African smoke fertilizes Amazon rainforest

Smoke from fires in Africa may be the most important source of fertilizer in the Amazon rainforest, Tropical Atlantic and Southern oceans, a new study has found. The smoke is particularly rich in phosphorus.

Nutrients found in atmospheric particles, called aerosols, are transported by winds and deposited to the ocean and on land where they stimulate the productivity of marine phytoplankton and terrestrial plants leading to the sequestration of atmospheric carbon dioxide.

A new study led by researchers at the University of Miami has now found that such particles from fires in Africa may be the most important fertilizer in the Amazon Basin and Tropical Atlantic Ocean.

“It had been assumed that Saharan dust was the main fertilizer to the Amazon Basin and Tropical Atlantic Ocean by supplying phosphorus to both of these ecosystems,” said senior author Cassandra Gaston in a statement. “Our findings reveal that biomass burning emissions transported from Africa are potentially a more important source of phosphorus to these ecosystems than dust.”

The researchers analyzed aerosols collected on filters from a hilltop in French Guiana, at the northern edge of the Amazon Basin, for mass concentrations of windborne dust and their total and soluble phosphorus content, according to the statement.

They then tracked the smoke moving through the atmosphere using satellite remote sensing tools, which enabled them to estimate the amount of phosphorus deposited to the Amazon Basin and the global oceans from African biomass burning aerosols using a transport model.

“Aerosols play a major role in Earth’s climate, however, there is a lot that we don’t understand regarding how they affect radiation, clouds, and biogeochemical cycles, which impedes our ability to accurately predict future increases in global temperature,” added Gaston.

“These new findings have implications for how this process might look in the future as combustion and fire emissions in Africa and dust transport patterns and amounts change with a changing climate and an increasing human population.”

Photo credit: Anna & Michal/ CC BY 2.0

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