Institutional expertise meets judicial confusion in the Aravalli hills definition case

On  November 20, 2025, the Supreme Court accepted a definition of the Aravalli Range based on a 100-metre elevation threshold above the surrounding land. On December 29, it stayed this very judgment and referred the matter back for reconsideration. The pause itself signals that the judgment warrants re-examination. As the court prepares to revisit the issue, several questions merit careful consideration.

An institutional tension requiring clarity

The November judgment sought to resolve what it described as “definitional chaos” across states. Yet the prior protection regime, though complex, was largely coherent. The 1992 notification under the Environment (Protection) Act (S.O. 319(E)) defined Aravalli areas through forest classifications and revenue categories such as Gair Mumkin Pahar, which explicitly identified these lands. In Haryana, Section 4 orders under the Punjab Land Preservation Act (1992) protected designated villages. In Delhi, notifications under the Indian Forest Act covered the Delhi Ridge. These overlapping mechanisms, administered state by state, provided consistent legal protection through four decades of Supreme Court oversight in the MC Mehta and Godavarman proceedings.

What was not chaotic was the technical definition. In its 2010 Status Report to the Supreme Court, the Forest Survey of India (FSI) defined the Aravallis using slope-based criteria (a gradient greater than 3 degrees), with a 100-metre foothill buffer and a 500-metre inter-hill distance. This definition was grounded in decades of ecological analysis of how the range functions: as a barrier to desertification, a water recharge system, and a wildlife corridor.

The November 20 judgment replaced this approach with a simplified elevation-based metric: hills rising more than 100 metres above the surrounding land, with the range defined as two or more Aravalli hills within 500 metres of one another. The judgment notes that “the Committee” recommended this approach. What is less clearly stated is that the Committee included representatives from the FSI, the Central Empowered Committee (CEC)—which had earlier been asked to examine the issue, but whose findings were largely set aside—and the Geological Survey of India (GSI). These are precisely the institutions whose prior analyses favoured different criteria.

By situating these institutions within a committee recommending a position they had not previously endorsed, their potential dissent was structurally pre-empted. They were unable to act as independent voices before the court in support of the ecological criteria they had earlier advanced.

The court’s amicus curiae, K Parameshwar, argued in favour of the FSI’s slope-based definition, but without institutional backing. This configuration, whether intentional or incidental, requires clarification as the court reconvenes. Did the FSI, CEC and GSI genuinely support the 100-metre definition, or were they positioned in a way that prevented meaningful challenge to a predetermined recommendation?

Unresolved claims

The central argument against the 100-metre definition is quantitative. An internal assessment attributed to the Government’s own FSI reportedly noted that, of 12,081 documented Aravalli hills measuring 20 metres or more in height, only 1,048—approximately 8.7 per cent—exceed 100 metres. Environmental groups and independent researchers have cited this figure. Subsequently, the FSI formally denied having conducted any such study. This creates a factual ambiguity that the court must resolve. Notably, the Supreme Court itself refers to this figure in its December 29, 2025 judgment.

What is not in dispute, however, is the underlying geomorphological reality: the Aravalli Range consists predominantly of small ridges and hillocks, not towering peaks. A 100-metre threshold will inevitably exclude the majority of documented hills. The significance of this exclusion lies not in statistics, but in ecology.

The Aravallis’ critical functions  maintaining continuity as a barrier against desert sands, sustaining grassland habitats, recharging aquifers, and enabling wildlife movement — depend on the integrity of the range as a whole, not on the prominence of individual peaks. The twelve identified gaps through which Thar Desert sands drift towards the north-eastern plains are critical precisely because smaller hills between them have degraded or disappeared. These modest landforms perform essential ecological work.

A spatial analysis conducted by the Ashoka Trust for Research in Ecology and the Environment (ATREE), using a 100-metre height threshold and a 30-metre Digital Elevation Model, indicates that more than 70 per cent of Rajasthan’s current Aravalli extent — covering 18,092 villages and spanning 83,380.9 square kilometres — is likely to be delisted under the new notification. This is roughly equivalent to delisting an area comparable in size to the state of Arunachal Pradesh. The projected losses are even more severe in Gujarat and Haryana, where 82 per cent of the current Aravalli extent is at risk of denotification. Delhi would lose its entire Aravalli extent unless protected through other legal instruments.

The analysis estimates a loss of nearly 41.8 per cent of natural vegetation in Rajasthan’s Aravallis, including two-thirds of the state’s savanna grasslands, all of its sand dunes, and 18.35 square kilometres of forest. Comparable losses are projected for Haryana’s Aravallis (41.2 per cent) and Gujarat’s Aravallis (32 per cent). Alarmingly, all natural vegetation within the Delhi Aravallis is at risk.

