Data Sources

We utilized the California Natural Diversity Database (CNDDB), a database managed by the California Department of Fish and Game. The CNDDB compiles the status and locations of rare plants and animals for the entire state of California.1 Rare or endangered species and communities in the CNDDB are referred to as “elements,” and an “element occurrence” is a site which contains a population of an “element."2 The data are not systematic surveys of the state, but instead are provided to the CNDDB by independent researchers, federal land management agency biologists (e.g. BLM, USFS), other agency biologists, biological consultants, and others.3 Therefore, the CNDDB (and consequently our analysis) cannot be considered comprehensive because it is subject to a number of inherent limitations. 

Potential general limitations:

  • Charismatic megafauna might be more heavily surveyed.
  • Data availability is weighted heavily towards areas that are of particular interest to researchers (e.g. national parks and certain ecosystem types).
  • Data availability is dependent on researchers knowing about the CNDDB and choosing to share their survey data.
  • Private land might not be well surveyed due to issues of access to land for research.

Potential desert-related limitations4:

  • Most botanical surveys are conducted in the spring in favored wildflower areas. Plants that grow or flower at other times of year are not well-surveyed.
  • Old collection data might need to be re-surveyed to determine if species are still present.
  • Surveys tend to occur on lands scheduled for some type of land use change, leaving many natural areas under-represented in the CNDDB.
  • Once areas are developed or an area is degraded, usually no follow-up survey is conducted.
  • Species may no longer be present in areas that have been developed, but have not been removed from the database.
  • Survey data may be concentrated around roads since those areas are easier to access.
  • Large areas have not been surveyed.

We acknowledge that the data used to create this tool is far from complete. It has been impressed upon us by several interviewees5 that the desert is not well-studied relative to other ecosystems and that current and/or complete data is sorely lacking. Nevertheless, we believe that the overall results are useful even with these data issues and hope that users will take the following ideas and associated techniques, and expand on them to improve the accuracy and completeness of analysis.

1 California Department of Fish and Game, California Natural Diversity Database, http://www.dfg.ca.gov/biogeodata/cnddb/.

2 California Natural Diversity Database, How to Read RareFind 3 Reports, 2007 (Sacramento, CA).

3 Roxanne Bittman, Lead Botanist, California Natural Diversity Database, Personal Communication, November 12, 2009.

4 Roxanne Bittman, Lead Botanist, California Natural Diversity Database, Personal Communication, November 12, 2009.

5 Jim Andre, Director, Sweeney Granite Mountain Desert Research Center; Roxanne Bittman, Lead Botanist, California Natural Diversity Database; Michael Connor, California Science Director, Western Watersheds Project; Frank Davis, Professor, University of California, Santa Barbara; Robert Fulton, Manager, CSU Desert Studies Center; Debra Hughson, Science Advisor, Mojave National Preserve; Kristeen Penrod, Conservation Director, Science and Collaboration for Connected Wildlands; Personal Communication, October – December 2009.