The carrying capacity of the world is thought to be around 4 billion (there are many numbers from different scientists). There is only so much water, food and other resources that we humans use everyday. Protecting the worlds resources from being consumed to the point of exhaustion is the only way humans and other life will continue to survive, and we depend on the survival of other plant/animal life. "Matter can neither be created or destroyed". Once it's gone, it's gone. If things continue the way they are, there will be a population crash because of a lack of resources. There are numerous studies done within ecosystems that show this poplation crash when resources are exhausted. I'll try to find some.
I too am concerned with the airlines and the economy but if and when the sh!t hits the fan, the economy nor the airlines will keep me hydrated or fed. It's all survival at that point. You can't eat or drink your money when the food supply is gone and the lakes dry out.