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?

Question

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

In: 43

Answer 1

No. Imagine if there was more CO2 than now. Plant growth would be faster, because there was more CO2 to use…and the amount of free CO2 would go down.

The balance between carbon as biomass vs carbon as CO2 is dependent on the relative rates of plant growth vs biomass decay (and a myriad of other processes that add or subtract CO2 from the air). And those rates depend in turn on the amount of CO2.

The equilibrium point is just the mix where the rates are equal. If you’re not at equilibrium, things drift in that direction until you are.