Species Status Assessment Report for the San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense)
Version 1.0
Image courtesy of US Navy
March 2020
U.S. Fish and Wildlife Service Pacific Southwest Region Sacramento, CA ACKNOWLEDGEMENTS
This document was prepared by the Texas A&M Natural Resources Institute in cooperation with the U.S. Fish and Wildlife Service and the United States Navy as part of the Service’s San Clemente Island Species Status Assessment Team.
We would like to recognize and thank the following individuals who provided substantive information and/or insights for our SSA: Sula Vanderplank, Dawn Lawson, Jon Rebman, Kim O’Connor, Bryan Munson, and Melissa Booker.
Additionally, valuable input into the analysis and reviews of a draft of this document were provided by Mitchell McGlaughlin and Andrea Williams. We appreciate their input and comments, which resulted in a more robust status assessment and final report.
Suggested reference:
U.S. Fish and Wildlife Service. 2020. Species status assessment report for the San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense), Version 1.0. March 2020. Sacramento, CA.
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EXECUTIVE SUMMARY
This Species Status Assessment (SSA) provides an analysis of the overall species viability for the San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense). To assess the viability of this subspecies, we, the U.S. Fish and Wildlife Service, used the conservation biology principles of resiliency, redundancy, and representation (3 Rs). Specifically, we identified the subspecies’ ecological requirements and resources needed for individual survival and reproduction. We described the stressors (threats) influencing these resources and evaluated current levels of population resiliency and subspecies redundancy and representation using available metrics to forecast the ability of this subspecies to sustain populations into the future. The San Clemente Island larkspur is an herbaceous perennial in the buttercup family (Ranunculaceae) that is endemic to San Clemente Island (SCI) off the coast of California. The San Clemente Island larkspur was federally listed as endangered on August 11, 1977. A five-year status review was completed in 2008 and recommended reclassification of the subspecies from endangered to threatened. A request for new information during an initiation for a new five-year status review was issued in 2010; no updated 5-year review has been published. San Clemente Island larkspur is one of two subspecies of Delphinium variegatum that occur exclusively on SCI, the other being Thorne’s larkspur (Delphinium variegatum spp. thornei). A third subspecies, Royal larkspur (D. v. spp. variegatum), occurs on the mainland. The taxonomic separation of San Clemente Island larkspur from Thorne’s larkspur is not very definitive from field observation. When the two subspecies were described, there were fewer locations and individuals known on the island, and the island subspecies were distinguished primarily by flower color, with Thorne’s larkspur noted to have generally bright blue (i.e., darker), slightly larger flowers than the San Clemente Island larkspur, which generally has white flowers. While this taxonomic treatment is still used, these color and flower size metric distinctions do not adequately separate these taxa. San Clemente Island larkspur occurs mostly in the northern portion of the island, and Thorne’s larkspur occurs in the southern portion of the island. However, in the middle of the island (and on the far southern end), the two flower colors coexist in many locations, with varying proportions of each color, and flower colors ranging from pure white to dark purple. Thus, expert opinion, genetic research, and careful consideration of taxonomic challenges sheds doubt on the existence of two distinct taxa on SCI, and it has been suggested that the two subspecies may be a single taxon separate from Delphinium variegatum or that the two subspecies might be better described as varieties. Genetic research using allozyme data to validate two taxa was inconclusive, and only additional genetic research can determine whether there are any significant genetic differences between the two flower forms present on the island. However, from a regulatory perspective, locations and individuals currently recognized as San Clemente Island larkspur must be assumed as such, and these are the focus of this assessment, although we account for locations where the population appears to be mixed or otherwise in question. Like most other California larkspurs, San Clemente Island larkspur can survive below ground when conditions are unfavorable and may remain dormant and not appear above-ground for one or more years. We assume that the subspecies is relatively long-lived. Because of this dormancy, and additionally because flower production in Delphinium can be highly variable and may be dependent upon quite localized weather conditions, exact numbers of individuals are difficult to locate and count. The subspecies is generally found within mid- to high- elevation grasslands on the east side of the northern and central portions of the island where it occurs in
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clay, loam, and rocky soils with soil-depths ranging from shallow to deep; however, it is more often associated with non-clay soils. Reported habitats have included costal grasslands as well as grassy slopes and benches, open grassy terraces, and chaparral and oak woods. Using a strict ruleset to avoid overcounting the subspecies and segmenting the island population by watershed for counting/management purposes, we estimate there are currently 18,956 individuals within 22 watersheds on SCI. Another two watersheds are known to be occupied, but data do not exist for estimated numbers of individuals. Two additional watersheds do not contain locations identified as San Clemente Island larkspur; however, these watersheds occur in an area where white individuals have been noted to be prominent within groups, and thus, we assume these groups are of mixed subspecies. We find that the subspecies currently has generally high levels of resiliency within watersheds and as a population overall, appears to have sufficient representation, based on the diverse areas it occupies and genetic studies, and sufficient redundancy, occupying many of the same areas it has been known to historically and increasing in numbers and distribution since listing. At listing under the Endangered Species Act (ESA), nonnative herbivores were the primary threat to San Clemente Island larkspur. As a result of their removal by 1992, habitat conditions improved and led to increases in the cover of native and nonnative plants on the island, including San Clemente Island larkspur and several other threatened and endangered species. In the absence of the primary threat, additional threats to San Clemente Island larkspur that have been identified include: (1) land use, (2) erosion, (3) nonnative plants, (4) fire and fire management, and (5) climate change. SCI is owned by the U.S. Department of the Navy (Navy) and, with its associated offshore range complex, the island is the primary maritime training area for the Pacific Fleet and Sea Air and Land Teams (SEALs) and supports training by the U.S. Marine Corps, the U.S. Air Force, and other military organizations. As such, portions of the island receive intensive use by the military and can involve the movement of vehicles and troops over the landscape and can include live munitions fire, incendiary devices, demolitions, and bombardment. However, very few individuals exist within these training areas; less than 1% of the population occurs in a training area that gets heavy use. Current erosion issues are localized, and erosion is generally decreasing on the island as the vegetation continues to recover. While San Clemente Island larkspur exist in watersheds where erosion resulting from the Assault Vehicle Maneuver Areas (AVMAs) could impact an estimated 344 individuals, an Erosion Control Plan is expected to prevent or correct erosion that may occur as a result of military operations and training in the AVMA. One other location of an estimated 70 individuals exists near a road where erosion impacts are projected to be higher, but still, this threat is minor. While not much is known about the tolerance of the subspecies to fires of different severities or frequencies, based on field observations and closely related species, fire does not appear to negatively impact San Clemente Island larkspur, and may even benefit the subspecies. We assume that San Clemente Island larkspur is not threatened by fire on SCI. Non-native annual and perennial grasses are widespread on SCI and have been for many decades. No assessment to track these invasive plants within occupied habitat areas has been done, but none is indicated at this time. San Clemente Island larkspur is found within naturalized, non-native grasslands, and there is the potential that these exotic annual grasses could out- compete San Clemente Island larkspur or affect fire regimes, making fires more likely. However,
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it does not appear as if these grasses are expanding, and they have been present during the recorded fire history, so we do not expect fire patterns to change due to these non-native grasses. The factor that appears to have the most potential to impact species viability in the future is climate change. However, we are unable to address the full impacts of climate change because the long-term effects on SCI remain unclear. Most importantly, the persistence and timing of the fog layer, which provides moisture and a refuge from the full impacts of warming, is unknown. However, we assume that climate change will not have major effects on San Clemente Island larkspur in the next 20 to 30 years, although we account for the possible short-term climate impacts. To help further ameliorate these remaining threats, the Navy implements a wildland fire management plan to address fire-management. The Navy addresses erosion and targeted removal of invasive species, in general, through the Integrated Natural Resources Management Plan (INRMP), addresses training-related erosion through the Erosion Control Plan, and addresses further introduction of invasive species through implementation of a biosecurity plan. While military training on SCI has been and will continue to be dynamic as it evolves to meet new requirements, changes are expected to be incremental, and impacts to federally listed and sensitive species will be addressed in environmental analyses required under the National Environmental Policy Act (NEPA) and ESA. To assess the future viability of San Clemente Island larkspur on SCI, we considered three future scenarios that encompass the uncertainty associated with military training: a status quo scenario, where nothing changes; an increased training scenario, where training within existing training footprints becomes more frequent; and an extreme training scenario, where we assume that training extirpates the subspecies within existing training footprints (and in associated areas where erosion may occur). Under a status quo scenario, we do not expect the occupied watersheds or numbers of individuals to change from current (Table A). In the two scenarios where training increases, the number of watersheds considered high or very high drops by one; two watersheds become extirpated under an extreme training scenario. Even under the extreme training scenario, however, the population is only reduced by about 400 individuals (Table A). While the current resiliency of the four additional watersheds assumed to be occupied is unknown, we do not expect resiliency in these watersheds to change from current under any of our scenarios. In the absence of major threats, we do not expect any stochastic impacts to affect San Clemente Island larkspur in a meaningful way over the next 20 to 30 years. We expect that the entire island population will maintain resiliency in the future under the most likely scenarios yet could see a minor decrease in resiliency under our most extreme scenario. Likewise, we do not project that current levels of representation or redundancy are likely to decrease over the next 20 to 30 years. While we do not know the historical abundance or distribution of this subspecies, we project that, outside of a catastrophic or unprecedented impact, the population is likely to retain its current levels of resiliency, representation, and redundancy over the next 20 to 30 years.
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Table A. The number of watersheds considered of very high, high, moderate and low resiliency and the total estimated population as considered current and in each of our four future scenarios for San Clemente Island larkspur. Watersheds without data but presumed to be occupied are not assigned a resiliency but are acknowledged in the total watershed count. Watersheds Very High High Moderate Low Total Individuals Current 7 7 5 3 22 (+4 assumed) 18,956 Status quo 7 7 5 3 22 (+4 assumed) 18,956 Increased training 7 6 6 3 22 (+4 assumed) 18,749 Extreme training 7 6 4 3 20 (+4 assumed) 18,542
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS ...... ii EXECUTIVE SUMMARY ...... iii TABLE OF CONTENTS ...... vii LIST OF TABLES ...... ix LIST OF FIGURES ...... x Section 1 – INTRODUCTION AND ANALYTICAL FRAMEWORK ...... 12 1.1 Status of the Subspecies ...... 13 Section 2 – SUBSPECIES BIOLOGY ...... 14 2.1 Taxonomy ...... 14 Genetics...... 14 Subspecies Considerations ...... 15 2.2 Subspecies Description ...... 18 2.3 Range and Distribution ...... 19 2.4 Habitat ...... 23 2.5 Life History ...... 27 Survival and Lifespan ...... 27 Reproduction ...... 27 Fire Tolerance ...... 29 2.6 Population size and abundance ...... 30 Current distribution ...... 34 Section 3 – SUBSPECIES NEEDS ...... 37 3.1 Population Resiliency ...... 38 Individual Level ...... 39 Population (Watershed) Level ...... 40 3.2 Representation and Redundancy ...... 40 Subspecies Level ...... 40 Section 4 – CURRENT CONDITION ...... 41 4.1 Populations ...... 41 4.2 Methods for Estimating Current Condition ...... 42 4.3 Current Condition Results...... 42 Within individual watersheds...... 42 Island-wide ...... 42 4.4 Current Subspecies Resiliency ...... 43
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4.5 Current Subspecies Representation...... 45 4.6 Current Subspecies Redundancy...... 46 Section 5 – FACTORS INFLUENCING VIABILITY ...... 47 5.1 Land Use (direct affects) ...... 48 Management efforts ...... 53 Summary ...... 53 5.2 Erosion and Roads ...... 54 Management efforts ...... 55 Summary ...... 56 5.3 Invasive plants ...... 56 Management efforts ...... 57 Summary ...... 58 5.4 Fire ...... 59 Management efforts ...... 64 Summary ...... 65 5.5 Climate Change ...... 65 Summary ...... 66 5.6 Other threats ...... 67 5.7 Summary of Factors Influencing Viability ...... 67 Section 6 – FUTURE CONDITIONS AND VIABILITY ...... 70 6.1 Introduction ...... 70 6.2 Methods...... 71 6.3 Future Resiliency ...... 71 6.4 Future Representation ...... 74 6.5 Future Redundancy ...... 74 6.6 Limitations and Uncertainties ...... 76 6.7 Conclusions ...... 77 References Cited ...... 78 APPENDIX A ...... 84 APPENDIX B ...... 86
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LIST OF TABLES
Table 1. Surveyed number of San Clemente Island larkspur individuals during various survey years (US Navy 2002, p. D.23; US Navy, unpublished data; USFWS 1984, p. 53; Junak and Wilken 1998, p. 120; Junak 2006, p. 67). Extent of each survey is unknown...... 31 Table 2. Number of watersheds with records of San Clemente Island larkspur collected in each decade. These represent only surveyed watersheds where San Clemente Island larkspur were found in that decade and do not account for watersheds that may have remained populated but were not surveyed in subsequent decades. Records from 2017 of Thorne’s larkspur in one watershed are now considered ambiguous; thus, that watershed is included in the 2010-2019 count, as it presumably contains some San Clemente Island larkspur, although though no official records were recorded there...... 32 Table 3. Total locations and individuals considered current, broken down into survey points retained by year. Our methodology estimates approximately 18,956 individuals at 74 locations...... 43 Table 4. The number of watersheds that fall into each of our resiliency categories, the numbers of individuals of San Clemente Island larkspur the watersheds in each category accounts for, and the percent of the total island wide population represented. Watersheds without data but presumed to be occupied are not included in the percentages...... 44 Table 5. Summary of training areas, their size, use, and the potential threats to San Clemente Island larkspur within each...... 50 Table 6. The number of locations and individuals of San Clemente Island larkspur within each type of training area and the approximate percent of the island-wide population represented...... 51 Table 7. Fire severity classes and definitions, reproduced from the US Navy 2009 Fire Management Plan for San Clemente Island, with severity classes adapted from the National Park Service (1992)...... 59 Table 8. Numbers and percentages of watersheds and individuals of San Clemente Island larkspur assessed to have varying levels of threats: none or low, threats that could potentially affect <50% of the locations or individuals within the watershed. No watersheds have threats that could potentially affect ≥50% of the locations or individuals within the watershed...... 68 Table 9. The number of watersheds considered of very high, high, moderate and low resiliency and the total estimated population as considered current and in each of our four future scenarios for San Clemente Island larkspur. Watersheds without data but presumed to be occupied are not assigned a resiliency but are acknowledged in the total watershed count...... 72 Table 10. Occupied watersheds with San Clemente Island larkspur data present, including the current number of locations and individuals present, the percent of locations and individuals in the training areas or near roads, whether the watershed overlaps the AVMA, and the projected individuals that will occur in that watershed in 20 to 30 years under each of three scenarios...... 84 Table 11. Conservation measures for terrestrial plants on San Clemente Island (SCI) as relevant to San Clemente Island larkspur, were taken from the Biological Opinion (BO; USFWS 2008) and Table 3-48 of the Integrated Natural Resources Management Plan (INRMP; US Navy 2013). Taken from Vanderplank et al., in prep...... 86
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LIST OF FIGURES
Figure 1. Species Status Assessment Framework. From USFWS 2016...... 13 Figure 2. One of several white individuals of D. variegatum within a mostly blue population located in SHOBA. This population is currently recognized as Thorne’s larkspur. Photo by T. McFarland...... 17 Figure 3. San Clemente Island in the Channel Islands off the coast of California...... 20 Figure 4. All recorded locations of the two subspecies of Delphinium variegatum on SCI and the associated watersheds. Watersheds with only San Clemente Island larkspur (1980-2017), only Thorne’s larkspur (2011-2014), and those presumed mixed are indicated. One watershed with only Thorne’s larkspur records is still presumed mixed due to ambiguity in this area, unknown survey parameters, and the definition to delineate the two subspecies now adopted by the US Navy...... 23 Figure 5. Distribution of San Clemente Island larkspur and soil types. (From Vanderplank et al., in prep.)...... 25 Figure 6. Vegetation types and distribution of San Clemente Island larkspur. (From Vanderplank et al., in prep.)...... 26 Figure 7. Watersheds with records of San Clemente Island larkspur (solid red) collected in each decade. Only records documented in each decade are shown, though they may have remained extant in subsequent decades when they were not surveyed or located. Watersheds assumed “mixed” are included. Two watersheds with Thorne’s larkspur records from 2010-2019 are included as assumed occupied as those watersheds are considered mixed; one of the two had historical SCI Larkspur records, and the other did not...... 33 Figure 8. Distribution of Delphinium variegatum considered current as per methodology described in Section 2.6. Individuals per location of each subspecies are indicated for points considered current. Historical locations and points are indicated, as are watersheds considered occupied by just San Clemente Island larkspur as well as watersheds considered to contain mixed populations...... 36 Figure 9. Watersheds considered current and historical (yellow) watersheds for San Clemente Island (SCI) larkspur. Watersheds containing recent locations identified as only San Clemente Island larkspur are indicated in pink, and those with both subspecies are indicated in blue. Four additional watersheds (purple) are considered currently occupied by San Clemente Island larkspur, but numbers and or distribution are unknown...... 37 Figure 10. Habitat and population factors that influence the viability of Delphinium variegatum ssp. kinkiense throughout its range...... 39 Figure 11. Current resiliency of San Clemente Island larkspur (SCI larkspur) (based on estimated number and distribution of individuals) by watershed...... 45 Figure 12. Factors affecting the viability of San Clemente Island larkspur...... 48 Figure 13. Locations of San Clemente Island larkspuras considered current in relation to the training areas on San Clemente Island, including the Impact Areas, the Training Areas and Ranges (TARs), the Assault Vehicle Maneuver Areas (AVMAs), the Infantry Operations Area (IOA), and Special Warfare Training Areas (SWATs). Current Restricted Access Areas (RAAs) are also shown, but these change as unexploded ordinances are removed...... 52
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Figure 14. Locations of San Clemente Island larkspur (SCI larkspur) considered current in relation to areas where fires have burned in the last 20 years (1999-2018, after the initiation of fire management), including number of fires in that time. Recent locations (2011-2014) of Thorne’s larkspur are also indicated...... 61 Figure 15. Locations of San Clemente Island larkspur (SCI larkspur) points considered current in relation to areas where fires where severity data is known have burned (2007-2018). Severity categories 1, 2, and 3 have the potential to burn herbaceous vegetation where they will not resprout; severity categories 4 and 5 have little to no effect. Recent locations (2011-2014) of Thorne’s larkspur are also indicated...... 62 Figure 16. Acres burned annually on San Clemente Island for years where fires were estimated since listing...... 63 Figure 17. Total acres on San Clemente Island that have burned annually in wildfires and acres that were recorded to have burned at a moderate to high severity (severity classes 1, 2, or 3)...... 63 Figure 18. Representation of locations of watersheds where no threats exist to San Clemente Island larkspur (SCI larkspur), or a low level of threats exist to the watershed (threats could potentially affect <50% of the locations or individuals within the watershed). No watersheds had a moderate level of threats (threats could potentially affect ≥50% of the locations or individuals within the watershed). Threats identified include locations or individuals within 100 ft of a road or 50 ft of the AVMR, in the TARs, and within the AVMA watersheds. Further, AVMA watersheds are considered to have a low threat level. Four additional watersheds are assumed to be occupied but lack data; however, no perceived threats to SCI larkspur exist in these watersheds...... 69 Figure 19. Resiliency estimates by watershed (based on number of individuals) currently as well as under each of our three future scenarios. Extant watershed counts do not account for recruitment into new watersheds. We assume the four additional watersheds remain occupied at current resiliency levels, which are unknown...... 73
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SECTION 1 – INTRODUCTION AND ANALYTICAL FRAMEWORK
The San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense) is an herbaceous perennial in the buttercup family (Ranunculaceae) that is endemic to San Clemente Island (SCI) off the coast of California. The San Clemente Island larkspur was federally listed as endangered on August 11, 1977 (USFWS 1977, p. 40682). The Species Status Assessment (SSA) framework (USFWS 2016, entire) is intended to support an in-depth review of the subspecies’ biology and threats, an evaluation of its biological status, and an assessment of the resources and conditions needed to maintain long-term viability. The intent is for the SSA Report to be easily updated as new information becomes available and to support all functions of the Endangered Species Program from Candidate Assessment to Consultations to Recovery. This SSA for the San Clemente Island larkspur is intended to provide an update on the subspecies’ biological condition and level of viability. For the purpose of this assessment, we generally define viability as the ability of San Clemente Island larkspur to sustain populations in their natural ecosystem up through and beyond a biologically meaningful timeframe, in this case, 20 to 30 years. We chose 20 to 30 years because beyond 20 to 30 years, the level of uncertainty associated with the impacts of climate change (specifically, the persistence and timing of the fog layer; see Section 5.5) becomes very high, making predictions unreliable. The available climate model projections for SCI are uncertain, but the impacts are more likely to be minimal within a 20- to 30-year timeframe. Using the SSA framework (Figure 1), we consider what the subspecies needs to maintain viability by characterizing the status of the subspecies in terms of its resiliency, redundancy, and representation (Wolf et al. 2015, entire).
