Environmental vegetarianism is the practice of vegetarianism or veganism based on the indications that animal production, particularly by intensive agriculture, is environmentally unsustainable. The primary environmental concerns with animal products are pollution including greenhouse gas emissions and the use of resources such as fossil fuels, water, and land.
Environmental impact of meat production
Industrial monoculture is harvesting large quantities of a single food species, such as maize, or cattle. Monoculture is commonly practiced in industrial agriculture, which is more environmentally damaging than sustainable farming practices such as organic farming, permaculture, arable, pastoral, and rain-fed agriculture.
According to a 2006 Food and Agriculture Organization report, industrialized agriculture contributes on a “massive scale” to climate change, air pollution, land degradation, energy use, deforestation, and biodiversity decline. The FAO report estimates that the livestock (including poultry) sector (which provides draft animal power, leather, wool, milk, eggs, fertilizer, pharmaceuticals, etc., in addition to meat) contributes about 18 percent of global GHG (greenhouse gas) emissions expressed as 100-year CO2 equivalents. This estimate was based on life cycle analysis, including feed production, land use changes, etc., and used GWP (global warming potential) of 23 for methane and 296 for nitrous oxide, to convert emissions of these gases to 100-year CO2 equivalents. Some sources disagree with some of the figures used in arriving at the FAO estimate of 18 percent. For example, the FAO report estimates that 37 percent of global anthropogenic methane emissions are attributable to the livestock sector, and a US NASA summary indicates about 30 percent. Because of the GWP multiplier used, such a difference between estimates will have a large effect on an estimate of GHG CO2 equivalents contributed by the livestock sector. Livestock sources (including enteric fermentation and manure) account for about 3.1 percent of US anthropogenic GHG emissions expressed as CO2 equivalents. This estimate is based on methodologies agreed to by the Conference of Parties of the UN FCCC. Data of a USDA study indicate that about 0.9 percent of energy use in the United States is accounted for by raising food-producing livestock and poultry. In this context, energy use includes energy from fossil, nuclear, hydroelectric, biomass, geothermal, technological solar, and wind sources. The estimated energy use in agricultural production includes embodied energy in purchased inputs.
Another agricultural effect is on land degradation. Much of the world's crops is used to feed animals. With 30 percent of the earth's land devoted to raising livestock, a major cutback is needed to keep up with growing population. A 2010 UN report explained that Western dietary preferences for meat would be unsustainable as the world population rose to the forecasted 9.1 billion by 2050. Demand for meat is expected to double by this date; meat consumption is steadily rising in countries such as China that once followed more sustainable, vegetable-based diets. Cattle are a known cause for soil erosion through trampling of the ground and overgrazing.
The ability of soil to absorb water by infiltration is important for minimizing runoff and soil erosion. Researchers in Iowa reported that a soil under perennial pasture grasses grazed by livestock was able to absorb far more water than the same kind of soil under two annual crops: corn and soybeans. Corn and soybean crops commonly provide food for human consumption, biofuels, livestock feed, or some combination of these.
The FAO initiative concluded that "the livestock sector emerges as one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global."
Environmental vegetarianism can be compared with economic vegetarianism. An economic vegetarian is someone who practices vegetarianism either out of necessity or because of a conscious simple living strategy. Such a person may base this belief on a philosophical viewpoint, such as the belief that the consumption of meat is economically unsound or that vegetarianism will help improve public health and curb starvation.
Environmental vegetarians call for a reduction of first world consumption of meat, especially in the US. According to the United Nations Population Fund "Each U.S. citizen consumes an average of 260 lbs. of meat per year, the world's highest rate. That is about 1.5 times the industrial world average, three times the East Asian average, and 40 times the average in Bangladesh." In addition, "the ecological footprint of an average person in a high-income country is about six times bigger than that of someone in a low-income country, and many more times bigger than in the least-developed countries."
The World Health Organization calls malnutrition "the silent emergency", and says it is a factor in at least half of the 10.4 million child deaths which occur every year. Some argue[who?] that the adoption of an Ovo-lacto vegetarian or entirely plant-based vegan diet is best, but may not be totally necessary, because even modest reductions in meat consumption in industrialized societies would substantially reduce the burden on our natural resources. For developed countries, a CAST report estimates an average of 2.6 pounds of grain feed per pound of beef carcass meat produced. For developing countries, the estimate is 0.3 pounds per pound. (Some very dissimilar figures are sometimes seen; the CAST report discusses common sources of error and discrepancies among such figures.) In 2007, US per capita beef consumption was 62.2 pounds per year, and US per capita meat (red meat plus fish plus poultry) consumption totaled 200.7 pounds (boneless trimmed weight basis).
