Can you Imagine the Earth having no presence of oxygen in it? What will happen if such an imagination becomes a palpable reality? Or,what would be the consequences if the current oxygen level in atmosphere takes up the decision of going up in its percentage? Well, it would be weird, isn’t it?..Let me try to demistify your curiosity.

About 3.45 billion years ago, earth was anoxic(ie there was no oxygen). Back then, the living beings on this planet were all some bacterias which didn’t need the oxygen to survive. It took another 1 billion years for the very first autotrophic bacteria to appear. They are kind of today’s cyanobacteria and began to part on photosynthesis and then released the very first free oxygen. In the initial centuries, the free oxygen released from the ocean by these bacterias couldn’t sustain in atmosphere because they immediately reacted with the dissolved iron and the organic matter to become other compunds. This immediate self-destruction is a unique chemical characteristic of Oxygen as its electronegativity is the second most only next to flouine.

The current percentage of Oxygen in atmosphere is 20.94% that remains balanced for almost many decades. Although deforestation keep on surging in an unimaginable level, Its implications on reducing the Oxygen level from the atmosphere is nearly zero. The reason being, it is not the fauna in the land that produce the large quantity of Oxygen, but it is the phytoplankton in the ocean that does this rite for millions of years. It is estimated that these tiny ocean plants contribute almost 70% of Oxygen to the earth’s atmosphere

Image of phytoplankton from Pixabay

Oxygen owes its existence to the life on earth in the same way the life on earth owes its existence to the oxygen

The mutual cooperation nurtures the existence of both the participants. To sabotage this equilibrium the current atmospheric oxygen level has to drastically go down or vigorously go up!


In fact, our earth had gone through every situations that we could only imagine now. Appearance of Oxygen wasn’t that good for living organisms at first. Oxygen caused mass extinction once by being responsible for Ice ages that lasted for millions of years. The newly appeared free oxygen set out to react with metane to reduce its quantity which in turn resulted in a frozen planet.

Image is drawn by me

In Carboniferous era, that began 359 million years ago and lasted till 299 million years ago [source], the percentage of Oxygen in atmosphere was too high; It was well above 35% as opposed to the current level of near 21% !
This higher percentage nurtured the lives of insects as their breathing style is not based on lungs. Also this period saw the growth of large sized animals in abundance due to the adequate oxygen supply available to the farther body parts . Not just amphibians and reptiles but also the size of insects was very high. The insects of that period measured more than 3 feets in length and height!

Image source- Pixabay

If the atmospheric oxygen level raises now,

  • Wildfires may spread faster,fuel efficiency would be higher in our gas vehicles and everything related to fire would get an enhancement as the Oxygen exquisitely helps the firing
  • Scaling Everest would no longer be as difficult as it used to be as the adequate availability of Oxygen makes it easier!
  • Giant insects will be back again.
  • We will die younger because Free radicals (i.e. O2-) are thought to exacerbate the aging process through Oxidative stress which interferes in numerous cellular processes: protein production, DNA replication, intercellular communication, and are also thought to contribute to MS, Alzheimers, Parkinsons, and a host of other ailments. This Quora Answer dealt with this interestingly.

The list will get larger if I list out everything!


La Rinconada located in Peru is the highest permanent human settlement. It is situated at a height of 5100 metres from the sea level! It is not a unique scenario, as per estimations obtained from various statistics, at least 140 million people in the world live permanently above 2,400 metres! These cities can be found primarily in three mountainous regions: the Himalayas in Asia, the Andes in South America and the Ethiopian Highlands of Africa. It is quite interesting to read Their way of life here. I’m mentioning about these cities here because, it is in high altitude regions that the quantity of Oxygen is too low. The Higher the altitude the lower is the air pressure; which means that the oxygen level would be much less than the world average of 21%.

To survive, our lungs must work more than what they do now to gather adequate oxygen in these places which in turn causes fatal illnesses in the long run. Thats why the moniker Death Region well suits to the altitude above 8000 metres.

La Rinconada,Peru-Wiki creative commons , Uploader-Hildegard Willer

As I mentioned in the beginning of this article, earth’s atmosphere had been oxygen free and continued to be like it for almost 1.25 billion years since its beginning 4.5 billion years ago. In fact, the oxygen had nothing to do with the initiation of life on earth but it played major role in the formation of multicellular complex organisms. Nitrogen molecules were in act when the first ever single cell organism was formed instead.

The main reason behind why we are able to walk freely and safely on this planet is the Ozone layer which protects every living organisms from hazardous UV rays emerging out of the Sun!

If we suppose the atmospheric Oxygen disappears at this very moment-

  • UV rays will attack each and every living organism and will cause damage in the fundamental building blocks of life, the DNA and Destroy the life from the earth!.
  • By chance, even if some organism manages to survive UV radiation, it can’t live without metabolism which needs oxygen to happen.Here, every organism except few bacterias and viruses would die!
  • Every chemical reaction taking place on the earth will have profound change in it which would make earth a planet completely different from what it is now.


Infact, the atmospheric oxygen level has never been the same as may appear it to be. It is slightly changing over time. Look at these measurements-

  • 28% -130m years ago
  • 29% -115m y.a.
  • 35% -95m y.a.
  • 33% -88m y.a.
  • 35% -75m y.a.
  • 29% -65m y.a.
  • 21% – now

The consistent change in its percentage can be attributed to so many factors, But when we analyse the contribution of human beings towards this declination, burning fossil fuels win the first place. A slight decrement of 0.035% in oxygen level has been taken place in last 30 years due to the increase in the production of Carbon-dioxide during this period. But it can in no way make a significant difference in global average of 21% even after 100 or 200 years. The reason being continual Photosynthesis! As I mentioned earlier it is the phytoplanktons that produce about more than 70% of total atmospheric oxygen. Along with this contributing to the global share is Amazon Rainforest with its 20% divident.

A balanced level of Oxygen in atmosphere is very much needed in order to life on earth to continue as it is now. The very existence of Oxygen depends on living beings in the same way the very existence of living organisms depend on oxygen!


Sathya Sankar

I'm a mechanical engineer by graduation and a high school teacher in my current profession. I write on a wide variety of topics that covers whatever I feel like I should!


Angel sankar · June 23, 2018 at 10:40 am

Great post…

Angel sankar · June 24, 2018 at 5:04 pm

Ha ha..

Indian Sanu · September 11, 2018 at 3:53 pm

If the current level of atmospheric oxygen will heavily increase then new species of organism will born, the population will increase and also many factories can establish to polite the air.

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