Mangrove Zone Research Articles

Butterflies of Sundarban Biosphere Reserve, West Bengal, eastern India: a preliminary survey of their taxonomic diversity, ecology and their conservation

The Indian Sundarbans, part of the globally famous deltaic eco-region, is little-studied for butterfly diversity and ecology. The present study reports 76 butterfly species belonging to five families, which is a culmination of 73 species obtained from surveys conducted over a period of three years (2009-2011) in reclaimed and mangrove forested areas and three species obtained from an earlier report. Six of these species are legally protected under the Indian Wildlife (Protection) Act, 1972. Random surveys were employed for both the study areas, supplemented by systematic sampling in reclaimed areas. The reclaimed and forested areas differed largely in butterfly richness (Whittaker’s measure of ß diversity = 0.55). For sample-based rarefaction curves, butterfly genera showed a tendency to reach an asymptote sooner than the species. Numerous monospecific genera (77.19% of the taxa) resulted in a very gentle but non-linear positive slope for the species-genus ratio curve. A species-genus ratio of 1.33 indicated strong intra-generic competition for the butterflies of the Indian Sundarbans. Mangrove areas were species poor, with rare species like Euploea crameri, Colotis amata and Idea agamarshchana being recorded in the mangrove area; while Danaus genutia was found to be the most frequent butterfly. Butterfly abundance was very poor, with no endemic species and the majority (53.9% of the taxa; n=41) were found locally rare. The changing composition of butterflies in the once species-poor mangrove zone of the fragile Sundarbans may interfere with their normal ecosystem functioning.

STRUKTUR DAN FISIOGNOMI VEGETASI MANGROVE DI REMPANG CATE KOTA BATAM

Structure and physiognomy of mangrove strongly influenced by the zonation that occurred in the area of mangroves growth. The differences of zona growth will effect to differences in the structure and composition of vegetation. There are three zones in the mangrove area, which is caused by the difference of flooding which also resulted in the difference to the salinity. The differences of growth zone will performed to the type vegetation performance (Physiognomy). This study is aims to prove the mangrove’s physiognomy that taken in the coastal area of Rempang Cate Batam, on March 2014 to June 2014. This study was a survey with data collection using a vertical transect plots 100 m. Based on the research that has been done obtained difference vegetation physiognomy stands for every level of growth in each zone growth. Proximally found 13 species of mangroves in 8 families. The results of the analysis of the vegetation on the trees growth level are, Ceriops decandra have the greatest significance important value 167.55% on sapling (juvenille ) level is dominated by Rhizophora apiculata 120%, and seedling growth level dominated by Rhizophora apiculata 186.80%. Keywords: Structure and physiognomy, mangrove zonation

The Ecological Behaviour of Community in Preserving Land Use in Coastal Areas of Parepare

Abstract: In 2011, the number of population of Pare-Pare City is around 130, 582 people which are spread out over four districts in the city of Pare-Pare. Most of the districts are located in the coastal region. The data illustrate that the coastal region in Pare-pare seems increasingly pressured by high population density in coastal areas prone to environmental degradation. From these communities, it seems that they are more likely to behave non-ecologically, such as throwing garbage in water bodies, building a house on the water, diminishing mangrove zones and various trends of environmental degradation which were caused by human action itself. This study use quantitative approach and hypotheses testing combined with survey method that uses questionnaire instruments. Instruments that used in this study were developed by the researchers. They include several questionnaires such as those of community's ecological behavior, their knowledge about environment, local wisdom, locus of control and their environmental attitude. Moreover, based on SEM analysis method, it can be concluded that the variables of environmental knowledge (X1), local wisdom (X2) and locus control (X3) have direct and significant impacts toward the environmental attitude (Y1). Furthermore, those variables also have similar impacts to the ecological behavior (Y2), whereas the variables of environmental attitude (Y1) do not have direct impact to the ecological behavior (Y2). This is shown with the significance value p-value>0.05. © 2014 Asian Network for Scientific Information.

