Since the early 1800s, the human population on Earth has been growing exponentially. The world population is estimated to be: 7,494,000,000 people in 2015.

Human Population History

In 1850, the human population reached its first billion. By 1930, it was 2 billion. By 1960, the human population reached 3 billion. Then in 1975, 4 billion, and so on…

The human population is now growing at a rate of about 3 people per second OR 260 thousand/day or 1.8 million per week or 93 million/year

Each dot represents 1 million people

The overall rate of population increase depends on the number of births and deaths, but also on the length of generations -- the age at which women have their first baby. For example, if all women had three kids with a 15-year average generation time, the rate of population growth would be 2.7%. If the average spacing were 30 years, the growth would drop in half -- to 1.35%.

Birth/Death Rates When a large proportion of a country's population is young, high population growth rates in a country are to be expected, even if the average total fertility rate is modest. The reason is that so many females are of childbearing age, that even a modest average total fertility rate results in a large number of births.

Total fertility rate (TFR) - average number of children a woman will have during childbearing years In 1995, the TFR was 3.1 children per woman This map shows the average number of children born to a woman during her lifetime. Childbearing years are usually considered to be the ages of

Why are fertility rates lower in developed countries? – social attitudes favoring small families – increasing cost of raising a child to age 18 $177,000 low-income family $231,000 middle-income $335,000 upper-income – increase in average age of marriage between 1958 & 1992 (from 20 to 24 for women, and from 23 to 27 for men) – More women working outside home – delayed reproduction Fertility Rates in the US peaked in 1957 at 3.7 children/woman

Personal hygiene and improved methods of sanitation have played a major role and preceded the impact of modern medicine and, in particular, the development of antibiotics capable of reducing death due to infection. Figure 5: Death Rates per 1000 over Time The combination of decreasing death rate due to the march of progress in sanitation and medicine, coupled with the decrease in birth rate due to changes in the economies, has led to a profound change in the population growth curve in the developed world. This change is called the Demographic Transition.

Carrying capacity - the maximum population that can be supported by the available resources. Biological Carrying Capacity - about 50 Billion Cultural Carrying Capacity - modified population at which a maximum population can be maintained at an acceptable standard of living.

According to the latest United Nations projections, the most likely scenario for population in 2050 will be around 9 billion, and will peak out slightly above 10 billion after 2200.

Impacts of continued growth in human populations include: The population of sub-Saharan Africa provides a clear example of a region suffering from over population. Their population is increasing by 3% yearly, while their food supply is only annually growing by 1%. This has led many economically low countries' environments to such extreme conditions as desertification.

As population grows: consumption of valuable resources and pollution increases, which threatens to overwhelm the Earth’s ability to provide for the human race and other life forms. Overpopulation creates: low living standards, outbreaks of civil wars, not enough jobs, poor food supplies, and reduced education standards.

As a result of this rapid growth: - Approximately 1.3 billion of the world's people are very poor, living on less than 1 dollar a day. And as population steadily increases, the gap between rich and poor is widening. - Some 60% of the 4.8 billion people in developing countries lack basic sanitation, and almost one-third have no access to clean water. -Nearly 1 billion people in the world are illiterate, two-thirds of them women. To resolve the problem of overpopulation, it will take a combined effort of the developed and developing countries to better the conditions of the whole planet, not just specific countries.

Global fertility rates have declined more rapidly than expected, as health care, has improved faster than anticipated, and men and women have chosen to have smaller families. About one-third of the reduction in long-range population projections, however, is due to increasing mortality rates in sub-Saharan Africa and parts of the Indian subcontinent. The most important factor is HIV/AIDS, which is spreading much faster that previously anticipated.

Possible Solutions 1)Train and educate the people of developing countries so that they can pursue industrialization. As they progress, they will be less dependent on other countries for assistance. 2) Educate the people in how to manage their existing natural resources. 3) Demonstrate to the people how their natural resources can be used to generate income (example: ecotourism)

Possible Solutions 4) Consider means of financing industrialization efforts. This an be in the shape of loans, outright gifts, etc. from countries which are already developed. 5) Educate the developing countries about agriculture. Help them discover which crops can be successfully grown in their climates and teach them how to grow these crops so that they will be less dependent on outside aid for food. 6) Educate the people about the effects of overpopulation.

Possible Solutions 7) Provide information on family planning and finance projects to provide this technology to the people. 8) Assist the countries in offering their own incentives to their citizens to reduce the birth rate (example: tax cuts for families which voluntarily have less children).

1) Train and educate the people of developing countries so that they can pursue industrialization. As they progress, they will be less dependent on other countries for assistance. 2) Educate the people in how to manage their existing natural resources. 3) Demonstrate to the people how their natural resources can be used to generate income (example: ecotourism and its associated benefits). 4) Consider means of financing industrialization efforts. This an be in the shape of loans, outright gifts, etc. from countries which are already developed. 5) Educate the developing countries about agriculture. Help them discover which crops can be successfully grown in their climates and teach them how to grow these crops so that they will be less dependent on outside aid for food. 6) Educate the people about the effects of overpopulation on their own nation. 7) Provide information on family planning and finance projects to provide this technology to the people. 8) Assist the countries in offering their own incentives to their citizens to reduce the birth rate (example: tax cuts for families which voluntarily have less children).