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Dehydration, Not Heat, Poses Unexpected Threat to America’s Bees

In a surprising twist that has caught the attention of the scientific community, researchers have discovered that America’s bees face a greater risk of death from dehydration than overheating as temperatures rise across the nation. This unexpected finding emerges from an extensive three-year study led by Bowling Green State University (BGSU) that spanned 10 major U.S. cities.

The comprehensive research project, supported by a $430,000 grant from the U.S. Department of Agriculture, tracked the health and abundance of bees across 60 urban farms and gardens, revealing crucial insights into the challenges facing these essential pollinators in an increasingly warming climate.

“It is vitally important to understand the connection between the climate and pollinator health,” explains Kevin McCluney, Ph.D., an associate professor of biological sciences at BGSU who led the research. “It’s estimated that the value of crops pollinated by bees is worth about $24 billion per year in the U.S. Bees are incredibly important to our food systems, which is why learning more about how bees are impacted by rising temperatures is crucial.”

The study’s scope was unprecedented, examining dozens of bee species across urban heat islands in six states: Ohio, Michigan, North Carolina, Georgia, Colorado, and Arizona. Cities under investigation included major metropolitan areas such as Atlanta, Denver, Detroit, and Phoenix, providing a diverse range of climate conditions and urban environments.

One of the most concerning findings centers on the decline of bumblebees, particularly in the Southwest. “Most bees are ectothermic, meaning their body temperature rises with air temperature,” McCluney notes. “Similar to humans, bees lose water as they get hotter, which can cause dehydration.” The research revealed that bumblebees have virtually disappeared from Phoenix and Tucson, while facing significant risks in all other studied cities.

This absence of bumblebees could have far-reaching implications for food production, particularly for crops requiring specialized pollination techniques. Unlike honeybees, bumblebees can perform buzz pollination – a method essential for plants like tomatoes that require vibration to release pollen from flowers.

However, nature may have already begun adapting to these changes. McCluney’s team observed that digger bees, which remain common in Phoenix and Tucson, can also perform buzz pollination, potentially filling the ecological niche left by declining bumblebee populations.

The study has assembled the largest known dataset of bee tolerances to heat and dehydration, creating a crucial baseline for understanding how these pollinators might fare as global temperatures continue to rise. Yet the findings have also opened new questions about the subtle effects of climate stress on bee populations.

The research team is currently investigating whether bees suffer adverse health effects even when approaching – but not exceeding – their temperature and hydration thresholds. They’re also exploring practical solutions, such as the strategic placement of shade, flowers, and water sources, to help bee populations cope with rising temperatures.

“There’s still so much we don’t know about how bees regulate temperature and hydration,” McCluney acknowledges. The team is seeking additional funding to deepen their understanding of climate impacts on pollinator health and develop effective mitigation strategies.

While the study highlighted some species’ resilience to urban heat, it also emphasized that bee populations face multiple concurrent threats, including habitat loss, pesticides, and diseases. This complex web of challenges suggests that efforts to protect these crucial pollinators will require a similarly multifaceted approach.


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