Resource Partitioning by Mangrove Bird Communities in North Australia

AbstractMangrove bird communities in north Australia comprise relatively few passerine species compared with other arboreal habitats in the region. Mangroves are dominated by a few tree species and there are potentially few resource axes available for partitioning by terrestrial birds. Competition for limited resources is predicted to cause strong niche differentiation and a highly structured, but low diversity, bird assemblage. Using multivariate and bipartite network analyses based on 1771 foraging observations (33% of 5320 behavioral observations), we examined resource partitioning by 20 terrestrial bird species in mangroves of north Australia. The mangrove bird community largely comprised generalist insectivores that partitioned insects by size with moderate‐to‐high interspecific overlap in diet. Gleaning for insects was the most common foraging mode. Few species specialized on nectar. Flowers of one or more mangrove species were available in every month of the year and insect abundance was correlated with flowering peaks. Niche differentiation by birds was determined by food type and foraging mode more than by broad spatial (mangrove zones) or temporal (seasonal) segregation of the use of resources. There was little evidence of bird species saturation or species sorting, suggesting loose species packing and a lesser role than expected for species interactions and interference competition in structuring the bird assemblage in mangroves.

Mangrove Evolution in Mayotte Island, Indian Ocean: A 60-year Synopsis Based on Aerial Photographs

The Island of Mayotte, in the Indian Ocean, is characterized by a highly diversified shoreline comprising numerous mangrove zones set within a vast coral reef and lagoon complex. An analysis of aerial photographs covering the period from 1950 to 2011 shows marked variability in the evolution of these mangroves and clear spatial differences in the dynamics of these communities over the 60-year period of analysis. The northern part of the island shows stability or a slight increase in mangrove area whereas the southern and western shores of the island have been characterized by a clear regression in mangroves. The total surface area of mangroves on Mayotte (7.03 km2 in 2011) has diminished overall by about 5 %, a relatively moderate figure relative to the world context of increasing diminution of mangrove area. The pattern of evolution of mangroves in Mayotte is explained jointly by development pressures on the coast and spatial variability in mangrove recovery determined by hydrological conditions and exposure to waves on this reef-fringed island. Mayotte Island acquired the status of a French administrative department in 2011 subject to both French and European Community legislation on the environment. In consequence, mangroves are now much better protected from future urbanization.

Establishing relative sea level trends where a coast lacks a long term tide gauge

Vulnerability assessment of coastal areas to projected sea level rise requires incorporation of historic trends in relative sea level change as an exposure factor. Most shorelines of developing countries lack long term tide gauges, such as the Pacific Islands region, which are especially vulnerable to climate change impacts. This study has the objective of demonstrating how long-term relative sea level trends can be derived from proxy records, on the tectonically unstable main island of Fiji. At Tikina Wai on the western coast, while elevations of present mangrove zones of Rhizophora stylosa, Rhizophora samoensis and Bruguiera gymnorrhiza were <1.2 m around mean sea level, sediment cores down to 3 m showed mangrove occurrence meters lower than they can grow today. Pollen analysis identified past locations of these mangrove species zones, and the present day elevations of the species were used to reconstruct past sea levels. Results of this study showed that relative sea-level has been slowly rising for the last several centuries at about 2.1 mm a−1, yet mangrove communities have remained resilient with nearly equivalent net sedimentation rates, though with some zone retreat landwards. With such local subsidence, the Tikina Wai district is more exposed to future sea level rise projections than stable coastal areas elsewhere, with additional exposure in having a micro-tidal range. Adaptation actions identified to address this risk include enhancement of sedimentation under mangrove communities through coastal and catchment planning to remove obstructions to sediment supply, reducing non-climate stresses to increase organic production, and replanting of degraded areas. Such information on relative sea level trends can be used to identify where adaptation resources are best concentrated.

Mangrove zonation and utilization by the local people in Ajuy and Pedada Bays, Panay Island, Philippines

The study was conducted in order to establish and describe the mangrove zones and the resource uses in Ajuy and Pedada Bays, Panay Island, Iloilo, Philippines. Plot or quadrat method coupled with informal community folk interviews were done. Cluster and principal component analyses indicated four mangrove zones: Zone 1 – Avicennia–Sonneratia zone; Zone 2 – Avicennia–Rhizophora zone; Zone 3 – Avicennia–Excoecaria–Bruguiera–Ceriops zone; and Zone 4 – Avicennia zone. Fishpond establishment was the main dominant activity. Additionally, subsistent and apparently sustainable localized fuel wood gathering was still evidently practiced by the fisherfolks. With the bays’ natural mangrove landscape greatly deformed and transformed, the study recommends two strategies which could serve as its turning point leading to a more sustainable utilization and conservation of the mangroves. First we recommend the creation of a landscape corridor and secondly, adoption of a mangrove aquasilviculture system as an alternative to the current extensive fishpond practice. Implementation of these two strategies can be facilitated by a strong biodiversity education program and a local ordinance.

