Mangrove Conversion Research Articles

Spatial variation of algal diversity due to conversion of mangrove to rice ecology in Sundarban, India

Spatial variation of algal diversity due to conversion of mangrove to rice ecology in Sundarban, India

Externalities on The Conversion of Mangrove into Salt Pond in Bipolo Village, Sulamu District, Kupang Regency, East Nusa Tenggara

The utilization of mangrove forest land for the expansion of salt pond areas with the aim of increasing salt production in Bipolo Village causes the loss of economic value of marine biota in the mangrove ecosystem. Mangrove ecosystem resources that are utilized as salt ponds if not accompanied by a rehabilitation process will cause a decrease in the function of the mangrove ecosystem. This will later become a challenge as well as create externalities that need attention from the Kupang district government in regulating the utilization of the mangrove ecosystem in Bipolo Village. This study aims to analyze the positive and negative externality values ??resulting from the development of salt pond businesses in Bipolo Village, Sulamu District, Kupang Regency. To determine the positive and negative externality values ??using the economic valuation method. Based on the results of the study, it is known that the salt pond business in Bipolo Village provides a negative externality value of Rp. 21,439,466,084 and a positive externality value of Rp. 235,280,000 which means that the opening of salt pond land has caused losses from the ecological side of the mangrove which is quite large compared to the benefits obtained.

Impacts of aquaculture practices on the sustainability of social-ecological systems in coastal zones of the Mekong Delta

Coastal and deltaic regions face increasing natural and human-induced hazards, such as cyclones, storm surges, erosion, and saline intrusion, exacerbated by climate change. In tropical zones, mangrove ecosystems provide vital protection against these threats, yet the conversion of mangroves to shrimp aquaculture undermines these benefits, even in protected areas.The Mekong Delta in Vietnam, historically rich in biodiversity and diverse habitats like mangroves and mudflats, has seen local communities thrive. However, rising global market demands have led to more intensive aquaculture models, posing new risks.This research examines the impact of shrimp farming models, from extensive to hyper-intensive, under multiple natural hazards and transformative processes like land conversion and mangrove restoration. Using risk assessment tools and data from local community interviews and focus groups, we present a model showcasing the influence of aquaculture on socio-ecological systems.Key findings reveal the interplay between livelihoods and landscape conversion, highlighting the risks and benefits of various shrimp farming models. The study stresses the need for stakeholder collaboration and improved wastewater treatment to enhance sustainability and environmental health in the Mekong Delta.

Global drivers of mangrove loss in protected areas.

Despite increasing efforts and investment in mangrove conservation, mangrove cover continues to decline globally. The extent to which protected area (PA) management effectively prevents mangrove loss globally across differing management objectives and governance types is not well understood. We combined remote sensing data with PA information to identify the extent and the drivers of mangrove loss across PAs with distinct governance types and protection levels based on categories developed by the International Union for Conservation of Nature (IUCN). Mangrove loss due to storms and erosion was prevalent across all governance types and most IUCN categories. However, the extent of human-driven loss differed across governance types and IUCN categories. Loss was highest in national government PAs. Private, local, shared arrangement, and subnational government agencies had low human-driven mangrove loss. Human-driven loss was highest in PAs with the highest level of restrictions on human activities (IUCN category I) due to mangrove conversion to areas for commodity production (e.g., aquaculture), whereas PAs that allowed sustainable resource use (e.g., category VI) experienced low levels of human-driven mangrove loss. Because category I PAs with high human-driven loss were primarily governed by national government agencies, conservation outcomes in highly PAs might depend not only on the level of restrictions, but also on the governance type. Mangrove loss across different governance types and IUCN categories varied regionally. Specific governance types and IUCN categories thus seemed more effective in preventing mangrove loss in certain regions. Overall, we found that natural drivers contributed to global mangrove loss across all PAs, whereas human-driven mangrove loss was lowest in PAs with subnational- to local-level governance and PAs with few restrictions on human activities.

