For humans, the Arctic is a harshly inhospitable place, but the conditions there are precisely what polar bears require to survive - and thrive. 'Harsh' to us is 'home' for them. Take away the ice and snow, increase the temperature by even a little, and the realm that makes their lives possible literally melts away.

The image of Earth from space transformed our view of ourselves. It is maybe the most important image that exists - because we can see ourselves in context in a way that otherwise would be really hard to explain. It should inspire us to wonder about it, to want to know everything we can about it and do everything we can to take care of it.

Santa Monica Bay is less polluted today than when I first moved to the area in the 1970s, because actions have been taken to avoid putting some of the noxious materials into the sea. I think people are more aware than they once were, the air is cleaner, water generally is, in spite of the fact that there are more people.

The end of commercial fishing is predicted long before the middle of the 21st century.

We still have the illusion that the ocean will recover. That even if we do have to lose sharks, people don't understand why this matters. The evidence is in front of us, and we fail to take it in and say, "Now I get it. Now I understand."

In terms of personal choices, let's all think more carefully about where we get our protein from.

When you are a child you learn your alphabet, your numbers, but increasingly, we must learn from the earliest stages that the highest priority has to be to maintain the world as a safe place for humankind.