But reserves are already under pressure as the global population explodes and crop production rises in tandem. An international team of researchers studied the rate at which existing groundwater was feeding into rivers, lakes and wetlands across the planet and how pumping for farming effected that process, known as streamflow.
They found that in around 20 percent of drainage basins the tipping point had already been reached where extraction outpaced streamflow. They also used climate change models to predict how streamflow will diminish in future and found that between 42 and 79 percent of the world's groundwater sites will be unable to sustain aquatic ecosystems by 2050.
Inge de Graaf, chair of environmental hydrological systems at the University of Freiburg, Germany, said this could have a devastating impact. "It's pretty clear that if there's no water in your stream anymore that your fish and plants are going to die," de Graaf told AFP. "About half of irrigated crops rely on groundwater. That's a lot (to lose)." The study, published in Nature, said regions heavily reliant on groundwater for crop production, including Mexico and the Ganges and Indus basins, were already experiencing declining river and stream flows due to overextraction.