The amount of greenhouse gas emissions from agriculture is significant: The agriculture, forestry and land use sector contribute between 13% and 21% of global
greenhouse gas emissions.[2] Emissions come from direct greenhouse gas emissions (for example from
rice production and
livestock farming).[3] and from indirect emissions. With regards to direct emissions,
nitrous oxide and
methane make up over half of total greenhouse gas emission from agriculture.[4] Indirect emissions on the other hand come from the conversion of non-agricultural land such as
forests into agricultural land.[5][6] Furthermore, there is also
fossil fuel consumption for transport and
fertilizer production. For example, the
manufacture and use of
nitrogen fertilizer contributes around 5% of all global greenhouse gas emissions.[7]Livestock farming is a major source of greenhouse gas emissions.[8] At the same time,
livestock farming is affected by climate change.
Farm animals' digestive systems can be put into two categories:
monogastric and
ruminant. Ruminant cattle for beef and dairy rank high in greenhouse gas emissions. In comparison, monogastric, or pigs and poultry-related foods, are lower. The consumption of the monogastric types may yield less emissions. Monogastric animals have a higher feed-conversion efficiency, and also do not produce as much methane.[9] Non-ruminant livestock, such as poultry, emit far fewer greenhouse gases.[10]
There are many strategies to reduce greenhouse gas emissions from agriculture (this is one of the goals of
climate-smart agriculture). Mitigation measures in the food system can be divided into four categories. These are demand-side changes, ecosystem protections, mitigation on farms, and mitigation in
supply chains. On the demand side, limiting
food waste is an effective way to reduce food emissions. Changes to a diet less reliant on animal products such as
plant-based diets are also effective.[11]: XXV This could include
milk substitutes and
meat alternatives. Several methods are also under investigation to reduce the greenhouse gas emissions from livestock farming. These include genetic selection,[12][13] introduction of
methanotrophic bacteria into the rumen,[14][15] vaccines, feeds,[16] diet modification and grazing management.[17][18][19]
Activities such as
tilling of fields, planting of crops, and shipment of products cause carbon dioxide emissions.[21] Agriculture-related emissions of carbon dioxide account for around 11% of global greenhouse gas emissions.[22] Farm practices such as reducing tillage, decreasing empty land, returning
biomass residue of crop to soil, and increasing the use of cover crops can reduce carbon emissions.[23]
Methane emissions
Methane emissions from livestock are the number one contributor to agricultural greenhouse gases globally. Livestock are responsible for 14.5% of total anthropogenic greenhouse gas emissions. One cow alone will emit 220 pounds of methane per year.[25] While the
residence time of methane is much shorter than that of carbon dioxide, it is 28 times more capable of trapping heat.[25] Not only do livestock contribute to harmful emissions, but they also require a lot of land and may
overgraze, which leads to unhealthy soil quality and reduced species diversity.[25] A few ways to reduce methane emissions include switching to plant-rich diets with less meat, feeding the cattle more nutritious food,
manure management, and
composting.[26]
Traditional
rice cultivation is the second biggest agricultural methane source after
livestock, with a near-term warming impact equivalent to the
carbon-dioxide emissions from all aviation.[27] Government involvement in agricultural policy is limited due to high demand for agricultural products like corn, wheat, and milk.[28] The United States Agency for International Development's (USAID) global hunger and food security initiative, the Feed the Future project, is addressing food loss and waste. By addressing food loss and waste, greenhouse gas emission mitigation is also addressed. By only focusing on dairy systems of 20 value chains in 12 countries, food loss and waste could be reduced by 4-10%.[29] These numbers are impactful and would mitigate greenhouse gas emissions while still feeding the population.[29]
Nitrous oxide emissions
Nitrous oxide emission comes from the increased use of synthetic and organic fertilizers.
Fertilizers increase crop yield production and allows the crops to grow at a faster rate. Agricultural emissions of nitrous oxide make up 6% of the United States' greenhouse gas emissions; they have increased in concentration by 30% since 1980.[30] While 6% may appear to be a small contribution, nitrous oxide is 300 times more effective at trapping heat per pound than carbon dioxide and has a residence time of around 120 years.[30] Different management practices such as conserving water through
drip irrigation, monitoring soil nutrients to avoid overfertilization, and using
cover crops in place of fertilizer application may help in reducing nitrous oxide emissions.[31]
Emissions by type of activity
Land use changes
This section needs to be updated. The reason given is: it needs more recent info e.g. on plowing and soil. Please help update this article to reflect recent events or newly available information.(July 2019)
Agriculture contributes to greenhouse gas increases through land use in four main ways:
Together, these agricultural processes comprise 54% of
methane emissions, roughly 80% of nitrous oxide emissions, and virtually all carbon dioxide emissions tied to land use.[33]
Land cover has changed majorly since 1750, as humans have
deforestedtemperate regions. When forests and woodlands are cleared to make room for fields and
pastures, the
albedo of the affected area increases, which can result in either warming or cooling effects depending on local conditions.[34] Deforestation also affects regional
carbon reuptake, which can result in increased concentrations of
CO2, the dominant greenhouse gas.[35] Land-clearing methods such as
slash and burn compound these effects, as the burning of
biomatter directly releases greenhouse gases and particulate matter such as
soot into the air. Land clearing can destroy the
soil carbon sponge.
