I wonder what kind of forest China is making? I was watching a really fascinating PBS documentary on Kanopy and it was talking about a lot of the planting efforts haven't been very good worldwide because planting a monoculture of trees doesn't do much and an old forest with tons of diversity stores twice as much carbon or more, which I thought was neat. So protecting existing forests is much better from a climate change standpoint. But either way, planting trees is better than nothing.
Given the goal is to introduce trees to prevent desertification, in this case the relative benefits of old growth are irrelevant.