POPULATION GROWTH, VARIATION &
IMPACT ON ENVIRONMENT
INTRODUCTION :
About 250 years ago, humanity existed relatively small numbers with limited technologies.
Any environmental disturbances caused by people were local and usually well with in the environments
capacity to absorb them.
In the last two centuries, developments have occurred that have created environmental problems beyond
nature’s assimilative capacity.
Explosive growth of population creates environmental pressure because of the sheer number of people on
earth.
Concept :
•
This section examines the interface between the growth in human population and the
environment.
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The population growth rates vary from nation to nation
•
Some nation show very high growth rates above 3 per cent.
•
On the other hand some nations are not growing
at all and few have declining population.
POPULATION :
A Population is defined as a group of individuals belonging to the same species which line in a given area at a given time.
The study of population change is known as
“population dynamics”.
POPULATION DENSITY :
ü It is expressed as the number of individuals of the population per unit area or per unit volume.
ü This varies in response to changes in the
environment and introduction with other living organism.
PARAMETERS AFFECTING POPULATION SIZE :
BIRTH RATE OR NATALITY :Number of live birth per 1000 people in a population in a given year.
DEATH RATE OR MORTALITY : Number of death per 1000 people in a population in a given year.
IMMIGRATION :
Arrival of individuals from neighbouring population.
EMIGRATION :
Dispersal of individuals from the
original population to new areas.
POPULATION GROWTH :
The rapid growth of the global’s population for the past 100 years results from the difference between the rate of birth and death.
CHARACTERISTICS OF POPULATION GROWTH:
EXPONENTIAL GROWTH :
Population growth shows the dramatic increase in global population in the past 160 years.
DOUBLING TIME :
It is the time required for a population to double its size at a constant annual rate.
Td = Doubling time = 70/r Where, r = annual growth rate
(e.g.) if a nation has 2% annual growth, its population will double in next 35 years.
INFANT MORTALITY RATE :
It is the percentage of infants, died out of those born in one year.
Even through this rate has decreased in the last 50 years the pattern differs widely in developing and
developed countries.
TOTAL FERTILITY RATES (TFR) :
It is the average number of children delivered by women in her life time.
The TFR values vary from 2 in developed countries to 47 in developing countries.
REPLACEMENT LEVEL :
Two parents bearing two children will be replaced by their off spring.
Due to infant mortality this replacement level is changed.
MALE – FEMALE RATIO :
The ratio of girls and boys should be fairly balanced in a society to flourish.
But the ratio has been upset in many countries including china and India.
DEMOGRAPHIC TRANSITION :
Population growth is generally related to economic development.
The death rates and birth rates fall due to improved conditions.
VARIATION OF POPULATION AMONG NATIONS :
Different regions of the world find themselves at
different stages of demographic transition from high to low mortality and fertility.
Their growth path also differ considerably, resulting in significant shifts in the geographical distribution of the world’s population.
At present the world’s population has crossed 7 billions.
This existing population is also not evenly distributed.
Less developed countries have 80% population while the developed countries have only 20%.
Pie Diagrams
VARIATION OF POPULATION BASED ON AGE STRUCTURE :
Their classification are…
Pre – productive population (0 – 14 years ) Re – productive population (15 – 44 years )
post re-productive population (above 45 years ) PYRAMID SHAPED VARIATION OF
POPULATION ( INCREASE ) : The large number of young age people will soon enter into reproductive age group population ( 15 – 44 years), which increases the population growth. But the less number of old age
people indicates less loss of population due to death.
(e.g.) India, Bangladesh, Ethiopia – Nigeria etc…
POPULATION EXPLOSION :
DEFINITION :
The enormous increase in population, due to low death rate (mortality) and high birth rate (Natality) is termed as population explosion.
The human population is not increasing at a uniform rate in all parts of the world.
Among the countries, the most developed country like USA has a slow growth rate, whereas the other
developing countries have exorbitant growth rates.
