The Rise of Beaver Dams are Changing the World: Increased Greenhouse Gas Release

Beavers may have once been on the verge of extinction, but they're making a comeback--and causing some unseen side effects. Scientists have found that these furry rodents have created more shallow standing water, and that they've caused the release of about 200 times methane than was the case in the year 1900.

In the sixteenth to nineteenth centuries, the fur trade nearly caused the extinction of beaver populations. Once trapping was limited and conservation efforts were put into play, though, the beaver population rebounded. Today, they've extended to their natural ranges.

That said, more beavers means more dams. These mammals create these structures in order to form standing open-water ponds and neighboring wetlands. These ponds are generally shallow, with dams seldom being more than 1.5 meters high. Yet one of the side effects of these ponds is that carbon builds up in their oxygen-poor bottoms and creates methane gas.

In this latest study, the scientists decided to assess exactly how much gas was being created. The researchers found that global beaver numbers have grown to a population of over 10 million. In addition, beavers have dammed up in excess of 42,000 square kilometers of aquatic bond areas, which are bordered with over 200,000 kilometers of shoreline habitat. Needless to say, this has also added to methane emissions. At the end up the 20^th century, beaver activities contributed 800 million kilograms of methane to the atmosphere each year.

"The dynamic nature of beaver-mediated methane emissions in recent years may portend the potential for future changes in this component of the global methane budget," said Colin Whitfield, one of the researchers, in a news release. "Continued range expansion, coupled with changes in population and pond densities, may dramatically increase the amount of water impounded by the beaver. This, in combination with anticipated increases in surface water temperatures, and likely effects on rates of methanogenesis, suggests that the contribution of beaver activity to global methane emissions may continue to grow."

The findings are published in the journal AMBIO.

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