IPCC on How to Tackle Climate Change, Part 6: What impact can the food system and dietary choices have on emissions?

Limiting global warming to 1.5C or 2C would mean “rapid and deep” emissions reductions in “all sectors” of the global economy, says the latest report from the United Nations’ Intergovernmental Panel on Climate Change (IPCC). Instead, emissions have continued to rise – albeit at a slowing rate – and it will be “impossible” to stay below 1.5C with “no or limited overshoot” without stronger climate action this decade, says the new document, which forms part of the IPCC’s sixth assessment report (AR6).  In this in-depth Q&A series, Carbon Brief unpacks the key findings of the latest report. (Read previous section here)

By Carbon Brief

6. What impact can the food system and dietary choices have on emissions?

“Food systems” are associated with roughly 42% of global greenhouse gas emissions, states the report, even as “there is still widespread food insecurity and malnutrition”. Between 1990 and 2018, greenhouse gas emissions from food systems grew from 14 to 17GtCO2e per year.

Looking at households’ carbon footprints, the food sector “dominates in all income groups”, even more than energy use. Globally, it counts for 28% of these footprints on average, with rice and cattle being the “major contributors”.

Food also accounts for 48% and 70% of household impacts on land and water resources, respectively, and these impacts rise with incomes driven by higher consumption of meat, dairy and processed food, says the report.

There is high agreement that mitigating food-sector emissions to their full potential “requires change at all stages, from producer to consumer and waste management” via integrated packages of policy including supply- and demand-side measures. 

Sustainable food systems that provide healthy diets for all are within reach, state the report’s authors after assessing literature on health, diets and emissions. However, they require “significant cross-sectoral action”, from better agricultural practices, consumers changing their diets, and food producers, distributors, retailers and consumers reducing food waste.

Shifting consumption towards plant-based diets has “high mitigation potential”, says the report. There is robust evidence that “diets high in plant protein and low in meat and dairy” make for lower GHG emissions.

The report estimates with high confidence that shifts to sustainable healthy diets have a “technical potential” to reduce emissions by 3.6GtCO2e, with a range of 0.5 to 8GtCO2e. This is the amount of emissions that could be saved if financial and other constraints are ignored.

Meats from ruminants such as sheep and cows have the highest GHG intensity. However, the report observes that beef from dairy systems is less emissions-intensive than beef reared in herds purely for meat, with emissions of 8-23kgCO2e per 100g protein and 17-94kgCO2e per100g protein, respectively.

It acknowledges the widely varying estimates, attributing this to the difference in production systems: intensive livestock rearing where cattle are largely fed grain versus pastoral practices, where herders move livestock from summer to winter pastures, or rear them on rangelands.

This is illustrated in the figure below, which shows the emissions intensity of different protein-rich foods, in kgCO2e per 100g protein from the highest (beef from beef cattle) to the lowest (nuts).

In addition to “substantial[ly]” lowering emissions from the food system, diets with a higher share of plant-based protein and reduced intake of “added sugars, salt and saturated fats” would cut land use and nutrient losses to the environment, as well as offering health benefits, the report says.

Beyond dietary changes, the report says there is limited evidence – but high agreement – that a suite of “emerging technologies” could bring “substantial reduction in direct GHG emissions from food production”. These include plant-based alternatives to animal products, cultured meat and “controlled environment agriculture”, which it describes as ”hydroponic or aquaponic cultivation systems that do not require soil”.

These technologies typically have lower water, land and nutrient footprints, but as some of them are energy-intensive, they need to have access to low-carbon energy.

Food waste is another aspect the report draws attention to. According to studies assessed by the report’s authors, roughly 20-40% of food

produced worldwide is wasted before it reaches the market, or goes to waste in households. It estimates that global food loss and waste accounted for 8-10% of total GHG emissions between 2010 to 2016.

Reducing food loss and waste globally has the technical potential to cut emissions globally by 2.1GtCO2e, with a range of 0.1-5.8GtCO2e, the report estimates with medium confidence.

Global food supply chains have a strong influence on per-capita food consumption emissions, particularly for red meat and dairy, the report notes, such that the highest per-capita food-related emissions “do not correlate perfectly with the income status of countries”. In other words, even relatively poorer countries may have a high per-capita food footprint.

As a result, the report says “it is crucial to focus on high-emitting individuals and groups within countries, rather than only those who live in high-emitting countries, since the top 10% of emitters live on all continents and one third of them are from the developing world”.

Changes in the food sector would have broad implications. Reducing food waste, coupled with dietary shifts, can “further reduce energy, land and resource demand” and result in “substantial” benefits in places where food is grown, putting food security there under less strain.

Both measures “have highly relevant repercussions” for land-use emissions, the report says, because they can free up land for other uses, such as afforestation or bioenergy. Moreover, shifts in diets and lowered pressure on land are also “reflected in reductions of land degradation” and reduced deforestation, says the report.

Key enablers for these shifts could include creating “novel narratives” in the media and entertainment industry to “help to break away from the established values, discourses and the status quo”. These might portray plant-based diets as healthy and natural, for example.

The report explores other measures that could be used to influence choices in the food sector, including taxes or carbon pricing on food, both of which it says would be “regressive”, meaning they disproportionately burden poorer members of society. Instead, it points to options including marketing regulations, procurement policies, dietary guidelines, labelling and “nudges”.

Next Section: How must global energy systems change to limit warming?

Authors:

Aruna Chandrasekhar holds an MSc in environmental change and management from the University of Oxford. She previously worked as a freelance journalist for a variety of publications, including the New York Times, Guardian, Scroll and Caravan.

Daisy Dunne holds a BSc in biology from the University of Bristol and a science journalism MA from City, University of London. She was The Independent’s climate correspondent from November 2020 to 2021. Prior to this, she was Carbon Brief’s science writer from 2017 to 2020.

Dr Simon Evans is our deputy editor and policy editor. Simon covers climate and energy policy. He holds a PhD in biochemistry from Bristol University and previously studied chemistry at Oxford University. He worked for environment journal The ENDS Report for six years, covering topics including climate science and air pollution.

Josh Gabbatiss covers climate and energy policy. Josh holds a BSc in zoology from the University of Bristol. He previously worked as science correspondent at The Independent and prior to that was a freelance journalist for a variety of scientific publications including New Scientist and BBC Earth.

Dr Zeke Hausfather is a climate science contributor for Carbon Brief. Zeke has masters degrees in environmental science from Yale University and Vrije Universiteit Amsterdam, and a PhD in climate science from the University of California, Berkeley. He has spent the past 10 years working as a data scientist and entrepreneur in the cleantech sector.