b'33Control of diffuse agricultural pollution and management of trans-boundary waterways: A comparative analysis of thepolicymaking process in Ireland and Northern IrelandAttorp A11School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne,NE17RU, U.K.Brexit is likely to trigger significant changes in the agri-food sector between Ireland, Northern Ireland and Great Britain, including shifts in market conditions, industrial organisation, and policy. This may have a disproportionately significant impact on the island of Ireland due to its highly integrated agri-food sector and shared ecosystems. Resultant challenges, if not properly ad-dressed, have the potential to negatively affect current provision of ecosystem services in agriculture, and undermine the overall sustainability of the industry. Many of the islands ecosystems are transboundary in nature, including numerous waterways. New regulatory regimes may result in different standards across a single water catchment area; changes to the management of a catchment in Northern Ireland can exhibit positive or negative externalities in the Ireland, and vice versa. One of the challenges for policy makers and farmers alike will be to determine how to weather upheavals in agri-environmental policy, practice and trade so that farmers on both sides of the border can collaboratively continue to thrive while also sustaining and improving existing land and waterway management practices. In doing so, there must be greater consideration of the factors that affect farmers decisions around land use management and practice. Farmers are driven not only by market factors and economic incen-tives but also by a complex mix of social, cultural and political factors, household and individual profile characteristics, and concern for the natural environment. Understanding these is critical to understanding how farmers adapt to policy changes.This project considers the potential impact of diverging agri-environmental policy onagricultural land use and trans-boundary waterway management on the island of Ireland. Using a range of qualitative methods (interviews, focus groups and case studies), I am investigating the various factors that affect farmers land use and waterway management practices in specific trans-boundary water catchment areas in the region, and to what degree these factors areconsidered in the policymaking process.77'