Climate change is looming large in the island state of Indonesia, where rising sea levels pose a major risk. But it’s actually a different problem that might force inhabitants of the Spermonde archipelago lying off Southern Sulawesi to leave their islands: drinking water is running low, and the existing water quality is getting worse.

A team of German and Indonesian scientists is pointing to climate change as a major source of that problem. Many of the islands get their drinking water from a freshwater lens – a layer of drained rainwater that accumulates in the soil. Just one lens is about ten to twenty centimeters deep and covers a large part of the archipelago.

Because of climate change, the island region is expected to be face more and more extreme weather patterns, from droughts to severe rain. But the torrents of water that hit the earth during monsoon seasons don’t have enough time to seep into the soil. Instead, the lion’s share flows over the earth’s surface and into the ocean. And the growing amount of sealed surfaces make matters worse: because the area is densely populated, a lot of ground is covered by streets and buildings. Plus, heavy storms – expected to become more frequent – are washing seawater onto the islands and into wells.

Still, climate change is just partly to blame for the dwindling water resources. Since the beginning of 20th century, not only the number of inhabitants but also the demand for drinking water has doubled. As there are no rules preventing anyone from digging wells anywhere and no official limit on how much water may be drawn from them, many locals have dug wells themselves. But they have little knowledge of the soil’s properties or the freshwater lenses when pumping. And when salty water from deep below mixes with the fresh water near the surface, it becomes increasingly brackish – bad for people and the environment.