Spatio-temporal changes in mangroves of Bhitarkanika National Park along the Eastern Coast of India over a three decades period using remote sensing spectral index NDVI

The present study assesses the areal extent and health condition of the mangroves in Bhitarkanika along the east coast of India, using routine remote sensing spectral index – normalized difference vegetation index (NDVI). Selected Landsat-5/8 images from three decades (1991–2021) were used for the calculation of NDVI (mean, SD, range) values for the assessment of mangrove health. The results indicate that the mean NDVI value slightly decreased from 0.56 (1991) to 0.43 (2021). Out of the total mangrove area, unhealthy mangroves increased from 10.91 sq. km in 1991 to 38.26 sq. km by 2021, while moderately healthy mangroves decreased from 40.15 sq. km in 1991 to 12.98 sq. km by 2021, due to various anthropogenic activities. The study also identified specific positive gains in some parts of the mangrove (north, east, and some patches of the southwest) due to the effective implementation of afforestation and reforestation efforts through government and local initiatives.