We have the capacity to alter the nature of nature. No, we don't have just the capacity - we are altering the nature of nature, the natural systems that cause the planet to function in our favor.

All through college, I had frequently been the only girl in a science class - which wasn't such a bad deal.

When you think about the real cost of so-called cheap energy that has driven our prosperity to unprecedented levels, for some of us, to our horror, we've realized that this has the potential for burning brightly and then snuffing out.

The diversity of life on Earth, generally, is astonishing. But despite those large numbers, it's also important to recognize that every species, one way or another, is vulnerable to extinction. And in our time on Earth... our impact on the diversity of life has been profound.

It's baffling why the issues relating to climate change - [which] have far more obvious and tangible and much more clear-cut evidence about the cause - have been slower for people to accept as a given.

Any astronaut can tell you you've got to do everything you can to learn about your life support system and then do everything you can to take care of it.

We have to look in the mirror first. What are we doing? How can we make a change? It always starts with looking in the mirror. Every individual can. Every individual can make a difference either by proactively doing something positive or by doing nothing. That's a decision, too.