Locavorism vs. Resource Efficiency
“By concentrating the growing of crops in ever more suitable locations, hydrocarbon-powered long distance trade not only maximized output and drastically lowered prices, but also significantly reduced the environmental impact of agriculture.”
“Turning our back on the global food supply chain and, in the process, reducing the quantity of food produced in the most suitable locations will inevitably result in larger amounts of inferior land being put under cultivation, the outcome of which can only be less output and greater environmental damage.”
An article of faith among local food activists is that modern industrial agriculture damages the environmental more than decentralized food systems. The article of faith is that concentrated impacts are worse than multiple, smaller operations–negative environmental scale economies, as it were.
This belief is erroneous, creating a gulf between (good) intentions and result. The low-productivity practices now advocated by locavores, ironically, are the very ones that previous generations of environmental activists blamed for deforestation, massive soil erosion, depletion and compaction, and outright ecological collapse.
Agricultural Alarmism Historically Considered
In an often quoted passage, Plato complained that Athens’ hinterland hills–once “covered with soil,” the plains “full of rich earth,” and the mountains displaying an “abundance of wood”–could now “only afford sustenance to bees.” Like the decline of small islands, Athens’s “richer and softer parts of the soil [had] fallen away, and the mere skeleton of the land … left.” 
Even though some scholars now suggest that the Greek philosopher was exaggerating to make a point,  fears of widespread land mismanagement and irremediable top soil losses recurred from then on.
In the 1939 classic, The Rape of the Earth: A World Survey of Soil Erosion,  for example, British writers Graham Vernon Jacks and Robert Orr Whyte argued that “as the result solely of human mismanagement, the soils upon which men have attempted to found new civilizations are disappearing, washed away by water and blown away by wind.”
They alarmingly wrote that the “destruction of the earth’s thin living cover is proceeding at a rate and on a scale unparalleled in history, and when that thin cover—the soil—is gone, the fertile regions where it formerly lay will be uninhabitable deserts,” just as had happened to “former civilizations and empires whose ruined cities now lie amid barren wastes that once were the world’s most fertile lands.” 
Erosion, they proclaimed, was the “modern symptom of maladjustment between human society and its environment. It is a warning that nature is in full revolt against the sudden incursion of an exotic civilization into her ordered domains.” 
Falsifying the Alarm
As is now obvious, despite localized damage the global catastrophe predicted by past activists never materialized because of the adoption of a new tools and strategies, from contour plowing, windbreaks, legume fallow crops, mulching and alley cropping to deferred and rotational grazing, drip irrigation, re-vegetation and no-till agriculture.
Unfortunately, one of the greatest advances in combating erosion in the last decades—“no-till” agriculture, which leaves the root systems of previous crops undisturbed, thereby retaining organic matter and greatly discouraging erosion—is decried by many activists because of its reliance on rDNA-modified plants and synthetic herbicides.
Be that as it may, the key point is that by concentrating the growing of crops in ever more suitable locations, hydrocarbon-powered long distance trade not only maximized output and drastically lowered prices, but also significantly reduced the environmental impact of agriculture.
Virginia’s Shenandoah Valley
As the agricultural economist Dennis Avery observes, with the development of the American corn and wheat belts in the 19th century, grain growers in Virginia’s Shenandoah Valley could no longer compete with producers whose yields were three times higher than theirs and whose farm machinery didn’t get damaged by buried rocks. In short order they had no choice but to switch to cattle grazing and wood production for which their land was better suited.
As a result, in today’s Shenandoah Valley wildlife is more common than in colonial and pre-colonial times, the area has gained beauty and the “huge soil erosion losses that cropping inflicted on its steep, rocky slopes” has long ended. True, the ecosystems of grain producing states from Indiana to Montana have been profoundly altered, but because their land is more productive and less prone to erosion, more grain is now being produced on fewer acres and, overall, more habitat is available for wildlife.
Avery further argues that, because of similar land use changes in many other locations, severe erosion problems are now largely confined “to poor countries extending low-yield farming onto fragile soils.” 
Of course, other agricultural analysts had in earlier times observed this phenomenon.  The Marxist theorist Karl Kautsky thus observed in 1899 that “as long as any rural economy is self-sufficient it has to produce everything which it needs, irrespective of whether the soil is suitable or not. Grain has to be cultivated on infertile, stony and steeply sloping ground as well as on rich soils.”
In time, however, the emergence of commodity production and overseas competition meant that “it was no longer necessary to carry on producing grain on unsuitable soils, and where circumstances were favorable it was taken off the land and replaced by other types of agricultural production,” such as orchards, cattle, and dairy farming.
Carbon-based Energy to the Rescue
Carbon-fuel powered international trade reduces overall water usage, as exporting food from locations where it is abundant to regions where it isn’t reduces the need to drain surface waters and aquifers in less-productive areas.
For instance, a country that imports one ton of wheat instead of producing it domestically is said to save about 1,300 cubic meters of local (or “indigenous”) water. As food production represents approximately 70% of human water use, the issue is not insignificant. Trading agricultural products grown in water-rich regions to drier ones is now often subsumed under the labels of “virtual,” “embedded,” “embodied,” or “hidden” water  to describe the environmental benefits of the practice, but it has long been a reality because of simple economic incentives.
