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Amenities & policies
Ski Smuggler's Notch
Frogs, Ethanol, Herbicides, and Why We Should Care
First published on garden.org on December 4, 2008, by Suzanne DeJohn
Although the authenticity of Chief Seattle's famous "All Things Are Connected" speech
is disputed, the underlying principle rings true: Whatever man does to the
web of life on Earth, he does to himself. A story I recently read in ScienceNews reminded
me of this.
Biologists have been alarmed at declining amphibian populations for several
decades, with some species showing bizarre deformities such as extra or missing
limbs. Numerous species are near extinction, and scientists can only speculate
on how many undiscovered amphibians have already been lost. Conservation
groups declared 2008 the Year of the Frog to raise awareness about the problem.
Researchers have suspected that farm chemicals, specifically herbicides,
might somehow be involved but it wasn't until recently that a direct link
A Decade-Old Dilemma
In the mid 1990s, scientists noted high rates of limb deformities in frogs,
which were debilitating if not fatal. Initially, the cause for the sudden
increase in these deformities puzzled scientists. Subsequent research pointed
to tapeworm infection as the cause, but the reason for higher tapeworm infection
rates was unknown.
According to the November 22, 2008 issue of the journal ScienceNews,
ponds contaminated with atrazine, the second-most widely used herbicide in
American agriculture, contain many more amphibian-infecting flatworms than
unaffected waters. At the same time, the chemical appears to diminish the
ability of larval frogs to fight off these parasites.
Now add in the results of new studies, which show that phosphate pollution,
caused by fertilizer runoff, boosts algae growth, which in turn increases
snail populations. These snails serve as intermediate hosts for developing
parasitic flatworms, further increasing the parasites' population.
Picture a pond near an agricultural field that's been fertilized with a soluble
fertilizer and also treated with atrazine herbicide. Rain washes some of
the chemicals into the pond. The fertilizer feeds an algae bloom, which in
turn causes the snail population to skyrocket. The snails harbor parasitic
larval tapeworms that are released as adults and go on to infect frogs. At
the same time, the atrazine is affecting the frogs' immune system, leaving
them particularly vulnerable to infection. The frogs don't have a chance.
Because they live both in water and on land, amphibians are especially vulnerable
to toxins and changes in their environment. They also breathe and take in
water through their very sensitive skin. Many species reproduce in vernal
pools -- temporary wetlands that occur in spring -- the occurrence of which
is affected by changes in weather patterns.
Why It's Important
Why should we care about a few frogs? Many would argue that we should care
about these diminutive denizens just as much as we worry about the more charismatic
polar bears and pandas. Frogs and other amphibians are vital parts of the
food web and their decline affects the survival of other species. Closer
to home, various frog species are the source of chemicals used in human medicines,
including pain killers, antibiotics, and treatments for stroke, HIV, and
Amphibians have been likened to the canary in the coal mine -- species that
are particularly vulnerable to environmental toxins. Their alarming decline
may serve as an early warning that our health and survival may be in jeopardy,
too. Researchers have discovered that atrazine exposure in frogs causes a
reduction in male hormones. Atrazine activates an enzyme that converts testosterone
to estrogen -- the same enzyme found in humans -- leading to speculation
about a connection between atrazine and diseases associated with hormone
levels, including breast and prostate cancers. Several studies have shown
a possible link between atrazine and cancer; however, the U.S. Environmental
Protection Agency disputes these studies and deems atrazine safe when applied
properly. (The European Union banned atrazine in 2004.)
Herbicides, Corn, and Ethanol
The herbicide atrazine is widely sprayed on cornfields to control weeds.
According to a report by Minnesota Public Radio, each year Minnesota farmers
apply just under two million pounds of it. Nationwide, farmers use tens of
millions of pounds annually. And now even more land is being converted to
corn production to supply new ethanol-producing plants. Ironically, although
ethanol produces less pollution than gasoline when burned, farmers growing
corn rely heavily on synthetic pesticides. The net result may mean more,
not less, pollution.
What's a Gardener To Do?
Atrazine is available only to commercial pesticide applicators, so you aren't
using it in your landscape. However, gardeners nationwide apply a staggering
amount of lawn and garden chemicals. Consider using eco-friendly techniques
to control pests (including weeds) and improve soil health. Also, try to
purchase foods from local farmers -- you can ask them about their pest control
philosophy and practices. Become an informed citizen so you can make your
voice heard when opportunities arise.
For more information visit these Web sites:
Living on Earth:
Syngenta, maker of atrazine: