The National Remote Sensing Centre (NRSC), ISRO, has released the 2025-26 Annual Report on the National Highways Green Cover Index (NH-GCI), a high-fidelity monitoring project covering approximately 30,000 km of National Highways across 24 states.
Utilising high-resolution Resourcesat-2/2A LISS-IV satellite imagery, the project calculates the Green Cover Index (GCI) for 1 km segments to evaluate vegetation density during the Operation and Maintenance (O&M) phase. The methodology, which achieved 90% agreement with ground-truth field observations, categorises highway stretches from "Poor" (0–25%) to "Very Good" (75–100%) based on NDVI thresholds. By operationalising biannual assessments and hosting data on the Bhuvan GIS portal, the NH-GCI acts as a primary mechanic for environmental performance benchmarking, allowing policymakers to identify canopy gaps and target greening interventions with surgical precision.
Key Pillars of the Green Cover Index (NH-GCI)
Satellite-Based NDVI Assessment: Applying Normalised Difference Vegetation Index (NDVI) thresholds to high-resolution imagery to distinguish green cover from other land types.
1 km Segmented Reporting: Categorising every kilometre of the national network into four classes—Poor, Moderate, Good, and Very Good—for granular spatial monitoring.
Mobile-Based Field Validation: Using a dedicated app for ground-truth verification, capturing field photographs at 4-5 locations on either side of the highway to match satellite data.
Web GIS Integration (Bhuvan): Providing a centralised platform for data visualisation, reporting, and real-time monitoring of plantation performance.
Biannual Change Detection: Monitoring vegetation twice a year to track the survival of saplings and the growth of mature canopies across diverse climatic zones.
State-Wise Benchmarking: Generating cumulative GCI values (e.g., Uttarakhand at 39.78, West Bengal at 41.32) to foster competition and accountability among regional highway units.
What is the "Green Cover Index" (GCI)? The Green Cover Index (GCI) is a metric that represents the percentage of land covered by green vegetation within a specific 1 km highway buffer or segment. It operates on the mechanical theory that healthy vegetation reflects near-infrared light differently than stressed or non-existent greenery. By measuring this reflectance via satellite, the GCI acts as a functional prerequisite for "Green Highway" audits, replacing manual, error-prone counting of trees with a scalable, objective, and cost-effective digital assessment. This high-fidelity data is essential for determining the ecological footprint of road infrastructure and meeting national plantation targets.
Policy Relevance: Greening India’s Infrastructure
Operationalising Environmental Audits: The NH-GCI acts as a primary mechanic for NHAI to transition from anecdotal reports of plantation success to a data-driven "Green Rating" for all highway projects.
Internalizing Carbon Sequestration: Future integration with carbon models provides a functional framework for the MoRTH to quantify the role of highways in India’s Net Zero 2070 commitments.
Bypassing Monitoring Lags: The use of AI/ML for automated classification serves as a prerequisite for real-time alerts on vegetation loss due to illegal felling or natural disasters.
Link to Sustainable Development: Aligning highway construction with a "Very Good" GCI rating is a foundational step for India to achieve its targets for increasing forest and tree cover under the National Mission for a Green India.
Follow the Full Report Here: NRSC/ISRO: National Highways Green Cover Index Annual Report 2025-26
