Topic 3 – human population, carrying capacity


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Topic 3 – human population, carrying capacity

  1. 1. Topic 3 – Human Population, Carrying Capacity and Resource Use
  2. 2. 3.8 Environmental Demands of Human Populations • An ecological footprint is the hypothetical area of land needed by an individual, group or society to fulfil its resource needs and assimilate all waste • An ecological footprint is not necessarily sustainable. It may refer to an unstable equilibrium (not that carrying capacity is real rather than hypothetical, and refers to a steady state equilibrium).
  3. 3. Ecological Footprint • A country with a total ecological footprint greater than its available land is in theory living beyond its means
  4. 4. Factors affecting ecological footprint • A large footprint could be caused by: – Reliance on fossil fuels – Increased use of technology (depending on its use) – High levels of importation – Large production of carbon waste – High food consumption – Meat-rich diets • Footprint could be reduced by: – Reduced resource consumption – Recycling and reuse of resources – Improved efficiency of resource use – Reduced pollution – Exportation of waste – Use of technology (to increase carrying capacity and efficiency of land use) – Reduced population
  5. 5. Approximate Ecological Footprints (2003) • USA – 10.3 ha cap-1 • Australia – 9.0 • Canada – 7.8 • Germany – 5.3 • UK – 5.2 • Switzerland – 5.1 • Mexico 3.0 (2007 data) • China – 1.6 • India – 0.8 In 2003, there were approx. only 1.8 ha available per person (including productive marine areas). Therefore many of us are living beyond the Earth’s ability to sustain the population Which country do you think currently has the largest ecological footprint?
  6. 6. Calculations • Ecological footprint is usually calculated in hectares • 1 hectare = 10 000m2 • This is aproximately the size of a football field (0.6-0.8 ha) or the field inside a 400m athletics track (about 1.2 ha) • The 2 basic calcs usually carried out are 1. Per capita land (and water) required for food consumption 2. Per capita land (and water) required for carbon waste absorbtion • They are are added together to give the total footprint
  7. 7. Calculations Per capita land requirement for food production (ha cap-1) = per capita food consumption per year (kg cap-1 yr-1) mean food production per hectare per year (kg ha-1 yr-1) Per capita land requirement to assimilate carbon waste (ha cap-1) = per capita CO2 emission per year (kg cap-1 yr-1) total CO2 fixation by vegetation per year (kg ha-1 yr-1) +Food given as kg equivalents of grain
  8. 8. Problems with the Calculation • It doesn’t consider the effects of pollutants other than CO2 • It doesn’t consider land (or water) needed to assimilate wastes other than CO2 • It doesn’t consider land lost through urbanisation
  9. 9. MEDCs vs LEDCs more/less economically developed countries 1. Which has the higher ecological footprint? 2. Why does North America have a particularly high per capita grain consumption? 3. Which are more dependent on fossil fuels? 4. Which has higher CO2 fixation and why? 5. Use the data to calculate per capita footprints: Area Per capita grain consumption kg cap-1 yr-1 Grain production kg ha-1 yr-1 Per capita CO2 emissions kg cap-1 yr-1 Net CO2 fixation by vegetation kg ha-1 yr-1 Africa 300 6000 200 6000 North America 600 300 1500 3000
  10. 10. The Human Population • World Population Clock • The current global birth rate is about 6 per sec • The current global mortality rate is about 3 sec • It took you about 10 seconds to read this, so how much has the world population changed? • How many children could a monogomous couple have in their lifetime and not contribute to population growth?
  11. 11. Policies on population dynamics and growth • There are 2 types of policy: • Pro-natalist (eg. France) • Anti-natalist (eg. China) • Please make notes from the video clips for each policy, and why it has been adopted
  12. 12. Fertility Rates Fertility rate is the mean expected number of children born to a woman in her lifetime (data from 2013 Census)
  13. 13. 2013 List by the CIA World Factbook
  14. 14. Methods of Population Control • Population control may use one or more of the following practices although there are other methods as well: • Contraception • Abstinence • Reducing infant mortality so that parents do not increase their family size to ensure at least some survive to adulthood • Abortion • Infanticide • Improving status of women causing departure from traditional sexual division of labour • War • Emigration • Immigration reduction • Sterilization • Euthanasia