Something 'Mind Blowing' Happened After People Built Artificial Beaver Dams
Beavers have recently become well known as environmental heroes, capable of transforming and regenerating landscapes to everyone's advantage.
The Scott River valley in northern California was once home to so many beavers it was known as Beaver Valley. Their dams created an enormous riverine wetland, providing habitat for juvenile coho salmon and a host of other wildlife. Then European fur trappers arrived in the 1830s and decimated the population, and much of the habitat created by their dams and wetlands was lost - taking with it the cold, slow-moving habitat favoured by coho salmon.
In their absence, an obvious immediate solution was to build artificial dams in order to recreate lost wetlands and boost the chances of threatened coho salmon. In 2015 the nonprofit Scott River Watershed Council built two artificial dams on a tributary called Sugar Creek. Wooden posts were hammered into the stream bed, interwoven with willow and conifer branches, then the gaps were plugged with gravel, straw and mud. Three years later, several more dams were built on another tributary, called French Creek.
From time to time, the remaining beavers even chipped in, repairing, modifying and sometimes expanding the dams. “When beavers do adopt a structure, their work is far superior to what we can accomplish,” says Charnna Gilmore from the Scott River Watershed Council.
The results were a huge success. Fish biologist Michael Pollock of NOAA called the results “mind blowing”.
The artificial dams held, creating around 97,000 square feet (9,000 square metres) of new habitat with the capacity to support more than 8,500 young salmon. Compared with areas where no new dams were built, the water in the restored habitats stayed cooler, avoiding temperatures known to stress the fish and slow their growth. Juvenile coho survival rates soared, from 8 percent before the dams were built in French Creek to 60 percent afterwards.
One of London's New Flood-Stopping Eco-Warrior Heroes: These beavers even stopped the local tube station from flooding.
