By TIM FAULKNER/ecoRI.org
News staff
Why are so many Rhode
Island lakes and ponds infested with invasive plants? Boaters and fishermen
typically introduce alien plant life as stowaways in water and as fragments on
waders, boots and fishing gear, according the state Department of Environmental
Management (DEM). Once established, these invasive plants spread, flowing
downstream to other bodies of water.
In fact, early 60
percent of the state’s lakes have at least one invasive species, according to
DEM.
But the damage is not
all caused by visiting fishermen and boaters. Lakes and ponds without public
access also take in fast-growing plants through birds, wildlife, aquariums,
water gardens and landscaping. Arnold Pond in Coventry and Hundred Acre Pond in
South Kingstown likely got their infestations of Brazilian elodea from the dumping of
an aquarium tank in the pond.
Between 50 to 60
applications for herbicide treatment are approved annually by the DEM for lakes
and ponds across the state. Most are requested by a lake association; others by
a municipality or individual. Once approved, the applicant hires an outside
vendor to apply the chemicals.
Herbicides have both
financial and environmental costs. Treatments cost between $300 and $1,000 an
acre. Harsh chemicals such as 2,4-D and glyphosate are often used.
The June 17 treatment
on some 10 acres of water along the shoreline of Hundred Acre Pond used two
types of pesticides: flumioxazin and diquat. It was the third treatment in
three years and the fourth in more than a decade. Hundred Acre Pond also lies
downstream from turf farms, and fertilizers from the farms are suspected of
running into the pond to feed plant life.
Diquat is non-selective,
meaning it kills more than the targeted invasive plants. In the confusing world
of pesticide databases, diquat is considered an acute toxin by the Pesticide Action Network; the
Environmental Protection Agency (EPA) relies on a 1985 report from
the Chevron Chemical Co. to offer a mystifying assessment of the chemical.
Other groups consider flumioxazin and diquat toxic
to mammals and fish.
Kace Quinn, who lives
near Hundred Acre Pond, said the first pesticide three years ago coincided with
a sharp drop in smallmouth bass, pike and pickerel throughout the pond. "I
haven't caught anything besides sunfish in years," he said. "I'm
sorry to say that the fishing spots around the pond that my family has been
using for generations are completely empty.”
Bass, especially, are
having trouble making beds on the shore side, he said. Quinn suspects that
pesticides and herbicides have caused the fish to decline. “It's a shame that
my kids will never have the same experiences I have had in this cherished
location," he said.
Elizaberth Herron,
program director for the University of Rhode Island's Watershed Watch, said
herbicide treatments have become more regulated and effective since the state
began requiring the use of licensed applicators. Certain herbicides destroy
some plants better than others, and the timing of the application is important,
she said.
“In some cases there
aren’t a lot other methods available,” Herron said. “You don’t want to be use
herbicides in every lake all the time but in certain cases they can be very
effective.”
The DEM and several
state groups such as the Rhode Island Natural History Survey and Save The Lakes
have built an effective campaign to monitor invasive plants and the health of
the state’s lakes, ponds, rivers and streams.
Every New England
state, except Rhode Island, runs a boat-ramp monitoring program requiring
boaters to clean their boats before entering the water. Instead, Save The Lakes
organizes volunteers to oversee the boat inspection program.
Maintaining a balance
between boating, fishing and swimming and a lack of natural predators to stop
invasive plants often makes herbicide use a necessity, according to officials.
"All it takes is
a little piece of weed on a boat to introduce something to the lake," said
Save The Lakes president Judy Colaluca. Doing nohing is not an option with
invasive plants, otherwise the lake or pond can fill in, Colaluca said. "Once
it's gone, it's gone,"