Research
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Food security, nutrition and health are urgent issues facing the global population and future generations. Here, three world-leading researchers answer questions on the current and future state of food nutritional quality and the impact of climate change on our essential resources.
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How are climate change and increased CO2 levels affecting food security?
Prof Kristie Ebi: Greenhouse gas emissions are detrimentally affecting the quantity and quality of our food in two ways. First, they are driving anthropogenic (resulting from human activity) climate change, which decreases yields of major cereal crops in some regions. Increased temperatures, changes in precipitation patterns, increased ozone concentrations, and more frequent and extreme heatwaves, floods, and droughts can reduce crop yields, particularly in the tropics. Lower crop yields will likely increase instances of stunting and wasting, particularly in people in low- and middle-income countries.
In 2023, the synthesis report of the sixth assessment cycle of the Intergovernmental Panel on Climate Change concluded that climate change has reduced food security. Although overall agricultural productivity has increased, climate change has slowed this growth over the past 50 years, globally. The report indicates high confidence in the following conclusions:
Climate change impacts are stressing agriculture, forestry, fisheries and aquaculture, increasingly hindering efforts to meet human needs
Climate-related extremes have affected the productivity of all agricultural and fishery sectors, with negative consequences for food security and livelihoods
Climate change will make some current food production areas unsuitable
Impacts on food availability and nutritional quality will increase the number of people at risk of hunger, malnutrition and diet-related mortality
Climate change will negatively impact food safety. Higher temperatures and humidity will favour toxigenic fungi, plant and animal-based pathogens, and harmful algal blooms (HABs).
Separately, carbon dioxide (CO2) is affecting the nutrient density of much of our food. Essential nutrients are critical for human health and development, and atmospheric CO2, water, nitrogen, and soil micronutrients are the foundation of plant growth. Insufficient nutrient intake can negatively impact human development and lead to a variety of adverse outcomes.
Since the late nineteenth century, CO2 concentrations have increased about 50%, with most of that increase since 1950. Continued increases in CO2 concentrations are expected to further alter the nutritional quality of approximately 85% of all plants, including wheat, rice, barley, oats, potatoes, grasses, and most trees. Higher concentrations of CO2 decrease protein and mineral concentrations by 5–15%, and B vitamins by up to 30%.
“In 2023, 713 to 757 million people worldwide faced hunger; this is 152 million more people than before the COVID-19 pandemic.”
These decreases in the nutritional quality of crops will exacerbate current challenges with food security. In 2023, 713 to 757 million people worldwide faced hunger; this is 152 million more people than before the COVID-19 pandemic. Overall, 2.4 billion people did not have sufficient access to nutritious, safe, and sufficient food year-round. Millions of children under five years of age continue to suffer from stunting (148 million or 22.3%), wasting (45 million or 6.8%), and being overweight (37 million or 5.6%).
What does ‘hidden hunger’ mean and who is affected by this?
Prof Kristie Ebi: Micronutrient deficiencies (hidden hunger) cause a much larger burden of disease than food insecurity, with approximately two billion people deficient in iron, zinc or other micronutrients. This occurs without a deficit in energy intake as a result of consuming an energy-dense but nutrient-poor diet. These deficiencies adversely affect cognitive development, metabolism, obesity, diabetes, and other health outcomes, potentially causing lifelong health issues.
Prof Kristie L. Ebi (Royal Society Wolfson Visiting Fellow, University of East Anglia; Professor, Center for Health and the Global Environment [CHanGE], University of Washington) has been conducting research on the health risks of climate variability and change for over 30 years, focusing on estimating current and future health risks of climate change; designing adaptation policies and measures to reduce these risks in multi-stressor environments; and quantifying the health co-benefits of mitigation policies.
What impact is climate change having on crop yields?
Prof Rachel Warren: Anthropogenic climate change is already having a negative effect on agriculture, due to direct and indirect effects of changes in climate. The changes in climate have already caused regionally different, but mostly negative, impacts on crop yields. This has resulted in a reduction in the growth of global crop production.
Yields of maize, wheat and rice are approximately 5% lower than they would be without climate change, and a further 5% lower due to the damage caused by tropospheric ozone. Methane, one of the greenhouse gases that contribute to climate change, also contributes to ozone production.
“Depending on future emissions, 8–30% of global cropland/pasture is projected to become climatically unsuitable for agriculture by 2100.”
The effects are particularly large in the African drylands. For example, in West Africa, anthropogenic climate change has reduced millet and sorghum yields by 10–20%, and 5–15%, respectively. As climate continues to change, further reductions in yields are expected, although quantifying this is not straightforward. Roughly speaking, each decade a further yield loss of 2.3% is projected for maize, 3.3% for soybean, 0.7% for rice and 1.3% for wheat due to climate change. This means that by the end of the century, maize yields could decline by 23% under a global warming of 4° C.
The larger the global warming, the larger the yield loss. Another way to look at this is to say that depending on future emissions, 8–30% of global cropland/pasture is projected to become climatically unsuitable for agriculture by 2100.
How are these impacts projected to change in the future?
