Alex, Morton and Raymo have touched on something I have quite a strong opinion on, for the planets sake alone. I usually keep it to myself because not a lot of people I talk to would agree.
I believe that the level of human population is the biggest threat to all living things future survival. I saw a program on TV not long ago of a meeting between Barack Obama and Sir David Attenborough. It was the first time I had heard a world leader mention the threat of an over populated planet and how we can address it.
I did hear a scientist say something once that I found quite humorous and it was that the only thing on this planet in plague proportions is humans.