Environmental impact of meat production

The environmental impact of meat production varies because of the wide variety of agricultural practices employed around the world. All agriculture practices have been found to have a variety of effects on the environment. Some of the environmental effects that have been associated with meat production are pollution through fossil fuel usage, and water and land consumption. Meat is obtained through a variety of methods, including organic farming, free range farming, intensive livestock production, subsistence agriculture, hunting and fishing.
Steinfeld et al. of the FAO (United Nations Food and Agriculture Organization) have stated that "...the livestock sector is a major stressor on many ecosystems and on the planet as a whole. Globally it is one of the largest sources of greenhouse gases and one of the leading causal factors in the loss of biodiversity, while in developed and emerging countries it is perhaps the leading source of water pollution." [In this and much other FAO usage (but not always elsewhere), poultry are included as "livestock".] However, only some fraction of these effects is assignable to meat production, because other important components of the livestock sector include provision of draft animal power, non-meat foods and non-food products. Livestock have been estimated to provide power for tillage of as much as half of the world’s cropland.Bradford, E. (Task Force Chair). 1999. Animal agriculture and global food supply. Task Force Report No. 135. Council for Agricultural Science and Technology. 92 pp. According to production data compiled by the FAO, 74 percent of global livestock product tonnage in 2011 was accounted for by non-meat products.FAOSTAT. [Agricultural statistics database] Food and Agriculture Organization of the United Nations, Rome. http://faostat3.fao.org/
==Consumption and production trends==
Consequences for the environment can result from changes in the amount of production to meet changes in demand for consumption. It has been estimated that global meat consumption may double from 2000 to 2050, mostly as a consequence of 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).FAO. 2006. World agriculture: towards 2030/2050. Prospects for food, nutrition, agriculture and major commodity groups. Interim report. Global Perspectives Unit, United Nations Food and Agriculture Organization. 71 pp. Global production and consumption of poultry meat have recently been growing at more than 5 percent annually. Trends vary among livestock sectors. For example, global per capita consumption of pork has increased recently (almost entirely due to changes in consumption within China), but global per capita consumption of ruminant meats has been declining.
==Grazing and land use==
In comparison with grazing, intensive livestock production requires large quantities of harvested feed. The growing of cereals for feed in turn requires substantial areas of land. However, where grain is fed, less feed is required for meat production. This is due not only to the higher concentration of metabolizable energy in grain than in roughages, but also to the higher ratio of net energy of gain to net energy of maintenance where metabolizable energy intake is higher.National Research Council. 2000. Nutrient Requirements of Beef Cattle. National Academy Press. A pound of beef (live weight) requires about seven pounds of feed, compared to more than three pounds for a pound of pork and less than two pounds for a pound of chicken. However, assumptions about feed quality are implicit in such generalizations. For example, production of a pound of beef cattle live weight may require between 4 and 5 pounds of feed high in protein and metabolizable energy content, or more than 20 pounds of feed of much lower quality.
Free-range animal production requires land for grazing, which in some places has led to land use change. According to the Food and Agriculture Organization (FAO), "Ranching-induced deforestation is one of the main causes of loss of some unique plant and animal species in the tropical rainforests of Central and South America as well as carbon release in the atmosphere." This for example has implications for meat consumption in Europe, which imports significant amounts of feed from Brazil.
Raising animals for human consumption accounts for approximately 40% of the total amount of agricultural output in industrialized countries. Grazing occupies 26% of the earth's ice-free terrestrial surface, and feed crop production uses about one third of all arable land.Steinfeld, H. et al. 2006. Livestock's Long Shadow: Environmental Issues and Options. Livestock, Environment and Development, FAO, Rome. 391 pp.
