Protecting the Delhi Ridge scientifically

The Delhi Ridge, the northernmost extension of the ancient Aravalli Range, forms the ecological backbone of the National Capital Territory of Delhi. Covering about 7,784 hectares, it moderates the local climate, supports its rich biodiversity, conserves soil and water, regulates hydrological processes and provides indispensable ecosystem services to one of the world’s most densely populated metropolitan regions. Sustaining these ecological functions requires scientific forest management based on sound ecological principles rather than isolated plantation activities.

The recently approved Forest Working Plan (FWP) for the National Capital Territory of Delhi provides the statutory and scientific framework for achieving this objective. The Forest Working Plan is the statutory document that governs scientific forest management in India. The FWP for Delhi (2026-27 to 2036-37), prepared by the Forest Research Institute (FRI), Dehradun, is the first comprehensive plan covering all forest divisions of the NCT as a single management unit. It was prepared through detailed field investigations, forest inventory, vegetation analysis, growing stock assessment, natural regeneration studies and ecological evaluation supported by Remote Sensing, GIS and GPS.

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After rigorous scientific, technical and statutory scrutiny by the Ministry of Environment, Forest and Climate Change, the Plan was approved. Consequently, its prescriptions constitute the scientific and statutory basis for management of Delhi’s fore sts, including e cosystem improvement and species selection. The Plan places all forests under the Protection-cum-Improvement Working Circle and identifies Prosopis juliflora, Eucalyptus spp. and Leucaena leucocephala as the three principal invasive species adversely affecting the ecological structure and functioning of the Ridge.

It therefore prescribes their phased replacement through assisted natural regeneration, enrichment planting and other silvicultural interventions. Species selection is not arbitrary but follows site-specific ecological conditions, recognising ridge tops, rocky slopes, valleys, drainage lines, shallow and deep soils, waterlogged areas and grasslands. Native Ridge species form the foundation of the planting strategy, while ecologically compatible indigenous species are incorporated wherever they better fulfil ecological and management objectives. The scientific rationale for species selection is reflected in the five pillars of the Working Plan.

The first pillar seeks improvement of growing stock through development of a structurally diverse multi-layered forest. Keystone Ficus species such as Peepal and Bargad form the upper canopy, characteristic Ridge species including Dhau, Khair, Hingot, Ber and Phulai strengthen ecological integrity, while indigenous shrubs improve habitat complexity, biodiversity and natural regeneration. The second pillar focuses on carbon sequestration and climate resilience. Long-lived, high-biomass species such as Peepal, Bargad, Arjun, Jamun, Gular, Pilkhan, Neem, Sheesham and Tamarind have been selected because of their capacity to accumulate substantial biomass and store carbon over long periods while enhancing resilience to heat and prolonged dry conditions.

The third pillar recognises the Ridge as Delhi’s largest natural green infrastructure for mitigating urban air pollution. Peepal, owing to its high Air Pollution Tolerance Index, together with Bargad, Gular, Pilkhan, Neem, Jamun and Arjun, provides broad canopy cover, effective interception of particulate matter, micro-climate regulation and multiple urban ecosystem services. The fourth pillar aims to accelerate ecological succession. Assisted natural regeneration, enrichment planting and soil and moisture conservation are complemented by native shrubs such as Curry Patta, Wild Karonda, Kurchi, Kair, Nirgundi and Phalsa, which stabilise soil, conserve moisture, support pollinators and protect young regeneration, thereby facilitating progressive restoration of a self-sustaining native forest.

The fifth pillar adopts an ecosystem-services approach to species selection. Each species has been selected for the complementary ecological functions it performs rather than in isolation. Ficus species serve as keystone species supporting birds and bats, Ridge species strengthen drought resilience and ecological integrity, while shrubs improve soil stability, water conservation and habitat quality. Together, they enhance the resilience and sustainability of the forest ecosystem. The Working Plan recognises that scientific ecosystem improvement extends far beyond plantation alone and emphasises that healthy forest ecosystems can be sustained only on healthy soils supported by an efficient water regime. Accordingly, Soil and Moisture Conservation (SMC) form a fundamental component of the management strategy.

Adopting an integrated watershed-based approach, the Plan prescribes restoration and protection of existing water bodies, creation of new water storage structures, rainwater harvesting, contour trenches, check dams, moisture conservation pits and other mechanical and biological measures to conserve rainwater, reduce surface runoff and soil erosion, enhance groundwater recharge, improve soil moisture, support natural regeneration, provide life-saving irrigation to young plantations during critical dry periods, and minimise the vulnerability of the Ridge forests to drought and fire.

The proposed species composition represents a functionally diverse forest ecosystem in which individual species complement one another in delivering multiple ecosystem services, including air pollution mitigation, carbon sequestration, biodiversity conservation, climate regulation, soil and water conservation, habitat improvement and long-term ecosystem resilience. Such an ecosystem services-based approach is fully compatible with the principles of modern scientific forest management. The prescriptions of the Forest Working Plan are therefore in conformity with the objective of improving the ecological health, resilience and long-term sustainability of the Delhi Ridge.

(The writer, a former member of the Indian Forest Service, retired as Principal Chief Conservator of Forests, Madhya Pradesh, and had served as Director, Forest Research Institute, Dehradun)