Coastal Wetland Loss Research Articles

Climate Change Adaptation: Putting Principles into Practice

Carrying out wildlife conservation in a changing climate requires planning on long timescales at both a site and network level, while also having the flexibility to adapt actions at sites over short timescales in response to changing conditions and new information. The Royal Society for the Protection of Birds (RSPB), a land-owning wildlife conservation charity in the UK, achieves this on its nature reserves through its system of management planning. This involves setting network-wide objectives which inform the 25-year vision and 5-year conservation objectives for each site. Progress toward achieving each site's conservation objectives is reviewed annually, to identify any adjustments which might be needed to the site's management. The conservation objectives and 25-year vision of each site are reviewed every 5 years.Significant predicted [corrected] long-term impacts of climate change most frequently identified at RSPB reserves are: loss of intertidal habitat through coastal squeeze, loss of low-lying islands due to higher sea levels and coastal erosion, loss of coastal freshwater and brackish wetlands due to increased coastal flooding, and changes in the hydrology of wetlands. The main types of adaptation measures in place on RSPB reserves to address climate change-related impacts are: re-creation of intertidal habitat, re-creation and restoration of freshwater wetlands away from vulnerable coastal areas, blocking artificial drainage on peatlands, and addressing pressures on freshwater supply for lowland wet grasslands in eastern and southeastern England. Developing partnerships between organizations has been crucial in delivering large-scale adaptation projects.

Succession in soil and vegetation caused by coastal embankment in southern Laizhou Bay, China—Flourish or degradation?

Coastal wetland degradation and loss caused by intensive human activities, such as land reclamation and embankment, is a serious environmental problem. In this paper, we studied the succession of soil and vegetation in a coastal wetland dominated by Chinese tamarisk (Tamarix chinensis) community after the construction of a seawall. When the intertidal wetland became supratidal wetland, soil salinity firstly decreased and the gradient from sea to land became weaker. Next, the area of vegetation and plant species diversity increased, and the phenomenon of plant zonation disappeared. We reasoned that the rooted cause of soil and vegetation succession was the change in hydrological environment. Moreover, a Drivers-Pressures-State-Impacts-Response (DPSIR) model was used to analyze the relationship between human activities and coastal wetland. Using this model, we presented the potential problems that might arise in this wetland and predicted that vegetation flourishing was only a short term phenomenon but wetland degradation was the final consequences due to excessive exploitation of groundwater. At last, we proposed a few of operable measures as responses to these potential problems from the perspective of coastal management.

Coastal wetland loss and environmental change due to rapid urban expansion in Lianyungang, Jiangsu, China

To address the growing need for developable land, many coastal cities are draining and filling wetlands, transforming them into urban built-up areas, and thereby substantially altering the structure and function of coastal ecosystems. We demonstrate an integrative approach for investigating the dynamics and impacts of coastal development in China’s Jiangsu Province, where urban expansion has resulted in extensive wetland losses and sea reclamation (the process of creating new land from ocean or coastal waters). Remotely sensed data reveal that landscape change in the study area has been accompanied by an increase in total impervious surface area and an increase in mean surface “heat island effect.” These indicators of change can be detected with remote sensing data and used to support a strategic environmental assessment (SEA) for urban coastal planning. Changes detected in Lianyungang during 2000–2006 suggest that reclaimed areas are environmentally sensitive and should be a focus of concern in future development planning, which has historically targeted coastal salt pond wetlands for conversion to land for the development. Given the current and projected rate of coastal development in China and elsewhere in the developing world, our findings and assessment approach have implications for coastal management decisions in the developing coastal zones of China and other regions of the world that are experiencing rapid urban growth.

