The Sahara Desert in North Africa and the Amazon rainforest in South America are separated by a distance of 3,000 miles, including a 1,600-mile expanse of the Atlantic Ocean. At first glance, the two regions would appear to have no connection to each other. However, according to a recent study published in the journal Geophysical Research Letters, millions of tons of nutrient-rich dust from the planet’s largest and hottest desert journey across the Atlantic every year, bringing phosphorus and other fertilizers to the world’s largest tropical rainforest.
For the first time, a team of scientists has been able to quantify the exact amount of dust that makes this transatlantic journey. Using data collected by NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite between 2007 and 2013, the researchers, led by Hongbin Yu -- a scientist at the University of Maryland -- calculated that each year, 182 million tons of dust leaves the Sahara Desert. Of this, over 27 million tons is deposited in the Amazon basin.
The Saharan dust, which contains huge deposits of dead microorganisms, is rich in phosphorus, which acts like a fertilizer and is essential for the Amazon rainforest’s survival.
“In the tropical region, phosphorus is quite limited, so it’s important to estimate how much dust from the desert is transported to Amazon,” Yu said, in a statement released by NASA. Incidentally, the phosphorus that reaches the Amazon -- nearly 22,000 tons a year -- is almost the exact amount lost due to surface run-off triggered by floods.
However, according to the study, the amount of dust transported to the Amazon changes from year to year. The researchers found that there was an 86 percent change between the highest amount of dust transported in 2007 and the lowest in 2011. Yu and his colleagues believe that this difference is the result of a variation in rainfall in the Sahel region, which is a long strip of semi-arid land on the southern border of the Sahara Desert.
“When the Sahel region was dry, the dust transport to the Amazon in the next year would increase. When it was wet, the dust transport would decrease,” Yu said, in the statement.
In the future, Yu and his colleagues plan to use data gathered by CALIPSO to study how the distribution of aerosols like smoke from fires and biological particles such as bacteria, fungi, pollen, and spores released by the plants are affected by dust from the Sahara Desert.
“This is a small world,” Yu said. “And we're all connected together.”