Meat production is a main driver of tropical deforestation
Average greenhouse gas emissions by food product
Grazing occupies 26% of the earth's ice-free terrestrial surface, and feed crop production uses about one third of all arable land or about 75% of agriculturally used land. The global food system is responsible for one third of the global anthropogenic GHG emissions, of which meat accounts for nearly 60%.
Cereal-use statistic showing an estimated large fraction of crops used as fodder
Some fraction of these effects is assignable to non-meat components of the livestock sector such as the wool, and egg and dairy production, and to the livestock used for tillage. Livestock have been estimated to provide power for tillage of as much as half of the world's cropland.
Changes in demand for meat may change the environmental impact of meat production by influencing how much meat is produced. 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). Global production and consumption of poultry meat have recently been growing at more than 5 percent annually. Meat consumption typically increases as people and countries get richer. There is a strong favorable relationship between meat consumption per capita and gross domestic product (GDP) per capita. According to an article written by Dave Roos "industrialized Western nations average more than 220 pounds of meat per person per year, while the poorest African nations average less than 22 pounds per person." 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), while global per capita consumption of ruminant meats has been declining.
In comparison with grazing, intensive livestock production requires large quantities of harvested feed, this overproduction of feed can also hold negative effects. The growing of cereals for feed in turn requires substantial areas of land.
It takes seven pounds of feed to produce a pound of beef (live weight), more than three pounds for a pound of pork, and less than two pounds for a pound of chicken. 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.
About 85 percent 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 six percent of soybeans are used directly as human food, mostly in Asia. In the contiguous United States, 127.4 million acres of crops are grown for animal consumption, compared to the 77.3 million acres of crops grown for human consumption.
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.
Free-range animal production requires land for grazing, which in some places has led to land use change. According to 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."
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 cultivable 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.
Land quality decline is sometimes associated with overgrazing, as these animals are removing much needed nutrients from the soil without the land having time to recover. Rangeland health classification reflects soil and site stability, hydrologic function, and biotic integrity. By the end of 2002, the US Bureau of Land Management (BLM) 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. Soil erosion associated with overgrazing is an important issue in many dry regions of the world. 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.
Environmental effects of grazing can be positive or negative, depending on management quality, and grazing can have different effects on different soils and different plant communities. Grazing can sometimes reduce, and other times increase, biodiversity of grassland ecosystems. In beef production, cattle ranching can provide supporting and habitat services by maintaining habitats that have evolved to thrive alongside grazing. Lightly grazed grasslands also tend to have higher biodiversity than overgrazed or nongrazed grasslands. 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. 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.
The livestock sector is also the primary driver of deforestation in the Amazon, with around 80% of all converted land being used for cattle rearing. 91% of land deforested since 1970 has been converted to cattle ranching.
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.
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. This excessive use of river water distresses ecosystems and communities, and drives scores of species of fish closer to extinction during times of drought.
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. Groundwater depletion is a concern in some areas because of sustainability issues (and in some cases, land subsidence and/or saltwater intrusion). 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. 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 percent of the grain fed to US livestock and poultry in 2010.: table 1–75 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, but only about 40 percent of US corn grain is fed to US livestock and poultry.: table 1–38
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. In the Eastern United States, a 1997 study found that 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).[failed verification] In North Carolina, where the study was done, measures have since been taken to reduce the risk of accidental discharges from manure lagoons;[further explanation needed] also, since then there is evidence of improved environmental management in US hog production. Implementation of manure and wastewater management planning can help assure low risk of problematic discharge into aquatic systems.
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 CO2 equivalents. 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 the 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 the 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 has estimated that agriculture (including not only livestock, but also food crop, biofuel and other production) accounted for about 10 to 12 percent of global anthropogenic greenhouse gas emissions (expressed as 100-year carbon dioxide equivalents) in 2005 and in 2010. According to a 2022 study quickly stopping animal agriculture would provide half the GHG emission reduction needed to meet the Paris Agreement goal of limiting global warming to 2°C.
In the US, methane emissions associated with ruminant livestock (6.6 Tg CH4, or 164.5 Tg CO2e in 2013) 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, 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. The magnitude of methane emissions were recently about 330 to 350 Tg per year from all anthropogenic sources, and methane's current effect on global warming is quite small. This is because degradation of methane nearly keeps pace with emissions, resulting in a 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).
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. 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. Among sheep production systems, for example, there are very large differences in both energy use and prolificacy; both factors strongly influence emissions per kg of lamb production.
