Restored marshes near Kingman and Heritage Islands sit in the shadow of RFK stadium in Northeast D.C. The marshes help return ecological functions to the urban Anacostia once provided by historic freshwater wetlands. Credit: Erica Goldman.

LAST YEAR, A CHILD TIPPED THE SCALES OF HISTORY. Since that birth, the world's population has shifted. More people now live in urban areas than in rural ones.

This waypoint is largely symbolic. We've been an urban species for quite some time. In China, over 600 million people live in cities. Shanghai alone is home to nearly 16 million. In New York City, the largest and most densely populated city in the United States, more than 8 million people live packed in a mere 305 square miles.

On the way to becoming the urban species that we are today, we've transformed our natural landscapes — sometimes beyond recognition. A patch of grass. A stand of trees. A degraded urban creek or river. In some places, these are the only reminders of the wilderness that came before.

In Washington, D.C., within sight of the U.S. Capitol, the Anacostia River has fallen victim to bygone agriculture and more recent urbanization. Much of the river has silted in. Left to accumulate the District's trash and sewage, it became a conduit for cholera, typhoid, and malaria. Its pristine marshes disappeared, replaced by expansive, polluted mudflats. Its story is a complex saga of changing land use and environmental decay, with strong subtexts of race and politics.

The wilderness that the Anacostia once embodied is long gone. Dense stands of wild rice, full of birds. Waters thick with fish. This ecological state of the river is relegated to historical accounts. But a growing push toward restoration aims to put some of that wildness back in the form of rebuilt marshes and parklands. And with less trash. These efforts hope to turn the clock back toward a greener, cleaner time.

Could a restored Anacostia River ever resemble the historic one? Or have the insults of urbanization changed the rules of the game too much? Sewage and stormwater. Invasive plant species. City-dwelling geese with an insatiable hunger for fresh vegetation. Are these realities of the urban realm compatible with a healthy natural system?

Probably. Given the opportunity, ecological systems tend to impress us with their resilience. We can provide a little nudge. Remove a few obstacles. Even the harshest, most degraded lands and water often prove able to support diverse plants and animals.

But what we expect from an engineered restoration effort might not be what we get. We can plant seeds, only to find that hardier invasive species muscle them out. We can tend young shoots, only to find them devoured by uninvited guests, non-native species that thrive in urban areas.

For the Anacostia River a restored ecosystem may reflect a new equilibrium, a new balance between the urban and the wild that can coexist in a city like Washington, D.C. We can have a vision for what we want that future to look like. We can set the course in motion — tend its progress, shape, steer. But what will happen when the time comes to let go?

— Erica Goldman