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Data from: Local government contribution to recovery of the giant gartersnake (Thamnophis gigas)


Greco, Steven (2020), Data from: Local government contribution to recovery of the giant gartersnake (Thamnophis gigas), Dryad, Dataset,


Recovery of a threatened or endangered species usually requires conservation and mitigation actions at the local level across the species' entire range (i.e., geographic limits of a species' spatial distribution). Depending on the size of the range it could involve numerous or few jurisdictions. Under the federal Endangered Species Act an optional off-set program allows local governments to create a Habitat Conservation Plan (HCP) to guide mitigative actions (streamlining permitting) and in the state of California this optionally can be complemented by a more robust program called a Natural Communities and Conservation Plan (NCCP). This project uses a case study of the giant gartersnake (GGS; Thamnophis gigas), a state and federally listed threatened endemic snake species in California’s Great Central Valley, to demonstrate various aspects of ‘contribution to recovery’ by each county government. ‘Recovery’ means raising the population of the species to levels that are sustainable over time and there are various ‘conservation standards’ associated with recovery planning: the jeopardy standard (with or without an HCP) and the recovery standard (with an HCP-NCCP). Using GIS technology, several spatial analyses were conducted to measure: (1) the number and density of known occurrences of the GGS in each county, (2) the percent of the GGS range contained by each county, (3) the percent of the range in each county that has an HCP, an HCP-NCCP, or no HCP, and (4) the percent of each recovery unit covered by an HCP, an HCP-NCCP, or no HCP. Results indicate that 22 counties cover the range of the GGS, however, 11 counties will be important contributors to recovery. More than half of the range (62%) of the GGS currently has a jeopardy standard covered by no HCPs, 24% of the range is covered by HCPs with a jeopardy standard, and just 14% has a recovery standard covered by an HCP-NCCP.


Spatial analyses were performed using ArcGIS version 10.5.1 and therefore any software version equal to or later than it will be able to view the files using the project file “Greco GGS GIS Data.mxd.” The ‘Clip’ function was used to extract the percent of GGS range contained in each county. The map overlay function ‘Union’ was used to spatially composite the GGS range map, the counties, and the conservation plan boundaries (HCPs and NCCPs).  The map overlay function ‘Union’ was also used to spatially composite the conservation plan boundaries (HCPs and NCCPs) and the recovery units. The GGS known occurrences analysis using the California Natural Diversity Database (CNDDB) data was performed using two techniques: a density map and a spatial join. The density map was created using the Spatial Analyst tool ‘Point density’ with a 1 km2 (1000 m x 1000 m) cell size and a 5 km radius. The point count for each county was done using a spatial join between the CNDDB GGS point data and the California counties vector layer.

Usage Notes

The following 16 files are included in this package. Note: Numbers in parentheses to the right of the equal sign refer to the numbered data sets to the left of the equal sign.

  1. Greco GGS GIS Data.mxd = ArcGIS v. 10.5.1 ArcMap Project file (set to relative paths)
  2. countyalb83.shp = California counties shapefile
  3. GGS_range_map_R079.shp = giant gartersnake geographic range map shapefile
  4. GGS_recovery_units_alb83.shp = recovery units shapefile for the giant gartersnake
  5. GGS_recovery_units_dissolve.shp = recovery units outside boundary shapefile
  6. GGS_data_and_labels.gdb = a geodatabase with two feature classes (7) and (8) and two annotation layers (9) and (10)—see below
  7. GGS_recovery_units_HCP_NCCP_Union = map union of (4) and (8)
  8. HCP_NCCP_in_Central_Valley_only_gdb = shapefile of all HCPs and NCCPs in the Central Valley in California
  9. HCP_NCCP_in_Central_Valley_only_gdbAnno = map labels
  10. HCP_NCCP_in_Central_Valley_only_gdbAnno2 = map labels
  11. union_HCP_county_GGS_new.shp = shapefile of map union of (2), (3), and (8)
  12. union_GGS_recovery_units.shp = shapefile of map union of (3) and (4)
  13. GGS_county_clip_new.shp = shapefile of (2) clipped with (3)
  14. GGS_county_clip_new_join2.shp = shapefile of (13) spatially joined with the CNDDB point data (point data are not included due to restrictions—see ‘Note’ below)
  15. 1km5kmsqkm = raster output layer of the point density map of GGS CNDDB point data (point data are not included due to restrictions—see ‘Note’ below)
  16. Giant Gartersnake Density.lyr = symbolized output of (15) classified using quantiles with six classes.

Note: I am not permitted to distribute the GGS CNDDB point data. Those data are licensed through the California Department of Fish and Wildlife.


U.S. Department of Agriculture, Award: Hatch Project 1011533