Cambridge O Level Environmental Management (5014): Human population – Study Guide

Human population is the last topic in the Cambridge O Level Environmental Management 5014 content list, but it underlies most of the others. More people need more food, water, energy and land, and so population change puts pressure on every environmental system you have studied. This guide covers where people live and how populations are made up (7.1), why populations grow or shrink (7.2) and how governments try to influence population size (7.3).

Where this fits in the specification

Use this topic as a source of linking arguments. Rising population drives deforestation (Topic 5), demand for farmland and soil erosion (Topic 2), water stress and energy use. At the same time, remember that environmental impact depends on consumption as well as numbers: one person in a high-income country usually uses far more resources than one person in a low-income country.

7.1 Population density, distribution and structure

Population density is the average number of people per unit area, usually per square kilometre.

Population density = total population / land area.

Distribution describes where people live within an area. Distribution is uneven because of physical factors (flat land, fertile soil, fresh water, mild climate, mineral resources) and human factors (jobs, services, transport links, government policy, safety).

Sparsely populated places tend to be deserts, mountains, polar regions and dense forests. Densely populated places tend to be river valleys, coastal plains and cities.

Age and sex structure

A population pyramid shows the percentage (or number) of males and females in each age group.

• A wide base with a rapid narrowing means high birth rates and a high death rate among older groups (a young population, typical of low-income countries).
• A straighter-sided pyramid means low birth and death rates and long life expectancy.
• A narrow base with a bulge in older groups indicates an ageing population.

The dependency ratio compares dependants (children under 15 and adults over 64) with the working-age population. A high ratio puts pressure on workers and public services.

7.2 Human population size

Population size changes because of three things:

• Birth rate: live births per 1 000 people per year.
• Death rate: deaths per 1 000 people per year.
• Migration: movement into (immigration) and out of (emigration) an area. Net migration is immigrants minus emigrants.

Natural increase = birth rate - death rate.

Rates per 1 000 are changed into a percentage by dividing by 10.

Why growth rates differ

Birth rates are higher where child mortality is high, where children help with farm work, where contraception and education for girls are limited, and where cultural or religious views favour large families. Birth rates fall as women gain education and paid work, as healthcare improves, and as urban living makes children more costly. Death rates fall with better food, clean water, sanitation and medicine, which is why many countries have grown quickly in the last century: death rates fell before birth rates did.

Some countries now have natural decrease because birth rates have fallen below death rates. Migration may then be the only source of growth.

Reasons for migration include push factors (unemployment, conflict, natural disaster, famine) and pull factors (jobs, safety, education, healthcare).

Worked example: natural increase and doubling time

A country has 8 400 000 people living on 1 200 km2. Its birth rate is 22 per 1 000 and its death rate is 8 per 1 000.

Density = 8 400 000 / 1 200 = 7 000 people per km2.

Natural increase = 22 - 8 = 14 per 1 000, which is 1.4% a year.

Extra people in one year (ignoring migration) = 8 400 000 x 14 / 1 000 = 117 600.

A quick estimate of how long the population would take to double uses the rule of 70: 70 / 1.4 = 50 years. This assumes the rate stays constant, which rarely happens, so quote it as an estimate.

Now include migration. Suppose 30 000 people arrive and 18 000 leave in the same year. Net migration = +12 000, so total change = 117 600 + 12 000 = 129 600, and the new population is 8 529 600.

Effects of population change

A rapidly growing population means shortages of housing, jobs and food, pressure on schools and hospitals, more waste and pollution, and loss of natural habitats. A shrinking or ageing population means fewer workers, higher pension and healthcare costs, and empty rural areas. Overpopulation (too many people for the resources available) and underpopulation are both used in discussion, but always give evidence rather than just using the words.

7.3 Managing human population size

Strategies depend on whether the aim is to slow growth or to encourage it.

Slowing growth (anti-natalist):

• Family planning services and free or cheap contraception.
• Education, particularly for girls, which tends to delay marriage and reduce family size.
• Improving healthcare so that parents are confident children will survive.
• Government laws or incentives, such as tax benefits for smaller families or, in some places, strict limits on the number of children (these raise human-rights concerns and can lead to an imbalance between boys and girls and a faster-ageing population).
• Raising the status of women and giving them access to paid work.

Encouraging growth (pro-natalist): payments to families, paid parental leave, subsidised childcare and housing support in countries with low birth rates.

Managing migration: quotas or visas, support for rural development to reduce the pull of cities, and international aid in source countries.

When evaluating a strategy, look at how effective it is, how quickly it works, how much it costs and whether it respects individual choice. Education and healthcare are slower but are widely seen as more acceptable than compulsion.

Common mistakes

• Giving density as people per square metre or forgetting the unit entirely.
• Using “birth rate” when the question asks for natural increase.
• Forgetting to convert per 1 000 into a percentage. 14 per 1 000 is 1.4%, not 14%.
• Describing a population pyramid without reading values from it. Quote the age group and percentage.
• Treating anti-natalist policies as having no downsides.

Exam technique

For calculate questions show your formula, substitution and answer with units. For describe the pattern on a map or pyramid, give the overall trend, then cite one or two specific values and one exception. For explain questions, link a cause to a population change (for example, falling child mortality leads to parents choosing fewer children). In evaluate questions, weigh a policy’s benefits against its limits and decide for which country it is best suited.

Check your understanding

1. Calculate density for 3 600 000 people in 900 km2. 3 600 000 / 900 = 4 000 people per km2.
2. A country has a birth rate of 30 and a death rate of 10 per 1 000. State its natural increase as a percentage. 20 per 1 000 = 2.0%.
3. Use the rule of 70 to estimate the doubling time at 2.0% growth. 70 / 2.0 = 35 years.
4. Give two push factors for migration. Unemployment and conflict (or famine, natural disaster).
5. What does a wide-based population pyramid show? High birth rates and a young population.
6. Explain how educating girls can lower the birth rate. Educated girls tend to marry later, find paid work and use family planning, so have fewer children.
7. State one problem of an ageing population. Fewer workers support more pensioners, raising healthcare and pension costs.
8. Give one criticism of a strict limit on family size. It restricts personal freedom and can cause a gender imbalance and a rapidly ageing population.

Frequently asked questions

How do you convert a birth rate or natural increase per 1 000 into a percentage? Divide the rate per 1 000 by 10. For example, a natural increase of 14 per 1 000 is 1.4% a year.

What is the rule of 70? The rule of 70 estimates how long a population would take to double: divide 70 by the annual percentage growth rate. A growth rate of 1.4% a year gives a doubling time of about 50 years.

What are push and pull factors in migration? Push factors drive people away from a place, such as unemployment, conflict, natural disaster or famine. Pull factors attract people to a new place, such as jobs, safety, education and healthcare.

What is the difference between anti-natalist and pro-natalist policies? Anti-natalist policies aim to slow population growth, for example through family planning and education for girls. Pro-natalist policies aim to encourage growth, for example through payments to families, paid parental leave and subsidised childcare.

What does a population pyramid with a narrow base show? A narrow base with a bulge in the older age groups indicates an ageing population.