Rising CO2 Levels Could Offset Drying Effects of Higher Temperatures

As the world warms, rising temperatures are expected to dry out the planet’s semi-arid rangelands. But a new study by U.S. scientists suggests that the effects of that drying are likely to be offset by the way in which plants react to elevated concentrations of CO2 in the atmosphere. Higher temperatures increase water loss to the atmosphere, but scientists from the U.S. Department of Agriculture (USDA) found that higher CO2 levels also cause leaf pores, or stomata, to partially close, which actually slows the evaporation process. The scientists are conducting an 8-year study on dry grasslands in Wyoming, and are simulating future climate conditions — when temperatures could rise by 5 degrees F and atmospheric CO2 concentrations could soar from today’s 390 parts per million to 600 ppm — by using infrared heaters and CO2 piped into experimental plots. The preliminary results of their studies, published in the journal Nature, show that dry grasslands are likely to experience no change in soil water and that warm season grasses may actually grow more quickly under future climate conditions. Dry rangelands make up roughly one third of the Earth’s surface and USDA scientists say their research may help ranchers and farmers plant grasses and crops that are likely to fare better as temperature and CO2 levels increase.