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Difficulty: HardEnvironmental Hazards, Degradation, and Management

To control the rapid advancement of desertification and soil degradation across the Sudano-Sahelian belt of Northern Nigeria, the establishment of shelterbelts of drought-resistant trees is widely promoted. Which of the following best explains how shelterbelts primarily mitigate land degradation in this vulnerable ecological zone?

  1. By reducing surface wind velocity to minimize mechanical deflation and retain soil moistureAnswer
  2. B
    By accelerating the in-situ chemical weathering of parent bedrock to continuously generate fresh topsoil layers
  3. C
    By converting non-renewable atmospheric carbon into permanent geological fossil fuel reserves
  4. D
    By replacing the mandatory statutory stages of Environmental Impact Assessments prior to land development

Answer

Shelterbelts primarily mitigate land degradation by reducing surface wind velocity to minimize mechanical deflation and retain soil moisture.
Shelterbelts consist of dense linear plantings of trees positioned perpendicular to prevailing wind directions. In semi-arid regions like Northern Nigeria, they significantly decrease surface wind speed, preventing wind deflation (the stripping away of fine topsoil particles) and reducing evapotranspiration, thereby preserving soil fertility and moisture.

Step-by-Step Solution

1
Identify the primary environmental hazard and degradation mechanism in Northern Nigeria's Sudano-Sahelian zone.
The region is predominantly affected by wind erosion (deflation) and desertification driven by strong dry winds acting on dry, sparse soil.
Sparse vegetative cover and high wind speeds make topsoil vulnerable to detachment and aerial transport.
2
Analyze the physical function of tree shelterbelts in environmental management.
Planted rows of trees perpendicular to prevailing winds create a friction barrier that reduces wind kinetic energy close to the ground.
Lowering wind velocity directly reduces soil particle lifting and evaporation rates.
3
Distinguish the primary mechanism from incorrect geological or administrative processes.
Mechanical wind reduction directly targets topsoil deflation, whereas weathering involves rock decay, fossil fuels form over geological time, and EIAs are regulatory planning steps.
Option analysis confirms that physical wind velocity reduction is the accurate functional mechanism of shelterbelts.

Key Concept

Desertification Control and Wind Erosion Mitigation via Shelterbelts
Estimated Time:2m 0s
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Topics

Environmental Hazards, Degradation, and Management

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