From global land grabs to urban food forestry: Land use decisions and climate impacts in food systems across scales

Background/Question/Methods

Local and global assessments often address similar issues, but come to different conclusions that cannot inform one another. To explore this phenomenon, and create frameworks to link these disparate approaches and inform management decision-making, I undertook both local and global analyses of two pressing issues: land-use decisions on where to grow crops, and climate impacts on crops.

For the land-use issue, at the local scale I examine the emerging phenomenon of urban food forestry (UFF), which links principles of urban agriculture and urban forestry to grow food trees in cities, and present calculations demonstrating the potential for UFF to meet food needs in a case study of Burlington, Vermont. At the global scale, I present a typology of land grabbing based on the location and type of crops grown in recent large-scale land acquisitions, using network analysis and geographic visualizations.

For the climate impacts issue, I present a local observational study of the effects of light and temperature on winegrape chemistry and yields in California, and a global study using statistical analyses of climate model products and a process-based crop model to project yields of wheat in India and Australia, and maize in Iowa and South Africa. 

Results/Conclusions

At the local scale, I find that an ambitious program to plant urban apple trees could more than provide for all Burlington residents’ recommended daily minimum fruit intake, or meet the deficit caloric intake of the city’s very food insecure population. Globally, I find that most crops currently being grown on large-scale land acquisitions are for fuel or flexible purposes, and that the food crops being grown are often poorly suited to the local climate; calorie production could be increased by up to 40% by switching to more locally-suited crops.

In studying both local and global climate impacts on crops using both observational and statistical approaches, I find critical periods and thresholds for climate extremes with disproportionate impacts on crop yields and composition. For example, warmer temperatures and high light intensities during ripening decreased phenolic compounds that give color and structure to wine, and high-yielding years for maize in Iowa have historically been associated with wetter summer conditions, which are likely to become less frequent in the future. I use these cases to examine the potential for adaptation to environmental stresses in agriculture, based on both empirical surveys and modeling of farmer behavior, using a typology for acceptable adaptation.