Alameda and Contra Costa Counties are endowed with an incredible richness of native plant species. This richness is due partly to our location at the convergence of the North and South Coast Ranges, the Sacramento-San Joaquin Delta, and the San Joaquin Valley. This convergence of botanical regions provides for a unique congregation of ecological conditions and native plants.
The East Bay Chapter of CNPS keeps track of these rare and endemic native plants and plant communities. Within our catalogue of native plant species there is an abundance of rarity: from Mount Diablo endemics to Pleistocene relicts; narrowly distributed taxa to peripheral populations; and species that have suffered extirpations from changes in vegetation composition resulting from the introduction of non-native plant species or directly from human development. Based on the CNPS Inventory of Rare, Threatened, and Endangered Plants of California, a total of 125 of these plant species are currently known from our Chapter area. These species are separated into six categories of rarity, called California Rare Plant Ranks (CRPR):
CRPR 1A: Plants Presumed Extinct in California (2 taxa)
CRPR 1B: Plants Rare, Threatened, or Endangered in California and Elsewhere (79 taxa)
CRPR 2A: Plants Presumed Extirpated in California, But More Common Elsewhere (0 taxa)
CRPR 2B: Plants Rare, Threatened, or Endangered in California, But More Common Elsewhere (9 taxa)
CRPR 3: Plants About Which We Need More Information – A Review List (4 taxa)
CRPR 4: Plants of Limited Distribution — A Watch List (31 taxa)