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Causes and Consequences of Mangrove Deforestation in the Volta Estuary, Ghana: Some Recommendations for Ecosystem Rehabilitation

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Abstract

The damming of the Volta River has resulted in reduced flooding and an increase in mangrove cutting, due to the virtual collapse of agriculture and fishing in the estuary. Another ecological consequence of the reduced level of flooding has been reduced dispersal of seedlings of the principal mangrove Rhizophora racemosa. Therefore, after cutting of this species, recolonisation is either by conspecifics growing at very high densities or by one of a number of weed species. Environmental data collected in the vicinity of the mangroves and each of the weed species have enabled suggestions to be made as to whether R. racemosa or Avicennia africana would be the more suitable mangrove to replant. Recommendations have also been made to introduce the palm Nypa fruticans to the area, together with the development of nature-based tourism, both of which would provide alternative means of income generation, thereby reducing the need to cut remaining mangroves.

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... But it was not clear how this species had been able to establish itself in still very saline sediments (Alvarez-León et al., 2004). An establishment of T. domingensis after the death of mangrove vegetation was already reported by Rubin et al. (1998). But in this case it was restricted to sites with low salinity (1-2 PSU). ...
... Nevertheless, most mangrove seedlings were observed outside or, rarely, at the border of the beds. These beds as well as floating aquatic meadows represented an obstacle for the spread of mangrove propagules (Rubin et al., 1998;Schubert, 1999). In our opinion, this was the main reason for the missing expansion of mangroves into the Typha beds. ...
Article
Over a period of 44 years, we observed the vegetation changes in the western part of the lagoon system of the Ciénaga Grande de Santa Marta, which is situated on the Caribbean coast of Colombia and is separated from the sea by a sandy barrier. Since the construction of the Barranquilla-Ciénaga Road between 1956 and 1960, the lagoon system has been exposed to different interventions in its hydrological make-up, as well as changes to the vegetation. During the time of our investigations, four periods with different plant cover were distinguished. In 1965, the road was bordered by dense mangrove forests. The low surface water salinity and the presence of freshwater plants indicated the influence of the Magdalena River. At the beginning of the seventies, the second period was marked by a decrease in the freshwater in-flow from the river, which led to an increase in salinity and a gradual decay of vegetation. In 1988, the areas formerly covered by mangroves had converted into salt flats. The third period began with the reconstruction of several channels (1995-1998) which renewed the freshwater in-flow from the river to the lagoons. The subsequent vegetation development was characterized by the establishment of Typha domingensis Pers. In 1999, a year with an unusually high amount of rainfall, this species covered most of the former mangrove area in the western part of the lagoon system. The very low surface water salinity favored its spread. The last period began in 2001/2002, when growth conditions for T. domingensis became unfavorable due to an increase in salinity. Instead, conditions for mangrove regeneration improved. This process was slower than expected and is still ongoing. The striking vegetation changes indicate the sensitivity of the coastal lagoon system to hydrological variability
... Such ponding or stagnant water conditions may result from altered hydrology, which can be caused by roads, berms, or the accumulation of sediment and debris in mosquito ditchesall of which can act to reduce drainage. Mangrove mortality due to altered hydrology has been documented following the construction of roads, dikes, or dams (Jiménez et al., 1985;Perdomo et al., 1999;Rubin et al., 1999;Lewis III et al., 2016). ...
... Coastal wetlands must increase substrate elevation at rates equal to or exceeding sea-level rise in order to maintain appropriate tidal inundation levels (Cahoon et al., 2019;Breithaupt et al., 2020); therefore, mangrove forests are at risk if trees produce fewer roots due to stress or mortality (McKee 2001;Cahoon et al. 2003Cahoon et al. , 2006Chambers et al., 2019). Multiple stressors are known to impact mangrove forests, including altered hydrology (Perdomo et al., 1999;Rubin et al., 1999;Lewis III et al., 2016), hurricane damage (Cahoon et al., 2003;Barr et al., 2012;Radabaugh et al., 2020), sediment deposition (Craighead and Gilbert 1962;Ellison 1998), land subsidence (DeLaune et al., 1994;Day et al., 2011), lightning strikes (Smith III et al., 1994;Whelan 2005), logging (Alongi and Carvalho 2008;Lang'at et al., 2014), and sea-level rise (Davis et al., 2005;Cahoon et al., 2019). In all cases, vegetation mortality and the resulting loss of live root biomass can lead to substrate elevation loss in a phenomenon known as peat collapse (Cahoon et al., 2003;Whelan 2005;Krauss et al., 2018;Chambers et al., 2019). ...
