Rising water salinity: a threat to mangroves of indian sundarbans
11 Aug 2014-Vol. 13
TL;DR: In this paper, a critical analysis on the impact of salinity on the growth of a common mangrove species (Hertiera fomes) was carried out in the framework of Indian Sundarbans, which has contrasting salinity profiles in different segments owing to barrage discharge and siltation phenomena.
Abstract: Mangroves constitute an important ecosystem because of their global extent and high productivity. These plants thrive in the intertidal zones of the tropics and subtropics that are characterized by regular tidal inundation and fluctuating salinity. Mangrove species are well adapted, both morphologically and physiologically, to survive under saline conditions, but in hypersaline environment their growth is reduced. The present chapter is a critical analysis on the impact of salinity on the growth of a common mangrove species (Hertiera fomes). The analysis has been carried out in the framework of Indian Sundarbans, which has contrasting salinity profiles in different segments owing to barrage discharge and siltation phenomena. Analysis of the decadal profile of salinity indicates a gradual lowering in the western Indian Sundarbans due to Farrakka barrage discharge and run-off from catchments. The central sector, however, exhibits a contrasting picture of increment of aquatic salinity through time, mainly due to disconnection of the Bidyadhari River with the Ganga–Bhagrirathi–Hooghly River system (in the western part). This has made the Matla River in the central Indian Sundarbans hypersaline in nature (that used to get water from the Bidyadhari River) finally leading to an insecure ecological condition for the growth and survival of mangroves. The possible remedial measures to combat the situation have also been listed considering the ecological framework of the study zone.
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TL;DR: This work traces the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries using a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover.
Abstract: Covering approximately 10,000 km2 the Sundarbans in the Northern Bay of Bengal is the largest contiguous mangrove forest on earth. Mangroves forests are highly productive and diverse ecosystems, providing a wide range of direct ecosystem services for resident populations. In addition, mangroves function as a buffer against frequently occurring cyclones; helping to protect local settlements including the two most populous cities of the world, Kolkata and Dhaka, against their worst effects. While large tracts of the Indian Sundarbans were cleared, drained and reclaimed for cultivation during the British colonial era, the remaining parts have been under various protection regimes since the 1970s, primarily to protect the remaining population of Bengal tigers (Panthera tigris ssp. tigris). In view of the importance of such forests, now severely threatened worldwide, we trace the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries. We apply a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover. While the mangroves’ areal extent has not changed much in the recent past, forest health and structure have. These changes result from direct human interference, upstream development, extreme weather events and the slow onset of climate change effects. Moreover, we consider the role of different management strategies affecting mangrove conservation and their intersection with local livelihoods.
177 citations
TL;DR: It was concluded that increased amounts of rainfall and associated flooding and sea level rise were responsible for recent seaward and landward extension of mangroves in this region.
Abstract: Across their range, mangroves are responding to coastal environmental change. However, separating the influence of human activities from natural events and processes (including that associated with climatic fluctuation) is often difficult. In the Gulf of Carpentaria, northern Australia (Leichhardt, Nicholson, Mornington Inlet, and Flinders River catchments), changes in mangroves are assumed to be the result of natural drivers as human impacts are minimal. By comparing classifications from time series of Landsat sensor data for the period 1987–2014, mangroves were observed to have extended seawards by up to 1.9 km (perpendicular to the coastline), with inland intrusion occurring along many of the rivers and rivulets in the tidal reaches. Seaward expansion was particularly evident near the mouth of the Leichhardt River, and was associated with peaks in river discharge with LiDAR data indicating distinct structural zones developing following each large rainfall and discharge event. However, along the Gulf coast, and particularly within the Mornington Inlet catchment, the expansion was more gradual and linked to inundation and regular sediment supply through freshwater input. Landward expansion along the Mornington Inlet catchment was attributed to the combined effects of sea level rise and prolonged periods of tidal and freshwater inundation on coastal lowlands. The study concluded that increased amounts of rainfall and associated flooding and sea level rise were responsible for recent seaward and landward extension of mangroves in this region.
70 citations
Cites background from "Rising water salinity: a threat to ..."
...Even so, optimum saline concentrations vary among species (Krauss and Allen 2003; Ye et al. 2005; Zaman et al. 2013)....
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TL;DR: Estimates of the variability of salinity and the biomass of a stenoecious mangrove species (Heritiera fomes) in the aquatic subsystem of the lower Gangetic delta based on a dataset from 2004 to 2015 show an increase in aboveground biomass of this endangered species shows an increase only in the former sector where the salinity is dropping and low growth in the latter, where theSalinity is increasing.
Abstract: The alterations in the salinity profile are an indirect, but potentially sensitive, indicator for detecting changes in precipitation, evaporation, river run-off, glacier retreat, and ice melt. These changes have a high impact on the growth of coastal plant species, such as mangroves. Here, we present estimates of the variability of salinity and the biomass of a stenoecious mangrove species (Heritiera fomes, commonly referred to as Sundari) in the aquatic subsystem of the lower Gangetic delta based on a dataset from 2004 to 2015. We highlight the impact of salinity alteration on the change in aboveground biomass of this endangered species that, due to different salinity profile in the western and central sectors of the lower Gangetic plain, shows an increase only in the former sector, where the salinity is dropping and low growth in the latter, where the salinity is increasing.
