Our Planet's Connections Across Oceans of Air
How Saharan dust sustains the Amazon on a world where everything is globally connected
Our world is one massively interconnected system of processes.
The spinning of the outer core drives the dynamo that sustains our magnetic field, which in turn leaves an imprint in some iron-bearing minerals in rocks and also allows for adult sea turtles, salmon, and some birds to return to the exact location where they were born.
The heating of the rock in the Earth’s mantle drives the convection that moves large amounts of rocky material, acting like a viscous fluid on geological time scales (though the mantle is not “molten”—it’s definitely solid rock). The heating from the mantle can drive crustal melting, leading to magma production and even lava if the material erupts volcanically at the surface. Some mantle rocks will sometimes get trapped on land (creating groovy systems for scientists who want to study geochemical processes related to those rocks, like water-rock reactions and geological hydrogen production—something my PhD advisor, Alexis Templeton, has been studying). Our mantle is connected to the surface of our planet in more ways—most important of all might be our plate tectonic system that allows for the continual production and recycling of crustal materials (and might have been one key feature to the development and diversification of life on Earth).
Up here at the surface of the planet, we can see the dynamics of connection on an incredible scale as well. The hydrological system allows for water to evaporite, condense, precipitate, and then coalesce through runoff and drainage—water is moved about in the atmosphere but also through surface and subsurface systems, sometimes getting trapped in aquifers below the surface or traveling over time to the oceans. Life itself has become incredibly connected to Earth’s surface processes—our eating, and breathing, and moving, and producing biomass all have give-and-take operations with the abiotic parts of our world. We humans are now acting as forces of geological and atmospheric change—we extract organismal remnant carbon from the subsurface, burn it for energy, emit that carbon along with other industrial gases into our atmosphere, and we even dig up and move remarkable amounts of Earth’s crust every year for our mining, industry, construction, and more.
It’s fun to think about it all. This marvel of interconnected systems—rivers of wind, deep sea currents, oceans teeming with life, forests abounding with organisms reaching out for starlight, magnetic and chemical patterns adopted within the rock and the living things, a constant bombardment of radiation and solid material from space while also shedding some of our world back to space, and then being part of a larger celestial realm that can inspire vocal bursts of transcendence.
One such connection across our planet comes from the way that the atmosphere can lift up and move organisms and particles of dust and other materials around the planet. One great example of this is in the way that the Amazon rainforest is fertilized by dust from the Saharan desert.
I've been through the desert on a horse with no name—which then carried me from the Sahara to the Amazon
Some of the dust from the Sahara goes on a most excellent adventure—some of it even landing as far away as the Amazon rainforest.
The Amazon is fertilized by a 5,000+ mile-long atmospheric conveyor belt. Dusts from the Sahara were first discovered to be raining down in the Caribbean and other regions around the Americas as early as the 1950s and 1960s. With developments of Earth observing satellites and better knowledge of atmospheric circulation, we started learning more and more about the connections and importance of this dust with regions like the Amazon.
In 2015, a multiyear research study by a team led by Dr. Hongbin Yu at NASA’s Goddard Space Flight Center quantified this massive transfer of material. Each year, an estimated 182 million tons of dust is carried by wind from regions like the Bodélé Depression in Chad—one of the most significant dust-producing regions on Earth. Of that, 27.7 million tons makes its way to the Amazon Basin, delivering crucial nutrients, especially phosphorus, that sustain the lush ecosystem.
One of the most important resources being delivered by this global atmospheric dispersion is phosphorus—a vital nutrient for plant growth.
Rainforests are the most biodiverse regions of our planet. While making up only some 2% of the land area of the planet, it’s estimated that rainforests contain more than half of all the species of plants and animals alone. And yet, it’s well known that the soils of rainforests tend to be extremely nutrient poor. Due to all of the trees and other plants, most of the nutrients are taken up from the soils. So that left a mystery for some time about where the necessary phosphorus was coming from to allow so much continued growth and biodiversity in the Amazon—until the delivery of the dusts from the Sahara were better explored.
Of the 27+ million tons of dust traveling across the planet from Africa to South America and coming down in the Amazon Basin, the phosphorus content alone is estimated to be some 22,000 tons annually, replenishing what is lost to natural erosion and rainfall in the rainforest.
This atmospheric bridge between two vastly different ecosystems illustrates the complex, life-sustaining feedback loops that operate on a planetary scale here on Earth.
