Saharan Dust: Great for Soil, Bad for Oceans

​Taylor Wilson, Conservation Technician and Outreach Assistant

You may have heard about the Saharan dust storms that blew across the country in the last few weeks. Believe it or not, this is a common phenomenon that happens yearly at some degree. This year, however, is the most dust we’ve had in 50-60 years. This type of dust storm can look like haze, loss of long distant visibility, milky skies, or a fine dust covering cars and homes especially after it rains.   

​The yearly dust storms are a part of a natural phenomenon that connects two polar opposite ecosystems: the Saharan desert to the Amazon rainforest. 

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How does this work?

Milky L.A. skies courtesy of Christopher Bannan on Twitter

1. In the Saharan summer the sun warms the sand, which warms the air near the surface.

2. This hot air rises and brings small particles of Saharan soil with it.
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3. As the hot, dusty air rises it joins in with the strong prevailing easterly winds and blows across the Atlantic to South America and the Gulf of Mexico. 

​Saharan soil is full of iron and phosphorus. These minerals act as a fertilizer in the Amazon, replenishing the minerals that are often leached out of soils by the frequent rains. Think of it this way: when you have a big year in your garden you have to replenish the nutrients lost in the soil. The Amazon needs the same thing. ​

Fish kill caused by algal blooms. Photo from arcgis.com

​​The issue with this comes from the deposit of phosphorus laden soil (dust) into bodies of water. This is especially a problem in the Gulf of Mexico. The gulf already experiences an abundance of phosphorus each year from agricultural runoff. Too much phosphorus can cause algal blooms (red tides), fish kills, and a myriad of other ecological issues. While Saharan dust storms are a natural event that deposit dust into the gulf every year, in conjunction with the algae issues already present from human activities water quality becomes a major problem.

Since the 2020 dust storm is so large, fish kills and water quality may be worse this year. In 2018 the algal blooms were worse than normal, and it was speculated that Saharan dust may be the culprit. Looking at the graph below, you can see that 2018 had a larger than average dust storm. Time will tell how the gulf is impacted in 2020.
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As the dust deposits over parts of the United States this year we may experience a variety of impacts in soil and water quality. These likely won’t be large enough to visualize an impact and there’s nothing we can do to control it. What you can do is enjoy the beautiful sunsets caused by light scattering dust particles, stay indoors if you experience respiratory issues, and continue to protect our soil and water resources where we can control impacts.  

​​Want to see more?

Visit EarthWindMap and set the Mode to Particulate. This shows you how the dust is moving in real time.  

For more information, visit the links below. 

• NASA's webpage on Saharan dust
• The Atlantic's Article on Saharan dust

Graph showing the AOD, a measure of dust, of storms in different years.