Loss Of Mangrove Area Research Articles

Net evaporation-induced mangrove area loss across low-lying Caribbean islands

Abstract Although mangroves provide many beneficial ecosystem services, such as blue carbon storage and coastal protection, they are currently under threat due to changes in climate conditions, such as prolonged drought exposure. Under drought conditions, evaporation exceeds precipitation and high soil salinities can lead to stunted growth and die-back. To quantify this interplay, we developed a database for low-lying and uninhabited mangrove islands in the Caribbean under various evaporation and precipitation regimes. We extracted physical and biological information from each island using remote sensing techniques and coupled it with a process-based model. We used this database to develop a model that explains both the spatial variability in vegetated area across the Caribbean—as a function of rates of evaporation and precipitation—and porewater salinity concentration and dispersion from island edge towards the interior of mangrove islands. We then used this validated model to predict mangrove area loss associated with increases in evaporation to precipitation rates by 2100 for different Shared Socioeconomic Pathways (SSP). Less wealthy Caribbean regions such as Belize, Puerto Rico, and Venezuela are disproportionally affected, with mangrove area losses ranging from 3%–7% for SSP 2.6 and 13%–21% for SSP 7.0. Furthermore, foregone carbon sequestration in lost biomass under SSP 4.5 and 7.0 scenarios could compromise the ability of low-lying Caribbean mangrove islands to vertically adjust to sea level rise.

QUANTIFICATION OF THE SUPPRESSION OF A MANGUEZAL AREA IN THE MUNICIPALITY OF VITÓRIA, ES, DUE TO THE URBAN EXPANSION OF BAIRRO MARIA ORTIZ

In view of the increase in population and the need for housing, natural and / or preservation areas are being replaced by large cities. It was analyzed about the suppression of natural environments, such as the loss of a parcel of mangrove that occurred to originate the Maria Ortiz neighborhood — Vitória / ES. In order to observe and quantify such losses, verify if such action continues to happen and the scenario of the time for the population to accomplish this feat. Therefore, it was necessary to survey historical data from the region under study and documentary research in georeferenced images from different decades for comparison purposes. Then, a case study was carried out based on the content of the materials obtained. In view of this, it appears that when comparing the images, a very significant loss of mangrove area over the decades and an accelerated evolution of the Maria Ortiz neighborhood regarding urban expansion, thus realizing that the neighborhood emerged from the extinction of a parcel area protected by law.

Decadal loss of above-ground biomass and subsequent potential CO2 emission from the Sundarbans mangrove ecosystem, India

Mangrove forests harbour some of the highest carbon densities of any ecosystem, yet their decline has resulted in potential carbon dioxide (CO2) emissions. The emission of CO2 due to the loss of above-ground biomass (AGB) of the Sundarbans mangrove ecosystem was calculated using the ArcMap and ERDAS software. Hence, classification of the Satellite images between 1990 and 2020 of the Indian portions of the Sundarbans was done.The total loss of mangrove area in the Indian part of Sundarbans is 138.4 km2 in the last 30 years. Around 57% of the total loss is due to erosion, 22% is converted to fallow lands, and the remainder is transformed into different landforms for human use. The AGB loss has led to the potential CO2 emission of 2028.4 ± 713.7 Gg, which costs $101.42 million in terms of the social cost of carbon (SCC).The stability analysis of the system showed that the fluctuations during the high tidal surges of cyclone ‘Aila’ that struck the coastline of the Bay of Bengal, resulted in the decrease of mangrove covers and acted as a driving force behind the depletion of ‘blue carbon’ of the Sundarbans.

