in Ethiopia. Under the right conditions, as coffee farmers would later discover to their dismay, arabica could be highly susceptible to the rust. But the rust was also kept in check by the environment of Ethiopia’s highland forests. The average temperatures of the highlands are, in places, cooler than ideal for the rust spores to germinate. The dense forest intercepted rainfall, which made it more difficult for the spores to germinate and spread. The forest also blocked the wind, which limited the circulation of rust spores. The comparatively low density of coffee plants in the forest also limited the opportunities for spores to find a host to reproduce upon. And, in Ethiopia, H. vastatrix was itself parasitized by hyperparasitic fungi found in the forest, of the genera Darluca and Verticillium.9
“Arabian” Coffee in the Islamic World, 1450–1700
The first people to regularly consume coffee likely left the forest cover intact, at first. The people of southwestern Ethiopia may have first consumed the leaves of the coffee—as a tisane—rather than the fruit. But at some point, they also began consuming the fruit. According to one often-repeated legend, a goatherd named Kaldi discovered coffee’s stimulant properties when his goats started dancing after eating coffee fruit. Although this charming story is likely not true in its specifics, it does suggest one way that people may have discovered the bean’s stimulant properties. There is some debate as to whether Ethiopians consumed coffee beans as a food—mixed with butter, honey, and spices—or as a drink.10 At first, the people of Kaffa likely foraged for coffee, harvesting the fruit from wild trees. At some point they realized, speculated the botanist Pierre Sylvain, that plants exposed to the sun yielded more coffee. So they began to manage the forest canopy, reducing the shade to increase the yields of wild plants. Some people transplanted wild coffee seeds and seedlings from the forest to gardens near their houses, where they cultivated coffee alongside other crops. As coffee became more popular in Ethiopia, people started moving coffee plants beyond their native range.11 These changes presented the rust with new opportunities to spread, though if it did, the levels of infection likely remained low. “Diseases and pests do not seem to be a problem in the coffee forest,” wrote Sylvain in 1956, “where man has not changed the biological equilibrium.”12 The rust was likely not a major problem on the semiforest or garden coffees either. The coffee plants were protected by a measure of genetic resistance, cropping practices, and temperatures that were favorable to the plant but inimical to the rust.
Coffee’s life as a global commodity began early in the fifteenth century CE, carried along trade routes that linked southern Ethiopia to the Red Sea through the port of Zeila. At first, the growth of coffee consumption in precolonial Africa did little to alter the relationship between the plant and the pathogen in Ethiopia because most coffee was harvested from wild plants.13 Sufi Muslims were instrumental in diffusing coffee consumption beyond Ethiopia. The monks in Sufi orders used caffeine to stay awake through their long rituals.14 They first carried the coffee habit to cities of the Arabian Peninsula in the early fifteenth century, including Aden and Mocha—which later became globally important as a center for coffee exports. By the 1490s, coffee had been introduced to Cairo; by the 1520s it was being consumed by the Ottoman court in Istanbul. The new drink also gave birth to a new institution: the coffeehouse. Coffee and coffeehouses spread in tandem to the major cities of the Ottoman Empire, including Mecca, Medina, and Aleppo. Until the mid-sixteenth century, most of this demand was supplied by Ethiopia. After the 1570s, Yemen supplanted Ethiopia as the world’s dominant center of coffee production.15
