The highly mechanized agricultural sector uses a significant amount of fossil fuel energy, and this also contributes to carbon dioxide emissions. Cattle emit methane as part of their digestive and excretory processes, as do termites who feast on the charred remains of trees. The large amounts of petrochemical fertilizers used to produce feed crops for grain-fed animals create significant amounts of nitrous oxides. Also, the increased refrigeration necessary to prevent animal products from spoiling adds chlorofluorocarbons to the atmosphere. Factory farming also contributes substantially to many other environmental problems, including soil erosion and depletion, extensive air and water pollution related to chemical fertilizer and pesticides, the destruction of tropical rain forests and other habitats, and increased use of pesticides and other dangerous chemicals.
Cattle ranching is a major cause of deforestation in Latin America.
The production of just one imported quarter-pound hamburger requires the clearing of up to 55 square feet of rain forest. Livestock overgrazing causes erosion and the creation of deserts throughout the world. U.S. cattle production has resulted in significant biodiversity losses. Animal-based agriculture is also extremely wasteful of resources. More than half the water consumed in the United States is used to raise livestock, primarily to irrigate land growing livestock feed.