What matters most in determining European farmers' participation in agri-environmental measures? A systematic review of the quantitative literature

Successful implementation of Europe's agri-environmental policies faces various obstacles, several of which are closely linked to participation. Effectively increasing adoption of agri-environmental-climate measures (AECM) requires a deeper understanding of farmers' motives. Various case -study research has targeted ex -post studies but offers context -specific recommendations. Earlier literature reviews provide certain insights, but have not yet clarified how the evidence on adoption can be optimally applied to AECM design. We explore farmer decisionmaking by synthetizing results from three decades of ex -post empirical studies on AECM adoption in Europe. Our approach applies a theoretically informed participation framework that offers practical insights for AECM design. We systematically scrutinize how different stage -specific constructs, grouped into 'alignment', 'opportunity', 'engagement', and 'contracting', influence farmer decisions. We identify eight determinants of participation and 38 variables capturing their contribution to decision -making. Variables explaining the role of social contexts and satisfaction with contract design are seldom observed but prove significant in around 60 percent of cases. Conversely, variables capturing the relevance of AECM to farmers and the opportunity of participation are frequently included, but often ineffective in explaining uptake. Enhancing the alignment of the measures with farmers' needs encourages adoption, but excessive alignment carries the risk of self-selection bias toward baseline -complying agents, which likely jeopardizes AECM additionality. Our findings highlight how crucial it is for adoption studies to properly account for farmers' opportunity costs and self-selection bias. We draw policymakers' attention to the importance of carefully considering all four constructs during policy design.