e way down into the depths of the ocean to an oxygen-free environment, where it will be retained for the long-term, eventually forming oil and gas. Because the algae never decomposed, the oxygen it made while it was alive is not offset, thus creating a small amount of extra oxygen. The same preservation process can happen on land with plants to create coal, but it requires special conditions. “The only real place is peat bogs,” said Denning. Only around one-millionth of all photosynthetic matter ends up buried in this way, Denning said, so in any given year, there’s only a tiny bit of oxygen being created. But over millions of years, that tiny surplus of oxygen added up — and it’s why today’s atmosphere is around 21% oxygen. No Lack of Oxygen The sheer amount of oxygen currently in the atmosphere is yet another reason why there’s no need to bemoan the Amazon’s burning out of fear that the planet’s oxygen will dwindle. It is true that if wide swaths of the Amazon went up in smoke, oxygen levels would fall, but only very, very slightly — and certainly not to levels that would pose a risk to humans. According to data collected by the Scripps Institution of Oceanography, each year, 19 out of every million molecules of oxygen, or 0.002%, are lost, primarily from burning fossil fuels. But there is so much oxygen in the atmosphere already that these minute changes are inconsequential. Shanan Peters , a University of Wisconsin-Madison geologist, told the Atlantic that even if every living thing on Earth other than humans burned up, oxygen levels would fall from 20.9% to 20.4%. And according to Denning, it would take millions of years to meaningfully deplete the globe’s oxygen supply. The notion that failing to preserve tropical rainforests would deplete the Earth’s oxygen goes back to at least 1996 , when Columbia geochemist and pioneering climate change researcher Wallace Broecker took the time to debunk the idea in a university magazine. Broecker, incidentally