Responding to the CO2 Coalition's "Fact #25" on CO2 and Soil Moisture
CO2 Coalition 's " Fact #25 " claims that increasing CO2 causes moister soil. We're told that increasing CO2 concentrations means that plant stomata are open for shorter periods, so plants become more efficient (water use efficiency or WUE increases) and don't take as much water from soils. From this they claim that "CO2 fertilization has been linked to decreases in global fire, drought and heat waves." It's true that studies have shown that in some ecosystems, elevated CO2 has been linked to better water use efficiency (WUE) and improved soil moisture. But CO2 Coalition is being a bit selective in the information they present, even in the two examples they provide. In their first example, they cite research from CSIRO that showed that increasing CO2 has lead to a boost in green foliage in desert areas, but there are also secondary effects: "On the face of it, elevated CO2 boosting the foliage in dry country is good news and could assist forest...