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Track: Natural Resources and Conservation
Patrick Gaul
State of California
1220 S Street
Sacramento, CA 95814
Telephone: 916-322-1950
Fax: 916-324-0475
E-mail: pgaul@dfg.ca.gov
The California Natural Diversity Database, a Spatial Model for Cataloging Biodiversity
Defining Issue: The Nature Conservancy's "Heritage Methodology" used in North and South America by affiliated Heritage Programs and Conservation Data Centers has become a standard method of cataloging biodiversity. This methodology provides tools and guidelines for storing locational and qualitative information about sensitive plant and animal species and natural communities. Although the information has a very strong spatial component, complications involved in defining and storing biological data sets have made the development of spatial models to manage and analyze this information slow and uncoordinated. With the ever increasing emphasis on bioregional planning, however, the need to apply flexible spatial analysis tools on a broad level has driven the search for a suitable geospatial data model. GIS Solution: In the Heritage model an "element occurrence" has long been defined as a data management tool, or abstraction, which describes an extant or historical population, part of a population, small
group of populations, or a stand of natural community. An element occurrence most commonly depicts, but is not limited to, rare, threatened, and/or endangered taxa or natural communities. These records contain various attributes, both spatial and aspatial. In the pre-GIS model, spatial attributes consisted of a centrum (latitude and longitude) and a radius (precision) around it indicating how accurately the feature had been mapped. This combination of centrum and radius of confidence defined the location and extent of the element occurrence. The fact that many of these spatial features overlapped each other greatly complicated the development of GIS representations. The California Natural Diversity Database (CNDDB), California's Heritage Program, has used the recently introduced ArcInfo "region" feature class to design and implement a new spatial model not previously possible. Methodology: The CNDDB model allows an element occurrence portrayed in a geographic information system to be represented by a
spatial feature with a real extent, as opposed to a point or line. To accurately depict the complex biological situations inherent in the Natural Heritage element occurrence model, these features are capable of overlapping with other features without loss of unique identity; capable of containing voids or "doughnut holes"; capable of representing complex situations containing several distinct spatial components, or parts, while still being considered a single occurrence; and capable of simultaneously representing the location of several element occurrences that share the same geographic location. Software: An ArcInfo Forms application has been developed to standardize and partially automate the process of entering, editing, and querying element occurrences and the automation of subset creation. The spatial model was designed in such a way as to allow for its use by ARC?INFO as well as ArcView clients. This presentation will discuss in detail the biological and geographical justifications for the spatial
model and some of the technical aspects involved in the development of the application that supports and enforces it.
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