Agricultural intensification has reduced semi-natural habitats and increased pesticide use threatening beneficial insects, such as bees, that sustain ecosystem function and services. Pesticide risk is dependent on substance-specific toxicity and exposure - the degree to which an organism encounters pesticides at a given time and place. We propose a trait-based framework to clarify how bee activity patterns (i.e., foraging syndromes) intersect with pesticide use in a landscape context-dependent fashion. We hypothesize pesticide exposure and risk to increase with the proportion of agricultural land and with foraging extent. Furthermore, within foraging syndromes, we expect the proportion of agricultural land to disproportionately affect more limited foragers so that they experience a greater pesticide exposure and risk as the proportion of agricultural land increases compared to more extensive and intermediate foragers. Finally, we expect pesticide exposure and risk to be correlated between sources of exposure (i.e., pollen or nectar). We test this framework and hypotheses with a landscape scale study in which we assayed pesticides in pollen and nectar from sentinel bees of three species aligning with limited (Osmia bicornis), intermediate (Bombus terrestris) and extensive (Apis mellifera) foraging syndromes.
Results/Conclusions
We found that landscape context determined pesticide exposure and risk, but differently so for risk among the three model bee species. Specifically, we found increasing risk with increasing dominance of agricultural land for B. terrestris and O. bicornis, but not for A. mellifera. We also found that pesticide risk was correlated among the three bee species and between pollen and nectar sources. This confirmed that, from a pesticide risk perspective, it is important to consider both the landscape context and differences between species and food sources. Our findings suggest bees’ traits will regulate exposure and risk in real landscapes, thus calling into question the suitability of single model species in more holistic and realistic environmental risk assessment of pesticides. Environmental risk assessment should consequently consider the interspecific differences in pesticide exposure and risk that arise from the intersection of bee traits, pesticide use and landscape context.
