UPSC Prelims 2021 Q61: Environment & Ecology – Ecosystems & Ecology Concepts
The vegetation of savannah consists of grassland with scattered small trees, but extensive
areas have no trees. The forest development in such areas is generally kept in check by one or
more or a combination of some conditions. Which of the following are such conditions?
1. Burrowing animals and termites
2. Fire
3. Grazing herbivores
4. Seasonal rainfall
5. Soil properties
Select the correct answer using the code given below.
- (a) 1 and 2
- (b) 4 and 5
- (c) 2, 3 and 4
- (d) 1, 3 and 5
Answer: (c) 2, 3 and 4
Explanation
What keeps savannahs from turning into forest?
Savannahs are tropical grasslands with scattered trees, as in East Africa's Serengeti.
Three conditions mainly stop trees from closing in.
| Condition | Role in savannahs | Key factor? |
|---|---|---|
| 1. Burrowing animals and termites | Shape soil and nutrients, but do not hold back forest on a large scale | No |
| 2. Fire | Regular dry-season fires kill tree seedlings; grasses regrow from roots | Yes |
| 3. Grazing herbivores | Elephants, antelopes and others eat or trample saplings | Yes |
| 4. Seasonal rainfall | A long dry season limits tree growth and favours grasses | Yes |
| 5. Soil properties | Matter locally, but are not the general control named in standard texts | No |
Answer: (c) 2, 3 and 4.
Why each option is right or wrong
- (a) Incorrect. Termites are not a main control, and the option leaves out grazing and seasonal rainfall.
- (b) Incorrect. Seasonal rainfall matters, but soil is not a main control, and fire and grazing are missing.
- (c) CORRECT. Fire, grazing herbivores and seasonal rainfall keep savannah forests in check.
- (d) Incorrect. It leaves out fire, the most important factor holding back trees in savannahs.
Key point
Savannah trees are kept in check by fire, grazing herbivores and seasonal (dry-season) rainfall.
Remember
Savannah controls: fire, grazing, seasonal rain.
Common mistakes
- Leaving out fire, which is the single biggest control on savannah tree cover.
- Overrating termites because they are prominent in savannah landscapes.
- Thinking savannahs are treeless only because of poor soils.
Exam tip
Savannah = fire + grazers + a long dry season. Remember the classic trio.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, Ch 15 (Biodiversity: biomes)
- UPSC Civil Services (Preliminary) 2021 — Official Answer Key, GS Paper I