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Changes in mangrove vegetation area and character in a war and land use change affected region of Vietnam (Mui Ca Mau) over six decades
... Then, LULCs were classified for previous images based on spectral signature and change information of the surface reflectance data. This method has been used commonly in previous studies for monitoring mangroves changes in Mekong Delta using remote sensing (Tran et al. 2015; Van et al. 2015;Hong et al. 2019;Hauser et al. 2020). Satellite classification considered six dominant LULC types within CMCNP including water bodies (rivers, canals, and the sea), bare land (land surfaces that are devoid of any type of land covers), residential area (impervious surface), aquaculture land (water and soil surface that are used for aquaculture), sparse mangrove (mangrove coverage is less than 70%), and dense mangrove (mangrove coverage was higher than 70%) (Vo et al. 2013). ...
... The previous studies using satellite images for mangrove classification accepted the overall accuracy as approximately as or higher than 80%. For example, Landsat images in Ca Mau were classified with overall accuracies ranging from 77.5% to 83.5% (Van et al. 2015). Besides, another study used Landsat images with the overall accuracies of 1988, 1998, 2008, and 2018 were 81.2%, 83.3%, 78.3%, and 81.9%, respectively (Hong et al. 2019). ...
... Particularly, dense mangroves decreased obviously from 3,324 ha (21.8%) in 1989 to 1,201 (7.9%) ha in 1995, and then increased to 3,667 ha (24%) in 1999. The reduction of shrimp production, the effort of afforestation (nearly 53,000 ha of mangroves by the government and 25,262 ha by foreign-funded projects were planted in Ca Mau during 1990s), and the preparation for the establishment of CMCNP contributed to the rehabilitation of mangroves in the late 1990s (Cuong 2012; Van et al. 2015). Sparse mangroves fluctuated per sub-period. ...
The study aims to assess the effectiveness of mangrove conservation in Ca Mau Cape National Park (CMCNP) during 1973–2018 using remote sensing and landscape metrics. The maximum likelihood method was used to classify time-series Landsat images with overall accuracy ranging from 87.8% to 90.3% and Kappa from 0.83 to 0.88. Additionally, landscape structure which expresses the spatial pattern and the connections between landscape elements such as number, size, and shape were assessed using landscape metrics including Number of patches, Landscape Shape, Largest Patch, Cohesion, Core, Contiguity, and Contagion index. The results showed that mangroves increased by 1,078 ha (7%), and the landscape structure was simple in the first period (1973–1979). In the second period (1979–2003), mangroves decreased by 1,411 ha (9.2%) during 1989–1995, and then they increased by 4,564 ha (29.9%) from 1995 to 2003. The landscape structure was fragmented, disconnected, and had irregular shapes during the beginning but improved at the late phase. In the third period (2003–2018), mangroves increased by 1,596 ha (10.5%). In which, dense mangroves increased by 2,500 ha (16.4%). And sparse mangroves decreased by 904 ha (5.9%). The landscape structure was more homogenous and connected than the second period. Since CMCNP was established in 2003, mangroves have enlarged year by year. The landscape structure became more aggregated. These proved the effectiveness of mangrove conservation in both quality and quantity.
... A study on changing rainfall patterns across the Mekong Delta by Lee and Dang (2018) found that climate variability has affected the temporal and spatial distribution of rainfall patterns in three recent decades. Van et al., 2015). Therefore, it is necessary to establish the rainfall IDF curves to support the prediction and design of engineering infrastructures. ...
... The study area is mostly located in the Ca Mau province of Vietnam, which lies between 08°3 3 0 À9°35 0 N latitudes and 104°42 0 À105°24 0 E longitudes, and the location of Ca Mau province on the map of Vietnam is shown in Figure 1. It covers an area of 5,331 km 2 , constituting 13.13% of the Mekong Delta with an average elevation of 0.5 m above sea level (Deb et al., 2015;Van et al., 2015). Ca Mau province consists of a 254 km coastline where flooding has frequently occurred in recent years (Lee and Dang, 2018;Vu et al., 2018). ...
... Ca Mau province consists of a 254 km coastline where flooding has frequently occurred in recent years (Lee and Dang, 2018;Vu et al., 2018). Topographically, the area is a low coastal plain, divided by a dense system of natural channels (Lee and Dang, 2019a;Van et al., 2015). The flow regime, therefore, is strongly dominated by tidal flows from the East Sea, the Gulf of Thailand and flow from the upstream Mekong River [Lee and Dang, 2020; Ministry of Natural Resources and Environment (MNRE), 2016]. ...
... A study on changing rainfall patterns across the Mekong Delta by Lee and Dang (2018) found that climate variability has affected the temporal and spatial distribution of rainfall patterns in three recent decades. Van et al., 2015). Therefore, it is necessary to establish the rainfall IDF curves to support the prediction and design of engineering infrastructures. ...
... The study area is mostly located in the Ca Mau province of Vietnam, which lies between 08°3 3 0 À9°35 0 N latitudes and 104°42 0 À105°24 0 E longitudes, and the location of Ca Mau province on the map of Vietnam is shown in Figure 1. It covers an area of 5,331 km 2 , constituting 13.13% of the Mekong Delta with an average elevation of 0.5 m above sea level (Deb et al., 2015;Van et al., 2015). Ca Mau province consists of a 254 km coastline where flooding has frequently occurred in recent years (Lee and Dang, 2018;Vu et al., 2018). ...
... Ca Mau province consists of a 254 km coastline where flooding has frequently occurred in recent years (Lee and Dang, 2018;Vu et al., 2018). Topographically, the area is a low coastal plain, divided by a dense system of natural channels (Lee and Dang, 2019a;Van et al., 2015). The flow regime, therefore, is strongly dominated by tidal flows from the East Sea, the Gulf of Thailand and flow from the upstream Mekong River [Lee and Dang, 2020; Ministry of Natural Resources and Environment (MNRE), 2016]. ...
... Ca Mau Peninsula is known for LTRs and represents Vietnam's most vulnerable to climate variability area (Deb et al., 2015;Lee and Dang, 2019a). In recent years, several HREs have led to flooding in the entire Ca Mau City and nearby areas including in 2006 (109 mm), 2008 (134.9 mm), 2014 (111.4 mm), 2015 (189.2 mm) and especially in 2019 (up to 212 mm), which are identified as warnings about negative ICV in Ca Mau Peninsula (Deb et al., 2015;Lee and Dang, 2020;Van et al., 2015). Therefore, it is necessary to establish the rainfall IDF curves to support the prediction and design of engineering infrastructures. ...
... The study area is mostly located in the Ca Mau province of Vietnam, which lies between 08°3 3 0 À9°35 0 N latitudes and 104°42 0 À105°24 0 E longitudes, and the location of Ca Mau province on the map of Vietnam is shown in Figure 1. It covers an area of 5,331 km 2 , constituting 13.13% of the Mekong Delta with an average elevation of 0.5 m above sea level (Deb et al., 2015;Van et al., 2015). Ca Mau province consists of a 254 km coastline where flooding has frequently occurred in recent years (Lee and Dang, 2018;Vu et al., 2018). ...
... Topographically, the area is a low coastal plain, divided by a dense system of natural channels (Lee and Dang, 2019a;Van et al., 2015). The flow regime, therefore, is strongly dominated by tidal flows from the East Sea, the Gulf of Thailand and flow from the upstream Mekong River [Lee and Dang, 2020; Ministry of Natural Resources and Environment (MNRE), 2016]. ...
Purpose
The purpose of this study is to evaluate the rainfall intensities and their limits for durations from 0.25 to 8 h with return periods from 2 to 100 years for Ca Mau City in Vietnam.
Design/methodology/approach
First, the quality of the historical rainfall data series in 44 years (1975–2018) at Ca Mau station was assessed using the standard normal homogeneity test and the Pettitt test. Second, the appraised rainfall data series are used to establish the rainfall intensity-duration-frequency curve for the study area.
Findings
Based on the findings, a two-year return period, the extreme rainfall intensities (ERIs) ranged from 9.1 mm/h for 8 h rainstorms to 91.2 mm/h for 0.25 h. At a 100-year return period, the ERIs ranged from 18.4 mm/h for 8 h rainstorms to 185.8 mm/h for 0.25 h. The results also show that the narrowest uncertainty level between the lower and upper limits recorded 1.6 mm at 8 h for the two-year return period while the widest range is at 42.5 mm at 0.25 h for the 100-year return period. In general, the possibility of high-intensity rainfall values compared to the extreme rainfall intensities is approximately 2.0% at the 100-year return period.
Originality/value
The results of the rainfall IDF curves can provide useful information for policymakers to make the right decisions in controlling and minimizing flooding in the study area.
... For example, the Mekong Delta is the site of the largest ecosystem restoration ever undertaken. About 55% of the Mekong Delta mangrove forest was destroyed in the USA-Vietnam war between 1964 and 1970 through use of the herbicide Agent Orange [42]. The Vietnamese subsequently restored 1,500 km 2 of mangrove in the Delta between 1978 and 1998 [42], planting on average about 6,000 ha per year. ...
... About 55% of the Mekong Delta mangrove forest was destroyed in the USA-Vietnam war between 1964 and 1970 through use of the herbicide Agent Orange [42]. The Vietnamese subsequently restored 1,500 km 2 of mangrove in the Delta between 1978 and 1998 [42], planting on average about 6,000 ha per year. The planted forest has a carbon stock estimated at 889 ± 111 Mg C ha −1 , comparable to that reached by natural forests [43]. ...
... For example, the Mekong Delta is the site of the largest ecosystem restoration ever undertaken. About 55% of the Mekong Delta mangrove forest was destroyed in the USA-Vietnam war between 1964 and 1970 through use of the herbicide Agent Orange [42]. The Vietnamese subsequently restored 1,500 km 2 of mangrove in the Delta between 1978 and 1998 [42], planting on average about 6,000 ha per year. ...
... About 55% of the Mekong Delta mangrove forest was destroyed in the USA-Vietnam war between 1964 and 1970 through use of the herbicide Agent Orange [42]. The Vietnamese subsequently restored 1,500 km 2 of mangrove in the Delta between 1978 and 1998 [42], planting on average about 6,000 ha per year. The planted forest has a carbon stock estimated at 889 ± 111 Mg C ha −1 , comparable to that reached by natural forests [43]. ...
Mangroves have been converted and degraded for decades. Rates of loss have declined over the past decades, but achieving resilient coastlines requires both conservation and restoration. Here, we outline the challenges for the global restoration of mangroves and what actions could enhance restoration. Ambitious global targets for mangrove restoration, if successful, could deliver global benefits of carbon sequestration, fisheries production, biodiversity, and coastal protection. However, large-scale mangrove planting efforts have often failed, and smaller projects may not deliver landscape-scale benefits, even though they are more suited to community management. Solutions to achieving global targets include reducing risks of large projects and increasing the uptake and effectiveness of smaller projects. Sustainable mangrove restoration requires investment in capacity building in communities and institutions, and mechanisms to match restoration opportunities with prospective supporters and investors. Global reporting standards will support adaptive management and help fully understand and monitor the benefits of mangrove restoration.
... The coastal areas were chosen because they include the typical and important wetland ecosystems of the MD, which are coastal mangrove forest and peatland Melaleuca forest wetlands. Mangrove forest in Ca Mau province, especially in Ngoc Hien district, is the largest and includes the last remaining old-growth mangrove forests in Vietnam, including the internationally acknowledged UNESCO Biosphere Reserve and RAMSAR site of Ca Mau Cape [44,45]. In addition, the Melaleuca forest of the region constitutes a large proportion of the total amount of this type of wetland in the MD. ...
... Mangrove forests in coastal zones of the MD have been decreasing over recent decades [84,85]. Our findings reveal that mangrove forests overall decreased by around −4.9% (-30 km 2 ), resulting in an annual loss of -0.20% (-1.2 km 2 ) for the period 1995/2020, which was relatively minor compared with the preceding decades [32,45,86]. For the period 2002/2013, the annual loss of mangrove forests was -0.41%, which is consistent with the findings of other studies in Ca Mau province in the MD over a similar period [43,87]. ...
Coastal wetlands in the Mekong Delta (MD), Vietnam, provide various vital ecosystem services for the region. These wetlands have experienced critical changes due to the increase in regional anthropogenic activities, global climate change, and the associated sea level rise (SLR). However, documented information and research on the dynamics and drivers of these important wetland areas remain limited for the region. The present study aims to determine the long-term dynamics of wetlands in the south-west coast of the MD using remote sensing approaches, and analyse the potential factors driving these dynamics. Wetland maps from the years 1995, 2002, 2013, and 2020 at a 15 m spatial resolution were derived from Landsat images with the aid of a hybrid classification approach. The accuracy of the wetland maps was relatively high, with overall accuracies ranging from 86–93%. The findings showed that the critical changes over the period 1995/2020 included the expansion of marine water into coastal lands, showing 129% shoreline erosion; a remarkable increase of 345% in aquaculture ponds; and a reduction of forested wetlands and rice fields/other crops by 32% and 73%, respectively. Although mangrove forests slightly increased for the period 2013/2020, the overall trend was also a reduction of 5%. Our findings show that the substantial increase in aquaculture ponds is at the expense of mangroves, forested wetlands, and rice fields/other crops, while shoreline erosion significantly affected coastal lands, especially mangrove forests. The interaction of a set of environmental and socioeconomic factors were responsible for the dynamics. In particular, SLR was identified as one of the main underlying drivers; however, the rapid changes were directly driven by policies on land-use for economic development in the region. The trends of wetland changes and SLR implicate their significant effects on environment, natural resources, food security, and likelihood of communities in the region sustaining for the long-term. These findings can assist in developing and planning appropriate management strategies and policies for wetland protection and conservation, and for sustainable development in the region.
