Question

Difficulty: EasyEnvironmental Hazards and Degradation

In semi-arid regions such as Northern Nigeria, unsustainable land use triggers severe desertification. Arrange the following environmental degradation processes in their correct chronological sequence, from the initial cause to the final ecological outcome.

  1. 1Widespread removal of vegetation through overgrazing and tree felling
  2. 2Exposure of topsoil to intense solar heating and wind erosion
  3. 3Drastic reduction in soil organic matter and water infiltration capacity
  4. 4Sand dune encroachment and total loss of biological productivity

Answer

The correct order of desertification stages begins with the widespread removal of natural vegetation, followed by topsoil exposure and wind erosion, leading to a drastic reduction in soil organic matter and water infiltration, and concluding with sand dune encroachment and total loss of land productivity.
Desertification begins with human disturbances like overgrazing and tree felling. This exposes topsoil to wind erosion and solar heating, leading to loss of organic humus and soil water infiltration, and culminates in sand dune encroachment and permanent land degradation.

Step-by-Step Solution

1
Identify the initial trigger of desertification
Vegetation clearing from overgrazing and fuelwood extraction leaves ground bare.
Plant cover protects topsoil from direct exposure to sun and wind.
2
Determine the immediate physical response of the exposed surface
Intense solar radiation and strong winds erode the exposed topsoil layer.
Unprotected dry soil is easily carried away by dry wind currents.
3
Trace the subsequent soil degradation effect
The soil loses its organic content, nutrients, and ability to hold moisture.
Without topsoil and organic humus, soil structure collapses.
4
Identify the terminal outcome of the process
Active sand dunes form and spread, turning productive land into desert.
This is the final state of desertification where plant life can no longer be sustained.

Key Concept

Process and stages of desertification in semi-arid environments
Estimated Time:1m 0s
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