1282. Impact of Climate Risks on Crop Yield Variability

Higher-than-average temperatures can lead to reduced average crop yields as well as increased crop yield variability by exacerbating hot and dry conditions if production systems are unable to mitigate the effects of these stresses.

The Agricultural Market Information System (AMIS) has published an article on the importance of monitoring the impact of climate risks on crop yield variability.

From 2000 to 2020, many parts of the world experienced hotter and drier weather during the maize growing season. To estimate climate risks to yield variability, it is important to monitor (1) regions where maize yields are already unstable, (2) regions where the climate has become warmer and drier over the past 20 years, and (3) regions where climate trends are most adversely affecting maize yield stability.

Investigating historical annual yield variability is a useful starting point to understand regions with the most volatile maize production systems. From 1980 to 2020, parts of Eastern Europe, India, and South Africa had the most volatile maize yields, with yield coefficients of variation exceeding 20%. In Western Europe and South America, yields were relatively stable, with coefficients of variation of about 15%. Corn yields were most stable in China and the United States, with coefficients of variation of about 10%.

The observed yield variation reflects the combined influences of plant genetics, weather, and inputs to the production system, such as irrigation and fertilizer. Of these factors, only weather is truly exogenous.

Since the turn of the century, weather during the corn-growing season in many parts of the world has become hotter and drier. These trends were most pronounced in Argentina, Brazil, and parts of Europe, which accounted for more than 20% of global corn production in 2023. On the other hand, China and the United States, which accounted for more than 50% of 2023 production, have seen less pronounced warming and little drying. The reasons for this are debated, but most climate models project that major corn-producing regions in China and the United States will continue to warm but experience relatively little drying in the future. However, yield variability in China and the United States has a significant impact on global yield variability and therefore requires close monitoring.

Many of the regions with the most yield variability are also those most vulnerable to drier and warmer growing season climates. Parts of Eastern Europe are particularly susceptible to extreme heat and dryness, and changing weather patterns are estimated to have reduced the average European yield by 1% between 2000 and 2020, a larger impact than in Africa, Asia, or Latin America. The impact of rising temperatures is not limited to reduced average yields. In many wet climates, rising temperatures only had a small effect on maize yields in years with sufficient moisture, but greatly exacerbated the effects of drought in other years. Rising temperatures are expected to increase interannual yield variability by further exacerbating unfavorable years. Indeed, rising temperatures between 2000 and 2020 increased maize yield variability by about 50% in Europe, Latin America, and North America. In Asia, on the other hand, the increase in variability from 2000 to 2020 due to the effects of rising temperatures was relatively gradual.

The observed effects of rising temperatures are quite recent. From 1980 to 2000, maize yield variability in many parts of the world was not significantly affected by changing weather patterns, except in Africa. The increase in maize yield variability over the past 25 years may be a harbinger of greater maize yield variability in the coming decades. As droughts become hotter and more damaging, year-to-year variability in maize production is likely to increase. Understanding why, where, and how fast variability is increasing can help identify areas for investment in breeding, policies, and technology.

Contributor: IIYAMA Miyuki, Information Program