Argentina released just 20 Canadian beavers into Patagonia in 1946 to start a fur industry, but with no natural predators, they multiplied into tens of thousands, building thousands of dams that flooded entire valleys and killed millions of native trees

Twenty North American beavers were introduced to Tierra del Fuego in 1946 for a fur industry. These beavers multiplied rapidly, creating thousands of dams and flooding native forests. The ecological changes caused by the beavers are extensive and difficult to reverse. Argentina and Chile have now agreed to coordinate management efforts for the invasive population. Removing the beavers offers the best chance to protect the region’s unique temperate forests.