CHAPTER 3 - PATTERNS OF POPULATION
0) Core Idea
Geographic Inquiry: Geographers analyze population patterns to understand complex processes of growth and movement over time, which affects cultural, political, environmental, and economic conditions.
Global Context: The global population reached 7.8 billion in December 2019. Today, more people are alive than at any other time in Earth’s history.
Major Clusters: Two-thirds of the world's population can be found in four regions:
East Asia
South Asia
Southeast Asia
Western Europe
3.1 WHERE PEOPLE LIVE: Factors Influencing Population Distribution
Learning Objective: PSO-2.A Identify the factors that influence the distribution of human populations at different scales.
1) Population Distribution Patterns
Definition: Population Distribution: Where people live within a geographic area.
Terms to Describe Patterns:
Uniform: Spread out evenly over an area.
Clustered (Agglomerated): Grouped or clumped together around a central point.
Linear: Forms long, narrow lines (e.g., along a river or highway).
Dispersed: Spread out across an area.
Random: Distributed without apparent order or logic.
Scales of Study: Geographers study population distributions at local, regional, national, and global scales.
2) Physical and Environmental Factors (Ecumenes)
People are more likely to settle where there are moderate climates, rich soils, and adequate water. Most people avoid areas that are too hot, too dry, too wet, or too cold.
A. Elevation
Populations are most heavily concentrated at
low elevations.80% of the world’s population lives below elevations of 1,500 feet.
Populations diminish rapidly as elevation increases.
Challenging Areas (Highlands): Rocky, steep regions (like Tibet) are less populated due to difficulty building structures, transportation links (roads/railways), and challenges for agriculture (colder temperatures).
Temperature Lapse Rate: The average temperature drops by approximately 3°F for every 1,000-foot rise in elevation.
B. Climate
Definition: Climate: The long-term patterns of weather in an area.
Temperate Climates: Areas with moderate temperatures and adequate precipitation are usually more densely populated.
Extreme Climates: Areas like the arid Sahara or subarctic/polar regions (Canada) limit population concentration due to the extreme impact on daily life and the lack of agricultural viability.
Technology (e.g., center-pivot irrigation in Saudi Arabia) has allowed some populations to live in previously uninhabitable dry areas.
C. Landforms and Soil
Preference: People prefer lowlands due to the ease of building, planting, and transporting goods.
Fertile Areas: Flat, low-lying areas (plains, river valleys, deltas) have deeper, fertile soil suitable for agriculture.
Alluvial Soil: Rich soils created when the flow of rivers slows, depositing soil particles. This supports dense populations and early civilizations (Nile, Tigris-Euphrates, Indus, Ganges, Huang He).
D. Water Accessibility
Necessity: Ready access to fresh, ample water is essential for human survival, agriculture, industrial use, sanitation, and hygiene.
Settlement Patterns: Coasts and waterways are often densely populated because they offer economic advantages and convenient transportation routes.
Examples: The Yangtze River Valley in China is a major population and manufacturing center due to the river system allowing transport and trade.
3) Human Factors
A. Economic Factors
Opportunity: People live where they can earn a living (agriculture, manufacturing, resource extraction).
Migration: Economic reasons are a major driver of migration, such as seeking job opportunities, better working conditions, and higher pay.
Resource Influence: The presence of natural resources (e.g., nickel in Norilsk, Siberia) can attract dense populations, even if the environment is harsh.
B. Political Factors
Instability/Conflict: Unstable political circumstances or war can compel citizens to leave their homes (e.g., forced migrations).
Government Policy: Governments can enact policies to actively redistribute population.
Examples: Brazil moving the capital from coastal Rio de Janeiro to the inland city of Brasília in 1960 to develop central Brazil. Nigeria moving its capital from Lagos to
Abuja in the 1980s.Forced Displacement: The forced migration of millions of enslaved people to the Americas to support colonial economies had massive effects on distribution. The Khmer Rouge forcing over 2 million residents from Phnom Penh to the rural countryside in 1975.
