Science Man and His Environment/Population

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

The current world's population is about 6.9 billion
 * China     1.3 billion
 * India     1.2 billion
 * US          311 million
 * Thailand     69 million

Definitions

 * Natality : Number of people born over a specified time period
 * Birth Rate : Number of births per 1000 people per year


 * Mortality : 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,


 * $$\textstyle Population Growth Rate = \frac{Birth Rate}{1000}-\frac{Death Rate}{1000}X100$$


 * or


 * $$\textstyle Population Growth Rate = \frac{Birth Rate - Death Rate}{10}$$

Examples - Population Growth Rate
 * Georgia   -0.57
 * Thailand   0.71
 * USA       0.89
 * Uganda    3.24


 * Population Density : Population per unit area

Examples - Population density
 * Mongolia       2 per sq. km
 * Thailand     135 per sq. km
 * Bangladesh  1033 per sq. km
 * Hong Kong   6418 per sq. km

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











Migration

 * Immigration : movement of population into an area


 * Emigration : 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     2.4
 * Thailand  10.8
 * Cambodia  58.1

the average number of years a newborn can expect to survive
 * Life Expectancy :

Examples - life expectancy
 * Japan     82.7
 * Thailand  73.6
 * Zimbabwe  46.6

Fertility
number of children born per woman in her lifetime
 * Total Fertility Rate :

number of children born to parents to replace them
 * Replacement Fertility Rate :
 * = 2.1
 * more than 2.0 since some women die before bearing children

Examples - total fertility rate
 * Ukraine   1.39
 * Thailand  1.63
 * Niger     7.19

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


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 6.8 billion.



= 70 years/Growth Rate (in percent)
 * Doubling Time : Time for the population to double in size

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 &rarr; Population &rarr; Effects

Effects of population growth

 * Food security
 * Problems providing food for all the mouths
 * Desertification, soil salinity, water shortage, etc. due to high agriculture pressures
 * Water and air pollution, global warming
 * Shelter
 * Spreading of disease from overcrowding
 * Land availability
 * Encroachment of people into wildlife areas
 * Pressures on natural resources (deforestation, poaching. fisheries)
 * Increased need for energy and mineral resources
 * Economic pressures (jobs)
 * Political unrest in areas of scarce resources

Ecological footprint
The ecological footprint is the amount of land that would be required to provide the resources for a population

Examples - ecological footprint
 * USA 10.9 ha per person
 * total      3 billion ha
 * India 1.0 ha per person
 * total      1 billion ha

- note that the India has four times the population of the US, but only use one-third the resources. If all countries had the footprint of the US we would need 3 Earths.

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.

Education
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.

Urbanization
The percent of people living in urban areas has been rapidly increasing. Currently half of all people live in cities.

By 2030, UN-Habitat estimates 60% will live in cities.

In Latin America 77% live in cities.

The problem is providing the necessary services to the cities inhabitants. For example, water, sanitation, police, and fire.

Solutions

 * Family Planning
 * Women's Education
 * 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.