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Nature's Delicate Balancing Act

USF biologists study thousands of records to gain an unprecedented understanding of how a changing climate is affecting seasonal activity in nature

Eastern Tiger Swallowtail in Tampa, Florida. Many butterflies time their life cycles to appear in the spring when flowers are blooming. Credit: Jeremy Cohen, PhD

In ecosystems around the world, changing seasons act as nature’s calendar, prompting animals to breed, flowers to bloom and insects to pollinate crops, along with many more time-sensitive events that are crucial to functioning ecosystems.

Sandhill crane mother and two chicks in Lakeland, Florida. Sandhill cranes must finish raising their chicks by the end of spring in time to migrate north every summer. Credit: Jeremy Cohen, PhD

The study of these seasonal activities is called phenology. As climate change alters seasonal temperature and precipitation patterns related to these seasonal activities, species interactions – like crop-pollinator, host-parasite and predator-prey interactions – can become mismatched.

For example, if insect populations rise and plants bloom at different times, then insects might not have enough food and plants might not be pollinated, compromising food production for humans. Thus, phenological mismatches driven by climate change can threaten the role that species interactions play in maintaining functioning and healthy systems.

Researchers at the University of South Florida have offered a deeper understanding of climate change effects on animal phenology in their study, "A global synthesis of animal phenological responses to climate change", published this week in Nature Climate Change.

By examining more than a thousand records of these phenological shifts dating back to the 1950s, the study revealed that various taxa, like insects, birds, amphibians and mammals, are shifting their seasonal activities at different rates in response to a changing climate.

“We found that cold-blooded species and those with small body sizes are shifting their phenological activities faster, or track changing climates more effectively, than warm-blooded or large-bodied species,” said the study’s lead author Jeremy Cohen, PhD, a postdoctoral researcher in the USF Department of Integrative Biology. “These differences could potentially cause mismatches between interacting species, such as migrating birds and their prey.”

The study also provides the first evidence that different locations have different drivers of climate change-induced phenological shifts. For example, at temperate latitudes, multidecadal trends in temperature were associated with phenological shifts, whereas at tropical latitudes, it was trends in precipitation. Jason Rohr, PhD, a USF professor and co-author of the study, explained that these patterns are sensible because seasonality is generally driven by temperature in temperate regions and rainfall in tropical regions.

Common tern female and chick on Long Island, New York. Shorebirds time their breeding to coincide with peak fish availability, usually in early summer. Credit: Jeremy Cohen, PhD

Cohen and Rohr, along with USF Associate Professor and co-author Marc Lajeunesse, PhD, say there is a benefit to taking a ‘weight-of-evidence’ approach to understanding phenological responses.

“When you synthesize thousands of records from the across the globe, as we have done, you can more confidently draw broad conclusions about phenological responses to climate change and better forecast the consequences of climate change,” Cohen said. 

“Our research elucidates the drivers of phenological responses and the traits of organisms that influence their ability to track changing climates,” said Rohr. “We expect these findings to improve our ability to forecast the locations, systems and species that might be at the greatest risk from climate change, and ideally mitigate any adverse effects that these changes might have on the services that ecosystems provide to humans.”

To read the full research article, click here.

Story by Aaron Hilf, University Communications and Marketing

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