... There has been a long history of mangrove reforestation in Vietnam dating back to its French colonial days. Much damage was done to the mangroves of Vietnam by herbicides used for defoliation by US military forces during the war in Vietnam ( Van et al., 2015). (Hong, 2000). ...
... to Van et al. (2015), the mangrove area in Ca Mau province was 71,435 ha in 195371,435 ha in , 33,083 ha in 199271,435 ha in , and 46,712 ha in 201171,435 ha in . The changes between 195371,435 ha in and 1992 reflect losses during the war and later to shrimp farming and gains after 1992 resulted from mangrove reforestation programs and other conservation efforts. ...
Globally, shrimp farms occupied an estimated 3.490 million hectares (Mha) of land and operated 2.426 Mha of production ponds in 2018. Extensive shrimp farms used 1.804 Mha of farm area (1.377 Mha of production ponds), but produced 11.4% of global shrimp production. An estimated 1.718 Mha of land was required to produce ingredients for feeds used in semi-intensive and intensive shrimp farming, bringing total land use to 5.160 Mha. Extensive production is located in the intertidal zone and much of this land formerly was or still is in mangrove areas. Expansion of shrimp farms into mangrove areas has slowed. Mangrove areas are inferior sites for shrimp farms, and governments have imposed stricter regulations to protect mangroves. Shrimp farming in mangrove areas is unnecessary to supply the global shrimp demand. Scenarios for increasing global shrimp production without further increase in shrimp farm area are presented. But, if the demand for shrimp continues to increase, it will be impossible to freeze the total land footprint for farmed shrimp, because the land needed for feed presently is roughly equal to the direct land use for shrimp farms. Direct land use for farms can be frozen through greater production pond yields.
... The study area focuses on Vietnam's southernmost district, Ngoc Hien, Ca Mau province, located in the Southern Mekong Delta between latitude 8 • 33 -8 • 45 N and longitude 104 • 42 45"-105 • 3 54"E, spanning an area of 743 km 2 (See Figure 1). The district has been well-studied for its importance as a major aquaculture hub and its significant reserves of Vietnam's largest and last remaining old-growth mangrove forests, including the internationally acknowledged RAMSAR site of Mui Ca Mau (2012) and UNESCO Biosphere Reserve (2009) [42][43][44]. The landscape supports both ecologically important mangrove ecosystems and the economic livelihoods based on aquaculture. ...
... The study area focuses on Vietnam's southernmost district, Ngoc Hien, Ca Mau province, located in the Southern Mekong Delta between latitude 8°33′-8°45′N and longitude 104°42′45″-105°3′54″E, spanning an area of 743 km 2 (See Figure 1). The district has been well-studied for its importance as a major aquaculture hub and its significant reserves of Vietnam's largest and last remaining old-growth mangrove forests, including the internationally acknowledged RAMSAR site of Mui Ca Mau (2012) and UNESCO Biosphere Reserve (2009) [42][43][44]. The landscape supports both ecologically important mangrove ecosystems and the economic livelihoods based on aquaculture. ...
Ecosystem services offered by mangrove forests are facing severe risks, particularly through land use change driven by human development. Remote sensing has become a primary instrument to monitor the land use dynamics surrounding mangrove ecosystems. Where studies formerly relied on bi-temporal assessments of change, the practical limitations concerning data-availability and processing power are slowly disappearing with the onset of high-performance computing (HPC) and cloud-computing services, such as in the Google Earth Engine (GEE). This paper combines the capabilities of GEE, including its entire Landsat-7 and Landsat-8 archives and state-of-the-art classification approaches, with a post-classification temporal analysis to optimize land use classification results into gap-free and consistent information. The results demonstrate its application and value to uncover the spatio-temporal dynamics of mangrove forests and land use changes in Ngoc Hien District, Ca Mau province, Vietnamese Mekong delta. The combination of repeated GEE classification output and post-classification optimization provides valid spatial classification (94–96% accuracy) and temporal interpolation (87–92% accuracy). The findings reveal that the net change of mangroves forests over the 2001–2019 period equals −0.01% annually. The annual gap-free maps enable spatial identification of hotspots of mangrove forest changes, including deforestation and degradation. Post-classification temporal optimization allows for an exploitation of temporal patterns to synthesize and enhance independent classifications towards more robust gap-free spatial maps that are temporally consistent with logical land use transitions. The study contributes to a growing body of work advocating full exploitation of temporal information in optimizing land cover classification and demonstrates its use for mangrove forest monitoring
... The TSAVI was calculated using a soil adjustment factor [46]. WDRVI is an NDVI type, but NIR (this band was used to measure WDRVI) was rescaled by a factor ranging from 0.1-0.5. This index increased the linearity between the biomass and NIR, thus reducing the sensor saturation [68]. The contribution of VH was reflected in the ratio between VH and VV, and the remaining indices, which had been proven useful in previous studies [1,14], had a significant contribution to the overall estimation. ...
... With AGB values between 56.72 and 339.85 Mg ha -1 (average = 125.63 Mg ha -1 ), the predicted spatial pattern of the AGB value was consistent with actual observations [2,68]. The non-mangrove forested areas, such as bare land and agricultural land, were removed from the result of the AGB map. ...
Background
Advances in earth observation and machine learning techniques have created new options for forest monitoring, primarily because of the various possibilities that they provide for classifying forest cover and estimating aboveground biomass (AGB).
Methods
This study aimed to introduce a novel model that incorporates the atom search algorithm (ASO) and adaptive neuro-fuzzy inference system (ANFIS) into mangrove forest classification and AGB estimation. The Ca Mau coastal area was selected as a case study since it has been considered the most preserved mangrove forest area in Vietnam and is being investigated for the impacts of land-use change on forest quality. The model was trained and validated with a set of Sentinel-1A imagery with VH and VV polarizations, and multispectral information from the SPOT image. In addition, feature selection was also carried out to choose the optimal combination of predictor variables. The model performance was benchmarked against conventional methods, such as support vector regression, multilayer perceptron, random subspace, and random forest, by using statistical indicators, namely, root mean square error (RMSE), mean absolute error (MAE), and coefficient of determination (R²).
Results
The results showed that all three indicators of the proposed model were statistically better than those from the benchmarked methods. Specifically, the hybrid model ended up at RMSE = 70.882, MAE = 55.458, R² = 0.577 for AGB estimation.
Conclusion
From the experiments, such hybrid integration can be recommended for use as an alternative solution for biomass estimation. In a broader context, the fast growth of metaheuristic search algorithms has created new scientifically sound solutions for better analysis of forest cover.
... Researches using optical images to map and monitor mangrove forests showed that the optical images provided information on the environmental resources faster and more accurately (Thu and Populus 2007;Nguyen et al. 2013;Vo et al. 2013;Son et al. 2015; Van et al. 2015;Tran, Tran, and Kervyn 2015). However, optical data is highly dependent on the weather. ...
Soil microorganisms are highly diverse and perform multiple and beneficial roles in soil ecosystems. However, the study of microbial communities is inherently difficult because only one percent of microorganisms grow in culture. Hence, there is a need to explore techniques that result in identifying microbial strains and, consequently, the diversity of microorganisms in a certain community. This chapter presents various techniques ranging from the conventional, culture-dependent methods that can discover and describe the microorganisms’ morphology, to culture-independent methods that are molecular or genetic-based. Included also in the discussion are easy-to-follow and highly specific methodologies from soil collection, microbial isolation, DNA extraction, molecular and PCR analysis, and statistical procedures. Microbial DNA extraction for upland and lowland paddy are presented. The study of soil metagenomes using molecular markers and metagenomics is also discussed.
... In Ca Mau province, net change in mangrove area was -0.34% annually between 2004-2009, mainly due to mangrove loss (Hauser et al. 2017). Deforestation rates have been significantly higher in natural mangrove forests than in mangrove plantations (Van et al. 2015). To address these losses, the Government of Vietnam has developed and implemented many mangrove protection policies and called for international support in restoring, replanting and protecting its mangrove areas. ...
... In order to effectively protect and develop mangrove forests in Mui Ca Mau, it is necessary to review and develop forestry mechanisms and policies with clear objectives and orientations to encourage the formation of a forest management system with the participation of the State and local community. From the beginning of 1990, to slow the rate of deforestation across the [32,43]. This study indicates that land use change in Ca Mau was mainly due to conversion from forest to shrimp farms, settlements areas and public constructions. ...
Mangrove forest plays a very important role for both ecosystem services and biodiversity conservation. In Vietnam, mangrove is mainly distributed in the Mekong delta. Recently, mangrove areas in this region decreased rapidly in both quality and quantity. The forest became bare, divided and scattered into many small patches, which was a major driver of ecosystem degradation. Without a quantitative method for effectively assessing mangrove health in the regional scale, the sustainably conserving mangrove is the challenge for the local governments. Remote sensing data has been widely used for monitoring mangrove distributions, while the characterization of spatial metrics is important to understand the underlying processes of mangrove change. The objectives of this study were to develop an approach to monitor mangrove health in Mui Ca Mau, Ca Mau province of Vietnam by utilizing satellite image textures to assess the mangrove patterns. The research result showed that mangrove areas increased double by 2015, but the forest had become more fragmented. We can be seen those changes in land use mainly come from land conversion from forest to shrimp farms, settlements areas and public constructions. The conserving existing mangrove forest in Mui Ca Mau should consider the relations between mangrove health and influencing factors indicated in the manuscript.
... Vegetation is often monitored through remote sensing (Lucas et al., 2020;Madarasinghe et al., 2020aMadarasinghe et al., , 2020b which in many cases is used as a quantitative tool to study total vegetation cover or to break the latter down into cover per species (Van et al., 2015). In some cases, remote sensing is used to quantify biomass (Hamdan et al., 2014;Lucas et al., 2021). ...
Mangrove forests are reported to be invaded by invasive alien species (IAS). This study was therefore aimed at studying the level of distribution of the IAS, Acacia auriculiformis A. Cunn. ex Benth. in mangrove ecosystems in the southern coast of Sri Lanka and assessing the risk to periphery of mangrove forest by considering the Rekawa mangrove forest as a model site. Growth performances of two mangrove species; Rhizophora mucronata and Avicennia marina in the presence of Acacia plants were also tested under three different competition levels; low, moderate and high. According to the results, infestation of Acacia plants was significant in the southern coast of Sri Lanka, particularly in Matara and Hambantota districts (p<0.05). Species diversity determined as the Simpson diversity index was high (0.77) in the periphery of the Rekawa mangrove forest. Four true mangroves and two associates co-occurring with A. auriculiformis in the periphery could be observed during the field validation experiment. The highest seedling (15.4±2.2 m) and sapling (11.2±2.8 m) densities were reported for A. auriculiformis plants. Dominance, calculated as the importance value index of different species in the mangrove periphery varied from 18.0-120.6 and the latter highest was recorded for Acacia which has the highest relative density (42.1%) and the relative dominance (52.5%). The total leaf area of the Rhizophora plants grown in the high-competition level was significantly lower than that of the control plants while the dry weights at three different competition levels; were significantly higher (p<0.05) than the control. This could be due to the higher root biomass allocation. In Avicennia plants, cumulative shoot height, total leaf area and dry weight of the plants grown at the high-competition level were significantly lower than that of the control plants (p<0.05). A. auriculiformis plants grown with these true mangrove species better performed and did not show any significant deviation from the respective control plants. The level of survival of Acacia was significantly reduced at 25 psu (p<0.05). Early intervention and serious scrutiny are much needed to reverse the possible impacts of IAS on mangrove forests and the need for forest conservation is emphasized.
... These activities include shrimp aquaculture, agriculture, urban expansion, firewood collection, and timber and charcoal production (Duke et al., 2007;Lee et al., 2014;Goldberg et al., 2020). In many South and South-East Asian countries such as Sri Lanka, India, Bangladesh, Indonesia, Vietnam, the Philippines and Thailand, shrimp farming is known to be one of the major contributing factors causing mangrove loss Dahdouh-Guebas et al., 2006a; Van et al., 2015;Abdullah et al., 2016;Richards & Friess, 2016). ...
1. Among the several threats to the conservation of mangrove ecosystems in most
South Asian countries, shrimp farming is predominant. Since the introduction of
shrimp farming in Sri Lanka in the 1980s, mangroves on the island’s north-western
coast have been continually cleared to create new shrimp farms, leading to a
decline in the social-ecological services provided by the mangrove ecosystems.
