This is the first time I've reviewed a book by a druid, although it wears its robes lightly. The book is The Ecotechnic Future by John Michael Greer. It takes its place in a genre that is small (in the context of the economics literature) but perhaps growing – namely the crossover between thermodynamics and economics. The founding title is Nicholas Georgescu-Roegen's The Entropy Law and the Economic Process (1971), which I found almost impossible to understand when I tried it a few years ago. There is a novel called The Burning by Thomas Legendre, which – like so many novels of ideas – is compellingly awful as fiction and mildly interesting for the ideas. And, coincidentally, a new title has just reached me, Thermoeconomics: A Thermodynamic Approach to Economics by John Bryant. (It needs more physics than I can muster, so anyone who'd like to read and review it please let me know.)

The starting point of The Ecotechnic Future is that we are at or past peak oil, a fact that makes painfully apparent the dependence of human society on fossil fuels. Greer compares humans to weeds, a species that triumphantly colonises an entire ecosystem by consuming all its resources. Sustainability requires us to shift to a different ecological strategy, more like hardwood trees than weeds, using resources far more efficiently but limiting our expansion as a species. He's rather cheerfully pessimistic about the prospects for attaining this state, predicting that we are likely to go through a long phase of eking out the use of fossil fuels, and then a further stage of salvaging what we can from industrial civilisation in a kind of post-oil Dark Ages, before reaching a new ecotechnic basis for society. On the way, we will see depopulation, mass waves of migration and the collapse of existing cultural and political orders. He sees the start of this 'culture death' already in the demise of traditional cultures and the pervasiveness of advertising-driven mass consumption and celebrity obsession.

What we need to do to navigate this impending collapse is return to a homesteading lifestyle, Greer argues. It was at this point that he lost my goodwill, after an interesting analysis of trends and plausible social strains in the first half of the book. The second half of the book is yet another expression of the profoundly unrealistic romantic yearning for an Arcadian past. Grow-your-own meals is not a practical basis for a transition to an energy-efficient economy when more than half the world lives at high density in cities and productivity levels in food production need to increase, and when the real gains in human welfare have indeed come from urbanisation and the possibilities for exchange that go along with it. Without pragmatism, nothing will happen.

So I was disappointed by the book as I read on. It's quite a good read. Greer has some nice turns of phrase – I like the idea of money as a “mass hallucination” for example. But there's still a gap in the literature for someone to bring the sensibility of economics to the realities of thermodynamics. The most interesting areas of economics have always been those at the borders with other disciplines – I firmly believe economics needs to be at least consistent with and preferably linked to the natural sciences. As it was when David Hume began to think about it in the 18th century, economics is the projection of scientific discovery onto human society, whether that's ecology (as is now in fashion), cognitive science (ditto) or physics – because we are part of the natural world and anything we do is subject to its laws.