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Beavers, beavers! Read all about it! Exc

November 12, 2015

Beavers, beavers! Read all about it!

Excerpted from the South River Watershed Alliance November Newsletter:

“Those dam beavers: Can they save the world?
The North American beaver is common along the South River. They are monogamous social animals and are second only to humans in their ability to manipulate their environment. Their homes, called lodges, are built from branches and mud. A pair of transparent eyelids enable them to see under water. Beavers use their broad, stiff tails like rudders to steer under water, for balance while sitting on land, and to slap the water as a warning of danger.
The work of beavers make them a keystone species in maintaining habitats that are relied on by many other animals. In addition to wetlands, beavers create standing dead wood (by drowning some trees) which is inhabited by insects and in turn attracts bird life.
Researchers at the University of Rhode Island have discovered that beavers can change the chemistry of water by removing nitrogen from fertilizers carried by stormwater runoff. Nitrogen causes algae blooms that use up oxygen in streams, rivers, and eventually parts of the ocean, leaving nothing for the fish and leading to large “dead zones.”
Biologists were studying the nitrogen content of streams and noticed something odd: whenever there were beaver ponds upstream, nitrogen levels dropped. Beaver ponds slow down river water, and they mix it with organic matter, which must have an effect on river chemistry, but scientists didn’t know exactly what was happening in that murky water.
So they made soda-bottle-sized “ponds” that let them study variations on the conditions the beavers set up in their real-life ponds. And they found a kind of reverse nitrogen fixation process was occurring – call it “denitrification.” Bacteria in the dirt and the plant debris turned nitrates into nitrogen gas. The gas bubbled up to the surface and mixed with the atmosphere once more. In some cases, the level of nitrogen in the water dropped 45%.
The effect was most pronounced in small streams, which lead to bigger rivers and eventually to the ocean. Beavers often set up their homes in these tiny streams-or they did before they were trapped or driven away. Re-introducing them might completely change downstream chemistry, make these environments more livable not just for the beavers, but for their fellow creatures, too.”

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