We recognize that our impact on the environment, in terms of pollution and resource depletion, is the product of our numbers times our per capita consumption of energy and materials.Thus, there are only three ways by which that impact can be reduced:
• By reducing the size of our population by a negative rate of population growth.
• By reducing overconsumption by simplifying lifestyles.
• By reducing resource depletion and pollution per unit of consumption through more efficient use of energy and materials.
Population size is by far the most critical of those three variables.Nevertheless, our present scale of economic activity is so large relative to the biosphere that all three measures are needed in order to reduce it to a sustainable level.