Minnesotans For Sustainability©
Sustainable Society: A society that balances the environment, other life forms, and human interactions over an indefinite time period.
Optimum Human Population
David Pimentel, Rebecca Harman, Matthew Pacenza, Jason
Pecarsky and Marcia Pimentel
According to the Washington, DC-based Population Crisis Committee, the world's human population, currently more than 5.5 billion, is projected to reach nearly 8.4 billion by the year 2025 and may reach a disastrous 15 billion by 2100. There are now 1.2-2 billion people living in poverty —malnourished, diseased and experiencing short life spans.
The Population Reference Bureau estimates that the average American consumes
about 23 times more goods and services than the average world citizen. Americans
also bum 10,000 liters (2600 gallons) of oil-equivalents per year —seven times
the world average. Clearly, achieving a US standard of living is impossible for
the rest of the world, based both on projections of future resource availability
and on population growth. The affluent standard of living now enjoyed by
Americans (made possible by our abundant supplies of fertile cropland, water and
fossil energy) is projected to decline if the US population doubles during the
next 63 years.
Approximately 0.5 hectares (1.25 acres) of cropland is needed to provide one person with a diverse, nutritious diet of plant and animal products.
The US supply of crop-land is at this level now, but the world average is
only 0.28hectares (.69 acres). Each year, more than ten million hectares (24.7
million acres) of once-productive land are degraded and abandoned.
Humans do not have any technologies that can substitute for the services provided by wild biota. In the US, there are approximately 500,000 species of plants, animals and microbes that provide essential functions (pollinating crops, recycling manure, purifying water and soil) and serve as a vital reservoir of genetic material. Yet the world is losing roughly 150 species per day from such human activities as deforestation, pollution, pesticide application and urbanization. In his book, Fundamentals of Ecology, E. P. Odum reports that, if sufficient natural biological diversity is to be maintained to ensure a quality environment, about one-third of the terrestrial ecosystem should be preserved as natural vegetation.
Limits to Solar Energy Growth
The United Nations Environment Program estimates that the US accounts for approximately 25 percent of the world's annual consumption of fossil fuels. All other developed nations combined use another 55 percent and developing nations, with approximately 75 percent of the world's population, consume only 20 percent.
In 1991, US Department of Energy estimates of national oil reserves plummeted. Instead of the 35-year supply forecasted in 1987, reserve predictions were lowered to 10-13 years at 1991 pumping rates. In 1850, when its population was only 23 million, the US was dependent on wood biomass (a form of solar energy) for 91 percent of its energy. Today, we depend on fossil fuels for 93 percent of our energy needs. With the imminent decline in fossil-fuel supplies, a transition should be made to renewable energy sources.
In the US, the annual amount of solar energy captured by vegetation —agricultural crops, forests, lawns, gardens and wild growth— is 54 quads (one quad equals one quadrillion British Thermal Units). Americans currently use 40 percent more fossil energy than the total amount of solar energy captured by plants.
Although the conversion of biomass crops, like corn, into fuel energy appears
promising at first glance, 72 percent more energy is used in the production of
ethanol than the energy it provides. Furthermore, the land area needed to
provide the raw material is enormous; about six hectares (15 acres) of corn
grain is needed to provide the ethanol fuel for one US car for one year.
Based on past experience, we expect that leaders will continue to postpone decisions on the human carrying capacity of the world until the situation becomes intolerable or, worse, irreversible. Nature will impose the ultimate control on the human population.
* Used with permission of the Earth Island Journal.
Originally published in the "Earth Island Journal", Summer 1994, Vol. 9 Issue 3.p26-30.
Copyright 1995, Earth Island Journal.
See at < http://www.earthisland.org/journal/naturres.html >.
Adapted from a longer article published in the May 1994 issue of Population and Environment.
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