Assessing the interconnected effects of policy interventions on shrimp farming expansion and mangrove ecosystems through system dynamics

Since the early 2000s, Ca Mau has experienced a rapid boom in shrimp farming, leading to the conversion of mangroves into shrimp ponds and impeding mangrove forest conservation. Despite its negative environmental impacts, shrimp aquaculture remains vital to Ca Mau’s economy by providing employment opportunities and contributing to the province’s gross domestic product. This study constructed a system dynamic model to analyze the complex system of shrimp aquaculture and mangrove forests under two development scenarios: the Business-as-Usual (BAU) scenario and the Policy scenario. In the BAU scenario, shrimp aquaculture will continue to expand, resulting in the conversion of more mangroves into ponds and a decrease in Ca Mau’s mangrove forest to 70,349 (± 888.801) hectares in 2050. However, this expansion will bolster rural employment and the province’s economy, generating 14,250 (± 0.336) billion VND (US$ 570 million) in 2050. Conversely, in the Policy scenario, stabilizing shrimp areas at 280,000 hectares as a policy target will regulate mangrove conversion, allowing mangroves to regenerate (77,016 (± 687.155) hectares in 2050) and enhancing carbon storage (65 × 106 (± 0.58 × 106) MgC in 2050). However, challenges arise in the Policy scenario concerning potential economic stagnation, conflicts with other development priorities, and rural job losses. Officials must consider more than just the area of shrimp ponds to achieve sustainable development. Effective land use strategies should be implemented to ensure equilibrium between shrimp aquaculture and mangroves. Diversifying economic activities and promoting alternative livelihoods can mitigate the dependence on shrimp farming and offset the effects of policy interventions.

The inclusion of Amazon mangroves in Brazil’s REDD+ program

The Legal Amazon of Brazil holds vast mangrove forests, but a lack of awareness of their value has prevented their inclusion into results-based payments established by the United Nations Framework Convention on Climate Change. Based on an inventory from over 190 forest plots in Amazon mangroves, we estimate total ecosystem carbon stocks of 468 ± 67 Megagrams (Mg) ha−1; which are significantly higher than Brazilian upland biomes currently included into national carbon offset financing. Conversion of mangroves results in potential emissions of 1228 Mg CO2e ha−1, which are 3-fold higher than land use emissions from conversion of the Amazon rainforest. Our work provides the foundation for the inclusion of mangroves in Brazil’s intended Nationally Determined Contribution, and here we show that halting mangrove deforestation in the Legal Amazon would generate avoided emissions of 0.9 ± 0.3 Teragrams (Tg) CO2e yr−1; which is equivalent to the annual carbon accumulation in 82,400 ha of secondary forests.

Carbon stocks and effluxes in mangroves converted into aquaculture: a case study from Banten province, Indonesia

Aquaculture is one of the main drivers of mangrove loss across Southeast Asian countries. The conversion of mangroves to aquaculture generates substantial loss of carbon stocks and reduces carbon storage capacity. Here, we present total ecosystem carbon stocks (TECS), carbon dioxide (CO2) and methane (CH4) effluxes obtained from mangrove forests (fringe and interior mangroves), silvofishery aquaculture ponds (dense and sparse mangroves), and non-silvofishery aquaculture ponds in Sawah Luhur, Banten, Indonesia. We found no significant difference in TECS across five land uses, ranging from 261 ± 14 Mg C ha-1 in non-silvofishery ponds to 574 ± 119 Mg C ha-1 in fringe mangroves. Most of these stocks were found in the soil carbon pool (87%) in fringe and interior mangroves. However, the conversion of mangroves to aquaculture ponds resulted in soil carbon loss from -6% to 60%. The highest soil CO2 effluxes during dry and wet seasons were observed in interior mangroves (151 ± 12 mg CO2 m-2 h-1). The highest soil CH4 effluxes were found in fringe mangroves with 0.13 ± 0.04 mg CH4 m-2 h-1. The highest aquatic CO2 and CH4 effluxes were found in dense silvofishery ponds, at 118 ± 7 mg CO2 m-2 h-1 and 0.38 ± 0.04 mg CH4 m-2 h-1, respectively. Our findings suggest that land use that includes mangroves (i.e., mangrove forest and/or silvofishery ponds) tends to have higher carbon stocks, soil, and aquatic CO2 and CH4 effluxes, compared to aquaculture ponds without mangroves. It is therefore crucial to maintain mangroves for natural carbon capture and storage through carbon stock enhancement.

