Where sand dunes disappear on Sable Island, so does the underground freshwater supply, according to new research underscoring the importance of dunes to the island's ecosystem. The dunes serve as a natural barrier, protecting against the relentless waves and temporary salinization of groundwater caused by ocean flooding. Dunes also help refresh the water table by funnelling water from rain and snow into aquifers that, in some places, are 40 metres deep.