Abstract
<title>Abstract</title> <p>The North Eastern Himalayan Region (NEHR) of India is one of the world's most ecologically diverse yet environmentally fragile regions, where rapid socio-economic development and climate change are intensifying ecological pressures. Developing reliable ecological security early-warning systems is therefore essential to supporting sustainable environmental management. This study developed an Ecological Security Early Warning Index (ESEWI) based on the Pressure–State–Response (PSR) framework to assess historical ecological security and forecast future trends across the NEHR at the district level. Based on 21 PSR indicators, ecological security was evaluated using a combined weighting and multilevel weighted comprehensive index method, projected using the Grey Model (GM), and the dominant driving factors were identified using the Geodetector model. The results reveal fluctuations in ecological security during 2000–2020, with mean Ecological Security Index (ESI) values ranging from 0.541 to 0.577. Model projections indicate a gradual decline in ecological security, with the ESEWI decreasing from 0.547 in 2025 to 0.522 in 2040, an overall reduction of 4.57%. The fraction of districts under a huge warning is projected to increase from 9.09% to 18.18%, whereas the fraction of districts under a serious warning is expected to rise from 29.09% to 40.00%, indicating a deterioration in regional ecological conditions. Geodetector analysis identified population density as the dominant driver of ecological security, with interactions between population density and forest cover showing greater explanatory power than either factor alone. This study demonstrates that the proposed framework provides a robust basis for ecological assessment, early warning, and sustainable environmental management in the ecologically fragile Himalayan region of India.</p>