WASHINGTON — THERE ARE those of us who wax nostalgic about the Furbish lousewort and the Tennessee snail darter without ever having laid eyes on either one. They remind of the glory days of the environmental movement, when the presence of an obscure endangered species could stop mighty dam-builders after all other defenses had failed.
Today, alas, the spotted owl has merely slowed the loggers of the Pacific Northwest, who want to keep cutting the old-growth forest which is the owl's only nesting place. The Bush administration has worked out a compromise which conservationists think will erase the species gradually rather than abruptly. After that the loggers can keep sawing, because then it won't matter.
But it will. One of the most promising scientific announcements of the year makes clear why.
Developers, dam-builders, loggers and sympathetic officials scoff at environmental concerns about endangered species, worries that seem effete to hard-hat wage-earners and hard-headed engineers. But now and then there is proof of why even the most humble species should be protected, because some day it may save human lives.
The other day, researchers reported in the British scientific journal Nature that a substance nicknamed PAP interferes with the process by which the AIDS virus reproduces itself inside infected cells. This substance also inhibits herpes simplex, polio and influenza, and some forms of cancer.
Scientists said that by linking PAP molecules to monoclonal antibodies, they had produced in the laboratory a ''very effective'' weapon against the AIDS virus. It apparently has more potential than AZT, now the mostly widely used anti-AIDS drug, because it attacks the virus in both its active and latent stages.
This may be just another progress report in the desperate, long-running laboratory war against AIDS. And it could be the breakthrough victims have been praying for, the most important medical discovery of our time. So far, no patients have been treated with PAP.
Whatever the prognosis, this is the lesson:
PAP stands for pokeweed anti-viral protein. Its source is one of the most common weeds in our country. Everyone who grew up in the South is familiar with it; without encouragement, it shoots up in abandoned farmyards, roadsides and wastelands.
Although the plant itself and its roots are poisonous to man, when the first leaves of spring are picked, boiled, drained and boiled again, they are relished as ''poke salad,'' properly pronounced ''sallet.'' A staple of poor Southern households, it is the uncultivated equivalent of turnip sallet.
Millions of barefoot children have picked its leaves, squeezed its deep purple berries to make ink and chopped its stalks out of garden margins for centuries. Although primitive herb doctors were held in high respect, none predicted that someday pokeweed might turn back the most vicious plague of modern man.
Pokeweed is far from an endangered species. But suppose it had been.
Suppose there was only one surviving patch of it, as there was only one surviving stand of Furbish lousewort where they wanted to build that dam in Maine, as there is only one surviving colony of spotted owls among those old trees in the Pacific mountains. If that patch stood in the way of a new shopping center or highway, it likely would have been bulldozed away before anybody could consider a lawsuit to protect it.
The Endangered Species Act was passed to make such lawsuits possible. It has been protested ever since. The most common objections are that it blocks progress, costs jobs. The most common bumper stickers make fun of it. They jeer at the idea that the survival of a fuzzy little plant, a two-inch minnow or a bird that hoots in the woods should in any way inconvenience the reigning species, Homo Sapiens.
Aside from PAP, scientists have found possible weapons against AIDS in an extract of castor beans, in a compound from the root of the Chinese cucumber and in two substances taken from St. Johnswort, a small, yellow-flowered plant that grows almost everywhere.
Who knows, the Furbish lousewort may contribute something, too. Whether it does or not, we can feel better knowing it's still there: First, because every species has its own reason for being, which may never be known to man -- and second, because someday in the next millennium the survival of our own species may depend on it.