Ecosystem engineers: beavers restoring the health of wetlands

A beaver swims in her pond in the Elbow Valley, Calgary, Canada. © J. Ashley Nixon

Beavers are in the news again. Recent features in The Guardian have announced their release in large numbers in Britain this year, where they became extinct about three hundred years ago. The return of Castor fiber, the European beaver, to Scotland in 2009 was the first formal reintroduction program of a once native mammal which triggered many other informal rewilding efforts.

Beavers saved by silkworms

Other news about beavers has demonstrated some of the conflict points between cousin Castor canadensis and its human co-habitants in Canada, who have been associated culturally with this big rodent for a very long time. Surprisingly, it wasn’t until 1975 that it was turned into a national symbol, in large part a tribute to its resilience to avoid extinction in the middle of the nineteenth century. At the peak of the fur trade, 100,000 beaver pelts were being shipped to Europe annually to make fur hats and coats. Fortunately for Castor, fashions shifted to cloth spun from the protein fibre of the mulberry silkworm and the dam beast was saved.

Ecosystem Services

Stories of beavers chewing through internet cables, stealing fence posts and flooding out communities cast this semi-aquatic actor as the bad guy. But really, he, she and their kits are just doing what they have always done-change up their environment to make it a better place in which to live. Their creation of ponds by damming up moving water attests to their civil engineering capabilities but underlying that is much more: the provision of ecosystem services.

The construction of beaver dams and ponds creates new wetland habitat and increases species biodiversity. This green infrastructure helps retain sediment, countering soil erosion and holding back phosphates and nitrates that might otherwise enrich the water. Ponds also ameliorate stream velocities, help moderate stream temperatures and provide valuable water storage, especially important in drought conditions. An ecological study conducted by Glynnis Hood and Suzanne Bayley in Elk Island National Park in the aspen-birch woodland region of Alberta, Canada, supports this. They found that beaver was associated with a nine-fold increase in open water area during wet and dry years compared to when the beaver was absent from those same sites.

Putting that together, beavers are performing a valuable watershed stewardship role, both for nature conservation and our climate change adaptation. Whenever you see them, think past the chewed-up cables to the good things that come with the restoration and maintenance of healthy wetlands.

Other photographs and related stories

You can read Part 2 of this story, Constructed by Castor here. For other photography of the natural heritage of Canada, including the Elbow River, click here.