Potential Effects of Sea-Level Rise on Coastal Wetlands in Southeastern Louisiana

Glick, P.; Clough, J.; Polaczyk, A.; Couvillion, B., and Nunley, B., 2013. Potential effects of sea-level rise on coastal wetlands in southeastern Louisiana. In: Brock, J.C; Barras, J.A., and Williams, S.J. (eds.), Understanding and Predicting Change in the Coastal Ecosystems of the Northern Gulf of Mexico, Journal of Coastal Research, Special Issue No. 63, pp. 211-233, Coconut Creek (Florida), ISSN 0749–0208.Coastal Louisiana wetlands contain about 37% of the estuarine herbaceous marshes in the conterminous United States. The long-term stability of coastal wetlands is often a function of a wetland's ability to maintain elevation equilibrium with mean sea level through processes such as primary production and sediment accretion. However, Louisiana has sustained more coastal wetland loss than all other states in the continental United States combined due to a combination of natural and anthropogenic factors, including sea-level rise. This study investigates the potential impact of current and accelerating sea-level rise rates on key coastal wetland habitats in southeastern Louisiana using the Sea Level Affecting Marshes Model (SLAMM). Model calibration was conducted using a 1956–2007 observation period and hindcasting results predicted 35% versus observed 39% total marsh loss. Multiple sea-level-rise scenarios were then simulated for the period of 2007–2100. Results indicate a range of potential wetland losses by 2100, from an additional 2,188.97 km2 (218,897 ha, 9% of the 2007 wetland area) under the lowest sea-level-rise scenario (0.34 m), to a potential loss of 5,875.27 km2 (587,527 ha, 24% of the 2007 wetland area) in the highest sea-level-rise scenario (1.9 m). Model results suggest that one area of particular concern is the potential vulnerability of the region's baldcypress-water tupelo (Taxodium distichum-Nyssa aquatica) swamp habitat, much of which is projected to become permanently flooded (affecting regeneration) under all modeled scenarios for sea-level rise. These findings will aid in the development of ecosystem management plans that support the processes and conditions that result in sustainable coastal ecosystems.

Predicting the Effects of Proposed Mississippi River Diversions on Oyster Habitat Quality; Application of an Oyster Habitat Suitability Index Model

ABSTRACT In an attempt to decelerate the rate of coastal erosion and wetland loss, and protect human communities, the state of Louisiana developed its Comprehensive Master Plan for a Sustainable Coast. The master plan proposes a combination of restoration efforts including shoreline protection, marsh creation, sediment diversions, and ridge, barrier island, and hydrological restoration. Coastal restoration projects, particularly the large-scale diversions of fresh water from the Mississippi River, needed to supply sediment to an eroding coast potentially impact oyster populations and oyster habitat. An oyster habitat suitability index model is presented that evaluates the effects of a proposed sediment and freshwater diversion into Lower Breton Sound. Voluminous freshwater, needed to suspend and broadly distribute river sediment, will push optimal salinities for oysters seaward and beyond many of the existing reefs. Implementation and operation of the Lower Breton Sound diversion structure as proposed wou...

Plant Source Influence onSpartina alternifloraSurvival and Growth in Restored South Carolina Salt Marshes

Abstract Continued loss of coastal wetlands due to anthropogenic causes along the Atlantic and Gulf coasts has increased the need to restore eroded or hardened structures along the shoreline back to natural marsh systems. The source of plant material used in these restoration plantings may have unintended consequences for the reestablishment of marsh systems, especially if the plant material is not adapted to the local environment. In this two-year field study, we tested the hypothesis that locally collected Spartina alterniflora (Smooth Cordgrass) will have higher plant performance than non-local commercially available plant material from native plant nurseries. We found that locally collected S. alterniflora plants had higher survivorship, aboveground biomass, and cumulative stem length than plants from non-local sources. There was a significant association between plant performance and genetic similarity at the end of the first field season. Based on our findings, we recommend the use of locally collec...

