Population and Pollution Notes

Population Changes

Population Dynamics

  • Population dynamics describe how populations change in size.

  • Size is affected by the ratio of births to deaths.

  • More births increase the size of the population.

  • More deaths decrease the size of the population.

  • Also affected by immigration or emigration.

Growth Rate

  • Birth rate = # births for a specific number of individuals in a specific time.

  • Death rate = # deaths for a specific number of individuals in a specific time.

  • Growth rate = difference between birth rates & death rates.

  • Example:

  • 20 births per 100 individuals per year.

  • 5 deaths per 100 individuals per year.

  • (20−5)/100=0.15∗100%=15%(20-5)/100 = 0.15 * 100\% = 15\% growth rate.

Age Structure

  • Relative number of individuals in each age category.

  • "Age" categories typically pre-reproductive, reproductive, & post-reproductive.

  • Why classify age this way?

  • Only individuals in the reproductive group contribute to population growth (births).

Growth Curves

  • Carrying capacity (K): # individuals that the environment can support.

  • Exponential growth:

  • Unrestricted growth, constant rate.

  • Requires adequate resources.

  • J-shaped curve.

  • Logistic growth:

  • Growth slows near K.

  • S-shaped curve.

Human Growth Curve

  • Shows estimated population from 1000 AD to the present day for different regions.

Factors Affecting Growth

  • Density-dependent: affect population growth more intensely as population gets larger.

  • Density-independent: affect population growth not related to population size.

Earth's Resources

Earth’s Carrying Capacity

  • Variable estimates, 5 – 20 billion people.

  • Depends on resource availability and choices.

  • Ecological footprint: resources needed to support a person’s lifestyle.

  • Wealthier populations have larger ecological footprints.

Earth's Carrying Capacity

  • Ecological creditors and debtors:

  • Ecodebt: Footprint more than 50% larger than biocapacity.

  • Ecocredit: Biocapacity more than 50% larger than footprint

Depletion of Resources

  • Desertification: grazing & farming increase soil erosion.

  • Deforestation: trees removed faster than replaced.

  • Overfishing: depletes fish populations.

  • Water shortages: freshwater used faster than replenished.

Tragedy of the Commons

  • Shared resources become easy to exploit.

  • Some benefit, but costs are shared.

  • Resource is overexploited and ruined for everyone.

Pollution and Climate Change

Water Pollution

  • Surface water: above-ground water bodies, polluted by various substances.

  • Groundwater: below-ground water sources, polluted by leaks and spills.

Air Pollution

  • Ozone (O3O_3) can be a pollutant and also blocks UV radiation.

  • CFCs are a major culprit of ozone breakdown.

Climate Change

  • Climate: Mean temperature, rain/snowfall, humidity for a region over many years.

  • Different from weather, which is short-term.

Climate Change

  • Climate change: changes in weather patterns over years.

  • Global climate is warming, mainly due to greenhouse gases.

Greenhouse Gases

  • Greenhouse gases: trap heat in the atmosphere.

  • Examples: Carbon dioxide, Methane, Nitrous oxide, CFCs.

Effects of Global Warming

  • Melting ice caps à rising sea levels.

  • Changing weather patterns.

  • Effects on human health: heat events, respiratory disease.

The Choice is Ours

  • Individuals, governments, and corporations need to change.

  • Preserve our planet through various actions and accountability.