scholarly journals Assessment and Attribution of Mangrove Forest Changes in the Indian Sundarbans from 2000 to 2020

2021 ◽  
Vol 13 (24) ◽  
pp. 4957
Author(s):  
Sourav Samanta ◽  
Sugata Hazra ◽  
Partho P. Mondal ◽  
Abhra Chanda ◽  
Sandip Giri ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Mangrove Forest ◽  
Vegetation Index ◽  
Health Indicators ◽  
Water Diversion ◽  
Mangrove Forests ◽  
River Channels ◽  
Monotonic Trend ◽  
Indian Sundarbans

The Indian Sundarbans, together with Bangladesh, comprise the largest mangrove forest in the world. Reclamation of the mangroves in this region ceased in the 1930s. However, they are still subject to adverse environmental influences, such as sediment starvation due to migration of the main river channels in the Ganges–Brahmaputra delta over the last few centuries, cyclone landfall, wave action from the Bay of Bengal—changing hydrology due to upstream water diversion—and the pervasive effects of relative sea-level rise. This study builds on earlier work to assess changes from 2000 to 2020 in mangrove extent, genus composition, and mangrove ‘health’ indicators, using various vegetation indices derived from Landsat and MODIS satellite imagery by performing maximum likelihood supervised classification. We show that about 110 km2 of mangroves disappeared within the reserve forest due to erosion, and 81 km2 were gained within the inhabited part of Sundarbans Biosphere Reserve (SBR) through plantation and regeneration. The gains are all outside the contiguous mangroves. However, they partially compensate for the losses of the contiguous mangroves in terms of carbon. Genus composition, analyzed by amalgamating data from published literature and ground-truthing surveys, shows change towards more salt-tolerant genus accompanied by a reduction in the prevalence of freshwater-loving Heiritiera, Nypa, and Sonneratia assemblages. Health indicators, such as the enhanced vegetation index (EVI) and normalized differential vegetation index (NDVI), show a monotonic trend of deterioration over the last two decades, which is more pronounced in the sea-facing parts of the mangrove forests. An increase in salinity, a temperature rise, and rainfall reduction in the pre-monsoon and the post-monsoon periods appear to have led to such degradation. Collectively, these results show a decline in mangrove area and health, which poses an existential threat to the Indian Sundarbans in the long term, especially under scenarios of climate change and sea-level rise. Given its unique values, the policy process should acknowledge and address these threats.

Recent Sediment Accumulation in a Mangrove Forest and Its Relevance to Local Sea-Level Rise (Ilha Grande, Brazil)

2008 ◽  
Vol 242 ◽  
pp. 533-536 ◽  
Author(s):  
Christian J. Sanders ◽  
Joseph M. Smoak ◽  
A. Sathy Naidu ◽  
Sambasiva R. Patchineelam
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Mangrove Forest ◽  
Sediment Accumulation ◽  
Recent Sediment

Geomophological and vulnerability analysis of a coastal delta under increased hydrological alteration over the past two centuries: Tana River delta, Kenya, East Africa.

2021 ◽  
Author(s):  
Peter Gitau ◽  
Stéphanie Duvail ◽  
Dirk Verschuren ◽  
Dominique Guillaud
Keyword(s):  
Sea Level Rise ◽  
East Africa ◽  
Sea Level ◽  
Coastal Dune ◽  
River Delta ◽  
River Channels ◽  
Dune System ◽  
The Past ◽  
Tana River ◽  
Coastal Dune System

<p>Coastal deltas worldwide are under risk of degradation due to the increasing impacts of sea-level rise, and continuous human alterations of river basin hydrology. This research highlights the geomorphological changes that have occurred within the Tana River delta in Kenya, an important deltaic ecosystem of high biodiversity value in East Africa.</p><p>The geomorphological features (river channels, floodplain, coastal dune system) and their evolution over the past two centuries were described. Aerial and satellite imagery was used to assess the magnitude and distribution of coastal changes from the 1960s to present.  Additionally, sediment cores recovered within the mangrove environment were analysed to establish the succession of sedimentation periods and patterns. Finally, we explored the response of the coastal processes of deposition and erosion under anthropogenic alterations of the hydrological system.</p><p>It was established that over the past two centuries Tana River has changed its main channel and outlet to the Indian Ocean on three occasions. A first river avulsion occurred in the 1860s, followed by a second avulsion in the late 1890s that was promoted by human interference through channel expansion and dyke construction. The third change in river course has occurred gradually over the past 20 years, amid human efforts to engineer the river channels.</p><p>From the sediment analysis and radiocarbon dating, it is ascertained that the lower deltaic region developed rapidly over the past ~180 years, facilitated by increased sedimentation from the main Tana River. On the other hand, analysis of the coastline changes indicate that there has been increased erosion of the coastal dune system and mangrove vegetation along the former river outlet, leading to rapid marine intrusion into local subsistence farming areas. By analysing the combined impacts of both natural river dynamics and human alteration we highlight how the integrity of the Tana River delta has increasingly become vulnerable under present sea level rise and continued upstream river alteration.</p>

