Population Distribution, Composition, and Migration Patterns

Overview of Population and Migration Patterns

• The distribution of human population is a fundamental element of human geography, influencing how people relate to one another, the demands placed on the environment, and community decision-making.

• People choose locations based on physical factors (proximity to food and water, moderate climates) and human factors (jobs, family proximity).

• Population Growth History: For most of human history, high birth rates were offset by high mortality, resulting in slow growth. In the last two centuries, advances in public health and medicine caused a global population explosion, though growth is now leveling off in wealthy nations like $Germany$, $South Korea$, and the $United States$.

• Migration Trends: Migration is often a choice to escape poverty or persecution and seek economic opportunity, religious liberty, or peace. However, forced migration has also occurred, such as the four-century enslavement of $Africans$ brought to the $Americas$.

Population Distribution and Factors of Settlement

• Population Distribution: The pattern of human settlement; the spread of people across the earth. Maps of distribution identify crowded, sparse, or empty areas.

• Population Density: A measure of average population per square unit (mile or kilometer); it indicates how crowded a place is.

• Physical Factors Influencing Distribution:

  • Midlatitudes: Most people live between $30^{\circ}$ and $60^{\circ}$ north and south of the equator. These regions have moderate climates and superior soils, particularly in the Northern Hemisphere.

  • Low-Lying Areas: People prefer areas of low altitude over mountains due to better soil for crops and proximity to oceans, which facilitate transport and moderate temperatures.

  • Fresh Water: Proximity to lakes or rivers is essential for drinking water, irrigation, transportation, and food.

  • Inhabitable Latitudes: Populations are low or nonexistent in mountains, deserts, high-latitude cold climates, and the tropics (due to disease and poor soil). $Polar$ regions have no permanent human populations.

• Human Factors Influencing Distribution:

  • Social/Economic: Newcomers move for safety, jobs, or to be near relatives. Cities grow as these attractions cluster.

  • Transportation: People prefer living near trade routes. Roads, rail lines, and rivers often produce linear settlement patterns.

  • Political Factors: Government decisions can create clusters in isolated spots. Example: $Canada$ established the military base $Alert$ on the northern edge of its territory in $1950$ to monitor the $Soviet Union$. It remains the world's most northerly community.

Scales of Analysis and Population Distribution

• Global Scale: High-elevation regions (e.g., $Himalayas$, $Andes$, $Rocky Mountains$) have cold climates and limited populations.

• City/Local Scale: Elevation might be desirable for cool breezes and flood safety. Climate variation is usually too small to affect settlement at this scale.

• Pollution: On a national scale, millions are attracted to industrialized cities for jobs despite pollution. On a local scale, people only live near pollution sources if they must due to lower property values.

• Government Influence:

  • National Level: Building a military base increases population.

  • State Level: Creating a state park can reduce population.

  • City Level: Zoning for high-rise apartments vs. single-family homes affects density.

• Social Stratification: The hierarchical division of people based on wealth, power, or ethnicity. This results in neighborhoods distinguished by characteristics, such as an industrial zone vs. an area with large homes and parks.

Methods for Calculating Population Density

• Arithmetic Population Density: Calculated by dividing total population by total area.

  • Example: In $2019$, the $United States$ had a population of approximately $328,239,523$ in a total area of $3,841,999\,sq.\,mi.$, resulting in a density of $85.4/sq.\,mi.$.

  • Limitation: It does not show distribution. Ten people per square mile could be evenly dispersed, clustered (nucleated) near a feature like a church, or linear along a road.

• Physiological Population Density: Calculated by dividing population by arable land (land suitable for crops).

  • This measure determines a region's carrying capacity (the population it can support without environmental damage).

  • Example: $Egypt$ has an arithmetic density of $226/sq.\,mi.$ but a physiological density of $8,078/sq.\,mi.$ because only $2.8\%$ of its land is arable. This suggests a need for high crop yields or food imports.

• Agricultural Population Density: Compares the number of farmers to the area of arable land.

  • High density indicates many farmers on little land, typical of less-developed countries where labor-intensive farming is required.

  • Low density indicates efficiency and technology, typical of developed countries. The $Netherlands$ has an agricultural density of $31/sq.\,mi.$, while $Bangladesh$ has $431/sq.\,mi.$.

Population Composition and Pyramids

• Population Composition: The makeup of ages and sexes in a population.

• Demographic Differences: $Utah$ had the youngest average age in the U.S. in $2018$ at $31.0$, while $Maine$ was the oldest at $44.9$. This dictates public policy (schools vs. senior services).

• Population Pyramids (Age-Sex Composition Graphs):

  • Vertical Axis: Shows age groups known as cohorts (usually 5-year bands).

  • Horizontal Axis: Shows population counts or percentages (Males on the left, Females on the right).

• Reading Trends in Pyramids:

  • Wide Base: Rapid growth, high percentage of children (e.g., $Niger$).

  • Symmetry: Usually indicates gradual change, though women typically outnumber men in older cohorts (age $65+$).

  • War Impacts: Clear loss of males aged $18$ to $40$ and a birth deficit (slowdown of births during conflict).

  • Baby Booms: Spikes in birth rates post-war or during economic abundance (e.g., U.S. boom $1946$–$1965$).

  • Echoes: A bulge resulting from a previous baby boom entering childbearing years.

