When I was born, the world's population was 3.5 billion. There are now 6.8 billion people on the planet. By 2050, that's expected to rise to 9.4 billion. What's more, the Earth's resources aren't growing; they're decreasing - and rapidly.

There is nothing more powerful than the made-up mind.

If you want to swim across the English Channel from England to France - you have to leave your doubt on the beach in England.

I think that I was slightly naive. I thought that if I showed people the beauty of the Arctic and the beauty of the polar bears that they would care so much that they would stand up and try to make a change.

If we pass on an unsustainable environment to our children we have failed them.

Climate change is the Everest of all problems, the thorniest challenge facing humankind.

Of all the creatures in the world that really frighten me - the hyena in Africa, the great white shark - leopard seals are near the top of the list. They're killers. If my team spots one, they'll pull me out of the water.