Species Status Assessment Report for the Chapin Mesa Milkvetch, Astragalus schmolliae
Prepared by the Western Colorado Ecological Services Field Office U.S. Fish and Wildlife Service, Grand Junction, Colorado January 2018
Photo of Chapin Mesa Milkvetch taken by USFWS employee
This document was prepared by Dara Taylor with assistance from other members of the Chapin Mesa milkvetch SSA Team, including Sarah Backsen (U.S. Fish and Wildlife Service).
Chapin Mesa milkvetch SSA Report i January 2018 Valuable peer and partner reviewers of a draft of this document were provided by Carol Dawson (Bureau of Land Management), Jennifer Ramp Neale (Denver Botanic Gardens), Erin Riggs (Utah Valley University Herbarium), David Anderson (Colorado Natural Heritage Program), Tova Spector (Mesa Verde National Park), Renee Rondeau (Colorado Natural Heritage Program), Jill Handwerk (Colorado Natural Heritage Program), and Jessica Smith (Colorado Natural Heritage Program).
Suggested reference:
U.S. Fish and Wildlife Service. 2018. Species status assessment report for the Chapin Mesa milkvetch (Astragalus schmolliae). Lakewood, CO.
Chapin Mesa milkvetch SSA Report ii January 2018 Executive Summary
This species status assessment (SSA) reports the results of the comprehensive biological status review by the U.S. Fish and Wildlife Service (Service) for the Chapin Mesa milkvetch (Astragalus schmolliae), and provides a thorough account of the species’ overall viability and, therefore, extinction risk. Chapin Mesa milkvetch is a narrow endemic perennial herb known to occur only in the southwestern corner of Colorado on land administered by Mesa Verde National Park and Ute Mountain Ute Tribal Park. This SSA report is intended to provide the best available biological information to inform the decision on whether or not Chapin Mesa milkvetch is warranted for listing under the Endangered Species Act (Act), and if so, whether and where to propose designation of critical habitat.
To evaluate the biological status of the Chapin Mesa milkvetch both currently and into the future, we assessed a range of conditions to allow us to consider the species’ resiliency, redundancy, and representation (together, the 3Rs). The Chapin Mesa milkvetch needs multiple resilient subunits distributed across its range to maintain its persistence into the future and to avoid extinction. A number of factors influence whether Chapin Mesa milkvetch subunits are considered to be resilient to stochastic events. These factors include (1) sufficient population size (density), (2) recruitment of Chapin Mesa milkvetch into the population, as evidence by the presence of all life stages at some point during the growing season, and (3) connectivity between populations. We evaluate a number of stressors that influence the health and resiliency of Chapin mesa milkvetch popuations such as: competition with nonnative invasive plant species (i.e. cheatgrass, musk thistle, etc.), wildfire, drought, fire management activities, development of infrastructure, trampling, herbivory, and climate change.
This species consists of one large interconnected population, and like many endemic (native or restricted to a certain area) plants, Chapin Mesa milkvetch is globally rare, but is locally abundant throughout its occupied habitat (Rondeau 2017, p. 1). Since Chapin Mesa milkvetch is considered to consist of one large population, for the purposes of our analysis, we divided the range of Chapin Mesa milkvetch into four representative units (Chapin Mesa, West Chapin Spur, Park Mesa, and Ute Mountain Ute Tribal Park). As we consider the future viability of the species, we believe that a greater number of self-sustaining units that are distributed across the known range of the species is associated with an overall higher viability of the species. We consider units without nonnative invasive species, development of infrastructure, and with a sufficient percentage of pinyon-juniper canopy cover, an intact native understory, sufficient percentage of seedling survival, and sufficient levels of winter and spring precipitation to be the most resilient.
Chapin Mesa milkvetch SSA Report iii January 2018 Future Scenarios
The viability of the Chapin Mesa milkvetch depends on maintaining multiple self-sustaining subunits over time. Climate change models forecast warmer temperatures and a decrease in precipitation, or change in the timing and type of precipitation by the year 2035. Given our uncertainty regarding the future effects of climate change, as well as the other stressors, we predict resiliency, redundancy, and representation of Chapin Mesa milkvetch under three plausible future scenarios. The scenarios we evaluated are as follows (scenarios are discussed in greater detail in Chapter 4. Species Future Condition and Status: Scenario 1 “Optimistic” - continuation of the current land management conditions under a “Warm and Wet” future climate change model; Scenario 2 “Moderate” - slight increase in fire management actives (i.e. fuels reduction activities) and infrastructure development under a “Moderately Hot” future climate change model; Scenario 3 “Pessimistic” - significant increase in fire management activities and infrastructure development under a “Hot and Dry” future climate change model. We evaluate each of these scenarios in terms of how it would be expected to impact resiliency, redundancy, and representation of the species by the year 2035.
