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Until the last century, all of the food energy available on this planet was derived from the sun through photosynthesis. Either you ate plants or you ate animals that fed on plants, but the energy in your food was ultimately derived from the sun. It would have been absurd to think that we would one day run out of sunshine. No, sunshine was an abundant, renewable resource, and the process of photosynthesis fed all life on this planet. It also set a limit on the amount of food that could be generated at any one time, and therefore placed a limit upon population growth. Solar energy has a limited rate of flow into this planet. To increase your food production, you had to increase the acreage under cultivation, and displace your competitors. There was no other way to increase the amount of energy available for food production. Human population grew by displacing everything else and appropriating more and more of the available solar energy. The need to expand agricultural production was one of the motive causes behind most of the wars in recorded history, along with expansion of the energy base (and agricultural production is truly an essential portion of the energy base). And when Europeans could no longer expand cultivation, they began the task of conquering the world. Explorers were followed by conquistadors and traders and settlers. The declared reasons for expansion may have been trade, avarice, empire or simply curiosity, but at its base, it was all about the expansion of agricultural productivity. Wherever explorers and conquistadors traveled, they may have carried off loot, but they left plantations. And settlers toiled to clear land and establish their own homestead. This conquest and expansion went on until there was no place left for further expansion. Certainly, to this day, landowners and farmers fight to claim still more land for agricultural productivity, but they are fighting over crumbs. Today, virtually all of the productive land on this planet is being exploited by agriculture. The process of pest displacement and appropriation for agriculture accelerated with the industrial revolution as the mechanization of agriculture hastened the clearing and tilling of land and augmented the amount of farmland which could be tended by one person. With every increase in food production, the human population grew apace. The rest of nature is forced to make due with what is left. Plainly, this is one of the major factors in species extinctions and in ecosystem stress. The Green Revolution resulted in the industrialization of agriculture. Part of the advance resulted from new hybrid food plants, leading to more productive food crops. This additional energy did not come from an increase in incipient sunlight, nor did it result from introducing agriculture to new vistas of land. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation. Of course, this is only a rough comparison to aid comprehension of the energy requirements for modern agriculture. In a very real sense, we are literally eating fossil fuels. However, due to the laws of thermodynamics, there is not a direct correspondence between energy inflow and outflow in agriculture. Yet, due to soil degradation, increased demands of pest management and increasing energy costs for irrigation (all of which is examined below), modern agriculture must continue increasing its energy expenditures simply to maintain current crop yields. Fossil fuels, on the other hand, are a stock-type resource that can be exploited at a nearly limitless rate. However, on a human timescale, fossil fuels are nonrenewable. They represent a planetary energy deposit which we can draw from at any rate we wish, but which will eventually be exhausted without renewal. The Green Revolution tapped into this energy deposit and used it to increase agricultural production. Total fossil fuel use in the United States has increased 20-fold in the last 4 decades. In the US, we consume 20 to 30 times more fossil fuel energy per capita than people in developing nations. The input figure for this ratio was based on FAO (Food and Agriculture Organization of the UN) statistics, which consider only fertilizers (without including fertilizer feedstock), irrigation, pesticides (without including pesticide feedstock), and machinery and fuel for field operations. Other agricultural energy inputs not considered were energy and machinery for drying crops, transportation for inputs and outputs to and from the farm, electricity, and construction and maintenance of farm buildings and infrastructures. Endosomatic energy is generated through the metabolic transformation of food energy into muscle energy in the human body. Exosomatic energy is generated by transforming energy outside of the human body, such as burning gasoline in a tractor. This assessment allowed the authors to look at fossil fuel input alone and in ratio to other inputs. Prior to the industrial revolution, virtually 100% of both endosomatic and exosomatic energy was solar driven. The ratio has changed tenfold in developed countries, climbing to 40 to 1. The vast majority of endosomatic energy is no longer expended to deliver power for direct economic processes. Now the majority of endosomatic energy is utilized to generate the flow of information directing the flow of exosomatic energy driving machines. Considering the 90/1 exo/endo ratio in the United States, each endosomatic kcal of energy expended in the US induces the circulation of 90 kcal of exosomatic energy. This disparity is made possible by nonrenewable fossil fuel stocks. Assuming a figure of 2,500 kcal per capita for the daily diet in the United States, the 10/1 ratio translates into a cost of 35,000 kcal of exosomatic energy per capita each day. Unfortunately, if you remove fossil fuels from the equation, the daily diet will require 111 hours of endosomatic labor per capita; Quite plainly, as fossil fuel production begins to decline within the next decade, there will be less energy available for the production of food. Technologically-enhanced agriculture has augmented soil erosion, polluted and overdrawn groundwater and surface water, and even (largely due to increased pesticide use) caused serious public health and environmental problems. Soil erosion, overtaxed cropland and water resource overdraft in turn lead to even greater use of fossil fuels and hydrocarbon products. More hydrocarbon-based fertilizers must be applied, along with more pesticides; As a result, the remaining topsoil is increasingly depleted of nutrients. On top of this, urbanization, road building, and industry claim another 1 million acres annually from farmland. The land area for harvesting biomass is likewise limited. For this reason, the development of solar energy or biomass must be at the expense of agriculture. Modern agriculture also places a strain on our water resources. The typical example is the Colorado River, which is diverted to a trickle by the time it reaches the Pacific. Yet surface water only supplies 60% of the water used in irrigation. The remainder, and in some places the majority of water for irrigation, comes from ground water aquifers. Ground water is recharged slowly by the percolation of rainwater through the earth's crust. A corn crop that produces 118 bushels/acre/year requires more than 500,000 gallons/acre of water during the growing season. Pesticide use on corn crops had increased 1,000-fold even before the introduction of genetically engineered, pesticide resistant corn. It is damaging the land, draining water supplies and polluting the environment. And all of this requires more and more fossil fuel input to pump irrigation water, to replace nutrients, to provide pest protection, to remediate the environment and simply to hold crop production at a constant. Yet this necessary fossil fuel input is going to crash headlong into declining fossil fuel production. As of one decade ago, Americans were consuming 1,450 gallons/day/capita (g/d/c), with the largest amount expended on agriculture. Likewise, water is pu...
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