Implications of climate change on the environmental risk assessment of chemicals applied in agricultural ecosystems

Climate change and pollution are major drivers of global biodiversity loss and freshwater ecosystems are particularly at risk from diffuse pollution from agrochemical landscapes. The predicted increase in the impact of climate change on weather systems may have important consequences for environmental exposure and ecological impacts of agrochemicals. However, current consideration of the effects of climate change on environmental risk assessments (ERAs) is limited to qualitative reviews or specific case studies. Therefore, there is a need to quantify the effects of climate change on agrochemical exposure and ecosystem sensitivity and integrate findings within ERAs. This thesis aims to address three major issues relevant to freshwater ERAs: firstly, how spatial and seasonal variation in climate change affects agrochemical fate via the soil matrix considering chemical persistence. Secondly, to assess what effect species composition has on assemblage sensitivity and how this varies by i) chemical type, and ii) the change in composition under climate change. Finally, multi-stressor of chemical and temperature shock was investigated for mitigation by multi-generation acclimation. The effects of climate change exhibited spatial and seasonal variation with precipitation and chemical degradation being major factors affecting chemical flux into freshwaters. Assemblage composition, including shifts under climate change, significantly affect sensitivity, although the extent of variation is chemical dependent. Temperature influenced reproductive strategy, but multi-stressors and temperature acclimation effects were limited. The conclusions from each chapter were drawn together by contextualising the results within an ERA framework using case study chemicals. These indicated that the change to risk is spatially variable and beyond existing uncertainty accounted for within ERAs. This demonstrates that application of these results to realistic chemical uses is insightful and that existing ERAs can be adapted to include climate change. This is necessary as this thesis indicated that specific chemicals and locations underwent a large increase in risk.