Redefining Aravalli Hills: Could This Put Delhi-NCR At Risk And Undermine Climate Planning? | Explainers News

At first glance, the controversy around the Aravalli Hills appears to be another familiar environmental debate — one more clash between conservation and development, between mining interests and green activists. But beneath the noise lies a quieter, more consequential issue that could reshape how India plans for climate change, water security, and disasters.

The problem is not just what the Aravallis are being used for. It is how they are now being defined.

A recent legal acceptance of a uniform definition that recognises only landforms rising 100 metres or more above surrounding terrain as “hills” has triggered concern among scientists, planners, and environmentalists. Their fear is not symbolic. It is practical. Large stretches of low-lying Aravalli ridges, ecologically active but gently sloped, could now vanish from official records.

When hills disappear from legal maps, they also disappear from climate models, risk assessments, and planning frameworks that rely on those maps.

Why The Aravalli Issue Is Beyond Mining Debates

Stretching over 800 km from Gujarat to Delhi, the Aravalli range is among the oldest mountain systems in the world. But age has softened its contours. Unlike the Himalayas, the Aravallis do not dominate skylines with dramatic peaks. Many sections appear as modest ridges, rocky outcrops, or undulating terrain barely rising above surrounding plains.

The Ministry of Environment, Forest, and Climate Change has said it would be wrong to conclude that landforms below 100 metres are automatically available for mining. According to the Centre, the definition protects the entire hill form, including its base, slopes, and associated features, based on contour mapping rather than absolute height alone.

That visual subtlety has often worked against them.

Yet scientists have long argued that these “low-relief” hills perform outsized ecological functions. They act as groundwater recharge zones in an otherwise water-stressed region. They slow the advance of desertification from the Thar. They break the force of dust storms sweeping towards Delhi-NCR. They moderate local temperatures and influence rainfall patterns. None of these functions depends on a hill being 100 metres tall.

From Scientific Geography To Legal Geography

The heart of the controversy lies in a growing mismatch between scientific geography and legal geography.

Scientific mapping identifies hills and ridges based on ecological function — how landforms influence water flow, soil stability, vegetation, microclimates, and weather systems. Legal mapping, however, often relies on administrative thresholds that are easier to define and enforce.

Scientific identification of hills and ridges is based on geomorphology rather than perception. It relies on an assessment of relative relief; how much a landform rises above its immediate surroundings, rather than absolute elevation alone. Using tools such as high-resolution satellite imagery, digital elevation models, contour mapping from the Survey of India, and ground-truthing, scientists map slope gradients, ridgelines, drainage patterns, and connectivity between elevated landforms. A ridge, in scientific terms, is not merely a high point but a continuous geomorphic structure that influences hydrology, wind flow, soil formation and ecological connectivity. The recent move to define hills based on a minimum relative elevation threshold seeks to introduce legal clarity, but scientifically, hills and ridges are understood as part of a continuum of landforms whose ecological role depends on their shape, slope, and position in the landscape, not just height,” said Aparna Roy, Fellow and Lead Climate Change and Energy at the Centre for New Economic Diplomacy (CNED).

How Does It Impact Planning?

The most significant consequences of this change are not unfolding in courtrooms or protests. They are emerging quietly inside planning offices across northwest India.

Urban master plans, climate adaptation strategies, groundwater assessments, and disaster-risk models depend heavily on topographical and ecological data. These datasets do not merely describe land; they determine where cities expand, where infrastructure is built, and where environmental safeguards apply.

“Climate adaptation and disaster-risk modelling depend on how landscapes are represented in law and planning frameworks. If certain hills or ridges cease to exist in legal or regulatory terms, there is a real risk that they will also disappear from climate models, land-use plans, and hazard assessments. This matters because even modest elevations influence flood pathways, groundwater recharge zones, wind patterns, and heat distribution. Excluding them from official datasets could lead to adaptation strategies that underestimate local flood risks, overestimate runoff, or misjudge water availability during droughts,” said Roy.

She further stressed that the insistence on scientific mapping before permitting any new activity does offer an opportunity: “if climate risk parameters, such as recharge potential, slope stability, and ecosystem services, are integrated into this mapping exercise, the new criterion could actually improve the precision of climate-resilient planning. The outcome will depend not on the definition alone, but on how comprehensively science is embedded into decision-making.”

What Happens To Climate Resilience Planning

Climate resilience depends on understanding how landscapes buffer extreme events. In arid and semi-arid regions, even minor landforms can shape wind patterns, trap moisture, and slow land degradation.

Low Aravalli ridges play a crucial role in moderating heat and reducing the intensity of dust storms that increasingly choke cities such as Delhi, Gurugram, and Jaipur. They also influence how rainwater percolates into aquifers, a critical function as groundwater tables plunge across Rajasthan and Haryana.

If these features fall outside legal protection, future climate plans may underestimate regional vulnerability. This is not theoretical. Climate models are only as accurate as the data they are allowed to include.

Understanding Risk To Groundwater & Drought Planning

Water security may be among the first casualties of this disconnect. The Aravallis act as natural sponges in a dry landscape. Their fractured rocks and shallow slopes allow rainwater to seep underground rather than rush away as surface runoff. Many rural communities depend on this slow recharge for wells and seasonal agriculture.

