F23AP03480

San Mateo Thornmint (ACANTHOMINTHA DUTTONII) is a federally endangered annual forb. Creekside Science has been working on recovery actions for this taxon since 2007, when there were 499 individuals at one occurrence at Edgewood Preserve in Redwood City, CA. Through propagation, habitat management, and direct seeding, we have succeeded in increasing numbers to 51,000 individuals amongst six occurrences by May 2022.

At this point there are two strategies. The first is scaling up our successes. The USFWS delisting criteria include maintaining a minimum of five self-sustaining occurrences with a minimum of 5000 individuals each over a minimum of 20 years. (Delisting requires ten occurrences.) To achieve this, we believe in most years each site needs to be well above 5000 individuals. For example, we documented at Site 4 (Butterfly) that numbers increased, with no seed input, from 8191 individuals in 2019 to 12,926 in 2020. But then in 2021 the numbers dropped to about 4000. In 2022, numbers rebounded to 8000, with no additional seed input (an excellent sign of passive recruitment). Assuming similar or more extreme weather fluctuations in the future, we know that 13,000 individuals is not enough to buffer against a population potentially dropping below a 5000 minimum the subsequent year, let alone over two decades or more.

At this point, none of the occurrences are self-sustaining because they are being actively managed, but most of them are promising because they show signs of passive recruitment and minimal management. We believe with continued propagation, nonnative annual grass management, hand pulling parasitic dodder, and direct seeding, we can downlist and even delist this species. We have a proven track record.

The second strategy is to find additional introduction sites. Not all the extant sites appear to be likely candidates to be long-term, self-sustaining populations. At least two are not showing the required signs of passive recruitment. Finding additional sites at Edgewood Preserve may be possible, but as a resiliency strategy, some introductions should be outside of the preserve to guard against stochastic events and other impacts. Much of the area within the Thornmint's documented historic range has been developed. The SF Water District is a large landowner and has allowed an introduction on its property. But they are uncomfortable with further introductions because they are concerned the presence of rare species could limit their ability to maintain infrastructure required to deliver water.

Ring Mountain County Park appears to have the soil composition, climate, and vegetative associates appropriate for supporting San Mateo Thornmint. As a Marin County Park, it is under permanent conservation status and is already being competently managed for listed species. There is currently no parasitic dodder in the preserve. We propose a feasibility study to further investigate the site, compare soil data, initiate stakeholder discussions (with regulators, CNPS, and neighbors), and initiate permitting. Adjacent properties may be explored also.

The San Mateo Thornmint has come close to extinction. We have tracked the original single occurrence and have documented the areas that we did not manage or add seed to. Those numbers dipped as low as 28 in 2017 and were up to only 126 in 2022. This represents what would have happened if we did nothing. We firmly believe that our efforts are preventing extinction of this species. We believe this project is entirely focused on the contributions to population viability outlined in this grants review criteria of resiliency, redundancy, and representation. Having larger populations, more populations, and more spread out populations are the basic tenets of increasing viability.

Creekside Center For Earth Observation

15.657 - Endangered Species Recovery Implementation

FWS Headquarters (HQ) [DOI - FWS]

Fish and Wildlife Service Region 8: Pacific Southwest [DOI - FWS]

California United States

State-Wide

F23AS00310 FY22/23 Recovery Challenge Fund (F23AS00310)