Human population and global environment

In this paper, Holdren and Ehrlich tackle the misconceptions they feel are both dangerous and common among decision makers:

“(1) the absolute size and rate of growth of the human population and has little or no relationship to the rapidly escalating ecological problems facing mankind;

(2) environmental degradation consists primarily of ‘pollution,’ which is perceived as a local and reversible phenomenon or concern mainly for its obvious and immediate effects on human health; and

(3) science and technology can make possible the long continuation of rapid growth in civilization’s consumption of natural resources” (p282).

In doing so, the authors classify environmental problems according to the damage they pose to human beings as either “direct assaults” or “indirect effects”. “Indirect effects” largely consist of the environmental problems that are posed to undermine the functioning of natural systems humans rely on. Though most attention at the time (1974) focused on minimizing “direct assaults” such as polluted water sources, the authors argue, “The most serious threats of all, however, may well prove to be the indirect ones generated by mankind’s disruption of the functioning of the natural environment” (p282). They support this argument by briefly reviewing “public-service” functions of the global environment and establishing that the operations of natural biological processes are both irreplaceable and indispensable, or non-substitutable. Unfortunately, through examples of desertification and deforestation, Holdren and Ehrlich demonstrate that civilization’s aim “to manage ecosystem in such a way as to maximise productivity,” is incompatible with “nature’s” tendency “to [manage] ecosystems in such a way as to maximize stability” (p287). This tendency is causing mankind, as a global and biological force, to become “comparable and even exceeding many natural processes,” pushing systems away from stability (p287). The scale of the resulting environmental deterioration is explained by the authors with the equation:

“Environmental disruption = population x consumption per person x damage per unit of consumption”  

–which is the basis for the I=PAT equation, also attributed to the authors. Thus, the population size, consumption and effect per unit of consumption interact multiplicatively to determine the extent of environmental disruption. The authors clarify, “For problems described by multiplicative relations like the one just given, no factor can be considered unimportant” (p288). Thus, actions taken to reduce the environmental disruption caused by humans “should include measures to slow the growth of the global population to zero as rapidly as possible. Success in this endeavor is a necessary but not sufficient condition for achieving a prosperous yet environmentally sustainable civilization” (p291). This article provides critical background on how human population size is considered to interact with consumption, and the importance of addressing both in efforts to reduce environmental disruption.