How Many Plant Species Are Native To California?

Max Yasuda, September 2024

As part of a project I'm working on to map native plant species, I needed a list of California native plant species/taxa names. After going down the rabbit hole, it turns out there are multiple authorities on the topic, and each one has a different final count. Note, for this post, only vascular plants are included. ### tl;dr The takeaway of this post is, depending on which list of California native plants you use, there are currently an upper bound of around 100 native vascular plant taxa missing from iNaturalist. I’m not sure how many POWO treats as accepted taxa outright, but I imagine most are accepted synonyms that should at least get added into the Names table on iNaturalist. There are however a bunch of cases where POWO considers something a synonym, Calflora, Jepson etc consider it a distinct ssp. or var., and lumping it in as a synonym under the Name table on iNat may hurt the conservation outcome. Unfortunately coverage of the “Establishment Means” tag on taxa in California is quite low, only around (estimated) 1/3 of species are marked native. And these are using PlaceID 14 which is the state of California, not the California Floristic Province. ### iNaturalist/POWO The first authority I'll mention is iNaturalist, who runs their own taxonomy system. They actually track which species are native under the ["Establishment Means"](https://www.inaturalist.org/taxa/51089-Quercus-wislizeni) section for a species, but unfortunately they do not provide a way to search or filter observations by where they are native to. To figure out how many plants in California are marked as Native, one has to export all `Plantae` observations from GBIF and filter through the massive dataset. I happened to have a copy of [Plantae for LA County](https://www.gbif.org/occurrence/download/0020325-240906103802322) already downloaded, so I analyzed the ~350,000 observations in that to produce this chart of how many plant taxa have Establishment Means. Since this data comes from GBIF, some of these observations with establishment means come from herbariums etc and not iNaturalist, but 80% of observations come from iNaturalist. For LA County, iNaturalist only has 1036 plant taxa marked as native, whereas Calflora for example has 3058 taxa. Even though this is only LA County, we can expect the statewide iNaturalist data to be similarly missing.So in summary iNaturalist's taxonomy system itself is not suitable for determining if a plant is native (At least in California), so we need to use another authority. The nice thing about iNaturalist's taxonomy system is they have a machine readable TaxonID for each taxon, and they also track name changes and synonyms for each taxon. This makes it great to work with as a software developer. Even though iNaturalist doesn't have the ability to filter by native plants, a workaround is to create a Project, add your taxa to the project, and then use the project as a filter in your searches. You can read more about that [here](https://www.inaturalist.org/journal/maxo/79403-california-native-invasive-endangered-and-special-species-on-inaturalist). When talking about vascular plants on iNaturalist, they are based on [Kew Garden's POWO](https://powo.science.kew.org/) (Plants Of The World). This means if POWO doesn't recognize something as a species, then neither should iNaturalist. ### Calflora The next authority is Calflora, who recognizes (as of this blog post) [8195](https://www.calflora.org/entry/advanced.html#active=1&nstatus=2&cat=ov&cols=0,10,1,2,4&srch=t) native vascular plant species in California. 8195 makes it the largest list of California Native Plant taxa. ### Jepson Jepson also publishes [a list of plant taxa Native to California](https://ucjeps.berkeley.edu/eflora/tools/). Their list weighs in at 7396 taxa. ### Burge et al. 2016 Finally, in the 2016 paper ["Plant Diversity and Endemism in the California Floristic Province"](https://www.researchgate.net/publication/302633705_PLANT_DIVERSITY_AND_ENDEMISM_IN_THE_CALIFORNIA_FLORISTIC_PROVINCE), Burge and the other authors made the "first attempt at a comprehensive list of the native and endemic plants of the CFP", but that "it is by no means a final or perfect list". [Their list](https://datadryad.org/stash/dataset/doi:10.5061/dryad.d4g4n) comes in at 6514 vascular plant taxa (although the paper mentions 6,143 vascular minimum rank taxa, so I'm not sure why there's a discrepancy). ### Comparing to iNaturalist So, with Burge et al, Calflora, and Jepson all claiming to have different numbers of native plant species, I decided to compare the 3 lists to iNaturalist to see which species are present or