Flies are more vulnerable to climate change than bees, study finds

Despite their reputation as noisy nuisances, flies play an important role as the most prolific pollinators on the planet, and a new study led by scientists at Penn State University shows that as global temperatures rise, flies This suggests that flies are increasingly at risk.

In a study recently published in the Journal of Melittology, an international team of researchers investigated the heat tolerance of different species of bees and flies from tropical and subtropical regions of the Americas. Their findings suggest that rising temperatures pose a greater threat to flies than bees, as bees can tolerate much higher temperatures and have a wider range.

“Bees and flies are essential for pollinating plants, both in the wild and in agriculture,” said Lorenzo Langstroth, early associate professor of entomology and pollinator health extension specialist at Penn State University, and author of the study. said Margarita López Uribe, lead author of . “However, these important insects are in decline due to habitat loss, pesticides, disease, and increasing threats from climate change.”

López-Uribe explained that flies play an important role as pollinators, second only to bees in terms of the amount of crops they pollinate and the habitat they provide. Flies are particularly important to the overall health and diversity of wild ecosystems, as they facilitate the reproduction of countless plant species and provide food and habitat for other organisms. Flies are also increasingly contributing to agriculture. For example, flies are the main pollinators of cacao trees, which produce the fruit that makes chocolate.

An analysis of the world’s crops in 2020 found that the 105 most widely grown crops that benefit from pollinators have a total economic value of more than $800 billion, and are the most popular crops consumed worldwide. It has been found that there are many nutritious fruit, vegetable and nut products. The study also found that flies, particularly hoverflies and blowflies, are consistently the top pollinators after bees.

“It’s time to give flies more recognition for their role as pollinators,” López-Uribe said. “Flies play an important role, but they don’t get as much attention, and they are just as vulnerable as bees.”

López-Uribe explained that insects are particularly vulnerable to rising temperatures because they have a limited ability to regulate their own body temperature. To understand how different pollinator species will cope with rising global temperatures, researchers have determined the “critical thermal maximum” (CTMax) of bees and flies, the maximum they can tolerate before losing their ability to move. temperature).

The research team found that bees can tolerate much higher temperatures than flies. On average, the CTMax of bees was 2.3 °C higher than that of flies. The researchers also found that time of day affected heat tolerance in bees. Bees that foraged during cool morning hours had higher CTMax than bees that were active during warmer afternoons. The study also found that geography influences heat tolerance.

The team collected the data during the lockdown period during the COVID-19 pandemic. This means that international students from Penn State and other universities who participated in this project conducted research in their home countries. López-Uribe explained that the challenge ended up being an asset, as the students were able to collect data on bee and fly species across the Americas.

“We sent all the equipment to conduct the research to students throughout the United States and South America,” López-Uribe said. “Students were collecting data at home using their kitchens to understand the thermal ecology that these insects tolerate. We were able to provide an international research experience.”

The researchers found that flies and bees from high-altitude tropical regions, such as Colombia’s Cajica, had lower CTMax values ​​than flies and bees from subtropical regions such as California and Texas. This suggests that insects in cool, high-altitude environments may be more vulnerable to even small increases in temperature.

“In alpine and subarctic environments, flies are the main pollinators,” López-Uribe said. “This study shows that there are entire regions that could lose their key pollinators as the climate warms, which could have devastating effects on their ecosystems. ”