Agroecohydrology: Key to Feeding 9 Billion?

Agricultural production necessary to feed 9 billion people in 2050 depends on increased production on existing croplands, and expanding onto 'marginal' lands. A high proportion of these lands are marginal because they are too steep or too dry to reliably support crop production. These same characteristics increase their susceptibility to accelerated erosion, leading (for most soil profiles) to further reductions in plant available water as infiltration and soil profile water holding capacity decline. Sustaining production on these marginal lands will require careful land use planning. In this paper, we present a land use planning framework that integrates 4 elements: (1) potential production (based on soil profile characteristics), (2) edaphic, topographic and climatic limitations to production, (3) soil resistance to degradation, and (4) resilience. This framework expands existing land capability classification systems through the integration of biophysical feedbacks and thresholds. State and transition models, similar to those currently applied to rangelands in the United States and other countries, are used to organize and communicate knowledge about the sustainability of different land use changes and management actions at field to regional scales. This framework emphasizes hydrologic characteristics of soil profiles and landscapes over fertility because fertility declines are more easily addressed through increased inputs. The presentation will conclude with a discussion of how research in ecohydrology can be more effectively focused to support sustainable food production in the context of increasingly rapid social and economic changes throughout the world.