While a warming climate in recent decades may be a factor in the waning of some local populations of frogs, toads, newts and salamanders, it cannot explain the overall steep decline of amphibians, according to researchers.
After analyzing many years of data for 81 North American amphibian species including more than 500,000 observations collected at more than 5,000 sites in 86 study areas by a broad coalition of herpetologists, it is clear a warming climate is not the primary driver in their disappearance, according to lead researcher David Miller, associate professor of wildlife population ecology in Penn State’s College of Agricultural Sciences.
The researchers focused on how colonization and persistence of local populations were related to annual variation in five climate variables thought to affect key components of amphibian life cycles: winter severity, snowfall, breeding water availability, summer soil moisture and maximum temperature.
“The influence of climate on amphibian populations is complex,” Miller said. “In the last 30 years, we have seen increases in temperature, while some spots have gotten drier and others have gotten wetter. In the big picture, those developments seem to counteract each other. As a result, the impact of climate change for the measures we focused on cannot explain the sharp decline we have seen and continue to see across amphibian populations.”
The study showed that, on average, 3.4 percent of amphibian species are disappearing from local amphibian habitats each year. That is the equivalent of losing half the species in any wetland, stream reach or forest site every 20 years. Miller believes these declines are a continuation of losses of amphibian populations that have been occurring since the 19th century when human land-use began destroying their habitats.