AbstractsEngineering

Sustainable phosphorus (P) management is emerging as a pressing concern at both global and local scales because P is an essential nutrient in agriculture and an important aquatic pollutant. While there has been considerable progress in our understanding of the problems caused by human alteration of the P cycle, there remain critical knowledge gaps that hinder our ability to effectively manage this key element. For example, although we know cities are hotspots of P movement on the landscape because they concentrate P inputs (food) and P outputs (food and sewage waste), we have limited knowledge about how P moves in and through cities and the role cities could play in more sustainable P management. We also do not know how important individual choices, such as diet, are in determining overall demand for P. In this thesis, I explore the role cities can play in improving P management, through diet and urban agriculture. Throughout, I focus on how an interdisciplinary approach that incorporates the ecological, social, and technological factors that drive urban P cycling can enhance our ability to answer questions about P management in cities.I first focused on the role of human dietary choices in P demand through time examining how changes in diets have altered demand for P resources over the past 50 years. My results indicate that the global per capita P footprint (the per person amount of mineral P required to produce food crop or animal products for consumption) increased 38% between 1961 and 2007. There is considerable variability in per capita P footprint and in the rate of change in per capita P footprint among countries, mostly associated with differences in meat consumption. In one city in a high-P consuming country (Montreal, Canada), I used substance flow analysis to quantify the P cycle in the food system and in the urban agriculture system of the city. I determined that most of the P entering Montreal accumulates in landfills and little is recycled. The majority of inputs applied to urban agriculture are from recycled sources (such as compost), hinting that, although urban agriculture is a quantitatively small component of the city's P cycle, it could be a catalyst towards more recycling. To assess this potential, I needed to understand not only the P cycle itself, but also the social, ecological, and technological driving factors of urban P cycling. To develop a complete set of social, ecological and technological drivers I might examine in Montreal, I conducted a comprehensive literature review of the drivers in urban P substance flow analyses from around the world. Using a systems thinking lens, I found eight categories of driving factors that should be included in an interdisciplinary analysis of urban P cycling. Including these categories of driving factors will improve researchers' ability to identify synergies between P management solutions and problems and other urban priorities and plans. Finally, I return to the Montreal case study to examine these categories of driving factors in detail. I used…