[elihu]

Well, trees can store a lot of carbon while they're alive. When they die, they release a lot of that back into the atmosphere as they decompose. So, trees are medium-term carbon storage. I expect we'll eventually need to figure out some way to store carbon long-term (for example, put it back in the ground in a way that it'll stay there).

[TheCoelacanth]

Trees are medium-term carbon storage. Forests are long-term carbon storage (the trees that die get replaced by new trees).

[elihu]

Once the forest is mature, though, it's mostly just storing the carbon, rather than acting as an effective sink. So maybe you need to cut some trees down from time to time, and store that wood somehow where the carbon will be locked up for a long time without taking up valuable land area.

The problem is that we keep pulling carbon out of the ground and introducing it into the ecosystem. If we don't have a corresponding method of removing it from the ecosystem, we'll eventually run out of room for forests that we can use to store it. Some of that happens by natural means, but we'd have a bit more breathing room if we could figure out how to make it happen faster.