• Resiliency describes the ability of populations to withstand stochastic events (arising from random factors). We can measure resiliency based on metrics of population health; for example, recruitment versus mortality rates and population size. Highly resilient populations are better able to withstand disturbances such as random fluctuations in recruitment rates (demographic stochasticity), variations in rainfall (environmental stochasticity), or the effects of anthropogenic activities.
• Representation describes the ability of a species to adapt to changing environmental conditions. Representation can be measured by the breadth of genetic or environmental diversity within and among populations and gauges the probability that a species is capable of adapting to environmental changes. The more representation, or diversity, a species has, the more it is capable of adapting to changes (natural or human caused) in its environment. In the absence of species-specific genetic and ecological diversity information, we evaluate representation based on the extent and variability of habitat characteristics across the geographical range.
• Redundancy describes the ability of a species to withstand catastrophic events. Measured by the number of populations, their resiliency, and their distribution (and connectivity), redundancy gauges the probability that the species has a margin of safety to withstand or can bounce back from catastrophic events (such as a rare destructive natural event or episode involving many populations).
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Figure 1. Species Status Assessment Framework. From USFWS 2016.
1.1 Status of the Subspecies
• San Clemente Island larkspur was listed as federally endangered on August 11, 1977 (USFWS 1977, p. 40682). • The subspecies was listed as California endangered in 1979 (CADFW 2018). • A Recovery Plan for Channel Island species, including San Clemente Island larkspur, was finalized in 1984 (USFWS 1984, entire) and identifies goals and objectives towards attaining recovery, but did not provide delisting criteria for reclassifying or delisting the subspecies (e.g. the size of populations and/or amount of suitable habitat needed). • A five-year status review was completed in March 2008 (USFWS 2008a, entire) and recommended reclassification of San Clemente Island larkspur from endangered to threatened. • A request for new information during the initiation of a new five-year status review was issued on 21 May 2010 (USFWS 2010, p. 28636).
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SECTION 2 – SUBSPECIES BIOLOGY
In this section, we provide biological information about the San Clemente Island larkspur, including its morphological description, taxonomic history, known life history, distribution and range, habitat, and estimated population size.
2.1 Taxonomy When it was listed in 1977 (USFWS 1977, p. 40682), the San Clemente Island larkspur was considered Delphinium kinkiense Munz, sufficiently distinct from other Delphinium and considered a separate species. The type specimen for the species was collected by R.M. Beauchamp on SCI in 1967 (Munz 1969). Subsequent to the listing, Warnock (1990a) reclassified D. kinkiense to a subspecies of Delphinium variegatum (Torrey & A. Gray subsp. [i.e. ssp.] kinkiense (Munz) Warnock) in recognition of its alliance with another island endemic taxon, D. variegatum ssp. thornei. This nomenclatural change was further supported in his taxonomic review of California Delphinium (Warnock 1990b, p. 73) and was followed in the floristic treatment (Jepson Manual) for California (Koontz and Warnock 2012). Delphinium variegatum ssp. kinkiense was acknowledged by the USFWS in the 2008 Five-Year Review (USFWS 2008a, p. 3). Thus, based on the most recent systematic (Warnock 1990b, entire) and floristic treatments for the genus (Koontz and Warnock 2012; Warnock 1997, entire), the listed taxon is now regarded as one of three subspecies of Delphinium variegatum. The taxonomic change to subspecies was made due to the similarities between this taxon and the other SCI endemic, Thorne’s larkspur (Delphinium variegatum spp. thornei). Warnock (1990a, p. 3) states, “Other than geographic separation between subspecies kinkiense and typical D. variegatum, no morphological features were found to consistently differentiate the two taxa.” Warnock explains that specimens of D. kinkiense fall within the range of variation of D. variegatum, further proposing that what had been described as D. kinkiense may represent plants of D. variegatum with an influx of genetic material from D. parryi. This reclassification did not change the definition, distribution, or range of what had been classified as San Clemente Island larkspur at the time of listing (Vanderplank et al., in prep.). However, the uncertainty regarding the validity of the subspecies is further discussed below.
Genetics San Clemente Island larkspur is one of three subspecies of Delphinium variegatum (Warnock 1990b, entire). Two of the three subspecific taxa of D. variegatum (San Clemente Island larkspur and Thorne’s larkspur) are endemic and restricted to SCI (Koontz and Warnock 2012; Dodd and Helenurm 2002, p. 613). The third subspecies, Royal larkspur (D. v. spp. variegatum), is found exclusively on mainland California and ranges from the coast to the foothills in central and northern California (Dodd and Helenurm 2002, p. 614). D. parryi is the only other Delphinium known from any of the Channel Islands (Vanderplank et al., in prep.), although it does not actually occur on SCI; while it was once assumed to, that was the result of an inaccurately labeled herbarium specimen (Raven 1963, p. 321). Dodd and Helenurm (2002, p. 613) used enzyme electrophoresis to study genetic variability among the three subspecies. Their methods involved using starch-gel electrophoresis to examine the frequency of expression of specific cellular enzymes (primary gene products known as “allozymes”) to obtain a measure of variation in the genes coding for those enzymes at 19 loci (each locus representing the position of alleles, which are different forms of a gene on
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the chromosome) (Dodd and Helenurm 2002, p. 615). About 40 individuals per group (except in instances of small group size) were sampled from 24 island groups, and seven populations were sampled across the range of the mainland subspecies. Based on floral color, 10 of the island groups appeared to be San Clemente Island larkspur, 11 appeared to be Thorne’s larkspur, and the three remaining island populations appeared to support individuals of both subspecies (Dodd and Helenurm 2002, p. 615). Dodd and Helenurm (2002, p. 620) did not find evidence for genetic differentiation between San Clemente Island larkspur and Thorne’s larkspur. They performed a statistical cluster analysis based on genetic similarity of populations and tested for a relationship between genetic distance and geographic distance on SCI. In general, most alleles are shared among all populations with differences among populations primarily found in allele frequencies. Of the genetic diversity found on SCI in both subspecies of Delphinium variegatum, 97 percent is found within populations and three percent is found among populations. The clustering of populations depicts “…a close relationship among all island populations with no obvious grouping of populations with respect to taxonomic identity (based on sepal color) or geography…” (Dodd and Helenurm 2002, p. 617). Because there was little genetic differentiation detected among populations of the two insular subspecies, and earlier work had suggested there is little morphological evidence for separating them (Dodd and Helenurm 2000, pp. 121–125), populations of the two insular subspecies were combined for reporting of standard measures of genetic variability. In comparison with other endemic plant species, Delphinium variegatum appears to be typical in its pattern of genetic diversity relative to its geographic range at both the population and taxon levels (Dodd and Helenurm 2002, p. 619). However, in comparison with other Delphinium, the genetic variation observed for the insular taxa of D. variegatum appears to be low. The data suggest that there is a higher level of gene flow among adjacent populations. If estimates of historical gene flow are indicative of current patterns, then gene flow among the 24 island populations studied appears to be high enough to prevent genetic differentiation among them. This is consistent with the general low level of genetic differentiation that has been found among populations of other species in the genus Delphinium (Dodd and Helenurm 2002, pp. 619–620). Dodd and Helenurm suggest that the high degree of similarity among populations is likely due to gene flow, and thus prevention of the isolation of populations or groups of populations may be important (2002, p. 620). The low level of genetic differentiation detected among populations suggests that successful reintroductions may be equally likely from any seed source (i.e. careful matching of seed source to reintroduction site may not be necessary). Seeds may not be needed from every population to capture genetic diversity in an ex situ conservation seed bank (Dodd and Helenurm 2002, p. 620).
Subspecies Considerations Differentiation of the two endemic subspecies of D. variegatum on SCI had been based on location (following the observations of Warnock 1990b), with a ‘northern larkspur’ (San Clemente Island larkspur) and a ‘southern larkspur’ (Thorne’s larkspur). The original distinction was based on just five herbarium specimens for both subspecies (Vanderplank et al., in prep). Today, with more groups of individuals, there is great confusion in the center of the island, since the taxonomic separation of San Clemente Island larkspur from Thorne’s larkspur is not very definitive from field observation (Dodd and Helenurm 2000, pp. 121–125).
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The most recent taxonomic treatment comes from the second edition of the Jepson Manual, which discourages the use of locality characters in the taxonomic keys for terminal taxa and therefore separates these two subspecies by sepal color, slope, and flowering time (Koontz and Warnock 2012). It is also noted that Thorne’s larkspur is commonly found on steeper slopes (Koontz and Warnock 2012). The island subspecies are currently distinguished primarily by flower color, with Thorne’s larkspur noted to have generally bright blue (i.e., darker), slightly larger flowers than the San Clemente Island larkspur, which generally has white flowers, consistent with distinctions noted in earlier works (Dodd and Helenurm 2000, p. 125; Koontz and Warnock 2012). San Clemente Island larkspur flowers are noted to be often somewhat smaller than those of Thorne’s larkspur, yet as with flower color, the floral size distinction is not always definitive. Intensive sampling of natural populations has shown that the two flower size metrics (lateral sepal length and lower petal blade length) do not adequately separate these taxa (Dodd and Helenurm 2000, p. 125). Although flowering times between the two subspecies are slightly offset and blue-flowered plants bloom slightly later than the white-flowered ones, environmental conditions may be responsible for this difference (Dodd and Helenurm 2000, p. 125). There is broad variation within locations and substantial overlap among the island subspecies for the three floral characters used to distinguish one from the other. Of the floral characters, sepal color appears to be the least ambiguous for differentiating the subspecies (Dodd and Helenurm 2000, p. 125; Dodd and Helenurm 2002, p. 614). However, it is still problematic. Both color forms clearly intergrade, especially in the middle of the island, where both colors and many shades of light to darker blue are present in many groups (Figure 2) (Dodd and Helenurm 2000, p. 125; Dodd and Helenurm 2002, p. 614).
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Figure 2. One of several white individuals of D. variegatum within a mostly blue population located in SHOBA. This population is currently recognized as Thorne’s larkspur. Photo by T. McFarland.
In the genus Delphinium, flower color is a variable trait and often has been used to distinguish two otherwise identical subspecies or varieties. This is true in the following species of Delphinium from the North American flora: D. californicum, D. carolinianum, D. hansenii, and D. hesperium (Koontz and Warnock 2012; Warnock 1997, entire). In contrast, D. parishii is a single taxon with flower colors that vary from blue to white. There are many additional examples of color variation in sepals and petals in the genus Delphinium (Warnock 1981, p. 40). For instance, a white form of Royal Larkspur has been collected from the mainland in Sonoma County (Vanderplank et al., in prep.). Further, herbarium specimens do not hold the color observed in live plants, and plants tend to dry with a bluer hue than observed in the field (Vanderplank et al., in prep). Thus, the flowers in the holotype of San Clemente Island larkspur SSA Report – San Clemente Island larkspur 17 March 2020
have a blue tint (Vanderplank et al., in prep.). The holotype for Thorne’s larkspur comes from an area of mixed flower color, and the type specimen includes three different flower colors, one of which is as white as the type specimen of San Clemente Island larkspur (Vanderplank et al., in prep.). Expert opinion, genetic research, and careful consideration of taxonomic challenges sheds doubt on the existence of two distinct taxa on SCI, and it has been suggested that the two subspecies may be a single taxon separate from Delphinium variegatum. Genetic research using allozyme data to validate two taxa (detailed below) was inconclusive, and Dodd and Helenurm (2002, p. 620) postulate that the two subspecies might be classified more appropriately as varieties or as a single subspecies. Koontz and O’Brien (2012) in an unpublished report concluded, “It is most probable that the variation observed in the island populations indicate that they are a single, highly variable taxon, and it would be most prudent to manage the two island taxa as a one unit in order to maintain the variation observed in the field.” Only additional genetic research can determine whether there are any significant genetic differences between the two flower forms present on the island and where they are mixed or hybridizing. Despite doubts regarding the classification of San Clemente Island larkspur, the most current published taxonomy still formally identifies two separate taxa. From a regulatory perspective, management responsibilities under the Endangered Species Act must focus on the conservation of San Clemente Island larkspur. This assessment therefore focuses on what is currently recognized as San Clemente Island larkspur but accounts for the locations where the population appears to be mixed, hybridized, or otherwise in question.
2.2 Subspecies Description San Clemente Island larkspur is an herbaceous perennial in the buttercup family (Ranunculaceae). It grows 14 to 85 cm (6 to 33 in) in height but generally is less than 50 cm (20 in) tall (Koontz and Warnock 2012). San Clemente Island larkspur has woody, branched roots (Munz 1969, p. 69). The primary roots in Delphinium are clustered around a small crown of the stem and shallowly seated in the top soil; dry and brittle during summer months; they absorb water and become fleshy, sending out secondary roots in response to late-autumn or early-winter rains (Epling and Lewis 1952, pp. 255–256). Vegetative growth arises from meristematic buds developed within the axils of leaves from shoots that died back in prior summers; these perennating buds are retained on the caudex (woody stem) below the soil surface irregularly sending up new shoots in following years (Baskin and Baskin 1974, p. 60; Kingsley 1911, p 308). The flowers are light blue to white in color and are bilaterally symmetrical with five petal- like sepals and four smaller petals. The uppermost sepal is a straight or downcurved spur that is characteristic for the genus. Flowers are borne along branched flower stalks typically bearing less than 12 flowers (Koontz and Warnock 2012; Junak and Wilken 1998, p. 121). Leaves are generally found along the lower one third of the stem and have few to many overlapping lobes that radiate from hairy petioles. The fruit is a follicle (dry, pod-like structure with a single suture), with up to three follicles possible per flower (Junak and Wilken 1998, p. 121). Each follicle bears many winged seeds that are likely wind dispersed when the fruit passively splits open (Junak and Wilken 1998, p. 121). Three floral characters, sepal color, lateral sepal length, and lower petal blade length, are used to distinguish the subspecies based on the most recent taxonomic treatment (Koontz and Warnock 2012). In general, Royal larkspur differs from the two island subspecies by having
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darker (deep versus bright or light blue) flowers and shorter lower petal blades (Dodd and Helenurm 2000, p. 116).
2.3 Range and Distribution San Clemente Island larkspur is endemic to SCI, located 64 miles (103 km) west of San Diego, California, and the southernmost of the California Channel Islands (Figure 3). The island is approximately 56 square mi (145 square km, 36,073 acres, or 14,598 hectares) (Junak and Wilken 1998, p. 2) and is long and narrow: 21 mi (34 km) long by 1.5 mi (2.4 km) wide at the north end and 4 mi (6.4 km) wide at the south end (USFWS 1984, p. 5). The island consists of a relatively broad open plateau that slopes gently to the west. Conspicuous marine terraces line the western slope of the island while steep escarpments drop precipitously to the rocky coastline on the eastern side along the southern half. Many canyons, some of which are up to 500 feet (152 meters) deep, dissect the southern part of the island. Mount Thirst, the highest point on the island, rises to approximately 1,965 feet (599 meters) (US Navy 2013, p. 1-4). Average monthly temperatures range from 58°F (14°C) to 66°F (19°C), with a monthly maximum temperature of 72°F (27°C) in August and a monthly minimum of 51°F (10°C) in December (US Navy 2013, p. 3-11). Average monthly relative humidity varies from 54% to 86% depending on location and time of year, and the island experiences dramatic fluctuations in annual rainfall, averaging 6.6 inches (16.8 cm) (US Navy 2013, pp. 3.11, 3.13). Precipitation is received mainly from November through April, with little from May through October. In addition to precipitation, fog drip during the typical dry season is a vital source of moisture to the SCI ecosystem (US Navy 2013, pp. 3.9, 3.13).
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Figure 3. Location of San Clemente Island in the southern Channel Islands off the coast of California.
The historical range and distribution of San Clemente Island larkspur on SCI is unknown because botanical studies were not completed before the plant’s decline. The final listing rule for San Clemente Island larkspur (USFWS 1977, p. 40682) failed to include specific information regarding the distribution and status of larkspur populations. Regarding the status of larkspur populations, the final rule merely summarized the comments of one individual who responded to the proposed rulemaking that San Clemente Island larkspur is “…uncommon in grasslands in Spring” (USFWS 1977, p. 40683). By 1984, USFWS (1984, p. 17, 35) noted that it occurred in 6 or 7 locations.
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Today, the species occurs across much of SCI (see Figure 8), and the subspecies is found both on the eastern escarpment, central plateau, and western terraces (Figure 5). Since the grazing pressure was removed on SCI, both subspecies of Delphinium variegatum have been noted to have expanded dramatically (O’Brien 2019, pers. comm.). There is speculation that as shrubs continue to recover, this species may be migrating away from slopes to flatter areas (O’Brien 2019, pers. comm.); however, there is no data to support the perceived decrease on slopes (Munson 2019, pers. comm.). The true range and distribution of San Clemente Island larkspur on SCI is somewhat unknown due to the ambiguity of the subspecies classifications, mostly within the central areas of the island (see Section 2.2). Monitoring and management of San Clemente Island larkspur on SCI has relied on the geographic concepts of a northern and southern larkspur, as detailed by Warnock (1997) and in consultation with Delphinium expert Dr. Jason Koontz (Professor of Biology, Augustana College, IL) in 2012. The analysis of Dodd and Helernum (2000, p. 125) separated populations by the presence of more than 80% light or dark colored flowers. In D. variegatum occurrences west of Ridge Road, white-flowered individuals generally occur from Middle Ranch Road north, and in occurrences east of Ridge Road, white-flowered individuals generally occur from Horton Road north. Occurrences south of these areas contain different proportions of white and blue-flowered individuals, as well as individuals with intermediate floral colors, though blue-flowered individuals generally become more prevalent in the south. However, in several central watersheds, both subspecies have been recorded, often within short distances of each other. The metrics surveyors were using to assign subspecies at the time of the survey are unknown (flower color or characteristics of individuals, proportion of blue versus white flowers in the area, north/south location, etc.). Thus, without further genetic work, the true subspecies or hybrid status of individual plants within these central locations is unknown. In 2019, the Navy delineated the range of San Clemente Island larkspur as those locations occurring in Box Canyon or north on the western side of the island and those individuals occurring in Boulders Canyon or north on the eastern side of the island. This delineation was used because groups at locations in these canyons and north have significant numbers of white individuals, while all locations south of these canyons are predominantly blue, with no significant numbers of white individuals present. However, one population of almost entirely white individuals exists on the southernmost end of the eastern escarpment in SHOBA. However, some groups previously defined as Thorne’s larkspur are located in north of these canyons are areas now considered San Clemente Island larkspur by the Navy (and thus receive ESA protections) based on this north/south cutoff. For this SSA, we will use a combination of the delineation used by the Navy (north/south) and the subspecies assigned to each location when they were surveyed. Thus, all locations south of Box Canyon on the western side and Boulders Canyon on the eastern side of the island will be considered Thorne’s larkspur (except for the southernmost location—see below); however, we will account for the areas of ambiguity north of these canyons. We assume that watersheds north of this line that have locations recorded as Thorne’s larkspur as “mixed” watersheds (even if all individuals there were identified as Thorne’s larkspur when surveyed), where the true proportion of each subspecies is unknown (Figure 4). However, locations and individuals that were recorded as Thorne’s larkspur are not considered in our analysis, and we instead only count the locations and individuals that were identified as San Clemente Island larkspur in any numerical analyses. Further, a location containing a large proportion of white individuals on the southernmost end of the eastern escarpment within SHOBA will also be
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considered “mixed.” These individuals were detected in 2010 (and were still extant in 2019; McFarland 2019, pers. comm.). They were recorded as Thorne’s larkspur, but separate, nearby (~50 m) point locations of San Clemente Island larkspur (with no count data available) were recorded in the same watershed in 2006 and 2012. Thus, this watershed has points for both subspecies within it, and the Navy has noted it is unclear which subspecies these individuals represent (US Navy in prep). While San Clemente Island larkspur have been recorded there in recent years and this watershed is considered occupied, no count information is known, so we do not include individuals here in our analyses. For the purposes of this SSA, we include the distribution data for Thorne’s larkspur recorded from 2011 to 2014 to provide broader context of the species as it occurs on SCI (Figure 4).