Birth rate of developing country=45 per 1000 population Birth rate of developed country=12.7 per 1000
population
DOUBLING TIME :
Doubling time can be defined as “number of years needed for a population to double in size”.
In many non – industrialized, poor developed countries like Asia, Africa and South America shows higher
growth rate.
In contrast the population of industrialized, developed countries like USA, UK, France and Italy shows lower growth rate.
CAUSES (OR) REASONS FOR POPULATION EXPLOSION :
Reduced death rate and increased birth rate by the invention of modern medical facility, which leads to population explosion.
Increase of life expectancy.
Ex: In 1950, the average life expectancy of human being was 50 years but now it is 61 years.
Illiteracy.
Effects of population explosion
I.
Over stress on natural resources
II.
Over production of wastes
III.
Food problem
IV.
Over stress on water resources
V.
Unemployment
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Effects Of
Population Explosion
Air Pollution .
Water Pollutions.
Increase in Demand For Food Resources
Deforestation
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Air pollution
How air pollution because of
Population Explosion
?
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Given Below-:
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Increase in Industries
Industries
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Increase in
Vehicle
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Water Pollution
How Water Pollution because of Population Explosion?
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Given Below-:
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Raw sewage and
industrial waste flows directed
to main River or Sea
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Bathroom and Garbage
sewage flow Directed to
the River or Sea.
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Increase in Demand For Food Resources
due to increase in
population needs
•
Increase in Deforestation For occupying land for day by day increase in
population .
For Agriculture For
Urbanizat
ion
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Use of population in positive a ways-:
For intense Labor for Private Sector which leads to
development of countries Economy.
For Increase in Defence
Sector of countries which lead strong position of countries.
For intense Labor for
Government Sector which leads to smooth running of
Administration of Governess.
Effects on Natural Resources:
In the near future, fossil fuel from oil fields will run dry
•
Existing agro systems will become too overburdened and will not be able to meet the demands for food.
•
Pastures will be overgrazed by domestic animals.
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The industrial growth required to meet the demands of the massively rising population will reinforce pollution of soil, water and air. Industrial gases in particular will cause greater global warming and will eventually lead to a rise in sea levels, flooding all low-lying areas and submerging
coastal agriculture as well as towns and cities
•
. The seas will experience a decline in the fish population.
•
Larger ozone holes will develop due to the discharge of
industrial chemicals into the atmosphere; this development in its turn will affect human health.
•
The population pressure will contribute to water the
depletion of fresh water and may lead to water ‘famines’.
•
The demographic pressure will also reinforce the degradation of ecosystems leading to extinction of thousands of species which have a great role in the sustainability of the planet.
EFFECT OF POPULATION
EXPLOSION :
Infant mortality is one of the most tragic indicators of poverty. There are still 34 developing countries, where more than 10 children die before he or she reaches the age of five.Population explosion leads to environmental degradation.
Many of the natural and renewable resources like forest, grassland are also under threat.
Increase in population will increase disease, economic inequity and communal war.
Effects on Natural Resources:
• Existing agro systems will become too overburdened and will not be able to meet the demands for food.
• In the near future, fossil fuel from oil fields will run dry
• Pastures will be overgrazed by domestic animals.
• The industrial growth required to meet the demands of the massively rising population will reinforce pollution of soil, water and air. Industrial gases in particular will cause greater global warming and will eventually lead to a rise in sea levels, flooding all low-lying areas and submerging coastal
agriculture as well as towns and cities
• The seas will experience a decline in the fish population.
• Larger ozone holes will develop due to the discharge of industrial chemicals into the atmosphere; this
development in its turn will affect human health.
• The population pressure will contribute to water the depletion of fresh water and may lead to water
‘famines’.
• The demographic pressure will also reinforce the degradation of ecosystems leading to extinction of thousands of species which have a great role in the sustainability of the planet.
