IB ESS Topic 8.1 Notes: Human Populations and Urban Systems (HL)

IB ESS: Topic 8.1 Notes on Human Populations (HL)

Population Growth and the Planet

  • Guiding questions framing the unit:

    • How can the dynamics of human populations be measured and compared?

    • To what extent can the future growth of the human population be accurately predicted?

  • Task themes across pages: discuss course learnings and evidence; consider factors that could alter population projections.

  • Drivers of population change (Page 5):

    • Fertility (births)

    • Mortality (deaths)

    • Migration (movement)

  • Projections and competing forecasts:

    • UN projection: world population levels out at about 10 imes 10^9 (10 billion) by the end of the 21st century (2100) and begins to decline thereafter.

    • Other organizations (e.g., Lancet) project a peak of about 9.7 imes 10^9 (9.7 billion) around 2060, followed by a decline.

    • Key question: what factors discussed in SL could shift these trajectories (e.g., education, gender equality, health care, policy, economic development, climate impacts)?

  • Regional patterns and drivers (Page 6):

    • Most population growth expected to come from Africa due to:

    • Lower gender equality and education for women (reproductive health, access to education).

    • Limited access to quality health care.

    • Europe: expected to decline due to higher female education and workforce participation, and higher living costs.

  • Conceptual framework: the Doughnut Economics model (Page 7–9):

    • Biocapacity disparity and crossing social foundations/planetary boundaries are visualized as a doughnut.

    • The doughnut hole (center) represents the proportion of people lacking essentials (food, housing, healthcare, political freedom).

    • SDGs aim to lift everyone out of the hole (meet basic needs).

    • Going outside the ecological ceiling (above) stresses Earth’s life-support systems.

    • Implication: greater population or higher consumption increases resource demand and waste; sustainable outcomes depend on aligning population/resource use with Earth’s limits.

  • Essentials and sustainability (Page 8–9):

    • Meeting basic needs (food, housing, healthcare, political freedom of expression) is a baseline.

    • If population growth and resource demand are controlled, sustainability (within the doughnut’s ecological ceiling) becomes more feasible.

  • Wealth, consumption, and biocapacity (Page 10):

    • Middle-class growth leads to higher consumption of water, meat, dairy, and fossil fuels, increasing waste.

    • Combined with population growth, this reduces the planet’s biocapacity and can push beyond sustainable limits if not managed.

  • Connections to policy, ethics, and real-world relevance:

    • Ethical implications of reproductive rights and gender equality.

    • Policy relevance of providing education, healthcare, and access to resources.

    • Practical implications for urban planning, infrastructure, and environmental stewardship.

Age–Sex Pyramids and Dependency Ratios

  • Age–sex pyramids are used to determine:

    • Dependency ratio

    • Population momentum

  • Dependency ratio definition (Pages 11–12):

    • Dependent groups: under 15 years and over 64 years.

    • Economically productive group: 15–64 years.

    • Dependency ratio (DR) measures the balance of dependents to workers.

    • High DR occurs with very high or very low fertility.

  • Dependency ratio formula (Page 12):

    • DR = rac{Y + O}{W} imes 100

    • Where:

    • Y = number of young dependents (under 15)

    • O = number of old dependents (over 64)

    • W = number of workers (ages 15–64)

    • Example calculation: DR = rac{11.105 + 9.341}{38.342} imes 100 = 53.33

    • Interpretation: for every 100 workers, there are about 53 dependents.

  • Follow-up task (Pages 13–14):

    • Calculate dependency ratios for five countries following the website task instructions.

  • Key features of dependency ratios (Pages 14–15):

    • A DR of 100 means one dependent per worker (a neutral burden).

    • Higher DR implies greater fiscal pressure on government services funded by taxes.

    • As the share of dependents increases, there are fewer workers to fund services, potentially raising taxes to support government needs.

    • Aging population effects: more people requiring pensions/health benefits and social support.

    • Government policy can influence DR (examples: China’s one-child policy; policies to attract foreign workers to offset aging populations).

