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 agricultural 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, animal methane, effluent waste, 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.
Meat is considered one of the prime factors contributing to the current sixth mass extinction. The 2019 IPBES Global Assessment Report on Biodiversity and Ecosystem Services found that industrial agriculture and overfishing are the primary drivers of the extinction crisis, with the meat and dairy industries having a substantial impact. The 2006 report Livestock's Long Shadow, released by the Food and Agriculture Organization of the United Nations, states 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, and in developed and emerging countries it is perhaps the leading source of water pollution." A 2017 study published in the journal Carbon Balance and Management found animal agriculture's global methane emissions are 11% higher than previous estimates based on data from the Intergovernmental Panel on Climate Change. Some fraction of these effects is assignable to non-meat components of the livestock sector such as the wool, egg and dairy industries, 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. A July 2018 study in Science asserts that meat consumption will increase as the result of human population growth and rising individual incomes, which will increase carbon emissions and further reduce biodiversity.
On August 8, 2019, the IPCC released a summary of the 2019 special report which asserted that a shift towards plant-based diets would help to mitigate and adapt to climate change. 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. In November 2017, 15,364 world scientists signed a Warning to Humanity calling for, among other things, drastically diminishing our per capita consumption of meat. A similar shift to meat-free diets appears also as the only safe option to feed a growing population without further deforestation, and for different yields scenarios.
Consumption and production trends
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. Global production and consumption of poultry meat have recently been growing at more than 5 percent annually. 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, while 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, 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, 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 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.
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 had evaluated rangeland health on 7,437 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 the quality of management, 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. 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 to rear cattle. 91% of land deforested since 1970 has been converted to cattle ranching.
Water use
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. A particularly important North American example where depletion is occurring involves the High Plains 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 is of particular interest, accounting for about 91.8 percent of the grain fed to US livestock and poultry in 2010. 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.
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. 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. In North Carolina, where the study was done, measures have since been taken to reduce the risk of accidental discharges from manure lagoons; 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.Greenhouse gas emissions
At a global scale, the FAO has recently estimated that livestock 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 accounted for about 10 to 12 percent of global anthropogenic greenhouse gas emissions in 2005 and in 2010., in Indonesia. Animals can provide a useful source of draught power to farmers in the developing world
A PNAS model showed that even if animals were completely removed from US agriculture, US GHG emissions would be decreased by 2.6%. The authors state this is because of the need to replace animal manures by fertilizers and to replace also other animal coproducts, and because livestock now use human-inedible food and fiber processing byproducts. This study has been criticized, and cannot be used to answer any question about what impact a dietary shift in the US would have globally, as it also does not take into account the effects that this change would have on meat production and deforestation in other countries. One of this further study on the matter has suggested that farmers would reduce their land use of feed crops; currently representing 75% of US land use, and would reduce the use of fertilizer due to the lower land areas and crop yields needed. A transition to a more plant based diet is also projected to improve health, which can lead to reductions in healthcare GHG emissions, currently standing at 8% of US emissions.
In the US, methane emissions associated with ruminant livestock are estimated to have declined by about 17 percent from 1980 through 2012. Globally, enteric fermentation accounts for about 27 percent of anthropogenic methane emissions, and methane accounts for about 32 to 40 percent of agriculture's greenhouse gas emissions 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, whereas atmospheric carbon dioxide content has been increasing greatly.
for exhaled methane production, CSIRO.
Mitigation options for reducing methane emission from ruminant enteric fermentation include genetic selection, immunization, rumen defaunation, outcompetition of methanogenic archaea with acetogens, introduction of methanotrophic bacteria into the rumen, diet modification and grazing management, among others. 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, reducing fossil fuel consumption, and increasing carbon sequestration in soils. Australian scientists discovered that adding the seaweed Asparagopsis taxiformis to the cattle's diet can reduce methane by up to 99%, and reported a 3% seaweed diet resulted in an 80% reduction in methane.
In New Zealand, nearly half of 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 in 2010. Livestock sources 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.
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.
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, such as dust, are all released along with the aforementioned methane and. 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 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 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 consumption
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.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 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.
Animal waste
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. 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 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 31 other industries, 4 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.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 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 implications for energy use and greenhouse gas emissions, considering that between about 43 and 88 MJ 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 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. Additional factors, such as odor control and carbon credits, may improve benefit to cost ratios.
Effects on wildlife
Grazing 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 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." The 2019 IPBES Global 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. WRI also states that around the world there is "an estimated 1.5 billion hectares 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."In North America, various studies have found that grazing sometimes improves habitat for
elk,
blacktailed prairie dogs,
sage grouse,
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 is often important in achieving grazing benefits for particular wildlife species.
Effects on antibiotic resistance
Approximately 90% of the total use of antimicrobials in the United States was for non-therapeutic purposes in agricultural production. Livestock production has been associated with increased antibiotic resistance in bacteria, and has been associated with the emergence of microbes which are resistant to multiple antimicrobials.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 remaining from ethanol production. For the marketing year 2009-2010, dried distillers grains used as livestock feed in the US was estimated at 25.5 million metric tons. Examples of waste roughages include straw from barley and wheat crops, and corn stover. Also, small-ruminant flocks in North America are sometimes used on fields for removal of various crop residues inedible by humans, converting them to food.Small ruminants can control of specific invasive or noxious weeds on rangeland. Small ruminants are also useful for vegetation management in forest plantations and for clearing brush on rights-of-way. These represent alternatives to herbicide use.