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] Agriculture contributes towards
climate change through direct
greenhouse gas emissions and by the conversion of non-agricultural land such as
forests into agricultural land.[3][4] Emissions of
nitrous oxide and
methane make up over half of total greenhouse gas emission from agriculture.[5]Animal husbandry is a major source of greenhouse gas emissions.[6]
The agricultural food system is responsible for a significant amount of greenhouse gas emissions.[7][8] In addition to being a significant user of
land and consumer of
fossil fuel, agriculture contributes directly to greenhouse gas emissions through practices such as
rice production and the raising of
livestock.[9] The three main causes of the increase in greenhouse gases observed over the past 250 years have been
fossil fuels, land use, and agriculture.[10] Farm animal digestive systems can be put into two categories:
monogastric and
ruminant. Ruminant cattle for beef and dairy rank high in greenhouse-gas emissions; monogastric, or pigs and poultry-related foods, are low. 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.[7] Furthermore, 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.[11] The amount of
greenhouse gases produced during the
manufacture and use of
nitrogen fertilizer is estimated at around 5% of
anthropogenic greenhouse gas emissions. The single most important way to cut emissions from it is to use less fertilizers, while increasing the efficiency of their use.[12]
There are many strategies that can be used to help soften the effects, and the further production of greenhouse gas emissions - this is also referred to as
climate-smart agriculture. Some of these strategies include a higher efficiency in livestock farming, which includes management, as well as technology; a more effective process of managing manure; a lower dependence upon fossil-fuels and nonrenewable resources; a variation in the animals' eating and drinking duration, time and location; and a cutback in both the production and consumption of animal-sourced foods.[7][13][14][15] A range of policies may reduce greenhouse gas emissions from the agriculture sector for a more
sustainable food system.[16]: 816–817
Activities such as
tilling of fields, planting of crops, and shipment of products cause carbon dioxide emissions.[18] Agriculture-related emissions of carbon dioxide account for around 11% of global greenhouse gas emissions.[19] 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.[20]
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.[22] While the
residence time of methane is much shorter than that of carbon dioxide, it is 28 times more capable of trapping heat.[22] 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.[22] 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.[23]
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.[24] Government involvement in agricultural policy is limited due to high demand for agricultural products like corn, wheat, and milk.[25] 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%.[26] These numbers are impactful and would mitigate greenhouse gas emissions while still feeding the population.[26]
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.[27] 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.[27] 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.[28]
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.[30]
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.[31] Deforestation also affects regional
carbon reuptake, which can result in increased concentrations of
CO2, the dominant greenhouse gas.[32] 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 and livestock-related activities such as deforestation and increasingly fuel-intensive farming practices are responsible for over 18%[33] of human-made greenhouse gas emissions, including:
64% of global nitrous oxide emissions (chiefly due to
fertilizer use.[33])
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.[34] 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.[35] 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.[36] Methane production by animals, principally ruminants, makes up an estimated 15-20% global production of methane.[37][38] Research continues on the use of various seaweed species, in particular
Asparegopsis armata, as a food additive that helps reduce methane production in ruminants.[39]
Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.[33] The way livestock is grazed also affects future fertility of the land. Not circulating grazing can lead to unhealthy compacted soils. The
expansion of livestock farms affects the habitats of native wildlife and has led to their decline. Reduced intake of meat and dairy products is another effective approach to reduce greenhouse gas emissions. Slightly over half of Europeans (51%) surveyed in 2022 support reducing the amount of meat and dairy products people may buy to combat climate change - 40% of Americans and 73% of Chinese respondents felt the same.[40]
The amount of
greenhouse gasescarbon dioxide,
methane and
nitrous oxide produced during the
manufacture and use of nitrogen fertilizer is estimated as around 5% of
anthropogenic greenhouse gas emissions. One third is produced during the production and two thirds during the use of fertilizers. The single most important way to cut emissions from it is to use less fertilizers. According to Dr André Cabrera Serrenho: ""We're incredibly inefficient in our use of fertilisers," "We're using far more than we need".[42] Nitrogen fertilizer can be converted by