Spatiotemporal dynamics of land use and cropping systems in the young meghna estuarine floodplain

To explore long-term changes in land use and land cover (LULC), cropping systems, and driving forces of LULC change, a study was carried out in Subarnachar upazila under the Young Meghna Estuarine Floodplain in Bangladesh. For studying LULC change and cropping systems, images from Landsat (TM) of 1989, Landsat (ETM+) of 2000 and 2010, and Landsat (Oli) of 2019 were used. A focus group discussion (FGD) was conducted to gather information on actors driving LULC changes. In the study area, five LULC categories—cropland, accreted land, settlements, mangrove forests, and water bodies were found. It reveals that cropland increased by 0.20% annually, while water bodies, accreted land, and mangrove forest decreased by 0.29, 0.17, and 0.23%, respectively. Settlements grew relatively at a faster rate (0.49%). The major land conversions between 1989 and 2019 were cropland to settlement (10.2%), mangrove forest to settlement area (3.2%), and mangrove forest to cropland area (4.0%). Other transformations included the shifting of accreted land to cropland and water bodies to settlements. From 1989 to 2019, double cropland increased by 0.71% annually due to the conversion of single to double cropland. Increased population pressure, especially for those displaced by the threat of river erosion, was a major factor in the conversion of cropland and mangroves into settlements. Due to the high demand for food in the study area, mangrove forests were converted to cropland and single cropland to double cropland more rapidly. These findings will assist farmers, stakeholders, and planners in developing and implementing optimal land use planning and sustainable agricultural production strategies in the region.
 Ann. Bangladesh Agric. (2023) 27 (1) : 1-15

Carbon Storage Assessment under Mangrove Restoration of Dongzhai Harbor in Hainan Island, China

Mangrove restoration is recognized as an effective strategy for enhancing the carbon storage capacity of natural ecosystems, advancing toward the “carbon neutrality” goal. The carbon storage effects of ecological restoration efforts remain insufficiently understood as previous studies have focused on carbon storage dynamics in ecosystems, yet the specific impacts of targeted mangrove restoration are less explored. This study utilizes multi-temporal remote sensing data and actual restoration data from Dongzhai Harbor Hainan Island to identify the mangrove wetland coverage and quantify the spatiotemporal evolution of carbon storage under various restoration efforts using the InVEST model. Additionally, we employed the PLUS model to simulate and compare carbon storage potential under multiple development goals. The findings reveal the following: (a) Mangrove restoration significantly increased the area of land with high carbon sink capability, resulting in a regional carbon storage increase of 210,001.68 tons from 2015 to 2021, with 97% of this increase attributable to ecological restoration. (b) Mangrove coverage is crucial for regional carbon storage, with an average of 443 tons of carbon stored per hectare. Decreases in carbon storage occurred mainly during the conversion of mangroves to aquaculture, and forests/agriculture to residential areas. Increases in carbon storage were seen in the reverse transitions. (c) Comparing the scenarios focused solely on mangrove protection with cultivated land protection, the carbon storage in Dongzhai Harbor is projected to reach its maximum by 2045 under the carbon storage priority scenario. Our findings build a scientific foundation for formulating effective mangrove conservation and restoration strategies.

Environmental legacy of aquaculture and industrial activities in mangrove ecosystems

