How will climate change affect crop yields in the future?

How much will climate change affect food production? Will it hurt or benefit crop yields? Can we feed 8, 9, or 10 billion people in a warmer world?

These are crucial questions that I’m trying to tackle in a three-part series on climate change and agriculture.

In my first article, I discussed the different ways climate change impacts crop yields and the effect they have already had on global food production. In this installment, we’ll look at how climate change could affect crop yields in the future.

As a quick reminder, there are three ways that CO₂ emissions and climate change can affect agriculture.

First, plants can benefit from higher CO₂ levels in the atmosphere; this is called “carbon fertilization”. Wheat and rice — so-called “C3” crops — can significantly benefit from more CO₂. Maize, millet, and sorghum — “C4” crops — benefit very little, except under drought conditions.

Second, crops are affected by higher temperatures. This can increase or decrease yields depending on the type of crop and where in the world you are grown. For farmers in temperate climates, where temperatures are lower than the “optimal” for that crop, moderate climate change can potentially increase average yields. For farmers in the tropics or subtropics where temperatures are already at or past the “optimal”, higher temperatures will directly reduce yields.

Finally, crops are affected by water availability. Yields decline significantly under water stress and the opposite — flood and waterlogging — so crop productivity will decrease if climate change increases the frequency or intensity of these events.

The ultimate impact on crop yields combines all of the above. They can either offset or boost one another. Considering just one could lead to the wrong conclusions. That’s why we get oversimplified and opposing headlines, such as “More CO₂ and climate change is good for agriculture” or “Higher temperatures will cause crop yields to collapse worldwide.”

The reality is more complex. Some crops in some places could benefit. Elsewhere, crop yields are at risk of a severe decline. Extreme events pose additional risks that could destabilize food systems in the future.

The impact of climate change on yields will depend on several factors: the type of crop, how much warmer the world gets (which will depend on how quickly we reduce our carbon emissions), where in the world you are, and what we do to adapt.

Before considering what adaptation is necessary, we must understand what to expect in a world in which we don’t adapt. For this reason, I’m focusing on that in this article, and in the third and final article of the series, I’ll then consider how to adapt.

Let’s start by focusing on the first two factors: the sensitivity of different crops at the global level under a range of warming scenarios.

For maize, the expected change is shown in the first panel of the chart: more warming means lower yields. Jonas Jägermeyr and colleagues used the latest modeling techniques to look at the impact of climate change on yields under a range of climate scenarios.¹ In the lowest warming scenario — so-called “RCP2.6”, where we keep global warming levels below 2°C compared to preindustrial levels — global yields decline by about 6%. In the most extreme case — “RCP8.5”, a pessimistic high-end scenario that leads to 3°C to 5°C of warming — they decline by about 24%. This worst-case scenario provides an upper limit on the potential magnitude of isolated climate impacts without any efforts to adapt to these new conditions.²

Other studies on maize find similar results.³ Since maize benefits little from carbon fertilization and maize is usually grown in warmer regions, global warming directly reduces global maize productivity. Even Europe, where temperatures are cooler, could see a decrease of up to 20%.⁴

The opposite is true for wheat. Global yields are expected to increase.⁵ The impact of carbon fertilization makes a crucial difference.

At 2°C of warming, one study estimated that wheat yields would decline by 6.6% without carbon fertilization. Once that was included, they projected a 1.7% increase.⁶ Winter wheat yields in Europe could decline by 9% by 2050 without CO₂ effects, but with them, this changes to a 4% increase.⁴

In the most extreme warming scenario — RCP8.5 — wheat yields are projected to increase by 18%.¹

The climate impacts on rice and soybeans are smaller. Higher temperatures will tend to have a negative impact on yields. But this is largely offset by gains from carbon fertilization. Uncertainties are large at the global level, especially for soybeans and rice, without clear negative or positive climate impacts. Regionally, the models show higher agreement and more robust results.

This result is mirrored in other studies.⁷ One large meta-analysis concludes that rice yields in China, India, Bangladesh, and Indonesia would see small yield increases, ranging from 0% to 10% in the most optimistic and extreme scenario.⁵

The previous section discussed what we can expect on the global level. What does it look like on the local level?

As a general rule, high-latitude or temperate countries will likely see less severe adverse climate impacts — and potentially even increases in yields, despite additional extreme weather events — while farmers in the tropics and subtropics face the largest yield declines, while also having a lower capacity to adapt.

There are several reasons for this.

First, in the warmer tropics, many crops are already close to their “optimal” growing temperature. Further warming will push them well past it.

Second, crops that benefit very little from carbon fertilization — maize, millet, and sorghum — are much more common in warmer climates. So, they’ll see a decline in yields due to increased temperatures without the benefits of carbon fertilization to offset it.

In the figure below, I have visualized the projected changes in crop yields for several crops across different latitudes. These results come from the work of Jonas Jägermeyr and colleagues, published in Nature Food.¹

The vertical line for each crop extends from 90° North at the top down to 60°S South of the equator. The horizontal axis shows us the projected change in yield due to climate change. On the right — and in blue — yields increase. On the left — shown in red — they decline.

Of course, where crops are grown matters. An increase or decrease in rice yields in Northern Europe makes no difference since almost no rice is grown there. So, for each crop, I’ve also shown a map of where these crops are grown today.⁸ This is lined up with the yield chart, so you can see where in the world yields might benefit or be vulnerable.

What we see is that most crops see yield benefits at higher latitudes.

We also see that crop yields are expected to decline around the equator and the tropics. But this zone is much larger for maize, stretching from around 60°N to 30°S of the equator. That’s further north than the UK, which means that the only regions where maize yields wouldn’t decline are Scandinavia, Russia, and Canada, regions in which very little maize is currently grown.

