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Longer, hotter autumns could prove dire for butterflies

A study found that warmer autumn conditions cause the insects to lose weight and spend precious energy while ensconced in their chrysalises, making it less likely they’ll make it to spring.

(CN) — Autumn seasons running too long and too hot can be an annoyance for people eager to make the jump to cooler temperatures. But for butterflies, that same delay might just prove deadly.

As experts have come to understand more about global climate change, we’ve also come to learn about the near-countless ways that it has disrupted the natural world. Rising sea temperatures have wreaked havoc on migratory fish, ice loss in the arctic has displaced entire groups of polar bears and walruses and extreme drought conditions have put numerous vulnerable plant species on their heels.

Now, new research reveals that climate change may claim yet another victim: butterflies.

In a study published Thursday in the British Ecological Society journal Functional Ecology, experts reveal they’ve conducted a series of experiments to see how butterflies — specifically green-veined white butterflies that are common throughout most of Europe and the U.K. — will hold up to the stress of climate change. They particularly wanted to learn how the insects would fare during longer and warmer autumn conditions, a time they typically spend inside their chrysalises waiting for the warmth of spring to bring them into the world.

What they found however does not bode well for the winged creatures. While they found that warmer conditions in the fall did not kill the butterflies outright, they nonetheless made it far more likely they wouldn’t survive in the long run.

“Climate change is making autumns warmer and last longer, and it was this specific combination of conditions that had the greatest impact on the butterflies in our study,” said Matthew Nielsen of the University of Oulu. “We show that stressful conditions experienced at one time of year can have lasting negative consequences at other times of year, linking changes in one season to consequences in others.”

Researchers came to these conclusions after first taking hundreds of chrysalises and putting them in a series of controlled environments, each with varying temperatures and for different amounts of time. They then placed their entire collection of chrysalises in the same winter conditions for exactly 24 weeks and tracked their survival progress until they reached a simulated springtime.

After the experiment was said and done, experts noted some troubling results. The chrysalises that were exposed to longer, hotter autumn conditions were losing way more weight and spending far too much energy on staying alive than those that were exposed to the more mild conditions. While they didn’t all die immediately, the more extreme fall temperatures made them far less likely to make it to spring alive.

Neilsen notes that part of this trouble stems from the fact that dormant creatures — like a butterfly in a chrysalis — do not have the same options for replacing lost energy as active animals do, causing environmental changes to hit them especially hard.

“Even though dormant animals use less energy than active animals, they use more when it’s warmer, and they can’t eat to replace that lost energy,” Nielsen said. “It is already established that warmer winters are actually worse for dormant animals than colder ones, and our findings show that warmer autumns are potentially even more dangerous.”

What’s more, researchers warn, is that these consequences in the real world could be much harsher than those reported in their labs. The lab experiment behind Thursday’s study offered the chrysalises constant, regulated conditions, but out in nature they will be subjected to the harsh and often unpredictable climate variations that happen day-to-day. Experts say these real-world conditions could prove even more costly for the butterflies.

Experts say these results are just the first step in their ongoing research. Thursday’s study was mostly focused on seeing if the butterflies could survive to adulthood, so future study on how the bigger picture of a butterfly’s life is influenced by climate change is next on their radar.

“In our study we only considered survival to adulthood, but there could be even more negative effects later in life, for example on the ability to find mates or the number of eggs laid. Studying how warming in autumn, winter, and spring interact will also be key to understanding the actual impacts of climate change on dormant animals.”

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