Diversity2015, 7(2), 149-169; doi:10.3390/d7020149 - published 22 May 2015 Show/Hide Abstract
Abstract: Covering approximately 10,000 km2 the Sundarbans in the Northern Bay of Bengal is the largest contiguous mangrove forest on earth. Mangroves forests are highly productive and diverse ecosystems, providing a wide range of direct ecosystem services for resident populations. In addition, mangroves function as a buffer against frequently occurring cyclones; helping to protect local settlements including the two most populous cities of the world, Kolkata and Dhaka, against their worst effects. While large tracts of the Indian Sundarbans were cleared, drained and reclaimed for cultivation during the British colonial era, the remaining parts have been under various protection regimes since the 1970s, primarily to protect the remaining population of Bengal tigers (Panthera tigris ssp. tigris). In view of the importance of such forests, now severely threatened worldwide, we trace the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries. We apply a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover. While the mangroves’ areal extent has not changed much in the recent past, forest health and structure have. These changes result from direct human interference, upstream development, extreme weather events and the slow onset of climate change effects. Moreover, we consider the role of different management strategies affecting mangrove conservation and their intersection with local livelihoods.
Diversity2015, 7(2), 137-148; doi:10.3390/d7020137 - published 30 April 2015 Show/Hide Abstract
Abstract: Mangrove is an evergreen, salt tolerant plant community, which grows in inter-tidal coastal zones of tropical and subtropical regions of the world. They are ecologically important for many fauna species and are rich in food resources and consist of many different vegetation structures. They serve as ideal foraging and nursery grounds for a wide array of species such as birds, mammals, reptiles, fishes and aquatic invertebrates. In spite of their crucial role, around 50% of mangrove habitats have been lost and degraded in the past two decades. The fauna diversity of mangrove habitat at Marudu Bay, Sabah, East Malaysia was examined using various methods: i.e. aquatic invertebrates by swap nets, fish by angling rods and cast nets, reptiles, birds, and mammals through direct sighting. The result showed that Marudu Bay mangrove habitats harbored a diversity of fauna species including 22 aquatic invertebrate species (encompassing 11 crustacean species, six mollusk species and four worm species), 36 fish species, 74 bird species, four reptile species, and four mammal species. The wide array of fauna species could be due to the availability of complex vegetation structures, sheltered beaches and tidal mudflats, which are rich in food resources and also offer safe foraging and breeding grounds for them. These heterogeneous habitats must be protected in a sustainable way in order to ensure the continued presence of aquatic and terrestrial fauna species for future generations.
Diversity2015, 7(2), 118-136; doi:10.3390/d7020118 - published 20 April 2015 Show/Hide Abstract
Abstract: Mangrove habitats are under severe land use pressure throughout the world and Australia is no exception. Here we describe the heterogeneity of mangrove habitat and its relationship with mangrove bird diversity. We examined the role of mangrove habitat complexity in determining the richness of avian mangrove dependent species (MDS) and interior species, overall bird species richness and density. High species richness (overall and MDS) and density in the mangroves was associated with plant species richness, the density of the understory and food resource distribution. Furthermore, habitat heterogeneity rather than patch area per se was a more important predictor of species richness in the mangroves. These findings stress the importance of habitat diversity and quality to the diversity and density of birds in mangroves. Thus, habitat heterogeneity within mangroves is a crucial patch characteristic, independent of mangrove patch size, for maintaining diverse avian species assemblages.
Diversity2015, 7(2), 105-117; doi:10.3390/d7020105 - published 17 April 2015 Show/Hide Abstract
Abstract: Mangrove is an ecosystem subjected to tide, salinity and nutrient variations. These conditions are stressful to most plants, except to mangrove plants that are well-adapted. However, many mangrove areas have extremely stressful conditions, such as salt marshes, and the plants nearby usually present morphological alterations. In Sepetiba Bay, two species of mangrove plants, Avicennia schaueriana and Laguncularia racemosa, have poor development near a salt marsh (SM) compared to plants at the riverside (RS), which is considered a favorable habitat in mangroves. The level of genetic diversity and its possible correlation with the morphological divergence of SM and RS plants of both species were assessed by AFLP molecular markers. We found moderate genetic differentiation between A. schaueriana plants from SM and RS areas and depleted genetic diversity on SM plants. On the other hand, Laguncularia racemosa plants had no genetic differentiation between areas. It is possible that a limited gene flow among the studied areas might be acting more intensely on A. schaueriana plants, resulting in the observed genetic differentiation. The populations of Laguncularia racemosa appear to be well connected, as genetic differentiation was not significant between the SM and RS populations. Gene flow and genetic drift are acting on neutral genetic diversity of these two mangrove species in the studied areas, and the observed genetic differentiation of A. schaueriana plants might be correlated with its morphological variation. For L. racemosa, morphological alterations could be related to epigenetic phenomena or adaptive loci polymorphism that should be further investigated.
Diversity2015, 7(2), 74-104; doi:10.3390/d7020074 - published 16 April 2015 Show/Hide Abstract
Abstract: Due to increasing recognition of the benefits provided by mangrove ecosystems, protection policies have emerged under both wetland and forestry programs. However, little consistency remains among these programs and inadequate coordination exists among sectors of government. With approximately 123 countries containing mangroves, the need for global management of these ecosystems is crucial to sustain the industries (i.e., fisheries, timber, and tourism) and coastal communities that mangroves support and protect. To determine the most effective form of mangrove management, this review examines management guidelines, particularly those associated with Integrated Coastal Zone Management (ICZM). Five case studies were reviewed to further explore the fundamentals of mangrove management. The management methodologies of two developed nations as well as three developing nations were assessed to encompass comprehensive influences on mangrove management, such as socioeconomics, politics, and land-use regulations. Based on this review, successful mangrove management will require a blend of forestry, wetland, and ICZM programs in addition to the cooperation of all levels of government. Legally binding policies, particularly at the international level, will be essential to successful mangrove management, which must include the preservation of existing mangrove habitat and restoration of damaged mangroves.
Diversity2015, 7(1), 60-73; doi:10.3390/d7010060 - published 6 March 2015 Show/Hide Abstract
Abstract: Socotra Cormorants (Phalacrocorax nigrogularis) are regionally endemic seabirds with restricted distribution. To better understand their nest selection, we assessed vegetation and soil elements in their nesting areas at Siniya Island of United Arab Emirates. Field sampling was done from three areas (2011 nesting area, 2012 nesting area and control area) in February and March in 2013. Sampling consisted of vegetation assessment in the field and close-range photography. Ground cover within quadrats was classified into the percent of (1) living cover, (2) dead cover, (3) droppings, (4) bare ground and (5) other. Soil samples were analyzed for thirteen elements. Multivariate stepwise discriminant analysis was performed to determine the importance of the attributes on nest sites. The contribution of Function 1 to the discriminant model was estimated to be 77.4%, whereas Function 2 contributed 22.6% to the discriminant model (P ≤ 0:05). Sites could not be classified adequately using ground cover alone; however, discriminant analysis using soil attributes could better distinguish sites. We noted that Fe and Mn had high discriminant ability in Function 1, whereas Al and Cr showed high discriminant roles for Function 2. The contribution of Function 1 to the model, using soil attributes, was estimated to be 90.7% (P ≤ 0:05). The combination of ground cover and soil attributes did not improve discrimination of nest sites. Furthermore, some soil variables (Ca, Na, Cd and Cr) were much higher than normal levels in soil, indicating high transport of marine nutrients to nesting sites, which could detrimentally affect surrounding vegetation.