Satellite observations spanning more than two decades have revealed a gradual decline in vegetation cover across Uttarakhand’s Himalayan regions, raising concerns over the growing impact of climate change, pollution and human activity on fragile mountain ecosystems.
Researchers analysing satellite data from 2001 to 2022 found that while Himalayan vegetation continues to respond to seasonal cycles—reviving after the monsoon and weakening before it—these natural rhythms are increasingly being disrupted. The findings suggest mounting stress on forests, grasslands and valley ecosystems that play a critical role in sustaining biodiversity and water resources.
Mountain regions are particularly sensitive to climate change, with rising temperatures, shifting rainfall patterns and increasing pollution intensifying ecological risks. Scientists warn that even small climatic variations can trigger large-scale environmental consequences in high-altitude areas.
The study was conducted by researchers from the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital—an autonomous institute under the Department of Science and Technology—along with collaborators from India and abroad. Their findings were published in the journal Environmental Monitoring and Assessment.
To track long-term changes in vegetation, the team used Google Earth Engine (GEE), a powerful global platform that processes large volumes of satellite data for environmental monitoring. The researchers analysed changes in vegetation using the Normalized Difference Vegetation Index (NDVI), a widely used satellite-based indicator that measures plant health and density.
Lower NDVI values indicate barren surfaces such as rocks, snow, water or exposed soil, while higher values reflect dense green vegetation, including forests, croplands and wetlands. The team also examined the Enhanced Vegetation Index (EVI), which offers improved sensitivity in areas with high biomass, along with key climate variables.
The analysis showed clear monthly, seasonal and annual variations in vegetation cover. NDVI and EVI values were consistently highest after the monsoon season and lowest before it. However, over the past two decades, researchers observed a worrying downward trend in vegetation health across several parts of the state.
The decline has been linked to multiple factors, including deforestation, agricultural expansion, illegal logging and rising pollution from urban and industrial sources. The study found that pollution does not impact vegetation uniformly; instead, certain locations experience more severe stress, compounding the effects of climate change.
Scientists warn that continued degradation of vegetation cover could have serious consequences for biodiversity, groundwater recharge, river systems and the ecological stability of the Himalayan region—effects that extend far beyond Uttarakhand to millions of people living downstream.
The researchers emphasised that satellite-based monitoring offers an effective early-warning system, enabling policymakers to identify vulnerable regions and take timely, targeted action.
