Bees confront aridity: heat and desiccation sensitivities predict bee abundances in a global hotspot of biodiversity

Authors: KAZENAL, MELANIE - University Of New Mexico; WRIGHT, KAREN - University Of New Mexico; Griswold, Terry; WHITNEY, KENNETH - University Of New Mexico; RUDGERS, JENNIFER - University Of New Mexico

Submitted to: Nature
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: What might happen to pollinators with changes in climate? And what would be the economic consequences and impacts to nature especially in dry parts of the country? A long-term study in a desert region tracked how populations of a very diverse group of bees changed across dry and wet years. The 16 year study compared bee declines with how the bees respond to heat and dryness. The data were used to predict bee communities into the future. Drought had the most impact. Almost three out of four species were affected by it. Those bees that best tolerated heat and dryness increased the most. These were mostly bigger bees. Forecasts for the future suggest declines for nearly half of the bee species. While overall abundance of bees was predicted to remain the same, this loss of species could affect pollination of plants. Results of this study provide evidence that changes in climate directly threaten bee diversity.

Technical Abstract: Climate change could pose an urgent threat to pollinators, with critical ecological and economic consequences. But for most insect pollinator species, we lack the long-term data and mechanistic evidence necessary to identify climate-driven declines and predict future trends. We documented 16 years of abundance patterns for a hyper-diverse bee assemblage in a warming and drying region, and linked bee declines with experimentally determined heat and desiccation tolerances. Finally, we used climate sensitivity models to project bee communities into the future. Aridity strongly predicted bee abundance for 71% of 668 bee populations (species x ecosystem combinations). Bee taxa that best tolerated heat and desiccation increased the most over time. Models forecasted declines for 44% of species and predicted more homogeneous communities dominated by drought-tolerant bee taxa, even while total bee abundance may remain unchanged. Such community reordering could reduce pollination services, because diverse bee assemblages typically maximize pollination for whole plant communities. We also found that larger-bodied bees dominated under intermediate or high aridity, pinpointing a valuable trait for understanding the effects of climate-driven bee community shifts on pollination. We provide evidence that climate change directly threatens bee diversity, and that bee conservation efforts should account for the stress imposed by climate.