Cities generate most of the global economy, and most of its energy use, resource demands and climate emissions. How we build cities over the next decades will largely determine whether we can deliver a bright green future.

I think we're going to start to see a new model of civic advocacy where people get together once in a while to protest, but it's more about an ongoing, sustained engagement in issues, networks and communities about which people care.

Urban retrofitting: creating different sorts of spaces and uses out of places that are already there.

At its very heart, Worldchanging is about using the best of people's new ideas, bringing them together and applying them to the massive problems that we all face.

There’s more to being an environmentalist than occasionally signing an online petition and mailing your check to the Sierra Club. Really the most effective environmental actions you can take have to do with crafting your home and surroundings, your workplace decisions and your investment habits.

For most people, using the Internet broadens their sense of who 'we' is and actually ends up leaving us in a place of greater compassion and understanding. It leaves us more connected to a larger group of people and more at one with a lot more people in our community.

The denser places get, the lower the amount of energy people use to get around it.