Why Defining the Aravalli Hills Has Become India’s Latest Ecological Flashpoint

Stretching nearly 680 km across Gujarat, Rajasthan, Haryana and Delhi, and older than the Himalayas by geological time, the Aravalli ranges are among India’s most critical — and most contested — ecological systems. What should have been a technical exercise to define these ancient hills has instead triggered protests, legal reversals and fears of large-scale ecological loss, exposing a deeper policy contradiction between conservation, mining and climate resilience.

Why the Aravallis matter far beyond geography

The Aravalli ranges act as a natural barrier against the eastward spread of the Thar desert and play a key role in deflecting westerly winds, bringing winter rainfall to Punjab, Haryana, Delhi and western Uttar Pradesh. Their forests function as vital carbon sinks, moderating winter air pollution in Delhi-NCR, while their fractured geology supports groundwater recharge and biodiversity across semi-arid north-west India.

Ecologically, these hills are far more than “elevated landforms”. They are integrated systems of ridges, slopes, scrub forests, valleys and aquifers — many of which lie well below dramatic hilltops.

How the Supreme Court entered the definition debate

On May 5, 2024, the Supreme Court of India directed the Union Environment Ministry to evolve a uniform definition of the Aravalli ranges. Acting on this, the Ministry of Environment, Forest and Climate Change constituted a panel headed by its Secretary, with representatives from the Forest Survey of India, Geological Survey of India and the Central Empowered Committee.

The panel analysed minimum, maximum and average elevations across 34 districts spanning four states. What emerged was a core problem: the Aravallis are not uniformly hilly. Some districts contain hills that are geologically unrelated to the Aravalli system, while large stretches of the true Aravalli extent consist of low ridges, degraded slopes and ancient landforms barely rising above surrounding terrain.

Why elevation and slope fail as defining tools

The panel found that neither elevation nor slope alone can reliably delineate the Aravalli ranges. Using elevation risks excluding ecologically integral low hills, while slope-based criteria risk including non-Aravalli landforms.

This tension is stark in Rajasthan. Earlier mapping by the Forest Survey of India used a 3-degree slope criterion, identifying over 40,000 sq. km — about one-third of the geographical area of 15 districts — as part of the Aravalli system. The same survey mapped 12,081 hills, of which only 1,048 rose above 100 metres.

Under the panel’s recommended 100-metre elevation rule, nearly 90% of these hills would fall outside the Aravalli definition.

The 100-metre rule — and why it alarmed conservationists

Despite these inconsistencies, the expert panel recommended defining the Aravalli as landforms with an elevation of 100 metres or more from local relief, along with supporting slopes and associated features. The Supreme Court approved this definition on November 20, 2025.

The rationale was not purely ecological. The panel explicitly noted that the Aravalli region hosts significant deposits of base metals such as lead, zinc and copper, precious metals like gold and tungsten, and in Delhi, rare and critical minerals including lithium, nickel, niobium and graphite — all crucial for energy transition, high-technology manufacturing and national security.

Environmental groups warned that a height-based definition would legally open vast tracts of lower hills and slopes to mining and real estate pressure, hollowing out the ecological spine of north-west India.

A judicial pause and unresolved questions

Amid sustained protests, the MoEFCC announced that no new mining leases would be granted until further studies were completed. Yet concerns persisted. On December 29, 2025, the Supreme Court took suo motu cognisance of the issue, stayed its own approval of the 100-metre definition, and ordered the constitution of a fresh expert committee to examine environmental impacts.

Significantly, the Court’s amicus curiae cautioned that adopting elevation as the sole criterion could expose lower hills to relentless mining — a concern echoed in earlier judgments in the “M.C. Mehta vs Union of India” cases of 1996, 2004 and 2008, which sought to protect the Aravallis from deforestation and mineral extraction.

The inconsistency at the heart of India’s hill protection

The controversy raises a larger policy question: India has no formal, uniform definitions for major hill systems such as the Himalayas, Western Ghats, Eastern Ghats, Vindhyas or Satpuras based on elevation or slope. Ecological protection in these regions has evolved through landscape-level understanding, not contour thresholds.

Applying a rigid numerical definition to the Aravallis risks creating a precedent where geomorphology is reduced to a bureaucratic filter rather than an ecological reality.

The green wall paradox

The debate also exposes a policy contradiction. In 2024, the MoEFCC announced an ambitious “green wall” project stretching nearly 1,400 km from Porbandar — Mahatma Gandhi’s birthplace — to Rajghat in Delhi. The plan envisages reforesting 1.15 million hectares across Delhi, Haryana, Rajasthan and Gujarat by 2027, using native species to restore forests, pastures and water bodies around the Aravallis.

Yet there is no publicly available data on what has been achieved so far or how future targets will be met. Critics argue that narrowing the legal definition of the Aravallis while promising landscape-scale ecological restoration undermines the credibility of both efforts.

What is really at stake

At its core, the Aravalli dispute is not about cartography, but about how India balances ecological security against extractive pressures. A definition that excludes low hills may satisfy administrative clarity, but it risks fragmenting one of the subcontinent’s oldest ecological systems.

As the Supreme Court reconsiders its approach, the unresolved challenge remains clear: protecting the Aravallis requires recognising them not as isolated hillocks defined by height, but as a continuous, living landscape whose value lies precisely in what does not rise dramatically above the ground.