Topic 3.7

Limits to Growth

Human Population Growth• Carrying Capacity– The maximum number of individuals of a species that

can be sustainably supported within a habitat. It occurs when birth rate is equal to death rate

• But does this really apply to human populations?• Do human populations actually have a carrying

capacity?• Well, there are many examples of direct and

indirect effects of drought, famine and war which act to reduce populations when they grow too large

Human Population Growth• Size of population isn’t the only factor which impacts

on natural resources• Other factors include:– Wealth (MEDC or LEDC)– Resource desire– Resource need (or use)– Age distribution– Rural or urban populations– Time (it is dynamic)

80% of the world’s population lives in MEDCs where birth rate is falling (or negative, e.g.Japan)20% of the world’s population lives in LEDCs where birth rate is increasing

Malthusian Theory

• Malthus believed that human populations grow exponentially, but resources only grow arithmetically (limited by land availability and existing technology)

• Food production can only therefore increase to a certain level

• Above this level, soil erosion and decreasing soil fertility cause productivity to decrease

• A natural check on population occurs

Thomas Malthus

Boserup Theory• An increase in population will simply stimulate

scientists to come up with ideas to increase food production

• “Necessity is the mother of invention”• Productivity has been increased by:

– Reclaiming land from the sea– Selective breeding and cross breeding– Developing high-yield plants – Genetic modification– Terracing– Hydroponics– Greenhouses– Irrigation– Artificial fertilisers– Switching to new crops (e.g. soya)– Fish farming

Ester Boserup

ProblemsMalthusian Theory Boserup Theory

Malthus assumes a ‘closed system’ of human population

Bosrup assumes a ‘closed system’ of human population

The distribution of food resources is not fair and equitable. Only the poor really suffer from lack of food

There are examples where human activities have led to desertification of huge tracts of land

Malthus could not have predicted the amazing changes in technology

In LEDCs, food shortages lead to emigration rather than innovation

Food resource availability has not really increased ‘arithmetically’

Innovation occurs in MEDCs and is not always shared with LEDCs

Malthus did not predict the globalisation of food supply

Perhaps both theories work, but in different ways. Malthus was referring to environmental limits, while Boserup refers to cultural and technological issues

https://www.youtube.com/watch?v=dN06tLRE4WE

Can Carrying Capacity Change?• If we cut down on our use of natural resources• It may be achieved by:– Recycling (reprocessing materials into new

products)– Re-use (returning materials to the manufacturer of

processor, or finding new uses ourselves)– Reduction (using less energy or resources)– Substitution (switching to renewable resources

from non-renewable)

https://www.youtube.com/watch?v=E8dkWQVFAoA

Questions1. Explain why it is difficult to apply the idea of

carrying capacity to a human population2. List and explain ways in which human

behaviour may increase our carrying capacity3. Compare and contrast the Malthusian and

Boserup theories of human population growth