Coastal Wetlands of China: Changes from the 1970s to 2007 Based on a New Wetland Classification System

A new classification of coastal wetlands along the coast of China has been generated that is compatible with the Ramsar Convention of 1971. The coastal wetlands have been divided into two broad categories with overall nine subcategories. On this basis, a series of coastal wetland maps, together covering the coast of mainland China, have been produced based on topographic maps acquired in the 1970s and satellite images acquired in 2007. These document substantial wetland losses over this period. In the 1970s, the total coastal wetland area in China was 5.76 × 104 km2, whereas in 2007, it was 5.36 × 104 km2, indicating a loss of 7 %. Over this approximately 40-year period, the area of natural coastal wetlands decreased from 5.74 × 104 to 5.09 × 104 km2, while that of artificial coastal wetlands increased from 240 to 2,740 km2. Due to shoreline and sea-level changes, newly formed coastal wetlands amounted to 2,460 km2, while coastal wetland loss amounted to 6,310 km2 in the period from the 1970s to 2007. When excluding shallow coastal waters (depths between 0 and −5 m), nearly 16 % of Chinese coastal wetlands have been lost between the 1970s and 2007.

Numerical modeling of hydrodynamics and sediment transport in lower Mississippi at a proposed delta building diversion

The Mississippi River Delta of south Louisiana USA is a highly engineered system with extensive levees, flood control, and diversion structures. This region is experiencing a high rate of coastal wetland loss. Solutions to divert or re-direct a portion of the River’s sediment to benefit wetlands and reduce coastal land-loss are considered. The question that must be answered, regarding the impact and feasibility of sediment diversions is: What is the sediment–water ratio at a diversion? To help answer this question a numerical model of hydrodynamics and sediment transport supported by extensive field data is used to analyze a proposed sediment diversion near Myrtle Grove, Louisiana. This location is at a River Kilometer 90 above the Head of Passes – exit of the Mississippi River to the Gulf of Mexico. The numerical model showed that the location of the diversion, the size and the alignment of the diversion channel are critical parameters affecting the sediment–water ratio captured by the diversion. The analysis shows that locating the intake near a lateral sandbar increases the sediment–water ratio in the diversion. Further, the analysis shows that a larger diversion channel with a favorable alignment orientation to the flow direction in the river results in higher sediment–water ratio.

Mitigating land loss in coastal Louisiana by controlled diversion of Mississippi River sand

The Bonnet Carre Spillway diverts floodwaters from the Mississippi River to Lake Pontchartrain, and was opened for 42 days during the 2011 flood. According to measurements of the newly deposited sediments, at least 31–46% of the river’s sand load was diverted into the spillway at this time, suggesting that such diversions can help mitigate coastal wetland loss.

Risk of Inundation to Coastal Wetlands and Soil Organic Carbon and Organic Nitrogen Accounting in Louisiana, USA

Exceeding 1.2 million acres (4856 km(2)) since the 1930s, coastal wetland loss has been the most threatening environmental problem in Louisiana, United States. This study utilized high-resolution LiDAR (Light Detection and Ranging) and DEM (Digital Elevation Model) data sets to assess the risk of potential wetland loss due to future sea level rises, their spatial distribution, and the associated loss of soil organic carbon (SOC) and organic nitrogen (SON) estimated from the State Soil Geographic (STATSGO) Database and National Wetlands Inventory (NWI) digital data. Potential inundation areas were divided into five elevation scales: < 0 cm, 0-50 cm, 50-100 cm, 100-150 cm, and 150-200 cm above mean sea level. The study found that southeastern Louisiana on the Mississippi River Delta, specifically the Pontchartrain and Barataria Basins, are most vulnerable to sea-level rise induced inundation. Accordingly, approximately 42,264,600 t of SOC and 2,817,640 t of SON would be inundated by 2050 using an average wetland SOC density (203 t per hectare) for the inundation areas between 0 and 50 cm. The estimated annual SOC and SON loss from Louisiana's coast is 17% of annual organic carbon and 6-8% of annual organic nitrogen inputs from the Mississippi River.

