Evaluating the impact of landscape structure and source-sink dynamics on non-target arthropod pesticide risk assessments in Germany

Abstract

The ELONTA project aimed at understanding the relationships between landscape structure, source-sink dynamics and the risk of pesticide use for Non-Target Arthropods (NTAs). It also investigated the effectiveness of introducing two landscape-based mitigation measures: grassy field boundaries and unsprayed field margins. The project used a model NTA species, Bembidion lampros, a small, univoltine, spring-breeding carabid beetle that is common in temperate European agricultural landscapes. The project combined high-resolution dynamic landscape models with advanced spatially-explicit population models to simulate changes in B. lampros population dynamics in agroecosystems. The impact of pesticide use on B. lampros populations and the effectiveness of mitigation measures were assessed in a set of 611 study plots of 10x10 km2 in Brandenburg and Lower Saxony regions, varying in landscape and farmland heterogeneity. Our analysis showed that beetle populations were better supported in more diverse and heterogeneous landscapes with a high proportion of herbaceous semi-natural habitats and permanent pastures. The negative impact of pesticide use was greater in more homogeneous landscapes with low initial beetle populations, high arable land coverage and low beetle source habitat coverage. The study showed that grassy field boundaries were a more effective mitigation measure than unsprayed field margins. It also revealed the influence of source-sink dynamics on the effect of pesticide application on B. lampros populations, with significant exclusive off-field effects that persisted despite mitigation measures. Landscape management in agroecosystems should focus on maintaining and protecting these habitats, especially in highly homogeneous landscapes.