Agricultural practices have been found to have a variety of effects on the environment to some extent. Animal agriculture, in particular meat production, can cause pollution, greenhouse gas emissions, biodiversity loss, disease, and significant consumption of land, food, and water. Meat is obtained through a variety of methods, including organic farming, free-range farming, intensive livestock production, and subsistence agriculture. The livestock sector also includes wool, egg and dairy production, the livestock used for tillage, and fish farming.
Animal agriculture is a significant contributor to greenhouse gas emissions. Cows, sheep, and other ruminants digest their food by enteric fermentation, and their burps are the main source of methane emissions from land use, land-use change, and forestry. Together with methane and nitrous oxide from manure, this makes livestock the main source of greenhouse gas emissions from agriculture. A significant reduction in meat consumption is essential to mitigate climate change.
Consumption and production trends
Multiple studies have found that increases in meat consumption are currently associated with human population growth and rising individual incomes or GDP, and therefore, the environmental impacts of meat production and consumption will increase unless current behaviours change.
Changes in demand for meat will influence how much is produced, thus changing the environmental impact of meat production. It has been estimated that global meat consumption may double from 2000 to 2050, mostly as a consequence of the increasing world population, but also partly because of increased per capita meat consumption (with much of the per capita consumption increase occurring in the developing world). The human population is projected to grow to 9 billion by 2050, and meat production is expected to increase by 40%. Global production and consumption of poultry meat have been growing recently at more than 5% annually. Meat consumption typically increases as people and countries get richer. Trends also vary among livestock sectors. For example, global pork consumption per capita has increased recently (almost entirely due to changes in consumption within China), while global consumption per capita of ruminant meats has been declining.
Resource use Food production efficiency About 85% of the world's soybean crop is processed into meal and vegetable oil, and virtually all of that meal is used in animal feed. Approximately 6% of soybeans are used directly as human food, mostly in Asia.
For every 100 kilograms of food made for humans from crops, 37 kilograms of byproducts unsuitable for direct human consumption are generated. Many countries then repurpose these human-inedible crop byproducts as livestock feed for cattle. Raising animals for human consumption accounts for approximately 40% of total agricultural output in industrialized nations. Moreover, the efficiency of meat production varies depending on the specific production system, as well as the type of feed. It may require anywhere from 0.9 and 7.9 kilograms of grain to produce 1 kilogram of beef, between 0.1 to 4.3 kilograms of grain to produce 1 kilogram of pork, and 0 to 3.5 kilograms of grains to produce 1 kilogram of chicken. FAO estimates, however, that about two thirds of the pasture area used by livestock is not convertible to crop-land.
Major corporations purchase land in different developing nations in Latin America and Asia to support large-scale production of animal feed crops, mainly corn and soybeans. This practice reduces the amount of land available for growing crops that are fit for human consumption in these countries, putting the local population at risk of food security.
According to a study conducted in Jiangsu, China, individuals with higher incomes tend to consume more food than those with lower incomes and larger families. Consequently, it is unlikely that those employed in animal feed production in these regions do not consume the animals that eat the crops they produce. The lack of space for growing crops for consumption, coupled with the need to feed larger families, only exacerbates their risk of losing food security.
According to FAO, crop-residues and by-products account for 24% of the total dry matter intake of the global livestock sector. A 2018 study found that, "Currently, 70% of the feedstock used in the Dutch feed industry originates from the food processing industry." Examples of grain-based waste conversion in the United States include feeding livestock the distillers grains (with solubles) remaining from ethanol production. For the marketing year 2009–2010, dried distillers grains used as livestock feed (and residual) in the US was estimated at 25.5 million metric tons. Examples of waste roughages include straw from barley and wheat crops (edible especially to large-ruminant breeding stock when on maintenance diets), and corn stover.
Land use Permanent meadows and pastures, grazed or not, occupy 26% of the Earth's ice-free terrestrial surface. Feed crop production uses about one-third of all arable land. More than one-third of U.S. land is used for pasture, making it the largest land-use type in the contiguous United States.In many countries, livestock graze from the land which mostly cannot be used for growing human-edible crops, as seen by the fact that there is three times as much agricultural land as arable land.
A 2023 study found that a vegan diet reduced land use by 75%.
Free-range animal production, particularly beef production, has also caused tropical deforestation because it requires land for grazing. The livestock sector is also the primary driver of deforestation in the Amazon, with around 80% of all deforested land being used for cattle farming. Additionally, 91% of deforested land since 1970 has been used for cattle farming. Research has argued that a shift to meat-free diets could provide a safe option to feed a growing population without further deforestation, and for different yields scenarios. However, according to FAO, grazing livestock in drylands "removes vegetation, including dry and flammable plants, and mobilizes stored biomass through depositions, which is partly transferred to the soil, improving fertility. Livestock is key to creating and maintaining specific habitats and green infrastructures, providing resources for other species and dispersing seeds".