And we’ve continued to refine our understanding of these nutrient cycles. Recent studies suggest that changes in global climate patterns, such as shifts in the frequency and intensity of the North Atlantic Oscillation, may affect the amount of dust transported each year. Furthermore, some researchers have explored how fluctuations in Saharan rainfall influence dust emissions, revealing that a wetter Sahara could significantly reduce dust transport over time.
On top of that, though, a recent study led by Juliana Nogueira explored the variation in sources of wind based nutrients in the Amazon Basin over the last 7,500 years by examining sediment cores from Lake Pata (within the Amazon rainforest). Their research shows a variety of likely sources outside of the Saharan dust for influencing the nutrient arrival in the rainforest over the millennia. They found connections with other regions in the north and south of Africa as well as soils from the central Andes mountains and wind deposited materials from Argentina being potential sources. They even show that southern African sources of dust may have played a larger role in delivering nutrients to the Amazon than the Saharan region in the past.
Overall, the connections between the atmosphere as a driver for lifting and transporting material around the planet and the health of the world's dynamic ecosystems is even wilder than many of us had thought back in 2015 (that’s when I personally had first read about the Saharan dust and Amazon connection).
There’s an awesome article from 2022 in Eos called Africa’s Earth, Wind, and Fire Keep the Amazon Green by J. Besl that’s worth a read if you want to explore more about the wind-laden connections between the Sahara and the Amazon.
All We Are is Dust in the Wind
This story of Saharan dust and Amazonian biodiversity offers us more than scientific intrigue—it provides a powerful and immediate view of our interconnected world.
I served for many years during my graduate studies as a volunteer exhibit facilitator at the Denver Museum of Nature and Science (DMNS). I love the museum, and have been honored in having gone back many times now to serve as a speaker in the 60 Minutes in Space lecture series. One of my favorite exhibit pieces in the museum that I’ve used to explore a range of topics with museum members and guests was the Science on a Sphere exhibit, where large 3D datasets from Earth (and other worlds) can be shown on a spherical display. Among the many datasets to explore—including the tracking of large passenger jets around the world, showing social media connections across the planet, and satellite based imagery of wildfire, squid fishing, and city lights at night—there are several datasets showing atmospheric chemistry, winds, and dispersal. It was a fantastic way to help others visualize the flow of material from Africa to South America borne on the winds (check out a digital version of the dataset on the Science on a Sphere website).
Of course, there are lots of great ways to visualize the movements of the dust. Here’s one fantastic video from NASA's Goddard Space Flight Center (with credit to Mark Malanoski (Global Science and Technology, Inc.) and Joseph V. Ardizzone (NASA/GSFC)):
Visualizing these patterns of connection can help us to think about the ways that our lives are so dependent on the processes of the Earth—from the spinning of the Earth’s core and flows of solid rock in the mantle to eruptions of lava, atmospheric dispersal of materials, movements of water, and the growth and development of life around the world.
Just as the biodiversity of the Amazon rainforest relies on distant nutrients for its survival, our human societies and our behaviors are impacted by change across the globe. None of us exists in isolation—no matter what kind of xenophobic or nationalist tendencies a government or a people may have. The coffee in your cup (if you’re a coffee drinker) might be grown on a hillside in Colombia, the bananas on your table in Ecuador, and the electronic devices we use every day are the products of raw materials sourced from multiple continents. And our mining and industrial behaviors in some regions impact our health and behaviors in other regions. Global trade connects the livelihoods of farmers, manufacturers, and merchants, creating webs of dependency so intricate that disruptions anywhere can ripple through supply chains, impacting what we eat, wear, or use.
And it's not just trade that binds us. Shifting weather patterns and intensifying climate events are already changing how and where we live, farm, and work. Droughts in the American West have led to water rationing, wildfires, and changes in agricultural output. Rising sea levels are impacting coastal communities, forcing governments to invest in new infrastructure or for people to consider relocation plans. As storms become stronger and seasons less predictable, the interconnected nature of human existence becomes ever more apparent—reminding us that, like the Amazon and the Sahara, we too are part of a global system of connected processes.
All of life as we know it has been born of the Earth, but the planet itself is also active and dynamic and arguably alive. As we like to say at Blue Marble Space, life is a planetary process.
Over the past 4 billion (ish) years, life has originated, evolved, adapted, thrived, been challenged, and become fully integrated into the processes of the planet. We humans have a long lineage of connection to that integration. We’ve built our lives from the connections we share with other lifeforms and with the world’s geological and atmospheric processes. We are riders on the Earth together, as Archibald MacLeish once remarked.
We’re born, live out our lives, and die on a world for which we ourselves form part of that intricate and connected system.
Perhaps we’re all a bit of dust in the wind.