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Density &
Land Use

Understand how geographers measure the concentration of people and the patterns of land use that shape settlements around the world.

AP Human Geography

What Is Density?

In human geography, density measures how a feature is spread across space. It answers the question: how much of something exists per unit of area?

Geographers use three main types of density to analyze population distribution: arithmetic, physiological, and agricultural.

Three Types of Population Density

Arithmetic Density
\( \frac{\text{Total population}}{\text{Total land area}} \). The simplest measure: total people divided by total land.
Physiological Density
\( \frac{\text{Total population}}{\text{Arable land area}} \). People per unit of farmable land: reveals food pressure.
Agricultural Density
\( \frac{\text{Number of farmers}}{\text{Arable land area}} \). Farmers per farmable land: indicates farming efficiency.

Why Density Matters

Density is not just a number: it shapes policy decisions, resource allocation, and our understanding of how people interact with their environment.

1
Resource planning: High physiological density signals potential food insecurity and pressure on arable land.
2
Infrastructure: High arithmetic density demands more roads, hospitals, and schools per area.
3
Economic insight: Low agricultural density often means mechanized farming and higher economic development.

Core Density Formulas

Arithmetic Density
\( \frac{\text{Pop}}{\text{Total Area}} \)
 Physiological Density
\( \frac{\text{Pop}}{\text{Arable Land}} \)
 Agricultural Density
\( \frac{\text{Farmers}}{\text{Arable Land}} \)
 Overall crowding people per sq km/mi Food pressure people per arable unit Farm efficiency farmers per arable unit Same denominator for physiological & agricultural: arable land

Physiological vs. Agricultural Density

Physiological Agricultural
Numerator Total population Number of farmers
Denominator Arable land Arable land
Measures Pressure on food supply Farming technology level
High value means More mouths per farm unit Less mechanization
Example (high) Egypt Bangladesh

Understanding Land Use Patterns

Land use describes how humans modify and utilize the physical environment. The dominant categories include residential, commercial, industrial, agricultural, and recreational uses.

Residential
Housing and living spaces: apartments, suburbs, rural homesteads.
Commercial
Business, retail, and office spaces concentrated in CBDs and malls.
Agricultural
Cropland, pasture, and livestock operations dominating rural areas.
Industrial
Factories, warehouses, and processing plants near transport nodes.

How Density Shapes Land Use

Urban Core High Density Suburbs Rural Distance from center: density decreases

How to Calculate Density

1
Identify the type: Determine whether the question asks for arithmetic, physiological, or agricultural density.
2
Find the numerator: Total population (arithmetic & physiological) or number of farmers (agricultural).
3
Find the denominator: Total land area (arithmetic) or arable land area (physiological & agricultural).
4
Divide and interpret: Compute the ratio and explain what the result means about population pressure or farming efficiency.

Example: Country X

Country X has a population of 50 million, a total area of 500,000 \( \text{km}^2 \), and arable land of 100,000 \( \text{km}^2 \).

Arithmetic
\( \frac{50{,}000{,}000}{500{,}000} = \) 100 \( \text{people/km}^2 \)
Physiological
\( \frac{50{,}000{,}000}{100{,}000} = \) 500 \( \text{people/km}^2 \)

Example: Comparing Two Countries

Country A Country B
Population 10 million 10 million
Total area 200,000 \( \text{km}^2 \) 200,000 \( \text{km}^2 \)
Arable land 150,000 \( \text{km}^2 \) 20,000 \( \text{km}^2 \)
Arithmetic density 50 \( \text{/km}^2 \) 50 \( \text{/km}^2 \)
Physiological density 67 \( \text{/km}^2 \) 500 \( \text{/km}^2 \)

Example: Agricultural Density

Country C has 2 million farmers and 50,000 \( \text{km}^2 \) of arable land. Country D has 200,000 farmers and 50,000 \( \text{km}^2 \) of arable land.

Country C
\( \frac{2{,}000{,}000}{50{,}000} = \) 40 \( \text{farmers/km}^2 \)
Country D
\( \frac{200{,}000}{50{,}000} = \) 4 \( \text{farmers/km}^2 \)

Land Use Models

Geographers have developed models to explain why certain land uses appear where they do. Two key models for AP Human Geography:

Von Thunen Model
Explains agricultural land use in concentric rings around a market center. Perishable goods (dairy, vegetables) are produced closest to the city.
Burgess Model
Explains urban land use in concentric zones: CBD at center, then factory zone, working-class housing, residential, and commuter zone.

Von Thunen's Agricultural Rings

Market Dairy & Intensive Perishable goods Timber & Firewood Heavy, costly to ship Grain & Field Crops Less perishable Ranching & Livestock Extensive, low value/area

Common Mistakes

✕ Confusing the Numerators
Using total population in the agricultural density formula instead of only farmers. Agricultural density counts only farmers.
✕ Ignoring Arable Land
Using total land area for physiological density. Physiological and agricultural densities use arable land only.
✕ Assuming High Density = Bad
High arithmetic density does not always mean overcrowding. Singapore is very dense but highly developed with excellent infrastructure.

Summary Comparison

Density Type Numerator Denominator Tells Us
Arithmetic Total population Total land area General crowding
Physiological Total population Arable land Food pressure
Agricultural Farmers only Arable land Farm technology

Question 1 of 5

A country has 30 million people, 600,000 \( \text{km}^2 \) of total land, and 120,000 \( \text{km}^2 \) of arable land. What is its physiological density?

Question 2 of 5

Which type of density is most useful for understanding the pressure a population places on its food-producing land?

Question 3 of 5

Country M has an agricultural density of 4 \( \text{farmers/km}^2 \). Country N has an agricultural density of 80 \( \text{farmers/km}^2 \). What can you most likely infer?

Question 4 of 5

In the Von Thunen model, which agricultural activity is located closest to the central market?

Question 5 of 5

Two countries have the same arithmetic density. Country P has a much higher physiological density than Country Q. What does this tell you about Country P?