C. Cultural Factors
Cultural factors that influence population changes include:
Religion
The roles and status of women (including socialization)
Familial attitudes regarding marriage and children
Preference for sons (which affects population composition).
D. Historical Factors
Past population distribution can influence present distribution.
Duration of Settlement: Densely populated areas often have an exceptionally long history of human habitation, while sparsely populated areas tend to have a less-established history.
Major Historical Movements: Events like the Migration period (300 to 700 C.E.) shaped population concentrations in Europe, North Africa, and Western Asia.
3.2 CONSEQUENCES OF POPULATION DISTRIBUTION
Learning Objective: IMP-2.B Explain the difference between and the implications of arithmetic and physiological population density.
1) Population Density: Measuring Concentration
Definition: Population Density: The number of people in a particular area.
Significance: It helps geographers understand how populations are distributed and the stress placed on resources.
A. Arithmetic Density
What it is: The total number of people divided by the total land area.
Why useful: The simplest measure; helps compare population concentrations between countries.
Limitation: It is a broad measure that doesn't account for clustering or non-habitable land (e.g., deserts, mountains).
B. Physiological Density
What it is: The total number of people divided by the amount of arable land (land suitable for agriculture).
Why useful: Provides insight into the capacity of a region to feed its population and the pressure placed on agricultural resources.
High Density Implication: A country with a much higher physiological density than its arithmetic density suggests a smaller percentage of its land is available for farming, indicating a higher strain on that land.
C. Agricultural Density
What it is: The number of farmers divided by the amount of arable land.
Why useful: Reflects farming efficiency and level of development.
Implication: Developed countries (MDCs) tend to have low agricultural density because technology and large farms allow few farmers to feed many people. Less developed countries (LDCs) have
high agricultural density, indicating more reliance on subsistence farming.
2) Implications of Density Measures
Density is a major factor in understanding
carrying capacity, which is the population an area can support without significant environmental damage.
Economic Implications:
Population Clustering: Leads to greater economic opportunity, as concentration of labor and markets drives wealth creation.
High Density: Can lead to higher costs for housing, land, and resources; may require greater government spending on infrastructure (roads, sewage, power, water).
Low Density: Can make infrastructure (schools, utilities) expensive and less efficient, leading to lower economic opportunity and reduced access to services.
Political Implications:
Resource Allocation: Governments must decide how to allocate resources (water, food, housing, energy) among concentrated populations, often leading to tensions between dense and sparse areas.
Government Efficiency: Low density in rural areas makes it difficult and expensive to deliver government services, while high density in urban areas creates complex management challenges.
Representation: High density can be difficult to manage for political representation (e.g., drawing legislative districts).
Social Implications:
Urban vs. Rural: High-density, clustered populations (urban) have better access to healthcare, education, and social services, while low-density, dispersed populations (rural) may have less access.
Cultural Contact: High density increases cultural contact and interaction, leading to greater cultural diffusion, but also competition for space.
Poverty: High density in less-developed regions can exacerbate poverty and slum conditions.
Environmental Implications:
Pollution: High density leads to more concentrated pollution (air, water, waste) and higher resource consumption per area, stressing the environment.
Resource Depletion: High physiological density implies overuse of arable land, leading to soil degradation, erosion, and potential desertification.
3.3 POPULATION COMPOSITION
Learning Objective: PSO-2.B Explain the role of and interpret various programs and policies used to manage population change.
1) Population Pyramids (Age-Sex Diagrams)
Definition: A bar graph that shows the distribution of a country’s population by age and gender.
What it shows: Allows geographers to visualize population composition (the demographic makeup of a place) by cohort (age groups, typically 5-year intervals).
Age: Vertical axis.
Gender: Horizontal axis (Left = Male, Right = Female).