Aquaculture and industrial activities have been recognized for their detrimental impact on coastal environment, particularly through large-scale mangrove conversion. This study employs interdisciplinary spatial, geochemical, and metagenomic approaches to examine the environmental legacy of past aquaculture and industrial activities in mangrove rehabilitation areas. The land use change of mangrove, aquaculture, and industrial area was investigated from 1990 to 2020. Mangrove coverage increased in the study area from 49.12 ha in year 1990 to 95.93 ha in 2020. This growth can be attributed to increasing environmental awareness related to issues such as tidal flooding, seawater intrusion, and coastal abrasion. However, despite increasing mangrove coverage, we still identified fecal bacteria communities in both sites, dominated by Campylobacteria, Gammaproteobacteria, and Deltaproteobacteria. Additionally, our functional prediction analysis revealed the presence of genes associated with pathogenicity, multidrug/antibiotic resistance, and xenobiotic degradation. We observed high nitrate concentration associated with aquaculture waste that was persistent in porewater even after the activity ended years ago. Low to moderate heavy metal concentration was found in the study sites, likely due to the role of mangroves as a biofilter. We conclude that mangrove restoration contributes to the lower environmental impact of anthropogenic activities on our sites. Therefore, it should be included in future coastal management plans to improve coastal water quality and ecosystem function in environmentally threatened areas.

Spatial–temporal distribution of mangrove species in the estuary of the Mamanguape river in the state of Paraíba, Brazil

Mangrove ecosystems are under pressure from various anthropic sources, such as changes in land use in watersheds and effects related to climate change. Thus, detailed monitoring of the distribution of mangrove species can provide important information concerning how such ecosystems are responding to these alterations. This study investigates the spatial–temporal distribution of mangrove species and quantifies the area of the mangrove in the Mamanguape River estuary in the state of Paraíba, Brazil. Land use and land cover changes in mangrove morest during the past 35 years (1985 to 2020) were determined using multi-temporal satellite imageries by Landsat TM and the Random Forest algorithm. The results indicated 17 classes, 9 of which belong to mangrove and 8 to associated classes. The classification of images presented overall accuracy varying between 81.9% and 92.3% and a Kappa coefficient of from 77.7% to 91.1%. We verified a trend of species distribution, in which A. schaueriana and R. mangle exhibited the greater coverage in areas under greater marine influence, while A. germinans and L. racemosa showed higher coverage in areas under greater influence of fresh water. The dominant class was composed of Rhizophora mangle, Avicennia schaueriana, and Laguncularia racemosa. Analyses into alterations of the composition of mangrove species in the estuary of the Mamanguape River indicate that the class of R. mangle, A. schaueriana, and L. racemosa and the class of A. schaueriana diminished, while the class of R. mangle and L. racemosa and the apicum class increased. There was a loss of 2.1% of the mangrove during the study period. During the year 2020 the area registered was 4,620 ha. The main causes of loss of the mangrove area were the installation of shrimp farming ponds, severe defoliation, and the conversion of mangroves into pasture. The mapping carried out in this study provides new insights into the conservation status of the mangrove forests in the Mamanguape River estuary and represents a valuable approach for informing replanting strategies and future management practices.

Mangrove monitoring revealed by MDPrePost-Net using archived Landsat imageries

Acting as a global vital entity in the coastal ecosystem, mangroves are currently facing major threats to destruction due to anthropogenic activities. Restoration and rehabilitation measures of mangroves are being carried out, including in Indonesia. To support conservation actions in many islands in Indonesia, spatio-temporal information on mangroves is required. Remote sensing with advanced techniques such as machine learning and deep learning has proven the capability to spatially observe mangroves. This study aims to monitor mangrove change in three study areas, i.e., South Sumatra, North Kalimantan, and Southeast Sulawesi, using a fully convolutional network (FCN)-based MDPrePost-Net. This method was developed originally to assess the mangrove degradation due to a major event (i.e., Hurricane irma 2017 in southwest Florida), whereas this study adopts it for an extended observation period (1989–2022 for South Sumatra, 1991–2021 for North Kalimantan, and 1990–2021 for Southeast Sulawesi) using medium-resolution Landsat imageries. We observed that the mangroves remain stable within the national parks designated by the government. Outside the national parks, mangrove conversion massively occurred even though the areas are assigned as protection forests. The classification results showed satisfactory accuracy values of more than 84%. The maps produced have an advantage in the spatial change analysis compared to the global datasets such as Global Mangrove Watch version 3.0. Our method has a limitation when cloudless images are not available. The integration with Synthetic Aperture Radar (SAR) images and a rigorous cloud removal method for the optical images may improve the results of mangrove monitoring.