2. Using aerial (1973) and satellite (1996–2020) images, this study assessed areal
changes in mangroves and shrimp farms in the Pambala-Chilaw lagoon complex and
Ihala Mahawewa, as well as the ecological footprint of shrimp farming in the study
area.
3. Mangroves around the Chilaw lagoon had decreased in areal extent by 45% from
1973 to 2020 of which 92% of this change was attributed to shrimp farming.
There was, however, a decrease in the areal extent of shrimp farms from 2001 to
2020, and a corresponding increase in mangroves from 2006 to 2020.
4. The ecological footprint of shrimp farming was assessed by comparing the
expected surface ratios with those recorded for shrimp farms with mangroves and
surface water bodies in the study area from 1973 to 2020. The results showed
that the current shrimp farming was unsustainable (i.e. high ecological footprint).
5. While the results support the current view that there is cause for cautious
optimism with mangrove conservation (as evidenced by an increase in mangrove
areal extent), it also reveals that semi-intensive shrimp farming in Sri Lanka and
probably other similar tropical countries is unsustainable.
6. If immediate actions such as effective regulation of shrimp farming activities and
mangrove restoration are not taken, the mangrove ecosystem will continue to
decline.
... Factors such as elevation, slope, distance to railway, and distance to waterway ranked lower, indicating that natural and traffic factors had less impact on the growth of construction land. Unlike previous studies, this study discovered that globalization, urbanization, and industrialization, which are the three most important human activities, ranked high in relative importance, indicating that human activities were still a dominant factor affecting the expansion of coastal construction land [61][62][63][64]. In Section 4.2, we analyze these three types of influencing factors in more detail. ...
Controlling land use change in coastal areas is one of the world’s sustainable development goals and a great challenge. Existing research includes in-depth studies of land use change in relatively developed regions, but research on economically less developed but fast-growing regions is lacking. Since the reform and opening up in Vietnam, the influences of globalization have prompted the economy of the coastal area to develop rapidly, making it one of the less developed but rapidly developing regions where human activities and global changes vigorously interact. Therefore, taking the coastal area of Vietnam as the study area, we used the land use change index and random forest model to analyze the spatial variations of land use change and its impact factors. The research shows that: (1) land use shows a trend of continuous and rapid increase in construction land, with the proportion of construction land increasing from 2.72% in 2000 to 4.40% in 2020. However, natural landscapes, such as forests and grasslands, are decreasing. (2) Land use also shows obvious spatial variation characteristics, which are mainly manifested in the differences in change rate, development intensity, and distribution characteristics. Among them, the region with the largest rate of change was the Central Coastal Area. The region with the highest development intensity is the Mekong River Delta. (3) The main factors affecting land use change are foreign direct investment (FDI), the industrialization index, and population. Based on that, we analyzed the mechanism influencing the above factors from the perspectives of urbanization and population growth, and industrialization and park construction, as well as globalization and FDI, which can explain well the relationship between the impact factors and the spatial variation. This study can provide a valuable decision-making reference for formulating reasonable regional land development policies and is a good example of land use research for other rapidly developing areas.
... The Government of Vietnam has been encouraging shrimp exports since the early 1990s, and shrimp farming has become widespread in most of the Mekong Delta's coastal provinces. The expansion of aquaculture in the 1990s resulted in the loss of around twothirds of Vietnam's remaining mangroves by 2000 (Van et al. 2014). Mangrove areas are now small Changes in mangrove forest area during 2016-2020and fragmented, and not uniform in terms of spatial location(Figures 5, 6, 7, 8, 9 and 10). ...
... Mangrove forests in Ngoc Hien district are the largest in the region and include the last reserve of old-growth mangrove forests in Vietnam. These forests are also internationally acknowledged as a Ramsar site and UNESCO Biosphere Reserve (Tue et al. 2014; Van et al. 2015). The fringe mangroves in the study area are likely to be limited at their landward side due to extensive aquacultural and agricultural land use in those areas, which will prevent the inland migration of mangroves and potentially squeeze the fringe mangrove area. ...
Sea level rise (SLR) due to global climate change negatively impacts coastal zones, in particular wetland and mangrove ecosystems. Mangroves in the Mekong Delta (MD) in Vietnam provide critical ecosystem services in the region; however, escalated relative SLR is likely to affect all ecosystems in the region, with mangroves probably more vulnerable than others. Given the fact that documented information and studies on SLR impacts on mangroves are limited for the region, this study aims to investigate potential changes in mangrove distribution in response to future SLR scenarios in the coastal area in the south of the MD using the Sea Level Affects Marshes Model (SLAMM). Wetland maps for 2013 derived from Landsat 8 OLI sensor, digital elevation model (DEM), and localized site-specific parameters (i.e., subsidence/accretion, erosion, historic trend of SLR, and over-wash) were used as input for the SLAMM to simulate spatial distribution of mangroves under different relative SLR scenarios (i.e., RCP2.6, RCP4.5, RCP8.5, more extreme SLR), and surface elevation change (i.e., subsidence, stable, and accretion) scenarios by the year 2100. Simulation results show that the average annual mangrove losses are likely to be 0.54% and 0.22% for subsidence and stable scenarios, respectively. The findings demonstrate the considerable impacts of SLR on MD mangrove ecosystems and the strong influence of subsidence processes. Inundation was also identified as a main driver responsible for the mangrove loss by the end of this century. Our results are in agreement with findings of other studies at global scales and observed data at regional scales. The results also demonstrate the potential of the approach developed herein for simulating mangrove dynamics under future relative SLR scenarios in the region with acceptable accuracy. The findings from the present study are useful sources for development of proper strategies for minimizing the impacts of SLR on mangrove ecosystems and their vital associated services, to protect and conserve the mangrove ecosystems in the region.
... Bagworms attack the shoots [61] and damage the roots, leading to the disruption of the regeneration of mangrove plants [62][63][64]. Disruption in the vegetation regeneration process can result in the loss of genetic material and a decreasing biodiversity [65]. ...
Mangroves are an important ecosystem that provides valuable social, economic, and environmental
services. Indonesia has placed mangroves on its national priority agenda in an important
effort to sustainably manage this ecosystem and achieve national climate commitments.
However, mangrove management is faced with complex challenges encompassing social, ecological,
and economic issues. In order to achieve the government’s commitments and targets regarding
mangrove restoration and conservation, an in-depth study on and critical review of mangrove management
in Indonesia was conducted herein. This work aimed to provide a comprehensive analysis
of the challenges and strategic recommendations for sustainable mangrove management in Indonesia.
SWOT analysis was carried out to understand the strengths, weaknesses, opportunities, and
threats related to mangrove management in Indonesia. To address these gaps, we reviewed the
existing policies, current rehabilitation practices, environmental challenges, and research and technology
implementations in the field. We found that strategies on mangrove ecosystem protection,
such as improving the function and value of mangrove forests, integrating mangrove ecosystem
management, strengthening political commitments and law enforcement, involving all stakeholders
(especially coastal communities), and advancing research and innovations, are crucial for sustainable
mangrove management and to support the national blue carbon agenda.
Keywords: mangroves; sustainable management; climate change; blue carbon; mangrove policy;
restoration; rehabilitation
... Bagworms attack the shoots [61] and damage the roots, leading to the disruption of the regeneration of mangrove plants [62][63][64]. Disruption in the vegetation regeneration process can result in the loss of genetic material and a decreasing biodiversity [65]. ...
... Bagworms attack the shoots [61] and damage the roots, leading to the disruption of the regeneration of mangrove plants [62][63][64]. Disruption in the vegetation regeneration process can result in the loss of genetic material and a decreasing biodiversity [65]. ...
Mangroves are an important ecosystem that provides valuable social, economic, and environmental services. Indonesia has placed mangroves on its national priority agenda in an important effort to sustainably manage this ecosystem and achieve national climate commitments. However, mangrove management is faced with complex challenges encompassing social, ecological , and economic issues. In order to achieve the government's commitments and targets regarding mangrove restoration and conservation, an in-depth study on and critical review of mangrove management in Indonesia was conducted herein. This work aimed to provide a comprehensive analysis of the challenges and strategic recommendations for sustainable mangrove management in Indone-sia. SWOT analysis was carried out to understand the strengths, weaknesses, opportunities, and threats related to mangrove management in Indonesia. To address these gaps, we reviewed the existing policies, current rehabilitation practices, environmental challenges, and research and technology implementations in the field. We found that strategies on mangrove ecosystem protection, such as improving the function and value of mangrove forests, integrating mangrove ecosystem management, strengthening political commitments and law enforcement, involving all stakehold-ers (especially coastal communities), and advancing research and innovations, are crucial for sustainable mangrove management and to support the national blue carbon agenda.
Citation: Arifanti, V.B.; Sidik, F.; Mulyanto, B.; Susilowati, A.; Wahyuni, T.; Subarno; Yulianti; Yuniarti, N.; Aminah, A.; Suita, E.; et al. Challenges and Strategies for Sustainable Mangrove Management in Indonesia: A Review. Forests 2022, 13, 695. https://doi.org/10.3390/ f13050695 Academic Editors: Victor H.
... Bagworms attack the shoots [61] and damage the roots, leading to the disruption of the regeneration of mangrove plants [62][63][64]. Disruption in the vegetation regeneration process can result in the loss of genetic material and a decreasing biodiversity [65]. ...
Mangroves are an important ecosystem that provides valuable social, economic, and environmental services. Indonesia has placed mangroves on its national priority agenda in an important effort to sustainably manage this ecosystem and achieve national climate commitments. However, mangrove management is faced with complex challenges encompassing social, ecological , and economic issues. In order to achieve the government's commitments and targets regarding mangrove restoration and conservation, an in-depth study on and critical review of mangrove management in Indonesia was conducted herein. This work aimed to provide a comprehensive analysis of the challenges and strategic recommendations for sustainable mangrove management in Indone-sia. SWOT analysis was carried out to understand the strengths, weaknesses, opportunities, and threats related to mangrove management in Indonesia. To address these gaps, we reviewed the existing policies, current rehabilitation practices, environmental challenges, and research and technology implementations in the field. We found that strategies on mangrove ecosystem protection, such as improving the function and value of mangrove forests, integrating mangrove ecosystem management, strengthening political commitments and law enforcement, involving all stakehold-ers (especially coastal communities), and advancing research and innovations, are crucial for sustainable mangrove management and to support the national blue carbon agenda. Citation: Arifanti, V.B.; Sidik, F.; Mulyanto, B.; Susilowati, A.; Wahyuni, T.; Subarno; Yulianti; Yuniarti, N.; Aminah, A.; Suita, E.; et al. Challenges and Strategies for Sustainable Mangrove Management in Indonesia: A Review. Forests 2022, 13, 695. https://doi.org/10.3390/ f13050695 Academic Editors: Victor H.
... The above-mentioned results, demonstrating Can Gio mangroves' ability to clean up the nearby surface water environment and absorb GHGs, confirm its critical role in helping the seaport and shipping industry compensate for GHG emissions and protect the environment. Since mangroves remain under threat due to the impacts of climate change and socioeconomic development pressures (Tong et al. 2004;Seto and Fragkias 2007;Son et al. 2016; Van et al. 2015), these findings also highlight the importance of conducting further studies, as well as proposing policies that encourage stakeholders in all sectors, including the shipping industry, to become actively engaged in payments for mangrove environmental services. ...
... The above-mentioned results, demonstrating Can Gio mangroves' ability to clean up the nearby surface water environment and absorb GHGs, confirm its critical role in helping the seaport and shipping industry compensate for GHG emissions and protect the environment. Since mangroves remain under threat due to the impacts of climate change and socioeconomic development pressures (Tong et al. 2004;Seto and Fragkias 2007;Son et al. 2016; Van et al. 2015), these findings also highlight the importance of conducting further studies, as well as proposing policies that encourage stakeholders in all sectors, including the shipping industry, to become actively engaged in payments for mangrove environmental services. ...
... They found that urban areas have encroached on peri-urban agricultural areas, while aquaculture has spread into agricultural land and lagoons; scattered vegetation in hilly areas was replaced by woodlands [26]. Van et al. analyzed the mangrove vegetation area change in Mui Ca Mau, Vietnam, from 1953 to 2011, with the help of aerial photographs and satellite images, and found that the mangrove areas showed a trend of a sharp decline in the first period and a slow increase in the later period, using the year 1992 as the boundary [27]. These trends were mainly influenced by war, overexploitation and land management policies. ...
High-accuracy, long-time-series and large-scale land classification mapping are essential for assessing the evolutionary patterns of land systems and developing sustainability studies. In this paper, using Google Earth Engine (GEE) and Landsat satellite remote sensing images, based on the Random Forest (RF) algorithm, we carried out remote sensing classification to obtain a year-by-year land use/cover data set in Vietnam over the past 21 years (2000–2020). Further applying principal component analysis and multiple linear regression methods, we examined the spatio-temporal characteristics, dynamic changes and driving mechanisms of land use change. The results show the following: (1) The RF classification algorithm supported by the GEE can quickly and accurately obtain a land use/cover data set. The overall classification accuracy is 0.91 ± 0.01. (2) The land cover types in Vietnam are dominated by woodland and cropland, with an area share of 54.62% and 37.90%, respectively. In the past 20 years, the area of built-up land has increased the most (+93.49%), followed by the area of water bodies (+54.19%), while the area of woodland has remained almost unchanged. (3) The expansion of built-up land is driven by regional economic development; the area changes in cropland, water bodies and woodland are influenced by both national economic development and climate change. The results of the study provide a basis for assessing land use policies in Vietnam and a reference methodological framework for rapid land mapping and analysis in other countries in the China–Indochina Peninsula.
