Population Growth and Control (Human)

The human population, or the number of people, on Earth has increased enormously during the past two centuries. Upon examining the reasons for this growth and the factors that could influence its continuance, it is not known whether Earth can sustain the great numbers of people predicted for the near future.

On October 12, 1999, the United Nations issued a population estimate that said the 6,000,000,000 mark had been reached. That figure is twice the population of 1960, a mere 40 years ago. Since the development of agriculture and the beginnings of settled human communities some 10,000 years ago, it took thousands of years for the human population to reach 1,000,000,000 around the year 1800. It took another 130 years to reach 2,000,000,000, but only 30 years to reach 3,000,000,000, 15 years to reach 4,000,000,000, 12 years to reach 5,000,000,000, and another 12 years to reach 6,000,000,000.

Today, the human population is growing at about 1.5 percent a year, or the equivalent of an additional 89,000,000 people a year. Every second five people are born and two people die, for a net gain of three people. The latest United Nations forecast for the year 2050 contains a projected low of 7,800,000,000 and a projected high of 12,500,000,000. However, if the world population continues to grow at its present rate, the high projection will be easily reached.

POPULATION HISTORY

The biological history of Homo sapiens (humans) extends back for more than 1,000,000 years. For almost all that time it consisted of a very small population that was barely staying alive by hunting and gathering. However, about 10,000 years ago, things began to change. People discovered primitive agriculture and began to domesticate a few plants and animals. With the discovery of the properties of metals and other technologies, the growth of the human population went from about 300,000,000 in the year a.d. 1 to about 500,000,000 in 1650. Around that time, the rate of population growth began to noticeably increase. High birth rates were accompanied by decreasing death rates due to better technologies for sanitation and medicine.

REASONS FOR POPULATION GROWTH

In 1800, the population reached 1,000,000,000. Yet in the past two centuries, its has skyrocketed to today's 6,000,000,000. There are three reasons why such unprecedented population growth has occurred. The first is the ability of the human species to adapt to new habitats. Early humans possessed the ability to learn and to remember, as well as the ability of being able to communicate what they knew to others. Humans have been able to use their technologies not only to disperse themselves virtually all over the globe, but to make their environment perfectly suitable for them if it is not naturally so. Today, people live in climates that might be considered extreme. They can live cooly in Phoenix, Arizona, in July; and they can play a professional football game indoors in Minnesota during a December blizzard. While most animals are "designed" to fit a certain habitat, humans have almost always made wherever they chose to live their habitat.

Humans have also been able to bypass what might have been natural limits on Earth's "carrying capacity." Carrying capacity is the maximum population that a habitat can support over a long period of time. However, humans have been able to increase that natural capacity by improvements in agriculture, as well as human use and management of natural resources. The use of fertilizers, pesticides, and irrigation is only some examples of how Earth can be exploited more efficiently to support greater numbers.

The third and probably most significant reason why our population has exploded in the past 200 years is that many of the natural or built-in limits on growth were eventually limited themselves or even done away with. While death is still inevitable for every human born, the death rate has gone down dramatically. This means that more people are living longer than they used to. Until fairly recently, people died early and regularly from many conditions that were really preventable. Childhood was an especially dangerous time, as youngsters often died from malnutrition (the physical state of overall poor health), the flu, or diarrhea. Contagious diseases would spread rapidly and kill great numbers in epidemics, especially in crowded cities. Today, however, simple improvements in hygiene and sanitation have prevented millions of early deaths. Furthermore, medical victories over diseases like cholera, measles, polio, whooping cough, and tuberculosis were based on the development of vaccines, antibiotics, and other new drugs. As a result, these diseases are no longer a threat.

EFFECTS OF CONTINUED POPULATION GROWTH

In 1798 the English economist, Thomas R. Malthus (1766–1834), was the first to draw attention to the fact that the growth of the human population could not keep on indefinitely. He argued that the population would eventually outgrow its food supply and start to fall back because of famine, disease, or war. It may once have been argued that human ingenuity has been able to overcome any of Earth's natural limits to population growth, and that Malthus's theories no longer applied. However, many argue that if the growth of the human population does not stabilize at some point, we may unhappily discover that there is an actual limit to the carrying capacity of the planet.

No one knows how many humans Earth can support. Some scientists argue that we have already reached it, given the rate at which developed countries (as opposed to less developed or third world countries) consume available natural resources. A goal of all population planners is what is called zero population growth. This desirable situation represents stability in that it happens when the birth rate roughly equals the death rate. Presently, the people of Earth are nowhere near such a stable figure.

[See alsoPopulation ]