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New Evidence Against a Causal Link between Amphibian Decline and Climate
A new paper has been published by Jason Rohr et al entitled, ‘Evaluating the links between climate, disease spread, and amphibian decline,’ November 11, 2008 in the Proceedings of the National Academy of Sciences (PNAS).
The Abstract states:
Human alteration of the environment has arguably propelled the Earth into its sixth mass extinction event and amphibians, the most threatened of all vertebrate taxa, are at the forefront. Many of the worldwide amphibian declines have been caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd), and two contrasting hypotheses have been proposed to explain these declines. Positive correlations between global warming and Bd-related declines sparked the chytrid-thermal-optimum hypothesis, which proposes that global warming increased cloud cover in warm years that drove the convergence of daytime and nighttime temperatures toward the thermal optimum for Bd growth. In contrast, the spatiotemporal-spread hypothesis states that Bd-related declines are caused by the introduction and spread of Bd, independent of climate change. We provide a rigorous test of these hypotheses by evaluating (i) whether cloud cover, temperature convergence, and predicted temperature-dependent Bd growth are significant positive predictors of amphibian extinctions in the genus Atelopus and (ii) whether spatial structure in the timing of these extinctions can be detected without making assumptions about the location, timing, or number of Bd emergences. We show that there is spatial structure to the timing of Atelopus spp. extinctions but that the cause of this structure remains equivocal, emphasizing the need for further molecular characterization of Bd. We also show that the reported positive multi-decade correlation between Atelopus spp. extinctions and mean tropical air temperature in the previous year is indeed robust, but the evidence that it is causal is weak because numerous other variables, including regional banana and beer production, were better predictors of these extinctions. Finally, almost all of our findings were opposite to the predictions of the chytrid-thermal-optimum hypothesis. Although climate change is likely to play an important role in worldwide amphibian declines, more convincing evidence is needed of a causal link. (Emphasis added by CRN).
November 13th, 2008 at 6:25 pm
[...] Human alteration of the environment has arguably propelled the Earth into its sixth mass extinction event and amphibians, the most threatened of all vertebrate taxa, are at the forefront. Many of the worldwide amphibian declines have … Original post [...]
November 14th, 2008 at 3:20 am
I find it interesting that even though the authors’ findings are completely contrary to AGW dogma they feel the need to include the final sentence, “Although climate change is likely to play an important role in worldwide amphibian declines, more convincing evidence is needed of a causal link”.
This is a common “disclaimer” added to the abstracts of studies that don’t appear to validate AGW theory.
Also who says that a warmer world would necessarily be worse for amphibians? They are noticeably more populous in locations with warmer climates.
Do you suppose Einstein, in his seminal work, “On the Electrodynamics of Moving Bodies”, should have added “Although the luminiferous aether is likely to play an important role in relativistic mechanics, more convincing evidence is needed of a causal link.”
Considering the battering that scientists that have questioned the orthodoxy have received I guess you can’t blame these guys for being careful to genuflect to the climate clergy.
November 14th, 2008 at 3:37 am
Yes, I’ve noticed the ‘nod’ to the ‘consensus’ in many papers.