The problem is that it doesn't address the root cause. Broadly speaking, there's two places carbon can be: in the biosphere or locked up geologically. Our fossil fuel emissions - by definition - came from geological deposits. We need to put them back into geological formations, otherwise when the trees we've planted die their carbon will just go back into the atmosphere.
Putting aside any quips about how our oil fields used to be part of the biosphere, I do think the current view is that forests are net carbon sinks, even accounting for decomposition.
Regardless, the time scale for growing and decomposing a forest is enormous and would buy a lot of flexibility in solving the problem more permanently if additional research shows them to not be efficient sinks long-term.
I hear this a lot, but does every bit of that really just go up into the air? Don’t trees often break down and become soil, and new trees grow on top of them?
The research I've seen in popular media says a lot of the carbon from old trees comes from an era before microbes could digest them - so dead trees just piled up for a long time and got buried. That doesn't happen anymore.
"Ward and Kirschvink say that 90 percent—yup, 90 percent!—of the coal we burn today (and the coal dust we see flying about Beijing and New Delhi) comes from that single geological period, the Carboniferous period."
