Sustentabilidad

insight review articles

Agricultural sustainability and intensive production practices
David Tilman*, Kenneth G. Cassman‡, Pamela A. Matson§ ||, Rosamond Naylor|| & Stephen Polasky†
*Department of Ecology, Evolution and Behavior, and †Department of Applied Economics, University of Minnesota, St Paul, Minnesota 55108, USA (e-mail: tilman@umn.edu) ‡Department of Agronomy and Horticulture,University of Nebraska, Lincoln, Nebraska 68583, USA §Department of Geological and Environmental Sciences, and ||Center for Environmental Science and Policy, Stanford University, Stanford, California 94305, USA

A doubling in global food demand projected for the next 50 years poses huge challenges for the sustainability both of food production and of terrestrial and aquatic ecosystems and theservices they provide to society. Agriculturalists are the principal managers of global useable lands and will shape, perhaps irreversibly, the surface of the Earth in the coming decades. New incentives and policies for ensuring the sustainability of agriculture and ecosystem services will be crucial if we are to meet the demands of improving yields without compromising environmental integrity or publichealth.

he benefits of agriculture have been immense. Before the dawn of agriculture, the hunter–gatherer lifestyle supported about 4 million people globally1. Modern agriculture now feeds 6,000 million people. Global cereal production has doubled in the past 40 years (Fig. 1a), mainly from the increased yields resulting from greater inputs of fertilizer, water and pesticides, new cropstrains, and other technologies of the ‘Green Revolution’2–4. This has increased the global per capita food supply2, reducing hunger, improving nutrition (and thus the ability of people to better reach their mental and physical potential) and sparing natural ecosystems from conversion to agriculture5. By 2050, global population is projected to be 50% larger than at present and global grain demand isprojected to double6–8. This doubling will result from a projected 2.4-fold increase in per capita real income and from dietary shifts towards a higher proportion of meat (much of it grainfed) associated with higher income. Further increases in agricultural output are essential for global political and social stability and equity. Doubling food production again, and sustaining food production at thislevel, are major challenges8–11. Doing so in ways that do not compromise environmental integrity4,12,13 and public health14,15 is a greater challenge still. We focus here on scientific and policy challenges that must be met to sustain and increase the net societal benefits of intensive agricultural production.

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of agricultural practices are costs that are typically unmeasured and often donot influence farmer or societal choices about production methods. Such costs raise questions about the sustainability of current practices. We define sustainable agriculture as practices that meet current and future societal needs for food and fibre, for ecosystem services, and for healthy lives, and that do so by maximizing the net benefit to society when all costs and benefits of the practicesare considered. If society is to maximize the net benefits of agriculture, there must be a fuller accounting of both the costs and the benefits of alternative agricultural practices, and such an accounting must become the basis of policy, ethics and action. Additionally, the development of sustainable agriculture must accompany advances in the sustainability of energy use, manufacturing,transportation and other economic sectors that also have significant environmental impacts.

Ecosystem services
Society receives many benefits, called ecosystem services17, from natural and managed ecosystems. Ecosystems provide food, fibre, fuel and materials for shelter; additionally they provide a range of benefits that are difficult to quantify and have rarely been priced18,19. Intact forests can...