Many of the world's aquifers are being pumped dry to support unsustainable agriculture.
We are used to thinking of water as a renewable resource. However much we waste and abuse it, the rains will come again and the rivers and reservoirs will refill. Except during droughts, this is true for water at the surface. But not underground. As we pump more and more rivers dry, the world is increasingly dependent on subterranean water. That is water stored by nature in the pores of rocks, often for thousands of years, before we began to tap it with our drills and pumps.
We are emptying these giant natural reservoirs far faster than the rains can refill them. The water tables are falling, the wells have to be dug ever deeper, and the pumps must be ever bigger. We are mining water now that should be the birthright of future generations.