Dishing dirt on top soil

A geomorphologist helps us appreciate Earth's crust for what it is: giver of all life

Dirt: The Erosion of Civilizations by David R. Montgomery, University of California Press. $24.95. 295 pages.

I recognized myself immediately in "Dirt: The Erosion of Civilizations" by David R. Montgomery, a book every suburban gardener -- and every thoughtful eater -- should read. When I first tried to grow tomatoes, I chose a patch of hard clay soil laid bare when the builders of my subdivision razored off the original topsoil. I brought in soil amendments and mulched, but not enough. During the hot summer, I watered the plants almost constantly. The stunted, gray stalks died of thirst attempting to drill roots through that hard clay.

We need deep, fertile soil for harvesting feel-good tomatoes -- and for civilization. Montgomery argues that all advanced societies have risen and fallen based on the fertility of their soil, and that if our globalized "island" community does not address basic soil problems, we will fall even more cataclysmically than those who have gone before.

Montgomery, a geomorphologist (specializing in how the surface of the earth changes), creates a big picture so large it extends back in time to the most recent Ice Age and, geographically, to every corner of the globe. He has a great job: in between paging through Roman treatises on agriculture, he gets caught in quicksand and is saved by his grad students. But "Dirt" is all business. Montgomery presents his data with equal parts restrained outrage and fascinated worry. He is a prophet with a vest full of soil samples.

After a necessary primer on the properties of soil -- ever heard of the O Horizon? -- Montgomery launches into a worldwide survey of the use and abuse of dirt, starting with the earliest farmers on the planet and ending in today's back yard. The account is packed with detail throughout, and though it errs on the academic side, it repaid this reader's attention again and again.

Montgomery takes us on a whirlwind tour of history's greatest civilizations, including Mesopotamia, Egypt, Greece, Rome, Mayan Central America and China, to show us that the unchecked erosion of topsoil contributes in large part, if not causes, that society's destruction.

The process is depressingly similar everywhere: Intensive agricultural exploitation of fertile lowlands produces a surge in population and more demand for food. Farmers move upward onto less-desirable slopes, deforesting as they go. Rain and wind plunder the soil from continuously plowed farmlands. Finally, cramped into remaining ribbons of fertile land along rivers, civilization must find other sources of food, or it falls apart.

North America has not escaped this process. Montgomery unfolds the destruction of the soil in Colonial times, when abundant land to the west discouraged farmers from sustainable practices. Astonishingly, as early as 1800, much of the East Coast was barren.

Tobacco and big agriculture also turn out to be culprits. Planting tobacco wears out the soil fast, but the leaf was so profitable to Colonial plantation owners that everything was sacrificed to its cultivation. Colonial governments taxed tobacco and made huge, short-term revenues. Farmers' concerns were ignored: "When Virginians requested a temporary ban on tobacco growing in 1662," Montgomery writes, "they were unsubtly told never to make such a request again."

Only in the Dust-Bowl-scarred 1930s -- and after too much expansion westward -- did the new U.S. Soil Conservation Service promote such principles as cover cropping, contour plowing and manuring. The legacy of our farming malpractice can be seen whenever we drive by "Entering Water and Soil Conservation District" signs on the highway.

Still more fascinating, however, are the accounts of "lab" island civilizations from the South Pacific to Iceland. Remember Easter Island (Rapa Nui) and its enigmatic stone heads? In hair-raising fashion, Montgomery details how colonists arrived, exploited the fragile ecosystem, developed a complex civilization, then ignored the ravages of deforestation and soil degradation, finally resorting to cannibalism when they could no longer farm and no trees were left to build canoes in which to escape.

Segue neatly to our island Earth and its global economy. Montgomery warns that we may also go the way of Easter Island if we do nothing to reverse trends. To his credit, he offers a full range of solutions, from the macro (population control) to the micro (suburban gardeners, keep on keepin' on).

Montgomery acknowledges that Doom by Dirt is not imminent worldwide. We can still fortify soil through chemical means, and genetically modified plants have given hope for higher crop yields. Still, he insists that we cannot go on forever increasing in population while depleting our land: Crop yields have peaked, and within decades, we will have exhausted the supply of oil for making chemical fertilizer.

It is time, Montgomery says, to spend less time on stone idols and more on compost.

I knew I needed to do a lot more work building up my weak subdivision soil before it could grow tomatoes, but I wanted a shortcut. David Montgomery shows that there is no shortcut to a sustainable world, where growing tomatoes in one's backyard is not only a pleasure but also a necessity.