Panel 1 - Environmental impact

As stated in the introduction to the "Undernutrition and malnutrition" panel, farm animals are really inefficient as "machines" which convert vegetal proteins into animal proteins; as a consequence, animal products use far more resources overall than vegetable. A huge global waste of resources is one of the least publicized, but most acutely felt consequences of the much-touted "Livestock revolution". It is undeniable that this waste of resources imposes a huge ecological burden on the planet. As pointed out by the World Watch Institute, as environmental science has advanced, it has become apparent that the human appetite for animal flesh is a driving force behind virtually every major category of environmental damage now threatening the human future: deforestation, erosion, fresh water scarcity, air and water pollution, climate change, biodiversity loss, social injustice, the destabilization of communities, and the spread of disease. In spite of this, per-capita meat consumption has more than doubled in the past half-century, even as global population has continued to increase. As a result, the overall demand for meat has increased five-fold. That, in turn, has put a higher and higher pressure on the availability of water, land, feed, fertilizer, fuel, waste disposal capacity, and most of the other limited resources of the planet. [WWI2004]

Land degradation

Land degradation is one of the most serious problems facing modern agriculture. While it takes from 20 to 1,000 years for a centimeter of soil to form, the United Nations have estimated that wind and water erode 1% of the world's topsoil each year. It is generally not well-known that animal farming is a major contributing factor to erosion. When animals graze land heavily they can cause soil erosion by compacting the soil and stripping the land of vegetation that holds soil in place. Industrial animal agriculture destroys topsoil because growing grains for this industry requires so much cropland. As a consequence, the world's supply of arable land per person has been declining steadily, decreasing from more than 0.40 hectars per person in 1961 to less than 0.25 hectars per person in 1999. An extreme example of land degradation is the phenomenon known as desertification. Agriculture can contribute to desertification both directly, through poor agricultural practices such as overcultivation, overgrazing, and overuse of water, and indirectly when land is deforested to create new cropland or new pastures for livestock. [Horrigan2002]

Internationally, severe problems of soil compaction, erosion and decreased soil fertility are being experienced in many cattle-ranching areas. These include the American West, Central and South America, Australia and Sub-Saharan Africa. The United Nations Environmental Programme (UNEP) estimates that 20 per cent of the world's grazing lands have been significantly degraded since 1945, with the pace of destruction increasing. [Cox2000]


In just ten years (from 1990 to 2000) the Brazilian Amazon lost an area of forest twice the size of Portugal: The vast majority of this area become pasture for cattle, for internal consumption and for exporting to Europe, Japan, USA.

The yearly rate of deforestation continued to increase the following years, and in 2002 it grew by 40%. 10% of the deforested area is used for soyabean cultivation (used for feeding cattle in factory farms), the remaining is devoted to pasture; after a few years it face a non-reversible desertification process, so that new land need to be cleared, in a downward spiral that further and further degrades the environment. Between 1997 and 2003 the volume of cattle exports from Brazil increased more than fivefold; 80% of this production increase took place in the Amazon. [Kaimowitz2003]

Chemicals pollution

Humans have practiced agriculture for more than 10,000 years, but only in the past 50 years have farmers become heavily dependent on synthetic chemical fertilizers and pesticides. Crops actually absorb only one-third to one-half of the nitrogen applied to farmland as fertilizer: the unused chemicals pollute soil and water. Given that, according to the FAO Food Balance Sheet, half of the cereals and 90% of soyabeans produced worldwide are used as animal feed, and that these chemicals are mostly used in monocultures for the production of animal feed, it is clear that the main responsibility for this overuse of chemicals stems from livestock production. If the land were used to produce human food in a sustainable manner, using rotation crops, far fewer chemicals would be necessary.

Energy use

Converting grain into meat entails a huge loss of food energy, particularly if cattle are doing the converting. The average amount of fossil fuel energy required to produce 1 kcal of proteins from meat is 25 kcal. This amount is more than 11 times greater than that needed for grain protein production, which is about 2.2 kcal. The ratio is 57:1 for lamb meat, 40:1 for beef cattle, 39:1 for eggs, 14:1 for milk and dairy and swine meat. [Pimentel 2003]

Fresh water

Water is a major category of the environmental impact of livestock farming. Agriculture, mostly devoted to livestock and feed production, consumes more fresh water than any other activity in the United States, and in general it accounts for 70% of overall water use in the world. The water required to produce various food and forage crops ranges from 500 to 2000 litres of water per kilogram of crop produced. Livestock directly uses only 1.3% of the total water used in agriculture; however, when the water required for forage and grain production is taken into account, water requirements dramatically increase.

Studies on water consumption for producing goods in general, and food in particular, never yield 'exact' figures, since results depend on a number of factors such as the kind of feed used for livestock, climate, soil quality, irrigation methods, crop genetics, the amount of product yielded by each animal, and other variables. The Pacific Institute reports a range of 15000 to over 70000 litres of water needed for producing one kilogram of beef, while for vegetable crops for direct human consumption they indicate a range of 500-2000 litres of water per kilogram (for greens, cereals, beans and soy) [Gleick2008].