Article
Mangroves experience stress or mortality when gas exchange by aerial root structures is hindered by sediment burial or constant inundation. The resulting loss of belowground roots and increased decomposition can lead to a loss of surface elevation through peat collapse, furthering the degree of inundation. This study identified ten live mangrove forests across Tampa Bay (Florida, USA) with stagnant water and/or abundant adventitious root growth (a sign of stress) and compared vegetative, water, and soil characteristics of stressed and reference mangrove forests to identify early indicators of stress and potential peat collapse. Two stressed sites were characterized by sandy, high-density soils and were hypothesized to have been stressed by a burial event. The remaining eight stressed locations had stagnant pools of discolored water with low dissolved oxygen (1.1 ± 1.3 mg L⁻¹). Soil from the hydrologic stress sites had significantly lower dry bulk density than reference mangrove sites (0.24 ± 0.14 g cm⁻³ vs. 0.40 ± 0.11 g cm⁻³), greater organic matter composition (49.3 ± 17.2% vs. 26.1 ± 9.0%), and a higher proportion of root material. Salinity and porewater dissolved organic carbon varied widely but were not significantly different between reference and hydrologic stress sites. Altered hydrology due to anthropogenic alteration can often be improved; thus, proactive restoration is recommended to prevent mortality and peat collapse in affected mangrove forests.
... Rahaman et al. (2004) observed that the natural environment of the area was significantly, and indeed, permanently altered, converting a river ecosystem into a lake ecosystem. Floods to the downstream floodplains were reduced, which led to the virtual collapse of agriculture and fishing (Rubin et al., 1998). Farming along the Volta was structured around the rise and fall of the river but the damming put an end to the natural cycles that had deposited nutrient-laden silts along the floodplains. ...
... Damming led to a drastic curtailment in subsistence agriculture production and animal grazing (Gorman and Werhane, 2008). The reduction in floods led to a reduction in the dispersal of mangrove seedlings while the collapse in fishing and agriculture led to an increase in mangrove cutting for fuelwood by the local communities (Rubin et al., 1998). Also water-borne diseases such as bilharzias, river blindness, malaria, and urinary schistosomiasis became public health concerns because they are common among the inhabitants of surrounding villages (Rahaman et al., 2004;Gorman and Werhane, 2008). ...
Article
The current acute needs for improved water resources and energy management in the contemporary development of Africa has renewed the interest in large dams in recent times, especially in the energy sector, because of the Millennium Development Goals (MDGs), concern about climate change, the variability in crude oil prices and alternative sources of funding for large dams. So, the rethink about large dams as an energy source in the face of fluctuations in the cost of crude oil and climate change is also based on finding cheaper and renewable sources of electricity. However, the renewable credentials of large dams, and their compatibility with sustainable development, are disputed. Using the Akosombo dam and the Bui dam project - both in Ghana - as case studies, this paper analyses the potential and significance of large dams within the ambit of Africa's contemporary development. The paper argues that despite criticisms of large dams and the promotion of alternatives, large dams are still very important to Africa's development as they are technologies with well known positive and negative socio-economic and environmental impacts which could be mitigated. The alternatives to large dams, in contrast, have relatively unknown long-term socio-economic and environmental impacts. In addition, there is scepticism among local people and other stakeholders about the alternatives to large hydropower dams because of the impression that some western-backed non-governmental organisations (NGOs), some northern countries, and some multilateral and bilateral institutions are intentionally seeking to undermine significant development in Ghana and other African countries.
... The general trend observed in the LULCC may be largely attributed to the increasing clearing of mangroves and invasion of mangrove affiliates such as Sesuvium portulacastrum and Paspalum vaginatum. These species have the ability to colonise available space quickly, and prevent its colonisation by mangroves (Rubin, Gordon & Amatekpor, 1998). They as well, tolerate any changes in environment (John & Lawson, 1990). ...
Thesis
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Mangrove forests provide a variety of valuable uses and resources for inhabitants of coastal communities. This study was aimed at assessing the health of mangrove forests at the estuaries of Kakum and Pra using multi criteria approach involving social, biological, chemical and physical factors. The study was conducted from March 2017 to August 2018. Socioeconomic data were gathered from 136 respondents through field surveys in ten communities around the two estuaries while remote sensing and Geographic Information System (GIS) were used to characterize mangrove cover change between the period 2005-2017. Species inventory, structural parameters, litter production and soil analyses were estimated in four study plots of sizes 0.25 ha within each mangrove forest whereas physico-chemical parameters of estuarine water were measured in situ. It was observed that coastal inhabitants harvested fuel wood, timber (poles), crabs, periwinkles and tilapia from these mangrove forests. Mangrove area at Kakum reduced by 41.58 % while that of Pra increased by 12.54 %, from 2005 to 2017. A total of 23 and 20 plants species, including five and three true mangroves were encountered at the Kakum and Pra mangrove forests, respectively. The mangrove species had low structural developments in terms of size and height. Annual litter production rate was lower at the Kakum mangrove forest (9.60 t ha-1 y-1) than at the Pra mangrove forest (10.72 t ha-1 y-1). The estuaries and mangrove sediments were of moderate quality. On the basis of computed mangrove health indices (MHI), the overall health of the Kakum mangrove forest was bad, whereas the Pra mangrove forest was moderately healthy. There is the pressing need for stakeholders to institute stringent management measures for sustainable conservation of both forests.
... This area serves as a nursery site for commercial marine fishes and shrimps and is known globally as a significant habitat for migrating birds. As a result of the ecological wealth of this zone, the Keta and the Songhor Lagoons, which form integral parts of the zone, have been designated as Ramsar sites (Rubin et al. 1998). ...
