Climate Change Causes Butterflies to Suffer and Invasive Species to Thrive

Butterflies may be in danger from climate change. Scientists have discovered that the combined heat from climate change and urbanization may reduce the number of eastern swallowtails and other native butterflies in Ohio.

In order to better understand how a shifting climate might impact these insects, the researchers analyzed 13 years of butterfly monitoring records at 83 locations statewide. These monitoring sites included locations in parks and preserves throughout Ohio. The scientists then compared this data with temperature records; sites in southern Ohio ranged 2 to 3 degrees Celsius warmer than northern sites, reflecting the amount of warming climate change models predict for the Midwest later this century.

So what did they find? It turns out that butterflies emerged up to three weeks earlier and reached peak numbers sooner in southern Ohio than mid- and northern Ohio. Yet warmer temperatures aren't always a good thing.

The scientists estimated heat from urbanization, calculating the percent of impervious surface within 1 kilometer of each monitoring site. When the heat was added to the already warmer temperatures in the south, seven species actually delayed their initial appearances and delayed their peak numbers.

"Butterflies need warmth from the environment to develop," said Ries, one of the researchers, in a news release. "As their environment gets warmer, they have more and more energy but at extremes, it's too hot and they die. Before it becomes lethal, too much heat can slow growth. That's why we see the delay."

In fact, the delays may leave species with fewer resources to feed on and limited time to lay eggs. It could also expose them to greater risk of predation, resulting in a smaller generation. In addition, invasive species, such as the cabbage white and European skipper, are more likely to thrive in these warmer conditions.

The findings could be useful for predicting the effects of environmental changes over the next decades, and could allow scientists to develop strategies to respond.

The findings are published in the journal Ecology.