1336. The Interaction Between Temperature Stress and Soil Moisture Stress and the Impact of Agricultural Productivity Variability

Along with average yield, interannual variability in crop yield is an important determinant of food security. While previous studies have shown increased yield variability due to global warming, it is increasingly clear that changes in water availability are also an important determinant of yield. A paper published in Science Advances quantified the impact of climate change on variability in yield of corn, soybean, and sorghum due to changes in temperature and soil moisture at a global scale. Rising temperatures and changes in water availability due to climate change are predicted to increasingly lead to yield losses. Extreme heat and cold, as well as drought and waterlogging, generally reduce yields. Extreme heat can reduce net photosynthetic rates, shorten the grain-filling period, and damage plant structures, especially those important for reproductive development. High temperatures can also increase water demand by increasing the vapor-pressure deficit (VPD), which controls evaporation and transpiration. When water demand is high and water supply is low—i.e., when root zone soil moisture is low—plants may close their stomata, reducing photosynthetic rates and carbohydrate production. Low water supply can promote root growth at the expense of grain production, and in severe cases, can cause crop death.

However, how climate change affects yield variability is much less understood than how it affects mean yield. This paper attempted to capture weather-induced annual yield variability through three mechanisms: temperature stress, soil moisture stress, and their covariance. The paper focused on the effects of changes in soil moisture instead of precipitation and quantified the impact of enhanced coupling between temperature and soil moisture on yield variability.

The analysis found that annual yield variability increased, on average, by 7.1%/°C for corn, 19.4%/°C for soybeans, and 9.8%/°C for sorghum. In addition to increased sensitivity to temperature variability due to warming, increases in radiative forcing and VPD (which controls evaporation and transpiration under climate change) increase the covariance between temperature variability and soil moisture, leading to increased yield variability as both hot and dry conditions negatively affect yield. This result is qualitatively consistent with findings that yield variability increases significantly in regions experiencing increasing warming or drying.

The paper cited several limitations of this analysis, including the fact that predictions of future changes in water supply are less certain than those of future temperature changes, highlighting the need for improved representation of the covariance between soil moisture and temperature in climate models. In particular, the authors point out that improving the quality and quantity of yield data used to train and test crop models—especially global data on crop development stages, during which crops may exhibit different sensitivities to temperature and water stress—is important for improving predictions of climate impacts on global agricultural productivity and food security.

The study's findings—that yield variability for major crops will increase globally under the impacts of climate change—suggest the need for adaptation measures. Optimizing sowing times, seed coating, and breeding for heat and drought tolerance could help mitigate increased yield variability due to heat and moisture shocks. While poor countries generally have lower capacity to develop and apply these technologies, crop diversification, particularly in sub-Saharan Africa, has been suggested to stabilize agricultural yields and mitigate productivity losses due to temperature and water stress. The paper's finding that increased yield variability due to climate change is controlled by local thermodynamic mechanisms suggests that local adaptation measures related to crop water supply, such as irrigation, may be particularly effective. However, in many agricultural regions around the world, irrigation water demand already exceeds sustainable water supplies, highlighting the importance of water resource management and planning to improve irrigation water efficiency.

(Reference)
Jonathan Proctor et al., Climate change increases the interannual variance of summer crop yields globally through changes in temperature and water supply, Science Advances (2025). https://www.science.org/doi/10.1126/sciadv.ady3575

Contributor: IIYAMA Miyuki, Information Program