Land quality decline is sometimes associated with overgrazing. Rangeland health classification reflects soil and site stability, hydrologic function and biotic integrity.National Research Council. 1994. Rangeland Health. New Methods to Classify, Inventory and Monitor Rangelands. Nat. Acad. Press. 182 pp. By the end of 2002, the US Bureau of Land Management had evaluated rangeland health on 7,437 grazing allotments (i.e. 35 percent of its grazing allotments or 36 percent of the land area contained in its grazing allotments) and found that 16 percent of these failed to meet rangeland health standards due to existing grazing practices or levels of grazing use. This led the BLM to infer that a similar percentage would be obtained when such evaluations were completed.US BLM. 2004. Proposed Revisions to Grazing Regulations for the Public Lands. FES 04-39 Soil erosion associated with overgrazing is an important issue in many dry regions of the world. However, on US farmland, much less soil erosion is associated with pastureland used for livestock grazing than with land used for production of crops. Sheet and rill erosion is within estimated soil loss tolerance on 95.1 percent, and wind erosion is within estimated soil loss tolerance on 99.4 percent of US pastureland inventoried by the US Natural Resources Conservation Service.NRCS. 2009. Summary report 2007 national resources inventory. USDA Natural Resources Conservation Service. 123 pp.
Environmental effects of grazing can be positive or negative, depending on the quality of management, and grazing can have different effects on different soils and different plant communities. Grazing sometimes reduces, but sometimes increases biodiversity of grassland ecosystems.Environment Canada. 2013. Amended recovery strategy for the Greater Sage-Grouse (Centrocercus urophasianus urophasianus) in Canada. Species at Risk Act, Recovery Strategy Series. 57 pp. A study comparing virgin grasslands under some grazed and nongrazed management systems in the US indicated somewhat lower soil organic carbon but higher soil nitrogen content with grazing.Bauer, A., C. V. Cole and A. L. Black. 1987. Soil property comparisons in virgin grasslands between grazed and nongrazed management systems. Soil Sci. Soc. Am. J. 51: 176-182. In contrast, at the High Plains Grasslands Research Station in Wyoming, the top 30 cm of soil contained more organic carbon as well as more nitrogen on grazed pastures than on grasslands where livestock were excluded. Similarly, on previously eroded soil in the Piedmont region of the US, pasture establishment with well-managed grazing of livestock resulted in high rates of both carbon and nitrogen sequestration relative to results obtained where grass was grown without grazing. Such increases in carbon and nitrogen sequestration can help mitigate greenhouse gas emission effects. In some cases, ecosystem productivity may be increased due to grazing effects on nutrient cycling.
==Water resources==
Estimated virtual water requirementsfor various crops (m³ /ton crop)
 	Hoekstra& Hung(2003)	Chapagain& Hoekstra(2003)	Zimmer& Renault(2003)	Okiet al.(2003)	Average
Beef 	 	15977 	13500 	20700 	16726
Pork 	 	5906 	4600 	5900 	5469
Cheese 	 	5288 	 	 	5288
Poultry 	 	2828 	4100 	4500 	3809
Eggs 	 	4657 	2700 	3200 	3519
Rice 	2656 	 	1400 	3600 	2552
Soybeans	2300 	 	2750 	2500 	2517
Wheat 	1150 	 	1160 	2000 	1437
Maize 	450 	 	710 	1900 	1020
Milk 	 	865 	790 	560 	738
Potatoes	160 	 	105 	 	133
Virtual water use for livestock production includes water used in producing feed. 
However, virtual water use data, such as those shown in the table, are often unrelated to environmental impacts of water use. For example, in a high-rainfall area, if similar soil infiltration capacity is maintained across different land uses, mm of groundwater recharge and hence sustainability of water use tends to be about the same for food crop production, meat-yielding livestock production, and saddle horse production, although virtual water use per kg of food produced may be several hundred L, several thousand L, and an infinite number of L, respectively. In contrast, in some low-rainfall areas, some livestock production is more sustainable than food crop production, from a water use standpoint, despite higher virtual water use per kg of food produced. This is because unirrigated land in many water-short areas may support grassland ecosystems in perpetuity, and thus may be able to support well-managed, extensive production of grazing cattle or sheep with a sustainable level of water use, even where large-scale production of more water-demanding food crops would be unsustainable in the long run due to inadequate surface water supplies and inadequate groundwater recharge to sustain a high level of withdrawn water use for irrigation. Such considerations are important on much rangeland in western North America and elsewhere that can support cow-calf operations, backgrounding of stocker cattle, and sheep flocks. In the US, withdrawn surface water and groundwater use for crop irrigation 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. U. S. Geological Survey Circular 1344. 52 pp.
