UPSC Prelims 2003 Q110: Environment & Ecology – Ecosystems & Ecology Concepts
Assertion (A): Unlike temperate forests, the tropical rain forests, if cleared, can yield
productive farm - land that can support intensive agriculture for several years even without
chemical fertilizers.
Reason (R): The primary productivity of the tropical rain forest is very high when compared to
that of the temperate forests.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is NOT the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (d) A is false but R is true
Explanation
Cleared tropical rain forests and agriculture
| Part | Verdict |
|---|---|
| A. Cleared tropical rain forests can yield farm land that supports intensive agriculture for several years without fertilisers | False: the soils are poor and nutrients are held in the vegetation, so fertility drops fast |
| R. Primary productivity of tropical rain forests is very high | True |
A is false because rain forest soils are poor and quickly lose fertility once the forest is cleared, while R is true.
Answer: (d) A is false but R is true.
Why each option is right or wrong
- (a) Incorrect. A is false, so R cannot explain it.
- (b) Incorrect. A is false, as cleared rain forest soils are poor.
- (c) Incorrect. R is true, so this code is wrong.
- (d) CORRECT. A is false because the soils lose fertility quickly, while R is true.
Key point
Rain forest nutrients are locked in biomass; clearing leads to laterites and erosion.
Remember
Cleared rain forest land quickly loses fertility.
Common mistakes
- Believing high productivity means fertile soil.
- Forgetting the leaching of tropical soils.
- Mixing temperate and tropical soil richness.
Exam tip
High biomass does not mean fertile soil in the tropics.
Sources
- NCERT Class XII Biology — Ecosystem
- Eugene P. Odum — Fundamentals of Ecology (tropical rain forest)