In climate change mitigation
According to a 2018 study in the journal Nature, a significant reduction in meat consumption will be "essential" to mitigate climate change, especially as the human population increases by a projected 2.3 billion by the middle of the century. A 2019 report in The Lancet recommended that global meat consumption be reduced by 50 percent to mitigate climate change.
On August 8, 2019, the IPCC released a summary of the 2019 special report which said that a shift towards plant-based diets would help to mitigate and adapt to climate change.
In November 2017, 15,364 scientists worldwide signed a "Warning to Humanity" calling for, among other things, drastically diminishing humanity's per capita consumption of meat.
Effect of air pollution on human respiratory health
Meat production is one of the leading causes of greenhouse gas emissions and other particulate matter pollution in the atmosphere. This type of production chain produces copious byproducts; endotoxin, hydrogen sulfide, ammonia, and particulate matter (PM), such as dust, are all released along with the aforementioned methane and CO2. Furthermore, elevated greenhouse gas emissions have been associated with respiratory diseases like asthma, bronchitis, and COPD, as well as increased chances of acquiring pneumonia from bacterial infections.
In addition, exposure to PM10 (particulate matter 10 micrometers in diameter) may produce diseases that impact the upper and proximal airways. Farmers aren’t the only ones at risk for exposure to these harmful byproducts. In fact, concentrated animal feeding operations (CAFOs) in proximity to residential areas adversely affect these individuals' respiratory health similarly seen in the farmers. Concentrated hog feeding operations release air pollutants from confinement buildings, manure holding pits, and land application of waste. Air pollutants from these operations have caused acute physical symptoms, such as respiratory illnesses, wheezing, increased breath rate, and irritation of the eyes and nose. That prolonged exposure to airborne animal particulate, such as swine dust, induces a large influx of inflammatory cells into the airways. Those in close proximity to CAFOs could be exposed to elevated levels of these byproducts, which may lead to poor health and respiratory outcomes.
Energy efficiency of meat and dairy 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.
An important aspect of energy use of livestock production is the energy consumption that the animals contribute. Feed Conversion Ratio is an animal's ability to convert feed into meat. The Feed Conversion Ratio (FCR) is calculated by taking the energy, protein, or mass input of the feed divided by the output of meat provided by the animal. A lower FCR corresponds with a smaller requirement of feed per meat out-put, therefore the animal contributes less GHG emissions. Chickens and pigs usually have a lower FCR compared to ruminants.
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 percent less greenhouse gas emissions, 12 percent less water use and 33 percent less land use, per unit mass of beef produced, than in 1977. These figures are based on an 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.
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.: Table I-1 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. 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 the Clean Water Act and Clean Air Act. For the livestock industry, inspections focused primarily on CAFOs. Of the 32 other industries, (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.
Manure provides environmental benefits when properly managed. Manure that is deposited on pastures by grazing animals is an effective way to preserve soil fertility. Many nutrients are recycled in crop cultivation by collecting animal manure from barns and concentrated feeding sites, sometimes after composting. For many areas with high livestock density, manure application substantially replaces the application of synthetic fertilizers on surrounding cropland. Manure was spread as a fertilizer on about 15.8 million acres of US cropland in 2006. 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 impact on 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 the production of synthetic nitrogenous fertilizers.
Manure can also have environmental benefits 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, North America, and elsewhere. The US EPA estimates that as of July 2010, 157 manure digester systems for bio-gas 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. Additional factors, such as odor control and carbon credits, may improve benefit to cost ratios. Manure can be mixed with other organic wastes in anaerobic digesters to take advantage of economies of scale. Digested waste is more uniform in consistency than untreated organic wastes, and can have higher proportions of nutrients that are more available to plants, which enhances the utility of digestate as a fertiliser product. This encourages circularity in meat production, which is typically difficult to achieve due to environmental and food safety concerns.
Grazing (especially overgrazing) may detrimentally affect certain wildlife species, e.g. by altering cover and food supplies. The growing demand for meat is contributing to significant biodiversity loss as it is a significant driver of deforestation and habitat destruction; species-rich habitats, such as significant portions of the Amazon region, are being converted to agriculture for meat production. World Resource Institute (WRI) website mentions that "30 percent of global forest cover has been cleared, while another 20 percent has been degraded. Most of the rest has been fragmented, leaving only about 15 percent intact." WRI also states that around the world there is "an estimated 1.5 billion hectares (3.7 billion acres) of once-productive croplands and pasturelands—an area nearly the size of Russia—are degraded. Restoring productivity can improve food supplies, water security, and the ability to fight climate change." The 2019 IPBESGlobal Assessment Report on Biodiversity and Ecosystem Services also concurs that the meat industry plays a significant role in biodiversity loss. Around 25% to nearly 40% of global land surface is being used for livestock farming.
