Aravalli range’s role in shielding Gangetic plains from Thar dust

Why in the News?

A massive dust storm recently affected Churu, Hanumangarh, Sri Ganganagar, Bikaner, Nagaur, Didwana-Kuchaman, Alwar and Sikar in Rajasthan, drawing attention to the critical role of the Aravalli Range in shielding the Indo-Gangetic Plains from Thar Desert dust. Scientists warn that degradation of the Aravallis due to mining, deforestation and land-use change is allowing more dust to reach Delhi, Punjab, Haryana and Uttar Pradesh, even during less intense storms.

What are the features of the Aravallis Range?

1. The Aravalli Range is one of the oldest surviving fold mountain systems on Earth. It serves as a vital ecological and climate-regulating spine across northwestern India.
2. Location and Extent
   1. Length: The range stretches approximately 670 to 700 kilometres.
   2. Alignment: It runs in a distinct south-west to north-east direction.
   3. States Covered: The range begins near Delhi, passes through southern Haryana and Rajasthan, and terminates near Ahmedabad in Gujarat.
3. Geological Significance
   1. Age: Formed during the Precambrian era (roughly 1.7 to 2.5 billion years ago), it predates the Himalayas by more than a billion years.
   2. Evolution: It was originally an immense mountain chain, potentially as tall as the modern Himalayas. Over eons, wind and water weathered it down into discontinuous, residual hills and ridges.
   3. Composition: The range consists of highly resistant metamorphic and igneous rocks, including quartzite, granite, schist, and gneiss
4. Key Peaks and Drainage
   1. Highest Point: Guru Shikhar on the Mount Abu massif in Rajasthan, standing at 1,722 metres (5,650 feet).
   2. Major Rivers: The western slopes give rise to the Luni River (which drains into the Rann of Kutch) and the Sabarmati River. The eastern slopes feed the Banas River, a major tributary of the Chambal-Yamuna system.

How do the Aravallis act as a natural shield against the Thar Desert dust?

Dust Interception Mechanism

1. Obstacle Dunes: Large sand deposits located on western slopes intercept dust-laden winds originating from the Thar Desert.
2. Wind Velocity Reduction: Mountain slopes reduce wind speed, causing suspended dust particles to settle.
3. Vegetation Barrier: Native vegetation acts as a natural scrubber, trapping dust and sand particles.
4. Sediment Retention: Dunes and vegetation prevent long-distance transportation of desert sediments.
5. Ecological Buffer: Protects densely populated Indo-Gangetic regions from excessive dust exposure.

Scientific Evidence

1. Field Observations: Obstacle dunes visibly demonstrate dust interception by the Aravallis.
2. Vegetation Similarity: Dune vegetation resembles desert ecosystems, indicating long-term dust deposition processes.

Why are dust storms becoming a growing concern in northern India?

1. Increasing Dust Transport
   1. Pre-Monsoon Phenomenon: Dust storms commonly occur between April and June.
   2. Heat Conditions: Intense heating and dry atmospheric conditions facilitate dust mobilization.
   3. Wind Systems: South-westerly and westerly winds transport dust across northern India.
2. Expanding Exposure
   1. IMD Climate Hazards Atlas: Identifies parts of northwest India within a high dust-storm frequency zone.
   2. Dust-Storm Frequency: Climatic normal ranges between 0.89 and 1.55 dust-storm days annually.
   3. Delhi Vulnerability: Long-term records place Delhi and adjacent districts within high exposure zones.
3. Emerging Trend
   1. Lower Threshold Transport: Dust now reaches northern plains even during less intense storms.
   2. Wind Speed Impact: Dust transport increasingly observed at wind speeds of 35-40 kmph.
   3. Changing Pattern: Earlier, dust transport generally required stronger and more intense storm systems.

How is degradation weakening the protective role of the Aravalli Range?

1. Mining Activities
   1. Mineral Extraction: Mining of red silica, granite and other minerals has damaged hill ecosystems.
   2. Landscape Fragmentation: Mining operations create physical gaps that facilitate dust movement.
2. Deforestation
   1. Vegetation Loss: Reduction in natural vegetation decreases dust-trapping capacity.
   2. Ecosystem Instability: Weakens soil retention and ecological resilience.
3. Urbanisation and Construction
   1. Land Conversion: Expands built-up areas at the cost of ecological landscapes.
   2. Habitat Disruption: Alters natural terrain and ecological continuity.
4. Land-Use Change
   1. Pastoral Activities: Intensive grazing pressures affect vegetation regeneration.
   2. Agricultural Expansion: Contributes to habitat modification and soil degradation.

