IF YOU have just endured a summer of hosepipe bans, brace yourself for some bad news. Worse droughts may be in store, according to a British researcher who has examined the response of plants to global warming and rising concentrations of CO2 in the atmosphere.
High summer temperatures and abundant CO2 both cause the pores, or stomata, in the leaves of plants to narrow, says John Lockwood of the University of Leeds. This process reduces evaporation, which in turn disrupts the recycling of rainwater. Lockwood has now estimated the magnitude of this drying effect.
When CO2 is in abundant supply, plants narrow their stomata because the smaller holes admit enough of the gas for photosynthesis to take place. A higher temperature, meanwhile, increases evaporation from the leaves up to a threshold of about 25 °C. Above this temperature, however, further increases have little effect on evaporation because plants restrict water ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content.