With the threat of extinction hanging over beavers conservation efforts to save the tree-munching architects have led to other, unanticipated, consequences. Beaver numbers are not simply higher in the traditional habitats; beavers have been introduced into new territories, such as in South America.
As more beaver colonies form, the rodents have an adverse effect on the climate by changing levels of methane gas. This happens because beaver colonies are formed in ponds constructed by the beaver dams. These tend to be pockets of shallow water (no more than 1.5 meters high.) Within this oxygen-poor standing water, methane gas levels build up and the gas, because it cannot dissolve in the water, is eventually released into the atmosphere.
It is estimated that global beaver numbers now exceed 10 million. Beaver dams extend over 42,000 square kilometers and affect 200,000 kilometers of surrounding water.
Beavers currently contribute 0.80 teragrams (or 800 million kilograms) of methane into the atmosphere.
The research is published in the journal AMBIO (Journal of the Human Environment.) The research article is titled “Beaver-mediated methane emission: The effects of population growth in Eurasia and the Americas.”