Human Populations

Introduction

Many people worry that overpopulation will cause or perhaps already is causing resource depletion and environmental degradation that threaten the ecological life support systems on which all depend. Family planning and birth control are essential for stabilizing populations. The number of children a couple decides to have and the methods they use to regulate fertility, however, are strongly influence by culture, religion, politics, and economics, as well as basic biological and medical considerations.

Human Population History

Many factors have contribute to the rapid population growth. Increase sailing and navigating skills stimulated commerce and communication between nations. Agricultural development, better sources of power, and better health care and hygiene also played a role. Modern knowledge in medicine, public and environmental health, and agriculture have started to control epidemics. More and more people are living, and living longer. We are now in an exponential or J curve pattern of growth. The population graph in the right side shows this exponential or J curve pattern. You can also notice that the human population started to dramatically increase after the industrial revolution and the major advances in medicine. Will this population explosion continue until we overshot the carrying capacity of our environment and experience a catastrophic dieback? In 1979 Thomas Malthus predicted that human population would growth faster than the ability to feed it. He argued that human population tend to increase at an exponential rate while food production either remains stable or increases only slowly.

Picture this:

It took almost all human history - until 1804 - for Earth's population to reach 1 billion. Every second, on average, five children are born somewhere in the earth. In that same second, two other people die. In just 12 years, from 1987 to 1999, the humans have increased their number by 1 billion. At the current pace, humanity is adding about 78 million more people every year - the population for France, Greece and Sweden combined, or a city the size of San Francisco every three days. The World Health Organization estimates that more than 3 billion people in the world suffer from malnutrition. According to the United Nations projections, the Earth's population will be 9 to 12 billion by 2050, depending on choices made by today's youth about bearing children.

Can technology make the world more habitable? Because of scientific progress food supplies have increase faster than population growth. Much of our growth in the past three hundred years has been based on availability of easily acquired natural resources, especially cheap, abundant fossil fuels.

Human Demography

Measure of people. It includes vital statistics about people, such as births, deaths, and where they live as well as total population size.

Fertility and Birth Rates:

• Fecundity - physical ability to reproduce

• Fertility - actual production of offspring

• Crude birth rate - number of birth in a year per thousand persons.

• Zero population growth - is the number of birth at which people are just replacing themselves.

In general, high birth rates correlate strongly with poverty, high infant mortality, low female literacy rates, and lack of paid employment for women.

Mortality and Death Rates:

• Crude death rate (Crude mortality rate) - number of deaths per thousand person in any given year.

Life Span - is the oldest age to which a species is known to survive. Life expectancy - is the average age that a newborn infant can expect to attaint in any given society. Percent natural increase of population - birth rate minus death rate. Percent total growth rate - includes immigration, emigration as well as births and deaths.

Population Growth:Opposing Factors

• Pronatalist Pressures - are factors that increase people desires to have children. Often children are valuable to the family not only for future income, but even more as a source of current income and help with household chores. In some societies, families with few or no children are looked upon with pity or contempt.

• Birth Reduction Pressures - are factors that decrease people desires to have children. In more highly developed countries many pressures tend to reduce fertility. The desire to have children is offset by a desire for other goods and activities that compete with childbearing and childreasing for time and money.

Demographic Transition

An Optimistic View- Some demographers claim that a demographic transition already is in progress in most developing nations. Total fertility rates have dropped nearly 40% in the past 20 years from 6.1 to 3.3 children per woman worldwide.

Factors that contribute to stabilizing populations:

• Growing prosperity and social reforms that accompany development reduce the need and desire for large families in most countries.
• Technology is available to bring advances to the developing world much more rapidly than was the case a century ago.
• Less developed countries have historic patterns to follow.
• Modern communications have caused a revolution of rising expectations that act as a stimulus to spur change and development.

A Pessimistic View - Many of the poorer countries of the world appear to be caught in a "demographic trap" that prevents them from escaping from the middle phase of the demographic transition. Human demands exceed the sustainable yield of food and water. Their populations may continue to grow until catastrophe intervenes.

Infant Mortality and Women's Rights - Survival of children is one of the most critical factors in stabilizing population. Better nutrition, improved health care, simple oral rehydration therapy, and immunization against infectious diseases have reduce child mortality rates, which have been accompanied in most regions by falling birth rates. Often the best way to improve child survival is to ensure the rights of mothers.

Family Planning and Fertility Control

Current Birth Control Methods

• Mechanical barriers
  condoms (male and female)
  cervical cap
  diaphragm

  Surgical methods

  vasectomy

  tubule ligation

  Chemical control

  pill

  Norplant

  Depo-Provera

  Physical barrier to implantation

  IUD

  Abortion

We have many more options now for controlling fertility than were available to our ancestors. Some techniques are safer than those available earlier; many are easier and more pleasant to use. Sometimes it takes deep changes in a culture to make family planning programs successful. Among these changes are improved social, educational, and economic status for women; higher values on individual children; accepting responsibility for our own lives; social security and political stability that give people the means and confidence to plan for the future; and knowledge, availability, and use of effective and acceptable means of birth control.

US census web site.

Human Population Growth web site.

Watch the population growth every 30 seconds.

Is Human Population Really the Problem?

Internet Guide to Demography and Population Studies.

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