There are many issues: - As you said, time scale: Forests and their ecosystem take a long time to form. Much longer time horizons that we are dealing with with

There are many issues: - As you said, time scale: Forests and their ecosystem take a long time to form. Much longer time horizons that we are dealing with with climate change - Strictly, yes, growing a tree and harvesting it and putting the harvested wood somewhere in a bunker removes carbon from the atmosphere. But in reality, the harvested wood is processed, and there's a lot of carbon emissions associated with that. Furthermore, it's not stored for thousands of years. It's e.g. used as paper, and then recycled or burned or whatever. - A forest is not just trees. There's a whole ecosystem, including soil, fungi, animals, insects, different species of trees and plants. This has many benefits to the biodiversity and resilience of that region, that also counter-acts climate change. Tree plantations on the other hand, are just one type of tree, that often are not even native to the that region. Tree plantations destroy ecosystems, so even if the carbon negative argument would be valid (it's not), this would not be a good idea.