What is the current state of degradation in the Aravalli ecosystem?

Forest Survey Findings

1. Hill Loss: Assessment found that 31 out of 128 Aravalli hills in Rajasthan had disappeared due to anthropogenic pressures.
2. Topographic Alteration: Significant reduction observed in hill systems between 200 and 600 metres above sea level.

Affected Regions

1. Naraina
2. Kalwar
3. Kotputli
4. Jhalana
5. Sariska

These areas have witnessed substantial ecological disturbance.

Government Assessment

1. Aravalli Restoration Framework: Identified mining, deforestation, urbanisation, construction activities, land-use change, pastoral pressures and encroachments as major causes of degradation.

What are the environmental and climatic consequences of Aravalli degradation?

1. Air Quality Impacts
   1. Dust Intrusion: Increased transport of desert dust towards Delhi, Punjab, Haryana and Uttar Pradesh.
   2. Particulate Pollution: Worsens PM10 and PM2.5 concentrations.
   3. Public Health Risks: Raises respiratory and cardiovascular disease burden.
2. Climate Impacts
   1. Rainfall Modification: Dust aerosols influence cloud formation and precipitation dynamics.
   2. Regional Climate Effects: Alter atmospheric circulation and radiation balance.
3. Agricultural Impacts
   1. Soil Quality Changes: Dust deposition affects soil properties.
   2. Crop Stress: Reduced productivity under frequent dust exposure.
4. Ecosystem Impacts
   1. Habitat Fragmentation: Reduces biodiversity connectivity.
   2. Desertification Risk: Facilitates eastward spread of arid conditions.

Why are ecological gaps in the Aravallis a strategic environmental concern?

1. Wildlife Institute Findings
   1. Gap Expansion: Twelve major gaps have been identified within the Aravalli system.
   2. Degradation Linkage: Expansion attributed to forest loss and inadequate ecological restoration.
2. Dust Corridor Formation
   1. Wind Channels: Openings facilitate unhindered movement of dust particles.
   2. Reduced Interception: Weakens the range’s barrier function.
3. Multi-State Implications
   1. Delhi: Air quality deterioration.
   2. Punjab and Haryana: Increased dust exposure.
   3. Uttar Pradesh: Greater environmental vulnerability.

What policy interventions are required to restore the Aravalli ecosystem?

1. Landscape Restoration
   1. Afforestation: Strengthens vegetative barriers across degraded stretches.
   2. Native Species Plantation: Enhances ecological adaptation and dust interception.
2. Mining Regulation
   1. Compliance Mechanisms: Ensures strict implementation of environmental clearances.
   2. Illegal Mining Control: Prevents further hill degradation.
3. Ecosystem-Based Management
   1. Watershed Restoration: Improves ecological stability.
   2. Soil Conservation: Reduces erosion and dust generation.
4. Institutional Coordination
   1. Inter-State Cooperation: Facilitates coordinated conservation across Rajasthan, Haryana, Delhi and Gujarat.
   2. Integrated Monitoring: Strengthens environmental surveillance using remote sensing and GIS.
5. Climate Adaptation
   1. Nature-Based Solutions: Enhances resilience against desertification and dust storms.
   2. Green Buffer Development: Supports long-term air quality management.

Conclusion

The Aravalli Range is not merely a geological feature but a critical ecological barrier that protects northern India from desert dust, air pollution and land degradation. Its continuing degradation due to mining, deforestation and unplanned development threatens the environmental security of Rajasthan, Delhi and the wider Indo-Gangetic Plains, making landscape restoration and sustainable management an urgent policy priority.

PYQ Relevance

[UPSC 2020] The process of desertification does not have climatic boundaries. Justify with examples

Linkage: The PYQ tests understanding of desertification, land degradation and the wider ecological impacts of environmental change beyond arid regions. The article shows how degradation of the Aravalli Range is enabling Thar Desert dust to spread into Delhi and the Indo-Gangetic Plains, illustrating that the effects of desertification can extend far beyond desert areas.