Human development may be shifting the seasonal calendar for pollinators, according to a new study from University of Florida researchers.

Researchers with the University of Florida Institute of Food and Agricultural Sciences found that pollinator activity began about 22 days later and ended about 21 days later in the most heavily human-modified landscapes compared with the least modified areas.

The findings were published in Royal Society Open Science and are based on more than 80,000 observations submitted to iNaturalist.

Pollinator seasons shifted later — but did not get longer

The researchers expected human-modified landscapes might extend the overall pollinator season. Instead, they found the season generally shifted later in the year without becoming longer.

The study examined a region stretching from Central Alabama to Central New York. Researchers compared pollinator activity in landscapes ranging from relatively natural areas to places more heavily affected by development, agriculture and roads.

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The analysis also accounted for differences in temperature, precipitation, geography and species.

“We often think about cities as changing where species can live, but our results suggest it may also change when certain species are active,” said Marina Marquis, the study’s lead author.

Different species responded in different ways

The shift was not the same for every pollinator. Researchers analyzed 52 species and found that 19 showed changes in at least one measure of seasonal activity.

Some species became active earlier in more heavily modified areas, while others began later. Activity periods also varied, with some species showing shorter seasons and others showing longer ones.

The study included multiple insect groups, including butterflies, beetles and moths.

“Cities, and those who live in cities, change vegetation, resources and many other features of the landscape at the same time,” Callaghan said. “If we are shifting the pollinator calendar, the big question is whether the plants and other species they interact with are shifting their calendars too.”

Timing could affect plants and pollinators

Pollinators depend on flowers for food, while plants rely on pollinators to reproduce. If the seasonal schedules of plants and pollinators no longer line up, those relationships could be disrupted.

“For pollinators, timing matters,” Marquis said. “Bees, butterflies and other pollinators need flowers for food, and plants need pollinators to reproduce. If one changes its schedule and the other doesn’t, that relationship could be disrupted.”

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Researchers said the findings highlight the need to better understand how urban growth and other changes to natural landscapes affect ecological relationships.

Public observations are helping researchers track change

The study also demonstrates the value of public contributions to iNaturalist, a platform where people can submit observations of plants and animals.

Those observations gave researchers access to information across a broad geographic area and multiple species, allowing them to study seasonal changes at a scale that would have been difficult to achieve otherwise.

“Platforms like iNaturalist give us a remarkable opportunity to study how nature is changing across species and entire regions — and to ask questions that simply weren’t possible at this scale before,” Callaghan said.

Researchers said understanding how wildlife responds to development will become increasingly important as cities continue to grow.