With Speed and Violence Fred Pearce - Global Commons Institute

University, two fifths of the dust in the global atmosphere comes from the
Sahara, and half of that comes from Bodele.
Some of this dust stays local. But much of it is carried on the prevailing
winds, which cross the desert wastes of Niger, Mali, and Mauritania before
heading out across the Atlantic. The red dust clouds can grow almost 2 miles
high as they approach America. They cause spectacular sunrises over Miami,
before falling in the rains of the Caribbean and the Amazon. And there have
been a lot of good sunrises in recent decades. The amount of dust crossing
the Atlantic grew fivefold between the wet 1 960s and the dry 1 980s.
The Sahara dust has a series of unexpected effects on the
Americas. According to hurricane forecasters in Florida, during dry, dusty
years in the Sahara, there are fewer hurricanes on the other side of the
Atlantic. It seems that dust in the air interrupts the critical updrafts of warm,
moist air that fuel the storms. Equally surprisingly, desert bacteria caught up
in the winds are being blamed for bringing new diseases to Caribbean coral
reefs, and even for triggering asthma among Caribbean children.
And there is another important link. Saharan dust storms carry huge
amounts of minerals and organic matter that enrich soils widely in the
Americas. Bodele dust seems especially valuable. Its dunes are the dried-out
remains of the bed of the vast Lake Megachad, which covered the central
Sahara until its abrupt demise. Most of the dunes are made not of sand or
broken rock but of the remains of trillions of diatoms, microscopic
freshwater creatures that once lived in huge numbers in the lake. These
fragments blow freely in the wind. That's why they make such plentiful dust
storms. And they also make great fertilizer. If Bodele had any rain, the
diatoms would make rich farmland. Instead, Chad's loss is the Americas'