When you hear of a new development, usually you think of a new business, house or apartment complex. It might surprise you, if you live next to a park, to learn that new houses are rising all the time near you. They’re houses for wildlife, and they’re often built by beavers.

Beavers don’t know the difference between a nice, ornamental crape myrtle in your yard and a Virginia pine standing on parkland. That’s sometimes a source of disagreement as to the true value of beaver houses. However, a three-year study by U.S. Geological Survey (USGS) Ecologist Dan Kroes shows their value in streams.

The USGS study shows that dams and lodges, as beaver houses are properly called, are important to water quality. Dams trap as much as two feet of sediment that would otherwise go downstream. Sediment in water is what makes streams cloudy or murky. Not only are sediment-filled streams unpleasant to look at, they don’t allow sunlight to play its role in aquatic food webs. If there are lakes downstream, the sediment settles and may eventually fill those lakes. Witness Lake Accotink in Springfield. It was 23 feet deep  when it was constructed in the 1940s, and despite numerous dredging efforts, it was a mere four feet deep by 2018.

Beaver dams and lodges also slow the water tumbling downstream. By extension, they reduce stream bank erosion that undercuts banks and fells trees. They slow the pace of streams, which improves drinking water quality, increases stream life and decreases flooding. It’s development that’s good for the environment.