Hydroperiod and Salinity Interactions Control Mangrove Root Dynamics in a Karstic Oceanic Island in the Caribbean Sea (San Andres, Colombia)

Mangroves sustain high soil accretion and carbon sequestration rates, yet it is still unknown if they can keep pace with increasing sea level rise (SLR) across a wider range of coastal geomorphic settings. Because accretion rates are controlled by mineral sediment inputs and organic matter accumulation, it is paramount to assess the relative contribution of root productivity to soil formation. Here, we evaluated root biomass, production, and turnover in three mangrove ecotypes to evaluate the role of soil nutrient limitation, stressors, and hydroperiod in controlling root dynamics in San Andres Island (SAI), a karstic oceanic island in the Caribbean Sea. Root production was modulated by soil stress conditions and not by nutrient availability as it has been reported for other karstic environments. The lowest root biomass allocation, and both production and turnover of fine roots were measured under low flooding duration, and low salinity (<20 PSU) and sulfide concentrations (0.84 ± 0.4 mM). Yet, when soil stress conditions increased during high flooding duration (6207 h y–1) and low oxygen conditions (Eh), root tissues reached the highest biomass and production values, including a relative fast turnover of fine roots (<2 mm; 0.75 y–1). Our results follow the predictions of the plant root longevity cost-benefit hypothesis where plants maintain roots only until the efficiency of resource acquisition is maximized by water and nutrient acquisition. Because of the importance of groundwater in controlling porewater salinity and mangrove root productivity in karstic oceanic islands such as SAI, water use and coastal development should be regulated in the short term to avoid the loss of mangrove area and concomitant ecosystem services.

Pond aquaculture effluents feed an anthropogenic nitrogen loop in a SE Asian estuary

Coastal aquaculture expansion resulted in mangrove area loss and ecosystem degradation in the past decades, mainly in tropical Asia. Despite increasing environmental concerns regarding nutrient and organic matter-rich effluents, little is known on the effects on adjacent estuarine and coastal food webs. To assess the impact and fate of anthropogenic nitrogen released from aquaculture facilities, we studied water quality and nitrogen (N) flow across an estuarine food web in an estuary in Hainan, China, using nitrogen stable isotopes (δ15N). We found higher δ15N values of ammonium, nitrate and suspended matter in the pond-covered inner estuary than further upstream, suggesting a strong influence of untreated pond effluents, which had a high δ15N (ammonium: ~16‰, nitrate: ~7‰, suspended matter: ~8‰). Fish and benthic invertebrates of the inner estuary had a higher δ15N than consumers further upstream and in similar aquaculture-free estuaries elsewhere, most likely due to direct or indirect uptake of 15N-enriched aquaculture effluents by phytoplankton and benthic algae. A major part of the artisanal catches from the estuary consists of small-size fish which is used as feed in the local aquaculture. Thus, estuarine fish incorporating aquaculture-effluent based food web signals are harvested and recycled as feed in aquaculture facilities, whose effluents sustain this local food web. The δ15N being at the high end of the global range on all trophic levels indicates an anthropogenic nitrogen loop in which some portion of the reactive nitrogen initially introduced into aquaculture ponds is continuously recycled and affects the estuarine food web. This recycling also indicates a shortcut in the otherwise inefficient nitrogen sink function of estuaries. Therefore, in areas with large-scale coastal aquaculture like in China and SE Asia the effect of reactive nitrogen from aquaculture sources on the performance of coastal ecosystems may be larger than previously thought.

Impact of 2004 co-seismic coastal uplift on the mangrove cover along the North Andaman Islands

The December 2004 earthquake and the subsequent tsunami have incurred devastating impacts on vital habitats along the Indian coastal region, where few of them are irreversible. The earthquake has uplifted the northern Andaman coast, resulting in a drastic reduction of tidal water influx into the adjoining mangrove-laden mudflats. Satellite images of the period from 2003 to 2019 were used to assess the impact of coastal upliftment on the northern Andaman mangroves. Through satellite data analysis, we report a loss of 6500 ha of northern Andaman mangroves. Tidal hydrodynamics simulation under the post-earthquake scenario showed a vast area of mudflats deprived of tidal influx. This reduction in the tidal inundation has incurred a gradual and permanent mangrove area degradation. The earthquake impact on the mangroves was not spontaneous, but a gradual process, where the mangroves were intact until Mach 2006. The earthquake and the resultant coastal uplift have significantly altered the coastal geomorphology as well as the plant demography of the study area. Field visit revealed the terrestrial vegetation growth along the erstwhile mudflats, and vast areas of mangrove peat are observed, surrounded by successions of marshy and terrestrial plants. As mangroves are preferred habitat for diverse marine and terrestrial organisms and act as a vital food source and juvenile shelters for various fish species, the extensive loss of mangrove area may adversely affect a large scale biological ecosystem.