Exceptional exemptions

Two developments in November 2025 occurred in close succession and merit examination together. 18 November 18, in a separate case, the Supreme Court permitted ex post facto environmental clearances, reversing its own May 2025 ruling that had declared the practice illegal. Two days later, on November 20, the court accepted the new Aravalli definition, while delicately carving out exceptions for critical, strategic and atomic minerals.

The ex post facto clearance ruling allows projects that commenced construction without prior environmental approval to seek retrospective clearance upon payment of penalties. In his dissent, Justice Ujjal Bhuyan described this as “a step in retrogression” that undermines India’s precautionary principle in environmental law. The majority opinion by Justice BR Gavai argued that refusing such clearances would result in the waste of “thousands of crores of rupees”.

The Aravalli judgment simultaneously permits the mining of atomic minerals (including uranium and thorium) and critical minerals such as lithium, cobalt, nickel, rare earth elements, tantalum and tungsten — effectively encompassing nearly all economically significant minerals found in the range.

This conjunction raises an important procedural question: does the ex post facto clearance framework now apply to mining in the Aravallis? If extraction begins without prior environmental clearance, can it subsequently be regularised? Does the so-called mining ban apply only to the newly defined Aravallis, or to the broader landscape?

The language of the November 20 judgment is ambiguous. The court directed the preparation of a Management Plan for Sustainable Mining (MPSM) through the Indian Council of Forestry Research and Education (ICFRE), stating that “till the MPSM is finalised by the MoEF&CC [Union Ministry for Environment, Forest and Climate Change] through ICFRE, no new mining leases should be granted”. However, this does not explicitly prohibit post-facto clearance for mining operations that have already commenced. Moreover, mining of atomic and critical minerals is now categorised as serving “strategic and defence projects”, placing it within exceptions under the Environmental Impact Assessment rules and allowing further regulatory leeway.

The judgment cannot be read in isolation. In January 2025, the government launched the National Critical Mineral Mission with an outlay of Rs 18,000 crore to ensure “sustainable, resilient and self-reliant” mineral supply chains. In September 2025, a ministry directive exempted critical and atomic mineral mining projects from mandatory public hearings and standard Environmental Impact Assessments, bypassing state-level clearances.

In December 2025, the Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India (SHANTI) Bill opened India’s nuclear sector to private companies for the first time since 1962. It capped operator liability at Rs 3,000 crore for reactors above 3,600 MW, with residual risk borne by the taxpayer. As uranium and thorium are now classified as atomic minerals exempted in the Aravalli judgment, private companies may prospect, extract and refine these minerals in the Aravallis, and operate nuclear plants with capped liability.

Four questions for reconsideration

On expertise and process: Will the court clarify whether the FSI, CEC and GSI genuinely supported the 100-metre definition? If not, how should their institutional positions inform the final definition?

On quantitative impact: Will the court commission an authoritative assessment of how many documented Aravalli hills fall below the 100-metre threshold? This does not require reliance on the disputed FSI study, but rather a comprehensive elevation-based survey.

On ecological function: What is the scientific consensus on the minimum elevation or slope required for the Aravallis to function as a desert barrier, wildlife corridor and water recharge system? Should ecological function, rather than arbitrary elevation, determine the definition?

On regulatory interaction: Will the post facto environmental clearance framework and exemptions for critical and atomic minerals apply to mining in the Aravallis? The judgment should clarify whether mining can commence without prior clearance and later seek regularisation, and whether the exempted minerals will be permitted going forward.

Institutional Stakes

By placing expert institutions within a committee they did not effectively control, and by adopting a definition that appears to contradict those institutions’ own analyses, the November 20 judgment marks a departure from the court’s traditionally meticulous approach to environmental adjudication. The subsequent stay suggests an implicit recognition of this concern.

On reconsideration, the court has an opportunity to reassert the primacy of institutional expertise, to demand quantified and transparent analysis rather than rely on contested figures, and to ground the definition of the Aravallis in the ecological functions they perform. These are not questions of environmental absolutism versus economic pragmatism. They are questions of whether a foundational definition will rest on sound ecological and technical reasoning, or on administratively convenient metrics.

The integrity of the Aravalli Range depends on how the court answers them.

Sachin Pernacca Sashidhar is a Senior Policy Analyst, at the Centre for Policy Design, ATREE; Milind Bunyan is a Fellow, Ecosystems and Human Well-being Programme, ATREE and Interim Lead ATREE’s Ecoinformatics Lab; Kripa MK is a Postdoctoral Research Associate at ATREE; and Abi T  Vanak is a Senior Fellow and Director at the Centre for Policy Design, ATREE. Views expressed are the authors’ own and do not necessarily reflect that of Down To Earth.