Natural Increase & Urban Growth

Natural Increase

Natural increase is the difference between the birth rate and the death rate of a population. It shows how much a population grows or shrinks naturally, without considering migration.

The formula for natural increase is:

Both birth rate and death rate are usually measured per 1,000 people per year.

Causes of natural increase:

• Improved healthcare: Advances in medical care reduce death rates, especially infant mortality, meaning more babies survive.
• Lower infant mortality: Better nutrition, vaccinations, and sanitation mean fewer babies die in their first year.
• Higher birth rates: In some areas, cultural or economic factors encourage larger families.

Natural increase leads to a rise in population size if birth rates exceed death rates. This growth affects the age structure, often increasing the proportion of young people.

For instance, if a country has a birth rate of $30 \text{ per } 1,000$ and a death rate of $10 \text{ per } 1,000$, the natural increase is:

This means the population grows by 20 people per 1,000 each year, ignoring migration.

Urban Growth

Urban growth is the increase in the population living in urban areas (towns and cities). It is caused by two main factors:

• Natural increase within urban populations (more births than deaths in cities).
• Rural-urban migration, where people move from countryside areas to cities seeking jobs and better services (covered in other topics; see 'Migration (Push-Pull Factors)').

Globally, urban growth is happening fastest in developing countries, especially in Asia and Africa. Many countries have seen rapid urbanisation over recent decades as more people move to cities and birth rates remain high.

The global pattern of urbanisation shows:

• High-income countries tend to have slower urban growth and lower birth rates.
• Low- and middle-income countries have faster urban growth due to higher birth rates and migration.
• By 2050, it is predicted that about $68\%$ of the world’s population will live in urban areas.

For example, in the UK, urban growth has slowed compared to some developing countries, but cities like London still grow due to natural increase and migration.

Example: If a city has an urban population of 1 million and a natural increase rate of $15 \text{ per } 1,000$ per year, the population will grow by:

So, the city’s population increases by 15,000 people in one year due to natural increase alone.

Effects of Natural Increase on Urban Areas

Natural increase in urban areas creates several challenges, especially in rapidly growing cities:

• Pressure on housing: More people need homes, often leading to overcrowding or the growth of informal housing (slums or shanty towns).
• Demand for services: Increased population means greater need for schools, hospitals, water supply, electricity, and waste disposal.
• Infrastructure strain: Roads, public transport, and sanitation systems may become overloaded, causing traffic congestion and pollution.
• Urban planning challenges: Rapid growth can outpace city planning, making it hard to provide adequate facilities and maintain quality of life.

For example, in cities with fast natural increase, local governments may struggle to build enough affordable housing or expand healthcare services quickly enough.

Example: If a city’s population grows by 20,000 people in a year due to natural increase, and the average household size is 4, the city needs:

new homes just to accommodate the natural increase in population.