For context, this would in theory allow about 1/3 historical cumulative emissions to be absorbed over a century or so. Which is a start, but nowhere near enough.
Also noteworthy: the bulk of forest-based carbon offsets have been fraudulent.
The paper is here
Trees decompose relatively slowly and offer a habitat to lots of animals. In addition, some CO2 is still stored in the ground. Decomposition is really not the issue, unlike what humans tend to do with wood (a lot of which is burned or made into cheap furniture and then burned).
CO2 from the ground in the form of oil, gas and coal (etc) goes into the air. CO2 from the air goes into trees. CO2 from dead trees goes into the carbon cycle. We need to remove carbon from the cycle. It is definitely part of the issue. Hence by stating that it might be a good idea to make forests specifically for the farming of carbon.
If you can think of another way to gather carbon cheaply and then get it out of the cycle I’d be happy to hear it!
What you mean are not “old-growth forests” (article) but plantations, although they might be managed a bit differently than tree plantations today. They will fail at fostering ecosystem diversity and will not be particularly resilient. Dead material is vital for a living, thriving forest.
Since you imply that your idea has no alternatives: If we reduce consumption of animal products, we can drastically reduce the amount of farmland (as 70% of worldwide farmland is used to feed animals who in turn “waste” a lot of their feed, as they are not turning plant calories into animal calories 1:1). In many regions, this will allow growing forests or re-establishing swamps which will then be able to store CO2 again. Even farmland that is sustainably managed can store a lot of CO2, that just means allowing some nature on farms again and plowing a lot less.