Thomas Crowther was an ecologist whose work inspired many tree planting projects, the problem is that this is a more complex idea than it first seems, and more importantly, mass plantations do not help.
Forests take up vast quantities of carbon, but the whole ecosystem must benefit, otherwise while trees may get planted, they are likely to fall foul of pests, or similar.
One of the simple requirements, is to plant trees more like a rainforest would. We cannot plant monocultures of a single tree – this is simply the equivalent of rolling out a picnic rug for the specific pests which feed on the tree in question. Instead, we need hundreds of tree species in each acre. Amazingly, without this, the trees ability to do what we want and draw down carbon dioxide is severely limited, so will fail.
Interestingly, preserving remaining forests has a far bigger impact on carbon dioxide removed from the atmosphere, so this is not only beneficial to the wildlife that lives there, it is also one of our most effective tools, to avoid climate change.
Think of all the primates, great apes and many other species that would be saved, if we just started to do what is best for ourselves.