Imagining the world without us is a recipe for despair and paralysis. I actually think it's more helpful to imagine the world before us, to look back at those unstable ecosystems of the Triassic and realize that were in another phase of unstable ecosystems. Knowing that, demystifying our situation as it were, makes it easier to think about solutions. We are not looking into the unknown. The only thing unknown about the situation is how we're going to fix it, and when.

We have converted huge swaths of land and ocean into human habitats where we live and grow food and harvest energy. But there's been a sea change in the past century.

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.

The early Triassic was a period when the planet was recovering from the worst mass extinction it had ever known - that was the end Permian extinction, where climate change caused in part by mega-volcanic eruptions wiped out ninety-five percent of life on Earth. It took about ten or twenty million years for the planet's ecosystems to stabilize. During that time you saw a lot of weird, out-of-balance ecosystems where, for example, crocodile-like predators ripped the crap out of each other along the coasts.

In fact, the early demographer Thomas Malthus believes that the only way the human population would ever check itself was by running headlong into a disaster, like a pandemic or famine. Sometimes we get so frustrated with the slowness of human political processes that we wish a giant flaming rock would solve the problem for us.

So science alone cannot solve this problem [mass extinction of humans]. It's something that we can only tackle by bringing science together with culture, economics, and even politics.

My first goal would be to reduce the perturbation in the carbon cycle. That would mean using carbon neutral sources of energy, and changing our agricultural practices to be less disruptive and polluting. I'm not talking about a policy here so much as changing the way our infrastructure works. That's why I'm so fascinated with changing the way we build cities, because they are the most developed forms of physical infrastructure for human habitation.