Vegetation and sediment characteristics in an expanding mangrove forest in New Zealand

Mangrove expansion in inlets has been widely observed in the North Island of New Zealand over recent decades. There is just one mangrove species in New Zealand, Avicennia marina var. resinifera. Our main objective was to investigate the response of mangroves to sedimentary patterns. Remote sensing and GIS was used to quantify the change in mangrove area. Vegetation and sediment characteristics were studied across seasons from December 2009 to August 2010. Comparison of digital images in 1940 and 2003 revealed that the mangrove area in our study inlet had increased by 21%. The mangroves created a rim of high fringe mangroves surrounding high-density but low height trees in the interior. The relatively low pH level and seasonally fluctuating pore water total dissolved salt (TDS) concentration reveal potentially stressful conditions in the interior mangrove zone, which may influence the forest structure in the interior.Total organic carbon (TOC), δ13Corg and δ15N along the transect indicated an increase of autochthonous organic carbon in the surface substrate landwards. The highest carbon accumulation was not observed in the fringe zone, in spite of it having the most vigorous growth of mangroves. Instead, the highest δ13C value (−23.36 ± 0.42‰, averaged over depth) and lowest C:N ratio (13.1 ± 2.0) in the fringe mangrove core reflected the preservation of allochthonous organic material in the fringe zone. Under the protection of seaward fringe mangroves, mangrove-derived carbon is retained and stored in the interior sediment.

Sedimentation, elevation and marsh evolution in a southeastern Australian estuary during changing climatic conditions

Mangrove and salt marsh vertical accretion and surface elevation change was measured at Kooragang Island within the Ramsar-listed Lower Hunter estuarine wetlands in New South Wales, Australia, using surface elevation tables and marker horizons over a ten-year period. We surveyed mangrove, salt marsh and a zone of mangrove encroachment into salt marsh. The period of analysis was dominated by El Niño (drought) climatic conditions, though included a series of east coast low pressure systems and associated storms over the central coast of NSW in June 2007. The storms may have initially caused scouring of sediments in the mangrove zone, followed by significant accretion within both the mangrove and salt marsh during the six months following the storms, with most of this accretion corresponding to spring tides several months after the storms. These accretion events were not accompanied by an equivalent elevation change, and robust elevation trends over the study period in mangrove and salt marsh indicate that the storms may have had little impact on the longer-term elevation dynamics within both the mangrove and salt marsh at Kooragang Island. Elevation dynamics in these zones appear to be regulated by vertical accretion over longer time periods and modulated by hydrology at shorter temporal scales. Elevation declined in the mangrove encroachment zone despite continued vertical accretion and we propose that this discrepancy may be associated with expansion of tidal creeks near the zone of mangrove encroachment or loss of salt marsh vegetation. This pattern of encroachment is consistent with observations from sites throughout the region and may be related to climatic perturbations (El Niño Southern Oscillation) rather than directly attributed to the storms.

Numerical study of the sensitivity of mangroves in reducing storm surge and flooding to hurricane characteristics in southern Florida

The sensitivity of the mangrove effect on reducing storm surge flooding to hurricane characteristics is investigated by using the numerical model Coastal and Estuarine Storm Tide (CEST). First, the attenuation of storm surge by mangroves is incorporated into the model by updating Manning’s coefficient based on the National Land Cover Dataset (NLCD) 2001. Then CEST is verified by comparing the model results with field observations in South Florida for Hurricane Wilma. Secondly, a set of numerical experiments using synthetic hurricanes with different intensity, forward speed, radius of maximum wind speed and travel direction are conducted for the sensitivity study. Results indicate that storm surge magnitudes and flooding areas are reduced by the mangrove zone more for fast moving hurricanes than slow moving hurricanes in the west coast of South Florida. In addition, increasing hurricane intensity and hurricane size lower the effect of mangroves on attenuating storm surge and reducing the flooding area. The mangrove zone plays a more effective role in reducing flooding areas from hurricanes that travel from east to west than from hurricanes that travel from west to east. The mangrove reduction effect is most sensitive to changes in hurricane forward speed. A 6.7m/s to 2.2m/s decrease in forward speed can result in a decrease in flood area reduction by mangroves that is equivalent to the decrease in flood area reduction by mangroves from Category 3 to 5 hurricanes.

