If plants get most of their mass from CO2 in the air, why is the biomass of plants higher than the amount of CO2 in the atmosphere?

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I was reading today that there’s something like 8 gigatons of CO2 in the air, but more than 400 gigatons of biomass on earth (which is mostly plants). Can someone explain how this happens to me?

Edit: My numbers were off. There’s about 10x as much CO2 mass in the atmosphere as there is biomass on Earth

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Anonymous 0 Comments

So, those numbers may or may not be accurate, but it doesn’t matter because there’s simply no reason they would need to be of comparable magnitude.

The system will be in a more-or-less equilibrium state, with carbon leaving the atmosphere to make biomass, and biomass decaying and emitting CO2 into the air. The amount of biomass and atmospheric CO2 will balance out at a level where the rates in and out are about the same.

(“More-or-less” and “about”, because we’re ignoring the effects of humans burning fossil fuels, and many, many other perturbations. But fundementally, there’s no reason that most of the carbon in the system couldn’t be tied up as biomass. )

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