26 June 2026

 

As heatwaves become more frequent and intense across the UK and globally, new attention is being drawn to the wide-reaching impacts of extreme high temperatures on crop productivity, soil health, and the sustainability of farming systems. 

Rising temperatures are not only reducing yields but also accelerating soil degradation and placing long-term food security at risk.

“Extreme heat fundamentally disrupts how crops grow and function,” said Professor Nicola Cannon, Professor of Agriculture at the Royal Agricultural University (RAU). “When temperatures exceed optimal thresholds, plants shut down critical physiological processes such as photosynthesis, which directly reduces growth and yield.

“High temperatures can drive rapid water loss in plants by increasing evaporation, creating conditions where water is lost faster than it can be taken up by the roots, leading to wilting, as plants lose turgor pressure. 

“In response, stomata, the microscopic pores responsible for gas exchange, close to conserve water, but this also restricts carbon dioxide uptake and reduces photosynthetic efficiency. Under sustained or extreme heat stress, plants may effectively cease growth, limiting biomass accumulation and carbon capture.”

 During key growth stages such as flowering and grain filling, heat stress can lead to poor pollination, reduced grain set, and ultimately can reduce yield. 

Reassuringly, winter wheat, the UK’s dominant cereal crop, has largely passed its most heat-sensitive developmental stage, with peak vulnerability occurring during pollen development in late May to mid-June. 

However, spring wheat, although less widely cultivated, enters this critical phase later in the season, typically from late June to early July, leaving it more exposed to current and forecast periods of elevated temperatures.

Below the crop, rising temperatures can also affect the soil system that underpins agricultural productivity. Higher soil temperatures can accelerate the breakdown of organic matter as different microbial communities flourish and these often feed off dead material in the soil which leads to enhanced carbon and nitrogen loss and therefore increased greenhouse gas emissions. 

At the same time, soil moisture levels decline, affecting microbial activity and nutrient availability. However, it is really difficult to fully predict how soil respond as it depends on soil type and exposure as it can either stimulate certain soil biology and in other cases supress it.   

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 combined effects of heat stress on crops and soils present a major challenge for sustainable agriculture. Reduced yields, increased input required such as irrigation, and declining soil health threaten both environmental and economic sustainability.

Professor Cannon highlighted that the issue extends beyond individual seasons. “This is not just about reducing current growing conditions,” she said. “Repeated exposure to extreme heat events can degrade the underlying resource base that farming depends on, making systems less resilient and more vulnerable over other extreme weather events such as flooding or erosion caused by intense rainfall.”

Globally, experts are generally emphasising that adapting farming systems will be essential. Strategies such as increasing crop diversity, maintaining living roots in the soil, improving soil organic matter, and adopting regenerative practices can help buffer against heat extremes.

The problem is compounded by a negative feedback loop, whereby extreme heat reduces plant growth and photosynthetic activity, leading to lower carbon sequestration and, in some cases, increased greenhouse gas emissions from stressed or degraded systems. 

This reduction in the land’s capacity to store atmospheric carbon further amplifies climate warming, increasing the likelihood and severity of future extreme weather events an example of a reinforcing climate feedback mechanism.

“Building resilience into farming systems is critical. Practices that improve soil structure, protect soils from extreme weather events, retain moisture, and support biological activity can help mitigate the impacts of high temperatures and make agriculture more adaptable to climate change,” concluded Professor Cannon.

“With climate projections indicating that extreme heat events will become more common, it is vital that there is a coordinated action from policymakers, industry, and the farming community.

“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.”