Chapter
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Changes in climatic conditions have been evident over West Africa in the past decades. Decrease in rainfall amount led to severe droughts during the 1970s and 1980s. There has been a shift of the climatic zones in a southerly direction. Consequently, most of the Volta Basin in Burkina Faso is now located in the Sahelian and Sudano-Sahelian zones. As a consequence of instability in the rainfall pattern, many rivers have dried up, large tracts of land cover have been degraded, and the water table is drawing down.
... The timber is also used illicitly for building material, fuel, smoking fish etc (UNEP, 2007). The damming of the Volta River in 1964 reduced downstream water supply, which affected a large stretch of mangroves, both ecologically and through intensified exploitation by communities who had lost their traditional livelihoods in agriculture and fishing (Rubin et al, 1999). ...
Article
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Interest in prospects for policy processes that contribute to development, climate change adaptation and mitigation, known as ‘climate compatible development’, has been growing in response to increasing awareness of the impacts of climate change. This paper provides insight into the complex political economy of climate compatible development in Ghana’s artisanal fisheries, a sector that has received comparatively little attention in climate change literature and policy processes. It focuses on two contentious policy areas where there is potential for climate compatible development, namely the subsidized premix fuel provided to artisanal fishermen, and mangrove protection. Regarding the premix subsidy, while there is theoretical scope for a ‘triple win’ outcome by removing the subsidy to reduce incentives to unsustainable fishing and supporting alternative policies, in practice this is highly problematic. Artisanal fishermen strongly oppose removing the subsidy on the grounds that it would damage their livelihoods, and do not have the confidence that they would be appropriately compensated for any hypothetical reform. Moreover, it is argued that removing it could have negative unintended consequences if fishermen are forced into alternative livelihoods that are themselves unsustainable. There is, however, a need to make considerable improvements to the distribution of the premix fuel so that it reaches the intended beneficiaries and is not siphoned off for contraband. Meanwhile, although improved mangrove protection could have significant ‘triple-win’ benefits, this area suffers from a lack of funding and administrative coordination across ministries and agencies, leading it to be neglected. The case studies reveal, therefore, that the major constraint to climate compatible development is institutional failing, rather than a lack of policies per se. The paper emphasizes the need to conceptualize climate compatible development as a process which is dynamic across space and time, such that potential for triple win outcomes is fluctuate to vary according to changing circumstances. It is necessary to recognize, furthermore, that pressures from a number of actors, including those at the grass roots, may demand short term improvements to current problems rather than aspiring to triple win outcomes in the long term, creating a major challenge for climate compatible development.
... This area serves as a nursery site for commercial marine fishes and shrimps and is known globally as a significant habitat for migrating birds. As a result of the ecological wealth of this zone, the Keta and the Songhor Lagoons, which form integral parts of the zone, have been designated as Ramsar sites (Rubin et al. 1998). ...
... Moreover, behind this zone, in higher grounds which are often only flooded during spring tides, A. germinans typically dominates. Studies in West Africa (Rubin et al. 1998;Din et al. 2002) have shown that the A. germinans is more tolerant than Rhizophora to the higher salinities present. The A. germinans are also more frequently dispersed in the drier reaches and commonly replaced by a barren hyper-saline flat in the highest grounds. ...
Article
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We provide a baseline account as to the type of mangrove that is typical for Guinea, Africa using field based and remotely sensed data. Specifically, the mangroves of the estuarine islands of Mabala and Yélitono were classified using satellite and airborne optical remote sensing data. Mangroves were mapped according to four classes: tall red (Rhizophora racemosa), medium red (R. racemosa), dwarf red (R. mangle and R. harisonii), and black mangrove (Avicennia germinans). Producer’s and user’s accuracies for the mapping of mangrove from non-mangrove areas were both 98%. When separating amongst the mangrove classes most of the confusion resulted from the medium red mangrove class. Of the 10,442ha of mangrove mapped, approximately 30% were classified as riverine, dominated by tall R. racemosa. The remaining mangrove areas were dominated by dwarf mangrove of either Rhizophora or A. germinans. Biophysical parameter data collected from 56 transects varied considerably amongst the classes. For the tallest mangrove class, the mean values of height, DBH, estimated LAI, stem density and basal area recorded were 13m, 15.1cm, 4.3, 838 stems/ha, and 25.9m2/ha, respectively. In contrast, for A. germinans, values of 3m, 4.6cm, 1.5, 2,877 stems/ha, and 6.0m2/ha were calculated, respectively. KeywordsCoastal forested wetlands-Mangrove structure-IKONOS-QuickBird-Digital airborne imagery-Inventory
... Therefore, efforts by communities towards replanting and restoration of degraded mangrove habitats have been welcomed by government and promoted by nongovernmental organizations. However, along some communities near the Volta River estuary of Ghana, replanting of mangroves has been unsystematic and unable to match the rate of degradation and exploitation (Rubin et al., 1999) while in a few areas where there has been continuous replanting, the relative size of mangrove forest has been maintained (Tieku, 2010). Though these replanting initiatives have seen variable successes in the area, local communities' motivation for undertaking these projects has been unclear. ...
