Increasing labor needed to harvest an acre of crops implies that crop yields rose over time. The number of person days required to harvest an acre of wheat increased from about two around 16oo to two and a half by the early 170os, and then to just over three in i86o. Overall crop yields increased by two and a half times in the six hundred years from I2oo to i8oo. So despite increasing yields, the tenfold population increase primarily reflected expansion of the area under cultivation.

During the same period about a quarter of England's cultivated land was transformed from open, common fields to fenced estates. By the end of the eighteenth century, common fields had almost disappeared from the English landscape. Loss of the common lands meant the difference between independence and dest.i.tution for rural households that had always kept a cow on the commons. Dispossessed, landless peasants with no work depended on public relief for food. Seeing the economic effects of the transformation of the English countryside, Board of Agriculture secretary Arthur Young came to see land enclosure as a dangerous trend destroying rural self-sufficiency. But enclosing and privatizing the last vestiges of communal property conveniently pushed a new cla.s.s of landless peasants to seek jobs just as laborers were needed in Britain's industrializing cities.

By the early nineteenth century, British farms had developed into a mixed system of fields and pastures. A roughly equal emphasis on cultivation and animal husbandry provided for constant enrichment of the soil with large quant.i.ties of manure, and cover crops of clover and legumes.

English population growth mirrored increases in agricultural production from after the Black Death to the Industrial Revolution. Between 1750 and 1850, England's cereal production and population both doubled. Did a growing human population drive up demand for agricultural products? Or did increased agricultural production enable faster population growth? Regardless of how we view the causality, the two rose in tandem.

Nonetheless, as the population grew, the European diet declined. With almost all of the available land in cultivation, Europeans increasingly sur vived on vegetables, gruel, and bread. Without surplus grain to feed animals through the winter, and later without access to the commons to graze cattle, eating meat became an upper-cla.s.s privilege. An anonymous pamphlet published in London in 1688 attributed ma.s.sive unemployment to Europe's being "too full of people" and advised wholesale emigration to America. At the start of the nineteenth century, most Europeans survived on 2,ooo calories a day or less, about the average for modern India and below the average for Latin America and North Africa. European peasants toiling in their fields ate less than Kalahari Desert bushmen who worked just three days a week.

Despite increased agricultural production, food prices rose dramatically in both England and France during the sixteenth and seventeenth centuries. Persistent famine between 169o and 1710 stalked a population larger than could be reliably fed. While enlightened Europe lived on the edge of starvation, Britain largely escaped the peasant unrest that sparked the French Revolution by importing lots of food from Ireland.

Real hunger, as much as the hunger for empire or religious freedom, helped launch Europe toward the New World. Beginning with Spain, the thickly settled and most continuously cultivated parts of western Europe most aggressively colonized the New World. Before the Romans, the Phoenicians and Greeks had settled Spain's eastern coast, but Iberian agriculture remained primitive until aggressive Roman cultivation. The Moors introduced intensive irrigation to Spain a few centuries after the fall of Rome. More than five hundred years of Moorish agriculture further degraded Spanish soils. By the fifteenth century, the fertile soils of the New World looked good to anyone working Spain's eroded and exhausted soil. Within a few generations, Spanish and Portuguese farmers replaced gold-seeking conquistadors as the primary emigrants to Central and South America.

By contrast, it took more than a century after Columbus for northern European farmers to begin heading west for religious and political freedom-and tillable land. English and French peasants were still clearing and improving land in their own countries. German peasants were busy plowing up newly acquired church land. Germany did not even begin to establish overseas colonies until the 185os. The northern European rush to America did not kick into full gear until the late nineteenth century. Relatively few people from northwestern Europe migrated to America while there was still fertile land at home.

As continental Europe filled in with farms, peasants moving up into the hills set the stage for crisis once eroding slopes could no longer support a hungry population. When eighteenth-century farmers began clearing steep lands bordering the French Alps, they triggered landslides that carried off soils and buried valley bottom fields under sand and gravel. By the late eighteenth century, the disastrous effects of soil erosion following deforestation of steep lands had depopulated portions of the Alps. Nineteenth-century geographer Jean-Jacques-Elisee Reclus estimated that the French Alps lost a third to more than half their cultivated ground to erosion between the time Columbus discovered America and the French Revolution. By then people crowding into cities in search of work could neither grow nor pay for food.

Figure i2. Mid-eighteenth-century agricultural landscape (Diderot's Encyclopedie, Paris, 175i-8o).

A decade of persistent hunger laid the groundwork for revolution as the homeless population of Paris tripled. According to the bishop of Chartres, conditions were no better in the countryside, where "men were eating gra.s.s like sheep, and dying like flies." Revolutionary fervor fed on long lines at bakeries selling bitter bread full of clay at exorbitant prices. Anger over the price of the little available for sale and the belief that food was being withheld from the market spurred on the mobs during key episodes of the French Revolution.

Dissolution of the n.o.bility's large estates freed peasants to grab still forested uplands. Clearing steep slopes triggered debris torrents that scoured uplands and buried floodplain fields under sand and gravel. Large areas of upper Provence were virtually abandoned. Between 1842 and 1852 the area of cultivated land in the lower Alps fell by a quarter from the ravages of landslides and soil erosion.

French highway engineer Alexandre Surell worked on devising responses to the landslides in the Upper Alps (Hautes-Alpes) in the early 1840s. He noted the disastrous consequences that followed when cultivation pushed into the mountains. Torrents cascading off denuded slopes buried fields, villages, and their inhabitants. Everywhere the forests had been cut there were landslides; there were no landslides where the forest remained. Connecting the dots, Surell concluded that trees held soil on steep slopes. "When the trees became established upon the soil, their roots consolidate and hold it by a thousand fibres; their branches protect the soil like a tent against the shock of sudden storms."8 Recognizing the connections between deforestation and the destructive torrents, Surell advocated an aggressive program of reforestation as the way to a secure livelihood for the region's residents. Plowing steep land was an inherently short-term proposition. "In the first few years following a clearing made in the mountains, excellent crops are produced because of the humus coat the forest has left. But this precious compost, as mobile as it is fecund, lingers not for long upon the slopes; a few sudden showers dissipate it; the bare soil quickly comes to light and disappears in its turn."9 Measures to protect the forest and the soil were often unsuccessful because it was more immediately profitable to clear and plant, even though deforested slopes could not be farmed for long.

