Using expert knowledge and modeling to define mangrove composition,functioning, and threats and estimate time frame for recovery

Mangroves are threatened worldwide, and their loss or degradation could impact functioning of the ecosystem. Our aim was to investigate three aspects of mangroves at a global scale: (1) their constituents (2) their indispensable ecological functions, and (3) the maintenance of their constituents and functions in degraded mangroves. We focused on answering two questions: “What is a mangrove ecosystem” and “How vulnerable are mangrove ecosystems to different impacts”? We invited 106 mangrove experts globally to participate in a survey based on the Delphi technique and provide inputs on the three aspects. The outputs from the Delphi technique for the third aspect, i.e. maintenance of constituents and functions were incorporated in a modeling approach to simulate the time frame for recovery. Presented here for the first time are the consensus definition of the mangrove ecosystem and the list of mangrove plant species. In this study, experts considered even monospecific (tree) stands to be a mangrove ecosystem as long as there was adequate tidal exchange, propagule dispersal, and faunal interactions. We provide a ranking of the important ecological functions, faunal groups, and impacts on mangroves. Degradation due to development was identified as having the largest impact on mangroves globally in terms of spatial scale, intensity, and time needed for restoration. The results indicate that mangroves are ecologically unique even though they may be species poor (from the vegetation perspective). The consensus list of mangrove species and the ranking of the mangrove ecological functions could be a useful tool for restoration and management of mangroves. While there is ample literature on the destruction of mangroves due to aquaculture in the past decade, this study clearly shows that more attention must go to avoiding and mitigating mangrove loss due to coastal development (such as building of roads, ports, or harbors).     

Recognition of co-existence pattern of salt marshes and mangroves for littoral forest restoration

Climate-change driven sea level rise causes a increase in salinity in coastal wetlands accelerating the alteration of the species composition. It triggers the gradual extinction of species, particularly the mangrove population which is intolerant of excessive salinity. Thus despite being crucial to a wide range of ecosystem services, mangroves have been identified as a vulnerable coastal biome. Hence restoration strategy of mangroves is undergoing rigorous research and experiments in literature at an interdisciplinary level. From a data-driven perspective, analysis of mangrove occurrence data could be the key to comprehend and predict mangrove behavior along different environmental parameters, and it could be important in formulating management strategy for mangrove rehabilitation and restoration. As salt marshes are the natural salt-accumulating halophytes, mitigating excessive salinity could be achieved by incorporating salt-marshes in mangrove restoration activities. This study intends to find a novel restoration strategy by assessing the frequent co-existence status of salt marshes, with the mangroves, and mangrove associates in different zones of degraded mangrove patches for species-rich plantation. To achieve this, we primarily design a novel methodological framework for the practice of knowledge discovery concerning the coexistence pattern of salt marshes, mangroves, and mangrove associates along with environmental parameters using a data mining paradigm of association rule mining. The proposed approach has the capability to uncover underlying facts and forecast likely facts that could automate the study in the field of ecological research to comprehend the occurrence of inter-species relationships. Our findings are based on published data gathered on the Sundarban Mangrove Forest, one of the world’s most important littoral forests. The existing literature reinforces the findings that include all the sets of frequently co-occurring mangroves, their associates, and salt marshes along the salinity gradient of coastal Sundarbans. A detailed understanding of the occurrence patterns of all these, along with the environmental variables, would be able to promote decision-making strategy. This framework is effective for both academia and stakeholders, especially the foresters/ conservation planners, to regulate the spread of salt marshes and the restoration of mangroves as well.     

Faunal impact on vegetation structure and ecosystem function in mangrove forests: A review

