If we look at climate research we also see a similar concern. Reforestation only work as a carbon sink if it also accompanies agreements to not harvest the tress and keep the forest as reservations. In simple terms, global reforestation in order to combat climate change has the same challenge as a global initiatives to create more forest reservations.
A global reforestation policy without extending the reservations is carbon neutral. It is much better than deforestation, but it won't fix the problem of fossil fuels putting out massive amount of carbon into the air.