Trained as a pharmacist, Parmentier served in the army and was captured five times by the Prussians during the Seven Years’ War. As a prisoner he ate little but potatoes for three years, a diet which to his surprise kept him in good health. His effort to understand how this could have happened led Parmentier to become a pioneering nutritional chemist, one of the first to try to figure out what is in food and why it sustains the body. When unseasonable rain and snow in 1769 and 1770 led to crop failures in parts of eastern France, a local academy announced a competition for “Plants that Could in Times of Scarcity be Substituted for Regular Food to Nourish Man.” Five of the seven entries touted the potato. Parmentier’s essay, the most impassioned and well documented, won the competition. It was the beginning of his career as a potato activist.
His timing was good. Four years after the famine, one of the first acts of the newly anointed king, Louis XVI, was to lift price controls on grain. Bread prices shot up, sparking what became known as the Flour War: more than three hundred civil disturbances in eighty-two towns. Throughout the disturbances Parmentier tirelessly advocated the potato as the solution. Proclaiming that France would stop fighting over bread if the French would eat potatoes, he set up one pro-spud publicity stunt after another: persuading the king to wear potato blossoms; presenting an all-potato dinner to high-society guests;3 planting forty acres of potatoes at the edge of Paris, knowing that famished sansculottes would steal them. His efforts were successful. “The potato,” announced a later supplement to Diderot’s Encyclopedia, “is the fruit that feeds more than half of Germany, Switzerland, Great Britain, Ireland and many other countries.”
In extolling the potato, Parmentier unwittingly changed it. All of Europe’s potatoes descended from a few tubers sent across the ocean by curious Spaniards. From a genetic point of view, the European stock had been created by dipping a teaspoon into the sea of genes in Peru and Bolivia. Parmentier was urging his countrymen to cultivate this limited sample on a massive scale. Because potatoes are grown from pieces of tuber, he was unknowingly promoting the notion of planting huge areas with clones—a true monoculture. The potato fields he was envisioning were thus radically different from their Andean forebears. One was a crazy gumbo, its ingredients unclear; the other was an orderly array of identical parts.
The effects of this transformation were so striking that any general history of Europe without an entry in its index for S. tuberosum should be ignored. Hunger was a familiar presence in the Europe of the Little Ice Age, where cold weather killed crops even as Spanish silver drove up prices. Cities were provisioned reasonably well in most years, their granaries monitored by armed guards, but country people teetered on a precipice. When harvests failed, food riots ensued; thousands occurred across Europe between 1400 and 1700, according to the great French historian Fernand Braudel. Over and over, rioters, often led by women, broke into bakeries, granaries, and flour mills and either stole food outright or forced merchants to accept a “just” price. Ravenous bandits swarmed the highways, seizing grain convoys to cities. Order was restored by violent action.
Braudel cited an eighteenth-century tally of famine in France: forty nationwide calamities between 1500 and 1778, more than one every decade. This appalling figure actually understates the level of scarcity, he wrote, “because it omits the hundreds and hundreds of local famines.” France was not exceptional; England had seventeen national and big regional famines between 1523 and 1623. Florence, hardly a poor city, “experienced 111 years when people were hungry, and only sixteen ‘very good’ harvests between 1371 and 1791”—seven bad years for every bumper year. The continent could not feed itself reliably. It was caught in the Malthusian trap.
As the sweet potato and maize did in China, the potato (and maize, to a lesser extent) helped Europe escape Malthus. When the agricultural economist Arthur Young toured eastern England in the 1760s he saw a farming world that was on the verge of a new era. A careful investigator, Young interviewed farmers, recording their methods and the size of their harvests. According to his figures, the average yearly harvest in eastern England from an acre of wheat, barley, and oats was between 1,300 and 1,500 pounds. By contrast, an acre of potatoes yielded more than 25,000 pounds—about eighteen times as much.4 Growing potatoes especially helped England’s poor, Young believed. “It is to be wished, that all persons who have it in their power to render this root more common among them, would exert themselves in it.” Potatoes, he proclaimed, “cannot be too much promoted.”
