The conclusion draws heavily on ideas and examples found in the last section of Edward O. Wilson's Consilience: The Unity of Knowledge (New York: Alfred A. Knopf, 1998). He discusses population growth and concludes the number of people Earth can sustain depends on the quality of life future generations are willing to accept. J.E. Cohen (How Many People Can the Earth Support? New York: W.W. Norton: 1995 and P.R. Ehrlich and J.P. Holden "Impact of population growth" Science 171: 1212-1217, 1971 go into greater detail on Earth's human carrying capacity. Norman Myers ("The world's forests and their ecosystem services," in Nature's Services - Societal Dependence on Natural Ecosystems, ed G.C. Daily, Washington D.C.: Island Press, 1997) calculates that for people of developing countries to attain the standard of living enjoyed by Americans we would need the equivalent of another three planet Earths.
Myers (1997) and Wilson (1998) review some of the signs that human population is negatively impacting the world environment such as agricultural per capita production, ocean fisheries, ground water supplies, erosion, poverty, and climate change. Vitousek, P.M. et al. ("Human appropriation of the products of photosynthesis," BioScience Vol. 36, 368-373, 1986) estimate that humans are are appropriating 40% of net primary production.
J.E. Lovelock presented his Gaia theory in Gaia: A New Look at Life on Earth, Oxford: Oxford University Press, 1982.
Technological fixes fot the world's environmental problems are mention in Wilson's consilience and discusses at greater length in J.H. Ausubel, "Can technology spare the earth?" American Scientist 84:166-178 1996. Natural plastic - a plastic made from plants rather than petroleum - is announced in Warren, S. "Cargill, Dow Chemical Join To Make 'Natural Plastic,'" The Wall Street Journal, 1/11/00.
The UN estimate for the cost of establishing fuelwood plantations to replace harvesting from natural forests is provided by Myers, Norman "The world's forests: problems and potentials," Environmental Conservation 23 (2):158-168, 1996.
Wilson (1998) provides a succinct review of the Biosphere II project, while J.E. Cohen and D. Tilman "Biosphere 2 and Biodiversity: the Lessons Learned So Far," Science 274:1150-1151, 1996 provide a more academic look at this elaborate experiment to recreate miniature ecosystems.
The role of environmental degradation and overpopulation in the downfall of great civilizations of antiquity is discussed in C. Runnels, "Environmental degradation in ancient Greece," Scientific American 272 (3): 72-75, 1995 [Greece]; R. Adams, Heartland of Cities, Chicago: University of Chicago Press, 1981 [Mesopotamia]; Sharer, R.J., The Ancient Maya, Stanford: Stanford University Press, 1994 [Mayans]; and Diamond, J., "Easter's End," Discover. Vol. 16, No. 8, Aug 1995 [Easter Island]].
The loneliness of a biologically impoverished Earth is a subject explored by David Quammen in Wild Thoughts from Wild Places, New York: Scribner 1998 and E.O. Wilson in On human nature, Cambridge: Harvard University Press, 1978
Myers, N. ("The world's forests and their ecosystem services," in Nature's Services - Societal Dependence on Natural Ecosystems, Ed G.C. Daily, Washington D.C.: Island Press, 1997) notes that the actions we take today will determine whether Earth will be biologically impoverished for the 500 trillion or more humans that may inhabit the earth in the future.