The last 20 years witnessed a real paradigm shift concerning the impact of biotic factors on ecosystem functions as well as on vegetation structure of mangrove forests. Before this small scientific revolution took place, structural aspects of mangrove forests were viewed to be the result of abiotic processes acting from the bottom-up, while, at ecosystem level, the outwelling hypothesis stated that mangroves primary production was removed via tidal action and carried to adjacent nearshore ecosystems where it fuelled detrital based food-webs. The sesarmid crabs were the first macrofaunal taxon to be considered a main actor in mangrove structuring processes, thanks to a number of studies carried out in the Indo-Pacific forests in the late 1970s and early 1980s. Following these classical papers, a number of studies on Sesarmidae feeding and burrowing ecology were carried out, which leave no doubts about the great importance of these herbivorous crabs in structuring and functioning Old world ecosystems. Although Sesarmidae are still considered very important in shaping mangrove structure and functioning, recent literature emphasizes the significance of other invertebrates. The Ocypodidae have now been shown to have the same role as Sesarmidae in terms of retention of forest products and organic matter processing in New world mangroves. In both New and Old world mangroves, crabs process large amounts of algal primary production, contribute consistently to retention of mangrove production and as ecosystem engineers, change particle size distribution and enhance soil aeration. Our understanding of the strong impact of gastropods, by means of high intake rates of mangrove products and differential consumption of propagules, has changed only recently. The role of insects must also be stressed. It is now clear that older techniques used to assess herbivory rates by insects strongly underestimate their impact, both in case of leaf eating and wood boring species and that herbivorous insects can potentially play a strong role in many aspects of mangrove ecology. Moreover, researchers only recently realized that ant–plant interactions may form an important contribution to our understanding of insect–plant dynamics in these habitats. Ants seem to be able to relieve mangroves from important herbivores such as many insects and sesarmid crabs. It thus seems likely that ants have positive effects on mangrove performance.     

Mangrove and coral reef sponge faunas: untold stories about shallow water Porifera in the Caribbean

Sponge faunas from coral reefs and mangrove ecosystems in the Caribbean have mostly been studied from an ecological perspective, with researchers considering the effects of physical and biological factors on their species distribution. To discern evolutionary patterns, this study analyzed the systematic composition, taxonomic diversity, and ecological properties (reproductive strategies, size, shape, endosymbiosis) of mangrove and reef sponge assemblages from seven distant Caribbean localities. Species composition was compared by use of cluster analysis (Sørensen’s), and taxonomic diversity by use of the biodiversity index average taxonomic distinctness (AvTD). Mangrove and reef-associated sponge faunas were found to be statistically dissimilar, with the AvTD values suggesting stronger taxonomic bias toward specific groups in mangroves, irrespective of geographic distance. Most Demospongiae orders have 30–50% more species in coral reefs than in mangroves. The richest reef genera (Agelas, Aplysina, Callyspongia, Petrosia, and Xestospongia) rarely colonize contiguous mangrove formations. The distribution and diversity of suprageneric taxa suggest that coral reef sponge assemblages might represent an older fauna. This historical interpretation would place mangrove subtidal habitats as the youngest marine ecosystem, rather than a below-optimum ecosystem. Life history traits support a biological split discussed here from the perspective of distinct evolutionary histories and different environmental conditions.     

Use of Mangroves by Lemurs

Despite an increasing recognition of the ecosystem services provided by mangroves, we know little about their role in maintaining terrestrial biodiversity, including primates. Madagascar’s lemurs are a top global conservation priority, with 94 % of species threatened with extinction, but records of their occurrence in mangroves are scarce. I used a mixed-methods approach to collect published and unpublished observations of lemurs in mangroves: I carried out a systematic literature search and supplemented this with a targeted information request to 1243 researchers, conservation and tourism professionals, and others who may have visited mangroves in Madagascar. I found references to, or observations of, at least 23 species in 5 families using mangroves, representing >20% of lemur species and >50% of species whose distributions include mangrove areas. Lemurs used mangroves for foraging, sleeping, and traveling between terrestrial forest patches, and some were observed as much as 3 km from the nearest permanently dry land. However, most records were anecdotal and thus tell us little about lemur ecology in this habitat. Mangroves are more widely used by lemurs than has previously been recognized and merit greater attention from primate researchers and conservationists in Madagascar.     

Ecosystem carbon stocks of mangrove forests along the Pacific and Caribbean coasts of Honduras