Modernism vs. Deforestation
Perhaps the least heralded triumph of high-yield agriculture and international trade is that, along with the concentration of human populations in large cities, they have played a crucial role in the expansion of forested areas in significant parts of the Earth in the last two centuries.
Contrary to the common belief that massive deforestation is a recent occurrence (with the bulk of it taking place in the tropical regions of the world during the last five decades), it is now acknowledged by specialists that perhaps as much as nine-tenths of all deforestation caused by human beings since the emergence of civilization occurred before 1950 as people needed to clear vast tracts of forested land in order to provide themselves with shelter, food, warmth and a multitude of implements. 
A reversal of these trends (not attributable to wars, epidemics or collapse of civilizations) began in the early decades of the 19th century in certain European countries through a process since labeled “forest transitions.”
In France, the forest area expanded by one-third between 1830 and 1960, and by a further quarter since 1960. Similar processes, although of varying intensity and scope, have been occurring in all major temperate and boreal forests and in every country with a per capita Gross Domestic Product (GDP) now exceeding U.S. $4,600 (roughly equal to the GDP of Chile) and in some developing economies, most notably China and India. 
While in some cases this outcome is attributed to aggressive governmental policies,  these efforts would have been unthinkable without drastically improved agricultural and forestry productivity (including the development of tree or “fiber farms”) that reduced harvesting pressures in other locations.
Of course, this transition also owed much to the more efficient transformation of wood into various products and to carbon-fuels that were the basis of substitutes for organic fibers, dyes and animal feed (when automobiles, tractors, and trucks became substitutes for horses and mules). 
Turning our back on the global food supply chain and, in the process, reducing the quantity of food produced in the most suitable locations will inevitably result in larger amounts of inferior land being put under cultivation, the outcome of which can only be less output and greater environmental damage. Such problems would obviously be made worse by the locavores’ rejection of technology-based approaches such as no-till farming.
 Plato. 360 BCE. Critias (translated by Benjamin Jowett) http://classics.mit.edu/Plato/critias.html
 G. V. Jacks and R. O. Whyte. 1939. The Rape of the Earth. A World Survey of Soil Erosion. Faber and Faber Ltd. The title of the American edition was the more prudish Vanishing Lands: A World Survey of Soil Erosion. The notion of the Earth (a female entity) being raped by industry (a male entity) is now a mainstay of so-called ecofeminism.
 Several 19th and early 20th-century French writers who made such comments are discussed in Pierre Desrochers and Hiroko Shimizu. 2010. L’autosuffisance alimentaire n’est pas gage de développement durable. Cahier de recherche de l’Institut économique Molinari http://www.institutmolinari.org/IMG/pdf/cahier1010_fr.pdf
 A. Y. Hoekstra (ed.). “Virtual Water Trade: Proceedings of the International Expert Meeting on Virtual Water Trade.” Value of Water Research Report Series No.12, UNESCO-IHE http://www.waterfootprint.org/Reports/Report12.pdf
 Pekka E. Kauppi, Jesse H. Ausubel, Jingyun Fang, Alexander S. Mather, Roger A. Sedjo and Paul E. Waggoner. (2006), ‘Returning Forests Analyzed with the Forest Identity’, Proceedings of the National Academy of Sciences 103 (46): 17574-17579 http://www.pnas.org/content/103/46/17574.full.pdf+html The term forest transitionas used in this essay is based on the Scottish geographer Alexander Mather’s concept of a reversal or turnaround in land-use trends for a given territory from net deforestation to net reforestation in times of economic and population growth. As such, it differs from the notion of forest transition commonly used by landscape biologists and physical geographers that describes landscape changes between different ecosystems such as grassland or tundra and forest.
In places with stable or growing populations and little ability to import forest products, continued declines in forest cover spur increases in prices of forest products, causing landowners to plant trees instead of crops or pasture grasses. Significant erosion problems and disastrous floods in deforested watersheds have also motivated government officials in developing countries to implement reforestation programs.
 For more detailed discussions of these issues and additional references, see Paul E. Waggoner. 1996. “How Much Land Can Ten Billion People Spare for Nature?” Daedalus 125 (3): 73–93; Indur M. Goklany. 2007. The Improving State of the World. Cato Institute; Pierre Desrochers. 2010. “The Environmental Responsibility of Business is to Increase its Profits (By Creating Value within the Bounds of Private Property Rights)”Industrial and Corporate Change 19 (1): 161–204; and Pierre Desrochers. 2008. “Bringing Inter-Regional Linkages Back In: Industrial Symbiosis, International Trade and the Emergence of the Synthetic Dyes Industry in the Late 19th Century.”Progress in Industrial Ecology 5 (5-6): 465–481.
With Hiroko Shimizu, Pierre Desrochers is author of The Locavore’s Dilemma: In Praise of the 10,000-mile Diet and posts at MasterResource. For a review of his book by Alex Epstein, see here.