While Surell fretted about how to restore upland forests, George Perkins Marsh toured France during his service as American amba.s.sador in Italy. Witnessing the long-term effects of forest clearing on both steep land and valley fields, Marsh saw that bare, eroded mountain slopes unfit for habitation no longer absorbed rainfall but rapidly shed runoff that picked up sediment and dumped it on valley fields.

An observant tourist, Marsh feared the New World was repeating Old World mistakes.

The historical evidence is conclusive as to the destructive changes occasioned by the agency of man upon the flanks of the Alps, the Apennines, the Pyrenees, and other mountain ranges in Central and Southern Europe, and the progress of physical deterioration has been so rapid that, in some localities, a single generation has witnessed the beginning and the end of the melancholy revolution.... It is certain that a desolation, like that which has overwhelmed many once beautiful and fertile regions of Europe, awaits an important part of the territory of the United States, and of other comparatively new countries over which European civilization is now extending its sway.10 Marsh compared what he saw in Europe to New York State, where the upper Hudson River was filling with sediment as farmers plowed up the forest. He held that gentle slopes in areas where rainfall was evenly distributed throughout the seasons could be reasonably farmed on a permanent basis. Ireland, England, and the vast Mississippi basin fit this definition. In contrast, steep terrain could not be plowed for long without triggering severe erosion, especially in regions with torrential rains or parching droughts.

French deforestation peaked in the early i8oos. In i86o the marquis de Mirabeau estimated that half of France's forest had been cleared in the previous century. Inspector of Forests Jonsse de Fontaniere echoed Surell's stark a.s.sessment of the prospects of the High Alps. "The cultivators of the land ... will be compelled ... to abandon the places which were inhabited by their forefathers; and this solely in consequence of the destruction of the soil, which, after having supported so many generations, is giving place little by little, to sterile rocks."1 i French authorities began pa.s.sing laws to protect and restore public and private woodlands in 1859. Clearing of European forests accelerated briefly, though, when twenty-eight thousand walnut trees were cut to supply European manufacturers with gunstocks during the American Civil War. Despite such profiteering, by 1868 almost two hundred thousand acres of the High Alps had been replanted with trees or restored to meadow.

Touring southern France before the Second World War, Walter Lowdermilk found intensive farming practiced on both steep slopes and valley floors. Some farmers maintained hillslope terraces like those built by the ancient Phoenicians. Lowdermilk marveled over how in eastern France, where terracing was uncommon, farmers would collect soil from the lowest furrow on a field, load it into a cart, haul it back up the slope, and dump it into the uppermost furrow. Centuries ago when this practice began, peasant farmers knew that they had upset the balance between soil production and erosion, and that people living on the land would inherit the consequences. They probably did not appreciate how far they were ahead of Europe's gentlemen scientists in understanding the nature of soils.

At the May 5, 1887, meeting of the Edinburgh Geological Society, vice president James Melvin read from an unpublished ma.n.u.script by James Hutton, the Scottish founder of modern geology. The rediscovered work revealed the formative geologic insights Hutton had gained from farming the land, observing and thinking about relationships among vegetation, soil, and the underlying rocks. In particular, Melvin appreciated the parallels between Hutton's century-old musings and Darwin's newly published book on worms.

Hutton saw soil as the source of all life where worms mix dead animals with fallen leaves and mineral soil to build fertility. He thought that hillslope soils came from the underlying rock, whereas valley bottom soils developed on dirt reworked from somewhere upstream. Soil was a mix of broken rock from below and organic matter from above, producing dirt unique to each pairing of rocks and plant communities. Forests generally produced fine soils. "[A forest] maintains a mult.i.tude of animals which die and are returned to the soil; secondly, it sheds an annual crop of leaves, which contribute in some measure to the fertility of the soil; and lastly, the soil thus enriched with animal and vegetable bodies feeds the worms ... which penetrate the soil, and introduce fertility as they Multiply. 1112 Antic.i.p.ating Darwin in recognizing the role of worms in maintaining soil fertility, Hutton also understood the role of vegetation in establishing soil characteristics. The visionary geologist saw soil as the living bridge between rock and life maintained by returning organic matter to the soil.

At the close of the eighteenth century-long before Melvin rediscovered Hutton's lost ma.n.u.script-Hutton argued with Swiss emigre Jean Andre de Luc over the role of erosion in shaping landscapes. De Luc held that ero sion stopped once vegetation covered the land, freezing the landscape in time. At issue was whether topography was the ultimate fossil, left over from Noah's flood. Hutton questioned de Luc's view, pointing to the turbid waters of flooding rivers as evidence of erosion endlessly working to lower mountains. "Look at the rivers in a flood;-if these run clear, this philosopher [de Luc] has reasoned right, and I have lost my argument. Our clearest streams run muddy in a flood. The great causes, therefore, for the degradation of mountains never stop as long as there is water to run; although as the heights of mountains diminish, the progress of their diminution may be more and more r.e.t.a.r.ded."13 In other words, steeper slopes eroded faster, but all land eroded.

Figure 13. French farmers loading soil from their lowest furrow into a cart to be hauled back uphill in the late 1930s (Lowdermilk 1953, 22, fig. 12).

A few years later Hutton's disciple, geologist and mathematician John Playfair, described how weathering created new soil at about the rate that erosion removed it. He saw topography as the product of an ongoing war between water and rock. "Water appears as the most active enemy of hard and solid bodies; and, in every state, from transparent vapour to solid ice, from the smallest rill to the greatest river, it attacks whatever has emerged above the level of the sea, and labours incessantly to restore it to the deep."14 Adopting Hutton's radical concept of geologic time, Playfair saw how erosion worked gradually to destroy land that dared rise above sea level. Yet the land remained covered by soil despite this eternal battle.

The soil, therefore, is augmented from other causes, ... and this augmentation evidently can proceed from nothing but the constant and slow disintegration of the rocks. In the permanence, therefore, of a coat of vegetable mould on the surface of the earth, we have a demonstrative proof of the continual destruction of the rocks; and cannot but admire the skill, with which the powers of the many chemical and mechanical agents employed in this complicated work, are so adjusted, as to make the supply and the waste of the soil exactly equal to one another.15 The soil maintained a uniform thickness over time even as erosion continuously reshaped the land.

