IB Diploma Programme Geography HL (first assessment 2019; 2017 guide). This topic covers the CORE's first unit in full — Population distribution—changing population — from the measures of population change (crude birth and death rates, natural increase) through the demographic transition model and population structure to migration, ageing and youthful populations, and population policy. The geographic concepts (POWER, PROCESS, POSSIBILITY, SCALE, SPATIAL INTERACTIONS) frame every answer, and the worked numbers below are original and reconciled.

Must-know for the changing-population unit:

Population distribution answers WHERE people live and WHY: the physical frame (climate, water, relief, soils), the economic frame (jobs, trade routes, cities), and history and politics (colonisation, conflict, policy). Distribution is described by DENSITY — arithmetic density $=$ population ÷ area; physiological density $=$ population ÷ arable area, exposing pressure on farmland. Sparse and dense are relative, and the WHY questions carry the marks: altitude and aridity thin populations; industry and coastlines thicken them.

The MEASURES of change: the crude birth rate 粗出生率 (CBR) is live births per 1 000 people per year; the crude death rate 粗死亡率 (CDR) is deaths per 1 000 per year; natural increase 自然增长 is their difference — a country with CBR 18 and CDR 9 has NIR $= 18 - 9 = 9$ per 1 000 $= 0.9\%$ a year, and a doubling time of about $70 / 0.9 \approx 78$ years (the rule of 70). TOTAL population change adds NET MIGRATION to natural increase: growth is births minus deaths plus incomers minus outgoers.

The demographic transition model 人口转变模型 (DTM) traces countries through five stages. Stage 1: high CBR and CDR, low growth (no country remains). Stage 2: death rates fall (medicine, sanitation) while births stay high — explosive growth, the classic LEDC profile. Stage 3: birth rates fall (education, urbanisation, women's work) — growth slows. Stage 4: both low, growth near zero — most MEDCs. Stage 5: births below replacement (CBR below CDR) — decline, as in Japan and Germany. The model's limits: it generalises from Europe's path, undervalues migration, and dates — but as a frame for comparing countries it remains the exam's workhorse.

POPULATION STRUCTURE is read from the population pyramid 人口金字塔: an EXPANSIVE pyramid (wide base) means high fertility and a youthful population (Nigeria-shape); a STATIONARY pyramid means near-replacement growth; a CONSTRICTIVE pyramid (narrow base, wide top) means ageing and decline (Japan-shape). The dependency ratio 抚养比 summarises the load: dependents (0–14 plus 65+) over the working group (15–64), times 100 — with 60 children, 30 elderly and 210 workers the ratio is $90/210 \times 100 \approx 43$ per 100. AGEING populations strain pensions and health care while labour shortens; YOUTHFUL populations strain schooling and jobs while promising a future demographic dividend; the two cases are evaluated, not just described.

POPULATION POLICY answers both: pro-natalist policy 鼓励生育政策 (France's childcare, leave and cash support) raises fertility in ageing societies; anti-natalist policy (China's one-child era, 1979 to 2015) lowered fertility at the price of an ageing population and a skewed sex ratio; some countries now pursue population-neutral policies on health, education and women's employment, letting fertility follow.

Migration 迁移 is a move crossing a boundary for more than a year: INTERNAL (rural to urban) or INTERNATIONAL, voluntary or forced. The explanations are push factors 推力因素 driving people out (unemployment, conflict, disaster, land shortage) and PULL factors drawing them in (jobs, safety, family, services), moderated by BARRIERS (cost, distance, borders, language) — Lee's model adds intervening obstacles and personal factors to the two lists. FORCED migrants who cross a border are refugees 难民 (1951 Convention: well-founded fear of persecution); those displaced within their state are IDPs; economic migrants move by choice and fall outside the Convention. IMPACTS flow both ways: origin communities lose the young and gain remittances (money sent home, a major GDP line for Nepal and the Philippines), relieve unemployment and receive return migration's skills; destinations gain labour and youth, and absorb integration costs and social strain. Internal migration drives urbanisation and, at scale, MEGACITY growth — the process the urban-environments option takes up.