Potatoes didn’t replace grain but complemented it. Every year, farmers left fallow as much as half of their grain land, to rest the land and fight weeds (they were plowed under in summer). Now smallholders could grow potatoes on the fallow land, controlling weeds by hoeing. Because potatoes were so productive, the effective result was, in terms of calories, to double Europe’s food supply. “For the first time in the history of western Europe, a definitive solution had been found to the food problem,” the Belgian historian Chris Vandenbroeke concluded. (The German historian Joachim Radkau was blunter: the key environmental innovations of the eighteenth century, he wrote, were “the potato and coitus interruptus.”) Potatoes (and, again, maize) became to much of Europe what they were in the Andes—an ever-dependable staple, something eaten at every meal. Roughly 40 percent of the Irish ate no solid food other than potatoes; the figure was between 10 and 30 percent in the Netherlands, Belgium, Prussia, and perhaps Poland. Routine famine almost disappeared in potato country, a two-thousand-mile band that stretched from Ireland in the west to Russia’s Ural Mountains in the east. At long last, the continent could, with the arrival of the potato, produce its own dinner.
Although the potato raised farm production overall, its greater benefit was to make that production more reliable. Before S. tuberosum, summer was usually a hungry time, with stored grain supplies running low before the fall harvest. Potatoes, which mature in as little as three months, could be planted in April and dug up during the thin months of July and August. And because they were gathered early, they were unlikely to be affected by an unseasonable fall—the kind of weather that ruined wheat harvests. In war-torn areas, potatoes could be left in the ground for months, making them harder to steal by foraging soldiers. (Armies in those days did not march with rations but took their food, usually by force, from local farmers.) Young’s interview subjects used most of their potatoes for animal feed. In bad years, they had been forced to choose whether to feed their animals or themselves. Now they didn’t have to make the choice.
The economist Adam Smith, writing a few years after Young, was equally taken with the potato. He was impressed to see that the Irish remained exceptionally healthy despite eating little else: “The chairmen, porters, and coal-heavers in London, and those unfortunate women who live by prostitution—the strongest men and the most beautiful women perhaps in the British dominions—are said to be, the greater part of them, from the lowest rank of people in Ireland, who are generally fed with this root.” Today we know why: the potato can better sustain life than any other food when eaten as the sole item of diet. It has all essential nutrients except vitamins A and D, which can be supplied by milk; the diet of the Irish poor in Smith’s day consisted largely of potatoes and milk. And Ireland was full of poor folk; England had conquered it in the seventeenth century and seized much of the best land for its own citizens. Many of the Irish were forced to become sharecroppers, paid for their work by being allowed to farm little scraps of wet land for themselves. Because little but potatoes could thrive in this stingy soil, Ireland’s sharecroppers were among Europe’s most impoverished people. Yet they were also among its most well nourished, because they ate potatoes. Smith drew out the logical consequences: if potatoes ever became, “like rice in some rice countries, the common and favourite vegetable food of the people,” he wrote, “the same quantity of cultivated land would maintain a much greater number of people.” Ineluctably, Smith believed, “Population would increase.”
Smith wa
s correct. At the same time that the sweet potato and maize were midwifing a population boom in China, the potato was helping to lift populations in Europe—the more potatoes, the more people. (The worldwide population boom was a sign and effect of the onset of the Homogenocene.) In the century after the potato’s introduction Europe’s numbers roughly doubled. The Irish, who ate more potatoes than anyone else, had the biggest boom; the nation grew from perhaps 1.5 million in the early 1600s to about 8.5 million two centuries later. (Some believed it reached 9 or even 10 million.) The increase occurred not because potato eaters had more children but because more of their children survived. Part of the impact was direct: potatoes prevented deaths from famine. The greater impact, though, was indirect: better-nourished people were less likely to die of infectious disease, the era’s main killer. Norway was an example. Cold climate had long made it vulnerable to famine, which struck nationwide in 1742, 1762, 1773, 1785, and 1809. Then came the potato. The average death rate changed relatively little, but the big spikes vanished. When they were smoothed out, Norwegian numbers soared.
