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Amazing: Saharan dust helps fertilize Amazon rainforest

The Sahara Desert and the Amazon rainforest are about as far apart as it gets in terms of similarity. One is dry and extreme, while the other is lush, moist and temperate. However, according to new NASA satellite findings, the two are inextricably, perfectly connected: Every year, nutrient-rich dust from the Sahara deposits almost the exact amount of phosphorous that washed out of the Amazon.

“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,” said lead author Hongbin Yu, an associate research scientist at the Earth System Science Interdisciplinary Center (ESSIC), a joint center of the University of Maryland and NASA’s Goddard Space Flight Center.

All told, the dust deposits 22,000 tons of phosphorous per year, much of it coming from the Bodélé Depression in Chad. As an ancient dry lake bed, it’s home to the remains of millions of dead microorganisms, which are loaded with phosphorous.

That’s essential for the Amazon rainforest, as frequent and heavy rains deplete the supply of phosphorous over time. Indeed, it appears that the Amazon couldn’t exist without the Sahara.

The data were collected by NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite between 2007 and 2013. Moving from Africa to South America and beyond the the Caribbean Sea, it’s the largest dust migration on the planet. By measuring the phosphorous in the Bodélé Depression, they were able able to model how much makes it to the Amazon. The period of data collection isn’t long enough to define a long-term trend, however.

“We need a record of measurements to understand whether or not there is a fairly robust, fairly consistent pattern to this aerosol transport,” said Chip Trepte, project scientist for CALIPSO at NASA’s Langley Research Center, who was not involved in the study.

It’s an important step in understanding how dust and other aerosolized particles make their way around the world. Rainfall in parts of the Sahara, for instance, have an impact on how much dust makes it to the Amazon. Increased vegetation in one region may lead to less soil exposure. Alternatively, increased rainfall could be a result of wind patterns unfavorable to the transatlantic migration.