Results of a four-year field study conducted by the U.S. Department of Agriculture found that “Rising carbon dioxide (CO2) levels can reverse the drying effects of predicted higher temperatures on semi-arid rangelands.”
Warmer temperatures increase water loss to the atmosphere, leading to drier soils. In contrast, higher CO2 levels cause leaf stomatal pores to partly close, lessening the amount of water vapor that escapes and the amount of water plants draw from soil. This new study finds that CO2 does more to counterbalance warming-induced water loss than previously expected. In fact, simulations of levels of warming and CO2 predicted for later this century demonstrated no net change in soil water, and actually increased levels of plant growth for warm-season grasses.
See the USDA news release here.
This result should not be surprising to anyone except climate alarmists who have long predicted global warming will increase evapotranspiration and decrease soil moisture. However many laboratory and field studies found that rising carbon dioxide reduces evapotranspiration and leads to higher soil moisture content, results similar to the USDA study. The USDA study was conducted on warm-season grasses. Other studies were conducted on a wide range of grasses, beans, sorghum, scrub oak, forbs, and food crops.