ContentContent

• Environmental Characteristics

• Opportunity and Constraints

• Human Activities in Tropical Desert

• Desertification

Where is Tropical Desert ?

Between 20 to 30 N and S. Subtropical High Pressure Zone. Sinking Limb of The Hadley Cell. Usually in Western Part of Continents.

Examples of Tropical Desert

Low Developed Countries: Sahara Desert High Developed Countries: Southern California West Australian

Opportunities And Constraints

AtmosphereHydrosphereLithosphere

Atmosphere

1.High insolation input

High temperature in daytime

Large diurnal range of temperature

2.Low annual rainfall, less than 250mm

Rainfall unreliable, variable and localized

Low relative humidity

Opportunities And Constraints

High temperature ---

Long growing season favors plant growth

Too high for people to live

High insolation input--- Solar energy

Hydrosphere

Low annual rainfall Small base flow Low discharge (except exotic rivers) Low water table But flash flood may happen

Opportunities And Constraints

Farming and navigation are difficult. Oasis Farming is possible where water table

is stable. Nomadic herding is possible.

LithosphereLithosphere Soils are salineSoils are saline Coarse texturedCoarse textured Alkaline (over pH 9)Alkaline (over pH 9) Little leaching and CECLittle leaching and CEC

Opportunities And Opportunities And ConstraintsConstraints

Rich in mineral resourcesRich in mineral resources

e.g. oil, salt.e.g. oil, salt. Large area for settlementLarge area for settlement Unfavorable for farmingUnfavorable for farming Sand StormSand Storm

Human activities in TD

1.Nomadic herding

people move with cattle and sheep from place to place for water and pasture.

2.Arable farming

It is the practice of extensive agriculture to produce crops without irrigation in regions with low rainfall.

3.Mining

Oil, rock salt, etc are mined

4.Scientific research

e.g. nuclear testing due to sparse population and space there

Case Study – Dubai Case Study – Dubai 杜拜杜拜

Where is Dubai ?Where is Dubai ?

Coast of the United Arab Emirates. Lies within the Arabian Desert. Sandy desert surrounding the city.

Economic Activities in DubaiEconomic Activities in Dubai

Before 1970s, agriculture was the major economic activities.

However the discover of oil made the rapid development of oil industry.

In the past 20 years, the government is developing the city into financial city. Oil industry accounts only 5% of the GDP.

Desertification

‧the degradation of land in arid, semi arid and dry sub-humid areas

‧resulting from various climatic variations, but primarily human activities

‧increase in population

→ demand for land ↑ ( for growing crops and grazing animals)

Causes

Human development → deforestation (for constructing buildings, extracting resources…)

→ population growth overcultivationsoil fertility ↓soil left exposed

Overgrazing compact soil together → reduce percolation rate → erosion ↑

Climatic factors rainfall ↓ vegetation cover ↓ soil exposed to wind erosion↑

1930s United States part of the Great Plains Dust Bowl →Overgrazing

→Drought

Since 1949‧China

‧population of rural area ↑ Overgrazing

• Soil becomes less productive.• Vegetation becomes damaged.• Food production is affected.

• Sustainable development• Afforestation• Construction of water channels to

supply water.• Control the population, so demand of

land can be reduced.