A new study from the Chinese Academy of Sciences finds that the water-saving effect of higher CO2 on plants is much smaller than previously thought. When plants close their pores to conserve water, the change in surface energy balance causes local warming that pulls more moisture from the land, canceling out over half of the expected benefit. In northern mid to high latitudes, the offset reaches 54 percent under current conditions and grows to 68 percent under a high emissions scenario. For key agricultural regions like the U.S. Corn Belt, European plains, and Chinese rice areas, this means the natural buffer against drought is far weaker than models assumed. The research, published in PNAS, warns against relying on plant physiology as a passive solution to water scarcity. Even where some soil moisture relief occurs, it competes with increasing heat and atmospheric dryness. The authors argue for active adaptation strategies such as better irrigation, drought resistant crops, and water planning that does not count on CO2 driven water savings. This has direct implications for carbon market assumptions about land based offsets and for climate adaptation planning in major food producing regions.
