The distribution and state of mangroves along the coast of Transkei,Eastern Cape Province,South Africa

The mangrove communities along the coastline of the former Transkei, now part of the Eastern Cape Province, have not been looked at in detail since Ward and Steinkes survey in 1982. Mangroves previously occurred in 17 estuaries but were now found in only 14 of the 76 estuaries visited, with a complete loss of mangroves evident in the Mnyameni, Mzimvubu and Bulungula estuaries amounting to 7.5 ha. Total mangrove loss amounted to 17.6 ha which represents a 6.5% loss over 17 years or 1.04 ha per annum. Tree cover had increased by 16.15 ha in eight other estuaries. This increase could be attributed to the inaccessibility of mangrove stands or to protection afforded by provincial nature reserves and hotel resorts. No new mangrove stands were recorded, although Steinke (pers. comm.) has recently recorded mangroves along the north bank of the Kei River. There has been little change in mangrove species composition in the different estuaries over the past 17 years. Total mangrove loss amounted to 17.6 ha which represents a 6.5% loss over 17 years or 1.04 ha per annum and the species recorded included Avicennia marina, Bruguiera gymnorhiza and Rhizophora mucronata. The mangrove fern Acrostichum aureum L. was recorded for the first time in the Mkozi estuary. Tree density for all estuaries was between 10 and 2594 trees ha^–1. The Mngazana and Mntafufu estuaries had the highest tree densities of 2594 and 1402 trees ha^–1 respectively, typical of riverine mangrove forests. Fringe mangroves were evident in most other systems. Removal of trees for wood has the greatest impact on mangrove cover. Fringe mangrove stands are particularly accessible to harvesters. Only 6% of the current area of trees is afforded some protection in conservation areas. The Mdumbi, Mzamba and Kobonqaba estuaries receive no conservation protection and harvesting has resulted in more than 50% of the trees being removed. The density of dead tree stumps was greater than the number of living trees and no seedlings or juvenile trees were found. Further removal of mangroves within the estuaries south of the Mzimvubu River is expected in the fringe mangroves, as most are unprotected and easily accessible.     

Assessing wetland services for improved development decision-making: a case study of mangroves in coastal Bangladesh

Mangroves provide valuable ecosystem services for the wellbeing of coastal communities. Assessment and valuation of these mangroves services are increasingly advocated in development and conservation decision-making. Translating the values of services into more explicit monetary terms requires understanding of stakeholder activities, socio-economic context and local organizational structure to effectively support decision-making. Based on a survey of 100 households of three villages of Sundarban in Bangladesh, mangroves services to local communities were identified and their economic values estimated. The households perceived 18 mangroves services, of which capture fisheries, fuel energy, storm protection, habitat for fish breeding and nursery grounds and aesthetic enjoyment were ranked the most important. For provisioning services, households obtained important monetary benefits annually from capture fishery (US$ 976 per ha), fuel energy (US$ 80 per ha), honey (US$ 53 per ha) and fodder (US$ 26 per ha). The average annual willingness to pay for storm protection, erosion control and habitat for fish breeding and nursery services were estimated, respectively, as US$ 13 per ha, US$ 2 per ha and US$ 9 per ha. However, unsustainable exploitation and salinity intrusion impacted the services provided by mangroves. This study provides an important insight into the services and values of mangroves for local welfare, and thus can inform policy for protection and better use of mangrove resources.     

