Cambridge IGCSE Environmental Management (0680): Human population – Study Guide

How many people live in a place, where they live and how old they are shape the demand for food, water, energy, housing and services. This topic gives you the measures that geographers and environmental managers use to describe population, then asks you to explain why populations change and how governments try to influence that change. Much of the marking is numerical, so practise the calculations until they are routine.

Where this fits in the course

In Cambridge IGCSE Environmental Management (0680) the topic has three sub-topics: density, distribution and structure; population size; and managing population size. It links to earlier topics because population pressure drives deforestation, water demand and pollution. Questions mix short calculations, graph reading and longer evaluations of policy.

Density, distribution and structure

Population density is the average number of people per unit area, usually per square kilometre: density = total population divided by area. It is an average, so it hides large differences within a country.

Distribution describes where people live. Dense areas are usually found where there is fertile land, a reliable water supply, a mild climate, jobs, trade routes and good infrastructure, while sparse areas are found in deserts, mountains, ice-covered land and dense forest, where conditions make settlement hard.

Structure describes the make-up of a population by age and sex, shown on a population pyramid.

• A wide base and narrow top means many children and a high birth rate with a short life expectancy, typical of lower-income countries.
• A pyramid with straighter sides and a broad middle means lower birth and death rates.
• A narrow base and broad top means an ageing population with few young people.

The dependency ratio compares those usually dependent on others (under 15 and over 64) with the working-age group (15 to 64): ratio = (young + old) divided by working-age x 100.

Population size

Population size changes through births, deaths and migration.

• Birth rate is the number of live births per 1,000 people per year; death rate is the number of deaths per 1,000 per year.
• Natural change = birth rate - death rate. Divide by 10 to turn a rate per 1,000 into a percentage.
• Net migration = immigration - emigration.

Why rates differ

Birth rates are higher where child mortality is high, where children contribute to farm work or support parents in old age, where contraception and education for girls are limited, and where cultural or religious beliefs favour large families. Death rates fall with better healthcare, clean water, sanitation, nutrition and vaccination. Wars, famines and epidemics raise them.

Demographic transition

The demographic transition model describes how birth and death rates change over time as a country develops. In stage 1 both are high and population is stable; in stage 2 death rates fall while birth rates stay high, so population grows fast; in stage 3 birth rates fall and growth slows; in stage 4 both are low and the total is stable or growing slowly. Some versions add a fifth stage in which births fall below deaths. The key explanatory point is that death rates fall first and birth rates follow later.

Doubling time

A quick estimate of how many years a population takes to double is 70 divided by the annual percentage growth rate. It assumes the rate stays constant, which real populations do not.

Managing population size

Governments may want to slow growth, encourage growth or cope with an ageing population.

Aim	Measures	Possible problems
Reduce growth (anti-natalist)	Family planning clinics, free contraception, education for girls, raising the status of women, financial incentives for small families	Cultural resistance, slow results, costs; strict laws can raise ethical issues
Increase growth (pro-natalist)	Child benefit, tax breaks, paid parental leave, childcare	Costly, with uncertain effect
Cope with ageing	Raising retirement age, encouraging skilled migration, pensions reform	Pressure on healthcare and workers

China’s one-child policy, introduced around 1980 and ended in 2015, is a well-known example. It slowed growth but also led to an imbalance between men and women and an ageing population, so it is useful when you need both an advantage and a disadvantage. Evidence suggests that education and wealth reduce birth rates strongly even without compulsion, which is why many experts favour voluntary approaches.

Worked example 1: density and growth

A fictional country has a population of 4.2 million living in an area of 14,000 square kilometres. Its birth rate is 31 per 1,000 and its death rate is 11 per 1,000.

1. Density = 4,200,000 / 14,000 = 300 people per square kilometre.
2. Natural change = 31 - 11 = 20 per 1,000.
3. As a percentage = 20 / 10 = 2.0 per cent per year.
4. Doubling time = 70 / 2.0 = 35 years.
5. Increase next year = 4,200,000 x 0.02 = 84,000 people, ignoring migration.

Worked example 2: dependency ratio

A town has 12,000 people aged 0 to 14, 54,000 aged 15 to 64 and 9,000 aged 65 and over.

1. Dependents = 12,000 + 9,000 = 21,000.
2. Dependency ratio = 21,000 / 54,000 x 100 = 38.9, to one decimal place.

This means about 39 dependants for every 100 people of working age. If the old-age group rises to 15,000 while the rest stay unchanged, the ratio becomes 27,000 / 54,000 x 100 = 50.

Common mistakes

• Forgetting to convert natural change per 1,000 into a percentage before using the 70 rule.
• Treating density as evenly spread across the country.
• Saying that birth rate and death rate both fall at the same time in stage 2.
• Ignoring migration when the question gives migration data.
• Describing a policy without stating its drawback.

Exam technique

When reading a population pyramid, give the shape, then the figures with units, then the meaning, such as a high birth rate. For calculations, write the formula, substitute, and give the answer with units or a percentage sign. For policy questions, name the measure, explain how it should change birth or death rates and add one limit. If the question says evaluate, give a judgement about which measure works best and why, in the context given.

Check your understanding

1. Define population density and give its usual unit. (People per unit area, normally per square kilometre.)
2. Why do death rates usually fall before birth rates in the demographic transition? (Health, food and sanitation improve quickly, whereas attitudes to family size change slowly.)
3. Calculate natural change as a percentage when birth rate is 18 and death rate is 8 per 1,000. (10 per 1,000, which is 1.0 per cent.)
4. Using 70 divided by the growth rate, estimate the doubling time at 1.4 per cent. (50 years.)
5. Give two reasons some areas have very low population density. (For example harsh climate and difficult relief, such as desert or mountains.)
6. Give one advantage and one disadvantage of a strict one-child style policy. (Slows growth; can cause a gender imbalance and an ageing population.)
7. A population has 20,000 aged under 15, 5,000 aged over 64 and 50,000 aged 15 to 64. Find the dependency ratio. (25,000 / 50,000 x 100 = 50.)
8. Name two non-compulsory ways to lower birth rates. (Education for girls and access to family planning.)

Frequently asked questions

How do you calculate population density? Divide the population by the area, usually giving the answer in people per square kilometre. Density is an average, so people are not evenly spread across the whole area.

What are the stages of the demographic transition model? In stage 1 birth and death rates are both high; in stage 2 death rates fall while birth rates stay high, so population grows fast; in stage 3 birth rates fall and growth slows; in stage 4 both are low. Some versions add a fifth stage in which births fall below deaths.

What is the dependency ratio? The dependency ratio compares those usually dependent on others (under 15 and over 64) with the working-age group (15 to 64): add the young and old, divide by the working-age group and multiply by 100.

Why are birth rates higher in some countries? Birth rates tend to be higher where child mortality is high, where children help with farm work or support parents in old age, where contraception and education for girls are limited, and where cultural or religious beliefs favour large families.

How should I read a population pyramid in Cambridge IGCSE Environmental Management 0680? Describe the shape, then quote figures with units, then explain the meaning, such as a high birth rate. A wide base and narrow top shows many children, while a narrow base and broad top shows an ageing population.