Worked example. A district of 2 million with CBR 24 and CDR 8 grows by natural increase of 16 per 1 000 a year; net out-migration of 12 per 1 000 (young adults leaving for the coast) leaves total growth near 4 per 1 000 — a population ageing even as it grows slowly, the exact profile that switches policy debate from jobs to elder care.

• Distribution factors physical, economic, historical, political; arithmetic vs physiological density (distribution).
• CBR/CDR per 1 000; NIR $=$ CBR $-$ CDR (18 − 9 → 0.9%); doubling time $\approx 70/$NIR (≈78 years); add net migration for total change (measures).
• DTM stages 1–5 with the CBR/CDR logic of each, and two limitations of the model (transition).
• Pyramid shapes (expansive, stationary, constrictive) with country profiles; dependency ratio 90/210 ≈ 43; ageing vs youthful strain evaluated both ways (structure).
• Pro-natalist (France), anti-natalist (China 1979–2015) and neutral policies with their trade-offs (policy).
• Push/pull/barriers (Lee); refugees vs IDPs vs economic migrants (1951 Convention); remittances and the two-sided impacts; internal migration → urbanisation (migration).

Boundary notes: Paper 1 (core) rewards command-term precision — "explain" needs a because-chain, "examine" needs strengths and limits; data-response items calculate NIR, doubling time and dependency ratios from given figures. All worked numbers are original and reconciled.

IB Diploma Programme Geography HL (first assessment 2019; 2017 guide). This topic covers the CORE's second and third units in full — Global climate—vulnerability and resilience (climate change and its causes, vulnerability, adaptation and mitigation) and Global resource consumption and security (patterns of consumption, renewable and non-renewable resources, food and water security, stewardship). The concepts SUSTAINABILITY, PROCESS and SCALE carry the answers, and the worked figures below are the stable published ones.

Must-know for climate and resources:

CLIMATE CHANGE has NATURAL causes — orbital (Milankovitch) cycles, solar variability, volcanic episodes — and ANTHROPOGENIC ones: the greenhouse effect 温室效应 intensified by carbon dioxide from fossil-fuel burning and land-use change, and methane from livestock, rice and leaks. The EVIDENCE triangulates: instrument records show about 1°C of warming since pre-industrial times; ice cores extend the carbon-dioxide record back 800 000 years; glaciers retreat and global sea level rises. The PARIS AGREEMENT (2015) frames the target: hold warming WELL BELOW 2°C while pursuing 1.5°C — the number every strategy answer measures itself against.

Vulnerability 脆弱性 is exposure plus sensitivity minus capacity: low-lying deltas and small island states face sea-level rise; arid margins face drought; poverty, weak governance and dependence on agriculture raise sensitivity; wealth and institutions lower it. Resilience 恢复力 is the capacity to absorb shocks and reorganise — Bangladesh's cyclone shelters and warning systems turned a death toll of hundreds of thousands (1970) into tens (2020s): the same hazard, transformed capacity. The response pair is the exam's spine: mitigation 缓解 attacks the CAUSE (decarbonising energy, reforestation, efficiency, carbon pricing), while adaptation 适应 adjusts to the IMPACT (sea walls, drought-resistant crops, managed retreat, early warning). Richer states can fund both; poorer states are most vulnerable and least resourced — the justice frame the essays want.

Global consumption patterns are UNEVEN and RISING: energy use per person in high-income states runs several times the low-income figure, and total demand grows with population and industrialisation. The ecological footprint 生态足迹 measures demand on nature in global hectares per person: the world average of about 2.6 gha against a biocapacity of about 1.6 gha means humanity uses the equivalent of roughly 1.7 Earths — overshoot that is only possible by drawing down natural capital. RESOURCES divide into renewable resources 可再生资源 (solar, wind, biomass, fish — restorable within human timescales when harvested within their regeneration rate: the sustainable yield) and non-renewable (coal, oil, gas, minerals — stock, not flow). Energy transitions shift the mix from fossil toward renewables, judged on cost, storage, land use and the minerals the transition itself mines.

