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Digital elevation model (DEM) provides elevation values of the terrain. At present several open source DEMs are available and its vertical accuracy varies from place to place. The present study assessed the vertical accuracy of 1 arc-sec data of Advanced Land Observing Satellite digital surface model (AW3D30) Version-3, Shuttle Radar Topographic Mission (SRTM) DEM (V3), Carto DEM (V3R1) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global DEM (V2) using Ice, Cloud, and land Elevation Satellite/Geoscience Laser Altimeter System (ICESat/GLAS) and Real Time Kinematic Global Positioning System (RTK GPS) data in Southeast coast of India. Root mean square error (RMSE) was calculated for DEMs, showed the elevation accuracy as 2.48 m (AW3D30), 3.02 m (SRTM DEM), 3.88 m (Carto DEM) and 8.02 m (ASTER GDEM) in the Tamil Nadu state while it was 2.29 m (AW3D30), 3.10 m (SRTM DEM), 3.93 m (Carto DEM) and 8.98 m (ASTER GDEM) in the 10 km buffer zone of coastal region and the results are satisfactory than the official product’s specifications. Landform analysis was carried out at selected RTK GPS surveyed sites where the elevation of different coastal landforms is validated with DEMs and it was found the AW3D30 showed least RMSE than others. This paper suggests that AW3D30 is best for representing terrain elevation values followed by SRTM and Carto DEMs which are apt choices for application studies.

Coral reefs of Lakshadweep perform a range of vital ecosystem functions and sustain the livelihoods of island communities. Coral reefs provide ecosystem services that are vital to human societies and industries through fisheries, coastal protection and tourism. The present study was undertaken during September and October 2015 to assess the status of reef health in 10 inhabited Islands of Lakshadweep following reef classification to imply conservation measures and also for the sustainable management by the dependent communities. Live coral cover, habitat complexity index, coral species richness, reef condition index, mortality index, morphological dominance, morphological diversity and coral conservation class were used to get an aggregate value of ‘composite condition’ index for determining the overall conservation values of coral reefs in these Islands. Kadmat reef had the highest live coral cover of 64.50% among the 10 inhabited islands. Bitra and Kiltan reef had good live coral cover of 62.75 and 52.25% respectively. The major benthic component in all the studied islands is live coral except in Amini and Andrott Islands. The recovery of corals has increased significantly in the last 5 years in Kadmat, Bitra, Kiltan and Bangarm after the 2010 mass bleaching event. Among the eight attributes, significant positive correlations were found between coral reef condition and live coral cover (r = 0.93, p 60% of stress tolerators. CC3 was assigned to Bangaram and Kadmat due to the presence of > 75% of ruderals. Mixed coral morphology was recorded in Agatti, Andrott, Kalpeni, Kavaratti, and Kiltan with approximately equal proportions of ruderals, competitors and stress tolerators, and these coral reefs were designated as CC4. Protection and conservation management measures, as well as sustainable resource use, have been suggested based on the live coral cover, conservation class, and coral reef health status.

This study reports the mapping, structural characteristics and distribution of mangrove species of the Andaman Islands. 79 mangrove patches were identified using Thiessen polygons of which, 53 accessible patches were surveyed during 2014–2015. Multiple linear transects were laid at each of the mangrove patches and data pertaining to diameter at breast height, basal area and height were recorded for all mangrove trees within a 10 × 10 m quadrat laid along the transects at 50 m intervals. Altogether, 178 quadrats were laid and 25 mangrove species representing 11 families and 14 genera were recorded. Of the 3073 mangrove plants enumerated in the present study, 96.06% were composed of trees (>4 m height), 1.99% of saplings (>1 m to ≤4 m height) and 1.95% of seedlings (≤1 m height). The number of species per quadrat ranged from 1 to 9 and majority of the quadrats had 2–3 species. Density and basal area of mangrove trees ranged from 1252 ha−1 to 2200 ha−1 and 30.8 m2/ha to 59.6 m2/ha, respectively. High diversity indices (Shannon-Wiener index ranged from 1.65 to 2.24; Simpson index from 0.74 to 0.85 and Pielou’s evenness index from 0.66 to 0.84) indicated greater diversity and even dispersion of mangroves in the Islands. The study also revealed that the mangrove forests of Andaman Islands were characterized by a mixed species composition. Most of the sites were represented by different combinations of dominant and co-dominant species, all from the family Rhizophoraceae. The present study highlights the need for conserving the mixed species mangrove forests of Andaman and Nicobar Islands and development of location-specific management plans for biodiversity conservation.

