Thousands of feet above your head, microbes are living—and reproducing—in the tiny drops of water that make up clouds. “This suggests that clouds are quite literally another habitat for life on Earth, and with an average covering of 60% of the planetary surface represent a pretty major ecosystem,” says Scharf.
Along with clouds, new research found that microbes ride the vast streams of dust that blow across the planet, a global cycle that brings Asian dust to North America, African dust to South America, African dust to Australia and seemingly every other combination imaginable.
It’s been estimated that about 7.1 million tons (64 teragrams) of aerosols – dust, pollutants and other atmospheric particles, including microorganisms – cross the Pacific each year. The aerosols are carried by wind storms into the upper reaches of the troposphere. The troposphere, the layer of air closest to earth up to about 11 miles (18 kilometers), is where almost all our weather occurs.
Riding the storms, the microbes can cross the Pacific Ocean in just over a week. “When the wind blows,” says Scharf, the population of Asiatic microbes in the continental U.S. climbs. “This means that there is real mixing of species going on, a microbial pollution that may have consequences for all manner of things, including local ecosystem function and even disease.”