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Over the past 50 years, humans have extracted the Earth’s groundwater stocks at a steep rate, largely to fuel global agro-economic development. Given society’s growing reliance on groundwater, we explore ‘peak water limits’ to investigate whether, when and where humanity might reach peak groundwater extraction. Using an integrated global model of the coupled human–Earth system, we simulate groundwater withdrawals across 235 water basins under 900 future scenarios of global change over the twenty-first century. Here we find that global non-renewable groundwater withdrawals exhibit a distinct peak-and-decline signature, comparable to historical observations of other depletable resources (for example, minerals), in nearly all (98%) scenarios, peaking on average at 625 km3 yr−1 around mid-century, followed by a decline through 2100. The peak and decline occur in about one-third (82) of basins, including 21 that may have already peaked, exposing about half (44%) of the global population to groundwater stress. Most

In the early 1970s, ecologist Barry Commoner wrote The Closing Circle, in which he discussed the rapid growth of industry and technology and their persistent effect on all forms of life. He suggested that we can reduce the negative effects by sensitizing, informing and educating ourselves about our connection to the natural world. Commoner summarized the basics of ecology into what he termed “laws of ecology.” Others have also used this idea to develop simple statements that help us understand and remember our connections to nature. Here are five laws of ecology: