Managed Retreat of Saline Coastal Wetlands: Challenges and Opportunities Identified from the Hunter River Estuary, Australia

Palynological, loss-on-ignition, and X-ray fluorescence data from a 5.25 m sediment core from a mangrove forest at the mouth of the Shark River Estuary in the southwestern Everglades National Park, Florida were used to reconstruct changes occurring in coastal wetlands since the mid-Holocene. This multi-proxy record contains the longest paleoecological history to date in the southwestern Everglades. The Shark River Estuary basin was formed ~ 5700 cal yr BP in response to increasing precipitation. Initial wetlands were frequently-burned short-hydroperiod prairies, which transitioned into long-hydroperiod prairies with sloughs in which peat deposits began to accumulate continuously about 5250 cal yr BP. Our data suggest that mangrove communities started to appear after ~ 3800 cal yr BP; declines in the abundance of charcoal suggested gradual replacement of fire-dominated wetlands by mangrove forest over the following 2650 yr. By ~ 1150 cal yr BP, a dense Rhizophora mangle dominated mangrove forest had formed at the mouth of the Shark River. The mangrove-dominated coastal ecosystem here was established at least 2000 yr later than has been previously estimated.

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Evolutions of 30-Year Spatio-Temporal Distribution and Influencing Factors of Suaeda salsa in Bohai Bay, China

Remote Sensing ◽

10.3390/rs14010138 ◽

2021 ◽

Vol 14 (1) ◽

pp. 138

Author(s):

Hongyan Yin ◽

Yuanman Hu ◽

Miao Liu ◽

Chunlin Li ◽

Yu Chang

Keyword(s):

Influencing Factors ◽

Coastal Wetlands ◽

Yellow River ◽

River Estuary ◽

Google Earth ◽

River Delta ◽

Liaoning Province ◽

Suaeda Salsa ◽

Bohai Bay ◽

Dynamic Changes

Suaeda salsa (L.) Pall. (S. salsa) acts as a pioneer species in coastal wetlands due to its high salt tolerance. It has significant biodiversity maintenance, socioeconomic values (e.g., tourism) due to its vibrant color, and carbon sequestration (blue carbon). Bohai bay region, the mainly distributed area of S. salsa, is an economic intensive region with the largest economic aggregate and population in northern China. The coastal wetland is one of the most vulnerable ecosystems with the urbanization and economic developments. S. salsa in Bohai Bay has been changed significantly due to several threats to its habitat in past decades. In this paper, we analyzed all available archived Landsat TM/ETM+/OLI images of the Bohai Bay region by using a decision tree algorithm method based on the Google Earth Engine (GEE) platform to generate annual maps of S. salsa from 1990 to 2020 at a 30-m spatial resolution. The temporal-spatial dynamic changes in S. salsa were studied by landscape metric analysis. The influencing factors of S. salsa changes were analyzed based on principal component analysis (PCA) and a logistic regression model (LRM). The results showed that S. salsa was mainly distributed in three regions: the Liao River Delta (Liaoning Province), Yellow River Delta (Shandong Province), and Hai River Estuary (Hebei Province, Tianjin). During the past 31 years, the total area of S. salsa has dramatically decreased from 692.93 km2 to 51.04 km2, which means that 92.63% of the area of S. salsa in the Bohai Bay region was lost. In the 641.89 km2 area of S. salsa that was lost, 348.80 km2 of this area was converted to other anthropic land use categories, while 293.09 km2 was degraded to bare land. The landscape fragmentation of S. salsa has gradually intensified since 1990. National Nature Reserves have played an important role in the restoration of suitable S. salsa habitats. The analysis results for the natural influencing factors indicated that precipitation, temperature, elevation, and distance to the coastline were considered to be the major influencing factors for S. salsa changes. The results are valuable for monitoring the dynamic changes of S. salsa and can be used as effective factors for the restoration of S. salsa in coastal wetlands.

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Continuous Change Mapping to Understand Wetland Quantity and Quality Evolution and Driving Forces: A Case Study in the Liao River Estuary from 1986 to 2018

Remote Sensing ◽

10.3390/rs13234900 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4900

Author(s):

Jianwei Peng ◽

Shuguang Liu ◽

Weizhi Lu ◽

Maochou Liu ◽

Shuailong Feng ◽

...

