Introduction to Southern California Coastal Wetlands Inventory

The Southern California Coastal Wetlands Inventory (the Inventory) is a database of existing information on 41 coastal wetlands that lie between the Mexican border and Pt. Conception in northern Santa Barbara County. Three types of information are presented for each site: 1) a map showing the historical extent of the wetlands; 2) a map showing recent distributions of habitat types; and 3) a "profile" which provides a brief summary of ecological conditions, land use and enhancement histories. The profile also includes an annotated list of sources. All of the information in the Inventory, both mapped and written, is derived from data that were generated previously. The Inventory is the first attempt to develop a database of it's kind for Southern California's wetlands, assembling data from the literature and linking it to maps of recent and historic habitat distribution. ¹

The purpose of the Inventory is to enable a regional perspective on coastal wetland resources and habitats. Providing basic descriptions of wetlands in the entire area, it emphasizes breadth rather than depth. It will be used to answer in broad terms such questions as: Where are the wetlands now?, Where were they historically?, What are some of the constraints to land use, restoration, enhancement, and protection in and around those areas? The Inventory also constitutes a foundation upon which new and other types of data can be added.

The Inventory is a component of the Governor's 1993 Wetland Conservation Strategy, which recommended development of a statewide wetland inventory to support identification of regional and statewide restoration and enhancement goals. The Inventory implements this recommendation for the Southern California region. It was prepared jointly by the Coastal Conservancy, the Coastal Commission and the U.S. Fish and Wildlife Service with funding from the U.S. EPA and the California Resources Agency. ² Overall guidance for the project came from the Southern California Wetlands Group, a committee representing regional, state, and federal resource agencies whose purpose is to improve coordination of wetlands protection and regulatory activities in the region.

Historic Maps

For each site in the Inventory there is a map of the historic wetland perimeter, shown on a United States Geological Survey 7.5' quadrangle. These maps were digitized from the earliest available "hard copy" or paper maps, primarily those prepared by the U S Coast and Geodetic Survey in the late 1800s. These historic boundaries also appear on the maps of recent habitat types. More specific information about the sources, methods used in preparation and additional features of the historic maps is provided in a separate introduction to the historic maps.

Habitat Maps

For each site there is also a map depicting vegetative communities. Their purpose is to provide general indications of the location, extent and subhabitats within Southern California wetlands. These maps also show the historical data, enabling an immediate comparison of former and recent wetland distribution. The maps were composed using the most recent and highest resolution digital data available for each site. The sources of data vary in the collection and interpretation methods used, as well as in the date and time represented. Care has been taken to provide the most accurate representation of the site given the available data, however the maps are not meant to constitute wetland delineations or depictions of jurisdictional boundaries. More specific information about the sources, methodologies, and additional features of the these maps is provided in a separate introduction to the habitat maps.

Wetland Profiles

The profiles are distillations of the most recent studies documenting physical and biological characteristics of each wetland area. Presented in tabular form they highlight hydrology, vegetative communities, animal use, species of concern, ownership, onsite and surrounding land use, and the history of enhancement efforts. The profiles also include an annotated list of sources. Their purpose is to provide an overall picture of ecological conditions at all of the sites rather than in-depth, detailed analyses. The information base from which the profiles are derived represents a diversity of dates, scope, level of detail and purposes for it's generation. In many cases the sources cited provide the only information available, in others, the most recent and/or comprehensive documents were selected from a number of studies. Features of the profiles and methods used in their development are further defined in a separate introduction to the wetland profiles. Also, an explanation of the profile categories provides additional information on the profile data.

Using the Inventory

The Inventory's primary function is as a planning tool. It brings together and summarizes a substantial amount of information which may also be of use to other sorts of analyses. For example, the Inventory can tell you about recent conditions at each site - one has recently supported nesting light-footed clapper rails; another recently had salt marsh but no cordgrass grew there; permanent structures have been built across this site; invasive exotics are among the dominant species here. You can also learn about the availability or lack of information about each area - few sites may have data on hydrology, water quality, plant and animal species that were collected in the same year; sources for some sites compare data from several years of consistent sampling; others report on a single survey, the only data collected in the last ten years. You can also ask basic questions about every site and get a sense of how things look from a regional perspective. How many of the sites' tributaries are free-flowing ? how many sites have some sort of industry in the immediate vicinity ? how many sites have recently supported nesting endangered birds ? endangered plants ? how many are surrounded by development ?

In exploring potential applications for the data, it is important for users to be aware of some characteristics of the Inventory that impose limitations on its uses. Of singular importance is the dynamic nature of the resource being described; responding to numerous forces both external and internal, the measurable components of a wetland can exhibit tremendous variation. The Inventory's reliance on existing information means that the source materials will represent a wide range of dates, scope and purpose. The brevity of the wetland profiles allows for a mere glimpse of the system as a whole. In addition, while the Inventory was reviewed for completeness and accuracy by wetland scientists and resource managers, no independent evaluation of the sources used in the profiles was undertaken. Professional judgement of U.S. Fish and Wildlife Service biologists determined the most appropriate data for developing the habitat maps. Finally, with these characteristics in mind it is important to state further that: 1) the information in the Inventory is of insufficient resolution to serve as the sole basis for regulatory decisions and is not intended for such use; and 2) the information in the Inventory is not meant to provide in-depth, definitive portrayals of the sites' current or potential condition or significance.

²U.S. Fish and Wildlife Service's work was contributed as in-kind service.