If we aim for what is no longer possible, we will achieve only delusion and frustration. But if we aim for genuinely worthwhile goals that can be attained, then even if we have less energy at our command and fewer material goods available, we might nevertheless still increase our satisfaction in life.

Early ecologists soon realised that, since humans are organisms, ecology should include the study of the relationship between humans and the rest of the biosphere. ... We don't often tend to think about the social sciences (history, economics and politics) as subcategories of ecology. But since people are organisms, it is apparent that we must first understand the principles of ecology if we are to make sense of the events in the human world.

Today, it is especially difficult for most people to understand our perilous global energy situation precisely because it has never been more important to do so.

The science is in: either we go cold turkey on our coal, oil, and gas addictions, or we risk raising the planet's temperature to a level incompatible with the continued existence of civilization.

We are about to enter a new era in which, each year, less net energy will be available to humankind, regardless of our efforts or choices. The only significant choice we will have will be how we adjust to this new regime. That choice - not whether, but how to reduce energy usage and make a transition to renewable alternatives - will have profound ethical and political ramifications.

If we aim for what is no longer possible, we will achieve only delusion and frustration. But if we aim for genuinely worthwhile goals that can be attained, then even if we have less energy at our command and fewer material goods available, we might nevertheless still increase our satisfaction in life.

If we do nothing, we still get to a post-carbon future, but it will be bleak. However, if we plan the transition, we can have a world that supports robust communities of healthy, creative people and ecosystems with millions of other species.