SSA Report – San Clemente Island larkspur 22 March 2020
Figure 4. All recorded locations of the two subspecies of Delphinium variegatum on SCI and the associated watersheds. Watersheds with only San Clemente Island larkspur (1980-2017), only Thorne’s larkspur (2011-2014), and those presumed mixed are indicated. One watershed with only Thorne’s larkspur records is still presumed mixed due to ambiguity in this area, unknown survey parameters, and the definition to delineate the two subspecies now adopted by the US Navy.
2.4 Habitat San Clemente Island larkspur was once associated with two main vegetation types: California Broadleaf woodlands and forests (which encompasses approximately 43.5 ac [17 ha] 0.12 % of the island), and California perennial grassland (which encompasses approximately SSA Report – San Clemente Island larkspur 23 March 2020
2,213.5 ac [895 ha], 6.3% of the island) (US Navy 2013). The species is now found in a broad range of habitats within the same general vegetation types and is widespread across the island. San Clemente Island larkspur is generally found within mid- to high- elevation grasslands on the east side of the northern and central portions of the island where it occurs in clay, loam, and rocky soils with soil-depths ranging from shallow to deep; however, it is more often associated with non-clay soils (Figure 5) (Vanderplank et al., in prep.). Reported habitats have included costal grasslands (Koontz and Warnock 2012) as well as grassy slopes and benches, open grassy terraces, and chaparral and oak woods (Warnock 1993 in USFWS 2008a). Currently, San Clemente Island larkspur occurs primarily on the east side of the island on gentle slopes with northern, northwestern, and eastern exposures. The higher-elevation plateau supports grasslands dominated by the native perennial bunch-grasses interspersed with annual forbs while the mid- and lower-elevation grasslands tend to be less floristically diverse and dominated by introduced annual grasses (Figure 6). They are primarily found within vegetation communities dominated by Artemisia californica, non-native grasslands, and Baccharis pilularis (Vanderplank et al., in prep.). Based on recent survey data, San Clemente Island larkspur is documented at elevations of 83 to 571 m (approximately 275 to 1875 feet) (Figure 6) and on slopes of 0 to 30 degrees, with the majority on moderately steep slopes of 6 to 25 degrees (Vanderplank et al., in prep.). Thorne’s larkspur is documented at similar elevations but is found on a broader range of slopes than San Clemente Island larkspur, occupying maximum slopes that are approximately 10 degrees steeper. The documented range of slopes is broader than that noted in the Jepson Manual (Vanderplank et al., in prep.). Elevation and slope have been considered indicators of species habitat preferences, and hence, geographic location has been used to classify the larkspur as one subspecies or the other (Munson 2019, pers. comm.).
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Figure 5. Distribution of San Clemente Island larkspur and soil types. (From Vanderplank et al., in prep.).
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Figure 6. Vegetation types and distribution of San Clemente Island larkspur. (From Vanderplank et al., in prep.).
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2.5 Life History Survival and Lifespan Like most other California larkspurs, San Clemente Island larkspur can survive below ground when conditions are unfavorable and may remain dormant and not appear above ground for one or more years (Epling and Lewis 1952, p. 255–257). The species begins to go dormant shortly after flowering, remaining dormant until early in the rainy season. The dormancy period (roughly May or June through November) is correlated with rainfall (O’Connor 2019, pers. comm.; US Navy 2009, p. 4.22). A study of seven species of Larkspur, including Delphinium variegatum on the mainland (Royal Larkspur), notes that even if dormancy is broken and plants produce leaves, many plants do not persist to flowering and re-enter dormancy for an indeterminate period of time (Epling and Lewis 1952, pp. 255-256; Lewis and Epling 1959, p. 512); species of Delphinium are known to have not flowered in a decade and examination of root-size suggested that the lifespan of an individual plant could be decades long (Epling and Lewis 1952, p. 256). Therefore, we assume that occurrences of San Clemente Island larkspur are similarly long-lived even though we have no information about the life-span of individual plants on SCI. Junak and Wilken (1998, pp. 129) recorded cursory information about the age-structure of San Clemente Island larkspur on SCI, noting in a few cases that some proportion of the standing populations included juvenile plants and some seedlings, but most occurrences they visited appeared to be comprised completely of adult plants. We do not have information that would allow us to understand the longevity of plants of the age structure of the colonies of San Clemente Island larkspur on SCI. Colonies of Delphinium may persist in one location for long periods, and other than the number of plants blooming in a given year, the total population of a colony appears to change very slowly or infrequently (Epling and Lewis 1952, pp. 256–257).
Reproduction Flower production in Delphinium can be highly variable and may be dependent upon quite localized weather conditions (Lewis and Epling 1959, p. 512) and soil-moisture (Inouye et al. 2002, pp. 545, 549). Plants may not flower until reaching 2-3 years of age (e.g., Waser and Price 1985, p. 1727 in reference to D. nelsonii). San Clemente Island larkspur generally flowers from March to April (California Native Plant Society 2001, in USFWS 2008a), but has been documented from January to April (Koontz and Warnock 2012). The flowers are bisexual and typically borne in terminal racemes and clusters of less than 12 flowers per stalk (Koontz and Warnock 2012). Blue and white flowered Delphinium species are largely pollinated by bumblebees (Waser and Price 1983, p. 343; Waddington 1981, p. 154). Anecdotal field observations of San Clemente Island larkspur pollinators include a large black and white solitary bee (Junak and Wilken 1998, p. 120) and hummingbirds (Munson 2019, pers. comm.). A pollinator study on SCI also documented Anthophora edwardsii (Apidae), two species of hymenoptera, and five members of the Diptera order: Lucilia sp. (Calliphoridae), and four Syrphidae species visiting flowers (SERG 2015b, p. 13). Given the spur-length of San Clemente Island larkspur, bumblebees or hummingbirds may be the primary pollinators (Jabbour et al. 2009, p. 814). Successful outcrossing within island populations indicates that pollination is effective, and, therefore, that populations of pollinators are likely to be ample.
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Junak and Wilken (1998, p. 121) assessed fecundity at three populations and found a mean of 8 (7–9) flowers and 5.4 fruits per inflorescence. Each flower has 3 pistils, each with its own style and stigma, so each is independently pollinated. The fruit is a follicle (dry fruit with a single suture), and up to three follicles per flower may form (Junak and Wilken 1998, p. 121). The average number of seeds per follicle was found to be 15–20, with a mean of 51.9 seeds per flower (Junak and Wilken 1998, p. 121). The seeds appear more or less smooth to the naked eye with undulating margins, making them likely wind dispersed when the fruit dehisces. On average, 64.5 to 78.5 percent of flowers produce fruits, with a significantly greater number of flowers than fruits (Junak and Wilken 1998, p. 122). This is consistent with self-incompatibility and/or a requirement for insect-mediated pollination. Seed germination (43 percent) was not significantly less than seed viability (53 percent) when analyzed around 20 weeks following collection, indicating that recruitment does not appear to be limited by fruit production (Junak and Wilken 1998, p. 122). Epling and Lewis (1952, p. 262) reported that distances between colonies of Delphinium of one- or two-tenths of a mile (176-352 yards; 160-320 m) was a sufficient barrier to both seed and pollen dispersal. Within D. nuttalianum (nelsonni) (Nuttall’s Larkspur), Waser and Price (1985, p. 1731) demonstrated an optimal out-crossing distance between parents; an out-crossing distance of 55 yards (50 m) resulted in greater reproductive fitness and survival of offspring. However, as noted, spatial distribution of above-ground, flowering individuals may be deceptive with respect to overall size of a colony; what seems like intervening space between colonies may be just a failure to express uniformly across microsites (Lewis and Epling 1959, p. 512). Therefore, distances between flowering patches may differ annually based on environmental conditions affecting plant-expression. The spatial distance between the majority of the known colonies of San Clemente Island larkspur north of the SHOBA boundary is less than 0.25 mi (400 m), a distance pollinators could certainly travel, with the largest distance between occurrences being about 1.9 mi (3 km) between northern and southern occurrences (USFWS 2008a, pp. 9-10). Delphinium seeds require darkness to germinate and must be buried in the substrate (Vanderplank et al., in prep.). Ex-situ seed-germination experiments have had mixed results possibly caused by innate seed-dormancy, but the Rancho Santa Ana Botanic Garden considered their ability to propagate San Clemente Island larkspur as poor (USFWS 2008a, p. 15). Seeds have been germinated in the greenhouse on SCI; 36 of 40 seeds germinated in initial trials (SERG 2011, p. 6). In contrast with the results of Junak and Wilken (1998, p. 122), Evans and Bohn (1987, p. 539) were unsuccessful getting freshly collected seeds to germinate. This may be due to a requirement for seeds to go through a period of dormancy prior to germination (Junak and Wilken 1998, p. 122). During efforts to collect seed for the purposes of plant propagation, Evans and Bohn (1987, p. 539) found seed predation to be heavy in one population of San Clemente Island larkspur. They found holes chewed through the bottom portion of seed capsules, but they were unable to ascertain the identity of the seed eater. During their survey efforts, Junak and Wilken (1998, p. 120) have not seen evidence of seed predation, although some seed predation by caterpillars has been noted in the field in some years (Munson 2019, pers. comm.). As of 2006, the Rancho Santa Ana Botanic Garden had a collection of about 7,780 seeds of San Clemente Island larkspur in their conservation seed bank (USFWS 2008a, p. 15), and recent communication indicates around 7,000 seeds as of 2012 (Vanderplank 2019, pers. comm.). However, based on their experience with this subspecies, they believed their ability to
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propagate San Clemente Island larkspur was “poor at this point” (USFWS 2008a, p. 15). The Soil Ecology and Restoration Group, however, has had good luck propagating seeds, but keeping them alive over summer has had limited success (Munson 2019, pers. comm.). The mating system for San Clemente Island larkspur is poorly understood. Dodd and Helenurm (2002, p. 618) conclude from their study of genetic variability among populations of D. variegatum that the two insular subspecies (San Clemente Island larkspur and Thorne’s larkspur) are largely outcrossing with a pattern of near random mating. Outcrossing rates for the mainland subspecies (Royal Larkspur) indicate that it sustains higher levels of inbreeding (Dodd and Helenurm 2002, p. 618).
Fire Tolerance The California Channel Island Species Recovery Plan states that “[F]ield observation following fire suggests that this species is adapted to fire during its dormant period” (USFWS 1984, p. 53). Following flowering, the subspecies begins to go dormant, remaining dormant until early in the rainy season. Because the dormancy period (roughly May or June through November) is correlated with rainfall, and because fire season is determined by fuel (vegetation) moisture levels, dormancy and fire season generally coincide (O’Connor 2019, pers. comm.; US Navy 2009, p. 4.22). The possible benefits of fire to San Clemente Island larkspur include reduction in competitive shading and/or nutrient uptake which would likely increase flowering and possibly visibility to pollinators. Epling and Lewis (1952, p. 263) found that establishment of novel colonies of D. variegatum from sown seed was most successful in recently burned areas rather than in areas within a fully developed vegetative community. Therefore, fire may enhance seed germination in colonies of San Clemente Island larkspur. The growth period of San Clemente Island larkspur is late-autumn through late-spring. While we do not have a comprehensive understanding of the timing of fire on SCI, in 2017, fires occurred during the months of June, July, and August (US Navy, unpublished data). As noted, shoot-production and flowering in Delphinium appears to be strongly influenced by ambient moisture, in either the soil or atmosphere. Therefore, localized habitat conditions and fog may reduce incidence of fire or fire-intensity should it occur during the growing season thereby minimizing the possibility of fire damage, but this is speculative. During drought years, few plants are likely to produce shoots and thus would likely not be burned; effects to roots in dry soils are unknown. Fire has proven beneficial for other species of Delphinium. Delphinium viridescens (Prairie Larkspur) from the eastern Cascades of Washington State is reported to be adapted to fire (Center for Plant Conservation 2019). That species is associated with mesic habitats and responds to fire by resprouting from underground rhizomes. Plants in burned plots also appear to be more robust than those in unburned plots, possibly due to reduced competition for light following fire (Harrod et al. 2000 in USFWS 2008a). The same pattern has been observed with D. cardinale (scarlet larkspur) (Clark et al. 2007, p. 105). Because San Clemente Island larkspur is exposed to a different climate and is associated with different habitat conditions, further study is needed to determine if it shares similar adaptations to fire. However, not much is known regarding the tolerance of this subspecies to fire, such as what the mechanism is for regrowth (e.g. from resprouts or seed) and what minimum fire return interval the subspecies can tolerate. If underground storage roots survive fires, plants could benefit from added nutrients, canopy opening and other aspects of altered competitive status created by an appropriately timed burn. If fires occur when plants are active or prior to seed set,
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they could impair seed recruitment and regeneration following fire and kill plants (US Navy 2002, p. D.23). If fires are severe, they could also affect the viability of underground storage roots. High fire frequency could also be a potential threat that could limit the distribution of the larkspur by overwhelming its tolerance threshold to fire (Brooks et al. 2004, p. 683; Jacobson et al. 2004, p. 1). Kellogg and Kellogg (1994, un-paginated Appendix I) reported that this subspecies may be enhanced or threatened by fire, but there was insufficient information from which to make an assessment.
2.6 Population size and abundance The 1976 Smithsonian report (41 FR 24523) and the 1977 proposed rule to list the San Clemente Island larkspur (USFWS 1977, p. 40682) did not include specific information regarding the size, number, or trends of populations for this subspecies. A report from 1979, during the period of goat grazing, stated only two isolated patches of the plant remained at that time (Table 1) (US Navy 2002, p. D.23). One of those two patches was found to support just one lone individual (Kellogg and Kellogg 1994, Appendix I). The Navy reportedly fenced those two patches to prevent their predation from feral pigs (US Navy 2002, p. D.23). The California Channel Islands Species Recovery Plan indicates that the number of known occurrences of the San Clemente Island larkspur had increased to at least seven grassland sites in 1984 (USFWS 1984, p. 53). However, there was no current information regarding the number of individuals at those locations. In 2014, previously unknown data were located containing point locations of San Clemente Island larkspur from 1980 by an S.J. Carlton. These data show a much broader distribution around the time of listing than is noted in the literature, with locations in 17 watersheds in 1980 (see Figure 7). However, there is no associated count data indicating numbers of individuals at these locations, and only 7 “grassland sites” are noted in the 1984 recovery plan, despite Susan J. Carlton having helped with the illustrations (USFWS 1984, p. 4). Thus, we cannot be certain whether or not these points represent locations documented in 1980. For the purposes of this SSA, we assume that they do. During sensitive plant surveys performed in 1996 and 1997, Junak and Wilken (1998, p. 120) documented 17 patches of San Clemente Island larkspur ranging in size from 7 to 1,450 individuals, estimating 5,400 plants total (Table 1). In a discussion of their 1996-1997 survey results, Junak and Wilken (1998, p. 120) noted that they did not visit a number of historical sites for the subspecies, suggesting that more San Clemente Island larkspur were likely to occur on the island than were reflected in their surveys. Surveys in 2003 through 2006 documented 15 locations and an estimated 1,871 individuals (Table 1) (Junak 2006, p. 67; US Navy 2008, p. 3.11-20). However, many occurrences mapped in the 1996-1997 surveys were not revisited, so the 2003-2006 surveys are thought to be a low representation of the total San Clemente Island larkspur population at the time (Vanderplank et al., in prep.). The 1996-1997 and 2003-2006 surveys have been combined in population reports (US Navy 2008, p. 3.11-20). Surveys conducted between 2011 and 2017 documented 74 locations and 21,981 individuals of San Clemente Island larkspur on SCI (Table 1) (US Navy, unpublished data). Surveys were done in 2011-2012, 2013, 2015, and 2017. Surveys in 2015 and 2017 were targeted at areas not covered in 2011 and 2012 (US Navy, unpublished data). While the 2011- 2012 points and the 2015 to 2017 points do not overlap, some points collected in 2013 may overlap the other years; thus, we report these surveys separately (Table 1). We attempt to address this potential double-counting in our assessment of the current distribution (Section 2.7.1 below).
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Table 1. Surveyed number of San Clemente Island larkspur individuals during various survey years (US Navy 2002, p. D.23; US Navy, unpublished data; USFWS 1984, p. 53; Junak and Wilken 1998, p. 120; Junak 2006, p. 67). Extent of each survey is unknown. Survey Year Locations Individuals 1979 2 unknown 1984 7 unknown 1996-1997 17 5,700 2003-2006 15 1,871* 2011-2012 24 2,371 2013 41 12,705 2015-2017 9 6,905 * many locations not visited, known to be a low representation
Because survey efforts have focused on documenting the plants rather than re-visiting and tracking the dynamics of known populations, there is little information for directly inferring population trends. The best trend information available is for one of the last two populations of San Clemente Island larkspur that were thought to remain in 1979. As part of a long-term study of SCI vegetation condition and trend, a vegetation monitoring plot was overlain at a location north of Stone Station where Howard Ferguson reported a single individual occurring in 1979 (Kellogg and Kellogg 1994; Tierra Data Inc. 2005). In 1992, though no direct population counts were made, 6 to 10 patches of 1 to 25 plants each were recorded at that location (Tierra Data Inc. 2005). “In 1995, a total of 564 plants were found, and 349 plants were present in 2000” (Tierra Data Inc. 2005, p. 80). Thus, the population north of Stone Station appears to have expanded from a single individual at the time of goat grazing to several hundred plants under fairly recent conditions. Elsewhere, the vegetation trend monitoring study has only captured San Clemente Island larkspur in one other monitoring plot where an individual plant was seen in 1994, but this plant has not been observed since (Tierra Data Inc. 2005). Using all records of San Clemente Island larkspur recorded on the island since listing, we tracked the locations and areas of the island that were known to be occupied over time. We used watersheds as a means of segmenting the population (see Section 4.1 for further explanation). Data indicate that the number of watersheds where surveys located San Clemente Island larkspur in each decade increased from a low of 2 in 1979 to 24 between 2010 and 2019 (2 additional watersheds are presumed to be mixed subspecies due to their location and ambiguity of flower color, although records in that decade were recorded as Thorne’s larkspur; see Section 2.6) (Table 2). Some historical locations are unknown to be extant currently due to a lack of repeat survey data and unknown survey extents (see Section 2.6); there are 7 watersheds that historically had recorded San Clemente Island larkspur in which the occupancy is currently unknown (see Section 2.6). However, the range has generally expanded over time, despite the potential loss of some of these areas; the subspecies is still known to occur in the majority of locations where it was documented historically, indicating that it is persisting in most of its historical locales, and it has been documented spreading into new areas (Figure 7).
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Table 2. Number of watersheds with records of San Clemente Island larkspur collected in each decade. These represent only surveyed watersheds where San Clemente Island larkspur were found in that decade and do not account for watersheds that may have remained populated but were not surveyed in subsequent decades. Records from 2017 of Thorne’s larkspur in one watershed are now considered ambiguous; thus, that watershed is included in the 2010-2019 count, as it presumably contains some San Clemente Island larkspur, although though no official records were recorded there. Decade Occupied Watersheds 1979 2 1980-1989 17 1990-1999 6 2000-2009 15 2010-2019 24* * does not include 2 watersheds with no recorded SCI Larkspur in that decade, but population assumed mixed (see subspecies considerations)
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Figure 7. Watersheds with records of San Clemente Island larkspur (solid red) collected in each decade. Only records documented in each decade are shown, though they may have remained extant in subsequent decades when they were not surveyed or located. Watersheds assumed “mixed” are included. Two watersheds with Thorne’s larkspur records from 2010-2019 are included as assumed occupied as those watersheds are considered mixed; one of the two had historical SCI Larkspur records, and the other did not.