45 citations
Cites background from "Rising water salinity: a threat to ..."
...the Gangetic delta, and their physiology is considerably influenced by surface water salinity (Zaman et al. 2014)....
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...Mangroves are the most widespread tree communities of the Gangetic delta, and their physiology is considerably influenced by surface water salinity (Zaman et al. 2014)....
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TL;DR: In this article, the authors applied vulnerability index models to appraise livelihood vulnerability to climate change of human communities living in coastal fronts of some selected mouzas of Namkhana Block part of the Indian Sundarbans.
Abstract: The study applies vulnerability index models to appraise livelihood vulnerability to climate change of human communities living in coastal fronts of some selected mouzas of Namkhana Block part of the Indian Sundarbans. Primary household surveys (528 households in seven mouzas) are carried out to procure data on indicators of socio-demographic profile, livelihood strategies, health, food, water, social networks, natural disaster and climatic fluctuations. The data then have been processed by indices like livelihood vulnerability index (LVI) and livelihood vulnerability index-intergovernmental panel on climate change (LVI-IPCC) to evaluate and compare vulnerabilities of mouzas currently suffering from physical processes like coastal erosion, embankment breaching and flood events. The research outcome implies that Baliara and Iswaripur mouzas are highly vulnerable (LVI score > 0.600 and LVI-IPCC score > 0.170); Narayanpur, Mousuni, Kusumtala mouzas are moderately vulnerable (LVI score 0.540–0.600 and LVI-IPCC score 0.060–0.170); and Bagdanga, Patibania mouzas are least vulnerable (LVI score > 0.540 and LVI-IPCC score < 0.060) to changing climate phenomena. The foremost reasons behind higher vulnerability are greater exposure to climatic fluctuation, natural hazards and higher sensitivity to improper access to food, health, water and finally lower adaptive capacity in terms of poor socio-demographic profile and livelihood security. Findings of the study provide a deeper understanding of people’s perception, adaptation and their ever-increasing vulnerability to changing climate. This approach based on indicators emphasizes sectors that necessitate particular intercession to design management plans for threatened communities. Such type of pragmatic approach of study formulates reliable methodology to quantify vulnerability and develop disaster management strategies to increase the resilience of vulnerable coastal people to climate change.
23 citations
TL;DR: In this article, Neogi et al. proposed a method for coastal development in Bangladesh, based on the Leibniz Center for Tropical Marine Ecology GmbH (LCMEG).
Abstract: Fil: Neogi, Sucharit Basu. Coastal Development Partnership; Bangladesh. Osaka Prefecture University; Japon. Leibniz Center for Tropical Marine Ecology GmbH; Alemania
19 citations
References
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4,091 citations
TL;DR: This paper discusses whole-plant responses to salinity in order to answer the question of what process limits growth of non-halophytes in saline soils and suggests that a message from the root is regulating leaf expansion.
Abstract: This paper discusses whole-plant responses to salinity in order to answer the question of what process limits growth of non-halophytes in saline soils. Leaf growth is more sensitive to salinity than root growth, so we focus on the process or processes that might limit leaf expansion. Effects of short-term exposure (days) are considered separately from long-term exposure (weeks to years). The answer in the short term is probably the water status of the root and we suggest that a message from the root is regulating leaf expansion. The answer to what limits growth in the long term may be the maximum salt concentration tolerated by the fully expanded leaves of the shoot; if the rate of leaf death approaches the rate of new leaf expansion, the photosynthetic area will eventually become too low to support continued growth.
1,312 citations
TL;DR: Mangroves are trees or bushes growing between the level of high water of spring tides and a level close to but above mean sea-level and the land animals found in mangrove forests include roosting flocks of fruit bats, fishing and insectivorous birds, and many insects are conspicuous.
Abstract: Publisher Summary Mangroves are trees or bushes growing between the level of high water of spring tides and a level close to but above mean sea-level Very few species of mangrove are deep rooted, or have persistent tap roots Almost all are shallow rooted but the root systems are often extensive and may cover a wide area Rhizophoraceous trees have seedlings with a long radicle which would seem well suited to develop into a tap root, but as soon as the seedling becomes established in the mud the radicle develops little further Trees of Avicennia and of Sonneratia develop several different kinds of roots The main rooting system consists of large cable roots which give off anchoring roots downwards and aerial roots or pneumatophores upwards These pneumatophores in their turn produce a large number of nutritive roots which penetrate the mineral-rich subsurface layers of the soil The land animals found in mangrove forests include roosting flocks of fruit bats, fishing and insectivorous birds, and many insects are conspicuous Of the marine animals, crabs and molluscs live permanently in the forest, and prawns and fishes come in on the tide to feed on the apparently abundant nutriment provided by the mangrove soils In South East Asia man uses mangrove areas for the establishment of ponds for the culture of fish and prawns, and for timber
881 citations
"Rising water salinity: a threat to ..." refers background in this paper
...They grow along protected sedimentary shores especially in tidal lagoons, embayment, and estuaries (MacNae, 1968)....