Also, the high virtual water use figures associated with meat production do not necessarily imply reduction of water use if food crops are produced, instead of livestock. For example, some grazing lands are unsuitable for food crop production, so that evapotranspirational water use would continue on land vacated by livestock, while additional water would be needed for crops to provide substituting food from lands elsewhere, and additional water would also be needed to produce substitutes for the non-food products of livestock. (In the US, Land Capability Classes V, VI and VII contain soils unsuited for cultivation, much of which is suitable for grazing. Of non-federal land in the US, about 43 percent is classed as unsuitable for cultivation.)
Irrigation accounts for about 37 percent of US withdrawn freshwater use, and groundwater provides about 42 percent of US irrigation water. Irrigation water applied in 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. 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 where depletion is occurring involves the High Plains (Ogallala) Aquifer, which underlies about 174,000 square miles in parts of eight states, and supplies 30 percent of the groundwater withdrawn for irrigation in the US.High Plains Aquifer. United States Geological Survey http://pubs.usgs.gov/ha/ha730/ch_c/C-text5.html Some irrigated livestock feed production is not hydrologically sustainable in the long run because of aquifer depletion. However, 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 percent 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 percent of US corn-for-grain production, and about 13 percent 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 percent of US corn grain is fed to US livestock and poultry. Together, these figures indicate that most production of grain used for US livestock and poultry feed does not deplete water resources and that irrigated production of grain for livestock feed accounts for a small fraction of US irrigation water use. However, where production relies on irrigation from groundwater reserves, water table monitoring is appropriate to provide timely warning if groundwater depletion occurs.
==Effects on aquatic ecosystems==
In the Western United States many stream and riparian habitats have been negatively affected by livestock grazing. This has resulted in increased phosphates, nitrates, decreased dissolved oxygen, increased temperature, turbidity, and eutrophication events, and reduced species diversity. Livestock management options for riparian protection include salt and mineral placement, limiting seasonal access, use of alternative water sources, provision of "hardened" stream crossings, herding, and fencing.BLM. 2006. Grazing management processes and strategies for riparian-wetland areas. U.S. Bureau of Land Management. TR-1737-20. 105 pp. In the Eastern United States waste release from pork farms have also been shown to cause large-scale eutrophication of bodies of water, including the Mississippi River and Atlantic Ocean (Palmquist, et al., 1997). However, in North Carolina, where Palmquist's study was done, measures have since been taken to reduce risk of accidental discharges from manure lagoons; also, since then there is evidence of improved environmental management in US hog production.Key,N. et al. 2011. Trends and developments in hog manure management, 1998-2009. USDA EIB-81. 33 pp. Implementation of manure and wastewater management planning can help assure low risk of problematic discharge into aquatic systems. (See Animal Waste section, below.)
==Energy consumption and greenhouse gas emissions==
At a global scale, the FAO has recently estimated that livestock (including poultry) accounts for about 14.5 percent of anthropogenic greenhouse gas emissions estimated as 100-year equivalents.Gerber, P. J., H. Steinfeld, B. Henderson, A. Mottet, C. Opio, J. Dijkman, A. Falcucci and G. Tempio. 2013. Tackling climate change through livestock - a global assessmaent of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations, Rome. 115 pp. A previous, widely cited FAO report using somewhat more comprehensive analysis had estimated 18 percent. Because this emission percentage includes contributions associated with livestock used for production of draft power, eggs, wool and dairy products, the percentage attributable to meat production alone is significantly lower, as indicated by the report's data. The indirect effects contributing to the percentage include emissions associated with production of feed consumed by livestock and carbon dioxide emission from deforestation in Central and South America, attributed to livestock production. Using a different sectoral assignment of emissions, the IPCC (Intergovernmental Panel on Climate Change) has estimated that agriculture accounted for about 10 to 12 percent of global anthropogenic greenhouse gas emissions (expressed as 100-year carbon dioxide equivalents) in 2005Intergovernmental Panel on Climate Change. 2007. Climate change 2007, Mitigation of climate change. Fourth Assessment Report and in 2010.Intergovernmental Panel on Climate Change. 2014. Climate change 2014, Mitigation of climate change. Fifth Assessment Report. Livestock production would account for some fraction of agriculture’s 10 to 12 percent, and meat production would account for some fraction of the figure assignable to livestock.
