The State of the Environment—An Overview - The Role Of Population In The Environmental Equation

Earth's population is believed to have grown more from 1950 through 2000 than it did during the previous 4 million years. For centuries, deaths largely offset births, resulting in a slow population growth. Beginning around 1950, high birth rates in developing countries, coupled with a reduction in mortality rates and reduced infant mortality (which led to an overall lengthening of the life span), dramatically impacted population growth. According to 2003 figures from the United Nations (UN), between 1950 and 1990 the global population more than doubled from 2.5 billion to more than 5.0 billion people. Another billion people are estimated to have been added between 1990 and 2000.

As shown in Figure 1.2 the vast majority of population growth is expected in less developed countries. This is significant to environmental issues because these countries are, or will be, undergoing their own industrial revolutions—a time when economic development or "progress" generally gets priority over environmental issues.

The growing number of people on Earth increases the demands on natural resources. More people require more food, fuel, clothing, and other necessities for life. All of these must be supplied from the planet's resources and from the Sun's energy. These facts—combined with the realization that the Earth's resources are limited, not infinite—pose serious questions about rapid population growth. Can the world's resources support its population while maintaining the environment, or will human needs overwhelm Earth's capacity to provide?

Most scientists believe that population growth will eventually cease. As a nation's economy develops and its standards of living rise, its population generally stabilizes. This "demographic shift" has already been observed in highly industrialized countries such as Japan and the nations of western Europe where the fertility rate is generally at or below replacement level. The UN projects that this slow decline in growth rates will continue until all regions of Earth have developed high standards of living, experienced a demographic shift, and had their populations stabilize. By the time this occurs, however, Earth's population is expected to have reached at least 9 billion people.

It is not known if Earth's resources can support a population of 9 billion. Some believe there is evidence that population growth is already pressing, or has exceeded, the capacity of natural resources in many areas. Environmentalists and others warn that without conservation, resource protection, and drastic measures to curb population, FIGURE 1.2
World population growth in more and less developed countries, 1950–2050 humankind and planet Earth might suffer serious harm. Other analysts do not share these opinions, however. Opposing the idea that natural resources and humankind is in danger, some analysts point to the fact that, at many times throughout history, there have been those who claimed in vain that industrial development could not be sustained. For example, at one time it was feared that, as the world ran out of whale oil for lamps, great cities would be left in darkness. This scenario, and other "doomsday" predictions did not come about because new technologies averted the expected disasters.