Summary
We anticipate that the largest Chapin Mesa milkvetch representative unit, Chapin Mesa, will continue to be occupied under all three scenarios, but with reduced levels of resiliency. Under Scenario 3 we do anticipate that there will be a reduction in resiliency, redundancy, and representation; which may put the species at an increased risk of stochastic and catastrophic events, such that the smaller representative units may no longer be occupied by Chapin Mesa milkvetch. However, this species inherently has, and has likely always had, a low level of redundancy and representation due to its narrow endemism. Because there is only one large representative unit and three very small units; this species is already at some risk of catastrophic events and may have low adaptability to changing conditions.
Chapin Mesa milkvetch SSA Report iv January 2018 Table of Contents Executive Summary ...... iii Table of Contents ...... v List of Figures and Tables...... iii Chapter 1: Introduction ...... 1 Chapter 2- Species Ecological Needs ...... 3 2.1 Biology and Life History...... 3 2.1.2. Historical and Current Range and Distribution ...... 4 2.1.3. Life History...... 7 2.2. Habitat ...... 8 2.3. Individual Needs ...... 8 2.4. Population Needs ...... 12 2.5 Species Needs ...... 13 Chapter 3. Current Condition ...... 14 3.1 Stressors Affecting Chapin Mesa milkvetch and Habitat ...... 14 3.2 Metrics for Evaluating Current Condition ...... 24 3.3 Description of Current Conditions ...... 28 3.4 Current Condition - Resiliency, Redundancy, and Representation ...... 33 Chapter 4. Species Future Condition and Status ...... 35 4.1 Characterization of Species’ Resiliency, Redundancy, and Representation by Future Scenarios ...... 38 Scenario 1 – Optimistic Scenario ...... 38 Scenario 2 – Moderate Scenario ...... 39 Scenario 3 – Pessimistic Scenario ...... 40 4.2 Summary of Evaluation of Scenarios ...... 42 Literature Cited ...... 42 Appendix A – Cause and Effects Tables ...... 46 Appendix B - Current Condition Tables ...... 56
Chapin Mesa milkvetch SSA Report v January 2018 LIST OF FIGURES AND TABLES
PHOTO TAKEN BY USFWS EMPLOYEE ...... ERROR! BOOKMARK NOT DEFINED. FIGURE 1. CHAPIN MESA MILKVETCH RANGE ...... 6
TABLE 1. RESOURCE NEEDS BY LIFE STAGE ...... 9
TABLE 2. ANNUAL LIFE CYCLE GANTT CHART ...... 10
FIGURE 2. ANNUAL LIFE CYCLE CONCEPTUAL MODEL ...... 11
FIGURE 3. CORE CONCEPTUAL MODEL FOR THE CHAPIN MESA MILKVETCH ...... 13
FIGURE 4. INFLUENCE DIAGRAM FOR THE CHAPIN MESA MILKVETCH ...... 15
FIGURE 5. FIRE HISTORY ON MESA VERDE NATIONAL PARK ...... 17
TABLE 3. EXISTING AND PROPOSED IMPACTS FROM FIRE MANAGEMENT ACTIVITIES IN CHAPIN
MESA MILKVETCH HABITAT IN MESA VERDE NATIONAL PARK FROM THE DRAFT
CONSERVATION PLAN (MVNP 2018, P. 13)...... 22
TABLE 4. EXISTING AND PROPOSED IMPACTS FROM DEVELOPMENT OF INFRASTRUCTURE IN CHAPIN
MESA MILKVETCH HABITAT IN MESA VERDE NATIONAL PARK FROM THE DRAFT
CONSERVATION PLAN (MNVP 2018, P. 17) ...... 23
FIGURE 6. CHAPIN MESA MILKVETCH REPRESENTATIVE UNITS ...... 25
TABLE 5. ACREAGE OF REPRESENTATIVE UNITS ...... 26
TABLE 6. METRICS USED TO MEASURE CURRENT CONDITION...... 32
TABLE 7. OVERALL CURRENT CONDITIONS ...... 33
TABLE 8. QUALITATIVE METRICS USED TO MEASURE FUTURE CONDITION ...... 38
TABLE 9. FUTURE CONDITION | SCENARIO 1 - OPTIMISTIC ...... 39
TABLE 10. FUTURE CONDITION | SCENARIO 2 - MODERATE ...... 40
TABLE 11. FUTURE CONDITION | SCENARIO 3 - PESSIMISTIC ...... 41
Chapin Mesa milkvetch SSA Report iii January 2018 Chapter 1: Introduction
Chapin Mesa milkvetch (Astragalus schmolliae), formerly known as Schmoll’s milkvetch, is a narrow endemic upright perennial herb that is primarily found on the tops of mesas in Southwestern Colorado in Montezuma County. Chapin Mesa milkvetch has been a candidate for listing under the Endangered Species Act of 1973 as amended (Act), since 2010 (75 FR 78514, December 15, 2010). The Species Status Assessment (SSA) is intended to be an in-depth review of the species’ biology and threats, an evaluation of its biological status, and an assessment of the resources and conditions needed to maintain populations over time (i.e. 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 listing to consultations to recovery. As such, the SSA Report will be a living document upon which other documents such as listing rules, recovery plans, and 5-year reviews would be based if the species warrants listing under the Act.
