The harmful environmental effects of livestock production are becoming increasingly serious at all levels—local, regional, national and global—and urgently need to be addressed, according to researchers from Stanford University, the United Nations Food and Agriculture Organization (FAO) and other organizations. The researchers, representing five countries, will present their findings on Feb. 19 at the annual meeting of the American Association of the Advancement of Science (AAAS) in San Francisco during a symposium entitled, "Livestock in a Changing Landscape: Drivers, Consequences and Responses."

Large-scale livestock operations provide most of the meat and meat products consumed around the world—consumption that is growing at a record pace and is projected to double by 2050, said symposium organizer Harold A. Mooney, professor of biological sciences at Stanford. "We are seeing tremendous environmental problems with these operations, from land degradation and air and water pollution to loss of biodiversity," he said, noting that the developing world is especially vulnerable to the effects of these operations.

Intensive and extensive systems

Symposium co-organizer Henning Steinfeld of the FAO Livestock Environment and Development initiative emphasized that intensive and extensive forms of production are beset with a range of different problems. In "intensive systems," animals are contained and feed is brought to them. "Extensive systems" generally refer to grazing animals that live off the land.

"Extensive livestock production plays a critical role in land degradation, climate change, water and biodiversity loss," Steinfeld said. For example, grazing occupies 26 percent of the Earth's terrestrial surface, and feed-crop production requires about a third of all arable land, he said. Expansion of livestock grazing land is also a leading cause of deforestation, especially in Latin America, he added. In the Amazon basin alone, about 70 percent of previously forested land is used as pasture, while feed crops cover a large part of the remainder.

"We are seeing land once farmed locally being transformed to cropland for industrialized feed production, with grasslands and tropical forests being destroyed in these land use changes, with resources feeding livestock rather than the humans who previously depended on those lands," added Mooney, who co-chaired the scientific advisory panel for the Millennium Ecosystem Assessment.

Climate change

According to the FAO, when emissions from land use are factored in, the livestock sector accounts for 9 percent of all carbon dioxide emissions derived from human-related activities, as well as 37 percent of methane emissions—primarily gas from the digestive system of cattle and other domesticated ruminants—and 65 percent of nitrous oxide gases, mostly from manure.

The problems surrounding livestock production cannot be considered in isolation, nor are they limited to the environmental impact, Mooney said, noting that economic, social, health and environmental perspectives "will be critical to solving some of these problems. We hope to develop a greater understanding of these complex issues so that we may encourage policies and practices to reduce the adverse effects of livestock production, while ensuring that humans are fed and natural resources are preserved, today and in the future."