The food system contributes more than 30% of the heat-trapping gases emitted by human activities globally each year. If those emissions continue to increase at their current pace, meeting the Paris Agreement’s 1.5°C (2.7°F) goal would be impossible even if non-food system emissions fell to zero immediately.
Food and climate impacts go both ways. Climate change creates significant risks to the food system, with rising temperatures and changing weather patterns threatening enormous damage to crops, supply chains and livelihoods in the decades ahead.
The food system touches everyone. Hundreds of millions of people work in agriculture and other aspects of food production, with the highest percentages in developing countries. More than a billion people, mostly women, prepare food as a central part of everyday activities. Food choices play a central role in human health and culture.
This InfoGuide provides background on the food system (Part 1), climate change (Part 2), the impact of the food system on climate change (Part 3) and the impact of climate change on the food system (Part 4). The final section (Part 5) presents strategies for reducing emissions from the food system and improving the resilience of the food system to climate change.
1. FOOD SYSTEM OVERVIEW
The food system spans a vast array of activities—from land clearing to fertilizer manufacturing to crop growing to livestock production to fish harvesting to meal preparation to landfill management. It includes food production, transport, processing, packaging, storage, consumption and disposal.
Figure 1: A simplified diagram of food system activities
A 2019 World Bank study estimated that the food system contributes $8 trillion per year to gross domestic product (GDP)—roughly 10% of the global economy.
- The food system supports the livelihoods of over 1 billion people.
- In general, agriculture’s share of the economy declines as countries grow wealthier.
- In low-income countries, agriculture contributes 22% of GDP on average.
- In middle-income countries, agriculture contributes 8% of GDP on average.
- In high-income countries, agriculture contributes 1% of GDP on average.
- In 2019, the export value of all food products traded internationally was over $1.8 trillion.
Roughly 35% of the world’s total land area excluding Antarctica is used for agriculture.
- Of the total land area used for agriculture, roughly two-thirds are pastures and rangelands for livestock grazing and production.
- Overgrazing is the number one cause of land degradation and desertification globally, causing about 35% of human induced soil degradation.
- The vast majority of tropical deforestation (75%–90%) stems from expanding agricultural land for the production of commodities such as beef, soy and palm oil. Deforestation is occurring most rapidly in Latin America, followed by Africa.
The food system and energy system are deeply intertwined. Every part of the food system uses energy. Roughly 30% of global energy consumption comes from the food system.
- Most energy used in the food system comes from fossil fuels, although renewable energy’s share is rising. Many agricultural production areas have good access to solar and wind resources.
- Roughly 5% of global natural gas demand is for the synthesis of nitrogen fertilizers.
Over 40% of human calories come directly from three crops: rice, wheat and maize. These three crops account for roughly two-thirds of all human calories (including rice, wheat and maize used as feed for livestock consumed by humans). Soybeans have the fourth largest production area of all crops globally.
- In 2018, Asia consumed roughly 88% of the world’s rice and 59% of the world’s wheat.
- The US produces the most maize in the world. In 2019, about a third of corn produced in the US was used for ethanol production, one-third for domestic animal feed and another third for domestic consumption and exports.
- In 2019/2020, Brazil led the world with 37% of global soy production, followed closely by the US with 36%. About 70% of global soy production is processed into protein meal for animal feed.
In 2018, global livestock production neared 24 billion chickens, 1.5 billion heads of cattle, 1.2 billion sheep, 1 billion goats and 980 million pigs.
- Between 2008 and 2018, the number of chickens raised annually grew 25%—by far the fastest growing livestock group. The number of goats grew by 16%, sheep by 10%, cattle by 5% and pigs by 4%. (The human population grew roughly 12% during this period.)
- China produces nearly half of global pig meat. The United States is the world’s largest producer of beef and poultry.
Fisheries and Aquaculture
In 2017, fish provided 17% of global animal protein intake and 7% of all protein consumed.
- In 2018, 54% of total fish production came from capture fisheries, while 46% came from aquaculture.
- Global fish consumption between 1961 and 2017 grew faster than all other animal foods.
More than 2.6 billion people lack access to clean cooking technologies, depending on biomass, kerosene or coal as their primary cooking fuel.
- In sub-Saharan Africa, more than 80% of households lack access to clean cooking. In India, roughly half of households lack such access.
