Chile’s Atacama Desert is one of the driest places on Earth, with some weather stations recording virtually no measurable rainfall for decades. Yet along parts of its Pacific coast, life survives because of a dense marine fog called the camanchaca.
The fog forms over the cold Humboldt Current and moves inland toward the coastal cliffs. Although it does not produce conventional rainfall, tiny droplets condense on rocks, plants and specially designed mesh collectors, providing a crucial source of moisture.
The fog supports unique lichens, cacti and other organisms that can absorb moisture directly from the humid air. Some lichens can rapidly become active when humidity rises and then dry out again when the fog disappears.
The phenomenon has also helped human communities. In the fishing village of Chungungo, northern Chile, large fog collecting nets were installed to capture droplets from the marine layer. The collected water has been used for drinking and agriculture, demonstrating that fog can become a practical water resource in an extremely dry environment.
Research around Alto Hospicio suggests that appropriately located fog collectors could potentially produce several litres of water per square metre of collection surface each day, although yields vary greatly depending on weather and location.
The system is also environmentally important. Fog delivers moisture and marine derived nutrients to organisms living on the desert’s coastal cliffs. However, these ecosystems are highly vulnerable to changes in the timing, altitude and frequency of fog caused by changing atmospheric and ocean conditions.
The Atacama shows that an ecosystem does not necessarily need rainfall to survive. In some places water suspended in the air can sustain plants, wildlife and even human communities.