Scientists Admit Global Warming Didn't Kill the Golden Toad
The golden toad of Costa Rica was declared extinct in 1994, five years after it was last sighted in the wild. The unfortunate toad's was the first extinction to be blamed on anthropogenic global warming and it has often been cited as an example of things to come if mankind doesn't change its CO2 spewing ways. But humanity's conviction of toadacide was premature and based on circumstantial evidence. After years of study scientists have a new finding: humans were not at fault after all.
A new online report in the Proceedings of the National Academy of Sciences identifies El Niño, which caused an unusually severe dry season at about the time the golden toad was wiped out, as the proximate cause for the toad's demise. Not that those who dearly wish to blame the extinction on global warming are rushing to accept the new conclusion. As reported in a news article in Science, here is the conventional wisdom regarding the fate of the golden toad:
As humans pumped carbon dioxide and other greenhouse gases into the atmosphere, Costa Rican rainforests became hotter and dryer in the mid-1980s. These conditions made the toad vulnerable to the chytrid fungus, which is thought to thrive in warmer, drier climes. Chytridiomycosis is a fatal skin disease that eventually causes convulsions, skin loss, and death in amphibians. Although amphibian populations all over the region declined, the golden toad’s limited habitat and small population made it especially vulnerable.
The new research was done by Columbia University climate scientist Kevin Anchukaitis and University of Maryland paleoclimatologist Michael Evans. They took samples from two trees in the region and then sliced the samples just 200 microns thick—about the width of a human hair. The slices were then analyzed in a mass spectrometer to measure the oxygen isotopes they contained. Isotope ratios associated with dry conditions alternated with wetter conditions, allowing the researchers to establish a history of the annual moisture cycle in the toad's habitat.
Not seen since 1989. Photo NOAA.
“We expected to see some kind of trend related to global warming, yet when we developed the record it turned out the strongest trends were El Niño-related,” says Anchukaitis. He further states that the impact of a single El Niño cycle on the amphibian indicates that climate change could have devastating consequences. Quoting from the report's abstract:
There is no evidence of a trend associated with global warming. Rather, the extinction of the Monteverde golden toad (Bufo periglenes) appears to have coincided with an exceptionally dry interval caused by the 1986–1987 El Niño event.
Christopher Still, a climatologist at the University of California, urged caution over the results. He cited the small sample size—the team sampled only two trees—and that interpreting oxygen isotopes in the cellulose of tropical trees is still a relatively new field. Even so Still said “the paper provides a much-needed long-term climate and hydroclimate context for this region.” Of course the authors of the report feel obliged to add a warning about climate change, just to stay in the good graces of their fellows: “The fact that our research suggests it was El Niño and not anthropogenic climate change shouldn’t be any comfort when considering the future impact of climate change.”
A Panamanian golden tree frog, another reputed victim of global warming.
Such caution and bowing to convention are to be expected but they do not change the fact that the authors felt confident enough to report a finding that will not be greeted warmly in climate change circles. Widespread amphibian extinctions in the mountains of the American tropics have previously been blamed on the interaction of anthropogenic climate change and a lethal pathogen. As I reported in an earlier blog post, this conclusion was already under suspicion (see “Frog Fatalities Not Caused By Global Warming”). That report was greeted by a number of childish attacks from closed minded climate change alarmists. I'm anxious to see the response to this report, which is basically a confirmation of the earlier work. The golden toad is dead and anthropogenic global warming is not looking so good either.Be safe, enjoy the interglacial and stay skeptical.