Among the many ecosystem services provided by mangrove ecosystems, their role in carbon (C) sequestration and storage is quite high compared to other tropical forests. Mangrove forests occupy less than 1 % of tropical forested areas but account for approximately 3 % of global carbon sequestration by tropical forests. Yet there remain many areas where little data on the size and variation of mangrove C stocks exist. To address this gap and examine the range of C stocks in mangroves at landscape scales, we quantified C stocks of Honduran mangroves along the Pacific and Caribbean coasts and the Bay Islands. We also examined differences in ecosystem C stocks due to size and structure of mangrove vegetation found in Honduras. Ecosystem C stocks ranged from 570 Mg C ha^?1 in the Pacific coast to ~1000 Mg C ha^?1 in Caribbean coast and the Bay Islands. Ecosystem C stocks on the basis of mangrove structure were 1200, 800 and 900 Mg C ha^?1, in low, medium and tall mangroves, respectively. We did not find significant differences in ecosystem C stocks on the basis of location (Pacific coast, Caribbean coast and Bay Islands) or mangrove type (low, medium and tall). Mangrove soils represented the single largest pool of total C in these ecosystems, with 87, 81 and 94 % at the Pacific coast, Caribbean coast and the Bay Islands, respectively. While there were no significant differences in total ecosystem stocks among mangrove types, there were differences in where carbon is stored. Mangrove soils among low, medium and tall mangroves contained 99, 93 and 80 % of the total ecosystem C stocks. In addition, we found a small yet significant negative correlation between vegetation C pools and pore water salinity and pH at the sampled sites. Conversion of mangroves into other land use types such as aquaculture or agriculture could result in loses of these soil C reserves due to mineralization and oxidation. Coupled with their other ecosystem services, an understanding of the size of mangrove ecosystem C stocks underscores their values in the formulation of conservation and climate change mitigation strategies in Central America.     

Local community attitudes towards mangrove forest conservation

Local communities have preferences and expectations regarding mangrove ecosystems that are typically underrepresented in valuation studies. Therefore, this study identifies how the local community of Mahahual (Mexico) perceives the ecosystem services provided by the mangrove forest and how these preferences differ between households. A survey was designed by one of the authors and local stakeholders building on previous knowledge and experts (local environmental research centre and non-governmental organisation Takata and its experts in biology and coastal conservation, ecotourism businesses’ owners, and the mayor of the village). The survey is used to cover a wide range of ecosystem services such as carbon sequestration, recreation and cultural activities as well as improved connectivity with local seagrass beds and coral reefs. Ecosystem services were specifically chosen by biologists and ecologists of the local NGO to perfectly reflect the local mangroves ecosystem. The small land area of the village, its low population and its rapid expansion offer a unique context, aiming at preserving the natural environment while keeping in mind that the main economy is based on tourism. While mangroves are greatly appreciated for the local protective services they provide such as coastal protection, local inhabitants also care about services that have a wider impact such as biodiversity and carbon sequestration. We find that the educational background of local inhabitants plays an important role in determining the importance of local ecosystem services and that information provision can help to counterbalance this effect. We also observe that preferences for specific ecosystem services differ based on how close residents live to the mangroves and to the coast, which accentuates the different needs and ideas of the households based on their local neighbourhood.     

红树林植被对大型底栖动物群落的影响

大型底栖动物是红树林生态系统的重要组成部分,从红树林大型底栖动物种类、红树林与其周边生境大型底栖动物群落的比较,以及生境变化对动物群落的影响等方面阐述了红树林植被与大型底栖动物群落的关系.从物种数量上看,软体动物和甲壳类动物构成了红树林大型底栖动物的主要部分.影响大型底栖动物分布的环境因素包括海水盐度、潮位和土壤特性等,但在小范围区域,林内动物的分布更多地与红树林植被特性和潮位有关.因此,由于红树林植被破坏或者恢复引起的生境变化,将导致大型底栖动物群落和常见物种种群的变化,尤其对底上动物影响明显;随着人工恢复红树林的发育,林内底栖动物的多样性相应增加,优势种也发生变化.相比位于相同潮位的无植被滩涂,红树林可促进潮间带生物多样性.     

Status and distribution of mangrove forests of the world using earth observation satellite data