Brazilian Mangrove Status: Three Decades of Satellite Data Analysis

Since the 1980s, mangrove cover mapping has become a common scientific task. However, the systematic and continuous identification of vegetation cover, whether on a global or regional scale, demands large storage and processing capacities. This manuscript presents a Google Earth Engine (GEE)-managed pipeline to compute the annual status of Brazilian mangroves from 1985 to 2018, along with a new spectral index, the Modular Mangrove Recognition Index (MMRI), which has been specifically designed to better discriminate mangrove forests from the surrounding vegetation. If compared separately, the periods from 1985 to 1998 and 1999 to 2018 show distinct mangrove area trends. The first period, from 1985 to 1998, shows an upward trend, which seems to be related more to the uneven distribution of Landsat data than to a regeneration of Brazilian mangroves. In the second period, from 1999 to 2018, a trend of mangrove area loss was registered, reaching up to 2% of the mangrove forest. On a regional scale, ~85% of Brazil’s mangrove cover is in the states of Maranhão, Pará, Amapá and Bahia. In terms of persistence, ~75% of the Brazilian mangroves remained unchanged for two decades or more.

The Mangrove Forests Change and Impacts from Tropical Cyclones in the Philippines Using Time Series Satellite Imagery

The Philippines is rich in mangrove forests, containing 50% of the total mangrove species of the world. However, the vast mangrove areas of the country have declined to about half of its cover in the past century. In the 1970s, action was taken to protect the remaining mangrove forests under a government initiative, recognizing the ecological benefits mangrove forests can bring. Here, we examine two mangrove areas in the Philippines—Coron in Palawan and Balangiga-Lawaan in Eastern Samar over a 30-year period. Sets of Landsat images from 1987 to 2016 were classified and spatially analyzed using four landscape metrics. Additional analyses of the mangrove areas’ spatiotemporal dynamics were conducted. The impact of typhoon landfall on the mangrove areas was also analyzed in a qualitative manner. Spatiotemporal changes indicate that both the Coron and Balangiga-Lawaan mangrove forests, though declared as protected areas, are still suffering from mangrove area loss. Mangrove areal shrinkage and expansion can be attributed to both typhoon occurrence and management practices. Overall, our study reveals which mangrove forests need more responsive action, and provides a different perspective in understanding the spatiotemporal dynamics of these mangrove areas.

Geospatial modelling of the inundation levels in the Sundarbans mangrove forests due to the impact of sea level rise and identification of affected species and regions

This research reveals the magnitude of mangrove area loss and future impacts on mangrove species composition and distribution due to rise in Mean Sea Level (MSL). In this study, a geospatial model of potentially inundated areas was developed using Digital Elevation Model (DEM) data to assess the potential impacts of sea level rise (SLR) on the spatial distribution of mangrove species and estimate the potential inundation and subsequent mangrove area loss. The mangrove areas of 2646 ha, 9599 ha and 74,720 ha are projected to be inundated and subsequently lost by the end of the twenty first century for the low, medium and high SLR scenarios respectively under the net subsidence rate −2.4 mm/year relative to the baseline year 2000. All the major five mangrove species of the Bangladesh Sundarbans will be affected and this can potentially contribute to a change in the present species composition and biodiversity of the forest. Results suggest that, under the extreme scenario, inundation and subsequent loss of different mangrove species will be substantial and this can bring a massive change in the species composition and their spatial distribution in the Bangladesh Sundarbans.