Prof Rachel Warren: Declining yields cause food price rises and create the risk of food insecurity in vulnerable countries or communities which lack the purchasing power to pay higher prices. Yet these estimates do not include the effects of heat waves or extremely hot, dry summers which can further reduce yields. Furthermore, warming can make it more difficult to transport perishable products to market.
Important cash crops are also at risk, which will damage the economies of countries. For example, a global warming of 3° C is projected to render much of Ghana unsuitable for growing cacao or coffee.
“In temperate regions, a number of serious crop pests are no longer killed by winter frosts due to climate change, leading to losses in crop productivity the following year.”
Climate change is altering the geographic ranges and seasonal persistence of key agricultural pests and pollinators, which is also not included in the above estimates. With global warming of 3° C, roughly half of agricultural pollinators are projected to lose about half of their geographic range, globally. In temperate regions, a number of serious crop pests are no longer killed by winter frosts due to climate change, leading to losses in crop productivity the following year. Pests and diseases and declines in pollinators reduce the quantity and quality of agricultural produce.
All these impacts increase with further climate change, with greater effects associated with greater global warming.
Interdisciplinary synthesist Rachel Warren is Professor of Global Change and Environmental Biology at the Tyndall Centre for Climate Change Research and School of Environmental Sciences, University of East Anglia, UK. She has over 20 years’ experience leading interdisciplinary and international teams to deliver policy relevant science on climate change. Her contributions as lead author of four Intergovernmental Panel on Climate Change (IPCC) reports, and the recent UNEP Making Peace with Nature report have informed world governments about increased climate change risks caused by global warming.
Who is most at risk to the impacts of climate change on food security?
Prof Nitya Rao: Climate change affects everyone, but the impacts are particularly severe for those already vulnerable – the poor, children, the elderly, rural communities directly dependent on farming, those with poor-quality housing, migrant workers, refugees, and so on. In The Unjust Climate, the FAO (Food and Agriculture Organisation) report that heat waves and floods widen the gap not only between the poor and non-poor but also between male- and female-headed households. A study of 24 low- and middle-income countries finds that if global temperatures rise another 1° C, female-headed households are projected to lose 34 percent more of their income than male-headed households (FAO 2024). This is because of the unequal access to resources including land, capital, labour, but also the social norms that restrict women’s choices, including the responsibility for domestic work and care. In South Asia, for example, as climate change and poverty push many men to migrate away from farms, women have taken on an increasing share of agricultural labour, without necessarily an easing in their reproductive work. These female farmers lack timely extension information and adequate capital to recover from shocks (FAO 2024; Leder 2022; Maharjan et al. 2020).
Among the undernourished, women consistently remain the most food insecure — the gap in food security between men and women is as high as 19 percentage points in some countries (Broussard 2019), and the situation for women is especially severe in countries affected by conflict (FSIN and GNAFC 2024). Various forms of discrimination — formal and informal, systemic and individual — block them from the resources and opportunities they need to take effective action for the well-being of themselves and others, and to contribute to transformative change across food systems and for climate resilience.
Are there solutions to address food security as the projected risk from climate change increases?
Prof Nitya Rao: Yes, there are solutions, but first, I do believe that women are agentic, despite all the structural constraints they confront, they fight back, finding the spaces individually or collectively to negotiate a better deal. Smallholder agriculture itself can be an adaptation strategy. When women are in everyday control of the land they farm, even if not its legal owners (only 13.6% of women are counted as operational landholders in India, for example, while over 60% of those in the workforce are employed in agriculture), they do diversify production, to grow vegetables, oilseeds, pulses in small portions of their land, alongside the major cereal crop. This gives them both better nutrition, and small amounts of income through the sale of surplus product in local markets. More important perhaps are different forms of social and technical innovations. Knowledge and skills in frontier technologies including soil and plant health management (including through bio-fertilisers and bio-pesticides), training in improved agronomic practices and health management of small ruminants, can help build the resilience of their land and livestock. Similarly, collectives (in India) have enabled women to overcome some of the resource constraints – to capital, land, extension and markets. More can be done to support and enable such collective action.
My own recent impact work has been around strengthening local and indigenous food systems through a documentation of local foods, assessment of their nutritional quality, legitimising this in the public domain (through a publication) and sharing the insights with the community members. There has been an intergenerational loss in traditional and indigenous knowledge due to several reasons including the structure of the agriculture research system, global pressure on the adoption of particular practices, the stigmatisation of indigenous culture in modern education systems leading to an alienation of the youth, and the easy access to ‘junk’ foods even in remote areas, amongst others. There is now global recognition, including by the IPCC (2014) that indigenous and local knowledges are important for addressing issues of climate change, and ensuring a just transition, but there remain practical barriers to overcome.
Prof Nitya Rao, Professor of Gender & Development, School of Global Development, University of East Anglia and Director of the Norwich Institute for Sustainable Development (NISD), has worked extensively as a researcher, teacher and advocate in the field of women’s rights, employment and education for over three decades. Starting as an activist committed to gender equality and women’s empowerment, her research interests include exploring the gendered changes in land and migration patterns amongst marginalised, rural communities, with a view to achieving livelihood, food and nutrition security, especially in contexts of climatic variability and economic precarity.
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