About the time Hutton and Playfair were trying to convince Europe's learned societies of the dynamic nature of soil over geologic time, parallel arguments about the controls on the size and stability of human populations were brewing. Europeans began questioning the proposition that greater population led to greater prosperity. On an increasingly crowded continent, limits to human population growth were becoming less abstract.

The Reverend Thomas Malthus infamously proposed that a boom-andbust cycle characterizes human populations in his 1798 Essay on the Principle of Population. A professor of political economy at Haileybury College, Malthus argued that exponentially growing populations increase faster than their food supply. He held that population growth locks humanity in an endless cycle in which population outstrips the capacity of the land to feed people. Famine and disease then restore the balance. British economist David Ricardo modified Malthus's ideas to argue that populations rise until they are in equilibrium with food production, settling at a level governed by the amount of available land and the technology of the day. Others like the marquis de Condorcet argued that necessity motivates innovation, and that agriculture could keep up with population growth through technological advances.

Malthus's provocative essay overlooked how innovation can increase crop yields and how greater food production leads to even more mouths to feed. These shortcomings led many to discredit Malthus because he treated food production and food demand as independent factors. He also neglected to consider the time required for agriculturally accelerated erosion to strip topsoil off a landscape or for intensive cultivation to deplete soil fertility. Although his views seemed increasingly naive as England's population kept growing, political interests seeking to rationalize exploitation of Europe's new working cla.s.s embraced them.

Malthus's ideas challenged prevalent views of human impact on nature in general and on the soil in particular. In Political justice, published five years before Malthus's essay, William G.o.dwin captured the fashionable view of the inevitable progress of human dominion over nature. "Threefourths of the habitable globe are now uncultivated. The improvements to be made in cultivation, and the augmentations the earth is capable of receiving in the article of productiveness, cannot, as yet, be reduced to any limits of calculation. Myriads of centuries of still increasing population may pa.s.s away, and the earth be yet found sufficient for the support of its inhabitants." 16 In G.o.dwin's view, scientific progress promised endless prosperity and ongoing advances in material well-being. The basic perspectives of Malthusian pessimism and G.o.dwinian optimism still frame debates about the relationships between human populations, agricultural technology, and political systems.

Published early in the Industrial Revolution, Malthus's ideas were adopted by those wanting to explain poverty as the fault of the poor themselves, rather than an undesirable side effect of land enclosure and industrial development. Taken at face value, Malthus's ideas absolved those at the top of the economic ladder from responsibility for those at the bottom. In contrast, G.o.dwin's ideas of material progress became a.s.sociated with the movement to abolish private property rights. Naturally, Malthus would have more appeal for a Parliament of wealthy landowners.

As intellectuals debated the earth's capacity to provide sustenance, the working cla.s.ses continued to live on the verge of starvation. Vulnerability to bad harvests continued well into the nineteenth century as European agriculture could barely keep up with the rapidly growing cities. High grain prices during the Napoleonic Wars further accelerated land enclosures across Britain. Then in 1815, after the eruption of Indonesia's Tomboro volcano, the coldest summer on record produced catastrophic crop failures. Food riots in England and France spread across the continent when hungry workers faced skyrocketing bread prices. The price of a loaf of bread remained a central point of working-cla.s.s protest as the discontent of the urban poor bred radicals and revolutionaries.

A potato blight that arrived from America in 1844-45 showed just how insecure food production had become. When Phytophthora infestans wiped out the Irish potato harvest in the summer of 1845 and the next year's crop failed too, it left the poor-who could not afford to buy food at market rates from the indifferent British government-with literally nothing to eat. Completely dependent on potatoes, the Irish population crashed. About a million people died from starvation or a.s.sociated diseases. Another million emigrated during the famine. Three million more left the country over the next fifty years, many bound for America. By 1900 the population of Ireland was a little more than half of what it had been in the 1840s. Why had the Irish become so dependent on a single crop, particularly one introduced from South America only a century before?

At first glance the answer appears to support Malthus. Between 1500 and 1846 the Irish population increased tenfold to eight and a half million. As the population grew, the average land holding dwindled to about o.2 hectares (half an acre), enough to feed a family only by growing potatoes. By 1840 half the population ate little besides potatoes. More than a century of intensive potato cultivation on nearly all the available land had reduced the Irish to living on the verge of starvation in good years. But a closer look at this story reveals more than a simple tale of population outpacing the ability to grow potatoes.

The potato grew in importance as a staple while Irish agriculture increasingly exported everything else to Britain and its Caribbean colonies. In 1649 Oliver Cromwell had led an invasion to carve Ireland into plantations to pay off with land the speculators who bankrolled Parliament in the English Civil War. Ireland's new landlords saw lucrative opportunities provisioning Caribbean sugar and tobacco plantations. Later, increasing demand for food in Britain's industrializing cities directed Irish exports to closer markets. In 1760 hardly any Irish beef went to Britain. By i8oo four out of five Irish cows sent to market ended up on British tables. The growth of Britain's urban population created substantial demand for food Irish landlords were happy to supply. Even after the official union of Ireland and England in i8oi, Ireland was run as an agricultural colony.

The potato increasingly fed rural Ireland as land was diverted to raise exports. In order to devote the best land to commercial crops, landlords pushed peasants onto marginal lands where they could grow little other than potatoes. Adam Smith advocated the potato as a means to improve landlords' profits in The Wealth ofNations because tenants could survive on smaller plots if they grew nothing but potatoes. By 1805 the Irish ate little meat. With most of the country's beef, pork, and produce shipped off to Britain, the poor had nothing to eat when the potato crop failed.

There was no relief effort during the famine. On the contrary, Irish exports to England increased. The British Army helped enforce contracts as landlords shipped almost half a million Irish pigs to England at the peak of the famine in 1846. This policy of expedience was not unusual. More food was available during many European famines than was accessible to peasants who had no backup when their crops failed. Poor subsistence farmers could not buy food on the open market. As the ranks of the urban poor grew, they too could not afford food at the higher prices famines produced. And without land they could not feed themselves. Food riots swept across Europe in 1848 in the wake of the potato blight and a poor grain harvest on the continent.

