Science: The Vanishing Earthworm

Early birds, anglers and farmers had bad news last week. Lumbricus terrestris —better known as the earthworm—is in serious trouble. U.S. Soil Conservationists Henry Hopp and Paul J. Linder have warned in Science magazine that the earthworm population in some sections of the U.S. is dipping alarmingly.

Color & Variety. To farmers who are not particularly worried about an earthworm shortage, Hopp & Linder point out that the earthworm is one of the world’s most efficient farmhands: it does an enormous amount of soil conservation. Toiling underground, the hard-working worms in one acre can eat, pulverize, fertilize, aerate and move ten tons of earth in a year’s time. Charles Darwin, who had a profound respect for the earthworm, doubted whether “there are many other animals which have played such an important part in the history of the world.”

Earthworms come in some 2,200 varieties, ranging in size from the one-inch species that inhabit old logs to the seven-foot Gippsland giant of Australia. Some affect bright colors, including purple, blue and green. Regeneration of lost tails—and sometimes heads—is only one of the worm’s accomplishments. A hermaphrodite, the earthworm carries both male & female reproductive organs in its many-segmented body. But two worms normally cross-fertilize each other; experts doubt that a single worm ever acts as both father & mother of its own eggs.

The U.S. earthworm population is declining because farmers have been scraping away the nation’s topsoil for generations. The five-hearted earthworm is coldblooded, cannot survive a sudden freeze. In free-plowed fields, where the earth is laid bare (and in entire areas, like the Corn Belt), earthworms die off in great numbers each winter.

Danger & Nerves. Hopp & Linder made a substrata survey of fields where there was no protective covering, discovered that all earthworm life was snuffed out in a single freezing spell. But in a burlap-covered acre, 995,000 worms survived; 1,610,000 slithered to safety beneath a protective acre of hay. The conservationists recommend a covering of chopped cornstalks or manure, or a quick-growing catch crop, to blanket the worms and tide them through the winter.

Freezing is not the only hazard in an earthworm’s uncertain life: burrowing beetles, bloodthirsty slugs, spiders and porcupines are all constant menaces. Worms stay below ground until nightfall, when they can safely emerge to do their courting and prowling. Living such a life, the earthworm is intensely nervous and sensitive to the slightest vibration of danger. Though blind, it has learned to pick up the tremors of an approaching sparrow and to snap back into its hole like a rubber band.