Our bucktoothed icon is hard-working and monogamous, steadfast and stable in the Canuck way. But beloved? Not when one drops a tree on your cottage or floods your land with its dam. These days, however, the beaver has a new brand: eco-saviour. An increasingly vocal group of scientists and conservationists believes the dam-building rodent is an overlooked tool to mitigate climate change – a natural remedy for our sick rivers and ravaged wildlife. Fly away with that, bald eagle.
Engineers with tails
It's the beaver's avid dam-building that makes it a star with conservationists. In 2002, when University of Alberta biologist Glynnis Hood was in the middle of getting her PhD, the Prairies experienced the worst drought on record. She watched the wetland dry up “right before her eyes.” But where beaver dams existed, the pond water remained. Poring through 54 years of historic aerial photos, records of beaver populations and climate data, she discovered that the ponds with active beaver lodges had nine times more water during droughts than ponds without dams. In dry summers, the beavers kept water from trickling out and built channels to guide the water in; they had more impact than any rainfall or drought. Dr. Hood says this wasn't a surprise to some of the older farmers, who often kept well-placed beavers on their land. Yet she would go to conferences where engineers would give presentations on river flow (with beaver dams in their photos) and never mention the animal. In wetland and river restoration, which in the U.S. has cost billions of dollars, the very creature responsible for shaping the landscape was largely absent from the discussion.
Natural pollution-busters
As an environmental engineer, the beaver is a full-service deal: raising the water table, increasing biodiversity, even cleaning up pollutants. In Washington State, where hot summers dry up forests and have caused severe water shortages, a pilot project found that beaver dams stored five to 10 times more groundwater reserves than rivers without dams, and slowed the spring runoff. And rather than casting the shadow of a concrete dam, they improve the view. Recent studies show that when beaver dams were added to wetland-restoration efforts, the population of frogs, toads and songbirds rebounded. Native foliage returned. The dams created waterholes for moose and other animals in times of low rainfall. They slowed down water flow in rivers and shored up banks, while preventing sediment and pollutants from being carried downstream. One study of a Russian river examined the impact of pollutants from a cheese factory: By the time, the water had passed through the dams, it was nearly as clean as before the factory. The 25 beaver ponds along the way appeared to be capturing the pollutants and breaking them down with bacteria.
Friends of the fish There is growing evidence that the presence of beavers improves endangered fish stocks. Beaver ponds are deeper, which means that they thaw earlier and freeze later, giving juvenile salmon more time to grow. The bark and branches that beavers drag into the water add nutrients and draw insects, which the young salmon eat. Deforestation and agriculture loosen the topsoil around many rivers and streams, which can suffocate life in a pond, but beaver dams prevent this from happening. In the past, beaver dams have been removed to create a single flowing river, or out of fears that the dams stopped the passage of adult salmon upstream. But the healthiest rivers are constantly changing and shifting – the very impact of beaver dams, which come and go. As Duncan Halley, a beaver researcher at the Norwegian Institute for Nature Research, points out, beavers populate six of the 10 largest salmon rivers in the country, without issue. Even in cases where beaver dams have been found to impede adult salmon, Dr. Halley says, no research has suggested that it was enough to affect river-wide populations.
