UK Wasp Populations Decline Amidst Extreme Summer Weather

Wasp populations across the United Kingdom appear to be significantly lower this summer, a trend scientists attribute to extreme weather conditions. Researchers note a noticeable scarcity of wasps, which are typically abundant during warmer months. This observation is supported by a decrease in media reports about wasp activity and fewer requests for wasp nest removal from professional pest controllers.

The decline raises concerns because wasps play crucial roles in ecosystems. They act as natural pest controllers, contribute to pollination, and aid in decomposition. The current anecdotal evidence, if confirmed by ongoing national monitoring surveys like the Big Wasp Survey, indicates a potential ecological shift.

The unusual weather patterns this spring may have impacted wasp queens. A warm, dry start was followed by unexpected cold, damp days and chilly nights. These fluctuations could have caused queens to abandon their newly established nests or perish, reducing the initial population of founding queens. This early disruption could have significantly limited colony growth.

Subsequent heatwaves throughout the summer may have further stressed wasp populations. While some insects benefit from warm weather, all insects have a critical thermal maximum (CTmax). Exceeding this temperature can lead to desiccation, muscle spasms, and death. For wasps, the CTmax is around 45 degrees Celsius (113 degrees Fahrenheit), a temperature potentially reached on ground surfaces during recent UK heatwaves.

Observations also indicate that the few wasps seen this summer are unusually small. Insect adult size is determined during larval development, influenced by food quality and quantity. Larvae reared in higher temperatures may develop faster but reach pupation at a smaller size. This phenomenon, potentially exacerbated by limited prey availability due to heat, aligns with a long-term trend of shrinking social wasp sizes linked to global warming.