This SSA Report for Chapin Mesa milkvetch is intended to provide the biological support for the decision on whether or not to propose to list the species as threatened or endangered under the Act and, if so, where to propose designating critical habitat. The SSA Report does not result in a decision by the Service on whether this species should be proposed for listing as a threatened or endangered species under the Act. Instead, this SSA Report provides a review of the available information strictly related to the biological status of Chapin Mesa milkvetch. The listing decision will be made by the Service after reviewing this document and all relevant laws, regulations, and policies, and the results of a proposed decision will be announced in the Federal Register, with opportunities for public input if appropriate.
For the purpose of this assessment, we generally define viability as the ability of Chapin Mesa milkvetch to sustain a population in the wild over time. Using the SSA framework, we consider what the species needs to maintain viability by characterizing the status of the species in terms of the three conservation biology principles of resiliency, redundancy, and representation (Service 2016, entire).
• Resiliency describes the ability of a species to withstand stochastic disturbance. Resiliency is positively related to population size and growth rate and may be influenced by connectivity among populations. Generally speaking, populations need abundant individuals within habitat patches of adequate area and quality to maintain survival and reproduction in spite of disturbance.
• Redundancy describes the ability of a species to withstand catastrophic events; it is about spreading risk among multiple populations to minimize the potential loss of the species from catastrophic events. Redundancy is characterized by the presence of
Chapin Mesa milkvetch SSA Report 1 January 2018 multiple, resilient populations distributed within the species’ ecological settings and across the species’ range. It can be measured by population number, resiliency, spatial extent, and degree of connectivity. Our analysis explores the influence of the number, distribution, and connectivity of subpopulations on the species’ ability to withstand catastrophic events (e.g., rescue effect).
• Representation describes the ability of a species to adapt to changing environmental conditions over time. It is characterized by the breadth of genetic and environmental diversity within and among populations. Measures may include the number of varied niches occupied, the gene diversity, heterozygosity or alleles per locus. Our analysis explores the relationship between the species life history, the influence of environmental factors on Chapin Mesa milkvetch phenology (is the study of the timing of life cycle events at the population level, most often in relation to climate), and the species’ ability to adapt to changing environmental conditions over time.
Our approach for assessing Chapin Mesa milkvetch viability involved three stages. In Stage 1, we described the species’ ecological requirements for survival and reproduction at the individual, population, and species levels using the 3Rs. In Stage 2, we assessed the species’ current condition in relation to the 3Rs (resiliency, redundancy, and representation) and ongoing factors (risk and beneficial factors) that led to the species’ current condition. In Stage 3, using the baseline conditions established in Stage 2 and the predictions for future risk and beneficial factors, we projected the future condition of Chapin Mesa milkvetch.
The species’ ecological needs (Stage 1) are summarized in Chapter 2; the current condition of the species and habitat (Stage 2) is summarized in Chapter 3; and the species future condition and status (Stage 3) are summarized in Chapter 4.
