Human beings and many other organisms have adapted to live in an atmosphere with an oxygen concentration consistently ranging from 20.9% to 21%. What would happen if the oxygen levels suddenly increased or decreased?
In Earth’s atmosphere, nitrogen makes up about 78%, while the remainder consists of carbon dioxide (CO2), carbon monoxide (CO), water vapor, and trace gases. Therefore, the standard oxygen concentration in the air is 20.9% to 21%.
Where Does Earth’s Oxygen Come From?
Our Earth has existed for approximately 4.6 billion years. Throughout such a long period, the planet has continually developed and changed, having experienced five terrifying mass extinctions. Humans have been on Earth for about 200,000 years, if not longer. Ultimately, the reason humans can survive on Earth is due to the planet’s natural environment.
Human life and many other organisms on Earth are inseparable from oxygen. (Image: Baidu)
Human life and many other organisms on Earth are inseparable from oxygen. In fact, during the first half of Earth’s history, it had no oxygen at all. It was not until the “Great Oxidation Event” occurred that oxygen was produced globally, allowing unicellular and multicellular organisms, as well as animals and even humans, the opportunity to begin life.
At the time of this event, the surge in oxygen levels was primarily due to cyanobacteria, also known as blue-green algae, which are photosynthetic bacteria that release oxygen. The abundant oxygen-rich environment contributed to the growth and size of many species of plants and animals. The high levels of oxygen combined with fresh air helped them become much healthier and larger than they are today.
Evidence shows that in 2012, two paleontologists, Matthew Clappen and Jared Carr from the University of California, Santa Cruz, published their research on the changes in wing lengths and sizes of over 10,500 insect fossils over the past 320 million years. They found that during the first 150 million years, the body size of these insects had a certain correlation with the oxygen concentration at that time. In environments with high oxygen levels, insects tend to grow larger. Not only insects, but many organisms and plants from that primordial era were also gigantic.
In the high oxygen environment of early Earth, many insect species were gigantic. (Image: Baidu)
However, this relationship gradually diminished over time, and organisms, plants, and animals became smaller. This partly proves that oxygen levels significantly affect species. We still know that without oxygen on Earth, no organisms could survive. If oxygen levels become thinner, the existence of species, including humans, will also be limited. That is why the oxygen levels in Earth’s atmosphere need to be regulated.
Why Is Oxygen Level on Earth 20.9%?
The oxygen level in Earth’s atmosphere is about 21%. Half of this oxygen is produced by trees and plants during photosynthesis. The other half is generated by the oceans, specifically by tiny marine organisms known as phytoplankton.
Humans and many types of organisms, plants, and animals have completely adapted to the 20.9% oxygen level in Earth’s atmosphere. Thanks to this adaptation, human civilization has been able to develop steadily. Consequently, some scientists have raised the question of whether a higher oxygen concentration on Earth would be beneficial. How would life on Earth change if oxygen levels exceeded 21%?
Pure oxygen is only truly beneficial to humans when used for short periods. (Image: Baidu)
If the oxygen level in Earth’s atmosphere were raised to 100%, the human respiratory system would undoubtedly benefit. There are many companies worldwide that provide pure oxygen to customers. Many customers report positive results after using these services, such as reduced dizziness and headaches, and improved health.
However, pure oxygen is only truly beneficial when used for short periods. If humans breathe 100% pure oxygen for an extended period, we may suffer from toxicity. Specifically, after inhaling too much pure oxygen for too long, individuals can feel chest tightness, followed by dizziness, headaches, lung and brain damage until consciousness fades and death occurs.
Moreover, we must remember that oxygen is a primary element present in fires. Therefore, excessively high oxygen levels in Earth’s atmosphere would make fires more intense. In fact, even a single match could spark a severe wildfire.
High oxygen levels would cause insects to grow to gigantic sizes. (Image: Baidu)
Additionally, 100% oxygen levels would have a significant impact on insect species. According to the research by paleontologists Matthew Clappen and Jared Carr, insects once grew to gigantic sizes over 300 million years ago. The reason for this considerable size difference was due to oxygen levels reaching 35% at that time. So, if oxygen levels were to reach 100%, one can only imagine how large insect bodies could grow and envision what the world would be like if they became gigantic. There would certainly be a risk of a new mass extinction occurring shortly thereafter.