Other studies give even higher requirements of water for animal food: a study by Pimentel at al. shows that for 1 kg of beef from factory farming, 100000 litres of water are needed (200000 litres if on rangeland), while confirming the much lower 500-2000 litres requirement for vegetable food (2000 litres of water for 1 kg of soybeans, 1910 for rice, 1400 for maize, 900 for corn, 500 for potatoes) [Pimentel1997]

Despite the variability both in water consumption estimates and in conditions of food production, a great and unanimous body of evidence leads to the unambiguous conclusion that producing animal food for human consumption requires from 3 to 50 times more water than vegetable products require. Considering the variability in animal species, farming methods, feed production methods, climate, soil quality etc. we can conclude that, on average, animal food water requirements are about ten times higher than those for vegetable food. This is enough to explain the large difference in the impact on water consumption between a strictly plant-based diet and one that contains animal products.

The executive director of the Stockholm International Water Institute declared "Animals fed on grain, and also those which rely on grazing, need far more water than grain crops. But in the developed world, and in parts of some developing countries, consumers are demanding more meat [...]. But it's going to be almost impossible to feed future generations the kind of diet we have now in western Europe and North America". He also added that the rich countries will be able to buy themselves a way out by importing virtual water, which means importing food (feed for animals or meat) from other countries, also from those which have not enough water. [Kirby2004]

Waste disposal

Where animals are raised under traditional methods, animal wastes are considered to be of great benefit - a key ingredient in rotation agricultural systems which produce a variety of foods and maintain the health of soil. However, when too many animals are raised on too small an area, the surrounding environment becomes unable to cope with their waste products. This happens routinely in present-day landless factory farming, so widespread in the developed world and quickly spreading in the developing one. Animal feeding operations (AFOs) are farms or feedlots where animals are kept and raised in confined areas. These animals produce large amounts of waste: For example, the amount of wet manure produced by a single dairy cow is equivalent to that produced by 20-40 people. [EPA2005]

Liquid slurry from livestock contains abnormally high levels of nitrogen and phosphorus because farm animals can only absorb a limited proportion of the amounts contained in their feed. When animal manure oozes into watercourses and waterways, the excess nitrogen and phosphorus it contains can ruin groundwater quality and damage aquatic and wetland ecosystems. Roughly 70-80 per cent of dietary nitrogen fed to cattle, pigs and laying hens, and 60 per cent of that fed to broiler chickens, is excreted in faeces and urine and ultimately ends up in the water system. [CIWF2004]

Excess manure are now being spread on farmlands, posing threats to drinking water and fisheries. The storage lagoons on factory farms are often stinking manure lakes and they have already spawned environmental disasters in many states, spilling disease-causing bacteria into neighbouring rivers and leaching manure into groundwater used for drinking. [NRDC1999]

Global warming and acid rain

Global warming is caused by energy consumption, because the main energy sources in today's world are carbon-rich fuels which, when burned, emit carbon dioxide or other planet-blanketing gases. As noted above, livestock farming is a major factor in the increase of use of such fuels. But livestock also emit global-warming gases directly, as a by-product of digestion. Cattle send a significant amount of methane, a potent global-warming gas, into the air. [WWI2004]

Research in the UK indicates that cattle and sheep gut fermentation is responsible for 95 per cent of methane produced from farming, with the rest created from slurry and manure. The same study shows that one third of nitrous oxide emissions come from slurry and manure, while 39 per cent of the nation's ammonia emissions are also derived from animal farms. [CIWF2002]

Moreover, the high ammonia content of animal wastes is a major cause of acid rain.


CIWF, "The Detrimental Impacts of Industrial Animal Agriculture", CIWF Trust, 2002

CIWF, "The global benefits of eating less meat", CIWF Trust, 2004

Cox J., Varpama S., "The 'Livestock Revolution' - Development or Destruction", Compassion in World Farming. September 2000.


Gleick P, Cooley H, Cohen M, Morikawa M, Morrison J, Palaniappan M (2010) The World's Water 2008-2009. Pacific Institute, Island Press.

Horrigan L., Lawrence R.S., Walker P., "How Sustainable Agriculture Can Address the Environmental and Human Harms of Industrial Agriculture", Environment Health Persepctive, May 2002, vol. 10, number 5

Kaimowitz D., Mertens B., Wunder S., Pacheco P. "Hamburger connection Fuels Amazon Destruction", Center for International Forestry Research (CIFOR), april 2003

Alex Kirby, "Hungry world 'must eat less meat'", BBC News Online, August 15 2004

Natural Resource Defense Council, "America's Animal Factories How States Fail to Prevent Pollution from Livestock Waste", NRDC Report, 1999

Pimentel D., Pimentel M., "Sustainability of meat-based and plant-based diets and the environment", Am J Clin Nutr 2003;78(suppl):660S-3S

Pimentel D., Houser J., Preiss E., White O., "Water Resources: Agriculture, the Environment, and Society", Bioscience, February 1997 Vol. 47 No. 2.

World Watch Institute, "Meat - Now, it's not personal!", World Warch magazine, July/August 2004