Site-specific and integrated adaptation to climate change in the coastal mangrove zone of Soc Trang Province, Viet Nam

The dynamic coastline of Soc Trang Province in the Mekong Delta of Viet Nam is in most parts protected from erosion, storms and flooding by a narrow belt of mangroves. However, the unsustainable use of natural resources and development in the coastal zone is threatening the protection function of this forest belt. This situation is exacerbated by the impacts of climate change, particularly by the increased intensity and frequency of storms, floods and by rising sea levels. Based on analysis of past experience of mangrove planting and historical changes in mangrove cover, an integrated and site-specific approach to adaptation to climate change has been put in place, which comprises mangrove planting and rehabilitation with emphasis on resilience to climate change, and participatory involvement of local communities in effective mangrove management and protection through co-management. To address uncertainties associated with the impacts of climate change, testing of new mangrove planting techniques has started. This includes mimicking successful natural regeneration for small-scale planting in sites with high wave energy and transformation of existing even-aged plantations into more diverse forests—both in terms of structure and species composition. The pre-requisite for mangrove rehabilitation in erosion sites has successfully been put in place: breakwaters made from bamboo have reduced erosion and stimulated sedimentation. The design and construction of the wave-breaking structures, which was based on a numerical model which simulates hydrodynamics and shoreline development, ensures that downdrift erosion can be avoided as far as possible. A comprehensive monitoring program has been established and initial results provide evidence for the effectiveness of the bamboo breakwaters. Early experience shows that co-management is an effective way of maintaining and enhancing the protection function of the mangrove forest belt and at the same time providing livelihood for local communities. Payment for ecosystem services contributes to sustainability of co-management as well as livelihood improvement.

Influence of mangrove zonation on CO2 fluxes at the sediment–air interface (New Caledonia)

Mangroves are the major ecosystems of tropical and subtropical coastlines. They are considered as a sink for atmospheric CO2 because they are characterized both by high net primary production, and by low rates of organic matter decomposition. However, a recent reassessment of the global mangrove budget suggests that organic carbon sinks have been underestimated, notably CO2 efflux from sediments and creek waters, and tidal export of dissolved inorganic carbon. Our objective was to understand the influence of mangrove zonation on the magnitude of CO2 fluxes at the sediment–air interface. Transparent and opaque dynamic closed chamber systems, coupled with an infra-red gas analyzer were used to measure CO2 fluxes. In addition, the physico-chemical properties (salinity, redox potential) of pore waters were determined, as well as the carbon content and the origin of surface sediments (Chlorophyll-a and δ13C). Depending on the type of measurement (in the dark with or without biofilm, in the light with biofilm) and mangrove stand (saltflat, Avicennia sp., or Rhizophora spp.), mean surface sediment CO2 fluxes ranged between 40±56 and 199±95mmol·m−2·d−1. We suggest that these differences mainly result both from the organic content and the redox conditions of the sediments, which are influenced by the physiological activities of the root system, and by the position and the elevation of the stand in the intertidal zone. In addition, the quality and abundance of biofilm, which also vary with the mangrove stand, also appear to strongly affect sediment CO2 fluxes as a result of chemical (metabolism) and also physical (barrier) processes.

English

An attempt was made to study the benthic biodiversity in Pichavaram mangrove ecosystem, Southeast coast of India. Monthly (duplicate) sampling was done in 3 stations, (Station I - fresh water zone, Station II - core mangrove zone and Station III - marine zone) for a period of one year from January 2008 to December 2008. As many as 22 species of benthic macro fauna were recorded in the study area (16 species of polychaetes, 4 species of crustaceans and 2 species of molluscs). The population density varied between 394 and 23,888 number/m2. The species diversity was ranged from 1.52 to 3.87; species richness was from 1.24 to 4.09 and species evenness from 0.71 to 0.96. The maximum diversity was recorded in Station II and minimum in I. As observed in the conventional indices, the values of taxonomic and phylogenetic diversity were also more in Station II compared to Stations I and III. K- Dominance curve drawn paralleled the trend of diversity indices. Cluster and MDS showed the similarity in faunal composition stations within the zones. Key words: Mangroves, benthos, biodiversity, polychaetes.