Agricultural economics began to shape radical thought. In the early 1840s, before he met Karl Marx, Friedrich Engels took issue with Malthus and argued that labor and science increased as fast as population and therefore agricultural innovation could keep pace with a growing population. Marx, by contrast, saw commercialized agriculture as degrading to both society and the soil. "All progress in capitalistic agriculture is a progress in the art, not only of robbing the worker, but of robbing the soil; all progress in increasing the fertility of the soil for a given time is a progress towards ruining the more long-lasting sources of that fertility."17 (Ironically, in the decade before the 1917 Russian Revolution, Czar Nicholas II pa.s.sed land reforms that began giving peasants t.i.tle to their land. Unlike the urban poor who rallied to Lenin's promise of "bread, peace, and land," rural peasants were slow to embrace the revolution Marx antic.i.p.ated they would lead.) Governments continued to export grain during famines well into the twentieth century. Soviet peasants starved in the 1930s when the central government appropriated their harvest to feed the cities and sell to foreign markets for cash to fund industrialization. In most famines, social inst.i.tutions or food distribution inequities cause as much hunger as absolute shortages of food.

The initial response to rising population in postmedieval Europe was to bring progressively more marginal land into agricultural production. Yields may have been lower than from traditional farmlands, but the food produced from these lands helped sustain population growth. Starting in the eighteenth century, European powers harnessed the agricultural potential of their colonies around the world to provide cheap imported food. European agricultural self-reliance ended when imports shifted from lux uries such as sugar, coffee, and tea to basic foodstuffs like grains, meat, and dairy products. By the end of the nineteenth century, many European nations depended on imported food to feed their populations.

As Western empires spread around the globe, colonial economics displaced locally adapted agricultural systems. Typically, introduction of European methods replaced a diversity of crops with a focus on export crops like coffee, sugar, bananas, tobacco, or tea. In many regions, sustained cultivation of a single crop rapidly reduced soil fertility. In addition, northern European farming methods developed for flat-lying fields shielded under snow in winter and watered by gentle summer rains led to severe erosion on steep slopes subject to intense tropical rainfall.

Europe solved its perennial hunger problem by importing food and exporting people. About fifty million people left Europe during the great wave of emigration between 1820 and 1930; many European peoples now have more descendants in former colonies than live in the motherlands. Colonial economics and policies that favored plantation agriculture unofficially encouraged soil degradation and perpetual hunger for fresh land. Paradoxically, the drive to establish colonies was itself driven by European land hunger fueled by degradation of upland regions and enclosure of communal farmland into large estates.

Europeans emerged from under the cloud of malnutrition and constant threat of starvation because their colonial empires produced lots of cheap food. Europeans outsourced food production as they built industrial economies. Between 1875 and 1885, a million acres of English wheat fields were converted to other uses. With a growing industrial economy and a shrinking agricultural land base, Britain increasingly ate imports. By i9oo Britain imported four-fifths of its grain, three-quarters of its dairy products, and almost half its meat. Imported food pouring into Europe mined soil fertility on distant continents to further the growth of industrializing economies.

After Europe's colonial empires dissolved at the end of the Second World War, Josue de Castro, chairman of the executive council of the United Nations Food and Agriculture Organization, argued that hunger not only prepared the ground for history's great epidemics but had been one of the most common causes of war throughout history. He viewed the success of the Chinese Revolution as driven by the strong desire for land reform among tenant farmers forced to surrender half their harvest from microscopic fields to owners of huge estates. Mao Ze-dong's strongest ally was the fear of famine. The chairman's most fervent partisans were the fifty million peasants he promised land.

Agitation for land reform in the third world colored the postcolonial geopolitical landscape of the twentieth century. In particular, subsistence farmers in newly independent countries wanted access to the large land holdings used to grow export crops. Since then, however, land reform has been resisted by Western governments and former colonies, who instead stressed increasing agricultural output through technological means. Generally, this meant favoring large-scale production of export crops over subsistence farming. Sometimes it meant changing a government.

In June 1954 a U.S.-backed coup overthrew the president of Guatemala. Elected in 1952 with 63 percent of the vote, Jacobo Arbenz had formed a coalition government that included four Communists in the fifty-sixmember Chamber of Deputies. An alarmed United Fruit Company, which held long-term leases to much of the coastal lowlands, launched a propaganda campaign pushing the view that the new Guatemalan government was under Russian control. It's unlikely that the few Communist party members in the government had that much clout; United Fruit's real fear was land reform.

In the late nineteenth century, the Guatemalan government had appropriated communal Indian lands to facilitate the spread of commercial coffee plantations throughout the highlands. At the same time, U.S. banana companies began acquiring extensive lowland tracts and building railways to ship produce to the coast. Export plantations rapidly appropriated the most fertile land and the indigenous population was increasingly pushed into cultivating steep lands. By the 1950s, many peasant families had little or no land even though companies like United Fruit cultivated less than a fifth of their vast holdings.

Soon after coming to power, Arbenz sought to expropriate uncultivated land from large plantations and promote subsistence farming by giving both land and credit to peasant farmers. Contrary to United Fruit's claims, Arbenz did not seek to abolish private property. However, he did want to redistribute more than ioo,ooo hectares of company-leased land to small farmers and promote microcapitalism. Unfortunately for Arbenz, U.S. Secretary of State John Foster Dulles had personally drafted the banana company's generous ninety-nine-year lease in 1936. With Dulles on United Fruit's side, even the pretense of Communist influence was enough to motivate a CIA-engineered coup in the opening years of the cold war.

Subsequent foreign investment opened more land for cash crops and cattle. International aid and loans from development banks promoted large projects focused on export markets. Between 1956 and i98o, large-scale monoculture projects received four-fifths of all agricultural credit. Land devoted to cotton and grazing grew more than twentyfold. Land planted in sugar quadrupled. Coffee plantations grew by more than half. Forced from the most fertile land, Guatemalan peasants were pushed up hillsides and into the jungle. Four decades after the 1954 coup, fewer than two out of every hundred landowners controlled two-thirds of Guatemalan farmland. As the size of agricultural plantations increased, the average farm size fell to under a hectare, less than needed to support a family.

