Satellites Track Shifting Himalayan Vegetation, ARIES Study Flags Climate Stress in Uttarakhand

Published in Environmental Monitoring and Assessment (Springer Nature), the research uses advanced satellite analytics to provide an early-warning lens on one of India’s most climate-sensitive mountain ecosystems.

Satellite observations of the Himalayas are revealing a striking story of seasonal resilience, ecological sensitivity, and mounting climate concern, as forests deepen in colour, grasslands revive, and valley flora shifts with changing seasons.

A new long-term study led by researchers from the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital — an autonomous institute under the Department of Science and Technology (DST) — has mapped Uttarakhand’s vegetation dynamics over 22 years, highlighting emerging declines linked to climate change, pollution, and human activity.

Published in Environmental Monitoring and Assessment (Springer Nature), the research uses advanced satellite analytics to provide an early-warning lens on one of India’s most climate-sensitive mountain ecosystems.

Himalayas: A Climate-Sensitive Ecological Hotspot

Mountain ecosystems are among the most vulnerable to climate change. Rising temperatures, shifting precipitation patterns, and increasing frequency of extreme events are altering vegetation growth cycles, biodiversity stability, and water resources.

Because the Himalayas serve as a critical ecological and hydrological lifeline for millions downstream, monitoring vegetation health at local and seasonal scales has become increasingly urgent.

Google Earth Engine Enables Large-Scale Vegetation Monitoring

To track these changes, ARIES scientists turned to Google Earth Engine (GEE) — a global satellite data processing platform widely used for environmental monitoring, land degradation studies, urban expansion mapping, and climate impact assessments.

GEE allows researchers to analyse decades of satellite imagery without the burden of massive data storage and preprocessing, making it a powerful tool for large-scale ecosystem studies.

NDVI: A Simple Index Revealing Complex Ecological Shifts

The team, led by Dr. Umesh Dumka, used the Normalized Difference Vegetation Index (NDVI) — a widely used satellite-based measure of vegetation greenness — to assess Uttarakhand’s vegetation changes from 2001 to 2022.

• Low NDVI values indicate barren land, rock, snow, sand, or exposed soil

• High NDVI values signal dense vegetation such as forests, croplands, and wetlands

Seasonal NDVI maps showed clear patterns across winter, pre-monsoon, monsoon, and post-monsoon periods, capturing Uttarakhand’s ecological rhythm over two decades.

EVI Analysis Strengthens Findings in Dense Forest Zones

The study also examined the Enhanced Vegetation Index (EVI), which offers improved sensitivity in high-biomass regions where NDVI may saturate.

Together, NDVI and EVI provided a robust picture of vegetation health across diverse Himalayan landscapes, from alpine zones to forested valleys.

Seasonal Patterns Shifting Over Two Decades

The results show that vegetation indices are typically:

• Highest after the monsoon

• Lowest before the monsoon

However, researchers found that these natural seasonal rhythms are beginning to shift, reflecting climate-driven stress on Himalayan ecosystems.

Using time-series analysis and spatial trend mapping through GEE, the study identified clear monthly, seasonal, and yearly variations — alongside worrying long-term decline signals.

Declining Vegetation Linked to Deforestation, Expansion, Pollution

The researchers observed a gradual decline in vegetation trends in several areas, attributing the changes to multiple interacting pressures, including:

• Deforestation

• Agricultural expansion

• Illegal logging

• Rising pollution from urban and industrial sources

Importantly, the study notes that pollution impacts vegetation unevenly, striking certain hotspots harder and compounding climate-related stress.

Implications for Biodiversity and Water Security

Vegetation decline in Uttarakhand is not just an ecological issue — it threatens:

• Himalayan biodiversity

• Watershed stability

• Forest ecosystem services

• Water availability for downstream populations

The findings underline how closely linked mountain vegetation health is to the broader environmental balance across northern India.

Satellite Science as an Early-Warning Tool

The study demonstrates that modern Earth observation and AI-enabled satellite platforms like Google Earth Engine can function as early-warning systems, helping policymakers and communities pinpoint where ecological intervention is most urgently required.

As climate pressures intensify, such tools will be essential for sustainable planning, conservation, and disaster risk reduction in fragile mountain regions.

Publication Details

The research is published in Environmental Monitoring and Assessment (Springer Nature):

https://link.springer.com/article/10.1007/s10661-025-14804-x

Media coverage:https://scienmag.com/google-earth-engine-insights-on-uttarakhands-vegetation-dynamics/