Agrochemicals interact synergistically to increase bee mortality

Area of Science:

• Ecology
• Environmental Science
• Agricultural Science

Background:

• Global pollinator declines are a significant concern, linked to various anthropogenic stressors.
• Individual stressors negatively impact bee populations, but their combined effects may be amplified.

Purpose of the Study:

• To quantitatively assess the threat posed by synergistic interactions between multiple anthropogenic stressors on bee populations.
• To evaluate the impact of combined agrochemicals, nutritional stressors, and parasites on bee mortality and other health indicators.

Main Methods:

• Conducted a meta-analysis of 356 interaction effect sizes from 90 studies.
• Included studies where bees were exposed to combinations of agrochemicals, nutritional stressors, and/or parasites.
• Analyzed effects on bee mortality, fitness, behavior, parasite load, and immune responses.

Main Results:

• An overall synergistic effect of multiple stressors was found to increase bee mortality.
• Strong evidence for synergy in bee mortality was observed when exposed to multiple agrochemicals at field-realistic levels.
• Interactions involving parasites and/or nutritional stressors were not greater than additive, and effects on other health proxies were additive or antagonistic.

Conclusions:

• Environmental risk assessments assuming additive effects of agrochemical exposure may underestimate the interactive impact on bee mortality.
• Current assessment schemes may fail to adequately protect pollinators, which are crucial for sustainable agriculture.
• The mechanisms driving synergistic interactions specifically for bee mortality remain unclear.