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Review of Dirt

August 15, 2009 pm31 5:08 pm
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Well, not really. Sort of a partial review. Preliminary. Brief comment.

Dirt is a book. The full title is Dirt: the erosion of civilization, by David Montgomery (the environmental David Montgomery, not the labor historian)

In less than 250 pages he does a pretty good idea of explaining what soil is, the history of what people thought about it, and the history of how people used (and mostly destroyed) it.

“It’s like the earth’s skin” he keeps saying. And as a non-scientist, the analogy is appealing.

When he deals with the past, the pattern he lays out is simple: a civilization uses up its soil, and moves on to other soil to use up; or a civilization uses up its soil, and the civilization declines.

Problem: we don’t have much new soil to move on to, all the best stuff is in the temperate zone (the soil in the tropics is not as good and gets depleted much more quickly), and we don’t really want to decline.

He makes the case for farming in different ways, smaller farms, less monoculture, drastic reduction in pesticide and fertilizer, more labor intensive farming, mulching/manure, contoured plowing, etc. etc. It is both radical, and reasonable.

– – — — —– ——– ————- ——– —– — — – –

Units! Units are the worst part of the book.

He’s only got four things to measure, but he makes it so hard to follow. We have depth of soil. That one he handles ok. He uses inches, and he uses feet. Reasonable.

Time. He uses years. Tens of years. Hundreds of years. Thousands of years. And generations. He should dump those generations. Unnecessarily confusing. But I’m being picky.

Areas. Acres. Hectares. Square miles. Size of ________ (fill in the country). This drove me nuts. Pick a small measure (acre or ha.) and stick with it. For larger areas, pick one familiar area, and compare all others against it. I like France. “An area one tenth the area of France” “an area half as large as France” “a bit larger than France” – If France is the wrong unit, pick another. But pick one, and stay with it. Otherwise the reader just gets confused. Most people do not offhand have the ability to compare lots of areas.

How fast does soil erode? Montgomery uses inches per century. Or years per inch. Or inches per year. Or inches per thousand years. The concept itself, that soil disappears, is foreign. Shifting units on top of this is confusing for no reason. I should have converted each figure to inches per century. Instead I just got frustrated as I read.

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Soil erosion is important. Soil is a resource that is disappearing like oil. We should know more.

Montgomery makes this information accessible. He emphasizes the importance, at a level technical enough for the science-interested layman. Aside from the units (just convert to inches per century) it is a relatively easy read.

It is worth knowing more about this topic, and Dirt is a good intro.

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