Coastal wetland adaptation to sea level rise: Quantifying potential for landward migration and coastal squeeze

Intertidal coastal wetlands, including tidal marshes and mangrove forests, are at risk of disappearing under the influence of global sea level rise (SLR). Loss of their ecosystem services could significantly impact global carbon budgets, increase coastal erosion and flooding and lead to loss of fisheries, particularly along densely populated coastal zones such as large estuaries and deltas. Regional to global-scale projections suggest a reduction in present-day coastal wetland area by 20% to 90% in response to projected rates of future SLR. Recent studies have highlighted the importance of coastal squeeze, i.e. the inhibition of inland migration of tidal coastal wetlands due to the existence of anthropogenic infrastructure, in combination with wetland loss due to sea level rise, which is aggravated by a global decline in coastal sediment supply.Nature-based adaptation, consisting of the reservation or creation of space for inland wetland expansion, is widely regarded as a promising strategy to counteract coastal squeeze and create/restore natural habitats through inland migration. Based on global and regional modelling outputs, this paper discusses how different scenarios of global population growth, expected declines in global sediment supply, delta subsidence and various coastal management strategies impact on global areas of intertidal coastal wetlands, and coastal squeeze in particular. For example, we estimate that until the year 2100 up to 280,000 km2 of coastal wetlands may be lost due to coastal squeeze. If strategically implemented on a regional to global scale nature-based solutions to coastal management could increase the global total area of intertidal coastal wetlands by up to 60%.However our current understanding of this process is very limited, partly due to the limited field evidence in sedimentary archives (e.g. during the early Holocene where SLR were high). We argue that this is related to the combined effects of wetland inland migration and wetland drowning during periods of high SLR rates, raising the question as to whether or not future coastal wetland will be able to provide ecosystem services comparable to those of natural systems.

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Cultural ecosystem services caught in a ‘coastal squeeze’ between sea level rise and urban expansion

Global Environmental Change ◽

10.1016/j.gloenvcha.2020.102209 ◽

2021 ◽

Vol 66 ◽

pp. 102209

Author(s):

Lindsey S. Smart ◽

Jelena Vukomanovic ◽

Erin O. Sills ◽

Georgina Sanchez

Keyword(s):

Ecosystem Services ◽

Sea Level Rise ◽

Sea Level ◽

Urban Expansion ◽

Cultural Ecosystem Services ◽

Coastal Squeeze

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Impact of Barrier Breaching on Wetland Ecosystems under the Influence of Storm Surge, Sea-Level Rise and Freshwater Discharge

Wetlands ◽

10.1007/s13157-019-01219-x ◽

2019 ◽

Vol 40 (4) ◽

pp. 771-785 ◽

Cited By ~ 1

Author(s):

Xiaorong Li ◽

Nicoletta Leonardi ◽

Andrew J. Plater

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

River Discharge ◽

Coastal Wetland ◽

Storm Surges ◽

Wetland Ecology ◽

Barrier Beach ◽

Wetland Ecosystems ◽

Wetland Habitats

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.

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Beyond just sea-level rise: considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change

Global Change Biology ◽

10.1111/gcb.13084 ◽

2015 ◽

Vol 22 (1) ◽

pp. 1-11 ◽

Cited By ~ 126

Author(s):

Michael J. Osland ◽

Nicholas M. Enwright ◽

Richard H. Day ◽

Christopher A. Gabler ◽

Camille L. Stagg ◽

...

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

Coastal Wetland ◽

Vulnerability Assessments

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Modelling Actual and Future Seawater Intrusion in the Variconi Coastal Wetland (Italy) Due to Climate and Landscape Changes

Water ◽

10.3390/w11071502 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1502 ◽

Cited By ~ 8

Author(s):

Mastrocicco ◽

Busico ◽

Colombani ◽

Vigliotti ◽

Ruberti

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Seawater Intrusion ◽

Coastal Wetland ◽

Coastal Lagoons ◽

Three Dimensional ◽

Climate Data ◽

Climate Change Effects ◽

Modelling Framework ◽

Groundwater Overexploitation

Coastal freshwater resources are commonly under high risk of being contaminated from seawater. The main processes that affect seawater intrusion are groundwater overexploitation, land use change, and climate change effects. In this context coastal lagoons represent the more sensitive environments prone to seawater intrusion. Numerical modelling is a useful tool to understand and predict seawater intrusion. In this study, a three-dimensional SEAWAT model is employed to simulate the seawater intrusion to coastal aquifers of Variconi Oasis (Italy). The present simulation was divided into a calibration and a validation model, then the model was used to predict the salinization trend up to 2050. Results show the role of the sea in salinizing the beach front, while the retrodunal environment is characterized by transitional environments. Future seawater intrusion scenarios considering only climate data showed no significative differences in respect to the actual situation. The same happens considering also a low sea level rise prediction. On the contrary, the worst scenario (high sea level rise prediction), depicts a quite different situation, with a saline intrusion in the Variconi oasis that will severely affect the fragile transitional ecosystem. This modelling framework can be used to quantify the effects of climate changes in similar coastal environments.

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Thresholds of sea-level rise rate and sea-level rise acceleration rate in a vulnerable coastal wetland

Ecology and Evolution ◽

10.1002/ece3.3550 ◽

2017 ◽

Vol 7 (24) ◽

pp. 10890-10903 ◽

Cited By ~ 7

Author(s):

Wei Wu ◽

Patrick Biber ◽

Matthew Bethel

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Coastal Wetland ◽

Acceleration Rate ◽

Rise Rate ◽

And Sea Level

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The status and future of tidal marshes in New Jersey faced with sea level rise

Anthropocene Coasts ◽

10.1139/anc-2020-0020 ◽

2021 ◽

Vol 4 (1) ◽

pp. 168-192

Author(s):

Judith S. Weis ◽

Elizabeth Burke Watson ◽

Beth Ravit ◽

Charles Harman ◽

Metthea Yepsen

Keyword(s):

New Jersey ◽

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

Coastal Wetland ◽

Storm Surges ◽

Tidal Marshes ◽

Wetland Ecosystems ◽

Marsh Loss ◽

Migration Pathways

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.

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