Subsidize charcoal in the region and sell it for 1/10 of what you get for turning the trees to charcoal. Destroy the charcoal economy. Then pay locals x amount per tree that is there while you point out that the reason that they are poor people living in a wasteland is because they cut the trees in the first place. If that doesn't work, make a guarded tiny tree reserve, close the roads and let them starve themselves to extinction.