  • Anomalies:

  • Bulge at ages $18$-$25$: College town.

  • Bulge in mature males: Mining towns or military bases (e.g., $Kuwait$ oil fields).

  • Bulge in elderly females: Retirement communities or assisted living zones.

Demographic and Epidemiological Transitions

• Demographic Balancing Equation: $Future\,Population = Current\,Population + (Births - Deaths) + (Immigrants - Emigrants)$.

• TFR (Total Fertility Rate): Average number of children born per woman aged $15$–$49$. It reflects cultural norms better than the CBR (Crude Birth Rate).

• Life Expectancy: Increased from $34$ years a century ago to nearly $70$ years today globally. Key factor: dropping Infant Mortality Rate.

• Rate of Natural Increase (RNI): $(CBR - CDR) \div 10$. Global RNI is approx $1.2\%$.

• Rule of 70: To find doubling time, divide $70$ by the annual growth rate (e.g., growth rate of $2.0$ means doubling in $35$ years).

• Demographic Transition Model (DTM):

  • Stage 1 (High Stationary): High birth/death; slow growth. (No countries today).

  • Stage 2 (Early Expanding): Death rates drop; rapid growth. (e.g., $Mali$, $South\,Sudan$).

  • Stage 3 (Late Expanding): Birth rates start to drop; growth slows. (e.g., $Mexico$, $Turkey$, $Indonesia$).

  • Stage 4 (Low Stationary): Low birth/death; stable population. (e.g., $United\,States$, $France$).

  • Stage 5 (Declining): Birth rate falls below death rate; shrinking population. (e.g., $Japan$, $Germany$).

• Epidemiological Transition Model:

  • Stage 1: Pestilence and Famine.

  • Stage 2: Receding Pandemics (improved sanitation).

  • Stage 3: Degenerative and Human-Created Diseases (heart disease, cancer).

  • Stage 4: Delayed Degenerative Diseases (medical advances).

  • Stage 5: Reemergence of Infectious Diseases (antibiotic resistance).

Population Theories and Policies

• Malthusian Theory (Thomas Malthus, 1798): Argued population grows exponentially while food grows arithmetically. Predicted mass starvation and a "Point of Crisis."

• Boserup Theory (Ester Boserup): Argued that population growth stimulates agricultural innovation ("Necessity is the mother of invention").

• Neo-Malthusians: Current theorists who fear population growth will deplete non-renewable resources (petroleum, metals) and lead to catastrophe.

• Population Policies:

  • Antinatalist: Seek to reduce births. Example: $China$'s "Later, Longer, Fewer" and the One-Child Policy ($1979$–$2016$). Resulted in gender imbalance ($118$ males per $100$ females).

  • Pronatalist: Seek to increase fertility through tax breaks, paid leave, and childcare (e.g., $Sweden$, $Japan$, $France$).

• The Changing Role of Women: Increased education ($Ghana$ study) and political participation correlate with lower fertility rates. When women stay in school longer, they delay marriage and childbirth.

Migration: Causes, Types, and Effects

• Push Factors: Negative conditions compelling departure (e.g., unemployment, discrimination, war, drought).

• Pull Factors: Positive conditions attracting migrants (e.g., jobs, safety, religious freedom).

• Intervening Obstacles: Economic (cost), Social (marriage), Political (visas), or Environmental (mountains/oceans).

• Ravenstein’s Laws of Migration:

  • Most migrants travel short distances (distance decay).

  • Long-distance migrants prefer large urban centers (Gravity Model).

  • Migration occurs in steps (step migration).

  • Rural-to-urban is the most common flow.

  • Every migration flow generates a counter migration.

  • Migrants are typically young adults; historically male for international moves, though females are increasing.

• Forced Migration:

  • Internally Displaced Persons (IDPs): Flee within their own country.

  • Refugees: Cross international borders due to fear of harm.

  • Asylum: Legal protection granted by a host country.

• Voluntary Migration: Includes transhumance (seasonal movement of livestock), guest workers (temporary labor), and chain migration (following relatives).

• Effects of Migration:

  • Origin Country: Relief from overcrowding; receiving remittances (money sent home); but suffers from brain drain (loss of skilled workers).

  • Receiving Country: Cultural contributions (ethnic enclaves like $Chinatown$); labor for motivated businesses; but potential conflict with native-born citizens.

Questions & Discussion

• Question: What advantages does the $United\,States$ have compared to $Egypt$ and $Japan$ in food production?

• Answer: The $United\,States$ has a high percentage of arable land (16.8\%\,compared\,to\,Egypt's\,2.8\%\,and\,Japan's\,11.7\%\) and a significantly lower physiological density (498/sq.\,mi.\,vs.\,8,000+\), allowing it to be a net exporter of food.

• Question: Why do retirees in the U.S. move to states like $Arizona$ and $Florida$?

• Answer: These are environmental pull factors (warm climate) and economic factors (lower cost of living in the $Sun\,Belt$), facilitated by air conditioning and the national highway system.

• Question: How does the agricultural density of $Bangladesh$ compare to the $Netherlands$?

• Answer: Although both are densely populated, the $Netherlands$ has an agricultural density of $31/sq.\,mi.$ (high efficiency/tech) while $Bangladesh$ has $431/sq.\,mi.$ (lower tech/more manual labor).