How do beaver dams reshape entire ecosystems?

The answer

Beavers are considered ecosystem engineers because their dams fundamentally transform landscapes. The largest known beaver dam, in Alberta, Canada, stretches over 2,790 feet (850 meters) and is visible in satellite imagery. Beaver dams create ponds that raise water tables, filter pollutants, reduce erosion, and create wetland habitats that increase local biodiversity by 30 to 50 percent. The ponds trap sediment and organic matter, creating rich soil. Beaver wetlands store significant amounts of carbon, buffer floods by holding back water during heavy rains, and slowly release water during droughts. When beavers were hunted nearly to extinction in North America, the loss of their dams contributed to the drying of vast wetland areas, a process now being reversed through beaver reintroduction programs.