Content 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  Atmosphere  Hydrosphere  Lithosphere

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.

Lithosphere Soils are saline Soils are saline Coarse textured Coarse textured Alkaline (over pH 9) Alkaline (over pH 9) Little leaching and CEC Little leaching and CEC

Opportunities And Constraints Rich in mineral resources Rich in mineral resources e.g. oil, salt. Large area for settlement Large area for settlement Unfavorable for farming Unfavorable for farming Sand Storm Sand 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 杜拜

Where is Dubai ? Coast of the United Arab Emirates. Lies within the Arabian Desert. Sandy desert surrounding the city.

Economic 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 areasdegradationaridsemi arid ‧ resulting from various climatic variations, but primarily human activitiesclimatic ‧ increase in population → demand for land ↑ ( for growing crops and grazing animals)

Causes  Human development → deforestation (for constructing buildings, extracting resources…) → population growth  overcultivation  soil 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.