3.2 4.5 Principles of population ecology and their application to human populations

biotic potential

natural reproductive potential of a species (low in humans due to high survival rates)

environmental resistance

mortality rates controlled by environmental factors preventing survival (disease)

biotic potential and environmental resistance applied to human population

overcome 'environmental resistance' through developments in technology and improved sanitation to have exponential growth

concept of underpopulation

too few people to use resources efficiently for a given level of technology

-increase in population will mean these are more effectively used

concept of optimum population

population working with all its resources will give highest standard of living for people of that area

-maximises income per capita, balance maintained by resource management

-constantly changing through development of new technology

concept of overpopulation

too many people in an area relative to available resources, reduce standard of living

characteristics of overpopulation

underemployment, outward migration, conflict

characteristics of underpopulation

inward migration, good living conditions, high levels of technology

What is carrying capacity?

the maximum population size an environment can support indefinitely

-earth can support 10billion at moderate levels of consumption but this will lower if we waste more resources due to comfortable lifestyles

ecological footprint

measure of demand placed by humans placed on earths natural resources

ecological footprint equation

total productive bio capacity/total population

implications of carrying capacity

-'J curve' rise in population overshoots carrying capacity such as Sahel

-globally 'S curve' suggesting population growth rates decline as environmental resistance is encountered, reaching equilibrium

environmental implications of ecological footprint

over cultivation reduces soil quality, degradation of natural ecosystems, more land used for industry

Population, Resources and Pollution Model (PRP)

A model that describes the positive and negative feedback loops between population, resources and pollution.

what does the PRP model demonstrate

-importance between human environment interaction

-uses concepts of positive and negative feedback

-provides insights into sustainable solutions such as encouraging less demand for resources will reduce pollution

-promotes 'system thinking'

positive feedback

enhances changes making a system more unstable and moving it away from equilibrium

positive feedback (PRP)

population increase -> increase agricultural productivity -> food availability increases population -> improves yields support population growth

negative feedback

counters any change to hold system in a more stable equilibrium

negative feedback (PRP)

population increase -> increase agricultural productivity -> soil erosion and infertility -> lack of food available so population declines

Malthus' view of population growth

population growth is exponential and food production is arithmetic so it'll eventually exceed carry capacity and 'crash' due to famine/disease

Malthus' theory positive and negative checks

positive = increased death through war, famine

negative = lower birth rate through abstinence, later marriage

Malthus' theory evaluation

-Congo war over resources 3million deaths

-reduced population growth as countries move through DTM

-technological improvements such as irrigation Rwanda 70% land productive for food

Club of Rome (Neo Malthusian) population growth

-population will rise and decline in 2050

-rapid resource depletion first half 21st century , food decline, industrial output decline and pollution will increase

evaluation of Club of Rome

-human race is adaptable such as renewable energy

-fossil fuels are predicted to run out

Boserup views on population growth

believed human intelligence could alter carrying capacity and enable it to extend upwards in line with population growth

Evaluation of Boserup theory

-biotechnology developments means there is 17% more food available per person compared to 1990

-uneven distribution and political instability still leaves 5 million in Yemen relying on food aid

-carrying capacity may not be improved in vulnerable areas such as India where 1° increase temperature rice yield loss of 20%

Simon's theory

as population has grown so have available resources leaving humans better off such as cropland improving

-climate change may show flaws in this theory