Why the Aravallis matter for the climate, air, and water of north India plains

Sand barrier

At over a billion years old, the Aravallis are one of the oldest mountain ranges in the world, formed during the Precambrian Era due to the collision of tectonic plates of the earth’s crust. The 700-odd-km range stretches across four states (Gujarat, Rajasthan, Haryana and Delhi) and 37 districts, with 560 km lying in Rajasthan.

The present-day range, however, is much eroded compared to what the Aravallis were at their birth. Their degradation is due to both natural factors and human activities.

Yet, the Aravallis provide priceless ecological services. If the Western Ghats are considered the water tower and climate regulator of peninsular India, the Aravalli range is an ecological shield for the plains of Northwest and North India.

The range acts as a shield for the northern plains against the incursion of sand from the Thar desert in the west. This also protects air quality in the North. Any rising incursion of sand would be disastrous for the Delhi-NCR Region, which is already struggling to contain local sources of pollution.

Moreover, the hills also bring in a healthy amount of rainfall, which is essential for agriculture and drinking water needs of settlements that are located around them. As per studies, deforestation, quarrying and erosion has already led to 12 major gaps in the Aravallis. These gaps extend from Magra hills in Ajmer district to Khetri-Madhogarh hills in Jhunjhunu district and northern most hillocks in Mahendragarh district of Haryana.

Aravallis: Water recharge & biodiversity

Although water drainage and recharge influenced by the Aravallis is not talked about enough, the hills’ rocky formations are essential to recharge aquifers and groundwater levels, and sustain seasonal rivers of Rajasthan and Gujarat.

The Centre’s Aravalli landscape restoration action plan documents the key role the Aravalli hills play on this front.

“It (the Aravalli range) is one of the main watersheds, separating the drainage of the Bay of Bengal, through rivers like the Chambal, and other tributaries of the Yamuna, from that of the Arabian Sea through the Mahi, Sabarmati, Luni, and other rivers,” the action plan states. The region is also home to important lakes and wetlands including Sambhar, Sultanpur, Pushkar, Fateh Sagar, and Jaisamand, the action plan adds.

Ecologist and curator of the Aravali Biodiversity Park, Gurgaon, Vijay Dhasmana, said that rocks in Aravallis are highly fractured, weathered and porous, allowing rainwater to percolate deep into the ground instead of running off the surface. “This vast but invisible reserve is crucial for the water security of rapidly growing towns and cities such as Faridabad, Gurugram, and Sohna. Any disruption to this recharge system, through mining, construction, or deforestation, poses a direct and serious threat to regional water availability,” Dhasmana said.

On the biodiversity and wildlife front, the ranges provide a unique dry, deciduous, and semi-arid landscape for a host of flora and fauna to flourish. The range is home to 22 wildlife sanctuaries, including 16 in Rajasthan, three of which — Ranthambore, Sariska, and Mukundra — are tiger reserves.

Key species found in this landscape include tiger, leopard, sloth bear, sambar, chital, desert fox, blackbuck, hyena, wolf, jackal, gharial, crocodile. These species are also crucial in helping preserve the semi-arid scrub forests and semi and dry savanna forests, such as those found in Sariska Tiger Reserve in Alwar. The uniform height definition, and management plan for sustainable mining as ordered by the Supreme Court before allowing new leases, will have to consider these ecosystem services.

The smaller Aravalli hillocks, if opened for mining, would shrink the wildlife corridors. “The ecological richness (of Aravallis) is rapidly declining, and now restricted to fragmented forest patches and protected areas, due to an increase in human pressure and forest loss. The Aravallis also sustain local livelihoods, and communities depend on fuelwood, fodder, fruits, vegetables, and medicinal plants,” Dhasmana said.

Challenges, need for safeguards

The Aravallis are already under immense pressure, and have faced degradation over the years due to urbanisation, industrial clusters, and mining, both legal and illegal. The Union government has itself accepted the large-scale degradation in its action plan under the ‘Aravalli Green Wall’ project.

“The Aravalli Range faces increasing threats due to deforestation, mining, grazing, and human encroachment. Forest lands around Sariska Wildlife Sanctuary were diverted before the 1980s, reducing its forest cover. Desertification is exacerbating as desert sands move eastward, compromising regions like Gurugram and Alwar. Mining activities have damaged aquifers, dried up lakes, and reduced the range’s ability to support wildlife,” the Centre’s action plan notes.

However, these challenges are only set to rise: the Aravallis, after all, are recognised as a repository of metals and minerals, including critical minerals. Even as the Supreme Court has placed a moratorium of sorts on new mining leases until a detailed mining plan study is undertaken, it has accepted Centre’s recommendation to make an exception for critical minerals.

The mountain range is home to lead, zinc, copper, gold, tungsten and has reserves of critical minerals such tin, graphite, molybdenum, niobium, nickel, lithium, and rare earth elements (REEs). These are considered to be of strategic relevance for energy transition, high-technology manufacturing, and national security.

Although the Centre says the new definition is only for mining purposes, how it plays out for the real estate sector remains to be seen. These pressures call for stricter protection of the mountain range, which is already under stress.