The remaining 125 square kilometers of wetlands are threatened by development, erosion, pollution, and sea-level rise. USGS scientists have begun a long-term study of the evolution of wetlands. As proposed in their National Coastal Geology Plan, scientists at the USGS have begun a long-term study of wetlands, especially sediment transport to and from wetlands and patterns of sediment distribution. Results of these studies will provide insight to the nature of wetlands around San Francisco Bay, the amount of sediment reworked and moved, as well as the distribution and ultimate fate of contaminants adhering to sediments. USGS scientists also are preparing a detailed inventory of sediment type and distribution on a fine scale from which a sediment history can be determined.
USGS studies indicate that the health of wetlands relates directly to the health of the Bay region.
Processes that govern sediment movement directly affect the distribution of wetlands. The U.S. Fish and Wildlife Service estimates that the San Francisco Bay region is the estuarine system in the United States that has been most modified over historical time. Coastal managers are examining the efficacy of wetland restoration using available dredge spoils as fill in currently diked areas such as salt ponds. The photographs have a spatial resolution of 2 to 4 meters. In CIR photographs such as these, vegetation appears in various shades of red and pink, depending mostly on the type and density of the vegetation.