Jack W. Dini
(This appeared in Plating & Surface Finishing, 94, 37, December 2007)
Hideously deformed frogs, multiple legs sprouting from their various body parts, are the poster amphibians of the environmental movement. Their fragile eggs are supposedly poisoned by agricultural pesticides and other insidious chemical slough, exposed to global warming, and to radiation streaming through the ozone hole. Frogs are utterly defenseless against man’s corruption of the environment.
So, what’s your reaction when you hear about these deformed creatures? A lot of folks would respond the way researcher Stanley Sessions of Hartwick College did when he heard about deformed frogs in Minnesota. “Actually, when I first heard about the Minnesota situation, I immediately suspected a chemical substance,” Sessions admitted. “That’s the first thing everybody thinks of. You see a screwed-up animal in the field and that’s the conclusion you jump to.”(1) Not even Sessions, who ultimately debunked the chemical substance issue with frogs, could ultimately resist the temptation.
Following this line of thought, let’s go on an excursion into the world of frogs to see how the public consciousness has been shaped by the media and environmentalists.
Yellow-legged frogs of the High Sierra
Bonner Cohen reports, “The mountain yellow-legged frog, Rana muscosa, began disappearing from the Sierra Nevada Mountains in the first half of the twentieth century, and the amphibian’s decline has become even more pronounced in recent decades. Today, the frog is absent from almost all the Sierra Nevada’s high-altitude lakes where it once thrived. The frog’s seemingly inexplicable demise has provoked much speculation in the media and among scientists, with parasites, ultra-violet radiation, fungal disease, and especially pesticides blamed for the frog’s troubles. (2)
Pesticides and herbicides drifting into the mountains from California central valley farmlands became the favored culprit, and the media and environmentalists played it to the hilt. A minimal amount of data, generated by the US Geological Survey (USGS) was all it took to spawn the inevitable lawsuits by environmental activists. They sued the California Department of Pesticide Regulation and the EPA for failing to review the impact of pesticides on California frogs and other amphibians. Alex Avery reports, “Collectively, these lawsuits have already cost hundreds of thousands of dollars and are far from over.” (3)
However, as Paul Harvey would say, here’s the rest of the story. It turns out that the disappearance of the yellow-legged frogs has an entirely different explanation. Folks had been stocking the lakes, rivers, and streams in the West with all types of fish, starting as early as the 1880s. As part of this action, trout were introduced into the glacial lakes of the Sierra Nevada and by 1924 wildlife biologists noted that mountain yellow-bellied tadpoles and trout were rarely seen in the same lakes. This continued with thousands of fingerlings being dropped by aircraft in high altitude lakes where there had been lots of frogs but not fish at all. (4) Guess what happened? The frog populations decreased.
Vance Vredenburg of the University of California at Berkeley began removing trout from five separate High Sierra lakes in the late 1990s. He saw frog population explosions and reported, “There are at least 10,000 lakes in the High Sierra. Ninety to 95 percent of them hold introduced species of trout but no more frogs at all. And there may be plenty of lakes that have plenty of frogs, but few or no fish. So the answer is pretty straightforward, and it doesn’t get much simpler: with no trout you get an immediate and dramatic response.” (5)
In 1995, a group of middle school pupils in Minnesota found some deformed northern leopard frogs and posted pictures of the poor creatures on the Internet. Mark Rosen observes, “The frog story had all the elements that make a newspaper reporters’ ears perk up: children—to provide excellent visuals and add just the right amount of ‘cute’ factor, a defenseless victim—the frogs, an ultimate evil—pollution, and a possible danger to everyone—the frogs could ostensibly be ‘canaries in a mineshaft.’” (6) By 1997, an alarming number of newspaper articles had been written on the topic, enough that Stanley Sessions, mentioned earlier in this article, was prompted to comment, “I have never seen a scientific or biological phenomenon grow so fast with so few publications.” Later in 1998 in a letter to Science magazine, Sessions noted that “Approximately half of the recent reports of deformed amphibians in the United States and Canada are from a single study (my own) of one site in California published in 1990.” (7)
In September 1997 the Minnesota Pollution Control Agency (MPCA) announced the results of tests at a press conference attended by the national media, including PBS and ABC’s “Nightline.” The MPCA officials announced that they had found water from sites where malformed frogs has been reported and it was very potent in deforming frogs in their laboratory experiment. However, they weren’t able to identify what it was in the water that had caused the problem. They then offered bottled water to families concerned about the wells in their areas. (4)
Bonner Cohen notes, “Bottled water may have eased the fears of local residents, but MCPA’s tests soon came under withering criticism from scientists with the EPA. According to EPA, it was simply a natural lack of calcium and other salts in Minnesota water that was deforming the laboratory raised African clawed frog embryos, not a chemical contaminant.” (8) As lead EPA researcher Joe Tietge put it; “You could probably take tap water from any county in Minnesota and get results like this. In science, spurious correlations happen all the time,” and they are “one of the weakest forms of evidence to support a hypothesis.” (9) Added another EPA researcher, “Results don’t mean anything if they are interpreted improperly. Anybody with a tropical fish aquarium knows that if you fill it with tap water it will kill the fish. That doesn’t mean your tap water isn’t safe to drink.” (10)
