Context dependency and differential arthropod responses belie simple agro-ecological management solutions

Abstract

Policies promoting agroecological management aim to counteract the adverse effects of agricultural intensification on biodiversity, and ecosystem health with varying effectiveness. This study evaluates the effects of agroecological management practices and environmental heterogeneity on biodiversity, pest control services, and crop yields in winter wheat, barley, and oilseed rape fields in Switzerland. We assessed plant species diversity, pest and predator populations, and crop yield across 44 agricultural fields managed with either conventional or agroecological practices, including the establishment of wildflower strips (WFS) and reduced pesticide use. Vegetation diversity was higher in agroecological fields compared to conventional fields, but this did not lead to an increase in predator populations. While ground-dwelling beetles are potentially enriched, neither spiders or parasitoids, nor pest abundances were higher in agroecological fields. Pest pressure was not affected by predator abundance, while yields were significantly higher in conventional fields, with the differences attributed to farming practices rather than the influence of vegetation diversity or pest presence. The effect of environmental heterogeneity varies across taxa and depends on the landscape feature considered.

Synthesis and applications

Our findings indicate that while agroecological practices can enhance vegetation diversity and support a diverse arthropod community, these benefits do not necessarily lead to improved pest control or increased yields. The variability in responses suggests that the effectiveness of such measures is highly context dependent. Therefore, tailored strategies that consider specific crop and landscape characteristics are needed to optimize pest management and maintain productivity in sustainable farming systems.