Key Points
- Flies are vital pollinators, second only to bees in global ecosystems and agriculture.
- Rising global temperatures threaten flies more than bees due to lower heat tolerance.
- Pollinators contribute over $800 billion annually to major global crops.
- Bees demonstrated higher “critical thermal maximum” (CTMax) values than flies, showcasing greater heat resilience.
Often dismissed as mere nuisances, flies play a crucial role as pollinators, second only to bees in their contribution to global ecosystems and agriculture. However, new research led by Penn State scientists reveals that these vital insects are increasingly at risk due to rising global temperatures. Published in the Journal of Melittology, the study examined heat tolerance in various bee and fly species across tropical and subtropical regions in the Americas. It found that flies are more vulnerable to higher temperatures than bees, with a broader habitat range and greater heat tolerance.
Margarita López-Uribe, a Penn State professor and lead author, emphasized the critical role of flies in pollination and their importance to wild ecosystems and agriculture. Flies are indispensable for pollinating plants such as cocoa trees, essential for chocolate production. Globally, pollinators contribute over $800 billion in economic value by benefiting 105 major crops. Despite their significance, flies receive far less recognition than bees, even as they face similar threats from habitat loss, pesticides, disease, and climate change.
The study focused on insects’ “critical thermal maximum” (CTMax), measuring the highest temperature they can endure before losing mobility. On average, bees showed a CTMax 2.3°C higher than flies. Geography and daily activity patterns further influenced heat tolerance. For example, bees foraging in cooler morning hours exhibited higher CTMax values than those active during warmer afternoons.
During the COVID-19 pandemic, international students collaborated remotely, conducting research in their home countries using kitchen setups to measure thermal thresholds. This innovative approach enabled data collection across diverse regions, providing insights into the vulnerability of high-altitude species. Flies and bees from cooler, high-elevation tropical areas like Cajicá, Colombia, demonstrated lower heat tolerance than those in subtropical regions like California and Texas.
The findings underline the potential ecological consequences of losing flies as primary pollinators in specific regions, particularly alpine and subarctic environments. López-Uribe warns that the loss of such critical pollinators due to climate change could have catastrophic effects on ecosystems and food production worldwide.