Aim Our scientific understanding of the extent and distribution of mangrove forests of the world is inadequate. The available global mangrove databases, compiled using disparate geospatial data sources and national statistics, need to be improved. Here, we mapped the status and distributions of global mangroves using recently available Global Land Survey (GLS) data and the Landsat archive. Methods We interpreted approximately 1000 Landsat scenes using hybrid supervised and unsupervised digital image classification techniques. Each image was normalized for variation in solar angle and earth–sun distance by converting the digital number values to the top‐of‐the‐atmosphere reflectance. Ground truth data and existing maps and databases were used to select training samples and also for iterative labelling. Results were validated using existing GIS data and the published literature to map ‘true mangroves’. Results The total area of mangroves in the year 2000 was 137,760 km² in 118 countries and territories in the tropical and subtropical regions of the world. Approximately 75% of world's mangroves are found in just 15 countries, and only 6.9% are protected under the existing protected areas network (IUCN I‐IV). Our study confirms earlier findings that the biogeographic distribution of mangroves is generally confined to the tropical and subtropical regions and the largest percentage of mangroves is found between 5° N and 5° S latitude. Main conclusions We report that the remaining area of mangrove forest in the world is less than previously thought. Our estimate is 12.3% smaller than the most recent estimate by the Food and Agriculture Organization (FAO) of the United Nations. We present the most comprehensive, globally consistent and highest resolution (30 m) global mangrove database ever created. We developed and used better mapping techniques and data sources and mapped mangroves with better spatial and thematic details than previous studies.     

The mangrove-based coastal and nearshore fisheries of Bangladesh: ecology,exploitation and management

The mangrove forest of Bangladesh, the largest continuous mangrove forest of the world, is one of the most important coastal features of the country. The existence of the mangrove has increased the values of other coastal and marine resources such as the coastal and marine fisheries by increasing productivity and supporting a wide biological diversity. The artisanal fishery, which is highly influenced by mangroves, has been contributing 85–95% of the total coastal and marine catch of Bangladesh. The mangrove also supports offshore and deep sea fisheries by playing a significant role as nursery ground for many deep sea fishes and shrimps including the giant tiger shrimp (Penaeus monodon) which is the major species of the industrial bottom trawl fishery of Bangladesh. The mangrove also contributes significantly in shrimp farming which has been the most significant export-oriented industry since the 1970s. However, the mangrove fisheries have been under intensive pressure from deleterious fishing activities and deliberate aquaculture development by destructing mangrove habitats. The impacts of mangrove have been reflected in the contribution of artisanal fishery catch that has been in a continuous decline since the 1980s. Shrimp farming has been the most destructive contributor to mangrove destruction with a corresponding loss of biological resources particularly the wild shrimp fishery. This paper reviews different aspects of the mangrove fisheries of Bangladesh and discusses the impacts of different fisheries. The paper identifies the importance of reviewing, amending and/or replacing the traditional management approaches by the new management techniques such as habitat restoration and stock enhancement in the natural environment; the paper also identifies the need for research findings in formulating and implementing new management approaches.     

Source water partitioning as a means of characterizing hydrologic function in mangroves

Mangrove ecosystems rely on seawater, rain-derived flow, and groundwater for hydrologic sustenance, flushing, and inflow of nutrients and sediments. The relative contribution of these source waters and their variability through time and space can provide key information concerning the hydrologic function of ecosystems. We used hydrologic tracers to partition source waters and trace their movements in the Enipoas stream, a river-dominated mangrove ecosystem on the island of Pohnpei, Federated States of Micronesia (FSM) and in the Yela watershed, an interior mangrove ecosystem on the island of Kosrae, FSM. The Enipoas site was characterized as a salt wedge estuary whose source water contributions alternated between predominantly seawater and rain-derived flow, depending on the tide. The source waters in the interior Yela site were also predominantly seawater and rain-derived flow, however the relative contribution of each was much more stable. The mean groundwatercontribution was 5% (SD 5 5.5) for the Enipoas site and 20% (SD 5 11.0) for the Yela site. Although a small contributor to flow, groundwater was a steady source of freshwater for both systems. Hydrologic linkages between mangroves and adjacent ecosystems were demonstrated by the temporal and spatial distribution of source waters.The 0.8 km Enipoas estuary, with its highly dynamic bi-directional flows, transported source waters along a hydrologic continuum comprised of coral reef, mangroves, and palm forest. In the interior mangroves of the Yela watershed, the presence of rain-derived flow and groundwater demonstrated a hydraulic connection between the mangroves and an upstream freshwater swamp. Interior mangroves with such linkages avoid stresses such as desiccation and heightened salinity, and thus are more productive than those with little or no freshwater flows.     

