This author looks at some of the negative aspects of space travel and colonization. I think it is worth being a realist and considering both the benefits and problems in any proposition. This author has some cogent arguments. He could be right, he could be wrong but we should consider his ideas, I think.
Why Not Space?
Do The Math, 12 October 2011
"In other words, I’m an insider—and a supporter. I whole-heartedly believe that space offers tremendous scientific promise." ...
"But I want to caution against harboring illusions of space as the answer to our collision course of growth on a finite planet. We live at a special time. We have enjoyed spending our inheritance of fossil fuels, and are feeling rather heady about our technological prowess. For many generations now, we have ridden an exponential growth track, conditioning ourselves to believe that our upward trajectory is an eternal constant of our existence."