Spatial and temporal changes in mangrove cover across the protected and unprotected forests of India

Mangroves are vulnerable to natural environmental changes and anthropogenic disturbances; but, the status and change dynamics at a national level are poorly understood. Consequently, this research is aimed to assess the changes in major mangrove forests of India between the period of 1989 and 2013, covering an area of 62678 km2 from five coastal states. Landsat satellite data, post-classification approach, and ground truth verification were used for the mapping of the mangroves and assessing the changes in protected and unprotected forest regions. Our findings revealed that mangrove extent has increased from 3006 km2 to 3406 km2 within the period of study. Of the mangrove extent, 91% in 1989 and 80% in 2013 were located in the protected forest regions. The annual average rate of increase in mangrove area was 0.55%/yr. The mangroves gained and lost were 918 km2 and 517 km2 respectively, of which 53% of the growth and 81% of the loss occurred in protected regions. Natural factors were responsible for 97% of gain and 92% of the loss of mangrove area. The anthropogenic drivers were responsible for the 8% of mangrove conversion. The extent of mangroves grown was greater than that of deforestation in India, unlike many other shrimp growing countries. The results of the present study indicate the areas of intense change in mangrove forests and also provide important insight into the supportive efforts of mangrove conservation.

Mangrove allocation for coastal protection and livelihood improvement in Kien Giang province, Vietnam: Constraints and recommendations

A management policy adopted by the Kien Giang Province, Vietnam, is to allocate mangroves areas using contracts with local community members who are dependent on mangrove resources for both mangrove protection and livelihood improvement. However, community members have not made the best use of the allocated areas, and mangroves have not been well protected. The policy is due to be revised in late 2016, as is legally required. This study used mixed methods to review the policy and its implementation with respect to mangrove protection requirements and use of mangroves for livelihood improvement and to provide recommendations for sustainable mangrove management in Kien Giang. The policy and its implementation is demonstrated to be a constraint to achieving its goal. Limited understanding of the policy of contractees resulted in ineffective and inefficient aquaculture and mangrove protection in almost all areas. Permitted thinning and selective harvests led to the creation of substantial gaps and disconnections in the established mangroves, making the entire coastline vulnerable to coastal erosion. Improper technical guidance on the configuration of mangrove allocations, and mangrove protection and transplantation methods resulted in the mangrove protected areas being fragmented and vulnerable to erosion. Permitted thinning and selective harvest practices should be reviewed to ensure adequate resilience and protection of mangrove areas, especially on critically eroding areas. Proper law enforcement should be put in place to ensure contracts are adequately implemented. Allocation and/or transferal of areas less than 1ha must be discontinued in the future to avoid further defragmentation and degradation. Technical guidance on configuring allocated mangrove areas should be established and incorporated into the updated policy that would help improve the effectiveness of the policy, and address problems relating to strengthening resilience and protection of mangrove areas in Kien Giang Province, Vietnam.Similar programs using mangrove area allocation to individuals and households in response to mangrove area loss exist elsewhere in the Mekong delta. Understanding the reasons for the very limited success of the Kien Giang program and local co-investigation in drawing lessons learnt can help guide other similar programs elsewhere in the Mekong Delta region.

Millennial to secular time-scale impacts of climate and sea-level changes on mangroves from the Doce River delta, Southeastern Brazil

This work integrates geomorphological, sedimentological, and palynological data with radiocarbon dating, as well as δ13C, δ15N, and C/N from sedimentary organic matter to provide a model of mangrove dynamics during the evolution of a wave-dominated delta in Southeastern Brazil. Mangrove dynamics are analyzed within the context of millennial and secular climatic and sea-level changes. Tidal flats, positioned at highest limit of the intertidal zone along the edge of a lagoon sheltered by beach ridges, were occupied by wetlands represented by mangrove and herbaceous vegetation during the mid-Holocene high sea level. After considering the relative sea-level fall and relatively higher fluvial sediment discharge, during the last ~6350 years, progradation took place along this shoreline, resulting in extensive beach ridge deposits that overlie transgressive muds. This process led to loss of mangrove area. Similar dynamics were repeated at ~3043 cal. yr BP, although in a relatively more distal (i.e. seaward) position. Between ~1337 and ~900 cal. yr BP, a tidal flat attached to the edge of a lagoon near the modern coastline was colonized by herbaceous vegetation (C4 plants). The next phase, which occurred between ~900 and ~400 or ~100 cal. yr BP, is marked by the transition from herbaceous to mangrove tidal flats with an increased trend of terrestrial organic matter. During the recent centuries, a mangrove vegetation became established, and there was an increased trend of estuarine-derived organic matter. This mangrove phase, recorded during the last century(ies), may be due to a relative sea-level rise. Under this scenario, erosion of beach ridges and expansion of lagoons and mangroves are expected along the littoral of the State of Espírito Santo in Southeastern Brazil.

