ARE WE MAKING AN OXYGEN TIPPING-POINT?

The percentage of oxygen in the earth's atmosphere has fluctuated during its history, and it is obviously no coincidence that mass extinctions have followed drops. The question is: are we creating another one? We are pumping carbon-dioxide into the sky at a rate the planet cannot handle, we are removing vast areas of forest by felling it or killing it with the effects of global overheating, and we are thus removing vast amounts of photosynthesis, a double-whammy that must surely reduce the amount of oxygen significantly.

Computer models predict that the Amazon, which is a huge part of the planet's 'lungs', will become a desert.

In a previous era when the planet became hot and arid and experienced a marked drop in the amount of photosynthesis, the percentage of oxygen plummetted to about 15%. Human beings would scarcely be functioning at that level. Our performance begins to drop off at 20%, only 1% below the 21% now in the atmosphere.

See NewScientist for the article that aroused the question in this posting.