Environmental policymaking is embedded in social-ecological systems (SES) that continuously evolve and change, often in unexpected and non-linear ways. Such challenges call for responsive policymaking that adjusts policy when new information and knowledge about social-ecological change is available. However, policy adaptation can be difficult as policies often emerge as an outcome of multiple interactions between state and non-state actors that pursue their different interests, aim to achieve their individual and shared goals and make sense of information and knowledge. Complexities inherent in SES can be better captured through diverse types of information and knowledge, while adaptation to social-ecological change can occur through innovation and learning. Research has emphasized the contribution of non-state actors or interest groups in realizing such processes in policymaking. However, interest group participation can also be a source of conflict or result in dominance of powerful interests and resistance to learning and policy change. This thesis aims to shed light on the dynamics of the policy process in social-ecological systems to better understand some of the mechanisms that drive its responsiveness to social-ecological change. It focuses on interest groups and their properties as well as the social and ecological conditions of their participation in the policy process to investigate how responsive and sustainable policies can emerge out of the “messy” political struggle. The thesis first explores the case of 2013 EU Common Fisheries Policy (CFP) reform to trace the mechanism of interest group influence and identify their contribution to the flow of information from SES. Further it applies the empirical mechanism in an agent-based model to: 1) test the scope conditions of the mechanism; 2) extend it to include interest group responses to change in the managed SES. Paper I of the thesis analyses theoretical frameworks of the policy process originating in public policy research to assess their suitability for capturing political complexity in SES governance research. Paper II looks at the CFP reform case, using process tracing to understand how interest groups have been able to achieve influence on the reform.  Paper III further investigates the case to find the role of interest groups in shaping information flows within the policy process. Paper IV uses empirical findings in Papers II and III, along with frameworks analyzed in Paper I to develop an agent-based model that explores how individual characteristics of political actors in interaction with political conditions and issue characteristics influence the responsiveness of the policy process and result in sustainable outcomes. I find that through interest group participation policies can better respond to change in the managed SES; however structural factors (such as presence of institutional ‘window of opportunity’, issue salience and beliefs of policymakers) can make the response adverse or weaken it. Interest groups also engage in transmitting and interpreting diverse information about policy impacts, social and ecological context of the issue and use framing to convey information that better supports their proposals.