Blue Carbon Stock of the Bangladesh Sundarban Mangroves: What could Be the Scenario after a Century?

The total blue carbon stock of the Bangladesh Sundarban mangroves was evaluated and the probable future status after a century was predicted based on the recent trend of changes in the last 30 years and implementing a hybrid model of Markov Chain and Cellular automata. At present 36.24 Tg C and 54.95 Tg C are stored in the above-ground and below-ground compartments respectively resulting in total blue carbon stock of 91.19 Tg C. According to the prediction 15.88 Tg C would be lost from this region by the year 2115. The low saline species composition classes dominated mainly by Heritiera spp. accounts for the major portion of the carbon sock at present (45.60 Tg C), while the highly saline regions stores only 14.90 Tg C. The prediction shows that after a hundred years almost 22.42 Tg C would be lost from the low saline regions accompanied by an increase of 8.20 Tg C in the high saline regions dominated mainly by Excoecaria sp. and Avicennia spp. The net carbon loss would be due to both mangrove area loss (~ 510 km2) and change in species composition leading to 58.28 Tg of potential CO2 emission within the year 2115.

Potential CO2 Emission Due to Loss of Above Ground Biomass from the Indian Sundarban Mangroves During the Last Four Decades

Sundarban, the largest single patch of mangrove forest of the world is shared by Bangladesh (~ 60 %) and India (~ 40 %). Loss of mangrove biomass and subsequent potential emission of carbon dioxide is reported from different parts of the world. We estimated the loss of above ground mangrove biomass and subsequent potential emission of carbon dioxide in the Indian part of the Sundarban during the last four decades. The loss of mangrove area has been estimated with the help of remotely sensed data and potential emission of carbon dioxide has been evaluated with the help of published above ground biomass data of Indian Sundarban. Total loss of mangrove area was found to be 107 km2 between the year 1975 and 2013. Amongst the total loss ~60 % was washed away in the water by erosion, ~ 23 % was converted into barren lands and the rest were anthropogenically transformed into other landforms. The potential carbon dioxide emission due to the degradation of above ground biomass was estimated to be 1567.98 ± 551.69 Gg during this period, which may account to 64.29 million $ in terms of the social cost of carbon. About three-forth of the total mangrove loss was found in the peripheral islands which are much more prone to erosion. Climate induced changes and anthropogenic land use change could be the major driving force behind this loss of ‘blue carbon’.

Mapping mangrove changes in the Matang Mangrove Forest using multi temporal satellite imageries

