Along the coast of northern Chile's Atacama Desert, mesh nets catch the fog that rolls in from the Pacific each morning, dripping water into collection tanks below. The technology is ancient in concept but increasingly vital: for millions of people in coastal arid zones across Chile, Morocco, Eritrea, and South Africa, fog is not weather — it is a water supply. [1]

A piece published Wednesday in Science assembles the clearest picture yet of how fog functions as a freshwater resource and what climate models say about its future. The news is not reassuring. As global temperatures rise, the temperature gradient between cool ocean surfaces and warm inland air — the mechanism that pulls fog ashore — is expected to weaken in many regions. [1] Climate projections suggest the fog belts along some of the world's driest coastlines could retreat or thin significantly by mid-century.

The stakes are not abstract. Fog harvesting systems already supplement municipal water supplies in parts of the Atacama and Morocco's Atlantic coast. Redwood forests in California get up to 40% of their annual water from fog drip. [1] Entire ecosystems are calibrated to a resource that has no entry in most national water budgets.

The Science piece arrives as fog research accelerates. Bay Area scientists launched a multi-year study in January to track fog's chemical composition and hydrological role along the California coast. [1] The findings frame fog not as a curiosity but as infrastructure — one that no government built, and that no government can replace if warming erases it.

-- DARA OSEI, London