Pollinators keep a later calendar in human-modified landscapes, study finds

Human development is reshaping not only where pollinators reside but also the timing of their activity, according to a study by University of Florida researchers. Analyzing over 80,000 observations from iNaturalist, the team discovered that pollinator seasons shifted later by about 22 days for the start and 21 days for the end in heavily human-modified landscapes in the eastern United States compared to less modified areas.

The overall pollinator season did not lengthen but rather moved later. The findings, published in Royal Society Open Science, shed light on how human alterations to natural areas may influence the seasonal timing of pollinators across various insect groups such as butterflies, beetles, and moths. Lead author Marina Marquis noted that cities not only modify the location where species can thrive but may also impact when certain species are active.

The researchers used data from a region spanning central Alabama to central New York, evaluating human impact through factors like development, agriculture, and roads, all while considering variables like temperature, precipitation, geography, and species distribution. Cities, with their confluence of development, agriculture, and infrastructure, alter vegetation, resources, and other environmental elements simultaneously.

The study raises the question of whether plants and other species that interact with pollinators are also adjusting their schedules in response to urbanization. The findings indicate that different pollinator species may react differently based on their biological traits, sensitivity to temperature changes, and relationships with plants.

Of the 52 species examined, 19 exhibited alterations in at least one aspect of their seasonal activity. Some species started earlier in more human-modified areas, while others delayed their onset. Additionally, some species experienced shortened or lengthened activity periods. This variation is crucial because pollinators rely on plants being available at the right time for sustenance and reproduction.

Discrepancies in schedules could potentially disrupt the delicate balance between pollinators and the plants they rely on. The study also highlights the value of citizen science contributions, such as those gathered through iNaturalist, in investigating ecological shifts on a large scale. As cities continue to expand, understanding how wildlife adapts to these modifications becomes increasingly crucial.