Anthropocene Coasts最新文献

Deltas require sufficient sediment to maintain their land area and elevation in the face of relative sea-level rise. Understanding sediment budgets can help in managing and assessing delta resilience under future conditions. Here, we make a sediment budget for the distributary channel network of the Rhine—Meuse delta (RMD), the Netherlands, home to the Port of Rotterdam. We predict the future budget and distribution of suspended sediment to indicate the possible future state of the delta in 2050 and 2085. The influence of climate and anthropogenic effects on the fluvial and coastal boundaries was calculated for climate change scenarios, and the effects of future dredging on the budget were related to port development and accommodation of larger ships in inland ports. Suspended sediment rating curves and a 1D flow model were used to estimate the distribution of suspended sediment and projected erosion and sedimentation trends for branches. We forecast a negative sediment budget (net annual loss of sediment) for the delta as a whole, varying from −8 to −16 Mt/year in 2050 and −11 to −25 Mt/year by 2085, depending on the climate scenario and accumulated error. This sediment is unfavourably distributed: most will accrete in the northern part of the system and must consequently be removed by dredging for navigation. Meanwhile, vulnerable intertidal ecosystems will receive insufficient sediment to keep up with sea-level rise, and some channels will erode, endangering bank protection. Despite increased coastal import of sediment by estuarine processes and increased river sediment supply, extensive dredging for port development will cause a sediment deficit in the future.

Following the significant coastal changes caused by Hurricane Sandy in 2012, engineered berm-dunes were constructed along the New Jersey coastline to enhance protection from future storms. Following construction, property values on Long Beach Island, NJ, increased in three beachfront communities. The projects were financed entirely through federal disaster assistance, but the percentage of future maintenance costs must be covered by local communities. Whether communities are willing or capable of financially contributing to maintenance remains unclear because (i) some homeowners prefer ocean views over the protection afforded by the berm-dune structures, and (ii) stakeholder risk perceptions can change over time. To investigate the relationships between berm-dune geometries, values of coastal protection, and ocean view values, we developed a geoeconomic model of the natural and anthropogenic processes that shape beach and dune morphology. The model results suggest that coastal communities may exhibit significant differences in their capabilities to maintain engineered dunes depending on stakeholder wealth and risk perception. In particular, communities with strong preferences for ocean views are less likely to maintain large-scale berm-dune structures over the long term. If these structures are abandoned, the vulnerability of the coast to future storms will increase.

Protected areas (PAs) are widely applied conservation instruments. Often, they are also expected to help secure livelihoods of poor subsistence, small-scale producers, making the management of PAs often dependent on community support. The usefulness of analyzing the perceptions of PAs among local users to improve the effectiveness of PA management is increasingly recognized; however, there are few studies on spatial perceptions, for example, how users perceive the PA’s geographical boundaries or its zoning, and how these can be used in PA zoning. Here, we analyze how local stakeholders perceive two sustainable-use PAs on the Amazon coast, the changes they have brought about, and their current management. We identify and link the mental models of different user groups to formal conceptualizations of the PAs in legal instruments and identify mismatches related to what the PA means to local stakeholders and where it is located, which need to be considered when building a zoning plan. Because of the frequent research in our study area, we also discuss possible research fatigue in this region. We highlight the challenges and opportunities related to promoting spatial literacy and awareness-raising regarding PAs. We recommend adapting legal instruments to include diverse territorial representations and alternative management tools.

A large-scale sand ridge group is distributed in the central Jiangsu coastal area, and a deposition muddy sea bank was developed in the nearshore area. Quantitative monitoring of coastline changes is of great significance for tidal beach development and protection. The shorelines of the central coast of Jiangsu within six periods (1973–2018) were extracted in this study, and their length changes over the years were analyzed. The Digital Shoreline Analysis System (DSAS) was employed to generate a cross section perpendicular to the baseline and calculate the linear regression rate (LRR) of the shoreline, changes in end point rate (EPR), and net shoreline movement (NSM), based on which the shoreline change features were analyzed. The DSAS results indicated that the shorelines in the study area maintained fluctuating growth and presented a continuous advancing trend towards the sea. From the changes in shoreline evolution distance during 1973–2018, the advancing shorelines in the study area accounted for over 50% of the total shorelines and presented first rising and then declining trends with the period of 2003–2013 taken as the time boundary. The average shoreline change rate was 207 m/year, and the periods with the highest change degrees were 1983–1993 and 1993–2013. The shoreline change tended to be stable during 2013–2018, and only a few estuaries and ports underwent obvious erosion and sedimentation.

Shipping fairways in estuaries are continuously dredged to maintain access for large vessels to major ports. However, several estuaries worldwide show adverse side effects to dredging activities, in particular affecting morphology and ecologically valuable habitats. We used physical scale experiments, field assessments of the Western Scheldt estuary (the Netherlands), and morphodynamic model runs to analyse the effects of dredging and future stresses (climate and sediment management) on a multi-channel system and its ecologically valuable intertidal flats. All methods indicate that dredging and disposal strategies are unfavourable to long-term morphology because dredging creates and propagates the imbalance between shallow and deeper parts of the estuary, causing a loss of valuable connecting channels and fixation of the tidal flats and main channel positions, while countering adverse effects by disposal strategy has limited effectiveness. Changing the disposal strategy towards main channel scour disposal can be economically and ecologically beneficial for the preservation of the multi-channel system. Further channel deepening will accelerate the adverse side effects, whereas future sea-level rise may revive the multi-channel system.

Coastal environments are subject to trace metal pollution via a combination of industry and urbanised sources. The pollutants accumulate within surface sediments, especially in the quieter backwaters of estuaries. An environmental assessment of the Port Hacking estuary, southern Sydney, Australia, was undertaken using 233 surface samples. Trace metal concentrations (Ni, Cr, Cu, Zn, Pb, and As) in these samples indicated that most elements in Port Hacking were below the relevant ANZECC/ARMCANZ guideline low trigger value (ISQG-low), but a few sites exceeded this value. The low trace metal concentrations are mainly because the catchment areas have limited urban development and few discharge points. In contrast, one site in Gunnamatta Bay has Zn and Cu concentrations that exceeded the high trigger value (ISQG-high), due to moored vessels, boatyards, and stormwater outlets in this vicinity. Port Hacking is considered to be relatively unpolluted and healthy when compared with other Sydney estuaries.

Salt marshes are key coastal ecosystems that provide habitats for wildlife, including invertebrates, fishes, and birds. They provide ecosystem services such as protection from storm surges and waves, attenuation of flooding, sequestration of pollutants (e.g., blue carbon), and nutrient removal. They are currently under great threat from sea level rise (SLR). We collected information about trends in the horizontal extent (acreage) of New Jersey salt marshes and recent elevation changes compared with the current local rate of SLR in New Jersey, which is between 5 and 6 mm year⁻¹. We found pervasive, although variable, rates of marsh loss that resulted from both anthropogenic disturbance as well as edge erosion and interior ponding expected from SLR. Elevation trends suggest that the current rates of SLR exceed most marsh elevation gains, although some Phragmites-dominated marshes keep pace with SLR. Four potential remedies to address current coastal trends of marsh loss were described in the context of New Jersey’s regulatory and management environment: protection of marsh inland migration pathways, altered management of Phragmites, thin layer sediment placement, and living shoreline installations. Proactive steps are necessary if coastal wetland ecosystems are to be maintained over the next few decades.