In the US, methane emissions associated with ruminant livestock (6.4 Mt in 2013)US Environmental Protection Agency. 2015. Inventory of U.S. greenhouse gas emissions and sinks, 1990-2013. EPA 430-R-15-004. are estimated to have declined by about 17 percent from 1980 through 2012. Globally, enteric fermentation (mostly in ruminant livestock) accounts for about 27 percent of anthropogenic methane emissions,Intergovernmental Panel on Climate Change. 2013. Climate change 2013, The physical science basis. Fifth Assessment Report. and methane accounts for about 32 to 40 percent of agriculture’s greenhouse gas emissions (estimated as 100-year carbon dioxide equivalents) as tabulated by the IPCC. Methane has a global warming potential recently estimated as 35 times that of an equivalent mass of carbon dioxide. However, despite the magnitude of methane emissions (recently about 330 to 350 Tg per year from all anthropogenic sources), methane’s current effect on global warming is quite small. This is because degradation of methane nearly keeps pace with emissions, resulting in relatively little increase in atmospheric methane content (average of 6 Tg per year from 2000 through 2009), whereas atmospheric carbon dioxide content has been increasing greatly (average of nearly 15,000 Tg per year from 2000 through 2009).
Mitigation options for reducing methane emission from ruminant enteric fermentation include genetic selection, immunization, rumen defaunation, diet modification and grazing management, among others.Boadi, D. 2004. Mitigation strategies to reduce enteric methane emissions from dairy cows: Update review. Can. J. Anim. Sci. 84:319–335 Martin, C. et al. 2010. Methane mitigation in ruminants: from microbe to the farm scale. Animal 4 : pp 351-365. The principal mitigation strategies identified for reduction of agricultural nitrous oxide emission are avoiding over-application of nitrogen fertilizers and adopting suitable manure management practices. Mitigation strategies for reducing carbon dioxide emissions in the livestock sector include adopting more efficient production practices to reduce agricultural pressure for deforestation (notably in Latin America), reducing fossil fuel consumption, and increasing carbon sequestration in soils.
In New Zealand, nearly half of [anthropogenic] greenhouse gas emission is associated with agriculture, which plays a major role in the nation’s economy, and a large fraction of this is assignable to the livestock industry.Voluntary Greenhouse Gas Reporting Feasibility Study. 2. Agricultural sector GHG emissions in NZ. http://maxa.maf.govt.nz/climatechange/slm/vggr/page-01.htm Some fraction of this is assignable to meat production: FAO data indicate that meat accounted for about 7 percent of product tonnage from New Zealand’s livestock (including poultry) in 2010. Livestock sources (including enteric fermentation and manure) account for about 3.1 percent of US anthropogenic greenhouse gas emissions expressed as carbon dioxide equivalents, according to US EPA figures compiled using UNFCCC methodologies.US EPA. 2009. Inventory of U.S. greenhouse gas emissions and sinks: 1990-2007. United States Environmental Protection Agency. 410 pp. Not all forms of meat and animal–based foods affect the environment equally. One study estimates that red meats are 150% more greenhouse gas intensive than chicken or fish. According to another research group, the ranking of some food products in relation to greenhouse gas emissions is lamb (#1), beef (#2), cheese (#3), and pork (#4). However, such ranking may not be broadly representative. Among sheep production systems, for example, there are very large differences in both energy useGee, K. 1980. Cultural energy in sheep production. In: Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton. pp. 425-430 and prolificacy;USDA. 2010. Agricultural Statistics 2010, Table 7-43. both factors strongly influence emissions per kg of lamb production.
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. (It excludes solar energy captured by photosynthesis, used in hay drying, etc.) The estimated energy use in agricultural production includes embodied energy in purchased inputs.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.
