Aravalli row: Why a 100-metre rule has triggered a mountain of concerns

The SC's acceptance of a 100-metre hill rule has alarmed experts who fear it could exclude large parts of the Aravallis from protection, affecting mining limits, forest cover and groundwater security

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For decades, the Aravallis have stood as a chain of ancient, weather-worn hills that once stretched unbroken across western and northern India. To most people in Delhi-NCR, they are simply the brown silhouettes glimpsed from highways, a leftover patch of wilderness on the edge of booming cities. But to ecologists, they are a natural wall that keeps desert dust at bay, a lifeline for groundwater, and one of the subcontinent’s oldest biodiversity systems.

 

And now that wall is at the centre of a redrawal of definitions — and a fierce argument.

 

On November 20, the Supreme Court accepted the Union environment ministry’s elevation-based definition of the Aravalli hills and ranges, and directed the Centre to carry out scientific mapping and prepare a “sustainable mining plan” for the range. The Court ordered that no fresh mining leases be granted until the mapping and plan are completed.

 

What exactly does the 100-metre rule say? 

The Centre panel’s definition treats a landform as part of the Aravalli only if it has at least 100 metres of elevation above the local relief, including the landform’s slopes and adjacent areas. Environmentalists point out that adopting this elevation threshold excludes large tracts of lower-lying but ecologically connected hills and ridges from the legal Aravalli boundary, potentially removing protections that had previously applied.

 

According to an internal assessment by the Forest Survey of India (FSI), only 1,048 of 12,081 mapped hills — just 8.7 per cent — meet the 100-metre height criterion, an Indian Express report noted. This means roughly 90 per cent of what was broadly considered Aravalli, including many “low hills” and ridges, may now be excluded from protection.

 

How have courts historically protected the Aravallis? 

Protection of the Aravallis has been litigated repeatedly in courts and tribunals. The National Green Tribunal (NGT) and various High Courts have previously recognised parts of the Aravallis as ecologically sensitive and issued curbs on illegal mining and encroachment. Several agencies have also issued notifications and “deemed forest” declarations for specific tracts.

 

The current matter reached the Supreme Court as states and petitioners sought a uniform demarcation and common standards across Rajasthan, Gujarat, Haryana, Delhi and adjoining areas.

 

The Ministry of Environment, Forest and Climate Change (MoEF&CC) identified 34 districts across four states as part of the Aravalli landscape, but several areas with a well-documented Aravalli presence were excluded. Chittorgarh, home to the UNESCO-listed fort, and Sawai Madhopur, where the Aravalli and Vindhya ranges meet at Ranthambore, do not appear in the official list.

 

In its affidavit, the ministry said the terrain shows significant diversity in elevation and slope, and that neighbouring non-Aravalli regions often share similar landforms. Relying solely on physical parameters could misidentify areas, it cautioned.

 

What ecological risks do scientists and conservationists highlight? 

Conservation groups warn that the new definition — and any corresponding opening to mining or development — could:

 

• Accelerate habitat loss and fragment wildlife corridors

 

• Damage groundwater recharge zones that sustain peri-urban agriculture

 

• Degrade native scrub and tree cover supporting birds and reptiles

 

• Raise long-term risks of desertification and dust in NCR

 

• Disrupt microclimates and push groundwater levels lower

 

Water-conservation experts emphasise that many “low ridges” are critical recharge zones. Disturbing them for mining or real estate projects could dry wells, drop water tables and threaten water security in entire districts, including urban zones dependent on Aravalli aquifers.

 

Cities adjoining the southern Aravallis — Gurugram, Faridabad, parts of western Uttar Pradesh and Rajasthan — have repeatedly linked illegal mining and land conversion to falling groundwater levels and degraded microclimates.

 

What is the Centre’s justification? 

The ministry argues that the 100-metre elevation rule provides a scientific and uniform benchmark across multiple states and will eliminate ambiguity around what constitutes the Aravalli range. It says regulated, “sustainable” mining will be permitted only after mapping, while core ecological and recharge zones will be preserved.

 

It adds that once the management plan is ready, restoration efforts — including under the Aravalli Green Wall Project — will be scaled up.

 

What happens next? 

The Supreme Court has ordered scientific mapping and a sustainable mining plan, and restrained new mining leases until the exercise is completed. Critics, however, warn that the damage may already be set in motion because once a landscape is “de-classified”, mining and real-estate interests could move faster than restoration plans.