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1p. 42, Ehrlich, P. R. 1994. Ecological Economics and the Carrying Capacity of the Earth. In: Jansson, A. M. Investing in natural capital: the ecological economics approach to sustainability. Island Press, pp. 38-56.

2Hardin, G. 1986. Cultural carrying capacity: a biological approach to human problems. BioScience, 36:350-367.

3Klein, D.R. 1968 The introduction, increase, and crash of reindeer on St. Matthew Island. Journal of Wildlife Management. 32:350-367 as cited by Hardin 1986.

4Whittaker, R. H. and Likens, G. E. 1975. The Biosphere and Man. In: Lieth, H. and Whittaker, R. H. Primary productivity of the biosphere. Springer Verlag, NY Inc.: NY, pp. 305-328.

5"World population has doubled since 1960 to 6.1 billion, with growth mostly in poorer countries, and is projected to increase to 9.3 billion by 2050. More people are using more resources with more intensity-and leaving a bigger "footprint" on the earth-than ever before." From United Nations Population Fund (UNFPA),, Oct. 2001.

6Cohen, J. E. 1995a. How many people can the earth support? W.W. Norton & Co.: NY. Marchetti (1978) estimates 1,000 billion and admits that it is unrealistic, but proposes with adequate technology it is theoretically feasible. Pearson & Harper's (1945) low estimate and is 0.9 based solely on grain production and a North American standard of living. Ehrlich's (1971) low estimate is 0.5 considering that in 1971 there were 7 times more people than the planet could maintain.

7Daily, G. C. and Ehrlich, P. R. 1992. Population, sustainability, and Earth's carrying capacity: a framework for estimating population size and lifestyles that could be sustained without undermining future generations. BioScience 42:761-71.

8Ehrlich 1994

9Daily, G. C., Ehrlich, A. H., and Ehrlich, P. R. 1994. Optimum Human Population Size. Population and Environment: A Journal of Interdisciplinary Studies 15,, Jan. 2001.

10Hardin 1986

11Pimentel et al 1999, p. 27

12Livernash & Rodenburg 1998

13Summarized from Daily et al. 1994

14Daily, G.C. and Ehrlich, P.R. 1996. Socioeconomic equity, sustainability, and Earth's carrying capacity. Ecological Applications. 6(4):991-1001.

15Daily et al. 1994; Daily and Ehrlich 1992

16Pimentel, D., Bailey, O., Kim, P., Mullaney, E., Calabrese, J., Walman, L., Nelson, F., and Yao, X. 1999. Will the limit of the Earth's resources control human numbers. Environment, Development and Sustainability 1:19-39.

17Daily and Ehrlich 1992

18World Energy Council, Survey of Energy Resources 1998,, October 2001

19Campbell, C.J. and Laherrere, J.H. 1998. The end of cheap oil. Scientific American. 278(3):78-83.

20Pimentel, D., Harman, R., Pacenza, M., Pecarsky, J., and Pimentel, M. 1994. Natural resources and an optimum human population. Population and Environment 15:347-369.

21Rees, W. E. 1996. Revisiting Carrying Capacity: Area-Based Indicators of Sustainability. Population and Environment: A Journal of Interdisciplinary Studies 17,

22 Cohen 1995a

23Cohen, J. E. 1995b. Population growth and Earth's human carrying capacity. Science 269:341.

24UNFPA 2001 population estimate

25Hardin 1986

26p. 4 of Whittaker, R. H., Likens, G. E., and Lieth, H. 1975. "Scope and Purpose of this Volume". In: Lieth, H. and Whittaker, R. H. Primary productivity of the biosphere. Springer-Verlag, NY, Inc.:NY, pp. 3-5.

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This article first printed in the ILEA Leaf, Winter 2002 issue.

Last Modified on April 13, 2002.