Such stories were recorded all over the continent. Hard hit by the shorter growing seasons of the Little Ice Age, mountain hamlets in Switzerland were saved by the potato—indeed, they thrived. When Saxony lost most of its agricultural land to Prussia in 1815, refugees filled its towns. To keep up with the rising numbers, farmers ripped out wheat and rye and planted potatoes. The potato harvest was enough to feed Saxony’s growing population but not enough for good nutrition—there wasn’t enough milk. Farmers in central Spain cut down olive and almond trees and planted potatoes. Village prosperity rose, followed by village numbers. And so on.
Just as American crops were not the only cause of China’s population boom, they were not the only reason for Europe’s population boom. The potato arrived in the midst of changes in food production so sweeping that some historians have described them as an “agricultural revolution.” Improved transportation networks made it easier to ship food from prosperous areas to places with poor harvests. Marshlands and upland pastures were reclaimed. Shared village land was awarded to individual families, dispossessing many smallholders but encouraging the growth of mechanized agriculture (the new owners could be guaranteed of keeping the returns if they invested in their farms). Reformers like Young popularized better cultivation methods, especially the use of manure from stables as fertilizer. Farmers learned to plant fallow fields with clover, which recharges the soil with nutrients. First domesticated by the Moors in Spain, clover helped prevent Europeans from destroying their pastureland soil by overgrazing. The advances were not confined to agriculture. American silver let Europeans build ships to increase trade, raising living standards. Some improvements occurred in the continent’s governance and even in its abysmal hygiene standards. As in China, the Little Ice Age began to wane.
In 2010 two economists at Harvard and Yale attempted to account for such factors by comparing events in parts of Europe that were similar except for their suitability for potatoes; any systematic differences, they argued, would be due to the new crop. According to the two researchers’ “most conservative” estimate, S. tuberosum was responsible for about an eighth of Europe’s population increase. Put baldly, the figure may not seem high. But the continent’s long boom had many causes. One way to think of this calculation is to say that it suggests the introduction of the potato was as important to the modern era as, say, the invention of the steam engine.
THE GUANO AGE
It was said that the islands gave off a stench so intense that they were difficult to approach. They were a clutch of dry, granitic mounds thirteen miles off the Peruvian shore, about five hundred miles south of Lima on the west coast of South America. Almost nothing grew on them. Called the Chincha Islands, they were never inhabited by Indians—not for long, anyway. Their sole distinction is their population of seabirds, especially the Peruvian booby, the Peruvian cormorant, and the Peruvian pelican. The birds are attracted by the strong coastal current, which pulls cold water from the depths. Phytoplankton feast on the nutrients that rise with the water. Zooplankton eat the phytoplankton and in turn are the primary food of the anchoveta fish, a cousin to the familiar anchovy. Anchoveta live in vast schools that are preyed upon by other fish. Predators and prey both are preyed upon by the Peruvian booby, cormorant, and pelican. All three have nested on the Chincha Islands for millennia. Over time they have covered the islands with a layer of guano as much as 150 feet thick.
Guano makes excellent fertilizer. Fertilizer is, at base, a mechanism for providing nitrogen to plants. Plants need nitrogen to make chlorophyll, the green substance in their leaves that absorbs the sun’s energy for photosynthesis. Nitrogen is also a key building block for both DNA and the proteins assembled by DNA. Although more than three-quarters of the atmosphere is made up of nitrogen gas, from a plant’s point of view nitrogen is scarce—the gas is made from two nitrogen atoms that cling to each other so tightly that plants cannot split them apart for use. In consequence, plants seek nitrogen from the soil, where it can be found in forms that they can break down: ammonia (NH3, or one nitrogen atom and three hydrogen atoms), nitrites (compounds that include NO2, a group of one nitrogen atom and two oxygen atoms), and nitrates (compounds that include NO3, a group of one nitrogen atom and three oxygen atoms). All are in less supply than farmers would like, not least because bacteria in the soil constantly digest nitrates and nitrites, turning the nitrogen back into unusable nitrogen gas. Land that has been farmed repeatedly always risks nitrogen depletion.
