New Delhi, Feb 10: Satellite-based monitoring has revealed a gradual decline in vegetation across the hills of Uttarakhand over the past two decades, raising concerns about the growing impact of climate change, pollution and human activity on fragile Himalayan ecosystems.
According to a study conducted by researchers from the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital—an autonomous institute under the Department of Science and Technology (DST)—satellite observations indicate shifting vegetation patterns between 2001 and 2022. The research highlights the climate sensitivity of mountain ecosystems, which are particularly vulnerable to changes in temperature, precipitation and environmental stressors.
The researchers used Google Earth Engine (GEE), a global platform that enables large-scale processing of satellite data, to analyse long-term vegetation trends in Uttarakhand along with associated climate and pollution variables. GEE is widely used for environmental monitoring, including studies on land degradation, urban growth and temperature change.
The team employed the Normalized Difference Vegetation Index (NDVI), a commonly used satellite-derived indicator of vegetation health, to track changes across seasons and years. Lower NDVI values indicate barren or sparsely vegetated areas such as rock, snow or exposed soil, while higher values reflect dense green vegetation, including forests and croplands.
The findings, published in the journal Environmental Monitoring and Assessment (Springer Nature), show clear seasonal patterns, with vegetation levels peaking after the monsoon and reaching their lowest before it. However, the study notes that these natural rhythms have begun to shift over the last two decades.
In addition to NDVI, the researchers analysed the Enhanced Vegetation Index (EVI), which provides improved sensitivity in areas with high biomass. Spatial and time-series analyses revealed declining vegetation trends in several regions, which the researchers linked to deforestation, agricultural expansion, illegal logging and rising pollution from urban and industrial sources.
The study also found that pollution impacts vegetation unevenly, intensifying stress in certain locations already affected by climate variability. These changes pose risks to biodiversity, water resources and ecological stability, with potential consequences for millions of people living downstream.
The researchers noted that satellite-based monitoring can serve as an early-warning system, helping policymakers and local communities identify vulnerable areas and prioritise timely environmental interventions.
