Extreme heat threatens UK food security and farm resilience

Extreme heat is threatening UK food security by disrupting crop growth, weakening soil health and increasing pressure on farm businesses, a leading agriculture expert has warned.

Professor Nicola Cannon, Professor of Agriculture at the Royal Agricultural University (RAU), said more frequent and intense heatwaves risk cutting yields, driving up irrigation demand and damaging the natural systems that underpin long-term food production. She called for coordinated action from policymakers, industry and farmers to strengthen farm resilience.

“Extreme heat fundamentally disrupts how crops grow and function,” said Professor Cannon. “When temperatures exceed optimal thresholds, plants shut down critical physiological processes such as photosynthesis, which directly reduces growth and yield.”

Under high temperatures, crops can lose water rapidly through evaporation, creating conditions where plants wilt because roots cannot replace moisture quickly enough. As a defence mechanism, plants close their stomata to conserve water, but this also limits carbon dioxide uptake and reduces photosynthetic efficiency. If heat stress continues, growth can slow or stop, limiting biomass accumulation and carbon capture.

Farmers are on the frontline of climate change. Supporting them with knowledge, tools, and long-term policy frameworks is essential if we are to safeguard food production and environmental sustainability for the future.”

Professor Nicola Cannon, Professor of Agriculture at the Royal Agricultural University (RAU)

Why timing could make or break yields

The immediate risk for UK growers depends on crop type and growth stage. Heat stress during flowering and grain filling can reduce pollination, limit grain set and cut final yields. Winter wheat, the UK’s dominant cereal crop, has largely passed its most heat-sensitive developmental stage, which typically occurs during pollen development from late May to mid-June. Spring wheat, however, reaches this critical phase later, usually from late June to early July, leaving it more exposed to current and forecast periods of elevated temperatures.

Extreme heat also threatens productivity below ground. Higher soil temperatures can speed up the breakdown of organic matter, alter microbial activity and reduce soil moisture. These changes affect nutrient availability and weaken the biological activity that helps soils support crops, retain water and recover from weather stress.

Professor Cannon added: “Soil is a living system, and extreme heat places that system under stress. We see reductions in biological activity, changes in nutrient cycling, and ultimately a loss of the resilience that healthy soils provide. Dry, degraded soils are also more prone to erosion and compaction, further reducing their ability to support crops and retain water.”

The wider food security risk

The warning comes amid wider concern about the UK food system’s exposure to shocks. In February, experts warned that war, cyber-attacks and extreme weather could disrupt UK food supplies, highlighting the need to strengthen domestic production and supply chain preparedness.

International risks are also rising. A strengthening El Niño weather pattern could increase the risk of droughts, floods and storms across parts of Africa, Asia and Latin America in 2026, threatening food production and livelihoods while raising the potential for wider supply disruption. In response, the Food and Agriculture Organization of the United Nations and the World Food Programme have launched a $202 million (£149 million) appeal to protect 8.8 million people across 22 high-risk countries.

Professor Cannon said repeated heat events threaten more than a single season’s output. Over time, they can erode the resource base that farms rely on, leaving soils and cropping systems less able to cope with future extremes such as flooding, erosion and intense rainfall.

Lower yields would not be the only consequence for the food sector. As farms use more water and inputs to protect crops, producers and processors could face higher costs and less predictable supply. Heat-stressed crops and degraded soils may also store less carbon, while some damaged systems could release more greenhouse gases, creating a feedback loop that further intensifies climate risk.Agricultural experts increasingly point to crop diversity, living roots, higher soil organic matter and regenerative practices as practical ways to help farms hold moisture, protect soil structure and support biological activity during heat extremes.

Professor Cannon said building resilience into farming systems would be critical as climate change makes extreme heat events more common. Practices that improve soil structure, protect soils from weather extremes, retain moisture and support biological activity could help farms adapt to rising temperatures.

She concluded: “Farmers are on the frontline of climate change. Supporting them with knowledge, tools, and long-term policy frameworks is essential if we are to safeguard food production and environmental sustainability for the future.”