Defining the Aravalli Hills Became an Ecological Flashpoint

The ecological significance of the Aravallis

Defining the Aravalli Hills Became an Ecological Flashpoint: Stretching nearly 680 km across Gujarat, Rajasthan, Haryana and Delhi, the Aravalli Hills are among the oldest fold mountains on Earth. Geologically, they predate the Himalayas by hundreds of millions of years.

Ecologically, the Aravallis act as a barrier against the eastward expansion of the Thar Desert. They deflect westerly winds and enable winter rainfall over Punjab, Haryana, Delhi and western Uttar Pradesh, supporting agriculture and water security.

Static GK fact: The Aravalli system is one of the world’s oldest mountain ranges, formed during the Proterozoic era.

More than visible hills

The Aravallis are not defined by dramatic peaks. Large parts consist of low ridges, scrub forests, valleys and fractured rock systems that support groundwater recharge in semi-arid regions.

These low-lying formations regulate Delhi-NCR air quality, act as carbon sinks, and sustain biodiversity adapted to dry climates. Ecologists argue that excluding such features ignores how landscapes function as integrated systems.

Judicial intervention and the definition debate

On May 5, 2024, the Supreme Court of India directed the Ministry of Environment, Forest and Climate Change to evolve a uniform definition of the Aravalli ranges.

The Ministry constituted an expert panel with representatives from the Forest Survey of India, Geological Survey of India, and the Central Empowered Committee. The panel examined elevation and slope data across 34 districts in four states.

Why elevation and slope proved inadequate

The panel found that elevation alone cannot capture the true extent of the Aravallis. Many ecologically crucial stretches barely rise above surrounding terrain, while some higher hills are geologically unrelated.

In Rajasthan, earlier Forest Survey mapping using a 3-degree slope criterion identified over 40,000 sq. km as part of the Aravalli system. Of the 12,081 mapped hills, only 1,048 exceeded 100 metres.

Static GK Tip: Slope-based mapping is commonly used in geomorphology to identify degraded hill systems and ancient ranges.

The controversial 100-metre rule

Despite these findings, the panel recommended defining the Aravallis as landforms with a minimum local relief of 100 metres, along with associated slopes. This definition was approved by the Supreme Court on November 20, 2025.

The panel also highlighted the region’s mineral wealth, including lead, zinc, copper, and strategic minerals such as lithium, nickel and graphite, linking the definition to energy transition and industrial security.

Environmental groups warned that this threshold would legally exclude nearly 90% of existing Aravalli hills, opening them to mining and construction.

Judicial pause and renewed scrutiny

Following sustained protests, the Ministry announced a pause on new mining leases. On December 29, 2025, the Supreme Court took suo motu cognisance, stayed its own approval, and ordered a fresh expert review.

The Court’s amicus curiae warned that height-based criteria could expose lower hills to unchecked extraction, echoing earlier judicial efforts to protect the Aravallis from degradation.

The policy contradiction

India does not define the Himalayas, Western Ghats, Eastern Ghats, Vindhyas or Satpuras using rigid elevation thresholds. Protection in these regions evolved through landscape-level ecological understanding, not numerical cut-offs.

Applying a strict definition only to the Aravallis risks reducing complex geomorphology into an administrative filter.

The green wall paradox

In 2024, the MoEFCC announced a 1,400 km green wall project from Porbandar to Delhi, aiming to restore 1.15 million hectares around the Aravallis by 2027. However, narrowing the legal definition while promising large-scale restoration exposes a credibility gap.

What is truly at stake

The dispute is not about cartography. It is about whether India recognises the Aravallis as a continuous living landscape or fragments them for administrative convenience.

Protecting this ancient system requires ecological realism, not just contour lines.

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