Forget fire, timber millers, urban sprawl, and SUVs. The real threat is
........... the EARTHWORMS
Alien Earthworms Altering Northeast Forest Ecology
KINGSTON, Rhode Island, June 25, 2003 (ENS) Some forests across the
Northeast are changing, but most observers will not notice the changes
unless they take a close look at the soil beneath their feet. The driving force
behind the changing forests are increasing numbers of alien earthworms.
They play a key role in recycling nutrients in the soil, but they may also be
altering habitat for plants, salamanders, birds and other wildlife.
Only a few forest stands are known to be affected, according to University of
Rhode Island soil scientists Josef Gorres and Jose Amador. But they say the
threat to forests from exotic earthworms is real. Most of the earthworm
species found in the Northeast are not native to the area.
Gorres and Amador are evaluating the environmental impact of the common
nightcrawler, one of the region's 16 to 20 species of earthworms. While the
spread of the worms in Rhode Island has not yet been evaluated, the
researchers note that bait cups littering popular fishing spots suggest that
local forests may be affected soon.
"These exotic earthworms arrived here either in plant materials imported by
European settlers, from fishing bait that escaped, and some that were
imported here for use in composting," Gorres said. "Any native earthworms
that may have been in New England thousands of years ago were crushed
by the glaciers."
When earthworms move into a new area, they feed on the organic material
on the forest floor and bring it down into their burrows. They feed primarily on
the top layer of leaf litter, as well as on the duff - the spongy layer of
decomposing vegetation beneath the leaf litter.
Gorres said that while earthworms do an excellent job of recycling nutrients,
"when they eat away the duff layer, all the plant seeds that germinate there,
like trillium and mayflowers and wood anemone, may disappear or may not
have any place to germinate.
Other creatures that live in the duff and forest litter like salamanders and
ground nesting birds may be affected as well, the researchers said. Within
a decade or two, the worms can essentially change the soil profile into
something like the black mineral rich soils that are found in many European
Funded by the U.S. Department of Agriculture and the Rhode Island
Agricultural Experiment Station, Gorres and Amador have set up study plots
in local forests to evaluate the impact of the worms. They expect that over
time the leaf litter and the duff layer in the protected plots will disappear
because of the voracious worms.
"At some point, the number of worms that can survive in a given area will be
regulated by the amount of new leaf litter that falls," said Amador. "We'll also
see a change in the plant and animal communities that live there."
Geoff Read <g.read at niwa.co.nz>
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