TIL about the Global Oxygen Cycle

It is fun to learn new stuff. Today I learned some interesting things about the global oxygen cycle. Of course, I had known about photosynthesis from my school days. It is the process which converts CO2 and H2O and produces oxygen and the stuff that trees and plants are made of.

Aside: Many people don’t realize that all plants are basically carbon and that the carbon comes from atmospheric carbon-dioxide. Therefore higher concentration of CO2 implies higher rate of plant growth, and so increasing CO2 concentration has the beneficial effect of faster plant growth (and not just global warming.)

Moving along. As you may know, the Amazon rain-forest is burning. That is great for all those environmentalists who believe in the catastrophic climate change bugaboo because it gives them another reason to say, “I told you so.” To drive home the point that the earth is going to hell in a handbasket, the claim is made that the Amazon provides 20% of the world’s oxygen.

Well, if that is so, then of course the terrifying message is that soon we will all be gasping for breath, as we would if we were in a burning house. Say goodbye to life on earth.

Fortunately for us, this is not so.

Amazon is burning. It is not good news for various reasons. But running out of oxygen is not one of them. Yadvinder Malhi over at “Travels in Ecosystem Science” explains “Does the Amazon provide 20% of our Oxygen?”

One thing I am often asked on is to comment on the statement that “the Amazon provides 20% of our oxygen”, a statement now being used by, among others, the President of France and the Secretary General of the UN. This statement is basically incorrect and based on a partial understanding of how ecosystems function.

Totally fascinating stuff, if you are the kind who likes to know stuff. First he explains that the Amazon produces only around 9% of the total production of oxygen from photosynthesis. Fine. But then he explains that “the Amazon consumes about as much oxygen as it produces.” So therefore, “in all practical terms, the net contribution of the Amazon ECOSYSTEM (not just the plants alone) to the world’s oxygen is effectively zero. The same is pretty much true of any ecosystem on Earth, at least on the timescales that are relevant to humans (less than millions of years).”

Here’s the concluding part of the piece:

The oxygen levels in the atmosphere are set on million year timescales by the subtle balance of geological, chemical and biological processes. They are not set by the short term (short term equals anything less than hundreds of thousands of years) activities or existence of current biomes.

A final point to make is that the atmosphere is awash with oxygen, at 20.95% or 209,500 ppm (parts per million). Carbon dioxide, by comparison, is around 405 ppm, over 500 times less than oxygen, and rising by around 2-3 ppm per year. Human activity (around 90% of which being fossil fuel combustion) has caused this oxygen concentration to drop by around 0.005% since 1990, a trivial amount. In parallel, the same activities have caused carbon dioxide concentrations to rise by by 37 ppm since 1990, or 10%. This is a much more substantial percentage because there is so little carbon dioxide in the atmosphere to begin with, so human activities that emit or absorb carbon dioxide can make a major difference. This is why we need to worry about the increase of  carbon dioxide in the atmosphere (and its resulting impact on climate), and why we don’t need to worry about running out of oxygen.

Go read it all. And remember to tell the climate change advocates to chill.


Author: Atanu Dey


%d bloggers like this: