The turkey and ham many are eating this holiday season don't just appear magically on the table. Most are the end product of an increasingly global, industrialized system that is resulting in costly environmental degradation. Better understanding of the true costs of this resource-intensive system will be critical to reducing its negative effects on the environment, says an interdisciplinary team of researchers led by Stanford University's Rosamond Lee Naylor, Walter Falcon, and Harold Mooney.

"Losing the Links Between Livestock and Land" appears in the Policy Forum in the Dec. 9 issue of Science. It represents a synthesis of research by professors at Stanford University, the University of Virginia, the University of California at Davis, the universities of Manitoba and British Columbia in Canada, and the United Nations LEAD (Livestock Development and Environment) program within the Food and Agricultural Organization of UN.

"Sixty years ago, the link between the livestock production and consumption was much more clear and direct, with most consumers getting their meat and dairy products from small, family-owned farms," says lead author Naylor, an economist. Co-author Falcon agrees. "When I was growing up in Iowa, almost all farmers kept both chickens and pigs."

Today, meat consumption has sky-rocketed, and large-scale intensive livestock operations provide most of those products, both in the U.S. and around the world.

Particularly striking is the growth in demand for meat among developing countries, Naylor notes. "China's meat consumption is increasing rapidly with income growth and urbanization, and it has more than doubled in the past generation," she says. As a result, land once used to provide grains for humans now provides feed for hogs and poultry.

Numerous factors have contributed to the global growth of livestock systems, Naylor notes, including declining feed-grain prices; relatively inexpensive transportation costs; and trade liberalization. "But many of the true costs remain largely unaccounted for," she says. Those costs include destruction of forests and grasslands to provide farmland for corn, soybeans and other feed crops destined not directly for humans but for livestock; use of large quantities of freshwater; and nitrogen losses from croplands and animal manure.

Nitrogen losses are especially problematic, says James Galloway of the University of Virginia. "Once nitrogen is lost to the atmosphere or to water, it can have a large number of sequential environmental effects. For example, ammonia emitted into the atmosphere can in sequence affect atmospheric visibility, forest productivity, lake acidity and eventually impact the nutrient status of coastal waters."

Naylor cited Brazil as a specific example of the large impact on ecosystems and the environment. "Grasslands and rainforests are being destroyed to make room for soybean cultivation," she said. The areas are supplying feed to the growing livestock industry in Brazil, China, India and other parts of the world, leading to "serious consequences on biodiversity, climate, soil and water quality."

Naylor and her research team are seeking better ways to track all costs of livestock production, especially the hidden ones related to ecosystem degradation and destruction. "What is needed is a re-coupling of crop and livestock systems," Naylor said. "If not physically, then through pricing and other policy mechanisms that reflect social costs of resource use and ecological abuse."

Such policies "should not significantly compromise the improving diets of developing countries, nor should they prohibit trade," Naylor added. Instead, they should "focus on regulatory and incentive-based tools to encourage livestock and feed producers to internalize pollution costs, minimize nutrient run-off, and pay the true price of water."

She cited efforts in the Netherlands to track nitrogen inputs and outputs for hog farms as one approach. In the U.S., the 2002 Farm Bill provided funds for livestock producers to redesign manure pits and treat wastes, but she notes that much greater public and private efforts are needed to reduce the direct and indirect pollution caused by livestock.

In the end, though, it may be up to consumers to demand more environmentally sustainable approaches to livestock production. "In a global economy with no global society, it may well be up to consumers to set a sustainable course," she added.

Seed funding for the research was provided by the Woods Institute for the Environment, which supports interdisciplinary approaches to complex environmental issues. Naylor, Falcon and Mooney are affiliated with the institute and with the Center for Environmental Sciences and Policy in Stanford's Freeman Spogli Institute for International Studies.

In addition to Naylor, Mooney and Falcon of Stanford and Galloway of Virginia, co-authors are Henning Steinfeld of the United Nations Food and Agriculture Organization; Galloway; Vaclav Smil, University of Manitoba; Eric Bradford, University of California at Davis; and Jacqueline Alder, University of British Columbia.