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As the debate regarding the Supreme Court’s December 20, 2025, verdict on the Aravalli hill range gets sharper, one of the main arguments put forth by critics is the fact that the low-lying hill range protects Delhi and much of the fertile Indo-Gangetic Plain against the Thar Desert.
The Aravallis are one of India’s and the world’s oldest hill ranges. As writer Pranay Lal wrote in Down To Earth (DTE) in 2019, “It took nearly two billion years (3.2 to 1.2 billion years ago) of shoving and pushing of tectonic plates and magma outpourings to create these oldest fold mountains in the world. Since then, these mountains have endured millions of years of sustained assault of lava flows, submergence by seas, uplift by force of gushing magma from the depths of the Earth, collision with landmasses and erosion by wind and rain.”
In the past four decades though, the range has been majorly decimated, mainly by the illegal mining and real estate lobbies.
However, the Supreme Court’s ruling on December 20, 2025, which accepted the Union Environment Ministry’s elevation-based definition of the Aravallis, could be a ‘death warrant’ for the range, according to environmentalists.
Under the new criterion, only landforms rising at least 100 metres above local relief, or clusters of such hills within 500 metres, will be officially recognised as part of the Aravalli range.
It was in 2017 that the Wildlife Institute of India came out with a study titled Mapping Landuse/Landcover Patterns in Aravallis Haryana with reference to status of key wildlife species.
“Aravallis with its lush green forests used to act as a green barrier and an effective shield against desertification. It checked the spread of the Indian Desert (Thar) towards eastern Rajasthan, Indo Gangetic plains, Haryana and Western UP. Today, the forests in the Aravalli hills no longer effectively act as a green barrier. The forests of Aravallis range are now the most degraded forests in India, most of the indigenous plant species have disappeared,” the study noted.
“Haryana lies on the northeastern fringe of the Thar Desert and experiences arid semi-arid climate. As a result, sand migration is common along the desert boundaries. Due to the depletion of the forest cover over the Aravallis the desert is migrating towards Haryana through the gaps,” it added.
Twelve gaps were identified through the interpretation of remotely sensed data products of 1972-75, 1982-84, 1994-96 and 2005-07, according to the authors.
The gaps extend from Magra hills in Ajmer district to Khetri-Madhogarh hills in Jhunjhunu district and the northern most hillocks in Mahendragarh district of Haryana.
But what about the fact that the Thar itself is experiencing increased precipitation?
“The north-western part of India, especially the western part of Rajasthan has been experiencing significant changes in rainfall pattern, aeolian terrain and demography,” P C Moharana, Priyabrata Santra, Deepesh Machiwal and D V Singh, scientists with Indian Council of Agricultural Reasearch-Central Arid Zone Research Institute, Jodhpur, had recently noted in an opinion article for DTE.
To this, Sachin Pernacca Sashidhar, a senior policy analyst at the Ashoka Trust for Research in Ecology and the Environment (ATREE), Bengaluru, noted that, the “greening” of the Thar will fail to prevent the desert’s expansion.
That is because the “greening” of the Thar, according to him, presents a fragile and potentially unsustainable ecosystem, driven by irrigation, shifting monsoon patterns, groundwater extraction, and invasive Prosopis juliflora, which may mask underlying land degradation risks.
He added that while irrigation and increased monsoon rainfall have boosted surface biomass, they have also caused salinisation and waterlogging in affected areas, potentially reducing soil productivity in the long term.
“Similarly, greening supported by intensive groundwater use carries risks of reversal if extraction outpaces recharge, while the invasive P. juliflora aggressively drains deep soil moisture and harms native biodiversity. If water resources become constrained without sustainable management, parts of this green cover could decline, potentially leaving degraded landscapes more vulnerable to erosion than the original desert biome,” noted Sashidhar.
He also pointed out that the “expansion” threatening Haryana and the National Capital Region is primarily atmospheric and wind-driven, manifesting as intense dust storms, suspended particulate matter, and heat transfer rather than the traditional “march” of sand dunes.
According to Sashidhar, containing this specific form of airborne desertification requires a contiguous physical windbreaker, which the Aravallis provide.
“However, if this shield is structurally compromised, these low-lying ridges and natural gaps could be the precise corridors through which dust-laden winds travel. Consequently, even if the desert core remains green, the destruction of this geological shield ensures that atmospheric desertification manifested as dust storms and drifting sands will bypass the vegetative cover and expand eastward through these newly opened breaches,” he concluded.
Ghazala Shahabuddin, ecologist and Visiting Professor at Ashoka University, Sonipat, however told DTE that the ecosystem services provided by the Aravallis were many.
“The Aravallis are an ancient topographical feature of the landscape with very multi-dimensional functions for biodiversity and humans. We therefore cannot see its function as being just that of a physical barrier. And we definitely cannot allow it to be blasted out of existence,” she said.