Bioenergy crops need more irrigation and will put pressure on water resources, models show
Corn is one of the sources of biofuel (Flickr/Alexander Steinhof)
By Megan Darby
Global warming is set to increase the risk of drought in the US, as elsewhere. So strategies to cut emissions should ease the problem, right?
Not necessarily, according to a paper from the University of Maryland and Pacific Northwest National Laboratory, published in PNAS.
Their models show that while mitigating climate change boosts water supply, this is outweighed by increased demand – primarily from water-hungry bioenergy crops.
In other words, green policies risk causing more water stress than climate change itself.
“If we don’t pay careful attention to water, we could end up with climate mitigation policies that yield such negative consequences,” lead author Mohamad Hejazi told RTCC.
Average total annual water deficit as a fraction of demand (county
scale) for the historical period and the deficit difference from historical
under RCP4.5 and RCP8.5 in the 2020s, 2050s, and 2080s (PNAS/Hetaji et al)
A regional breakdown shows the arable plains of the Midwest feeling the pinch in the second half of the century.
A scenario involving less bioenergy saw water demand rise 12% instead of 42%, with nuclear and geothermal energy the main drivers.
But the authors noted bioenergy was seen as a cost-effective option, with potential for negative emissions if coupled with carbon capture and storage.
The study will fuel a fierce debate around the role of plant-based fuels in cutting emissions.
They play a significant part in most climate models, but have been criticised for competing with food crops for land.