Human Population

The huge increases in size of the human population have resulted in a substantial degradation of environmental conditions. The changes have largely been characterized by deforestation, unsustainable harvesting of potentially renewable resources (such as wild animals and plants that are of economic importance), rapid mining of non-renewable resources (such as metals and fossil fuels), pollution, and other ecological damages.

At the same time that human populations have been increasing, there has also been a great intensification of per-capita environmental impacts. This has occurred through the direct and indirect consequences of increased resource use to sustain individual human beings and their social and technological infrastructure: meat production, fuel-burning, mining, air and water pollution, destruction of wild habitat, and so forth.

This trend can be illustrated by differences in the intensity of energy use among human societies, which also reflect the changes occurring during the history of the evolution of sociocultural systems. The average per-capita consumption of energy in a hunting society is about 20 megajoules (millions of joules) per day (MJ/d), while it is 48 MJ/d in a primitive agricultural society, 104 MJ/d in advanced agriculture, 308 MJ/d for an industrializing society, and 1025 MJ/d for an advanced industrial society. The increases of per-capita energy usage, and of per-capita environmental impact, have been especially rapid during the past century of vigorous technological discoveries and economic growth.

In fact, global per-capita economic productivity and energy consumption have both increased more rapidly during the twentieth century than has the human population. This pattern has been most significant in industrialized countries. In 1980, the average citizen of an industrialized country utilized 199 gigajoules (GJ, billions of joules) of energy, compared with only 17 GJ/yr in less-developed countries. Although industrialized countries only had 25% of the human population, they accounted for 80% of the energy use by human beings in 1980. Another illuminating comparison is that the world's richest 20% of people consume 86% of the goods and services delivered by the global economy, while the poorest 20% consumes just 1.3%. More specifically, the United States—the world's richest country as measured on a net, though not on a per-capita, basis—consumes approximately 25% of the world's natural resources and produces some 75% of its hazardous wastes and 22% of its greenhouse gas emissions, while having only about 4.5% of the world's population.