Article
Even though global interest in mangrove research has increased in recent years, unveiling their immense ecological and economic roles, very little work has been done to investigate the primary driving factors motivating long-term community-based mangrove restoration and management on local scales. In Ghana, policy makers and coastal management practitioners have recently embraced the concept of community-based and co-management of coastal and marine resources. Community-based and co-management approaches require that key stakeholders, most notably the resource users themselves, play significant roles and responsibilities in the management process. However, there is little evaluation of the process in Ghana to assess the success or otherwise, particularly of the few and long standing examples of community-based approaches in coastal resource management. With special reference to an over two decade old community-based mangrove forestry programme along the Volta estuary of Ghana, this paper provides concepts for examination of the ecological and socioeconomic factors influencing mangrove restoration and management by fishers, fish mongers, farmers and their socioeconomic groupings. Participatory GIS mapping and the use of orthophotos generated for the period 1974-2011 provided additional information on temporal evolution of the extent of mangrove areas restored and managed by local stakeholders. Socioeconomic assessment of mangrove products utility was done through questionnaire interviews. The results indicate that livelihoods and economic benefits are the primary factors that motivate local stakeholders' participation in mangrove restoration and management. Mangroves provisioning services, markets and low livelihoods diversification are major drivers of mangrove resources exploitation. The study has shown that mangroves resources can be sustainably exploited, restored and managed if local customary rules are enforced and institutional arrangements put in place to mediate mangrove exploitation and regeneration rates. Such an approach if well developed, could promote coastal resources conservation with high economic returns for the users.
... Since the 1970s, some large-scale or successful cases have been reported from Florida ( Lewis, 2000), Australia ( Saenger, 1996), and the Sundarbans ( Saenger and Siddiqi, 1993). Thereafter, the ecological effects of introduced mangroves have been addressed by studies in West Africa ( Rubin et al., 1998;Sunderland and Morakinyo, 2002), Hawaii ( Sweetman et al., 2010), and French Polynesia ( Polidoro et al., 2010). In China, massive mangrove afforestation has occurred extensively since the 1980s ( Lin and Fu, 2000). ...
... Human activities remain a major cause of degradation and loss of mangrove ecosystems in all parts of the world. Rubin et al. (1999) describe the destruction of the mangrove forests of the Volta River Estuary in Ghana due to two dams on the Volta River, and local timber harvesting. Zabbey (2008) and listed oil spillage, overexploitation for fuel wood, conversion to other forms of development, dredging and industrial discharges, and unhindered spread of Nypa fruticans (nypa palm) as major threats to mangroves in the Niger Delta. ...
Article
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Mangrove restoration has been undertaken with varying degrees of success in many tropical and subtropical marine shorelines around the globe. However, mangrove reforestation in the Niger Delta, Africa's largest delta and mangrove belt is, at best, rudimentary. Here, we present floristic results on two opportunistic artificial mangrove regeneration case studies aimed at restoring mangrove swamps damaged by oil pollution (Bodo Creek) and colonized by invasive Nypa fruticans (nypa palm) (Kono Creek) in Ogoniland, eastern Niger Delta, Nigeria. Nursery raised seedlings of the delta's dominant Rhizophora racemosa were planted 1 m apart in zigzag fashion at both locations. Planting at the oil-polluted site was preceded by soil quality investigation and bio-stimulation with fertilizer, whereas at Kono Creek, there was no addition of fertilizer before and after planting. A 3-year post planting evaluation of survival rate, growth, and girth parameters showed better performance of mangroves at the Bodo Creek restoration than at the Kono Creek restoration, with survival rates of 72% and 12%, respectively. In sharp contrast to the Bodo Creek restoration, few stands of the planted mangroves at the Kono Creek restoration had started producing propagules. Investigations of soil quality, and where necessary, followed by remedial treatment, particularly augmenting key nutrients, are critical precursors of successful artificial mangrove regeneration. ©2016 by the Board of Regents of the University of Wisconsin System.
... The timber is also used illicitly for building material, fuel, smoking fish etc (UNEP, 2007). The damming of the Volta River in 1964 reduced downstream water supply, which affected a large stretch of mangroves, both ecologically and through intensified exploitation by communities who had lost their traditional livelihoods in agriculture and fishing (Rubin et al, 1999). ...
... Sediment delivery to the Mekong Delta has already been halved and could drop to 4 % of baseline if all planned dams for the catchment are constructed (Kondolf et al., 2014a). Elsewhere in the tropics, dam construction has been associated with the loss of mangrove habitat, such as at the Volta estuary in Ghana (Rubin et al., 1999). The morphology of the lower Zambezi's floodplains and delta were dramatically transformed by reduced sediment loads associated with the Cahora Bassa megadam in Mozambique (Davies et al., 2001). ...