Fish use of restored mangroves matches that in natural mangroves regardless of forest age

The loss and degradation of mangrove forests have triggered global restoration efforts to support biodiversity and ecosystem services, including fish stock enhancement. As mangrove restoration accelerates, it is important to evaluate outcomes for species that play functional roles in ecosystems and support services, yet this remains a clear knowledge gap. There is remarkably little information, for example, about how fish use of mangroves varies as restored vegetation matures, hampering efforts to include fisheries benefits in natural capital assessments of restoration. We used unbaited underwater cameras within two distinct zones of mangrove forests—fringe and interior—at five pairs of restored-natural mangrove sites of increasing age from restoration in southeast Queensland, Australia. We used deep learning to automatically extract data for the four most common species: yellowfin bream (Acanthopagrus australis), sea mullet (Mugil cephalus), common toadfish (Tetractenos hamiltoni), and common silverbiddy (Gerres subfasciatus). The abundance of these species varied among sites and zones, but was equal or greater in restored sites compared to paired natural sites. Despite younger restored sites having dramatically lower structural vegetation complexity, abundances did not increase with restoration site maturity. Furthermore, while yellowfin bream and sea mullet were more abundant in the fringe zone, we observed similarities in how fish used fringe and interior zones across all sites. Our paired, space-for-time design provides a powerful test of restoration outcomes for fish, highlighting that even newly restored sites with immature vegetation are readily utilized by key fish species.     

Local Management of Mangrove Forests in the Philippines: Successful Conservation or Efficient Resource Exploitation?

Recent environmental narratives suggest that local people are effective stewards of forest resources. Local restoration and management of mangrove forests, in particular, are now widely advocated as a solution to achieve both economic and environmental conservation goals. This paper presents findings from a study of 2 coastal sites in the Philippines that are renowned and often showcased as success stories in community-based, mangrove reforestation and management. These cases are especially intriguing because local tree planting and management emerged in both areas long before governments and nongovernment organizations began to promote such activities. These management systems are a successful economic innovation in that planted mangroves protect homes and fish pond dykes from wave and wind damage, and the production of high-value construction wood is dramatically enhanced through intensive plantation management. Mangrove plantations are an efficient alternative to harvesting from unplanted, natural mangroves and their spread may reduce harvesting pressures on existing forests. However, mangrove plantations are structurally and compositionaly very different from unplanted forests, a finding of particular concern given that such plantations are increasingly encroaching into and replacing natural forests. Furthermore, planted forests are not typically viewed by planters in terms of their environmental conservation values and are frequently cut and cleared to make space for alternative uses, especially fish farming and residential settlement. The suggestion that these local mangrove management systems are successful for conservation thus needs to be qualified.     

Mangroves and brackishwater pond culture in the Philippines

Around 50% of mangrove loss in the Philippines can be traced to brackishwater pond construction. The decrease in mangroves from 450 000 ha in 1920 to 132 500 ha in 1990 has been accompanied by expansion of culture ponds to 223 000 ha in 1990. The history of fishpond development in the country includes a government-sponsored fishpond boom in the 1950-g and 1960s, the proconservation decade of the 1970s followed by a shrimp fever in the 1980s. Production from brackisshwater ponds has increased from 15 900 mt worth P7.6 million in 1938 to 267 000 mt valued at P6.5 billion in 1990. On the other hand, the maximum valuation of over $11 000 ha^–1 yr^–1 for unmanaged and managed mangrove forests makes them economically on par with the most profitable pond farming systems. The loss of mangrove systems and their varied goods and services is the single most important consequence of brackishwater pond culture in the Philippines. Moreover, intensive shrimp farming is associated with other ecological and socioeconomic effects such as pollution of coastal waters and decline in domestic food crops. New legislation and enforcement of existing laws, conservation of remaining mangroves, massive rehabilitation of denuded mangrove areas, and promotion of sustainable aquaculture and fisheries are recommended.     