Chapin Mesa milkvetch SSA Report 2 January 2018 Chapter 2- Species Ecological Needs
In this chapter, we provide basic biological information about the Chapin Mesa milkvetch, including its physical environment, taxonomic history and relationships, morphological description, and reproductive and other life history traits. We then outline the resource needs of individuals, populations, and the species as a whole. Here we report those aspects of the life history of the Chapin Mesa milkvetch that are important to our analysis. Data on this species was provided by Mesa Verde National Park, Colorado Natural Heritage Program, and the Ute Mountain Ute Tribe.
2.1 Biology and Life History
Taxonomy The Chapin Mesa milkvetch was first collected in 1890 by Alice Eastwood, but was misidentified as a relative of Astragalus coltonii (Colton’s milkvetch), because the specimen was no longer in flower (Peterson 1981 p. 4). It wasn’t until 1945 when it was formally recognized as a species, when C.L. Porter named it “Astragalus schmolliae” after Dr. Hazel Marguerite Schmoll (Porter 1945, pp. 100-102; Barneby 1964, pp. 277-278; Isely 1998, p. 417). Chapin Mesa milkvetch is a member of the family Fabaceae (legume family), and was previously known by the common name Schmoll’s milkvetch. The new common name of Chapin Mesa milkvetch was proposed in 2015 to replace Schmoll’s milkvetch. Representatives from Mesa Verde National Park (MVNP), the Ute Mountain Ute Tribe, Colorado Natural Heritage Program (CNHP), and the U.S. Fish & Wildlife Service (Service) agreed that it is appropriate to associate the species’ common name with its location. Therefore, we have accepted Chapin Mesa milkvetch as the new common name for Astragalus schmolliae. The current accepted classification is:
Class: Magnoliopsida Subclass: Rosidae Order: Fabales Family: Fabaceae Genus: Astragalus Species: Astragalus schmolliae
General Description The stems of Chapin Mesa milkvetch are purplish below, green above, tall (45-60 centimeters (cm)), branching from the base, with short, stiff appressed hairs (lying closely and flatly against the plant’s surface) on the foliage. Leaves are pinnate with 11-13 linear leaflets, 1-2 millimeters (mm) wide, 1-3 cm long. Flowers are yellowish-white or cream colored; 12-13 cm long with
Chapin Mesa milkvetch SSA Report 3 January 2018 bracts that extend under the flower that have black hairs. The distinguishing characteristic of the species is the leathery pod. Pods are almost straight when immature, but at maturity the lower (dorsal) suture is concave, and the upper (ventral) suture is convex, making the pod curve downward. Pods are 25-40 mm long, 2-4 mm wide, obcordate (in the shape of a heart with the pointed end at the base) in cross section, without an internal septum, 10-15 seeds per pod (Porter 1945 in Peterson 1981, p. 5).
2.1.2. Historical and Current Range and Distribution
The historical range of this species, prior to being described in 1945, is unknown. We have no information to indicate that the historical range differs from or is the same as the current range.
Chapin Mesa milkvetch’s global distribution is constrained almost entirely to Chapin Mesa within Mesa Verde National Park and the Ute Mountain Ute Tribal Park in southern Colorado, with some outlying subunits on neighboring Park Mesa and West Chapin Spur (Figure 1) (Rondeau 2017, p. 1). Chapin Mesa milkvetch habitat occupies approximately 2,000 ac (809 ha) in Mesa Verde National Park (CNHP 2010, pp. 12–19; Anderson 2004, p. 25, 30). This species is considered to consist of one large interconnected population, and like many rare plants, Chapin Mesa milkvetch is globally rare, but is locally abundant throughout its occupied habitat (Rondeau 2017, p. 1). Similar habitat is widespread on nearby mesas where the species has not been found; suggesting that the species’ distribution may be limited by habitat variables that are not yet understood (Anderson 2004, p. 8; Anderson 2017, pers. comm.). In previous years, all of the mesas within Mesa Verde National Park have been visited and walked extensively but no other populations have been found (Anderson 2017 pers. comm.).
On the Ute Mountain Ute Tribal Park, populations have been identified and appeared to be more abundant on the western aspect compared to the eastern aspect of Chapin Mesa (Clow 2017, pers. comm.); however it is unclear at this time how much occupied habitat occurs on the Ute Mountain Ute Tribal Park, because formal surveys have not been done there.