Dynamic System Model to Predict Global Sea-Level Rise and Temperature Change

Climate-change-based global sea-level rise is of concern because it contributes to significant loss of coastal wetlands and mangroves and to increasing damage from coastal flooding in many regions of the world. Physical mechanisms that describe the dynamic global climate systems and the effect of this system behavior on sea-level rise are inherently complex. In this study, conducted using systematic analysis of historic data on temperature change and sea-level rise, a linear dynamic system model is proposed to predict global sea-level rise and mean surface temperatures. Unlike the semiempirical approaches proposed in the recent literature, this model incorporates the inherent interaction between temperature and sea-level rise into the model. The resulting model, recognized from the historic data, shows that the rate of sea-level rise is proportional to temperature, and this rise is also a function of the temporal state of the sea level. Similarly, the rate of temperature change is a function of the temporal state of the temperature and is also affected by the sea-level rise. The proposed model is also used to predict the sea-level rise during the 21st century. DOI: 10.1061/(ASCE)HE.1943-5584.0000447. © 2012 American Society of Civil Engineers. CE Database subject headings: Climate change; Sea level; Temperature effects; Dynamic models; Predictions. Author keywords: Climate change; Complex systems; Sea-level rise; Temperature change; Dynamic model.

Estimating the Provision of Ecosystem Services by Gulf of Mexico Coastal Wetlands

Gulf of Mexico (GOM) coastal wetlands contribute to human well-being by providing many ecosystem services. The GOM region continues to experience substantial losses of coastal wetlands, but the magnitude of reduction in ecosystem services resulting from the loss of GOM coastal wetlands is unknown. To gain an appreciation of the impact of GOM coastal wetland loss on ecosystem services, recent literature was reviewed to derive quantitative estimates of ecosystem services provided by GOM coastal wetlands. GOM coastal wetlands provide essential habitat for the production of juvenile shrimp, which supports the GOM’s most valuable commercial fishery; protect coastal communities from storm surge; improve water quality by removing nitrogen from surface waters; and are valuable sinks for greenhouse gases due to high rates of carbon sequestration combined with low rates of methane emission. Using 1998 to 2004 as a baseline, the potential loss of ecosystem services associated with loss of coastal wetlands is presented. Additional research is needed to quantify wetland services at multiple geospatial and socioeconomic scales, to determine the effect of wetland loss on ecosystem services, and to demonstrate the impact of future management decisions on the capacity of GOM coastal wetlands to provide services that affect human well-being.

Patterns of waterbird community composition across a natural and restored wetland landscape mosaic, Yellow River Delta, China

Habitat restoration can help mitigate the extensive loss and degradation of estuarine and coastal wetlands that have consequently eroded the integrity of many migratory flyways and wintering habitat for waterbird populations. Assessing the impact of restoration strategies however relies on empirical data on waterbird community distribution patterns across natural and restored wetland components. We conducted habitat and waterbird surveys across six natural and restored wetland regions in the Yellow River Delta Nature Reserve (YRDNR), eastern China, between 2007 and 2009. We recorded 93 waterbird species, including populations of 21 global conservation importance species. Community composition was stratified into distinctive clusters with compositional structure changing across these natural, modified and restored wetland components. NMDS ordination revealed that waterbird communities in restored wetlands were significantly different from those in natural and modified wetland components. Community distribution patterns were strongly influenced by environmental gradients (most noticeably salinity), water-level regulation, vegetation composition and differences in protected status. We found marked temporal patterns in waterbird community composition, which may be predictable for the different wetland components across the YRDNR landscape. Our study highlights the conservation benefits of restoring smaller wetland components in improving the ecological integrity of the wider wetland landscape mosaic for waterbird populations. A more coherent and intensive landscape management of water-level regulation and restoration of salinity gradients will be fundamental for wetland and waterbird conservation throughout the YRDNR.

Preventing land loss in coastal Louisiana: Estimates of WTP and WTA

A dichotomous-choice contingent-valuation survey was conducted in the State of Louisiana (USA) to estimate compensating surplus (CS) and equivalent surplus (ES) welfare measures for the prevention of future coastal wetland losses in Louisiana. Valuations were elicited using both willingness to pay (WTP) and willingness to accept compensation (WTA) payment vehicles. Mean CS (WTP) estimates based on a probit model using a Box–Cox specification on income was $825 per household annually, and mean ES (WTA) was estimated at $4444 per household annually. Regression results indicate that the major factors influencing support for land-loss prevention were income (positive, WTP model only), perceived hurricane protection benefits (positive), environmental and recreation protection (positive), distrust of government (negative), age (positive, WTA model only), and race (positive for whites).