A review of mangrove rehabilitation in the Philippines: successes,failures and future prospects

From half a million hectares at the turn of the century, Philippine mangroves have declined to only 120,000 ha while fish/shrimp culture ponds have increased to 232,000 ha. Mangrove replanting programs have thus been popular, from community initiatives (1930s–1950s) to government-sponsored projects (1970s) to large-scale international development assistance programs (1980s to present). Planting costs escalated from less than US$100 to over $500/ha, with half of the latter amount allocated to administration, supervision and project management. Despite heavy funds for massive rehabilitation of mangrove forests over the last two decades, the long-term survival rates of mangroves are generally low at 10–20%. Poor survival can be mainly traced to two factors: inappropriate species and site selection. The favored but unsuitable Rhizophora are planted in sandy substrates of exposed coastlines instead of the natural colonizers Avicennia and Sonneratia. More significantly, planting sites are generally in the lower intertidal to subtidal zones where mangroves do not thrive rather than the optimal middle to upper intertidal levels, for a simple reason. Such ideal sites have long been converted to brackishwater fishponds whereas the former are open access areas with no ownership problems. The issue of pond ownership may be complex and difficult, but such should not outweigh ecological requirements: mangroves should be planted where fishponds are, not on seagrass beds and tidal flats where they never existed. This paper reviews eight mangrove initiatives in the Philippines and evaluates the biophysical and institutional factors behind success or failure. The authors recommend specific protocols (among them pushing for a 4:1 mangrove to pond ratio recommended for a healthy ecosystem) and wider policy directions to make mangrove rehabilitation in the country more effective.     

Local Mangrove Planting in the Philippines: Are Fisherfolk and Fishpond Owners Effective Restorationists?

Local fisherfolk and fishpond owners have been practicing “restoration” of mangrove forests in some parts of the Philippines for decades, well before governments and non‐government organizations began to promote the activity as a conservation tool. This paper examines ecological characteristics of these mangrove plantations and compares them to natural mangroves in the same areas. Mangrove planters were interviewed and plantation and natural mangrove forests were surveyed to measure forest structure, composition and regeneration. Compared with natural forests, mangrove plantations were characterized by high densities of small stems, shorter and narrower canopies, and fewer species. For both economic and ecological reasons, the vast majority of people dispersed and planted only Rhizophora mucronata/stylosa and, furthermore, they often thinned other species out of planted areas. There was remarkably little subsequent recruitment of other, nonplanted mangrove species into plantations up to 50 and 60 years of age. This pattern held across a diversity of sites, including plantations that had not been selectively cut or weeded. Important ecological and economic benefits result from local mangrove planting, but catalyzing diverse forest regeneration—at least in the short to medium term—is not one of them. The lesson: if you want to restore diverse mangrove forests, you have to plant diverse mangrove forests.     

Valuing mangrove benefits: contribution of mangrove forests to local livelihoods in Bhitarkanika Conservation Area,East Coast of India

The consumptive benefits of mangrove forests to subsistence economy receive little recognition. This paper quantifies the value of provisioning services of mangrove forests to local livelihoods in terms of forestry and fishery products. To examine the use of mangrove products, 324 households from 36 villages in the Bhitarkanika Conservation Area located in East Coast of India were surveyed using structured questionnaires. For estimating the contribution of mangrove forests to fish productivity, fish production was evaluated in three stages—inshore fishery, offshore fishery and the role of mangrove forests as nursery ground for fish and shellfish. The findings revealed that 14.2% of the fuel need of each household was being met by the forests. Other forestry products used were timber, honey and thatch grass. During the study, 14 species of fish and three of shellfish were recorded. The total catch for inshore fishery was estimated as 3.77 kg h⁻¹ having market price of US2.25. In offshore fishery the number of species caught as well as income from the catch was higher in areas with mangroves (US 2.25. In offshore fishery the number of species caught as well as income from the catch was higher in areas with mangroves (US 44.61 h⁻¹) than in those without mangroves (US$ 2.62 h⁻¹). The market price of the forestry and fishery products used by the people was estimated as US$ 2.62 h⁻¹). The market price of the forestry and fishery products used by the people was estimated as US 107 household⁻¹ annum⁻¹. The resources extracted from mangrove forests contributed to more than 14.5% of the total income of the household. This was around 30% for the households residing in the immediate vicinity of the forests. This study suggests that provisioning services provided by the mangrove forests are of significant importance to the coastal communities as they increase the resilience and sustainability of the local economy.     

