Energy and Human Ecology

Energy as an Ecological Concept

In the 1960s, Howard Odum helped develop the “systems ecology” approach, which situated energy flows at the center of analysis. A self-proclaimed energetic determinist, Odum suggested that all natural and social systems could be [Page 895]understood in terms of the energy available to accomplish work. Indeed, the very basis of life on Earth depends on plants making use of solar energy through the process of photosynthesis and respiration, which, in turn, provide energy for a variety of herbivores and omnivores, who, in turn, provide energy for carnivores. Moreover, since humans harnessed the concentrated sources of solar energy latent in fossil fuels (coal, oil, and natural gas), Odum suggested that energy is also at the basis of seemingly unnatural processes such as urbanization and industrialization. Through characteristic flow diagrams and circuit models, Odum and other systems ecologists mapped the ecological flows of energy and matter in a variety of systems from wetlands to households.

This systems ecological approach considers energy from the basis of the laws of thermodynamics. Although there are several debates on several laws, most agree that the first two are the most important. The first law states that from the perspective of an open system, energy can never be created or destroyed but only change forms. Ecologists can trace the different forms of energy from the sun through plants and animals, but the total amount of energy in the universe remains the same. The second law states that in an isolated system—such as Earth—entropy, or the incapacity of an energy system to do work, tends to increase over time. The second law is obviously most applicable to human and natural systems constrained by the availability of useable energy in a given environment. Moreover, modern society's dependence on the concentrated energy of finite fossil fuel reserves makes the second law even more worrisome. For example, when the concentrated energy of petroleum is burned within an internal combustion engine and dissipated into carbon dioxide gas, its capacity to do work is no longer present. As the combustion of fossil fuels yields greater and greater entropy dissipation, the second law of thermodynamics should predict that human societies will inevitably come up against profound and, perhaps, unsolvable energy constraints.

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