Livestock
Livestock produces the majority of greenhouse gas emissions from agriculture and demands around 30% of agricultural
fresh water needs, while only supplying 18% of the global
calorie intake. Animal-derived food plays a larger role in meeting human
protein needs, yet is still a minority of supply at 39%, with crops providing the rest.[36]: 746–747
Out of the
Shared Socioeconomic Pathways used by the
Intergovernmental Panel on Climate Change, only SSP1 offers any realistic possibility of meeting the 1.5 °C (2.7 °F) target.[37] Together with measures like a massive deployment of
green technology, this pathway assumes animal-derived food will play a lower role in the global diets relative to now.[38] As a result, there have been calls for phasing out
subsidies currently offered to livestock farmers in many places worldwide,[39] and
net zero transition plans now involve limits on total livestock headcounts, including substantial reductions of existing stocks in some countries with extensive animal agriculture sectors like Ireland.[40] Yet, an outright end to human consumption of meat and/or animal products is not currently considered a realistic goal.[41] Therefore, any comprehensive plan of
adaptation to
effects of climate change, particularly the present and future
effects of climate change on agriculture, must also consider livestock.
Livestock activities also contribute disproportionately to land-use effects, since crops such as
corn and
alfalfa are cultivated in order to feed the animals.
In 2010,
enteric fermentation accounted for 43% of the total greenhouse gas emissions from all agricultural activity in the world.[42] The meat from ruminants has a higher carbon equivalent footprint than other meats or vegetarian sources of protein based on a global meta-analysis of lifecycle assessment studies.[43] Small ruminants such as sheep and goats contribute approximately 475 million tons of carbon dioxide equivalent to GHG emissions, which constitutes around 6.5% of world agriculture sector emissions.[44] Methane production by animals, principally ruminants, makes up an estimated 15-20% global production of methane.[45][46]
Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.[47] The global
food system is responsible for one-third of the global anthropogenic
GHG emissions,[48][49] of which meat accounts for nearly 60%.[50][51]
The
IPCC Sixth Assessment Report in 2022 stated that: "Diets high in plant protein and low in meat and dairy are associated with lower GHG emissions. [...] Where appropriate, a shift to
diets with a higher share of plant protein, moderate intake of animal-source foods and reduced intake of
saturated fats could lead to substantial decreases in GHG emissions. Benefits would also include reduced land occupation and nutrient losses to the surrounding environment, while at the same time providing health benefits and reducing mortality from diet-related non-communicable diseases."[53]
Mean greenhouse gas emissions for different food types[54]
Food Types
Greenhouse Gas Emissions (g CO2-Ceq per g protein)
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.[55] There are calls to phase out livestock subsidies as part of a
just transition.[56]
In the context of global GHG emissions, food production within the global food system accounts for approximately 26%. Breaking it down, livestock and fisheries contribute 31%, whereas crop production, land use, and supply chains add 27%, 24%, and 18% respectively to the emissions.[57]
A 2023 study found that a
vegan diet reduced emissions by 75%.[58] Research in New Zealand estimated that switching agricultural production towards a healthier diet while reducing greenhouse gas emissions would cost approximately 1% of the agricultural sector's export revenue, which is an order of magnitude less than the estimated health system savings from a healthier diet.[59]
Research continues on the use of various seaweed species, in particular
Asparegopsis armata, as a food additive that helps reduce methane production in ruminants.[60]
CO2 is actually re-emitted into the atmosphere by plant and soil respiration in the later stages of crop growth, causing more greenhouse gas emissions.[65]
In 2022,
greenhouse gas emissions from rice cultivation were estimated at 5.7 billion tonnes CO2eq, representing 1.2% of total emissions.[66] Within the agriculture sector, rice produces almost half the greenhouse gas emissions from
croplands,[67] some 30% of agricultural
methane emissions, and 11% of agricultural
nitrous oxide emissions.[68]Methane is released from rice fields subject to long-term flooding, as this inhibits the soil from absorbing atmospheric oxygen, resulting in
anaerobic fermentation of organic matter in the soil.[69] Emissions can be limited by planting new varieties, not flooding continuously, and removing straw.[70]
It is possible to cut methane emissions in rice cultivation by improved water management, combining dry seeding and one drawdown, or executing a sequence of wetting and drying. This results in emission reductions of up to 90% compared to full flooding and even increased yields.[71]
