If "natural growth" is best, it'd be possible to measure it. It seems somewhat straightforward to measure the carbon content of an area before its forested (or re-forested), and then measure it afterwards, and see which method does better.
In my experience: agriculture wins in regards to hitting goals and targets. Nature will never grow as much food as our farming system, period. Similarly, I expect that our farming system (tweaked for carbon-capture instead of wood and/or other growth targets) would be superior at handling a specific goal (ie: Carbon capture) than nature.
In my experience: agriculture wins in regards to hitting goals and targets. Nature will never grow as much food as our farming system, period. Similarly, I expect that our farming system (tweaked for carbon-capture instead of wood and/or other growth targets) would be superior at handling a specific goal (ie: Carbon capture) than nature.