Mangrove Spatial Distribution in the Indian Sundarbans: Predicting Salinity-Induced Migration in a Changing Climate

Abstract

This study contributes to understanding the physical and economic impacts of progressive, climate-driven aquatic salinization on the spatial distribution of mangrove species in the Indian Sundarbans, which accounts for about two-fifths of the 10,200 km2 tidal-wetland forest delta. To estimate future mangrove distribution, a five-step analysis was undertaken, using high-resolution spatial assessments. A current (2015) basemap and overlays of salinity tolerance for major mangrove species and their assemblages and projected location-specific aquatic salinity for 2050 were used to predict salinity-induced migration. The results show gain-and-loss patterns, with salt-tolerant species predominating at the expense of freshwater species. These changes are likely to reduce the flow of ecosystem services, adversely affecting the livelihood options of poor people in adjacent areas. Effective management will require establishing baseline data for monitoring system changes over time, protocols for maintaining species health, and support for mangrove regeneration and restoration. Resources should also be directed to alternative livelihoods for mangrove-dependent households. The study recommends an integrated policy approach, focused on rising salinity, changes in mangrove dynamics, and the welfare of mangrove-dependent communities.

Solving the fourth‐corner problem: forecasting ecosystem primary production from spatial multispecies trait‐based models

“…2007, Mukhopadhyay et al. 2019) have projected a 5–10% decadal increase in salinity. The river network annually transports about 2.4 billion metric tons (or Mg) of sediments in the Sundarbans (Mitra and Zaman 2016) and sediment burial of aerial roots (inhibits root aeration) is a major reason for limited mangrove growth and regeneration failure (Mitra and Zaman 2016, Sarker et al.…”

“…2019, Mukhopadhyay et al. 2019), we considered E5 as the worst stress scenario for the ecosystem by 2050.…”

“…As a result, the average soil salinity level has already increased by 60% since 1980 (Aziz and Paul 2015). Several geomorphological or hydrological prediction models (IWM 2003, Wahid et al 2007, Mukhopadhyay et al 2019 have projected a 5-10% decadal increase in salinity. The river network annually transports about 2.4 billion metric tons (or Mg) of sediments in the Sundarbans (Mitra and Zaman 2016) and sediment burial of aerial roots (inhibits root aeration) is a major reason for limited mangrove growth and regeneration failure (Mitra andZaman 2016, Sarker et al 2019b).…”

“…S2) for five future stress scenarios (E1, 10%; E2, 20%; E3, 30%; E4, 40%; and E5, 50% increase in salinity and siltation), and then used them to forecast traits and forest productivity under these novel environments. Based on the available geomorphological or hydrological model-based forecasts of salinity and siltation in the literature (IWM 2003, Wahid et al 2007, Islam and Gnauck 2011, Ghosh et al 2019, Mukhopadhyay et al 2019, we considered E5 as the worst stress scenario for the ecosystem by 2050.…”

Challenges towards the Sustainability and Enhancement of the Indian Sundarban Mangrove’s Blue Carbon Stock

“…Overall, species richness and evenness are declining in the Indian Sundarban, as only the genera Avicennia and Excoecaria are gradually replacing a myriad of less salt-tolerant mangrove species in this region, as these genera can acclimatize under a varying range of salinity [ 111 ]. Mukhopadhyay et al [ 112 ] projected the future species assemblage in the Indian Sundarban for the year 2050. They inferred that if the salinity keeps increasing in this way, fewer salt-tolerant species will replace a much higher number of oligohaline species all through the Indian Sundarban, compromising its overall species biodiversity.…”