28 Million Tonnes of Saharan Dust Replenish Amazonian Soils

Tonnes of mineral dust from the Sahara traverse the Atlantic Ocean annually and supply the Amazon rainforest with essential nutrients. Scientists at the Earth System Science Interdisciplinary Center (ESSIC) were able to approximate the amount of Saharan dust and phosphorus that replenish the forest’s leached soils.

In the report published online in the journal Geophysical Research Letters, around 22,000 tonnes of phosphorus settles in the South American jungle every year. This is 0.08 percent of the 27.7 million tonnes of Saharan dust that journeys through the Atlantic. The phenomenon illustrates the importance and behaviour of dust in the Earth’s system. Hongbin Yu, the study’s lead author, said that dust will affect the climate while changes in the climate will affect dust at the same time.

The research team concentrated analysis on the Saharan dust transatlantic transport because it is the most massive and distant dust transport that reaches various regions of the planet. They based their study and estimates on data gathered by NASA's Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite from 2007-2013. Dust samples from the Bodele Depression, stations in Miami and on Barbados were used for estimation of phosphorus content in African dust and the amount being deposited in the Amazon. The results of the study are significant because these highlight the essential role of windborne particles on the planet.

In 2005, scientists studied dust movements and samples from the Bodele Depression in Chad Africa, known as the dustiest place on the planet. Chemical studies reveal that the sediments taken from the former lakebed are rich in phosphorus and iron, which are essential for plant growth. Nutrients in Amazon soils get leached by frequent downpour. Dust transport from the Sahara sustain the forest cover by bringing constant supply of nutrients to the rainforest.

There is a need though to observe the trends further as there is inconsistency in the amount of Saharan dust transported every year. Long-term studies would be pursued before making any conclusions on the phenomenon. An 86 percent difference was observe between the highest amount measured in 2007 and the least in 2011. The research team attributes this change to weather variations in the Sahel, the semi-arid region that stretches across the southernmost area of North Africa. Sustained heavy rainfall promotes plant life that lessens soil exposure to wind erosion. Another probable explanation is the impact of heavy rains on air movements that scoop up dust from the African desert before making the transatlantic transport. The ESSIC is an institute established by the University of Maryland and NASA Goddard Space Flight Center.

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