Rare Plant Density by County in California

A total of 2260 native plants are listed as rare in California.  On a density basis, the mean density is 0.33 plants/km² (based on October 2011 CNPS Inventory records) for the 406,388 km².  The inequality on a density basis is evident in the map:  the counties with the highest density statewide are in the San Francisco Bay region, generally.    Most of the northern counties of the state have a density that is less than the mean density, while the larger area counties of southern California have a density that is <1/4 of the mean (that is, below 0.16).  Another hot-spot are the southern three coastal counties. 

Of course absolute numbers for many low density counties are high: Inyo County supports 275 rare plants and San Bernardino County 374, yet on a density basis these jurisdictions are very low.  Kings County supports only 22 plants and is also low density.