Global estimates
Between 2010 and 2019, agriculture, forestry and land use contributed between 13% and 21% to global greenhouse gas emissions.[2]Nitrous oxide and
methane make up over half of total greenhouse gas emissions from agriculture.[4]
In 2020, it was estimated that the
food system as a whole contributed 37% of total greenhouse gas emissions, and that this figure was on course to increase by 30–40% by 2050 due to population growth and dietary change.[72]
Older estimates
In 2010, agriculture,
forestry and
land-use change were estimated to contribute 20–25% of global annual emissions.[73]: 383
Agriculture is often not included in government emissions reductions plans.[74] For example, the agricultural sector is exempt from the
EU emissions trading scheme[75] which covers around 40% of the EU greenhouse gas emissions.[76]
Almost 20% of greenhouse gas emissions come from the agriculture and forestry sector.[77] To significantly reduce these emissions, annual investments in the agriculture sector need to increase to $260 billion by 2030. The potential benefits from these investments are estimated at about $4.3 trillion by 2030, offering a substantial economic return of 16-to-1.[78]: 7–8
Mitigation measures in the food system can be divided into four categories. These are demand-side changes, ecosystem protections, mitigation on farms, and mitigation in
supply chains. On the demand side, limiting
food waste is an effective way to reduce food emissions. Changes to a diet less reliant on animal products such as
plant-based diets are also effective.[79]: XXV
With 21% of global methane emissions, cattle are a major driver of global warming.[80]: 6 When rainforests are cut and the land is converted for grazing, the impact is even higher. In Brazil, producing 1 kg of beef can result in the emission of up to 335 kg CO2-eq.[81] Other livestock, manure management and rice cultivation also emit greenhouse gases, in addition to fossil fuel combustion in agriculture.
Important mitigation options for reducing the greenhouse gas emissions from livestock include genetic selection,[82][83] introduction of
methanotrophic bacteria into the rumen,[84][85] vaccines, feeds,[86] diet modification and grazing management.[87][88][89] Other options are diet changes towards
ruminant-free alternatives, such as
milk substitutes and
meat analogues. Non-ruminant livestock, such as poultry, emit far fewer GHGs.[90]
It is possible to cut methane emissions in rice cultivation by improved water management, combining dry seeding and one drawdown, or executing a sequence of wetting and drying. This results in emission reductions of up to 90% compared to full flooding and even increased yields.[91]
There are different actions to adapt to the future challenges for crops and livestock. For example, with regard to rising temperatures and
heat stress, CSA can include the planting of
heat tolerant crop varieties,
mulching, boundary trees, and appropriate housing and spacing for cattle.[94]
^Friel, Sharon; Dangour, Alan D.; Garnett, Tara; et al. (2009). "Public health benefits of strategies to reduce greenhouse-gas emissions: food and agriculture". The Lancet. 374 (9706): 2016–2025.
doi:
10.1016/S0140-6736(09)61753-0.
PMID19942280.
S2CID6318195.
^Parmar, N.R.; Nirmal Kumar, J.I.; Joshi, C.G. (2015). "Exploring diet-dependent shifts in methanogen and methanotroph diversity in the rumen of Mehsani buffalo by a metagenomics approach". Frontiers in Life Science. 8 (4): 371–378.
doi:
10.1080/21553769.2015.1063550.
S2CID89217740.
^Martin, C. et al. 2010. Methane mitigation in ruminants: from microbe to the farm scale. Animal 4 : pp 351-365.
^Eckard, R. J.; et al. (2010). "Options for the abatement of methane and nitrous oxide from ruminant production: A review". Livestock Science. 130 (1–3): 47–56.
doi:
10.1016/j.livsci.2010.02.010.
^Kerr R.B., Hasegawa T., Lasco R., Bhatt I., Deryng D., Farrell A., Gurney-Smith H., Ju H., Lluch-Cota S., Meza F., Nelson G., Neufeldt H., Thornton P., 2022:
Chapter 5: Food, Fibre and Other Ecosystem Products. In
Climate Change 2022: Impacts, Adaptation and Vulnerability [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke,V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, US, pp. 1457–1579 |doi=10.1017/9781009325844.012
^Parmar, N.R.; Nirmal Kumar, J.I.; Joshi, C.G. (2015). "Exploring diet-dependent shifts in methanogen and methanotroph diversity in the rumen of Mehsani buffalo by a metagenomics approach". Frontiers in Life Science. 8 (4): 371–378.
doi:
10.1080/21553769.2015.1063550.
S2CID89217740.
^Martin, C. et al. 2010. Methane mitigation in ruminants: from microbe to the farm scale. Animal 4 : pp 351-365.
^Eckard, R. J.; et al. (2010). "Options for the abatement of methane and nitrous oxide from ruminant production: A review". Livestock Science. 130 (1–3): 47–56.
doi:
10.1016/j.livsci.2010.02.010.