This was the story of Ireland all over again, with a Latin American twist-Guatemala is a steep country in the rain-drenched tropics. But like Irish meat, Guatemalan coffee is sold elsewhere. And like its coffee, Guatemala's soil is also leaving as adoption of European agricultural methods to tropical hillslopes ensures a legacy of major erosion. The combination of cash crop monoculture and intensive subsistence farming on inherently marginal lands increased soil erosion in Guatemala dramatically, sometimes enough to be obvious to even the casual observer.

In the last week of October 1998, Hurricane Mitch dumped a year's worth of rain onto Central America. Landslides and floods killed more than ten thousand people, left three million displaced or homeless, and caused more than $5 billion in damage to the region's agricultural economy. Despite all the rain, the disaster was not entirely natural.

Mitch was not the first storm to dump that much rain on Central America, but it was the first to fall on the region's steep slopes after the rainforest had been converted into open fields. As the population tripled after the Second World War, unbroken forest surrounding a few cleared fields was replaced by continuously farmed fields. Now, most of the four-fifths of the rural population farm tiny plots on sloping terrain practicing a small-scale version of conventional agriculture. While accelerated erosion from farming Central America's steep slopes has long been recognized as a problem, Hurricane Mitch ended any uncertainty as to its importance.

After the storm, a few relatively undamaged farms stood out like islands in a sea of devastation. When reconnaissance surveys suggested that farms practicing alternative agriculture better survived the hurricane than did conventional farms, a coalition of forty nongovernmental agencies started an intensive study of more than eighteen hundred farms in Guatemala, Honduras, and Nicaragua. Pairing otherwise comparable farms that prac ticed conventional and so-called sustainable agricultural practices, teams inspected each farm for soil condition, evidence of soil erosion, and crop losses. Across the region, farms operated with sustainable methods such as polyculture, hillside terracing, and biological pest control had two to three times less soil erosion and crop damage than conventional farms under chemical-intensive monoculture. Gullies were less p.r.o.nounced and landslides were two to three times less abundant on sustainable farms than on conventional farms. Sustainable farms had less economic damage as well. Perhaps the most telling result of the study was that more than nine out of ten of the conventional farmers whose farms were inspected expressed a desire to adopt their neighbors' more resilient practices.

Central America was but one of many regions where the growth of large, export-oriented plantations after the Second World War turned former colonies into agricultural colonies serving global markets. Commercial monocultures also displaced subsistence farmers into marginal lands across Asia, Africa, and South America. In the new global economy, former political colonies continued to serve the interests of wealthier nations-only now trading soil for cash. But this is not all that new: the United States was in the same position before its own revolution.

WESTWARD HOE

Since the achievement of our independence, he is the greatest Patriot, who stops the most gullies.

PATRICK HENRY.

SEVERAL YEARS AGO, ON A BREAKNECK research trip down rough dirt roads through a recently deforested part of the lower Amazon, I saw how topsoil loss could cripple a region's economy and impoverish its people. I was there to study caves created over a hundred million years as water slowly dissolved iron-rich rocks that lay beneath soils resembling weathered frying pans. Walking through an iron cave impressed upon my imagination how long it must have taken for dripping water to carve them. Just as striking on this trip were the signs of catastrophic soil loss after forest clearing. Yet what really amazed me was how this human and ecological catastrophe-in-themaking did not change people's behavior, and how the modern story of the lower Amazon paralleled the colonial history of the United States.

Standing on the edge of the Carajas Plateau, I straddled the skeletal remains of an ancient landscape and another still being born. Beside me, high above the surrounding lowlands, I could see landslides chewing away at the sc.r.a.ps of the ancient plateau. On all sides of this jungle-covered mesa, erosion was stripping off a hundred million years' worth of rotted rock along with the deepest soil I'd ever seen.

Since the time of the dinosaurs, water dripping through the equatorial jungle and leaching into the ground has created a deep zone of weathered rock extending hundreds of feet down to the base of the plateau. After South America split off from Africa, the resulting escarpment swept inland eating into the ancient uplands from the side. Standing on the cliff at the edge of the plateau-a small remnant of the original land surface-I admired the wake of new rolling lowlands that fell away toward the Atlantic Ocean.

The Carajas Plateau is made up of banded iron-almost pure iron ore deposited by an anoxic sea long before Earth's oxygen-rich atmosphere evolved. Buried deep in the earth's crust and eventually pushed back to the surface to weather slowly, the iron-rich rock gradually lost nutrients and impurities to seeping water, leaving behind a deeply weathered iron crust.

Aluminum and iron ore can form naturally through this slow weathering process. Over geologic time, the ample rainfall and hot temperatures of the tropics can concentrate aluminum and iron as chemical weathering leaches away almost everything else from the original rock. Although it may take a hundred million years, it is far more cost-effective to let geologic processes do the work than to industrially concentrate the stuff. Given time, this process can make a commercially viable ore-as long as weathering outpaces erosion. If erosion occurs too rapidly, the weathered material disappears long before it could become concentrated enough to be worth mining.

On top of the Carajas Plateau, a gigantic pit opened a window into the earth, extending hundreds of feet to the base of the deep red weathered rock. Huge, three-story-tall trucks crawled up the terraced walls, dragging tons of dirt along the road that snaked up from the bottom. Viewed from the far side, the hundred-foot-tall trees left standing on the rim of the pit looked like a fringe of mold. Gazing at this bizarre sight in the midday sun, I realized how the thin film of soil and vegetation covering Earth's surface resembles a coating of lichen on a boulder.

Speeding off the plateau, we dropped down to the young rolling hills made of rock that once lay beneath the now-eroded highlands. As we drove through virgin rainforest, road cuts exposed soil one to several feet thick on the dissected slopes leading down to the deforested lowland. Leaving the jungle, we saw bare slopes that provided stark evidence that topsoil erosion following forest clearing led to abandoned farms. Around villages on the forest's edge, squatters farmed freshly cleared tracts. Weathered rock exposed along the road poked out of what had until recently been soilcovered slopes. The story was transparently simple. Soon after forest clearing, the soil eroded away and people moved deeper into the jungle to clear new fields.

