Japan's Dietary Transition and Its Impacts

5. Environmental Impacts: Land, Water, Nitrogen, and Ocean

5 Agriculture is a clever manipulation of artificial ecosystems in order to maximize their net primary productivity. Some of these agroecosystems are relatively species rich, involving complex rotations of crops, even interplanting, as well as the maintenance of perennial plants in hedgerows or tree groves separating the fields, contributing biodiversity and reducing soil erosion. Other agroecosystems are brutally simplified monocultures, with continuous plantings of a single crop, usually a staple cereal. All of them share the same essential requirements for land, water, macronutrients, and micronutrients; all of them would have their yields lowered by excessive competition from weeds; and most of them may need protection from microbial attacks and grazing by insects and vertebrates. This means that productive agroecosystems require suitable soil (or considerable, and often continuous, efforts to improve soil quality by enhancing its organic matter), a reliable water supply, timely provision of nutrients (the need dominated by supplies of nitrogen, almost always the most important macronutrient whose timely delivery determines the final crop yield), and services that will keep both weeds and heterotrophic invaders in check. In traditional agroecosystems, these essential services were delivered by a great deal of human exertion, sometimes made easier by using animals or simple mechanical devices. As a result, large amounts of labor were needed for field preparation (plowing, harrowing ), construction of irrigation infrastructures, collection and application of organic fertilizers, and weeding. In modern agroecosystems, these services make use of fossil fuels or electricity to power field machinery (including irrigation pumps), transport inputs to fields and harvests to markets, and indirectly to produce Environmental Impacts: Land, Water, Nitrogen, and Ocean 132 Chapter 5 all agricultural machinery, synthesize agricultural chemicals (fertilizers, herbicides, fungicides, pesticides), and process crops by drying, milling, extraction, or fermentation. Rising inputs of fuels and electricity have changed the human role in agriculture from that of a critical prime mover of the system to a controller and manipulator of direct and embedded energy flows and, of course, an indispensable developer of better cultivars and more productive ways of cropping. Fisheries and mariculture have also become highly dependent on external energy inputs of fuel and electricity, and in affluent countries, more energy is used in food processing , storage, wholesale, and retailing than in agriculture and fishing. Environmental impacts of modern food production and food supply systems are thus both universal and country specific. The most commonly encountered problems in cropping are losses of arable land due to the encroachment of residential and industrial construction and transportation networks, degradation of soil quality (most often due to poorly controlled soil erosion and declining content of organic matter), unsustainable water withdrawals and wasteful water use in irrigation (processes leading to depletion of aquifers and, in arid regions, soil salinization), and excessive applications of nitrogenous fertilizers leading to impacts ranging from elevated emissions of nitrous oxide to eutrophication of fresh and coastal waters. Japan, thanks to its high share of bunded paddy fields, does not have a severe soil erosion problem, and during the past generation, its losses of arable land to nonagricultural uses have been less important than the voluntary abandonment of farmland, a consequence of shrinking domestic cropping and increasing food imports. As far as water use is concerned , monsoonal Japan has an abundant supply, and its well-managed irrigation systems use it quite efficiently. Nevertheless, intensive fertilization required to produce high yields from limited farmland has burdened Japanese waters with excessive nitrate loads and put arable land at the top of major sources of a greenhouse gas: nitrous oxide (N2O) from nitrification and denitrification of nitrogenous fertilizers. Rice paddies are the second largest source, after ruminants, of another greenhouse gas: methane (CH4) generated by anaerobic fermentation in anoxic soils. And Japan’s exceptionally high consumption of seafood has a large impact on the status of major fish stocks and the maintenance of marine biodiversity. Environmental Impacts 133 Moreover, modern energy-intensive agriculture has also made comparative production advantages more pronounced, a development has been furthered by the fact that the intercontinental food trade became much more affordable as a result of inexpensive commodity shipments (dry, wet, frozen) in large bulk carriers and containerized exports of processed food. Japan’s high reliance on food imports, with most of them coming not from nearby Asian countries but other continents, thus creates additional carbon dioxide (CO2) emissions from transportation. Quantifying these impacts is not easy because the additional costs due to transportation and environmental...