California Gap Analysis
are underway by public and private groups to assess the status of
biodiversity in California. Most are being conducted at local to
sub-regional scales, and many are focused on species or communities
of special concern. Previously lacking has been an overview of the
management status of species and communities both statewide and
in the western U.S. as a whole. Our Geographic Information System
(GIS) -based Gap Analysis of biodiversity in California is part
of a national Gap Analysis
Program (GAP) which coordinates state and regional gap analyses
being coordinated by the National Biological Service.
The term "Gap
Analysis" refers to the evaluation of the management status of plant
communities, vertebrate species and vertebrate species richness
by GIS overlay of biological distribution data on a map of existing
biological reserves. Maps are produced at relatively low spatial
detail (e.g., 1:100,000 map scale) to provide a broad overview of
the distribution of biota and their management status, and to identify
landscapes that contain large numbers of potentially unprotected
vegetation types and vertebrate species. Such areas can then be
studied in more detail as candidates for additional management and
conservation efforts to fill gaps in the reserve network.
Because of the
California's size and complexity, we conducted our analysis on an
regional basis, using the ten
major regions of the state as defined in The Jepson Manual
of Higher Plants of California (J. C. Hickman, editor; University
of California Press, 1993) An up-to-date vegetation/land-cover
map has been produced for each region using digital Thematic
Mapper (TM) satellite data.
was guided by vector overlays of existing vegetation maps, land
use maps and forest inventory data. Upland types were mapped with
a minimum mapping unit (MMU) of 100 hectares (247 acres). Major
wetland areas were mapped using a 40 hectare (99 acre) MMU, and
smaller wetlands are encoded as attributes of larger upland polygons.
Wildlife-Habitat Relationships System (WHR), in conjunction
with digital species range maps, was applied to the vegetation map
to predict the current distribution of potential habitat for each
native terrestrial vertebrate species (455 species). For an example,
map of the predicted distibution for the black-headed grosbeak .
Land management was derived from maps of land ownership that we
updated and classified into management
has been funded by many government and corporate sponsors
and supported by many cooperators
who have shared data and expertise. Many people
worked to produce the CA-GAP database.
To learn more
about the concept of Gap Analysis, visit the National
Gap Analysis home page at the University of Idaho, or see Scott
et al. 1993, in Wildlife Monographs
Find out what
is being done in other
states and ecoregions.