A semi-empirical approach to projecting future sea-level rise

Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany.
Science (Impact Factor: 31.48). 02/2007; 315(5810):368-70. DOI: 10.1126/science.1135456
Source: PubMed

ABSTRACT A semi-empirical relation is presented that connects global sea-level rise to global mean surface temperature. It is proposed that, for time scales relevant to anthropogenic warming, the rate of sea-level rise is roughly proportional to the magnitude of warming above the temperatures of the pre-Industrial Age. This holds to good approximation for temperature and sea-level changes during the 20th century, with a proportionality constant of 3.4 millimeters/year per degrees C. When applied to future warming scenarios of the Intergovernmental Panel on Climate Change, this relationship results in a projected sea-level rise in 2100 of 0.5 to 1.4 meters above the 1990 level.

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    Edited by Michael Westphal, Gordon Hughes, Jorn Brommelhorster, 01/2013;
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    ABSTRACT: The output of this project is an assessment of the total ecosystem services provided by all habitat types in the Pine Island Sound, Sanibel Island, and Captiva Island study area. This assessment will be made available to local governments for use in developing wetlands planning, restoration and enhancement plans. In addition, an ecosystem services topography (ECOSERVE) layers were generated that can be combined with other ecosystem services layers for functional analyses by geographic boundary (watershed, municipality, county, etc.). Projections of alternate futures of ecosystem services resulting from land use changes and anticipated climate changes were completed. This project identified all the habitat types found in the study area which encompassed Pine Island Sound, Sanibel Island, Captiva Island, North Captive Island, Cayo Costa, Useppa Island and other islands within Pine Island Sound and included the tidal extents of Pine island Sound on the western side of Pine Island and the nearshore Gulf of Mexico west and south of the barrier islands. In the process we updated the existing crosswalk reference for the varied definitions of habitat types utilized by the federal government, the state of Florida, regional agencies, local government and other resource management agencies in southwest Florida, to obtain a unified set of defined southwest Florida wetland types. We identified existing referred and gray scientific literature that provides measures of the ecosystem services for each habitat type indentified. We identified and defined the ecosystem services provided by each wetland type. We identified defined reference condition habitats within the study area utilizing existing reference sites and locating new valid reference sites for evaluation. This includes provisioning services; regulating services; supporting services; hydrologic, water quality, water storage, vegetative, biogeochemical cycle, wildlife, fishery, recreational aesthetic, and cultural services. We utilized a existing assessment of reference sites (Beever wt al. 2011) for the identified ecosystem services utilizing the standardized methods developed by the federal (HGM) and State of Florida (UMAM) governments. As needed we ground truthed for type and functional assessment a representative sample of wetland type sites within Pine Island Sound, and on Sanibel Island, Captiva Island and Cayo Costa. We identified and evaluated available digital and hard copy map products and wetland occurrence information held by federal, state, regional and local agencies for the study area. We compiled digital information for the wetland areas in a variety of functional conditions with a concurrent evaluation of the ecosystem services provided by wetlands in each relative condition. From these sources we generated an combined updated map of the habitat extents and types for the study area. This is the first map of its kind for the study area and indeed in south Florida. We then geographically positioned the ecosystem services values information on the combined map to create a map of ecological services topographies (ECOSERVE) in a GIS form. The intersected ECOSERVE GIS information layers were combined to generate a total ecosystem services provided map. We then generated two alternate future ECOSERVE topographies related to anticipated land use changes resulting form build out of the future land use map for the year 2030 and a future with one-foot of additional sea level rise that could occur in a period from 2027 to 2222, but most likely by 2162 if current rates of sea level rise continue. The ECOSERVE method can be utilized to forecast and back cast alternate future and past landscapes. With more time and funding we could look at increased sea level rise extents, the benefits and costs of different land acquisitions, the consequences in terms of ecosystem services of various changes in wetland and upland extents resulting from restoration or development plans, the consequences of natural and man-made disasters, the implementation of alternative wetland protection and land conservation programs, as well as the potential impacts of making no changes to current land use, management, or regulatory policy. Utilization of the ECOSERVE layers will allow permit reviewers to evaluate the impact, for example, of development and restoration on the ecosystem services attributable to the wetlands types being impacted.
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    ABSTRACT: The salt marsh community of the Southwest Florida Ecosystem is one of the most unique salt marsh systems in the United States. The subtropical climate of Florida supports a combination of temperate salt marsh vegetation and tropical mangroves that intermix to form an important transitional ecotone that is subject to extremes of temperature, salinity, winds, evaporation, and storm. Ecosystem services of salt marshes include a base of the estuarine detrital food pathway, nurseries and escape from predation habitat for many species of aquatic life including the early life stages of game fish and commercial fish , recreational fishing, commercial fishing and harvesting, hunting, migratory bird habitat, bird watching, other forms of ecotourism such as kayaking, carbon sequestration, storm protection, water quality treatment, stabilization of sediment and shorelines, increases in market-based property appraisal