We do not have precise or recent data pertaining to total population size for the species; however estimates from the early 2000s range from 294,499 – 482,786 Chapin Mesa milkvetch plants on Mesa Verde National Park, with earlier estimates higher than later estimates (Anderson 2004, p.30; CNHP 2010, pp. 1-21). We do not know the density or extent of the population on the Ute Mountain Ute Tribal Park. Regular monitoring has occurred in Mesa Verde National Park since 2001 in established monitoring plots. However, the demography plots do not represent a random sample, and cannot be used to estimate population size or overall population density. In addition, there is a data collection gap from 2003-2011. The plots include areas that have been burned by wildfires (areas where pinyon-juniper canopy cover has been reduced to zero), and areas that have not been burned. Based on this monitoring, we cannot detect an upward or downward trend in this rare plant population, or a difference in density between burned/unburned areas in Mesa Verde National Park (Rondeau 2016, p. iii). The data suggests that burned plots
Chapin Mesa milkvetch SSA Report 4 January 2018 may be losing density in comparison to the unburned plots; however, additional monitoring is needed to confirm this trend (Rondeau 2017c, pers.comm.). For specific years, there were significant differences between burned and unburned plots. For five years sampled after a fire (2003, 2011-2014) the burned plots had higher densities of Chapin Mesa milkvetch plants than did unburned plots, and the difference was significant in 2011 and 2012. For three subsequent years (2015-2017) the unburned plots had higher densities, but these differences were not significant in any year. In 2015, the number of plants emerging in monitored plots increased to their second highest density since monitoring began in 2001, likely due to above average winter precipitation (Rondeau 2016, p 10-14).
Chapin Mesa milkvetch SSA Report 5 January 2018
Figure 1. Chapin Mesa milkvetch Range
Chapin Mesa milkvetch SSA Report 6 January 2018 2.1.3. Life History
Chapin Mesa milkvetch plants emerge in early spring and usually begin flowering in late April or early May. Flowering continues into early or mid-June (Friedlander 1980, p. 63, Peterson 1981, p. 14). Fruit set begins in late May and occurs through June, and by late June most fruits, while still attached to the plant, have opened and released their seeds. The typical plant life span of Chapin Mesa milkvetch is unknown, but individuals are thought to live up to 20 years (Colyer 2002 in Anderson 2004, p. 11). During very dry years, and like many other Astragalus species, the plants can remain dormant with no above-ground growth (Colyer 2003 in Anderson 2004, p. 11). However, some plants will remain dormant even during years with seemingly favorable conditions (Spector 2017d, pers. comm.). Species of Astragalus can exhibit adult whole-plant dormancy with no production of annual shoots during a growing season or portion of a growing season (Lesica 1995, Van Buren and Harper 2003 in DBG 2016, p. 3). Emergence of above- ground stems from mature Chapin Mesa milkvetch plants and corresponding stem abundance is highly correlated with the amount of winter precipitation (Rondeau et al. 2016, p. 10-11).
Seed viability is high, between 94 and 100 percent (Anderson 2004, p. 49), and the patterns of seed germination suggest the species maintains a persistent seed bank (Anderson 2004, p. 47). The longevity of seeds of Chapin Mesa milkvetch is not known, but many legumes, including members of the genus Astragalus, have seeds as long-lived as 97 years old (Anderson 2004, p.48). Recruitment appears to be highly episodic, and is probably greatest in years that are moist in April through May (Anderson 2004, p. iv; Rondeau et al. 2016, p.16). Studies of other Astragalus species indicate that the group generally possesses hard impermeable seed coats with a strong physical germination barrier. As a result, the seeds are generally long-lived in the soil and only a small percentage of seeds germinate each year (Morris et al. 2002, p. 30). However, we do not know if the seed germination strategy for other Astragalus species is comparable to the strategy used by the Chapin Mesa milkvetch. Most Chapin Mesa milkvetch seedlings germinate between April and June after at least three days of moist soil conditions from spring moisture (Rondeau et al. 2016, p. 18).
