The current status of mangroves along the Kenyan coast: a case study of Mida Creek mangroves based on remote sensing

Mangroves form a unique ecosystem of limited extent covering an area of about 53 000 ha along the Kenyan coast which need protection from overexploitation. Background information on the areal extent and status of these mangroves is limited and makes their protection and management difficult.A model study has been carried out on the Mida Creek mangroves based on a double sampling approach starting with SPOT multispectral satellite imagery followed by ground checks to provide information on species composition, density and distribution of mangroves. The utilization of mangroves and uses around and within the mangroves were determined.During this study, seven mangrove species were identified in Mida Creek, namely:Avicennia marina, Bruguiera gymnorrhiza, Ceriops tagal, Rhizophora mucronata, Sonneratia alba, Xylocarpus granatum andLumnitzera racemosa. This report briefly outlines the present utilisation of mangrove species. It is recommended that a multidisciplinary management plan be developed in order to conserve and manage the mangroves of Kenya on a sustainable yield basis.     

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.     

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.     

Plants and traditional knowledge: An ethnobotanical investigation on Monte Ortobene (Nuoro, Sardinia)

Background

Worldwide there is growing research interest in the ethnobiology of mangrove forests. Notwithstanding that, little information has been published about ethnobiology of mangrove forests in Cameroon. The aims of this study were a) to analyze the harvesting methods and the local selling of mangrove wood products by loggers in the vicinity of Wouri estuary and b) to investigate the patterns of subsistence uses of mangrove wood products around the Douala-Edea reserve.

Methods

Semi-structured interviews were conducted with 120 active mangrove loggers in 23 Douala wood markets and 103 households located in three villages (Mbiako, Yoyo I and Yoyo II) close to Douala-Edea reserve. In each of the three densely populated villages, every second household was chosen for sampling while in all markets, mangrove loggers were chosen randomly. In addition, log diameters were measured in each market using a wooden foldable tape measure. A post hoc analysis (Newman-Keuls test) was performed in order to detect the common wood class diameter sold in the Douala wood markets.

Results

The analysis of the loggers' survey data has shown that large logs of Rhizophora with diameter greater than 40 cm were common in the Douala wood markets and were more closely associated with loggers who used chainsaws. In addition to the general mangroves wood products selling, the analysis on a subsistence level (households' survey) suggests the local population's dependence on mangroves, with multiple uses of Rhizophora racemosa Meyer, R. harrisonii Leechman, Avicennia germinans L. Stearn., Laguncularia racemosa Gaertn. f. and Conocarpus erectus L. timbers for furniture, fences, smoking fish, and fuelwood. Finally, Nypa fruticans (Thunb.) Wurmb. leaves were used as thatching material for house walls and roofs.

Conclusion

Our findings revealed that big logs of Rhizophora were commonly sold by the loggers. A majority of loggers (60%) reported that mangrove marketed wood constitute a principal source of income. Most of the villagers (85.83%) often depend on mangroves for subsistence needs and for them there is no substitute for mangrove wood. Therefore, more efforts should be undertaken at the national level to implement conservation, management and sustainable use of these coastal forests.     

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.     

Patterns of local wood use and cutting of Philippine Mangrove Forests

Small-scale wood harvesting from mangrove forests is a commonplace yet barely studied phenomenon. This paper integrates bio-ecological and ethnographic methods to examine local wood use and cutting of mangrove forests in two areas of the Philippines. Findings reveal considerable site variation in cutting intensity, with heavier cutting typically closer to settlements and in forest stands that are not effectively regulated by government or private interests. Overall, cutting is responsible for almost 90% of stem mortality in both natural and plantation forests. Field measurements confirm ethnographic evidence indicating that harvesting for construction wood, but not fuelwood, is both species- and size-selective. Mangrove management and conservation efforts can be made more effective by better understanding how local people are harvesting wood resources from these forests.     

Status and exploitation of the mangrove and associated fishery resources in Zanzibar

The distribution and growth forms of the mangroves on Zanzibar island (Unguja and Pemba) were investigated. Pemba island, with approximately 12000 ha of mangroves, had nine species; and Unguja island, with 6 000 ha, had eight. Average cropping intensities in Pemba island varied between 350–1937 cut plants per ha while in Unguja these were between 777–3567 cut plants per ha. In Pemba, mangrove forests were relatively less heavily exploited compared to those in Unguja, where clear felling was common. Charcoal, lime and salt production are the major activities which involve heavy utilization of mangrove wood.The fishery resources (shellfish and finfish) associated with the mangrove vegetation were also investigated by examining the composition of fish catches at landing stations in mangrove as well as nonmangrove zones of fishing districts. A survey on the fauna associated with mangrove forests was also conducted. A number of the local commercial fish species were found to be associated with the mangrove vegetation. The fishes of the genusLethrinus and the rabbit fishSiganus were found to constitute the bulk of the fish caught from waters adjacent to mangroves using movable traps. The molluscPyrazus sp., which is commonly used by the local people for food and bait, was found only in the mangroves.     