... Albeit forest ecosystems can suffer directly in some extreme cases [e.g. defoliation with Agent Orange during the Vietnam War ( Van et al., 2015)], armed conflicts' impact on forests are more likely to occur through an increase or decrease of existing regional drivers of LUC through different mechanisms. For instance, the displacement of local population (Hagenlocher et al., 2012), the use of landmines (Berhe, 2007), the need of natural resources to finance warfare efforts (Global Witness, 2013), unstable political institutions or insecure land tenure (Dávalos, 2001) resulting from armed conflict exert an important impact in deforestation drivers such as logging, mining or agriculture production. ...
Um das 1,5°C Ziel zu verhindern, müssen bis 2020 die globalen anthropogenen CO2 Emissionen Sektor-übergreifend ihren Spitzenwert erreichen und bis 2050 auf Netto-Null-Emissionen sinken. Der AFOLU Sektor hat einen Anteil von 23% an den globalen Treibhausgasemissionen (THGE). Neben der Möglichkeit THGE zu vermeiden, bietet die Implementierung von Klimaschutzmitigation auch Synergien um die Ernährungssicherheit, Nährstoff- und Wassereffizienz zu verbessern sowie Landdegradation umzukehren. Eine kritische Bedeutung hat die Abholzung von tropischen Waldflächen durch die mehr als ein Drittel der Emissionen im Bereich des AFOLU entsteht. Vor diesem Hintergrund werden vorliegend, mit Fokus auf die Abholzung in der tropischen Zone, die indirekten Auslöser der THGE innerhalb des AFOLU untersucht. Diese Auslöser werden zunächst auf einer globalen Skala analysiert, wobei die Rolle der Variabilität von Preisveränderungen international gehandelter Waren und weiterer sozio-ökonomischer Indikatoren auf regionale Waldumwandlungsprozesse betrachtet wird. Anschließend analysiert diese Arbeit den Aspekt des Waldverlustes im Zusammenhang mit politischer Instabilität und bewaffneten Konflikten. Zudem werden regionale Lösungen zur Mitigation in weiteren Sektoren adressiert. Insbesondere wird die Möglichkeit zur THGE-Einsparung in silvopastoralen Systemen untersucht um das Zusammenspiel zwischen intensiver Viehbewirtschaftung und der Kohlenstofffixierung besser zu verstehen. Darüber hinaus werden regionale Lösungen mit Hilfe von Basisorganisationen bzw. gemeindebasierten Initiativen (CBI) zur THGE-Einsparung in den Bereichen Energie, Nahrungsmittel, Transport und Abfall erforscht. Diese Arbeit liefert vielfältige Beiträge zum Verständnis der indirekten Auslöser von Abholzung und den damit verbundenen THGE innerhalb der tropischen Zone, sowie zur Förderung lokaler Lösungen für die sektorübergreifende THG-Minderung.
... Forest cover change in regions with armed conflicts is especially shaped by the strategic forest usage of the involved armed groups (Castro-Nunez et al., 2017b). Deforestation in conflict regions may be fostered through the exploitation of natural resources, such as timber and minerals (Sánchez-Cuervo and Aide, 2013), direct fighting actions (Dudley et al., 2002; Van et al., 2015), cultivation of illicit crops (Davalos et al., 2011), and the resettlement of displaced people (Ordway, 2015). In contrast, armed conflicts can reduce deforestation through forced migration (Sánchez-Cuervo and Aide, 2013;Burgess et al., 2015), disruptions in agriculture and other economic activities (Le Billon, 2000;Hecht et al., 2006;Burgess et al., 2015), and access restrictions that can take diverse forms such as landmines and infrastructure sabotage (Berhe, 2007). ...
Using Colombia as a case study, this analysis provides insights on deforestation dynamics in times of conflict and peace and the different factors driving these dynamics. We performed time series clustering of yearly deforestation data (2001–2018) from 708 out of 1,122 mainland Colombian municipalities (accounting for 98% of the total deforestation areas in Colombia) and produced regression models using a gradient tree boosting framework (XGBoost) to identify drivers that explain varying, local-level deforestation dynamics. Municipalities were characterized by seven categories of deforestation dynamics, with the Amazon region being largely represented by only four categories and the Andes region displaying all categories of deforestation dynamics. Notably, six of the seven representative categories exhibit substantial increases in deforestation in the years following the peace agreement. The regression analysis revealed that coca cultivation area, number of cattle, and municipality area are the top three drivers of deforestation dynamics at national, regional, and category levels. However, the importance of the different variables varied according to the different spatial dimensions. Results provide further understanding on how the drivers of deforestation change not only at a regional scale, as assumed by much of the current literature about drivers of deforestation, but also at a lower scale of analysis (intraregional and intradepartmental variation in the case of Colombia). Insights from this study can be used to understand deforestation dynamics in other countries experiencing times of conflict and peace and will support decision-makers in creating programs that align actions for peacebuilding, climate change mitigation, and biodiversity conservation more effectively.
... Other researchers used supervised classification with maximum likelihood algorithm using Landsat data (Pathmanandakumar, 2019;Dan et al., 2016;Omar et al., 2018), Sentinel 2B (Chamberlain et al., 2020), and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) (Saito et al., 2003). A supervised classification using maximum likelihood classification was also conducted with the assistance of aerial photographs (Sulong et al., 2002;Van et al., 2015). Another study adopted remote sensing datasets (SPOT 4 and 5 imagery), object-based image analysis, and Support Vector Machine classifier (Pham et al., 2016). ...
The mangrove forest ecosystem protects the land area from the tidal wave hence preventing the coastal areas and properties from severe damage. Mangroves provide valuable ecological services and goods, sediment retention, food sources of some animals, and stabilisation of the coastal areas. Unfortunately, the species have been experiencing an extensive loss in many parts of the world. This paper aims to detect the changes in mangrove forests and possible changes in the Selangor river basin area. The methodology uses remote sensing data via supervised classification on a maximum likelihood algorithm to analyse the distribution of mangrove forests at the Selangor River basin for a thirty-two-year period, from 1989 to 2021. The findings indicate that the percentage of mangroves in the study area has reduced over the study period. The coverage of mangroves has reduced from 24.29 percent (1989) to 15.57 percent in 2008, and continued to reduce to 13.12 percent in 2021. The research finding indicates a decrease in mangroves due to aquaculture, tourism, agriculture, and other human activities. Such a trend may risk coastal and river erosion, thus necessitating a revision of the management policies for environmental protection. Keywords: mangrove, forest, remote sensing, Selangor river basin
... Restoration of BCEs at large scale is potentially feasible for mangroves and tidal marshes, with tenfold growth in the number of documented restoration projects of BCEs since the turn of the century 19 , although it remains challenging for seagrass meadows 20 . One of the largest ecosystem restoration projects ever undertaken was the restoration of ~1,487 km 2 of mangroves in the Mekong Delta destroyed by the US Air Force during the Vietnam War 19,21 . To date, the planted forest in Can Gio Mangrove Forest Park, Vietnam, has since 1978 accumulated an estimated 152 Tg carbon dioxide equivalent (CO 2 e), across the 447 km 2 of mangroves restored at this site 22 , even with the impact of typhoons. ...
Blue carbon ecosystems (BCEs), including mangrove forests, seagrass meadows and tidal marshes, store carbon and provide co-benefits such as coastal protection and fisheries enhancement. Blue carbon sequestration has therefore been suggested as a natural climate solution. In this Review, we examine the potential for BCEs to act as carbon sinks and the opportunities to protect or restore ecosystems for this function. Globally, BCEs are calculated to store >30,000 Tg C across ~185 million ha, with their conservation potentially avoiding emissions of 304 (141–466) Tg carbon dioxide equivalent (CO2e) per year. Potential BCE restoration has been estimated in the range of 0.2–3.2 million ha for tidal marshes, 8.3–25.4 million ha for seagrasses and 9–13 million ha for mangroves, which could draw down an additional 841 (621–1,064) Tg CO2e per year by 2030, collectively amounting to ~3% of global emissions (based on 2019 and 2020 global annual fossil fuel emissions). Mangrove protection and/or restoration could provide the greatest carbon-related benefits, but better understanding of other BCEs is needed. BCE destruction is unlikely to stop fully, and not all losses can be restored. However, engineering and planning for coastal protection offer opportunities for protection and restoration, especially through valuing co-benefits. BCE prioritization is potentially a cost-effective and scalable natural climate solution, but there are still barriers to overcome before blue carbon project adoption will become widespread.
... In Vietnam, remote sensing is used to monitor and evaluate mangrove ecosystems for mangrove forest management. However, most of these activities have concentrated on mangroves in the Mekong Delta [30,[33][34][35][36][37][38][39][40][41][42][43][44][45] and fewer studies have been conducted in northern Vietnam. Most projects in northern Vietnam are concentrated in the highly developed Red River delta (Region 1 [46]) [47][48][49][50][51] and Hai Phong (Region 1) [52][53][54][55][56]. ...
Mangrove forests can ameliorate the impacts of typhoons and storms, but their extent is threatened by coastal development. The northern coast of Vietnam is especially vulnerable as typhoons frequently hit it during the monsoon season. However, temporal change information in mangrove cover distribution in this region is incomplete. Therefore, this study was undertaken to detect change in the spatial distribution of mangroves in Thanh Hoa and Nghe An provinces and identify reasons for the cover change. Landsat satellite images from 1973 to 2020 were analyzed using the NDVI method combined with visual interpretation to detect mangrove area change. Six LULC classes were categorized: mangrove forest, other forests, aquaculture, other land use, mudflat, and water. The mangrove cover in Nghe An province was estimated to be 66.5 ha in 1973 and increased to 323.0 ha in 2020. Mangrove cover in Thanh Hoa province was 366.1 ha in 1973, decreased to 61.7 ha in 1995, and rose to 791.1 ha in 2020. Aquaculture was the main reason for the loss of mangroves in both provinces. Overall, the percentage of mangrove loss from aquaculture was 42.5% for Nghe An province and 60.1% for Thanh Hoa province. Mangrove restoration efforts have contributed significantly to mangrove cover, with more than 1300 ha being planted by 2020. This study reveals that improving mangrove restoration success remains a challenge for these provinces, and further refinement of engineering techniques is needed to improve restoration outcomes.
... Many studies conducted on mangrove ecosystems have used multi-spectral satellite data for determining spatio-temporal change (Wang et al., 2004;Giri et al., 2007;Kamal and Phinn, 2011;Khairuddin et al., 2016). Researchers have used suitable satellite image resources including Landsat series, Sentinel, SPOT, IRS series, Quickbird, IKONOS for mapping spatial mangrove distribution (Nayak and Bahuguna, 2001;Rahman et al., 2013;Van et al., 2015). The purpose of our study is to analyze the spatialtemporal variation in the Sundarban world heritage site over the last 29 years in four different periods (1990,1999,2009, and 2019) using freely available multi-temporal Landsat imagery. ...
The space borne remote sensing satellite systems are increasingly used in ecological monitoring, growth dynamics, and mapping of mangrove extent worldwide. Sundarban is the largest, diverse contiguous productive mangrove ecosystem and is increasingly threatened by both environmental changes and anthropogenic forces. The study focuses on the spatio-temporal dynamics in the Indian Sundarban mangrove ecosystem using time-series Landsat satellite imagery during the periods from 1990–1999, 1999–2009, and 2009–2019. The maximum likelihood classifier approach has been applied for image classification and post-classification comparison techniques for change detection analysis over the study period. The findings revealed a decline of 3.76% areal extent of mangroves forest between 1990 and 2019. The areal extent of the Indian Sundarban mangrove areas has been maintained at a relatively constant despite the high population density in its immediate surrounding region. The overall accuracies of 72%, 83%, 79%, and 85.9% were recorded for the classified satellite image of 1990, 1999, 2009, and 2019, respectively. The present study is of great significance to the restoration and conservation of the mangrove forests in response to global climatic change.
... Both expansion and contraction of societies may affect landuse. Pandemics (Little, 2007), migration (Conn et al., 2002), war (Van et al., 2015), genocide (Robinson et al., 2000), continental discovery (Sandor et al., 2002) etc., have all driven land-use change in human history and pre-history. In modern times, there have been more subtle changes, due to increasing concentrations of CO 2 in the atmosphere (Zhu et al., 2016). ...
Approximately 22% of sun-like stars have Earth-like exoplanets. Advanced civilizations may exist on these, and significant effort has been expended on the theoretical analysis of planetary systems, and accompanying practical detection instruments.
