S-Cool Revision Summary
S-Cool Revision Summary
- The term 'population density' is used to describe the pattern of where people live in the world.
- There are many reasons for the differences in population density. They can be divided into physical factors and human factors.
- Physical reasons include accessibility, climate, relief, resource, soil and vegetation.
- Human reasons include economic factors, political factors and social factors.
The population of the world grows according to two factors: birth rate and death rate. The relationship between these two is called the natural increase.
The relationship between birth rate and death rate has been used to create a four stage model of a country's population change, called the demographic model.
Stage One: High birth rate (BR) and high death rate (DR).
Stage Two: BR remains high, but DR falls by the end of the stage.
Stage Three: BR falls rapidly, and DR continues to slowly fall.
Stage Four: BR and DR low, at under 10 per 1000.
It has been suggested that a new fifth stage should be added to the model, due to some countries having higher DR than BR.
- Different shaped population pyramids indicate the stage of development that a certain country has reached.
- Population pyramids can indicate the BR and DR of a country.
- Population pyramids can also show the percentage of the population, which is described as being "dependant".
- Population pyramids can be used to help planning for the future also, as they can used to project the percentages of certain age-groups in the population over the next 50 years.
- Migration is defined as a permanent or semi-permanent change in where someone lives.
- Migrations fall into two groups, they can be voluntary (where the migrant decides to move) or forced (where the migrant has little choice but to move).
- The decision to migrate can be a very complex one, or could simply be for one reason. The migration normally involves considering the positive aspects of the move (called the pull factors) and the negative reasons for the move (called the push factors).
- Push factors are the things encouraging someone to move from a place.
- Pull factors are the things that entice someone to a new place.
- En-route factors, or intervening obstacles, are things that might hinder the migration.
- Refugee movement (forced migration). Example: The Kosovo Albanians: March 1999.
- The most common example of voluntary migration is the movement of people from rural areas to urban areas. This is called rural to urban migration.
- In LEDC's the movement to urban areas is even greater than in MEDC's. This is sometimes called "the bright lights syndrome".
- World population growth is increasing, and is already causing many problems.
- The population growth in the LEDC's could lead to a range of problems including: urban areas will become increasingly overcrowded, the problem of massive unemployment will occur, as well as more pollution and traffic congestion.
- The drop in birth rates, as well as the increasing life expectancy of people in MEDC's, has led to problems in these countries also. As the percentage of elderly dependants increases, there will be less people of working age to support a larger dependant population. Health care resources will have to be increased.
- In 1798 Thomas Malthus produced an interesting theory on how population and food resources might continue. He said that as the population continued to grow at a geometric rate, it would slowly catch up the food supply, which only grew arithmetically.
- In 1965 Esther Boserup put forward a different theory claiming that humans will develop new technologies to increase food production whenever they need to.
- Countries, such as Japan and the Netherlands have tried to increase the land available for their growing urban areas by reclaiming land from the sea and draining marsh lands.
- Some developed countries have tried to boost their declining populations by encouraging the in-migration of migrant workers.
- Population policies have been introduced in some countries to try to curb the rapid growth.
- Education in contraception and family planning has become very important.
- Irrigation schemes have been vital in increasing the agricultural yields of many areas of the developing world.