“With a changing climate, the increasing severity of flooding and drought, and unsustainable use of groundwater to meet increased food production demands due to population growth, the world’s freshwater resources are under a level of stress unseen before,” said Jay Famiglietti, senior water scientist at the NASA Jet Propulsion Laboratory at the California Institute of Technology. The Nature article, published online today, is based on an unprecedented level of data gathered using NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, other satellites and traditional sources. In this first-of-its-kind study, the authors relied heavily on observations by the GRACE mission of terrestrial water storage. The result is a startling new global map that depicts changing freshwater availability during the 2002-2016 period. “Our study points to a distinctive, underlying pattern of the mid-latitude areas of the world getting dryer, while the bordering tropical and high latitude areas are getting wetter,” said Famiglietti. “The observed trends reinforce the projections of the Intergovernmental Panel on Climate Change models that global precipitation will generally decrease in the mid-latitudes, and increase in low and high latitudes by the end of the century.” Embedded within this pattern are 34 major global hotspots where freshwater storage has changed over the 14-year study period, two-thirds (23) of which have been, or probably been, caused by global change or human water management. A majority of the hotspots (19) are losing water rapidly because of excessive groundwater pumping, or the melting of ice sheets or glaciers. The key environmental challenge of this century could be globally sustainable water resources management, said the authors, noting a recent study that estimates five billion of the global population of 7.6 billion people live in areas where water security is at risk.