Ecological Debt is an unusually wide-ranging book, from a writer who understands that climate change, debt, resource depletion, development and lifestyle are all intricately bound together. To do justice to one issue, you have to follow the threads through them all. That could have resulted in a complete tangle of a book, but the idea of ecological debt serves as a locus that keeps it from unravelling.
Ecological debt is basically taking out an environmental overdraft, either on the earth itself or on somebody else. If we assume that everyone has an equal right to emit carbon, for example, then some countries and individuals are using more than their fair share of the atmosphere. That creates climate debtors and climate creditors, and the usual roles of debt are reversed. We are used to thinking of poor countries as heavily indebted, but "it is the inescapable debts of the rich that threaten our collective future".
That's the radical notion that Simms explores here. The richest countries in the world owe both an environmental debt to poorer countries, and a historical one, through colonialism and conquest. Considering that future development is constrained by limited resources and the climate, he argues that we should re-consider the idea of economic growth in rich countries, and start sharing the wealth better: "There is no more fundamental issue than the distribution of wealth in a climate constrained world economy".
That is of course a pretty unwelcome conclusion, but the idea of 'ecological debt' allows Simms to repackage a message that would otherwise be freighted with unhelpful ideology. Economic rebalancing is a moral imperative, neither charity nor socialist idealism - it would be righting a wrong, and repaying a debt.
The book does pack a little too much in - this is the updated 2009 edition, and the last few chapters lose focus a little. Overall however, this is a powerful and creative exercise in joining the dots between the several converging crises of the 21st century.