- Household air pollution—primarily from cooking smoke—is associated with nearly 2.5 million premature deaths annually. In many developing countries, the burden of collecting fuel for cooking falls disproportionately on women and children, who also face greater exposure to pollutants from cooking smoke.
Undernourishment and Obesity
The food system is plagued by distributional inequities.
- There are enough protein, carbohydrates and fat produced each year to meet the dietary needs of every person on Earth. Yet nearly 2 billion people suffered from undernourishment in 2019. Of those 2 billion, 690 million people—9% of the world’s population—faced hunger.
- At the same time, another 2 billion adults are overweight or obese. The global prevalence of diabetes has nearly doubled in the past 30 years and is predicted to continue increasing due to dietary changes.
- Within many countries, there are problems with undernourishment and obesity simultaneously.
- The COVID-19 pandemic has significantly increased the number of hungry people globally. In addition, some comorbidities that increase the risk of hospitalization and death from COVID-19 -- including diabetes, hypertension and heart disease -- are associated with unhealthy high-calorie diets (such as those rich in refined carbohydrates, added sugar, saturated fats and red meat).
Food Loss and Waste
Roughly one-third of food that is produced is never consumed. This food is either lost in the field on the way to the consumer or wasted in institutional settings, stores, homes or restaurants.
- About 30% of all food loss and waste occurs at the production stage.
- In 2016, approximately 14% of global agricultural production was lost during postharvest and distribution.
- Roughly 8% of the world’s annual food supply is wasted by households and restaurants as they prepare and dispose of their daily meals.
- Over 10% of the world’s total energy consumption is used to provide food that is lost or wasted.
The conversion of natural forests to produce food commodities is the single greatest driver of habitat loss globally.
- Agriculture is estimated to drive about 70% of biodiversity loss and 80% of deforestation globally.
- The food consumed in one country can have an impact on the biodiversity of another. For example, 95% of the impact of Swiss food consumption is felt abroad, with coffee, cocoa and palm oil plantations all contributing to habitat loss in other countries.
2. CLIMATE CHANGE OVERVIEW
Atmospheric concentrations of heat-trapping gases are now higher than any time in human history. This is changing the Earth’s climate.
- The principal heat-trapping gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluorinated gases (such as HFCs and SF6). These are also commonly referred to as greenhouse gases.
- Carbon dioxide is responsible for roughly 76% of the warming impact of these gases globally. Methane is responsible for roughly 16%, nitrous oxide for 6% and fluorinated gases for 2%.
- The Intergovernmental Panel on Climate Change (IPCC) finds with very high confidence that atmospheric concentrations of heat-trapping gases are now higher than any time in at least 800,000 years.
- The Earth’s average surface temperature has risen about 1.14°C (2.05°F) since the late 19th century.
- The seven warmest years on record have been the past seven years.
Human activities are the principal cause of the buildup of heat-trapping gases in the atmosphere. Those activities include burning fossil fuels (coal, oil and gas) and land use change.
- Roughly 25% of global emissions come from electricity and heat production, 21% come from industry and 14% come from transport.
- Roughly 24% of global emissions come from agricultural, forestry and other land use.
The impacts of a changing climate are being felt across the globe.
- Storms and heat waves have increased in frequency and intensity in recent decades.
- Warming air temperatures and droughts made more likely by climate change have directly contributed to increased fire risk in many parts of the world. Changes in climate over the past 30 years are associated with a doubling of extreme fire weather conditions in California.
The world is not on a path to meet globally-agreed climate change goals.
- More than 190 nations have adopted the Paris Agreement, which calls for “holding the increase in global average temperature to well below 2°C (3.6°F) above pre-industrial levels” and “pursuing efforts to limit the temperature increase to 1.5°C (2.7°F) above pre-industrial levels.”
- However, policies currently in place around the world would result in a global average temperature increase of 2.9°C (5.2°F) by 2100, and many policies to limit emissions are not being fully implemented.
Billions of people face extraordinary risks unless the buildup of heat-trapping gases in the atmosphere slows and then reverses in the decades ahead.
- Those risks include more severe and frequent storms, floods, droughts and heat waves, as well as sea level rise.
- Climate change is expected to increase heat-related mortality rates and the incidence of lung and heart disease associated with poor air quality. Higher temperatures and more frequent flooding events caused by climate change contribute to the spread of infectious and vector-borne communicable diseases such as dengue, malaria, hantavirus and cholera.