Submersed Aquatic Vegetation of the Jean Lafitte National Historical Park and Preserve

The Barataria Preserve unit of Jean Lafitte National Historical Park and Preserve is located in wetlands of the upper Barataria-Terrebonne estuary near New Orleans, LA and subject to perturbations that affect aquatic resources. A study of submersed aquatic vegetation (SAV) was conducted to determine community composition, distribution, and abundance. Seven native species—Cabomba caroliniana, Ceratophyllum demersum, Heteranthera dubia, Najas guadalupensis, Potamogeton pusillus, Vallisneria americana, and Zannichellia palustris—and three exotic species—Egeria densa, Hydrilla verticillata, and Myriophyllum spicatum—were present. The highly invasive, exotic, floating fern Salvinia molesta was also present. The Preserve is affected by a coastal restoration project designed to return Mississippi River flow to the upper Barataria Estuary. Preserve SAV did not conform to the general estuarine management paradigm of decline and loss with nutrient introductions. Instead, freshwater dominated the Preserve, and sufficient light was present to support robust SAV growth in ponds, canals, and Lake Cataouatche. Native and exotic species formed large surface mats that clogged waterways. Vallisneria americana may be decreasing due to the increase in nuisance SAV and floating plants.This study is the first of its kind for any wetland habitat in the states of the Northern Gulf Coast and therefore will be an important baseline to future studies both generally and specifically for the Preserve as Louisiana's coastal wetland waterways experience change brought on by the general coastal wetland loss from sea level rise and efforts to restore the wetlands.

Sea-level rise vulnerability in the countries of the Coral Triangle

Sea-level rise is a major threat facing the Coral Triangle countries in the twenty-first century. Assessments of vulnerability and adaptation that consider the interactions among natural and social systems are critical to identifying habitats and communities vulnerable to sea-level rise and for supporting the development of adaptation strategies. This paper presents such an assessment using the DIVA model and identifies vulnerable coastal regions and habitats in Coral Triangle countries at national and sub-national levels (administrative provinces). The following four main sea-level rise impacts are assessed in ecological, social and economic terms over the twenty-first century: (1) coastal wetland change, (2) increased coastal flooding, (3) increased coastal erosion, and (4) saltwater intrusion into estuaries and deltas. The results suggest that sea-level rise will significantly affect coastal regions and habitats in the Coral Triangle countries, but the impacts will differ across the region in terms of people flooded annually, coastal wetland change and loss, and damage and adaptation costs. Indonesia is projected to be most affected by coastal flooding, with nearly 5.9 million people expected to experience flooding annually in 2100 assuming no adaptation. However, if adaptation is considered, this number is significantly reduced. By the end of the century, coastal wetland loss is most significant for Indonesia in terms of total area lost, but the Solomon Islands are projected to experience the greatest relative loss of coastal wetlands. Damage costs associated with sea-level rise are highest in the Philippines (US $6.5 billion/year) and lowest in the Solomon Islands (US $70,000/year). Adaptation is estimated to reduce damage costs significantly, in particular for the Philippines, Indonesia, and Malaysia (between 68 and 99%). These results suggest that the impacts of sea-level rise are likely to be widespread in the region and adaptation measures must be broadly applied.

Land Cover Changes of the Lake Pontchartrain Basin: 1982–2005

Describing the nature and extent of land resources and changes over time has become increasingly important, especially in rapidly growing metropolitan areas. In this study, two Landsat satellite image scenes were examined to identify land use and land cover changes for the Lake Pontchartrain Basin between 1982 and 2005. Classification accuracies were based upon ground truth data obtained by global positioning system field collection and photo interpretations. A postclassification change detection analysis was used to identify areas that have experienced conversions in land use or land cover. Comparisons of the land cover maps reveal that a steady growth in population and an increase in commercial and residential development have caused extensive changes to critical habitats throughout the basin. The maps also indicate that the loss of coastal wetlands, combined with shoreline erosion, remains one of the most serious environmental problems facing the Pontchartrain Basin today. The postclassification change detection analysis showed that critical habitats accounted for nearly 40% of the total urban growth between 1982 and 2005. Results also showed that for the time period studied, approximately 25 square miles (15,994 acres) of marsh was converted to open water. This is an overall average decrease of approximately 640 acres per year.