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TL;DR: In this paper, the authors estimate that about 50% of terrigenous materials delivered to the world's oceans are delivered through just twenty-one major river systems and that 70% of this C occurs in coastal margins from 0° to 10° latitude.
Abstract: Nearly 50% of terrigenous materials delivered to the world's oceans are delivered through just twenty-one major river systems. These river-dominated coastal margins (including estuarine and shelf ecosystems) are thus important both to the regional enhancement of productivity and to the global flux of C that is observed in land-margin ecosystems. The tropical regions of the biosphere are the most biogeochemically active coastal regions and represent potentially important sinks of C in the biosphere. Rates of net primary productivity and biomass accumulation depend on a combination of global factors such as latitude and local factors such as hydrology. The global storage of C in mangrove biomass is estimated at 4.03 Pg C; and 70% of this C occurs in coastal margins from 0° to 10° latitude. The average rate of wood production is 12.08 Mg ha−1 yr−1, which is equivalent to a global estimate of 0.16 Pg C/yr stored in mangrove biomass. Together with carbon accumulation in mangrove sediments (0.02 Pg C/yr), the net ecosystem production in mangroves is about 0.18 Pg C/yr. Global estimates of export from coastal wetlands is about 0.08 Pg C/yr compared to input of 0.36 Pg C/yr from rivers to coastal ecosystems. Total allochthonous input of 0.44 Pg C/yr is lower than in situ production of 6.65 Pg C/yr. The trophic condition of coastal ecosystems depends on the fate of this total supply of 7.09 Pg C/yr as either contributing to system respiration, or becoming permanently stored in sediments. Accumulation of carbon in coastal sediments is only 0.41 Pg C/yr; about 6% of the total input. The NEP of coastal wetlands also contribute to the C sink of coastal margins, but the source of this C is part of the terrestrial C exchange with the atmosphere. Accumulation of C in wood and sediments of coastal wetlands is 0.205 Pg C/yr, half the estimate for sequestering of C in coastal sediments. Burial of C in shelf sediments is probably underestimated, particularly in tropical river-dominated coastal margins. Better estimates of these two C sinks in the tropics, coastal wetlands and shelf sediments, is needed to better understand the contribution of coastal ecosystems to the global carbon budget.
476 citations
TL;DR: The Sundarban is the habitat of many rare and endangered animals (Batagur baska, Pelochelys bibroni, Chelonia mydas), especially the Royal Bengal tiger (Panthera tigris) as mentioned in this paper.
Abstract: The Sundarban, covering about one million ha in the delta of the rivers Ganga, Brahmaputra and Meghna is shared between Bangladesh (~60%) and India (~40%), and is the world’s largest coastal wetland. The area experiences a subtropical monsoonal climate with an annual rainfall of 1,600–1,800 mm and severe cyclonic storms. Enormous amounts of sediments carried by the rivers contribute to its expansion and dynamics. Salinity gradients change over a wide range of spatial and temporal scales. The biodiversity includes about 350 species of vascular plants, 250 fishes and 300 birds, besides numerous species of phytoplankton, fungi, bacteria, zooplankton, benthic invertebrates, molluscs, reptiles, amphibians and mammals. Species composition and community structure vary east to west, and along the hydrological and salinity gradients. Sundarban is the habitat of many rare and endangered animals (Batagur baska, Pelochelys bibroni, Chelonia mydas), especially the Royal Bengal tiger (Panthera tigris). Javan rhino, wild buffalo, hog deer, and barking deer are now extinct from the area. Large areas of the Sundarban mangroves have been converted into paddy fields over the past two centuries, and more recently into shrimp farms. The Sundarban has been extensively exploited for timber, fish, prawns and fodder. The regulation of river flows by a series of dams, barrages and embankments for diverting water upstream for various human needs and for flood control has caused large reduction in freshwater inflow and seriously affected the biodiversity because of an increase in salinity and changes in sedimentation. Heritiera fomes (locally called Sundari, from which Sundarban derives its name), Nypa fruticans and Phoenix paludosa are declining rapidly. During the past three decades, large parts of the remaining Sundarban have been protected for wildlife, particularly tiger, through the creation of several sanctuaries and a biosphere reserve. Parts of the Sundarban in both India and Bangladesh have been declared World Heritage sites. However, its biodiversity continues to be threatened by a growing human population that not only places pressure on its biological resources, but also impacts on the freshwater inflows from upstream areas. Oil exploration in coastal areas is also emerging as a new threat. Further threats arise from global climate change, especially sea level rise. The future of the Sundarban will depend upon the management of freshwater resources as much as on the conservation of its biological resources.
438 citations