3. FOOD SYSTEM IMPACTS ON CLIMATE CHANGE
The IPCC estimates that the food system is responsible for 21%–37% of heat-trapping gases emitted by human activities globally. A study published in Nature in March 2021 estimates that the food system is responsible for a third of heat-trapping gases emitted globally. Work from the authors of this paper confirms that estimate.
Figure 2: Food system emissions, by category, as a percentage of total anthropogenic emissions (2018)
Food-Related Forestry and Land Use Change
Forestry and land use changes related to the food system are responsible for between 5% and 14% of all anthropogenic emissions of heat-trapping gases.
- Agriculture is responsible for approximately three-quarters of global emissions associated with forest loss.
- In 2018, agricultural land use and land use change were responsible for emissions of nearly 4 Gt CO2-eq (roughly 8% of global emissions of heat-trapping gases). This included emissions from cutting forests, burning savanna and draining peatlands.
Pre-Production emissions include emissions associated with fertilizer and pesticide manufacturing and the production of farm equipment such as tractors and irrigation pumps. There is currently a dearth of country-level data on emissions from these sources.
Agriculture is a major source of methane and nitrous oxide emissions. Roughly half of anthropogenic methane emissions and three-quarters of anthropogenic nitrous oxide emissions come from within the farm gate.
Roughly 15% of global emissions of heat-trapping gases come from livestock.
- Cattle are the main source of global livestock emissions (65%–77%).
- In 2018, enteric fermentation (part of the digestive process of ruminant animals such as cattle, sheep, goats and buffalo) was responsible for 2.1 Gt CO2-eq of methane emissions—the largest component of farm-gate emissions and roughly 4% of global emissions of heat-trapping gases.
- In 2018, livestock manure was responsible for 1.0 Gt CO2-eq of nitrous oxide emissions—roughly 2% of global emissions of heat-trapping gases.
Fertilizers, rice paddies and on-farm energy use are each significant emissions sources.
- In 2018, synthetic fertilizers were responsible for 0.7 Gt CO2-eq of nitrous oxide emissions—roughly 1.4% of global emissions of heat-trapping gases.
- In 2018, rice cultivation was responsible for 0.5 Gt CO2-eq of methane emissions—roughly 1% of global emissions of heat-trapping gases.
- In 2018, on-farm energy use contributed approximately 1.0 Gt CO2-eq of emissions, representing about 2% of global emissions.
Dietary choices play a large role in determining the amount of heat-trapping gases emitted from the food system.
- In general, animal-based food products are associated with higher emissions than plant-based foods.
- Beef generates the highest emissions of heat-trapping gases per kilogram (kg) of commodity produced, outpacing milk, pork, eggs and all crops.
- According to the best available estimates, the food items with the highest CO2 emissions per kg are the following:
- Beef: 60 kg CO2-eq per kg
- Lamb and mutton: 24 kg CO2-eq per kg
- Cheese: 21 kg CO2-eq per kg
- In general, CO2-equivalent emissions from crop products are 10–50 times lower than most animal products, per kg of product.
- In general, animal products produce more CO2 per unit of protein as well. The emissions per 100 grams of protein for several popular food sources are listed below: 
- Beef: 49.9 kg CO2-eq
- Cheese: 19.8 kg CO2-eq
- Poultry: 5.7 kg CO2-eq
- Eggs: 4.2 kg CO2-eq
- Grains: 2.7 kg CO2-eq
- Soybeans: 2.0 kg CO2-eq
- Nuts: 0.26 kg CO2-eq
Roughly 45% of total energy use by the food sector is attributable to food processing and distribution.
- Nearly 40% of all food that is produced requires refrigeration.
- The food sector cold chain is responsible for almost 2% of global anthropogenic greenhouse gas emissions.
Food transportation is responsible for roughly 6% of all food system emissions globally. (In the United States, the figure is 11%.)
- About 60% of the miles that food products travel globally are via water.
- Relatively little food is transported by air freight. However, perishable foods that are shipped internationally by air have a carbon footprint between 5 times and 20 times more than if they were transported by road and rail transport, respectively.
- Domestic food transport alone contributed about 0.5 Gt CO2-eq emissions in 2018, representing about 1% of global emissions.
In developing countries, cooking often utilizes traditional low-efficiency stoves, which generate significant negative impacts on both climate and health.
