Book Reflection: Dirt: The Erosion of Civilizations by David Montgomery (Part I)

Dirt: The Erosion of Civilizations by David Montgomery of the University of Washington was simply a book on a library shelf among four other soil tomes. That was all the library had to offer for my self-education effort for the UN’s International Year of Soils. Fine. The “erosion of civilizations” part suggested something epic.

The first chapter introduced me to an aspect of Charles Darwin that was never mentioned in all the science classes I have taken, documentaries watched, nor read in general science or history books. Perhaps it is silly to someone else that I never knew Darwin’s affair with British earthworms, but I thought the story rivaled the one about finches in the Galapagos. I even wrote a previous post about it.

But that was the only chapter until the last that focused on soil formation instead of soil erosion and degradation. In between these symbolically optimistic chapters were eight chapters of human-induced disaster stories spanning from the dawn of agriculture to current times.

Mesopotamia, ancient Egypt, ancient China, Greece, Roman Empire, European Middle Ages, colonialism, the American frontier, Dust Bowls, Island societies and the Green Revolution all starred in this story of soil husbandry. Many had their own chapters.

There is a very repetitive theme in this book. Most early agriculturalists, at least the sedentary ones, figured out how to terrace, use manure and other natural fertilizers, and plow along the contours of the land—it wasn’t just, say, China that knew how to terrace, as some people think.


Then in every major society people would eventually reproduce beyond what the land would support. The hills would lose soil that was loosened by plowing and brittle from water and organic (earthworm-created) material loss and the people would migrate to the lowlands. Then the lowland crops would suck all the moisture in the ground until the water table met the surface, bringing salt with it.

That is where Mesopotamia failed. While the author never assumes soil degradation caused the end of this ancient civilization, he does discuss all the scientific evidence suggesting these events coincided. Egypt and China had different rain cycles where the rain arrived closer to harvest season, floods bringing in fresh silt, and thus avoided major issues until dams and levees were constructed.

Greece did the same thing as Mesopotamia. Rome took things a step further and conquered other lands to import the grains they could no longer grow. In this step of the soil versus civilization cycle that small farms can no longer support families but a rich fellow can buy large tracts of abandoned land and then pay for tenant farmers. Shortly after this trend develops the tradition of farming dies out and people farm with faster and easier techniques such as plowing in straight lines, which causes more erosion, and not actively adding fertilizer.

Eventually people had to go back to investing in terracing, fertilizing and rotating crops—ancient techniques that permitted agriculture, but was not as talented at losing soil and nutrients as the techniques used during societal booms.

By the Middle Ages the warming of the climate supported more agriculture, but by then the Church owned much of Europe and the farmer was a tenant and echoed the same issue as Rome.

David Mongomery
David Montgomery, professor of Earth and Space Science at University of Washington. He has written three general audience science books and appeared in the documentary, “DamNation“. (Photo courtesy of the John D. and Catherine T. MacArthur Foundation)

The United States took things another step further—and has since taken a step back, and another step forward, and another step back…. But I will put that in a separate post—I have ranted enough.

I have a dark sense of humor that appreciates the illogical oddities of human behavior, so this book was as amusing as was depressing.

Mostly I learned so much. Even the topics I considered myself well acquainted with had room for the immense details and nuances that other sources never covered. The book may have been written for a more academic audience, but it is very readable for the general audience.  Every time I learned something I had many more questions and then the questions were addressed later in the book. I got to the point where I assumed and took for granted that almost all of my curiosities would be addressed—the writer was that thorough and reliable.

Considering the content it covers and how well it was covered, I feel sad to return the book to the library and sadder that most people will never read it or anything similar.


5 thoughts on “Book Reflection: Dirt: The Erosion of Civilizations by David Montgomery (Part I)

  1. I am a retired economist, and now, a natural farmer following the natural farming practice of Fukuoka. I am recently doing my own research on how human civilizations have affected climate by their agricultural practices. My theory is when people remove trees and shrubs to create more farmland or grazeland, the surface areas of vegetation will drastically reduce, leading to higher rate of evaporation, less rainfall, and more unstable climate. A combination of these results in the death of more trees and shrubs in the entire area, the loss of even more surface area of vegetation. This in turns results in a much lower relative humidity close to the ground, and hence even less precipitation. Within a few hundred years, a desert will be formed.

    1. That’s an interesting thought and makes perfect sense. Ecologists tend to have a biology bias and see vegetation as layers of habitat while physical scientists tend to look at the interplay between non-biological elements, but plants are a large reservoir of water. They not only hold water in the soil with their roots, but debris delays evaporation and an appreciable amount of water gets trapped in the grooves of bark. Also whether in a forest or a tall grassland, plants grow in height tiers which allows water to diffuse, get used, and not run off to cause drastic floods. With more vegetation evaporation would be gradual from the plants’ surface (and across the landscape) instead of limited to the lower surface area of rivers and lakes. Air moisture depends a lot on local and regional surface moisture, so having better distribution of surface moisture could better distribute rain systems. Logically I can see how that would offer climatic stability. Of course, now I want to research the topic and learn the details! Thanks for bringing it up.

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