Analytical Steps
Conservation Sites were identified through a
combination of computer assisted and manual processes that evaluated the following
data. (1) Records for Conservation Targets from Natural Heritage Program
databases; (2) Target occurrence data
provided by experts (May 1998 Experts Workshop) and from primary and grey
literature not currently in a digital database (e.g., wilderness study area reports); (3) spatial data sets for
the Ecoregion's topography, hydrography, land use/land cover, GAP vegetation
(and equivalent data for Mexico), land management status, and Thematic Mapper
satellite imagery; and (4) indices of
biophysical variation from biophysical modeling exercise.
Expert-nominated areas that captured multiple
Conservation Targets from multiple taxa were used as the nuclei for identifying
Conservation Sites. These nuclei can be
readily seen in the Xprtmerg shapefile
as a convergence of overlapping polygons.
Most polygons nominated by experts contained multiple Conservation
Targets. Therefore, the convergence of
taxonomic polygons not only captured multiple taxa, but also multiple
Conservation Targets within a taxon.
Expert-nominated areas (polygons) varied in the
precision with which boundaries were delineated, so we evaluated each expert
polygon against the rationale provided for the polygon to determine if
additional information was needed to refine the polygon's size and shape. Boundary adjustments were made based on
additional information and to correct for errors in digitization.
Conservation Target data from Heritage Programs were
then displayed to identify additional Targets contained within or proximate to
the expert-identified areas. We
modified the boundary of expert-nominated areas to capture additional
Conservation Targets where such a modification would not include areas with
incompatible land uses (e.g., urban
areas) or include Target occurrences that were not considered viable (e.g., fish Targets in the de-watered
portion of the Gila River in Maricopa and Yuma counties). These boundary adjustments typically
resulted in small adjustments to sites (i.e.,
extending or contracting boundary one to several miles).
In many cases, experts nominated areas for which
corroborating Heritage data was available.
In most cases we adopted the experts' boundaries for an area because
Heritage point data typically does not capture the entire Target population found
in a particular area. (See Alldata, XprtInfo and look at Readme.doc for linking Target
information to this file.)
Combined Heritage and experts
data were then displayed over spatial data sets to: (1) determine if additional
Conservation Targets would be captured by modifying delineated boundaries; (2)
capture ecological gradients represented in the biophysical model; or (3)
determine if the proposed area overlapped with incompatible land uses and,
therefore, should be modified to capture only areas where conservation
potential exists. Boundary adjustments
were also made to capture adjacent areas that contained similar, unfragmented
habitat such as riparian areas adjacent to riverine systems identified for fish
Targets, mountain ranges adjacent to bajadas
(sloping plain bordering mountain range) identified for desertscrub
communities, etc.
Results of the biophysical
model (Biophys grid) were overlaid
on preliminary Conservation Sites to calculate the extent to which biophysical
units were captured by Sites. Locations
of under-represented units were highlighted for assessment and possible
inclusion, or for future field inventory.
A number of preliminary Conservation Site boundaries were then modified
to include under-represented units.
Results of Conservation Site
Identification
Two types of sites were identified,
landscape-scale Conservation Sites and Special Element Sites. Most landscape-scale Conservation Sites
comprise large areas¾such
as a series of mountain ranges and intervening valleys, a canyon complex, or
riverine system¾and
contain multiple Conservation Targets.
Special Element Sites are small, localized areas containing some of the Ecoregion's rarest Conservation Targets
that could not be captured in landscape-scale Sites.
Characteristics
of Landscape-scale Conservation Sites
A
total of 100 landscape-scale Conservation Sites was identified: 41 in the
Arizona Uplands; 35 in the Lower Colorado River Valley; 16 in the Plains of
Sonora; and 8 in the Central Gulf Coast Subdivision (see ecobnd_2.shp). In
total, Conservation Sites cover approximately 26.6 million acres (10.8 million
ha), or about 50% of the Ecoregion’s landmass.
Conservation
Sites vary in size from 403 acres to 5.7 million acres (163 ha to 2.5 million
ha), with most sites falling into two size classes, 5,000 to 50,000 acres (2023
to 20,234 ha) and 100,001 to 500,000 acres (40,469 to 202,343 ha. At the gross scale of this analysis the
boundaries delineated for Conservation Sites are conceptual, not precise. The delineated boundaries are intended to
serve as a starting point for a more detailed analysis of stresses and
potential conservation management actions.
However, the relative sizes and shapes of Conservation Sites are
important in that they represent expert opinion on habitats and areas needed to
support the Conservation Targets found within the site and represent some of
the best remaining conservation opportunities in the Ecoregion.
Sonoran Ecoregion Data Dictionary for: Conserv_p.dbf - Landscape-scale Conservation sites (polygons)
|
Field Name |
Field Type |
Width (Decimals) |
Attributes |
|
Cs_num |
Integer |
3 |
Conservation site number |
|
Sitname |
Character |
60 |
Conservation site name (name often reflects geographic feature in the area) |
|
Area |
Real |
16(3) |
Area (sq. meters) |
|
Perimeter |
Real |
16(3) |
Perimeter (meters) |
|
Hectares |
Real |
16(3) |
Area (hectares) |
|
Acres |
Real |
16(2) |
Area (acres) |
Sonoran Ecoregion Data Dictionary for: Conserv_l.dbf – Landscape-scale Conservation sites (lines)
|
Field Name |
Field Type |
Width (Decimals) |
Attributes |
|
Id |
Integer |
11 |
ID number |
|
Cs_num |
Integer |
3 |
Conservation site number |
|
Sitname |
Character |
60 |
Conservation site name (often reflects geographic featuer in the area) |
|
Area |
Real |
16(3) |
Area (sq. meters) |
|
Perimeter |
Real |
16(3) |
Perimeter (meters) |
|
Hectares |
Real |
16(3) |
Area (hectares) |
|
Acres |
Real |
16(2) |
Area (acres) |
|
Length |
Real |
16(3) |
Length of arc (meters) |