Yemen enjoyed a virtual monopoly on global coffee production and trade until the early eighteenth century. This was driven in part by imperial politics: the Ottomans conquered Yemen in the late 1530s, and in the 1550s they also attempted to gain control of parts of Ethiopia. The Ottomans began to promote coffee cultivation in the 1570s, and taxes on coffee offered local and imperial governments a significant source of revenue. Coffee gradually made its way into the Red Sea trading networks that linked Yemen to the Ottoman Empire and the worlds of the Mediterranean and the Indian Ocean. In 1635, the Qasimi ousted the Ottomans from Yemen, though the Qasimi state continued to sell coffee to consumers in the Ottoman Empire. In the early eighteenth century, Cairo merchants purchased about half of Yemen’s total coffee production.16 The historian Nancy Um characterizes the Qasimi as the “coffee imamate.” The imam received a quarter of the sale price, and coffee generated more revenue for the state than any other crop.17 Yemeni coffee reached growing populations of coffee drinkers in places as far afield as Surat in Mughal India in the east, and London, Amsterdam, and Paris in the west. European traders first appeared at Mocha around 1610; a century later, European trading companies were a regular presence. In the eighteenth century, Yemen exported between 12,000 and 15,000 tons of coffee per year.18
Coffee cultivation in Yemen likely began sometime in the fifteenth or sixteenth century as coffee drinking became more popular in the Middle East. The anthropologist Daniel Varisco suggests that coffee was one of a trio of major crops (along with mango and qat) that were introduced to Yemen in the fifteenth century CE. Both coffee and qat (another stimulant plant) were introduced to Yemen from Ethiopia.19 This movement was part of a much larger history of global botanical exchanges; Yemen had often served as a relay point between African and Asian biota.20 These transfers had greatly enriched Yemen’s agriculture—farmers there cultivated wheat, millet, sorghum, watermelons, citrus, sugar cane, and dozens of other exotic crops. The coffee plant was, at first, integrated into existing agricultural ecosystems, particularly in the interior highlands, often in terraces on the side of steep hills.21
Yemen’s climate was marginal for arabica cultivation; it lacked the rainfall and forest cover of arabica’s home in Ethiopia. Farmers in the Yemeni highlands used artificial shade trees to protect the delicate arabica plants in areas otherwise exposed to the full sun during the long dry season.22 The French traveler Jean de la Roque, who visited Yemen’s coffee farms in the early eighteenth century, wrote that were it not for the shade trees, “the [coffee] blossoms would soon be burnt up, and never produce any fruit, as it happens to those trees that have not the advantage of such a neighborhood; and in effect these [shade trees] stretch out their branches to a prodigious length, which are so disposed in an exact circle, as to cover everything underneath.”23 Through the dry season, farmers sustained the coffee plants by irrigating them using water collected in reservoirs during the rainy season. During the warm and moist rainy season, which lasts approximately from April to September, the countryside receives between 800 and 2,000 millimeters of rain.
While the coffee plant prospered on the Arabian Peninsula, H. vastatrix did not. It is possible that the fungus has never been introduced to Yemen. The fungus feeds on the leaves of the coffee plant, and arabica was most likely brought to Yemen as seeds, which are much easier to transport. But even if the fungus had crossed the Red Sea on live plants or in some other way, it would have struggled to survive in Yemen. The rust spores would have struggled to survive and reproduce during the long dry season and cool nights of Yemen’s coffee zones. When the botanist Pierre Sylvain surveyed coffee cultivation in Ethiopia and Yemen in the 1950s, he was struck by the sharp differences between the health of coffee farms on either side of the Red Sea. He found that in Yemen, coffee could be cultivated at elevations as low as 1,000 meters; at a similar altitude on the Ethiopian side of the Red Sea, “diseases and insects would make coffee cultivation hazardous.”24 In the mid-1950s, Sylvain found no H. vastatrix anywhere in Yemen, which is telling because the rust was, by then, present in every other coffee-growing region in the Indian Ocean basin. Yemeni farming practices may also have helped limit the disease. Yemeni farmers managed disease in coffee (and other crops) by cultivating healthy seedlings and by using shade trees to limit the amount of dew on the leaves.25 None of these disease-control practices were unique to the coffee plant, nor were they specifically directed at controlling the rust. But this broader history reminds us that the health of Yemen’s coffee farms was not only an accident of geography.
The rust’s absence from Yemen matters since Yemen—not Ethiopia—was the center of diffusion for the world’s cultivated arabicas.