Groundwater models that treat these ridges as functional ecosystems help planners predict drought risk and manage extraction. But if legal definitions exclude these zones, future assessments could be weakened, leaving already fragile water systems even more exposed.

What Will Be Environmental Impact On Assessments?

One of the most immediate concerns raised by environmental lawyers is how the new definition could reshape environmental impact assessments.

Environmental Impact Assessments (EIAs) rely on legally recognised categories to determine whether a project requires scrutiny, mitigation, or clearance. If a hill ecosystem no longer qualifies as a “hill” in law, projects located there may face fewer regulatory hurdles, regardless of ecological impact.

This creates a perverse incentive structure, where development is channelled into areas that are environmentally sensitive but legally undefined.

Over time, this could accelerate the fragmentation of already stressed ecosystems under the cover of compliance.

What About The Communities Living On Legally Invisible Landscapes?

For communities living along the Aravalli ridges, the issue is deeply personal. Many tribal and rural populations depend on these landscapes for grazing, farming, forest produce, and water. Their relationship with the land is shaped by ecological realities, and not legal terminology.

“From an ecological perspective, elevation thresholds offer administrative simplicity but only a partial picture of reality. Ecosystems do not function in discrete vertical bands. In semi-arid systems like the Aravallis, even low-lying hillocks and gentle ridges play outsized ecological roles by regulating surface runoff, supporting vegetation adapted to thin soils, and maintaining microclimates. A ridge that rises 40 or 50 metres in an otherwise flat landscape can be as ecologically consequential as a higher hill elsewhere. The ecological reality is that the Aravalli system is one of the oldest fold mountain ranges in the world, heavily eroded over millennia, and its value lies less in dramatic elevation and more in its role as a living landscape that supports groundwater recharge, biodiversity, and climatic buffering. Any definition that treats ecological importance as synonymous with height risks overlooking these functional dimensions,” explained Roy.

The fear is that once these hills lose legal recognition, communities may lose protection as well, from land acquisition, mining expansion, or infrastructure projects. Landscapes that sustain livelihoods could become open for exploitation, simply because they no longer “exist” on paper.

Roy stressed that for rural communities across Rajasthan and Haryana, the Aravalli landscape is inseparable from water security. “If such landforms fall outside regulatory protection and are altered through mining or large-scale excavation, recharge pathways can be disrupted, leading to falling groundwater levels and greater dependence on deeper, costlier extraction. This directly affects drinking water availability, livestock, and agriculture, particularly in regions already experiencing climate stress. For these communities, the issue is not abstract environmental protection but the stability of everyday water access in an increasingly uncertain climate.”

Why Delhi-NCR Should Pay Attention

The implications are especially stark for Delhi-NCR, a region already grappling with heatwaves, air pollution, and water stress.

The Aravallis form one of the last natural barriers against desert dust entering the capital. Studies have repeatedly linked degradation of these hills to worsening air quality and rising temperatures.

If low-lying ridges around Gurugram, Faridabad, and South Delhi fall outside legal protection, the region could lose one of its few remaining ecological buffers at a time when climate extremes are intensifying.

Roy explained that the “fragmentation of the Aravalli system” could exacerbate air pollution, urban flooding during intense rainfall, and groundwater depletion. “It is important to recognise that legal clarity can help enforcement if it is paired with robust ecological safeguards. The real implication for Delhi-NCR lies in whether planning authorities continue to treat the Aravallis as an integrated ecological system rather than a collection of legally defined elevations. In a region grappling with climate extremes, the cost of ignoring functional landscapes- regardless of their height, could be significant.”

A Debate Framed Too Narrowly

So far, public debate has largely framed the issue as a question of mining permissions or environmental activism. That framing misses the larger governance challenge.

This is about how India defines nature in law, and what happens when that definition fails to capture ecological complexity.

Climate change is already testing the limits of India’s planning systems. Floods, heatwaves and droughts are becoming more frequent and intense. In such a context, narrowing legal recognition of natural features risks undermining preparedness rather than strengthening it.

Why Uniformity May Not Mean Safety

Supporters of the new definition argue that uniform standards bring clarity and consistency. That may be true from an administrative standpoint.

But environmental systems are not uniform. A hill’s value does not lie solely in its height. Its location, composition, and interaction with surrounding ecosystems matter just as much. By prioritising a single metric, policy risks sacrificing nuance.

Thus, effective governance requires laws that reflect ecological function, not just geometric thresholds.

What Happens If This Gap Persists

If scientific and legal geographies continue to drift apart, India could find itself planning for a climate future using incomplete maps.

Disaster response plans may underestimate risk zones. Water strategies may misjudge recharge areas. Urban expansion could push deeper into fragile landscapes without adequate safeguards.

These are not dramatic collapses. They are slow erosions — the kind that only become visible when it is too late.

When Maps Don’t Match The Ground

Ultimately, the Aravalli controversy is a reminder that maps are not neutral. What they include and exclude shapes policy, investment, and risk.

When hills vanish from maps, they do not vanish from the real world. They continue to influence weather, water, and life. The danger lies in pretending otherwise.

As India prepares for an increasingly uncertain climate future, the question is no longer just how fast it grows, but how well it sees the land beneath its feet.

If planning begins to ignore landscapes simply because they are hard to define, the cost will be paid not in paperwork, but in resilience lost.