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The genus Coffea includes over a hundred described species, all of them native to tropical forest regions of Africa, Madagascar, or other western Indian Ocean islands (Davis et al. 2006). These shrubs or small trees grow in the understory of secondary forests and along forest edges, including along streams. The cherry-like fruits attract birds and mammals, which disperse the hard seeds (coffee beans are seeds with the ovary and seed coat removed). Coffee beans that have passed through the digestive tract of an Asian Palm Civet (Paradoxurus hermaphroditus) are reportedly less bitter and can command a very high price. The alkaloid caffeine is present in many coffee species, not only in the seeds but also in the fruit pulp, leaves, and other parts. The raw seeds have no special flavor or aroma and discovery of the technology of cleaning, roasting, grinding, and brewing coffee developed outside its native range. Coffee is among the most valuable commodities exported by developing countries (Jaramillo et al. 2006; DeKochko et al. 2010). Around 99% of the world's coffee comes from two species, Coffea arabica (Arabian Coffee) and C. canephora (Robusta Coffee), with the remainder coming from another half dozen species, notably C. liberica, the beans of which are used in cheap blends. (Sauer 1993)
Coffee growers often grow their trees under a simulated forest canopy of taller trees, often legumes such as Albizzia, Inga, and Gliricidia. In some regions, such as in Brazil, C. arabica is frequently grown without shade. Coffee trees grown without shade tend to mature earlier and to produce larger yields, but they also tend to decline at a younger age than do shade-grown trees. (Sauer 1993) Although there is now extensive evidence that agroecosystems based on shade-grown coffee preserve biodiversity significantly more effectively and are more ecologically sustainable than non-shade coffee monocultures, Tejeda-Cruz et al. (2010) discuss the risk that the promotion of shade-grown coffee, which can be sold at a premium price, can encourage growers to convert additional forest to agriculture, resulting in the loss of many forest-associated species that are rare or absent in shade coffee plantations (Tejeda-Cruz et al. 2010 and references therein). This problem illustrates the complex economic factors that must be considered in developing conservation programs.
Virtually all the world's C. arabica plantations are derived from two transfers of a few plants in the early 1700s, one by the Dutch (which provided the progenitor of the typical variety C. arabica var. arabica) and the other by the French (which provided the progenitor of Bourbon coffee, C. arabica var. borbonica). Further genetic bottlenecks occurred as arabica coffee was spread throughout the tropics, with the progeny of a single tree apparently seeding all the arabica plantations in the New World--and, in a strange twist, coffee growing in East Africa was apparently established with stock arriving via the West Indies in the late 19th century. (Sauer 1993)
Coffea arabica grows wild in mountain forests at elevations of 1,500 to 2,000 meters in southern Ethiopia and adjacent Sudan. Wild C. arabica in the Ethiopean highland forests represents an endangered and potentially extremely valuable genetic resource for coffee breeders (Hein and Gatzweiler 2006). DeKochko et al. (2010) review current knowledge of coffee genetics and genomics.
The coffee industry was apparently born in Yemen, which was exporting coffee by the 1500s. By 1700, coffee houses had become important social institutions in cosmopolitan cities throughout Europe as well as in New York and Boston. (Sauer 1993) Decaffeinated coffee has been available since around 1905 (Vaughan and Geissler 1997).