Australia is home to roughly 1,700 native bee species, and on a scorching summer day, two of them might share the same patch of ground. One burrows into the cool earth and waits out the heat. The other is sealed inside a paper-thin plant stem, exposed to the full force of the sun with almost no insulation between it and the air outside.
New research suggests that where a bee chooses to nest may be one of the most consequential decisions it makes — not just for surviving a hot afternoon, but for surviving a warming world.
A tale of two nests
Australia’s 1,700 native bee species generally fall into four broad nesting types: ground burrows, wood cavities, plant stems, and small existing twig holes. That grouping turns out to matter enormously when temperatures climb.
Underground nests act as natural insulators. Soil absorbs and buffers heat, so bees sheltering below ground never experience the full intensity of what is happening at the surface. On a scorching afternoon, the temperature difference between above and below ground can be striking.
Stem-nesting bees have no such refuge. Their homes sit fully exposed, with thin plant walls offering almost nothing in the way of a thermal buffer. The structural reality of that nesting choice creates a stark divide in daily heat exposure — one that is becoming harder to ignore as global temperatures rise.
What the study measured — and how
The research, published in Nature Communications, examined heat tolerance across 95 native bee species from eastern mainland Australia, stretching from the tropical north down to the cooler south. Seven universities contributed: Macquarie University, The University of Sydney, La Trobe University, Flinders University, University of Wollongong, Adelaide University, and The University of Queensland.
The team explored how heat tolerance has evolved differently depending on nesting type. Stem-nesting species showed the lowest capacity to escape unfavorable temperatures compared to their ground- and wood-nesting relatives.
Ninety-five species across a vast geographic range makes this one of the most comprehensive assessments of bee climate vulnerability conducted to date. Lead author Dr. Carmen da Silva, a Research Fellow at Macquarie University’s Pollinator Futures Research Centre, described stem-nesting bees as likely “the most impacted by anthropogenic climate change in the near term.”
The tropical paradox: already hot, still at risk
One of the study’s more counterintuitive findings involves geography. Bee species living closer to the equator showed the highest overall climate vulnerability — even though they are already adapted to hot conditions.
The explanation lies in proximity to physiological limits. Many heat-tolerant tropical bees already live near the upper edge of what their bodies can handle, so additional warming, even modest amounts, may push them past that threshold with little room to adjust. Dr. Vanessa Kellermann of La Trobe University, a senior author on the study, put it directly: species with the highest heat tolerance were not necessarily the safest from warming, precisely because they already inhabit extremely hot environments.
This challenges a common assumption in climate biology — that heat-adapted species are automatically more resilient. For tropical native bees, which are vital pollinators for crops including macadamia nuts, avocados, mangos, and lychees, that assumption could prove costly.
Why losing these pollinators would matter
Native bees support both wild ecosystems and agricultural productivity. The species facing the greatest risk — stem-nesters and tropical bees — are often the very ones performing pollination that is difficult or impossible to replace.
Dr. da Silva noted that bees sustain native ecosystems while also playing a crucial role in crop production. Losing key pollinator species does not affect only those species. Effects move through food systems and plant communities in ways that compound over time, and the threat does not arrive in isolation either. Warming and drying climate trends layer on top of habitat loss, pushing cumulative pressure well beyond what any single stressor would produce alone.
Behavior as a window into survival
The study makes a broader methodological argument: understanding bee behavior — particularly nesting habits — is as important as measuring physiological heat tolerance when assessing climate risk. Temperature thresholds alone do not tell the whole story.
Dr. Ros Gloag of the University of Sydney, a co-senior author, emphasized how much remains unknown. Much of Australia’s native bee diversity is poorly studied, meaning many vulnerable species may not yet appear on any conservation radar. Future research directions include expanding surveys of lesser-known species and modeling how habitat modification affects nest-site availability for stem nesters. As the climate continues to shift, knowing where a bee sleeps may be just as telling as knowing how much heat it can endure.