Find ways to share the suburbs with the “engineers of nature” the beavers


Across the country, suburban areas such as Greenbelt, Maryland, and Arlington, Virginia, have wetlands, lakes, and streams that were created or reshaped by large brown, flat-tailed, orange-toothed rodents.

Beavers, like humans, modify their environment to meet their needs. Known as the engineers of nature, they knock down trees to build huts to live in and dams to raise the water level to protect themselves from predators. Dams also slow the flow of water while filtering out sediment and pollutants that would otherwise flow downstream. The resulting wetlands often attract wildlife diversity where there was none.

There are challenges, however. Beaver dams sometimes cause flooding and most people prefer live, upright trees. Communities face a delicate balance in learning to coexist with beavers.

In late 2019, many people enjoying the Washington & Old Dominion (W&OD) Trail near Glencarlyn Park in Arlington became beaver fans as a furry family transformed Sparrow Pond – a stormwater management area. artificial and filled with sediment – an oasis for muskrats, birds and frogs. , turtles and deer.

Yet such activity has raised concerns. As the beavers worked, they raised the water level by about 5 feet. The increased depth allows beavers to survive underwater if the pond freezes in winter. But county officials were concerned about the impact of rising waters on the steep bank of soil supporting the paved hiking and biking trail.

“As a local government, it is our job to strike the right balance between protecting the W&OD trail and the beavers,” said Lily Whitesell of the county environmental services department.

In April, the county installed a “beaver deflector” – a pond leveler. Beavers often rush to patch leaks in their dams. Baffles stabilize water levels by creating a hidden outlet for high water to escape through the dam, without the beavers noticing.

Beavers inhabit Buddy Attick Lake Park in the Greenbelt. Visitors love to see them but also love the mature trees in the park. Recently, Eagle Scout Andrew Jones, 18, hosted a tree caging event – placing wire mesh around large tree trunks to protect them while preserving beaver habitats.

“About 20 volunteers caged 60 trees to discourage beavers from gnawing and overeating,” Jones said. “It also protects people from injury from randomly falling trees. “

“We cover the trees we don’t want them to eat while providing others they love,” said Luisa Robles, sustainability specialist at Greenbelt. New trees are periodically planted just for the beavers. “We have to learn to give up some of our desires to share the Earth’s resources,” she said.

When water levels or food sources decline, beavers move. At Sparrow Pond, the summer rains brought in more sediment as the deflector kept water from rising. The beavers have not been seen for weeks. 8-year-old Saffiya Khan, whose family visits the pond periodically to view wildlife, said: “If the beavers are gone, I will be really sad.”

Heavy rains in late September brought good news for Saffiya. A beaver came back doing what the beavers do: check the dam for necessary repairs. The Sparrow Pond restoration project in 2023 will improve sediment management, restore appropriate water depth, and improve wildlife habitat without creating problems for the trail.

“A beaver baffle will also be included so that beaver families can make the pond their home in the future,” the project flyer said. The balancing act continues. Watch beavers build a dam in a “Leave It to Beavers” music video on PBS at


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