I'm an old member of Greenpeace. I worried intensely, as I think most of my friends did, that the world was coming apart.

We worry about the seemingly ever-increasing number of natural catastrophes. Yet this is mainly a consequence of CNN - we see many more, but the number is roughly constant, and we manage to deal much better with them over time. Globally, the death rate from catastrophes has dropped about fifty-fold over the past century.

When thinking about the future, it is fashionable to be pessimistic. Yet the evidence unequivocally belies such pessimism. Over the past centuries, humanity's lot has improved dramatically - in the developed world, where it is rather obvious, but also in the developing world, where life expectancy has more than doubled in the past 100 years.

I think it's great that we have organisations like Greenpeace. In a pluralistic society, we want to have people who point out all the problems that the Earth could encounter. But we need to understand that they are not presenting a full and rounded view.

My belief is that what comes across on the television is a capture of my enthusiasm and my passion for wildlife.

Even if the ocean on Enceladus starts out being as microbially poor as the pelagic ocean on Earth, which is the worst case, we still have a chance of seeing lots of organisms in the plumes.

After the ignominious collapse of the Copenhagen global climate change summit in 2009, Bolivia organised a People's Summit with 35,000 participants from 140 countries - not just representatives of governments, but also civil society and activists.

I've always liked trees. And then, growing up, I took an interest in ecology, hedges being destroyed, the landscape being turned into prairies.