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Topic 8: Human populations and urban systems

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  1. 8.1 Human populations

    1. • Births and immigration • Crude birth rate, immigration rate

    2. • Deaths and emigration are outputs from a human population • Crude death rate (number of deaths per 1,000 people in a population per year) and emigration rate (number of emigrants per 1 • The rates can be used at a variety of scales—from small urban areas, like a town, to a country to a region or to the global population

    3. • Population dynamics can be quantified and analysed by calculating total fertility rate, life expectancy, doubling time and natural increase • Total fertility rate is the average number of births per woman of childbearing age • Life expectancy is the average number of years that a person can be expected to live, usually from birth, if demographic factors remain unchanged • Doubling time is the number of years it would take a population to double its size at its current growth rate; it can be calculated by using the rule of 70

    4. • The global human population has followed a rapid growth curve • Models are used to predict the growth of the future global human population • UN projection models indicate three scenarios linked to future fertility rates • There is uncertainty about how future human fertility rates may change, leading to the three scenarios in the models

    5. • Population and migration policies can be employed to directly manage growth rates of human populations • These may be anti-natalist or pro-natalist, thereby directly addressing birth rates, or they may address immigration and emigration • These policies may use a variety of cultural, religious, economic, social and political factors to achieve their aims • Include: named examples

    6. • Human population growth can also be managed indirectly through economic, social, health, development and other policies that have an impact on births, deaths or migration • Many development policies addressing areas such as, but not limited to, gender equality, education, improvements in public health and welfare will indirectly affect births • Include: two named examples

    7. • The composition of human populations can be modelled and compared using age–sex pyramids • The pyramid is measured in absolute numbers or as a percentage of the total population • It shows the proportion of the population of either gender in each age group

    8. • DTM describes changing birth and death rates through stages of development • Used to analyse population change over time

  2. 8.2 Urban systems and urban planning

    1. • Biotic components: plants, animals, life forms • Abiotic components: soil, water, air, climate, topography

    2. • Built-up area with high population density • Buildings and infrastructure • Cities, towns, suburbs

    3. • Buildings, microclimate, transport, goods/services • Power/energy, water/sewage, humans, plants, animals

    4. • Population shift from rural to urban areas • Land becomes more built-up and industrialized

    5. • Greater proportion now live in urban systems • Push-pull factors, forced vs. voluntary

    6. • Movement from dense central to lower-density peripheral areas • Urban sprawl

    7. • Loss of agricultural land, forests, ecosystems • Water quality changes, river flow changes, air pollution

    8. • Decide best land and building use • Meet stakeholder needs: physical, domestic, environmental, commercial

    9. • Quality housing, public transport, green spaces • Renewable resources, waste recycling, energy efficiency

    10. • Treats urban system as ecosystem • Urban ecology: green spaces, wildlife habitats • Urban farming: beekeeping, horticulture, city farms • Biophilic design: green walls/roofs, water features, natural light • Resilience planning: vertical farming, flood-adaptive building • Regenerative architecture: air-scrubbing building skins, energy export

  3. 8.3 Urban air pollution

    1. 8.3.1Urban air pollutants

      • NOx, sulfur dioxide, carbon monoxide, particulate matter • PM2.5 (≤2.5 µm), PM10 (≤10 µm)

    2. 8.3.2Primary pollutant sources

      • Natural: forest fires, dust, volcanic eruptions • Anthropogenic: burning for clearance, fossil fuels, construction dust

    3. 8.3.3Fossil fuel combustion

      • Most common urban air pollutants • Primary: PM2.5, PM10, CO, SO₂ • Secondary: tropospheric ozone

    4. 8.3.4Management strategies

      • Public transportation, cycling infrastructure, trees • Green walls, catalytic converters, pedestrianized areas

    5. 8.3.5Acid rain formation

      • NOx + SO₂ react with water and oxygen • Produces nitric and sulfuric acid

    6. 8.3.6Acid rain impacts

      • Terrestrial: soil leaching, toxification, foliage damage • Freshwater: toxicity, impacts on fish/invertebrates • Buildings: corrosion of marble, limestone, steel • Human health: tissue damage, lung inflammation

    7. 8.3.7Acid rain management

      • Alter human activity (alternative energy) • Control at release (scrubbers, catalytic converters) • Restore damaged systems (healthcare, lake treatment)