natural histories: amphibian decline

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The spring peepers have been peeping their little hearts out at the nature center the past few evenings.

Although the frog populations at Ijams seem healthy, worldwide that is not the case. Here's an excerpt from my book Natural Histories.

"Biologists that study amphibians and reptiles are called herpetologists. Like the scientists that study birds, herpetologists have been keeping records of amphibian populations for years. In the late 1980s some of these specialists realized they weren’t seeing or hearing the numbers of amphibia they once had. These declines were believed to be localized because no one had ever attempted a global survey. That’s when a group including Jeff Houlahan with the Ottawa-Carleton Institute of Biology in Ontario, Canada began to pull together data from reports and published accounts from all over the globe. In time the study accumulated information on 936 amphibian populations from 200 researchers located in 37 countries in eight regions of the planet. What they discovered affirmed their worst fears: the declines weren’t just local, but global.

Amphibian populations—frogs and toads, salamanders and newts—have been decreasing since 1960: overall a steep drop from 1960 to 1966 followed by a smaller but steady slide between 1966 and 1997. The initial sharp downswing in the early 1960s was approximately 15 percent a year. It was followed by a slow fall of 2 percent a year from 1966 to the late 1990s.

The global declines weren’t exactly the same in all locations. Both North American and Western Europe showed population loss for the six years after 1960, but only in North America did the slow decline continue after 1966. The initial decline in the early 1960s was more dramatic in Western Europe than North America but the continued slump had lasted longer in the latter until by 1997 both continents had lost about the same in overall numbers.

If you do the math, using the annual 15 percent loss for the years 1960 to 66, followed by the 2 percent annual loss from 1966 to 97 the total decline is over 80 percent in just over 40 years. Of the 936 amphibian populations in the study, 61 had disappeared altogether.

That’s startling, but do we know the cause?"




- Natural Histories published by UT Press.

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