Accurate population estimates of San Clemente Island larkspur do not exist and are difficult to obtain. Individual plants may not flower every year or even emerge (Epling and Lewis 1952, p. 256), which makes them hard to detect among other plants, especially in
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grasslands or thick vegetation. Therefore, it is likely that the actual number of individuals has been underestimated. The ability of individuals to stay dormant in the ground and the influence of annual precipitation on seed germination and whether individuals emerge from dormant root stock also complicates tracking long-term trends. Few plants emerge during drought conditions, but emergence rates are high in wet years (Epling and Lewis 1952, p. 256). Difficulty distinguishing the two subspecies of Delphinium variegatum has left many ambiguous historical records of San Clemente Island larkspur, including some white-flowered individuals near the southern end of the eastern escarpment inside SHOBA. As noted in Section 2.4, while we consider this watershed to be occupied by San Clemente Island larkspur, the only location points with numbers of individuals associated were recorded as Thorne’s larkspur, and we treat them as such. Locations for San Clemente Island larkspur in that watershed recorded in 2006 and 2012 lack associated data (Vanderplank et al., in prep.).
Current distribution To assess the current condition of San Clemente Island larkspur across its range on SCI for the purposes of this document, we first defined what will be considered the current distribution; no existing singular dataset provided an encompassing, but conservative, estimate. The 2011 and 2012 surveys, along with the supplemental surveys in 2015 and 2017 (conducted in areas not surveyed in 2011 and 2012), were the most recent and extensive surveys to date, but these surveys likely do not represent the full distribution of San Clemente Island larkspur on the island. For instance, surveys in 2013 recorded San Clemente Island larkspur in other locations. The full extent of the survey area is not known because areas within which plants were not found were not documented, but it is known that these surveys did not cover the entirety of the island. Available data consist only of presence data, with no known corresponding absence data. However, additional survey data exist from 1996 through 2013, and these data include additional locations not documented in the main survey years where we know effort did not overlap. Because they are explicitly stated to not have overlapping search areas, we started with the 2011–2012, 2015, and 2017 data points, assuming these to be the most reliable and most recent survey effort. We then supplemented these data with additional location points based on a set of rules designed to generate a dataset that conservatively estimates the current distribution of San Clemente Island larkspur. To avoid including locations where plants are no longer present, we only kept records recorded in the last 15 years. Experts concurred that records as old as 15 years are still likely to persist. Many of these locations have been visited in the last several years and are known to still exist (Munson 2019, pers. comm.). However, because the number and spacing of the individuals actively growing may vary tremendously from year to year, the actual population of San Clemente Island larkspur is unknown. The true number of individuals can only be assessed if counted in the best years (Epling and Lewis 1952, p. 257). Therefore, to conservatively define the current distribution and abundance of San Clemente Island larkspur, we used the 2011–2012, 2015, and 2017 survey points, as well as additional point locations that met the following criteria: 1) Has all associated data (count of individuals at the point and year) 2) From the past 15 years (2004–present). 3) Does not occur within 50 m of a 2011-2012, 2015, or 2017 survey point. 4) Does not occur within 50 m of a retained survey point from 2013 or 2014 if it is older than that point.
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5) Does not occur within 100 m of a retained survey point from between 2005–2010 if it is older than that point. We took the following steps to map this distribution: 1) We buffered the 2011-2012, 2015, and 2017 data points by 50 m then deleted all points from other years that fell within these buffers. 2) We buffered the remaining 2013 data points (the next most recent year) by 50 m, and deleted all remaining points that fell within these buffers. 3) We then buffered the remaining 2010 data points by 100 m, deleting all remaining points that fell within the buffers. 4) We repeated this process with the 2009, then 2006, in that order (we did not have survey points from 2007, 2008, 2005, or 2004). Use of this methodology is based the following assumptions: 1) Points recorded in the same year are considered separate, regardless of distance apart. 2) Recorded point locations may be inaccurate up to 50 m for newer points (2011 through 2017) and 100 m for older points (2010 and older), so to avoid double counting, we selected the more recent point if two points fell within these distances of each other.
This yielded 74 locations totaling 18,956 individuals occupying 22 watersheds (Figure 8). Five of these 22 watersheds are considered mixed and also contain individuals identified as Thorne’s larkspur (Figure 9). An additional 4 watersheds are also assumed to be occupied by San Clemente Island larkspur but are not included in our analyses due to a lack of data; one has never had any records within it, but based on location and the ambiguity with Thorne’s larkspur, is assumed to; another has historically had individuals identified as San Clemente Island larkspur, but the record is too old; two others in the southernmost part of the eastern escarpment have points identified as San Clemente Island larkspur within them, but there is no associated count data (Figure 9). Using our methodology and this strict ruleset, only 8 locations from 2013 were removed. However, counts at locations in 2013 were generally higher than the other years, perhaps due to environmental conditions in 2013 that made San Clemente Island larkspur easier to detect (more individuals flowering, more prominent in the vegetation community, etc.). Because our methodology favored 2011, 2012, 2015 and 2017 survey years over 2013, regardless of the number of individuals at points, some of the 2013 points that were removed contained upwards of 600 individuals, even though the nearby point that was retained from another survey year represented many fewer individuals. Therefore, by following a rigorous rule set, we are likely underestimating the population.
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Figure 8. Distribution of Delphinium variegatum considered current as per methodology described in Section 2.6. Individuals per location of each subspecies are indicated for points considered current. Historical locations and points are indicated, as are watersheds considered occupied by just San Clemente Island larkspur as well as watersheds considered to contain mixed populations.
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Figure 9. Watersheds considered current and historical (yellow) watersheds for San Clemente Island (SCI) larkspur. Watersheds containing recent locations identified as only San Clemente Island larkspur are indicated in pink, and those with both subspecies are indicated in blue. Four additional watersheds (purple) are considered currently occupied by San Clemente Island larkspur, but numbers and or distribution are unknown.
Without repeated survey data in some of the historical locations, it is unknown whether individuals observed 40 years ago still persist. Compared to the historical distribution, there are 7 watersheds that were once occupied that are no longer considered occupied (Figure 8).
SECTION 3 – SUBSPECIES NEEDS
In this section, we synthesize the information in the preceding sections to highlight the overall needs of the subspecies. We start with the individual level, then move to the population SSA Report – San Clemente Island larkspur 37 March 2020
level, and then finally to the subspecies level. The needs for each level address that level; for example, if the needs of the subspecies cannot be met, the subspecies will eventually go extinct. The needs are also cumulative across levels. That is, if the needs of an individual cannot be met, then that individual will not survive, and as such, it will not contribute to a population. Extrapolating up, if the needs of all the individuals in a population are not met over time, the population will not persist. Similarly, if the needs of a population cannot be met, that population will not persist, and in turn, it will not contribute to the subspecies. Thus, failure to meet individual-level or population-level needs (on a large enough scale) can ultimately lead to subspecies extinction as well. If the needs of some number of individuals in a population are being met, allowing for an adequate population size and with sufficient rate of growth, then that population is resilient. The number of resilient populations and their distribution (and their level of connectivity) will determine the subspecies’ level of redundancy. Similarly, the breadth of genetic or environmental diversity within and among populations will determine the subspecies’ level of representation. Thus, for the subspecies to sustain populations in the wild over time and be viable, the populations need to be able to withstand stochastic events (to have resiliency), and the subspecies’ population as a whole needs to be able to withstand catastrophic events (to have redundancy) and to adapt to changing environmental conditions (to have representation). For the purpose of this report, we define viability as the ability of the subspecies to sustain populations in the wild over time. We describe the subspecies’ needs at the individual, population, and subspecies’ levels in terms of its resiliency, redundancy, and representation.
3.1 Population Resiliency For San Clemente Island larkspur to maintain viability, its population or some portion thereof must be resilient so that it can withstand stochastic factors such as drought, erosion, or other types of disturbance. Other factors that influence the resiliency of San Clemente Island larkspur populations include ecological integrity of the plant community, population size, and dispersal ability. Influencing those factors are elements of San Clemente Island larkspur ecology that determine whether populations can grow to maximize habitat occupancy, thereby increasing resiliency of populations (Figure 10). These factors and habitat elements are discussed below.
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Figure 10. Habitat and population factors that influence the viability of Delphinium variegatum ssp. kinkiense throughout its range.
Individual Level At the individual level, San Clemente Island larkspur require suitable soil, adequate pollinator activity, and habitat conditions that include adequate water, sunlight, and nutrients, with limited natural or anthropogenic destructive disturbance. Outcrossing within groups of San Clemente Island larkspur indicate that pollination is likely not limiting this subspecies, and no obvious barriers to pollinator movement exist on the island. The association of San Clemente Island larkspur with grasslands, even those dominated by nonnative annual grasses within parts of its range, suggests that it can withstand competition for sunlight and other resources, even where other plants are dense and competition may be fierce. However, the ability to go dormant for long periods of time may assist San Clemente Island larkspur in collecting adequate energy for survival in situations where available resources are not adequate.
Seeds Seed production is likely dependent upon pollination by an insect or avian pollinator (USFWS 2011, p. 2). We have no indication that seed-set in San Clemente Island larkspur is limited or any indication that seeds produced in the field are non-viable. If seeds do require darkness to germinate, and as they are likely dispersed in close proximity to the parent plant, then some bare ground amidst co-occurring vegetation may be necessary for seeds to reach soil and become buried. Because recruitment was improved in recently burned habitat in an experimental situation (Epling and Lewis 1952, p. 263), excessive co-occurring vegetation cover may prevent seeds from entering the soil seed bank or reduce the germination fraction through competitive exclusion.
Vegetative Plants Adequate moisture is likely required either in total precipitation, timing of precipitation, soil-moisture, and/or relative humidity to promote buds to break dormancy and to persist through SSA Report – San Clemente Island larkspur 39 March 2020
flowering. This may occur at a highly localized scale and could be affected by soil moisture- holding capacity, ambient temperatures, and fog. This subspecies appears to grow in both clay and non-clay soils, which have vastly different water-holding capacities. There is no documented limitation on vegetative growth based on soil-type. Both native and non-native plants may compete with San Clemente Island larkspur for nutrients, light, and water and if sufficiently dense, exclude plants of this subspecies.
Population (Watershed) Level Habitat must be maintained to support a sufficiently large number of individuals needed for population persistence, although what population size is sufficient is unknown. Habitat features must be sufficiently contiguous or absent dispersal barriers such that necessary levels of population dispersal and gene-flow within each watershed are achieved to maintain sufficient levels of genetic diversity and preclude deleterious effects to the population from inbreeding depression and genetic drift (Ellstrand and Elam 1993, entire). However, the necessary levels of dispersal and gene flow are unknown for this subspecies. The extent of the distribution of San Clemente Island larkspur may well be significantly underestimated as not all plants in a colony emerge in any given growing season. Groups of San Clemente Island larkspur require sufficient moisture in habitat microsites to allow plants within colonies to break dormancy, flower, and potentially set seed. If exotic annual grasses or native shrubs reduce habitat suitability for colonies, colonies within an occurrence will need suitable habitat into which they can naturally expand, or absent that occurring naturally, management of invasive species and/or encroaching shrubs to allow their persistence in situ. Fire, especially if it occurs outside of the growing season, may enhance persistence of plants of this subspecies by enriching soil-nutrients and eliminating competition from neighboring plants. Responses to stochastic events such as particularly severe or high frequency of wildfire, erosion that results in slope failure and destruction of plants, inadvertent habitat destruction during training will likely depend on adequate distribution of colonies across the landscape to sustain processes such as gene-flow for the subspecies and/or recolonization of habitat from seeds produced in adjacent colonies. No impediments to the movement of pollinators (for gene flow) or dispersal events within watersheds appear to exist on SCI. While it appears that plenty of potential habitat exists for this subspecies, the subspecies is not found throughout it, and limitations may exist that are currently unknown. The degree to which habitat is unfragmented and how much unoccupied habitat is available determines how much dispersal of new individuals is possible, which influences gene flow, local adaptation, extinction risk, colonization probability, and the potential for organisms to move with a changing climate (Taylor et al. 1993, p. 572).
3.2 Representation and Redundancy Subspecies Level For the subspecies to be viable, there must be adequate redundancy (suitable number and distribution of individuals) to allow the subspecies to withstand catastrophic events. Redundancy improves with increasing numbers of occupied watersheds and with increasing numbers of individuals in each. Habitat for San Clemente Island larkspur must be sufficiently contiguous or absent dispersal barriers such that necessary levels of population dispersal and gene-flow can SSA Report – San Clemente Island larkspur 40 March 2020
occur among watersheds to maintain sufficient levels of genetic diversity (Ellstrand and Elam 1993, entire). This subspecies will be most viable by occupying a range of watersheds in multiple habitats across the island. For instance, by occupying both the western and eastern sides of the island, which have differing moisture patterns, the subspecies might be buffered from a localized catastrophic impact, such as a severe fire, or an island-wide catastrophic impact such as a prolonged drought, which could affect San Clemente Island larkspur on the eastern and western sides of the island differently due to differences in soil, slope, insolation, fog, rainfall, or other variables. Proximity of other individuals in other occupied watersheds will allow gene flow among watersheds and individuals and improve the chances of dispersal to new locations or across watersheds, which would allow the subspecies to persist and become reestablished after catastrophes. Again, while much of the island seems habitable to this subspecies, additional habitat limitations may exist that are currently unknown. No barriers to the movement of pollinators (for gene flow) or dispersal appear to exist on SCI, although terrain may favor recruitment within rather than across watersheds. Also, for subspecies viability, there must be adequate representation (genetic and environmental diversity) to allow the subspecies to adapt to changing environmental conditions. Representation improves with increased genetic diversity and/or diverse environmental conditions within and among populations. Results from the population genetics assay suggest that diversity may have been retained over time in the soil seed bank. This may have occurred as plants that persisted in areas that escaped grazing pressure retained genetic diversity through outcrossing. In addition to genetic data, adequate representation for this subspecies would be indicated by the population being distributed throughout multiple habitat types and across multiple elevations, indicating that the subspecies is adapted to these different environmental and habitat conditions.
SECTION 4 – CURRENT CONDITION
In this section, we describe the current condition of San Clemente Island larkspur using our definition of the current distribution (Section 2.6). We describe the current condition using the 3Rs based on the subspecies’ current distribution, population size, and trends.
4.1 Populations Resiliency is typically measured at the population level. While we consider San Clemente Island larkspur to represent a single population, as it is widespread on the northern part of the island with no natural division in its range, for monitoring and tracking the population in the future, we noted that a delineation of the population into watershed units would be useful, and such a delineation could further help to quantify threats across the range. Watersheds have been suggested for use in delineation for monitoring purposes by the Navy (Vanderplank et al. 2019, pp. 6–7), as every point on the island can be easily assigned to a watershed and watershed boundaries on SCI are not expected to change significantly during the 20 to 30-year time frame of this analysis. We divided the subspecies range into watershed units to assess resilience. These units are not meant to represent “populations” in a biological sense; rather, these units were designed to subdivide the subspecies range in a way that facilitates assessing and reporting the variation in current and future resilience across the range.
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In this document, we assessed the subspecies’ ability to withstand stochastic events in each watershed, and how these occupied watersheds contribute to the viability of the entire island population (the subspecies).
4.2 Methods for Estimating Current Condition To assess the resiliency of San Clemente Island larkspur, we assess the overall condition of the population by evaluating occupancy, locations, and estimated individuals within each watershed. We also examine the population trends which indicate the ability of San Clemente Island larkspur to withstand and recover from stochastic events. Using our assumptions in our analysis of the current distribution of the subspecies (Section 2.6), we define the subspecies’ current resiliency based on the locations and numbers of individuals that are assumed to be extant currently. We assume that the individuals have persisted despite the existing threats at their current levels, and that current resiliency of each watershed is a product of the number of individuals within it. Watersheds with higher numbers of individuals are more resilient than those with fewer individuals; however, if all of the individuals within a watershed are in just one location, we assume that they are less resilient than a watershed with the same number of individuals that are spread out across multiple locations, as plants will be more likely to persist through stochastic events if one localized event is unable to affect all the plants in the entire watershed. We note that the true number of individuals present in each watershed is unknown, both due to sampling inconsistencies, difficulty of detection, time since sampling, and the issue of dormancy or suppression of flowering of some individuals in some years. However, these counts of individuals still provide a general metric of abundance. In addition to the numbers of individuals currently present, resiliency is also affected by the population trend; we will therefore revisit the trend data to look for evidence of the population trajectory for San Clemente Island larkspur on SCI. Therefore, to evaluate the resiliency of San Clemente Island larkspur, we will assess the minimum conservative estimate of the number of watersheds, locations, and numbers of individuals based on the methodology outlined in Section 2.6, both within individual watersheds and island-wide. Further, we will evaluate the trajectory of the island-wide population based on the best scientific data through counts of locations and populations over time.
4.3 Current Condition Results Within individual watersheds. Number of individuals: Only 3 of the 22 occupied watersheds by the locations considered current have a local population of under 50 individuals (Table 10 in Appendix A). Seven have over 500 individuals. However, 8 watersheds (36%) have just one documented location within the watershed (Table 10 in Appendix A).
Island-wide Number of occupied watersheds: There are 216 watersheds delineated on SCI, and our current distribution of San Clemente Island larkspur encompasses 22 of these, with an additional two known to be occupied but with no count data available, and two more assumed to be occupied but with no distribution data (Figure 8). SSA Report – San Clemente Island larkspur 42 March 2020
Number of individuals: Our assessment of the current distribution of San Clemente Island larkspur includes 74 locations representing 18,956 individuals (Table 3). The vast majority of these individuals were detected in 2013 and 2015.
Table 3. Total locations and individuals considered current, broken down into survey points retained by year. Our methodology estimates approximately 18,956 individuals at 74 locations. Year Locations Individuals 2006 7 93 2009 1 16 2011 17 1,848 2012 7 523 2013 33 9,571 2015 1 5,500 2017 8 1,405 Total 74 18,956
Trends (counts over time): As reported in Section 2.6, counts of individuals have increased since listing from just two known occurrences with an unknown number of individuals at the time of listing to an estimated 18,956 individuals currently. Due to the difficulties inherent to counting Delphinium regarding their ability to stay dormant, etc., we cannot say with any certainty how much growth has actually occurred over time or to what extent the growth is attributed to differences in survey effort or survey extent. However, the population has grown since listing. Survey data indicates that the number of occupied watersheds, locations, and number of individuals have increased since listing (Table 1, Table 2), and we do not have data that indicates the subspecies is decreasing in any locations.
4.4 Current Subspecies Resiliency Trends indicate that the population of San Clemente Island larkspur on SCI has been increasing over time and withstanding current stochastic effects such as drought cycles, impacts from fire, erosion, or military training and land use, and the presence of nonnative and invasive species. Therefore, to quantify resiliency, we will use the number of individuals within each watershed. We first assess the resiliency of each watershed, and then scale up to the entire population on the island. We binned our assessed resiliency scores by watershed based on number of individuals; these breakpoints are based loosely on expert opinion but are mainly for visualization and have no verifiable biological meaning. Resiliency scores are as follows: • Very high—populations with >500 individuals. • High—populations with 200–500 individuals. • Moderate—populations with 50–199 individuals. • Low—populations with <50 individuals.
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However, for any watershed where all San Clemente Island larkspur occurred in just one location, we lowered the resiliency score by one level. Having all the individuals in just one location means that a single localized impact could extirpate that watershed’s population, regardless of how many individuals are present. Resiliency scores for individual watersheds can be found in Table 10 in Appendix A. Of the 22 occupied watersheds with data available, 7 (31.8%) are considered very highly resilient, 7 (31.8%) are considered highly resilient, 5 (22.7%) are considered moderately resilient, and 3 (13.6%) are considered to have somewhat low resiliency (Table 4, Figure 11). When we scale this up to the entire population, we find that 14 watersheds are high to very highly resilient and account for almost 93% of the entire population. Another 5 watersheds account for almost 7% of the population that is moderately resilient (Table 4). We assume another four watersheds are occupied; however, resiliency in those watersheds cannot be estimated due to a lack of data. Given the population trends and trajectory, the overall population appears to be resilient in the presence of the current level of stochastic pressures and threats and the current level of conservation and management efforts, based on our metrics.
