4.3. Population–resource relationships Flashcards
Overpopulation
A situation where the population exceeds the available resources of a country
Under Population
A situation where the population is too small relative to the available resources in a country
Carrying Capacity
The number of individuals an environment can support, taking into account the resources available, without significant negative impacts to individuals and the environment
Population Ceiling
First suggested by Malthus, it is a saturation level where the population equals the carrying capacity of the environment.
Optimum Population
the size of a population that produces the best results according to chosen end targets
The J-Curve
J curves start at a fast exponential growth and then collapses / crashes (diebacks). This happens from overpopulation, where the population can no longer be supported. Where the population exceeds carrying capacity it is called as an overshoot.
The S-Curve
The S-curve starts with exponential growth but after a certain amount of population the growth halts at a constant population amount due to the effect of a limiting factor (in this case the carrying capacity of the environment).
Malthus’ Theory Core Principles
- Population if unchecked, grows at a geometric rate
- Food only increases at an arithmetic rate, land is finite
- The effect of these 2 powers must be kept equal
Malthus’ Theory: “Checks”
Malthus suggested once this ceiling (catastrophe) has been reached, further growth in population would be prevented by negative and positive checks. He saw checks as a natural method of population control. They can be split up into 2 groups
1) Negative Checks were used to limit the population growth. It included abstinence / postponement of marriage which lowered fertility rate
2) Positive Checks were ways to reduce population size by events such as famine, disease, war- increasing the mortality rate and reducing life expectancy.
Malthus’ Theory was right
- There has been a world population explosion
- Africa - repeated famines, wars, food crisis, environmental degradation, soil erosion, crop failure, disastrous floods (positive checks)
- Rwanda - genocidal massacre of 800,000 Rwandans in 1994 was due in part to ethnic hatred but also to population. Too many farmers dividing same amount of land into increasingly smaller pieces that became inadequate to support the farmers family
- China’s one child policy - an example of a negative check. The government was concerned that people soon wouldn’t have enough food to feed themselves and adopted the policy to reduce birth rates.
Malthus’ Theory was wrong
- Technological improvements which he could not foreseen
- The increased amount of cropland due to irrigation
- Reduced population growth as countries move through the Demographic Transition Model. By early 1970s fertility rates around the world dropping and the population growth has fallen since then by over 40%
Boserup’s Theory
Boserup believed that people have the resources of knowledge and technology to increase food supplies. Her theory is opposite to Malthus’s - she suggested that population growth has enabled agricultural development to occur.
- “Necessity is the mother invention” - When we have to, we find a way to increase food production and stay alive
- She assumes that people knew of the techniques required by more intensive systems and used them when the population grew
- Demographic pressure (population density) promotes innovation and higher productivity in use of land (irrigation, weeding, crop intensification, better seeds) and labour (tools, better techniques).
Boserup’s Theory was right
- Boserup argued that the changes in technology allowed for improved crop strains and increased yields
- GM crops
- ‘Green revolution’ - (e.g. High yielding varieties of crop. Example = IR-8 rice)
Boserup’s Theory was wrong
- Some agricultural processes have been proved to be unsustainable in the long run
- Aspects of ‘Green revolution’ (e.g. HYV require lots of water
- Land degradation from intensive farming (e.g. Sahel and desertification, salt marsh reclamation)
- Migration - people move away from over populated areas
Natural Causes of food shortages
- Soil exhaustion
- Drought
- Floods
- Tropical Cyclones
- Pests and Disease