Most of the world’s biggest maize-growing regions, the United States, China, South America, and Sub-Saharan Africa, could see significant declines, reaching 20% to 25% in some of the most extreme scenarios.

Projections for other crops are less bleak. Wheat production in Europe could see a yield increase. Production in northern India could, too, but there would be declines in southern states.

Impacts on soybean and rice yields will probably be smaller. Most of these crops are grown in regions where there are not huge increases or declines. Soybean production in the United States might benefit, but less so in South America.

A range of other studies find similar results. A major review by Ehsan Eyshi Rezaei and colleagues looked at projected crop yields under low and high warming scenarios.⁵ Even in low-warming scenarios, the impacts on maize yields were negative everywhere, from France to the United States, and China to Brazil.

Wheat yields were expected to benefit almost everywhere. Rice yields were expected to change very little. Millet and sorghum yields in India and West Africa, where these crops are widely grown, were negatively impacted.

In the footnote, I list other studies — they all come to similar conclusions.⁹

Most of the studies so far have focused on the average impacts on crop yields based on changes in temperature, and carbon fertilization. One aspect that could introduce more volatility in production (and food prices) is more extreme changes in water patterns. As we saw earlier, flooding or high drought stress can have a large impact on yields.

A large study that looks at the potential increase in waterlogging in future climate scenarios finds that yield penalties under high climate scenarios could increase from 3% to 11% in the past, to 10–20% by 2080.¹⁰ The authors highlight that these impacts can be offset by changing crop practices (which I’ll cover in my next article) but without adaptation, more intense rainfall could make food markets more volatile.

Another key point is that even if global yields of wheat increase, and rice and soybean are positive, the negative expectations for maize, millet, and sorghum are very concerning.

These are staple crops for many of the poorest and most food-insecure countries in the world. The injustice of climate change is that it will be those who are already the worst off who will be hit hardest.

The charts below show per capita supplies of maize and millet per person each year. This is the amount of these crops that are available for consumption at the end of the supply chain. Maize makes up a huge amount of diets in South America and Southern Africa. Millet is heavily concentrated in Sub-Saharan Africa. You can see that this is the same for sorghum.

This is also where hunger rates are highest, crop yields are already lowest, most of the population works in agriculture, and earns very little. Yield declines not only threaten food security but could also push farmers deeper into poverty as they get worse and more volatile harvests.

This is the brutal reality of climate change — which I’ve written about before in the context of temperature-related deaths. Richer countries that have contributed most to carbon emissions could see yields increase because wheat happens to benefit from climate change. Those who are suffering from hunger today are expected to see their yield decline.

Now that we see what we can expect from the world’s food production, we can ask what we can do to counter this injustice. Two points are important: climate change is not the only factor that matters for the level of agricultural production in the future and even based on current knowledge we know that the scope for improvements thanks to all those other factors is large.

In my previous article on the historical impacts of climate change on yields, I pointed out that reporting a “5% decline” is often not what people imagine it to be. They might assume that this means yields in 10, 20, or 50 years will be 5% lower than they are today.

But that’s not the case. I used the example of changes in yields from 1961 through to today. Studies suggest that yields of key crops have “declined” by around 5% due to climate change. Yet global yields have increased by more than 200% over this period.

What this “5% decline” actually means is that yields are 5% lower than they would have been in a world without climate change. Yields have increased but would have increased even more without warming.

The same is true when we think about changes in the future. Climate change will make crop production in some regions much more vulnerable. Holding everything else constant, yields would decline. But there are other things we can do to mitigate this risk and counteract some of these pressures.

There are still huge yield gaps across the world today. “Yield gaps” are the difference between the yields that farmers currently get and could get if they had access to the best seeds, fertilizers, pesticides, irrigation, and practices that already exist today.

Let’s take the example of Kenya and maize. Farmers currently grow around 1.4 tonnes per hectare. However, researchers estimate that farmers could get 4.2 tonnes if they had access to the best technologies and practices available today.¹¹ That means the yield gap is 2.8 tonnes. You can see this in the chart below.

In some of the worst climate scenarios, Kenya could see a 20% to 25% decline in maize yields. If nothing else changed, that would cut its current yield of 1.4 tonnes to around 1.1 tonnes: a drop of 0.3 tonnes.

However, the current yield gap of 2.8 tonnes is much larger than the 0.3 tonnes drop that might be expected with climate change.

Of course, adopting the best agricultural practices and technologies and stopping climate change would increase yields even more. But it’s still possible for yields to increase over time, even if they rise at a slower rate than they would in a more stable climate. This won’t happen on its own. It will require serious investments to shrink existing yield gaps, and new ones into developing more temperature and drought-resistant crops that are more resilient.

That brings us to the third article in this series: how we can adapt our food systems to protect farmers from the negative impacts of climate change.

Appendix: What about non-staple crops such as fruits, vegetables, and legumes?

This article is part of a series on climate change and agriculture:

Crop yields have increased dramatically in recent decades, but crops like maize would have improved more without climate change

Climate change has slowed the productivity of key crops such as maize and soybeans, but might have had small positive impacts on wheat.

How will climate change affect crop yields in the future?

Maize yields could see significant declines, but wheat could increase. Impacts across the world will be very different.

Hannah Ritchie (2024) - “How will climate change affect crop yields in the future?” Published online at OurWorldinData.org. Retrieved from: 'https://ourworldindata.org/will-climate-change-affect-crop-yields-future' [Online Resource]

@article{owid-will-climate-change-affect-crop-yields-future,
    author = {Hannah Ritchie},
    title = {How will climate change affect crop yields in the future?},
    journal = {Our World in Data},
    year = {2024},
    note = {https://ourworldindata.org/will-climate-change-affect-crop-yields-future}
}

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