A comparison of the vegetation and soils of natural, restored, and created coastal lowland wetlands in Hawai‘i

The loss of coastal wetlands throughout the Hawaiian Islands has increased the numbers of created (CW) and restored (RW) wetlands. An assessment of these wetlands has yet to occur, and it has not been determined whether CWs and RWs provide the same functions as natural wetlands (NWs). To address these concerns, vegetation and soil characteristics of 35 wetlands were compared within sites along hydrologic gradients and among sites with different surface water salinity and status (i.e., CW, RW, NW). Only 16 of 85 plant species identified were native and three of the four most abundant species were exotic. Vegetative characteristics differed primarily across salinity classes, then along hydrologic zones, and to a lesser extent among CWs, RWs, and NWs. Soil properties exhibited fewer differences across salinity classes and along hydrologic zones and greater differences among CWs, RWs, and NWs. The dominant presence of invasive species in coastal Hawaiian wetlands suggests that it will be difficult to locate reference sites that can be used as restoration targets. Differences in edaphic characteristics suggested that RWs/CWs do not exhibit the same functions as NWs. Future restoration and creation should include planting of native vegetation, controlling invasive vegetation, and alleviating inadequate soil conditions.

Mississippi Delta subsidence primarily caused by compaction of Holocene strata

Coastal subsidence causes sea-level rise, shoreline erosion and wetland loss, which poses a threat to coastal populations. This is especially evident in the Mississippi Delta in the southern United States, which was devastated by Hurricane Katrina in 2005. The loss of protective wetlands is considered a critical factor in the extensive flood damage. The causes of subsidence in coastal Louisiana, attributed to factors as diverse as shallow compaction and deep crustal processes, remain controversial. Current estimates of subsidence rates vary by several orders of magnitude. Here, we use a series of radiocarbon-dated sediment cores from the Mississippi Delta to analyse late Holocene deposits and assess compaction rates. We find that millennial-scale compaction rates primarily associated with peat can reach 5mm per year, values that exceed recent model predictions. Locally and on timescales of decades to centuries, rates are likely to be 10 mm or more per year. We conclude that compaction of Holocene strata contributes significantly to the exceptionally high rates of relative sea-level rise and coastal wetland loss in the Mississippi Delta, and is likely to cause subsidence in other organic-rich and often densely populated coastal plains.

A Dutch geoscience perspective on the Katrina disaster

AbstractA combination of geological and anthropogenic processes have rendered the U.S. Gulf Coast in general – and the Mississippi Delta in particular – extremely sensitive to coastal hazard. Thus, the Katrina disaster was not a question of ‘if’ but of ‘when’. This contribution outlines the geo-environmental context of the Mississippi Delta that evolved during the 20th century and set the stage for Hurricane Katrina’s devastation. This includes a brief discussion of the processes responsible for coastal erosion and wetland loss, the proposed measures to combat these problems, and the policy decisions (or, rather, the lack thereof) made so far. A connection is made with the 1953 storm surge that devastated the southwestern Netherlands and had a profound impact on Dutch science and engineering by providing the impetus for the widely known and highly praised Delta Plan, as well as for unprecedented studies of Holocene sea-level change. Whether a similar route will be followed for the Gulf Coast is primarily dependent on the amount of political will. Results are presented of recent studies of crustal movements in the Mississippi Delta that show surprising long-term stability of the Pleistocene basement, evidence that could prove critical for decision makers with regard to the rebuilding process. Finally, the neglect of the precarious situation along the Gulf Coast by the federal government is viewed as a possible metaphor for current U.S. policies with respect to science in general, and to global warming in particular.“Land that sits below sea level. Levees and dams that stand against nature’s fury. Countryside that sinks more every year. New Orleans? No. Holland: a nation whose flood protections makes ours look primitive and slapdash”John McQuaid, The Times-Picayune, November 13, 2005