Greenhouse gas emissions from agriculture

Greenhouse gas emissions from agriculture are large: the agriculture, forestry and land use sectors contribute between 13% and 21% of global greenhouse gas emissions. Direct greenhouse gas emissions include those from rice and livestock farming. Indirect emissions from the conversion of non-agricultural land such as forests into agricultural land are also very important. With regard to direct emissions, nitrous oxide and methane makeup over half of total greenhouse gas emissions from agriculture. A 2023 review emphasizes that emissions from agricultural soils are shaped by factors such as soil type, climate, and management practices. It also highlights several mitigation strategies, including conservation tillage, precision agriculture, improved water use, and the application of biochar, that can reduce emissions and enhance soil carbon storage. 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. Livestock farming is a major source of greenhouse gas emissions. 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. Non-ruminant livestock, such as poultry, emit much less greenhouse gas. 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. 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, introduction of methanotrophic bacteria into the rumen, vaccines, feeds, diet modification and grazing management.

Global estimates Total emissions from agrifood systems in 2022 amounted to 16.2 billion tonnes of carbon dioxide equivalent (Gt CO2eq) of GHG released into the atmosphere, an increase of 10%, or 1.5 Gt CO2eq compared with 2000. 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. 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.

Older estimates In 2010, agriculture, forestry and land-use change were estimated to contribute 20–25% of global annual emissions.

Emissions by type of activity

Land use changes Agriculture contributes to greenhouse gas increases through land use in four main ways: CO2 releases linked to deforestation Methane releases from rice cultivation Methane releases from enteric fermentation in cattle Nitrous oxide releases from fertilizer application 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. Land cover has changed majorly since 1750, as humans have deforested temperate 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. Deforestation also affects regional carbon reuptake, which can result in increased concentrations of CO2, 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. Although carbon accounting estimates the greenhouse gas increase when natural land is first farmed, it has been argued that the opportunity cost of land used inefficiently should also be counted to show the importance of agricultural productivity.

Livestock

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