Timing and climate shape future harvests

Climate change is already reshaping the conditions for food production – and how much bread ends up on the table.

Crops such as wheat and grapes are adapted to particular climatic conditions – and when those conditions shift, so do yields.

This could mean less wheat for bread and fewer grapes for wine – but also greater year-to-year fluctuations that farmers cannot simply plan their way out of.

For wheat, the most widely grown crop in the European Union (EU), a team of researchers has now used AI to uncover when and how climate change affects the harvest – within the patterns that can be read from the data.

They analysed 20 years of climate data from across the EU alongside corresponding data on wheat yields.

This provides new insight into which factors have influenced the harvest – and are likely to do so in the future, although uncertainty remains higher in regions with less data and more variable growing conditions.

“We wanted to identify which factors are most critical for wheat yields and whether the same factors matter equally in different regions across Europe. With this study, we identify factors that are important across the EU as well as factors that matter regionally,” explains a lead author, Sheng Wang, Associate Professor from the Center for Landscape Research in Sustainable Agricultural Futures at Aarhus University in Denmark.

The research has been published in Computers and Electronics in Agriculture.

AI reveals what drives the harvest

The researchers fed the AI vast quantities of data, and the model was continuously tested against other types of models to ensure that the results were robust – rather like having a model go through 20 years of weather diaries page by page and link every single change in the weather to how the plants actually grew and yielded in the field.

One part consisted of wheat yields from a wide range of European countries over the past 20 years.

The other part covered climatic conditions such as temperature, precipitation, cold spells, soil moisture, heat-waves and solar radiation from across the EU. The analysis purposely focused on climate change impact, and did not directly include management factors such as fertiliser use, variety selection and cultivation methods even though they can also affect yield in practice.

“We used the explainable machine learning model to link climatic conditions with year-to-year variation in wheat yields and identify the key factors – not just what is associated with yields but what actually drives them up or down in different parts of Europe.”

The models were also designed not only to provide answers but to show what drives them – a bit like opening a black box and seeing which climate factors, in each individual case, tip yields up or down, without necessarily capturing all the biological and practical conditions in the field, where reality is often more complex than the model.

“Our study is the first to apply explainable models to these crop-yield and climate datasets at the EU level. This improves understanding of how climate change affects wheat yields regionally,” explains Sheng Wang.

North and south are affected differently

The study revealed several interesting similarities in the climate factors influencing wheat yields across the EU.

The model showed that solar radiation, temperature and air dryness (vapour pressure) are particularly important. This aligns well with previous research and with classical crop models, in which these factors are known to affect photosynthesis, water loss and growth – although the relationship is not straightforward and can vary depending on both growth stage and local conditions.

Regions also clearly differed .

“In southern Europe, heat stress and drought are often decisive for yields, because high temperatures and dry air can cause the plants’ stomata to close and slow growth. In northern and eastern Europe, by contrast, cold winters can damage severely or delay plant development.”

In parts of northern and eastern Europe, cold winters were linked to yield losses of up to 2.5 tonnes per hectare – partly because frost can damage plants at their most vulnerable stages.

Small windows determine the harvest

The analysis also suggests that timing matters just as much as climate itself. There are brief biological windows during the year when plants are especially vulnerable and when the weather can decisively affect the harvest.

Winter wheat is sown in autumn, overwinters in the soil and emerges in spring, before being harvested in June or July.

“Wheat is particularly sensitive to cold snaps in spring, when the shoots are emerging and are not yet protected. In southern Europe, the same applies to heat-waves, which can stress the plants during their growth phase.”

In northern and eastern Europe, soil moisture at the time of autumn sowing strongly affects yield – because this is when the plants establish their root systems – and heavy rainfall or flooding during this period can therefore reduce the harvest the following year.

“When we talk about flooding in Denmark, it is often about basements and streets – but far less often about what it does to next year’s harvest in the fields. There are critical stages, and we need to understand how climate affects crops and how we might be able to improve yields,” says Sheng Wang.

He explains that this could include better models for weather forecasting, enabling farmers to hit the narrow window when plants have the best conditions to establish themselves – and when the timing of sowing can make the difference between a good and a poor harvest, even though the weather in practice can still be difficult to predict accurately from year to year.

Agriculture also shapes the climate

According to Sheng Wang, understanding climate factors holds great potential – not only for wheat but also for crops more broadly.

“This can both increase yields and influence the EU’s overall climate footprint, because improved growing conditions change how plants absorb and release greenhouse gases. In addition, the relationship between crop production and climate is complex and depends on many factors, not all of which can be captured in a single model.”

Around 29-33% of Denmark’s greenhouse gas emissions come from agriculture, and these emissions are influenced by whether crops grow and management activities under optimal conditions or not.

“Our overall research focuses on understanding how climate change affects crops, but also how crop growth also affects agricultural greenhouse gas emissions for climate change mitigation. With better understanding, we can develop sustainable agroecosystems that both increase yields and reduce agriculture’s climate footprint – and make food production more resilient in a climate that is becoming increasingly unpredictable,” says Sheng Wang.