The longevity of technological civilizations is unknown, as is the probability of less advanced societies becoming technological. Accordingly, searching for pre-industrial extra- terrestrial societies may be more productive.
Using the earth as a model, a consideration of possible detectible proxies suggests that observation of seasonal agriculture may be possible in the near future – particularly in ideal circumstances, for which quantitative analysis is provided. More speculatively, other detectible processes may include: species introduction; climate change; large urban fires and land-use or aquatic changes.
Primitive societies may be both aware that their activities may be observed from other pla- nets, and may deliberately adjust these activities to aid or conceal detection.
... However, there is an enormous decrease of mangroves for the construction of those shrimp and fish ponds [6,39,52,53,55]. There have been set rules by the Vietnamese government to protect the mangroves. ...
Mangroves are forest ecosystems growing in (sub)tropical saline coastal environments. With their unique root structure they serve as important natural coastal protection and provide habitats with excellent conditions for cultivating fish, shrimp and crab species. Despite all benefits mangrove forests are disappearing at alarming rates around the world but especially in Asia such as the Mekong Delta coast. Therefore, this research focusses on the Ca Mau Province in Vietnam. The Ca Mau province is the southernmost province of Vietnam with mangroves present along the coastlines, the Mui Ca Mau National Park and in mixed mangrove aquaculture farms. Remote sensing has been widely proven to be essential in mapping mangrove ecosystems. Previous research used either expensive optical and radar data sources or free but lower resolution systems. This study is the first that uses the new Copernicus Sentinel-1 radar and Sentinel-2 multispectral satellite missions that provide free available data with high spatial (10-20 meter) and temporal (10-12 days) resolution. Since optical data is prone to cloud effects and radar data is hard to interpret, both data sets are combined to investigate improvements for classifying mangroves. The data is processed in the new online Google Earth Engine platform providing a powerful tool for big data applications such as land cover classification. Optical data is found to separate mangroves by their spectral reflectance mainly in the near-infrared wavelength domain. The dominant mangrove species in the Ca Mau province, Rhizophora Apiculata and Avicennia Alba, are found to be separable from comparing unsupervised clustering results with ground truth locations. The C-band radar signal is dominated by volume scattering, indicating the density of the canopy. Especially VV-polarization has good correlation with canopy parameters. To improve information from the radar signal a temporal analysis is executed. Seasonal variations are quantified and show an increase according to the spatial succession of mangroves. Pioneer species, such as Avicennia genus, show less seasonal variations than mature species, such as Rhizophora genus. With the previous information five classes are defined: urban area, water and three mangrove classes: Rhizophora Apiculata species in extensive shrimps, Rhizophora Apiculata species in natural environment and Avicennia Alba species. A classification method is set-up in the Google Earth Engine with a Random Forest classifier using the satellite data inputs and ground truth training input of the five classes. A combination of the optical data with the temporal information of the radar data is found to be the best data input for separating those five classes. Classification results are obtained for discriminating mangrove types up to an overall accuracy of 87\%. The classification gets less reliable when mangrove species are mixed or at locations where the ground truth training input was scarce. With the resulting yearly land cover maps land cover changes can be detected. Comparing the land cover map of 2017 with a mangrove cover product of 2000 shows a regression along the southern coastline. No significant changes inside the shrimp farms are found between 2016 and 2017 but with the future availability of a long time series of Sentinel-1 and 2 data those can be detected with the method that is resulted from this study.
... This is the case for the mangroves of Vietnam. The dynamics of their area is estimated either over long periods of time, or by detailed studies of small regions [3,8,9]. ...
... Researches using optical images to map and monitor mangrove forests showed that the optical images provided information on the environmental resources faster and more accurately (Thu and Populus 2007;Nguyen et al. 2013;Vo et al. 2013;Son et al. 2015; Van et al. 2015;Tran, Tran, and Kervyn 2015). However, optical data is highly dependent on the weather. ...
Soil microorganisms are highly diverse and perform multiple and beneficial roles in soil ecosystems. However, the study of microbial communities is inherently difficult because only one percent of microorganisms grow in culture. Hence, there is a need to explore techniques that result in identifying microbial strains and, consequently, the diversity of microorganisms in a certain community. This chapter presents various techniques ranging from the conventional, culture-dependent methods that can discover and describe the microorganisms’ morphology, to culture-independent methods that are molecular or genetic-based. Included also in the discussion are easy-to-follow and highly specific methodologies from soil collection, microbial isolation, DNA extraction, molecular and PCR analysis, and statistical procedures. Microbial DNA extraction for upland and lowland paddy are presented. The study of soil metagenomes using molecular markers and metagenomics is also discussed.
... Researches using optical images to map and monitor mangrove forests showed that the optical images provided information on the environmental resources faster and more accurately (Thu and Populus 2007;Nguyen et al. 2013;Vo et al. 2013;Son et al. 2015; Van et al. 2015;Tran, Tran, and Kervyn 2015). However, optical data is highly dependent on the weather. ...
The emergence of unmanned aerial vehicles (UAVs) or drones has led to their widespread use in agriculture by scientists and farmers for the purposes of mapping, monitoring, and landscape management. However, the high cost of drones, together with the risk and difficulty of flying any drone, has marginalized the small-scale farmers from exploring the potential of the UAV technology appropriate to their context. In this report, we aim to introduce a simple documentation methodology to small-scale permaculture farmers using a budget-friendly drone that would promote permaculture design, agroecological farm management, and stimulate environmental awareness. The study developed a 10-step methodology based on experience in the field that maximizes the features of the drone. Originally intended as an entry-level UAV, the Ryze Tello was used as a documentation tool to generate baseline data on farm biodiversity and system component interactions as well as landscape heterogeneity. Using aerial photos from the drone’s built-in camera, the researchers were able to gather valuable data in four (4) small-scale permaculture farms in the Philippines. Collecting such data would enable farmers to observe and interpret both anthropogenic and natural patterns and processes occurring throughout the year. The results of the study suggest the development of more drones like the Tello with improved features in the near future to empower more farmers to make design-based decisions that would ensure both farm productivity and ecosystem health.
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... Researches using optical images to map and monitor mangrove forests showed that the optical images provided information on the environmental resources faster and more accurately (Thu and Populus 2007;Nguyen et al. 2013;Vo et al. 2013;Son et al. 2015; Van et al. 2015;Tran, Tran, and Kervyn 2015). However, optical data is highly dependent on the weather. ...
Balili River in Benguet, northern Philippines remains polluted despite more than a decade of rehabilitation efforts; thus, an alternative clean-up method, such as phytoremediation, is timely and worth investigating. This chapter describes the phytoremediation potentials of selected local dominant aquatic macrophytes of the river, namely; Amaranthus spinosus, Eichhornia crassipes, Eleusine indica and Pennisetum purpureum in pilot-scale constructed wetlands and subjected to varying hydraulic retention time (HRT) treatments. Results showed significant improvement of the wastewater quality in almost all parameters of water assessment. At optimal HRT, total suspended solids, dissolved oxygen, nitrate, and mercury were significantly lowered at values passing the particular minimum water quality standard, while biological oxygen demand, phosphate, and lead were slightly above the minimum standards. Against these reduction rates, total and fecal coliform still did not pass the water quality standard for class A water. The pollution reduction efficiencies of the aquatic macrophytes were significantly affected by HRT. Significant pollution reduction was observed as early as day 1, while optimal reduction was recorded at 3-4 days HRT. Among the macrophytes, P. purpueum, generally, had the best pollution reduction efficiency. Results of the study showed that local dominant aquatic macrophytes are promising phytoremediators and provide a good template for coming up with a full-scale constructed wetland for the rehabilitation of Balili River as well as for other eutrophic rivers in the country.
... Researches using optical images to map and monitor mangrove forests showed that the optical images provided information on the environmental resources faster and more accurately (Thu and Populus 2007;Nguyen et al. 2013;Vo et al. 2013;Son et al. 2015; Van et al. 2015;Tran, Tran, and Kervyn 2015). However, optical data is highly dependent on the weather. ...
... In terms of mapping the forest/nonforest cover, this study's map (merging all forest classes as one and merging all nonforest classes as the other), showed a very higher accuracy (95.7%, Supplementary Table S2). In addition, the higher-accuracy mangrove cover class in this map can facilitate studies associated with blue carbon assessments [99] or mangrove ecosystem services [100,101]. ...
Highly detailed and accurate forest maps are important for various applications including forest monitoring, forestry policy, climate change, and biodiversity loss. This study demonstrates a comprehensive and geographically transferable approach to produce a 12 category high-resolution land use/land cover (LULC) map over mainland Vietnam in 2016 by remote sensing data. The map included several natural forest categories (evergreen broadleaf, deciduous (mostly deciduous broadleaf), and coniferous (mostly evergreen coniferous)) and one category representing all popular plantation forests in Vietnam such as acacia (Acacia mangium, Acacia auriculiformis, Acacia hybrid), eucalyptus (Eucalyptus globulus), rubber (Hevea brasiliensis), and others. The approach combined the advantages of various sensor data by integrating their posterior probabilities resulting from applying a probabilistic classifier (comprised of kernel density estimation and Bayesian inference) to each datum individually. By using different synthetic aperture radar (SAR) images (PALSAR-2/ScanSAR, PALSAR-2 mosaic, Sentinel-1), optical images (Sentinel-2, Landsat-8) and topography data (AW3D30), the resultant map achieved 85.6% for the overall accuracy. The major forest classes including evergreen broadleaf forests and plantation forests had a user's accuracy and producer's accuracy ranging from 86.0% to 95.3%. Our map identified 9.55 × 10 6 ha (±0.16 × 10 6 ha) of natural forests and 3.89 × 10 6 ha (±0.11 × 10 6 ha) of plantation forests over mainland Vietnam, which were close to the Vietnamese government's statistics (with differences of less than 8%). This study's result provides a reliable input/reference to support forestry policy and land sciences in Vietnam.
... Mangrove forests are widely located in the intertidal zone with an estimated area of 152,361,000 ha in tropical and sub-tropical shorelines of the world [1][2][3]. The mangrove ecosystem is significant as an ecological service in coastal neighborhoods through providing natural resources to local livelihoods (i.e., provision of fuel, food, timber, and construction materials) [4,5], and being a habitat for diversity of flora and fauna [6]. ...
This study aimed at evaluating the spatiotemporal patterns of mangrove forest variations for three ecological zones of the Can Gio biosphere reserve (i.e., core, buffer, and transition zones) and its relation to land use/land cover changes. Time series Sentinel-2 Imagery—which presents the Normalized Different Vegetation Index (NDVI), obtained through the Google Earth Engine and Overlap Similarity Algorithm—was used to characterize vegetation cover in the study area. Furthermore, the Cohen’s Kappa agreement was applied to examine the accuracy of mangrove classification, and the Mann–Kendal (MK) significance was used to analyze the spatiotemporal trends of mangrove forests. The results showed that an NDVI value greater than 0.3 recorded the reflected signal of mangrove population in the study area with an O-index greater than 0.85. A Cohen’s Kappa statistic of agreement of 0.7 and an overall classification accuracy of 83% was obtained. Regarding the trend in mangrove forest patterns, an increase in area of 669 ha and 579 ha explored at the buffer and core zones, respectively, while the largest declined mangrove area of 350 ha was investigated at the buffer zone, followed by a transition at 314 ha during the study period due to the interconversion of shrimp farming and the expansion of built-up areas. Moreover, the study also described the negative impacts of the sea-encroached urban-tourism zone on mangrove patterns in the foreseeable future. The results from this study will act as a basic fundamental authentic report for local governments in proposing strategies for the shielding of mangrove forests and economic development from negative consequences in foreseeable future.
The imperative for vulnerable populations to adapt to greater environmental variability is increasing in lockstep with the onset of wide‐ranging climate change impacts. However, while critical adaptation research emphasizes the necessity of addressing the underlying drivers of vulnerability to climate change, mainstream approaches to adaptation stress economic growth as a prerequisite for climate responses. Accordingly, capital‐intensive adaptation measures promote competitiveness to spur economic growth in the Vietnamese Mekong Delta, where more than 18 million people face environmental hazards such as seawater intrusion, flood, drought and cyclones. This study evaluates competitiveness as a mandate for effective climate change adaptation. It finds that adaptation can advance either competition or vulnerability reduction, but it cannot logically or pragmatically pursue both.
National borderlands as the spatial carrier and forefront to exert geopolinomical influence and implement geopolinomical strategy, most have same or similar eco‐geographical structure characteristics, such as land cover. However, there are different development trends in different national relationships, and land use and land cover changes (LUCC), especially in the border areas of neighboring countries. In general, armed conflict in border areas is accompanied by the severe, immediate and long‐lasting LUCC like forest loss. Here, by means of geospatial analysis, Uppsala Conflict Data Program and Climate Change Initiative Land Cover dataset were used to investigate the linkages between the armed conflict and LUCC or the patterns and processes of LUCC before, during and after armed conflict across the globe and its borderlands from 1992 to 2020. The main and key insights are: (1) nearly 1/2 of global armed conflict has occurred and re‐occurred in the borderlands since 1992, leading to about 1/6 of LUCC globally; (2) the impact of armed conflict on LUUC is hysteretic based on the intensity of conflict, especially the borderlands; (3) the transfer rate of land use is high during the conflict, and tends to be stable in the post‐conflict period; (4) the absolute amount of armed conflict damage to forest land is larger, but the changes rate of impervious surfaces far more than the former, or nearly 18 times. These findings improve the understanding of the impact of armed conflict on LUCC, including the border areas. This study could provide a proxy and benchmark for exploring the cause‐effect and impact‐response between geopolinomical relations and the borderlands LUCC. This article is protected by copyright. All rights reserved.
