Humans are shifting freshwater resources across Earth. This will continue as people move and eat more. Many equatorial regions are drying, while tropical areas are getting wetter. If this continues, many cities could struggle to find enough water in the future. NASA spent 14 years studying freshwater resources. It was part of a mission called GRACE, which stands for Gravity Recovery and Climate Experiment.
Jay Famiglietti, a co-author of the research, said: "The study shows that humans have really drastically altered the global water landscape in a very profound way." He warned that: "We see it as a driver of climate change." Professor Famiglietti said that over 40 per cent of the hot areas looked at in the research were drier than twenty years ago. He said this was because of human activity. One reason was too much pumping of groundwater for farming.