The world’s dustiest place keeps the Amazon alive

The Tweet: “Sand from the Sahara desert is blown by the wind all the way to the Amazon and fertilizes the rainforest by recharging its minerals.”

Dust from one of the least hospitable locations on Earth provides life giving nutrients to the Amazon rainforest. Each year 40 million tons of dust is transported from the Sahara, across the Atlantic to the Amazon basin. Here, the dust re-fertilise the soil, giving back many of the minerals needed to support such a rich ecosystem. Scientists have foundthat more than half of all the dust blown over to the Amazon comes from a single spot in the Sahara that covers just 0.2 per cent of the desert’s surface. It’s called the Bodélé depression.

Located northeast of Lake Chad, the Bodélé depression is a large basin once thought to be part of a much larger lake. The depression is located between two mountain chains that channel and accelerate winds over the desert’s surface. Now the Bodélé depression is labelled the dustiest place on Earth, and each day 0.7 million tons of dust is whipped up from its surface and cast high and wide, with much of it reaching the Amazon.

Joseph Prospero, an atmospheric chemist at the University of Miami, studies the dust blown across the Atlantic from the Bodélé depression. “Looking at satellite images, day after day you see these huge plumes coming out of that region,” he said.

The nutrients carried in the dust are essential to supporting the Amazon, as Charlie Bristow, a sedimentologist at the University of London and lead author of a study into the Bodélé depression published in 2010 explains: “The Amazon is essentially a leached or leaching system,” with much of the soil nutrients washed away in rains or carried away in the rivers, “so although it is very productive, it is actually quite nutrient-poor.”

Minerals like phosphor and iron are found in the dust particles blown to the Amazon. These are needed in many essential plant functions. The dust is rich in these important minerals because they are residues from the desert’s former life as a lake bed. Dubbed Megachad, the ancient lake would have been “bigger than all the Great Lakes of North America put together”, Bristow says. “Pretty close to the area of California.”

So a huge lake the size of California, now dried up and forgotten, is responsible for one of the largest, richest and most diverse ecosystem on the planet. The dustiest place on Earth keeps the Amazon alive.

Image: NASA/ Flickr

This post was first published on The Untweetable Truth (11/02/2014)

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