Investigation of the sky optical conditions over selected stations in the major vegetation zones of Nigeria

Data-set of monthly global solar irradiance covering periods of at least 20 years over selected stations in Nigeria have been utilised to investigate the sky optical conditions over the five major vegetation zones of the country. The monthly variation of the clearness index for the selected stations has been investigated. Results show that the clearness index has its minimum in August which indicates reduced insolation during the monsoon month of August and maximum around November, December and February which shows high insolation. Statistical analysis of the monthly clearness index which gives the percentage depletion by the sky of the incoming insolation and the subsequent characterisation of the sky conditions based on this were also done. The results show that cloudy sky conditions prevail in the rainforest and mangrove swamp zones (e.g. Lagos, KT=0.40) while clear sky conditions prevail in the Sudan and Sahel vegetation (e.g. Nguru KT=0.66) and Kano (KT=0.65).

Avian species-assemblage structure and indicator bird species of mangroves in the Australian monsoon tropics

Mangroves are threatened worldwide yet they host diverse avian assemblages, especially in Australia. We examined the diversity, density and habitat use of birds in northern Australian mangroves to determine the influence of habitat patch-size and floristic composition on the structure of mangrove bird assemblages. Birds were surveyed using line transects in 13 mangrove patches. A total of 70 species was encountered, with a mean density of 11.7 individuals ha−1 including 11 of 12 known mangrove-dependent species. Many species were strongly associated with, and indicative of, a specific mangrove plant zone, emphasising the importance of the number of zones to bird diversity at a site. Of six functional guilds, the insectivores were most dominant, followed by nectarivores. Accordingly, avian assemblage structure was influenced by mangrove flowering phenology. Large mangrove patches supported fewer species than many smaller patches of equivalent combined area, and species richness was independent of area. In addition, there was no density compensation or a density—area relationship, implying that assemblages are not saturated with species and species interactions do not determine assemblage structure. In order of increasing importance, avian assemblage structure in mangroves is determined by the type and diversity of mangrove zones, the timing of mangrove flowering and the nature of the matrix surrounding mangroves.

Vulnerability to climate change of mangroves: assessment from cameroon, central Africa.

Intertidal mangrove ecosystems are sensitive to climate change impacts, particularly to associated relative sea level rise. Human stressors and low tidal range add to vulnerability, both characteristics of the Doula Estuary, Cameroon. To investigate vulnerability, spatial techniques were combined with ground surveys to map distributions of mangrove zones, and compare with historical spatial records to quantify change over the last few decades. Low technology techniques were used to establish the tidal range and relative elevation of the mapped mangrove area. Stratigraphic coring and palaeobiological reconstruction were used to show the longer term biological history of mangroves and net sedimentation rate, and oral history surveys of local communities were used to provide evidence of recent change and identify possible causes. Results showed that the seaward edge of mangroves had over two thirds of the shoreline experienced dieback at up to 3 m per year over the last three decades, and an offshore mangrove island had suffered 89% loss. Results also showed low net sedimentation rates under seaward edge mangroves, and restricted intertidal elevation habitats of all mangroves, and Avicennia and Laguncularia in particular. To reduce vulnerability, adaptation planning can be improved by reducing the non-climate stressors on the mangrove area, particularly those resulting from human impacts. Other priorities for adaptation planning in mangrove areas that are located in such low tidal range regions are to plan inland migration areas and strategic protected areas for mangroves, and to undertake management activities that enhance accretion within the mangroves.

Coral calcification under increasing atmospheric CO2 concentration and global warming in the southern South China Sea

Mangrove, seagrass, and coral habitats often lie adjacent to each other in the tropics and subtropics. Lateral carbon fluxes and their consecutive effects on CO2 dynamics and air–water fluxes along the ecosystem continuum are often overlooked. We measured the partial pressure of CO2 in water and associated biogeochemical parameters with a high temporal resolution and estimated air–water CO2 fluxes along the ecosystem continuum. Their lateral fluxes were estimated by using a biogeochemical mass-balance model. The results showed that the waters surrounding mangrove, seagrass, and coral habitats acted as a strong, moderate, and weak source of atmospheric CO2, respectively. The mangrove zone acted as a net source for TAlk, DIC, and DOC, but as a net sink for POC. The contribution of riverine and mangrove-derived OM was substantially high in mangrove sediment, indicating that net transport of POC towards the coastal sea was suppressed by the sediment trapping function of mangroves. The seagrass zone acted as a net source of all carbon forms and TAlk, whereas the coral zone acted as a net sink of TAlk, DIC, and DOC. The lateral transport of carbon from mangroves and rivers offset atmospheric CO2 uptake in the seagrass zone. DOC degradation might increase DIC, and other biogeochemical processes facilitate the functioning of the coral zone as a DOC sink. However, as a result of DIC uptake by autotrophs, mainly in the coral zone, the whole ecosystem continuum was a net sink of DIC and atmospheric CO2 evasion was lowered. We conclude that lateral transport of riverine and mangrove-derived DIC, TAlk, and DOC affect CO2 dynamics and air–water fluxes in seagrass and coral ecosystems. Thus, studies of lateral carbon fluxes at local and regional scales can improve global carbon budget estimates.

