in areas separated from crop production will likely need to be addressed, as discussed in the NRC report (2008). Given those structural changes, creative strategies to reintegrate livestock and crops at the regional scale may be required (Powell et al., 2004).
Many processes and issues need to be addressed by landscape- and watershed-level planning and analysis.
Sustainability and robustness of agroecosystems are defined by economic, social, and environmental characteristics at the farm, landscape, and regional levels. The scale and diversity of individual enterprises on the landscape is an important determinant of, for example, nutrient and water movement and vulnerability to extreme events. Also, higher-level catchment strategies are needed to optimize land and water use, address competition for water, and avoid developing overdrafts (InterAcademy Council, 2004). Similarly, spatial arrangements of habitats and their connectivity across the landscape are critical for effective management of native biodiversity (Kristhanson et al., 2009). The use of Geographic Information Systems (GIS) technology will be essential for the examination of landscape-and regional-level questions. The increasing numbers and scale of animal confinement operations that are evolving in response to market demand for quality livestock products, within Africa and in response to global market opportunities, present an important need for assessment of nutrient flows and local loading. Positioning of such facilities within watersheds to facilitate nutrient dispersal on the landscape for conservation and protection of water quality will present a new range of problems that require policy guidance, just as they do in highly developed economies.
Management of grazing lands involves pastoralists being able to respond to variability in the spatial and temporal availability of resources. Strategies used include movement of livestock to follow quality and quantity of feed and water, flexible stocking rates, and herd diversification (IAASTD, 2009). Grazing systems are being challenged by changes in land tenure arrangements and stresses because of climate change. The latter will change the carrying capacities for livestock because of alternative predictions for changes in rainfall under different scenarios for climate change. The use of GIS will enable the development of spatially explicit models to provide insights into productivity patterns of the system and development of policies to ensure sustainability (IAASTD, 2009). Useful resources and linkages, particularly for African scientists, are available at the website of the International Livestock Research Institute (International Livestock Research Institute, 2009b).
When considering the relevance of lessons learned in the United States to sub-Saharan Africa, it is important to recognize key differences between the two regions. Nonetheless, the concepts of sustainability and many of the broad approaches presented in this report are relevant and concur with conclusions from some recent international reports and they are summarized below.
Use of a systems approach with an interdisciplinary focus and understanding is essential, as is an awareness of the social, economic, and policy context within which farming systems operate.
Technologies to address soil, water, and biotic constraints are needed that integrate ecological processes and use locally available resources in combination with judicious use of external inputs when necessary.
Promising technological approaches include improving soil quality by organic