Unfortunately Ecological Abe
An observation came from a friend who had visited the national capitol. "It was nice, of course, but some of the monuments were grubbier than I expected." I didn't pay much attention to her comment at the time; Washington, D.C., is a major modern city as well as a virtual historical park, and major cities are dirty. It was no surprise that federal clean-up crews couldn't keep up with the crud.
That conversation took place a few years ago, but it returned to mind recently when I read an article in the May/June 1992 issue of Wildlife. It turns out that the Lincoln Memorial, at least, wasn't dirty mainly because of city grime. The mighty marble version of Honest Abe was playing host to a simple but populous ecosystem, leaving the monument befouled---and even endangered---by the by-products of life.
This chain of life began with midges, tiny flying insects that find the warm and once swampy Washington area a comfortable home. In their flying phase of life, midges mostly want to find mates to keep midgekind going. Under the right conditions, they swarm in uncountable hordes looking for Mr. or Ms. Right---a buggy singles-bar scene gone berserk. In technical terms, they have carefully synchronized reproductive phenology. More informally put, myriads of midges hear their biological clocks sounding the alarm all at once.
Actually, perhaps they see the alarm. Sunset sets the little flies abuzzing.
Like many flying insects, they are attracted to lights. Just at sunset, the National Park Service turned on floodlights illuminating the capitol's monuments, including Lincoln Memorial. There, the sheltering portico provided a haven for masses of courting midges, distracted from the business of breeding by the lights.
To other organisms, the midge swarms looked like a bountiful free lunch. The Lincoln Memorial's nooks and crannies harbored quantities of midge-eating critters, especially spiders. The predators barely had to work for a living, since so many confused midges were smashed into the statue.
The fat and lazy spiders, in turn, were numerous enough to draw bug-eating birds. Birds show no respect for monumental statuary, and they defecate whenever and wherever they must. The Park Service clean-up crews confronted dense bird droppings, cluttered spiderwebs, and flattened midges by the bucketful.
The organic debris was messy and not particularly good for the statue, but cleaning it away could do even more harm. The Lincoln Memorial also does collect city grime, which is simply the visible residue of air pollution. Many airborne pollutants are acidic---in fact, acid rain has been chewing away limestone buildings and marble statues all over the world. The Lincoln statue's marble is protected from the rain by the roof above it, but water washing away the buggy mess generates its own acid-rain effect. The cleaning water washes the pollutants into pores in the marble, and the acid seepage attacks the stone.
The National Park Service seemed to be in a perfect Catch-22 quandary. Its popular Washington tourist attraction couldn't be left in the dark; it couldn't be left filthy; but it also couldn't be eaten away by high-risk cleaning. Then someone had a bright idea: Find out when the midges called it a night.
The midges, it turned out, quit early. Most give up hunting mates by an hour after sunset. Last summer, as an experiment, the NPS decided to leave the Lincoln Memorial floodlights dark for another hour. Numbers of dead midges on the statue dropped by 90 percent. It was the beginning of the end for Lincoln's unplanned ecosystem.
It may be too much to hope for, but it would be nice if the feds gave an award to whoever saved both taxpayer dollars and the beloved monument with a little scientific research. While they're at it, maybe they should give awards as well to the workers who had to tally before-and-after midge corpses mashed on the statue.