In this paper, multiplicative version of degree distance of a graph is defined and tight upper bounds of the graph operations have been found.

Holistic development of islands need an integrated planning rather than a sector-based approach. In pristine islands such as the Lakshadweep group of islands, India, where land is a scarce resource, focused and scientific planning is essential to balance economic well-being with environmental concerns and ecological conservation. We have assessed the major challenges that currently exist in the islands of Lakshadweep vis-a-vis the opportunities that would promote ecotourism, keeping in mind the fragility of the coral reefs, and the heavy dependence on traditional fisheries. Interventions, primarily focusing on enhancing potable water, control of land-based pollution (both sewage and solid waste), fisheries, and biodiversity conservation are highlighted.

Salt marshes are one among the most productive coastal ecosystems, mostly confined to low-energy coasts of temperate and high latitude. Tropical and sub-tropical salt marshes are generally less studied. The present study attempts to assess the status of salt marsh vegetation along the Indian coast regarding its species composition, density, and zonation pattern. Satellite images were used to map salt marshes along the coastal region and to perform field surveys for status assessment at selected sites between November 2014 and July 2018. The total extent of salt marshes in India is estimated as about 290 km2. A total of 14 salt marsh species are found distributed along the Indian coast, belonging to 11 genera under six families. The most diverse family is represented by Amaranthaceae. The overall mean density of salt marsh vegetation is estimated to be 19 ± 1 plants per m2 with the highest density recorded in Lakshadweep (28 m−2) followed by Tamil Nadu (23 m−2), West Bengal (19 m−2), Maharashtra (18 m−2), Andhra Pradesh (17 m−2), Gujarat (15 m−2) and Puducherry (10 m−2). The zonation pattern of salt marsh vegetation in pure stands is detailed from observations. Conservation implications on salt marshes have been discussed. This study provides insight into salt marshes in the tropical environment.

Saltmarshes are an important marginal coastal ecosystem influenced by tidal movement and are created by the interaction of the halophytic vegetation and sediment trapped from inundating water. This study gives the baseline information on saltmarsh distribution and diversity along the Southeast coast of India. Saltmarsh locations were identified and mapped using satellite images of 2010 of IRS P6 LISS III (23.5 m resolution) & LISS IV (5.8 m) and LandSAT 8 OLI (30.0 m resolution). A total of 37 saltmarsh vegetation sites were identified along Tamil Nadu and one in Puducherry Union Territory. Seven species of saltmarsh flora are reported under four genera and three families: Arthrocnemum indicum (Willd.) Moq., Salicornia brachiata (Roxb), Sesuvium portulacastrum (L.), Suaeda fruticosa (Forssk), S. maritima (L.) Dumort, S. monoica (Forssk) and S. nudiflora (Moquin). The maximum benthic coverage by the saltmarsh community observed at Arucottuthurai was 93.3% and a minimum percentage cover of 28% was observed at Pazhaiyar. The biodiversity indices calculated for all study sites displayed maximum saltmarsh diversity (Shannon-Wiener H’ = 2.295 ± 0.001) at Vedaranyam and a minimum diversity (H’ = 0.759 ± 0.001) at Thirukazhipalai. A total of 23 species representing 16 fauna and seven flora were observed as associates from the saltmarsh ecosystem. Saltmarsh ecosystem provides unique breeding sites for macro fauna and roosting ground for avifauna, provide livelihood options for coastal communities and protects the integrity of coast. Rapid coastal development and aquaculture pose a major threat to this ecosystem. This study helps to protect, conserve and sustainably use this ecologically important coastal ecosystem and prepare specific management strategies by stakeholders.