However, technology, economic forces and population pressure lead inevitably to charcoal. It allows people in the cities to have access to forest energy, which would rapidly become impractical if bulky firewood had to be hauled into towns from ever-more distant forests. If large amounts of high-density energy are needed, as in metal smelting or quicklime production for plaster, the consumption of charcoal (hence, wood) skyrockets. Britain’s forests were pretty much denuded by the time the Romans got there. (No, it didn’t go into ships, it went into steel weapons.) Most of the civilized countries in southern Europe, such as Greece and Italy, lost their natural forests shortly after the beginning of the Iron Age. The Maya also consumed huge forest acreage for the production of plaster for their temples. And we all know what’s happening in Haiti–environmental devastation, flooding, loss of topsoil, landslides.

The pattern we seem to see is hauntingly familiar. Increasing the concentration or availability of a commodity (such as energy) almost inevitably seems to lead to increasing overall inefficiency and decreasing sustainability. The increased benefit seems to last only as long as the original resource isn’t depleted. Then everything collapses.