Growth in human numbers and in material living standards lead to increased production which, given the technologies that are nowadays employed, result in a rapid depletion of many natural resources and to the production of numerous pollutants which are not only disagreeable and dangerous but are also, in some cases, employed on a scale which cannot be absorbed and dissipated by the natural environment.
The demands made by the increasing population were previously assumed to be well within the capacity of the Earth, as far as concerned its ability to supply the physical and chemical requirements for continued life and to absorb waste products. However, the late 1970s brought into focus the finite nature of non-renewable resources and the Earth's limited carrying capacity. The more people there are on Earth, the more will be the demand for the limited natural resources to support life and development, and the more will be the attendant environmental pressures. This will certainly continue to be the case for decades to come, especially in developing countries, where population growth is especially great in the cities, 17 of which top the 10 million mark and are expanding in a chaos of unplanned, under-serviced housing. If present trends continue, the populations in urban areas will double in the next decade, and many of these new citizens will live in squatter settlements.
Population pressure is forcing traditional farmers to work harder, often on shrinking farms on marginal land, simply to maintain a subsistence income. In Africa and Asia the rural population nearly doubled between 1950 and 1985, with a corresponding decline in land availability. This trend can only continue.
In 1997, it was estimated that the USA would miss its year 2000 greenhouse gas target by roughly 13 percent. This overshoot alone was greater than the entire 1990 carbon emissions of India, a country with 970 million people. The most significant component of the failure could be America's high population growth rate relative to other developed countries. The population was increasing by 0.9 percent (2.5 million) per year, more than three times the average for the rest of the industrialized world. Between 1990 and 2000, the US population was expected to grow 9.3 percent. Population growth therefore accounted for more than two-thirds of the 13 percent US carbon emission increase in that decade. In comparison, the UK, Germany and Russia – the three major developed countries that could be able to meet the Rio targets – had populations that were growing slowly or decreasing.