Lesson 3 Causes and impacts of soil erosion 3.6.pptx

environmental management lesson on soil erosion : causes and effects

1. 3.6 Causes and impacts of soil erosion Chapter 3 pg 75- 77

2. Learning Objectives: Keywords: Overcultivation Overgrazing Wind erosion Gulley erosion Desertification Famine Malnutrition Core: State and describe the causes of soil erosion. Extended: Describe and explain the impacts of soil erosion  Challenge: Research how soil erosion can be reduced.  3.6 Causes and impacts of soil erosion pg75-77

3. Syllabus points

4. Respecting others' rights

5. Soil erosion Soil erosion is a naturally occurring process.  It affects all types of land and plays an important role in shaping the landscape around us. Soil erosion is naturally slow though human activity such as agriculture can rapidly change the landscape around us.

6. The silent soil crisis https://www.youtube.com/watch?v=NJhpoYwAqFA Watch the video up to 3 minutes to understand the extent of the issue.

7. Soil horizons The topsoil layer is the most fertile. The structure of the topsoil provides the most root growth as it holds water and also allows for air spaces. Loss of this layer by erosion affects its fertility.

8. In your assigned pairs, summarise each type of erosion using your textbook page 75. Pairs will explain the process to the class as well as ask and answer questions. 20 minutes

9. Types of soil erosion: Removal of natural vegetation: Overgrazing Overcultivation Wind erosion Water erosion [GROUP5] [GROUP3] [GROUP 2] [GROUP4] [GROUP1]

10. Roots of existing plants help bind the soil together, once plants are removed the soil structure is not strong enough to withstand heavy rainfall.  Heavy rainfall and other run off picks up the topsoil in its way and moves it away from its original location.  Tree roots are useful in slowing down the speed of flowing torrents of water and providing places for any soil that is carried along to get trapped and deposited. With vegetation removed there may be nothing left to prevent run off and soil erosion. Removal of natural vegetation

11. Removal of natural vegetation

12. Overcultivation Regularly cultivated soil starts to lose its soil structure, ploughing or digging breaks up large clumps into smaller amounts. This may be good in the short term for sowing and the development of the seedlings. The mechanical breakdown of soil means that the soil particles are more vulnerable to erosion

13. Pressure on grazing land means that depending on the number of livestock. Constant grazing weakens the plants as their leaves are eaten and they are left with no means for  photosynthesising . This weakens the plants and can lead to their death.  Large numbers of animals also trample down and damage plants.  Animal hoofs an also compact soil and reduces air spaces in the soil reducing the root hair cell's ability to respire. Overgrazing

14. Water erosion The most common cause for soil erosion. Water erosion takes place in different ways: By heavy rainfall: large rain droplets move soil particles with force and they are now easier to erode in different ways. Rainwater run-off: excess water that is not absorbed by the soil will transport soil away from the area. Water entering the soil is reduced if the soil surface has been capped or compacted by feet/machines. Gulley erosion: Gullies and streams contain a volume of water moving at speed that erodes the local soil at even deeper layers. Forming deeper crevices. Gullies are naturally formed from rainwater run-off flow. It is worse in sloped areas where wtaer run off is faster

15. Past paper practise 5 minutes

16. Impacts of soil erosion: 1.Topsoil is removed: the most productive layer is absent (subsoil lacks in nutrients ad air spaces). 2.Organisms living in the topsoil lose their habitat: impact on the entire ecosystem. 3.Silting up of water courses: flooding occurs as water bodies can’t hold excess water (space taken up by silt).

17. Impacts of soil erosion: 4.Silt deposits can form lagoons: providing breeding grounds for mosquitoes. Silt affects the quality and availability of water for drinking. 5.Aquatic organisms are buried under the silty layer: preventing light from reaching the underwater plants (low oxygen levels in ecosystem no photosynthesis). 6.Desertification: the process by which fertile land becomes desert. Severe droughts lead to migration of the whole community. Risk of famine and malnutrition, leading to lesser food source.

18. Plenary: 5 minutes

19. Plenary:

20. Learning Objectives: Keywords: Irrigation Salinisation Soil erosion Soil capping Desertification Overproduction Oversupply Mechanisation Core: State the impacts of agriculture on humans and the environment. Extended: Describe and explain the impacts from the misuse of irrigation, choice of crops, overproduction and mechanisation on humans and the environment. Challenge: Research how food waste is managed 3.4 Impacts of agriculture pg70-72