WATER: agriculture takes roughly 70% of global freshwater withdrawals, industry and municipalities the rest; water security 水安全 fails where demand crosses supply — aquifer depletion, glacier-fed rivers losing their store, and pollution — and is measured by access to safe water, not raw availability. FOOD: food security 粮食安全 stands on four pillars — AVAILABILITY (production and imports), ACCESS (affordability and distribution), UTILISATION (nutrition and safety) and STABILITY (across seasons and shocks) — so a famine can occur amid availability where access collapses. The strategic choice the unit ends on: CONSUMERISM (consume more, secure supply) versus resource stewardship 资源管护 (consume differently — efficiency, circular economies, demand management, the SDG logic of using less to live well), with the ecological-footprint arithmetic as the scoreboard.

• Natural vs anthropogenic climate causes; the three evidence streams; the 2°C/1.5°C Paris frame (climate).
• Vulnerability as exposure + sensitivity − capacity; resilience with the Bangladesh contrast; mitigation vs adaptation with named examples of each (climate).
• Footprint vs biocapacity: 2.6 vs 1.6 gha ≈ 1.7 Earths; overshoot as capital drawdown (resources).
• Renewable vs non-renewable with sustainable yield; the energy-transition trade-offs (resources).
• Water: agriculture ≈ 70% of withdrawals; security as access, not availability (resources).
• Food security's four pillars applied; famine amid availability; consumerism vs stewardship evaluated (security).

Boundary notes: Paper 1 rewards named PLACE examples at a stated SCALE (local, national, global) and precise use of "mitigation" and "adaptation"; the footprint, share and threshold figures above are the stable published values used as the unit's arithmetic spine.

IB Diploma Programme Geography HL (first assessment 2019; 2017 guide). This topic equips the THEMES menu and the INTERNAL ASSESSMENT: the seven option themes (SL schools teach two, HL three; each kit below gives the scope, one anchor concept and one place example) and the fieldwork inquiry cycle with its sampling strategies and statistics. The worked numbers are original and reconciled.

Must-know for options and fieldwork:

FRESHWATER: the drainage basin 流域 is the unit of study; the storm hydrograph 暴雨水文曲线 plots discharge against time — rising limb, peak, falling limb, and LAG TIME (storm to peak): urban basins shorten the lag and steepen the peak (concrete sheds water). Management runs from HARD engineering (dams, embankments) to SOFT (afforestation, river restoration, floodplain zoning), traded off against cost and ecology.

OCEANS AND COASTAL MARGINS: waves erode (hydraulic action, abrasion) and deposit (spits, beaches); landforms pair process with rock structure (headlands and bays, stacks). Coastal management: hard (groynes, sea walls — shifting the problem downdrift) versus SOFT (beach nourishment, MANGROVE planting) versus MANAGED REALIGNMENT — letting the coast adjust where defence costs exceed asset value (a frequent evaluation case).

EXTREME ENVIRONMENTS: glacial processes (erosion by ice, transport, deposition: troughs, moraines) and hot-arid processes (wind and flash floods — dunes, wadis); each environment read as opportunity (tourism, minerals) against challenge (water, access, fragility).

GEOPHYSICAL HAZARDS: plate margin 板块边缘 mechanics (constructive, destructive, conservative) drive volcanoes, earthquakes and tsunamis; hazard risk $=$ hazard magnitude $\times$ exposure $\times$ vulnerability — which is why the same magnitude devastates one city and spares another (2011 Tōhoku: magnitude 9.0, world-class warning saved most lives; the tsunami still overwhelmed defences). Park's response curve models the human recovery arc.