A 2010 report from the United Nations Environment Program's (UNEP) International Panel of Sustainable Resource Management states that global shift towards a vegan diet is critical for mitigating global issues of hunger, fuel poverty and the worst impacts of climate change. The panel declared: "Impacts from agriculture are expected to increase substantially due to population growth and increasing consumption of animal products. Unlike fossil fuels, it is difficult to look for alternatives: people have to eat. A substantial reduction of impacts would only be possible with a substantial worldwide diet change, away from animal products."
According to Cornell scientists, "the heavy dependence on fossil energy suggests that the US food system, whether meat-based or plant-based, is not sustainable", but they also mention that: "lactoovovegetarian diet is more sustainable than the average American meat-based diet". 
Some environmental activists claim that adopting a vegetarian diet may be a way of focusing on personal actions and righteous gestures rather than systemic change. Dave Riley, an Australian environmentalist, states that "being meatless and guiltless seems seductively simple while environmental destruction rages around us", noting that animals can contribute to the food chain.
Bill Mollison has argued in his Permaculture Design Course that vegetarianism exacerbates soil erosion. This is because removing a plant from a field removes all the nutrients it obtained from the soil, while removing an animal leaves the field intact. On US farmland, much less soil erosion is associated with pastureland used for livestock grazing than with land used for production of crops. Robert Hart has also developed forest gardening, which has since been adopted as a common permaculture design element, as a sustainable plant-based food production system.
- New York Time's Article: Rethinking the Meat-Guzzler
- FAO report
- Public health benefits of strategies to reduce greenhouse-gas emissions: food and agriculture http://www.sciencedirect.com/science/article/pii/S0140673609617530
- Livestock’s Long Shadow: environmental issues and options http://www.fao.org/docrep/010/a0701e/a0701e00.HTM
- Augenbraun, H., E. Mathews and D. Sarma. 1997. The global methane cycle. http://icp.giss.nasa.gov/education/methane/intro/cycle.html
- EPA. 2011. Inventory of U.S. greenhouse gas emissions and sinks: 1990-2009. United States Environmental Protection Agency. EPA 430-R-11-005. 459 pp.
- Canning, P., A. Charles, S. Huang, K. R. Polenske, and A Waters. 2010. Energy use in the U. S. food system. USDA Economic Research Service, ERR-94. 33 pp.
- Carus, Felicity (2010-06-02). "UN urges global move to meat and dairy-free diet". The Guardian. Retrieved 2011-10-26.
- Livestock Grazing- Combats or Spreads Desertification? http://www.kkl.org.il/kkl/english/main_subject/curb%20global%20warming/livestock%20grazing-combats%20or%20spreads%20desertification.x
- C.Michael Hogan. 2009. Overgrazing. Encyclopedia of Earth. Sidney Draggan, topic ed.; Cutler J. Cleveland, ed., National council for Science and the Environment, Washington DC
- Bharati et al. 2002. Agroforestry Systems 56: 249-257
- United States Leads World Meat Stampede | Worldwatch Institute
- "The Startling Effects of Going Vegetarian for Just One Day". Archived from the original on 7 Oct 2012. Retrieved 10 February 2013.
- Katherine Manning. "Eat Better and Improve Your Health For Less Money". Archived from the original on 16 Jan 2013. Retrieved 10 February 2013.
- Day of 6 Billion: October 12 U.S. Scorecard
- UNFPA State of World Population 2004
- "Hungry world 'must eat less meat'". BBC News. August 16, 2004. Retrieved May 2, 2010.
- Bradford, E. et al. 1999. Animal Agriculture and Global Food Supply. Council on Agricultural Science and Technology. 92 pp.
- USDA. 2010. Agricultural Statistics 2010, Table 13-7
- UN urges global move to meat and dairy-free diet
- The role of the International Panel for Sustainable Resource Management
- Sustainability of meat-based and plant-based diets and the environment - Pimentel and Pimentel 78 (3): 660S - American Journal of Clinical Nutrition
- "Does meat make the meal?".
- NRCS. 2009. Summary report 2007 national resources inventory. USDA Natural Resources Conservation Service. 123 pp.
- Robert Hart (1996). Forest Gardening. p. 45.
- Eco-Eating: Eating as if the Earth Matters (it does!) Comprehensive source with many categories and links.
- Meat Eating and Global Warming a list of articles making the vital connection between meat and climate change
- Ecological footprint calculator Two fields are dietary considerations.
- Dr. Ruth Fairchild of the UWIC's report on veganism and CO2-emissions
- The Vegetarian Society UK - information portal
- Vegan Society - Environment