Reproduction Chapin Mesa milkvetch requires pollination by insects to set fruit; flowers require a strong insect for pollination because the insect must force itself between the petals of the papilionaceous (butterfly shaped) flowers (Green 2012, p. 2). However, the reproductive biology of Chapin Mesa milkvetch has not been widely studied, particularly in regards to pollination requirements. In 2012, a reproductive mechanism study was conducted for the Chapin Mesa milkvetch (Green 2012, pp. 1, 4-5). Geitogamy (the fertilization of a flower by pollen from another flower on the same or genetically identical plant involving a pollinating agent), autogamy (self-fertilization), and xenogamy (fertilization of a flower by pollen from a flower on a genetically different plant involving a pollinating agent) treatments were done on twelve caged plants. The geitogamy and autogamy treatments produced significantly fewer fruits, with flowers producing fruit less than
Chapin Mesa milkvetch SSA Report 7 January 2018 10% of the time, and with some of the pods more than 20% smaller than the average size and barren of seeds. The xenogamy treatment resulted in 60% of flowers successfully producing fruit. These results are a strong indication that Chapin Mesa milkvetch is an obligate entomophile (requiring insects to transport pollen) (Green 2012, p. 5). The most frequently observed pollinator was the long horned bee (Eucera fulvitarsis); other observed pollinators were Anthophorid bees and Bombyliid flies (Green 2012, pp. 1, 4-5). Reproductive anatomy is not present on seedlings or yearling Chapin Mesa milkvetch plants, indicating that the plant does not become reproductively viable until approximately five or more years of age (Rondeau 2017b pers. comm.).
2.2. Habitat
The habitat for Chapin Mesa milkvetch is dense pinyon-juniper woodland of mesa tops in the Mesa Verde area and the Ute Mountain Ute Tribal Park at elevations between 1,981 to 2,286 meters (m) (6,500 to 7,500 feet (ft)) (Anderson 2004, p. ii). It grows primarily in deep red loess soil on mesa tops in old-growth or recently burned pinyon-juniper woodlands (Rondeau 2017, p.1). No Chapin Mesa milkvetch plants are found in the mountain shrublands at upper elevations on Mesa Verde. The old growth pinyon-juniper woodlands in the Mesa Verde area are considered to be a relatively rare vegetation type, with mean stand ages of 400 years (Floyd et al. 2004, p. 269). Pinyon-juniper trees are easily killed by fires and are slow to regenerate (Romme et al. 2003, p 344.). The fire regime of the pinyon-juniper woodlands on the mesa tops of the Mesa Verde area is characterized by lightning caused, infrequent (~400-year rotation) stand- replacing fires, as opposed to low-severity, stand-thinning fires (Romme et al., 2003; Floyd et al. 2004, p. 286). Large scale, stand replacing fires in the Mesa Verde area correlate with drought periods, especially following periods of significantly low precipitation in May or the preceding winter (October through March) (Floyd et al. 2015, p. 269). In 2012, nine plants were found in Navajo Canyon and seven along canyon benches near Square Tower House and Oak Tree House; suggesting that Chapin Mesa milkvetch is not limited to mesa tops, although mesa tops remain the species’ core habitat (Anderson 2004, p. 33, Spector 2017d, pers. comm.). Density and abundance of Chapin Mesa milkvetch in these locations are low, although the species does flower and produce seed there (Spector 2017d, pers. comm.).
2.3. Individual Needs
In this section, we describe and evaluate the resource needs and/or the circumstances that are necessary for Chapin Mesa milkvetch at the individual level.
We evaluate the individual needs of Chapin Mesa milkvetch in terms of the resource needs and/or the circumstances that are necessary to complete each stage of the life cycle, including adults, yearlings, seedlings, and seeds. The life history of Chapin Mesa milkvetch is closely tied
Chapin Mesa milkvetch SSA Report 8 January 2018 to its specific habitat requirements for all stages of the species’ life cycle. Therefore, the species’ specific habitat is a necessary and integral part of each stage of the life cycle.
The density of Chapin Mesa milkvetch is strongly correlated with winter precipitation; years with “wet” winters (precipitation falling primarily as snow) precede high density counts and years with dry winters translate to low or no emergence (Rondeau 2017, p. 3). This pattern is evident regardless of whether the habitat has been burned or not (as explained further below). Climate requirements for seedling emergence and survival are not well known; however, we infer that spring moisture is also critical, as seedling survival relies on growing deep roots quickly (Rondeau 2017, p. 9). It is likely that winter moisture coupled with winter temperature is also important for seedlings due to available soil moisture for seedling survival (Rondeau 2017, p. 16). Large pollinators are essential to adult Chapin Mesa milkvetch individuals for fruit production. Table 1 summarizes the resources that are needed by life stage. Table 2 and Figure 2 depict the life stages of the species throughout the year, as well as a detailed life cycle model for Chapin Mesa milkvetch.
