CNPS Unveils New Updates to the California Rare Plant Inventory

By Aaron Sims

CNPS is pleased to announce a series of new features and updates to California’s online inventory of rare plants. The Rare Plant Inventory (RPI) is a widely-used resource guiding rare plant protection, conservation planning, land acquisition, and management in California. This updated 9.5 version of the RPI brings a suite of powerful new search capabilities, including: 

• BLM and US Forest Service Sensitive Species 
• IUCN Red List Status 
• Plants with seeds banked as part of California Plant Rescue (CaPR) 
• Microhabitats (serpentine, gabbro, limestone, and many more!) 
• California island-specific searches and endemism 
• Threat List from the CNDDB

With generous funding provided by the Schwemm Family Foundation, public searches on threats and the display of threat summary statistics are now available for over 1,800 rare California plants for the first time! [Previously, threat searches on California rare plants have only been available using the California Natural Diversity Database (CNDDB)]. Now, CNPS brings this capability to the public in a powerful new Advanced Search.  

Not only are individual threats to rare plants now searchable in an easy–to–access and use platform, but all rare plants in the CNDDB now also have summary statistics of documented threats in their Plant Detail pages. The following images and captions illustrate the unique and powerful features of our new Threat List statistics in the RPI. (Please see our Release Notes for a full list of highlighted changes from the previous version.) 

The rare Bay Area Region endemic fragrant fritillary (Fritillaria liliacea, CRPR 1B.2) is documented from 15 different types of threats, with grazing, invasive plant impacts, and development being the top three impacts documented for this species. Moreover, we now know that over 50% of fragrant fritillary’s occurrences have documented threats. 

Blochman’s dudleya (Dudleya blochmaniae subsp. blochmaniae, CRPR 1B.1) is a rare plant known only from coastal Southern California and Baja California, Mexico. Prior to the implementation of the Threat List, it was documented to have five different types of threats: grazing, trampling, development, erosion, and invasive plants. With new Threat List statistics, we now know that over 50% of its occurrences in California are impacted by at least 15 different types of threats, with development being the highest, impacting 20% of its occurrences, followed by grazing and invasive plants, each impacting 17% of its occurrences. 

La Panza mariposa-lily (Calochortus simulans, CRPR 1B.3) is a rare plant found only in California’s central coast. For the past 40+ years this species was presumed to not be threatened or only minimally threatened. However, information from new Threat List statistics indicates that 60% of its occurrences have documented threats, resulting in the need to review its Threat Rank to potentially change from 0.3 to 0.2.  

Wilkin’s harebell (Campanula wilkinsiana, CRPR 1B.2) is a rare plant only known from the Klamath and Cascade ranges in Northern California. Prior to the availability of the new Threat List display, this species was thought to only be threatened by grazing, recreational activities, and trail construction. As it turns out, Wilkin’s harebell has 10 documented threats, with foot traffic/trampling, recreational use, and logging being the highest documented threats, each impacting 20–25% of its occurrences.  

Many thanks to the Schwemm Family Foundation for funding the new Threat List searches and summaries, and the CNDDB for their long-time partnership with CNPS and for providing permission and access to use their threat data on rare plants.  

Images by Aaron Sims unless noted. For more information, questions, or feedback on the Rare Plant Inventory, contact rareplants@cnps.org.