Climate change and copper may be hurting amphibians far more than anyone first thought. Scientists found that the extinction of two amphibian species, the southern toad and the southern leopard frog, may occur more quickly due to these impacts.
Copper is naturally found in aquatic environments. In fact, a little bit of copper can help facilitate physiological process. With that said, at elevated levels, copper can be toxic. This means that when contaminants enter wetlands where amphibians and other creatures reproduce, it can drastically impact their survival.
In this latest study, researchers examined data from wetlands, in addition to data that covered warming trends in the southeastern U.S., where the two amphibian species live. More specifically, they ran 1,000 simulations for a 50-year time span. Simulated populations were allowed to exist for about 15 years before copper was added.
"Studies often examine the impact of single environmental stressors on a species, but, in reality, a species is often hit by several stressors at once," said Stacey Lance, one of the researchers involved in the new study at the Savannah River Ecology Laboratory in South Carolina. "It could be multiple types of pollutants or, in this case, a metal pollutant that accumulates in wetlands along with wetland habitat changes associated with climate change."
The researchers found that, at varying levels, the separate and combined effects of copper and climate change could actually increase the risk of population extinction. This is a condition that results in a population that's reduced to having less than 10 adult females.
"Climate change may cause the ponds to dry too early," said Scott Weir, one of the researchers involved in the study. "When this happens the tadpoles born that year are unable to metamorphose and get out of the pond, so they die. We refer to this as catastrophic reproductive failure."
Researchers found that changes in temperature and precipitation patterns could result in catastrophic reproductive failure frequencies of 10 percent to 40 percent or more.
"This frequent reproductive failure could represent an extinction tipping point for some species," Weir said. "If leopard frogs suffer complete reproductive failure once every three years, that population has a 63 percent chance of extinction. For toads, that percentage is about 25 percent."
The findings were published in the April edition of the journal Ecological Applications.
