Tone and imagery in Music videos

The video is called What we've done so he is trying to say look at the mistakes we as humans have made. We have made these mistakes but we should try and change and not make the same mistakes again. The grass growing then reversing the footage shows change since they are in the desert and at the end the grass grows back. It shows all the historic footage of all the terrible things people have done the K.K.K, Hitler, 9/11 and how we have to change for the better because all these thing were terrible tragities caused by humans.