A few miles in from the forest edge, family farms and small villages gave way to cattle ranches. As subsistence farmers pushed farther into the forest, ranchers took over abandoned farms. Cows can graze land with soil too poor to grow crops, but it takes a lot of ground to support them. Largescale cattle grazing prevents the forest from regrowing, causing further erosion and sending frontier communities farther and farther into the jungle in an endless push for fresh land. The vicious cycle is plainly laid out for all to see.

Instead of clearing small patches of forest for short periods, immigrants to the Amazon are clearing large areas all at once, and then accelerating erosion through overgrazing, sucking the life from the land. The modern cycle of forest clearing, peasant farming, and cattle ranching strips off topsoil and nearly destroys the capacity to recover soil fertility. The result is that the land sustains fewer people. When they run out of productive soil, they move on. The modern Amazon experience reads a lot more like the history of North America than we tend to acknowledge. Yet the parallel is as clear as it is fundamental.

Between forty million and one hundred million people lived in the Americas when Columbus "discovered" the New World-some four million to ten million called North America home. Native Americans along the East Coast practiced active landscape management but not sedentary agriculture. Early colonists described a patchwork of small clearings and the natives' habit of moving their fields every few years, much like early Europeans or Amazonians. While there is emerging evidence of substantial local soil erosion from native agriculture, soil degradation and erosion began to transform eastern North America under the new arrivals' more settled style of land use.

Intensive cultivation of corn quickly exhausted New England's nutrientpoor glacial soils. Within decades, colonists began burning the forest to make ash fertilizer for their fields. With more people crowded into less s.p.a.ce, New Englanders ran out of fresh farmland faster than their neighbors in the South. Early travelers complained about the stench from fields where farmers used salmon as fertilizer. And in the South, tobacco dominated the slave-based economies of Virginia and Maryland and soil exhaustion dominated the economics of tobacco cultivation. Once individual family farms coalesced into slave-worked tobacco plantations, the region became trapped in an insatiable socioeconomic system that fed on fresh land.

Historian Avery Craven saw colonial soil degradation as part of an inevitable cycle of frontier colonization. "Men may, because of ignorance or habit, ruin their soils, but more often economic or social conditions, entirely outside their control lead or force them to a treatment of their lands that can end only in ruin."' Craven thought frontier communities generally exhausted their soil because of the economic imperative to grow the highest value crop. The tobacco economy that ruled colonial Virginia and Maryland was exactly what Craven had in mind.

In 16o6 James I granted the Virginia Company a charter to establish an English settlement in North America. Founded by a group of London investors, the company expected their New World franchise to return healthy profits. Under the leadership of Captain John Smith, on May 14, 1607, the first load of colonists landed along the banks of the James River sixty miles up Chesapeake Bay. Hostile natives, disease, and famine killed two-thirds of the original settlers before Smith returned to England in 1609.

Desperately searching for ways to survive, let alone earn a profit, the Jamestown colonists tried making silk, then gla.s.s; harvesting timber; growing sa.s.safras; and even making beer. Nothing worked until tobacco provided a profitable export that propped up the colony.

Sir Walter Raleigh is often credited with introducing tobacco to England in 1586. Whether or not that dubious honor is actually his, Spanish explorers brought both leaf and seeds back from the West Indies. Smoking became immensely popular and the English developed quite a taste for Spanish tobacco grown with slave labor in the Caribbean. Sold at a premium to London merchants, tobacco offered just what the Jamestown colonists needed to keep their colony afloat.

Unfortunately, England's new smokers did not like Virginian tobacco. With an eye toward competing in the London market colonist John Rolfe (perhaps better remembered as Pocahontas's husband) experimented with planting Caribbean tobacco. Satisfied that the stuff "smoked pleasant, sweete and strong," Rolfe and his compatriots shipped their first crop to England. It was a hit in London's markets, comparing favorably with premium Spanish tobacco.

Soon everybody was planting tobacco. Twenty thousand pounds were sent to England in 1617. Twice as much set sail in the next shipment. Captain Smith praised Virginia's "l.u.s.ty soyle" and the colonial economy quickly became dependent upon tobacco exports. On September 30, 1619, colonist John Pory wrote to Sir Dudley Carleton that things were finally turning around. "All our riches for the present doe consiste in Tobacco, wherein one man by his owne labour hath in one yeare raised to himselfe to the value of zoo sterling and another by the meanes of sixe Servants hath cleared at one crop a thousand pound English."2 Within a decade, one and a half million pounds of Virginian tobacco reached English markets each year.

Americas colonial economy was off and running. Within a century, annual exports to Britain soared a thousandfold to more than twenty million pounds. Tobacco so dominated colonial economics that it served as an alternative currency. The stinking weed saved the faltering colony, but growing it triggered severe soil degradation and erosion that pushed colonists ever inland.

Colonial tobacco was a clean-tilled crop. Farmers heaped up a pile of dirt around each plant with a hoe or a light one-horse plow. This left the soil exposed to rainfall and vulnerable to erosion during summer storms that hit before the plants leafed out. Despite the obvious toll on the land, tobacco had a singular attraction. It fetched more than six times the price of any other crop, and could survive the long (and expensive) journey across the Atlantic. Most other crops rotted on the way or could not sell for enough to pay for the trip.

Colonial economics left little incentive to plant a variety of crops when tobacco yielded by far the greatest returns. So Virginians grew just enough food for their families and devoted their energy to growing tobacco for European markets. New land was constantly being cleared and old land abandoned because a farmer could count on only three or four highly profitable tobacco crops from newly cleared land. Tobacco strips more than ten times the nitrogen and more than thirty times the phosphorous from the soil than do typical food crops. After five years of tobacco cultivation the ground was too depleted in nutrients to grow much of anything. With plenty of fresh land to the west, tobacco farmers just kept on clearing new fields. Stripped bare of vegetation, what soil remained on the abandoned fields washed into gullies during intense summer rains. Virginia became a factory for turning topsoil into tobacco.

