pNew Delhi: The Aravalli Hills, one of the oldest mountain ranges in the world, have long served as a natural shield against desertification for multiple states across their nearly 700-kilometre-long span, including the Delhi-National Capital Region (NCR). The hills block sand and dust from the Thar Desert, while also aiding groundwater recharge and sustaining rich biodiversity.ppHowever, environmentalists warn that a recent ruling by the Supreme Court could significantly impact these ecologically vital hills. Environmentalist Vimlendu Jha said, "This new definition that talks about the Aravalli hills only more than 100 metres will actually be called Aravalli hills, and the rest is actually open for mining initially, and eventually, of course, for real-estate and other developmental activities... Which primarily would mean that 90 per cent of Aravalli will completely disappear, or will be ready, or will be okay to be so-called 'developed' in that sense...That means that you are further exposing this entire region, not just Delhi, but the entire region to further contamination or pollution."pp"So, given the backdrop of air pollution, this entire move, when the Supreme Court, on the one hand, was talking about taking long-term measures, and rather than actually looking at protecting those natural safeguards that this region has, we are actually exploiting it further," he said.ppIn its November 2025 order, the apex court accepted the government's new definition for the Aravallis, which states that only landforms rising 100 metres or more above local ground level, along with their slopes and adjacent land, will be officially recognised as part of the range.