Global Warming – Frog Decline Link Is Disproven

Published July 1, 2008

A new study in the peer-reviewed PLoS Biology, a journal of the Public Library of Science, has disproven sensationalist media reports of global warming causing a mass die-off of tropical frogs.

The study by a team of scientists specializing in zoology and animal health reported, “analyses found no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis.”

Media Ran Scare Stories

In January 2006 the news media created widespread fear and alarm with stories claiming “the first clear proof that global warming is causing outbreaks of an infectious disease that is wiping out entire frog populations.”

The stories were based on preliminary research by a team of scientists who were predisposed to the notion that as the Earth warms, many species are likely to disappear. In a Nature magazine article they argued global warming was behind the spread of a fungus in Central America that was decimating tree frog populations.

Ignoring the researchers’ clear bias and predisposition toward finding global warming as the cause of declining frog populations, MSNBC, BBC, the Washington Post, The New York Times, and many other prominent media outlets were quick to cover the Nature report and point the finger at global warming.

Warming Wasn’t Culprit

After more thorough, updated analysis, another group of scientists reported in the March 25 issue of PLoS Biology, “we found no evidence that climate change has been driving outbreaks of chytridiomycosis.”

Instead, the scientists found the preliminary Nature study used flawed methodology and overlooked very basic real-world information.

Moreover, the PLoS Biology scientists reported, “in Central America, temperature is predicted to increase, and rainfall is predicted to decrease, making many of these areas less favorable for [chytridiomycosis].”

Scientists Skeptical, Media Fooled

The media should have been suspicious of the preliminary Nature report and presented more balanced coverage, many scientists believe.

“I do not support the contention that climate change has an indirect effect on causing amphibian declines due to chytridiomycosis,” said Cynthia Carey, Ph.D., a professor at the Department of Integrative Physiology at the University of Colorado at Boulder.

“The paper claiming this indirect effect omitted a number of critical data that do not support the hypothesis, ignored the fact that Batrachochytrium dendrobatidis [which causes chytridiomycosis] can kill effectively over a range from 4ºC to almost 30ºC and therefore doesn’t need increasing temperatures to be lethal, and did not prove that many of the ‘claimed’ declines and extinctions were in fact due to Batrachochytrium dendrobatidis,” Carey continued.

More Warming Before

Mike Alexander, Ph.D., a meteorologist with the National Oceanic and Atmospheric Association who worked with Carey on another paper addressing the issue, is likewise skeptical of the claims in the Nature article.

“When I asked the biologists they indicated that the frogs and toads have been in their present location for thousands and perhaps millions of years,” Alexander said. “Over that time they would have experienced all types of climate fluctuations [such as the] advance and retreat of glaciers, large El Niño events, long stretches without El Niño, droughts, etc.

“The impact of global warming was relatively small on the tropics during the twentieth century and certainly around 1980,” Alexander continued. “Thus, the amphibians should have experienced much more extreme conditions over the past than they did in the recent past, say the last 30 years.”

Correlation Is Not Causation

“There are also cause-and-effect issues,” Alexander noted. “Let’s say that the recent amphibian declines are independent from global warming. If one looks at whether it was warmer before or after the declines, one would still find that it is more likely that it would be warmer afterwards–as in general the temperature has risen over the past decade or two–but that does not mean the warmer temperatures caused the declines.”

“This is just one more example of how alarmists, including scientists on a mission, jump the gun, touting any environmental harm as being caused by global warming, regardless of the counterevidence,” said Sterling Burnett, Ph.D., a senior fellow for the National Center for Policy Analysis.

“Sadly, the scientific press, in the form of the journal Nature, evidently saw one of their all-too-regular lapses in peer review–all too regular, that is, with regard to ‘humans are causing the end of the world through global warming’ reporting,” Burnett said.

“Thankfully, rather than just passing this off as one more claim in the mainstream, a consensus position if you will, more thoughtful and honest researchers have debunked the myth that human-caused global warming is behind the frogs’ unfortunate demise,” said Burnett.

Aleksandrs Karnick ([email protected]) writes from Indianapolis, Indiana.

For more information …

Karen R. Lips, Jay Diffendorfer, Joseph R. Mendelson III, Michael W. Sears, “Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines, PLoS Biology: