View source for Greenhouse gas emissions from agriculture/ja

<languages />
{{See  also/ja|:en:Effects of climate change on agriculture}}
[[File:Global greenhouse gas emissions from food production.png|thumb|世界の温室効果ガス排出量の4分の1は食料生産と農業に起因する（2019年のデータ）]]
'''農業からの温室効果ガス排出量'''は''著しい''。農業、林業、土地利用部門は、世界の[[:en:greenhouse gas emissions|温室効果ガス排出量]]の13%から21%を占める。排出は''直接的な''温室効果ガス排出（例えば、[[Rice/ja|稲作]]や[[livestock/ja|畜産]]から）と''間接的な''排出から生じる。直接排出に関しては、[[nitrous oxide/ja|亜酸化窒素]]と[[methane/ja|メタン]]が農業からの総温室効果ガス排出量の半分以上を占める。
2023年のレビューでは、農地の排出量が土壌の種類、気候、管理慣行などの要因によって形成されることが強調されている。また、不耕起栽培、精密農業、水利用の改善、バイオ炭の施用など、排出量を削減し、土壌炭素貯蔵を強化できるいくつかの緩和戦略も強調されている。一方、間接排出は、[[:en:forest|森林]]などの非農業用地を農地に転換することから生じる。さらに、輸送や[[fertilizer/ja|肥料]]生産のための[[fossil fuel/ja|化石燃料]]消費もある。例えば、[[:en:Haber process|窒素肥料]]の[[:en:Haber process|製造]]と使用は、世界の温室効果ガス排出量全体の約5%を占める。[[:en:Environmental impacts of animal agriculture|畜産]]は温室効果ガス排出の主要な発生源である。同時に、[[Effects of climate change on livestock/ja|畜産は気候変動の影響を受ける]]。 

家畜の消化器系は、[[monogastric/ja|単胃動物]]と[[ruminant/ja|反芻動物]]の2つのカテゴリーに分けられる。肉牛や乳牛などの反芻動物は温室効果ガス排出量が上位に位置する。それに比べて、単胃動物、つまり豚や家禽関連の食品は排出量が少ない。単胃動物の消費は排出量を減らす可能性がある。単胃動物は飼料転換効率が高く、メタンもあまり生産しない。家禽などの非反芻動物は、温室効果ガスの排出量がはるかに少ない。

農業からの温室効果ガス排出量を削減するための戦略は多く存在する（これは[[:en:climate-smart agriculture|気候スマート農業]]の目標の一つである）。フードシステムにおける緩和策は、需要側の変化、生態系保護、農場での緩和、[[:en:supply chain|サプライチェーン]]における緩和の4つのカテゴリーに分けられる。需要側では、[[:en:food waste|食品廃棄]]を制限することが食品排出量を削減する効果的な方法である。[[plant-based diets/ja|植物性食品]]への依存度を低くする食事への変更も効果的である。これには、[[Milk substitute/ja|牛乳代替品]]や[[Meat alternative/ja|肉代替品]]が含まれる。また、畜産からの温室効果ガス排出量を削減するために、遺伝子選抜、[[Methanotroph/ja|メタン酸化細菌]]のルーメンへの導入、飼料の変更、放牧管理など、いくつかの方法が研究されている。

== 世界的な推定{{Anchor| Global estimates}} ==
[[File:World Farm-gate Greenhouse Gas Emissions By Activity.svg|thumb|活動別の世界の農場における温室効果ガス排出量]]
2022年のアグリフードシステムからの総排出量は162億トンの[[carbon dioxide/ja|二酸化炭素]]換算（Gt CO2eq）の温室効果ガスが大気中に放出され、これは2000年と比較して10%（1.5 Gt CO2eq）の増加である。

<div lang="en" dir="ltr" class="mw-content-ltr">
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.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Between 2010 and 2019, agriculture, forestry and land use contributed between 13% and 21% to global greenhouse gas emissions. [[Nitrous oxide]] and [[methane]] make up over half of total greenhouse gas emissions from agriculture.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Older estimates ===
In 2010, agriculture, [[forestry]] and [[land-use change]] were estimated to contribute 20–25% of global annual emissions.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
== Emissions by type of activity ==
{{See also|Environmental impact of agriculture}}
=== Land use changes ===
[[File:2019 Greenhouse gas emissions per capita by region - variwide bar chart - IPCC AR6 WG3 - Fig SPM.2c.svg|thumb|upright=1.5 | Substantial land-use change contributions to emissions have been made by Latin America, Southeast Asia, Africa, and Pacific Islands. The area of rectangles shows the region's total emissions in 2019.]]Agriculture contributes to greenhouse gas increases through land use in four main ways:
* CO<sub>2</sub> releases linked to [[deforestation]]
* Methane releases from [[rice|rice cultivation]]
* Methane releases from [[enteric fermentation]] in cattle
* [[Nitrous oxide]] releases from [[fertilizer]] application
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
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.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
[[Land cover]] has changed majorly since 1750, as humans have [[deforestation|deforested]] [[temperate region]]s. When forests and woodlands are cleared to make room for fields and [[pasture]]s, the [[albedo]] of the affected area increases, which can result in either warming or cooling effects depending on local conditions. Deforestation also affects regional [[RuBisCO|carbon reuptake]], which can result in increased concentrations of [[carbon dioxide|CO<sub>2</sub>]], the dominant greenhouse gas. 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]].
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Livestock ===
{{See also|Environmental impacts of animal agriculture}}
[[File:Livestock near Walnut Farm - geograph.org.uk - 3240836.jpg|thumb|Livestock farms where methane is emitted from the cattle.]]
[[File:World Emissions Intensity Of Agricultural Commodities (2021).svg|thumb|Meat from cattle and sheep have the highest emissions intensity of any agricultural commodity.]]
[[File:Environmental-impact-of-food-by-life-cycle-stage.png|thumb|upright=1.4|[[Greenhouse gas emissions]] across the [[supply chain]] for different foods]]
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Livestock produces the majority of greenhouse gas emissions from agriculture and demands around 30% of agricultural [[fresh water|freshwater]] 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.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Out of the [[Shared Socioeconomic Pathways]] used by the [[Intergovernmental Panel on Climate Change]], only SSP1 offers any realistic possibility of meeting the {{convert|1.5|C-change|F-change}} target. Together with measures like a massive deployment of [[green technology]], this pathway assumes animal-derived food will play a lower role in global diets relative to now. As a result, there have been calls for phasing out [[subsidies]] currently offered to livestock farmers in many places worldwide, 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. Yet, an outright end to human consumption of meat and/or animal products is not currently considered a realistic goal.Therefore, any comprehensive plan of [[Climate change adaptation|adaptation]] to the [[effects of climate change]], particularly the present and future [[effects of climate change on agriculture]], must also consider livestock.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Livestock activities also contribute disproportionately to land-use effects, since crops such as [[Maize|corn]] and [[alfalfa]] are cultivated to feed the animals.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
In 2010, [[enteric fermentation]] accounted for 43% of the total greenhouse gas emissions from all agricultural activity in the world. 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. 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. Methane production by animals, principally ruminants, makes up an estimated 15-20% of global production of methane.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Worldwide, livestock production occupies 70% of all land used for agriculture or 30% of the land surface of the Earth. The global [[food system]] is responsible for one-third of the global anthropogenic [[Greenhouse gas emissions|GHG emissions]], of which meat accounts for nearly 60%.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Cows, sheep and other [[Ruminant|ruminants]] digest their food by [[enteric fermentation]], and their [[Burping|burps]] are the main [[methane emissions]] from [[land use, land-use change, and forestry]]: together with methane and [[nitrous oxide]] from [[manure]], this makes livestock the main source of greenhouse gas emissions from agriculture. In addition, manure left on pasture, applied to soil, and treated in management systems together contribute to 7%–10% of global agricultural greenhouse gas emissions.
</div> 

<div lang="en" dir="ltr" class="mw-content-ltr">
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 [[Plant-based diet|diets with a higher share of plant protein]], moderate intake of animal-source foods and reduced intake of [[Saturated fat|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."{{Bar chart|title=Mean greenhouse gas emissions for different food types|label6=[[Poultry]]|label13=[[Legumes]]|data12=1.2|label12=[[Maize]]|data11=1.2|label11=[[Wheat]]|data10=1.7|label10=[[List of root vegetables|Starchy Roots]]|data9=6.8|label9=[[Egg as food|Eggs]]|data8=8.6|label8=[[Fishery|Non-trawling Fishery]]|data7=9.1|label7=[[Dairy]]|data6=10|data5=10|float=right|label5=[[Pork]]|data4=12|label4=[[Aquaculture|Non-recirculating Aquaculture]]|data3=26|label3=[[Trawling|Trawling Fishery]]|data2=30|label2=[[Recirculating aquaculture system|Recirculating Aquaculture]]|data1=62|label1=[[Ruminant|Ruminant Meat]]|data_max=62|width_units=em|bar_width=20|data_type=Greenhouse Gas Emissions<br>(g CO<small>2</small>-C<small>eq</small> per g protein)|label_type=Food Types|data13=0.25}}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&nbsp;°C. There are calls to phase out livestock subsidies as part of a [[just transition]].
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
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.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
A 2023 study found that a [[vegan]] diet reduced emissions by 75%.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
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 for New Zealand, which is an order of magnitude less than the estimated health system savings from a healthier diet.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Research continues on the use of various seaweed species, in particular [[Asparagopsis armata|Asparegopsis armata]], as a food additive that helps reduce methane production in ruminants.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Fertilizer ===
{{Excerpt|Fertilizer|Contribution to climate change|file=no}}
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Crop management ===
</div>


