note that it might have been possible to resolve or reduce some of these knowledge gaps with available data and information. The monitoring results from the Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA) projects provide an extremely rich and unique source of information, and although considerable analysis of the monitoring data has been carried out, it is believed that significantly more general information could have been extracted and contributed to confidence in the LCA Study and design. The critical knowledge gaps lie in the causal factors of land loss—ecological, hydrological, socioeconomic, and anthropogenic (e.g., engineering). Where possible, views of the most suitable approaches to reducing these gaps are shared.

The U.S. Army Corps of Engineers’ [USACE] LCA Study describes these knowledge gaps as “uncertainties” and lists the following four types (see Chapter 6):

• Type 1: Physical, chemical, geological, and biological baseline conditions

• Type 2: Engineering concepts and operational methods

• Type 3: Ecological processes, analytical tools, and ecosystem response

• Type 4: Socioeconomic and political conditions and responses

These are broad characterizations of uncertainties, and in this chapter, more specific knowledge gaps are identified. The LCA Study appropriately considers adaptive management as one approach to dealing with uncertainties. Real estate issues, considered here as one of the socioeconomic knowledge gaps, are discussed in the LCA Study.

It is interesting that various investigators who have studied wetland loss in Louisiana for decades hold different views as to the dominant cause(s). Possible causes include canals cut for access to oil and gas facilities; oil and gas exploration; the grazing by fur-bearing animals (i.e., nutria); and the maintenance of a fixed water course for the Mississippi River and the associated losses of freshwater, nutrients, and sediments to deep water. Although it is understood that all of these are contributors, there was a surprising divergence of assessments by experts as discussed below. Establishing the relative importance of various causes of land loss would have been helpful to the architects of the overall restoration development and execution. If the relative causes were known area by area, it would be possible to target the most appropriate solutions more effectively. The gap in knowledge of land loss rates is discussed in Box 7.1.