A New Definition to Aravalli's

The Supreme Court’s 2025 verdict introducing a uniform legal definition of the Aravalli Hills is a landmark moment for environmental governance in India. By defining Aravalli Hills based on relative relief (≥100 m above local relief) and spatial clustering, the judgment aims to bring clarity and consistency across Delhi, Haryana, Rajasthan, and Gujarat.

However, from an environmental and geomorphological perspective, this definition may have serious unintended consequences.

The Aravalli range is one of the oldest and most eroded mountain systems in the world. Much of its ecological value lies not in prominent peaks, but in low-relief ridges, hillocks, pediments, and discontinuous uplands. A relief-based threshold, when applied strictly, risks placing nearly 90% of the Aravalli landscape outside the legal definition, potentially reclassifying ecologically sensitive terrain as developable land.

To examine this scientifically, I implemented a Google Earth Engine (GEE)–based workflow using:

1. SRTM DEM (30 m)

2. Dissolved district-level AOI covering all Aravalli districts

3. A local relief model (height above the lowest enclosing contour)

4. Identification of hills ≥100 m above local relief

5. Mapping of remaining areas as legally developable

The results reinforce a key concern: large contiguous portions of the Aravalli system fail to meet the new relief threshold, despite their well-documented role in:

1. Blocking hot, dry winds from the Thar Desert

2. Regulating regional temperature

3. Supporting groundwater recharge

4. Sustaining dry deciduous and scrub biodiversity

While the verdict improves legal precision, it also highlights a deeper policy challenge:

"Can a single geomorphological threshold adequately protect an ancient, ecologically integrated landscape?"

Effective conservation of the Aravallis requires supplementary ecological criteria such as hydrological function, vegetation continuity, and landscape connectivity alongside relief-based definitions. Without this, legal clarity may come at the cost of long-term environmental resilience.

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