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Study: Saharan Dust Feeds Amazon Rainforest

Saharan Dust Feeds Amazon Rainforest
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The barren sands of the Sahara Desert sustain life in an unexpected place: the Amazon Rainforest across the Atlantic Ocean, according to new research.

A report in Geophysical Research Letters shows that enough Saharan dust blows across the Atlantic each year to roughly replace the phosphorous that washes out of the Amazon’s poor soils during rainfall and flooding.

Huge plumes of storm-blown Saharan dust are among the planet’s most prominent atmospheric features in satellite images, “second only to clouds,” said University of Miami atmospheric scientist Joseph Prospero.

Prospero first recognized in the 1970s that considerable amounts of Saharan dust can blow all the way across the Atlantic Ocean.

It’s been hard to accurately measure exactly how much. But “It’s obvious there’s a lot of dust,” he said. “When it rains in Barbados or even here in Miami during the summer months, you actually get a layer of mud in the bottom of a bucket.”

All that dust can lower air quality. But the new research shows it also does some good.

Plant food

Scientists used satellite measurements to track Saharan dust as it blew over the Atlantic.

Over the course of seven years, they found that an average of 28 million metric tons per year fell in South America’s Amazon River basin. It included about 22,000 tons of phosphorus, a nutrient critical for plant growth and a key ingredient in commercial fertilizer.

“African dust could play an important role in preventing phosphorus depletion from the [Amazon] basin,” said University of Maryland atmospheric scientist and lead author Hongbin Yu.

Earlier research showed dust from Asia has helped sustain Hawaii’s rainforests for millennia, he noted. Other studies have found Asian pollution crossing the Pacific Ocean to cloud skies in the United States.

It all shows that our small planet is more interconnected than we imagine.

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    Steve Baragona

    Steve Baragona is an award-winning multimedia journalist covering science, environment and health.

    He spent eight years in molecular biology and infectious disease research before deciding that writing about science was more fun than doing it. He graduated from the University of North Carolina at Chapel Hill with a master’s degree in journalism in 2002.