It's not a good time to be a frog. The dodo was just one species of bird when it went the way of T-Rex. But according to some conservation scientists, we may be in an early stage of the extinction of an entire class of animals -- amphibians, including frogs, toads and salamanders.
More to the point, say anti-pesticide campaigners mixing animal metaphors, amphibians are canaries in the mine. Big Agriculture, they say, is polluting the world with chemicals, slaying our helpless aqua buddies. Humans, you're next.
If you haven't yet heard this narrative, be prepared. Friday is the 3rd annual "Save the Frog Day," billed as a worldwide event. It's a good cause, in theory. One-third of amphibian species are threatened. Some 200 species have completely disappeared since 1980. But what's causing this phenomenon? How do we tease science from ideological politics to settle on reasonable public policy responses?
Earlier this year, what appeared to be an independent website, FrogTV: The Story of a Frog, His Mutation and Your Health, premiered on the Internet, promoting the 'blame pesticides' line. Along with Save the Frogs, it features a rogue's gallery of alleged poisons: atrazine, Roundup, chlorothalonil. The takeaway: "Over half of the DNA found in frogs is also found in humans, so if these pesticides kill frogs, imagine what they do to us!"
The answer, almost certainly, is "nothing serious". The common use of pesticides does not harm frogs, let alone people. Basic science: Humans and nematodes (worms) are 70 percent genetically similar, but shared DNA does not equate to functional similarity. Heck, we share one third of our genes with daffodils. Amphibians are not proxies for humans. Frogs are permeable beings. They don't swallow water like we do. They absorb most of the moisture and some of their oxygen through their skin.
Why are frogs dying? Scientists agree the overwhelming cause is chytrid fungus, which is thought to have emerged from Africa. It coats a frog's porous skin, which cuts off its water supply and limits its oxygen. Climate change and habitat loss almost certainly make up most of the rest of the explanation. What about chemicals? Pesticides are concentrated in agricultural areas, which by and large are nowhere near sizable amphibian habitats. The frog population falloff is occurring at similar levels in all regions of the world, including in areas where extensive pesticide use is minimal or even nonexistent.
The pesticides-are-dangerous theory originated with and substantially rests on the credibility of the research of controversial University of California endocrinologist Tyrone Hayes. He's published numerous studies purporting to show that clawed frogs exposed to low doses of atrazine produce males with ambiguous genitalia and soprano-like croaks--hermaphrodites.
Hayes labels atrazine an "endocrine disruptor"--a novel, widely-circulated notion that exposure to certain chemicals can radically alter sexual development. The key issue: At what level of exposure might estrogen modifiers, which range from chemicals to nuts, tofu and dozens of other foods known as phytoestrogens, effect development? Could they be contributing to the decline in the frog population and by proxy to human health problems?
These are serious science questions. The endocrine disruption notion targeting pesticides and plastic additives is gradually losing favor among scientists. As for Hayes's work, the Environmental Protection Agency and independent scientists from around the world have determinedly tried to replicate Hayes's findings to no avail. Studies have consistently shown that "a risk to human health [from atrazine is] essentially nonexistent."
Most recently, in March 2010, Hayes authored a paper arguing that atrazine demasculinized frogs throughout all life stages. If pesticides are misused or overused, humans could be endangered and restrictions would be warranted.
But the science community is unconvinced by Hayes' singular contention that exposure to miniscule doses of pesticides is dangerous--the low dose endocrine disruptor theory. Australia's Department of Environment, Water, Heritage and the Arts carefully reviewed the study, finding the lab work flawed, and recommending no change to its conclusion that atrazine is safe as used.
Biologist Werner Kloas of Berlin's Humboldt University, who believes chemicals should be banned for precautionary reasons if the evidence is merely ambiguous, has found no impact on frogs at concentrations comparable to those investigated by Hayes.
Most recently, Yale School of Forestry & Environmental Studies professor David Skelly, who had long promoted Hayes' work, was flabbergasted to discover that deformities among frogs in field studies were lowest in farmlands, where pesticides are common, as compared to cities and suburbs. "[W]e found that in those kinds of landscapes where corn is being grown, the great majority of the ponds we sampled didn't have any deformities at all," he wrote. "To my knowledge (and I have participated in two EPA panels that reviewed available results) nobody else has been able to get this ultra low concentration effect."
So what's behind this broadside? Consider Frog TV, the anti-chemical attack forum that promotes Hayes' controversial findings as the rationale for its campaign. It appeared mysteriously in January to much viral fanfare. A little digging outed the source: It's a promotional campaign cooked up by Organic Valley, a key member of the Organic Trade Association, whose marketing philosophy is to exploit the crisis in the frog population and demonize conventional agriculture.
Environmental challenges are complex. Data is more important than ideology. If we don't rely on science to guide us, we might make the day for Whole Foods Market devotees, but it would have a devastating effect on the nutritionally poor and the world food supply. And by diverting the focus on the real problem, ameliorating the fungus, frogs will be no better off.