Anthropocene Coasts最新文献

In the deep central part of the Bohai Sea off the coast of northern China, long-term observations show significantly lower dissolved oxygen (DO) concentration near the bottom in summer during 2006–2018 than during 1978–2005. The decrease in bottom DO is closely linked to changes in phytoplankton community driven by nutrient structure changes in the water column. From literature review, observations in the phytoplankton community structure indicate an increase in the abundant proportion of dinoflagellate to diatom and miniaturization since the 21st century. The new dominate species of dinoflagel-late and the pico- and nano-celled algae detritus, with slow sinking rate and long residence time, favor the efficient oxygen consumption in the water column and lead to oxygen depletion enhancement and DO concentration decrease after 2006. Analyses also suggest that water temperature, stratification, and resuspension of sediment play less significant roles in long-term variations of DO. The linkage of hypoxia formation to changes of phytoplankton community answers why hypoxia in the Bohai Sea started to occur in the recent decade while eutrophication began since the 1980s. The identified new mechanism of hypoxia formation may be applicable to other coastal seas where eutrophication has led to changes in the phytoplankton community, and should be considered in biogeochemical models.

Energetic swell waves, particularly when they coincide with high water levels, can present significant coastal hazards. To better understand and predict these risks, analysis of the sea levels and waves that generate these events and the resulting coastal impacts is essential. Two energetic swell events, neither of which were predicted by modelled flood forecasts, occurred in quick succession in the English Channel. The first event, on 30 January 2021, produced moderate significant wave heights at or just below the 0.25 year return period along the southwest English coast, but combined with significant swell caused overtopping at East Beach in West Bay and at Chesil Beach. The second event, on 1 February 2021, generated the highest wave energy periods measured at many locations along the southern English coastline and, at high water, caused waves to run up over the promenades at Poole Bay and Christchurch Bay and caused overtopping at Hayling Island. Both events are described in detail, and their spatial footprints are mapped through a joint return period analysis using a copula function. It is found that typical joint return period analysis of water level and significant wave height underestimates potential impacts, while a joint consideration of water level and wave power (P) describes the 31 January event better and a joint consideration of water level and energy period (T_e) best describes the 1 February event. Therefore, it is recommended that T_e and P are adopted for coastal monitoring purposes, and that future studies further explore the use of both parameters for swell monitoring.

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.