About 7,000 years ago, the Sahara Desert was a lake teeming with micro-organisms and algae. When this lake dried up, sand rich in nutrients – especially phosphorus – remained and became what we now know as the Sahara. The Amazon Rainforest – in turn – is a crucial ecosystem for regulating the Earth's climate, representing about half of the remaining tropical forests on the planet. Changes in forest cover and productivity can have significant consequences on the carbon cycle, atmospheric circulations, hydrological cycle and climate at regional and global scales.

The geographical distance between the Sahara Desert and the Amazon Rainforest is more than 5,000 kilometers, but the relationship between these two biomes is surprising and essential to maintaining biodiversity in the largest tropical forest in the world: study by NASA (National Aeronautics Administration) and Space – US federal government agency responsible for research and development of technologies and space exploration programs) revealed that more than 27 million tons of sand and about 22 thousand tons of phosphorus travel from the Sahara to the Amazon every year . In addition, the researchers measured the chemical formation of substances in the atmosphere of the Amazon, using an optical instrument called Lidar, which demonstrated the presence of elements such as aluminum, manganese, iron and silicon in the dust found at the site, all in proportions similar to those found in the Sahara dust.

Surprisingly, the data from this research prove that the desert is an important provider of nutrients for the South American region and responsible for a large part of the torrential rains that fall in the Amazon.

According to NASA publications through the Research Center Goddard Space Flight Center, the long-term productivity of the Amazon rainforest may depend largely on atmospheric dust deposition, which may come from a distant ecosystem such as the Sahara desert. The presence of African dust in the Amazon Basin has been observed for nearly two decades, but the amount of dust and associated phosphorus is still not well understood. Part of this sand is carried by the wind during the gigantic sandstorms that hit the region of Chad, in North Africa, and is carried for almost 5 thousand kilometers to South America. This research was carried out through Satellite Observations called CALIOP. Since June 2006, CALIOP has been measuring 3D distributions of backscattering, extinction and depolarization ratio of atmospheric aerosols (very fine particles that are found suspended in the air) from clear skies and above clouds on a global scale. These advanced satellite observations are ideal for quantifying intercontinental transport and aerosol deposition, especially in the Amazon region.

After almost two decades of studies, it is known that the amount of Phosphorus, nutrients and silicon found in particles collected in the Amazon is the same as that found in Sahara dust. Furthermore, there is a correlation between the presence of these aerosols and the movement of air masses. The next step in the research is to understand the temporal extension of this process and predict how long the Sahara will be able to continue fertilizing the Amazon.

This relationship between the Sahara Desert and the Amazon Rainforest highlights the complexity and importance of global ecosystems and reminds us of the surprising and essential interconnection between different regions of the world: the desert is also responsible for bringing torrential rains to the region, through the phenomenon known as "flying rivers". These rivers are air masses loaded with water vapor that move from the Amazon towards other regions of the continent, bringing humidity and rain to these places. In the case of the Amazon rainforest, a portion of these atmospheric aerosols that function as a nucleus for rainwater condensation come from the Sahara.

In addition, dust from the Sahara can also affect air quality in the Amazon region. The presence of sand particles in the atmosphere can contribute to the formation of clouds, but in excess it can harm the health of people and local ecosystems, being an important element to maintain the ecological balance of the region. It is essential to continue studying and monitoring this phenomenon to ensure the preservation of the Amazon's biodiversity.

The Sahara's Influence on Climate Around the Globe

In addition to contributing nutrients and influencing flying rivers and air quality in the Amazon, dust from the Sahara can also affect the global climate.

This same study published by NASA shows that desert dust can affect cloud formation and temperature in different regions of the world. When dust is transported through the air, it can interact with solar radiation, affecting the temperature of the earth's surface and atmosphere. In addition, the phenomenon influences the amount of precipitation in different regions, which can have significant impacts on agriculture, water availability and biodiversity.

Another survey published in the journal Nature Communications showed that the movement of particles from the Sahara can affect the amount of rainfall in East Africa and the Arabian Peninsula, contributing to the formation of storm clouds, decreasing the amount of rain in some areas and increasing in others.

Collaborating with the same line of research, another study published in the journal Science showed that dust from the Sahara can affect the amount of snow that falls in the mountains of Colorado, in the United States. Uplift in the Sahara influences the reflectivity of snow, causing it to melt more quickly, which can affect water supplies in some regions.

Therefore, Saharan dust is an important element for understanding the impacts of climate change in different regions of the world, and its contribution to the Amazon is just one part of a much broader and more complex phenomenon. Contrary to what many believe, the preservation of the Sahara is extremely important for the world. This vast desert exerts a significant influence on the global climate and is an important regulator of the Earth's climate. Through the process of reflectivity, the Sahara helps reflect the sun's rays back into space, which helps keep the global temperature at a tolerable level. In addition, changes in vegetation and sand cover can affect the intensity and frequency of extreme weather events such as dust storms, hurricanes and prolonged droughts in different parts of the world, which makes it crucial that actions are thought to preserve the Sahara and protect its biodiversity, consequently contributing to mitigating the impacts of climate change and ensuring a sustainable future for all.