As news circulated of the record-setting fires raging across the Amazon rainforest this month, so has a statistic that reinforces the significance of the world's largest tropical rainforest: The Amazon produces 20% of the world's oxygen supply.
But a Northwestern University researcher has pushed back against that claim, saying that the release of the greenhouse effect-causing gas carbon dioxide is more concerning than a nonexistent threat to the world's oxygen levels.
"The fact that they're throwing up this 20% number, to me, implies that they're trying to say that our oxygen supply is in danger," said Neal Blair, professor of environmental engineering and earth and planetary sciences at Northwestern.
"And our oxygen supply is in no way in any danger."
Contemporary ecosystems contribute very little to the atmosphere's oxygen, Blair said. Oxygen from plants has accumulated in the atmosphere over millions of years, making animal life possible.
"You can burn down the whole Amazon forest, and you would see a tiny, tiny, tiny drop in our oxygen levels, but we wouldn't notice it," Blair said.
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Although oxygen isn't an issue, Blair said carbon dioxide being released from the lost trees is a concern.
"The consumption of oxygen when we burn forests, for instance, is not going to hurt us," he said.
"On the other hand, we don't actually have a lot of CO2 in the atmosphere compared to oxygen. So if you add CO2 to the atmosphere, then you can make a bigger difference."
Through photosynthesis, trees play a vital role in sucking carbon dioxide out of the atmosphere, which is critical in slowing climate change, said Kerry Cesareo, senior vice president at the World Wildlife Fund.