According to a study led by Dartmouth College, USA, future plants will consume more water than they do now, leading to less available water for those in North America and Eurasia.
The research suggests the globe will be considerably dryer despite anticipated precipitation rises from place like the USA and Europe, areas already suffering from water stresses.
Challenging the expectations in climate science that plants will make the world wetter in the future, this study argues that due to climate change plant will need to consume more water than they do now. Scientists have long believed that as the concentrations of carbon dioxide in the atmosphere increase, plants will reduce their water consumption. This was once believed because as more carbon dioxide enters the atmosphere, plants can photosynthesise the same amount while relaxing the pores on their leaves, meaning less water loss.
These new findings reveal that this effect is only limited to the tropics and at extremely high latitudes. For much of the mid-latitude areas, projected plant responses to climate change will make the land drier.
“Approximately 60 percent of the global water flux from the land to the atmosphere goes through plants, called transpiration. Plants are like the atmosphere’s straw, dominating how water flows from the land to the atmosphere. So vegetation is a massive determinant of what water is left on land for people,” explained lead author Justin S. Mankin, an assistant professor of geography at Dartmouth and adjunct research scientist at Lamont-Doherty Earth Observatory at Columbia University. “The question we’re asking here is, how do the combined effects of carbon dioxide and warming change the size of that straw?”
Using climate models, researchers examined how freshwater availability may be affected by changes in the way precipitation is divided among plants, rivers and soils. The research team used a novel method, precipitation portioning. Developed by Mankin and his colleagues, used the method to calculate the future runoff loss to future vegetation in a warmer, carbon dioxide-enriched climate.