To be with another scientist and make a discovery and share that with a global audience, or working with bear biologists in Alaska, by helicopter - [it's] really what I've given my whole life to. And I get to do that just about every week.

Many of the medicines we use today, to fight everything from AIDS to cancer, originate as a toxin in an amphibian skin. When we lose these animals, we lose resources. We lose keystone species in the environments where they live.

We live in uncertain times when it comes to the future of life on Earth.

We know that when push comes to shove, [we can] drive ourselves to save our planet.

I'm really worried about what the world is going to be like when my daughters are young women, [when] they are young leaders or mothers or businesspeople - whatever they're going to be. I'm afraid they're going to have a less healthy and less biologically rich planet.

Whether it's exploring the woods around where I grew up, or even today exploring the coastal habitats and environments where I live in New England, or in a remote wilderness we're featuring in one of my series - I love to be in the field and I love to explore.

We are not far away from the point of no return when it comes to life on earth, and we have some radical choices to make.