Correct option is A
Explanation-
Option A - Selective logging of forests opens up the canopy and grasses take over
Logging is an artificial (human-driven) activity, not a natural ecological factor. Savannas are natural ecosystems, maintained by climate, fire, and herbivory, not by human logging. While logging may resemble savanna-like structure temporarily, it is not a natural cause of savannas.
It does NOT explain natural savanna occurrence → Correct answer
Option B - Low rainfall maintains low tree cover that helps grasses establish
This is a key natural driver of savannas. Low rainfall prevents dense forests and favors grass dominance.
Trees struggle, grasses thrive → classic savanna structure.
Correct explanation for savanna presence
Option C - Fires do not allow trees to establish closed canopies
Frequent fires destroy tree saplings but grasses regenerate quickly. Fire is essential in maintaining open grassy areas and limiting forest formation.
Valid ecological factor in savanna maintenance
Option D - Browsing by herbivores limits tree establishment
Large herbivores like elephants or deer feed on young tree shoots, preventing forest regeneration. This suppresses woody growth and helps maintain the grassland structure.
Accurate cause for sustaining savanna conditions
Only Option A refers to human disturbance (logging) and not a natural ecological process — so it does NOT explain the natural occurrence of savannas.
Correct answer: Option A - Selective logging of forests opens up the canopy and grasses take over
