Marsh persistence under sea-level rise is controlled by multiple, geologically variable stressors

Mitchell, Molly; Herman, Julie; Bilkovic, Donna Marie; Hershner, Carl

doi:10.1080/20964129.2017.1396009

Cited by 40 publications

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References 56 publications

(55 reference statements)

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“…Human impacts are typically perceived as barriers to wetland migration, but people also facilitate sea-247 level driven land conversion, and the net-impact can be difficult to discern. Historical marsh migration 248 rates likely decrease with the degree of coastal development in the Chesapeake Bay region, but the 249 relationship is weak and highly site specific 19,85 . Elsewhere, suburban lawns convert to marsh as quickly 250 as adjacent forests 37 , and reclaimed agricultural areas are particularly susceptible to salinization and 251 land conversion 40 .…”

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“…In contrast, ghost forests are rare in 239 Western Europe and China because extensive seawalls and dykes protect uplands from sea level rise and 240 coastal flooding 31,84 . Large flood control structures are less common in the United States, but migration 241 of wetlands into submerging uplands may instead be prevented by local barriers including berms, 242 bulkheads, roads, ditches with floodgates, and impervious surfaces80,85 . For example, 42% of all land less 243 than 1 m above spring high water is currently developed along the U.S. Atlantic coast, whereas less than 244 10% is currently protected against development86 .…”

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Sea-level driven land conversion and the formation of ghost forests

2019

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4 5 6 Ghost forests created by the submergence of low-lying land are one of the most striking indicators of 7 climate change along the Atlantic coast of North America. Although dead trees at the margin of 8 estuaries were described as early as 1910, recent research has led to new recognition that the 9 submergence of terrestrial land is geographically widespread, ecologically and economically 10 important, and globally relevant to the survival of coastal wetlands in the face of rapid sea level rise.11 This emerging understanding has in turn generated widespread interest in the physical and ecological 12 mechanisms influencing the extent and pace of upland to wetland conversion. Choices between 13 defending the coast from sea level rise and facilitating ecosystem transgression will play a 14 fundamental role in determining the fate and function of low-lying coastal land. 15 16 Sea level rise rates have been accelerating since the end of the 19 th century, impacting low elevation 17 land along coasts and estuaries around the world 1 . Sea level rise enhances flooding and saltwater 18 intrusion, and threatens coastal communities, infrastructure, and ecosystems 2-4 . Ghost forests and 19 abandoned farmland are striking indicators of sea-level driven land conversion. Dead trees and stumps 20 surrounded by marshland, for example, represent relic forestland that has been replaced by intertidal 21 vegetation. Similarly, bare soil and wetland plants at the edges of agricultural fields indicate the 22 65 coastal land submergence. The review ends with implications for land management, and highlights 66 uncertainty in local flood defense strategy as the key knowledge gap limiting our ability to predict future 67 sea-level driven land conversion and its impact on coastal ecosystems. 68 69 Extent and physical controls of historical land submergence 70 Ghost forests, abandoned agricultural fields, and other indicators of historical land submergence occur 71 throughout low-lying and gently sloping portions of the Atlantic and Gulf coasts of North America 15-20 72 (Fig. 1). Land submergence is most extensive within the mid-Atlantic sea-level rise hotspot that stretches 73 from North Carolina to Massachusetts, where relative sea level is rising three times faster than eustatic 74 rates 27 . For example, 400 km 2 of uplands in the Chesapeake Bay region have converted to tidal marsh 75 since the mid-1800s 19 , and large tracts of hardwood and cedar forest death have been observed in 76 Delaware Bay 16 . However, ghost forests are not confined to the sea level rise hotspot. Ghost forests 77 have also been documented throughout the Florida Gulf Coast 17,18 , the St. Lawrence estuary of Canada 15 , 78 and tidal freshwater forests in South Carolina, Georgia, and Louisiana 21,28 . There has been 148 km 2 of 79 forest conversion over 120 years along the Florida Gulf Coast 17 , and near complete loss of pine forests in 80 the Lower Florida Keys 29 . Surprisingly, the phenomenon has not been widely documented on coastal 81 plains outside of...

