06/01/2026
How does climate change affect bees?
In Custer County, South Dakota, erosion has sheared open a west-facing sandy cliff at one of our partner bison ranches, exposing hundreds — maybe thousands — of vertical nest tunnels built by ground-nesting sweat bees, most likely the brown-winged striped sweat bee (Agapostemon splendens). Cavity-nesting leafcutter bees, perhaps the common little leafcutter bee (Megachile brevis), share this cliff. In the exposed brood cells, every occupant is dead: the same generation, at the same depth.
A synchronous mass mortality event.
Ground-nesting bees spend most of their lives sealed in shallow cells just centimeters down, exposed to heat with nowhere to retreat. In a “normal” year, that’s fine. But weather here is turning extreme, and that spells trouble for these pollinators. In mid-July 2024, temperatures on the ranch jumped from the 60s into the 100s within days and held there for two weeks; a “derecho” (a vast, fast-moving thunderstorm complex that produces destructive “straight-line” winds) swept across western South Dakota with measured gusts above 100 mph (NWS Rapid City), and the ranch manager reported golf-ball-sized hail — shredding the ranch’s plants, and possibly exposing these very nests. By the time I surveyed the site that August, the vegetation was scorched. I was so focused on that, I didn’t look up and notice the nests until this spring.
The drought underneath it all is deepening. The ranch logged about 3 inches of precipitation in the eight months between my September and mid-May visits — against a norm of roughly 7.5 inches for January through May alone. The National Weather Service ranked January–March 2026 the second-driest start to a year in Custer County in 132 years, and the Black Hills are now in extreme drought.
A brood cell a few centimeters down can’t escape a surface that overheats, gets battered by “once-in-a-lifetime” hail and wind every few weeks, or sits in a landscape that no longer holds water. This is one of the less visible ways a warming, drying climate reduces bee populations — community by community, below ground and out of sight.
