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Nutrients from the Sahara to the Amazon

Satellite image shows wind carrying dust from the Sahara towards South America in 2021


Dust containing minerals from the Sahara desert is carried by the wind to Europe and the Americas in varying volumes. Every year, primarily between January and April when rainfall is heaviest, an average of 52 milligrams per square meter (mg/m2) of iron, 21 mg/m2 of magnesium, and 0.97 mg/m2 of phosphorus cross the Atlantic Ocean and reach the Amazon rainforest, partially offsetting the volume of nutrients that the Amazon River transports from the rainforest to the sea (Atmospheric Chemistry and Physics, November 1). These figures were obtained by researchers from the University of São Paulo (USP) and colleagues from China, the USA, and Germany, who estimated the amount of particles transported through the air between 2013 and 2017 with the aid of a mathematical computer model. According to the study, the annual dust flow averages 2 g/m2 in the rainy season, much higher than in the dry period (August to November), when only 0.35 g/m2 of dust from the desert is carried to the Amazon rainforest. If the wind is blowing in the right direction, the volume can reach 2.6 g/m2, as it did in 2015. “Over millennia, this flow of nutrients has contributed to the rainforest’s exuberance, boosted by nutrients from the Sahara,” says USP’s Paulo Artaxo, who participated in the study.