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Sea-level driven land conversion and the formation of ghost forests

2019

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“…Marsh retreat potential is linked to local land use and surrounding elevations (Mitchell, Herman, Bilkovic, & Hershner, ). Living shorelines built in low elevation areas will naturally be able to migrate landward, as long as the surrounding land use is compatible.…”

Section: Living Shoreline Siting Is Critical For Enhanced Longevitymentioning

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Embracing dynamic design for climate‐resilient living shorelines

Mitchell¹,

Bilkovic²

2019

Journal of Applied Ecology

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climate change, coastal resilience, defenses, erosion, green infrastructure, marsh, nature-based, sea level rise This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. How to cite this article: Mitchell M, Bilkovic DM. Embracing dynamic design for climate-resilient living shorelines. J Appl

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“…In very narrow fringing marshes, riparian overhang may be sufficient to detrimentally shade the Spartina underneath, thereby resulting in reduced growth and stem density. In one of the major sub-estuaries of the Chesapeake Bay, the York River, researchers identified that fringing and extensive marshes were the most at-risk marsh types, while embayed marshes are doing well (Mitchell et al 2017). If erosion rates outpace landward migration of the marsh, the marsh will eventually disappear.…”

Section: Distribution and Condition Indexmentioning

confidence: 99%

“…Coastal squeeze has been noted in a number other systems (Doody andWilliams 2004, Torio andChmura 2013) and represents one of the major ecological concerns for intertidal habitats with accelerating sea level rise. In one of the major sub-estuaries of the Chesapeake Bay, the York River, researchers identified that fringing and extensive marshes were the most at-risk marsh types, while embayed marshes are doing well (Mitchell et al 2017). The areas of greatest loss were developed watersheds with greater exposure dominated by fringing marshes-areas where we would expect high densities of ribbed mussels.…”

Section: Distribution and Condition Indexmentioning

confidence: 99%

Shorescape‐level factors drive distribution and condition of a salt marsh facilitator (Geukensia demissa)

2018

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Ribbed mussels (Geukensia demissa) are a highly abundant bivalve filter feeder throughout the salt marshes of the U.S. Atlantic Coast. These mussels form a mutualistic relationship with smooth cordgrass Spartina alterniflora wherein the grass provides habitat and shade to the mussels, and the mussels stabilize the sediment and fertilize the grass. Salt marshes are, however, rapidly changing and eroding as humans modify the coast, and the rate of sea level rise is accelerating. In order to understand how ribbed mussels may respond to their changing habitat, we collected mussel density and distribution data from 30 marshes covering the range of geomorphic settings found in lower Chesapeake Bay. We used a combination of in situ and GIS-derived spatial variables to develop spatially applied models of ribbed mussel density and physical condition. Of the estimated 1.06 billion ribbed mussels in Virginia, we found that mussels were most abundant along the front edge of marshes in wide creeks, rivers, or bays with dense Spartina and minimal proximal forest, set in agriculturally dominated areas. In contrast, mussel condition was highest in fringing marshes located in narrow tidal creeks. Ribbed mussels responded to factors at a variety of scales, ranging from extremely local (0.5 m) to larger shorescapes (≥300 m). The methods that we used to create models linking both aquatic and terrestrial variables to explain the variation in ribbed mussel populations along the shoreline provide a valuable tool for identifying baselines and assessing potential for change across estuary-level spatial scales not only for ribbed mussels in the Chesapeake Bay, but also for other sessile, intertidal species in other systems.

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Marsh persistence under sea-level rise is controlled by multiple, geologically variable stressors

Cited by 40 publications

References 56 publications

Sea-level driven land conversion and the formation of ghost forests

Sea-level driven land conversion and the formation of ghost forests

Embracing dynamic design for climate‐resilient living shorelines

Shorescape‐level factors drive distribution and condition of a salt marsh facilitator (Geukensia demissa)

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