Why In News?

A study by the Indian Institute of Science Education and Research (IISER) revealed that destroyed ancient grasslands may never fully recover their original (Ancient) ecological composition.

What Are Ancient (Old-Growth) Grasslands?

Ancient or "old-growth" grasslands are primary, long-established open grassy biomes shaped over thousands of years by natural evolutionary forces, seasonal drought, grazing megafauna, and low-intensity wildfire regimes.

Slow-Growing Perennial Flora: Dominated by long-lived perennial grasses and forbs characterized by tough, fibrous leaves, high root-to-shoot ratios, and underground bud banks designed to endure extreme climatic stress.

Endemic Biodiversity Sanctuaries: Harbor highly specialized, co-evolved wildlife species, ranging from critically endangered avian fauna to subterranean insects and distinct soil microbiota.

What Are Secondary Grasslands?

Regrowth Following Anthropogenic Clearing: Secondary grasslands are open habitats that recolonize land following severe human intervention, such as agricultural plowing, clear-felling, open-cast mining, or heavy livestock overgrazing.

Altered Plant Composition: Dominated by short-lived, fast-growing annual grasses, opportunistic weeds, and ruderal species that possess rapid seed dispersal mechanisms but lack the ecological resilience of native perennials.

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Severed Underground Linkages: Plowing and soil compaction permanently destroy ancient subterranean bud banks, disrupt fungal mycorrhizal networks, and deplete organic carbon stratified over centuries.

Persistent Ecological Divergence: Even after decades or centuries of total agricultural abandonment, secondary grasslands fail to transition back to the botanical diversity of primary grasslands.

Highlights of The IISER-PNAS Study 

Comprehensive Global Dataset: Analyzed 742 plant species across temperate and tropical grasslands spanning six continents (Asia, Africa, North America, South America, Europe, and Australia).

Universal Functional Divergence: Ecological gap between old-growth and secondary grasslands is consistent globally: secondary grasslands are universally populated by species with higher specific leaf area and rapid nutrient acquisition, while ancient grasslands preserve stress-tolerant, slow-growing perennials.

Longevity Trap: Native perennial plants in ancient grasslands prioritize survival over rapid growth; once cleared, they cannot outcompete aggressive colonizer species in disturbed soils.

Centuries-Long Deficit: Structural and functional differences persist for centuries, confirming that grassland degradation is functionally irreversible under passive natural recovery. 

Ancient (Old-Growth) Grasslands vs Secondary Regenerated Grasslands

  • Ecosystem Age: Ancient grasslands have evolved undisturbed over millennia; secondary grasslands develop within years or decades following human abandonment.

  • Flora Profile: Ancient biomes feature long-lived, slow-growing perennial tussock grasses with tough leaves; secondary biomes are dominated by fast-growing annual weeds and opportunistic grasses.

  • Carbon Sequestration: Ancient grasslands lock vast, stable carbon pools deep underground within extensive root systems; secondary grasslands hold volatile, shallow, and significantly smaller carbon reserves.

  • Restoration Potential: Ancient grasslands, once plowed, cannot naturally regenerate their historical floristic diversity; secondary grasslands require intensive, costly active interventions (seed sourcing, soil inoculation) to mimic native conditions.

Why Is Grassland Restoration Difficult?

Exhaustion of Soil Seed & Bud Banks: Deep plowing obliterates the subterranean regenerative organs (tubers, corms, rhizomes) that ancient grasses depend upon for post-disturbance recovery.

Loss of Soil Microbiome and Mycorrhizae: Soil disturbance eradicates specialized arbuscular mycorrhizal fungi (AMF) that native perennial grasses rely on to extract phosphorus and moisture during prolonged droughts.

Invasive Species Encroachment: Fast-growing ruderal weeds rapidly colonize exposed soil, preempting sunlight, water, and space, thereby suppressing the slow germination of native grass seeds.

Altered Hydrology and Soil Chemistry: Agricultural fertilizers leave residual nitrogen and phosphorus spikes that favor non-native annual weeds over nutrient-efficient native perennials.

Why Are Grasslands Critical For Ecological Security?

Climate-Resilient Carbon Storage: Grasslands store approximately 34% of global terrestrial carbon, primarily underground; unlike forests, where fires release canopy carbon directly into the atmosphere, grassland fires leave subterranean root carbon intact.

Water Table Recharge and Soil Conservation: Deep, fibrous root systems facilitate rainwater infiltration, recharge shallow aquifers, reduce flash-flood runoff, and prevent topsoil erosion.

Harboring India's Most Threatened Fauna: Indian grasslands are mandatory habitats for critically endangered species, including the Great Indian Bustard (Ardeotis nigriceps), Lesser Florican, Bengal Florican, Blackbuck, Indian Gazelle (Chinkara), and the Indian Grey Wolf.

Pastoral Economy & Food Security: Sustain millions of livestock in India, supporting the milk, meat, and wool economies of traditional pastoralist communities (e.g., Maldharis, Dhangars, Gujjars, Bakarwals).