Ecology: Biology of Interaction. 6.05. The Food Security Problem
Human existence depends on use of primary production. Each person requires roughly 1 million kcal per year. Although total food production exceeds demand by several tens of percent, high losses and uneven distribution create persistent shortages.
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6.04. Can Earth’s population size be limited?
D. Shabanov, M. Kravchenko. Ecology: Biology of Interaction Chapter 6. Human Ecology and Nature Conservation
6.06. The Pesticide Problem
6.06. The pesticide problem 6.05. The food security problem Human existence depends on use of primary production. Each person needs about 1 million kcal per year; total human population exceeded 6 billion. More food is produced (by several tens of percent), but due to high losses and poor distribution it is insufficient where needed. Human food accounts for about 1% of net biosphere production, while livestock feed accounts for about five times more. Partial reduction of human pressure on biosphere may be linked to reduced meat consumption and, in longer term, to population stabilization. Depending on how ecosystems are exploited, their productivity may differ substantially. Fish-farming ponds are an example. In Western Europe and North America, aquaculture is often oriented toward predatory fish for sport fishing (secondary productivity even with supplemental feeding reaches 112–175 kg/ha), while in many developing countries it is oriented toward detritivorous and herbivorous fish (without supplemental feeding around 1750 kg/ha). Reducing meat consumption in developed countries to levels typical of developing countries could free food surplus capable of feeding 2–3 billion people (over 90% of plant food energy is lost during conversion into meat). In the 20th century, technological achievements of developed countries spread to developing countries and supported population growth there. Besides medical advances, this growth was supported by agricultural development known as the Green Revolution. During the 1950s–1960s, with UN support, high-yield varieties of rice, wheat, and other crops were disseminated in Asia and Latin America, and advanced agricultural practices were introduced, increasing yields 3–5 times. Thanks to the Green Revolution, humanity reached today’s population levels. Unfortunately, methods that drove the Green Revolution can now provide only limited additional yield growth. For example, past food growth was supported by expansion of arable land. Arable area increased from 1950 to its peak in 1981 by about 24%. Today arable area is shrinking due to erosion, salinization, drying, and conversion to cities and roads. Deforestation and plowing of virgin lands cannot compensate losses caused by inefficient land use. A major 20th-century yield factor was irrigation. Over several decades, freshwater volume used for irrigation increased several-fold, reached a maximum, and then began to decline. This is linked to depletion of freshwater sources and salinization of fields. Perhaps the most catastrophic example of excessive freshwater withdrawal for irrigation is the disappearance of the Aral Sea, once the world’s fourth-largest inland sea. Located in Uzbekistan and Kazakhstan, it dried up and fragmented into several smaller water bodies as Amu Darya and Syr Darya waters were diverted for irrigation (Fig. 6.5.1). [IMG_1] Fig. 6.5.1. Reduction of Aral Sea area and its satellite image taken in 2007. White areas in the image are salt flats. Some irrigation reserves remain, mainly through drip-irrigation systems delivering water directly to plant roots. Unfortunately, introduction of such systems requires significant resources, as do all forms of agricultural mechanization. At present, these measures still require substantial fossil-energy inputs. Another pathway to improve agricultural efficiency is fertilizer use. Because agriculture removes part of produced biomass from fields, without replenishment of biogen stocks fields rapidly become depleted. Replenishment may be achieved with both organic inputs (e.g., manure or plant biomass) and mineral fertilizers. Unfortunately, organic fertilizers alone are insufficient: replenishing field losses requires extracting biogens from other ecosystems. Recycling exactly the same biogens removed from fields is difficult at current technological level because they enter urban waste streams mixed with toxic compounds. Societies using untreated human waste as fertilizer suffer from parasitic diseases. This implies continuing need for mineral fertilizers. Their broad introduction increased yields, but reserves of this method are now largely exhausted. On major agricultural lands, optimum biogen supply is close to achieved. Some progress remains possible via fertilizers better retained in soil and less prone to leaching, as well as less toxic and cheaper compounds. Finally, one pillar of the Green Revolution was breeding high-yield crop varieties. Potential of traditional breeding methods is also substantially utilized. Consider a long-standing breeding goal: enabling cereal crops to form mutualism with nitrogen-fixing bacteria. Attempts to solve this have continued for decades. It is plausible this will eventually be solved, likely using genetic engineering. Will this substantially increase crop yields? Surprisingly, likely not. Cereals are already supplied with nitrogen, primarily from fertilizers. Mutualism with nitrogen fixers could solve many problems (reduce energy costs of fertilizer production/application, decrease fertilizer runoff into water bodies, etc.) but would not by itself dramatically increase food available to humanity. According to UN assessments, major regional agricultural problems include: Europe — industrial land pollution, forest destruction; North America — widespread monocultures; Southwest Asia — overpopulation, overgrazing, threat to gene pool; Southeast Asia — destruction of tropical forests, threat to gene pool; South America — destruction of tropical forests, loss of traditional crops; Africa — overpopulation, tropical deforestation, overgrazing, desertification. Importantly, expected global warming will shift climatic zones, and soils cannot shift correspondingly at the same pace. 6.04. Can Earth’s population size be limited?
Ecology: Biology of Interaction Chapter 6. Human Ecology and Nature Conservation
6.06. The pesticide problem
6.06. The Pesticide Problem