I'm passionate about sustainability.  To be honest I don't know if global warming is natural or man-made but sustainability is common sense.  You don't need a reason other than the principal that you don't exploit people or the environment and you conserve resources to allow future generations to enjoy them TOO!  It's so simple but we have forgotten it in the last 50-100 years.  I'm confident that with global communication and widespread economic development, we will see change in the next 5 years, accelerating in the next 10.