Harvesting the Biosphere: What We Have Taken from Nature

4. Phytomass Harvests

4 Phytomass Harvests Modern phytomass harvests fit mostly into four distinct categories. Food harvests have been transformed as humans have evolved from simple foragers collecting edible plants, hunting animals, and catching aquatic species to agriculturalists relying first on extensive shifting cultivation and later on intensive methods of farming, including large-scale domestication of animals and worldwide fishing efforts. Phytomass use as fuel was relatively limited in all foraging societies, but it increased with a sedentary existence and with the use of wood and charcoal in the production of metals. Because the evolution of agriculture also involved the domestication of animals, the third major purpose of biomass harvest has been to secure feed for these mammals and birds. I hasten to add that the order of harvest purposes just presented is valid only in terms of its evolutionary appearance. In many late nineteenth-century societies fuelwood was mostly displaced by coal, but large quantities of feed were needed for draft animals as agricultural activities continued to rely heavily on draft horses and cattle. This animal labor was in turn displaced by machines, and wood became a marginal fuel in all modern affluent societies, but the importance of animal feed has only increased: metabolic imperatives mean that the annual total of feed phytomass that is required to produce an abundance of meat, eggs, and dairy products now greatly surpasses that of global food harvests and is also greater than the aggregate of woody biomass used for fuel in all affluent economies. The final, less homogeneous category subsumes all uses of plants as raw materials . The earliest uses of phytomass in crafting simple tools go far back into our hominin past, but once again, only sedentary habitation resulted in a voluminous need for construction timber (in maritime societies also for building ships) and wood for agricultural implements (hoes, plows, harrows), household utensils, furniture , and an enormous variety of increasingly sophisticated manufacturing tools 42 Chapter 4 Traditional cereal cultivars yielded much more straw than do modern varieties (and much more straw than grain). Joachim Patinir’s 1514 Rest on the Flight to Egypt (now hanging in Madrid’s Prado) illustrates that reality: a scene on the far right of the painting shows a peasant harvesting wheat, with the grain ears well above his head and all but hiding armed men carrying halberds. (the process that culminated in the intricate designs of the early modern era) and conveyances (wheelbarrows, carriages). Other important uses of phytomass as raw material include the use of fibrous plants (cotton, flax, hemp, agave) to make cloth (as well as ropes), as a source of colorants and medicines, and the pulping of woody biomass to produce paper. The number of plants ever harvested by humans for food, fiber, medicinal and ornamental uses, and animal feed runs into the thousands, but only about 50 species have accounted for the bulk of all harvested phytomass during the millennia of preindustrial agriculture, and this number was reduced by large-scale intensive cultivation and modern dietary preferences to fewer than 20 dominant species. A similar simplification has affected wood harvests: large-scale monoculture tree plantings, begun in the late eighteenth century, and modern afforestation favor a small number of fast-growing species, now increasingly grown on intensively managed tree plantations. Phytomass Harvests 43 Crops and Their Residues Food harvests in temperate and subtropical latitudes of the Old World have been traditionally dominated by half a dozen major cereal grains (wheat, rice, barley, rye, oats, buckwheat), leguminous grains (beans, peas, lentils, soybeans), and oil seeds (olives, rapeseed, linseed, sunflowers, peanuts), supplemented by a large variety of leafy and root vegetables, fruits, and nuts. Premodern diets in the Americas shared a heavy reliance on corn and beans, and three of the hemisphere’s major crops, potatoes, tomatoes, and peppers, became worldwide favorites within a few centuries after their introduction to Europe, Asia, and Africa. The large-scale production of sugar crops (sugarcane and sugar beets) is of an even more recent origin. Crop harvests are reported in terms of fresh phytomass, whose water content varies from less than 10% for some seeds to more than 90% for many vegetables; staple grains are marketed with a moisture content of less than 15%, while tubers have more than 70%. Depending on the time and method of harvesting, water content varies appreciably even for the same cultivar of staple grains. The moisture content of cereal grains at harvest...