King James saw the tobacco business as an attractive way to raise revenue. In 16i9 the Virginia Company agreed to pay the Crown one shilling per pound on its shipments to England in exchange for restrictions on Spanish tobacco imports and on tobacco growing in England-a monopoly on the popular new drug. Just two years later, new regulations mandated that all tobacco exported from the colonies be sent to England. In 1677 the royal treasury pocketed ioo,ooo from import duties on Virginian tobacco and another 50,000 from Maryland tobacco. Virginia returned more to the royal pocketbook than any other colony; more than four times the revenue from the East Indies.

Not surprisingly, colonial governments piled on to use tobacco to raise revenue. Once hooked on the new source of cash, they quickly squashed attempts to stem reliance on tobacco. When Virginians requested a temporary ban on tobacco growing in 1662, they were unsubtly told never to make such a request again. The secretaries for the colony of Maryland tried to ensure that colonists did not "turn their thoughts to anything but the Culture of Tobacco."3 The short-lived fertility of the land under tobacco cultivation encouraged rapid expansion of agricultural settlements. Abandoning fields that no longer produced adequate returns, Virginia planters first requested permission to clear new land farther from the coast in 1619. Five years later, planters at Paspaheigh sought permission from the colonial court to move to new land, even though fifteen years before their governor had p.r.o.nounced their lands excellent for growing grain. Little more than two decades later, tobacco farmers along the Charles River pet.i.tioned the governor for access to virgin lands because their fields "had become barren from cultivation." Seventeenth-century Virginians complained about the extreme loss of soil during storms; it was hard to overlook the destructive gullies chewing up the countryside. Moving inland, planters encountered soils even more susceptible to erosion than those along the coast and in the major river valleys. Pushing south as well, by 1653 tobacco farmers were clearing new fields in North Carolina's coastal plain where there was still plenty of fresh land.

As soil fertility declined along the coast, farmers moved inland. The potential for access to the rich lands beyond the mountains motivated Virginians during the French and Indian War. Colonial farmers were enraged at mother England when the peace treaty of 1763 effectively closed the western lands to immediate settlement. Lingering resentment over debilitating tobacco taxes and perceived obstructions to westward expansion helped fuel dissatisfaction with British rule.

Colonial agriculture remained focused on tobacco in the South despite depressed prices stemming from oversupply and the requirement that the whole crop be shipped to England. By the middle of the eighteenth century, government duties accounted for about 8o percent of the sale price of tobacco; the planter's share had dropped to less than 1o percent. Anger over perceived inequities in the regulation, sale, and export of tobacco simmered until the Revolutionary War.

Particularly in the South, the ready availability of new lands meant that farmers neglected crop rotation and the use of manure to replenish soils. Published in 1727, The Present State of Virginia blamed the rapid decline in soil fertility on failure to manure the fields. "So it is at present that Tobacco swallows up all other Things, every thing else is neglected.... By that time the Stumps are rotten, the Ground is worn out; and having fresh Land enough ... they take but little Care to recruit the old Fields with Dung."4 Moving on to fresh ground was easier than collecting and spreading manure-as long as there was plenty of land for the taking.

Other contemporary observers also noted that tobacco consumed the full attention of planters. In a 1729 letter to Charles Lord Baltimore, Benedict Leonard Calvert concisely summarized the influence of tobacco on colonial agriculture. "In Virginia and Maryland Tobacco is our Staple, is our All and Indeed leaves no room for anything Else."5 Tobacco reigned as undisputed king of the southern colonies.

The need for continual access to fresh land encouraged the establishment of large estates. Low prices in the glutted tobacco market of the late seventeenth century created opportunities to consolidate large holdings when small farmers went out of business. Just as in Rome two thousand years before, and in the Amazon almost three centuries later, abandoned family farms ended up in the hands of plantation owners.

In New England, some colonists began experimenting with soil improvement. Connecticut minister, doctor, and farmer Jared Eliot published the first of his Essays Upon Field Husbandry in 1748 reporting the results of experiments on how to prevent or reverse soil degradation. Riding on horseback to call on his parishioners and patients, Eliot noticed that the muddy water running off bare hillsides carried away fertile soil. He saw how deposition of mud washed from the hills enriched valley bottom soils and how loss of the topsoil ruined upland fields. Eliot recommended spreading manure and growing clover for improving poor soils. He endorsed marl (fossil sea sh.e.l.ls) and saltpeter (pota.s.sium nitrate) as excellent fertilizers almost equal to good dung. Bare soil left exposed on sloping ground was particularly vulnerable to washing away in the rain. Sound as it was, few colonial farmers heeded Eliot's advice, particularly in the South where new land was still readily obtained.

Benjamin Franklin was among those who bought Eliot's essays and began experimenting with how to improve his land. Writing to Eliot in 1749 he confided his concern about how difficult it would be to convince American farmers to embrace soil husbandry. "Sir: I perused your two Essays on Field Husbandry, and think the public may be much benefited by them; but, if the farmers in your neighborhood are as unwilling to leave the beaten road of their ancestors as they are near me, it will be difficult to persuade them to attempt any improvement."6 Eliot likened farmers who did not return manure and crop wastes to the fields to a man who withdrew money from the bank without ever making a deposit. I imagine that Franklin concurred.

Commentary on the depleted state of colonial soils was routine by the end of the eighteenth century. Writing during the Revolutionary War, Alexander Hewatt described farmers in the Carolinas as focused on shortterm yields and paying little attention to the condition of their land.

Like farmers often moving from place to place, the princ.i.p.al study with the planters is the art of making the largest profit for the present time, and if this end is obtained, it gives them little concern how much the land may be exhausted.... The richness of the soil, and the vast quant.i.ty of lands, have deceived many.... This will not be the case much longer, for lands will become scarce, and time and experience, by unfolding the nature of the soil ... will teach them ... to alter [their] careless manner of cultivation.?

Hewatt was not alone in his bleak a.s.sessment of American agriculture.

Many Europeans who traveled through the southern states in the late 170os expressed surprise at the general failure to use manure as a soil amendment. Exiled French revolutionary Jacques-Pierre Brissot de Warville toured the newly independent United States in 1788 and wondered at the ruinous style of agriculture. "Though tobacco exhausts the land to a prodigious degree, the proprietors take no pains to restore its vigour; they take what the soil will give, and abandon it when it gives no longer. They like better to clear new lands, than to regenerate old. Yet these abandoned lands would still be fertile, if they were properly manured and cultivated."8 Careless waste of good land perplexed European observers accustomed to cheap labor and a shortage of fertile land.

