees to flourish and increasing biodiversity. According to one study, the amount of fresh water a single colony adds to a local ecosystem each day is the equivalent of at least a once-in-200-years flood event.

To see a beaver today, I drove some 30 miles from Oakland, where I live, to suburban Martinez, California, where a beaver family has moved into the creek that cuts through town. There, a delightful beaver-believer couple showed me around the colony, pointing out the subtleties of beaver construction and anatomy, as a pair of yearlings swam below us.

The beaver evolved to live in and out of water, and the result feels a bit schizophrenic. Your standard beaver comes with webbed hind feet and a scaly, flat tail (perfect for maneuvering underwater and for balancing on land), as well as grasping paws and a pair of buckteeth. It is further equipped with nose valves that close underwater and eye membranes that act as swim goggles. Adult beavers weigh about 40 pounds and are appealing in the way squirrels are: they’re cute, but they’re still rodents. From a historical perspective, the beaver’s most fateful feature is its coat, a combination of thick underfur and longer guard hair that allows the animal to thrive in widely varying climes. It is rugged enough to let the beavers of northern Canada linger beneath the surface of frozen ponds, but light enough to help keep the animal cool during hot New Mexico summers. Unfortunately for beavers, these qualities also make for very fine hats.

Eastern Washington, where Amanda Parrish and her team are implementing their “Beaver Solution,” is today home to about 50,000 beavers, compared with a onetime high of perhaps 5 million. Because of rising temperatures, the snowpack is melting earlier and earlier in springtime, causing trillions of gallons of fresh water to gush down from the mountains, overwhelming streams and sluicing over the ground too fast to nourish the ecosystem.