Intensification and other changes in the livestock industries influence energy use, emissions and other environmental effects of meat production. For example, in the US beef production system, practices prevailing in 2007 are estimated to have involved 8.6 percent less fossil fuel use, 16.3 percent less greenhouse gas emissions, 12.1 percent less water use and 33.0 percent less land use, per unit mass of beef produced, than in 1977.Capper, J. L. 2011. The environmental impact of beef production in the United States: 1977 compared with 2007. J. Anim. Sci. 89: 4249–4261. These figures are based on analysis taking into account feed production, feedlot practices, forage-based cow-calf operations, backgrounding before cattle enter a feedlot, and production of culled dairy cows.
==Animal waste==
Unless well managed, manure and other substances from livestock operations may cause water contamination. 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 implementation of a plan for management of manure nutrients, contaminants, wastewater, etc., as applicable, to meet requirements under the Clean Water Act.US Code of Federal Regulations 40 CFR 122.42(e) There were about 19,000 CAFOs in the US as of 2008.United States Environmental Protection Agency. Appendix to EPA ICR 1989.06: Supporting Statement for the Information Collection Request for NPDES and ELG Regulatory Revisions for Concentrated Animal Feeding Operations (Final Rule) In fiscal 2014, the EPA (Environmental Protection Agency) concluded 26 enforcement actions for various violations by CAFOs.US EPA. National Enforcement Initiative: Preventing animal waste from contaminating surface and ground water. http://www2.epa.gov/enforcement/national-enforcement-initiative-preventing-animal-waste-contaminating-surface-and-ground#progress Environmental performance of the US livestock industry can be compared with several other industries. The EPA has published 5-year and 1-year data for 32 industries on their ratios of enforcement orders to inspections, a measure of non-compliance with environmental regulations: principally, those under Clean Water Act and Clean Air Act. For the livestock industry, inspections focused primarily on CAFOs. Of the 31 other industries, 4 (including crop production) had a better 5-year environmental record than the livestock industry, 2 had a similar record, and 25 had a worse record in this respect. For the most recent year of the five-year compilation, livestock production and dry cleaning had the best environmental records of the 32 industries, each with an enforcement order/inspection ratio of 0.01. For crop production, the ratio was 0.02. Of the 32 industries, oil and gas extraction and the livestock industry had the lowest percentages of facilities with violations.US EPA. 2000. Profile of the agricultural livestock production industry. U.S. Environmental Protection Agency. Office of Compliance. EPA/310-R-00-002. 156 pp.
With good management, manure has environmental benefits. Manure deposited on pastures by grazing animals themselves is applied efficiently for maintaining soil fertility. Animal manures are also commonly collected from barns and concentrated feeding areas for efficient re-use of many nutrients in crop production, sometimes after composting. For many areas with high livestock density, manure application substantially replaces application of synthetic fertilizers on surrounding cropland. Manure was spread as a fertilizer on about 15.8 million acres of US cropland in 2006.McDonald, J. M. et al. 2009. Manure use for fertilizer and for energy. Report to Congress. USDA, AP-037. 53pp. Manure is also spread on forage-producing land that is grazed, rather than cropped. Altogether, in 2007, manure was applied on about 22.1 million acres in the United States. Substitution of animal manure for synthetic fertilizer has important implications for energy use and greenhouse gas emissions, considering that between about 43 and 88 MJ (i.e. between about 10 and 21 Mcal) of fossil fuel energy are used per kg of N in production of synthetic nitrogenous fertilizers.Shapouri, H. et al. 2002. The energy balance of corn ethanol: an update. USDA Agricultural Economic Report 814
Manure can also have environmental benefit as a renewable energy source, in digester systems yielding biogas for heating and/or electricity generation. Manure biogas operations can be found in Asia, Europe,Erneubare Energien in Deutschland - Rückblick und Stand des Innovationsgeschehens. Bundesministerium fűr Umwelt, Naturschutz u. Reaktorsicherheit. http://www.bmu.de/files/pdfs/allgemin/application/pdf/ibee_gesamt_bf.pdfBiogas from manure and waste products - Swedish case studies. SBGF; SGC; Gasföreningen. 119 pp. http://www.iea-biogas.net/_download/publi-task37/public-member/Swedish_report_08.pdf North America, and elsewhere. The US EPA estimates that as of July 2010, 157 manure digester systems for biogas energy were in operation on commercial-scale US livestock facilities. System cost is substantial, relative to US energy values, which may be a deterrent to more widespread use, although additional factors, such as odor control and carbon credits, may improve benefit /cost ratios.NRCS. 2007. An analysis of energy production costs from anaerobic digestion systems on U.S. livestock production facilities. US Natural Resources Conservation Service. Tech. Note 1. 33 pp.
