Green Goes Underground

Sunday, April 16, 2006

The Metrorail system operates along 106 miles of track, much of it underground, some of it deep underground. Its subterranean tunnels, dimly lit and lined with concrete, are hardly the place one would expect to find much life, but life there is.

The Woodley Park-Zoo/Adams Morgan stop is one of the deepest stations in the Metro system. Its platform is more than 150 feet below street level and features barrel-vaulted concrete ceilings, ceramic tiled floors and not an ounce of natural light. Yet dozens of specimens of Adiantum capillus-veneris , or common maidenhair fern, provide surprising splashes of green amid the station's dark grays, browns and shadowy blacks. These ferns have made a remarkably innovative choice of habitat, says Andrew Baldwin, a professor of botany at the University of Maryland.

Along the base of the station walls are banks of fluorescent lights that shine upward. In the quiet between trains, one can hear the trickle of water as it seeps through cracks or drainage holes in the concrete walls. There, in the light and the water, a soft, spongy moss grows, which provides a foundation upon which the ferns can take root.

The dampness- and limestone-loving ferns grow along almost the entire length of the station's 300-foot-long platform. Some appear quite healthy, sending branches and leaflets up through the metal grating that is designed to protect the fluorescent tubes. Because the ferns are on the other side of the tracks from the platform, they grow without human intervention.

The Metro's species of maidenhair fern is not catalogued in Maryland or the District, and in Virginia it is known to exist only in Wythe County far to the west. It is listed as endangered in North Carolina and threatened in Kentucky, yet it is thriving in the Woodley Park-Zoo/Adams Morgan Metro station.

The underground stations of the Metrorail system are sterile by design, so it is ironic that one should host such a growing colony of plants. But the plants make do with what they have, where they find it. Survival is like that -- unpicky, because the choices are few for any given species.

The ferns took a chance. The tiny spores, perhaps arriving at the station stuck to the exterior of a train or carried down the escalator shafts by the wind, chanced upon suitable conditions and germinated in a setting far from natural, finding a niche where they can be protected and undisturbed.

What would happen if someday this Metro station were abandoned by people and left to natural forces? Almost certainly, the space would be claimed by mosses and plants, insects and animals that, given adequate amounts of light, water and food, would gladly make themselves a home in a concrete tunnel 150 feet underground.

-- Matthew D. Taylor

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