National Geographic : 2010 Oct
SATELLITE IMAGE: DIGITALGLOBE WHERE IN THE WORLD? Home Improvement Deep within Alberta, Canada's Wood Buffalo National Park, a massive engineering project is under way. The builders? Beavers. The job? Maintaining and expanding a dam likely begun by their ancestors decades ago. Today it's more than half a mile long---the largest beaver dam known to exist. Landscape ecologist Jean Thie spotted the structure in October 2007 while using satellite technology to study melting permafrost. "This is the beaver belt, " he explains, referring to the region's now dense population, which has rebounded from near extinction since the fur trade ended. Level, remote land also benefits these animals, letting them build without the nuisances and threats of fast-flowing water and humans. That means freedom to gather branches and mud for lodging and food storage, two keys to beaver prosperity. So how many beavers does it take to build such a dam? No one can say. But the colony is clearly vast---and resourceful. Says wildlife biologist Clay Nielsen, "Beavers are second only to humans in modifying their living space to fit their needs." ---Catherine Barker Visible from space, the world's largest known beaver dam stretches across nearly 3,000 feet of wetlands in northern Alberta, Canada.