PS 40-108 - From threats to opportunities: Comparing global regions using Pressure-State-Impact metrics of reactive nitrogen use

Abstract: How might countries currently lagging in nitrogen management potentially emerge as international innovators? Eliminating leaks and improving recycling in the “nitrogen pipeline” offer several opportunities. Regional comparisons of threats from excess reactive nitrogen (Nr) – that unintentionally released through combustion, agriculture, and human waste – can help motivate stakeholders and target management actions. We developed a list of priority indicators of nitrogen impacts, following the Driver-Pressure-State-Impact-Response model (DPSIR), for water quality, air quality, greenhouse gas emissions, ecosystem biodiversity, and soil quality. We then compared seven global regions that differ in nitrogen accessibility and socio-economic status, using publicly available data, including literature review, government and agency (WHO, FAO) statistics, and regional monitoring efforts, as collated by colleagues in each of seven different regions. We assessed the extent to which national or regional regulatory standards matched those of international agencies (WHO, UNEP), and how that match related to indicator status in the different regions. Finally, we identified regional data gaps and management opportunities for several key metrics of nitrogen impacts.

Recent assessments suggest increasing impacts from Nr to water quality, air quality, GHG emissions and biodiversity. However, N trajectories best reflect timing of development and regulatory oversight, which vary across countries, and across locations and sectors within countries. High income countries in multiple regions that saw the greatest impacts on water and air quality in the late 20^th century also typically had earliest implementation of regulations to reduce N emissions and related impacts, with most dramatic benefits for air quality. In contrast, even in developed countries, few standards exist for nonpoint release of Nr from agriculture, whose impacts can predominate in many regions (e.g., NH₃ emissions for air quality, NO₃^- leaching for water quality). Management efforts to address these impacts may take a long time to achieve water quality goals, due to nutrient storage and complex ecological interactions. Similarly, infrastructure for human waste disposal in developed countries releases, rather than recycles, Nr. Recent rapid development and population growth without matching infrastructure and regulatory standards have led to the most rapid growth of Nr impacts in developing countries, particularly in China and South Asia. Some countries in several regions still lack sufficient Nr for productive agriculture, leading to degradation of soil fertility. Developing countries that currently lack infrastructure could implement strategies emphasizing biological N fixation and better recycling of human and animal wastes, avoiding the current flow-through Nr model of developed countries.