June 19, 2014
The Problem Of Soil Erosion

David Montgomery's book Dirt: The Erosion of Civilizations does an excellent job of surveying the historical impact of agricultural practices that some civilizations to collapse. While the historical record is not complete enough to say how much reduced ability to grow crops (whether through erosion, salt build-up, and climate change) contributed to the Roman Empire's collapse in other cases the signals are more clear.

What's cause for concern: many of today's societies have learned nothing from this historical record. Here is an excerpt of Montgomery's book where he discusses present day soil erosion in Central America:

Modern deforestation in the Petén is beginning to repeat the cycle of erosion after a thousand years of soil development. Since the early 1980s landless peasant farmers have turned much of the region's forest into traditional Mayan milpas (small cultivated fields). A twentyfold increase in population from 1964 to 1997 has transformed the region from nearly unbroken forest to a nearly deforested landscape.

Cultivation on hills really rips away the topsoil quickly.

Soils on most of the region's hillslopes consisted of an organic horizon above a thin mineral soil sitting directly on weakly weathered limestone bedrock. One study found that unde the region's last virgin forest, hill-slope soils were about ten to twenty inches thick, whereas modern cultivated fields are already missing three to seven inches of topsoil ‐ most of the O and A horizons. In some places, the rapid erosion followed modern slope clearing and cultivation had already stripped the soil down to bedrock.

Damage done in decades takes takes many centuries to restore. The Romans, Greeks and other civilizations suffered from erosion many centuries ago.

Think about what this portends for the food supply in Central America in the coming decades. Don't feel complacent about that. The United States has a big soil erosion problem, a growing population due to immigration, and we aren't growing new farm fields. The USDA expects the United States to become a net meat importer in 2015, partly due to drought. Think the US is a big grain export powerhouse? US wheat exports peaked in 1982.

Share |      Randall Parker, 2014 June 19 10:51 PM 

Brett Bellmore said at June 20, 2014 3:27 AM:

"The USDA expects the United States to become a net meat importer in 2015, partly due to drought."

Mainly due to turning animal feed into sub-standard fuel for cars, though. "Drought" is the traditional excuse used by command economies to explain away screwing up their agricultural sector, and, thanks to the regulatory state, the US is taking on some characteristics of command economies.

destructure said at June 20, 2014 6:37 AM:

I'm all for stopping soil erosion due to deforestation. But the biggest cause of soil erosion is desertification. This guy claims to know what causes it and how to fix it. I think he's right. Of course, he dresses it up in terms of man-made global warming which is bollocks to anyone who's ever bothered to look at the temperature chart of the last 400, 10K or 800K years. Still, I'm all for stopping desertification.


Angie said at June 20, 2014 8:41 AM:

The agriculture is the first point of view in all states, because a healthly economics need to have a solid agriculture.

Chinaski said at June 20, 2014 8:54 AM:

To stop deforestation, grow grass, eat animals

James Bowery said at June 20, 2014 1:12 PM:

Here's an explanation of civilizational collapse from the perspective of political economy:

"Indeed, given the centralization of asset ownership that has resulted from the subsidy of non-subsistence property, a subsidy inherent in civilization, it may be the failure to use this tax base is the ultimate cause of the repeated decay of civilizations from ancient times."


Soil erosion results from taxation of subsistence. If people have to extract not only their subsistence from the land -- "subsistence" being defined in the way it used to be defined by the iron law of wages (what it takes to raise children to replacement viability which would include passing on productive land) -- but also to supply the surpluses of the parasite classes (whose accumulations are not taxed because the tax base is on economic activity rather than net assets), then the soil will be mined to pay off the parasites.

Chinaski said at June 20, 2014 7:39 PM:

I meant desertification, not deforestation. There was an interesting TED lecture on this, a project in Africa in which letting grass take over reduced erosion greatly.

No combines needed.

destructure said at June 20, 2014 9:51 PM:


Yeah. That's the youtube link in my comment. I'm glad to see it made an impression on someone besides me.

Joseph Hertzlinger said at June 22, 2014 8:48 PM:

If the Mesopotamian civilizations collapsed due to resource depletion, it's amazing how the resources undepleted themselves in time for the Caliphate. If the Roman Empire collapsed due to resource depletion, it's amazing how the resources undepleted themselves in time for the Renaissance.

Nick G said at June 24, 2014 1:58 PM:

A helpful perspective on analyses of the collapse of civilizations: pre-modern civilizations were primarily agricultural, and had very, very low growth rates. So, ag problems were key, and empires with high growth rates were essentially ponzi schemes, looting their neighbors until they reached a limit and collapsed.

Any analysis of the growth and decline of pre-modern civilizations has very, very limited application to modern times.

I'd be curious about the economics of vertical farming.

Shapeshifter said at June 25, 2014 7:30 AM:

Joseph Hertzlinger: True. And it is amazing how the Amazon rainforest is undepleting itself over large areas while it is being depleted in others. It's hard work for puny humans to beat back mother nature -- even for a very short time.

How long did it take for barren volcanic islands such as Hawaii to become lush paradises? Water is key, since all the biological ingredients are floating on the wings, the winds and the waves.

Microbes, fungi, lichens, minerals, water, migrating plant seeds, all come together to build new soil and new life. Humans do the same, and are always building new soil for organic gardens. But humans could do a hell of a lot more soil building if they wanted. In the long run it doesn't matter, nature will shape and reshape the biome in endless patterns over the eons without human help.

Doomers read from a long list of topics, but they still have to recycle the list over and over. They are largely irrelevant to the scheme of things.

Nick G said at June 26, 2014 11:11 AM:

it is amazing how the Amazon rainforest is undepleting itself over large areas

Do you have sources for this? It doesn't sound right.

Randall Parker said at June 28, 2014 8:08 AM:


You are being intellectually lazy. Try reading Montgomery's book. He provides lots of info about how many inches of topsoil get generated over various periods of time,

If you read the book you will learn about multi-century cycles of soil depletion, collapse, and sparsely populated areas during which soil built back up again. You can learn what conditions make erosion happen faster (e.g. hillsides).

Do you realize how much time transpired between some of the events you refer to?

I am posting less lately and reading many more books precisely so I will have a clue on the topics I am most interested in. I am reading many books about rise of fall of civilizations. I provide links to some of those books here.

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