not present in the iNaturalist/POWO taxonomy system. First, I downloaded the 3 above databases into CSV files. The Burge et al. data was already available as an .XLS, but unfortunately I had to scrape the HTML of Jepson and Calflora, who do not offer machine readable downloads of their taxonomy. I also downloaded the `inaturalist-taxonomy.dwca.zip` file from iNaturalist which includes their entire current taxonomy database, not including all the synonyms. Then, using [this code that I wrote](https://github.com/max-mapper/inaturalist-taxonomy-import), I looked up all of the ~25,000 species names on the 3 lists and tried to find an exact match on iNaturalist. My results, including the above mentioned 3 databases, are available in [this google spreadsheet](https://docs.google.com/spreadsheets/d/1-c45X-BvIVbgSPacDXsyR9OIywnIWtghAa1_K3lS6v8/edit?gid=1121254792#gid=1121254792). I also included the [California Rare Plant Rankings (CRPR)](https://rareplants.cnps.org/) database, which I also had to scrape due to lack of machine readable downloads. The last tab in the spreadsheet, `MissingFromiNat`, has a list of all species that iNaturalist does not recognize. I'll include them here for sake of completeness. ### Species missing from iNaturalist For a breakdown by data source see the above linked spreadsheet. ``` Acmispon tomentosus var. glabriusculus Amsinckiopsis kingii var. harknessii Antirrhinum pusillum Arctostaphylos campbelliae Aristida schiedeana var. orcuttiana Atriplex gypsophila Brickellia californica var. jepsonii Brickellia subsessilis Bromus sitchensis var. maritimus Bromus sitchensis var. polyanthus Carex norvegica ssp. inferalpina Castilleja applegatei ssp. martinii Cheilanthes fibrillosa Cheilanthes parishii Chenopodium album var. stevensii Chylismia cardiophylla subsp. cedrosensis Cimicifuga elata var. alpestris Cleomella oxystyloides Collinsia sparsiflora var. bruceae Descurainia pinnata ssp. intermedia Downingia ornatissima var. mirabilis Drepanocladus polycarpos Eleocharis acicularis var. gracilescens Eleocharis acicularis var. occidentalis Eleocharis engelmannii var. detonsa Elymus elymoides ssp. hordeoides Elymus elymoides var. hordeoides Engellaria obtusa Eriastrum brandegeeae Eriastrum sapphirinum ssp. ambiguum Erigeron foliosus var. mendocinus Eriogonum blissianum Eriogonum elongatum var. vollmeri Eriogonum inerme var. hispidulum Eriogonum microthecum var. corymbosoides Eriogonum microthecum var. johnstonii Eriogonum microthecum var. lacus-ursi Eriogonum wrightii var. taxifolium Eriophyllum lanatum var. aphanactis Eucephalus glabratus Ferocactus fordii var. grandiflorus Gentiana affinis var. parvidentata Gilia achilleifolia subsp. abrotanifolia Githopsis pulchella var. glabra Harfordia macroptera var. fruticosa Harfordia macroptera var. galioides Heterotheca brandegeei Heterotheca oregona var. rudis Hierochloe hirta ssp. arctica Horkelia californica var. frondosa Ivesia argyrocoma var. moranii Laphamia intricata Laphamia inyoensis Laphamia megalocephala Laphamia megalocephala var. megalocephala Laphamia megalocephala var. oligophylla Leptosiphon ciliatus ssp. neglectus Lessingia virgata var. glomerata Lipocarpha aristulata Lupinus holmgrenianus Lupinus littoralis var. variicolor Lupinus odoratus var. pilosellus Malacothrix insularis Mammillaria goodridgii var. rectispina Mesoptychia polymorpha Mirabilis laevis var. cedrosensis Myosurus apetalus var. borealis Nama densa var. parviflora Noccaea fendleri subsp. siskiyouense Orobanche ludoviciana var. arenosa Panicum alatum var. longiflorum Pellaea glaciogena Phacelia malvifolia var. loasifolia Phacelia umbrosa Pityopus californica Planodes virginica Polycarpon tetraphyllum ssp. depressum Potentilla millefolia var. klamathensis Potentilla norrelmukana Prunus subcordata var. kelloggii Rhododendron occidentale var. paludosum Sedum obtusatum subsp. boreale Sedum obtusatum subsp. retusum Senecio clevelandii var. heterophyllus Silene occidentalis ssp. longistipitata Spergularia macrotheca var. talinum Streptanthus glandulosus ssp. arkii Streptanthus glandulosus ssp. raichei Streptanthus morrisonii ssp. hirtiflorus Streptanthus morrisonii ssp. kruckebergii Streptanthus tortuosus var. foliosus Streptanthus tortuosus var. oblongus Streptanthus tortuosus var. optatus Streptanthus tortuosus var. pallidus Thalictrum fendleri var. quadrinervatum Thysanocarpus curvipes ssp. longistylus Thysanocarpus curvipes subsp. amplectans Thysanocarpus curvipes subsp. longistylus Torreyostellaria jamesiana Tragia nepetifolia var. dissecta Trifolium appendiculatum Xylonagra arborea subsp. wigginsii ```

This work by Max Yasuda is licensed under CC BY-NC 4.0 

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