The play between dust and life has continued to pique the interest of scientists especially due to its’ new kid on the block’ status. It turns out that the Sahara desert supplies the world’s oceans as well as the Amazon rainforest with valuable dust. While this has not been the case for a majority of Earth’s history, it is today.[mfn] The source is mainly from the Bodélé Depression in Chad where rocks in the region are broken down by processes such as weathering, erosion and pulverization.[mfn]
So you might be thinking why is the dust from here any different from dust everywhere else in the world? The answer is minerals, more specifically iron and phosphorus.These are vital in the development of plant life as they assist them in making chlorophyll, photosynthesis, transfer genetic material and maintain chloroplast structure.[mfn]
The deep oceans have access to sunlight, carbon and water for plant growth but they do not have enough minerals. This is why the deep ocean is blue while nutrient rich coastal waters are green. Phytoplankton (microscopic plants in the ocean) are known for aiding in carbon dioxide absorption but the restricted amounts of iron and phosphorus means they can only absorb a limited amount from the atmosphere.[mfn]
The deep oceans have access to sunlight, carbon and water for plant growth but they do not have enough minerals. This is why the deep ocean is blue while nutrient rich coastal waters are green. Phytoplankton (microscopic plants in the ocean) are known for aiding in carbon dioxide absorption but the restricted amounts of iron and phosphorus means they can only absorb a limited amount from the atmosphere.
Researchers from the University of South Carolina thought up a way to sample specific quantities of seawater to identify the various isotopes of iron in it.[mfn] They collected up to 600 samples of seawater from across the North Atlantic and set to work. They found that some of the iron came from deep within the crust through hydrothermal vents, another fraction came from sediment from the South African coast, and another came from oxygenated muds on the American East coast. What was really impressive is that about 71% to 87% of the iron samples were delivered by dust storms from the Sahara desert. Who’d have thought that a myriad of organisms in the deep ocean would directly depend on one of the world’s harshest regions?
In 2006, Israeli researchers found that more than half the dust needed to fertilize the Brazilian rainforest blew in just from Chad.[mfn] Two years later a team in Liverpool, UK confirmed the role of Saharan dust as a mineral source for the Atlantic Ocean. An estimated 50 million tons of Saharan dust is blown across the Atlantic to the Amazon every year. [mfn]
Researchers have begun to theorize that airborne dust might play a role in cloud formation and have a spillover effect on climate related catastrophes like hurricanes.[mfn] This dust could help us tweak the global thermostats and potentially mitigate effects from global warming. The verdict is still out but looking extremely hopeful.
When researchers found out about North Africa’s importance to the world’s oceans I’m pretty sure they weren’t expecting it to be dust. The Sahara desert is simultaneously fertilising the Amazon rainforest and Atlantic ocean while providing a natural mitigator to the effects of global rising temperatures. While this isn’t enough for us to let our guard down, who knows what a few more years of research can uncover?
Juliana Nogueira et al., “Dust Arriving in the Amazon Basin over the Past 7,500 Years Came from Diverse Sources,” Communications Earth & Environment 2, no. 1 (January 4, 2021): 1–11, https://doi.org/10.1038/s43247-020-00071-w.
Joana A. Rizzolo et al., “Mineral Nutrients in Saharan Dust and Their Potential Impact on Amazon Rainforest Ecology,” Journal of Atmospheric Chemistry and Physics, July 7, 2016, https://doi.org/10.5194/acp-2016-557.