3.2.4.5 Principles of population ecology and their application to human populations
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3.2.4.5 Principles of population ecology
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AQA
Notes on:
- Population growth dynamics. Concepts of overpopulation, underpopulation and optimum population. Implications of population size and structure for the balance between population and resources; the concepts of ‘carrying capacity’ and ‘ecological footprint’ and their implication...
3.2.4.5 Principles of population ecology and their application to human
populations
Types of resources:
- Natural (e.g. water, soil)
- Human (e.g. enterprise, education)
- Renewable (e.g. solar energy, forests)
- Non-renewable (e.g. fossil fuels, minerals)
The rate at which resources are consumed is strongly influenced by population and
development. Population growth enriches human resources (such as labour and enterprise)
it also raises the demand for, and the exploitation of, resources.
Population growth depends on:
- Fertility rates, which globally have fallen from about 4.3 in 1970 to just below 2.5
today – they may continue to fall, stabilise, or rise.
- Mortality rates, which in turn are influenced by general health, disease, conflict and
other factors.
The rate at which people use resources is critical. Industrialising countries such as China,
India and Brazil have generated much of the recent demand for oil, fish, water and meat. As
these nations develop, people move into the middle class and substitute cars for bicycles,
meat and rice, and indoor plumbing for wells.
Demand for resources is expected to grow faster than population growth. These resources
include oil, ores and minerals. Some resources, such as wild marine fish, appear to have
reached peak production. Resource peaks need not lead to crisis however because humans
can develop alternative technologies and substitute resources. These alternatives need to
be sustainable. The world has become globalised, allowing resources to move freely from
one country to another. World trade fills in many of the resource ‘gaps’ so that shortages
are rare. This will continue to work provided trade flow is not derailed by rising resource
nationalism and huge price rises. However, derailment is likely to occur for those resources
where no alterative resource or technology exists to take the place of a dwindling supply.
If there is the ability for development and the resource base to sustain rising levels of
consumption, there is the promise that rising levels of human welfare, standard of living,
well-being and quality of life. If this capability does not exist, deterioration in the condition
of the population seems inevitable. The nature of the balance between resources,
development and population growth that is of paramount importance. Three different
states of ‘balance’ may be recognised, each at the national and individual levels:
- Over-consumption – at a national level occurs when, and where, population growth
races ahead of the current availability of resources and the present level of
economic development. It involves low standards of living, and its symptoms include
poverty, malnutrition, disease and environmental damage. However, at a personal
level, over-consumption involves affluence, a profligate use of resources and obesity.
- Under-consumption – at a national level is rare today. It exists where resources and
development could support a larger population without any serious depletion of
, known reserves. Under-consumption at an individual level is widespread; involving
poverty, malnutrition, disease and short life expectancy.
- Sustainable consumption – sought after but difficult to achieve nationally. It requires
a stable population, innovative development and the consumption of renewable
rather than non-renewable resources. The living standards of future generations are
not threatened by present consumption.
Population theories
- Malthus (1798) – argued that food supply act as a ceiling to population growth and
that population growth takes place at a faster rate than the increase in food supply.
- Boserup (1965) – argued that population growth stimulates increased food supply,
either by improving the productivity of farming or by importing supplies.
- The Club of Rome (1972) – predicted that if the current trends in population growth,
industrialisation, food production, pollution and resource depletion where
maintained, the limits to global population growth would be reached within 100
years. Population would then decline. Before that point, policies could be introduced
to decrease fertility and therefore lower the rate of population increase.
Population ecology applied to the human population
Developments in technology, improved food supplies, sanitation and healthcare have been
the main reasons behind the exponential growth in population over the past two hundred
years. In effect, human population has overcome much of the environmental ‘resistance’
that was limiting growth. For the last 200 years, human population has been through a ‘log
phase’ of exponential growth. World population is still growing rapidly although the rate of
growth is starting to slow down.
The combination of climate, land size and number of people affects the level of over/ under
population.
, Optimum population = refers to a population size in an area which, working with all the
resources, will give the highest standard of living for the people of that area. It maximises
the income per capita and is a balance which most nations will try to achieve through direct
or indirect population or resource management. It is constantly changing, for example the
development of new technology may increase the resources available.
Overpopulation = exists when there are too may people in the area relative to the available
resources, putting pressure on those resources. A continued increase in population will
reduce the average quality of life for all. With no advances in technology and no increase in
resources, only a fall in population may increase living standards.
Underpopulation = occurs when there are too few people to use the resources efficiently
for a given level of technology. An increase in population would mean a more effective use
of resources and increased living standards for all. Developed countries with access to
resources and advanced technology but with relatively small population such as Canada,
Australia and Norway are examples of underpopulated countries and with the potential to
support larger populations.
Characteristics of overpopulation and underpopulation compared
Overpopulation Underpopulation
Low per capita income/ poverty High per capita income (not maximised)
Unemployment/ underemployment Low unemployment
Outward migration Inward migration
Insufficient food, minerals and energy Good living conditions
resources
Prone to natural disasters High levels of technology
War, conflicts, tribalism
➢ Biosphere = the biological component of Earth systems (the others being
atmosphere, hydrosphere and lithosphere) .
➢ Carrying capacity = the maximum population size that an area or environment can
sustain indefinitely.
➢ Ecological footprint = a measure of the demand placed by humans on Earth’s natural
ecosystems.
➢ Overshoot = an ecological term referring to a point when the population and its
associated consumption of resources exceed the long-term carrying capacity of its
environment.
➢ Total productive bio-capacity = all the food, water and energy resources produced by
the Earth’s natural systems annually to sustain us.
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