Plant protection UAVs to induce ecological risks in ditches and ponds of rice growing regions: hydrological driving processes and mitigation strategies

Plant protection UAVs can rapidly cover large areas of farmland during insect outbreaks, significantly improving pest control efficiency. However, in rice-growing regions of plain river network areas, concentrated pest control by UAVs simultaneously causes multi-point pesticide export from fields, which tends to intensify the superimposed effect of pesticide pollution loads in ditch–pond systems. Yet, the ecological risks and corresponding acute toxicity to aquatic organisms from concentrated UAV operations remain poorly understood. In this paper, by synthesizing existing knowledge on hydrological processes across different spatial scales, we summarize that concentrated UAV operations alter pesticide fate and transport mainly at two stages: the input stage from fields to surrounding ditches and ponds, and the routing stage within the ditch–pond network. Furthermore, we review the challenges that existing numerical models face in reflecting these changes and discuss possible solutions. We also propose an integrated mitigation strategy along the field–ditch–pond continuum to enhance pesticide removal efficiency at both stages. Finally, we identify key research priorities to guide future monitoring, modeling, and ecotoxicological assessments. Overall, this paper aims to highlight the ecological risks of large-scale UAV operations and to inform the development of strategies that minimize their impact on surface waters while promoting UAV applications in plant protection.