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Another alien earthworm in USA story

Geoff Read g.read at niwa.co.nz
Thu Jun 26 00:00:10 EST 2003

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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