I have long thought that mainstream environmentalism is essentially a belief system for pessimists. In their eyes, we are on a downward path from some idealised golden age, and things can only get worse. This seems to be an inbuilt human trait, as each generation seems to find reasons why things were better when they were young and why the next generation (perhaps with their own children as exceptions) are taking society to hell in a handbasket. The green movement gives a pseudo-scientific gloss to this.
Of course, it is arguable that the discontent we all feel at times is what drives the human race to innovate and change things. Nothing is ever perfect and, as we make an improvement in one area, we often create other problems or have the leisure to find something else which needs fixing. The fact that greater prosperity doesn't necessarily make us any happier is sometimes used as an argument against continued economic growth; putting environmental goals before economic ones.
Now the Social Issues Research Council has published a report which suggests that, as a nation, Brits are more optimistic than we might believe. But, being Brits, we are very self-effacing about this and don't really want to admit it. Nevertheless, in my (optimistic) view, this seems to confirm my feeling that the majority of people worry less about the big environmental issues than does a vocal and influential cadre of pessimists.