Dirt: The Erosion of Civilizations, by David R. Montgomery ★★★★½

Montgomery introduces us to the basic concepts of soil science, and then starts a tour of soil usage over the ages. He highlights ancient civilizations in the Old and New Worlds and what we know of their agricultural practices— and calls out erosion, soil depletion, salinization, and desertification as consequences that facilitated the downfall of their nations. (This is not a how-it-really-happened crank history book; he’s just asserting that a failure to conserve soil resources weakened them.) He also notes which ones figured out the right techniques of conservation and how they were able to persist much longer.

The problems extend to recent history as well: he calls out bad practices in the past few centuries all over the world and provides ample information about what went right and wrong. Under normal geological conditions, soil is created very slowly, and shortsighted agriculture can strip it away far faster than it can be created normally. But there are alternatives to just plowing up soil, planting a monoculture, and using industrial fertilizer to make up for using up the soil, and he explains them— including many techniques used in organic farming (though he also calls out industrial organic farming as just as unhealthy). Montgomery’s bottom line is that we need better mechanisms than short-term markets to provide proper incentives to take care of the soil (he believes this is a sensible place for government to intervene), and that the right techniques will vary with each patch of soil; there is no one-size-fits-all answer, but there is a big toolkit of agroecology that every farmer should have available. The alternative is using up in human time a resource that can only be replenished in geological time: a sure route to the downfall of our own global civilization.