Butterflies flourish in the summer heat — for now

Europe has seen record temperatures this summer. A high of 46 degrees Celsius (115 degrees Fahrenheit) was registered in Spain, and in some German cities, temperatures hovered around 40 degrees Celsius (104 degrees Fahrenheit). While most animals struggle with the heat, there is one notable exception.

For most butterfly species, the heat wave was a welcome surprise during the typically rainy summers of northwestern Europe. "Their flight period is limited by cool, damp weather. And if they don't fly, they don't feed," Paul Ashton, head of the biology department at Edgehill University in the United Kingdom, told DW. So, no rain, no problems — at least for adult butterflies.

While the hot, dry weather now is good for butterflies in terms of flying and feeding, they're likely to encounter problems with these conditions. "Going into autumn, and egg-laying and caterpillar-hatching, there could be problems down the line," Ashton said. After long periods of extreme heat, flowers where butterflies would normally lay their eggs could dry up.

The brown argus, found in Scotland and northern England, can't just switch to another flower if the plant of its choice is all dried up. The species lays its eggs exclusively on the rock rose. This plant, in turn, only grows on rocky, thin soil — which means it'll shrivel up faster in hot, dry weather.

A lack of plants for egg-laying means fewer caterpillars. So while you're likely to see more butterflies out and about this summer, don't expect tons of caterpillars this fall. In the long run, the heat wave isn't great for butterflied either. As insects around the world decline, the trend holds true for butterflies as well.

To save butterflies and other insects like bees, many cities have started to sow wildflowers. Residents in Bonn, the former capital of West Germany, have created this meadow: "Bonn blooming and abuzz" provides food for insects in summer and a resting place in winter.

Over the long run, global warming is hurting butterflies like the marsh fritillary. These high-altitude species "are adapted to flying in very cool conditions," Ashton said. In Scotland, the marsh fritillary lives in altitudes above 600 meters. If it gets too warm, it moves higher. But there's a limit to how high it can go before it doesn't find the plants it needs anymore — and dies.

Ashton said one of the main reasons for the decline of butterflies, aside from global warming, is habitat loss. "It's partly due to developments, and partly due to agricultural intensification," the ecologist explained. If we want to keep seeing butterflies, and not just in display boxes, we need to act now. Planting beautiful wildflowers in your backyard could be a start!