Ca Mau and Kien Giang, the two provinces of the Mekong Delta bordering the Gulf of Thailand, are facing major environmental challenges affecting the agriculture and aquaculture sectors upon which many livelihoods in this region depend on. This study maps the suitability of these two provinces for paddy rice cultivation and shrimp farming according to soil characteristics and current and future environmental conditions for variables found to significantly influence the yield of those two sectors, i.e., the level of saltwater intrusion, water availability for rainfed agriculture, and the length of the growing period. Future environmental conditions were simulated using the MIKE 11 hydrodynamic model forced by four hydrodynamic scenarios, each one representing different extents of saltwater intrusion during both the dry and rainy seasons, while also considering the availability of water resources for rainfed agriculture. The suitability zoning was performed using a GIS-based analytic hierarchy process (AHP) approach, resulting in the categorisation of the land according to four suitability levels for each sector. The analysis reveals that paddy rice cultivation will become more suitable to Kien Giang province while shrimp farming will be more suitable to Ca Mau province if the simulated future environmental conditions materialise. A suitability analysis is essential for optimal utilisation of the land. The approach presented in this study will inform the regional economic development master plan and provide guidance to other delta regions experiencing severe environmental changes and wishing to consider potential future climatic and sea level changes, and their associated impacts, in their land use planning.
Knowledge on the spatial distribution of land use/land cover (LULC) change is critical for developing sustainable socioeconomic and ecological pathways. Here we aimed to explore the rural landscape transformation through the analysis of LULC spatio-temporal dynamics in the entire Vietnamese Mekong Delta over the recent three decades, using Landsat imageries and a supervised random forest classifier. Results indicated that in the 1990s, dominant LULC types were arable cropland, wetland, and permanent crops, which covered approximately half of the delta (20,900 km2), 28% and 8%, respectively. From 1990 to 2019, the wetland area decreased from 28% to 5% due to the expansion of aquaculture and the arable cropland. The aquaculture, however, expanded more rapidly than other land use conversions, namely, from 2% to 19%, and covered almost the entire coastal zone of the delta over the recent three decades. Although mangrove forests slightly recovered by 58 km2 from 2005 to 2019, the overall trend from 1990 to 2019 showed an intense loss of 740 km2 due to widespread conversions into aquaculture. The paper unravels the complex dynamics between land-cover change, socio-economic development and associated land-use policies, which have significant implications for the change in rural landscapes.
Vietnam mangrove forests have long been recognized to play important roles in coastal protection against soil erosion and storms/strong waves, supplying seafood, land reclamation, and carbon accumulation. Mangrove forests were severely damaged by the Second Indochina War and the shrimp aquaculture boom of the 1980s and 1990s. In recent decades, the rate of mangrove forest decline has been reduced due to increased efforts in mangrove restoration, though mangrove conversions to other land uses still occur locally. In this study, we analyzed Landsat data using the Google Earth Engine (GEE) platform to (1) determine the national distribution of mangroves; (2) identify the spatiotemporal change of mangrove cover; and (3) quantify the proportional conversion of mangroves to different land uses in Vietnam between 1995 and 2019. Vietnam lost 13,261 ha (7.3%) of its mangrove forest during the study period at a rate of 0.3% per year. Mangrove extent decreased 24,966 ha during 1995–2010, but increased 11,705 ha during 2010–2019. Spatially, mangrove extent decreased in southern regions, but increased in northern and central regions. Aquaculture and agriculture expansion were the major drivers that accounted for 43.4% and 24.8% of the total mangrove loss, respectively. In northern and central regions, infrastructure development was also identified as an additional driver of mangrove deforestation, while in the southern regions, erosion was identified as an increasing threat to mangroves. These results can assist managers and decision makers in mangrove, management, and ecological service evaluations as well as in forest inventories and national reporting. Our findings also suggest using the GEE platform to analyze public archive satellite images is an effective tool to monitor nationwide mangrove forest change over time in Vietnam.
Mangroves are one of the most potential tidal wetlands characterized by their hydrological, ecological, and geological features. They form the diversified and biologically productive ecosystem, populated with heterogeneous groups of plant taxonomy. The transboundary Sundarban mangrove wetland (89°02′ to 89°55′E and 21°30′ to 22°30′N) is situated on the Ganges–Brahmaputra–Meghna river network. This represents the largest continuous tract of mangrove forest in the world, spanning across Bangladesh (62%) and India (38%). The chapter gives an illustrative account of the diversity and distribution patterns of mangroves in India and other coastal regions across the world, along with their anomalous biogeographical patterns, mangrove landform classification and their morphological structure and adaptation strategies. In addition, the mangrove ecosystem goods and services, carbon storage efficiency and application of remote sensing for mangrove mapping have been discussed. A haven for rich biodiversity, Sundarban harbors several rare and globally threatened plants and animals. The overall common key threats for mangrove ecosystems are land-use changes, overexploitation of natural resources, chemical pollution from point and diffusive sources, reduced freshwater supply and silt deposition. Both India and Bangladesh should implement bilateral monitoring programs to resolve those emerging problems and formulate necessary management strategies to restore this diversified and iconic mangrove ecosystem.
In the last few decades, the mangroves ecosystems in Vietnam have been strongly affected by various factors: spraying of Agent Orange during the war, monoculture, urbanization, development of intensive shrimp farming, as well as coastal erosion and climate change. During the first half of the 20th century, Eugène Poilane – the most prominent collector of Indochinese flora – explored and surveyed various types of forest ecosystems throughout French Indochina, including various mangrove ecosystems. The work and observations carried out by this intrepid and courageous naturalist is of remarkable rigor and meticulousness. Eugène Poilane’s work – his botanical specimens, manuscripts and fieldwork notebooks – help us trace the floristic diversity of mangrove species, their abundance and distribution. It also provides detailed information about indigenous knowledge and uses of the various species, the operational management and economic value of mangroves, all within the unique socio-cultural and environmental context of the French colonial era in southeast Asia. His observations, from 1919 to 1941, suggest that the mangroves were already strongly modified by humans in the begining of the 20th century: a sort of anthropized landscape. Eugène Poilane leaft an unparalleled scientific heritage and unpublished documentation that can be exploited by anyone interested not only in the floristic diversity of French Indochina, but also in the evolution of these ecosystems, the uses of plant species, as well as the socio-cultural, economic and political transformations of these environments.
Mangroves play an important role in sustaining a healthy coastal environment, providing a natural habitat to various species, a stable shoreline and forestry products. However, the extent of mangroves developed along the tidal coast of the Mekong delta in southern Vietnam has faced and still faces the impact from both natural and anthropogenic drivers. Since the area of mangroves in the coastal Mekong delta is not well documented, this study aims to quantitatively document the evolution of the mangrove area over the past 48 years, i.e. between 1973 and 2020. Satellite Landsat images, along with a classification method comprising Iso Cluster and Maximum Likelihood algorithms, have been used for mapping land cover types including mangroves, aquaculture, soils, plants and water surfaces along the coastal districts of the Mekong delta. The study shows that remote sensing and GIS techniques can be applied to obtain mapping of the land cover, as well as detect and analyse spatial and temporal changes caused by e.g. coastal erosion or aquaculture expansion. The findings reveal that the total mangrove area of an estimated 185,800 ha in 1973 decreased significantly to 102,160 ha in 2020. Approximately 2150 ha/yr of the total mangrove loss over 1973–2020 was due to invasion by aquaculture, while roughly 430 ha/yr was lost due to coastal erosion. A slight increase in mangrove area occurred since 2010 as a result of the implementation of a series of projects to protect against coastal erosion and to restore mangroves by the Vietnamese government and international non-governmental and governmental organizations, although the success rates of mangrove restoration are relatively low. The survival of mangrove forests in the Mekong delta is related to the main pressure drivers: pollution, land use conversion, insufficient sediment sources, coastal erosion and coastal mangrove squeeze. Therefore, an integrated mangroves and shrimp farming model is one of the most appropriate approaches to achieve a beneficial balance between both aquaculture and mangroves.
Mangroves are important as a result of the wide range of ecosystem services and the biological diversity they support. Due to their low relief, mangroves are likely to be under threat from sea level rise, although the extent of this threat is unknown as a result of the wide geographical variation in mangrove characteristics both within and between regions. How mangroves will respond to global sea level rise is influenced by a range of factors including neotectonics, sediment availability, subsurface biological inputs of organic material, local sea level rise, species diversity and type, as well as the combination of other global change factors affecting them such as changes in precipitation, storminess, temperature, pollution, damming, and environmental protection. In some cases, increased inundation due to sea level rise has resulted in increased rates of sedimentation and positive surface elevation change, while in other cases it has led to losses due to drowning. Here we evaluate how sea level rise, combined with other global change factors, is likely to impact mangrove resilience in the future.
Les mangroves présentent des fonctions et valeurs écologiques, socio-économiques et d’atténuation du changement climatique majeures et vitales pour la population littorale dans le monde et à Madagascar. Leur richesse en fait des milieux intensément exploités, les soumettant à de fortes pressions naturelles et anthropiques. Pourtant à Madagascar « les mangroves sont très mal comprises et nous n'avons pas en main les éléments nécessaires à un bon diagnostic » alors qu’on associe celles de la région Sud-ouest à un état de perpétuelle régression. Cette thèse a pour objectifs l’identification, la cartographie et la quantification de la dynamique d’évolution (depuis 1949) des mangroves de 5 sites du Sud-Ouest : Manombo-Fitsitike, Ambondrolava, Ankiembe, Sarodrano et Andriambe. Elle vise aussi à diagnostiquer les différents facteurs d’évolution en faisant la part des pressions anthropiques et naturelles. Pour atteindre ces objectifs, deux approches ont été adoptées : la géomatique se basant sur l’analyse diachronique d’images Spot de 1987, 1998, 2012 et 2014 associées à des photos aériennes de 1949 et des recherches sur terrain avec des inventaires floristiques, des mesures physico-chimiques, des analyses granulométriques des substrats et des enquêtes. Les résultats montrent des dynamiques d’évolution complexes et contrastées entre progression, stabilité et régression. Au final, en s’appuyant sur les connaissances acquises sur les dynamiques d’évolution des mangroves sur plus de 60 ans, il est possible de mettre à la disposition de tous un outil d’aide à la décision et à la gestion durable et adéquate pour protéger et conserver ces écosystèmes, particulièrement dans le contexte du changement climatique qui va impacter les dynamiques d’évolution naturelles et les forçages anthropiques.
Investigation of mangrove vegetation structure, regeneration and human impact, plus a rapid assessment of biomass/carbon, in Kien Giang Province, Vietnam, on the Mekong Delta facing the Gulf of Siam.
Mui Ca Mau at the southern tip of Vietnam supports a large area of mangroves
and has a high value for biodiversity and scenic beauty. This area is
affected by erosion along the East Sea and accretion along the Gulf of
Thailand, leading to the loss of huge stretches of mangroves along the East
Sea and, in some cases, loss of environmental and ecosystem services provided
by mangroves. In this study, we used remotely sensed aerial (1953), Landsat
(1979, 1988 and 2000) and SPOT (1992, 1995, 2004, 2008, 2009 and 2011)
images and the Digital Shoreline Analysis System (DSAS) to quantify the rate
of mangrove shoreline change for a 58 yr period. There were 1129 transects
sampled at 100 m intervals along the mangrove shoreline and two statistical
methods, namely end point rate (EPR) and linear regression rate (LRR), were
used to calculate the rate of change of mangrove shorelines and distance from
1953 to 2011. The study confirms that erosion and accretion, respectively, are
significant at the East Sea and Gulf of Thailand sides of Mui Ca Mau. The East Sea
side had a mean erosion LRR of 33.24 m yr−1. The accretion trend at the
Gulf of Thailand side had an average rate of 40.65 m yr−1. The
results are important in predicting changes of coastal ecosystem boundaries
and enable advanced planning for specific sections of coastline, to minimize
or neutralize losses, to inform provincial rehabilitation efforts and reduce
threats to coastal development and human safety.
Using the Web of Science® database (Institute of Science
Information – ISI, Philadelphia, PA, USA) we analysed pre- (1972-2004) and
post-tsunami (2005) clues about the protective buffer offered by mangroves
and other coastal vegetation in peer-reviewed ISI-rated scientific literature.
