The fact that we have been able to perturb the carbon cycle with our industrial revolution is evidence of how vulnerable we are - because when we destroy our environments, we destroy our food and energy supplies. In short, we destroy ourselves.

One reason that we're so adaptable is that humans are excellent tool users and homebuilders. When our environment doesn't provide us with something that we need, we try to make it ourselves out of whatever is available, whether that's rock or wood or ore or DNA.

Eventually, humans invented agriculture, which could be understood as a way of turning the natural world into a tool for our use. There's evidence that we have been domesticating crops and animals for at least 15,000 years, adapting ecosystems to our preferred way of life.

Humans are a great survivor species but our survival will be pretty grim if all of the plants and animals we depend on die out. That's why any human survival strategy has to include a plan to maintain our environment roughly in the state that it's in now.

I think small animals can escape from many kinds of natural disaster more easily. There are just more places for them to hide, and more ways for them to find safe habitats. So this means that rats are set up to rule the Earth, but most of us already knew that. Now you know why.

Part of what I wanted to do in my book was point out that we have almost reached the point where we can prevent a mass extinction with the science and technology we have today. We can build carbon neutral cities.

Sometimes it's hard to take everyday concerns seriously when you think about vanished ecosystems that existed 300 million years ago and were eradicated by giant explosions. My goals haven't changed, because my goal has always been to save the world!