The Role of Human Activities in Environmental Change: Characterizing Agricultural Nitrous Oxide Emissions, Assessing International Nitrous Oxide Policy, and Developing a Framework for Community Engagement

Abstract

The increasing complexity of global environmental challenges necessitates a multifaceted blend of scientific research, policy formulation, and active public involvement for successful intervention. Such challenges, with climate change at the forefront—propelled by the human-induced rise in greenhouse gases—call for urgent and cohesive action from varied sectors. Notably, nitrous oxide (N2O) emissions present a critical concern due to its significant role in stratospheric ozone depletion and its extraordinary global warming potential, which is 298 times greater than that of carbon dioxide over a 100 year timescale. In the U.S., the primary source of N2O emissions is found within the agricultural sector, primarily through the use of nitrogen fertilizers in soil management practices.

Discrepancies in our understanding of N2O emissions can lead to voids in policymaking, underscoring the need for policies informed by the most current science. Additionally, effective science communication and engagement from all relevant parties are essential in bridging the gap between research findings and their application in policy and community practices. This dissertation aims to highlight the importance of a cohesive and integrated approach to climate change action. It explores specific scientific approaches for N2O emissions, examines policy tools and frameworks to mitigate N2O emissions, and cultivates accessible science and community engagement.

Foremost in the dissertation is the use of airborne observations over the U.S. Corn Belt to characterize and quantify N2O emissions. Here, the connection between atmospheric observations and surface emissions is linked by using the Stochastic Time-Inverted Lagrangian Transport (STILT) model, further refined by a Bayesian inversion structure to quantify emissions. Noticeable differences in emissions emerge across time and space, pinpointing that a small fraction of sites (25% of the studied areas) are responsible for a disproportionate quantity of total emissions (52-77%).

Subsequently, the dissertation highlights the critical role of integrating N2O mitigation into worldwide climate policy agendas. New Zealand is set to become the first country in the world to price agricultural emissions from 2025. This dissertation investigates New Zealand's strategies for handling N2O emissions, showcasing their policies and considering their adaptability as a model for other countries.

The final segment of the dissertation emphasizes the necessity for partnership between geoscientists and communities to forge equitable, science-based climate solutions. It addresses a significant lapse in geoscience doctoral education that often omits the translation of climate science into practical policy and decision-making. As a case in point, it describes an innovative University of Michigan course, which facilitated a collaboration between students, faculty, and the Washtenaw County Water Resources Commissioner's Office, culminating in the development of implementable climate action plans.