Unique Study Reveals Unforeseen Connections between Insect Activity and Weather Irregularities

The importance and accessibility of natural history collections have grown over time, thanks to digital advancements that bring them to a wider audience for research purposes. Illustration by Emile-Allain Séguy

As Earth’s climate continues to warm due to greenhouse gas emissions, we’re witnessing a rise in extreme and unexpected weather events. However, forecasting and examining the outcomes of these weather irregularities, by their very nature, are complex tasks.

Scientists propose that museum samples may hold crucial insights. In an unprecedented study, a University of Florida team employed natural history specimens to illustrate that unusual hot and cold days can expand the activity span of butterflies and moths by nearly a month.

“The findings were completely unexpected,” stated principal investigator Robert Guralnick, a curator of biodiversity informatics at the Florida Museum of Natural History.

Most research examines climate change and its effects through the lens of average temperature rise. As the climate warms, flora and fauna in specific regions become active sooner in the spring, postpone dormancy until later in the fall, and gradually adjust their habitats to align with their optimal survival climate.

Unpredictable weather introduces an additional level of complexity to these patterns, producing unknown impacts and obscuring the scientists’ ability to forecast the future of global ecosystems.

“There have been indications in scientific studies that weather anomalies can have an accumulated effect on ecosystems, but there hasn’t been any comprehensive research addressing this issue,” Guralnick explained.

This gap, he clarified, is primarily due to a shortage of adequate data. While climate data has been consistently gathered across the globe for over a century, records noting the location and activity of species are less common.

Increasingly, natural history museums are seen as a potential solution to this problem. The most longstanding museums have collected specimens for centuries, and recent digitization efforts have made these collections widely accessible. However, digital museum records come with their unique challenges and drawbacks.

In a pioneering study, University of Florida researchers employed natural history specimens to show that unusually warm and cold days can extend the active period of moths and butterflies by almost a month. Credit: Illustrations by Emile-Allain Séguy

In 2022, study collaborator Michael Belitz created a dataset of moths and butterflies from museum collections to guide other researchers seeking to use similar data. The outcome was a detailed guide on how to collect, arrange, and analyze information from natural history specimens.

Equipped with this comprehensive resource, Belitz and his team aimed to detect any signals from erratic weather patterns. They limited their analyses to the eastern United States, utilizing records for 139 moth and butterfly species gathered from the 1940s to the 2010s.

The findings were clear: Abnormal warm and cold weather has significantly shifted insect activity, more so than the average rise in global temperature over the past several decades.

The location and timing of extreme weather events dictated how insects reacted. In higher latitudes, warm winter days led to moths and butterflies becoming active earlier in the spring. Unusually cold days kept insects active for longer across all latitudes, with a mix of exceptionally high and low temperatures having the most pronounced effect.

“Insects struggle to perform optimally when they experience a series of abnormally cold and warm days,” Guralnick said. “If the cold doesn’t kill them, it slows them down, potentially driving them into a state of dormancy. However, insects can recover rapidly from cold snaps and subsequently experience extended lifespans due to sudden temperature drops.”

At first glance, longer insect activity periods might appear beneficial. However, co-author Lindsay Campbell, a mosquito researcher, warns that prolonged or altered insect lifespans might lead to increased opportunities for pathogen transmission.

“We see a correlation between El Niño and outbreaks of Rift Valley fever in East Africa. There are also anecdotal reports linking unusually warm or hot and dry springs followed by heavy rainfall to increased outbreaks,” said Campbell, an assistant professor at the University of Florida.

Long-term ecosystem stability relies on the coordinated activity of its constituent parts. If insects become active too early, they risk finding plants that have not yet sprouted leaves or flowers, wasting their energy in a fruitless quest for food.

Moreover, with an ever-changing benchmark for ‘extreme’ weather, it remains uncertain whether insects will be able to adapt to the changes.

“As average temperature and climate variability rise, an organism’s resilience will significantly decrease,” Guralnick warned. “Today’s extreme events will become even more intense in the future, and eventually, the capacity to cope with these changes will reach its limit.”

Reference: “Weather anomalies more important than climate means in driving insect phenology” by R. P. Guralnick, L. P. Campbell, and M. W. Belitz, 5 May 2023, Communications Biology.
DOI: 10.1038/s42003-023-04873-4

The study received funding from the National Science Foundation and the National Institute of Food and Agriculture.

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• Understanding the Effects of Climate Change on Insect Behavior
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