Ecological engineering for successful management and restoration of mangrove forests

Great potential exists to reverse the loss of mangrove forests worldwide through the application of basic principles of ecological restoration using ecological engineering approaches, including careful cost evaluations prior to design and construction. Previous documented attempts to restore mangroves, where successful, have largely concentrated on creation of plantations of mangroves consisting of just a few species, and targeted for harvesting as wood products, or temporarily used to collect eroded soil and raise intertidal areas to usable terrestrial agricultural uses. I document here the importance of assessing the existing hydrology of natural extant mangrove ecosystems, and applying this knowledge to first protect existing mangroves, and second to achieve successful and cost-effective ecological restoration, if needed. Previous research has documented the general principle that mangrove forests worldwide exist largely in a raised and sloped platform above mean sea level, and inundated at approximately 30%, or less of the time by tidal waters. More frequent flooding causes stress and death of these tree species. Prevention of such damage requires application of the same understanding of mangrove hydrology.     

Patterns of mangrove forest disturbance and biomass removal due to small-scale harvesting in southwestern Madagascar

Wetlands Ecology and Management - Informal small-scale mangrove wood harvesting has received limited attention, though it is a widespread threat to mangroves in many parts of the tropics. We...     

The implications of harvesting on the population structure and sediment characteristics of the mangroves at Mngazana Estuary,Eastern Cape,South Africa

The Mngazana Estuary has the third largest area of mangroves in South Africa (118 ha) and one of the main environmental threats is the cumulative effects of long term small scale harvesting from local communities. This study investigated the change in aerial cover of the mangrove forest over time and assessed the effect of harvesting on the microenvironment and the population structure of Rhizophora mucronata (preferred harvested species) in both harvested and non-harvested sites. In 1982 there were 150 ha of mangroves of all species and since then 32 ha (21%) of the forest area has been lost. Areas of the estuary where mangroves have been completely removed showed significant differences in sediment characteristics. Changes in population size, ratios of adult trees to juveniles (harvested sites—1:5.5, non-harvested sites 1:3.4) and significant differences in height structure are some of the indications that harvesting is affecting the mangrove populations. Results show that while it is necessary to suggest proposals aimed at the sustainable use of the Mngazana mangroves, it is equally important in the short-term to make available alternative sources of materials to replace mangrove poles for building. The formation of the Mngazana Mangrove Management Forum provides an ideal opportunity to drive Participatory Forest Management (PFM) but this would require scientific and management support. The data shown here will provide ecological information required for PFM.     

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.     

The mangroves of the north coast of Haiti

The study of five mangrove forests was undertaken during the summer of1998 on the north coast of Haiti. Photo-interpretation detected areachanges between 1978 and 1989; the areas were reduced by an averageof 43% each. Two of the sites, Salée River mangrove andHaut-du-Cap River mangrove, were characterized by means of a vegetationsurvey and water and soil analysis. Tree density averaged 58,750 stems/haand 114,250 stems/ha respectively, while tree height averaged 2 m.Interviews with villagers indicated that all the assessed mangroves areintensively harvested for charcoal and fuel wood. This extraction seems tobe the main human disturbance, resulting in changes in forest structure,although heavy fishing and conversion to residential sites constitutedisturbances in some mangroves. The situation is critical but probably notirreversible. However, the socio-economic and environmental conditionsprevailing in the country and the lack of basic information on Haitianmangroves are major obstacles to their preservation.     

Sustainable Utilization and Economic Development of Some Plant Resources in Northern Pakistan

Overshadowed by the vast impact that habitat loss has on targeted plant species survival, it is easy to overlook the fact that utilization and harvesting of species can often result in their genetic depletion and in an often rapid downward trend of their population status. In this regard an ethnobotanical study on the medicinal plants of Shawar valley, District Swat was conducted with the aims to document medicinal plants and to examine the current status of the medicinal plants trade as well as the market chain starting from collectors to consumers. The survey reported 50 species of plants belonging to 33 families as ethnomedicinally important. These species were used as crud drugs by the local people and folk-lore for treating diseases in traditional system of medicine. The detailed local uses, recipe preparation along with their local names and diseases treated were recorded for each species.Market survey revealed that the structure of medicinal plant trade is complex and heterogeneous, involving many players. The collectors are often not aware of the high market prices and medicinal values, and most of the collected material is sold to local middlemen at a very low price. There was an increase of 3 to 5 folds in prices from collectors to the national market.Recommendations were given in the spheres of training sustainable harvesting and post harvesting of wild medicinal plant resources, trade monitoring, equitable sharing of benefits of wild resources, improved control on harvesting and trade for the conservation of resources, enhancement of cultivation efforts, future research into trade in wild harvested plants, community participation in natural resource management and value addition in the herbal products to maximize the benefits.     

