Why in news?

A massive dust storm in Churu, Rajasthan recently — affecting districts including Hanumangarh, Sri Ganganagar, Bikaner, Nagaur, Alwar, and Sikar — went viral on social media.

This drew attention to a critical but underappreciated ecological reality: the Aravalli range serves as India's natural shield protecting the densely populated Indo-Gangetic plains from Thar Desert dust storms.

However, this shield is rapidly weakening due to mining, deforestation, and urbanisation.

What’s in Today’s Article?

• Dust Storms Over Northern India — The Climatic Context
• The Aravalli Range — India's Natural Dust Shield
• State of the Aravalli Range — Alarming Degradation
• Consequences of Aravalli Degradation

Dust Storms Over Northern India — The Climatic Context

• Dust storms originating from the Thar Desert are a regular pre-monsoon phenomenon in northern India (April-June), fuelled by intense heat, dry conditions, and south-westerly and westerly winds.
• The IMD's Climate Hazards and Vulnerability Atlas of India (based on 1981-2010 data) shows that parts of northwest India fall in the highest dust-storm frequency class — averaging 0.89 to 1.55 dust-storm days.
• Delhi and neighbouring districts already lie in a high-exposure zone. In June specifically, Delhi records a storm frequency of 2.5 days — the highest in the country for that month.
• As the Aravallis degrade, the impact of these storms is intensifying.

The Aravalli Range — India's Natural Dust Shield

• The Aravalli range stands physically between the Thar Desert and the Indo-Gangetic plains — one of the world's most densely populated regions.
• When dust-laden winds blow in from the Middle East and the Thar Desert during the pre-monsoon months of April to June, they run into the Aravallis, lose speed, and drop their load of sand — preventing it from reaching Delhi, Punjab, Haryana, and Uttar Pradesh.
• This natural filtering process is visually evidenced by "obstacle dunes" — large sand deposits found on the western slopes of the Aravallis, directly exposed to hot winds from the west.
• The vegetation growing on these dunes resembles desert flora. Where additional tree cover exists, winds must pass through it — creating a "natural scrubbing effect" that reduces the movement of sand and dust.
• As per the environmental researchers, these dunes are visual proof of the protective role the Aravalli range plays in interception of dust.

State of the Aravalli Range — Alarming Degradation

• A Forest Survey of India (FSI) assessment of 2018 found that 31 of the 128 Aravalli hills in Rajasthan had completely disappeared due to anthropogenic (human-caused) pressures.
• There has also been a significant loss of hills with 200-600 metres elevation in areas like Naraina, Kalwar, Kotputli, Jhalana, and Sariska.
• The Environment Ministry's Aravalli Restoration Framework flagged multiple causes behind the degradation:
  • Mining of red silica, granite, and other minor minerals
  • Deforestation and loss of vegetation cover
  • Urbanisation and construction activities
  • Land-use change and encroachments
  • Pastoral activities (overgrazing)
• A 2009 Wildlife Institute of India (WII) study identified 12 gaps in the Aravalli range that have expanded further due to forest degradation and inadequate vegetation cover.
• These gaps act as unprotected corridors through which dust freely passes into the northern plains.

Consequences of Aravalli Degradation

• The weakening of the Aravalli shield has multiple cascading consequences:
  • Increased Dust Storm Frequency — Growing gaps in the range threaten to increase the frequency of sand and dust storms in Delhi, Punjab, and Uttar Pradesh.
  • Worsening Delhi's Air Quality — Regular dust-laden winds contribute to particulate matter pollution — directly degrading air quality in the national capital region.
  • Impact on Rainfall — The range's degradation can affect rainfall patterns in surrounding regions — as mountains and forests influence precipitation.
  • Alteration of Solar Radiation — Dust can affect the scattering of sunlight, temporarily altering surface temperatures over large areas — with implications for agriculture, human health, and regional climate.
• Scientists have underscored the need for "long-term investigation and analysis on dust frequency and load over northern India" — indicating that the full consequences of Aravalli degradation are still being understood.