The stream valley near Baltimore-Washington Airport is not what you would call pristine. Yet it somehow has managed to harbor a rare flower, the swamp pink, that has almost disappeared in the wild.
About 100 of these flowers have held their own since they were discovered there in 1984. That an entire colony of the rare flowers should exist along the axis of one of the fastest-growing corridors in the country is little short of miraculous.
On one side of the valley are the railroad tracks, where Amtrak and MARC trains roar by. On the far side, the earth has been leveled to make way for a sprawling industrial park. Smack down the middle of the valley, a sewer line runs parallel to the stream, the route defined by concrete manholes popping from the moist ground like mutant mushrooms. Even the sky above bears witness to human domination of this landscape, as the jets taking off every few minutes from the airport drown out the first tentative songs of the spring peepers.
This might seem an unlikely place to search for rare and delicate flowers, but Andrew Moser had come there one afternoon in early May to look for swamp pinks, Helonias bullata, a member of the lily family listed by the federal government as a threatened species throughout its original range from New York to Georgia. The state lists the flowers as endangered in Maryland.
Mr. Moser, an endangered species biologist with the U.S. Fish and Wildlife Service, quickly found proof that the stream valley still supports an array of life. Looking down into the clear, fast-flowing water, he spotted a crayfish scuttling along the bottom. "This water looks fairly nice," he observed, an indication that the habitat here remained healthy.
He found further evidence just a few yards away, where something long and black suddenly rustled through the thin branches of a bush. "A black rat snake," he observed, "They're the best climbers around."
Somewhere out there along the swampy banks of the stream were the swamp pinks. And this was the time of year for them to bloom. Discovered when the state wanted to do some clearing of trees on some of its land at the airport, the flowers have been monitored since then.
Mr. Moser was not optimistic about finding any in bloom. Under ideal circumstances, only a relatively small percentage of the plants actually put forth blooms. Among such a small population, three or four blooms would represent a good year. No flowers had been reported in the last several seasons.
Threading his way among the oaks and maples, Mr. Moser searched the spongy ground. Then he spotted what he was looking for, almost completely covered by leaf litter: a ground-hugging circle of greenish brown, blade-shaped leaves radiating like spokes. And, rising from the middle, one coiled bright green shoot, this year's new growth.
"I doubt it's going to bloom, such a small sprout," said Mr. Moser. Swamp pinks tend to grow in clumps, and soon Mr. Moser had located several more groups.
Then he spotted what he had not expected to see. "Here's one in bloom," he called. There it was: a thin green stem about 2 feet tall topped by a cone of tiny pink blossoms. A few feet away he spotted yet another. A little more searching turned up two more plants in flower.
That four of these plants should have bloomed was remarkable, especially when you consider just how narrow are the conditions needed by swamp pink to survive.
The key is water -- plenty of it, but not too much. Think of the swamp pinks as creatures that need to keep their feet wet but their pants dry. As their name implies, they are found in swampy areas, but not in standing water. The water table has to be high, at or just below the surface. But if the area is subject to flooding or holds standing water, the flowers are unlikely to flourish.
Compounding their situation, swamp pinks don't propagate well seeds. Mostly they spread through what biologists call clonal rhizomal growth. In layman's terms, that means new plants sprout from the spreading roots of older plants. Reliance on such clone strategy can be very risky. A plant that reproduces well through seed production can get through an occasional dry summer. The seed will survive even if the mother plant does not.
But for a plant like swamp pink, a single season dry enough to kill the adult plants probably means the end of the colony.
So the miracle of the swamp pink near BWI is really the miracle of thewatershed in which it persists. Despite the development going on all around, the water levels remain constant enough to sustain the flower.
"There's probably something underneath, like a clay area, holding the water up," Mr. Moser surmised.
The flowers still grow at five sites in Maryland, including one other place in Anne Arundel County. Dan Boone, an ecologist with the Wilderness Society, suspects that swamp pinks may once have been much more common around the airport, but that they have now retreated to this one little refuge along the stream. The stream and the associated swamps represent in his image "a lifeboat of sorts" for the swamp pink and other rare plants in the area. "It's a stronghold for biological diversity," he said.
Even though this stronghold has held out so far, it remains extremely vulnerable to changes in drainage patterns. The area the swamp pink inhabits could remain undisturbed by human activity, but the flowers could still die if changes in drainage upstream were to alter the stream flows or underground seepage patterns that maintain the crucial balance of the water table.
That's an issue that the Maryland Aviation Administration has to keep in mind as it moves ahead with plans to expand the airport. For example, a new east-west runway that the state hopes to construct late this decade would be built in the upper reaches of the swamp pink's watershed.
Michael C. West, the aviation agency's associate administrator for planning and engineering, said the runway project would be designed so as to not harm the rare flowers. As part of an environmental impact study of the project, state and federal environmental agencies will make recommendations for protecting the plants. The state would then adopt in its designs "any special features we could incorporate in the project to make sure there would be no effect on the plant," Mr. West said.
The main protection the state can offer now is to leave the habitat undisturbed by keeping people away. That means keeping secret the exact location of the plants.
The state's Natural Heritage Program has the prime responsibility for protecting the flowers. Katharine McCarthy, a coastal plain biologist with the Natural Heritage Program, thinks construction of a new runway need not harm the flowers if sufficient precautions are taken to preserve water flows. "My guess is that it's far enough from the population [of swamp pinks]," she said of the runway. "If it's done well, it will not be a problem for the species."
She admires the plant's ability to hang on despite the development going on all around it. "Barring some disaster, I'm optimistic for it in the short term," she said.
The long term is another matter. Because the new cloned swamp pinks are genetically identical to their parent, the rare flowers near the airport may have difficulty adapting to climatic changes such as global warming, Ms. McCarthy said.