Cyclone Sidr Impacts on the Sundarbans Floristic Diversity

Abstract

The Sundarbans -the world's largest single block of tidal halophytic mangrove forest situated at the southwest of Bangladesh, plays a vital role in maintaining environmental sustainability of the country and the world in general. This study identified and quantified the extent and degree of damage caused to the floristic diversity of the Sundarbans by the tropical cyclone Sidr in 15 November 2007. It also quantified the extent and rate of the post-cyclone regeneration in the damaged flora. Unsupervised classification -ISODATA and the normalized difference vegetation index (NDVI) were carried out over a temporal series of 2007-2010 on four Landsat 7 Enhanced Thematic Mapper Plus (ETM +) images for the months of February. Land change analysis from the classification results show that three important floristic taxa -Heritiera fomes (Sundari), Excoecaria agallocha (Gewa) and Sonneratia apetala (Kewra) have been significantly affected by the cyclone. NDVI analysis indicates that 45% area of the Bangladesh's part of the Sundarbans (approximately 2500 sq.km) was affected due to the cyclone action. Results further indicated that the average rate of post-cyclone floristic growth in 2009-2010 is four times higher than the average rate in [2008][2009]. Thus the study identified a temporary loss of the diversity (in terms of relative abundance) in the affected three floristic taxa of the Sundarbans after that severe exogenous perturbation; which took three years to regenerate. Moreover, it showed the higher efficiency and promptness of remote sensing techniques in similar cases than the ground data based studies.

Climate Variability and Mangrove Cover Dynamics at Species Level in the Sundarbans, Bangladesh

“…Climatic conditions of all the three stations are similar due to the close association between rainfall and temperature [22]. In this region, temperature varies between 11 °C and 37 °C, while rainfall fluctuates between 1600 mm and 2000 mm.…”

“…The Sundarbans is at the Ganges delta where the three mighty river systems: Ganges, Brahmaputra and Meghna converge [15,21,22], and is characterized by a complex pattern of tributaries [23]. The Sundarbans extends between 21°32′ to 22°40′N latitude and 88°05′ to 89°51′E longitude ( Figure 1) and covers an area of around 10,000 km 2 .…”

A Remote Sensing Approach to Subsidence and Vegetation Degradation in a Reclaimed Mine Area 

“…forests exhibit values ranging from 0.6 to 0.8 [49], whereas lowly productive vegetation exhibits NDVI values close to 0, e.g. shrubs and grasslands exhibit values between 0.2 and 0.3 [58,60]. NDVI also identifies values close to -1 as damaged vegetation, i.e.…”

Sundarbans mangrove forest of Bangladesh: causes of degradation and sustainable management options

“…It is known as one of the most diverse and productive ecosystems in the world (Borrell et al 2016). Apart from being a unique ecosystem, Sundarbans provide extensive protection to coastal populations from cyclones, tidal flooding, erosion and other natural disasters (Das and Vincent 2009;Payo (November 17, 2007) and Aila (May 25, 2009), Sundarbans acted as a protective barrier for the coastal communities (Islam 2013;Bhowmik and Cabral 2013). This forest consists of 200 islands, detached by 400 inter connected tidal rivers and canals (Banglapedia 2010).…”