Global warming will increase crop yields in the Global North, largely thanks to increased “carbon fertilisation” and temperature increases towards the optimal for growing crops, but will decrease it in the Global South where typical crops are less affected by carbon fertilisation and temperatures are already at optimal levels. 

That is according to a paper by Hannah Ritchie “How will climate change affect crop yields in the future?” published online at OurWorldinData.org. 

With a global population projected to reach 10bn by 2050 and the average temperature increase expected to increase by 2C above the pre-industrial baseline, missing the 1.5C Paris Agreement targets, the pressing question is: can the world continue to feed itself in a warmer climate?

Recent studies highlight the complex relationship between CO₂ emissions, climate change and agricultural productivity. Jonas Jägermeyr and colleagues, using advanced modelling techniques, have explored how climate change might influence the yields of staple crops, offering both optimistic and concerning projections.

The role of CO₂ and temperature

The first factor influencing crops is the potential benefit of “carbon dioxide fertilisation,” where higher levels of atmospheric CO₂ stimulate plant growth. Wheat and rice, classified as "C3" crops, are expected to benefit significantly from this process. Maize, millet and sorghum – "C4" crops – on the other hand, show little to no benefit, except under drought conditions.

However, rising temperatures present a more nuanced challenge. For farmers in cooler temperate regions such as in Europe, moderate warming could enhance yields by bringing temperatures closer to the crops' optimal growing range. In contrast, in tropical and subtropical areas where crops already face near-optimal temperatures, any further increase could lead to significant yield declines, scientists say. 

Water availability remains another critical factor. As bne IntelliNews reported, extreme changes in rainfall patterns are expected in the future that will lead to more frequent droughts and floods, which will stress crops, exacerbating yield losses in vulnerable regions.

Projected declines in maize yields

Maize, a staple crop for millions, faces a particularly grim outlook. According to Jägermeyr's models, global maize yields are projected to decline by 6% in a low-warming scenario where temperatures rise by less than 2°C. Under more extreme conditions, with warming reaching 3°C to 5°C, the drop could be as much as 24%. This worst-case scenario assumes no adaptation by farmers to the changing climate.

The negative impacts on maize will not be uniform across the globe. Sub-Saharan Africa, the United States, China, and South America, which are all major maize-growing regions, could see yield losses of up to 25% in the most severe scenarios. Even Europe, with its cooler climate, could experience declines of up to 20%.

“Global warming directly reduces global maize productivity,” Riichie notes. “Even in Europe, where temperatures are cooler, yields could drop significantly under certain scenarios.”

Mixed prospects for wheat and rice

Wheat, which is the dominate crop in the Global North, presents a contrasting narrative. While higher temperatures alone might lower yields, carbon fertilisation could more than offset these declines, particularly in temperate regions. Projections indicate a potential increase in global wheat yields, even under extreme warming scenarios. By 2050, wheat yields in Europe could rise by as much as 18%, depending on the degree of warming and CO₂ concentration.

Rice and soybeans, which are found more in the Global South,  offer a more ambiguous picture. While rising temperatures could reduce yields, carbon fertilisation might mitigate these losses. Regional studies predict modest yield increases for rice in countries like China, India and Indonesia, though global projections remain highly uncertain. Rice has the main advantage of being grown in waterlogged earth and so suffers less from changes in rainfall patterns. 

Unequal burden on developing countries

While some regions could benefit from higher yields, the most vulnerable populations – especially those in the tropics and subtropics – are expected to face the harshest impacts. Climate change will worsen the food insecurity for billions of people in the poorest parts of  the world, while leaving the richer parts less affected. Many of the crops grown in these regions, such as maize and millet, will not benefit from carbon fertilisation and are already near their optimal growing temperatures.

The situation is particularly dire in sub-Saharan Africa and parts of South America, where these crops make up a significant portion of the diet. Declining yields threaten not only food security but also the livelihoods of millions of smallholder farmers, who rely on these crops for income.

“Yield declines not only threaten food security but could also push farmers deeper into poverty as they get worse and more volatile harvests,” Richie says.

Water stress and future risks

In addition to temperature and CO₂ changes, more extreme water patterns are likely to make food production even more volatile. A study looking at future waterlogging scenarios warns that yield penalties under high-emission scenarios could increase from 3% to as much as 20% by 2080, largely due to more intense rainfall and flooding. Without adaptation, these changes could create significant disruptions in food markets, further straining global food supplies.

A divided future

The impacts of climate change on agriculture will be unevenly distributed across the world. Wealthier countries, particularly those in temperate zones, may benefit from increased yields in some crops. Meanwhile, the poorest and most food-insecure regions face substantial losses. This disparity underscores the injustice of climate change: those who contribute the least to global emissions will suffer the most from its consequences.

While adaptation strategies and new agricultural technologies may offer some hope, the overarching message remains clear. The ability of the world to feed its growing population will be severely tested by climate change, and urgent action is required to mitigate its most damaging effects.