Analysis of Mangrove vegetation health index by implementing NDVI classification method based on Landsat image data: Case study from Zuari Estuary Goa, India

Mangrove ecosystems are among the most productive and biologically complex ecosystems in the world providing many ecosystem services for human wellbeing, hence they have an outstanding relevance ecologically and economically. Mangrove habitats are temporarily inundated and often located in inaccessible regions. In Goa, fringing mangroves are distributed in Zuari and Mandovi estuaries based on topography and environmental conditions. These estuarine regions are used as inland waterways for transportation of iron ore, tourism, infrastructure development like bridges, jetties, highways, resorts and hotels, residential apartments, restaurants, small roads etc. Zuari estuary is located at lat. 15°25'N and long. 73°59'E on the central west coast of India. The images were downloaded from United States Geological Survey website (USGS). The radiometric and geometric corrections were made to reduce the undesirable noise component and changes in the amount of incoming radiance from sensors. Anderson level 1 classification was used for the classification purpose. The mangroves were digitized using hybrid classification method. For mangrove demarcation Google Earth Pro and visual interpretation techniques were used. Normalised Difference Vegetation Index (NDVI) analysis was adapted to perceive the health status of mangroves covers in the study area. The NDVI results were divided into three categories: (0.00-0.15 Stressed), (0.15-0.30 Moderately healthy), (0.30-0.47 Very healthy). Rhizophora and 01sp. each of Aegiceras, Bruguiera, Kandelia, Acanthus and Excoecaria along with mangrove associates like Acrosticum, Clerodendron, Salvadora, Ipomoea and Derris. Sonneretia alba and Avicennia marina were found to be dominating followed by Rhizophora mucronata. Stressed patches of mangroves can be attributed to the human interference from the surrounding regions, changes in water salinity, increase in pollution levels due to mining activities (transportation of iron ore from barges), infrastructure development etc. Moderately healthy and very healthy patches of mangroves may be associated with suitable ecological and natural conditions favouring healthy growth and also lack of anthropogenic interference and awareness about the importance of mangroves.