In the documentary Salt of the Earth about the life and work of Brazilian photographer Sebastião Salgado, there's a memorable part at the end where he shows how he and his wife planted thousands (maybe millions?) of trees on his parents' barren, deforested land in Brazil and how it made a remarkable recovery back to healthy rainforest, with many endangered species returning, so according to that it looks possible. At one point in his career, after decades of photographing deprivation, famine, genocide and war, he seemed a broken man and it was this that helped him regain some hope and inspired him to continue his work. Well worth a watch if you haven't seen it: