by Sara Dollen, City Wildlife
The District of Columbia’s compact urban environment might not seem like a haven for nature, except for pigeons, squirrels, starlings, and rats. But in fact, Washington, DC is home at least 390 vertebrate species and thousands of invertebrate species, according to the District’s Department of Energy and Environment’s (DOEE’s) 2015 Wildlife Action Plan. Why so many, and what can we do to preserve this biodiversity?
The basis of the answer lies with the foundation of all ecosystems — geology. The District of Columbia was built on an invisible geographical boundary known as the Atlantic Seaboard Fall Line, where two physiographic provinces, or geographic regions with distinct landscapes shaped by the area’s evolutionary history, climate, and geology, meet. The fall line divides D.C. diagonally from northeast to southwest. To the east, the Coastal Plain province, with its soft sediments and a flat landscape, dominates over half of D.C. West of the fall line, the Piedmont Plateau sports hills of exposed, weathered rocks and lots of freshwater streams.
It is no coincidence that D.C. was built on the Fall Line; many major East Coast cities, including Baltimore, Philadelphia, and Richmond, lie on the Fall Line, which was an attractive place for Native Americans and European colonists for several reasons. First, the diversity of landscapes meant there were varying soil types suited to a variety of crops. Plus, an abundance of flowing water provided fresh water and powered mills. Lastly, and perhaps most significantly, the Fall Line marked the point where waterways become too small for seagoing ships to continue inland, creating a natural place for a port.
But the geology shaping our landscape is not the only thing that makes DC biodiverse today. Washington, D.C. as a city has been relatively good at preserving natural space, making it one of the “greenest” cities in the U.S. The District has one of the highest percentages of parkland in the United States, with 24 percent of its total area reserved for parks. Moreover, with D.C. sitting right at the junction of the Anacostia and Potomac rivers, 10.6 percent of the city’s square mileage is water. And thanks in large part to the efforts of our friends at Casey Trees, tree canopy covers about 35 percent of the city. These terrestrial and aquatic habitats are key to D.C.’s biodiversity, which in turn explains why City Wildlife has admitted more than 18,000 wild animals representing more than 290 distinct species in our eleven years.
However, it is important to note that while D.C. is a leader in American urban biodiversity, the city’s nature is a miniscule fraction of the lush forests and wetlands which once covered the District. According to the Anacostia Watershed Society, 93 percent of the District’s historical tidal wetlands and over 60 percent of non-tidal wetlands have been destroyed. The DOEE has an interactive story map about the District’s lost streams. The extent of forest loss from historical coverage is unknown, but with less than 1 percent of old-growth forest left on the East Coast, all forests we have in D.C. today are at least second-growth. More alarming is that recent research by the National Park Service suggests that 9 out of 11 of D.C. forests fail to regenerate after disturbance because of natural and human-caused factors: climate change, invasive species, and diseases.
For these reasons and more, it is of the utmost importance that we all do our part to conserve the District’s remaining natural habitats and to foster the development of new habitats. People can support wildlife and wildlife habitats by staying alert for calls to action when habitats are up for development or when new conservation legislation needs support. Every voice, every action, and every show of support — no matter how big or small — matters for the future of the District of Columbia’s wonderful biodiversity.
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