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Green Beat: Leave it to beaver

Monica Pearson is on a mission to bring back the frogs

  • Wed Jun 7th, 2017 6:00am
  • Life

By David Clements

Monica Pearson is on a mission to bring back the frogs.

Our region was formerly a better place for frogs because wetlands were more abundant. Many wetlands have been lost to development and farmland like the 11,000 acre Sumas Lake that was drained in the 1920s.

There are only so many areas left that could become “re-wetlanded” to become home for the endangered Oregon spotted frog, but Monica found a very promising one. I’ll let her tell the rest of the story…

“This project was proposed by the Vancouver Aquarium and Earth Rangers, who raised over $75,000 to help save the Oregon Spotted Frog.

“We identified a field where the historic wetland had been drained for agriculture but wasn’t in use any more because it was still too wet in Metro Vancouver’s Aldergrove Regional Park.

“Our goal was to learn about restoring a shallow marsh wetland specifically for Oregon Spotted Frogs, despite the presence of invasive Reed Canarygrass and American Bullfrogs.

“Research that I did a few years ago suggested that keeping a marsh shallower than 30 cm would be good for Spotties, and bad for Bullies, but it’s also great for invasive Reed Canary Grass, which we don’t want.

“When building a wetland, you need to be aware of your water budget. We weren’t certain that there would be enough to keep the wetland wet all year long, especially in a long summer drought.

“We expected that much of the wetland would dry up through the summer but less than two years after we had built the wetland in 2013, we discovered that the wetland was not only holding water year round, but actually getting deeper.

“Why? Beavers! Through some truly impressive engineering, some local beavers first plugged up drainage ditches, then re-routed water into those ditches from a nearby stream, and were filling it from the bottom. It was like filling a bathtub from the drain.

“The result was stable water levels through the whole year — a much better outcome than we ever expected! There are over 100 bird species using the site, dragonflies, fish and many native frog species breeding in the wetland.”

Alas, now the beavers are making the water too deep for their specifications, so Monica and her team are needing to try to further manage the wetlands, in connection with Metro Vancouver.

The surprise intervention of beavers in Monica’s project is encouraging in an age when so often our goals for rehabilitating nature seem out of reach, and we forget that creation itself might be able to lend a hand — or at least a paw.

David Clements, Ph.D. is Professor of Biology and Environmental Studies at Trinity Western University