Every year the East Bay Chapter’s database, Rare, Unusual, and Significant Plants of Alameda and Contra Costa Counties, is updated and expanded throughout the year as a result of ongoing field monitoring and digital research by volunteers and others. Since the database’s launch on the chapter website in 2016, we have accumulated much new data, adding to the wealth of data that had already been gathered since the Unusual Plants Project’s inception in 1990.
Tasked with the important job of tracking our many unusual (locally rare) plants and identifying their locations, conditions, and vulnerability, Unusual Plants Project volunteers have greatly increased our knowledge and understanding of these plants in our two-county area.
Over the years, however, it became apparent that our location and rarity assessment systems did not always work perfectly. Thus, we re-examined the two systems over the last few years and initiated some fine-tuning and improvements.
In 1990, when the project began, the Unusual Plants Committee set up a rarity ranking system based on the number of locations where a plant occurred plus several other criteria assessing threats and vulnerability. However, much of the information available at that time was fairly general. For example, “Tilden Park” might have been listed as a plant’s location with no indication of where in Tilden Park the plant occurred or how many populations were in the park. So locations didn’t always present an accurate picture of a plant’s distribution.
As a remedy, we introduced a Region system in 1996, dividing the two counties into 40 regions based mainly on vegetation and geology. Rarity was then assessed by how many regions a plant occurred in as well as by the other standard criteria. This helped correct several problems, such as the fact that certain areas of the East Bay had been much more extensively botanized than others. But we eventually realized that this system was still skewing some of the data, just in other ways.
Because one of the goals over the years has been to develop more precise locations instead of many of the general locations mentioned above, we determined in 2017 that enough detailed location data had been gathered that we could identify most of the general locations down to individual populations. Therefore, we could develop a new and more precise system to address rarity on the basis of populations while still applying the other criteria that assessed threats and vulnerability.
Our first step was to determine which records referred to the same population and which to different populations, and then to assign a number to each different population, thus making them easier to track over time. This was a daunting project. As an individual population is monitored or reported over the years, different observers may describe the same location differently. We had to examine the location descriptions carefully, which required extensive knowledge and familiarity with “the lay of the land” in the entire two-county area. The advent of GPS coordinates and smartphones has made this a much easier task recently and as we go forward.
Unfortunately, several older, more general records, such as those identified with the “Tilden Park” location, could not be given population numbers because the area described actually contained several populations, and there was no way of determining which population a particular record referred to. We reviewed the field notes of several early botanists in the area and in some cases were able to find more precise locations, but many still remain general.
So far we have assigned population numbers for species in the East Bay chapter’s rarity ranking system that are ranked A1 or A2 (more about the ranks below), as these are the species subject to CEQA (California Environmental Quality Act) consideration. Eventually we will also address the B- and C-ranked species, which make up a two-tiered watch list.
With the assigned population numbers, it has become easier to track the rarity of each plant species in our two-county area, and also to determine which species are most in need of monitoring and when an individual population was last monitored.
In this new Populations system, regions are still considered, but as a secondary factor. “Number of Regions” now appears as one category on the list of criteria. In addition, we have also added a new criterion, “Aging populations with little regeneration.”
With the focus now on populations rather than regions or locations, we also had to revisit and revise the ranking system.
In reviewing the A1-ranked plants, we noted that very few had more than one or two current populations in a region. In fact, most species that were ranked A1 using the Region system had a total of only one to three current populations in the whole two-county area, and only a few had four or five populations. Thus, in the new Populations system, we determined that an A1 rank should be assigned to plants having between one and three current populations in the East Bay, or up to five populations if they meet certain other criteria assessing vulnerability. The situation was similar with the other ranks, and we applied the same method.
A list of the current rank definitions and criteria is posted on the CNPS East Bay website.
With this new system in place, we were ready to begin a rarity reassessment of each of the East Bay’s unusual plant species. Before starting, however, we conducted extensive field surveys in 2019 and 2020, updating several records and also finding some new populations. In addition, we conducted an extensive digital research project in 2020, reviewing several websites for additional data, including Calflora, iNaturalist, CalPhotos, and the Consortium of California Herbaria. Only verifiable data from these sites were included.
For the rarity reassessment, we first divided the populations for each species into current and historical, with 25 years as the dividing line. If a population is not reported in 25 years or more, it is considered historical and not included when determining rarity rank. It is, however, important to be aware of these historical populations, as they can indicate if a particular species might be in decline.
We then gave each species a temporary rank according to how many total current populations it had in the East Bay. Next, we reviewed the distribution of the species’ populations in the two counties by looking at which regions, and how many regions, they occurred in, and whether the populations were clustered together or spread across the two counties.
We then evaluated the other criteria for each species to determine if it might be more vulnerable than the number of its current populations would indicate and would therefore qualify for a higher rank. At the conclusion of all of these evaluations, we assigned a final rank to each species.
The reassessment resulted in several rank changes, and as of December 15, 2020, there are 248 A1-ranked unusual plants in the East Bay, 169 A2-ranked plants, 113 A1x-ranked plants (they exist as historical populations only, because they have not been reported in the past 25 years), 144 B-ranked plants, and 133 C-ranked plants. It should be noted that the database is fluid, and as research continues these numbers can change. It’s also important to note that these numbers are only for the unusual (locally rare) plants and do not include the statewide rare plants that occur in the East Bay. (See the CNPS Rare Plants Program or the California Natural Diversity Database for more information on statewide rare plants.)
Of the 248 A1-ranked species, 94 have only one current population in the East Bay, 89 have two, and 39 have three. In addition, 21 have four populations here but meet other criteria and thus qualify for an A1 rank, and five species have five populations here but also meet other criteria.
Research and monitoring continue, and we are currently determining priorities for field surveys of populations most in need of monitoring this spring. Digital research also continues, and we are reviewing several of the websites mentioned earlier at least once a week. We are also moving forward on identifying individual populations for the B-ranked plants.
We can always use more volunteers for field work. Many populations in many places still need to be monitored and updated. In addition, some populations still need better location descriptions and coordinates so they can be tracked more easily in the future.
Due to the pandemic, there will unfortunately be no in-person field orientation for volunteers this year, and volunteers will be asked to work largely on their own. Project coordination and communication will be by email.
Volunteers generally “adopt” a plant or several plants to monitor, or a park or place where several plant populations need to be monitored. This year a volunteer can also choose to adopt a genus or adopt a species and its varieties or subspecies.
In February, lists of priority plants and places to be monitored will be available. Volunteers can choose from these lists or choose other plants or places if they prefer. While we will automatically send the lists to current volunteers, others who would like to help survey can request them by contacting Dianne Lake, firstname.lastname@example.org.
— Dianne Lake, Unusual Plants Committee Chair, CNPS East Bay Chapter