The Amazon River basin contains the world’s largest tropical rain forest, with the highest biodiversity of plant species on Earth. The Sahara is the world’s largest, hottest desert — a place where almost nothing grows.
The two places would seem to have nothing in common. Yet dust from the 3-million-square-mile Sahara is an important factor in fertilizing the Amazon. When strong winds sweep across arid northern Africa, clouds of dust rise and sweep westward across the Atlantic, bearing phosphorus. And a lot of this essential nutrient lands in the Amazon basin, which needs that phosphorus because so much is lost annually in floods and surface runoff.
Scientists seeking to understand changes in the Earth’s large-scale ecological systems wanted to know just how much dust was involved. A video shows how images taken by a NASA satellite between 2007 and 2013 enabled researchers to calculate that an average of 182 million tons of dust leaves the Sahara each year, and 27 million tons makes it to the Amazon rain forest. An estimated 22,000 of those tons is phosphorus — roughly equal to the amount of the nutrient the Amazon loses to runoff.
Hongin Yu, lead author of the study based on the satellite data, says the next question is establishing how that dust may affect climate — and how climate change might affect the life-giving dust. “This is a small world,” Yu said, “and we’re all connected together.”