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We take the air we breathe for granted. Dry air is a complicated mixture of gases by volume including:


78.09% nitrogen

20.95% oxygen

0.93% argon

0.04% carbon dioxide


and small amounts of other gases.


Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

Air composition, temperature, and atmospheric pressure vary with altitude. Air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres, in space suits and underwater SCUBA breathing apparatus.


Without that 21% of oxygen in the air we'd not be able to breathe to oxygenate out blood to make our muscles work for us - and we could not use our brain to think.


Oxygen in air is also vital for burning wood, coal and for internal combustion engines. A lot depends on the continued production and quality of air in a sustainable society.


Fortunately, trees and phytoplankton produce oxygen for us to breathe, in that respiration process trees lock up carbon dioxide to build a useful material called wood.


A study from 2015 suggests that global warming threatens oxygen production by phytoplankton. The study led by Sergei Petrovskii, Professor in Applied Mathematics from the University of Leicester's Department of Mathematics, has shown that an increase in the water temperature of the world's oceans of around six degrees Celsius - which some scientists predict could occur as soon as 2100 - could stop oxygen production by phytoplankton by disrupting the process of photosynthesis.

While mainstream research often focuses on the CO2 cycle, as carbon dioxide is the agent mainly responsible for global warming, few researchers have explored the effects of global warming on oxygen production.

The team developed a new model of oxygen production in the ocean that takes into account basic interactions in the plankton community, such as oxygen production in photosynthesis, oxygen consumption because of plankton breathing and zooplankton feeding on phytoplankton.

"About two-thirds of the planet's total atmospheric oxygen is produced by ocean phytoplankton -- and therefore cessation would result in the depletion of atmospheric oxygen on a global scale. This would likely result in the mass mortality of animals and humans.








TREES FOR HUMAN BREATHING - On average, one tree produces nearly 260 pounds of oxygen each year or 118 kilograms. A human breathes about 9.5 tonnes of air in a year, about 23 percent of that is oxygen, by mass. We extract a little over a third of the oxygen from each breath. That works out to a total of about 740kg of oxygen per year. Which is, very roughly, six or seven trees’ worth.

The world's rainforests are responsible for between 20 and 30 percent of total the oxygen produced in the world each year. The Amazon rainforest alone produces nearly 20 percent of the world's oxygen.



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