Seventy years of continuous encroachment substantially increases ‘blue carbon’ capacity as mangroves replace intertidal salt marshes

Shifts in ecosystem structure have been observed over recent decades as woody plants encroach upon grasslands and wetlands globally. The migration of mangrove forests into salt marsh ecosystems is one such shift which could have important implications for global ‘blue carbon’ stocks. To date, attempts to quantify changes in ecosystem function are essentially constrained to climate‐mediated pulses (30 years or less) of encroachment occurring at the thermal limits of mangroves. In this study, we track the continuous, lateral encroachment of mangroves into two south‐eastern Australian salt marshes over a period of 70 years and quantify corresponding changes in biomass and belowground C stores. Substantial increases in biomass and belowground C stores have resulted as mangroves replaced salt marsh at both marine and estuarine sites. After 30 years, aboveground biomass was significantly higher than salt marsh, with biomass continuing to increase with mangrove age. Biomass increased at the mesohaline river site by 130 ± 18 Mg biomass km^?2 yr^?1 (mean ± SE), a 2.5 times higher rate than the marine embayment site (52 ± 10 Mg biomass km^?2 yr^?1), suggesting local constraints on biomass production. At both sites, and across all vegetation categories, belowground C considerably outweighed aboveground biomass stocks, with belowground C stocks increasing at up to 230 ± 62 Mg C km^?2 yr^?1 (± SE) as mangrove forests developed. Over the past 70 years, we estimate mangrove encroachment may have already enhanced intertidal biomass by up to 283 097 Mg and belowground C stocks by over 500 000 Mg in the state of New South Wales alone. Under changing climatic conditions and rising sea levels, global blue carbon storage may be enhanced as mangrove encroachment becomes more widespread, thereby countering global warming.     

Ethnobotany of Mangroves among Jing People’s Folks

Mangrove plants are closely connected with folk customs of Jing ethnic group, and it is one of the symbols of Jing people as marine people. However, rapid economic development and globalization have brought about critical challenges to the cultural traditions of Jing people, and traditional knowledge of mangroves is being lost among Jing ethnic group. To protect folk customs on mangroves of Jing people, we have conducted a series of surveys on mangrove plants which have been used for folk customs of Jing people via ethnobotanical and taxonomical methods. The results showed that there were 14 mangrove plant species used in Jing people’s traditional folk customs. Four species of mangrove plants were used for religious belief, 11 species used in social customs and 7 species for material customs. Avicennia marina, Acanthus ilicifolius and Rhizophora stylosa are with the highest relationship with folk customs for Jing people. Our research can provide more comprehensive interpretation for characteristic on marine culture of Jing people, and improve the knowledge on ethnobotany of mangroves.     

A review on the present status and management of mangrove wetland habitat resources in Bangladesh with emphasis on mangrove fisheries and aquaculture

The mangrove forest of Bangladesh, the largest continuous mangrove bulk, is one of the most important features of the coastal area of the country. The existence of the mangrove has increased the values of other coastal and marine resources such as the coastal and marine fisheries by increasing productivity and supporting a wide biological diversity. The deltaic mangrove of Bangladesh is ecologically different from the other, mostly nondeltaic mangroves of the world and is unique also in its floral and faunal assemblage; therefore, a number of endangered plants and animals that are extinct from other parts of the world, are existing in Bangladesh mangrove. However, the mangrove has been under intensive pressure of exploitation for the last few decades which, in addition to direct clearance and conversion have placed the mangrove under extreme threat. Shrimp farming is the most destructive form of resource use the mangrove has been converted to, which contributed significantly to mangrove destruction with a corresponding loss of biological resources. Concerns have been raised among the ecologists, biologists, managers and policy makers since the early 1990s; deliberate destruction of mangrove and unplanned development of coastal aquaculture particularly shrimp aquaculture have been put under extreme criticism and the sustainability has been questioned. The present status of the mangrove resources including mangrove fisheries and aquaculture and management practices have been reviewed in this paper; impacts of different forms of human interventions and resource use have also been discussed. It is suggested that the management options and the policy aspects should be critically reviewed and amended accordingly; beneficiaries and stakeholders at all levels of resource exploitation must take part and contribute to conservation and management. An immediate need for mangrove conservation has been identified.     