Unlike mammalian urine, bird urine is a semisolid substance. Because of this difference, birds can build up reefs of urine in a way that mammals cannot (except, occasionally, for big colonies of bats in caves). Even among birds, though, Chincha-style guano deposits—heaps as big as a twelve-story building—are uncommon. To make them, the birds must be relatively large, form big flocks, and defecate where they live (gulls, for instance, release their droppings away from their breeding grounds). In addition, the area must be dry enough not to wash away the guano. The waters off the Peruvian coast receive less than an inch of rain a year. The Chinchas, the most important of Peru’s 147 guano islands, house hundreds of thousands of Peruvian cormorants, the most prolific guano producers. According to The Biogeochemistry of Vertebrate Excretion, a classic treatise by G. Evelyn Hutchinson, a cormorant’s annual output is about thirty-five pounds. Arithmetic suggests that the Chincha cormorants alone produce thousands of tons per year.
Centuries ago Andean Indians discovered that depleted soils could be replenished with guano. Llama trains carried baskets of Chincha guano along the coast and perhaps into the mountains. The Inka parceled out guano claims to individual villages, levying penalties for disturbing the birds during nesting or taking guano allocated to other villages. Blinded by the shine from Potosí silver, the Spaniards paid little attention to conquered peoples’ excremental practices. The first European to observe guano carefully was the German polymath Friedrich Wilhelm Heinrich Alexander von Humboldt, who traveled through the Americas between 1799 and 1804. A pioneer in botany, geography, astronomy, geology, and anthropology, Humboldt had an insatiable curiosity about everything that crossed his path, including the fleet of native guano boats that he saw skittering along the Peruvian coast. “One can smell them a quarter of a mile away,” he wrote. “The sailors, accustomed to the ammonia smell, aren’t bothered by it; but we couldn’t stop sneezing as they approached.” Among the thousands of samples Humboldt took back to Europe was a bit of Peruvian guano, which he sent to two French chemists. Their analysis showed that Chincha guano was 11 to 17 percent nitrogen—enough to burn plant roots if not properly applied. The French scientists touted its potential as fertilizer.
Few took their advice. Supplying European farmers with guano would involve transporting large quantities of excrement across the Atlantic, a project that understandably failed to enthuse shipping companies. Within several decades, though, the picture changed. Agric
ultural reformers throughout Europe had begun to worry that the ever-more-intense agriculture necessary to feed growing populations was exhausting the soil. As harvests leveled off and even decreased, they looked for something to restore the land: fertilizer.
At the time, the best-known soil additive was bone meal, made by pulverizing bones from slaughterhouses. Bushels of bones went to grinding factories in Britain, France, and Germany. Demand ratcheted up, driven by fears of soil depletion. Bone dealers supplied the factories from increasingly untoward sources, including the recent battlefields of Waterloo and Austerlitz. “It is now ascertained beyond a doubt, by actual experiment upon an extensive scale, that a dead soldier is a most valuable article of commerce,” remarked the London Observer in 1822. The newspaper noted that there was no reason to believe that grave robbers were limiting themselves to battlefields. “For aught known to the contrary, the good farmers of Yorkshire are, in a great measure, indebted to the bones of their children for their daily bread.”
From this perspective, avian feces began to seem like a reasonable item of commerce. A few bags of guano appeared in European ports in the mid-1830s. Then Justus von Liebig weighed in. A pioneering organic chemist, Liebig was the first to explain plants’ dependence on nutrients, especially nitrogen. In his treatise Organic Chemistry in Its Application to Agriculture and Physiology (1840), Liebig criticized the use of bone fertilizer, which has little nitrogen. Guano was another story: “It is sufficient to add a small quantity of guano to a soil consisting only of sand and clay, in order to procure the richest crop of maize.” Liebig was enormously respected; he was an avatar of the Science that had brought new, productive crops like the potato and maize, and new ways of thinking about agriculture and industry. Organic Chemistry was quickly translated into multiple languages; at least four English editions appeared. Sophisticated farmers, many of them big landowners, read Liebig’s encomium to guano, flung down the book, and raced to buy it. Yields doubled, even tripled. Fertility in a bag! Prosperity that could be bought in a store!
1493: Uncovering the New World Columbus Created Page 26