Effects of Waves by Boats on Mangrove in Dongzhai Harbor of Hainan

The effect of boat-generated waves on mangrove forests could be reflected by width change of tidal inlets by using satellite image in this study. Our results showed that the distributions of mangrove zone on the side of tidal inlets were degenerated by boat-generated waves from 2009 to 2011 in Dongzhai Harbor Mangrove Natural Reserve. The main reason of this change was strong erosion of tidal flat caused by the waves generated by high speed and frequencies boats for tourists. To protect the mangrove forests of the tidal inlets, the drive speed and pass frequencies of the boats in waterway should be restricted and decreased.

The role of mangroves in attenuating storm surges

Field observations and numerical simulations indicate that the 6-to-30-km-wide mangrove forest along the Gulf Coast of South Florida effectively attenuated storm surges from a Category 3 hurricane, Wilma, and protected the inland wetland by reducing an inundation area of 1800 km2 and restricting surge inundation inside the mangrove zone. The surge amplitude decreases at a rate of 40–50 cm/km across the mangrove forest and at a rate of 20 cm/km across the areas with a mixture of mangrove islands with open water. In contrast, the amplitudes of storm surges at the front of the mangrove zone increase by about 10–30% because of the “blockage” of mangroves to surge water, which can cause greater impacts on structures at the front of mangroves than the case without mangroves. The mangrove forest can also protect the wetlands behind the mangrove zone against surge inundation from a Category 5 hurricane with a fast forward speed of 11.2 m/s (25 mph). However, the forest cannot fully attenuate storm surges from a Category 5 hurricane with a slow forward speed of 2.2 m/s (5 mph) and reduced surges can still affect the wetlands behind the mangrove zone. The effects of widths of mangrove zones on reducing surge amplitudes are nonlinear with large reduction rates (15–30%) for initial width increments and small rates (<5%) for subsequent width increments.

Interactions between mangroves and exotic Spartina in an anthropogenically disturbed estuary in southern China

Cordgrass (Spartina alterniflora) was introduced to China in 1979 from the United States for reducing coastal erosion. It grows vigorously in China and has spread over much of the Chinese coast, from Leizhou Peninsula to Liaoning, a range of more than 19 degrees of latitude. On the southern coast of China, S. alterniflora has invaded mangrove-dominated habitats during the last two decades, but little is known about interactions between native mangroves and invasive S. alterniflora. We studied the distribution and competitive interactions between native mangroves and S. alterniflora in the Zhangjiang Estuary at four tidal sites along a salinity gradient: oligohaline upstream, mesohaline, polyhaline, and euhaline downstream. S. alterniflora occurred at all four sites, and several mangrove species occurred at all but the downstream euhaline site. S. alterniflora has invaded the estuary widely and has spread to the lower tidal margins of mangroves. It has not invaded mangrove areas with a closed canopy but has established in the mangrove zone where the canopy was opened by human disturbance. Ramets of S. alterniflora transplanted into the understory of mangrove stands with closed canopies died within 10 weeks, but 37.5% survived and grew well on open mud flats. S. alterniflora had virtually no competitive effect on mangrove seedlings planted at the upstream oligohaline site. However, S. alterniflora competitively reduced biomass of mangrove seedlings to 33% over a period of 14 weeks at the mesohaline and polyhaline sites where human disturbance has opened the mangrove canopy. In contrast, S. alterniflora marginally facilitated growth and survival of experimental seedlings at the downstream euhaline site. In China, mangroves occur along the coastline south of Whenzhou, but they have been severely disturbed and removed widely, mainly by mariculture activities. Natural vegetation patterns and our experimental results suggest that, without intervention, S. alterniflora could gradually replace these mangroves in mid-salinity regions of Chinese estuaries.