They Paved Paradise and Killed the Fish

A group of Maryland state biologists, making an unusual series of public appeals about the environmental cost of unchecked development, are using the Severn River as a great example of a very bad thing.

The scientists, leaving their usual realm of laboratories and research vessels, have made presentations to county boards and environmental groups, including some in Charles County. Their message is that when too much of a river's watershed is eaten up by concrete and asphalt, the result is a cascade of mud and pollution that can deplete fish populations.

They say the Severn, where yellow perch populations have dropped sharply as streets and shopping centers have sprouted nearby, makes for a sad Exhibit A.

"It's our poster child for how bad things can get," said Jim Uphoff, a scientist with the Maryland Department of Natural Resources and a leader in the outreach effort. "I say, 'Okay, [if] you guys develop to this level, or past this level, this is what we've seen with yellow perch in the Severn River.' "

The relationship between concrete on the land and fish in the water is not an obvious one. Explaining why one hurts the other requires discourses on the absorbent properties of dirt and the oxygen needs of algae. But Uphoff and four fellow biologists from the Department of Natural Resources are trying to make the connection better known.

They call themselves the Impervious Serfs -- a joke, because they spend most of their time talking about so-called impervious surfaces.

These are parts of the land that have been covered in something man-made and solid, such as asphalt or a house, which water can't easily penetrate. When these hard surfaces cover more than 10 percent of a watershed, the area of land from which rainwater drains to a stream, problems begin to abound.

That's because the surfaces short-circuit nature's way of dealing with rainwater. Before the land was settled, the scientists say, the water would usually soak into the ground and would release slowly into creeks and streams.

But now, rainwater hitting hard surfaces is shunted into storm drains, moving at high speed. It erodes loads of dirt, which clouds the water, buries plants downstream and brings toxic chemicals and other pollutants that feed unnatural algae blooms.

These blooms are a particular problem because they consume underwater oxygen, which fish and crabs need to breathe.

"It's not just one thing," Uphoff said during an interview at his office across the Chesapeake Bay from Anne Arundel County in Stevensville. "It's multiple. There are multiple insults to the system."

There are problems with uncontrolled, polluted storm water all over the Chesapeake region: The Anacostia River, for instance, has historically had some of the worst troubles, with a watershed that is at least 23 percent covered in impervious surfaces.