Approaches and Challenges to Assess Nitrogen Impacts using the Driver-Pressure-State-Impact-Response Framework
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The global nitrogen science-policy community lacks a holistic framework for assessing nitrogen (N) impacts on food production, ecosystems, health, and climate. This results in reduced effectiveness and societal welfare benefits in addressing N challenges and creates the potential for N management in one area to produce N problems in another, or spill-over. Because the pathways leading to N impacts are complex and connected, integrated approaches are vital to prevent such spillovers. Increased and more consistent application of the pressure-state-impact response curves can help direct N policy by identifying pathways to change. The International Nitrogen Management System, INMS, was established to provide such a holistic framework. As part of INMS, we applied the DPSIR (Driver, Pressure, State, Impact and Response) framework to identify both direct and indirect pathways to N impacts focusing on indicators that describe relationships between pressures to states and between states and impacts. We identified seven types of impact domains: greenhouse gas balance, human health, terrestrial ecosystems, aquatic ecosystems, agricultural products, cultural services, and non-agricultural products. We developed a comprehensive searchable Nitrogen Matrix of Impacts and Pressures (N-MIP) that can be used to trace causes to effects and the methods used to develop causal relations and a mathematical response function typology to define the Pressure to State (P-S), State to Impact (S-I) and overall Pressure to Impact relationships. Examples will be provided to illustrate how P-I relations are used to assess the impacts, including economic valuation, of N on agriculture, health, ecosystems, and climate. The mathematical response function typology may have value for policy development by identifying how an impact may respond before, at, or after a human health or environmental response threshold is crossed. Because the methods are applicable across all places and systems, the comprehensive, generic, methodology described to assess N impacts across countries and regions provides a scientific foundation that can be used by regional, national, and international governing bodies to develop policies toward more N sustainable use.