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Introduction to ecosystems


[image - desert]
A typical desert scene


Online Activities
[Online activities]: n Activities related to this topic
Ecosystems - Half a Minute Game
Ecosystems - Interactive Diagram
Ecosystems - Fling the teacher
[Podcast]: n Audio file for playback on mobile devices and personal computers

Where are Deserts found?
Deserts are mainly found around the Tropics of Cancer and Capricorn.orn.

What are Deserts?
Deserts are areas of the earth's surface which recieve less than 25cm or 10 inches of rainfall every year. They contain little or no vegetation. The main characteristics of deserts are:

  • rare clouds
  • little rain
  • very hot days
  • very cold nights

How did Desert get like this?

[Hadley Cell] You may be wondering "If deserts are so hot......why are they found along the tropics and not at the equator where the earth's temperatures are the highest?". The diagram on the left should explain this!

A. As you would expect, temperatures at the equator are highest. Warm air rises containing evaporated moisture.
B. The air cools, condenses and forms clouds.
C. Heavy equatorial rainfall occurs (like in the rainforest!)
D. The cool, dry air then begins descending. The air warms up. Any moisture in the air is held as water vapour (invisible).

E. Cloudless sky.

Because the tropics are largely cloudless they get very hot during the day. There are few clouds to insulate these areas during the night. Therefore, temperatures drop to very low levels overnight. It's just like going to bed without any blankets!

What is the impact of humans on the Desert?
Deserts are increasing in size daily. This is partly due to human actions. Poor farming techniques, such as overgrazing and overcultivation in areas of savanna grassland, are causing soil erosion and desertification.

What is the future for the Desert? - Sustainable Development
Coming soon!



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