Land use, climate, and agricultural sustainability
Climate is a key determinant of crop production, but land use and land cover change associated with agriculture can also influence local climate by altering the surface energy budget. Understanding the impacts of climate change on agriculture will require better understanding of land-atmosphere connections in agricultural landscapes. Recent work using observational data has demonstrated how intensification of cropland productivity (2016), and associated increases in evapotranspiration, have suppressed extreme temperatures over croplands in the United States. Ongoing efforts are further characterizing the connections between intensification, the hydrologic cycle, and temperatures using observations and models, as well as understanding the consequences of these relationships for climate impacts assessment.
Land use practices are also related to farmer perceptions of climate change, an association that may influence the adoption of adaptation measures (2016).
For an overview of how climate change will influence the global food system, see our new Annual Reviews paper (2017).
Intensification throughout the Green Revolution led to large increases in crop production on existing lands, but often with substantial environmental tradeoffs associated with intensive management practices. My work has analyzed the spatial patterns of intensification potential through yield gap closure, as well as estimating potential spatial changes to irrigation and NPK fertilizer associated with increases in production (2012). As part of this work, a global crop-specific dataset of fertilizer application was developed, available for research purposes on earthstat.org. In a related study, we showed that there are large production and environmental gains possible from more optimal spatial allocation of nitrogen resources (2014). Using historical nitrogen budget data, we demonstrated that this opportunity space has actually increased since the 1960s as the allocation of nitrogen between regions has become less efficient (2017).
Stagnation of crop yield increases are of major concern given ongoing increases in food demand. With Deepak Ray and others, we analyzed the most complete dataset of time-series crop census data ever compiled (13,500 census units, 2.5 million observations). Roughly 1/3 of the world's croplands are experiencing stagnant yield trends (2012) and current yield trends are not keeping pace with the expected doubling of food demand (2013).
The ecosystems around us provide valuable provisioning, regulating, supporting, and cultural services. Agriculture can be thought of as an ecosystem service itself, and as a major beneficiary of other ecosystem services (including soil formation and pollination). My work with the Natural Capital Project provided users of the InVEST software access to databases of agricultural production and management. A recent research collaboration in this area highlighted the importance of pollination for micronutrient production (2014).