soil bacteria to
nitrous oxide, a
greenhouse gas.[43] Nitrous oxide emissions by humans, most of which are from fertilizer, between 2007 and 2016 have been estimated at 7 million tonnes per year,[44] which is incompatible with limiting global warming to below 2 °C.[45]
In 2022,
greenhouse gas emissions from rice cultivation were estimated at 5.7 billion tonnes CO2eq, representing 1.2% of total emissions.[46] Within the agriculture sector, rice produces almost half the greenhouse gas emissions from
croplands,[47] some 30% of agricultural
methane emissions, and 11% of agricultural
nitrous oxide emissions.[48]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.[49] Emissions can be limited by planting new varieties, not flooding continuously, and removing straw.[50]
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.[5]
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.[51]
Older estimates
In 2010, agriculture,
forestry and
land-use change were estimated to contribute 20–25% of global annual emissions.[16]: 383
Agriculture is often not included in government emissions reductions plans.[53] For example, the agricultural sector is exempt from the
EU emissions trading scheme[54] which covers around 40% of the EU greenhouse gas emissions.[55]
Several mitigation measures for use in developed countries have been proposed:[56]
breeding more resilient crop varieties, and diversification of crop species
using improved agroforestry species
capture and retention of rainfall, and use of improved irrigation practices
use of emerging water harvesting techniques (such as
contour trenching)
Research in New Zealand estimated that switching agricultural production towards a healthier diet while reducing greenhouse gas emissions would cost approxiately 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.[57]
In developing countries
Agriculture is responsible for over a quarter of total global greenhouse gas emissions.[58] Given that agriculture's share in global
gross domestic product (GDP) is about 4%, these figures suggest that agricultural activities produce high levels of
greenhouse gases. Innovative agricultural practices and technologies can play a role in
climate change mitigation[59] and
adaptation. This adaptation and mitigation potential is nowhere more pronounced than in developing countries where agricultural productivity remains low; poverty, vulnerability and food insecurity remain high; and the direct effects of climate change are expected to be especially harsh. Creating the necessary agricultural technologies and harnessing them to enable developing countries to adapt their agricultural systems to changing climate will require innovations in policy and institutions as well. In this context, institutions and policies can play an important role at multiple scales.
State- or NGO-sponsored projects can help farmers be more resilient to climate change, such as irrigation infrastructure that provides a dependable water source as rains become more erratic.[60][61] Water catchment systems that collect water during the rainy season to be used during dry periods can also be used to mitigate the effects of climate change.[61] Some programs, like the Asociación de Cooperación para el Desarrollo Rural de Occidente (C.D.R.O.), a Guatemalan program funded by the United States' government until 2017, focus on agroforestry and weather monitoring systems to help farmers adapt. The organization provided residents with resources to plant new, more adaptable crops to alongside their typical maize to protect the corn from variable temperatures, frost, etc. C.D.R.O. also set up a weather monitoring system to help predict extreme weather events, and would send residents text messages to warn them about periods of frosts, extreme heat, humidity, or drought.[62] Projects focusing on irrigation, water catchment, agroforestry, and weather monitoring can help Central American residents adapt to climate change.
The Agricultural Model Intercomparison and Improvement Project (AgMIP)[63] was developed in 2010 to evaluate agricultural models and intercompare their ability to predict climate impacts. In sub-Saharan Africa and South Asia, South America and East Asia, AgMIP regional research teams (RRTs) are conducting integrated assessments to improve understanding of agricultural impacts of climate change (including biophysical and
economic impacts) at national and regional scales. Other AgMIP initiatives include global gridded modeling, data and information technology (IT) tool development, simulation of crop pests and diseases, site-based crop-climate sensitivity studies, and aggregation and scaling.
At the
2019 United Nations Climate Summit, the Global EverGreening Alliance announced an initiative to promote
agroforestry and
conservation farming. One of its goals is to
sequester carbon from the atmosphere. The coalition aims to restore tree cover to a territory of 5.75 million square kilometres, achieve a healthy tree-grass balance on a territory of 6.5 million square kilometres, and increase carbon capture in a territory of 5 million square kilometres.By 2050 the restored land should sequester 20 billion tons of carbon annually. The first phase of the initiative is the "Grand African Savannah Green Up" project. In 2019, millions of families had already implemented these methods, and the average territory covered with trees in the farms in
Sahel reached 16%.[64]
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.[67]
^
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