Biomes Of The World


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Biomes Of The World

  1. 1. Biomes of the World Deserts
  2. 2. Deserts: Quick Facts <ul><li>A desert is a region of the earth that receives less than 25 centimeters of rainfall annually. </li></ul><ul><li>Thirty percent of the earth’s surface is covered by desert. </li></ul><ul><li>Most of the world’s deserts lie somewhere between the 20˚ and 30˚ lines of latitude on the western side of the continents </li></ul>
  3. 3. Desert Conditions <ul><li>Deserts occur where evaporation of rainwater is greater than the volume of rain in that area. </li></ul>
  4. 4. Hot Days and Cold Nights <ul><li>Because there is generally no cloud cover in a desert, heat is lost through evaporation. </li></ul><ul><li>The lack of moisture in the air, combined with the lack of vegetation allows the surface of the desert to release heat quickly once the sun has set. </li></ul>
  5. 5. West Coast Deserts <ul><li>Deserts generally occur in these areas because of climatic conditions. </li></ul><ul><li>Hot, dry air is blown westward across the desert, causing the average temperature to increase. </li></ul>
  6. 6. West Coast Deserts <ul><li>Cold ocean currents from the west coast meet with the warm westward winds. </li></ul><ul><li>Because evaporation from cold water is generally low, the amount of moisture in the air is limited, meaning less rain. </li></ul>
  7. 7. North America Deserts <ul><li>American deserts are different from most deserts because they exist separate from others, surrounded usually by mountain ranges. </li></ul><ul><li>Also, the well-known symbol of deserts, cacti, are found only in North American deserts. </li></ul>
  8. 8. Common Desert Plants <ul><li>North America </li></ul><ul><ul><li>cacti and small brush </li></ul></ul><ul><li>southern Africa </li></ul><ul><ul><li>aloe plant </li></ul></ul><ul><li>northern Africa and the Middle East </li></ul><ul><ul><li>date palm </li></ul></ul>
  9. 9. Desertification <ul><li>This is the process of semi-arid areas (areas with little annual rainfall) on the edges of deserts becoming drier and changing into full deserts </li></ul>
  10. 10. Why Does Desertification Occur? <ul><li>Some believe that desertification is a natural process resulting from the climate changed causing lower rainfall and a shorter wet season. </li></ul><ul><li>Those that believe desertification is caused by mankind point to pressure from overpopulated areas and the overuse of land to explain their theory. </li></ul>
  11. 11. Total Land Affected Worldwide <ul><li>Worldwide over 8.1 million square kilometers (roughly the size of Brazil) has been affected by desertification. </li></ul>
  12. 12. Slowing the Process <ul><li>The best way to slow desertification would be to dramatically reduce overgrazing, deforestation, and excessive cultivation of the land. </li></ul><ul><li>As well, reforestation programs will help to bind the water to hold in soil. </li></ul>