The sky may not be falling, but the earth’s soil is eroding faster than it is being replaced and modern civilization’s future is endangered.  Our earth in David R. Montgomery’s words “is an oasis in space rendered hospitable by a thin skin of soil that, once lost, rebuilds only over geologic time.”  Mr. Montgomery makes a persuasive case in Dirt, The Erosion of Civilizations (University of California Press, Berkeley and Los Angeles, California, 2007) that the twin problems of soil degradation and accelerated erosion (with an estimated twenty-four billion tons of soil lost annually around the world) eventually determine the fate of civilizations, and that humanity’s well-being requires “prioritizing society’s long-term interest in soil stewardship.”  Since 1945, moderate to extreme soil erosion has degraded 1.2 billion hectares of agricultural land- an area the size of China and India combined: “One estimate places the amount of agricultural land used and abandoned in the past fifty years as equal to the amount farmed today.”  Who can deny Mr. Montgomery’s central point that when people run low on food, “the thin veneer of behavior that defines culture and even civilization itself is at risk?”

Mr. Montgomery is a geomorphologist, who studies how landscapes change through geologic time, and focuses on how the interplay among climate, vegetation, geology and topography influences soil composition and thickness.  But although he does not call himself one, he is also a historian, who has provided an extraordinary and readable history of world agriculture and of American agriculture in particular.  Mr. Montgomery has the ability to convey his scientific knowledge in a readable and understandable way, and Dirt, The Erosion of Civilizations deserves a wide readership.  Like Michael Pollan in The Omnivore’s Dilemma (The Penguin Press, New York, New York, 2006), Mr. Montgomery also concludes that industrial agricultural practices, which require cheap fertilizers and cheap oil to make them, cannot be sustained and there are disastrous consequences ahead.  Like Mr. Pollan and Maria Rodale, in her passionate Organic Manifesto, Mr. Montgomery advocates for a system of food production that rejects the “persistent agricultural myth” that large mechanized farms are more efficient than small traditional farms that “treat soil as a locally adapted biological system rather than a chemical system.”  In Mr. Montgomery’s convincing view, using biology and ecology, rather than chemistry and genetics, can be the basis for the “unglobalization of agriculture” which will become increasingly attractive and cost effective as the oil runs out later this century.  Agriculture consumes 30% of our oil use, and David Montgomery predicts that petroleum-based industrial agriculture will end sometime later this century as oil and natural gas become too valuable to use for fertilizer production.

Mr. Montgomery bravely addresses the emotional and contentious issue  that the world’s population has reached an unsustainable level, and he details uncomfortable facts in a cool-headed and scientific way.  In Mr. Montgomery’s words, “Agriculture  can be understood as a natural behavioral response to increasing population”  from the earliest known semi-agricultural people, who lived on the slopes of the Zagros mountains between Iraq and Iran about thirteen thousand to eleven thousand years ago (about 11,000 to 9000 BC), to modern times.  Merely hunting gazelles and gathering wild cereals and legumes could not sustain the growing human population of the ancient lands of the Middle East.  In Mr. Montgomery’s words, people were forced to adopt “the labor-intensive business of agriculture.”  But when the maximum food production achievable by agriculture is reached, and the population cannot be fed, there are dire behavioral responses and civilization collapses.  In the year 20,000 BC, when the glaciers melted in the most recent glaciation, the earth’s population has been estimated by scientists at 4 million humans.  Scientists have further estimated that the earth’s population grew 1 million over the next 5,000 years to reach 5 million in 15,000 BC.  Fifteen thousand years later, by the time of Christ, the earth’s population is estimated by scientists at 200 million, with the peak population in pre-Biblical Mesopotamia estimated at 20 million.  Two thousand years later, in our time, the earth’s population is 6.5 billion humans.

Mr. Montgomery notes that in the world’s most intensively farmed regions, to feed one human requires .2 hectares per person.  Presuming that it would be possible to increase the average global agricultural production to this level of .2 hectares per person, the earth could support 7.5 billion people.  However, Montgomery warns that given the continued loss of productive cropland, it is estimated that by 2050, the amount of available farmable land will drop to less than 0.1 hectares per person.  Norman Borlaug, the Nobel Prize winning “green revolution” pioneer, has opined that the earth could support 10 billion humans with the proviso that additional “major advances in agricultural technology” are required.  However, these “optimistic” views, although exceeded by “the National Conference of Catholic Bishops apparent belief that the world could comfortably support forty billion people,” must be compared to the views of “Stanford University biologists Paul and Anne Ehrlich who maintain that we have already passed the carrying capacity of the planet, which they put at about three billion people.”  Ted Turner’s dyspeptic view “that four hundred million would be plenty” is a head-spinning fantasy.

