The Amazon rainforest relies on dust from the Sahara

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A single spot in the Sahara desert is responsible for over half the Amazon basin's annual supply of minerals, researchers say.

In a study published in Environmental Research Letters, scientists show that dust winds arising from the Bodélé depression — northeast of Lake Chad — are the main mineral source fertilising the Amazon rainforest in Latin America.

Using recent advances in satellite instrumentation, researchers produced the first quantitative estimate of the dust emission: 56 per cent of the Amazon's total annual mineral supply.

It was known that West African dust winds played an essential role in the Amazon mineral supply. But the rate of emission from the Bodélé depression has not been measured until now.

According to the study, the soil of the Amazon rainforest is shallow, poor in nutrients and almost without soluble minerals. The health and productivity of the Amazon basin depends on nearly 50 million tons of mineral-containing dust transported annually across the Atlantic ocean from the Sahara.

The Bodélé is known to be the biggest source of dust in the world. This has been attributed to its shape and geography. Wedged in a narrow path between two mountain chains, the depression directs and accelerates surface winds.

Lead researcher Dr Ilan Koren, of the Weizmann Institute in Israel, told SciDev.Net the research posed more questions than it answered. Key questions remain, such as for how long the area has emitted such a huge amount of dust, and how long it will continue. “We are now studying how long the Bodélé — and all Sahara regions — have contributed to the Amazon, and what the forest was like before," he said.

Link to the full article in Environmental Research Letters

Reference: Environmental Research Letters 1, 014005/doi:10.1088/1748-9326/1/1/014005