The press release only talks about the methods, not the actual implications. To say everyone was surprised is also a bit odd as obviously some imagery was already accessible and you can see green spots on your typical maps app. And people actually live in these areas so someone could have asked them...

But thats nitpicking, for me the question is: what does this mean? are these recently desertified areas and the trees are just the last survivors? Are these areas becoming more or less rich in trees? Is this only regional or is the density similar to other areas of the sahara? What lessons does this contain for the great 'wall of trees' 20+ African nations are working on to stop desertification? ...?