The Matang Mangrove Forest is the largest single mangrove forest in Peninsular Malaysia, covering an area of more than 40,000 ha. As a national treasure, it lies under the jurisdiction of both the federal and state authorities. Monitoring temporal changes of mangrove area on a large scale requires a more efficient tool. Remote sensing is often a reliable alternative to ground-survey methods that provides useful source of information and coverage that is timely and complete especially in mangroves areas where accessibility is difficult. In this study, status and changes of land use and land cover in the Matang Mangrove Forest during the past 18 years (1993–1999, 1999 to 2011 and 1993 to 2011) were determined using multi temporal satellites, and threats to the ecosystems were also identified. Classification of land use and land cover approach was implemented using the maximum likelihood classifier (MLC) along with vegetation index differencing (NDVI) technique. Classification accuracy at 85.7%, 90%, and 88.9% with Kappa statistics of 0.82, 0.88, and 0.94 respectively for 1993, 1999 and 2011 image were obtained. The overall change in the area during the 18-year period indicated the loss of mangrove area at 8017.3 ha, while 2998 ha was newly planted or rehabilitated. The present study revealed that Rhizophora apiculata and Rhizophora mucronata are still being preserved, accounting to more than 80% of the total species. Temporal changes of the mangrove for the 18-year period showed that the mangroves were converted to water bodies at 31.1%, dry land forest at 30.6%, oil palm plantation at 18.9%, aquaculture at 11.1%, paddy plantation at 4.9%, horticulture at 3.1%, and urban settlement area at 0.3%. Threats towards the mangrove area were due to erosion, tree harvesting rotation, transitional forest, shrimp ponds, illegal agricultural activities and trespassing. The findings indicated an approach in collecting regular and appropriate mangrove forest area database and detection of activities that violate regulations. This will provide adequate information to the stakeholders in enhancing the management practise and for legislative purposes. Hence, combinations of these approaches has been proven to be adequate in detecting changes in the mangrove area and indicating the nature of the changes which will promote and enhance the management planning process towards sustainability of the Matang Mangrove Forest.

Tide- and rainfall-induced variations of physical and chemical parameters in a mangrove-depleted estuary of East Hainan (South China Sea)

The estuarine dynamics favoring the coexistence of mangroves, seagrass and corals at small river mouths are often poorly understood. We characterize the tidal, day/night and rainfall-induced short-term dynamics in salinity, pH, dissolved oxygen (DO), chlorophyll a (chl a), total suspended matter (TSM), water transparency, surface currents and dissolved nutrients (NOx−, NH4+, PO43−, Si(OH)4) of the Wenchang/Wenjiao Estuary (East Hainan, tropical China). Samples were taken at three fixed sites along the estuary during 24 h spring tide cycles in different seasons. Salinity, DO, water transparency and pH generally increased seawards while nutrients decreased. All parameters varied with the tidal cycle, partially in interaction with the diel cycle. Nutrients, chl a and TSM usually fluctuated inversely with water level. Stratification was strong. Inflowing bottom water was of higher salinity, DO and pH and lower temperature and nutrient concentrations than the surface water. Tidal mixing provided regular ventilation of the estuary and limited eutrophication effects of nutrients from aquaculture, agriculture and urban effluents. Under dry weather conditions, the brackish-water lagoon functioned as a sink of nutrients due to efficient uptake by phytoplankton. Presently, the runoff from common intense rains in the watershed affects the estuary with little time delay due to terrestrial deforestation, channelization and loss of mangrove area. The frequency, strength and duration of intermittent estuarization of the back-reef areas have likely increased in the past and deteriorate present seagrass and coral health.

The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern

Mangrove species are uniquely adapted to tropical and subtropical coasts, and although relatively low in number of species, mangrove forests provide at least US $1.6 billion each year in ecosystem services and support coastal livelihoods worldwide. Globally, mangrove areas are declining rapidly as they are cleared for coastal development and aquaculture and logged for timber and fuel production. Little is known about the effects of mangrove area loss on individual mangrove species and local or regional populations. To address this gap, species-specific information on global distribution, population status, life history traits, and major threats were compiled for each of the 70 known species of mangroves. Each species' probability of extinction was assessed under the Categories and Criteria of the IUCN Red List of Threatened Species. Eleven of the 70 mangrove species (16%) are at elevated threat of extinction. Particular areas of geographical concern include the Atlantic and Pacific coasts of Central America, where as many as 40% of mangroves species present are threatened with extinction. Across the globe, mangrove species found primarily in the high intertidal and upstream estuarine zones, which often have specific freshwater requirements and patchy distributions, are the most threatened because they are often the first cleared for development of aquaculture and agriculture. The loss of mangrove species will have devastating economic and environmental consequences for coastal communities, especially in those areas with low mangrove diversity and high mangrove area or species loss. Several species at high risk of extinction may disappear well before the next decade if existing protective measures are not enforced.