Although surrounded by the vast Pacific ocean, fresh water is a scarce commodity on Rapa Nui, as the island is known to its inhabitants. No rivers or streams cross its surface and there are only three small crater lakes, which regularly dry up during periodic droughts.
However, as first reported by European explorers in the late 1700s, the people of Easter Island appeared to drink directly from the sea. Today, animals - most famously horses - can be observed doing the same thing.
Due to a quirk of geology, rainwater immediately sinks down through the porous bedrock, where it feeds an underground aquifer. That freshwater emerges at spots on the coastline known as coastal seeps.
Robert DiNapoli, a postdoctoral research associate in environmental studies and anthropology at Binghamton University, explained the phenomenon: “At some of these locations on the shoreline, there is so much water coming out [from the seeps] that it’s basically fresh. It’s somewhat...