The use of ever increasing amounts of land for meat production and livestock rearing instead of plants and grains for human diets is, according to sociologist David Nibert, "a leading cause of malnutrition, hunger, and famine around the world."
Water use
Globally, the amount of water used for agricultural purposes exceeds any other industrialized purpose of water consumption. About 80% of water resources globally are used for agricultural ecosystems. In developed countries, up to 60% of total water consumption can be used for irrigation; in developing countries, it can be up to 90%, depending on the region's economic status and climate. According to the projected increase in food production by 2050, water consumption would need to increase by 53% to satisfy the world population's demands for meat and agricultural production.
Groundwater depletion is a concern in some areas because of sustainability issues (and in some cases, land subsidence and/or saltwater intrusion).Konikow, L. W. 2013. Groundwater depletion in the United States (1900-2008). United States Geological Survey. Scientific Investigations Report 2013-5079. 63 pp. A particularly important North American example of depletion is the High Plains (Ogallala) Aquifer, which underlies about 174,000 square miles in parts of eight states of the USA and supplies 30 percent of the groundwater withdrawn for irrigation there. Some irrigated livestock feed production is not hydrologically sustainable in the long run because of aquifer depletion. Rainfed agriculture, which cannot deplete its water source, produces much of the livestock feed in North America. Corn (maize) is of particular interest, accounting for about 91.8% of the grain fed to US livestock and poultry in 2010.USDA. 2011. USDA Agricultural Statistics 2011. About 14 percent of US corn-for-grain land is irrigated, accounting for about 17% of US corn-for-grain production and 13% of US irrigation water use,USDA 2010. 2007 Census of agriculture. AC07-SS-1. Farm and ranch irrigation survey (2008). Volume 3, Special Studies. Part 1. (Issued 2009, updated 2010.) 209 pp. + appendices. Tables 1 and 28.USDA. 2009. 2007 Census of Agriculture. United States Summary and State Data. Vol. 1. Geographic Area Series. Part 51. AC-07-A-51. 639 pp. + appendices. Table 1. but only about 40% of US corn grain is fed to US livestock and poultry. Irrigation accounts for about 37% of US withdrawn freshwater use, and groundwater provides about 42% of US irrigation water. Irrigation water applied in the production of livestock feed and forage has been estimated to account for about 9 percent of withdrawn freshwater use in the United States.Zering, K. D., T. J. Centner, D. Meyer, G. L. Newton, J. M. Sweeten and S. Woodruff.2012. Water and land issues associated with animal agriculture: a U.S. perspective. CAST Issue Paper No. 50. Council for Agricultural Science and Technology, Ames, Iowa. 24 pp.
Almost one-third of the water used in the western United States goes to crops that feed cattle. This is despite the claim that withdrawn surface water and groundwater used for crop irrigation in the US exceeds that for livestock by about a ratio of 60:1.Kenny, J. F. et al. 2009. Estimated use of water in the United States in 2005, US Geological Survey Circular 1344. 52 pp. This excessive use of river water distresses ecosystems and communities, and drives scores of species of fish closer to extinction during times of drought.
A 2023 study found that a vegan diet reduced water usage by 54%.
A study in 2019 focused on linkages between water usage and animal agricultural practices in China. The results of the study showed that water resources were being used primarily for animal agriculture; the highest categories were animal husbandry, agriculture, slaughtering and processing of meat, fisheries, and other foods. Together they accounted for the consumption of over 2400 billion m3 embodied water, roughly equating to 40% of total embodied water by the whole system. This means that more than one-third of China's entire water consumption is being used for food processing purposes, and mostly for animal agricultural practices. +Estimated water requirements for various foodsFoodstuffLitres perkilocaloriegram ofproteinkg offoodstuffgram offatSugar crops0.69N/A197N/AVegetables1.3426322154Starchy roots0.4731387226Fruits2.09180962348Cereals0.51211644112Oil crops0.8116236411Pulses1.19194055180Nuts3.63139906347Milk1.8231102033Eggs2.2929326533Chicken meat3.0034432543Butter0.72N/A55536.4Pig meat2.1557598823Sheep/goat meat4.2563876354Bovine meat10.1911215415153
Water pollution Water pollution due to animal waste is a common problem in both developed and developing nations. The USA, Canada, India, Greece, Switzerland and several other countries are experiencing major environmental degradation due to water pollution via animal waste. Concerns about such problems are particularly acute in the case of CAFOs (concentrated animal feeding operations). In the US, a permit for a CAFO requires the implementation of a plan for the management of manure nutrients, contaminants, wastewater, etc., as applicable, to meet requirements under the Clean Water Act. There were about 19,000 CAFOs in the US as of 2008. In fiscal 2014, the United States Environmental Protection Agency (EPA) concluded 26 enforcement actions for various violations by CAFOs.the US EPA. National Enforcement Initiative: Preventing animal waste from contaminating surface and groundwater.