Modern pollen rain in mangroves from San Andres Island, Colombian Caribbean

The precise characterisation of present-day mangrove ecosystems from modern pollen rain facilitates the accurate use of fossil pollen data for late Quaternary sea level and environmental reconstructions. Here, we investigate whether the analysis of pollen rain data corroborates existing floristic and structural characterisation of different mangrove types at the Caribbean island of San Andrés, Colombia. At 82 plots along 20 transects of four distinct mangrove types, samples were obtained of (i) surface sediments for pollen analysis, and (ii) a range of environmental parameters (including inundation levels, salinity and pH). This information was compared to previously sampled mangrove composition and tree basal area. In surface sediment samples 82 pollen taxa were found, from which 19 were present in the vegetation plots. However, because pollen may be transported by wind and/or watercourses, the overall floristic composition of the different forest types may not necessarily be reflected by the pollen spectra. Local vegetation (i.e. mangroves and beach) represented > 90% of the pollen spectra, while the regional one (i.e. hinterland forests) represented < 5% of it. Unlike the four mangrove types that were previously described in the vegetation, the analysis of pollen samples suggested only three distinct types of forest.The groups were characterised based on (i) the dominance of at least one of the true mangrove species from pollen data ordination and the presence of associated species, and (ii) their relationship with environmental parameters. Rhizophora was present in all plot samples, but did not contribute to forest type separation. In fact, just three true mangrove species proved reliable indicators of (i) high salinity and fringe mangroves (i.e. Avicennia), (ii) high pH levels and landward mangroves (i.e. Conocarpus), and (iii) natural or anthropogenic caused disturbance of forest stands (Laguncularia and associated Acrostichum fern). Hence our study confirms that mangrove pollen spectra can be accurately used to describe different mangrove environments for fossil based palaeoecological reconstructions.     

An initial assessment of mangrove resources and human activities at Mahout Island,Arabian Sea,Oman

This study was initiated to provide information on mangrove structure, communities, wildlife, socio-economics and human impacts on one of the most important areas of mangroves in Oman at Mahout Island, located on the Arabian Sea coast. The island is fringed with a luxuriant vegetation of mangroves formed by Avicennia marina (Forsk.) Vierh. Tree height, diameter at breast-height (dbh) and basal area (m²) show progressive increases from the upper to the lower level of the shore. Density (number of stems/0.1 ha) is variable, showing three peaks in transects across western and southern mangroves. The northern mangroves are the most developed, characterized by muddy substrate, followed by the western on a sandy bottom, and the southern surrounded by rock-flat. The mangroves support a large number of fishes, shrimps, crabs and molluscs. Wildlife are represented by shorebirds, waterfowls, turtles and dolphins.The Mahout population consists of bedouins, mostly supported by fishing. It is semi-settled with seasonal migration in summer to large towns. Fishing activities are usually between September and May. Shrimps and fish are the main natural resources. Human impacts were identified and qualitatively assessed: overutilization of mangroves by woodcutting or livestock grazing; litter and pollution; killing of turtle and other wildlife; removal of benthic marine organisms; the proposed construction of a fishery harbor; and the potential of mariculture and tourism. Management, based on sustainable development, should be undertaken to protect Mahout resources.     