Invasion in the Niger Delta: remote sensing of mangrove conversion to invasive Nypa fruticans from 2015 to 2020

AbstractInvasive species are a leading threat to biodiversity worldwide. Nypa palm (Nypa fruticans) has emerged as the predominant invasive species in the Niger Delta region of Nigeria. While endemic mangroves have high rates of carbon sequestration, stabilize coastlines and protect biodiversity, Nypa does not provide these services outside its native region of Southeast Asia. Oil exploration and urbanization in this region also exacerbate mangrove loss and Nypa spread. As Nypa is difficult to distinguish from endemic mangrove species in remotely sensed data, estimates of mangrove and ecosystem services losses in Nigeria are highly uncertain. Here, we analyse multisensor satellite data with machine learning to quantify the rapid expansion of Nypa from 2015 to 2020 in Nigeria. Using Landsat imagery and random forest classification, we quantify total potential Nypa extent in Nigeria in 2019. We then produced a Nypa extent map using iterative combinations of Sentinel‐1 SAR, Sentinel‐2 MSI and ALOS PALSAR. Random forest classifications using SAR data from ALOS and Sentinel‐1 were best suited for mapping Nypa extent with similar accuracies (78% and 75%, respectively). Based on data availability and accuracy, we focussed our change analysis on Sentinel‐1 SAR. Our results show ~28 000 ha of mangroves were converted to Nypa in Nigeria by 2020 and covered a larger extent than endemic mangroves, compounding the effect of the existing degradation and deforestation in the region. We also compared forest height and complexity estimates from Global Ecosystem Dynamics Investigation LiDAR to further distinguish between endemic mangroves and Nypa in three dimensions. Nypa structural variability, measured by top‐of‐canopy height, vegetation cover, plant area index, and foliage height diversity, was lower than that of mangroves. At current rates of Nypa expansion, the entire area of study would be invaded by Nypa by 2028, with potentially detrimental consequences to the ecosystem services provided by mangroves.

Realizing Gender Equality in Coastal Areas: Conservation of Critical Land and Empowerment of Women

The conversion of mangroves into shrimp ponds occurred in the coastal area of Kampung Beting, Pantai Bahagia Village, Bekasi Regency, West Java Province, Indonesia, in the period 1990–2010. High income from shrimp ponds makes people ignore the ecological functions of mangrove forests, one of which is to prevent abrasion. However, since 2010, the destruction of hundreds of hectares of mangrove forests, worsened by climate change that hits almost the whole world, especially island countries like Indonesia, has submerged the shrimp ponds in Pantai Bahagia Village with sea water. Now, not only the shrimp ponds as their major income have disappeared, but also their living space is also threatened by severe abrasion. Gender inequality and the marginalized role of coastal women also make the socio-economic conditions of the community become worse. This study observes the role of women in Pantai Bahagia Village in responding to environmental and socio-economic problems in their area. This study uses a phenomenological approach, data is collected through observation, interviews, and documentation. The results of the study show that women's empowerment plays a role in conserving critical land. Women's responses to environmental problems in their area include: 1) creating changes in women's awareness and behavior as an effort to repair and restore damaged mangrove land, and 2) carrying out activities to protect mangrove plants. Women's responses to socio-economic problems include 1) women's active involvement in productive economic activities 2) Utilization of non-timber mangrove products in processed food and crafts. Finally, this study recommends a concept to address critical coastal land issues, namely by involving women in various activities, both nature conservation and empowerment activities.

