Multi Criteria Decision Making (MCDM) Approach for Mangrove Health Assessment using Geo-informatics Technology

Abstract

Mangroves are coastal wetland forests established in the intertidal zones of estuaries, backwaters, deltas, creeks, lagoons, marshes and mudflats of tropical and subtropical latitudes. World-wide mangroves are disappearing at an alarming rate. Mangroves form one of the most important ecosystems of coastal areas. In real sense, mangrove is the Kalpvriksh (divine tree which fulfills all the desires) for the coastal communities. It nurtures and safeguards the local ecology of the coastal areas and provides livelihood options to the fishermen and pastoral families. Amongst the maritime States of India, Gujarat has the second highest mangrove cover after West Bengal. Additionally, during last three decades Gujarat has more than doubled its mangrove cover. In Gujarat State, mangroves are well developed in Lakhpat taluka (block) situated in Kachchh district. In recent past, Gulf of Kachchh experienced both natural and anthropogenic changes which made it a distinctive site to analyze how natural processes and anthropogenic activities determine the changes in mangrove vegetation density and health of mangroves in coastal areas. Multi-temporal Landsat TM data covering Lakhpat taluka (block) of February-1995, February-2017and Sentinel-2 multi-spectral data (spatial resolution 10 m) of April-2017 was analysed. The mangrove vegetation around the coastal areas was identified and classified into dense and sparse density classes based on Normalized Difference Vegetation Index (NDVI) thresholding approach. The health assessment of mangroves in Lakhpat taluka was attempted using Multi Criteria Decision Making (MCDM) approach including various parameters like mangrove density based on NDVI, Distance of mangroves from human settlement, Distance of mangrove from Industries and Ports which have direct impact of growth and health of mangroves, Erosion/Accretion over the period of last 22 years and availability of Saline water flow during the high tide for good mangrove growth. The buffers layers of various distances for example, 0 to 10 km, 10 to 20 km and 20 to 35 km were generated from the existing mangroves using Sentinel-2 multi-spectral image in GIS environment. The results indicate that the NDVI which is single parameter indicating the mangrove stand / vigour, growth condition and resulting health of mangroves in the area. This factor has been given highest weightage as compared to other parameters. The major anthropogenic factors like human Pressure and presence of Industries and Ports have negative impact on the mangrove health. Therefore, it was observed that presence of human settlements and Industries and Ports with the buffer region of 0 to 10 km distances from mangroves are unhealthy or prone to degradation in this region. The results of health assessment are very useful for sustainable planning and management of mangroves in the coastal areas of Lakhpat Taluka. The mangrove restoration and regeneration activity needs to be carried out as suggested by Upadhyay et al., 2015 with active participation of Community Based Organizations (CBOs) to increase the mangrove density as well as mangrove health in this region.