This was the foundation of the great flourishing of Mesopotamia, but it faced two great problems: salinisation from irrigation (just as Australia has done in the past few decades), which did for the Sumerians, and silting up of irrigation channels as the growing population moved into easily eroded upland areas in search of farming land, a huge problem for China for the past couple of thousand years. Such erosion was also a problem in Bronze Age and classical Greece. Montgomery quotes Plato on the region around Athens: "The rich, soft soil has all run away leaving the land nothing but skin and bone."
If the detail is fascinating, and some of the areas new, this is familiar territory, which Jared Diamond has already popularised. It is when Montgomery moves into the modern era that he reaches new, and frightening, territory.
The effects of inappropriate farming and drought of the American dustbowl era are well known, but Montgomery goes back, and forward, from that. He looks at how tobacco farming, based on slave labour, locked its proponents into a cycle of declining soils (with its clean-till cultivation promoting erosion), which required an expansion across the frontier, which had to be into slave states - otherwise the value of the "asset" (the slaves) would collapse. And slave labour, with unwilling, low-skilled workers, was no way to work to counteract these effects.
And then he looks forward: how after the mechanisation of agriculture after the second world war, the same kind of careless, mass production agriculture, that ploughed across the landscape with no regard to its local characteristics, had much the same effects. In the Palouse region of eastern Washington, a 1950 survey found that all of the original topsoil was missing from 10 per cent of farmland, and between 25 and 75% of the soil was missing from an additional 80% - just 10% was in something like its original condition. Slope is a major factor in this, and less than 50% of US croplands have a slope of 2%, and therefore are at relatively low risk of erosion. "The steepest 33% of US cropland is projected to fall out of production over the next century."
And that's a worry for more than the US. Before the second world war, Montgomery says, western Europe was the only grain-importing region. Latin America produced nearly double the quantity of North America in the 1930s, the Soviet Union was also a major exporter, Africa was self-sufficient. Now, the only major grain exporters are North America, Australia, and New Zealand. It is worth quoting the summary of the current state of play:
Worldwide, over two billion acres of virgin land have been plowed and brought into agricultural use since 1860. Until the last decades of the twentieth century, clearning new land compensated for loss of agricultural land. In the 1980s the total amount of land under cultivation began declining for the first time since farming reached the land between the Tigris and the Euphrates. In the developed world, the rate at which new (and generally marginal) land was brought under cultivation fell below the rate at which land was being exhausted. Although we use a little more than a tenth of the Earth's land surface to grow crops, and another quarter of the world's surface for grazing, there is little unused land suitable for either. About the only places left that could be used for agriculture are the tropical forests where thin, highly erodible soils could only briefly support farming....
Acorss the planet, moderate to extreme soil erosion has degraded 1.2 billion hecatres of agricultural land since 1945 - an area the size of China and India combined.... The United Nations estimates that 38% of global cropland has seriously degraded since the Second World War. ... average cropland erosion of 10 to a hundred tons per hectare per year removes soil about 10 to a hundred times faster than it forms.
And then there's the threat of global warming. The west of the American Midwest breadbasket is already marginal cropping land, while predicted vigour in the hydrological cycle is going to increase soil erosion from rainfall.
Article comments
1 - Victor Plenty
"not so much farming as mining" -- what an apt description for many of the methods used to produce so much of our food supply today. I'm surprised nobody else has commented on your review, Natalie. Is anything more universal than the human need for food?
We have only just begun to scratch the surface (quite literally) of the miraculous processes that convert bare ground into things we can use for food. Still, the outlines of a better way are being discovered by pioneers in permaculture, organic farming, and other sustainable practices.
If we continue to treat the soil like a mine, sooner or later the mine will play out. If we learn to nurture the soil as a living system, we can ensure a healthy food supply for future generations.
2 - James Sinnamon
(This has been cross-posted to Philobiblion)
Great book!
I thoroughly endorse it.
My only reservation is that David Montgomery is a bit more optimistic about our prospects for being able to fix up our global agricultural system than others, for example Canadian soil biologist, Peter Salonius Peter Salonius, who believes that our soils are so degraded that the world’s soils may only be able to sustain hundreds of millions of humans rather than billions of humans once the artificial boost to soil productivity made possible with fossil-fuel-dervied fertilisers is no longer available.
If Peter Salonius is right, then we are in deep trouble. Of course, I hope he is wrong and that David Montgomery is right.