Why the Aravalli Hills matters to North India

One of the world’s oldest mountain systems, the Aravalli Hills have returned to the national spotlight after a recent Supreme Court decision endorsed a new, uniform definition of what officially qualifies as an “Aravalli hill”. While the ruling may appear technical, environmentalists warn it could have far-reaching consequences for ecological protection, land use, and climate resilience across large parts of North India.

Why the Aravallis are geologically unique

The Aravalli Range is unlike any other mountain system in India. Estimated to be nearly two billion years old, it dates back to the Proterozoic era — long before the Himalayas, dinosaurs, or even complex life forms evolved. Stretching across Gujarat, Rajasthan, Haryana and Delhi, the range has survived tectonic shifts, erosion, and climatic transformations that have erased many other ancient formations worldwide.

Its low, weathered hills and rocky ridges may lack dramatic height, but scientists emphasise that age and ecological function — not altitude — define the Aravallis’ significance.

What the Supreme Court decision has changed

The Aravallis are in the news following the Supreme Court’s acceptance of a definition proposed by a committee under the Ministry of Environment, Forest and Climate Change. Under this framework, a landform will be recognised as an “Aravalli hill” only if it rises at least 100 metres above the surrounding terrain. An “Aravalli range” will be defined as two or more such hills located within 500 metres of each other.

Critics argue that this height-based definition risks excluding large stretches of low-lying ridges, hillocks, and forested slopes that are geologically part of the Aravalli system but may now fall outside formal protection. These areas, they warn, could become vulnerable to mining, real estate development, and infrastructure expansion.

Why the ruling has triggered public concern

The decision has sparked protests and online campaigns such as “Save Aravalli” across Rajasthan, Haryana and the Delhi-NCR region. Conservationists fear that redefining the hills narrowly could undo decades of judicial and administrative efforts to protect fragile landscapes from illegal mining and encroachment.

Government agencies maintain that more than 90% of the Aravalli region remains protected and insist that mining regulations have not been diluted. However, environmental groups counter that once land slips out of the legal definition, long-term safeguards weaken — especially in rapidly urbanising districts.

The Aravallis as North India’s ecological shield

Beyond their geological value, the Aravallis perform critical ecological functions. They act as a natural barrier that slows the eastward spread of the Thar Desert, influence wind patterns, and reduce the movement of dust and sand into the Indo-Gangetic plains. The hills also aid groundwater recharge and help stabilise local rainfall patterns in an otherwise arid and semi-arid region.

Equally important is their role as wildlife corridors, allowing animal movement between fragmented habitats — a function that becomes more vital as forests shrink and cities expand.

Key wildlife landscapes shaped by the Aravallis

Some of North India’s most significant protected and semi-protected landscapes are embedded within the Aravalli system:

• Mount Abu Wildlife Sanctuary: The highest point of the Aravallis and Rajasthan’s only hill station, supporting rich biodiversity.
• Aravalli Biodiversity Parks in Gurugram and Delhi-NCR: Restored landscapes that highlight how degraded Aravalli land can be revived.
• A rugged forest landscape where tigers, leopards and hyenas thrive amid rocky outcrops.
• A rare urban wildlife reserve showcasing leopards coexisting with a growing city.
• A forested stretch surrounding the historic fort, home to wolves, bears and leopards.
• The northernmost extension of the Aravallis, acting as the capital’s green lung.

Why the stakes go beyond conservation

The debate over the Aravallis is not merely environmental. It intersects with urban planning, groundwater security, air quality, and climate adaptation in one of India’s fastest-growing regions. Experts warn that weakening protection for low-lying ridges could worsen dust storms, accelerate desertification, and strain already stressed water tables in Haryana, Rajasthan and Delhi.

As courts, planners and policymakers grapple with defining the Aravallis, scientists stress the need for an ecosystem-based approach — one that recognises the range as a continuous geological and ecological system rather than a collection of hills measured solely by height.

At a time when climate risks are intensifying, the future of these ancient hills may determine how resilient North India remains in the decades to come.