Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance

Coastal marshes take up atmospheric CO2 while emitting CO2, CH4, and N2O. This ability to sequester carbon (C) is much greater for wetlands on a per area basis than from most ecosystems, facilitating scientific, political, and economic interest in their value as greenhouse gas sinks. However, the greenhouse gas balance of Gulf of Mexico wetlands is particularly understudied. We describe the net ecosystem exchange (NEEc) of CO2 and CH4 using eddy covariance (EC) in comparison with fluxes of CO2, CH4, and N2O using chambers from brackish and freshwater marshes in Louisiana, USA. From EC, we found that 182 g Cm-2 yr-1 was lost through NEEc from the brackish marsh. Of this, 11 g Cm-2 yr-1 resulted from net CH4 emissions and the remaining 171 g Cm-2 yr-1 resulted from net CO2 emissions. In contrast, -290 g Cm2 yr-1 was taken up through NEEc by the freshwater marsh, with 47 g Cm-2 yr-1 emitted as CH4 and -337 g Cm-2 yr-1 taken up as CO2. From chambers, we discovered that neither site had large fluxes of N2O. Sustained-flux greenhouse gas accounting metrics indicated that both marshes had a positive (warming) radiative balance, with the brackish marsh having a substantially greater warming effect than the freshwater marsh. That net respiratory emissions of CO2 and CH4 as estimated through chamber techniques were 2–4 times different from emissions estimated through EC requires additional understanding of the artifacts created by different spatial and temporal sampling footprints between techniques

New approaches to sediment management on the inner continental shelf offshore Coastal Louisiana

Coastal restoration in Louisiana requires clean sands for beach and dune restoration, whereas mixed sediments are required to rebuild marshes. The Louisiana coastal erosion problem is especially dire because it occurs on several fronts with the narrowing and overtopping of barrier islands and loss of back barrier bay and interior marshlands. Coastal restoration efforts in Louisiana depend on emplacement of sediment to build up barrier island and deltaic systems. Discovery of usable sediment is thus a vital factor in restoration efforts because up to 80 of some restoration project budgets can be allocated to exploration, exploitation, and emplacement of sediment. Because this cost is directly proportional to the distance of borrow sources from the project area, the cost-effectiveness of barrier island restoration and marsh creation depends on locating sufficient sediment volumes that are suitable for placement on beaches and dunes and for creating marshes. The restoration of Louisiana\u27s barrier islands and the creation of coastal marshes are critically dependent on the availability of suitable modern marine and riverine sediments and other buried fluvio-deltaic deposits. It is thus imperative that a comprehensive sediment management plan be developed to systematically and efficiently identify and allocate suitable sediment resources. At present, coastal and barrier island restoration projects are included in regional planning efforts, and the restoration project is decided before sediment sources are considered. The new approach proposed here is based on planning projects around locations of dredgeable sedimentary deposits in order to optimize sediment resources. Centralization of voluminous historical geoscientific and oil and gas infrastructure data is being accommodated in a new data management system called the Louisiana Sand Resource Database (LASARD). Managing sediment resources more strategically optimizes regional planning strategies and reduces construction costs. The Louisiana Sediment Management Plan (LASMP) conceptualizes systematic planning and better coordination of essential components of the huge restoration and protection effort currently undertaken in Louisiana. © Coastal Education & Research Foundation 2010

A Review of How Uncertainties in Management Decisions Are Addressed in Coastal Louisiana Restoration

Louisiana has lost over 4800 km2 of coastal land since 1932, and a large-scale effort to restore coastal Louisiana is underway, guided by Louisiana’s Comprehensive Master Plan for a Sustainable Coast. This paper reviews science-based planning processes to address uncertainties in management decisions, and determine the most effective combination of restoration and flood risk reduction projects to reduce land loss, maintain and restore coastal environments, and sustain communities. The large-scale effort to restore coastal Louisiana is made more challenging by uncertainties in sediment in the Mississippi River, rising sea levels, subsidence, storms, oil and gas activities, flood-control levees, and navigation infrastructure. To inform decision making, CPRA uses structured approaches to incorporate science at all stages of restoration project planning and implementation to: (1) identify alternative management actions, (2) select the management action based on the best available science, and (3) assess performance of the implemented management decisions. Applied science and synthesis initiatives are critical for solving scientific and technical uncertainties in the successive stages of program and project management, from planning, implementation, operations, to monitoring and assessment. The processes developed and lessons learned from planning and implementing restoration in coastal Louisiana are relevant to other vulnerable coastal regions around the globe

Aspects of adaptive management of coastal wetlands: Case studies of processes, conservation, restoration, impacts and assessment

Coastal wetlands are dynamic and include the freshwater-intertidal interface. In many parts of the world such wetlands are under pressure from increasing human populations and from predicted sea-level rise. Their complexity and the limited knowledge of processes operating in these systems combine to make them a management challenge.Adaptive management is advocated for complex ecosystem management (Hackney 2000; Meretsky et al. 2000; Thom 2000;National Research Council 2003).Adaptive management identifies management aims,makes an inventory/environmental assessment,plans management actions, implements these, assesses outcomes, and provides feedback to iterate the process (Holling 1978;Walters and Holling 1990). This allows for a dynamic management system that is responsive to change. In the area of wetland management recent adaptive approaches are exemplified by Natuhara et al. (2004) for wild bird management, Bunch and Dudycha (2004) for a river system, Thom (2000) for restoration, and Quinn and Hanna (2003) for seasonal wetlands in California. There are many wetland habitats for which we currently have only rudimentary knowledge (Hackney 2000), emphasizing the need for good information as a prerequisite for effective management. The management framework must also provide a way to incorporate the best available science into management decisions and to use management outcomes as opportunities to improve scientific understanding and provide feedback to the decision system. Figure 9.1 shows a model developed by Anorov (2004) based on the process-response model of Maltby et al. (1994) that forms a framework for the science that underlies an adaptive management system in the wetland context