Rising CO₂ levels threaten large bees more than small ones, new study finds

A new study published in Global Ecology and Biogeography shows that rising carbon dioxide levels in the atmosphere are harming large-bodied bees more than smaller pollinators. Researchers examined 25 sites in Pakistan and found that big bees like Bombus asiaticus and Xylocopa pubescens had smaller populations and lower genetic diversity in areas with high CO₂. Smaller bees and hoverflies, however, appeared to cope better or even thrive under elevated CO₂ conditions. The study controlled for altitude, temperature, humidity, and rainfall, isolating CO₂ as a key variable. The authors suggest that higher CO₂ reduces protein in pollen and alters nectar chemistry, which hits larger bees harder because they have higher metabolic demands. Large bees are critical pollinators because they carry more pollen and fly longer distances. The findings are relevant globally, including in Australia where genera like Xylocopa and Amegilla are at risk. The article recommends protecting habitat, planting bee-friendly trees, and reducing competition from introduced honey bees to help larger species adapt.