The dynamic of mangroves and ponds changes in East Kalimantan, Indonesia

‘More than 50% of Indonesia’s mangrove is lost over the last 30 years, which makes Indonesia has the fastest rate of mangrove destruction in the world. East Kalimantan Province has the third largest mangrove in Indonesia, behind Papua and Riau Province. Mangroves in East Kalimantan experienced great pressure from land conversion into ponds. Hence, this study focuses on mangrove and pond conversion trendlines based on 3 times spatial analyses using an automated method through the Google Earth Engine (GEE) platform using Landsat from 1990, 2000, and Sentinel 2019 imagery data. The total area of mangroves identified in 1990 was 268,147 Ha, in 2000 was 227,202 Ha or a decrease by 15%, and in 2019 was 215,514 Ha or a decrease by 5%. The amount of mangrove area that continues to decrease is aligned with the pond increasing in all East Kalimantan that identified in 1990 was 9,935 Ha, then extremely increase until in 2000 identified an area of 61,083 Ha and increased again in 2019 to reach 86,471 Ha. The analysis shows that it is dominated by the conversion of mangroves to ponds throughout East Kalimantan reaching 65% of the total reduction that occurred both in the period 1990-2000 and 2000-2019.

Floristic richness and diversity of Bintuni mangrove, Bird's Head Peninsula, West Papua, Indonesia

Abstract. Kasihiw P, Bawole R, Marwa J, Murdjoko A, Wihyawari A, Heipon Y, Cabuy RL, Benu NMH, Hematang F. 2023. Floristic richness and diversity of Bintuni mangrove, Bird's Head Peninsula, West Papua, Indonesia. Biodiversitas 24: 2887-2897. Mangrove ecosystems play an important role in the functions of coastal protection, fish and other living-organism habitats, carbon storage, and the livelihood of local people. Yet, mangrove forests generally face ecological threats like anthropogenic pressures. However, fewer studies were carried out in this area, so this research aimed to reveal the vegetation diversity and richness in Bintuni, not only the true mangroves but also the mangroves associates with three different conditions, namely sandy areas called protection forests, disturbed forests called production forests, and delta called nature reserve. The results showed that species vegetation in the Bintuni Mangrove could be differentiated as true mangroves (29.82%) and mangrove associates (70.18%) of the total species richness of mangrove vegetation where in terms of taxonomic composition, the three forests encompassed 25 families, 47 genera, and 57 species clustered into 9 lifeforms. Then, the vegetation diversity and richness were highest in the nature reserve, and 34 (59.65% of total species number) species of vegetation in common share in three forest types. Consequently, frequent checking of vegetation richness is important since the Bintuni mangrove does not seem to have a significant threat like massive conversion of mangrove.

Black Mangrove Powder Extracts with Variation of Temperature and Length of Time using Ultrasound-Assisted Extraction (UAE)

Black mangrove fruit, which is often found in mangrove forest regions of Indonesia, is one source of natural antioxidants that has the potential to be utilized as raw material for functional foods. This investigation focused on black mangrove powder extracts' chemical and phytochemical contents using an ultrasonic-assisted extraction technique. 70% ethanol was used as a solvent for the extraction process. Temperature and extraction time were the two treatments used in this study. A1=30°C, A2=35°C, and A3=40°C for the extraction temperatures, and B1=15 minutes, B2=20 minutes, and B3=25 minutes for the extraction times. Total phenol, total flavonoid, tannin, vitamin C, and antioxidant activity were among the test’s parameters. This research used a Randomized Block Design (RBD) with two components and three replications. Furthermore. To identify the ideal concentration of black mangrove powder extracts, the data were statistically evaluated using ANOVA at a significance level of 95%, and then processed using DX13.0® Software’s Response Surface Methodology (RSM) Optimal Custom Design tool. The ideal circumstances were attained at a temperature of 50°C for 10 minutes, with a desirability value of 0.80. It is anticipated that the best option will result in a yield of 38.34%. nutritional breakdown: crude fibers at 1.88%, ash at 0.33%, fat at 1.332%, protein at 4.40%, and water at 9.17%. and phytochemical components, including tannins (0.11%), total phenols (1778.07 g GAE/g), flavonoids (92.11 g GAE/g), vitamin C (5.84 mg), and antioxidant activity (43.33%). This research suggests that the conversion of black mangroves into nutrient-rich products has an increase in added value and has potential nutritional and phytochemical contents.

