In the past few decades, Earth's natural systems have endured more pressure than in all preceding human history.

If we have a hope of really understanding our place in nature and of carving out a place for ourselves that is sustainable, it's primarily because of the new level of communication. It used to be, 'What you don't have in your mind, you have on your shelf.' But now we have the Web.

Historically, girls have not been encouraged to be scientists, to be explorers, and there's a social kind of constraint, of course. Having the responsibility, a disproportionate part of the responsibility, for caring for families, caring for children. I know this challenge from firsthand experience because I have three children and four grandsons.And some of the time I have spent as a scientist and as an explorer has meant choosing to not be with my children and grandchildren as much as I might otherwise have done had I not been a scientist, an explorer.

If somebody dumps something noxious in my back yard, the dumper is the last one I would call on to repair the damage.

Fortunately, we know more about the problems that we have than in all preceding history. We know now the consequences of the things that we put into the air, into the water - of the way we treat life on Earth.

Earth as an ecosystem stands out in the all of the universe. There's no place that we know about that can support life as we know it, not even our sister planet, Mars, where we might set up housekeeping someday, but at great effort and trouble we have to recreate the things we take for granted here.

We understand that we must make peace with nature - that our lives depend on it.