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by Howard Fienberg April,
Those amphibians seem
to have it rough.
over six years, we've seen news stories about a global decline of frogs and
toads, as well as increasing numbers of amphibian deformities. No one knows
exactly what is causing them, but a link to chemical pollution has been the
most popular candidate.
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For a public raised on a cartoonish diet of toxic scares, it has a visceral
appeal. Monty Burns' nuclear power plant on the Simpsons dumps toxic waste into
the river, which produces three-eyed fish. Why shouldn't we suspect the same
kind of culprit when we encounter four-legged frogs in real life?
But these stories are not just about frogs. After all, unless a frog's name
is Kermit, he is not likely to evoke significant public sympathy. In some ways,
these stories are really about humanity. The frogs serve as environmental warning
signs, implying that the pollution we produce could easily cause the same problems
in us. So it should be no surprise that a new study linking deformed frogs to
a widely-used weed killer found an eager, if frightened, audience.
Published in the Proceedings of the National Academy of Sciences (PNAS), the
study linked the common herbicide Atrazine to developmental defects in a species
of frog. Laboratory experiments with the herbicide seemed to disrupt the hormones
in a species of male African frogs, adversely affecting their sexual development.
So, the decline in frogs could be linked to males with, ahem, diminished capacities
or, even scarier, hermaphroditic tendencies.
Only the results were limited to the lab. The real world might be quite different.
Do researchers actually know what is harming frogs? Unfortunately,
no. Do they know that humans are also at risk? No. It is not necessarily unreasonable
to propose that amphibians could serve as a kind of leading health indicator
for future human health difficulties. But chemical pollution is not the only
possible cause of the frogs' foibles. Many other factors have been fingered,
including global warming, excessive ultraviolet light radiation (caused by the
depletion of the ozone layer), heavy metal contamination, acidification of the
water, viruses and bacteria.
Following hard on the heels of the PNAS study came yet another frog study, this
one with a different focus. Rather than toxic pollution, this study centered
on a common parasite. Examining many different species of amphibians, researchers
found that trematode parasitic infections were strongly associated with the
frequency of limb deformities. This study, published in a less prestigious journal
Ecological Monographs (EM), appeared unlikely to garner any media reporting
But Carl T. Hall paid attention. Hall, a superb science writer for the San Francisco
Chronicle, happened to write the only lengthy, intelligent article on the PNAS
study. He followed up four days later with a lengthy story on the EM study.
The only other journalist to report on the EM study was Jeff Barnard, whose
Associated Press story has languished on the wire, unpublished.
Which study to believe?
Just because the EM study found a possible link to parasites
does not mean that the PNAS's proposed link to Atrazine is wrong. It is possible
they are both correct or both incorrect. Even if the parasite theory wins out,
humans may still be to blame for the problem. It may be that increased fertilizer
runoff could be increasing algae levels, which could lead to more snails (coming
to eat the algae) which could be carrying the parasite.
But there's not a lot to go on. We don't even know for certain if the observed
deformities are all that unusual, or that the frog populations are actually
declining. Frog deformities appear much more common nowadays than in the past,
but we have no baseline measurement for comparison. Frog-focused researchers
have been trying to collect systematic population data worldwide, but the work
is still in its infancy.
So, there's no end in sight to our amphibian confusion.
The sometimes poor media coverage of the amphibian decline has
not helped public understanding. But some toad tales are more embarrassing than
others. Boston's Metrowest Daily News had a scary article April 15 about a mutant
toad discovered by four-year-old Casey Dicken in a backyard swimming pool. Publishing
a photo, the newspaper described these two toads as "conjoined, un-identical
twins." It even included a reference at the end of the story to the pollution-deformed
frogs link. But three days later, the newspaper admitted it had hopped to conclusions
"Looks can be deceiving. It's as simple as that. To the untrained observer,
two toads enjoying a romantic moment together could easily be mistaken for an
exotic, two-headed mutant. ... But in the end, it was nature, not science-fiction,
that explained the apparent phenomenon. It was just a couple of horny toads."
Maybe we all should stop hopping to conclusions.
Read the original article at: TechCentralStation
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