Table 4. The number of watersheds that fall into each of our resiliency categories, the numbers of individuals of San Clemente Island larkspur the watersheds in each category accounts for, and the percent of the total island wide population represented. Watersheds without data but presumed to be occupied are not included in the percentages. Watersheds Individuals Percent Total Very High 7 10,024 52.9% High 7 7,575 40.0% Moderate 5 1,277 6.7% Low 3 80 0.4% Unknown 4 - -
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Figure 11. Current resiliency of San Clemente Island larkspur (SCI larkspur) (based on estimated number and distribution of individuals) by watershed.
4.5 Current Subspecies Representation Genetic data and subspecies distribution on SCI suggest that there is just one population of San Clemente Island larkspur. Because of the high degree of genetic similarity among populations, the loss of any single population should not cause a significant loss of genetic variation for the San Clemente Island larkspur. However, the amount of genetic variation found among groups on the island suggests the representation for San Clemente Island larkspur and Thorne’s larkspur is adequate, and genetic drift (random changes in gene frequencies as a consequence of small population size) should not rapidly erode genetic diversity (Dodd and Helenurm 2002, p. 620). Therefore, the taxon is unlikely to experience low fitness due to the loss of individuals from the population due to catastrophic pulse events, such as trampling, major erosion events, or severe fires (Helenurm et al. 2005, p. 1226). Further, the subspecies occupies
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varying elevations, slopes, and habitats across the island, indicating that it has environmental plasticity and adaptability.
4.6 Current Subspecies Redundancy Only two watersheds were known to be occupied at listing, but 24 watersheds are currently recorded as occupied by San Clemente Island larkspur, with an additional two assumed to be occupied (Table 2). Additionally, the number of known individuals has grown substantially since listing. While the historical distribution is unknown, several locations where San Clemente Island larkspur were recorded historically currently have unknown occupancy, and these may have been lost; while the general range has expanded since listing, redundancy may be reduced form historical levels. Given the population size and distribution, and considering the likely potential catastrophic events, we envision that the subspecies has adequate redundancy, and only an unusually severe event could foreseeably threaten the subspecies’ viability. A major erosion event (such as caused by periods of heavy rainfall) or a severe drought are the most plausible potential impacts; an outbreak of an invasive, predatory, or pathogenic species is also possible but highly speculative. However, erosion events would be localized, and unlikely to threaten a large percentage of the population. Further, given San Clemente Island larkspur’s ability to remain dormant during drought years, we expect this subspecies would withstand even a major drought, and given the subspecies’ distribution, we’d expect at least some individuals would be able to collect adequate fog moisture or tap water reserves in the soil. However, depending on the length and severity of drought, impacts to the species could be substantial. Like all endemics, San Clemente Island larkspur has a small range and is confined to SCI and would be unable to disperse elsewhere.
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SECTION 5 – FACTORS INFLUENCING VIABILITY
The following discussion provides a summary of the factors that are affecting or could be affecting the current and future condition of the San Clemente Island larkspur throughout some or all of its range. The current habitat conditions for San Clemente Island larkspur on SCI are the result of historical land use practices. SCI was used legally and illegally for sheep ranching, cattle ranching, goat grazing, and pig farming (USFWS 2012, p. 29-91, US Navy 2013a, p. 2-3). Goats and sheep were introduced early by the Europeans, and cattle, pigs, and mule deer were introduced in the 1950s and 1960s (US Navy 2013a, p. 3-185). These non-native herbivores greatly changed the vegetation of SCI and were cited in the final rule (USFWS 1977, p. 40863) for the listing of San Clemente Island larkspur as the main cause of this subspecies’ decline. Sheep were removed from the island in the 1930s, but feral goats and pigs were not completely eradicated until 1993 (pigs removed around 1990, feral goats in 1991, and the remaining judas goats in 1993) (Keegan et al. 1994, p. 58; USFWS 2012, p. 29093). Although San Clemente Island larkspur may not have been a primary target of the mammalian herbivores, overgrazing and browsing probably led to the direct loss of plants through trampling and rooting. These grazing, browsing, and rooting animals also altered the habitat by creating trail networks with bare, compacted soil. Overgrazing, erosion, and other impacts to the vegetation led to severe habitat degradation and loss of suitable habitat that likely curtailed the range of San Clemente Island larkspur and other plant endemics on the island (USFWS 1997, p. 42697). The current distribution of San Clemente Island larkspur is likely a product of topographical features that made certain areas inaccessible to goats and therefore provided refugia for San Clemente Island larkspur to survive the intense browsing. Further, seeds may have survived in the soil seed bank in other areas of the island, and together, these refugia determined the pattern of San Clemente Island larkspur’s expansion and recolonization of the island. At the time of listing, grazing of feral goats and rooting of feral pigs were viewed as serious threats to the continued existence of San Clemente Island larkspur (USFWS 1977, p. 40682). The removal of this threat by 1992 significantly improved the prospects of survival for this subspecies. We assess the current factors influencing viability of this subspecies both as they apply to just the distribution of what is currently considered San Clemente Island larkspur (Figure 12).
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Figure 12. Factors affecting the viability of San Clemente Island larkspur.
5.1 Land Use (direct affects) SCI is owned by the U.S. Department of the Navy (Navy) and, with its associated offshore range complex, the island is the primary maritime training area for the Pacific Fleet and Sea Air and Land Teams (SEALs) (USFWS 2012, p. 29078). The island also supports training by the U.S. Marine Corps, the U.S. Air Force, the U.S. Army, and other military organizations. As the western most training range in the eastern Pacific Basin, where training operations are performed prior to troop deployments, portions of the island receive intensive use by the military (US Navy 2008a, p. 2.2). Various training activities occur within particular land use designations and training areas on the island. Military training activities within some of these training areas can involve the movement of vehicles and troops over the landscape and can include live munitions fire, incendiary devices, demolitions, and bombardment (Table 5). The direct effects of military training and other land uses will be discussed here; indirect effects, such as erosion and fire, will be discussed in separate sections below. SCI supports 20 terrestrial Training Areas and Ranges (TARs), four Assault Vehicle Maneuver Areas (AVMAs), and the Infantry Operations Area (IOA). TARs are operating areas that support demolition, over-the-beach, and tactical ingress and egress training for Naval Special Warfare personnel (US Navy 2008a, p. 2.7). AVMAs are designated for off-road vehicle use, including tracked vehicles, and the IOA is designated for dispersed foot traffic by military units in support of a battalion-sized landing (US Navy 2008a, p. 2.37) (Figure 13). While the IOA is a broad designated area for foot traffic, use has been, and is anticipated to continue to be, concentrated around the AVMR (Artillery Vehicle Maneuver Road). Soldiers fan out from but move in concert with artillery vehicles, which are restricted to the AVMAs and AVMR; accordingly, foot traffic occurs predominantly within 50 feet of the AVMR, within the IOA (Booker 2019, pers. comm.). Other major potential impacts (artillery firing points [AFPs] and SSA Report – San Clemente Island larkspur 48 March 2020
bivouacking) within the IOA also occur near the road (USFWS 2008b, pp. 42, 164). This buffer around the AVMR makes up less than 1% of the IOA (Table 5). Additionally, six near-shore Special Warfare Training Areas (SWATs) have been designated on and around SCI (Figure 13). These large areas encompass land, water, and associated airspace. They are used as ingress and egress of small troops to specific TARs. Basic and advanced special operations training is conducted within these areas by Navy and Marine Corps units (US Navy 2013a, p. 2.10; US Navy 2008a, p. 2.7). Thus, impacts from training in these areas is infrequent and dispersed, with no detectable impacts from training in the SWATs in the last 10 years (Booker 2019, pers. comm.). The Shore Bombardment Area (SHOBA) is the largest terrestrial training area on SCI and supports a diversity of military training (including Anti-Surface Warfare, Amphibious Warfare, Naval Special Warfare, Bombing Exercises, and Combat Search and Rescue) (Figure 13). SHOBA occupies roughly the southern third of the island and encompasses approximately 13,824 ac (5,594 ha) (US Navy 2008a: Tables 2–7; US Navy 2009, p. 2–4). Areas of intensive use within SHOBA include the two Impact Areas and three TARs, which lie within the Impact Areas. Impact Areas support naval gun firing, artillery firing, and air-to-ground bombing (US Navy 2008a, p. 2–7; US Navy 2013a, p. 2–8). Collectively, the Impact Areas and TARs within SHOBA encompass 3,400 acres [1,376 ha], which amounts to 24.6% of the area within SHOBA. Much of the remainder of SHOBA serves as a surface danger zone (buffer) around Impact Areas I and II, and 59% of SHOBA is not within the (IOA), Impact Areas, or a TAR and therefore not subject to any direct training activities. Some areas, particularly the escarpment along the eastern coast, have limited training value because precipitous terrain hinders ground access. The Impact Areas sustain live fire, which is a recurrent source of fires. Most fires are of low severity. Fuel breaks are installed each year (and have been recently restricted to roadsides) prior to fire season to help prevent spread of fire to areas outside of the Impact Areas for protection of natural resources. Fire will be discussed in greater detail in Section 5.4. Because parts of SHOBA are used for bombardment, access to this area is restricted for nonmilitary personnel on days when bombing is occurring. Individuals conducting surveys or working on invasive species control projects are granted access to areas outside of the Impact Areas within SHOBA when military activities requiring exclusive use are not occurring. Because of the frequency of training, access to SHOBA can be restricted for periods of time. The IOA encompasses approximately 25% of the island, the Impact Areas encompass about 9.4% of the island, TARs, which in places overlap the IOA, Impact Areas, and AVMAs, cover 5.5 % of the island, and the AVMAs, which fall entirely within the IOA, encompass about 3% of the island (US Navy 2008a, pp. 2.17, 2.45; US Navy 2008b, pp. 3.11–3.52) (Table 5, Figure 13). Altogether, 34.8% of the island’s area is located in one of these training areas, although training does not occur uniformly within each; much of the island is void of any infrastructure. In comparison to many other military installations, there is a very low visual presence of the military on SCI (McFarland 2019, pers. obs.). In 2008, the Southern California Range Complex Final Environmental Impact Statement/Overseas Environmental Impact Statement (EIS/OEIS) (US Navy 2008a) and the accompanying Biological Opinion: San Clemente Island Military Operations and Fire Management Plan (BO) (USFWS 2008b) were finalized, and together, these documents allowed for increased training at SCI and addressed obligations for fire management and listed species management (US Navy 2008a, p. 2.1–2.52). To avoid underestimating impacts and to ensure adequate coverage under all applicable federal laws and regulations, including but not limited to
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the National Environmental Policy Act (NEPA), the ESA, and the Clean Water Act, the analyses considered a training tempo that was at the highest reasonably anticipated level. It is unlikely that the maximum operational tempo will be reached for all activities simultaneously because overseas deployments, availability of personnel and assets, planning and construction timelines, development of platforms and systems, and other factors can lower the tempo and/or delay implementation; however, it was necessary to analyze the potential impacts of such a tempo (O’Connor pers. comm., 2019). Training began to increase soon after issuance of the 2008 BO and Record of Decision (ROD) for the EIS, but increases in some types of training, particularly those that required acquisition of assets, development of platforms and systems, and/or planning and construction, have increased more gradually, and some have not reached the operational tempo in the documents. One example of the latter type of activity is the battalion-sized landing planned to occur within the Assault Vehicle Maneuver Corridor, which will be discussed further in Section 4.2. In contrast to the AVMAs, the TARs (all except TAR 19) were fully developed and utilized shortly after issuance of the ROD and have been in use since. TARs 10 and 17 were of particular concern due their location on the west side of the island within high-density, federally listed San Clemente Bell’s sparrow (Artemisiospiza belli clementeae) habitat and the introduction of new ignition sources to the west shore (O’Connor 2019, pers. comm.). However, after approximately 11 years of use, no fires have occurred in either of these TARs, and there to not appear to be training impacts to the Bell’s sparrow in these areas (Meiman et al. 2018, p. 39).
Table 5. Summary of training areas, their size, use, and the potential threats to San Clemente Island larkspur within each. Training area Size (Acres) % of island Use Threat vehicular Soil erosion, trampling, devegetation AVMAs (3) 1,060.5 2.9% maneuvering (habitat removal) IOA 8,827.6 24.5% dispersed foot traffic Trampling, soil erosion TARs (20) Varies by TAR: Varies by TAR, but limited to (terrestrial 1,968.2 5.5% demolition, small trampling, localized ground only) arms, combat, etc. disturbance Impact Areas Devegetation (habitat removal), fires 3,399.7 9.4% bombing, live fire (2) (accounted for separately)
Range schedulers are aware of the natural resources obligations within SHOBA, and at least 1 day a week is usually allowed for natural resources programs to conduct their activities. Weeks with reduced natural resource access, including infrequent events that exclude natural resources personnel from SHOBA for 10 to 20 days, are announced in advance and provide natural resources managers the opportunity to plan accordingly. Impact Areas I and II have been indefinitely closed ‘‘for any purpose, including monitoring and management of endangered and sensitive species and their habitat’’ for safety reasons (US Navy 2008a, p. 2–45). Access to additional areas on the island where unexploded ordnance has been found is often restricted for natural resources personnel, but these areas are removed once they are assessed by unexploded ordnance specialists and are deemed safe for entry (Figure 13). When closed, these restricted
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access areas (RAAs) can be accessed if accompanied by a trained unexploded ordnance technician (Munson 2019, pers. comm.). Land use has been considered a threat to San Clemente Island larkspur due to the various military training activities that are supported by SCI. Training and other land use activities have multiple potential impacts to San Clemente Island larkspur, including disturbances to soil and vegetation, spread of nonnative plant species, creation of road ruts and trails, and compaction of soils (USFWS 2008b, pp. 110-112). However, less than 10% of the population considered current lies within one of these training areas (Table 6). Only two locations totaling 42 individuals occur in a TAR (TAR 21), none are located in an AVMA, and the Impact Areas are outside the known range of San Clemente Island larkspur. Eight locations of San Clemente Island larkspur occur in the IOA (including the location in the TAR) (Table 6). Thorne’s larkspur is not known to occur in any of the training areas except the IOA.
Table 6. The number of locations and individuals of San Clemente Island larkspur within each type of training area and the approximate percent of the island-wide population represented.
Locations Individuals % of population TAR 2 42 0.22% AVMA 0 0 0.00% IOA 8 1805 9.52% Impact Areas 0 0 0.00%
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Figure 13. Locations of San Clemente Island larkspuras considered current in relation to the training areas on San Clemente Island, including the Impact Areas, the Training Areas and Ranges (TARs), the Assault Vehicle Maneuver Areas (AVMAs), the Infantry Operations Area (IOA), and Special Warfare Training Areas (SWATs). Current Restricted Access Areas (RAAs) are also shown, but these change as unexploded ordinances are removed.
Military training activities within training areas (primarily the IOA, TAR, or AVMA) can entail the movement of vehicles and troops over the landscape and thus include the potential of trampling or crushing individuals or groups of plants. Based on the distribution of San Clemente Island larkspur and types of troop movements likely to occur, impacts due to trampling and crushing are most likely to occur within the IOA and along roads. It is unknown whether
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increases in troop and vehicle movements within the TARs and the IOA have resulted in the loss of individual plants. However, any effects of foot traffic on a local occurrence of this subspecies would be dispersed (because the Marines are spread out), minor (trampled leaves or broken branches), infrequent (up to twice per year, generally less), and temporary (USFWS 2008b, p. 91-102; Vanderplank et al., in prep.). Further, the majority of documented locations of San Clemente Island larkspur occur outside of these areas (Table 6). Steep slopes along the eastern escarpment may also afford the San Clemente Island larkspur that occur there some topographic protection from vehicle and troop movements. Although the designation of RAAs could make it more difficult to schedule surveys needed to assess potential training-related habitat impacts in some watersheds in the future (Figure 13), surveys are not precluded within the RAAs, and other federally listed species, including the San Clemente bush mallow (Malacothamnus clementinus) and the San Clemente loggerhead shrike (Lanius ludovicianus mearnsi), are monitored regularly within them.
Management efforts The Navy has demonstrated its efforts to help conserve and manage listed species on the island through amelioration of habitat impacts by military activities through implementation of the 2008 BO (USFWS 2008b) and Integrated Natural Resources Management Plan (INRMP) (US Navy 2013a), including invasive species control island-wide, including near listed species, biosecurity protocols, public outreach to promote compliance, restoration of sites that support sensitive plants, habitat enhancement for sensitive and listed species, fuelbreak installation to minimize fire spread, and fire suppression inside and outside of SHOBA to protect threatened, endangered, and other priority species (US Navy 2013a, p. 3.45; Vanderplank et al. 2019, pp. 15, 18-19; Munson 2019, pers. comm.). Changes to training have and will be subject to environmental review under applicable laws and regulations, including NEPA and ESA, and impacts to federally listed and sensitive species will be addressed (O’Connor 2019, pers. comm.).
Summary About 35% of SCI is located within a training area (Table 5), and only 12% of the current population of San Clemente Island larkspur occur in these areas (Table 6). While dispersed foot traffic is possible throughout the entirety of the IOA, we expect the majority of impacts associated with the IOA to be within a 50 ft buffer around the AVMR; however, no individuals occur within this buffer. We will discuss this impact further in Section 4.2, concerning roads. Thus, less than 1% of the population occurs in an area that experiences heavy use (TARs) (Table 6). Military activities on San Clemente Island have been and will continue to be dynamic as they evolve to meet new requirements. The Navy has begun evaluating the need for changes to the actions analyzed in the 2008 EIS and associated BO. Any changes are expected to be incremental, as they have been in the past. Such changes are subject to environmental review under applicable laws and regulations, including NEPA and ESA, and impacts to federally listed and sensitive species will be addressed. There is also ongoing management of related threats (including wildland fire, soil erosion, invasive species) pursuant to the San Clemente Island Integrated Natural Resources Management Plan.
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5.2 Erosion and Roads Erosion and associated soil loss caused by degradation of the vegetation due to the browsing of feral goats and rooting of feral pigs modified the island’s habitat significantly and resulted in increased erosion over much of the island, especially on steep slopes where denuded soils could be quickly washed away during storm events (Johnson 1980, p. 107; Tierra Data Inc. 2007, pp. 6–7; US Navy 2013a, pp. 3.32–3.33). Since the feral animals were removed, much of the vegetation has recovered, and natural erosion on the island has decreased significantly (US Navy 2013a, p. 3-33, Vanderplank et al. 2019, p. 15). Erosion problems currently are limited to localized areas, and because of topography and soil characteristics, there always will be the potential for localized erosion to occur at sites across the island. Accelerated soil erosion from anthropogenic causes tends to occur at the heads of canyons, ephemeral drainages, and in areas where groundwater drainage causes “piping,” the formation of underground water channels, which occur on clay soils. Military training activities could lead to erosion that could impact San Clemente Island larkspur, but few individuals occur in these training areas (Table 6) (Tierra Data Inc. 2007, pp. 1– 45). If erosion were to occur or be initiated in a single watershed, the effects would be confined to that watershed. Piping has been noted within the range of San Clemente Island larkspur (USFWS 2008b, p. 107); however, there is no record of any plants being lost to erosion. Erosion was the primary concern associated with use of the Assault Vehicle Maneuver Corridor (AVMC), which connects the AVMAs. However, the Navy has delineated unpaved roads that will channel vehicle traffic through some portions of the AVMA, confining vehicles to these roadways, which reduces loss of vegetation cover and allows for better control of erosion (Vanderplank et al., in prep.). As noted in Section 5.1, no known San Clemente Island larkspur occur in the AVMAs or AVMC. Of the watersheds that could be impacted by the AVMAs, only 2 are occupied, comprising 5 locations and 344 individuals. Implementation of the Erosion Control Plan (US Navy 2013b, entire) is expected to prevent erosion from adversely affecting San Clemente Island larkspur, but even if the plan were to fail to meet its objectives, few individuals would be affected by erosion. Though the operational tempo analyzed in the EIS and BO has not been achieved to date, even when it is, development of and adherence to the Erosion Control Plan will continue to reduce impacts in the AVMC below the already low levels projected in the EIS. Roads can concentrate water flow, causing incised channels and erosion of slopes (Forman and Alexander 1998, pp. 216–217). Along the eastern escarpment, San Clemente Island larkspur is found in steep canyons in proximity to the main road where it may experience runoff during storm events (US Navy 2008a, pp. G–4, G–8). Increased erosion near roads could potentially degrade habitat, especially along the steep canyons and ridges. However, no increased erosion has been noted as stemming from the roadway, thus the impact of this runoff is likely minimal. It was proposed that plants that occur within 500 ft (152 m) of a paved or unpaved road could be subject to road effects that degrade the habitat quality (Forman and Alexander 1998, p. 217; USFWS 2013 p. 45427). However, based on expert opinion and observations on San Clemente Island since the 2013 rule, the likelihood of impacts to San Clemente Island larkspur from runoff or other erosional processes stemming from roads is very low, and increased erosion associated with roads is not evident as far from the road network as analyzed in the proposed rule (O’Connor 2019, pers. comm.). The conditions of roads on San Clemente Island are evaluated and maintained, which minimizes the potential for habitat impacts adjacent to them, particularly as the distance from the roads increases. Erosion stemming from a
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roadway would have a high chance of being noticed early and managed accordingly. Still, as a precaution, the SSA team, consisting of both USFWS and US Navy employees, decided that a 100 ft (30 m) buffer around roads is a more appropriate distance over which negative impacts to habitat could be perceptible and should be evaluated. Likewise, the likelihood of crushing individual plants during military training involving foot traffic in maneuvers along roads tends to be more concentrated close to roads and decreases farther away (see Section 5.1) (O’Connor 2019, pers. comm). Additionally, other indirect effects associated with roads, such as the introduction and spread invasive plants (see Section 5.3), are most likely alongside roads. It is important to note that much of the invasive species control on San Clemente Island is focused along roads for this reason, and new occurrences of invasive species generally are more likely to be noticed and eradicated if they occur adjacent to roads. The expert team applied the same distance (100 ft [30 m]) when considering these other potential mechanisms of habitat degradation associated with roads. Of the distribution considered current, only 1 location comprising 70 individuals is located within 30 m (100 ft) of a road. Island-wide, this represents 1% of the total locations and 0.3% of the total individuals. This location that could see road impacts is just one of five in the watershed, comprising 11% of the total individuals in the watershed. Two additional locations of Thorne’s larkspur occur within 30 m of a road, comprising 27 total individuals in two watersheds.
