In 2015, scientists reported evidence that vast plumes of dust from the Sahara Desert help replenish phosphorus in the Amazon rainforest, linking the world’s largest desert to its largest rainforest through what researchers described as one of the planet’s most significant natural nutrient transfers. The findings were detailed in papers led by atmospheric scientist Hongbin Yu of the University of Maryland’s Earth System Science Interdisciplinary Center (ESSIC), working with NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Results were published in Geophysical Research Letters and in a related study in Remote Sensing of the Environment.
A 10,000-mile atmospheric river
Scientists have known for decades that large plumes of Saharan dust travel thousands of miles across the Atlantic Ocean, forming vast tan clouds visible from space before settling over South America. In April 2015, NASA described the connection as a “10,000 mile long intermittent atmospheric river of dust” linking Africa and the Amazon basin. Using data from NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite, CALIPSO, launched in 2006, Yu and colleagues quantified for the first time how much dust completes the trans-Atlantic journey. According to the team, an average of 182 million tons of dust leave the Sahara each year. Of that, 27.7 million tons, about 15 percent, are deposited over the Amazon basin annually. Another analysis reported 28.8 million tons reaching the region. NASA equated this to roughly 689,290 semi-trucks’ worth of dust departing the desert and 104,908 dust-filled semi-trucks being dumped into the Amazon each year.
The lidar instrument aboard the CALIPSO satellite sends out pulses of light that bounce off particles in the atmosphere and back to the satellite. It distinguishes dust from other particles based on optical properties. Credits: Scientific Visualization Studio, NASA’s Goddard Space Flight Center
CALIPSO, short for “Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation,” uses a laser-based lidar instrument to scan the atmosphere and measure the vertical distribution of dust and other aerosols, enabling three-dimensional tracking of the Sahara–Amazon plume between 2007 and 2013.
Phosphorus: a missing nutrient
The Amazon rainforest is renowned for its biodiversity but is also characterised by nutrient-poor soils. Around 90 percent of Amazonian soils are deficient in phosphorus, an essential nutrient for plant growth. Heavy rainfall and river systems wash tens of thousands of tons of nutrients, including phosphorus and nitrogen, out of the basin each year. Across the Atlantic, the Sahara contains significant phosphorus deposits, particularly in the Bodélé Depression in Chad, an ancient lakebed rich in the remains of long-dead microorganisms. Frequent dust storms from this region lift phosphorus-rich particles into the atmosphere. In a 2015 paper in Geophysical Research Letters, Yu and colleagues provided the first satellite-based estimate of how much phosphorus is transported within that dust. After analysing CALIPSO data alongside dust samples collected from research stations in Chad, Barbados and Miami, the team concluded that approximately 22,000 tons of phosphorus reach the Amazon annually from the Sahara.
An aerial view of fishing boats from the Caju Una community fishing in the Porto stream, Marajo Island, Para state, Brazil, Saturday, Nov. 1, 2025. (AP Photo/Eraldo Peres)
That figure closely matches the estimated amount of phosphorus lost each year from the rainforest through hydrological processes. “This is a small world, and we’re all connected together,” Yu said at the time. The researchers wrote in the paper: “This suggests that African dust may have important implication for maintaining the health of Amazon rainforests over the long term. Without the phosphorus input from African dust, the hydrological loss would greatly deplete the soil phosphorus reservoir over a time scale of decades or centuries and affect the health and productivity of the Amazon rainforest.” They cautioned, however, that uncertainties remain, noting that they still do not know “the amount of dust needed to provide adequate phosphorus for maintaining the productivity of the Amazon rainforest.”
Extreme variability and the Sahel link
The researchers also found that the volume of dust transported across the Atlantic fluctuated sharply from year to year. Between 2007 and 2011, there was an 86 percent difference between the largest dust plume, recorded in 2007, and the smallest, in 2011. Yu and his colleagues identified a potential link between rainfall in the Sahel, a semi-arid region south of the Sahara, and dust transport. When rainfall in the Sahel was higher, the amount of dust carried across the Atlantic decreased.
Dust and sand blown from the Sahara Desert covered parts of Europe, turning the sky and snow orange.
The precise mechanism remains uncertain. Yu suggested that increased rainfall might promote vegetation growth in the Sahel, reducing exposed soil available for wind erosion. Alternatively, rainfall patterns may correlate with wind systems that lift dust into the upper atmosphere, which acts as a transport corridor toward the Americas. “We know that dust is very important in many complex ways,” Yu said. “Dust affects climate and, at the same time, climate change will affect dust.” He added: “As researchers, we ask ourselves two basic questions: ‘How much dust is transported? And how does climate change affect the amount of dust that travels across the Atlantic?’”
A global Earth system connection
Each individual dust particle measures only a fraction of the width of a human hair, yet collectively they form one of the largest intercontinental material transfers on Earth. The work by Yu and colleagues underscored the extent to which distant ecosystems remain interconnected through atmospheric processes. By quantifying both the total dust flux and its phosphorus content, the 2015 studies provided evidence that the Sahara plays a measurable role in sustaining the long-term nutrient balance of the Amazon rainforest, even as scientists continue to investigate how climate variability may influence that delicate trans-Atlantic exchange.