Macrobenthic infauna of mangroves and surrounding beaches at Gazi Bay,Kenya

Twelve sites around Gazi Bay, Kenya, were examined for macrobenthic infauna. Stations differed in human disturbance, vegetation, and sediment type (sandflat, beach, denuded and virgin mangrove sites, with Sonneratia, Rhizophora, Avicennia, Ceriops or Bruguiera vegetation).Sixteen higher taxa were counted; Isopoda, Amphipoda, Polychaeta, Cumacea and Tanaidacea were determined to family level (sometimes to genus or species). Total densities of infauna ranged from 265 to 6025 ind m^–2.Gazi mangals had higher macrobenthos densities than other mangrove sediments described in literature and than the Gazi sandflats. The densities found in Gazi sandflats were comparable to similar habitats elsewhere.Virgin mangrove sediments were rich in mud and organic material, and were characterized by high densities of macro-Oligochaeta and Mollusca. Sandflats, beaches, exploited (denuded) and less dense mangroves or mangroves higher in the tidal zone (Bruguiera) were much more sandy and had a high abundance of Polychaeta and Nemertini.Structural patterns in the macrobenthos were only vaguely associated with vegetation type. Human impact (cutting) has resulted in a drastic decrease in densities of macro-infauna, possibly related to a reduction of organic material in the sediment.     

Habitat‐dependent occupancy and movement in a migrant songbird highlights the importance of mangroves and forested lagoons in Panama and Colombia

Climate change is predicted to impact tropical mangrove forests due to decreased rainfall, sea‐level rise, and increased seasonality of flooding. Such changes are likely to influence habitat quality for migratory songbirds occupying mangrove wetlands during the tropical dry season. Overwintering habitat quality is known to be associated with fitness in migratory songbirds, yet studies have focused primarily on territorial species. Little is known about the ecology of nonterritorial species that may display more complex movement patterns within and among habitats of differing quality. In this study, we assess within‐season survival and movement at two spatio‐temporal scales of a nonterritorial overwintering bird, the prothonotary warbler (Protonotaria citrea), that depends on mangroves and tropical lowland forests. Specifically, we (a) estimated within‐patch survival and persistence over a six‐week period using radio‐tagged birds in central Panama and (b) modeled abundance and occupancy dynamics at survey points throughout eastern Panama and northern Colombia as the dry season progressed. We found that site persistence was highest in mangroves; however, the probability of survival did not differ among habitats. The probability of warbler occupancy increased with canopy cover, and wet habitats were least likely to experience local extinction as the dry season progressed. We also found that warbler abundance is highest in forests with the tallest canopies. This study is one of the first to demonstrate habitat‐dependent occupancy and movement in a nonterritorial overwintering migrant songbird, and our findings highlight the need to conserve intact, mature mangrove, and lowland forests.     

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.     

Observations on the Endemic Pygmy Three-Toed Sloth,Bradypus pygmaeus of Isla Escudo de Veraguas,Panamá

Our objective was to ascertain the population status of the Pygmy Three-toed Sloth, Bradypus pygmaeus, an IUCN Critically Endangered species, on Isla Escudo de Veraguas, Panama. Bradypus pygmaeus are thought to be folivorous mangrove specialists; therefore we conducted a visual systematic survey of all 10 mangrove thickets on the island. The total mangrove habitat area was measured to be 1.67 ha, comprising 0.024% of the total island area. The population survey found low numbers of B. pygmaeus in the mangrove thickets and far lower numbers outside of them. The connectivity of subpopulations between these thickets on the island is not established, as B. pygmaeus movement data is still lacking. We found 79 individuals of B. pygmaeus; 70 were found in mangroves and 9 were observed just beyond the periphery of the mangroves in non-mangrove tree species. Low population number, habitat fragmentation and habitat loss could lead to inbreeding, a loss of genetic diversity, and extinction of B. pygmaeus.     

Developing management plans for the mangrove forest reserves of mainland Tanzania

The mangroves of Tanzania are currently not being managed although they are legally gazetted as forest reserves. The management of this overexploited and under estimated natural resource rests with the Forest and Beekeeping Division in the Ministry of Natural Resources and Tourism. It is the Division's intention to conserve the mangroves of Tanzania, therefore steps are being taken to reach that goal. So far the Division, through its established mangrove project, has done an inventory of all the mangroves of mainland Tanzania with the assistance of NORAD. Aerial photography and ground checks were used to assess the state of all the mangrove reserves in the country. Literature search and a socio-economic study was also undertaken.The inventory revealed that the area covered by mangrove vegetation is 115 901 ha while the previous records indicate about 80 000 ha. If the bare saline areas, water bodies, and salt pans which are part of the mangrove reserves are included, the area amounts to 172 879 ha for the Tanzania mainland. The mangrove reserves have already been mapped in 30 sheets. Some sheets are mapped using a scale of 1:25 000 while others are mapped in 1:50 000 scale. The maps show the vegetation types, the area of each vegetation type, and the stand density and height of each compartment.The paper therefore presents the current status of the mangroves of Tanzania in respect to area, distribution and vegetation types. Included are the strategies being used to develop the mangrove management plans for Tanzania.     