<div lang="en" dir="ltr" class="mw-content-ltr">
==== Rice production ====
[[File:NP_Rice_Emissions18_(5687953086).jpg|right|thumb|Research work by the [[International Center for Tropical Agriculture]] to measure the greenhouse gas emissions of rice production.]]
{{excerpt|Rice#Greenhouse gases from rice production|file=no}}
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
== Emissions by type of greenhouse gas ==
Agricultural activities emit the [[greenhouse gas]]es [[carbon dioxide]], [[methane]] and [[nitrous oxide]].
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Carbon dioxide emissions ===
Activities such as [[Tillage|tilling]] of fields, planting of crops, and shipment of products cause carbon dioxide emissions. Agriculture-related emissions of carbon dioxide account for around 11% of global greenhouse gas emissions. Farm practices such as reducing tillage, decreasing empty land, returning [[biomass]] residue of crops to the soil, and increasing the use of cover crops can reduce carbon emissions.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Methane emissions ===
[[File:Methane-emissions-agriculture (OWID 0666).png|thumb|Methane emissions from agriculture, 2019. Methane (CHa) emissions are measured in tonnes of carbon dioxide-equivalents]]
[[File:The Global Methane Budget 2008–2017.png|thumb|Global methane budget.]][[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. While the [[residence time]] of methane is much shorter than that of carbon dioxide, it is 28 times more capable of trapping heat. Not only do livestock contribute to harmful emissions, but they also require a lot of land and may [[Overgrazing|overgraze]], which leads to unhealthy soil quality and reduced species diversity. 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 [[compost]]ing.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
Traditional [[Rice|rice cultivation]] is the second biggest agricultural methane source after [[livestock]], with a near-term warming impact equivalent to the [[Climate change and aviation|carbon dioxide emissions from all aviation]]. Government involvement in agricultural policy is limited due to the high demand for agricultural products like corn, wheat, and milk. 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%. These numbers are impactful and would mitigate greenhouse gas emissions while still feeding the population.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
=== Nitrous oxide emissions ===
[[File:Global Nitrous Oxide Budget 2020.png|thumb|Global nitrous oxide budget.]]Nitrous oxide emission comes from the increased use of synthetic and organic fertilizers. [[Fertilizer]]s increase crop yield production and allow 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. 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. Different management practices such as conserving water through [[drip irrigation]], monitoring soil nutrients to avoid overfertilization, and using [[cover crop]]s in place of fertilizer application may help in reducing nitrous oxide emissions.
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
== Reducing emissions ==
{{Further|Climate change mitigation|Climate-smart agriculture}}
Agriculture is often not included in government emissions reduction plans. For example, the agricultural sector is exempt from the [[European Union Emission Trading Scheme|EU emissions trading scheme]] which covers around 40% of the EU greenhouse gas emissions.
</div>

{{excerpt|Climate change mitigation/ja#Agriculture, forestry and land use|file=no}}

== 関連項目 ==
{{Portal|Climate change|Environment|Energy}}
* [[:en:Agroecology|アグロエコロジー]]
* [[:en:Effects of climate change on agriculture|農業に対する気候変動の影響]]
* [[:en:Effects of climate change on livestock|家畜に対する気候変動の影響]]
* [[:en:Environmental issues with agriculture|農業に関する環境問題]]

== 外部リンク ==
* [http://www.fao.org/climatechange/en/ Climate change] on the [[Wikipedia:Food and Agriculture Organization|Food and Agriculture Organization]] of the United Nations website.
* [http://www.ifpri.org/publication/climate-change-1 Report on the relationship between climate change, agriculture and food security] by the [[Wikipedia:International Food Policy Research Institute|International Food Policy Research Institute]]
* [http://www.adb.org/features/12-things-know-2012-rice Climate Change, Rice and Asian Agriculture: 12 Things to Know] Asian Development Bank

{{Climate change}}
{{agriculture footer}}

[[Category:Climate change and agriculture| ]]
[[Category:Greenhouse gas emissions]]
{{二次利用/ja|date=12 July 2025, at 03:13}}