- Solid-fuel cooking in developing countries is associated with greenhouse gas emissions of 0.5–1.2 Gt CO2-eq per year, representing roughly 1.5%–3% of total anthropogenic emissions. This figure does not include emissions associated with cooking using electricity and LPG—which characterizes much of the cooking in developed countries—or renewable sources such as biogas and solar.
- Although both electric and gas cookstoves generate fewer emissions than solid-fuel cookstoves, there are still significant differences between the two. For instance, the greenhouse gas emissions associated with cooking with a gas stove can be roughly 6 times higher than with an electric stove.
Food Loss, Waste and Disposal
Per capita rates of food loss and waste have been rising globally, and the emissions associated with food loss and waste are accelerating in parallel.
- Over 10% of the world’s total energy consumption is used to create food products that are never consumed, and roughly 8% of anthropogenic greenhouse gas emissions result from producing, shipping, storing and processing food that is lost or wasted.
- The methane generated from solid food waste in landfills is responsible for roughly 2% of all anthropogenic greenhouse gas emissions.
4. CLIMATE CHANGE IMPACTS ON FOOD SYSTEMS
Impact on Crop Yields
The buildup of heat-trapping gases in the atmosphere suppresses global average crop yields. This is due to the effects of high temperatures on growing periods and critical growth stages, more severe droughts and storms, the spread of pests, and other factors.
- Between 1981 and 2010, climate change lowered global average yields of maize by 4.1%, wheat by 1.8% and soybeans by 4.5% as compared to what yields would have been without climate change.
- Climate change may lead to crop yield increases in some temperate regions in the near term, in part because greater CO2 concentrations lead to enhanced photosynthesis in some crops (the CO2 fertilization effect). However, in the longer term, all agricultural regions will suffer.
- Climate change is projected to have the most dramatic negative impacts on crop yields in the tropics and subtropics, where hundreds of millions of smallholder farmers live and work.
- The majority of crop models show declining global crop yield over the 21st century at a 2°C (3.6°F) increase in global warming, with direct yield losses occurring in some crops in the near term and higher yield losses in almost all crops likely to occur in the second half of the century.
Impact on Nutritional Content and Health
Increasing concentrations of heat-trapping gases in the atmosphere have negative impacts on the nutritional quality of globally important crops.
- Decreases in protein content and micronutrients have been found for crops grown under high CO2 conditions.
Such changes could have a negative impact on global health, as an estimated two billion people already suffer from dietary deficiencies of zinc and iron.
Figure 3: Estimated impact of elevated atmospheric CO2 on the nutritional content of rice and wheat
Impact on Food Security
Climate change is likely to increase malnutrition and lead to less healthy diets in lower- and middle-income countries.
- Subsistence farmers are particularly vulnerable to climate change. Many are located in the tropics, rely entirely on rainwater and have relatively little adaptive capacity. Nearly two-thirds of the labor force living in extreme poverty work in agriculture.
- Climate change may have a severe impact on childhood nutrition in vulnerable populations. By one estimate, climate change could increase childhood stunting by 23% in sub-Saharan Africa and up to 62% in South Asia, after factoring in population growth, food price increases and the potential impacts of climate change on cereal yields.
- The climate risk for subsistence farmers in sub-Saharan Africa is borne disproportionately by women. This is in part due to significant male out-migration from rural villages.
5. MITIGATION AND ADAPTION STRATEGIES
Dozens of strategies can help reduce emissions of heat-trapping gases from the food system and improve the resilience of the food system to climate change. Governments, companies, NGOs and individuals can all contribute. Options with high potential for impact are listed below.
Reducing Emissions from the Food System
Strategies for reducing emissions of heat-trapping gases from the food system are often divided into two broad categories: supply side and demand side. Supply-side strategies focus on land use, agricultural production and food distribution. Demand-side strategies focus on food consumption and consumer choice.
Measurement and monitoring of the emissions impact of many of these strategies can be challenging. In addition, system effects must be considered before pursuing one of these strategies with the goal of reducing emissions. (Shorter food delivery supply chains can be counterproductive, for example, if food is grown in energy intensive greenhouses powered by fossil fuels.)
The potential for quick and cost-effective emissions reductions in this area is significant. The IPCC found with high confidence that roughly 3%–8% of global emissions of heat-trapping gases could be cut by 2030 with crop and livestock measures at costs in the range of $20–$100 t CO2-eq.
