8.1

Why is the Earth’s population growing?

• Advances in healthcare, improved living conditions, and reduced mortality rates, all of which are leading to longer life spans

• Advancements in agriculture and technology have ensured more consistent food supplies, leading to reduced famine and malnutrition.

• As birth rates remain high in many regions - especially in developing countries - the combination of increased births and decreased mortality contributes to the continued rise in population growth.

What are the implications of population growth?

Resources/ Environment/ Economy/ Infrastructure/ Society/ Health

Births and immigration are

inputs to a human population.

Crude birth rate

(number of live births per 1,000 people in a population per year)

Immigration rate

(number of immigrants per 1,000 population per year)

Factors impacting CBR:

Level of education, Material ambition, Economic prosperity (as GDP increases the birth rate decreases, while increasing costs leads to a birth rate decrease), The need for children

Deaths and emigration are

outputs from a human population.

Crude death rate

(number of deaths per 1,000 people in a population per year)

Emigration rate

(number of emigrants per 1,000 population per year)

Factors impacting CDR:

• CDR has decreased over the past 10 years due to improvements in food, housing, clean water supply

• Age of country's population

• Social class

• Occupation

• Place of residence and shelter

Population dynamics can be quantified and analysed

by calculating total fertility rate, life expectancy, doubling time and natural increase.

Total fertility rate

average number of births per woman of childbearing age

• Critical value is 2.2 – known as the replacement rate

• TFR of 2.2 means that the population will remain stable, less than that and the population will decline and more means it will increase.

Factors affecting birth rates and fertility rates:

• Role of children in the labour force or education

• Urban living

• Access to healthcare and family planning services

• Access to education

• Women's status and having choices with regards to work, education, family planning

• Traditional “roles” of females and cultural roles

• Lifestyle choice

• Government policies

Natural increase

is calculated by subtracting CDR from CBR, divided by 10

• NIR determines changes in population size.

• If fertility is greater than mortality then the NIR is positive

• If mortality is greater than fertility the NIR is negative, and is a decrease in population.

Life expectancy

average number of years that a person can be expected to live, usually from birth, if demographic factors remain unchanged.

Doubling time

number of years it would take a population to double its size at its current growth rate; it can be calculated by using the rule of 70. To do this, divide 70 by the growth rate (as a percentage).

The global human population has followed a rapid growth curve.

Models are used to predict the growth of the future global human population.

UN projection models indicate three scenarios linked to future fertility rates.

Population projections to 2100 from three organisations: the UN, the Institute for Health Metrics and Evaluation (IHME), and the International Institute for Applied Systems Analysis (IIASA). In the UN one, there are 3 main scenarios; UN High fertility scenario, UN probabilistic median, UN low fertility scenario

UN High fertility scenario:

where fertility remains higher than the median. This scenario assumes slower declines in fertility rates than expected. This could lead to a higher peak population compared to the probabilistic median.

UN probabilistic median

This is considered the most likely scenario by the UN. It takes into account current trends in fertility rates and other factors like mortality and migration. This projection gives a central estimate for the peak population and timing

UN low fertility scenario:

which falls lower than the probable median. This scenario assumes a faster decline in fertility rates than expected. This could lead to an earlier peak population and a lower overall peak compared to the probabilistic median.

Population and migration policies can be employed to directly manage growth rates of human populations.


• Pro-natalist policies: attempts to increase growth rates of populations

• Anti-natalist policies: attempts to limit or slow down the CBR.

• Immigration policies and emigration policies.

Singapore’s Population Control and Pro-Natalist Policies


• Impact: Singapore has historically had both pro-natalist policies to increase birth rates and policies to manage population growth. In the 1960s and 1970s, it implemented policies like the "Stop at Two" campaign to reduce birth rates, followed by pro-natalist policies in the 1980s to encourage larger families.

• Outcome: Singapore’s population policies have led to a steady fertility rate close to replacement level, though recent trends have shown a need to adjust to encourage higher birth rates amidst an aging population.

China’s One-Child Policy (1979–2015)

• Impact: China's one-child policy, introduced in 1979, aimed to control the country's rapidly growing population. The policy restricted families to having only one child, with some exceptions. This resulted in a drastic reduction in the birth rate, helping to prevent overpopulation.

