Population models

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Population models

It is possible you will be asked about the consequences of Population growth. Firstly, it is important that you appreciate two contrasting viewpoints.

The first is from Malthus, who was writing at the end of the 18th century. He believed that only bad could come from population growth. Population he said grows faster than food supply. This he said was because food supply can only grow arithmetically, for example, 1 then 2 then 3-4-5-6-7-8 but, population grows geometrically 2-4-8-16-32-64.

Consequently, there is no way food supply can keep up with population growth.

Growth of population and food supply

Population grows exponentially, for example, 1-2-4-8-16-32-64.

Food supply grows arithmetically, for example, 1-2-3-4-5-6.

Therefore, population will inevitably exceed food supply.

He then went on two say that there are two possible outcomes.

Firstly, he said population could exceed food supply only to be positively "checked" (reduced) by famine, war, and disease.

Malthus' positive checks

* Population exceeds food supply and is kept in check by war, famine, or disease. It then drops below the food supply. As the population recovers, so the cycle continues.

Alternatively, the population could pre-empt the food shortages and so slow their population growth keeping it within the limits of the food supply. Malthus called these negative checks. These negative checks would include later marriages and abstinence from sex (Remember Malthus was writing before wide spread contraception!). People would make these decisions sub-consciously as food prices increased and standard of living fell.

Malthus' negative checks

* Here, as population starts to approach the limits of the food supply, so growth slows. Malthus says this slowing is caused by delayed marriage.

Boserup, on the other hand, said that food supply would increase to accommodate population growth. As a population found that they were approaching food shortages they would identify ways of increasing supply whether through new technology, better seeds, new farming methods. In the graph you can see that food supply will increase with population:

Boserup's theory

* Boserup argues that as the population approaches the limits of the food supply, that food supply increases as new technology improves yeilds.

So who is correct? The following table lists arguments for both sides:

Evidence for Malthus: Evidence for Boserup:
Famines are frequently happening in less developed world countries. These are also often in countries that have a fast growing population. There is enough food to feed the world - this is an indisputable fact. The problem lies with distribution - it is not always where it is needed.
Whilst a very old theory Malthus can be adapted for today if we say that increasing population cannot be sustained by the environment. The 'Club of Rome' applies Malthusian ideas to the modern world and says that if population continues to grow our attempts to cater for it will lead to great environmental disasters. This would include global warming, oil spillage, ozone depletion, desertification. Famine is more likely to be the result of a natural disaster, war or the country growing too many cash crops. Cash crops are grown to sell overseas - such as cotton or tea. In times of famine the countries are often producing large cash crop harvests. They need the money to try and pay off foreign debts.
Malthusian supporters argue that everything at the moment may appear ok but this doesn't mean we won't face future disasters. New farming machinery and re-organisation has greatly increased the efficiency of farms and consequently the yields.
A lot of people believe that future conflicts could be fought over water supplies. Is Malthus' idea correct except that he should have replaced food with water? The green revolution produced seeds that could increase yields by up to eight times.