Pollution and Climate Change Are Deforming and Killing Alaska's Frogs
The other day I walked past a car with a bumper sticker that read, “I brake for frogs.”
That’s a great message, but here’s the irony: Those very same brakes could be one of the factors contributing to the worldwide decline of frogs and other amphibian species.
Brake pads, those things you need to change on your car, contain copper. Every time you brake, the pads shed an infinitesimal amount of copper onto the road, which can then run off into nearby streams and lakes. The copper, when combined with other environmental factors, is apparently bad news for frogs.
That’s the gist of a study published this week in the journal Ecosphere, which found that even the smallest traces of copper can have big consequences for amphibians.
Researchers exposed Alaskan wood frog tadpoles to water with copper levels measuring less than two parts per billion—half the amount known to exist in some Alaskan ecosystems—along with small variations in temperature. Scientists did the same thing to dragonfly larvae, one of the tadpoles’ major predators.
Although both species suffered, the tadpoles came out much worse. In experiments with added copper and warmer water, the dragonfly larvae simply exhibited less activity. The tadpoles, on the other hand, were more active and spent more time closer to the surface—possibly looking for more oxygen. Both behaviors made them easier prey. As a result, the dragonflies attacked the tadpoles three times more often, and the first attacks occurred within four minutes, much faster than the usual 34 minutes.
Although few of these dragonfly attacks were fatal, many of the tadpoles that survived grew up with deformities or missing limbs stemming from their injuries, something that would further reduce their ability to thrive as adults.
“We found these really surprising results from just a pretty small but relevant shift in temperature and a very small addition of copper,” said Mari Reeves, an ecologist with the U.S. Fish and Wildlife Service and coauthor of the new paper. “This is an example of how more than one thing can interact in the environment in a very simple system.”
The study doesn’t link copper in the environment to brake pads or any other specific source, but the frogs were sourced as eggs from Alaska’s Kenai National Wildlife Refuge. The refuge, according to the paper, is crisscrossed by more than 200 miles of roads, and roads are a major source of copper contamination worldwide. Reeves’ previous research in Kenai found copper not just in the water but in the skeletons of abnormal frogs discovered there.
“Rainfall carries copper and other dangerous heavy metals from roads directly into the waterways where frogs and salamanders live and breed,” said Kerry Kriger, executive director of Save the Frogs, who was not involved with the current study.
So, Why Should You Care? Nearly one-third of the world’s amphibians are already threatened with extinction, and frogs are an important indicator of water quality, something that both humans and wildlife depend on. As tadpoles, they keep waterways clean by feeding on algae, and as adults, they act as natural bug control, limiting insect populations that can spread illness and fatal diseases to humans.
Reeves said not enough people are looking for copper and other contaminants in the environment because the process to find them is both difficult and expensive. But this research comes at a critical time for frogs.
“We’re just not paying attention, and we’re losing this whole group of organisms that have been on the planet for 350 million years,” Reeves said. “They eat bugs for us, and they’re an incredible food source for a lot of species.”
Mitigating some of these contaminant effects could be relatively easy. “We can engineer solutions, whether that’s changing the way we make brakes or treating the things that go through our gutters,” Reeves said. “A lot of these things aren’t very hard.”
Reeves said she hopes this research will work as an incentive toward more frog conservation. “If we just thought about them a little more, we would probably end up conserving them,” Reeves said.