Scientists are warning future generations that they face an environmental “time bomb”. According to Phys.org, the world’s groundwater systems are taking decades to respond to the impact of climate change.
Groundwater is the largest usable source of freshwater on the planet, according to Phys.org. More than two billion people rely on groundwater to drink and to irrigate crops.
According to the site, groundwater reserves are already under pressure as the global population explodes and crop production rises in lockstep.
Extreme weather events such as drought and record rainfall could also have a lasting impact on how quickly reserves replenish, according to a Nature Climate Change study.
An international team of researchers used computer modeling of groundwater datasets to put a timescale on how reserves may respond to the changing climate, according to Phys.org.
"Groundwater is out of sight and out of mind, this massive hidden resource that people don't think about much yet it underpins global food production," said Mark Cuthbert, from Cardiff University's School of Earth and Ocean Sciences.
According to Phys.org, Cuthbert and his team found that only half of all groundwater supplies are likely to fully replenish or re-balance within the next 100 years—potentially leading to shortages in drier areas.
"This could be described as an environmental time bomb because any climate change impacts on recharge occurring now, will only fully impact the base flow to rivers and wetlands a long time later," Cuthbert said.
The process through which rainwater is filtered through bedrock and accumulated underground can take centuries and varies greatly by region, according to site. As climate change delivers longer droughts and bigger superstorms, the extremes of rainfall become more pronounced, impacting groundwater reserves for generations to come.
"Parts of the groundwater that's underneath the Sahara currently is still responding to climate change from 10,000 years ago when it was much wetter there," Cuthbert said to the site. "We know there are these massive lags."
The team said their research showed one of the "hidden" impacts of climate change, and called for immediate action to ensure future generations aren't left high and dry.