Pattern and process in mangrove forests of the Andaman Islands

Abatract The structural and functional aspects of mangrove forests of the Andaman Islands were described. The mangrove forests of Andaman are highly diversified and rich in species composition. Twenty-six species were collected, Rhizophora lamarckii and R. stylosa were reported for the first time from these islands. The mangroves of Andaman are very productive in comparison to other forest types. Maximum production of biomass was found in the undisturbed Oralkatcha forest. Maximum litter fall was also found at Oralkatcha.     

Biotic interactions mediate the expansion of black mangrove (Avicennia germinans) into salt marshes under climate change

Many species are expanding their distributions to higher latitudes due to global warming. Understanding the mechanisms underlying these distribution shifts is critical for better understanding the impacts of climate changes. The climate envelope approach is widely used to model and predict species distribution shifts with changing climates. Biotic interactions between species, however, may also influence species distributions, and a better understanding of biotic interactions could improve predictions based solely on climate envelope models. Along the northern Gulf of Mexico coast, USA, subtropical black mangrove (Avicennia germinans) at the northern limit of its distribution grows sympatrically with temperate salt marsh plants in Florida, Louisiana, and Texas. In recent decades, freeze‐free winters have led to an expansion of black mangrove into salt marshes. We examined how biotic interactions between black mangrove and salt marsh vegetation along the Texas coast varied across (i) a latitudinal gradient (associated with a winter‐temperature gradient); (ii) the elevational gradient within each marsh (which creates different marsh habitats); and (iii) different life history stages of black mangroves (seedlings vs. juvenile trees). Each of these variables affected the strength or nature of biotic interactions between black mangrove and salt marsh vegetation: (i) Salt marsh vegetation facilitated black mangrove seedlings at their high‐latitude distribution limit, but inhibited black mangrove seedlings at lower latitudes; (ii) mangroves performed well at intermediate elevations, but grew and survived poorly in high‐ and low‐marsh habitats; and (iii) the effect of salt marsh vegetation on black mangroves switched from negative to neutral as black mangroves grew from seedlings into juvenile trees. These results indicate that the expansion of black mangroves is mediated by complex biotic interactions. A better understanding of the impacts of climate change on ecological communities requires incorporating context‐dependent biotic interactions into species range models.     

Mangrove blue carbon stocks and dynamics are controlled by hydrogeomorphic settings and land‐use change

Globally, carbon‐rich mangrove forests are deforested and degraded due to land‐use and land‐cover change (LULCC). The impact of mangrove deforestation on carbon emissions has been reported on a global scale; however, uncertainty remains at subnational scales due to geographical variability and field data limitations. We present an assessment of blue carbon storage at five mangrove sites across West Papua Province, Indonesia, a region that supports 10% of the world's mangrove area. The sites are representative of contrasting hydrogeomorphic settings and also capture change over a 25‐years LULCC chronosequence. Field‐based assessments were conducted across 255 plots covering undisturbed and LULCC‐affected mangroves (0‐, 5‐, 10‐, 15‐ and 25‐year‐old post‐harvest or regenerating forests as well as 15‐year‐old aquaculture ponds). Undisturbed mangroves stored total ecosystem carbon stocks of 182–2,730 (mean ± SD: 1,087 ± 584) Mg C/ha, with the large variation driven by hydrogeomorphic settings. The highest carbon stocks were found in estuarine interior (EI) mangroves, followed by open coast interior, open coast fringe and EI forests. Forest harvesting did not significantly affect soil carbon stocks, despite an elevated dead wood density relative to undisturbed forests, but it did remove nearly all live biomass. Aquaculture conversion removed 60% of soil carbon stock and 85% of live biomass carbon stock, relative to reference sites. By contrast, mangroves left to regenerate for more than 25 years reached the same level of biomass carbon compared to undisturbed forests, with annual biomass accumulation rates of 3.6 ± 1.1 Mg C ha^?1 year^?1. This study shows that hydrogeomorphic setting controls natural dynamics of mangrove blue carbon stocks, while long‐term land‐use changes affect carbon loss and gain to a substantial degree. Therefore, current land‐based climate policies must incorporate landscape and land‐use characteristics, and their related carbon management consequences, for more effective emissions reduction targets and restoration outcomes.     

