It’s important to keep in mind that climate change doesn’t mean only warmer average temperatures — it also fosters weather variability and the prevalence of extreme cold temperature events, a new paper reports.

Image credits Manfred Richter.

A team of researchers from Binghamton University investigated the effect of climate change on amphibian health and susceptibility to parasites. The researchers focused on cold weather variability, a less-discussed consequence of climate change, and discovered that it makes amphibians more susceptible to some hazards while lessening the risk of others (such as parasites). They hope the study will help showcase the important role cold weather variability, not just warmer temperatures, play in the context of climate change.

Change goes both ways

“There is a lot of misconception that global climate change only refers to an increase in warming temperatures,” says Jessica Hua, assistant professor of biological sciences at Binghamton and paper co-author. “We feel that the research in this paper is important because it highlights that global climate change is more complex than just an increase in average temperature. In fact, global climate change is also predicted to increase the prevalence of extreme cold temperature events, as well as increase the amount of variation in temperature fluctuations.”

While climate change is recognized as “one of the most serious issues facing us today,” its impact on animal and plant populations isn’t known in depth. Weather variability, in particular, can have dramatic effects on natural systems. For example, rising mean temperatures prompt organisms to breed earlier in the spring, the team explains, which paradoxically increases their risk of experiencing wild fluctuations in temperature during early development — especially cold weather.

These temperatures don’t have to fall into the ‘deadly’ range to cause damage, the team adds, to alter how susceptible amphibians are to other stressors. To investigate the issue further, they placed wood frog embryos in various cold temperature regimes, researchers looked specifically at the consequences of exposure to these lower temperatures.

Amphibians exposed to constant cold conditions as embryos were more susceptible to road salt contamination, but were able to recover as they aged, the team reports. This is particularly relevant, as salt use on roads is predicted to increase exactly as these extreme cold temperature events are taking place. The frogs exposed to cold temperatures as embryos were also smaller overall as they aged, and developed at a slower pace. This ended up protecting them against parasites as their small stature made them less attractive targets.

These results were not anticipated, the team adds, and determining whether the impact from the cold was harmful or helpful for the amphibians overall is difficult to gauge.

“We initially predicted that exposure to cold temperatures would be stressful to developing embryos. As a consequence, we expected that exposure to stressful conditions early in life would make amphibians less able to deal with other stressors later in life (i.e. parasites),” Hua said. “We were also surprised because past studies have found that cooler temperatures can increase amphibian susceptibility to another parasite (the fungus, chytrid). In this case, the negative effects of the cooler temperatures on amphibians are driven by the fact that the fungus survived better in cooler temperatures.”

Amphibian populations are on the decline globally, so considering the effects of cold temperatures may be important in understanding how to better protect them in the future, the team concludes.

The paper “The effects of different cold-temperature regimes on development, growth, and susceptibility to an abiotic and biotic stressor” has been published in the journal Ecology and Evolution.