At the close of the eighteenth century, newly arrived settler John Craven found Virginia's Albemarle County so degraded by poor farming practices that the inhabitants faced the simple choice of emigrating or improving the soil. Writing to the Farmer's Register years later, Craven recalled the sad state of the land. "At that time the whole face of the country presented a scene of desolation that baffles description-farm after farm had been worn out, and washed and gullied, so that scarcely an acre could be found in a place fit for cultivation.... The whole of the virgin soil was washed and carried off from the ridges into the valleys."9 Visiting Virginia and Maryland the following year, in i8oo, a baffled William Strickland declared that he could not see how the inhabitants scratched a living from their fields.

In 1793 Unitarian minister Harry Toulmin left Lancashire for America to report to his congregation on the suitability of the new country for emigration. Land hunger and the rising price of food in Britain increased pressure to leave for America, particularly for those living on fixed incomes and low wages in the industrializing economy. In addition, many Unitarians and others sympathetic to the progressive ideals of the American and French revolutions abandoned their homeland for the New World when the new French Republic declared war on England.

Finding agricultural prospects poor along the Atlantic seaboard, Toulmin procured letters of introduction from James Madison and Thomas Jefferson to John Breckinridge, who had quit a Virginia congressional seat to emigrate to Kentucky. Toulmin's letters and journals provide a vivid description of Kentucky's soils at the time of first settlement. Reporting on the agricultural potential of Mason County in northern Kentucky, Toulmin described the gently undulating country as well endowed with rich soil. "The soil is in general rich loam. In the first-rate land (of which there are some million of acres in this county) it is black. The richest and blackest mold continues to about the depth of five or six inches. Then succeeds a lighter colored, friable mold which extends about fifteen inches farther. When dry it will blow away with the wind."10 Testimony such as Toulmin's helped draw people west from the coast. It also proved far more prophetic than he could have imagined.

About the time of the American Revolution, some of the founding fathers began to worry about the impact of mining the soil on the country's future. George Washington and Thomas Jefferson were among the first to warn of the destructive nature of colonial agriculture. Ideological rivals, these prosperous Virginia plantation owners shared concern over the long-term effects of American farming practices.

After the Revolution, Washington did not hide his scorn for the shortsighted practices of his neighbors. "The system of agriculture, (if the epithet of system can be applied to it) which is in use in this part of the United States, is as unproductive to the pract.i.tioners as it is ruinous to the landholders."" Washington blamed the widespread practice of growing tobacco for wearing out the land. He saw how poor agricultural practices fueled the desire to wrest the greatest return from the ground in the shortest time-and vice versa. In a 1796 letter to Alexander Hamilton, Washington predicted that soil exhaustion would push the young country inland. "It must be obvious to every man, who considers the agriculture of this country ... how miserably defective we are in the management of [our lands] .... A few years more of increased sterility will drive the Inhabitants of the Atlantic States westward for support; whereas if they were taught how to improve the old, instead of going in pursuit of new and productive soils, they would make these acres which now scarcely yield them any thing, turn out beneficial to themselves." 12 Washington's interest in progressive agriculture began long before the Revolution. As early as 1760, he used marl (crushed limestone), manure, and gypsum as fertilizers and plowed crops of gra.s.s, peas, and buckwheat back into his fields. He built barns for cattle in order to harvest manure, and instructed reluctant plantation managers to spread the waste from livestock pens onto the fields. He experimented with crop rotations before finally settling on a system that involved interspersing grains with potatoes and clover or other gra.s.ses. Washington also experimented with deep plowing to reduce runoff and r.e.t.a.r.d erosion. He filled gullies with old fence posts, trash, and straw before covering them with dirt and manure and then planting them with crops.

Perhaps most radical, however, was Washington's realization that soil improvement was next to impossible on large estates. Dividing his land into smaller tracts, he instructed his overseers and tenants to promote soil improvement. Washington's efforts focused on preventing soil erosion, saving and using manure as fertilizer, and specifying cover crops to include in rotations.

Returning to Mount Vernon after the Revolution, Washington wrote English agriculturalist Arthur Young for advice on improving his lands. Young embraced Washington as a "brother farmer" and agreed to provide the American president with any a.s.sistance desired.

In 1791 Young asked Washington to describe agricultural conditions in northern Virginia and Maryland. Washington's reply indicates that the old practices that encouraged soil erosion and exhaustion remained widespread. In particular, the practice of growing steadily falling yields of tobacco, followed by as much corn as the exhausted land could produce, continued to reduce soil fertility. With limited pasture and livestock, few farmers used manure to prolong or restore soil fertility. Washington explained that American farmers had a strong incentive to get the most out of their laborers regardless of the effect on their soil; workers cost four times the value of the land they could work. He also reported a growing tendency to abandon tobacco in favor of wheat, even though wheat yields were barely comparable to medieval European yields. American agriculture was wearing down the New World.

Thomas Jefferson too worried that Americans were squandering the productive capacity of their land. Where Washington blamed ignorance of proper farming methods, Jefferson saw greed. "The indifferent state of [agriculture] among us does not proceed from a want of knowledge merely; it is from our having such quant.i.ties of land to waste as we please. In Europe the object is to make the most of their land, labor being abundant; here it is to make the most of our labor, land being abundant. "13 When a perplexed Arthur Young questioned how a man could produce five thousand bushels ofwheat on a farm with cattle worth only 150, Jefferson reminded him that "manure does not enter into this because we can buy an acre of new land cheaper than we can manure an old one." 14 Better short-term returns were to be had by mining soil than by adopting European-style husbandry. In Jefferson's view, failure to care for the land was the curse of American agriculture.

The relationship between eighteenth-century plantation owners and their poorer neighbors bolsters Jefferson's argument. Wealthy landowners generally exhausted their land growing tobacco, used their slaves to clear new fields, and then sold their old fields to farmers lacking the means and the slaves to clear and work a tobacco plantation. Plantation owners often bought food from neighboring farms to feed their own families. Cotton and tobacco so dominated agriculture that before the Civil War the South was a net importer of grains, vegetables, and farm animals.