Assessing vegetation health and fragmentation in Aizawl District using Normalized Difference Vegetation Index

Aim: To study the vegetation dynamics in Aizawl District, Mizoram, India, from 2013 to 2023, inorder to analyze the impact of urban expansion and reforestation efforts on forest cover and landscape fragmentation.

Methodology: Landsat 8 imagery 8OLI/TIRS Collection 2 Level 1 and Level 2 from 2013, 2018 and 2023 was processed to calculate Normalized difference vegetation index (NDVI) in QGIS, then reclassified vegetation into density classes (non-vegetated area, sparse vegetation, slightly dense vegetation, moderately dense vegetation, and highly dense vegetation). Spatial autocorrelation, using Moran’s I, assessed vegetation patterns, while Fragstats software quantified class and landscape metrics for spatial pattern analysis (Class metrics- PLAND, PD, ED, LSI, AI, and Landscape metrics-PD, LSI, SIDI, AI).

Results: Vegetation density fluctuated, initially declining from 2013 to 2018, and then recovering in 2023, according to NDVI analysis. Moderately dense vegetation class expanded 36.4% in 2013 to 42.8% in 2023 over the decade, while non-vegetated areas increased 3.2% in 2013 to 4.4% in 2023. Patch Density and Landscape Shape Index of the overall landscape indicate ongoing fragmentation, 65.47 and 333.102 in 2013 declining to 62.42 and 337.368 in 2018, though increased slightly to 72.03 and 322.992 by 2023. Simpson’s Diversity Index (SIDI) rose from 0.7035 in 2013 to 0.7135 in 2018 before dropping to 0.6965 in 2023, indicating reduced landscape diversity and niche habitats, while the Aggregation Index (AI) increased from 63.14 to 64.04, reflecting reduced fragmentation and greater consolidation, particularly in moderately dense vegetation. Moran’s I index followed a similar trend, decreasing from 0.679 in 2013 to 0.602 in 2018, and then rising back to 0.673 in 2023.

Interpretation: The findings suggest that urban expansion is a key driver of fragmentation, yet reforestation initiatives and minimal practice of shifting cultivation contribute to vegetation consolidation. Enhanced management strategies are recommended to preserve habitat connectivity and promote sustainable land use, supporting ecological resilience in Aizawl District.

Key words: Aizawl, Normalized Difference Vegetation Index, Remote sensing, Vegetation fragmentation