📘 Q.17 IAS Prelims 2021 — Environment & Ecology (Savanna Ecosystems)🧷 Authentic Classroom Explanation by IAS Monk
📌 The Question:
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?
- Burrowing animals and termites
- Fire
- Grazing herbivores
- Seasonal rainfall
- 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
✅ Correct Answer: (c) 2, 3 and 4
🧠 Classroom Explanation:
Savannas are not forests in waiting. They are stable ecological systems, maintained by a powerful interaction of climate and biological disturbances.
Let us examine the key controls:
🔹 Fire — Correct ✔️
Periodic natural and anthropogenic fires prevent saplings from maturing into trees.
Grass recovers quickly after fire, but tree seedlings do not.
📌 Fire is one of the strongest tree-suppressing forces in savannas.
🔹 Grazing Herbivores — Correct ✔️
Large grazers like zebras, antelopes, buffaloes and cattle:
- Consume young shoots and saplings
- Prefer grass, reinforcing grass dominance
📌 Continuous grazing breaks the forest regeneration cycle.
🔹 Seasonal Rainfall — Correct ✔️
Savannas experience:
- Short wet season
- Long dry season
This rainfall pattern:
- Supports grasses with shallow roots
- Disadvantages deep-rooted forest trees
📌 Forests require year-round moisture, which savannas lack.
🔹 Why NOT the others?
❌ Burrowing animals & termites
They modify micro-habitats, sometimes enhancing tree growth near mounds. They do not suppress forests at landscape scale.
❌ Soil properties
Savanna soils are often not extremely poor. Climate and disturbance matter more than soil alone.
🔍 Curiosity Raiser:
🌍 Many African savannas would turn into forests within decades if fire and grazing stopped — proving savannas are actively maintained ecosystems, not degraded forests.
📚 Enrich Notes (UPSC Gold):
• Savannas are shaped by the Fire–Grazing–Rainfall triad
• Tree–grass balance is a dynamic equilibrium, not succession failure
• Savannas dominate regions 8°–20° latitude from the Equator
• Important for carbon cycling, megafauna, and pastoral economies
📌 Key concept:
👉 Disturbance ecology — ecosystems maintained by regular disruption.
🪶 IAS Monk Whisper:
When fire burns, grazers feed, and rains pause — forests step back, and savannas stand firm.