  • Sub-components of dependency (Page 16):

    • Child dependency vs Old-age dependency

  • Notable country examples (Page 17):

    • Niger:

    • Overall DR: 108.92

    • Youthful dependency: 103.50

    • Old-age dependency: 5.42

    • Qatar:

    • Overall DR: 18.38

    • Youthful dependency: 16.17

    • Old-age dependency: 2.22

  • Limitations and problems (Page 18):

    • Age group delineations do not fit all contexts (LICs). Child labor, education completion ages vary by country.

    • Retirement ages are fluid and vary by country (e.g., Turkey: 52 (men), 49 (women); Norway/Iceland: 67).

Population Momentum (Pages 19–21)

  • Concept: population momentum explains continued population growth even after fertility declines.

    • It depends on the size of the cohort of women of reproductive age and their age distribution.

    • A larger proportion of young people leads to more births when they reach reproductive age, sustaining growth despite lower fertility rates.

  • Data example (Page 19): LIC vs HIC demonstration

    • LIC: Age 15–49 = 90; Age 50+ = 10; Total = 100; TFR = 2;

    • Births = 90 imes 2 = 180; Final population = 90 + 10 + 180 = 280

    • HIC: Age 15–49 = 50; Age 50+ = 50; Total = 100; TFR = 2;

    • Births = 50 imes 2 = 100; Final population = 50 + 50 + 100 = 200

  • Key takeaway: even with replacement-level fertility (TFR ≈ 2), population can rise temporarily due to momentum.

  • Watch resources (Pages 20–21):

    • Dependency Ratio (video): reinforces understanding of the concept.

    • Population Momentum (video): visual demonstration of the concept.

Trends in Population (Indonesia and Japan) and the Demographic Transition Model (DTM)

  • Indonesia (Pages 23–26):

    • DTM stage: currently Stage 3 (declining birth rates, lower death rates, stabilized growth).

    • Past (1970s–1980s): high birth rates declined due to family planning programs (e.g., "Two Children Enough").

    • Present: fertility ~ 2.3 children per woman; rapid urbanization; rising education levels; growing middle class; growth slowing, especially in urban areas.

    • Future (next 30 years): expected to move toward Stage 4 by 2050 with a stabilized population around 335 imes 10^6 (335 million); potential for a demographic dividend from a young population, with aging coming later.

  • Japan (Pages 27–31):

    • DTM stage: Stage 5 (very low birth and death rates; shrinking, aging population).

    • Past (1950s–1980s): post-WWII economic growth, healthcare improvements, urbanization; birth rate declined as women entered workforce; rising costs influenced family size.

    • Present: fertility ~ 1.3 children per woman; aging population; shrinking labor force; high living costs and work culture deter family growth.

    • Future (next 30 years): population projected to decline further, potentially below 100 imes 10^6 by 2050; by mid-century, around 40 ext{%} of the population may be over 65.

  • Influences on both populations (Page 31): comparative factors

    • Historical: post-WWII growth, urbanization, aging, etc.

    • Economic: living costs, urbanization, middle-class growth; work culture influencing family size.

    • Social: aging vs youthful population dynamics.

    • Political: effectiveness of policies (family planning, incentives) in shaping birth rates.

  • Demographic Transition Model (DTM) refresher (implicit):

    • Stage 2: high birth rates begin to fall with improving healthcare.

    • Stage 3: birth rates fall further; population growth slows.

    • Stage 4: low birth and low death rates; stable or slowly growing population.

    • Stage 5: very low birth rates plus aging population; potential population decline.

Environmental Issues and Migration

  • Environmental drivers of migration (Pages 32–35):

    • Climate change, drought, land degradation promoting environmental migration.

    • Migration can be driven by sudden onset events (floods, droughts, fires, storms) and slow onset events (desertification, sea-level rise, saltwater intrusion).

  • Climate migration discourse (Page 33):

    • The Economist: "Climate migrants: what to do?" (watch note, context for policy discussions).