In North America, various studies have found that grazing sometimes improves habitat for
blacktailed prairie dogs,
and mule deer. 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. 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.
A 2022 report from World Animal Protection and the Center for Biological Diversity found that, based on 2018 data, some 235 million pounds (or 117,500 tons) of pesticides are used for animal feed purposes annually in the United States alone, in particular glyphosate and atrazine. The report emphasizes that 100,000 pounds of glyphosate has the potential to harm or kill some 93% of species listed under the Endangered Species Act. Atrazine, which is banned in 35 countries, could harm or kill at least 1,000 listed species. Both groups involved in the report advocate for consumers to reduce their consumption of animal products and to transition towards plant-based diets in order to reduce the growth of factory farming and protect endangered species of wildlife.
Effects on antibiotic resistance
A CDC infographic on how antibiotic-resistant bacteria have the potential to spread from farm animals
While levels of use vary dramatically from country to country, for example some Northern European countries use very low quantities to treat animals compared with humans, worldwide an estimated 73% of antimicrobials (mainly antibiotics) are consumed by farm animals. Furthermore, a 2015 study also estimates that global agricultural antibiotic usage will increase by 67% from 2010 to 2030, mainly from increases in use in developing BRIC countries.
Increased antibiotic use is a matter of concern as antibiotic resistance is considered to be a serious threat to human and animal welfare in the future, and growing levels of antibiotics or antibiotic-resistant bacteria in the environment could increase the numbers of drug-resistant infections in both. Bacterial diseases are a leading cause of death and a future without effective antibiotics would fundamentally change the way modern human as well as veterinary medicine is practised. However, legislation and other curbs on antibiotic use in farm animals are now being introduced across the globe. In 2017, the World Health Organization strongly suggested reducing antibiotic use in animals used in the food industry.
The use of antibiotics for growth promotion purposes was banned in the European Union from 2006, and the use of sub-therapeutic doses of medically important antibiotics in animal feed and water to promote growth and improve feed efficiency became illegal in the United States on 1 January 2017, through regulatory change enacted by the Food and Drug Administration (FDA), which sought voluntary compliance from drug manufacturers to re-label their antibiotics.
A review concluded that "low and moderate meat consumption levels are compatible with the climate targets and broader sustainable development, even for 10 billion people".
A study quantifiedclimate change mitigation potentials of 'high-income' nations shifting diets – away from meat-consumption – and restoration of the spared land, finding that if these were combined they could "reduce annual agricultural production emissions of high-income nations' diets by 61%".
Measures which increase state revenues from meat consumption/production could enable the use of these funds for related research and development and "to cushion social hardships among low-income consumers". Meat and livestock are important sectors of the contemporary socioeconomic system, with livestock value chains employing an estimated >1.3 billion people.
Beneficial environmental effects
One environmental benefit of meat production is the conversion of materials that might otherwise be wasted or turned into compost to produce food. 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. 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.
According to a study, wild boars are causing soil disturbance that, among other problems, globally results in annual carbon dioxide emissions equivalent to that of ~1.1 million passenger vehicles, implying that as of 2021 hunted wild pig meat – unlike other meat products – has beneficial effects on the environment even though the effect would diminish if wild boards are introduced for purposes of meat production and consistently retaining small populations of boars may be preferable.
^McGrath, Matt (6 May 2019). "Humans 'threaten 1m species with extinction'". BBC. Retrieved 3 July 2019. Pushing all this forward, though, are increased demands for food from a growing global population and specifically our growing appetite for meat and fish.
^Watts, Jonathan (6 May 2019). "Human society under urgent threat from loss of Earth's natural life". The Guardian. Retrieved 3 July 2019. Agriculture and fishing are the primary causes of the deterioration. Food production has increased dramatically since the 1970s, which has helped feed a growing global population and generated jobs and economic growth. But this has come at a high cost. The meat industry has a particularly heavy impact. Grazing areas for cattle account for about 25% of the world’s ice-free land and more than 18% of global greenhouse gas emissions.
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