Will corn still be a worthwhile crop in Europe in 2100?

2100 is the year when many members of Salles’ generation will celebrate their 100th birthday. It’s also the year that environmental engineering students typically use for making projections about the lasting effects of climate change: glacier melting, rising temperatures, extreme weather events and more.

For her master’s project, Salles also wanted to project into the unknown future. She browsed through the websites of the EPFL research labs working in her areas of interest – water management and geographic information systems – and came across a project offered by tenure-track assistant professor Sara Bonetti: estimating grain-crop yields in 2100 in Switzerland and Europe. “Projections from large climate models can provide us with estimates of future changes in rainfall and temperature patterns, which are crucial drivers of crop productions,” says Salles, who originally comes from the Paris region. “Another thing I liked about the project is that it involved analyzing forecasts of rainfall time series.”

Worst-case scenario

Climate-change scientists generally base their projections on different scenarios, from the best case in which aggressive measures are taken to limit global warmings, to the worst case characterized by no implementation of climate policies and limited uptake of renewable energies. “Unfortunately, the best-case scenario is no longer possible,” says Salles. “So I opted for the most extreme worst-case scenario: Representative Concentration Pathway (RCP) 8.5.” This scenario is based on the assumption that the current level of carbon emissions will continue, with no real effort being made by emitters. Under RCP 8.5, the average annual temperature in Switzerland will rise by 3°–5°C, and we could see temperature spikes of over 40°C. In addition, extreme weather events such as torrential rain, heat waves, and floods will occur more often.

It will become impossible to grow corn without irrigation, but the use of irrigation systems could lead to conflict about how water is allocated.

Salles set out to investigate how all this would affect corn production. Corn is the second-largest grain crop in Europe behind wheat. The drawback to corn is that its growth season – and therefore the season when it needs water the most – is in July and August, or precisely the months when water will become increasingly rare. “This will especially impact major grain-producing countries like Germany, the Netherlands, Ukraine and France,” says Salles. “It will become impossible to grow corn without irrigation, but the use of irrigation systems could lead to conflict about how water is allocated.”

Shifting climates

To generate her projections, Salles examined four climate variables that are particularly important for corn production – the number of rainy days, the number of consecutive dry days, the rain intensity and the mean annual temperature – by comparing data from 2000 with forecasts for 2100. “I ran this analysis for Switzerland by dividing the country into six regions, and then I did the same thing for all of Europe,” she says. “I found that some kinds of climates are likely to undergo significant shifts, such as the boreal climate of northern Europe, the Atlantic climate of Brittany and the British Isles, and the continental climate of Eastern Europe.” Salles also found that some hydroclimatic conditions typical of the Mediterranean climate, which currently covers 19% of Europe, will expand to 41.6% of the European land area by 2100.

Which crop to grow?

Regarding rainfed corn crops, Salles estimates that yields will drop by 80% between 2000 and 2100 in Europe’s main corn-producing countries. This raises the question of whether it will still make sense to grow corn or switch to different crops – an issue that crossed her mind as she reviewed her findings. “To ensure the region’s food security, farmers may have to switch to the kinds of grains that are currently grown in southern Europe, such as sorghum and millet,” she says. “We’ll also need to rethink the logic behind growing corn, given that two-thirds of what’s produced in Europe goes to livestock feed.”

According to her projections, corn yields will only increase in northern Europe. In Switzerland, yields on the Plateau will increase by 35%, while Ticino and Valais Cantons will experience more frequent droughts and periods with little rainfall – tough conditions for agriculture. Limited by the scope of her master's project, the student was unable to evaluate which alternative crops will be more suitable under future climatic conditions, but research is ongoing at Sara Bonetti’s lab to quantify climate change impacts on cropland suitability.

Buoyed by her master’s project, which received one of the highest grades in her class, Salles now plans to pursue a PhD in environmental engineering. She chose this field because it “addresses concrete subjects that are grounded in reality” and “aims to develop solutions to the problems we’re all familiar with.”