NCERT Class 8 Environment & Ecology — Chapter 1: Conservation of plants and animals

Correct Option

The correct option is

The removal of topsoil exposing infertile rocky layers

Explanation

Desertification is defined as land degradation in arid, semi-arid, and dry sub-humid areas resulting from various factors, including climatic variations and human activities. In the specific context of soil erosion, it refers to the physical loss of the land's biological productivity due to the removal of fertile soil layers.

Option Analysis

• The natural expansion of arid deserts due to climate cycles is Incorrect: Desertification is not merely the natural expansion of existing deserts due to long-term climate cycles. It primarily refers to the degradation of previously productive land into a desert-like state due to mismanagement and environmental stress.
• The removal of topsoil exposing infertile rocky layers is Correct: Soil erosion, particularly sheet erosion, washes away the nutrient-rich topsoil (A-horizon). When this fertile layer is completely removed, the hard, infertile rocky subsoil or bedrock is exposed. This renders the land incapable of supporting vegetation, effectively turning it into a barren, desert-like landscape.
• The accumulation of sand dunes in agricultural lands is Incorrect: The accumulation of sand dunes (wind deposition) is a symptom or feature of desert environments. However, the question asks about the process of degradation via erosion (removal), not deposition.
• The loss of soil moisture solely due to evaporation is Incorrect: The loss of soil moisture due to evaporation relates to aridity or drought conditions. While this contributes to desertification, it does not describe the physical process of soil erosion.

Key Takeaway

Desertification, driven by soil erosion, is the process where fertile topsoil is stripped away, exposing infertile rocky layers and rendering the land permanently unproductive.