The Amazon Produces 20% of the World's Oxygen

The Amazon rainforest is often called "the lungs of the planet," a powerful image suggesting it breathes out the oxygen we all depend on. While it is a colossal oxygen factory, this nickname is slightly misleading. The science lies in a delicate balance. Through photosynthesis, the vast jungle does indeed generate an enormous amount of oxygen. However, the forest is also teeming with life that consumes oxygen. The trees themselves use it for respiration, especially at night, and trillions of microbes on the forest floor consume it as they decompose fallen leaves and other organic matter.

In a mature, stable ecosystem like the Amazon, these two processes—production and consumption—are in near-perfect equilibrium. The oxygen created by a new leaf is eventually balanced out by the oxygen consumed when that same leaf dies and decays. As a result, the rainforest's net contribution to the world's atmospheric oxygen is almost zero. This doesn't diminish its critical importance, but it does shift the focus of its global role.

So where does most of our oxygen come from? The answer lies in the world's oceans. Microscopic marine organisms called phytoplankton, drifting in the sunlit upper layers of the water (Review), are the true workhorses. Through photosynthesis, these tiny algae are responsible for producing at least half of the planet's oxygen. Meanwhile, the Amazon's most vital function for the global climate is not oxygen production, but its role as a massive carbon sink, storing billions of tons of carbon in its trees and soil, and as an unparalleled reservoir of biodiversity.