Well-fed Plants Could Help Temper Future Drought

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Looking ahead at the water cycle.

A new USGS study finds that the drying effect of a projected warmer climate in the future could be partially countered by a decreased need of plants for water.

The very same carbon dioxide that is the main driver of climate warming is also a plant "food," essential for building plants. Thanks to air that is richer in carbon dioxide, plants need not open their leaves' pores as widely as they would in an environment with lower carbon dioxide. The narrower openings would leak less water to the atmosphere and hence remove less water from the soil.

"The one big job of leaves is to take in food in the form of carbon dioxide," explains USGS scientist Chris Milly, an author of the study, "but the execution of this process allows water to leak out of the leaves. Well-fed plants don't need such leaky leaves to get their food, so they leave more water in the ground, where it can both support streamflow and recharge groundwater supplies.”

As a result of this slight, but important increased availability of water in the soil, future droughts may be less frequent and less intense than many past studies have predicted.

According to widely-accepted climate forecasts, as the earth warms in coming decades, its atmosphere will tend to draw more water from the ground, either directly from the soil by simple evaporation or through plants whose stems act like straws to release water into the atmosphere by means of transpiration. Many previous studies have suggested that a thirstier atmosphere and correspondingly drier soils will then rob streams and groundwater reservoirs of their water supply, contributing to widespread drought around the world.

Potential changes in the Earth’s water cycle due to climate change are among the most serious issues scientists face in anticipating the years ahead.  This study helps refine our view of how a future water cycle is most likely to look.

The study, “Potential evapotranspiration and continental drying,” is published in the journal Nature Climate Change.