What is most pressing, what are the knock-on effects of our actions and what should we do first? Do we all need to become vegetarian? How can we fly in a low-carbon world? Should we frack? How can we take control of technology? Does it all come down to population? And, given the global nature of the challenges we now face, what on Earth can any of us do? Fortunately, the environmental thinker and writer has crunched the numbers and plotted a course of action that is practical and even enjoyable.