The notion that the Amazon region represents the “lungs of the World” or produces 20% of the world’s oxygen is pure mythology, and completely false.
But is still repeated years after years by mindless politicians, nutcase celebrities, innocently ignorant third-grade teachers, Third-World activists, rabid eco-Nazis, and the habitually clueless legions of tree-hugging media writers who have no idea what they are talking about.
Actually, photosynthesis takes up carbon dioxide from the air but produces oxygen as represented by this ‘simple’ chemical equation:
6CO2 + 6H2O —> C6H12O6 + 6O2
In other words, under normal conditions the Amazon forest is in a steady state. Oxygen is produced by photosynthesis and consumed by decay. If these were out of balance, then the mass of wood in the Amazon must change.
That means if the Amazon were to disappear today, instantly (e.g. we harvested all the wood and used it to build houses) then the oxygen and carbon dioxide in the atmosphere would continue on at the same level. Until, that is, the wood rots. Then the carbon dioxide levels would increase.
Except for the biomass decrease from human-caused fires, the biomass of the Amazon has not been changing. That means that no net carbon-dioxide is being removed from the atmosphere, so no net oxygen is being released from carbon dioxide.
Recently the Amazon biomass has been changing due to fires. When that happens, the wood and other carbohydrates in the trees combine with oxygen and produce CO2 and H2O (see photosynthesis equation above). The fires thus have major consequences for regional climate, the rich Amazonian biodiversity, air quality and human health, and some consequence for global carbon emissions (though still small compared to the amount being emitted by fossil fuel combustion in industrialised parts of the world).
But under normal situations, when the biomass of the Amazon is not changing, there is no net production of oxygen or carbon dioxide.
So Where Do the 20% Come From?
The next table shows the total photosynthesis (also known as Gross Primary Productivity or GPP) of each major land biome. We need to multiplying by 2.67 to convert to total oxygen production.
Hence total oxygen production by photosynthesis on Land is around 330 Pg of oxygen per year. The Amazon (just under half of the tropical forests) is around 16% of this, around 54 Pg of oxygen per year.
Rounded up, this is where the 20% figure comes from. 16% of the oxygen being produced on LAND today is from photosynthesis in the Amazon.
What about the Phytoplankton in the Oceans?
The phytoplankton in the oceans also photosynthesise, generating around 240 Pg of oxygen per year. This is about 4 times more than the Amazon. So total global photosynthesis (land and sea) produces about 570 Pg of oxygen per year. Therefore in terms of TOTAL global photosynthesis, photosynthesis in the Amazon contributes around 9%. This is much smaller, but still substantial.
Ecosystems Are at Equilibrium
The Amazon consumes about as much oxygen as it produces. Plants produce oxygen through photosynthesis but the the same plants consume the equivalent of over half the oxygen they produce in their own respiration. The remaining 40% of the Amazon oxygen budget is consumed mainly by microbes breaking down the dead leaves and wood of the rainforest. So, in all practical terms, the net contribution of the Amazon ECOSYSTEM (not just the plants alone) to the world’s oxygen is effectively zero.
Incidentally, many writers who don’t understand this, and mistakenly think that the Amazon produces net oxygen, double their error by using a backwards metaphor. They refer to the Amazon basin the “lungs of the world.” But lungs are the organ that removes oxygen from the air and replaces it with carbon dioxide, not the other way around.
The often quoted figure represents the disturbing triumph of quasi-religious ‘fake news’ from governments and MSM. So take a deep breath, there isn’t a shortage of oxygen. Source