The human species is capable of amazing things. We've pulled ourselves up and out of the food chain, leaving us living long and safe lives with no worry of being attacked by predators.
As the world becomes larger, the need for ways to get from point a to point b becomes greater. Cars, ships, planes, none of that is cutting it anymore. Earth is changing, and the pollutants let off by these forms of travel are making sure that it changes for the worse. That's where you come in.