LEISURE, TOURISM AND SPORT: tourism's global growth; the Butler model 巴特勒模型 traces a destination from exploration through involvement, development and consolidation to stagnation, then decline or rejuvenation; carrying capacity 承载力 and overtourism (Venice's day-tripper caps) demand management (limits, dispersal, pricing).

FOOD AND HEALTH: food systems from farm to table; famine as access failure (topic 02's pillar logic); the epidemiological transition 流行病学转变 — deaths shift from infectious diseases (stage 1) to chronic degenerative diseases (late stages) as development proceeds — with obesity rising where calories cheapen. Health indicators (life expectancy, infant mortality) track the transition.

URBAN ENVIRONMENTS: urbanisation and the growth of megacities 特大城市 (10 million plus); land-use models (Burgess's concentric zones, Hoyt's sectors — descriptions to test, not truths); urban stress (housing, congestion, waste) and regeneration (brownfield renewal, transport investment) as the response pair.

The IA (SL 25%, HL 20%) is a FIELDWORK REPORT on primary data the student collects. THE CYCLE: a FIELDWORK QUESTION (place-specific and answerable) with one or more HYPOTHESES (testable, directional; for statistics, a NULL hypothesis of no relationship); METHODS chosen to match the question, with a RISK ASSESSMENT and ETHICS; DATA COLLECTION by SAMPLING, since a census is impossible: Random sampling 随机抽样 (every point equally likely — unbiased, may miss clusters), Systematic sampling 系统抽样 (every nth point or along a transect — even coverage, risks matching a periodic pattern) and Stratified sampling 分层抽样 (proportional samples per known sub-zone — representative of structure, needs prior knowledge); point, line and quadrat frames; then PRESENTATION (maps, graphs), ANALYSIS, CONCLUSION and EVALUATION (limitations and modifications).

ANALYSIS runs from descriptive summaries (means, medians and the interquartile range) to statistical tests. SPEARMAN'S RANK measures a monotonic association. For eight pairs with no tied ranks, an exact two-sided test at the 5% level has a critical absolute value of about $0.738$. A reported $r_s = 0.714$ (rounded) is below this threshold, so do not reject the null hypothesis of no rank association; this does not prove that no association exists. State the sample size, treatment of ties, alternative hypothesis and test method. For a chi-squared independence test on a 2 x 2 count table, the degrees of freedom are 1. With independent observations and sufficiently large expected counts, $\chi^2 = 5.2 > 3.84$ rejects independence at the 5% level. Check these assumptions before using the chi-squared approximation.

Worked example. Question: does pedestrian density fall with distance from the city-centre plaza? Hypothesis: density declines with distance. Method: systematic sampling — counts per 2 minutes at every 100 m along four transects (stratified by direction). Analysis: a scatter graph with Spearman's rank; evaluation: one rainy hour, four transects, morning only — the modifications name themselves.

• Hydrograph anatomy with the urban lag-time effect; hard vs soft flood management (freshwater).
• Erosion/deposition process-landform pairs; groyne consequences vs managed realignment (coasts).
• Glacial and arid process pairs; the opportunity/challenge frame (extreme).
• Margin types with their hazards; the risk product with the Tōhoku contrast (hazards).
• Butler's stages in order; carrying capacity and Venice-style management (tourism).
• Epidemiological transition stages; famine as access failure (food and health).
• Burgess and Hoyt read as models to test; megacity growth, stress and regeneration (urban).
• The fieldwork cycle end to end; the three samplings' strengths and costs; the $r_s$ and $\chi^2$ decisions with critical values (fieldwork).

Boundary notes: option papers reward SPECIFIC PLACES at a stated scale, and the fieldwork criterion set marks EXPLAINED method choices and correctly executed statistics. All worked numbers are original.

IB Diploma Programme Geography HL (first assessment 2019; 2017 guide). This topic is the HL-ONLY EXTENSION Geographic perspectives—global interactions: power, places and networks; human development and diversity; global risks and resilience. Everything the core measured at national scale is here read as a NETWORK: flows of goods, capital, information and people, the power relations that steer them, the development and diversity they reshape, and the risks and governance that answer them. The worked figures are the stable published ones.