In Dirt, The Erosion of Civiizations, David Montgomery has provided a stunning parade of examples of the collapse of various societies when the pressure of a growing population and an inadequate food supply collide.  As early as 6000 BC, whole villages in what is now central Jordan were abandoned as a direct result of top soil erosion and degraded soil fertility caused by intensive agriculture and goat grazing which undermined crop yields to feed an increasing population. Examples of Iceland and Haiti show that no region of the earth is untouched from the devastation resulting from loss of top soil and degraded soil fertility.  Once Iceland’s slopes were deforested, strong winds blowing off its central ice caps helped stripped the soil from half the once forested area of the island, so that “soils built up over thousands of years disappeared within centuries.”  According to Montgomery, the central part of Iceland “where the soil has been completely removed is now a barren desert where nothing grows and no one lives.”   In Haiti, which means “green island” in Arawak, the native language, “cultivation on steep slopes converted about a third of the country to bare rocky slopes incapable of supporting agriculture.”

Montgomery’s detailed descriptions of the collapse of more ancient civilizations are fascinating.  Maya civilization in the Yucatan and Central America (Mesoamerica) grew from a population of less than 200,000 in 600 BC to more than a million by 300 AD, and at its peak in 800 AD, the population reached “at least three million and perhaps as many as six million.”  Montgomery describes the way Maya agriculture exhausted its soil:  The tropical soils of the Yucatan peninsula and Central America are thin and easily eroded, and under sustained cultivation, the initial high productivity after clearing and burning the cleared forest (which had fertilized the soil and guaranteed good crops for a few years),  rapidly declined.   The lack of domesticated animals in Maya agriculture meant no manure for replenishing the depleted soils and compounded the problem.  Maya civilization collapsed about 900 AD when food production no longer could sustain the population, with some Maya cities abandoned with buildings half finished.  Archeologist Richard Hansen, quoted in “Lost City of the Maya” by Chip Brown (with wonderful accompanying photographs by the National Geographic photographer, Christian Ziegler), Smithsonian Magazine, May 2011 [www.smithsonianmag.com/history-archaeology/El-Mirador-the-Lost-City-of-the-Maya.html], echoes Mr. Montgomery’s analysis.  Mr. Hansen, an American archaeologist, who is leading efforts to solve the mystery of the lost Maya city of El Mirador, a 2,500-year old metropolis that is “more impressive and even older than the better-known Tikal” believes that what “caused the wholesale collapse of the society sometime between A.D. 100 and 200” was the runoff of clay into the marshes (with their nutrient-rich mud) after the massive deforestation of the surrounding area- deforestation caused by a demand for firewood the Maya needed to make lime plaster (which they used to plaster “everything, from major temples like La Danta to their plazas and house floors, which over time got thicker and thicker, an extravagance Hansen attributed to the temptations of ‘conspicuous consumption”’).

Montgomery’s account of the unraveling of the Roman Empire from the stress of feeding a growing population from deteriorating lands is extraordinary in its historical details.  Tertullian, the first Christian to write in Latin, wrote in 200 AD: “We overcrowd the world. The elements can hardly support us.  Our wants increase and our demands are keener, while Nature cannot bear us.”  To some degree, the need to secure food launched Roman colonialism: Rome conquered the North African coast between Carthage (Libya) and Egypt for its ability to produce grain with “two hundred thousand tons of grain a year shipped from Egypt and North Africa to feed the million people in Rome.”  Similarly, in Montgomery’s view, European colonialism was rooted in its perennial hunger problem, which it solved “by importing food and exporting people,” with 50,000,000 leaving Europe from 1820 to 1930.