But what would happen if the oxygen levels in Earth’s atmosphere dropped below 20.9%? In the book “The Oxygen Crisis” by American author Roddy Newman, it is noted that compared to prehistoric times, the oxygen levels in Earth’s atmosphere have decreased by one-third and have stabilized at 20.9%. The reason for this decline in oxygen levels is that 10,000 years ago, forest cover on Earth was twice as expansive as it is now. This also means that current oxygen levels are only half of what they were at that time.
Oxygen levels in the oceans have also decreased similarly. According to NASA reports, the amount of single-celled plants producing oxygen has reduced to about 70% of what it was 30 years ago. Meanwhile, the United Nations reports nearly 150 dead zones caused by industrial and agricultural waste being released into the oceans. These pollutants have led to a decrease in oxygen levels in these areas to the point where no marine organisms can survive. The lack of oxygen in the oceans also causes gene mutations, affecting the reproductive capabilities of marine organisms.
Whether oxygen levels in the atmosphere increase or decrease significantly threatens the world. (Image: Baidu)
Regarding the scenario where oxygen levels in the atmosphere continue to drop below 20.9%, Professor Ervin Laszlo, an American advisor to the United Nations on systems science and philosophy, believes that human health would be the first affected. When oxygen levels are too low, cells and organs become oxygen-deprived, weakening the immune system and causing reduced functionality. Physiological disorders occur when the oxygen ratio in the air drops to 16-17%. When oxygen levels fall to 7-8%, this can lead to fatal outcomes.
If oxygen levels were to drop to 0%, concrete structures could collapse instantly. This is because oxygen serves as a special binding agent for concrete. The absence of oxygen would also result in a pitch-black sky. While all of this occurs, the Earth’s crust would completely shatter as it is composed of 45% oxygen. Hence, this crust would continue to break apart until nothing remains.
Thus, whether the oxygen level is more or less than 20.9%, it is certain that our world, especially humankind, would be severely affected.
How to Maintain Oxygen Levels at 20.9%?
Over millions of years, the oxygen level in the air has stabilized at 20.9%. This level of oxygen is ideal for the organisms on Earth. The balance of oxygen and other gases is ensured by the natural cycle: animals exhale CO2, plants use it and release oxygen.
However, our vegetation is increasingly disappearing. It is estimated that up to 13 million hectares of forest (equivalent to the area of Greece) are lost each year. Humans are cutting down trees to meet the growing demands of agricultural and industrial production. If the disappearance of trees is not stopped, humanity will not be able to survive in the future, as the air will no longer be suitable for respiration. To survive, the best thing humans can do is carry oxygen masks to filter the remaining oxygen in the air.
Furthermore, the balance of oxygen and other gases in the atmosphere has created the ozone layer at an altitude of 8-30 km above the Earth’s surface. At the same time, it protects life on Earth by absorbing the Sun’s ultraviolet radiation.
Unfortunately, a study published by Princeton University in New Jersey, USA, in the journal Science indicates that the amount of oxygen in the Earth’s atmosphere has decreased by 0.7% over the past 800,000 years. Researchers measured the oxygen levels in ice cores from Greenland and Antarctica. According to the research team, these areas still contain countless gas bubbles that represent the Earth’s atmosphere over millions of years. By analyzing the nitrogen isotope ratios in these ice cores, they determined the specific rate of oxygen concentration reduction as mentioned above.
To maintain the appropriate oxygen levels for humans and other organisms on Earth, we need to limit tree cutting, reduce fossil fuel combustion… (Photo: Baidu)
Notably, Professor Daniel Stolper, the head of the research team, further indicated that in the past 200 years, the industrialization phase of human society has been the most abnormal period. The oxygen level in the atmosphere has rapidly decreased by 0.1% due to fossil fuel burning, oxygen consumption, and carbon dioxide production.
Every year, humanity burns 7 billion tons of fossil fuels, affecting the free oxygen content in the atmosphere. At the current rate of photosynthesis, it may take about 2,000 years to restore the ideal oxygen levels in the Earth’s atmosphere.
From this, it can be seen that the balance of oxygen levels in the Earth’s atmosphere will never be permanent. If humanity does not recognize and change this soon, the prospect of a mass extinction is the outcome awaiting us.