Management efforts The Navy monitors and evaluates soil erosion on SCI and uses multi-year data to assess priorities for remediation (SERG 2006, entire; SERG 2015a, entire). Efforts are made to restore areas where erosion occurs, through revegetation efforts and the installation of erosion control materials (SERG 2017, p. 2). The Navy incorporates erosion control measures into all site feasibility studies and project design to minimize the potential to exacerbate existing erosion and avoid impacts to listed species The INRMP requires that all projects include erosion control work (US Navy 2013a, p. 3–33). These conservation actions include best management practices, choosing sites that are capable of sustaining disturbance with minimum soil erosion, and stabilizing disturbed sites (US Navy 2013a, pp. 3.33–3.37). Originally, the AVMAs were to allow for the most extensive off-road movement of tracked vehicles, and the area within them was anticipated to experience increased soil erosion due to reductions in vegetation cover (Vanderplank et al. 2019, p. 16). To address soil erosion within the AVMC, the US Navy included a conservation measure in the 2008 EIS to develop an erosion control plan for portions of the AVMC, including the AVMAs, Artillery Firing Points (AFPs), Artillery Maneuver Points (AMPs), and IOA, that would accomplish the following: (1) minimize soil erosion within these training areas and minimize offsite impacts; (2) prevent soil erosion from adversely affecting federally listed or proposed species or their habitats; and (3) prevent soil erosion from significantly impacting other sensitive resources, including sensitive plant and wildlife species and their habitats, jurisdictional wetlands and non-wetland waters, the Area of Special Biological Significance surrounding the island, and cultural resources. The plan includes specific guidelines for the development and application of best management practices (BMPs) to minimize impacts to sensitive resources, including San Clemente Island larkspur and its habitat, site-specific erosion control recommendations, restrictions of vehicle maneuvering when soils are wet, operator education, vegetation management measures, methods to prevent gully development and restore existing gullies, and an adaptive management and monitoring plan
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to assess the effectiveness of and modify BMPs as needed (US Navy 2013b, p. 37-50, 111; Vanderplank et al. 2019, p. 16). The plan is prescriptive; measures have been or will be implemented prior to use of areas to which they apply. Following issuance of the BO and signature of the ROD, funding was secured, the Erosion Control Plan was developed, and the final plan received concurrence from the US Fish and Wildlife Service (O’Connor 2019, pers. comm.). Subsequent to finalization of the Erosion Control Plan in 2013, development of the AVMAs has involved working with military operators to determine more precisely how areas would be used based on findings and recommendations in the plan, and implementation has taken a phased approach. This effort has resulted in the delineation of unpaved roads to channel vehicle traffic through some portions of the AVMAs, which will substantially reduce the level of ground disturbance from those anticipated in the EIS. Design of these roads will be the focus of future planning efforts. Areas in which roads are being developed have not been used and a battalion sized landing has not been conducted yet, but platoon sized landings involving 14 AAVs have been conducted approximately quarterly in other portions of the AVMAs and the IOA (O’Connor 2019, pers. comm.).
Summary Despite existing levels of erosion on the island, the distribution of San Clemente Island larkspur has increased since listing. Current erosion issues are localized, and erosion is generally decreasing on the island as the vegetation continues to recover. The Navy incorporates erosion control measures into all projects to minimize the potential to exacerbate existing erosion and avoid impacts to habitat and listed species. Although the erosional processes and potential related threats to San Clemente Island larkspur must be considered at an island-wide scale, because erosion impacts are localized and managed, the loss of individuals due to erosion is unlikely. Implementation of the Erosion Control Plan (US Navy 2013b, entire) is expected to prevent or correct erosion that may occur as a result of military operations and training in the AVMA and IOA. As proposed, implementation of the plan should prevent erosion from adversely affecting San Clemente Island larkspur, but even if the plan were to fail to meet its objectives, few current locations of individuals would be affected by erosion. However, by incorporating recommendations from the erosion control plan and working with military operators to determine more precisely how areas would be used, the Navy has delineated unpaved roads that now channel vehicle traffic through some portions of the AVMA. Therefore, vehicles are confined to these roadways, which reduces loss of vegetation cover and allows for better control of erosion (Vanderplank et al. 2019, p. 16).
5.3 Invasive plants Contemporaneous with and likely aided by feral grazing animals, a large number of invasive non-native plant species have become naturalized on SCI. At listing, the spread of nonnative plants was identified as a threat to vegetation recovery (USFWS 1977, p. 40682, 40684), and nonnative plants are considered an island-wide threat to the native vegetation (USFWS 2012, p. 29117). While not all non-native plants present a threat to San Clemente Island larkspur and other native species, non-native plants can alter habitat structure and ecological processes such as fire regimes, nutrient cycling, hydrology, and energy budgets, and they can compete with native plants for water, space, light, and nutrients (USFWS 2012, p. 29117).
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Non-native annual grasses noted at the end of the grazing period are now widespread on SCI with the most-common being Avena barbata (slender wild oat), Bromus madritensis ssp. rubens (red brome), B. hordeaceus (soft brome), B. diandrus (ripgut brome) and Hordeum murinum (false barley) (Keeley and Brennan 2015, p. 4). The invasion of nonnative annual grasses on the island may have caused the greatest structural changes to San Clemente Island larkspur habitat, especially on the coastal terraces and in swales (USFWS 2007, p. 4-5). Annual grasses vary in abundance with rainfall, potentially changing the vegetation types from shrublands to grasslands and increasing the fuel load in wet years (Battlori et al. 2013, p. 1119). Although most of the invasive species likely were brought to the island while it was being ranched, invasions by previously undocumented non-native grasses continued to be found on SCI; e.g., the discovery of Schismus sp. and the fire-tolerant weeds Brachypodium distachyon (purple false brome) (USFWS 2007, p. 5), Ehrharta calycina, and E. longiflora (African veldt grasses) (US Navy 2013a, p. 3-90). San Clemente Island larkspur occurs within grasslands, where there has been a proliferation of non-native plant species, especially annual grasses. Invasive perennial grasses also exist, but grasslands dominated by perennials have a more open structure and thus less competition for resources (O’Connor 2019, pers. comm.). San Clemente Island larkspur occurs in areas that are dominated by non-native annual grasses, with which they compete for light, water, and nutrients. Surveys conducted between 2011 and 2017 found 13 of 74 locations of San Clemente Island larkspur in communities dominated by invasive grasses (US Navy, unpublished data; Vanderplank et al., in prep). Populations of San Clemente Island larkspur near roads may be subject to effects that degrade the habitat quality along the road (Forman and Alexander 1998, p. 217). This disturbance along roadsides tends to create conditions (high disturbance, seed dispersal from vehicles, ample light and water) preferred by nonnative species (Forman and Alexander 1998, p. 210). Nonnatives, including Foeniculum vulgare and Mesembryanthemum crystallinum (crystalline iceplant), have been found in the disturbed shoulders along China Point in SHOBA (Braswell 2011, pers. obs. in USFWS 2012), but these nonnatives have not been considered a threat to locations of San Clemente Island larkspur. Potential impacts of nonnative plants on San Clemente Island larkspur include precluding germination (i.e., competitive exclusion), preventing pollination (e.g., San Clemente Island larkspur plants are not obvious to pollinators due to tall stands of non-native grasses), and carrying fire in areas that would not otherwise burn. While there may be these or other unquantified indirect effects to the fitness of San Clemente Island larkspur due to the invasive species already present on the island, they do not seem to be impeding recovery. Further, since the removal of feral grazers, the vegetation has been recovering and is no longer comprised of the early seral communities that are the first to colonize disturbed areas (Stratton 2005, p. 216). The island has more intact habitats, reduced erosion, and a stronger suite of native competitor species, making the conditions less favorable to invasion. Some habitats that underwent considerable invasion historically, such as the central grasslands, are still heavily dominated by non-native species.
Management efforts The Navy has monitored and controlled the expansion of highly invasive non-native plant species on an ongoing basis since the 1990s (O’Connor 2019, pers. comm.), and primary target species have included Brassica tounefortii (Saharan mustard), B. nigra (black mustard),
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Foeniculum vulgare (fennel), Asphodelus fistulosus (aspohodel), Stipa milaceae (smileo grass), Ehrharta calycina (African veldt grass), Plantago coronopus (buckhorn plantain), Tragopogon porrifolius (salsify), and Caprobrotus edulis (iceplant); additional priority species may also be controlled as they are located (e.g., SERG 2016, p. 45-46). In general, the Navy treats over 100,000 individuals of these various species annually. Control of these invasive plants benefits the ecosystem on SCI by reducing their distribution and minimizing the potential that they will invade habitat occupied by listed and at-risk taxa. Because invasive species introductions are more likely to occur along roadsides and because roads function as corridors for the spread of invasive species propagules, much of the invasive species treatment on the island focuses on roadsides; however, other areas highly susceptible to invasive species introductions (such as graded areas, soil stockpiles, and mowed areas) also are focal areas for control. High-priority invasive plants are treated at locations across the island. This control strategy has minimized the need to treat invasive plant species within areas occupied by federally listed plants. While many conservation measures to limit the introduction and spread of nonnative plants are included in the INRMP (US Navy 2013a, pp. 3.289–3.290) and required in the 2008 BO (USFWS 2008b, pp. 58–66) (Table 11 in Appendix B), the recently-completed Naval Auxiliary Landing Field San Clemente Island Biosecurity Plan (US Navy 2016, entire) will help more effectively control the arrival of potentially invasive propagules than similar plans on non- military islands. The plan works to prevent and respond to new introductions of non-native species and bio-invasion vectors. Through implementation of this plan and the ongoing island- wide nonnative plant control program, potential impacts from nonnative plants are expected to be minimized (O’Connor 2019, pers. comm.; Munson 2019, pers. comm.).
Summary Non-native species are extensively distributed across SCI both as a result of post-grazing colonization of weedy species in highly disturbed habitat and accidental introduction of new weeds which may inevitably occur inadvertently through human activities. However, all vegetation communities have been recovering on SCI since the final removal of feral grazers, and naturalized grasslands (the most fire-prone of non-native vegetation communities) constitute a small proportion of the island at this time. Non-native annual and perennial grasses, however, are widespread on the island and have been for many decades. No assessment to track weediness within occupied habitat areas has been done, but none is indicated at this time. San Clemente Island larkspur is found within naturalized, non-native grasslands (see Figure 6 above), and there is the potential that these exotic annual grasses, which are widespread on the island, could affect fire regimes. However, it does not appear as if these grasses are expanding, and they have been present during the recorded fire history. This potential is further addressed in Section 5.4. The Navy makes significant efforts to control highly invasive non-native perennial grasses and non-native forbs to preclude their expansion into habitat areas and areas in which weed control would be difficult due to terrain and access challenges. We have no information on the relative presence of weedy plants within habitat occupied by San Clemente Island larkspur, but as noted, the role of invasive grasses on fire regime might be more of a potential threat to recovery than simple presence of non-native plants within habitat areas. Because data on the abundance and density of invasive plants and monitoring of change over time are lacking, we have no way to quantitatively assess the effect of non-native, invasive species on San Clemente Island larkspur individual fitness. However, this subspecies’ range has expanded despite the presence of nonnative plants on SCI.
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5.4 Fire Fire was not identified as a threat to San Clemente Island larkspur in the 1984 Recovery Plan, but rather was considered a potential benefit to this subspecies if habitat burned during the plant’s dormant period, although no explicit benefit was described (USFWS 1984, p. 53). However, the five-year review (USFWS 2008a, p. 19-20) listed fire as a potential threat. Generally, the plant is dormant during the fire season (May through November; US Navy 2009, p. 4.21) and seems tolerant of and perhaps adapted to fire, but increased fire frequency or increased fire severity may be potential threats that could limit the distribution of San Clemente Island larkspur in the future. Early fires could also be a threat, should fire season begin early. The history of fire on the island prior to 1979 is largely unknown, but while the island was used for ranching, fires were set intermittently to increase the cover of forbs and grasses (US Navy 2009, p. 3-2; US Navy 2013a, p. 3.47). After the island was purchased by the U. S. Department of the Navy in 1934, however, fire became a more common occurrence throughout much of the island. Fire history for most of the island has been documented since 1979. Since that time, over 50 percent of the island has experienced at least one wildfire with smaller areas on the island having burned up to ten times between 1979 and 2018 (US Navy 2013a, p. 3-47; US Navy, unpublished data). While the historical fire return interval on San Clemente Island is unknown, fires have burned a portion of 76 watersheds island-wide during the past 20 years. The number and extent of fires (acres burned) varies annually as does fire severity (Figure 16, Figure 17). Most fires are ignited in the Impact Areas, and thus, the majority of acreage that has burned has been concentrated in SHOBA (Figure 14) (US Navy 2013a, p. 3-45). Most of these fires are classified as a severity of 4 or 5, considered lightly burned or scorched, which typically do not kill herbaceous vegetation (Table 7) (US Navy 2009, p. 4-52). For fires with associated severity data (2007 to present), 15.6% of the area burned has been of a severity class that has detrimental effects on herbaceous vegetation, class 1 through 3, considered completely burned to moderately severe (Figure 15). The largest area that burned at these severities burned in 2017 (Figure 17). Typically, due to the patchy nature of fires, not all areas within a fire footprint are burned uniformly; therefore, not all plants in a burn polygon are necessarily burned or burned at the same severity (SERG 2012, p. 39).
Table 7. Fire severity classes and definitions, reproduced from the US Navy 2009 Fire Management Plan for San Clemente Island, with severity classes adapted from the National Park Service (1992). Effects on Effects on Effects on Fire severity class litter/duff herbs/grasses shrubs Effects on trees 1 Completely Burned Burned to ash Burned to ash Burned to ash, Burned to ash or few resprouts killed by fire 2 Heavily Burned Burned to ash Burned to ash Burned to ash, Killed by fire or some resprouts severely stressed 3 Moderately Burned Burned to ash Burned to ash Burned to Crown damage singed, some only to smaller resprouts trees
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Effects on Effects on Effects on Fire severity class litter/duff herbs/grasses shrubs Effects on trees 4 Lightly Burned Blackened, but Burned to ash, Singed/stressed, No effect on mature not evenly some resprouting many trees, may kill converted to ash resprout/recover seedlings/saplings 5 Scorched Blackened Singed/stressed, Not affected, No effect on trees many slight stress resprout/recover 6 Unburned* – – – – *Unburned inclusions within a fire should be marked as 6.
The Navy significantly expanded the number of locations where live fire and demolition training can take place as of 2008 (USFWS 2008b, p. 21– 37). In addition to demolitions, certain proposed munitions exercises involve the use of incendiary devices, such as illumination rounds, white phosphorous, and tracer rounds, which pose a high risk of fire ignition. However, the biggest fire years in the last 20 years (2012 and 2017) have burned less than half the acreage of the biggest fire years between the time of listing and now (Figure 16). Fires topping 8,000 acres burned in 1985 and 1994, before fuel breaks were routinely installed and other fire management was carried out (O’Connor 2019, pers. comm.). Currently, fire does not seem to negatively affect San Clemente Island larkspur. Of the distribution considered current, only five locations identified as San Clemente Island larkspur totaling approximately 458 individuals occur in an area that has burned in the last 20 years, and none of these areas burned more than once (Figure 14). Further, these locations were all discovered following the fire; two locations totaling approximately 320 individuals were discovered in 2013 following a 2012 fire, and three locations totaling approximately 138 individuals were discovered in 2017, the same year a fire burned that area. While increased fire frequency or increased fire severity have been suggested as potential threats to San Clemente Island larkspur in the future, no existing data support this. First, the risk of frequent fire within the range of San Clemente Island larkspur is low. Areas that have burned more than once in the past 20 years are mostly in SHOBA, within the range of Thorne’s larkspur (Figure 14). The risk of larger, frequent fires is higher in Impact Areas I and II within SHOBA (USFWS 2008b, p. 50), although fires are occasionally ignited by activities in training areas north of SHOBA (US Navy 2013, p. 3-45-3–47; USFWS 2018, GIS data). Although fire ignition points are concentrated in the military training areas, fires that escape these areas could potentially spread to other areas of the island, but due to vegetation and topography, these fires have generally been confined to the same small areas (Munson 2019, pers. comm.). Exotic annual grasses, which are widespread on the island, could potentially affect fire regimes by carrying fire in areas that would normally not burn. However, it does not appear as if these invasive grasses are expanding, and they have been present during the recorded fire history. While increased fire frequency could lead to localized changes in vegetation on San Clemente Island, current fire frequencies across the majority of the island are still relatively infrequent, even given the intensified military uses over the last decade (Figure 14).
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Further, more frequent fires do not appear to preclude the presence of Delphinium variegatum. Locations of Thorne’s larkspur have burned up to seven times since 1979 (U. S. Department of the Navy 2019 data).
Figure 14. Locations of San Clemente Island larkspur (SCI larkspur) considered current in relation to areas where fires have burned in the last 20 years (1999-2018, after the initiation of fire management), including number of fires in that time. Recent locations (2011-2014) of Thorne’s larkspur are also indicated.
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Figure 15. Locations of San Clemente Island larkspur (SCI larkspur) points considered current in relation to areas where fires where severity data is known have burned (2007-2018). Severity categories 1, 2, and 3 have the potential to burn herbaceous vegetation where they will not resprout; severity categories 4 and 5 have little to no effect. Recent locations (2011-2014) of Thorne’s larkspur are also indicated.
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Figure 16. Acres burned annually on San Clemente Island for years where fires were estimated since listing.
Figure 17. Total acres on San Clemente Island that have burned annually in wildfires and acres that were recorded to have burned at a moderate to high severity (severity classes 1, 2, or 3).
Further, the species has been noted following severe fire. In 2017, a large fire burned 1,522 acres, almost all (98%) of which were of moderate to high severity (3, 2, or 1 severity class) along part of the eastern escarpment within SHOBA, where no other recorded fire has burned (Figure 15). After having seemingly gone out, the fire restarted the next day and response
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was therefore delayed, prompting changes to monitoring fires that are thought to be out (O’Connor 2019, pers. comm.). Despite the severity of this fire, Thorne’s larkspur were observed within this area in 2019 (McFarland 2019, pers. comm.), indicating that the fire did not preclude that subspecies’ persistence there. Extremely hot fires could damage the shallow roots of San Clemente Island larkspur, but there are no documented instances of this being an issue.