==Effects on wildlife==
Grazing (especially, overgrazing) may detrimentally affect certain wildlife species, e.g. by altering cover and food supplies. However, habitat modification by livestock grazing can also benefit some wildlife species. For example, in North America, various studies have found that grazing sometimes improves habitat for
elk,
blacktailed prairie dogs,
sage grouse,Neel. L.A. 1980. Sage Grouse Response to Grazing Management in Nevada. M.Sc. Thesis. Univ. of Nevada, Reno.
mule deer,
and numerous other species. A survey of refuge managers on 123 National Wildlife Refuges in the US tallied 86 species of wildlife considered positively affected and 82 considered negatively affected by refuge cattle grazing or haying. Such mixed effects suggest that wildlife diversity may be enhanced and maintained by grazing livestock in some places while excluding livestock in some places. The kind of grazing system employed (e.g. rest-rotation, deferred grazing, HILF grazing) is often important in achieving grazing benefits for particular wildlife species.
==Beneficial environmental effects==
Among other environmental benefits of meat production is conversion of materials that might otherwise be wasted, to produce high-protein food. For example, Elferink et al. state that "Currently, 70 % of the feedstock used in the Dutch feed industry originates from the food processing industry." US examples of "waste" conversion with regard to grain 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 amounted to 25.0 million metric tons.Hoffman, L. and A. Baker. 2010. Market issues and prospects for U.S. distillers' grains supply, use, and price relationships. USDA FDS-10k-01 Much soy meal used as livestock feed is produced from material left after extraction of the soybean oil used in foods and in production of biodiesel, soaps and industrial fatty acids. Similarly, canola meal for livestock feed is produced from material left after oil extraction (for food and biodiesel) from canola seed. Examples with regard to roughages include straw from barley and wheat crops (feedable especially to large-ruminant breeding stock when on maintenance diets),Anderson, D. C. 1978. Use of cereal residues in beef cattle production systems. J. Anim. Sci. 46: 849–861.Males, J. R. 1987. Optimizing the utilization of cereal crop residues for beef cattle. J. Anim. Sci. 65: 1124-1130. and corn stover.Ward, J. K. 1978. Utilization of corn and grain sorghum residues in beef cow forage systems. J. Anim. Sci. 46: 831-840.Klopfenstein, T. et al. 1987. Corn residues in beef production systems. J. Anim. Sci. 65: 1139–1148. Also, small-ruminant flocks in North America (and elsewhere) are sometimes used on fields for removal of various crop residues inedible by humans, converting them to food.
There are environmental benefits of meat-producing small ruminants for control of specific invasive or noxious weeds (such as spotted knapweed, tansy ragwort, leafy spurge, yellow starthistle, tall larkspur, etc.) on rangeland. Small ruminants are also useful for vegetation management in forest plantations, and for clearing brush on rights-of-way. These represent food-producing alternatives to herbicide use.Launchbaugh, K. (ed.) 2006. Targeted Grazing: a natural approach to vegetation management and landscape enhancement. American Sheep Industry. 199 pp.
==See also==
*Agroecology
*Cheap meat
*Economic vegetarianism
*Environmental impact of agriculture
*Environmental vegetarianism
*Ethics of eating meat
*Farmageddon (book)
*Meat Atlas
*Stock-free agriculture
*Sustainable agriculture
*Sustainable diet
==References==
== Further reading ==
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*Animal Waste and Water Quality: EPA's Response to the Waterkeeper Alliance Court Decision on Regulation of CAFOs Congressional Research Service
Category:Air Pollution
Category:Rural issues
Category:Urban issues