scholarly journals Alteration and Remediation of Coastal Wetland Ecosystems in the Danube Delta: A Remote-Sensing Approach

Author(s):  
Simona Niculescu ◽  
Cédric Lardeux ◽  
Jenica Hanganu
2021 ◽  
Vol 13 (20) ◽  
pp. 4106
Author(s):  
Shuai Wang ◽  
Mingyi Zhou ◽  
Qianlai Zhuang ◽  
Liping Guo

Wetland ecosystems contain large amounts of soil organic carbon. Their natural environment is often both at the junction of land and water with good conditions for carbon sequestration. Therefore, the study of accurate prediction of soil organic carbon (SOC) density in coastal wetland ecosystems of flat terrain areas is the key to understanding their carbon cycling. This study used remote sensing data to study SOC density potentials of coastal wetland ecosystems in Northeast China. Eleven environmental variables including normalized difference vegetation index (NDVI), difference vegetation index (DVI), soil adjusted vegetation index (SAVI), renormalization difference vegetation index (RDVI), ratio vegetation index (RVI), topographic wetness index (TWI), elevation, slope aspect (SA), slope gradient (SG), mean annual temperature (MAT), and mean annual precipitation (MAP) were selected to predict SOC density. A total of 193 soil samples (0–30 cm) were divided into two parts, 70% of the sampling sites data were used to construct the boosted regression tree (BRT) model containing three different combinations of environmental variables, and the remaining 30% were used to test the predictive performance of the model. The results show that the full variable model is better than the other two models. Adding remote sensing-related variables significantly improved the model prediction. This study revealed that SAVI, NDVI and DVI were the main environmental factors affecting the spatial variation of topsoil SOC density of coastal wetlands in flat terrain areas. The mean (±SD) SOC density of full variable models was 18.78 (±1.95) kg m−2, which gradually decreased from northeast to southwest. We suggest that remote sensing-related environmental variables should be selected as the main environmental variables when predicting topsoil SOC density of coastal wetland ecosystems in flat terrain areas. Accurate prediction of topsoil SOC density distribution will help to formulate soil management policies and enhance soil carbon sequestration.


2018 ◽  
Vol 10 (9) ◽  
pp. 1390 ◽  
Author(s):  
Subrina Tahsin ◽  
Stephen C. Medeiros ◽  
Arvind Singh

Coastal wetlands (CWs) offer numerous imperative functions that support a diverse array of life forms that are poorly adapted for other environments and provide an economic base for human communities. Unfortunately, CWs have been experiencing significant threats due to meteorological and climatic fluctuations as well as anthropogenic impacts. The wetlands and marshes in Apalachicola Bay, Florida have endured the impacts of several extreme hydrologic events (EHEs) over the past few decades. These extreme hydrologic events include drought, hurricane, heavy precipitation and fluvial flooding. Remote sensing has been used and continues to demonstrate promise for acquiring spatial and temporal information about CWs thereby making it easier to track and quantify long term changes driven by EHEs. These wetland ecosystems are also adversely impacted by increased human activities such as wetland conversion to agricultural, aquaculture, industrial or residential use; construction of dikes along the shoreline; and sprawl of built areas. In this paper, we review previous works on coastal wetland resilience to EHEs. We synthesize these concepts in the context of remote sensing as the primary assessment tool with focus on derived vegetation indices to monitor CWs at regional and global scales.


2021 ◽  
Vol 13 (16) ◽  
pp. 8690
Author(s):  
Caiyao Xu ◽  
Lijie Pu ◽  
Fanbin Kong ◽  
Bowei Li

Coastal ecological protection and restoration projects aimed to restore and recover the ecological environment of coastal wetland with high-intensity human reclamation activity, while the integrity of the coastal wetland system with human reclamation activity and the ability of individual land use types to control the overall system were not fully considered. In this study, a six-stage land use conversion network was constructed by using a complex network model to analyze coastal land use dynamic changes in the coastal reclamation area located in eastern China from 1977 to 2016. The results showed that land use types had gradually transformed from being dominated by natural types to artificial types, and the speed of transformation was accelerating. The proportion of un-reclaimed area decreased from 93% in 1977 to 46% in 2007, and finally fell to 8% in 2014 and 2016. Tidal flat and halophytic vegetation were the main output land use types, while cropland, woodland and aquaculture pond were the main input land use types. Cropland had the highest value of betweenness centrality, which played a key role in land use change from 1992 to 2014. The land use system of the coastal reclamation area was the most stable in 2002–2007, followed by 1984–1992, and the most unstable in 2007–2014. The Chinese and local government should carry out some measures to improve the land use in coastal wetland ecosystems, including the allocation and integration of land use for production space, living space, and ecological space, and develop multi-functionality of land use to realize the coastal high-quality development and coastal ecological protection and restoration.


