How do disturbances create heterogeneity in ecosystems? Illustrate with examples from savanna and forest biomes.

Ecological disturbances such as fire, grazing, storms, treefalls or the death of a large animal are discrete events that alter resources and suppress organisms locally. Because they strike unevenly in space and time, they break a uniform landscape into a mosaic of patches at different stages of recovery. This patchiness is ecological heterogeneity.

How disturbances generate heterogeneity

• Resource pulse: a disturbance suddenly releases or concentrates nutrients or light in one patch, unlike its surroundings.
• Selective suppression: some species decline while others benefit, which resets succession only in that patch.
• Patch-age mosaic: patches with different times since disturbance coexist side by side.
• Behavioural feedback: animals respond to the altered patches, which reinforces the differences.

Disturbance → resource pulse / mortality → altered soil & vegetation
            → changed animal use → long-lived patch mosaic

Fig: Disturbance-to-heterogeneity pathway

Savanna biome

• Carcass nutrient pulse: a Kruger National Park study found that an elephant carcass turns its site into a "coldspot", where high levels of some substances suppress the diversity of soil microbes and plants [1].
• Simultaneous "hotspot": the surviving plants grow highly nutritious leaves, which draw more impala and buffalo to graze there [1].
• Long legacy: the effects last more than seven years [1], so a single death leaves a lasting patch in the savanna mosaic.
• Fire and grazing likewise keep tree–grass patches at different stages of recovery.

Forest biome

• Canopy gaps: treefalls and storms open the canopy, and light-demanding pioneer species colonise the gaps. The forest becomes a mosaic of gap, regrowing and mature phases.
• Megafaunal engineers: African forest elephants of Central Africa's tropical forests play key ecosystem roles. They are now Critically Endangered, and the savanna elephant is Endangered [2].
• Anthropogenic disturbance: India holds more than 60% of wild Asian elephants, whose habitats are increasingly fragmented, so corridors are vital [3]. Railway lines through forests caused 81 elephant deaths in five years, which led to underpasses, ramps and speed limits [4]. Heterogeneity of this kind breaks up habitat and degrades it.

Disturbances, then, create heterogeneity through uneven resource pulses and selective suppression that persist over time, whether from a carcass on the savanna or a gap in the forest. Conservation should therefore keep natural disturbance regimes and healthy megafaunal populations intact, and reduce harmful human-caused fragmentation. Doing so would advance SDG 15 (Life on Land) and India's constitutional duty to protect forests and wildlife under Article 51A(g).