Recent progresses in mangrove conservation,restoration and research in China

Aims In this paper, we highlighted some key progresses in mangrove conservation, restoration and research in China during last two decades.Methods Based on intensive literature review, we compared the distribution and areas of existing mangroves among selected provinces of China, discussed the issues associated with mangrove conservation and restoration and highlighted major progresses on mangrove research conducted by key institutions or universities in mainland China, Hong Kong, Taiwan and Macao.Important findings The population boom and rapid economic developments have greatly reduced mangrove areas in China since 1980s, leaving only 22?700 ha mangroves in mainland China in 2001. Chinese government has launched a series of programs to protect mangroves since 1980s and has established mangrove ecosystems as high-priority areas for improving environmental and living resource management. During last three decades, a total of 34 natural mangrove conservation areas have been established, which accounts for 80% of the total existing mangroves areas in China. Mangrove restoration areas in Mainland China accounted for <7% of the total mangroves areas in 2002. A great deal of research papers on Chinese mangroves has been published in international journals. However, more systematic protection strategies and active restoration measurements are still urgently needed in order to preserve these valuable resources in China.     

Competition and abiotic stress affect the size of mangroves near their geographic range limit

竞争和非生物胁迫影响处于地理分布边界的红树植物的个体大小 关于红树植物竞争的研究大多局限于幼苗和人工林。我们首次对天然红树林中成年红树的种内竞争进行了控制实验研究,旨在检验竞争和非生物因子在决定红树植物个体大小中的相对重要性。研究样 地位于靠近红树林地理分布边界的美国德克萨斯州阿兰萨斯港(Port Aransas)附近区域。该区域的红树林由“灌丛”状的黑红树(萌芽白骨壤,Avicennia germinans)单一物种组成。我们对10个样方中原生红树 林进行疏伐,形成系列红树林覆盖度梯度,在2013–2019年期间观测各样方中红树植物的生长指标,量化分析红树林覆盖度对红树植物生长的影响;并于2019年调查了红树林的冠层高度。研究结果表明,在该研究期间,红树植物的相对生长速率随着红树林覆盖度的增加而降低,100%红树林覆盖度样方中的红 树植物大小几乎没有增长,说明它们已经达到了该红树林密度条件下的最大尺寸。在红树林覆盖度降低 的样方中,株高明显增加,在红树林覆盖度为11%的样方中,红树植物株高增加了约52%。对比临水岸 边和林内两种生境中的样方,处于临水岸边生境的红树林冠层高度比处于林内生境的高约30%,且这两 种生境的红树林冠层高度均随红树林覆盖度的增加而降低。叶片叶绿素含量和冠层光截留量的测定数据 显示,该区域红树植物的生长也受到氮限制的影响。由此表明,处于地理分布边界的“灌丛”状红树林一 方面受到营养的限制,另一方面红树植物种内个体间仍存在较为强烈的竞争,且种内竞争对红树植物生长的影响较该红树林内非生物生境因子更为重要。     

A review on the ichthyofaunal diversity in mangrove based estuary of Sundarbans

The two great rivers of India the Ganga and the Brahmaputra form their estuary at the lower part of West Bengal and most of the part of this estuarine system is surrounded by Sundarban mangrove forest. This mangrove based estuarine ecosystem harbors a large number of fin fishes i.e. more or less 267 species of fishes which belong under 81 families. Estuary’s own ecological characters and mangrove’s all beneficial features support this high species diversity here. But due to continuously increasing natural and anthropogenic stresses, nowadays this entire species community faces a tremendous problem of extinction. 82 species under 24 families loss their juveniles in a significant number regularly due to wild harvest of lucrative prawn seeds. The present article aims to review the roles of estuary and mangroves in enrichment of finfish diversity and the possible threats causing harm to the same.     

