Species Status Assessment for San Clemente Island Lotus

Species Status Assessment Report for the San Clemente Island Lotus (Acmispon dendroideus var. traskiae) Version 1.0 Photo courtesy of USFWS 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 also like to recognize and thank the following individuals who provided substantive information and/or insights for our SSA: Kimberly O’Connor, Bryan Munson, Melissa Booker, Dawn Lawson, Sula Vanderplank, Sandy Vissman, and Andrew Bridges. Additionally, valuable input into the analysis and reviews of a draft of this document were provided by Mitchell McGlaughlin. We appreciate his 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 Lotus (Acmispon dendroideus var. traskiae), Version 1.0. March 2020. Sacramento, CA. SSA Report – San Clemente Island Lotus ii March 2020 EXECUTIVE SUMMARY This Species Status Assessment (SSA) provides an analysis of the overall species viability for the San Clemente Island Lotus (Acmispon dendroideus var. traskiae). To assess the viability of this taxon, we, the U.S. Fish and Wildlife Service (Service), used the conservation biology principles of resiliency, redundancy, and representation (3 Rs). Specifically, we identified the taxon’s 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 taxon redundancy and representation using available metrics to forecast the ability of this taxon to sustain populations into the future. Acmispon dendroideus var. traskiae is a semi-woody, flowering subshrub, endemic to San Clemente Island (SCI) and is one of five taxa in the genus Acmispon found on the island. There are no other varieties of A. dendroideus found on the island. At listing, nonnative herbivores were the primary threat to Acmispon dendroideus var. traskiae. As a result of their removal, habitat conditions improved and led to changes in the cover of native and nonnative plants on the island, further evidenced by the increases in A. d. var. traskiae and several other threatened and endangered taxa since the feral animals were removed. In the absence of the primary threat, additional threats to A. d. var. traskiae that have been identified include: (1) land use, (2) erosion, (3) nonnative plants, and (4) fire. Additionally, we looked at the potential threat due to hybridization and the emerging threat of 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. Altogether, 34.8% of the island’s area is located in designated training areas, and much of the island is void of any infrastructure. Most of the population of Acmispon dendroideus var. traskiae falls outside of these designated training areas; thus, direct impacts to the population are minimal. Erosion, neither naturally occurring nor that induced by human activities, has affected any documented occurrence of A. d. var. traskiae to date. While the full impact of invasive species on A. d. var. traskiae is unknown, the effects are likely minimal or localized, given the expansion of A. d. var. traskiae on the island despite the presence of invasive species. Future impacts from fire remain uncertain. Fires are typically small, of low severity, and infrequent, and given they are most often ignited due to training, their typical locations are somewhat predictable. However, an increase in the frequency or severity of fires in the future, potentially due to short-term impacts of climate change, increased training, or an increase in invasive grasses, could have additional impacts to A. d. var. traskiae. We found that 50% of watersheds and 66% of individuals are located in areas where no quantifiable threats exist. Only 22% of watersheds and 10% of individuals are associated with a threat that could potentially adversely impact 50% or more of the locations, individuals, or area within the watershed. To help further ameliorate these remaining threats, the Navy implements a wildland fire management plan (US Navy 2009) 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 the SSA Report – San Clemente Island Lotus iii March 2020 biosecurity plan. Military training on SCI has been and will continue to be dynamic as it evolves to meet new requirements, and changes that may affect Acmispon dendroideus var. traskiae are unknown. For instance, future training may include introduction of new training methods, equipment, and activities that would affect fire-frequency, fire-severity, or erosion. However, changes are expected to be incremental, as they have been in the past, and impacts to federally listed and sensitive species will be addressed in environmental analyses required under the National Environmental Policy Act (NEPA) and ESA. The factors that appear to have the most potential to impact species viability in the future are land use, fire, and climate change, including potential compounded effects. However, we are unable to address the long-term impacts of climate change because how climate change will affect SCI remains 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 Acmispon dendroideus var. traskiae in the next 20 to 30 years, although we account for possible short-term climate impacts. Therefore, we consider the future of A. d. var. traskiae in terms of its threats and conservation efforts over the next 20 to 30 years. Therefore, to assess the future viability of Acmispon dendroideus var. traskiae, we considered three future scenarios that encompass the uncertainty associated with fire and military training, as well as uncertainty in the levels of recruitment over time: Scenario 1, our status quo scenario, assumes fire patterns and severity continue and current training impacts are maintained. Scenario 2 assumes increased training impacts and increased fire frequency/severity (due to short-term climate change impacts or the increase in training). Scenario 3 also assumes a threat increase but assumes extreme fire frequency/severity and extreme training impacts. We present the resulting population size as a range using a low and high recruitment estimate (Table A). Our methods predict that, in the next 20 to 30 years, the number of occupied watersheds is likely to increase, assuming that the species will be able to colonize new watersheds. The numbers of watersheds considered highly or very highly resilient increases in our most optimistic scenario and decreases by 3 in our most pessimistic. However, the resulting population estimates in all three scenarios do not drop below 20,000 individuals, and the current population estimate is within the range of estimates for the scenarios where additional threats are modeled (Scenarios 2 and 3) (Table A). In the absence of major threats (Scenario 1), with no factors limiting sustained recruitment, we do not expect any stochastic impacts to affect Acmispon dendroideus var. traskiae in a significant way over the next 20 to 30 years. We therefore expect that the entire island population is likely to increase in resiliency under Scenario 1. Even under the Scenario 3, despite localized extirpations in some of the northernmost and southernmost parts of its range, the total population still only is projected to potentially see a decrease of about 1,000 individuals island-wide and may increase from current. Thus, we still expect the island population will remain resilient to normal stochastic impacts (Table A). We likewise do not expect representation or redundancy to decrease in a meaningful way. Thus, we expect that the species would be able to sustain most major catastrophic events, such as unprecedented fires, major erosion events (such as caused by periods of heavy rainfall), or an outbreak of an invasive, predatory, or pathogenic species, or a change in environmental conditions. Only an unusually severe and unprecedented catastrophic impact could threaten the viability of the species. For instance, if the fire footprint changes and more severe fires break out where the species is numerous, like along the eastern escarpment, could have major impacts to SSA Report – San Clemente Island Lotus iv March 2020 the population size, and thus, redundancy. Also, severe or extensive droughts, coupled with other

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