Which of the following are the possible causes of soil erosion? I. bush burning II. over grazing III. reafforestation IV. excavation

Analyze the question: You are asked to pick the activities that can cause soil erosion. Note that reafforestation (III) is the odd one out, so you should check it carefully.

Explain the concept: Soil erosion is the removal of topsoil by agents such as running water and wind. It becomes worse when the soil loses its protective vegetation cover or is loosened and exposed.

Evaluate each statement:

• I. Bush burning: Causes erosion. It destroys the vegetation cover and exposes the soil to rain and wind. It also kills the organisms that help bind the soil.
• II. Overgrazing: Causes erosion. Too many animals eat the grass cover and trample the soil, leaving it loose and bare.
• III. Reafforestation: Does not cause erosion. It means replanting trees. Roots bind the soil and the canopy reduces the impact of raindrops, so it is a method of controlling erosion.
• IV. Excavation: Causes erosion. Digging, quarrying and mining disturb and loosen the soil and leave it exposed to water and wind.

Result: The causes are I, II and IV only.

Answer: Option B (I, II and IV only).

Tip: When a question asks for causes of erosion, look for the words that mean removing or disturbing cover (burning, clearing, overgrazing, digging, mining). Words that mean restoring cover (reafforestation, afforestation, mulching, cover cropping, terracing) are control measures, not causes.