1960-2010年广西红树林空间分布演变机制

为全面摸清1960—2010年广西红树林空间分布及其演变机制,采用多源遥感数据提取不同年度的红树林空间分布信息,分析了广西红树林空间分布动态特点,采用基于斑块的红树林空间演变机理分析方法,研究了1960/1976—2010年广西红树林空间演变机制。结果表明:1960/1976年、1990s年、2001年、2007年和2010年广西红树林斑块数量分别为1020、829、1094、1718个和1712个,面积分别为9062.5、7430.1、7015.4、6743.2、7054.3 hm2,近50年间红树林面积减少了22.16%,年均减少0.53%,斑块数量增加了67.8%;斑块平均面积由1960/1976年的8.9 hm2减小至2010年的4.1 hm2,大斑块数量显著减少,斑块破碎化严重;不同时期、不同区域和海湾,红树林面积和斑块数量的变化量、变化速率均不同;1960/1976年的斑块中,只有24个斑块至2010年时尚保持稳定,占2.4%,绝大部分斑块都发生了某种程度的变化。进一步分析结果表明:1960/1976—2010年,斑块消失(46.1%)、碎化(40.4%)、萎缩(13.5%)是面积减少的主要途径,新增(70.0%)和碎化(29.9%)是斑块数量增加的主要途径,但在不同时期,斑块数量和面积在各个途径上发生的变化量不尽相同;养殖塘和盐田建设(80.0%)、工程建设(10.9%)和围垦(9.1%)是面积净减少的驱动因子,自然过程(92.6%)和人工造林(7.4%)是斑块数量净增加的驱动因子,不同驱动因子在不同时期对斑块数量和面积变化的影响程度不同;斑块数量变化主要由自然过程作用下通过新增(39.6%)、消失(-9.1%)两个途径,以及养殖塘和盐田作用下通过消失(-15.3%)、碎化(14.5%)两个途径发生,斑块面积变化主要由自然过程影响下通过新增(17.5%)、扩张(12.6%)、消失(-6.1%),以及养殖塘和盐田建设驱动下通过斑块消失(-14.8%)、碎化(-13.9%)、萎缩(-6.6%)3个途径发生。     

Soil organic carbon stocks in estuarine and marine mangrove ecosystems are driven by nutrient colimitation of P and N

Mangroves play an important role in carbon sequestration, but soil organic carbon (SOC) stocks differ between marine and estuarine mangroves, suggesting differing processes and drivers of SOC accumulation. Here, we compared undegraded and degraded marine and estuarine mangroves in a regional approach across the Indonesian archipelago for their SOC stocks and evaluated possible drivers imposed by nutrient limitations along the land‐to‐sea gradients. SOC stocks in natural marine mangroves (271–572 Mg ha^?1 m^?1) were much higher than under estuarine mangroves (100–315 Mg ha^?1 m^?1) with a further decrease caused by degradation to 80–132 Mg ha^?1 m^?1. Soils differed in C/N ratio (marine: 29–64; estuarine: 9–28), δ¹⁵N (marine: ?0.6 to 0.7‰; estuarine: 2.5 to 7.2‰), and plant‐available P (marine: 2.3–6.3 mg kg^?1; estuarine: 0.16–1.8 mg kg^?1). We found N and P supply of sea‐oriented mangroves primarily met by dominating symbiotic N₂ fixation from air and P import from sea, while mangroves on the landward gradient increasingly covered their demand in N and P from allochthonous sources and SOM recycling. Pioneer plants favored by degradation further increased nutrient recycling from soil resulting in smaller SOC stocks in the topsoil. These processes explained the differences in SOC stocks along the land‐to‐sea gradient in each mangrove type as well as the SOC stock differences observed between estuarine and marine mangrove ecosystems. This first large‐scale evaluation of drivers of SOC stocks under mangroves thus suggests a continuum in mangrove functioning across scales and ecotypes and additionally provides viable proxies for carbon stock estimations in PES or REDD schemes.     

Ethnobiology, socio-economics and management of mangrove forests: A review

There is growing research interest in the ethnobiology, socio-economics and management of mangrove forests. Coastal residents who use mangroves and their resources may have considerable botanical and ecological knowledgeable about these forests. A wide variety of forest products are harvested in mangroves, especially wood for fuel and construction, tannins and medicines. Although there are exceptions, mangrove forest products are typically harvested in a small-scale and selective manner, with harvesting efforts and impacts concentrated in stands that are closer to settlements and easiest to access (by land or by sea). Mangroves support diverse, local fisheries, and also provide critical nursery habitat and marine productivity which support wider commercial fisheries. These forests also provide valuable ecosystem services that benefit coastal communities, including coastal land stabilization and storm protection. The overlapping of marine and terrestrial resources in mangroves creates tenure ambiguities that complicate management and may induce conflict between competing interests. Mangroves have been cut and cleared extensively to make way for brackish water aquaculture and infrastructure development. More attention is now given to managing remaining forests sustainably and to restoring those degraded from past use. Recent advances in remotely sensed, geo-spatial monitoring provide opportunities for researchers and planners to better understand and improve the management of these unique forested wetlands.