Human Population

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To introduce the problems with human population growth

This section is in two parts:

  1. Define terms used in population analysis
  2. Note effects of excessive population on the environment and factors which affect that growth


There are some who say that the population growth is the most serious of all environmental problems

The current world's population (2020) is about 7.8 billion[1]

China 1.44 billion
India 1.38 billion
US 331 million
Indonesia 273 million
Thailand 70 million


Number of people born over a specified time period
Birth Rate 
Number of births per 1000 people per year
Number of deaths over a specified time period
Death Rate 
Number of deaths per 1000 people per year
Population Growth Rate 
Birth rate minus death rate. Usually given as percent of population

Note that the birth and death rate is the number per thousand, whereas the population growth rate is in percent (per hundred). Therefore,

[math]\textstyle Population Growth Rate = (\frac{Birth Rate}{1000}-\frac{Death Rate}{1000})X100[/math]
[math]\textstyle Population Growth Rate = \frac{Birth Rate - Death Rate}{10}[/math]

Examples - Population Growth Rate

Hungary -0.24
Spain 0.04
Thailand 0.31
Bangladesh 1.20
Australia 1.54
Oman 3.59
Uganda 3.59
Population Density 
Population per unit area

Examples - Population density (per sq. km)

Mongolia 2
Spain 94
Thailand 137
Netherlands 508
Bangladesh 1265
Singapore 8358

Age Distributions

Age Distribution 
number of people of each age in a population
Often given using age groups of five years
Shown using a Population Pyramid
Angola has a high growth rate (2.8%). Population is very young
Bangladesh used to have growth rate, but has slowed recently (currently 1.6%
Argentina is a slow growing country (1.0%). Note the contracting of the population below 15 years age
The USA has a growth rate about the level of Argentina (0.9%), but has had slow growth rate for a longer period
Germany has a negative growth rate (-0.1%). The population is older


movement of population into an area
movement of population out of an area

Then the total population growth rate is then

Population Growth Rate = Birth Rate + Immigration - Death Rate - Emigration

Migration is usually not a significant factor except where war or other conditions cause mass movement of people.

Health Care

The two best indicators of the quality of health care are infant mortality and life expectancy.

Infant Mortality 
number of deaths of those under 1 year old per 1000 births
Child Mortality 
number of deaths of those under 5 years old per 1000 births

Examples - infant mortality

Sweden 2
Thailand 8
Brazil 13
Laos 39
Chad 74
Life Expectancy 

the average number of years a newborn can expect to survive

Examples - life expectancy

Japan 84.4
Thailand 76.8
Russia 72.3
Nigeria 54.2


Total Fertility Rate 

number of children born per woman in her lifetime

Replacement Fertility Rate 

number of children born to parents to replace them

= approx. 2.1
more than 2.0 since some women die before bearing children or choose not to have children

Examples - total fertility rate

Korea 1.11
Thailand 1.53
China 1.69
India 2.24
Niger 6.95

If the total fertility rate exceeds the replacement rate, then the population growth rate will rise (and vice versa). Note there will be a delay between the two.

Population Growth

Graph of y=2x

The number of members for each generation increases geometrically = 2x2x2x...

Therefore the total size of the population must increase exponentially = 2^n with n the number of generations

Population Growth Curve

A population growth curve begins with a lag phase. During the lag phase population grows very slowly.

After the lag phase we then get the exponential growth phase also called the log phase.

Finally the birth and death rates will begin to approach each other. This leads to a deceleration phase followed by a stable equilibrium stage.

Human population curve

Humans have had a long lag period. It took until 1800 to reach 1 billion people. Then the second billion only took 130 years.

In the last eighty years population has increased from 2.0 to 7.8 billion.

Human population growth curve

Doubling Time 
Time for the population to double in size

= 70 years/Growth Rate (in percent)

Effects versus Factors

In the discussion below what we call effects are the effects of increased population on the environment. Factors are what causes population growth rate to increase.

Factors → Population → Effects

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A suggestion is that you first think about what the effects and factors are before you read the following sections. Feel free to discuss this with your fellow students.

Effects of population growth

  • Food security
  • Water, air, and land pollution; global warming
  • Land availability
  • Agricultural pressures
  • water (70% of human water usage is from agriculture)
  • land
  • soil erosion, soil degradation
  • desertification, soil salinity
  • pollution from fertilizers and pesticides
  • Pressures on natural resources
  • energy resources
  • mineral resources (metals, glass, stone, cement, gems, etc.)
  • forest resources
  • fisheries
  • water
  • Pressures on ecosystems
  • deforestation
  • habitat loss
  • extinction of species
  • poaching
  • encroachment of people into wildlife areas
  • Economic pressures
  • jobs
  • costs of material resources
  • economic divide
  • Health care
  • spreading of disease from overcrowding
  • shortage of doctors, nurses, etc.
  • shortage of medicines, vaccines, and medical equipment
  • Social
  • shelter (housing)
  • education (shortage of teachers)
  • infrastructure (fire, police, utilities, transport, etc.)
  • Political unrest/war due to scarce resources


Economic factors

The role of children in the economy is important in determining birth rate.

Many families feel they need children to help raise income. For example, farmers families are often large because the children can help on the farm.

Another important point is the cost of raising and educating children. Where the costs are higher, then couples will often delay having children until they are financially better off.

Cultural and Religious Factors

Culture and religion are important in determining number of children born. The role of women is especially important. In some cultures the role of women is to marry and have children. In other cultures women marry later and have fewer children.


Fertility rates have a direct correlation to women's education. The education of women is the single most important factor in reducing the world's population growth.

Birth Control

Attitudes toward birth control vary widely around the world. The most important point is to give women choice in when to have a family and how large it will be.

Health style

As mentioned above the best indicators of public health are infant mortality and life expectancy.

Life expectancy has generally risen over the years. However, recently it has decreased in Africa due to the AIDS epidemic. In some African countries up to one-third of adult are infected with HIV.

Government Policy

The government's policy toward population growth can be very important. Some countries (for example, Thailand, China, and Bangladesh) have encourage family planning, etc. Other countries (such as Singapore) have encouraged people to have more children.


  1. Family Planning
  2. Women's Education
  3. Respect for women's and children's rights

Case Study: Thailand

Thailand reduced its population growth rate from 3.2% to 1.6% in just 15 years.

It has a family planning program supported by the government, the Buddhist church, and nonprofit organizations. Program led by Meechai Viravidaiya aka Mr. Condom.

Thailand also has good educational and employment opportunities for women and a good health care system for mothers and children.

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Web Resources

The following sites have statistics and reports on population:

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Pick a country and look at the population issues of that country. Especially, consider what problems the country has -- each country has different problems. As a starting point look at the resources listed below.

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Pick a country and go to the population statistics for the UN HERE. Then using the statistics, answer the following questions:
  1. What is the population of the country
  2. Is the population growth rate of the country, high or low?
  3. Based on the data, what is state of the health care in the country? On what do you base this?
  4. Do you expect the population growth rate to increase or decrease. Why?
  5. How does the country compare to the other countries in its region? Its economic group? The world? (hint: go to here to find the UN region and economic group)
  6. What is the predicted population, given the different variants?
  7. In your opinion, what is the most important population issue in the country?

For more specific instructions on using the UN database see this page


  1. All population data except total world population and US population taken from the UN's World Population Prospects 2019. Total world population and US population taken from the US Census Bureau's Population Clock, viewed in June 2021.