Linking system-level indicators of performance, pressures and impacts to better manage nitrogen
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Background/questions/methods Due to the complexity of the nitrogen cycle, nitrogen thresholds are defined differently across the globe and even within governance systems. All life requires nitrogen, yet it can be challenging to identify the line where the net benefits of nitrogen end and harm begins. In many cases, this line varies according to where the impact is felt (air, drinking water, stream water, estuaries), and depends upon the metrics measured (human health outcomes vs. macroinvertebrate diversity). The United States has regulations associated with nitrogen impacts on air quality, drinking water quality and surface water quality. Many of these connect to the DPSIR (Drivers, Pressures, States, Impact and Response), the causal framework for describing the interactions between society and the environment adopted by the European Environment Agency. The United States addresses nitrogen reductions generally through industry design and performance standards, which are closely connected to drivers in the DPSIR framework. Some of these performance standards include guidelines or thresholds that relate to pressures, such as loads of nitrogen, or states such as nitrate concentrations in water or nitric oxide concentrations in air. A challenge exists in linking regulations related to N pressures and states to the drivers. For example, N surplus might be used as the basis of a performance standard for agriculture, but the relationship to nitrogen concentrations in groundwater or surface water, while generally correlated, is variable across space and dependent on a variety of local anthropogenic and natural factors. Managing the nitrogen problem at the system level is thus very challenging across diverse landscapes and political jurisdictions. Results/Conclusions To connect nitrogen balances and budgets to impacts, it is important to understand the underlying relationships between drivers, pressures, states and impacts of nitrogen release to the environment. In this presentation we explore performance indicators across sectors (drivers), linking them to pressures and impacts, and to existing thresholds and guidelines applied in a management and regulatory context. Examples will be provided of connecting landscape nitrogen inputs to agricultural nitrogen surplus to surface water and drinking water concentrations. We also examine the potential of using water quality trading to manage nitrogen, using US National Nutrient Input Inventory to identify areas where N surplus imbalances exist in combination with good opportunities for nutrient trading. Continued analysis of these types of connections will allow managers to explore these potential focal areas for water quality trading and better inform efforts to reduce nutrient pollution.