Amazon: why scientists now call it the “Heart of the Earth” instead of its “lungs”
For decades, the Amazon Rainforest has been described as the “lungs of the Earth,” a powerful image that helped raise awareness of the importance of this vast bioma. Today, however, the scientific community considers this definition inaccurate and prefers different metaphors, such as the “heart of the Earth,” which better reflects the Amazon’s role in maintaining the planet’s natural balance.
The myth of the “lungs”
The expression “lungs of the Earth” stems from the idea that the rainforest produces enormous amounts of oxygen through photosynthesis. In reality, although Amazonian trees release oxygen during the day, most of it is later consumed by the forest itself: plants, animals, fungi, and bacteria all respire and decompose organic matter.
As a result, the Amazon’s net contribution to the oxygen in Earth’s atmosphere is close to zero. As ecologist Yadvinder Malhi of the University of Oxford explained: “The net effect of the Amazon on atmospheric oxygen is essentially zero” .
Michael Coe, a scientist at the Woods Hole Research Center, has also emphasized that there are many reasons to protect the Amazon rainforest, but oxygen production is not one of the main ones.
Recent studies show that the oxygen we breathe primarily comes from biological processes carried out by marine phytoplankton over millions of years in the world’s oceans.
More like a heart than lungs
If the “lungs” metaphor is misleading, the “heart” analogy is far more accurate. Just as the heart pumps blood and distributes vital resources throughout the body, the Amazon moves immense amounts of water and energy that influence the climate across much of the planet.
Every day, billions of trees absorb water from the soil and release it into the atmosphere through evapotranspiration. This process generates massive streams of moisture, referred to by scientists as “flying rivers,” which transport water vapor thousands of kilometers and help produce rainfall across much of South America.
The Amazon does much more than host extraordinary biodiversity: it actively regulates the water cycle, rainfall patterns, regional temperatures, and numerous climate processes that affect regions far beyond the rainforest itself.
Another essential function of the Amazon is its ability to store carbon. Trees absorb carbon dioxide from the atmosphere and convert it into biomass, helping slow global warming.
For decades, the Amazon rainforest has been considered one of the world’s most important carbon sinks. However, increasing pressure from deforestation, wildfires, and climate change is reducing this capacity. Several studies indicate that some parts of the forest now absorb less carbon dioxide than they release, temporarily shifting from carbon sinks to net sources of emissions.
This phenomenon is of great concern to scientists because it could trigger a vicious cycle: less forest means less CO₂ is absorbed, leading to greater global warming and creating conditions that are even more favorable to wildfires and environmental degradation.
A biological engine
Calling the Amazon the “heart of the Earth” does not mean abandoning the poetic image that made it famous. Instead, it replaces it with a metaphor that better reflects current scientific understanding.
A heart does not produce the air we breathe, but it keeps the entire body functioning by distributing essential resources. Likewise, the Amazon is not Earth’s primary producer of oxygen, but it is one of the planet’s great biological and climate engines: it regulates the water cycle, influences the global climate, stores carbon, and safeguards unparalleled biodiversity.
For these reasons, many researchers now believe that calling the Amazon the “heart of the Earth” is a more accurate and scientifically grounded metaphor than the traditional “lungs of the planet.”
Photos: Nicolò Cozzi, Amazônia Archive