Review on mangrove restoration: Re-greening the sea coast

Mangroves are important coastal resources that can provide exceptional ecosystem benefits. Several of its ecosystem functions, including sediment buildup, carbon sequestration, and storm surge protection, are being recognized as practical tools for climate change adaptation and mitigation. Its unique capacity to endure extreme environmental circumstances makes them; in particular, the only viable option for ecosystem-based adaptation in exposed coastal locations. Mangroves are among the most severely damaged tropical ecosystems, and they are continuing to disappear as a result of increased human activity. Especially in the Asia-Pacific region, where they exist in the form of complex socio-ecological systems, mangroves remain heavily threatened due to numerous anthropogenic activities. Mangroves are under grave danger; hence it is imperative that prompt steps be taken to methodically conserve and restore their ecosystems. The Asia-Pacific region is the location of nearly half of the existing mangroves, scattered over some of the poorest and post-conflict states. Dependence on traditional sources of income and the recent trend of coastal development have had a negative impact on the region's mangrove sustainability. Lacks of supportive policies and mangrove conversion to non-forest uses has been further fueled by insufficient institutional intervention. Nevertheless, in recent years, participatory, multi stake holder-based approaches for mangrove conservation and/or restoration have gained immense popularity in the region of Asia pacific. Participatory management which exemplifies an ameliorative approach can also support sustainable development, community empowerment, and social inclusion. Despite its asserted superiority, a number of new sustainability challenges need to be carefully examined and reconciled due to conflicting results of earlier experiences.

Impact of brackish water aquaculture and mangrove degradation on global carbon balance

One of the most productive and supportive ecosystems, the mangroves, have faced a sharp decline of 1.04 million hectares globally, mostly due to population pressure and environmental changes related to the recent effects of global warming and climate change. The loss of area, species migration, altered ecological services etc. are among the most discussed concerns, as evident from the volumes of literatures. However, these issues have overshadowed the fact that along with biodiversity, globally we are losing an important and efficient carbon sink - the mangrove lands. The lost mangrove patches and their conversion to aquaculture, agriculture, or simply settlement areas significantly alter the carbon budget. Sometimes conversion of mangroves to agriculture or aquaculture farms even reverses the roles and the sink has been reported to have become a source of carbon - alternatively known as blue carbon emission. This article provides an overview of the impacts of coastal aquacultures, particularly established in expense of mangrove lands and its consequence on global carbon budget. It has been observed that this globally predominant land use change practices not only significantly reduce the carbon sink capacity but also frequently act as indirect source of the same.

Carbon stocks and sequestration rate in mangroves and its major influencing factors from highly urbanised port city, southern India

This study estimated the total ecosystem carbon stock (TECS) and sediment carbon sequestration rate through burial for fragmented mangrove habitats of Kochi, south-west coast of India. The mean TECS of Kochi mangroves was estimated at 335.33 ± 184.47 t C ha−1, with above ground biomass of 171.68 ± 104.42 t C ha−1, belowground biomass of 83.30 ± 41.98 t C ha−1, litterfall carbon as dead biomass of 7.12 ± 2.81 t C ha−1 and soil carbon stock of 73.22 ± 39.40 t C ha−1. The average historical soil carbon sequestration rate of Kochi mangroves was also estimated as 2.95 t C ha−1 yr−1. The study revealed that there was significant variability in TECS and sediment carbon burial rate among riverine, estuarine and marine mangrove habitats and it appears that, the biological factors especially mangrove plant structure, species, age, litterfall production, crab density, mangrove conversion to aquaculture ponds and other urban pressure played major roles in driving the variability in carbon stocks and storage. While the sediment particle size, bulk density and the environmental settings played a secondary role. Very low TECS and soil carbon sequestration rate was found in aquaculture converted mangrove habitat. The CO2e of ecosystem carbon stock (496311.20 t CO2 e) and soil CO2 burial (10.62 t CO2 e ha−1 yr−1 respectively) of mangroves of Kochi, revealed that even with high urban pressure and anthropogenic activities which resulted in fragmented distribution, they are still potent in long term carbon sequestration unless it is not further disturbed. Therefore, conservation and restoration of mangrove habitats based on understanding of the regional controlling factors of carbon stock and carbon burial is a need for scientific climate change mitigation efforts. The study will also contribute to fill the gaps in global mangrove carbon stock assessments for avoiding uncertainties.