Mapping of mangrove distribution and assessment of above-ground biomass for the blue carbon potential along the southern coast of Tamil Nadu

Ranjith, L and Vinod, K and Kalidas, C and Linga Prabu, D and Sarathapriya, D and Mathan Babu, A and Rajendran, P and Asha, P S and George, Grinson (2025) Mapping of mangrove distribution and assessment of above-ground biomass for the blue carbon potential along the southern coast of Tamil Nadu. Regional Studies in Marine Science. pp. 1-44. ISSN 2352-4855 (In Press)

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Abstract

Remote sensing enables large-scale mangrove mapping and monitoring of changes even in areas with limited access to field surveys. This study aimed to map the extent of mangrove distribution, document major species, estimate above-ground biomass, and assess the carbon sequestration capacity of mangroves at three locations in Thoothukudi (Punnakayal, Palayakayal, and Tuticorin) and two locations in Kanyakumari (Manakudy and Pantry) along the southern coast of Tamil Nadu, India. Using multispectral Landsat 8 Operational Land Imager (OLI) satellite imagery from 2013 to 2021 and applying the Normalised Difference Vegetation Index (NDVI), the estimated mangrove extent fluctuated over the years, showing an overall increase from 3.057 km² in 2013 to 4.161 km² in 2021. As of 2021, mangrove cover in Thoothukudi accounted for 87.7% of the total, with contributions from Palayakayal (34%), Tuticorin (30.3%), and Punnakayal (23.4%), while the Kanyakumari region contributed 12.3%. The results of morphological and molecular species identification of mangroves showed that the Thoothukudi region's most prominent genus is Avicennia from the Avicenniaceae family, while the Kanyakumari region recorded members of the Rhizophoraceae family, Bruguiera, and Rhizophora. Six species reported during the rapid field survey (2021), Avicennia marina, A. officinalis, Rhizophora mucronata, Bruguiera cylindrica, Bruguiera gymnorhiza and Ceriops tagal. The estimated carbon sink potential was 724 kilotons of carbon per year (as of 2021), with Avicennia and Rhizophora being the major contributors to the blue carbon potential in the study area. These findings provide essential baseline information on the relatively under-studied mangrove habitats of the Kanyakumari region, highlighting its potential for conservation. Overall, this study underscores the importance of mangroves in climate change mitigation and their role as significant carbon sinks. The satellite-based insights presented herein can support more effective mangrove forest management across the southern coastal region of Tamil Nadu.

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