It might sound like something out of a science fiction novel, but is actually the product of years of scientific observation. Atmospheric scientists at NASA’s Goddard Space Flight Center in Maryland have found that clouds of dust from the Sahara desert end up in the Amazon, where they provide essential nutrients to the tropical rainforest.
Satellites images and data collected by NASA’s CALIPSO satellite show dust clouds from the world’s largest desert, which covers a third of the African continent, traveling 3,500 miles across the Atlantic Ocean to fetch up in the South American rainforest. Amazingly, the dust contains precisely those nutrients needed by plant life in the Amazon.
Data collected over the years from 2007 to 2013 shows that an average of 182 million tons of dust from the Bodélé depression in Chad travels across the Atlantic each year. The dust, originating at the site of an ancient lake bed, is rich in phosphorous due to the presence of large quantities of decayed microorganisms.
Phosphorous is an essential plant nutrient, and the basic component of commercial fertilizer. It is also in short supply in the Amazon, where the soils are poor in nutrients. Its only local source of phosphorous is decaying plant matter. It is also being steadily depleted as rainfall and floods wash it away into rivers and streams. The dust carries 22,000 tons of phosphorous to the Amazon each year, almost exactly replacing the amount that is lost.
Hongbin Yu, lead scientist on the project and his colleagues chose to study the Sahara dust because it is the largest transport of dust on the planet. The amount of dust transported each year varies considerably, depending upon the amount of rainfall in the Sahel. The larger goal of the study is to determine the relationship between atmospheric dust and other aerosols and climate change.
Yu said: “We know that dust is very important in many ways. It is an essential component of the Earth system. Dust will affect climate and, at the same time, climate change will affect dust. First we have to try to answer two basic questions. How much dust is transported? And what is the relationship between the amount of dust transport and climate indicators?”
