The global decline in estuarine and coastal ecosystems (ECEs) is affecting a number of critical benefits, or ecosystem services. We review the main ecological services across a variety of ECEs, including marshes, mangroves, nearshore coral reefs, seagrass beds, and sand beaches and dunes. Where possible, we indicate estimates of the key economic values arising from these services, and discuss how the natural variability of ECEs impacts their benefits, the synergistic relationships of ECEs across seascapes, and management implications. Although reliable valuation estimates are beginning to emerge for the key services of some ECEs, such as coral reefs, salt marshes, and mangroves, many of the important benefits of seagrass beds and sand dunes and beaches have not been assessed properly. Even for coral reefs, marshes, and mangroves, important ecological services have yet to be valued reliably, such as cross-ecosystem nutrient transfer (coral reefs), erosion control (marshes), and pollution control (mangroves). An important issue for valuing certain ECE services, such as coastal protection and habitat-fishery linkages, is that the ecological functions underlying these services vary spatially and temporally. Allowing for the connectivity between ECE habitats also may have important implications for assessing the ecological functions underlying key ecosystems services, such coastal protection, control of erosion, and habitat-fishery linkages. Finally, we conclude by suggesting an action plan for protecting and/or enhancing the immediate and longer-term values of ECE services. Because the connectivity of ECEs across land-sea gradients also influences the provision of certain ecosystem services, management of the entire seascape will be necessary to preserve such synergistic effects. Other key elements of an action plan include further ecological and economic collaborative research on valuing ECE services, improving institutional and legal frameworks for management, controlling and regulating destructive economic activities, and developing ecological restoration options.

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/10-1510.1

The value of estuarine and coastal ecosystem services

Changes in climate extremes and their impacts on the natural physical environment: An overview of the IPCC SREX report

The risk of flood disasters is increasing for many coastal societies owing to global and regional changes in climate conditions, sea-level rise, land subsidence and sediment supply. At the same time, in many locations, conventional coastal engineering solutions such as sea walls are increasingly challenged by these changes and their maintenance may become unsustainable. We argue that flood protection by ecosystem creation and restoration can provide a more sustainable, cost-effective and ecologically sound alternative to conventional coastal engineering and that, in suitable locations, it should be implemented globally and on a large scale.

Ecosystem-based coastal defence in the face of global change

For more than a century, coastal wetlands have been recognized for their ability to stabilize shorelines and protect coastal communities. However, this paradigm has recently been called into question by small-scale experimental evidence. Here, we conduct a literature review and a small meta-analysis of wave attenuation data, and we find overwhelming evidence in support of established theory. Our review suggests that mangrove and salt marsh vegetation afford context-dependent protection from erosion, storm surge, and potentially small tsunami waves. In biophysical models, field tests, and natural experiments, the presence of wetlands reduces wave heights, property damage, and human deaths. Meta-analysis of wave attenuation by vegetated and unvegetated wetland sites highlights the critical role of vegetation in attenuating waves. Although we find coastal wetland vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios; indeed large-scale regional erosion, river meandering, and large tsunami waves and storm surges can overwhelm the attenuation effect of vegetation. However, due to a nonlinear relationship between wave attenuation and wetland size, even small wetlands afford substantial protection from waves. Combining man-made structures with wetlands in ways that mimic nature is likely to increase coastal protection. Oyster domes, for example, can be used in combination with natural wetlands to protect shorelines and restore critical fishery habitat. Finally, coastal wetland vegetation modifies shorelines in ways (e.g. peat accretion) that increase shoreline integrity over long timescales and thus provides a lasting coastal adaptation measure that can protect shorelines against accelerated sea level rise and more frequent storm inundation. We conclude that the shoreline protection paradigm still stands, but that gaps remain in our knowledge about the mechanistic and context-dependent aspects of shoreline protection.

The present and future role of coastal wetland vegetation in protecting shorelines: answering recent challenges to the paradigm

Salt marshes protect coastlines against waves. Wave flume experiments show that marsh vegetation causes substantial wave dissipation and prevents erosion of the underlying surface, even during extreme storm surge conditions.

/pdf/wave-attenuation-over-coastal-salt-marshes-under-storm-surge-cenihcxco5.pdf

Wave attenuation over coastal salt marshes under storm surge conditions

: This report summarizes the life-cycle design and optimization of structures on three islands in Chesapeake Bay. The islands are Poplar, James, and Barren. The life-cycle analysis is accomplished using a new method termed Empirical Life-Cycle Simulation (ELS). The historical storms selected for simulation include both winter storms (extratropical storms) and hurricanes (tropical storms). Historical water levels due to the combined effect of historical storms and astronomical tides are simulated using a numerical model of the entire Chesapeake Bay. A localized wind-wave growth model is used to hindcast historical waves. The waves are transformed to a number of analysis stations around each island using a separate numerical model. For each analysis location, 148-year time histories of waves and water levels at 3-hour intervals are produced for use in the life-cycle analysis phase of the study. A new empirical time series simulation method for waves and water levels is proposed so that the effects of potential future wave and water level climate can be analyzed. Finally, analysis of storm maximum and external analysis of waves and water levels is described for each island. The results of the wave and water level analyses and simulations described above are used to optimize the structure cross sections over the life cycle. Least-cost structural alternatives that also minimize maintenance requirements are proposed based on these investigations.

