Monday, May 23, 2011

Beavers mitigate climate change

The beaver's new brand: eco-saviour
Erin Aderssen, Globe and Mail: Our bucktoothed icon is hard-working and monogamous, steadfast and stable in the Canuck way... An increasingly vocal group of scientists and conservationists believes the dam-bulding rodent is an overlooked tool to mitigate climate change -- a natural remedy for our sick rivers and ravaged wildlife...

It's the beaver's avid dam-building that makes it a star in 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... But where beaver dams existed, ponds remained. Poring over 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... 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... A pilot project found that beaver dams stored five to 10 times more groundwater reserves than rivers without dams, and slowed the spring runoff.

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... They slowed down water flow in rivers and shored up banks, while preventing sediment and pollutants from being carried downstream... Beaver ponds appear to be capturing the pollutants and breaking them down with bacteria...

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... Even in cases where beaver dams have been found to impede adult salmon... no research has suggested that it was enough to affect river-wide populations... 'It's about $10,000 a hectare to replace wetlands, and you've got something to do it for free,' Dr. Hood says.
Image source here.