Looking for the real culprit? It appears to be a parasitic flatworm called trematodes. Two papers that appeared in Science in 1999 proposed a parasite theory. (11, 12) As Alex Avery notes, “Northern leopard frogs in the wild are afflicted at an early age by a tiny parasitic flatworm called trematodes (Ribeiroia). The parasites are shed by snails in ponds where they are picked up by frog tadpoles. Once in the tadpoles, they cause cellular dislocations that lead to deformities in adult frogs.” (3) The parasite theory was first proposed by Stanley Sessions who initially blamed chemicals. Sessions says of the trematodes, “It’s about as close to using an egg beater on the limb bud cells as you can get.” (13)
After publishing his theory, Sessions met with high skepticism. He concluded that the entire frog investigation was being manipulated and important evidence ignored in efforts to promote further research funding. He suggested that other researchers were tilting their hypothesis toward a chemical contaminant in an effort to garner more funding. (14)
More recent reports support Sessions’ findings. Pieter Johnson and colleagues noted that the extent and frequency of the frog deformities was not all that unusual. They surveyed museum frog specimens collected 100 years ago and found similar rates and kinds of deformities. (15)
Time magazine’s report on global warming’s effect on frogs in Costa Rica
Jumping on the global warming scare, Time magazine published a special report in their April 3, 2006 issue. Here’s what they say about frogs, “With habitats crashing, animals that live there are succumbing too…Last year, researchers in Costa Rica announced that two-thirds of 100 species of harlequin frogs have vanished in the past 30 years, with the severity of each season’s die off following in lockstep with the severity of that year’s warming.” (16)
Courtesy of Marlo Lewis, here are some facts Time didn’t report, “The frogs are not perishing from heat. Annual Costa Rican temperatures have remained remarkably flat during 1979 to 2005. Rather, the frogs are dying from a fungal infection carried by a class of organisms known as chytrids. Time argues global warming is increasing cloud cover, which limits the frogs exposure to sunlight—a natural disinfectant that ‘can rid the frogs of this fungus.’ However, there has been no observed change in Central American cloud cover between 1984 and 2004. So what is causing the frogs to perish in Coast Rica? According to the journal Diversity and Distribution, the chytrid fungus was most likely introduced by humans, possibly eco-tourists and, or field researchers, wrote University of Virginia climatologist Patrick Michael’s in a January 11 story in World Climate Report.” (17)
Lastly, on the topic of global warming, recent research indicates that global warming isn’t triggering a fungal disease killing off Arizona frogs. The culprit in this case also appears to be the chytrid fungus (18).
Leopard frogs and atrazine
Alex Avery describes Dr. Tyrone Hayes, a California researcher, as “the newest media darling in the supposed ‘global frog crisis.’ Over the past four years, Hayes has been profile by National Geographic magazine, Discover magazine, National Public Radio, and virtually every major newspaper in the country.” (3)
Hayes claims that traces of atrazine, one of the most widely used farm weed killers in North America, are affecting frogs from California to the Carolinas. Avery points out, “The media has run with this theory, placing it at the heart of all supposed frog ills. Hayes doesn’t’ argue that atrazine kills frogs or causes deformities. Instead he says that atrazine feminizes male frogs, chemically castrating them. Therefore, Hayes agues, atrazine ‘likely has a significant impact on amphibian populations’ and should be banned.” (3)
Contrary views: Hayes can’t explain why after 30 years of extensive atrazine use, frog populations are still thriving in the areas where it is heavily used. Nor can he provide any field evidence that atrazine has harmed a single frog anywhere. Further, and most importantly, scientists from four universities have been unable to reproduce Hayes” laboratory results. (3)
This short trip into the world of frogs provides one example of how public consciousness has been shaped by the media and environmentalists. Whether frogs are disappearing in California, Costa Rica, or Arizona, or deformed in Minnesota, the popular assumption is that a chemical or global warming is the cause. (19) When you dig deeper into this issue, other explanations backed by sound scientific evidence provide a different view.
1. William Souder, A Plague of Frogs, (Minneapolis, University of Minnesota Press, 2002), 227
2. Bonner Cohen, The Green Wave, (Washington, DC, Capital Research Center, 2006), 114
3. Alex Avery, “Rachel Carson Syndrome: Jumping to Pesticide Conclusions in the Global Frog Crisis,” Hudson Institute, May 2007
4. Bonner Cohen, The Green Wave, 116
5. V. Vredenburg, “Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog,” Proceedings of the National Academy of Science, 101, 7646, 2004
6. Mark Rosen, “The Mysterious Vanishing Frogs of North America,” MIT Open Courseware, Writing and the Environment, Spring 2005
7. Stanley K. Sessions, Science, 279, 459, January 23, 1998, (In Letters)
8. Bonner Cohen, The Green Wave, 117
9. William Souder, A Plague of Frogs, 245
10. William Souder, A Plague of Frogs, 244
11. S. K. Sessions, R. A. Franssen and V. L. Horner, “Morphological Clues From Multi-Legged Frogs: Are Retinoids to Blame?” Science, 284, 800, April 1999
12. P. T. J. Johnson, et al., “The Effect of trematode infection on amphibian limb development and survivorship,” Science, 284, 802, April 30, 1999
13. Kristin Leutwyler, “Biologists figure out what accounts for certain side-show frogs,” ScientificAmerican.com, May 3, 1999
14. William Souder, A Plague of Frogs, 229
15. P. T. J. Johnson, et al., “Limb deformities as an emerging parasitic disease in amphibians: Evidence from museum specimens and resurvey data,” Conservation Biology, 17, 1724, 2003
16. Jeffrey Kluger, “The Tipping Point,” Time, 167, 28, April 3, 2006
17. Marlo Lewis, “Time’s Climate Change Issue Rife With Deception,” Environment & Climate News, 9, 11, June 2006
18. Tony Davis, “Arizona frog fungus not blamed on warming,” Arizona Daily Star, January 23, 2006
19. Bonner Cohen, The Green Wave, 118