Beavers remove nitrogen from rivers

New research shows that beavers prevent harmful levels of nitrogen from reaching vulnerable estuaries. But their important role in the marine ecosystem is under threat from development.

Beavers were once highly prized for their fur. Now scientists are lauding their role in protecting marine ecosystems. New research from the University of Rhode Island shows that the ponds created by beavers slow down the movement of water and in turn prevent harmful levels of nitrogen from reaching the area’s vulnerable estuaries.

The danger of high nitrogen levels to marine ecosystems cannot be overstated. Nitrogen levels – which have soared in northeast waters due to the use of fertilizers and septic systems from urbanisation – can cause algal blooms and low oxygen levels in estuaries, where rivers meet the ocean. Both phenomena are linked with fish deaths. While most famous in the Gulf of Mexico, dead zones are increasingly becoming a problem along the coastline of the northeastern United States.

Researchers noticed that nitrogen levels were lower in estuaries when a beaver pond was upstream. They realised that since water moves slowly through beaver ponds, it allows time for organic matter to build up within the ponds that is capable of transforming nitrogen into nitrogen gas, thus removing it from the system. This process can remove between 5 to 45 per cent of the nitrogen in the water, depending on the pond and the amount of nitrogen present.

The research has some interesting implications and could change the way people think about beavers and their ponds.

“Most of these beavers are in areas with smaller streams, not big rivers,” says Julia Lazar, who conducted the work as part of her doctoral dissertation and is now working as an environmental consultant. “These smaller streams are usually the first to be developed, causing a decrease in beaver populations. So, it may be important to keep these areas from being developed so they can have effects on nitrogen levels downstream.”


Photo credit: Stewart Ho, flickr/Creative Commons

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