• Outcome: By 2015, China's population growth slowed significantly, and the policy was replaced with a two-child policy due to concerns about an aging population and shrinking workforce.

India's Family Planning Policies (1950s–Present)

• Impact: India was one of the first countries to introduce a national family planning program, aiming to reduce its high fertility rates. Over the decades, the government promoted the use of contraceptives, sterilization, and awareness campaigns.

• Outcome: These policies helped reduce India's fertility rate from over 5 children per woman in the 1950s to about 2.3 children per woman in recent years.

Pro-Natalist Policies in France

• Impact: France has implemented several pro-natalist policies to encourage higher birth rates in the face of an aging population. These policies include tax incentives, subsidized childcare, and parental leave benefits.

• Outcome: These measures have helped maintain relatively high fertility rates in France compared to other European countries, with fertility rates hovering around 2.0 children per woman.

Human population growth can also be managed indirectly

through economic, social, health,development and other policies that have an impact on births, deaths or migration.

Many development policies addressing areas such as, but not limited to, gender equality, education, improvements in public health and welfare will indirectly affect births, deaths and migration.


• 1994: International Conference on Population and Development (ICPD)

• Focus: Shifts from population control to improving reproductive health, gender equality, and access to family planning.

• 2000: Millennium Development Goals (MDGs), United Nations

• 8 Goals aimed at reducing poverty, improving education, and health.

• 2015: MDG Review

• Outcome: MDGs showed progress, but some areas (e.g., gender equality) needed more attention.

2015: Sustainable Development Goals (SDGs)

• 17 Goals focusing on a broader, more inclusive development approach.

• aims to achieve these goals by 203

Other programs that can manage population growth:

• Social programmes: They can allocate resources for education, healthcare, and social security based on population age structure and growth.

• Economic planning: Project labour force trends, anticipate demand for housing and infrastructure, and plan for economic growth.

• Public health initiatives: Identify areas with high mortality rates or low life expectancy to target healthcare interventions.

• Migration policies: Understand potential population shifts due to migration patterns

The composition of human populations can be modelled and compared using age–sex pyramids

The pyramid is measured in absolute numbers or as a percentage of the total population. It shows the proportion of the population of either gender in each age group.

What are age sex pyramids used for?

• help demographers determine the potential for future growth of specific age groups as well as the total population

• overall shape of the pyramid indicates potential growth

• age structure diagrams not only reveal populations’ growth trend, but also point to future social conditions

How does age structure affect population growth?

• a wide base indicates a high birth rate

• narrow base indicates a low birth rate

• concave slopes indicate a low death rate

• buldges in the slope suggest baby booms or high rates of immigration or in-migration

• slices in the slope indicate emigration or out-migration or age/sex-specific death

The demographic transition model (DTM) describes

the changing levels of births and deaths in a human population through different stages of development over time.

There are five stages of the DTM,

including death and then birth rates declining to produce an exponential increase, stabilization and possible decline in population.

*Consider the relationship of specific age–sex pyramids to appropriate stages.

Demographic Transition Model (DTM) Stages

1. High Stationary, 2. Early Expanding, 3. Late Expanding, 4. Low Stationary, 5. Declining

1 High Stationary 


Death rate and birth rate are both high and there is a slow population growth and fluctuation.

2 Early Expanding 


Birth rates remain high but the death rate decreases and the population rises.

3 Late Expanding


Birth rates begin to fall and the death rate continues to fall as well as however, the population growth rises.

4 Low Stationary 


Birth rate and death rate are both low and the population is steady.

5 Declining 


In this stage, population aging and population decline will eventually occur to some extent, presuming that sustained mass immigration does not occur.

Criticisms of the DTM

• The model is MEDC based and the relationship between economic development and population growth does not seem to be the same in LEDCs.

• Some LEDCs are going through the stages much faster as the medical advances have been made, contraception is already in existence and education is widespread.

• It does not take account of natural disasters, epidemics such as AIDS or wars etc.

• It does not take into account government policies designed to manage the population.

• It does not factor in migration, which can have a significant impact on population change.

• Cultural and religious factors have maintained high birth rates in many LEDCs so they are stuck in stage 2.