Must-know for global interactions (HL):

Global interactions 全球互动 are the flows that bind places: traded goods and services (world exports run at roughly a quarter of world output), capital (direct investment seeking profit and safety), information (over 60% of humanity now uses the internet), and people (migrants, tourists, students). A global network 全球网络 has NODES (hub cities commanding finance and information) and LINKS (trade routes, cables, air corridors), and POSITION IN THE NETWORK is power: well-connected places compound their advantage while poorly connected ones pay a distance penalty.

POWER is organised as a core–periphery 中心—边缘 system (with a semi-periphery between): the core owns the high-value command functions (design, finance, brands), the periphery supplies materials and low-cost labour. The transnational corporation is the network's chief actor — coordinating production across borders, with outsourcing 外包 and offshoring relocating routine work to cheaper locations while headquarters keep research, branding and profit. But the flows run both ways: emerging-economy TNCs now invest outward, remittances to low- and middle-income countries exceed the foreign direct investment they receive, and states bargain, tax and regulate: POWER is contested, not simply imposed.

DEVELOPMENT is multidimensional: the Human Development Index 人类发展指数 (0 to 1: health, schooling, income) ranks wellbeing beyond GDP alone, and the Gender Inequality Index 性别不平等指数 exposes the gaps within countries (maternal health, adolescent fertility, parliamentary seats, education). Development as capability — the freedoms people actually have — reframes the whole measurement debate, and remittance and aid flows show transfers following need and kinship, not only profit.

DIVERSITY under interaction: global media and brands push HOMOGENISATION (the same stores, the same sounds), while cultures answer with HYBRIDISATION: glocalisation 全球本土化, the global adapted to the local — and with reassertion: indigenous movements protecting language, land and knowledge against both states and markets. Cultural diversity is then read like biodiversity: a resource under pressure, with the loss of languages as its extinction curve.

Global risks 全球风险 cross borders faster than any policy: a pandemic (COVID-19 cut world output by about 3% in 2020 and rewrote supply chains), financial contagion (crises transmitted through interlinked markets), geopolitical conflict (war, sanctions and energy shocks), and climate change (topic 02's core pressure, now a systemic risk). INTERCONNECTION is the amplifier — the same networks that carry trade carry risk: one chokepoint closed (a canal, a strait, a chip plant) and distant production lines stop: SUPPLY-CHAIN FRAGILITY is the concrete face of global risk.

RESILIENCE at every scale is the answer the unit examines: diversified suppliers and strategic stockpiles at state level; regional blocs and redundancy in networks; household savings and social protection at the micro scale. And above states sits global governance: the UN system and its agencies, the WTO's trade rules, treaties and finance initiatives, and CIVIL SOCIETY — NGOs, movements and watchdogs that name risks states prefer unsaid. The Sustainable Development Goals (17 goals, 2015–2030) are its shared scoreboard, and their premise is the topic's conclusion: no single state can secure development, diversity or climate alone.

• The four flows with the exports ≈ 25% of world output figure; nodes and links; network position as power (networks).
• Core–semi-periphery–periphery; the TNC's division of functions; outsourcing vs headquarters; counter-flows (emerging TNCs, remittances > FDI) (power).
• HDI's three dimensions and the GII's four; development as capability (development).
• Homogenisation vs glocalisation; indigenous reassertion; languages as the diversity measure (diversity).
• The four risk families with the 2020 ≈ −3% pandemic figure; chokepoints and supply-chain fragility (risks).
• Resilience at three scales; UN/WTO/civil society; the 17 SDGs as scoreboard (governance).

Boundary notes: the HL extension paper rewards SCALE (local to global) and RELATIONSHIPS (power, interdependence) argued with named examples; every figure above is the stable published value. All worked numbers are reconciled with the core units.