Article
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The impact of large dams is a popular topic in environmental science, but the importance of altered water quality as a driver of ecological impacts is often missing from such discussions. This is partly because information on the relationship between dams and water quality is relatively sparse and fragmentary, especially for low-latitude developing countries where dam building is now concentrated. In this paper, we review and synthesize information on the effects of damming on water quality with a special focus on low latitudes. We find that two ultimate physical processes drive most water quality changes: the trapping of sediments and nutrients, and thermal stratification in reservoirs. Since stratification emerges as an important driver and there is ambiguity in the literature regarding the stratification behavior of water bodies in the tropics, we synthesize data and literature on the 54 largest low-latitude reservoirs to assess their mixing behavior using three classification schemes. Direct observations from literature as well as classifications based on climate and/or morphometry suggest that most, if not all, low-latitude reservoirs will stratify on at least a seasonal basis. This finding suggests that low-latitude dams have the potential to discharge cooler, anoxic deep water, which can degrade downstream ecosystems by altering thermal regimes or causing hypoxic stress. Many of these reservoirs are also capable of efficient trapping of sediments and bed load, transforming or destroying downstream ecosystems, such as floodplains and deltas. Water quality impacts imposed by stratification and sediment trapping can be mitigated through a variety of approaches, but implementation often meets physical or financial constraints. The impending construction of thousands of planned low-latitude dams will alter water quality throughout tropical and subtropical rivers. These changes and associated environmental impacts need to be better understood by better baseline data and more sophisticated predictors of reservoir stratification behavior. Improved environmental impact assessments and dam designs have the potential to mitigate both existing and future potential impacts.
... Similar deaths of mangroves in a protected area due to modified hydrology are reported in Turner and Lewis (1997). Rubin et al. (1999) describe the destruction of the mangrove forests of the Volta River Estuary in Ghana due to two dams on the Volta River, and local timber harvesting. Ellison (2000) notes that "[D]espite repeated claims that mangrove forests can be managed sustainably . . . ...
Article
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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.
... Secondly, specific research on zonal classification of mangroves based on uses like timber and fuelwood harvest, collection of NTFPs, ecotourism and landscaping, wildlife conservation and protective functions will be of major concern (Iftekhar and Takama, 2008). Moreover, scientific literature on the possibility of introduction of exotic species depending on local environmental conditions and existing species associations will be beneficial for CBMM (Rubin et al., 1998). As pointed out by Field (1999), site-specific researches in assisting the communities to sort out practical problems like site selection, choice of species and zonation, monitoring and maintenance measures, estimation of gestation periods and usability of resources should be the focus at present. ...
Article
Tropical coastal wetlands form complex and dynamic ecosystems based on a mixture of vegetation, soil, and water components. Optical remotely sensed data have often been used to characterize and monitor these ecosystems, which are among the environments most threatened by climate change and anthropogenic activity worldwide. The present study sought to evaluate the spectral response of Landsat-5 Thematic Mapper (TM) images for the interpretation of different wetlands and associated environments at the mouth of the Amazon River, including mangroves, saltmarshes, beaches, and dunes, as well as secondary vegetation, water with different levels of sediment suspension, and human occupation. A Spectral Angle Mapper (SAM) classifier was applied to the analysis of Landsat-5 TMsatellite imagery to evaluate the potential for the mapping of these coastal wetland land cover classes. The characterization and comparison of the different spectral classes were obtained through the collection of at least 20 polygonal samples (5 × 5 pixels) for each class, with a total of 4,544 points. Spectral separability indices for each pair of classes were based on an Analysis of Variance, with Tukey post-test. The results indicated that most land cover classes could be separated spectrally with Landsat-5 TM. The overall accuracy and Kappa indices for the results of the classification were 86.1 and 0.84 %, respectively. The results of this spectral analysis demonstrated the potential of the SAM classifier for the classification of the different tropical wetlands in a typical Amazon coastal setting from optical remotely sensed data.
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Genetic diversity within and among six natural populations of Nypa fruticans from China, Vietnam, and Thailand was assessed using SSR and ISSR analysis. Our results showed an extremely low level of genetic diversity of N. fruticans (at the species level, P = 11.76% and 2.88%, He = 0.0279 and 0.0113, I = 0.0470 and 0.0167 by SSRs and ISSRs, respectively) across a total of 183 individuals. No genetic variation was detected within any population except for the Thailand population by SSRs (P = 11.76%, He = 0.0417; I = 0.0622). The bottlenecks during glacial epochs, founder effects, and propagation pattern may be responsible for the extremely low level of genetic diversity of N. fruticans.
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Interest in mangrove rehabilitation has increased rapidly since 2003, as has awareness of the damaging effects of natural and anthropogenic pressures that contribute to mangrove loss, which is estimated at 1-2 % per annum. The major pressures are from urbanization and other development in all areas and forestry and fisheries especially where communities depend on mangroves for their livelihood. However rehabilitation success has been uncertain, reflecting gaps in integration between human and ecological components of the rehabilitation system. In particular there are government level issues of gaps and inconsistency in policy and failure in application. Some rehabilitation efforts have had limited success for several reasons including: having insufficient information, using inappropriate methods, not involving local communities, or not following all the steps in the processes that have been identified in the literature. A multi-disciplinary and integrated approach is needed to assist future planning and this needs capacity from a variety of areas in government, research and community. The review concludes with hope for a future where governments work with communities to develop policies and strategies for rehabilitating mangrove for resilience to changing environments.
