How to Destroy the Planet

By Eric Roston - 2012-04-20T12:50:43Z

Photograph by NASA

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Killer Oxygen

THREAT: Global oxygen levels spike when a new kind of photosynthesizing organism takes root. Levels climb high enough that lightning can start uncontrolled fires even in a rainforest. People, animals and other organisms not used to the new gaseous mix are disabled with oxygen poisoning.

REALITY: Oxygen is the waste product of microorganisms called cyanobacteria. They still thrive today, as do their cousins, the chloroplasts in plants and trees.

The Earth's atmosphere had little oxygen for half its history. Geologists read iron formations in rocks more than 2 billion years old as evidence that a massive shift occurred when oxygen arrived. Microorganisms unable to live with the new gas may have died off in an "oxygen holocaust," as some scientists have argued.

Breathe deeply. An overoxygenating critter doesn't exist, and even if it did, the time scale for dramatically changing the percentage of atmospheric oxygen would be in the millions of years. Rising levels of carbon dioxide, not oxygen, are the threat this century.

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