Apart from providing a literature review on the above topic, this study reveals
that papers dealing with or suggesting the protective function of mangroves
have been well represented in scientific literature since the 1970s. However,
high-profile journals and their associated media engine tremendously failed
to pick up the importance of the scientific findings related to mangrove
ecosystems. Apparently, the tsunami strike of 26 December 2004 raised the
status of mangrove research overnight, and to a level that was of immediate
interest to researchers in a broad range of other disciplines, and thus fit for
high-profile journals. However, the database showed a highly significant
inverse relationship between the impact factor of the journals in which posttsunami mangrove papers were published and the pre-tsunami mangrove
expertise of the authors. While suggesting that the above trend is worrying,
we present a research framework that should receive much more attention in
research in the future by many journals of low and high impact factor. In the
light of mangroves and protection against a wide range of water-related
impacts - not only tsunamis but also cyclones, sea-level rise, daily tidal action
and heavy El-Niño rains - it should be investigated which type of mangrove
formation or coast-geomorphological settings has which effect. Root type,
vegetation structure and species composition are categories with a lot of
variation within, and may be considered in parallel with for instance a lagoon setting with a fringing forest. Detangling the effect of such complexity under various
water-related impacts will allow fully exploring and understanding the power of
mangroves and other coastal vegetation as protective buffers. These priorities in
fundamental research should be considered in parallel with research and policy
measures on the conservation and restoration of mangroves, taking into account links
with the socio-economic reality of local communities.
Mui Ca Mau at the southern tip of Vietnam supports a large area of mangroves and has a high value for biodiversity and scenic beauty. This area is affected by erosion along the East Sea and accretion along the Gulf of Thailand, leading to the loss of huge stretches of mangroves along the East Sea and, in some cases, loss of environmental and ecosystem services provided by mangroves. In this study, we used remotely sensed aerial (1953), Landsat (1979, 1988 and 2000) and SPOT (1992, 1995, 2004, 2008, 2009 and 2011) images and the Digital Shoreline Analysis System (DSAS) to quantify the rate of mangrove shoreline change for a 58 yr period. There were 1129 transects sampled at 100 m intervals along the mangrove shoreline and two statistical methods, namely end point rate (EPR) and linear regression rate (LRR), were used to calculate the rate of change of mangrove shorelines and distance from 1953 to 2011. The study confirms that erosion and accretion, respectively, are significant at the East Sea and Gulf of Thailand sides of Mui Ca Mau. The East Sea side had a mean erosion LRR of 33.24 m yr(-1). The accretion trend at the Gulf of Thailand side had an average rate of 40.65 m yr(-1). The results are important in predicting changes of coastal ecosystem boundaries and enable advanced planning for specific sections of coastline, to minimize or neutralize losses, to inform provincial rehabilitation efforts and reduce threats to coastal development and human safety.
The decline of Philippine mangroves from half a million hectares in 1918 to only 120 000 ha in 1994 may be traced to local exploitation for fuelwood and conversion to agriculture, salt beds, industry and settlements. But brackishwater pond culture, whose history is intertwined with that of mangroves, remains the major cause of loss. The paper discusses the institutional issues — aquaculture as development strategy, low economic rent of mangroves, overlapping bureaucracy and conflicting policies, corruption, weak law enforcement and lack of political will — relevant to this decline. Recommended policies are based on these institutional factors and the experiences in mangrove rehabilitation including community-based efforts and government programs such as the 1984 Central Visayas Regional Project. These recommendations include conservation of remaining mangroves, rehabilitation of degraded sites including abandoned ponds, mangrove-friendly aquaculture, community-based and integrated coastal area management, and provision of tenurial instruments.
The status of poetry both in the writing curriculum and in wider popular culture is best described as mixed (Wilson, 2009). In spite of a strong post-war tradition of enthusiasm for the teaching of poetry writing, it is currently felt to be marginalised in the writing curriculum (Dymoke, 2007; Ofsted, 2007). This paper reports on the beliefs, attitudes and values revealed by a small-scale questionnaire survey of teachers of poetry writing. It finds that teachers of poetry writing adhere to a personal growth model of English teaching. Furthermore, there is evidence that teachers believe that intuition is central to the composing process of poetry. However, there is also evidence in their responses of the need for explicit teaching of design processes in poetry composition. It would appear that teachers reconcile the apparent conflict in their adherence to a model of teaching poetry writing which requires both inspiration and shaping by using a very subtle blend of different kinds of teaching prompts in the classroom. On this evidence, teachers' knowledge about pedagogy goes beyond what they know as readers to help children become writers of poetry. I argue that teachers demonstrate flexible thinking in their poetry writing pedagogy and this is evidence both of the wariness they feel towards the performative culture they work within and a celebration of practice which remains outside of formal scrutiny.
The Integrated Tropical Coastal Zone Management at AIT is an area of specialization under the Schools of Environment, Resources and Development and Civil Engineering. This interdisciplinary field aims to develop human resources for coastal zone management in the Asia and the Pacific regions where the coastal areas encompass a diverse array of resources and ecosystems with intense human activities. ITCZM MONOGRAPH SERIES The series contains an extract based on the M.Sc. theses to reach the public.
Matang Mangrove Forest Reserve (MMFR) in Peninsular Malaysia is under systematic management since 1902 and still considered as the best managed mangrove forest in the world. The present study on silvimetrics assessed the ongoing MMFR forest management, which includes a first thinning after 15 years, a second thinning after 20 years and clear-felling of 30-year old forest blocks, for its efficiency and productivity in comparison to natural mangroves. The estimated tree structural parameters (e.g. density, frequency) from three different-aged mangrove blocks of fifteen (MF15), twenty (MF20), and thirty (MF30) years old indicated that Bruguiera and Excoecaria spp. did not constitute a significant proportion of the vegetation (<5%), and hence the results focused majorly on Rhizophora apiculata. The density of R. apiculata at MF15, MF20 and MF30 was 4,331, 2,753 and 1,767 stems ha-1, respectively. In relation to ongoing practices of the artificial thinnings at MMFR, the present study suggests that the first thinning could be made earlier to limit the loss of exploitable wood due to natural thinning. In fact, the initial density at MF15 was expected to drop down from 6,726 to 1,858 trees ha-1 before the first thinning. Therefore the trees likely to qualify for natural thinning, though having a smaller stem diameter, should be exploited for domestic/commercial purposes at an earlier stage. The clear-felling block (MF30) with a maximum stem diameter of 30 cm was estimated to yield 372 t ha-1 of the above-ground biomass and suggests that the mangrove management based on a 30-year rotation is appropriate for the MMFR. Since Matang is the only iconic site that practicing sustainable wood production, it could be an exemplary to other mangrove locations for their improved management.
Mangrove forests prominently occupy an intertidal boundary position where the effects of sea level rise will be fast and well visible. This study in East Africa (Gazi Bay, Kenya) addresses the question of whether mangroves can be resilient to a rise in sea level by focusing on their potential to migrate towards landward areas. The combinatory analysis between remote sensing, DGPS-based ground truth and digital terrain models (DTM) unveils how real vegetation assemblages can shift under different projected (minimum (+9 cm), relative (+20 cm), average (+48 cm) and maximum (+88 cm)) scenarios of sea level rise (SLR). Under SLR scenarios up to 48 cm by the year 2100, the landward extension remarkably implies an area increase for each of the dominant mangrove assemblages except for Avicennia marina and Ceriops tagal, both on the landward side. On the one hand, the increase in most species in the first three scenarios, including the socio-economically most important species in this area, Rhizophora mucronata and C. tagal on the seaward side, strongly depends on the colonisation rate of these species. On the other hand, a SLR scenario of +88 cm by the year 2100 indicates that the area flooded only by equinoctial tides strongly decreases due to the topographical settings at the edge of the inhabited area. Consequently, the landward Avicennia-dominated assemblages will further decrease as a formation if they fail to adapt to a more frequent inundation. The topography is site-specific; however non-invadable areas can be typical for many mangrove settings.
Qualitative and quantitative characterization of mangrove vegetation structure and dynamics is required for assessment of coastal habitat vulnerability. Changes in mangrove forests around Douala, Cameroon, have been documented using aerial photography between 1974 and 2009. The distribution pattern of tree species was also assessed in 2009 following the point-centered quarter method (PCQM+) protocol. Pristine mangroves observed in 1974 had been disturbed markedly in 2003 and 2009. Some of the pre-existing mangroves were entirely replaced by settlements, road, and crops (maize, bean, banana, oil palm, green vegetables, and sugar cane plantations). From 1974 to 2003, 39.86 % of mangrove forests have disappeared; the net loss of 22.10 % occurred between 2003 and 2009 alone. Mangrove forest area had decreased 53.16 % around Douala over a 35-year period from 1974 to 2009 concurrent with a substantial increase of settlements (60 %), roads (233.33 %), agriculture areas (16 %), non-mangrove areas (193.33 %), and open water (152.94 %). Field survey showed that almost one third of the quadrants in the remaining mangrove forest were empty. The disrupted mangrove forest has an overall mean height, absolute density, and basal area of 19.80 m, 158 trees ha−1, and 110.44 m2 ha−1, respectively. In comparison with scientific literature on mangrove degradation, this puts the mangroves around Douala at the top of the “peri-urban mangrove degradation” list. In addition, beyond listing of mangrove plants on the Red List of Threatened Species which will seldom lead to widely distributed species being listed, we call for the creation of a Red List of Locally Threatened Ecosystems, which in contrast is likely to list mangroves as an ecosystem under critical risk of (local) extinction in many countries around the globe, in particular, peri-urban sites.
By taking the advantages of remote sensing technology, changes of land cover in Ca Mau
Peninsular (the Southern part of the Mekong delta) and erosion of riverbank of the Mekong River have
been defined. Change detection using time-series optical and radar satellite images (Landsat, SPOT and
Radarsat) is the main approach in this study. Typical land cover in Ca Mau Peninsular is mangrove; its
changes are observable by analysing imageries from 1973 to 2008. The results showed that more than
half of the mangrove area was converted into shrimp farms. This made forest cover severely declined.
Riverbank of the Mekong River also was detected to be eroded and accreted in a complicated form.
Locations along the left and right banks of Tien and Hau river are defined as hot spots that are seriously
suffered erosion. Topographic maps in 1966-1968 were taken into account as base line data, which was
analyzed along with satellite images from 1989 to 2009. In addition, the Digital Shoreline Analysis System
(DSAS) package was taken to analyze trend of changes in terms of changing prediction.
Rates of direct and coupled nitrification-denitrification were measured with 15N isotope techniques in intact sediment cores from fringe, basin, and riverine mangroves in Terminos Lagoon, Mexico. We used intact sediment cores to evaluate differences in denitrification rates. The lack of 15N, production in all cores amended with 200 (or 100) pmol core- 1 15NH,+ and the high recovery of 15N in the sediment in five of eight such experiments indicate that coupled nitrification-denitrification was not important to nitrogen transfor- mation during the 8-10-d incubations. However, when we added 450 II.01 core-* 15NH,+ and *5N0,-- to cores from the riverine mangrove, N2 production rates ranged from 28.9 to 22 1.1 pmol N m-2 h-l for each nutrient. We compare coupled nitrification-denitrification rates among different types of mangrove forests under natural conditions in the neotropics. Our results with nitrogen isotopes suggest that the uptake of inorganic N from tidal waters within mangrove ecosystems does not necessarily represent a nitrogen sink via denitrification, but rather a retention of nitrogen in mangrove sediments.
Seedling recruitment underpins natural regeneration and contributes to the restocking of forest stands, which in the long term determines the structure and functioning of mangrove ecosystems. Propagule predation (among other factors) has been found to play an important role in determining seedling distribution patterns in many mangrove stands. The role of propagule predation in influencing the observed regeneration in a Rhizophora mucronata reforested stand (9 yr old) with various spontaneously established mangrove species was investigated by looking at the effects of pruning, position (planted/vertical or prone/horizontal on the forest floor to simulate stranding) and species (Rhizophora mucronata, Ceriops tagal and Bruguiera gymnorrhiza) found to be spontaneously growing in the plantation. Predation intensity was higher (p = 0.05) in the pruned part of the stand than in the unpruned part. Prone propagules were preyed on more (p = 0.05) than the planted category, while R. mucronata was the species least preyed on compared to C. tagal and B. gymnorrhiza, suggesting that predation favors the recruitment of R. mucronata into this conspecific stand. Significant differences among prone and planted propagules suggest that predation is intense during the stranding phase, and this may play a critical role in limiting seedling establishment and subsequent recruitment. Predation is suggested to be a regulator of competition in this high-density stand by eliminating or reducing potential competitors, alluding to a 'mutual relationship' between crab predators and mangrove trees.