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The area of mangrove in Ghana has suffered significant depletion in the last 30 years. Causes of loss are based on anthropogenic pressures which will increase with population rise and the climate variability. The impact of this loss of mangrove cover reduces ecosystem services such as fish breeding and nursery as well as erosion control. These losses have a negative effect on marginalised coastal populations, especially women and the elderly. The FAO and CBD ecosystem approach to natural resource management provides a tool for government to revisit the issue of mangrove management in Ghana using adaptive management, participatory engagement with local communities and a holistic approach involving various disciplines. The immediate assessment of frameworks such as the ITTO Action Plan for Mangroves; the World Bank Code of Conduct for Mangrove Ecosystems for their implementation in the Ghanaian context should be carried out by Government. Capacity to apply the FAO system of ecosystem management needs to be built in Ghana.
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Mangrove Coasts are shorelines fringed by mangrove and saltmarsh vegetation. They form a significant part of coastal tidal wetlands as distinctive habitats of tropic and temperate shorelines. Tidal wetlands have vegetation of varying complexities from forested mangrove woodlands, thick mangrove and saltmarsh shrubbery, low dense samphire plains, to microlagal covered saltpans (Tomlinson 1994). In the tropics, mangroves are often the dominant shoreline ecosystem comprised chiefly of flowering trees and shrubs uniquely adapted to coastal and estuarine tidal conditions (Duke 2011). They form distinctly vegetated and often densely structured habitat of verdant closed canopies cloaking coastal margins and tidal waterways of equatorial, tropical and subtropical regions of the world. Normally, but not exclusively, these vegetation assemblages grow in soft sediments above mean sea level in the intertidal zone of sheltered coastal environments and estuarine margins (Fig. 1). The plants of Mangrove Coasts are well-known for their morphological and physiological adaptations coping with salt, saturated anoxic soils and regular tidal inundation; notably with specialised attributes like: exposed air-breathing roots above ground; extra, above-ground stem support structures; salt-excreting leaves; low water potentials and high intracellular salt concentrations to maintain favorable water relations in saline environments; and viviparous water-dispersed propagules. With such attributes, these habitats have essential roles in coastal productivity and connectivity, often supporting high biodiversity and biomass not possible in upland vegetation, especially in more arid regions. Mangrove Coasts are key sources of primary production with highly dependant trophic linkages between plants and animals, as nursery and breeding sites of benthic and arboreal life, as well as physical shelter and protection from severe storms, river flows and large tsunami waves. Within tropical latitudes, mangrove coasts nestle mostly between two other iconic ecosystems of coral reefs and tropical rainforests. All three are intimately inter-connected, providing mutual protection and sustenance. Each of these ecosystems also create biota-structured environments, where the organisms themselves provide and build the physical structure amongst which associated life is nurtured and sheltered. Without this living structure, these habitats and the many organisms dependant on them, simply would not exist. This essentially identifies how such a large group of plants and animals are so vulnerable. For example, bordering Mangrove Coasts, colonial coral reefs often flourish in the shallow warm seas created and protected from land runoff by mangrove vegetation (Duke & Wolanski 2001). Mangroves absorb unwanted nutrients and sediments of turbid waters to stabilize eroding and depositional shorelines. In modern human times, this buffering role also includes the capture of harmful chemicals in runoff waters from agricultural lands. The specialised plant assemblages of Mangrove Coasts provide a broad range of essential, and often under-valued, ecosystem services along with their more acknowledged roles as habitats of high productivity, and as fishery nursery sites (Robertson & Duke 1990). In such ways, the consequences of disturbing Mangrove Coast habitats are expected to have far-reaching implications and impacts on neighbouring ecosystems and dependant biota. See: http://www.springerreference.com/index/chapterdbid/350631
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Mangroves are the unique intertidal plant formations growing in sheltered tropical and subtropical coastal areas. Due to increasing population and economic development, they had been severely damaged in the last several decades, facing degradation and loss. In recent years, many measures were undertaken to rehabilitate mangroves in different countries. However, followed by anthropologic disturbance and natural disasters, the lacking of technical support for afforestation, lower survival rate of afforestation, and careless managementled to slow enhancementof mangrove area. Then lower survival rate was the primary threshold to mangrove restoration. The recent advances of mangrove restoration within four processes were reviewed, namely; (1) site-species matching, which includes temperature, substrates and hydrological factors of afforestation sites; (2) selection and introduction of mangrove species, that includes status of native specie's selection and exotic one's introduction; (3) applicationof silviculture techniques, including planting, seedling and sapling nursing techniques, and afforestation cost's comparison; and (4) post-cultivated management and monitoring, including the sapling's watching, diseases and pest's prevention and resistance, and ecological monitoring. Coupled with the field survey's results, some basic principles and appliedcases were generalized. Finally, based on the current status of mangrove restoration in China, there is a discussion on the future emphasis of mangrove restoration researches, which is (1) undertaking mangrove rehabilitation in the abandonedaquaculture ponds; (2) monitoring on the restoration of biodiversity in the mangrove ecosystem; (3) researching on allelopathy in mangrove ecosystem more elaborately; (4) afforesting mixed stands with different mangrove species; and at last but not the least (5) implementing ecological restoration of mangrove wetlands.