Author(s):  
Erin Keenan ◽  
Jeffy Henderson ◽  
Lauren Malo ◽  
Diana Pedersen

               Our research team is concerned with potential reptile and amphibian road mortality through Little Cataraqui Creek wetland along Front Rd. and Bath Rd. in Kingston, Ontario. The coastal marsh is a provincially significant wetland that supports species of migrating and breeding waterfowl, wetland dependent reptiles and amphibians, and may support some of Ontario’s threatened turtle species. The coastal wetland also provides a protected nesting area for a migrating species within Lake Ontario. Specific species of turtles, salamanders and frogs will be investigated.  Our team will identify general breeding, nesting and migratory behavior patterns of associated wetland species, and establish potential indirect effects on the wetland ecosystem due to population decline. Traffic volume and speed limits of Front Rd. and Bath Rd. at Little Cataraqui Creek Wetland will be identified, and any current wildlife crossing systems in place will be evaluated. Based on this research, our team will establish the significance of wildlife road mortality within Little Cataraqui Creek Wetland at Front Rd. and Bath Rd., and propose suitable mitigation techniques. These techniques may include implementing structural design solutions such as road barriers, culverts, etc., as well as increasing public awareness of wildlife crossing on Bath Rd. and Front Rd. by proposing appropriate traffic laws in the area. Themes include wetland species breeding and nesting behavior, and urban/traffic development issues surrounding wetland ecosystems.


Wetlands ◽  
2019 ◽  
Vol 40 (4) ◽  
pp. 771-785 ◽  
Author(s):  
Xiaorong Li ◽  
Nicoletta Leonardi ◽  
Andrew J. Plater

Abstract Coastal wetland ecosystems and biodiversity are susceptible to changes in salinity brought about by the local effects of climate change, meteorological extremes, coastal evolution and human intervention. This study investigates changes in the salinity of surface water and the associated impacts on back-barrier wetlands as a result of breaching of a barrier beach and under the compound action of different surge heights, accelerated sea-level rise (SLR), river discharge and rainfall. We show that barrier breaching can have significant effects in terms of vegetation die-back even without the occurrence of large storm surges or in the absence of SLR, and that rainfall alone is unlikely to be sufficient to mitigate increased salinity due to direct tidal flushing. Results demonstrate that an increase in sea level corresponding to the RCP8.5 scenario for year 2100 causes a greater impact in terms of reedbed loss than storm surges up to 2 m with no SLR. In mitigation of the consequent changes in wetland ecology, regulation of relatively small and continuous river discharge can be regarded as a strategy for the management of coastal back-barrier wetland habitats and for the maintenance of brackish ecosystems. As such, this study provides a tool for scoping the potential impacts of storms, climate change and alternative management strategies on existing wetland habitats and species.


2015 ◽  
Vol 17 (4) ◽  
pp. 753-762
Author(s):  
Mingquan Wu ◽  
Shakir Muhammad ◽  
Fang Chen ◽  
Zheng Niu ◽  
Changyao Wang

A new model performance better than the MODIS GPP product for wetland ecosystems was proposed and validated.


2019 ◽  
Vol 16 (2) ◽  
pp. 425-436 ◽  
Author(s):  
Hilary Ford ◽  
Angus Garbutt ◽  
Mollie Duggan-Edwards ◽  
Jordi F. Pagès ◽  
Rachel Harvey ◽  
...  

Abstract. Carbon stored in coastal wetland ecosystems is of global relevance to climate regulation. Broadscale inventories of this “blue” carbon store are currently lacking and labour intensive. Sampling 23 salt marshes in the United Kingdom, we developed a Saltmarsh Carbon Stock Predictor (SCSP) with the capacity to predict up to 44 % of spatial variation in surface soil organic carbon (SOC) stock (0–10 cm) from simple observations of plant community and soil type. Classification of soils into two types (sandy or not-sandy) explained 32 % of variation in SOC stock. Plant community type (five vegetation classes) explained 37 % of variation. Combined information on soil and plant community types explained 44 % of variation in SOC stock. GIS maps of surface SOC stock were produced for all salt marshes in Wales (∼4000 ha), using existing soil maps and governmental vegetation data and demonstrating the application of the SCSP for large-scale predictions of blue carbon stores and the use of plant community traits for predicting ecosystem services.


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