ESS – Unit 8 Notes
8.1 – Human Population Dynamics
Exponential growth refers to a growth rate that is increasingly rapid, or an accelerating rate of
growth. The world’s population has grown exponentially. Most of this growth is quite recent and
much of it has been in South Asia and East Asia. Up to 95 per cent of population growth is taking
place in less economically developed countries (LEDCs). Rapid growth is likely to take place until at
least 2050. The world’s population is expected to stabilize at about 12 billion by around 2050–80.
Population growth can create:
great pressure on governments to provide for the needs of their people.
increased risk of famine and malnutrition.
greater differences between the richer countries and the poorer countries.
increased pressure on the environment.
More resources are needed to look after the increasing number of people. The consumption of
resources per capita in LEDCs is much less than the consumption of resources in more economically
developed countries (MEDCs). In MEDCs, population growth rates are much lower. As the wealth of
people in LEDCs increases, people eat more meat and dairy products. These products come from
higher up the food chain. This means that more land is needed to produce the food. The increased
need for food will require more land and water to produce the food. It will also require more fossil
fuels for chemical fertilizers and for transport.
IMPORTANT: global population growth has begun to stabilize – although it is still rapid, it is
no longer exponential.
Crude Birth Rate (CBR) and Crude Death Rate (CDR)
1. Crude birth rate - defined as the number of live births per thousand people in a population.
total number of births
Crude Birth Rate ( CBR )= ×1000
total population
2. Crude death rate - the number of deaths per thousand people in a population.
number of deaths per year
Crude Death Rate ( CDR ) = ×1000
total population
crude - a rate that does not take into account the age-structure of a population.
Fertility
The fertility rate is the average number of births per woman of child-bearing age. It is the completed
family size if fertility rates remain constant. In general, the highest fertility rates are found among
the poorest countries, and very few LEDCs have made the change from high birth rates to low birth
rates. In contrast, most MEDCs have reduced their birth rates.
Natural Increase and Doubling Time
Natural increase is the increase in population as a result of birth rates being higher than death rates.
Natural increase is usually measured in per cent (%). Natural decrease occurs when death rates are
higher than birth rates. Natural increase and decrease do not take into account any gains or losses
from migration.
, Natural Increase =Crude Birth Rate−Crude Death Rate
Doubling time refers to the length of time it takes for a population to double in size, assuming that
its natural increase remains constant.
Population Pyramids
A population pyramid is a bar graph on its side which shows variations in the age structure and sex
structure of a population. The following diagrams show the population pyramids for Swaziland.
Swaziland is an LEDC in southern Africa. The population pyramids are for the years 2000 and 2025.
Population pyramids tell us a lot of information about the age and sex structure of a population:
a wide base indicates a high birth rate – such as Swaziland in 2000.
a narrow base suggests a falling birth rate – such as Swaziland in 2025.
bulges in the slope suggest high rates of in-migration.
gaps in the pyramid may indicate out-migration or age-specific deaths. The relative lack of
people over the age of 50 years in Swaziland in 2025 is predicted because of the increasing
impact of AIDS.
8.1 – Human Population Dynamics
Exponential growth refers to a growth rate that is increasingly rapid, or an accelerating rate of
growth. The world’s population has grown exponentially. Most of this growth is quite recent and
much of it has been in South Asia and East Asia. Up to 95 per cent of population growth is taking
place in less economically developed countries (LEDCs). Rapid growth is likely to take place until at
least 2050. The world’s population is expected to stabilize at about 12 billion by around 2050–80.
Population growth can create:
great pressure on governments to provide for the needs of their people.
increased risk of famine and malnutrition.
greater differences between the richer countries and the poorer countries.
increased pressure on the environment.
More resources are needed to look after the increasing number of people. The consumption of
resources per capita in LEDCs is much less than the consumption of resources in more economically
developed countries (MEDCs). In MEDCs, population growth rates are much lower. As the wealth of
people in LEDCs increases, people eat more meat and dairy products. These products come from
higher up the food chain. This means that more land is needed to produce the food. The increased
need for food will require more land and water to produce the food. It will also require more fossil
fuels for chemical fertilizers and for transport.
IMPORTANT: global population growth has begun to stabilize – although it is still rapid, it is
no longer exponential.
Crude Birth Rate (CBR) and Crude Death Rate (CDR)
1. Crude birth rate - defined as the number of live births per thousand people in a population.
total number of births
Crude Birth Rate ( CBR )= ×1000
total population
2. Crude death rate - the number of deaths per thousand people in a population.
number of deaths per year
Crude Death Rate ( CDR ) = ×1000
total population
crude - a rate that does not take into account the age-structure of a population.
Fertility
The fertility rate is the average number of births per woman of child-bearing age. It is the completed
family size if fertility rates remain constant. In general, the highest fertility rates are found among
the poorest countries, and very few LEDCs have made the change from high birth rates to low birth
rates. In contrast, most MEDCs have reduced their birth rates.
Natural Increase and Doubling Time
Natural increase is the increase in population as a result of birth rates being higher than death rates.
Natural increase is usually measured in per cent (%). Natural decrease occurs when death rates are
higher than birth rates. Natural increase and decrease do not take into account any gains or losses
from migration.
, Natural Increase =Crude Birth Rate−Crude Death Rate
Doubling time refers to the length of time it takes for a population to double in size, assuming that
its natural increase remains constant.
Population Pyramids
A population pyramid is a bar graph on its side which shows variations in the age structure and sex
structure of a population. The following diagrams show the population pyramids for Swaziland.
Swaziland is an LEDC in southern Africa. The population pyramids are for the years 2000 and 2025.
Population pyramids tell us a lot of information about the age and sex structure of a population:
a wide base indicates a high birth rate – such as Swaziland in 2000.
a narrow base suggests a falling birth rate – such as Swaziland in 2025.
bulges in the slope suggest high rates of in-migration.
gaps in the pyramid may indicate out-migration or age-specific deaths. The relative lack of
people over the age of 50 years in Swaziland in 2025 is predicted because of the increasing
impact of AIDS.