scholarly journals Thresholds of mangrove survival under rapid sea level rise

Science ◽  
2020 ◽  
Vol 368 (6495) ◽  
pp. 1118-1121 ◽  
Author(s):  
N. Saintilan ◽  
N. S. Khan ◽  
E. Ashe ◽  
J. J. Kelleway ◽  
K. Rogers ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Carbon Sink ◽  
Vertical Accretion ◽  
Mangrove Forests ◽  
Relative Sea Level ◽  
Relative Sea Level Rise ◽  
Emissions Scenarios ◽  
Organic Sediments ◽  
Timing Of Initiation

The response of mangroves to high rates of relative sea level rise (RSLR) is poorly understood. We explore the limits of mangrove vertical accretion to sustained periods of RSLR in the final stages of deglaciation. The timing of initiation and rate of mangrove vertical accretion were compared with independently modeled rates of RSLR for 78 locations. Mangrove forests expanded between 9800 and 7500 years ago, vertically accreting thick sequences of organic sediments at a rate principally driven by the rate of RSLR, representing an important carbon sink. We found it very likely (>90% probability) that mangroves were unable to initiate sustained accretion when RSLR rates exceeded 6.1 millimeters per year. This threshold is likely to be surpassed on tropical coastlines within 30 years under high-emissions scenarios.

scholarly journals Variations in Persistence and Regenerative Zones in Coastal Forests Triggered by Sea Level Rise and Storms

2019 ◽  
Vol 11 (17) ◽  
pp. 2019 ◽  
Author(s):  
Sergio Fagherazzi ◽  
Giovanna Nordio ◽  
Keila Munz ◽  
Daniele Catucci ◽  
William S. Kearney
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Forest Disturbance ◽  
Remote Sensing Data ◽  
Storm Events ◽  
Coastal Forests ◽  
The North ◽  
Significant Difference

Retreat of coastal forests in relation to sea level rise has been widely documented. Recent work indicates that coastal forests on the Delmarva Peninsula, United States, can be differentiated into persistence and regenerative zones as a function of sea-level rise and storm events. In the lower persistence zone trees cannot regenerate because of frequent flooding and high soil salinity. This study aims to verify the existence of these zones using spectral remote sensing data, and determine whether the effect of large storm events that cause damage to these forests can be detected from satellite images. Spectral analysis confirms a significant difference in average Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) values in the proposed persistence and regenerative zones. Both NDVI and NDWI indexes decrease after storms triggering a surge above 1.3 m with respect to the North American Vertical Datum of 1988 (NAVD88). NDWI values decrease more, suggesting that this index is better suited to detect the effect of hurricanes on coastal forests. In the regenerative zone, both NDVI and NDWI values recover three years after a storm, while in the persistence zone the NDVI and NDWI values keep decreasing, possibly due to sea level rise causing vegetation stress. As a result, the forest resilience to storms in the persistence zone is lower than in the regenerative zone. Our findings corroborate the ecological ratchet model of coastal forest disturbance.

scholarly journals MANGROVE FOREST CHANGE IN NUSA PENIDA MARINE PROTECTED AREA, BALI - INDONESIA USING LANDSAT SATELLITE IMAGERY

2019 ◽  
Vol 15 (2) ◽  
pp. 141 ◽  
Author(s):  
August Daulat ◽  
Widodo Setiyo Pranowo ◽  
Syahrial Nur Amri
Keyword(s):  
Satellite Imagery ◽  
Vegetation Cover ◽  
Protected Area ◽  
Mangrove Forest ◽  
Vegetation Index ◽  
Marine Protected Area ◽  
Mangrove Forests ◽  
Forest Change ◽  
Landsat Satellite ◽  
The Impact