Still, David Montgomery has not entitled his remarkable book, Famine, The Erosion of Civilization for a reason.  Although he has sketched a dire future of an inadequate food supply for a growing world population if current trends continue (and also discusses in detail famines in China in 1920-21 when 500,000 died from hunger and 20,000,000 were reduced to eating anything that grew as well as the 1845 Irish famine), his ultimate focus is on “good old dirt.”   Mr. Montgomery becomes almost rhapsodic in his view of dirt “as a valuable inheritance” which is a “strategic resource” as important as oil.  (With the United States Department of Agriculture [USDA] estimating that it takes 500 years to produce an inch of topsoil, Mr. Montgomery’s view of soil as a strategic resource is entirely justified.)  Dig into rich, fresh earth, and Mr. Montgomery notes you can feel the life in it, a whole world of life eating life, a biological orgy recycling the dead back into new life, an enticing and wholesome aroma- the smell of life itself.  He observes that his own focus on dirt was shared by Charles Darwin whose last book explored how the “the ground beneath our feet cycles through the bodies of worms,” which transform dirt and rotting leaves into soil.  Darwin was fascinated by his discovery of Roman tiles buried two and one-half feet in the English countryside, and he collected and weighed earthworm castings ultimately concluding that new topsoil built up a few inches every century thanks to the efforts of countless worms.  Darwin’s research revealed that “400 pounds of worms lived in an acre of good English soil.”  Like Darwin, Mr. Montgomery’s deep appreciation of worms and soil leads naturally to his thorough analysis of agricultural practices which help to remedy the loss of billions of tons of soil annually and undergirds his ultimate focus on the earth’s soil rather than human failure and famine.  In a single, brilliant paragraph, Mr. Montgomery articulates the argument for non-industrial agriculture, an agroecology based on biology and ecology rather than chemistry and genetics.  He notes that “tilling the soil can kill large soil-dwelling organisms, and reduce the number of earthworms.  Pesticides can exterminate microbes and microfauna.  Conventional short-rotation, single-crop farming can reduce the diversity, abundance, and activity of beneficial soil fauna, and indirectly encourage proliferation of soilborne viruses, pathogens, and crop-eating insects.”  David Montgomery makes a strong case that  “generally, so-called alternative agricultural systems tend to better retain soil-dwelling organisms that enhance soil fertility.”  The growing adoption of alternative practices such as (i) terracing steep fields to reduce soil erosion, (ii) no-till methods which minimizes direct disturbance of the soil, (iii) leaving crop residue at the ground surface to serve as mulch helping to retain moisture and retard erosion (instead of plowing it under), and (iv) interplanting crops to provide more complete ground cover and retard erosion, all of which Mr. Montgomery emphasizes are not “new ideas”,  lends hope for the future of the Earth’s soil.

As a footnote, Mr. Montgomery’s analysis of the “salt problem” from increased irrigation, with a special focus on California’s Central Valley’s “salty ground unlike anything back East,” deserves highlighting.  Salty soil increased as irrigation spread across the golden state of California:  “Every new irrigated field raised the local groundwater table a little more.  Each summer, evaporation pumped more salt up into the soil.”  The salt in California’s Central Valley was not “seawater salt” but salt in the soil which weathered out of rocks, dissolving in soil water, and then reprecipatating where the water evaporated.  Christopher Henke in his Cultivating Science, Harvesting Power also addresses the problem of salty soil in his analysis of agriculture in California’s Salinas Valley.  In the case of the Salinas Valley, sea water is intruding into ground water along the Monterey Bay coast with the increased pumping of ground water for crop irrigation.  Mr. Montgomery, in an earlier section of his book, describes how pre-Biblical Mesopotamia, with its estimated peak population of 20 million, collapsed from the lack of food to feed its people, which resulted from the build-up of salt in its agricultural land from the “sustained irrigation” which generated “enough salt to eventually poison crops.”

Americans have a unique and fortunate place from which to lead the world into a future of sustainable food production.   According to Mr. Montgomery, there are three great regions on our planet Earth “where thick blankets of easily farmed silt can sustain intensive farming even once the original soil disappears.”  The wide expanses of the world’s loess belts in the American (U.S. and Canada) plains, Europe, and northern China are the Earth’s breadbaskets, and we Americans are truly blessed to be living in one of the world’s loess belts.  Most of the rest of the planet has “thin soils over rock” which must be carefully nurtured by the practice of intensive organic agriculture which rebuilds the thin soils.  A hopeful sign is that thin soils have been rebuilt : Mr. Montgomery uses the modern evolution of agriculture in Cuba as proof of this potential to produce sufficient food in places not blessed with the richness of America’s soils.  With the collapse of the Soviet Union, Cuba’s fertilizer and pesticide imports fell by 80 percent and oil imports fell by 50 percent, and according to Montgomery, Cuban agriculture needed to double food production using half the inputs required by conventional agriculture.  Industrialized state farms were privatized, creating a network of small farms, and through necessity, the new small private farms and thousands of tiny urban market gardens became organic.  By 2004, Havana’s formerly vacant lots produced nearly the city’s entire vegetable supply.  Agricultural self-sufficiency by labor-intensive agriculture was achievable by Cuba, a developing country not part of the world’s loess belts (although Montgomery notes that meat and dairy remain in short supply in Cuba).

David R. Montgomery’s Dirt, The Erosion of Civilizations is a warning of a future that must be forestalled.  He honors the memory of Albert Schweitzer by challenging the philosopher’s bleak assessment, quoted by Rachel Carson in her dedication of Silent Spring that “Man has lost the capacity to foresee and forestall.  He will end by destroying the earth.”  Like Rachel Carson, David Montgomery has not lost the capacity to foresee, which gives some hope that Schweitzer’s apocalyptic conclusion may yet be forestalled.  May the ethic of land stewardship thrive and protect Mother Earth’s soil (FW Barrie, 4/28/11). [http://www.ucpress.edu/book.php?isbn=9780520258068]