LAUSR

Farmers' conservation decisions are central to addressing regional environmental challenges, such as biodiversity loss, water quality impairment, or climate change. However, three decades of substantial investment in agri-environmental programs has not yielded widespread adoption or improved environmental outcomes. It remains difficult to explain why farmers adopt despite an extensive body of research on the topic. One possible reason for this is that researchers are limiting the types of metrics they are analyzing to explain farmer decisions. We systematically and critically evaluated the social science adoption literature to address three important gaps: (1) How are adoption studies measuring adoption effectiveness? (2) How do studies integrate individual farmer perspectives into broader institutional (i.e., social and governance) contexts? (3) What are the most prevalent metrics that adoption research uses to characterize the human-natural system? We coded 174 studies and found that only 10% connect adoption decisions to conservation outcomes or undertake longitudinal research, while the dominant approach in adoption research excludes the institutional contexts in which farmers are situated. The most prevalent metrics focus on farmer demographics, financial and technical capacity to adopt, and economic motivations. The lack of attention to both conservation outcomes and longitudinal studies limits researchers' ability to analyze the effectiveness of CP adoption. To advance our understanding of adoption, we recommend that future research measure conservation outcomes and track how knowledge about adoption effectiveness feeds back into farmer perceptions and social norms towards adoption. Research should also consistently measure how agri-environmental programs mediate the social acceptability of adoption. Lastly, institutional metrics that can be widely incorporated into coupled human-natural systems research will advance synthesis efforts to better explain why farmers adoption conservation practices.