Nusa Penida, Bali was designated as a Marine Protected Area (MPA) by the Klungkung Local Government in 2010 with support from the Ministry of Marine Affairs and Fisheries, Republic of Indonesia. Mangrove forests located in Nusa Lembongan Island inside the Nusa Penida MPA jurisdiction have decreased in biomass quality and vegetation cover. It’s over the last decades due to influences from natural phenomena and human activities, which obstruct mangrove growth. Study the mangrove forest changes related to the marine protected areas implementation are important to explain the impact of the regulation and its influence on future conservation management in the region. Mangrove forest in Nusa Penida MPA can be monitored using remote sensing technology, specifically Normalized Difference Vegetation Index (NDVI) from Landsat satellite imagery combined with visual and statistical analysis. The NDVI helps in identifying the health of vegetation cover in the region across three different time frames 2003, 2010, and 2017. The results showed that the NDVI decreased slightly between 2003 and 2010. It’s also increased significantly by 2017, where a mostly positive change occurred landwards and adverse change happened in the middle of the mangrove forest towards the sea.

scholarly journals Physiological consequences of rising water salinity for a declining freshwater turtle

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Mickey Agha ◽  
Yuzo R Yanagitsuru ◽  
Nann A Fangue ◽  
A Justin Nowakowski ◽  
Laura V Kojima ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Plasma Osmolality ◽  
Water Diversion ◽  
Freshwater Turtle ◽  
Freshwater Species ◽  
Freshwater Turtles ◽  
Elevated Salinity ◽  
Western Pond Turtle

Abstract Sea-level rise, drought and water diversion can all lead to rapid salinization of freshwater habitats, especially in coastal areas. Increased water salinities can in turn alter the geographic distribution and ecology of freshwater species including turtles. The physiological consequences of salinization for freshwater turtles, however, are poorly known. Here, we compared the osmoregulatory response of two geographically separate populations of the freshwater Western Pond Turtle (Actinemys marmorata)—a species declining across its range in western North America—to three constant salinities: 0.4 ppt, 10 ppt and 15 ppt over 2 weeks. We found that turtles from a coastal estuarine marsh population regulated their plasma osmolality at lower levels than their conspecifics from an inland freshwater creek population 45 km away. Plasma osmolalities were consistently lower in estuarine marsh turtles than the freshwater creek turtles over the entire 2-week exposure to 10 ppt and 15 ppt water. Furthermore, estuarine marsh turtles maintained plasma osmolalities within 1 SD of their mean field osmolalities over the 2-week exposure, whereas freshwater creek turtles exceeded their field values within the first few days after exposure to elevated salinities. However, individuals from both populations exhibited body mass loss in 15 ppt water, with significantly greater loss in estuarine turtles. We speculate that the greater ability to osmoregulate by the estuarine marsh turtles may be explained by their reduced feeding and drinking in elevated salinities that was not exhibited by the freshwater creek population. However, due to mass loss in both populations, physiological and behavioural responses exhibited by estuarine marsh turtles may only be effective adaptations for short-term exposures to elevated salinities, such as those from tides and when traversing saline habitats, and are unlikely to be effective for long-term exposure to elevated salinity as is expected under sea-level rise.

scholarly journals Mangroves facing climate change: landward migration potential in response to projected scenarios of sea level rise

2014 ◽  
Vol 11 (3) ◽  
pp. 857-871 ◽  
Author(s):  
D. Di Nitto ◽  
G. Neukermans ◽  
N. Koedam ◽  
H. Defever ◽  
F. Pattyn ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ground Truth ◽  
Avicennia Marina ◽  
Mangrove Forests ◽  
Important Species ◽  
Digital Terrain ◽  
Terrain Models ◽  
Migration Potential ◽  
The One

Abstract. Mangrove forests prominently occupy an intertidal boundary position where the effects of sea level rise will be fast and well visible. This study in East Africa (Gazi Bay, Kenya) addresses the question of whether mangroves can be resilient to a rise in sea level by focusing on their potential to migrate towards landward areas. The combinatory analysis between remote sensing, DGPS-based ground truth and digital terrain models (DTM) unveils how real vegetation assemblages can shift under different projected (minimum (+9 cm), relative (+20 cm), average (+48 cm) and maximum (+88 cm)) scenarios of sea level rise (SLR). Under SLR scenarios up to 48 cm by the year 2100, the landward extension remarkably implies an area increase for each of the dominant mangrove assemblages except for Avicennia marina and Ceriops tagal, both on the landward side. On the one hand, the increase in most species in the first three scenarios, including the socio-economically most important species in this area, Rhizophora mucronata and C. tagal on the seaward side, strongly depends on the colonisation rate of these species. On the other hand, a SLR scenario of +88 cm by the year 2100 indicates that the area flooded only by equinoctial tides strongly decreases due to the topographical settings at the edge of the inhabited area. Consequently, the landward Avicennia-dominated assemblages will further decrease as a formation if they fail to adapt to a more frequent inundation. The topography is site-specific; however non-invadable areas can be typical for many mangrove settings.

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