Life-Cycle Analysis of Mid Bay and Poplar Island Projects, Chesapeake Bay, Maryland

Flood Shoal Response to Inlet Modifications at Barnegat Inlet, New Jersey

The purpose of this study was to analyze the December 1993 breach at Grays Harbor, WA, and assess the threat to the Federal Navigation Project had the breach not been filled the following fall. The study was conducted by quantifying evolution of breach morphology; numerically simulating the ocean wave and water level conditions producing the current through such a breach, including investigation of wide-area implications for the current in Grays Harbor; and numerical modeling breach evolution. Available data on the breach evolution were analyzed with a Geographic Information System. The width of the breach and erosion of the adjacent shoreline are quantified from aerial photographs. Shoreline position and bottom configurations in the vicinity of the now-closed breach are the basis of numerical modeling of wave- and tide-driven currents. Estimates are made of the wave and current climate at South Beach, Pt. Chehalis, and in Half Moon Bay under the assumption of a breach at the jetty. Hydrodynamics for various alternatives of further erosion of the breach are modeled to evaluate flow patterns in a developed breach condition. Sediment transport and evolution of the breach are modeled to assess the potential for continued breach growth and long-term assessment of breach stability. Study products are intended to assist the U.S. Army Engineer District, Seattle, in developing a long-term management plan for protecting Federal navigation project features.

Breach History and Susceptibility Study, South Jetty and Navigation Project, Grays Harbor, Washington

: This report documents a study performed for the U.S. Army Engineer District, Seattle to identify and evaluate feasible methods for reducing annual maintenance dredging in the outer Federal navigation channel at Grays Harbor, WA, by modification of the north jetty. Main interest was in potential reduction of southward sand bypassing the north jetty and preservation of the jetty should the neighboring beach erode. Considerable information and predictive capability were generated concerning the behavior of the Federal navigation channel and adjacent coastal and inlet shorelines. The study was conducted as a coordinated multi-disciplinary approach involving field measurement, physical modeling of the hydrodynamics and potential sediment pathways, geomorphic analysis and sediment budget formulation, and numerical modeling of waves, circulation and sediment transport, including modeling of shoreline change and bypassing. Numerous alternatives were considered and subjected to a screening process to identify feasible engineering and physically constructible alternatives within broad criteria. Six alternatives passed the screening and were evaluated. The alternatives concerned an innovative submerged spur that would be placed parallel to the shoreline along the north jetty, partial and full rehabilitation of the north jetty, and a combination of these alternatives with structures of different lengths. The sediment-control alternatives were evaluated relative to the existing condition. The study revealed many wide-area processes controlling sedimentation in and around Grays Harbor. The scale of change in southward- directed bypassing of sediment expected to occur after construction of any of the evaluated alternatives was found to be small compared to the scale of transport at the Grays Harbor entrance from sources originating outside the entrance or by being reworked and redistributed within the entrance.

North Jetty Performance and Entrance Navigation Channel Maintenance, Grays Harbor, Washington. Volume 2. Appendices

: The purpose of this CHETN is to examine storm surge and wave reduction benefits of marsh restoration, as well as the impact of future wetland degradation on local surge and wave conditions. Storm surge simulations of representative moderate and severe hurricanes were performed using the ADCIRC storm surge model, with the inclusion of radiation stress gradients from the STWAVE nearshore wave model. Coupled model simulations were made for wetland landscape configurations in south Louisiana that involved hypothetical restored and degraded wetland features. This is the first in a series of tech notes on the influence of marshes on storm surge and waves.

/pdf/influence-of-marsh-restoration-and-degradation-on-storm-41dt0tl7lp.pdf

Mary A. Cialone

Papers

Life-Cycle Analysis of Mid Bay and Poplar Island Projects, Chesapeake Bay, Maryland

Flood Shoal Response to Inlet Modifications at Barnegat Inlet, New Jersey

Breach History and Susceptibility Study, South Jetty and Navigation Project, Grays Harbor, Washington

North Jetty Performance and Entrance Navigation Channel Maintenance, Grays Harbor, Washington. Volume 2. Appendices

Influence of Marsh Restoration and Degradation on Storm Surge and Waves