Management efforts The San Clemente Island Wildland Fire Management Plan (FMP) stipulates monitoring of live fuel moisture and establishes a threshold below which training requirements are altered to reduce ignition risk (US Navy 2009, pp. 4.15–4.16). These live fuel moisture levels, combined with wind speed, define a fire danger rating which at various levels indicate specific munitions that are allowable and precautions that must be in place (standby firefighting engine, crew, and other resources, helicopter on fire alert, etc.) (US Navy 2009, p. 4.19). The FMP stipulates that San Clemente Island larkspur is a management focus plant, such that individuals are given special consideration and protection from fires (US Navy 2009, p. 4.10). The Navy’s fire management program maintains ground and aerial suppression assets to fight fires in all areas outside of Restricted Access Areas and Impact Areas (US Navy 2013a, p. 3.45) (see Figure 13). While most fires burn themselves out in a short amount of time, fires are monitored closely after ignition (Munson 2019, pers. comm.). If a threat is perceived to lives, structures, or sensitive species, the fire is fought unless there is a threat of unexploded ordnance or another a safety risk, such as high winds. Since the 2017 fire on the eastern escarpment, monitoring for complete extinguishment has increased, and increased monitoring requirements will be included in all future versions of the FMP (Munson 2019, pers. comm.). The US Navy has constructed fuelbreaks around the Impact Areas to manage the spread of fire beyond their boundaries (USFWS 2012, p. 29118). However, these fuelbreaks rarely have helped contain a fire as fires have infrequently approached them, and those that did were only sometimes contained by the fuelbreak. Thus, fuelbreak locations and installation methods have changed over time, and for the 2019 fire season, fuelbreaks were installed only along the existing roadways (Munson 2019, pers. comm.). As roads already serve as fuelbreaks, increasing the width of this vegetation gap through application of a fire retardant along the existing roadways creates a more effective fire management tool. These fuelbreaks were designed with the protection of the sensitive species and resources on the eastern escarpment, which is protected by Ridge Road, in mind (Munson 2019, pers. comm.). Maintenance of these fuelbreaks reduces the likelihood and frequency of fires spreading. Fuelbreaks on SCI are created using herbicides and strip burning and are maintained using herbicides and fire retardant (Phos-Chek D75F) (USFWS 2008b, pp. 97–98). The Navy avoids application of Phos-Chek within 300 ft (91.4 m) of mapped listed species locations to the extent that has been allowable with previous fuelbreak installation (USFWS 2008b, pp. 97–98). The Navy conducts preseason briefings for firefighting personnel on the guidelines for fire suppression and limitations associated with the use of Phos-Chek (USFWS 2008b, pp. 97–98). To minimize the potential for effects to listed species, the Navy considers the documented locations of listed species on the island as fuelbreak lines are developed (USFWS 2012, p. 29119). The Navy also conducts annual reviews of fire management and fire occurrences that allow for adaptive management and aim to minimize the frequency and spread of fires that could result in loss of individuals of San Clemente Island larkspur (USFWS 2012, p. 29121).
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Summary We currently have no information regarding the ecological response of San Clemente Island larkspur to different combinations of fire intensity and frequency, but current fire patterns do not seem to inhibit this subspecies. Observational, anecdotal, and GIS data suggest San Clemente Island larkspur is not significantly affected by fires, likely due to fire location, frequency, severity, and timing. Too-frequent or high-intensity fire may harm the subspecies directly or harm its habitat by exacerbating erosion potential (SERG 2013, p. 53), perhaps if lengthy periods of drought retard vegetative recovery following fire (USFWS 2008b, p. 11). However, the Navy has been successful in fire management and is working to reduce the impacts of fire to San Clemente Island larkspur.
5.5 Climate Change Since the listing of San Clemente Island larkspur (USFWS 1977, p. 40684), the potential impacts of ongoing, accelerated climate change have become a recognized threat to the flora and fauna of the United States (IPCC 2007, pp. 1–52; PRBO 2011, pp. 1–68). Climate change is likely to result in warmer and drier conditions, with high overall declines in mean seasonal precipitation but with high variability from year to year (IPCC 2007, pp. 1–18; Cayan et al. 2012, p. ii; Kalansky et al. 2018, p. 10). SCI is located in a Mediterranean climatic regime with a significant maritime influence. Current models suggest that southern California will likely be adversely affected by global climate change through prolonged seasonal droughts and rainfall coming at unusual periods and in different amounts (Pierce 2004, pp. 1–33, Cayan et al. 2005, pp. 3–7, CEPA 2006, p. 33; Jennings et al. 2018, p. iii; Kalansky et al. 2018, p. 10). Climate change models indicate a 4 to 9 degrees Fahrenheit (2 to 4 degrees Celsius) increase in average temperature for the San Diego Area of southern California by the end of the century (Jennings et al. 2018, p. 9), with inland changes higher than the coast (Cayan et al. 2012, p. 7). By 2070, a 10 to 37 percent decrease in annual precipitation is predicted by some models (PRBO 2011, p. 40; Jennings et al. 2018, p. iii), though other models predict little to no change in annual precipitation (Field et al. 1999, pp. 8–9; Cayan et al. 2008, p. S26). SCI typically receives less rainfall than neighboring mainland areas (Tierra Data Inc. 2005, p. 4). However, predictions of short and long-term climatic conditions for the Channel Islands remain uncertain. It is unknown at this time if climate change in California will result in a warmer trend with localized drying, higher precipitation events, and/or more frequent El Niño or La Niña events (Pierce 2004, p. 31). Low-level temperature inversions are common along the California coast and Channel Islands, and these inversions form cloud cover, which is expressed as fog when it is low enough to intersect terrain. This cloud cover, otherwise known as the marine layer, has a strong influence on coastal ecosystems and SCI (US Navy 2013a, pp. 3.13, 3.26). Although the island has a short rainy season, the presence of fog during the summer months helps to reduce drought stress for many plant species through shading and fog drip, and many species are restricted to this fog belt (Halvorson et al. 1988, p. 111; Fischer et al. 2009, p. 783). Thus, fog could help buffer species from extinction brought on by climatic change, as evidenced by the elevated levels of endemism along the coast of Baja California and on the Channel Islands (Vanderplank 2014, p. 5). Climate on the Channel Islands continues to support paleoendemic plants, such as Lyonothamnus, which once was widespread in the southwest of North America and is thought to have been extirpated on the mainland as conditions became warmer and drier (Bushakra et al. 1999, pp. 473-475). However, coastal fog has been decreasing in southern California in recent decades, possibly due SSA Report – San Clemente Island larkspur 65 March 2020
to urbanization (which would not affect SCI) or climate change (Williams et al. 2015, p. 1527; Johnstone and Dawson 2010, p. 4537; LaDochy and Witiw 2012, p. 1157), and costal cloud cover and fog are poorly addressed in climate change models (Qu et al. 2014, p. 2603-2605). Warming projections in California, particularly the possibility that the interior will experience greater warming than the coast (Cayan et al. 2012, p. 7), suggest that the fate of coastal fog is uncertain (Field et al. 1999, pp. 21–22; Lebassi-Habtezion et al. 2011, p. 8-11). Iacobellis et al. (2010, p. 129), however, showed an increasing trend in the strength of low-level temperature inversions, which suggests that the marine layer is likely to persist and may even increase. Recent work examining projected changes in solar radiation and cloud albedo show projected increases in cloud albedo during the dry season (July–Sept) and decreases during the wet season (Nov–Dec, Mar–Apr) (Clemesha 2020, entire). The summer projections mean an increase in fog and low clouds the decreases in the winter likely reflect a decrease in a combination of precipitation and fog (Clemesha 2020, pers. comm.; Clemesha 2020, entire). Such a scenario would moderate the effects of climate change on the Channel Islands and would be expected to reduce its potential threat to island plants, including San Clemente Island larkspur. Dry season low clouds and fog are particularly important to plant growth, survival and population dynamics in arid systems through both a reduction in evapotranspiration demand and potentially water deposition (Corbin et al. 2005, p. 511, Johnstone and Dawson 2010, p. 4533, Oladi et al. 2017, p. 94). Because SCI typically is drier than neighboring mainland areas (Tierra Data Inc. 2005, p. 4), the models may understate the effects to the island vegetation. Less rainfall and warmer air temperatures could limit the range of San Clemente Island larkspur, although there is no direct research on the effects of climate change on the subspecies. Changes in temperature or rainfall patterns has the potential to affect biotic interactions, such as decoupling the timing of plant phenology versus insect activity. Additionally, changes in sea level and temperature may be more acute on small islands, due to their high vulnerability (surrounded by ocean) and low adaptive capacity (from limited size) (IPCC 2007b, p. 1). Sea levels are predicted to rise between 0.9 and 1.4 m by 2100 (Cayan et al. 2012, p. 24), which would not directly affect San Clemente Island larkspur. Predicting impacts to San Clemente Island larkspur due to climate change are further complicated by the timing of increased or decreased rainfall; wetter conditions in the winter and early spring can lead to more growth early in the season which can provide more fuel for fire later. However, wetter summers and falls can prevent the fuel from drying out enough to burn (Lawson 2019, pers. comm.). Therefore, making predictions about future fire patterns as affected by climate change is difficult. We focus on a 20 to 30-year window, in which we do not expect major impacts to San Clemente Island larkspur from these long-term effects of climate change. However, in this short-term 20 to 30-year window, climate change may result in more frequent or severe fires, heavy periods of rainfall that could lead to major erosion events (see Section 5.2), or periods of drought (Kalansky et al. 2018, p. 10).
Summary The impacts of predicted future climate change to San Clemente Island larkspur remain unclear. While we recognize that climate change is an important issue with potential effects to listed species and their habitats, information is not available to make accurate predictions regarding its effects to San Clemente Island larkspur (USFWS 2012, p. 29121). However, given
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the timeframe presented in climate change studies, a major impact on San Clemente Island larkspur from climate change is unlikely to occur in the next 20 to 30 years. Climate changes within a 20 to 30-year time frame are likely but are also not easily predicted; fires (addressed in Section 5.4) may become more frequent or severe. Droughts may become more frequent or severe. Heavy rainfall events that may cause localized erosion (addressed in Section 5.2) are hard to predict, but these impacts would be localized.
5.6 Other threats Subsequent to the listing, Evans and Bohn (1987, p. 539) found seed predation to be heavy in one population of San Clemente Island larkspur. They found holes chewed through the bottom portion of seed capsules but were unable to ascertain the identity of the seed eater. More recent surveys have not found evidence of seed predation (Junak and Wilken 1998, p. 121), and the subspecies appears to be persisting despite this perceived threat. Presently, there are no diseases on San Clemente Island that are known to pose a significant threat to the larkspur.
5.7 Summary of Factors Influencing Viability The habitat for San Clemente Island larkspur is still potentially threatened by destruction and modification associated with land use, erosion, the spread of nonnatives, and fire. To help ameliorate these threats, the Navy implements a fire plan (US Navy 2009) to address fire- management. The Navy addresses erosion and targeted removal of invasive species, in general, through the INRMP, addresses training-related erosion through the Erosion Control Plan, and addresses further introduction of invasive species through implementation of the biosecurity plan (US Navy 2013a, entire; US Navy 2013b, entire; USFWS 2008, pp. 1–237; US Navy 2016, entire). As noted above, only about 12% of the population of San Clemente Island larkspur occur in a training area, but only 2 locations comprising 42 individuals fall into an area of high use within these training areas (a TAR). Therefore, direct impacts from training to the subspecies are insignificant. One location with 70 individuals occurs near a road, and five locations totaling 344 individuals occur in watersheds that could potentially see increased erosion from the AVMAs, although the likelihood of individuals being directly impacted by erosion in either of these cases are minimal. Through implementation of the island-wide protective measures applied to project design, road-maintenance and repair, and the Erosion Control Plan to address training-related erosion, the threat of erosion is not considered significant across the range of San Clemente Island larkspur nor Delphinium variegatum in general. While the full impact of invasive species on San Clemente Island larkspur is unknown, the effects are likely minimal or localized, given the expansion of both the subspecies and Delphinium variegatum on the island despite the presence of invasive species. Natural resource managers have been successful at decreasing the prevalence of particularly destructive nonnatives; while specific efforts may or may not directly impact the larkspur, the significant efforts that the Navy makes to prevent the expansion of more invasive species (listed above) into habitat areas constitutes a significant benefit to the island ecosystem overall. Fire, given the current pattern and fire return interval, does not appear to pose a threat to either subspecies. Fires within the distribution of San Clemente Island larkspur are typically small, of low severity, and infrequent, and given they are most often ignited due to training, their typical locations are somewhat predictable. The San Clemente Island larkspur and SSA Report – San Clemente Island larkspur 67 March 2020
Thorne’s larkspur appear to be resilient to fires at their current interval. Seemingly, only an extreme increase in fire frequency could affect the subspecies in the future, but it is unknown what that fire return interval would need to be. Climate change may influence this taxon by affecting germination or persistence of adult plants if drought or increasing temperatures result in significant changes in vegetation communities on San Clemente Island. Effects of climate change, especially how it will affect the persistence of the fog layer, are speculative. Therefore, the magnitude of this rangewide threat and how it may affect this taxon is unknown at this time, but we do not foresee a major impact from climate change in the next 20 to 30 years. In this short term, however, climate change may promote increased fire frequency and/or severity, lead to localized erosion due to periods of heavy rainfall, or lead to increased periods of drought. Potential changes to military training and testing on SCI are being considered, and changes that would affect San Clemente Island larkspur are currently unknown. For instance, future training may include expansion of or additions to terrestrial designated training areas, introduction of new training methods, equipment, and activities that would affect fire frequency, fire severity, or soil erosion. While military training on SCI has been and will continue to be dynamic as it evolves to meet new requirements, changes are expected to be incremental, as they have been in the past. Such changes are subject to environmental review under applicable laws and regulations, including NEPA and ESA, and impacts to federally listed and sensitive species will be addressed. Therefore, we consider the main threats to San Clemente Island larkspur to be: 1) training impacts to individuals located within the training areas (AVMAs or TARs), 2) impacts from training or erosion to individuals within 100 ft of a road or 50 ft of the AVMR (to account for troop movements as well as erosion potential), and 3) impacts from erosion within the AVMA watersheds. No individuals currently exist within the AVMAs or within 50 ft of the AVMR. While other threats to San Clemente Island larkspur exist to various degrees throughout its range (invasive grasses and other species, potential of trampling within the SWATs, IOA, or elsewhere, erosion events, etc.), we consider these threats to be minor enough and infrequent enough that they will not have major or lasting impacts to the subspecies. Looking at each of our main threats by watershed, we found that only three watersheds (14%), totaling 1,005 of the estimated individuals (5%) had low total threats (Table 8, Table 10 in Appendix A). Watersheds with low total threats were defined as those where potential impacts from roads, training, or erosion potentially threatened less than 50% of the number of locations or individuals within each watershed. We assumed that presence in an AVMA watershed is a low-level threat, unlikely to threaten the locations present; even if erosion became an issue in these watersheds, individuals would have to be within the path of erosion within the watershed to be impacted, as the entire watershed is unlikely to erode. Therefore, we found that 19 watersheds (82%) are located in areas with no identifiable major threats and represent 95% (17,951) of the total number of individuals on SCI (Table 8, Table 10 in Appendix A). The three watersheds where threats exist are spread out within the subspecies’ distribution (Figure 18).
Table 8. Numbers and percentages of watersheds and individuals of San Clemente Island larkspur assessed to have varying levels of threats: none or low, threats that could potentially affect <50% of the locations or individuals within the watershed. No watersheds have threats that could potentially affect ≥50% of the locations or individuals within the watershed. SSA Report – San Clemente Island larkspur 68 March 2020
Watersheds Individuals Threats Watersheds Individuals (%) (%) none 19 17,951 82% 95% low 3 1,005 14% 5%
Figure 18. Representation of locations of watersheds where no threats exist to San Clemente Island larkspur (SCI larkspur), or a low level of threats exist to the watershed (threats could potentially affect <50% of the locations or individuals within the watershed). No watersheds had a moderate level of threats (threats could potentially affect ≥50% of the locations or individuals within the watershed). Threats identified include locations or individuals within 100 ft of a road or 50 ft of the AVMR, in the TARs, and within the AVMA watersheds. Further, AVMA watersheds are considered to have a low threat level. Four additional watersheds are assumed to be occupied but lack data; however, no perceived threats to SCI larkspur exist in these watersheds.
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SECTION 6 – FUTURE CONDITIONS AND VIABILITY
We have considered what San Clemente Island larkspur needs for viability and the current condition of those needs (Sections 3 and 4), and we reviewed the factors that are driving the current, and future conditions of the subspecies (Section 5). We now consider what the subspecies’ future condition is likely to be. We apply our future forecasts to the concepts of resiliency, representation, and redundancy to describe the future viability of San Clemente Island larkspur. Using our analysis of the factors influencing viability in Chapter 5, we evaluate the current threats to San Clemente Island larkspur.
6.1 Introduction Since the removal of feral browsers and grazers from SCI by 1992, few threats exist to the viability of San Clemente Island larkspur on the island, and there are many ongoing management efforts designed to minimize these threats. The subspecies currently occupies a broad distribution on the island and exists mostly in locations that occur outside the training areas, are unlikely to experience to vehicular and foot traffic, and have been unlikely to experience erosion events. In much of its distribution, the subspecies exists in large numbers in areas where there are no threats to its habitat. The largest threat to the long-term future viability of the subspecies may be climate change. However, how climate change will affect SCI long term remains unclear, and most importantly, the persistence and timing of the fog layer, which provides moisture and a refuge from the full impacts of warming, is unknown. Short term climate impacts of climate change could include extended periods of drought, increased fire frequency or severity, or erosion from heavy rainfall events; these will be addressed under future redundancy (Section 6.6). Climate change could also lead to an increase in fire frequency or severity, but if sources of ignition do not change, we do not expect fires to threaten San Clemente Island larkspur. The potential for fires to burn in novel areas (within the range of San Clemente Island larkspur) is difficult to predict and will also be addressed under future redundancy (Section 6.6). Based on our review of the literature and models on climate change, we assume that climate change will not have major effects on San Clemente Island larkspur in the next 20 to 30 years. Therefore, we consider the future of San Clemente Island larkspur in terms of its threats and conservation efforts over the next 20 to 30 years. Potential impacts to San Clemente Island larkspur within this 20- to 30-year period would be to those individuals that exist within boundaries of a TAR, near a road (within 100 ft, where individuals could experience other road impacts such as trampling or erosion), or in an AVMA watershed (were the Erosion Control Plan to fail to manage erosion adequately). While the individuals known to exist in these areas have persisted currently, future increases in the amount or location of training (including increased foot traffic and maneuvering along roads) could affect the individuals within these locations. We assumed that training areas and roads would impact the same areas as they have historically; our models do not account for a change to training area footprints. We do not and cannot anticipate these sorts of changes; while they are possible, such changes would be subject to environmental review as discussed above. While impacts from training, roads, and the AVMAs have locations that are somewhat reasonable to predict, severe erosion events, although unlikely, are harder to predict. Therefore, we consider severe erosion events as catastrophic impacts, and we account for these potential
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impacts in our assessment of redundancy and representation. Therefore, to assess the future viability of San Clemente Island larkspur, we considered future scenarios that account for potential impacts to individuals where threats exist.
6.2 Methods Training and land use in the AVMA, TARs, and along roads represent a potential threat to San Clemente Island larkspur, but these threats are only present in three watersheds and could affect only 1,005 of the estimated known individuals. While we cannot predict exactly how training will change over time, increases in training tempo are common. Using the percent of individuals that occur either within a training area or near a road, we looked at the total number of individuals that could be affected by increased training in each of these three watersheds. While we know that San Clemente Island larkspur can withstand some training impacts, evidenced by their presence within a TAR, the actual realized impacts of increased training on San Clemente Island larkspur is unknown. Therefore, to capture this uncertainty, we modeled future training impacts as: • Status quo: no impact • Increased training: Assume that 50% of all locations and individuals within the TARs or AVMA watersheds or near roads perish. • Extreme training: Assume that all locations and individuals within the TARs or AVMA watersheds or near roads perish.
