People and over population are the biggest threat to the world. Darwinism un checked snuffs out those who are to weak to survive. Modern society creates a crutch for them. Food programs in africa and such. The world economies will industrialize the rest of the world one country at a time and they will suck up resources while spewing toxic pollutants into the air, water and environment. Example: Japan, China, Middle East and India.
Even if we consume and pollute nothing these countries are trying to emulate what we have and we cannot control their pollution. I see that as a huge problem.
I for one am an avid outdoorsman and always do what I can to protect the environment. My next home will run on solar power. Self reliance is the best way to hedge against the issue's we face in our uncertain future.
In the words of Maynard from Tool. "Learn to swim".