Returning to a Planetary Boundary for Nitrogen: Science, Economics and Policy

Abstract

My dissertation studies several of the major scientific, economic and policy issues central to managing global nitrogen (N) pollution.

Chapter 2 uses the terrestrial component of an Earth System model to evaluate how global improvements in N use efficiency (NUE) could affect agricultural nitrous oxide (N2O) emissions - an important component of global N pollution. Emissions are projected to increase significantly in a business-as-usual scenario - driven by growth in global fertilizer and manure consumption - though less markedly than previous estimates, due to increased crop N uptake. Nevertheless, global NUE scenarios could reduce global N2O emissions below 1990-2000 levels, delivering important climate and stratospheric ozone benefits.

Chapter 3 is the first evaluation of improved N management measures to consider the economic interests of the fertilizer industry in tandem with farmers and the environment. It demonstrates that the regulatory "sweet spot" - where improved N management benefits the environment, reduces farmers' costs, and increases fertilizer industry profitability - is more likely to occur in China than the U.S. due to the currently extensive over-application of fertilizer, which creates a greater potential for economic gains from improved N management. The fact that the environmental benefits of improving N management consistently dwarf its economic impacts on farmers and the fertilizer industry suggests that policy-makers should consider investing in side-payments to increase stakeholder support.

Chapter 4 addresses the major scientific, legal, technical and policy questions that would have to be considered by the Parties to the international ozone regime if they decided to control N2O. It identifies several legal avenues for controlling N2O, provides a sector-by-sector overview of the major N2O mitigation strategies, and outlines how existing policies managing N2O and other N compounds could be harnessed to implement controls. Finally, it describes three of the major challenges and potential co-benefits of controlling N2O (and N pollution more broadly): food security, equity, and the N cascade.

Chapter 5 concludes with a research proposal to study how calls for an international response to N pollution can be reconciled with the reality that solutions are often locally specific.