Participatory appraisal for potential community-based mangrove management in East Africa

Mangroves are among the most threatened ecosystems in the world and the coastal forests of East Africa are no exception to this trend. Although conservation, rehabilitation and sustainable management plans have been developed in various tropical regions, only a few locally based approaches have been launched along the Indian Ocean coast of Africa. In order to identify possible conditions for sustainable management of mangroves based on socio-economic and ecological considerations, we present a participatory approach designed to evaluate the relationships between mangroves and human activities and the use of multi-criterion analysis to identify management solutions. To achieve this goal, all the subjects involved in mangrove management (local communities, institutions and researchers) took an active part in the process. The research was carried out in three communities relying on mangrove swamps: Kisakasaka village on the island of Zanzibar, Mida Creek in Kenya, both relying on mangrove forests known to be endangered by over-exploitation, and Inhaca Island in Mozambique, where mangroves are more pristine. Families were the hub of the research and the importance of each of their economic activities was assessed. We then examined the methods by which mangroves are exploited by the local community and by other stakeholders working in the study areas. Our results show that the mangroves in Inhaca are exploited only for household needs and the pressure on the forests is still ecologically sustainable. In contrast, there is a well-established demand for mangrove products in Kisakasaka and Mida Creek and the mangroves represent an essential source of income for the families, resulting in an ecologically unsustainable rate of exploitation. Therefore, possible alternatives to the current management practices were identified in the two areas by means of a participatory approach. Multi-criterion analysis was then used to compare and discuss the alternatives in terms of social, economic and ecological criteria.     

粤东沿海红树林物种组成与群落特征

南海地区是全球红树林分布的中心区域之一。粤东沿海位于南海地区的北界,红树林物种组成和群落结构具有边缘性。利用卫星影像解译辅助技术,对筛选的23处红树林群落进行样地调查,记录了真红树植物12种,半红树植物6种,伴生植物7种。各群落平均高度为1.50—8.60 m,林相以灌丛、小乔木林为主。红树林群落Shannon-Wiener多样性指数为0.533—1.239,均匀度指数为0.662—0.957,天然林和人工林之间数值差异不显著。等级聚类分析将粤东沿海的红树林划分为演替早期人工林、演替早期天然林、演替中期天然林和演替后期天然林4个类别,各群落立地条件差异较大,沉积物总有机碳、盐度、总氮含量与群落分布状况的相关性较高。与1985年的报道相比,尽管该地区记录的红树林植物种类从20种增加至24种,但个别伴生植物消失以及半红树植物种群萎缩说明该地区红树林面临较大的环境压力。在物种多样性和均匀度均方面,粤东沿海红树林群落低于成熟红树林。过去数十年的围垦导致天然红树植物种群萎缩、生境破碎化是主要因素。基于该地区红树林群落的现状,未来人工林和残次天然林的优化改造是红树林恢复重建的重点,红树林恢复和保育的重点区域包括深圳湾的福田、范和港的蟹洲和韩江口的六合围。