Are we failing to protect threatened mangroves in the Sundarbans world heritage ecosystem?

Abstract

The Sundarbans, the largest mangrove ecosystem in the world, is under threat from historical and future human exploitation and sea level rise. Limited scientific knowledge on the spatial ecology of the mangroves in this world heritage ecosystem has been a major impediment to conservation efforts. Here, for the first time, we report on habitat suitability analyses and spatial density maps for the four most prominent mangrove species - Heritiera fomes, Excoecaria agallocha, Ceriops decandra and Xylocarpus mekongensis. Globally endangered H. fomes abundances declined as salinity increased. Responses to nutrients, elevation, and stem density varied between species. H. fomes and X. mekongensis preferred upstream habitats. E. agallocha and C. decandra preferred down-stream and mid-stream habitats. Historical harvesting had negative influences on H. fomes, C. decandra and X. mekongensis abundances. The established protected area network does not support the most suitable habitats of these threatened species. We therefore recommend a reconfiguration of the network to include these suitable habitats and ensure their immediate protection. These novel habitat insights and spatial predictions can form the basis for future forest studies and spatial conservation planning, and have implications for more effective conservation of the Sundarbans mangroves and the many other species that rely on them.

Impacts of climate change on coastal ecosystems of Bangladesh

“…Sea-level rise contributes to direct loss of vegetative cover (Loucks et al 2010). Climate change disturbs plant physiology, phenology and reduces vegetation (Sarker et al 2016). Fresh water influx during the dry season is currently below the normal ecological flow (i.e., 234 cumec) necessary to balance the riverwater salinity (Moly, Mirza, Rahman & Saadat 2015) and below the minimum required flow (i.e., 194 cumec) to maintain the oligohaline (i.e., low saline) zones of the mangroves (Aziz & Paul 2015).…”

“…This salt intrusion has large impacts on both ecological and socio-economic systems which provide essential social, economic and ecosystem services for the region. Hence, its highly diverse ecosystems, like the world's largest single tract of mangroves (the Sundarbans), wetlands (vast network of rivers of the Ganges-Brahmaputra tidal plains) and inlands (mostly crop-agriculture) have already started to be severely affected by this salinization (Rabbani et al 2013, Rasel et al 2013, Sarker et al 2016). In addition, this salinization leads to extreme drinking water scarcity for about 6.2 million people in this region (Abedin et al 2014).…”

“…Although fifth assessment report additionally mentioned increasing ocean acidity (Wong et al 2014). These changes will ultimately increase salinity (Passeri et al 2015) and this most likely affects biodiversity by degrading habitats (Sarker et al 2016) and livelihoods of many coastal people, leading to economic losses and poorer living and health conditions (Huq et al 2015). These impacts are already being felt across Bangladesh's south-west coast (Karim and Mimura 2008;Ali 1999;Mirza 1998).…”

Assessing Species Vulnerability to Climate Change in Tropical Asia: Implications for Biodiversity Conservation and Forest Management

“…The tea plantations adjacent to the evergreen forests in the north-eastern region may also experience moisture stress (Ahmed et al 1999). Sarker et al (2016) reported that globally endangered Heritiera fomes abundance declined as salinity increased, and historical harvesting reduced the stem density of the threatened species in Sundarbans mangroves. Another study reported that annual and monsoon precipitation, as well as salinity intrusion, mainly influence the growth of H. fomes (Chowdhury et al 2016).…”

Adaptive co-management as an approach to tourism destination governance – a case of protected areas in Bangladesh

“…There is little tourism infrastructure in the Sundarbans and safety and security of visitors has also been a concern. However, like Lawachara National Park the Sundarbans also face challenges in developing tourism due to a lack of planning (Sarker, Reeve, Thompson, Paul, & Matthiopoulos, 2016;WWF [World Wide Fund For Nature], 2017). The area does however, have much potential as a nature-based tourism destination.…”