Analysing ethnobotanical and fishery-related importance of mangroves of the East-Godavari Delta (Andhra Pradesh, India) for conservation and management purposes

Mangrove forests, though essentially common and wide-spread, are highly threatened. Local societies along with their knowledge about the mangrove also are endangered, while they are still underrepresented as scientific research topics. With the present study we document local utilization patterns, and perception of ecosystem change. We illustrate how information generated by ethnobiological research can be used to strengthen the management of the ecosystem. This study was conducted in the Godavari mangrove forest located in the East-Godavari District of the state Andhra Pradesh in India, where mangroves have been degrading due to over-exploitation, extensive development of aquaculture, and pollution from rural and urbanized areas (Kakinada). One hundred interviews were carried out among the fisherfolk population present in two mangrove zones in the study area, a wildlife sanctuary with strong conservation status and an adjacent zone. Results from the interviews indicated that Avicennia marina (Forsk.) Vierh., a dominant species in the Godavari mangroves, is used most frequently as firewood and for construction. Multiple products of the mangrove included the bark of Ceriops decandra (Griff.) Ding Hou to dye the fishing nets and improve their durability, the bark of Aegiceras corniculatum (L.) Blanco to poison and catch fish, and the leaves of Avicennia spp. and Excoecaria agallocha L. as fodder for cattle. No medicinal uses of true mangrove species were reported, but there were a few traditional uses for mangrove associates. Utilization patterns varied in the two zones that we investigated, most likely due to differences in their ecology and legal status. The findings are discussed in relation with the demographic and socio-economic traits of the fisherfolk communities of the Godavari mangroves and indicate a clear dependency of their livelihood on the mangrove forest. Reported changes in the Godavari mangrove cover also differed in the two zones, with significantly less perceptions of a decrease in the protected area, as compared to the adjacent non-protected area. A posteriori comparisons between sequential satellite imagery (retrospective till 1977) and respondents that were at least 15 years back then, revealed a mangrove decrease which was however perceived to different extents depending on the area with which the fishermen were familiar. While local needs had not been incorporated in the existing policy, we created a framework on how data on ethnobotanical traditions, fishery-related activities and local people's perceptions of change can be incorporated into management strategies.     

Poverty and institutional management stand-off: a restoration and conservation dilemma for mangrove forests of Tanzania

Mangrove forests of Tanzania are reserved by law, but the capacity to effectively enforce this institution has remained far from reach and mangrove forests continue to be exploited as cheap sources of wood and forest land for other uses. Often, the rural poor who depend on mangroves for their subsistence are pointed out by the state institutions as culprits of the degradation. Promisingly though, this paradigm is being offset by the emerging positive view about human proclivity for caring and nurturing common resources. Traditional and community based forest management practices are emerging as appropriate alternatives to state control and institutional arrangement for ensuring sustainable management of forest resources. Nonetheless, community based management has not yet been robustly implemented for mangrove forests in Tanzania. Retrospectively, this paper argues that nationalization of mangrove forests has not been successful in reversing mangrove degradation. The experiences have instead been the frictions between people and the state, as desperate rural poor continue to plunder on and make a living at the expense of mangrove forests. The paper exemplify how policy failure, weak or dysfunctional state institutions in Tanzania compounded by little participatory awareness and self commitment are ruining the restoration and conservation initiatives.     

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.     

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.     

Bioactivities,bioactive compounds and chemical constituents of mangrove plants

This review article presents the traditional and medicinal uses, and examines recent investigations on the biological activities of extracts, and chemicals identified from mangroves and mangal associates. Metabolites identified from mangrove plants are classified according to ‘chemical classes’, and some of their structures are illustrated. The article also presents some of the functions of the chemicals present and attempt to emphasize and create an awareness of the great of potential mangroves and mangal associates possess as a source of novel agrochemicals, compounds of medicinal value, and a new source of many already known biologically active compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

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).     

广东林业生态省建设与红树林保护

广东是我国红树林分布最多的省份之一,有红树植物17科31种,红树林湿地面积21 438.3hm²,主要分布在粤西,其次是珠江三角洲地区。红树林具有防灾减灾、净化环境、调节区域小气候、保护生物多样性等重要生态功能。在广东林业生态省建设中,保护和发展红树林被列为八大林业生态工程之一。本文对红树林的生态功能进行了具体分析;阐述了广东红树林资源分布现状、红树林在广东林业生态省建设中的作用以及保护、发展状况;指出目前红树林还面临围海造田、围海养殖、沿海城市化、废水污染等威胁,红树林保护任务艰巨;并就加强红树林保护提出建议。