Give fresh heed to the earthworm, mighty protector of the planet

On Books

February 01, 2004|By Michael Pakenham

If you are a gardener, or intend to become one, now's the time to commence dreaming. Give a warm thought to your vital partner, the earthworm, without whom there would be little or no compost on earth. Which brings me to The Earth Moved: On the Remarkable Achievements of Earthworms, by Amy Stewart (Algonquin, 240 pages, $23.95).

Stewart is a garden columnist for North Coast Journal in California and writes for other magazines and newspapers. Her previous book was From the Ground Up: The Story of a First Garden (Algonquin, 272 pages, $18.95). She insists she is not a scholar, but her research is formidably impressive, drawing on dozens of scientists.

Do you really want to read about creepy, crawly, slimy creatures? Yes. Take it from me.

Stewart writes only about earthworms -- not about caterpillars, cutworms, tapeworms or their like. But there are many varieties in her chosen taxonomic class, Oligochaeta. Night crawlers and red wigglers are most prominent.

Charles Darwin wrote his last book about earthworms. He was among the earliest scientists to trace their enormous contributions to the richness of soil -- and thus to life in general. He estimated more than 50,000 earthworms could inhabit an earth acre -- but modern scientists have found as many as 1 million and in rare cases as many as 8 million.

They consume leaves, decaying woody materials and soil, and produce "cast" or "castings," a charming euphemism for dung. "They alter its composition," Stewart writes of the earth in which they work, "increase its capacity to absorb and hold water, and bring about an increase in nutrients and microorganisms. In short, they prepare the soil for farming. They work alongside humans, extracting a life from the land. They move the earth, a remarkable accomplishment for a creature that weighs only a fraction of an ounce."

Earthworms delve several inches or even feet beneath the surface, rising at night to feed. One worm will eat something like a third of its body weight daily -- "a healthy earthworm population can move almost twenty tons of soil per acre." Their travels perforate the earth -- in a minuscule way, plowing.

Stewart writes clearly, and sometimes poetically. Her fondness for Darwin is unbridled and her enthusiasm for worms approaches adoration: "Worms are ruminators; they sift through whatever surrounds them, turn it over, explore it, move through it. They are deliberate creatures, in no great hurry, but always in motion, twisting and burrowing, shrinking and contracting, and eating. They spend their lives in a kind of active meditation. ... For a being with such a simple brain, they seem, in this way, almost thoughtful. ... They don't chirp or sing, they don't gallop or soar, they don't hunt or make tools or write books. But they do something just as powerful: they consume, they transform, they change the earth."

So, how much do you want to know about them?

Earthworms breathe through their skin and have no lungs. Their hearts come in pairs -- how many depends on the species, some have as many as five pairs of hearts. (No, no one has witnessed a worm playing poker.) They have several blood vessels. They have gizzards that grind food. They have brains, though primitive ones. They rest but apparently do not sleep. They are hermaphrodites, each with both male and female sexual organs -- pores -- both of which must match for mating. Small epigeic worms, like red wigglers, live for several years and reproduce quickly. A night crawler can go as far as eight feet down into the earth, rising to the surface at night in search of food. One can live as long as six years.

Worms seem extraordinarily resistant to predation or parasitism. They thrive on many varieties of protozoa and nematodes, and they seem resistant to many bacterial infections, though they share the gloomy underground with hosts of mites, bacteria, ants, spiders, millipedes, beetles, sow bugs, springtails, scorpions and fungi, all intricately connected in a "food web."

That's a trifling start.

I challenge you: However repulsive you believe earthworms are, if you read this book, they will emerge your friends -- earning genuine affection and respect.

Their ecology is intricate. Most of the earthworms in North America came from Europe with plant roots in the early Colonial periods. They moved west with plantings of various sorts and have been further distributed, by landscapers' containers, mud caked on ATV tires or horses' hoofs, even by fishermen dumping bait cans at the end of the day.

In the 19th century, European earthworms were introduced in New Zealand. The land in which they were planted became as much as 70 percent more productive. Some grasses increased by 20 times in worm-populated pasture. Grazing sheep flocks doubled.

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