Fundamentally not to waste energy. If we were all to reduce our demands for energy, it would make an enormous amount of difference.

We really need to kick the carbon habit and stop making our energy from burning things. Climate change is also really important. You can wreck one rainforest then move, drain one area of resources and move onto another, but climate change is global.

All our environmental problems become easier to solve with fewer people and harder - and ultimately impossible to solve - with ever more people.

No one will protect what they don't care about, and no one will care about what they have never experienced.

An understanding of the natural world and what's in it is a source of not only a great curiosity but great fulfillment...

You'll discover in countries where women have control over their own bodies, where they have education, where they have birth control, where they have facilities and where they are literate, when those things happen, the birth rate falls.

There are perfectly good independent small nations.