The correct option is (c).
Explanation
The decline of the Harappan Civilization is attributed to a complex combination of ecological, climatic, and tectonic factors rather than a single event. Various theories have been proposed by scholars to explain the gradual urban collapse.
- Statement 1 is correct: One of the prominent ecological theories suggests that the Harappans depleted their surrounding forests. Large-scale deforestation was likely driven by the need for fuel to bake bricks (used extensively in construction) and to smelt copper ores. This loss of forest cover would have led to soil erosion and climatic instability.
- Statement 2 is incorrect: Grazing by large herds of cattle, sheep, and goats destroys vegetation. Overgrazing removes the green cover, exposing the topsoil to erosion and contributing to desertification. Therefore, grazing would decrease, not increase, the green cover.
- Statement 3 is correct: Hydrological changes were a critical factor. Evidence indicates that some cities, like Mohenjo-daro, suffered from repeated and devastating floods. Conversely, other regions suffered due to the drying up of rivers (such as the Saraswati/Ghaggar-Hakra system) or the shifting of river courses, which disrupted agriculture and water supply.
Key Takeaway: The decline of the Indus Valley Civilization was primarily driven by environmental degradation, including deforestation, overgrazing, and significant hydrological changes such as flooding or the drying up of vital river systems.