Keyword(s):

Coastal Wetlands ◽

Coastal Wetland ◽

Driving Forces ◽

Land Reclamation ◽

River Estuary ◽

Tidal Flats ◽

Liaoning Province ◽

Coastal Zones ◽

Continuous Change ◽

Landsat Images

Coastal wetland ecosystems, one of the most important ecosystems in the world, play an important role in regulating climate, sequestering blue carbon, and maintaining sustainable development of coastal zones. Wetland landscapes are notoriously difficult to map with satellite data, particularly in highly complex, dynamic coastal regions. The Liao River Estuary (LRE) wetland in Liaoning Province, China, has attracted major attention due to its status as Asia’s largest coastal wetland, with extensive Phragmites australis (reeds), Suaeda heteroptera (seepweed, red beach), and other natural resources that have been continuously encroached upon by anthropogenic land-use activities. Using the Continuous Change Detection and Classification (CCDC) algorithm and all available Landsat images, we mapped the spatial–temporal changes of LRE coastal wetlands (e.g., seepweed, reed, tidal flats, and shallow marine water) annually from 1986 to 2018 and analyzed the changes and driving forces. Results showed that the total area of coastal wetlands in the LRE shrank by 14.8% during the study period. The tidal flats were the most seriously affected type, with 45.7% of its total area lost. One of the main characteristics of wetland change was the concurrent disappearance and emergence of wetlands in different parts of the LRE, creating drastically different mixtures of wetland quality (e.g., wetland age composition) in addition to area change. The reduction and replacement/translocation of coastal wetlands were mainly caused by human activities related to urbanization, tourism, land reclamation, and expansion of aquaculture ponds. Our efforts in mapping annual changes of wetlands provide direct, specific, and spatially explicit information on rates, patterns, and causes of coastal wetland change, both in coverage and quality, so as to contribute to the effective plans and policies for coastal management, preservation, and restoration of coastal ecosystem services.

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Challenges and opportunities for sustaining coastal wetlands and oyster reefs in the southeastern United States

Journal of Environmental Management ◽

10.1016/j.jenvman.2021.113178 ◽

2021 ◽

Vol 296 ◽

pp. 113178

Author(s):

Tricia Kyzar ◽

Ilgar Safak ◽

Just Cebrian ◽

Mark W. Clark ◽

Nicole Dix ◽

...

Keyword(s):

United States ◽

Coastal Wetlands ◽

Southeastern United States ◽

Oyster Reefs ◽

Challenges And Opportunities

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Spatial and seasonal variations in physico-chemical parameters of the Imo River Estuary, Niger Delta, Nigeria

Journal of Aquatic Sciences ◽

10.4314/jas.v35i1.4 ◽

2020 ◽

Vol 35 (1) ◽

pp. 29-38

Author(s):

L. E. Obuba ◽

A.A. Nlewadim ◽

A. Uka

Keyword(s):

Water Quality ◽

Coastal Wetlands ◽

River Estuary ◽

Oxygen Demand ◽

Principal Component ◽

Chemical Parameters ◽

Physico Chemical ◽

Chemical Factors ◽

Analysis Of Results

Variations in the water quality of the Imo River estuary was investigated by measuring values of selected physico-chemical parameters. Samples were collected bi-monthly between April 2015 and March 2016, covering the dry and wet seasons of the year. Three stations were selected: upstream (Kalibiama), midstream (Opobo) and downstream (Queenstown). Analysis of results showed that physico-chemical parameters were affected more on seasonal than spatial scale. Principal component analysis carried out indicated that values of most of the parameters recorded within the stations clustered together. On the other hand, dispersed values were recorded in months and seasons with significant variations at (p≤0.05) among most parameters. The high spatial variations in phosphates, suspended solids and lead could be associated to human activities like laundry and waste disposal within Opobo and Kalibiama stations. While, high seasonal variability in most parameters could be associated with intense sunshine, cloud cover and tidal intrusion/dilution due to runoff. It can be concluded that nutrient fluxes due to nitrogenous fertilizers are not a problem within the estuary. However, chemical factors and biodegradable components which cause fluctuations in biological oxygen demand are more of the challenge. Keywords: Land-use, nutrient flux, water-quality, pollution, coastal wetlands.

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