IPCC Assessment in depth, Part 5: What does the IPCC report say about impacts on food and agriculture?

The threat that climate change poses to human well-being and the health of the planet is “unequivocal”, says the latest report from the United Nations’ Intergovernmental Panel on Climate Change (IPCC). In this in-depth Q&A series, Carbon Brief unpacks the key findings of the report and the developments since the IPCC’s last assessment. (Read previous section here)

By Carbon Brief

Climate change is “increasingly hindering efforts” to meet the nutritional and calorific needs of humanity, according to the new report.

Climate change impacts – including weather extremes, such as droughts, floods and marine heatwaves – are putting strain on agriculture, aquaculture, forestry and fisheries. Each step in the supply chain from production to consumption, including storage and transportation, will also be affected by climate change.

The report finds medium evidence, but high agreement that “sudden food production losses” due to extreme events have been increasingly frequent “since at least [the] mid-20th century”.

There is high confidence that extreme weather events will push some current food-growing areas “beyond the safe climatic space for production”. Under the very high emissions scenario SSP5-8.5, about one-third of “currently suitable area” is projected to become unsuitable by the end of the century; the report notes that these impacts “will be much less under RCP2.6”.

The CMIP6 suite of models and the latest generation of crop models, which simulate how crops will respond to changing environmental conditions, project that climate change will affect the yields of major crops “sooner than previously anticipated”. This is attributed to both “warmer climate projections and improved crop model sensitivities”.

A temperature rise of 2C by the end of the century will have “large negative impacts” on food production systems around the world, the report says, while higher temperatures will pose “even greater risk”. Land that is currently used for growing crops and rearing livestock “will increasingly become climatically unsuitable”, while outdoor workers and animals will be “increasingly expose[d]” to dangerous heat stress.

Crops are negatively affected by climate change in several ways. One study cited in the report estimated nearly a 10% yield reduction in four major crops between 1850 and 2010, even when taking into account the “positive effect” of CO2 fertilisation.

The chart below shows how five climate change impacts – changing soil nutrients, increased pests and disease, decreased rainfall, increased ozone stress and increased heat stress – will impact soya (left) and wheat (right) yields around the world. The shading indicates the stress level of a given impact, with darker colours meaning a higher level of stress.

In addition to the threat of yield reductions posed by climate change, elevated levels of CO2 have been shown to reduce important nutrients including protein, iron and zinc in a wide range of plants “to varying degrees” depending on the species, the report states. Continued increases in CO2 levels are projected to cause reductions “in a wide range of minerals and nutrients” of 5-10%, depending on the crop.

The specific impacts of climate on agriculture vary by crop and by region. In eastern Asia and northern Europe, climate change has so far increased wheat yields, the report notes, while its effects are “mostly negative” on crop yields and quality across sub-Saharan Africa, South America, the Caribbean, southern Asia and western and southern Europe.

Most research into the effects of climate change on crops has focused on staple crops, such as maize, rice and wheat, but “emerging” work is beginning to focus on the yields of other crops, the report states.

The chart below summarises the different ways that climate change is projected to affect certain types of crops. The plus signs indicate positive impacts on productivity, the minus signs indicate negative impacts and the circles indicate mixed impacts recorded in the literature. The shading shows the confidence in attribution, with darker colours indicating a higher level of confidence.

There is medium evidence but high agreement that changes in the reproductive rates and distributions of pests, pathogens, weeds and disease vectors will increase the stress on both crops and livestock under future climate change. Since 1960, there have been “significant poleward expansions” of many key crop pests and pathogens at an average rate of 2.7km per year, although different pests respond differently to climate factors.

These are “serious concerns” that are “under-researched” due to the complexity of the interactions between multiple species, the report

says. As a result, “their consequences on future crop production and food security are hard to predict”. In addition to reducing yields, pests and pathogens can increase post-harvest food losses.

There is high confidence that climate change is already impacting livestock production through both “direct impacts” – increased mortality due to heat stress – and “indirect impacts”, such as reducing the quality of grasslands used for grazing.

Drought, rising temperatures and other drivers are “reducing herd mobility, decreasing productivity, increasing incidence of vector borne diseases and parasites and reducing access to water and feed”, the report states.

For each temperature increase of 1C above animals’ thermal “comfort zones”, animals consume 3-5% less food, reducing both their productivity and fertility. Higher temperatures also “enhanc[e] susceptibility…to disease” by suppressing the immune system.

Warming of 2C by 2050 is “projected to result in 7-10% declines in livestock numbers” globally, although there are persistent uncertainties around the future productivity and composition of grazing lands, the report notes.

The report states with high confidence that the effects of climate change will also “significantly alter” the availability and quality of aquatic foods.

Warming, ocean acidification and declining oxygen levels will all have negative impacts on key fisheries and aquaculture species, the report says, while inland and coastal aquatic systems will additionally be affected by sea level rise. (See “What impact is global warming having on marine life?”)

One study cited in the report found a 4% reduction in the “maximum sustainable yield of several marine fish populations” due to ocean warming globally between 1930 and 2010, with some regions experiencing much higher declines.

Climate change’s impacts on fisheries “will be particularly high in tropical regions” due to large reductions in catch, the report states. These changes “can have significant consequences for human nutrition”, particularly in lower-income countries where fewer nutritional alternatives are available.

The report finds that climate change’s impacts on water availability is an “emerging issue” and notes that “increased occurrence of drought combined with limited access to irrigation water is already a key constraint” on agriculture. Drought-related crop loss has “increased in recent years”, and has affected “about 75% of the global harvested area”, the report says.

The report also warns of the risk of “multi-breadbasket failures”, in which synchronous droughts or other extreme weather events affect crop production in multiple regions of the world. These risks “had not been quantified” when AR5 was produced.

There is limited evidence that “synchronised crop failures are increasing with ongoing climate change” and medium confidence that these risks will increase.

“Social inequalities”, such as gender, socioeconomic status and ethnicity, “can compound vulnerability” to the effects of climate change for both producers and consumers, the report says. It notes that women are “more vulnerable” to climate-related food insecurity than men and Indigenous livestock keepers are at higher risk than their non-Indigenous counterparts due to “historical land dispossession, discrimination and colonialisation”.

The report states that climate change is already affecting “all dimensions of food security”: availability, access, utilisation (food quality and safety) and stability. As a result, there is high confidence that the number of people at risk of “hunger, malnutrition and diet-related mortality” will increase in the future.

These projections range from 8 million more people under SSP1-6.0 to 80 million under SSP3-6.0 as “compared to a world with no climate change”. Nearly 80% of this at-risk population is projected to occur in Africa and Asia.

The report notes with high confidence that there are “various adaptation options [that] are currently feasible and effective at reducing climate impacts”. These include sustainable resource management, incorporating Indigenous and local knowledge and diversifying crops and species. However, there are many financial barriers to implementing these options and “vastly more public and private investment is required” to do so.

Next: What risks does climate change pose to the world’s cities?

All sections:

1. What is the IPCC report?
2. How is climate change affecting land ecosystems?
3. What impact is global warming having on marine life?
4. How is climate change affecting the world’s water?
5. What does the IPCC report say about impacts on food and agriculture?
6. What risks does climate change pose to the world’s cities?
7. What does the report say about public health, conflict and migration?
8. How does climate change affect poverty and progress towards the sustainable development goals?
9. How is the world adapting to climate change?
10. What the latest IPCC report says about carbon fee and dividend

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.

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.