  • Impacts of extreme weather and sea-level rise (Page 34):

    • Extreme weather events threaten homes, infrastructure, livelihoods; frequent/severe events can force displacement.

    • Sea level rise/enduring coastal inundation disrupts freshwater supplies and housing.

  • Desertification, land degradation, and resource scarcity (Page 35):

    • Desertification reduces arable land, increasing food insecurity and migration.

    • Water scarcity and disrupted climate patterns threaten agriculture and livelihoods.

  • Case study: Tuvalu to New Zealand (Pages 36–37):

    • Tuvalu features: nine low-lying islands; morphology dependent on coral; shallow freshwater lakes; high population density; livelihoods heavily reliant on fisheries.

    • Climate impacts: sea-level rise, saltwater intrusion, drought forcing displacement.

    • In the last 10 years: roughly 74 ext{%} of households affected by climate change; 8% of migrants named climate change as the reason for migrating.

  • Case study context: Mozambique (Page 38):

    • Task: follow instructions to analyze trends in population and emigration due to repeated cyclones

    • Note: involves understanding how repeated tropical cyclones influence emigration patterns and the wider social-ecological system.

Connections to SL/Foundational Principles

  • Population dynamics are a function of interlinked factors: fertility, mortality, migration, education, health care, economy, policy, and culture.

  • The Doughnut Economics framework connects social foundations (essentials for life) with ecological ceilings (planetary boundaries) to assess sustainability in relation to population and consumption.

  • Demographic indicators (dependency ratio, age structure, momentum) inform policy needs in economics, healthcare, education, pensions, and social protection.

  • The Demographic Transition Model explains broad population patterns as societies develop; variations exist by country due to policy choices, economic structure, culture, and technology.

Formulas and Key Numbers (LaTeX)

  • Dependency ratio:

    • DR = rac{Y + O}{W} imes 100

    • Example: DR = rac{11.105 + 9.341}{38.342} imes 100 = 53.33

  • Example demographic momentum calculation (LIC vs. HIC):

    • LIC: births = 90 imes 2 = 180; Final population = 90 + 10 + 180 = 280

    • HIC: births = 50 imes 2 = 100; Final population = 50 + 50 + 100 = 200

  • Population projections (illustrative):

    • UN projection: 10 imes 10^9 by 2100

    • Lancet projection: 9.7 imes 10^9 around 2060

  • Fertility rates (examples):

    • Indonesia: ext{TFR} \, ext{~} 2.3

    • Japan: ext{TFR} \, ext{~} 1.3

  • Population totals and stages:

    • Indonesia projected final population: 335 imes 10^6 by ~2050

    • Japan aging share: notional projection that by mid-century, around 40 ext{%} over 65 years old

Summary of Practical Implications

  • Population growth interacts with resource use and environmental limits; policies supporting education, healthcare, and gender equality can influence fertility and thus shape future population trajectories.

  • Dependency ratios inform fiscal planning (tax revenue vs. pension/health demands) and influence retirement age policies and social protection schemes.

  • Population momentum means even rapid declines in fertility may not immediately halt population growth; planning must account for continued growth and aging.

  • Climate change and environmental degradation contribute to migration, with cases like Tuvalu illustrating climate-driven displacement and adaptation needs.

  • Understanding trends in different countries (Indonesia, Japan) helps anticipate economic opportunities and challenges associated with the Demographic Transition Model.

Study Prompts and Connections to Exam Prep

  • Compare UN vs Lancet projections and discuss factors that could shift trajectories.

  • Explain how the Doughnut Economics model frames sustainability concerns related to population and consumption.

  • Compute a dependency ratio from given age-structure data and interpret the result for policy implications.

  • Describe population momentum using the LIC vs HIC example; explain why momentum can drive growth even if TFR is at replacement level.

  • Outline how demographic transitions in Indonesia (Stage 3 moving toward Stage 4) differ from Japan (Stage 5) and what regional factors drive these differences.

  • Discuss how climate-related events (extreme weather, sea-level rise, desertification) influence migration patterns, using Tuvalu as a case study.