Man-Land relationship in

Tropical Deserts

• Distribution of the world’s deserts• Impacts of the environment on human

activities :A. Climatic Impact on human

activitiesB. Problems in development

• Impacts of human activities on the environment: A. Desertification

1.Cultivation2.Mining3.An increase in population

B. Prevent desertification• Comment

• They are between the lines of latitude 20 degrees north and 20 degrees south of the equator.

• Deserts occur mainly at these latitudes because of high-pressure regions of dry air producedby the descending limb ofthe Hadley cell.

Distribution of world’s deserts

The location of Sahara Desert

Impacts of the environment on human activities

A. Climatic Impact on human activities1. Diseases2. Population3. Flash Flood

B. Problems in development1. Problem of cultivation2. Problem of transport3. Problem of water supply4. Problem of sand dunes migration

C. Conclusion of impacts of the environmenton human activities

Impacts of the environment on human activities

A. Climatic Impact on human activities1.DiseasesStrong and glaring sunlight may affect the eyes of human beings. Mirage (an optical illusion) and Dehydrations may also form on hot and windless day.

• High temperature in daytime may lower mental ability.

2. PopulationBecause of hot and dry climate and a adverse physical environment (will be mentioned latter) in Sahara, very few people are willing to live in there. Uneven distributed and sparse population e.g. >1000 people / sq. km in oasis, but <1 person /sq. km in the rest of Sahara. It makes development and exploitation of nature resources difficult.

3. Flash Flood As the rainfall is heavy and occasion, soil cannot infiltrate all the rainfall, flash flood is common. The effects of flash flood on man are far greater than those of sand dune. Also, it makes development and exploitation of nature resources difficult.

B. Problems in development1. Problem of cultivation

1.The physical environment is unfavorable to cultivation because:1/3 of Sahara is eroded rock and lava. 1/3 is made up of sand dunes. They are unsuitable for cultivation.

2.There are high mountains like Ahaggar Mountain, Tibesti Mountain.

3.Adverse climatic conditions with extreme temperature, intense insolation and insufficient rainfall limiting cultivation.

4.Soil is thin and immature and infertile.Sometimes, a layer of salt is left onthe surface after evaporation.

5.Attack of locusts, which may destroythe crops.

6.Diseases such as Malaria may spreadand attack man.

2. Problem of transportRoad transportHigh cost of transporting buildingmaterials,difficult to recruit specialists and labour and technical problems. Sea transportMost rivers in Sahara are non-navigable because they are too shallow.

3. Problem of water supplyAs river in Sahara are too shallow, many methods are used to increase water supply.Method 1- Use of underground waterUnderground waters are known as “artesian”,“pressure” or “ confined” water when the aquifer is confined by impermeable beds above and below, with the rock strataarranged in a gently inclined downwardsforming a shallow basin and the aquifer outcropping on the margins.

Method 2- Use of surface watera.Using pipelines and canals to tap the

rivers from Ahaggar or Atlas Mountain and convey to cultivated lands. But there are little or no permanent rivers. Streams only last for a short time.

b.Multi-purpose projects to supply perennial irrigation, e.g. Aswan Dam in Egypt.

c.Creation of inland lake.

4.Problems of sand dunes migrationSand dunes move rapidly which can cover roads or fields.

Remedies: a. Long- term stabilization

can be achieved by growing crops such as Acacia in areas where rainfallis >150mm/year. The deep roots can help to stabilize them.

b. Short-term stabilization can be achieved by spraying the dunes with a mixture of heavy oil and synthetic rubber.

C.Conclusion of Impacts of theenvironment on human activities :

climate Diseases Problems indevelopment

Flash FloodProblem of cultivationProblem of transportProblem of water supply Problem of migration people are low

income andsparse

Impacts of human activities on the environment:

A. Desertification1. Cultivation2. Mining3. An increase in population

B. Prevent Desertification1. Sand fences2. Vegetation cover3. Tree fences4. Keeping camels

A.Desertification

• Desertification simply means the spread of desert-like conditions into areas which formerly supported a vegetation cover.

Impacts of human activities on the environment:

1.Cultivation• The physical environment is

poor in Sahara desert as one-third of the Sahara is eroded rock and lava. One-third is made up of sand dunes. Therefore, dry-land farming is the most dominant in the Sahara desert.

• However, irrigation also causes variable problems. First of all, salinization of soil occurs as much irrigated water is lost through evaporation and transpiration.

• Also, silting can lead to an increase in the level of farmlands which makeirrigation even more difficult in the Sahara desert.

• Moreover, waterlogging of the soil occurs when the infiltration of large volumes of water which lead to an increase in the water table.

• In addition, overcultivation on marginal land without practicing proper soil and water conservation can lead to the spread of desert-like conditions into formerly non-desert areas.

• Mining can lead to the development of industries, particularly, oil and gas refining, and the production of salts and chemicals. However, mining may lead to destruction of the soil structure, exposing soil which is then more easily eroded.

2. Mining

•Due to an increase in the population in the Sahara desert, the pastoral farmers are able to enlarge their herds.•However, due to many animals grazing, it may exceed the carrying capacity of land in which is deteriorated. This may lead to drought in the Sahara Desert

3. An increase in population

Overgrazing

Desertification

B. Prevent Desertification

1.Sand fences•Sand fences are used throughout the Middle East and the United States, the same way snow fences are used in the north.

Sand fence

2. Vegetation cover• Shrubs and trees planted within

the grids are protected by the straw until they take root. In areas where some water is available for irrigation, shrubs planted on the lower one-third of a dune's windward side will stabilize the dune..

4. Tree fences• Oases and farmlands in

windy regions can be protected by planting tree fences or grass belts.

4. Keeping Camels• Increase the production of meat

by keeping camels instead of sheep, goats and cattle because camels can graze further from their sources of water.

Comment:Fung Sin Man (11) Before doing the project, I think that it is easy to handle. However, when I start to do it, I find that it is difficult to find the detail information, especially our project is mainly talk about the Sahara Desert. Therefore, this is our major difficulty. However, our group’s partnership is good. We have well communication, so when we can solve the problem together.Besides, we also can divide the work fairly. Each of us can have different work to do, so to conclude, this project can finish successfully.

Wan Yeuk Ki (26)Through this project, I know more about tropical deserts, such as impacts of man on environment. Not only the distribution and climate of tropical deserts but also deeper investigation of one of the tropical deserts-Sahara . Besides, this project makes me take an interest on Sahara.Lastly, I want to thank my members’ contribution.

Yu Long Sze (32)When I have finished our geography assignment, I also have learnt that the Sahara desert where is extremely unsuitable for people to live. Due to the extreme climate and lack of vegetation cover in the Sahara desert, the environment is not only unsuitable for people to live, it is also unsuitable for plants to live.Indeed, we can finish our assignment on time, I must thank for my partners due to they all did the good job. Therefore, we can all overcome the difficulties that we suffered. However, I am proud of my group’s spirit that is never give up our work!

ReferencesReferences

•• Revise Revise GcseGcse Geography Geography Letts Letts

•• http://www.fed.cuhk.edu.hhttp://www.fed.cuhk.edu.hk/geo/AL/core/pastPaper/k/geo/AL/core/pastPaper/

•• http://www.danheller.com/http://www.danheller.com/sahara.htmlsahara.html

•• http://www.thesahara.net/http://www.thesahara.net/sahara_facts.htmsahara_facts.htm

•• http://www.nationalgeograhttp://www.nationalgeographic.com/wildworld/profilephic.com/wildworld/profiles/terrestrial/pa/pa1327.hts/terrestrial/pa/pa1327.htmlml