By modeling these training increases, we attempted to project plausible although unlikely scenarios where 50% to 100% of all individuals within the TARs or AVMA watersheds or near roads perish over time. Any changes to training would have to be substantial to affect the subspecies in this way; this assumes that all area within the training area would be utilized and severely degraded, road impacts would preclude San Clemente Island larkspur from being near roads, and all the area within AVMA watersheds would also be degraded. We will model these potential future effects on resiliency over 20 to 30 years, the maximum projection we feel we can project out to before the effects of climate change cause too much uncertainty. We apply each of these scenarios to the number of individuals considered current in each of the three watersheds where threats exist and project the resulting population size. While we project that any individuals lost to these threats perish and do not return, in reality, over a 20- to 30-year period, it is likely that individuals would return and become reestablished in future years.
6.3 Future Resiliency Population changes within individual watersheds under each scenario can be found in Table 10 in Appendix A. Under a status quo scenario, we do not expect the occupied watersheds or numbers of individuals to change from current (Table 9). In the two scenarios where training increases, the number of watersheds considered high or very high drops by one; two watersheds become extirpated under an extreme training scenario. Even under the extreme training scenario, however, the population is only reduced by about 400 individuals (Table 9). While the current resiliency of the four additional watersheds assumed to be occupied is unknown, we do not expect resiliency in these watersheds to change from current under any of our scenarios (Figure 19). SSA Report – San Clemente Island larkspur 71 March 2020
Table 9. The number of watersheds considered of very high, high, moderate and low resiliency and the total estimated population as considered current and in each of our four future scenarios for San Clemente Island larkspur. Watersheds without data but presumed to be occupied are not assigned a resiliency but are acknowledged in the total watershed count. Watersheds Very High High Moderate Low Total Individuals Current 7 7 5 3 22 (+4 assumed) 18,956 Status quo 7 7 5 3 22 (+4 assumed) 18,956 Increased training 7 6 6 3 22 (+4 assumed) 18,749 Extreme training 7 6 4 3 20 (+4 assumed) 18,542
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Figure 19. Resiliency estimates by watershed (based on number of individuals) currently as well as under each of our three future scenarios. Extant watershed counts do not account for recruitment into new watersheds. We assume the four additional watersheds remain occupied at current resiliency levels, which are unknown.
In the absence of major threats, we do not expect any stochastic impacts to affect San Clemente Island larkspur in a meaningful way over the next 20 to 30 years. We expect that the
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entire island population will maintain resiliency in the future under the most likely scenarios yet could see a minor decrease in resiliency under our most extreme scenario.
6.4 Future Representation Except in the event of extreme training increase, we do not expect any locations of San Clemente Island larkspur to become extirpated, and even extreme training increases appear to have minimal impacts on this subspecies due to its distribution outside of these areas. However, the high degree of genetic similarity among populations means that the loss of any single population should not cause a significant loss of genetic variation for the San Clemente Island larkspur, and current levels of representation appear adequate for the subspecies. Therefore, we do not expect representation to decrease from current levels, even under our most extreme scenario.
6.5 Future Redundancy Except in the event of extreme training increase, we do not expect the number of watersheds occupied by San Clemente Island larkspur to decrease from current estimates. Under the unlikely extreme training scenario, two watersheds become extirpated, but these extirpations are a product of erosion originating from the use of the AVMAs. Given the implementation of the Erosion Control Plan and the speculation as to whether even major erosion events could affect an entire watershed, it seems unlikely that all of these locations would be affected. Still, redundancy may decrease from current levels given an increase in impacts, but the decrease would be slight, as very few individuals are projected to be affected. While most of the current population occurs outside of areas where threats currently exist and where we project threats may increase, unforeseen unprecedented or catastrophic impacts could occur that might affect individuals outside of these areas. Severe erosion events resulting from heavy rainfall, a potential effect of climate change, could remove individuals, but this would occur within localized areas. An increase in or change to the distribution of invasive grasses could affect the San Clemente Island larkspur in some areas, by increasing competition or changing the fire pattern such that fires burn more severely and threaten the larkspur, even when it is dormant. However, continued management efforts on the island would make the possibility of more extreme fires, new invasive species, or major erosion events unlikely. Only an unprecedented, unusually severe or catastrophic impact could threaten the viability of the species. For instance, the effects of multiple, severe drought years, coupled with other stressors, could have substantial impacts to species viability. A severe drought could impact the vegetation island-wide, but the San Clemente Island larkspur is likely well suited to withstand drought, due to their ability to go dormant. However, depending on the length and severity of drought, we cannot rule out impacts to the subspecies. While redundancy may already be reduced from unknown historical levels, we expect this subspecies will maintain similar levels of redundancy as it currently has, and thus should retain its ability to withstand most major catastrophic events, such as a major erosion event (perhaps caused by a period of heavy rainfall), severe/frequent fire in novel areas, extreme drought, or an outbreak of an invasive, predatory, or pathogenic species. Erosion or fire would likely affect only a small percentage of the population, even if it occurred in an area where the subspecies is most abundant. Still, like all local endemics, San Clemente Island larkspur is constrained to San Clemente Island, and therefore it is at risk of any catastrophic island-wide impact. Although not predicted in next 20 to 30 years and not projected in current model
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predictions, an impact such as sustained drought some other unknown effect of climate change that would have island-wide impacts has the potential to reduce redundancy of San Clemente Island larkspur.
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6.6 Limitations and Uncertainties In any species status assessment, the process of projecting a population into the future requires making strategic simplifications of reality, accounting for multiple uncertainties, and making informed assumptions when necessary. Our assessment addressed some of the key uncertainties and yielded useful predictions for characterizing the future status of San Clemente Island larkspur, and through the use of predictive constructs and multiple scenarios, we captured a range of plausible conditions in the future. However, there are still limitations to these predictions; we outline these uncertainties and assumptions of the analyses below. Our assessment of the current population used data collected between 2004 and 2017 (Table 3), following a rule set designed to prevent overcounting. However, the rule set assumes that numbers of individuals have not changed since they were counted and that all individuals in those watersheds are known. The reality is that the size of the population and the number of currently occupied watersheds is unknown, and there is evidence that the population may in fact be much larger than our estimate, given the difficulty in locating this subspecies and the varying numbers of individuals that may or may not flower each year. Further, we assumed that only individuals recorded as San Clemente Island larkspur in the field represent this subspecies. In reality, most of the central part of the island contains groups of individuals that vary in color, and there is no clear way to delineate one subspecies from the rest without further genetic study. The US Navy is currently recognizing more individuals as San Clemente Island larkspur based on proportions of white individuals within the groups. Our future scenarios also did not account for population growth or recruitment into new watersheds; we assumed that individuals within each watershed will not recruit more individuals into those watersheds. Given that we do not truly know how many individuals are currently present or have been present at any point in time, we did not want to overestimate growth over the projected timeframe. However, data indicate that the population is expanding, and in reality, some growth would be expected. We also made assumptions regarding how training, erosion from the AVMAs, and impacts from proximity to roads would affect the numbers of individuals in each watershed where these threats may occur; again, no quantifiable data exists to accurately predict these impacts. Our estimates of these impacts were made in an attempt to avoid underestimating these threats. We also assumed that training, impacts from AVMA watersheds, and proximity to roads would impact the same areas as they have historically; our models do not account for a change to training area footprints. While we do not anticipate these sorts of changes, they cannot be ruled out. Further, we assumed that the presence of non-native annual grasses will not affect the susbspecies or fire regime in the future in any meaningful way. These grasses have been present on the island for decades, and no data indicate that they are increasing. Current fire patterns are what they are despite the non-native species, and the subspecies exists in great numbers in generally the same locations it has historically and has expanded into new areas despite these widespread grasses. Still, there may be impacts that have yet to be realized. We also assumed that the Navy will continue to manage habitats on the island into the future, continuing their efforts to manage fire, invasive species, and erosion. If the Navy were to cease being good land stewards, our conclusions would likely be invalidated.
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The final major uncertainty regarding the future of SCI is the impacts of climate change in the long term and drought impacts in the shorter term. While we do not expect climate change to have major impacts to the vegetation on SCI in the next 20 to 30 years, data may change as climate science evolves and new climate models come out. In the short term, drought cycles, which have been a part of the historical climate on SCI, may intensify. The full impacts of rainfall patterns and the future of the fog layer are unknown.
6.7 Conclusions Despite historical and current land uses, historical drought, historical and current fire patterns, and other existing threats, San Clemente Island larkspur has increased both its distribution and population size on SCI. While we do not know the historical abundance or distribution of this subspecies, currently, we expect that San Clemente Island larkspur has good resiliency, redundancy, and representation and expect it should withstand most stochastic impacts, environmental changes, and reasonably plausible potential catastrophic events on SCI. Projecting the population into the future, given even extreme impacts from increased fire frequency, fire severity, and training, we find that the vast majority of the population (95%) occurs outside areas where these threats are projected to occur. Thus, outside of a catastrophic or unprecedented impact and given continued management efforts and land stewardship practices by the Navy, we expect the population will retain somewhat similar levels of resiliency, redundancy, and representation as it currently has.
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Tierra Data Inc. 2005. San Clemente Island vegetation condition and trend analysis 1992–2003. Report prepared for the Southwest Division, U.S. Naval Facilities Engineering Command, San Diego, California. Pp. 1 to 96 and Appendices. ______. 2007. Project increase in sheet and rill erosion due to military operations proposed on San Clemente Island. Report prepared for the Southwest Division, U.S. Naval Facilities Engineering Command, San Diego, California. Pp. 1 to 36 and Appendices. U. S. Department of the Navy [US Navy]. 2002. Integrated Natural Resources Management Plan (INRMP) Naval Auxiliary Landing Field San Clemente Island, California. Prepared by Tierra Data Systems. 784 pp. ______. 2013a. Integrated Natural Resources Management Plan (INRMP) Naval Auxiliary Landing Field San Clemente Island, California. Prepared by Tierra Data Inc. 784 pp. ______. 2013b. Erosion Control Plan for San Clemente Island. Prepared by Science Applications International Corporation, Carpinteria, CA. 132 pp. ______. 2016. Naval Auxiliary Landing Field San Clemente Island Biosecurity Plan FINAL. November 2016. Prepared by ManTech SRS Technologies, Inc. U.S. Fish and Wildlife Service [USFWS]. 1977. Determination that seven California Channel Island animals and plants are either endangered species or threatened species [endangered: San Clemente loggerhead shrike, Lanius ludovicianus mearnsi; San Clemente broom, Lotus scoparius ssp. traskiae; San Clemente bushmallow, Malacothamnus clementinus; San Clemente Island larkspur, Delphinium kinkiense; San Clemente Island Indian paintbrush, Castilleja grisea. Threatened: island night lizard, Klauberina riversiana; San Clemente sage sparrow, Amphispiza belli clementae]. Fed. Reg. 42: 40682–40685. ______. 1984. Recovery Plan for the Endangered and Threatened Species of the California Channel Islands. U.S. Fish and Wildlife Service, Portland, Oregon. 165 pp. ______. 2008a. Delphinium variegatum ssp. Kinkiense (San Clemente Island larkspur) 5-Year Review: Summary and Evaluation. Carlsbad, CA. ______. 2008b. Biological Opinion for San Clemente Island Military Operations and Fire Management Plan, Los Angeles County, California (Service File FWS–LA–09B0027– 09F0040). [November, 2008]. ______. 2010. Endangered and Threatened Wildlife and Plants; Initiation of 5-Year Reviews of 34 Species in California and Nevada; Availability of 96 Completed 5-Year Reviews in California and Nevada. Federal Register 75: p. 28636-28642). ______. 2012. Delphinium bakeri (Baker's larkspur) 5-Year Review: Summary and Evaluation. June 2012. 18 pp. ______. 2013. Reclassification of Acmispon dendroideus var. traskiae (=Lotus d. subsp. traskiae) and Castilleja grisea as threatened throughout their ranges. Final Rule. Fed. Reg. 78: 45405–45439. ______. 2016. USFWS Species Status Assessment Framework: an integrated analytical framework for conservation. August 2016 version 3.4 Vanderplank, S. 2014. Endemism in an Ecotone: From Chaparral to Desert in Baja California, Mexico. Pages 205–218 in Carsten Hobohm, Editor. Endemism in Vascular Plants. Springer Publishing, Dordrecht. Vanderplank, S., K. O’Connor, B. Munson, and D. Lawson. 2019. A Conservation Assessment for Castilleja grisea (San Clemente Island Paintbrush, Orobanchaceae). Rancho Santa Ana Botanic Garden Occasional Publications, Number 17, vi + 34 pages.
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Vanderplank, S., K. O’Connor, B. Munson, and D. Lawson. In prep. A Conservation Assessment for Delphinium variegatum subsp. kinkiense (San Clemente Island larkspur, Ranunculaceae). Waddington, K.D. 1981. Factors Influencing Pollen Flow in Bumblebee-Pollinated Delphinium virescens. Oikos 37: 153-159. Warnock, M. J. 1981. Biosystematics of the Delphiniumn carolinianumn Complex (Ranunculaceae). Systematic Botany 6: 38-54. Warnock, M. J. 1990a. New taxa and combinations in North American Delphinium (Ranunculaceae). Phytologia 68:1-6. http://direct.biostor.org/reference/63604 Warnock, M. J. 1990b. Taxanomic and ecological review of California Delphinium. Collectanea Botanica 19:45-74. Warnock, M.J. 1993. Delphinium. In: J. C. Hickman [ed.], The Jepson Manual: Higher Plants of California. 916-922. University of California Press, Berkeley, California, USA. Warnock, M.J. 1997. Delphinium. Pp. 196-240 In: Flora of North America Editorial Committee ed. Flora of North America, Volume 3, Oxford University Press, New York. Waser, N.M., and M.V. Price. 1983. Optimal and actual outcrossing in plants, and the nature of plant-pollinator interaction. pp. 341-349. In C.E. Jones and R.J. Little [eds.], Handbook of Experimental Pollination Biology, Scientific and Academic Editions, Van Nostrand Reinhold Company, Inc., New York, NY. ______. 1985. Reciprocal transplant experiments with Delphinium nelsonii (Ranunculaceae): Evidence for local adaptation. American Journal of Botany 72: 1726-1732. Williams, A. P., R. E. Schwartz, S. Iacobellis, R. Seager, B. I. Cook, C. J. Still, G. Husak, and J. Michaelsen. 2015. Urbanization causes increased cloud base height and decreased fog in coastal Southern California, Geophys. Res. Lett., 42, doi:10.1002/2015GL063266. Wolf. S., B. Hartl, C. Carroll, M.C. Neel, and D.N. Greenwald. 2015. Beyond PVA: why recovery under the Endangered Species Act is more than population viability. BioScience 65:200-207.
Personal communications
Booker, Melissa (title). 2019. Documentation of take aways from series of phone calls, document edits, etc. between January and November 2019. Clemesha, Rachel (Scripps Institution of Oceanography). 2020. Email to Dawn Lawson, Re: Progress Report Fog and Coastal Low Cloud Analysis for San Clemente Island. Monday January 27, 2020. Lawson, Dawn (Adjunct Faculty, Biology Department, San Diego State University). 2019. Telephone conversation with T.M. McFarland (Texas A&M NRI), April 2019 and email to Kim O’Connor (US Navy) November 25, 2019. O’Brien, Bart (Botanist, Tilden Botanical Garden, Berkley, CA). 2019. Phone log: 2/2/19 conversation with Bart O’Brien re DeVaKi. Email to Nancy Ferguson at USFWS Carlsbad Field office, March 18, 2019. O’Connor, Kim (Conservation Program Manager, US Pacific Fleet). 2019. Documentation of take aways from series of phone calls, document edits, etc. between January and November 2019.
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McFarland, Tiffany (Senior Research Associate at Natural Resources Institute, Texas A&M University). 2019. Personal observations from trip to San Clemente Island, April 2019. Munson, Bryan (Botany Program Manager, Naval Base Coronado). 2019. Documentation of take aways from series of phone calls, document edits, etc. between January and November 2019.
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APPENDIX A
Table 10. Occupied watersheds with San Clemente Island larkspur data present, including the current number of locations and individuals present, the percent of locations and individuals in the training areas or near roads, whether the watershed overlaps the AVMA, and the projected individuals that will occur in that watershed in 20 to 30 years under each of three scenarios. Locs Inds Locs in Ind in near near Training Training roads Roads Status Increased Extreme Watershed Locations Individuals (%) (%) (%) (%) AVMA quo training training WS_1009 2 206 Yes 206 103 0 WS_1018 1 373 373 373 373 WS_1021 1 5,500 5,500 5,500 5,500 WS_1033 3 138 3% 0% Yes 138 69 0 WS_1034 11 3,633 3,633 3,633 3,633 WS_1043 1 569 569 569 569 WS_1052 1 50 50 50 50 WS_1053 2 56 56 56 56 WS_1056 3 364 364 364 364 WS_1060 3 694 694 694 694 WS_1062 3 537 537 537 537 WS_1064 3 413 413 413 413 WS_1065 1 410 410 410 410 WS_1066 5 661 1% 0% 661 626 591 WS_1071 11 2,754 2,754 2,754 2,754 WS_1072 10 203 203 203 203 WS_1077 1 300 300 300 300 WS_1080 5 704 704 704 704 WS_1083 1 10 10 10 10 WS_1088 1 20 20 20 20 WS_1092 2 320 320 320 320 SSA Report – San Clemente Island larkspur 84 March 2020
Locs Inds Locs in Ind in near near Training Training roads Roads Status Increased Extreme Watershed Locations Individuals (%) (%) (%) (%) AVMA quo training training WS_1215 3 1,041 1,041 1,041 1,041 Total 74 18,956 18,956 18,749 18,542
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APPENDIX B
Table 11. Conservation measures for terrestrial plants on San Clemente Island (SCI) as relevant to San Clemente Island larkspur, were taken from the Biological Opinion (BO; USFWS 2008) and Table 3-48 of the Integrated Natural Resources Management Plan (INRMP; US Navy 2013). Taken from Vanderplank et al., in prep.
Source Measure Requirements INRMP AVMC-M-7 Require the following measures to reduce the potential for transport and BO of invasive plants to the island. Prior to coming to SCI, military and non-military personnel will be asked to conduct a brief check for visible plant material, dirt or mud on equipment and shoes. Any visible plant material, dirt or mud should be removed before leaving for SCI. Tactical ground vehicles will be washed of visible plant material, dirt and mud prior to embarkation for SCI. Additional washing is not required for amphibious vehicles after 15 minutes of self-propelled travel through salt water prior to coming ashore on SCI. INRMP G-M-1. Continue invasive species control on an island-wide scale, with and BO emphasis on the AVMC, IOA, TARs and other operations insertion areas such as West Cove, Wilson Cove and the airfield. A pretreatment survey to identify areas needing treatment, one treatment cycle and a retreatment cycle (when necessary) will be planned each year to minimize the distribution of invasive species. Where feasible, the Navy will include future construction sites in a treatment and retreatment cycle prior to construction. INRMP G-M-9. Conduct monitoring and control activities for invasive non-native and BO plant species outside of the Impact Area boundaries. Navy installations will prevent the introduction of invasive species and provide for their control per EO 13112. The Navy will identify actions that affect the introduction of invasive species, prevent their introduction, respond rapidly to their control, monitor populations, restore affected native species and their habitat, conduct research and develop technologies to prevent further introductions, and promote public education of the issue. BO A goal will be reducing the percent cover of invasive plants from 2008 the 1992-1993 baseline of 41% on terrace faces and 53% on terrace flats.
INRMP FMP-M-10. Conduct prescribed fire experiments to evaluate their effectiveness and BO in controlling non-native annual plants. INRMP FMP-M-11. Establish post-fire recovery plots to monitor recovery and identify and BO new infestations of non-native invasive plants associated with both wildfire and prescribed fire.
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Source Measure Requirements INRMP FMP-M-12. Evaluate burn areas and prioritize them, as appropriate, for and BO inclusion in the weed eradication program. INRMP To prevent the transfer of invasive species from the mainland to SCI, soil and fill brought to the island are treated with herbicide before importation (INRMP 2012). INRMP Further prevention for the transfer of invasive species to the island is established through the Do Not Plant list maintained by the Naval Facilities Engineering Command, Southwest Botanist and Landscape Architect (INRMP 2012).
INRMP The NRO participates in a Channel Islands biosecurity working group which meets quarterly to discuss and develop measures to prevent non-native species from invading Channel Islands ecosystems, and to share resources and knowledge of potential threats to the islands (INRMP 2012).
SSA Report – San Clemente Island larkspur 87 March 2020