On second thought, the world doesn't necessarily
need anything. It'll exist whether or not we do (and if it doesn't exist, then it
really doesn't need anything
).
I think the question should be more along the lines of "What do we
want most for the world right now? And why?"
To answer the why of my initial desire of a "will to live", it is simply so that the world can continue existing. And perhaps also a "will to change", so that the world can evolve and grow (hopefully in a positive way according to our standards, which I'll let others fill in the details).