Ecological Models

Imbedded within population ecology is the notion of carrying capacity, which basically asserts that there is a maximum population size for a particular set of environmental conditions. One population growth model, out of several that have been postulated, asserts that exceeding the maximum would result in degrees of environmental degradation, ultimately leading to a collapse of the entire ecosystem. This issue will be taken up in the next section.

It is generally assumed that during the period of exclusive foraging/hunting economy of our past, human groups could and did live in a "state of harmony" with nature, that is, within the constraints of carrying capacity. Whether this was intentional through a realized and understood concept of conservation of resources, or whether it was simply a matter of having a relatively low level of exploitative technology, is not always clear. Probably it was some of each. Certainly there was and still is a recognition by a numerous cultures of the connectedness between people and the environment through cosmology, subsistence, and even sophisticated understanding of ecological concepts. There is, of course, the highly practical understanding that living too long in one place can raise the risk of certain diseases and parasitic infections due to accumulated wastes. Hence, it might be argued that migrating to avoid pollution was one impetus for human population expansion.

The shifting of subsistence patterns from hunting/ foraging to that of sedentary agriculture very likely occurred during continuous periods of population growth. Whether or not population growth was a key stimulus to the development of agriculture, or whether agriculture was the base from which rapid population growth could take place, has been subject to theoretical dispute (Bogin, 2001). On the one hand, the Boserup theory of positive demographic pressure contends that increasing population brought forth increasing demand for food, followed by more intense efforts for food procurement through evermore effective agricultural technology (Livi-Bacci, 2001). The "classic" theory proposed by Childe argued that population growth was proceeded by discoveries and diffusion of new ideas concerning animal and plant domestication that resulted in a more secure, predictive food base (Livi-Bacci, 2001). Yet a third theory proposed by Cohen (1977) would explain the origins of agriculture somewhat along the lines of Boserup in that population pressure did contribute to an increasing reliance upon agricultural pursuits. In more specific terms, Cohen proposed that as hunting-gathering groups had begun to occupy the more productive areas, then under a model of continuous growth, subsequent groups would be relegated to making a living in areas that were nutritionally less adequate but yielded higher amounts of calories. Under this regime, populations increased in size while decreasing in quality of life, at least as measured by dietary intake. It is well known that deficiencies in diet can lead to a higher risk of contracting infectious and parasitic diseases. Hence, early sedentary populations are likely to have maintained a high level of mortality, to go along with an even higher level of fertility.

As noted earlier, it also seems likely that earlier human groups might well have avoided major problems in exceeding carrying capacity by migrating to new areas whenever pressure on local areas became too great. In more recent times, however, opportunities for migration were not very open, and this has prompted some new thinking and theory-building that promoted development and consumption on a sustainable level.

Sustainable development has its roots in Malthus of the late 1700s, but it was not until 1970 and thereafter that the concept was fully formed in bringing attention to excessive human exploitation of resources along with detrimental environmental consequences. Stemming from the 1992 Earth Summit held in Rio de Janeiro, goals and objectives of sustainable development were drafted to incorporate social, economic, and ecological concerns. Fundamental to any action taken was to insure human rights and needs for the present without compromising those of future generations. At the Rio Earth Summit, all countries were called on to formulate their own National Strategies for Sustainable Development (NSSD) and two target dates were proposed—2002, when NSSD was to be introduced, and 2005, when NSSD would begin implementation (NSSD, 2001).

How does NSSD deal with population growth and control? Conceptually, it does clearly recognize the impact uncontrolled development has on the environment, but maintains that this is not solely due to population size but to local concentrations of people who garner unequal exploitation and distribution of resources. The concept of sustainable development, if it is to have worldwide application, must deal with a number of interconnected issues plaguing developing countries such as economic disparity and political unrest, severe poverty and inadequate food supply, and highly fatal diseases, notably HIV/AIDS and malaria.

Sustainable development also has to marshal strategies that deal with loss of biodiversity in many plant and animal communities, as well as a corresponding form of diversity reduction observed in human communities that seems to characterize globalization. Effective population regulation in ecological systems depends on maintaining diversity in life forms that offer resilience, flexibility, and stability in the face of changing conditions. There is good reason to make the same claim for maintaining cultural diversity. Yet worldwide trends clearly indicate that consumerism, especially of Western goods and behaviors, is eroding once unique cultural identities. There is the recognition of this in the NSSD strategy statement as it calls for a balance between globalization and decentralization, the latter being an effort to maintain lower levels of control and influence (NSSD, 2001).

On theoretical grounds, sustainable development appears to provide a set of sound strategies for correcting current problems in population-environment interactions that will ensure a brighter future for generations ahead. Implementation of the NSSD plan, for example, presents challenging but hopefully not insurmountable difficulties.

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