of landscapes in part to commodity support payments because these supports provide a strong incentive for farmers to focus on planting program crops by monocropping and to maximize yields per dollar of cost (that is, to focus on only two of the four sustainability goals). Risk management policies can affect sustainability initiatives because some crop insurance products carry substantial subsidized premium structures that can potentially encourage farmers to grow monocrops, which could increase the vulnerability of highly erodible soils and reduce system resilience. Conservation programs are a mechanism for encouraging adoption of particular farming practices, but they are voluntary programs, often with a small proportion of farms participating. Public programs designed to increase incentives to move toward greater sustainability are increasing, but they remain a small portion of the federal and state agricultural policy portfolio.

Although market, policy, and institutional contexts are important drivers of the trajectory of U.S. agriculture, the response of individual farmers to the incentives and disincentives created by market conditions and policy contexts can be diverse. Efforts to promote widespread adoption of different farming practices and systems for improving sustainability will require an understanding of how variability among individual, household, farm, and regional-level characteristics affect farmers’ response to incentives and disincentives. The scientific research to date is inadequate to assess the full impacts of current and proposed policy frameworks.

RECOMMENDATION: Because of the critical importance of macro-structural or institutional drivers of farmer behavior, the U.S. Department of Agriculture should increase investment in empirical studies of the ways that current and proposed market structures, policies, and knowledge institutions provide opportunities or barriers to expanding the use of farming practices and systems that improve various sustainability goals so that the department can implement changes in policies and institutions that are identified as effective to meeting those goals.

Transformation of the agriculture sector will not occur overnight. It will take long-term research and experimentation by the public and private sectors in partnership with farmers. The two parallel approaches to improving sustainability proposed by the committee would ensure incremental improvement toward sustainability, while long-term systemic changes in agricultural systems are being pursued.

RELEVANCE OF LESSONS LEARNED TO SUB-SAHARAN AFRICA

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. African farmers produce a wide variety of crops using diverse farming systems across a range of agroecological zones. Most systems are rain-fed, and many soils are severely depleted of nutrients. External inputs are expensive. High transportation costs and lack of infrastructure often inhibit access to outside resources and markets. Specific management approaches need to be developed in that context. 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. The committee concluded that:

  • An interdisciplinary systems approach is essential to address the improvement and sustainability of African agriculture that recognizes the social, economic, and



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