Frog Populations Declining

Human impact has become a buzz word again in the last few decades. Rachel Carson sparked a major catalyst when she wrote Silent Spring all those years ago. Although, it seemed like interest in human impact on the environment waned for quite a few years sometime between the late 1960’s and early 1990’s. I mean, does anyone else remember the huge issue with McDonald’s using styrofoam packaging for their hamburgers that arose and jumpstarted the “Reduce Reuse Recycle campaign” in the early 90’s? How did we manage to get through two decades (70’s and 80’s) of styrofoam gobbling without ever once questioning the waste buildup we were creating? Maybe it was the drugs.


Well, that “Reduce Reuse Recycle” campaign in the 1990’s certainly did a number, because I am happy to report that we are still moving forward with environmental policies. Even here at DePauw, we have a Green Report Card, a Carbon footprint, DEPP (DePauw Environmental Policy Project), a sustainability intern, recycling etc .You get the point, right? Human impact is huge. Which is why, when I stumbled across this article on Science Daily called “Amphibians as Environmental Omen Disputed,” I had to write about it. The article is based off the paper “An examination of amphibian sensitivity to environmental contaminants: are amphibians poor canaries?” which was recently released in the Journal Ecology Letters, unfortunately, all I could locate was the abstract. I thought it was interesting because a lot of the concern around human impact seems to be how we are impacting the world for ourselves, as humans. Yes, I know there is plenty of literature about how we are impacting animals, I just don’t think it is thought of by the average, not-so-biologically-geeky person. More specifically, I doubt many people wonder how their use of shampoo is affecting their local amphibian population. I guess that’s why I thought it was interesting, so below I have included a brief summary of the article.
Almost twenty years ago, a new story was released after the National Research Council conference in Irvine California. The story noted the rapid decline of some amphibian species and claimed that the decline was because amphibians were particularly sensitive to environmental threats. The prevailing thought behind this claim was that due to the frog’s permeable skin that allows for the ready uptake of chemicals and other pollutants in the surrounding environment. Additionally, it was believed that a dual aquatic-terrestrial life cycle and a relatively rudimentary immune system made them very susceptible to human-mediated environmental changes.

Logically, these thoughts seem to make sense. Well, at least it did to me. However, recent scientists have questioned this concept. They have pointed out that there was not an adequate comparison of amphibian sensitivity to environmental challenges relative to other taxa. In response a group of scientists from University of South Dakota, Yale University and Washington State University have examined an additional 1,279 species, using Environmental Protection Agency’s (EPA) Aquatic Toxicity Information Retrieval database.
As it turned out, comparing toxicity levels was a good plan. They found that frogs have a range of reactions, from being moderately susceptible to not at all susceptible. The results show that frogs are not that different from other animals. Yes, they can be a possible indicator of potential exposure to different chemicals in the environment, but they are certainly not a leading indicator species like they were once believed to be. So how do you explain the rapid decline researchers observed during the 80’s and 90’s?
Other research has suggested the decline in populations is due to habitat destruction and alteration, introduction of exotic predators, and acid rain. Yet, there are still many examples of populations that have declined, and no one seems to know why.
I wholly support the continued study of declining amphibian populations as well as other organisms. Maybe they are just natural fluctuations occurring in the populations, although many researchers are hard pressed to believe this. It may not be the result of chemical accumulation as was once accepted, for it seems their skin is far less permeable then we once believed. Something is causing the decline, and I believe it is undoubtedly related to human impact. Research has already successfully linked some declining populations with human impact, as was previously mentioned; it is only a matter of time before the mystery losses are explained.

References:
http://www.jstor.org/stable/3892876?seq=1
http://www3.interscience.wiley.com/journal/122658158/abstract
http://www.jstor.org/stable/3974636
http://www.jstor.org/sici?origin=sfx%3Asfx&sici=0888-8892(2001)15%3A4%3C903%3AADAECU%3E2.0.CO%3B2-D

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~ by jamiegrivas on December 1, 2009.

4 Responses to “Frog Populations Declining”

  1. Most of what I have heard about frogs as indicator species for environmental health includes some talk of mutations – frogs with two heads, extra legs, etc. If man-made chemicals are not responsible for these mutations, I would be very surprised. On the other hand, I have also read that global warming might be an even bigger cause of amphibian population decline world-wide than chemicals. It might not directly be responsible for the declines, but it causes things like pandemic diseases to spread more easily in the warmer climate, or it can alter the normal breeding cycles of some species if temperatures don’t fluctuate as much as they should. Global warming is just another issue human impacts have accelerated, so should we dismiss frogs as indicator species? I think not. There are plenty of other human-caused factors that are probably impacting the environment. Simply because we have not found the correct reason amphibian populations are declining on a global scale does not mean we should ignore the decline as a warning. If two-headed frogs aren’t something to worry about, then I’m not sure what is.

    This article talks about the current theories of amphibian population decline. http://74.125.155.132/scholar?q=cache:ZFsqest2wvgJ:scholar.google.com/+frog+species+decline+and+global+warming&hl=en&as_sdt=2000

  2. This sounds like a really interesting article, and it represents one of my favorite things about science: throwing away previous conclusions and starting over. I think that some good ol’ scientific visualization would be nice here. After looking through the JSTOR article, I couldn’t really find any figures (though I didn’t look extremely hard). Given the fact that this article is trying to uncover correlations between environmental factors and frog populations, and the large database of information, this is a really exciting upheaval of existing scientific truth.

  3. Thanks for talking about this topic. A lot of interesting points were brought up given how impacting our behaviors are. After reading what you wrote I couldn’t help thinking about the little icons that are cemented into my neighborhood’s sewer drains. They have the triple arrow for recycling as well as a fish saying, “This water goes directly to the river!” I’d like to think that all of the little steps put in place through environmental awareness and sustainability campaigns are going to gradually reduce our impact. Maybe the subliminal messages in all of those Captain Planet shows we watched as kids are finally paying off.

  4. I recently watched a program on MSNBC called 100 heartbeats, narrated and hosted by the great Jeff Corwin, that had a whole section on the dangers amphibians currently face, and how this is related to the dangers our environment faces. Jamie doesn’t lie: there is a TON of research on the life history and status of amphibian populations. One of our own DePauw Professors, Janet Vaglia, is studying local populations of wild salamanders. I performed research with her two summers ago, and while we were not taking into account any environmental variables, we did have to travel lonnng and far before locating any for our research. My rambling point is that amphibians, as the oldest ancestral forms of tetrapods, are worth understanding, even if they are understood through the crisis of possibly losing them. They are incredibly unique creatures who have some fascinating processes for gas exchange that we just can’t find anywhere else! Save the amphibians!

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