Significance/Purpose: Reveals historical events (wars, baby booms, epidemics) and helps forecast future social and economic needs (healthcare, education, pensions).
2) Shapes of Pyramids and Their Meaning
The shape of a pyramid is determined by the
fertility rate (birth rate) and mortality rate (death rate).
3) Demographic Measures and Anomalies
Dependency Ratio: The ratio of the population not in the labor force (dependents: 0-14 and 65+) to the working population (15-64).
High Dependency Ratio: Implies a greater financial burden on the working population to support the young and/or old.
LDCs: Burden is high due to a large young dependent population (high CBR).
MDCs: Burden is high due to a large old dependent population (low CBR, high life expectancy).
Sex Ratio (Gender Balance): The number of males per 100 females.
Global Average: Slightly more males than females at birth, but females typically outlive males.
Anomalies/Imbalances: Can be caused by:
Wars: Creates a deficit of working-age males.
Immigration: Countries receiving large numbers of guest workers may have a male surplus.
Cultural Preferences: Countries with a strong preference for sons (e.g., India, China) often result in a male surplus due to sex-selective abortions.
High Female Mortality: Due to neglect or poor healthcare.
4) Demographic and Social Consequences of Population Structure
Aging Populations (MDCs):
Challenge: The large proportion of elderly people requires greater healthcare spending (e.g., hospitals, nursing homes, specialized doctors).
Economic Strain: Fewer young workers to pay taxes to support the elderly, leading to potential labor shortages and calls for migration.
Youthful Populations (LDCs):
Challenge: Strain on school systems and job markets as a large number of young people enter the workforce.
Strain on Resources: Increased demand for basic resources (food, water, housing).
3.4 MEASURING GROWTH AND DECLINE
Learning Objective: PSO-2.C Explain the data used to calculate population and rates of population change.
1) Core Population Measures (Rates and Totals)
A. Crude Birth Rate (CBR)
What it is: The total number of live births in a year for every 1,000 people alive in society.
Global Range: Highs (over 40, found in Sub-Saharan Africa) and Lows (under 10, found in Europe).
B. Crude Death Rate (CDR)
What it is: The total number of deaths in a year for every 1,000 people alive in society.
Unexpected Pattern: MDCs often have higher CDRs than LDCs because MDCs have a large proportion of elderly people.
C. Natural Increase Rate (NIR) or Rate of Natural Increase (RNI)
What it is: The percentage growth or decline in a population per year.
Formula: NIR = (CBR - CDR) / 10 (The division by 10 converts the rate from per 1,000 to a percentage).
World NIR: Historically high in the mid-20th century, but dropping today. The world NIR is approximately 1.1%.
D. Doubling Time
What it is: The number of years needed to double a population, assuming a constant rate of natural increase.
Rule of 70 (Approximation): Doubling Time = 70 / NIR (as a percentage).
E. Total Fertility Rate (TFR)
What it is: The average number of children a woman will have throughout her childbearing years (15-49).
Significance: Predicts future population growth better than CBR, as it factors out the current age structure.
Replacement Level: The TFR needed to keep a population stable is 2.1.
F. Infant Mortality Rate (IMR)
What it is: The annual number of deaths of infants under 1 year of age, compared with total live births (expressed per 1,000 live births).
Significance: IMR reflects a country's healthcare system, sanitation, and nutrition.
MDC vs. LDC: High IMRs are found in LDCs (reflecting poor care); Low IMRs are found in MDCs.
G. Life Expectancy (at birth)
What it is: The average number of years an infant can be expected to live.
Significance: Reflects the overall health and quality of life in a country.
2) Demographic Accounting Equation (The True Growth Rate)
Concept: Population change is not just determined by births and deaths, but also by migration.
Formula (General): Total Population Change=(Births−Deaths)+(Immigrants−Emigrants).
Components:
Natural Change: (Births - Deaths)
Net Migration: (Immigrants - Emigrants)