In ancient Greek times Thales said that water was the primary element, and that everything else was derived from it. Anaximenes said no: It's all condensed or thinned from soulful air. Heraclitus was a fan of fire. But no one, it would seem, ever made a case for dirt. It's a bit too muddled and muddy, perhaps, to seem fundamental.

The most-publicized environmental movements of today seem to follow a similar pattern, safeguarding the purity of air or water, or fearing death by nuclear fire. Dirt has none of the same glamour, and it never seemed pure. It's full of worms and rocks and dung and all the grungy junk little boys were supposed to be made out of.

But as David R. Montgomery suggests in his new book, Dirt: The Erosion of Civilizations (University of California Press, 285 pages, $24.95), the resource that's most fundamental to the way we live—and potentially the most at risk—might nonetheless be the stuff under our shoes. To be blunt: Without it, we don't eat.

Through much of the book, Montgomery charts how the fall of civilizations is often linked to the state of the soil, in particular its susceptibility to erosion. North Africa and the Middle East, now deserts of shifting sands, used to be the breadbaskets of the Mediterranean. The population of once-thriving Easter Island had to resort to eating each other after they bled their hillsides dry. And in the Mississippi basin, millions of tons of soil are donated each year to the Gulf of Mexico.

The narrative Montgomery describes for each fallen or falling civilization is simple, and repeats itself with variations. It goes kind of like this: The population goes up, so farmers use more aggressive farming practices to feed the growing populace. The food production increases accordingly, until the last of the fertile soil either gets its game salted or deposits itself uselessly at the bottom of the ocean. At which point nobody can grow their apples, their corn or their luxuriant pomegranates.

So what's the solution Montgomery proposes? It ain't better fertilizer, and it seriously is not better irrigation (unless you want to turn our nation's midsection into a salt flat). No, it's pretty simple: Farm multiple crops on much smaller plots, which, believe it or not, have higher growth and cost efficiencies than the big industrial wheat fields. That, and could you please leave poor Oklahoma and the hill country entirely alone, please?

The book is academic in tone, which means the prose is occasionally as arid as some of the soil Montgomery describes. Likewise, the author is tireless in hammering home his thesis with often repetitive examples. However, he does also leaven his argument with cocktail-party anecdotes about the dirty dealings of U.S. soil policy, or Darwin's much-mocked fixation on the earthworm's thankless work. And if this doesn't sound like cocktail banter to you,'re obviously not going to the right parties.

David R. Montgomery reads from

Dirt: The Erosion of Civilizations

on Thursday, June 28, at Powell's City of Books, 1005 W Burnside St., 228-4651. 7:30 pm. Free.