Improving Resilience of the Food System
The food system often relies on long supply chains that are vulnerable to climate disruption at many points. Policies to improve the climate resilience of the food system focus on ensuring a stable food supply and sustainable farmer livelihoods, as well as improving food availability and access.
Many policy tools are available to implement strategies such as the above. The choice of policy tools will vary from jurisdiction to jurisdiction, depending on local circumstances. Such tools include public funds for research and development, tax incentives, direct payments, regulatory standards, and education through agricultural extension services. Policies that focus on energy use more broadly (such as fuel efficiency standards for vehicles or energy efficiency standards for refrigerators) will also reduce food system emissions.
Policies that help reduce emissions from the food system or improve food system resilience can have important benefits in other areas. These include the following:
- improving public health,
- enhancing rural livelihoods,
- empowering women and indigenous peoples,
- promoting animal welfare, and
- protecting biodiversity.
Food Climate Partnership
The Food Climate Partnership is a joint effort of scholars at the Center on Global Energy Policy at Columbia University, the Agricultural Model Intercomparison and Improvement Project (AgMIP), and New York University. The Food Climate Partnership works to address knowledge gaps, promote better policies and improve public understanding of issues related to the food system and climate change. We work closely with experts at the Statistics Division of the Food and Agriculture Organization (FAO) of the United Nations to ensure that data on food systems are properly analyzed and communicated.
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 Ibid, 9.
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 Ibid.; Francesco N. Tubiello, “Greenhouse Gas Emissions Due to Agriculture,” in Encyclopedia of Food Security and Sustainability, eds. Pasquale Ferranti, Elliot M. Berry, and Jock R. Anderson (Elsevier, 2019), 196–205, https://doi.org/10.1016/B978-0-08-100596-5.21996-3; Crippa et al., “Food Systems Are Responsible.”
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 28 megatonnes of CH4 from solid food waste (Tubiello et al., “Greenhouse gas emissions from food systems”) is 8% of the 359 megatonnes of total anthropogenic CH4, as seen in Marielle Saunois et al., “The Global Methane Budget 2000–2017,” Earth System Science Data 12, no. 3 (July 2020), https://doi.org/10.5194/essd-12-1561-2020.
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 See, e.g., Tao et al., “Responses of Wheat Growth and Yield to Climate Change in Different Climate Zones of China, 1981–2009,” Agricultural and Forest Meteorology 189–190 (June 2014), 91–104, https://doi.org/10.1016/j.agrformet.2014.01.013, cited in Mbow et al., “Food Security,” 452.
 Samuel Levis, Andrew Badger, Beth Drewniak, Cynthia Nevison, and Xiaolin Ren, “CLMcrop Yields and Water Requirements: Avoided Impacts by Choosing RCP 4.5 over 8.5,” Climatic Change 146 (February 2018), 501–15,
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 Ibid. On February 26, 2021, the Biden administration set $51 as an interim estimate of the social costs imposed by a ton of CO2 emissions, pending a further and more detailed scientific review; Juliet Eilperin and Brady Dennis, “Biden is hiking the cost of carbon,” Washington Post, February 26, 2021, https://www.washingtonpost.com/climate-environment/2021/02/26/biden-cost-climate-change/.
 Margot Hurlbert et al., “Risk Management and Decision Making in Relation to Sustainable Development,” in Climate Change and Land, eds. P.R. Shuka et al. (in press, 2019), 695–718, https://www.ipcc.ch/site/assets/uploads/sites/4/2021/02/10_Chapter-7_V2.pdf.
 Emi Suzuki, “World’s Population Will Continue to Grow and Will Reach Nearly 10 Billion by 2050,” World Bank Blogs, July 8, 2019, https://blogs.worldbank.org/opendata/worlds-population-will-continue-grow-and-will-reach-nearly-10-billion-2050.
 Phillip Baker and Sharon Friel, “Food Systems Transformations, Ultra-Processed Food Markets and the Nutrition Transition in Asia,” Globalization and Health 12 (December 2016), 80, https://doi.org/10.1186/s12992-016-0223-3.
 A. Steensland, 2020 Global Agricultural Productivity Report: Productivity in a time of pandemics, ed. T. Thompson (Virginia Tech College of Agriculture and Life Sciences, 2020).