values and aesthetic values. From existing scientific literature, southwest Florida salt marsh provides habitat to a variety of resident and transient organisms including 301 plant species, 422 invertebrate species, 217 fish species, 11 amphibians, 31 reptiles, and 15 mammals; including 6 federally listed and 27 state listed animal species. Mangroves primarily dominate the CHNEP shoreline (Drew and Schomer 1984). Monotypic stands of black needlerush (Juncus roemerianus) are more common in slightly elevated areas with lower ranges of tidal inundation and dominate salt marsh communities around the mid-estuarine transition zones at the mouths of rivers (e.g., Myakka and Peace Rivers) and creeks (Hancock). Parts of the interior habitat of Sanibel Island have bands of salt marsh dominated by Baker’s cordgrass (Spartina bakeri) and leather fern (Acrostichum aureum and danaeifolium). Although almost 74 percent of salt marsh habitat is protected in the CHNEP, habitat continues to be lost to human-induced impacts including development, alterations of hydrology, and pollution. Salt marshes in Charlotte Harbor Estuary have been directly destroyed or impacted from construction activities for residential and commercial purposes including construction for seawalls, drainage ditches for agriculture and mosquito control, boat facilities, and navigation channels. Man-made hydrological alterations have reduced the amount of freshwater flow from some rivers (e.g., Peace, Myakka), while artificially increasing the flow through others (e.g., Caloosahatchee). The primary focus of this project is the extent and nature of salt marshes and the adaptation of salt marshes to climate change. This report includes the results of a new study to inventory and determine the areal extent of salt marsh types throughout the Charlotte Harbor National Estuary Program (CHNEP) study area; determine the vulnerability of those marshes to climate change; identify the need and opportunities for avoidance, minimization, mitigation, and adaptation (AMMA) to climate change, and recommend strategies to implement alternate AMMA. This report is designed for local for use by governments, stakeholder groups and the public at large in developing coastal and land use planning, and avoidance, minimization, mitigation and adaptation of climate change impacts to salt marshes throughout the CHNEP study area. This is the first salt marsh mapping in the CHNEP that includes a mapping of the salt marshes by type. There are 12 different types of salt marsh in the CHNEP. Seventy percent of the salt marshes of the CHNEP are high marsh and 30% of the salt marshes are fringing marsh. The fringing marsh is found on major rivers and tributaries.The salt marshes are moving landward where there is opportunity to do so. The current pace of sea level rise appears to be at pace that allows marsh migration on mainland shores. In contrast, in other locations salt marshes are drowning where there is no location to move to such as the center of islands in Pine Island Sound. Elsewhere areas of former salt marsh have been replaced by: deeper water salt marsh types, mangrove forest, or open water. Leather fern marshes have been significantly impacted by freeze events associated with recent extremes in winter climate. Recovery appears to be occurring very slowly. Barriers to the movement of salt marshes have already contributed to the disappearance of salt marshes from areas of former shoreline extents. These barriers include the standard model example of sea walls, and bulkheads, but also include spreader canals, road beds, rip rap revetments, borrow pits, stormwater treatment beam barriers, and even golf course bunkers. The best solution to maintain salt marsh habitats in the CHNEP is planned relocation and adaptations allowing the salt marshes to maintain themselves at the elevations of sea level that occur through time. There are adaptations that can be undertaken to assist in salt marsh migration and in some locations this has been occurring. These adaptations include; 1) Maintaining the existing marsh migration corridors that have been established on Cape Haze, the Eastern Charlotte Harbor shoreline, and Estero Bay Preserve State park and identify the highest priority marsh migration corridors so that they can protect these areas from future development. 2) Acquisition/Protection of inland/landward buffer zones to provide an opportunity for salt marsh habitats and wildlife to migrate inland. 3) Support the restoration of existing salt marshes by removal of exotic vegetation, backfilling ditches, removal of barriers to tidal connection, and degradation of exotic dominated uplands to make the salt marsh more resilient and capable of self-sustaining substrate building and migration. 4) Stop shoreline hardening including seawalls, bulkheads, rip-rap, and "living shorelines" backed by rip-rap. Use natural shoreline vegetation for shoreline stabilization instead 5) Re-engineer existing vertical shoreline infrastructure to a sloped soil based shoreline with GeoWeb or other permeable stabilization. 6) Restore impaired water flows to enhance sediment supply for salt marsh deposition. Restoration of natural hydrology could facilitate sediment accretion and building of deltaic salt marsh wetlands 7) Make roadway berms permeable to marsh migration and hydrology by bridging and culverting or abandon coastal road corridors with associated bermed road beds. 8) Back-fill mosquito control ditches to reduce depth and sediment loss. 9) Backfill or reslope shores of borrow pits, agricultural pits, and spreader waterways to allow salt marsh establishment and establishment of marsh migration corridors 10) Sediment-slurry addition to assist in marsh sediment building processes For some watersheds of the CHNEP it is unlikely these adaptations will be employed because there is no physical space remaining for salt marshes to move into and because of competing human interests for maintaining higher elevation uplands in direct proximity to open waters and wetlands and navigation channels to access deeper waters. It is necessary to refine the CHNEP salt marsh environmental indicators and targets related to quantities and qualities, as appropriate, to the future distribution of salt marshes in a world with higher sea levels and a changed climate. It is possible utilizing the tools developed in this study to do so provide the CHNEP conference proceeds to this decision.

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