Assessment of vegetation transformation and anthropogenic impact on forest degradation in the Nilgiri Biosphere Reserve of India

Forest degradation is havoc for the biosphere reserves and their periphery areas. The Nilgiri Biosphere Reserve (NBR), recognised by UNESCO as a biodiversity hotspot and India’s first biosphere reserve, is currently facing numerous natural and anthropogenic challenges. It causes various environmental and ecological imbalances and human-wildlife conflicts. The major issue in this biosphere reserve is the absence of a transition zone and its limits, and due to that, anthropogenic imprints are likely to be high in the other zones. Hence, this study addresses the anthropogenic impact on forest degradation and identifies the hot spots. Therefore, a long-term (2000–2023) vegetation change was estimated by time series analysis. The anthropogenic forest degradation index (AFDI) is then calculated to understand the human impact on NBR. This analysis consists of thematic variables like topographic, environmental and anthropogenic aspects. For evaluation purposes, a multicriteria evaluation approach is applied using the Analytical Hierarchy Process (AHP). The vegetation changes analysis shows a 19.7% decline and a 16% increase in the study region, with a high correlation R2 = 0.75. However, the forest cover loss is depicted as 1.6% of the area lost in two decades, and the annual rate of change is 0.155%. Furthermore, the AFDI result indicates forest degradation in NBR, with approximately 29.2% of the geographical area categorised as very high or high, particularly in regions where manipulation and restoration zones are highly degraded. The integrated environmental and forest degradation analysis identified vulnerable hot spots with high degradation rates (about 25.9%) and cold spots with low or no degradation (about 25.4%), with a 90% to 99% confidence level. Overall, forest degradation within NBR remains a tough concern, exacerbated by future population pressures and the resulting demand for forest resources, which often leads to their conversion into plantations, agricultural activity, and other infrastructural developments.