In response to widespread global degradation of mangrove forests, many initiatives have been undertaken to reforest degraded sites. However, many of these replantings are mono- specific, raising questions regarding habitat change and reduced ecological functions in mangrove plantations compared to natural mixed mangrove forests. The main objective of this study was to determine whether colonising mangrove juveniles can be recruited into the adult tree layer and thus enhance the structural complexity of previously reforested monospecific stands. Vegetation structure of originally monospecific replanted mangrove stands (Sonneratia alba and Rhizophora mucronata) that were 8 yr old was assessed. Instantaneous juvenile (seedling/sapling) diversity and abundance were determined. Adjacent natural stands were used as reference sites. The R. mucronata stand had the same species richness as its natural reference and thus had a higher Complexity Index due to recruitment of non-planted species into the adult tree population than in a previous assessment when it was monospecific. Juvenile species richness and diversity were similar between the R. mucronata stands (reforested and natural); however, the total juvenile density was significantly higher (p < 0.05) in the natural stand (7390 ± 660 juveniles ha -1 ) than in the reforested stand (2048 ± 667 juveniles ha -1 ). In contrast, the adult vegetation layer of the S. alba reforested stand remained monospecific, suggesting 100% mortality of previously observed non-planted mangrove juveniles. Many replanted mangroves around the globe are monocultures and are thus likely to have low thresholds to pertur- bations, as they do not benefit from the 'portfolio effect' provided in mixed species stands. Successful recruitment of non-planted species into replanted monospecific mangroves stands may therefore enhance ecosystem productivity and stability. However, more research needs to be conducted on traits of different mangrove species and their contribution to ecosystem productivity and sensitivities to environmental perturbations.
This paper presents an automated method for mangrove stand recognition (delineation and labeling) and species mapping based on fuzzy per‐pixel classification techniques of a QuickBird satellite image. The four dominant mangrove species in Gazi Bay (Kenya) are mapped with an overall accuracy of 72 percent, where the two socio‐economically most important species are mapped with user accuracies above 85 percent. Mangrove stand maps were compared to visual delineations done by an expert interpreter and the quality was based on the quantity of overlap one has with the other. An overall correspondence up to 86 percent was achieved.
The lower reaches of River Kelantan form a vast delta (1200 ha) consisting of bay, mangrove and estuary on the northeast coast of Peninsular Malaysia. The present study was conducted to assess the mangrove vegetation at Tumpat based on ground-truth and remote sensing measurements. The mangroves are composed of several species including Nypa fruticans, Sonneratia caseolaris, Avicennia alba, Rhizophora apiculata, R. mucronata and Bruguiera gymnorrhiza, in order of dominance. The point-centred quarter method (PCQM) was used to estimate the stem density (number of stems/0.1 ha) and basal area (m/0.1 ha) at selected sites on the ground. Recent high-resolution multispectral satellite data (QuickBird 2006, 2.4 m spatial resolution of the multispectral image) were used to produce land-use/cover classification and Normalized Differential Vegetation Index (NDVI) mapping for the delta. The area statistics reveal that mangroves occupy 339.6 ha, while coconut plantation dominates the vegetation (715.2 ha), followed by settlements (621.6 ha), sandbar (148.4 ha), agriculture (89 ha) and aquaculture (42.7 ha). Although the relationship between the spectral indices and dendrometric parameters was weak, we found a very high significance between the (mean) NDVI and stem density (p = 1.3 × 10). The sites with young/growing and also mature trees with lush green cover showed greater NDVI values (0.40–0.68) indicating healthy vegetation, while mature forests under environmental stress due to sand deposition and/or poor tidal inundation showed low NDVI values (0.38–0.47) and an unhealthy situation. Overall, a combination of ground survey and remote sensing provided valuable information for the assessment of mangrove vegetation types (i.e. young/growing or mature forest) and their health in Tumpat, Kelantan Delta.
ha -1 ), and the former's mean height was also similar to that of western creek sites (1 and 2), but lower than the eastern creek sites (4 and 5). The western creek sites had the highest seedling mortality (61 % for both) and lowest growth rates recorded over the two year period compared to a mortality of 45 % for the eastern sites. An analysis of seedling growth over the two years as a function of measured environmental factors showed a weak interaction, with height above datum (HAD) and canopy cover showing the highest correlation of only 30 %. The high mortality on the western creek sites may be attributed to harsh environmental conditions due to the limited expanse of the intertidal area of the western creek mangroves compounded with anthropogenic pressure due to its proximity to human settlements. Overall, C. tagal forests at Gazi Bay seem to be more vulnerable to environmental stress because they occur at the upper intertidal area, which limits their long-term structural development. Of the four species common at Gazi, C. tagal is the least structurally developed with very low basal areas and mean heights, which are both important determinants of wood quality. These upper-shore forests therefore require management approaches distinct from those of other species to ensure that their natural regeneration and overall structural development are not unsustainably compromised.
We studied the vegetation structure dynamics of mangroves, in order to contribute to an overall view on the conditions of propagule establishment from the moment they detach from the parental tree. Microtopographical measurements, quantitative data on vegetation, and propagule counts were collected in Gazi Bay (Kenya) and utilized in a 'geographical information systems' (GIS) environment where all modelling took place based on digital terrain modelling (DTM). Suitability maps were created for propagules of Rhizophora mucronata and Ceriops tagal to analyse the disper- sal possibilities (through stranding or self-planting) for the present situation, and for cases of degra- dation and sea level change. The GIS-analyses take into account the available information derived from the field data, but alterations that go hand in hand with degradation and/or sea level changes (e.g. erosion patterns, rates of sediment supply, wave action) were not considered, since our main focus was the behaviour of propagules. We found that the study area has the potential to successfully rejuvenate at present; however, increasing anthropogenic pressure may have severe consequences on propagule dispersal within this mangrove stand, mainly through the loss of aerial root masses, as these were shown to provide stranding areas for propagules. A relatively modest rise in sea level within a time span of 20 yr could affect the distribution pattern and the specific proportion of the juve- nile vegetation layer, leading to notable floristic modifications from a regional point of view.
Over the past few decades, clearing for shrimp farming has caused severe losses of mangroves in the Mekong Delta (MD) of Vietnam. Although the increasing importance of shrimp aquaculture in Vietnam has brought significant financial benefits to the local communities, the rapid and largely uncontrolled increase in aquacultural area has contributed to a considerable loss of mangrove forests and to environmental degradation. Although different approaches have been used for mangrove classification, no approach to date has addressed the challenges of the special conditions that can be found in the aquaculture-mangrove system in the Ca Mau province of the MD. This paper presents an object-based classification approach for estimating the percentage of mangroves in mixed mangrove-aquaculture farming systems to assist the government to monitor the extent of the shrimp farming area. The method comprises multi-resolution segmentation and classification of SPOT5 data using a decision tree approach as well as local knowledge from the region of interest. The results show accuracies higher than 75% for certain classes at the object level. Furthermore, we successfully detect areas with mixed aquaculture-mangrove land cover with high accuracies. Based on these results, mangrove development, especially within shrimp farming-mangrove systems, can be monitored. However, the mangrove forest cover fraction per object is affected by image segmentation and thus does not always correspond to the real farm boundaries. It remains a serious challenge, then, to accurately map mangrove forest cover within mixed systems.
Because shrimp culture in the Mekong Delta develops rapidly, it has negatively impacted the environment, socio-economics and natural resources. In particular, mangrove forests have been altered by the shrimp culture. The area of mangrove forests in the region has been reduced and this is seen especially in Tra Vinh province. The results obtained from GIS (Geography Information System) and RS (Remote Sensing) show the status of mangrove forests in Tra Vinh province in 1965, 1995 (Northeastern part of Tra Vinh Province) and 2001. In 1965, the area of mangrove forests was 21,221 ha making up 56% of total land-use, while in 2001 it was 12,797 ha making up 37% of total land-use. Also based on GIS analysis, over the 36 years (1965-2001), the total coverage of mangrove forests have decreased by 50% since 1965. However, the speed of mangrove forest destruction in the period from 1965 to 1995 was much less than that in the period from 1995 to 2001. The average annual reduction in mangrove forest coverage in the first period (1965-1995) was 0.2% whereas it was 13.1% in the later period (1995-2001). For the long time, mangrove deforestation has been caused by war, collection of firewood and clearing for agriculture, and recently, shrimp farming has significantly contributed rate of mangrove destruction.
Background - In the light of loss of mangrove forests and related biodiversity world-wide the overall objective of the online 'Mangrove Reference Database and Herbarium' is to give a current and historic overview of the global, regional and particularly the local distribution of true mangrove species. Databasing and website construction - All data are based on records containing species location information of all mangrove species (approximately 75). All the mangrove zones around the world are recorded in this database and a species list is available for the sites that have been studied or sampled. In addition, the database provides written and visual information on plant physiognomy, ecological adaptations to the intertidal mangrove habitat and nomenclature. Images of herbarium specimens are included as vouchers. Objectives - The website (http://www.vliz.be/vmdcdata/mangroves/) wants: (1) to offer a relational database for all true mangrove plant species using an expandable taxonomic tree; (2) to display a fact sheet for each mangrove plant species; (3) to present a searchable online distribution map for each species based on point-locations submitted by researchers world-wide in order to display historic as well as current distribution maps using a GIS-interface; (4) to preserve a herbarium reference specimen for each true mangrove species; and (5) to provide an automated determination key to identify mangroves world-wide. Results - The result is a functional database that can be rapidly updated and that provides information for research, management and conservation projects on the world's mangroves (biogeographical, forest management or ecological restoration in the light of species present).
Long-term decadal retrospection in spatio-temporal imagery analyses can only be carried out using aerial photographs, which are still the most detailed remotely sensed data available. Visual interpretation of such imagery is most efficient and inexpensive in the light of ecosystem monitoring research in developing countries, which are often unable to cope with the development or the cost of acquisition of commercial space-borne imaging (e.g. IKONOS, Quickbird). In this light, the present paper explicitly analyses the methodological use of image attributes of air-borne imagery from mangrove forests, and investigates the consistency and constraints of mangrove image attributes in visually interpreted air-borne imagery. Six image attributes are analysed, and their application is illustrated using various mangrove sites in Kenya and Sri Lanka. Comparison of identification keys reveals that minor attributes such as 'ecological position' are informative, and that image attributes for a particular species or genus are apparently less plastic and more widely applicable than formerly assumed. Emphasis on compulsory fieldwork is made and constraints related to reflection and interference, amongst others, are discussed.
c1 Correspondence: Dr Patrik Rönnbäck e-mail: pat@ecology.su.se
In recent years, mangroves have been seriously threatened by shrimp culture development in the Mekong delta of Vietnam. As one way of protecting the mangroves, efforts have been made to develop shrimp-mangrove integrated farming systems through State Forestry Fisheries Enterprises (SFFEs), involving a participatory approach. The present study investigated the shrimp-mangrove farming systems in Ngoc Hien district at the southern tip of the Mekong delta through a detailed farm-level survey, including technical, environmental, social and economic factors. A total of 161 shrimp-mangrove farms on the east and west coasts of Ngoc Hien district were surveyed. The results showed that on the East coast of the delta, the pH of the bottom soil, the water alkalinity, gate width ratio (ratio of gate width to pond area), pond age and mangrove density, and flooding level of ‘flat’ (flat is where the mangroves are planted) in the dry and rainy seasons were significantly correlated with shrimp pond yields. On the west coast, the pH of the bottom soil, dissolved inorganic phosphorus, ditch area, and flooding level of ‘flat’ were found to be significantly correlated with shrimp pond yields. An economic analysis, based solely on the economic returns from shrimp culture showed that the farming systems with a mangrove coverage of 30-50% of the pond area gave the highest annual economic returns. The results demonstrate a better economic return to farmers who maintain mangroves in their farming systems.
Mangroves in Madagascar cover 327 000 ha to 340 300 ha. Several authors have studied these mangroves, but we do not yet have a complete knowledge of these ecosystems. The present study is an attempt to respond to this concern by analyzing dynamics and changes in the extent of the mangrove forest in the Mangoky delta (SW Madagascar) between 1951 and 2000. The comparison between base maps and Landsat TM images shows that the mangrove area remained relatively stable, even increasing slightly (+189 ha) between 1951 and 1979. From 1979 to 1994, its area decreased from 21 426 ha to 11 706 ha (−9720 ha). It then increased again (+84 ha) between 1994 and 2000. The balance was a decrease of 41.74% between 1951 and 2000. These figures may be compared with national (−15% in 56 years) and world (−35% for the last 20 years) statistics. Three main reasons are given to explain these changes: (1) the hydrological and sedimentological behavior of the Mangoky River; (2) the mechanism of plant succession, which depends on tides and on the characteristics of the substratum and (3) human activities and logging, which have increased since the 1980s in the Mangoky delta.
This paper reviews the evolution of land use and mangrove forest management in a coastal commune in Central Vietnam from its early period of environmentally sound management under a common property regime, through State and cooperative management, to individual household allocation under the economic reforms of the 1990s. It analyses in particular the introduction of shrimp culture and its environmental and socioeconomic consequences. The case study demonstrates that, while opening up many economic opportunities, Vietnam's economic reforms have had uneven impacts on income inequality. Like many cases in Asia and Latin America, the disruption of common property resources – through the introduction of aquaculture as a livelihood opportunity and producer of an export crop – leaves farmers indebted and natural resources polluted. But, ironically, it was the financially better-off aquaculture farmers, who had more capacity for risk-taking and investing, who ended up most indebted, in comparison with poorer farmers who had already sold their ponds. The latter were less integrated into the market economy and relied more on marine product collection. This paper suggests that attention to local contexts and histories can contribute to a better understanding of the causes and consequences of environment-poverty interfaces.