The
Mighty Worm
6/21/2005
The Christian Science Monitor
By Keely Parrack
Look out the window.
See a patch of earth? How many worms do you think live there? Every acre is
home to as many as 1 million worms. This means that for every square foot (12
inches by 12 inches), there could be 23 earthworms.
Fossil evidence
shows that wormlike creatures have been around for more than half a billion
years. They existed in the time of dinosaurs and even survived the mass
extinction 65 million years ago - the one that finished off the dinosaurs.
Earthworms typically live anywhere that's not extremely hot or extremely cold.
Glaciers are
extremely cold. They also act like giant bulldozers, scraping off the top layer
of soil. So by the end of the last Ice Age in North America (about 10,000 years
ago), earthworms in what is now Canada and the US had been wiped out. Most of
the earthworms found today in North America are immigrants. They came here in
potted plants and ship ballasts from Europe. We're glad worms have found good
homes here, for the most part.
As settlers moved
West, worms moved with them. Worm eggs were carried on the soles of dirty shoes
and in horses' hooves. They hitched rides on wagon wheels and, again, in pots.
The worms arrived in California with the Forty- Niners during the Gold Rush. In
all, it took only 200 years for earthworms to make their homes all across
America.
Nature's 'ploughs of the earth'
Earthworms eat their
way through soil. They ingest bacteria and small particles and enrich the earth
with their waste products, called castings. The burrowing action also allows
more water and air to enter the soil, making it richer. This deceptively simple
creature is largely responsible for all the rich soil on Earth. Its journey
across America has created some of the richest farmland in the world.
Nineteenth-century
British scientist Charles Darwin, who wrote "The Origin of Species"
about evolution in 1859, studied worms. He wrote a whole book about worms
called "The Formation of Vegetable Mould Through the Action of Worms, With
Observations on Their Habitats" in 1881. ("Vegetable mould" is
what soil used to be called.)
Darwin called worms
"ploughs of the earth" because of their ability to eat soil and eject
it as castings. He believed that worm castings and the movement of worms were
wholly responsible for the top layer of rich soil. Darwin claimed that worms
were one of the most important creatures in the ecosystem. He also noted the
amazing ability of worms to bury things in the soil - from coins to Roman
ruins. Archaeologists should be very grateful for worms!
Wiggling in the dark
The worms in your
garden are probably nightcrawlers. They pull organic material - leaves, remains
of plants and animals - into their burrows. The best time to look for worms is
at night. Worms are sensitive to light and dig away from it.
Red wigglers are
another common worm, though probably not in your yard. They do not make
burrows. They feed on the surface of the soil, eating organic material that has
started to decompose. Red wigglers are popular with farmers and gardeners.
Their diet also makes them perfect for composting kitchen scraps into rich
soil. They are commonly used in worm composters. (These are special boxes with
trays and lids where worms digest household scraps - except for meat and dairy
waste.)
Red wigglers eat
half their body weight in food every day. Matt Abbruscato, owner of Foothill
Worm Farm in Pleasanton, Calif., does the math: "One pound of red worms
eats one-half pound of food per day. Thirty-two pounds of worms eat 16 pounds
of food waste a day." That's what he needs to feed his 30 bins of worms.
That's a lot of waste not going to a landfill.
Mr. Abbruscato sells
worm castings, red wigglers, and a fertilizer he calls "worm tea,"
made from worm castings. The "tea bag" is a large lump of castings in
a cheesecloth sack. It is steeped in water to create a strong infusion that is
poured over plants.
"Castings
provide a really good defense against pests," he says.
Abbruscato sells
mainly to private customers and to schools running composting projects.
Customers love the effects of the castings and worm tea. Roses grow bigger.
Vegetables taste better. Abbruscato says this is because chemical fertilizer
makes food taste blander.
Every three or four
months, Abbruscato's worm population doubles. But worms hibernate in winter.
Eggs won't hatch until the soil is 55 to 60 degrees F, he says. The eggs look
like little white pearls in the soil. When they hatch, they leave a brown shell
behind.
'I'll have the bluejeans special'
Abbruscato loves to
experiment with the worms' food choices. They definitely have preferences, he
says. "They will eat any organic material," he says. That includes
cotton jeans, shirts, and even "my wife's old nightgown. They went through
that in about four days."
He holds up what's
left of a pair of jeans - just the Levi's tag and the zipper. The worms like to
eat the bacteria and decomposing material. "With the jeans, they are
eating the bacteria that eats the jeans," Abbruscato says. When they eat
the bacteria, they end up eating the jeans, too.
In some places,
however, worms are seen as a problem. Forests from Minnesota to Rhode Island
are battling a worm invasion. Worm-free since the Ice Ages, these remote
forests have been getting on just fine without worms.
With the arrival of
worms in the past few decades, some forest floors have been cleared. The worms
have eaten all the leaves and decomposing vegetation underneath them called
"duff." Many seeds germinate in the duff. Without it, some seeds
won't grow, and some animals lose their habitat. Water runs off the empty
forest floor quickly, changing the drainage of the forest. The humble worm is
changing the ecosystem, wiping out some native plant species.
This sudden invasion
could have happened only with human help. The offending worms are probably the
offspring of fishing bait discarded at the end of the day.
Scientists are
working on ways to regenerate these forests. Car tires can transport worm eggs,
so road building is being halted in sensitive areas. Native plants are being
grown and replanted in the forests.
We are finally
realizing just how mighty the humble earthworm can be.
Some earthworms can be as long as your car
Most earthworms are
a few inches long, but some of the world's biggest worms can grow up to 22 feet
- longer than an SUV! Here are several examples:
United States: The
Oregon Worm grows two to three feet long, and it gives off the smell of lilies
when handled. It burrows five feet deep and is rarely seen. In fact, there have
been no official sightings since the 1980s.
The Giant Palouse
was found in Washington State. It grows up to two feet long - about the length
of a baseball bat. It hasn't been spotted since 1978. Population growth and
development may be to blame.
Australia: The Giant
Gippsland can grow to three feet, but it can stretch up to 10 feet. It's rarely
seen, but Australian farmers can hear gurgling sounds coming from the ground as
it moves through the earth.
New Zealand: The
North Auckland Worm grows 4-1/2 feet long and gives off light at night. It's so
bright you can read by its light.
South Africa: The
South African Giant Earthworm grows to be up to 22 feet and is the largest
earthworm known. The record-setting specimen was found beside a road in
William's Town, South Africa, in 1967. The worms normally grow to only about
six feet. (Did I say "only"?)
Worms can do that?!
* Some earthworms
can survive two miles below the surface, where temperatures can reach 160
degrees F.
* Some worms can digest
pollution. Scientists are figuring out if the worms could be used as toxic-soil
detectors, the way canaries were used as poisonous-air detectors in mines.
* The slime or mucus
made by an earthworm helps to keep its skin moist so it can breathe. It also
helps it move smoothly through its burrow.
* A snakelike
indigo-blue worm with white and yellow markings lives in the Philippines. It
crawls on the forest floor.
* Earthworms are
nature's power bars. They make a great snack for animals and are a key part of
the food chain.
(c) Copyright 2005. The Christian
Science Monitor
|