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Mangroves form coastal forests largely confined between 30°north and south of the equator. This range is determined mainly by low and extreme temperatures and, to a lesser extent, by rainfall. They are thus abundant in many lesser developed countries with fast rising populations which exert strong development pressure on this ecosystem. In recent years, pressures of increasing population, food production and development have led to a significant proportion of the world's mangrove resource being destroyed at a rate faster than they are being regenerated. Much of their elimination has been to create land for aquaculture, particularly shrimp ponds, but in many instances shrimp ponds are quickly abandoned as a result of falling production, leaving highly degraded land on which mangroves do not naturally re-establish themselves. It is estimated that shrimp ponds in Asia rarely last for more than five to ten years, leaving irreversibly degraded environments. The scale of mangrove clearance may be huge: in the Philippines, for example 70% were lost in a period of 60 years, and similar or even greater clearance rates have been seen in 'New World' areas too. A popular view of mangrove forests is that they are very productive, and under some conditions they compare well with terrestrial forests. The qualitative importance of mangroves as habitat, nursery and source of food for both commercial fisheries species and other non-commercial fauna is generally accepted, as is the fact that a large number of juvenile fish use mangroves as nursery habitats. However, there is a lack of well established quantified relationships between fish yields and area of mangrove, though several studies support the hypothesis that coastal fish resources are closely linked to estuaries and mangroves, even if controversy remains about their degree of dependence. Apart from being a productive shoreline ecosystem, mangroves can help stabilise dynamic coastlines. There is now an upsurge in the number of rehabilitation projects, but of the 90 or so countries around the world that possess mangroves only some 20 have attempted any form of mangrove replanting, and only nine have planted more than 10 km2 since 1970. Mangrove rehabilitation can bring into conflict the aims of maximising biodiversity and providing maximum benefit to the human communities that rely on them. Often, however, the objective of rehabilitation is sustainable production, and the knowledge that now exists about the extent, structure and function of mangrove ecosystems is substantial and growing; mangroves are fashionable at the end of the 20th century. There is an urgent need to use this to improve their sustainable use for the benefit of the people who rely upon them, and future work must focus on efficient ways to use and rehabilitate mangrove ecosystems for sustainable purposes. Despite the problems, enormous progress has been made on understanding the structure, function and use of mangroves during this century. Above all there has been a cathartic shift in their understanding, importance and usefulness, much of which has been achieved by education. It is on this basis of understanding that the sustainable use of mangrove ecosystems must be further developed.
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This report presents a study on factors contributing to challenges and opportunities experienced in the Volta Delta today. Each of these factors – from population growth and migration, to economic development and industry, and to climate change and sea level rise – contribute to ongoing changes within the Ghana Delta. Challenges related to flooding and erosion, salt water intrusion, irrigation, drainage, and sanitation, are extensively discussed in this report, after which an overview of adaptive measures and technical methods and tools to support sustainable delta management for the Volta Delta is provided
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The study examines vegetation – environment relationships. Vegetation measurements included species frequency, density, diameter and tree height, while environmental measurements were soil particle size distribution, acid properties (pH, Al, SO4), nutrient cations (Ca, Na, Mg, K), organic carbon, nitrogen, phosphorus and chloride content. Nypa fruticans was the dominant species in the A stratum (> 3 m tall) while Rhizophora mangle was dominant in the B stratum (1–3 m tall). The C stratum (< 1="" m="" tall)="" was="" dominated="" by="" mangrove,="" nypa="" and="" raphia="" saplings.="" silt="" was="" dominant="" and="" the="" most="" variable="" particle="" size="" fraction.="" a="" principal="" components="" analysis="" of="" the="" soil="" data="" indicated="" the="" first="" three="" dominant="" components="" influencing="" the="" vegetation="" were="" salinity,="" nutrient="" and="" soil="" texture.="" tree="" height="" and="" density="" correlated="" highly="" with="" the="" salinity="" and="" soil="" texture="" gradients="" (p="">< 0.01),="" while="" basal="" area="" correlated="" with="" salinity="" and="" nutrient="" gradients="" (p="">< 0.01).="" while="" avicannia="" africana="" in="" the="" a="" stratum="" was="" influenced="" largely="" by="" the="" salinity="" and="" soil="" texture="" gradients.="" nypa="" fruticans="" in="" the="" b="" stratum="" was="" influenced="" by="" salinity="" and="">
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In the early 1980s, a strategy for graphical representation of multivariate (multi-species) abundance data was introduced into marine ecology by, among others, Field, et al. (1982). A decade on, it is instructive to: (i) identify which elements of this often-quoted strategy have proved most useful in practical assessment of community change resulting from pollution impact; and (ii) ask to what extent evolution of techniques in the intervening years has added self-consistency and comprehensiveness to the approach. The pivotal concept has proved to be that of a biologically-relevant definition of similarity of two samples, and its utilization mainly in simple rank form, for example ‘sample A is more similar to sample B than it is to sample C’. Statistical assumptions about the data are thus minimized and the resulting non-parametric techniques will be of very general applicability. From such a starting point, a unified framework needs to encompass: (i) the display of community patterns through clustering and ordination of samples; (ii) identification of species principally responsible for determining sample groupings; (iii) statistical tests for differences in space and time (multivariate analogues of analysis of variance, based on rank similarities); and (iv) the linking of community differences to patterns in the physical and chemical environment (the latter also dictated by rank similarities between samples). Techniques are described that bring such a framework into place, and areas in which problems remain are identified. Accumulated practical experience with these methods is discussed, in particular applications to marine benthos, and it is concluded that they have much to offer practitioners of environmental impact studies on communities.
