How we are using up our home, how we are living and polluting the planet is frightening. It was evident when I was a child. It's more evident now.

We were unusually brought up; there was no gender differentiation. I was never thought of as any less than my brother.

I always give the analogy of the Earth at Night picture, of 7.3 billion of us, right? And everyone says, "Well, that's population." Well, if you took the entire world's population and you lived at the density of Manhattan proper - not a bad place to live - how much space do 7.3 billion people take up? The state of Colorado. At which point I end my lectures, because I want you to be thinking ... is this really a question of population, or is this a question of land use and resource consumption? And let's face it, the top 1.3 billion of us are doing all the damage. Sorry.

The only thing that mattered was what you were to do in life, and it wasn't about money. It was about teaching, or learning.

I always say I'm no different than a 19th-century landscape painter, it's just that we have these incredible tools to look at the Earth and look at the world around us differently.

If we forget what used to be, then we’ve lost an ability to really be sensitive to our surroundings.

It terrified me to have an idea that was solely mine to be no longer a part of my mind, but totally public.