For many hundreds of years, the Aravali hills have been instrumental in shaping the climate of the upper Indo-Gangetic plain. From rainfall, temperature and aquifer recharge to soil conservation , biodiversity and ecology, every factor has been dependent on this millennia-old range. But despite their life-sustaining and life-conserving qualities, the Aravalis and their tropical dry-deciduous forests have gained very little attention.And that’s because degradation of these hills — the range has shrunk by 40% over the last four decades, from 10,462 square kilometres in 1972-75 to 6,116 sqkm today — has always been viewed as an issue localised to a few districts of south Haryana, even though it affects the entire Indo-Gangetic plain, including Delhi-NCR, parts of Punjab, and as far as western Uttar Pradesh.The Aravali range functions as a check on the movement of sand from the Thar Desert to Delhi-NCR, Haryana and western UP. Besides playing a key role in recharging aquifers and conserving soil, it also curbs wind velocity and evaporation to ensure sufficient rainfall in the region. Moreover, it helps prevent floods and the worst effects of climate change in the Great Indian Desert, by acting as a barrier to rain-bearing winds heading towards the deserts of Rajasthan.A study by the Haryana government, conducted with the help of data acquired using remote sensors, showed there are at least 12 breaches in the Aravali range totalling 93km. These gaps extend from Magra peak in Ajmer, Rajasthan, to the rises in Madhogarh and Khetri in Jhunjhunu district, and the hills towards the north of Mahendragarh district in Haryana. And it is through the longest of the gaps (22km), called Singhana-Digrota, that dust storms blow into Delhi-NCR. The affected area under sand dunes in the 12 gaps is 5,680 sq km.In another study, carried out by the Wildlife Institute of India (WII) in 2017, it was revealed that sand dunes have been found in Harchandpur village of Sohna, as close as 20km from Gurgaon and 60km from Delhi. Worryingly, the sands of the Thar are inching ever closer to the National Capital Region.Dr Kushagra Rajendra, head of the department, Amity School of Earth and Environmental Sciences, highlighted the critical role played by the Aravalis in checking both wind velocity and evaporation to prevent sand migration from the Thar desert. “A desert is created when soil for a long time is devoid of moisture, which binds the soil grains and allows vegetation to grow and cover the ground. For many years, the wellforested Aravalis acted as a constraint and checked the spread of the Indian desert towards upper Indo-Gangetic plains,” he explained. “The desert is in the west from Budelkhand and Malwa plateau is in the east. Before monsoon, the wind pattern is directed from the desert towards the plateau and Gangetic plains. It carries a lot of dust and sand along with wind, but Aravalis check the wind velocity.”Indeed, at one time, the forests in the Aravalis would give rise to seasonal rivers. But the gradual degradation of the range, over the last 40-50 years, has accelerated the spread of desert. “It has led to desertification on the western side, and flooding in eastern Rajasthan, as winds carrying rain can easily move from west to east.” The Aravalis, Dr Rajendra said, are no longer an effective barrier against extreme weather events due to rampant mining, extensive land use change, and exploitation of the landscape.According to a study conducted by the department of geography at Mohanlal Sukhadia University, Udaipur, the Aravalis would attract rainfall towards a swathe of north and northwest India for 60 to 80 days a year, around 40 years ago. The hills drew both the Arabian Sea and Bay of Bengal monsoon currents, and it was in this hilly region where both currents met. “These monsoon currents, after entering the coastal areas, used to blow right up to the foothills of the Aravalis and start ascending the green and (moisture-laden) hill slopes, causing effective condensation process and leading to excess (to normal) rainfall,” the report stated. “However, due to deforestation , the trans-evaporation process has altered, decreasing the total number of rainy days from 60 to 80, to 18 to 30 days per year.”The Aravali hills help perform a couple of important functions as well, drainage of excess water and recharge of groundwater. A Central Ground Water Board (CGWB) report released in June 2017 referred to the hills as “major recharge zones for surrounding plains (with which) aquifers in Aravalis are interconnected, and any alteration in the pattern can disturb the groundwater condition of the entire south Haryana and Delhi.” Experts have said degradation is to blame for the decrease in soil fertility in the upper northern plains, and the increase in salinity in the groundwater. “The uppermost layer of the soil is the most fertile. As we are losing forest cover in the Aravalis, massive soil erosion is taking place, thereby eroding the upper layer of the soil,” said Dr Anil Kumar Singh of the National Academy of Agricultural Sciences, Delhi.Soil salinity, Dr Singh added, is responsible for reducing soil fertility which, in turn, “adversely” affects the overall quality of the soil. “Soil salinity is caused mainly by three factors in this region — inherent salinity, irrigation by saline water, and deterioration of groundwater quality,” he explained.In 1992, the Aravali ranges in Gurgaon and Alwar (Rajasthan) were notified as an ecologically sensitive area by the National Capital Region Planning Board. However, successive governments in Haryana have failed to give these hills the status of ‘notified forest’. Besides, refusal to grant ‘deemed forest’ status, exclusion of the entire range in the ambit of NCZ (natural conservation zone), and failure to enforce the Tree Act (in force in Delhi to protect the Ridge, a part of the Aravalis), have contributed to the fragile state of the range.“The problem is that the Haryana government hasn’t taken enough steps to protect the Aravalis, which play an important role in maintaining ecological balance in the entire northern plains,” summed up Ajay Kumar Saxena, programme manager, forestry team, Centre for Science and Environment.Some have stressed the importance of reviving the Aravalis as part of the disaster management plans of all affected states. Among them is Rajendra Singh, winner of the prestigious Stockholm Water Prize in 2015, who told TOI, “Degradation of the Aravalis and massive deforestation has already led to a lot of disasters, including desertification in Delhi and Haryana, droughts in Haryana, western UP and Delhi, and floods in the desert, as it is changing the monsoon pattern of the entire upper northern plains. Governments of all affected states should come together and work on a war footing to save the Aravalis,” urged Singh, popularly known as the ‘Water Man of India’.

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