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This book explains the history and politics of dam building worldwide. It describes the many technical, safety and economic problems that afflict the technology, and explores the role played by international banks and aid agencies in promoting it. The author also examines the rapid growth of the international anti-dam movements, and stresses how replacing large dams with less destructive alternatives will depend upon opening up the dam industry's practices to public scrutiny.
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Nipa palm (Nypa fruticans,) is a useful, versatile, and fairly common component of mangrove forests of Asia and Oceania. Because of its usefulness, it has been introduced into West Africa. In addition to a host of local subsistence uses ranging from medicines to hats and raincoats, some important commercial uses have led to management efforts and are initiating a new interest in its potential. Sap production from nipa produces an intoxicating beverage, sugar, vinegar, and alcohol that may be used as fuel. The tapping of nipa for sap involves a rather unusual kicking or beating process called “gonchanging. ” Further research in nipa sap production, together with development of more efficient collection and handling methods, might greatly enhance the usefulness of this palm.
Lower Mangrove Project Remote Sensing Component
  • S Adu-Prah
  • G Gyamfi-Aidoo
  • G T Agyepong
Adu-Prah, S., Gyam®-Aidoo, G. and Agyepong, G. T. (1997) Lower Mangrove Project Remote Sensing Component. Lower Volta Mangrove Project Technical Report. Series Editor: Gordon, C. DFID/Ghana Wildlife Department/Ghana Environmental Protec-tion Agency.
Mangrove vegetation Non-parametric multivariate analyses of changes in community structure
  • V J Chapman
Chapman, V. J. (1976) Mangrove vegetation. J. Cramer Publishing Company, Vaduz, Liechtenstein. Clarke, K. R. (1994) Non-parametric multivariate analyses of changes in community structure. Australian Journal of Ecology 18, 117±143.
A working plan for the Matang Mangrove Forest Reserve, Perak. Fourth Revision. State Government of Perak Darul Ridzuan
  • B K Gan
Gan, B. K. (1995) A working plan for the Matang Mangrove Forest Reserve, Perak. Fourth Revision. State Government of Perak Darul Ridzuan, Malaysia.
The botany of mangroves Mangrove resource utilisation and community-based management in the Lower Volta: a socio-anthropological study. Lower Volta Mangrove Project Technical Report
  • P B Tomlinson
  • Uk Tsikata
  • I E Senah
  • K Awumibila
Tomlinson, P. B. (1986) The botany of mangroves. Cambridge University Press, Cambridge, UK. Tsikata, I. E., Senah, K., Awumibila, M. (1997) Mangrove resource utilisation and community-based management in the Lower Volta: a socio-anthropological study. Lower Volta Mangrove Project Technical Report. Series Editor: Gordon, C. DFID/Ghana Wildlife Department Ghana Environmental Protection Agency.
Restoration of mangroves in the United States of America: a case study in Florida
  • S C Snedekar
  • P D Biber
Snedekar, S. C. and Biber, P. D. (1996) Restoration of mangroves in the United States of America: a case study in Florida. In Restoration of mangrove ecosystems, ed C. D. Field, pp. 170±188. International Society for Mangrove Ecosystems, Okinawa, Japan. Tomlinson, P. B. (1986) The botany of mangroves. Cambridge University Press, Cambridge, UK.
Mangrove resource utilisation and community-based management in the Lower Volta: a socio-anthropological study
  • I E Tsikata
  • K Senah
  • M Awumibila
Tsikata, I. E., Senah, K., Awumibila, M. (1997) Mangrove resource utilisation and community-based management in the Lower Volta: a socio-anthropological study. Lower Volta Mangrove Project Technical Report. Series Editor: Gordon, C. DFID/Ghana Wildlife Department Ghana Environmental Protection Agency.
The status, exploitation and conservation of mangrove communities in the Lower Volta region, Ghana. Lower Volta Mangrove Project Technical Report. Series Editor: Gordon. C. DFID/Ghana Wildlife Department/Ghana Environmental Protection Agency
  • J A Rubin
Rubin, J. A. (1997) The status, exploitation and conservation of mangrove communities in the Lower Volta region, Ghana. Lower Volta Mangrove Project Technical Report. Series Editor: Gordon. C. DFID/Ghana Wildlife Department/Ghana Environmental Protection Agency.
ed) (1996) Restoration of mangrove ecosystems. International Society for Mangrove Ecosystems
  • K R Clarke
Clarke, K. R. (1994) Non-parametric multivariate analyses of changes in community structure. Australian Journal of Ecology 18, 117±143. Field, C. D. (ed) (1996) Restoration of mangrove ecosystems. International Society for Mangrove Ecosystems, Okinawa, Japan. Field, C. D. (1997) The restoration of mangrove ecosystems. Intercoast Network, Special Edition 1, 11±12.