Table 1. Resource Needs by Life Stage
Life Stage Resources Resource Function Deep reddish loess soils, pinyon-juniper over story, intact native understory, elevation, mesa Habitat, nutrition, and Seeds tops, soil nutrients, precipitation, and available dispersal. soil moisture. Deep reddish loess soils, pinyon-juniper over story, intact native understory, elevation, mesa Seedlings Habitat and nutrition. tops, soil nutrients, precipitation, and available soil moisture. Deep reddish loess soils, pinyon-juniper over Yearlings/immature story, intact native understory, elevation, mesa Habitat and nutrition. tops, soil nutrients, and precipitation. Deep reddish loess soils, pinyon-juniper over story, intact native understory, elevation, mesa Habitat, nutrition, and Adults tops, soil nutrients, large pollinators, and reproduction. precipitation.
Chapin Mesa milkvetch SSA Report 9 January 2018 Table 2. Annual Life Cycle Gantt Chart
Life Stage Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Seed germination* Emergence* Flowering Fruit set Seeds released Vegetative state Senescence* Dormancy* *The seed germination strategy is unknown for Chapin Mesa milkvetch; this time frame is based off of the knowledge of other Astragalus species that may or may not be comparable. This plant can remain dormant with no above-ground growth during very dry years; the lighter color of pink is used to depict this. Emergence is the penetration of the soil surface by a plant (adult/yearling). Plant senescence is the process of aging in plants.
Chapin Mesa milkvetch SSA Report 10 January 2018
Figure 2. Annual Life Cycle Conceptual Model depicting transition of life stages described in Table 2.
Chapin Mesa milkvetch SSA Report 11 January 2018 Uncertainties relating to Individual Needs
The life cycle of the Chapin Mesa milkvetch is not fully understood. We do not know the life span of individuals, although it is expected that this plant may live for twenty or more years (Rondeau 2017b pers. comm.). We do not know how long Chapin Mesa milkvetch individuals remain immature before they become reproductive adults, although it is hypothesized that individuals are reproductive after five or more years (Rondeau 2017b pers. comm.). It is unclear how long seeds remain viable in the seedbank; however, we do know that they remain viable for at least 14 years (Rondeau 2017b pers. comm.). We do not fully understand the factors that define and constrain this species to its small range. There are potentially suitable mesas adjacent to Chapin Mesa that appear to have similar habitat characteristics, but the species is not found there (Spector 2017d, pers. comm.).
2.4. Population Needs We evaluate the population needs of the Chapin Mesa milkvetch in terms of what is required for self-sustaining subunits. The measure of resiliency is based on a population’s ability to withstand or recover from environmental or demographic stochastic events, such as changes in precipitation or decreased plant density, for example. We evaluate resiliency in terms of resources and/or the circumstances that are necessary to maintain population abundance, distribution, high plant densities, and reproduction.
The following conditions are needed to support self-sustaining subunits:
• Plant Density – we believe that density may be an indication of the suitability of conditions and habitat that are present; because in areas where plant density is high, the species’ resource needs are available. We expect that Chapin Mesa milkvetch needs some level of density for this population to be sustainable; however, we do not have the information to quantify what level of density is needed at this time. • Connectivity – in order for Chapin Mesa milkvetch populations to be self-sustaining, they need to be connected such that gene flow is occurring between units. In order to have connectivity, occurrences of the species must be approximately 1km or less from each other; the 1km distance is based on dispersal distances that pollen or seed can travel from an existing location to a new location (Nature Serve 2002, p. 24-26) via pollinators or wind and water dispersal of seeds. • Recruitment – in order for Chapin Mesa milkvetch to be sustainable, the population must maintain a sufficient level of recruitment to persist; however, we do not have information to quantify the rate of recruitment needed.
Chapin Mesa milkvetch SSA Report 12 January 2018 These demographic or distribution factors that subpopulations need to be resilient are influenced by the presence of habitat or resource factors, which correspond to individual needs. These influences are displayed in the core conceptual model in Figure 3.
Uncertainties Relating to Population Needs
We lack demographic information for most Chapin Mesa milkvetch representative units aside from the Chapin Mesa unit, where some demographic monitoring has occurred. Without sufficient demographic information, we are unable to quantify the specific levels of each demographic factor that the subunits need. However, we know that these factors must be present at sufficient levels for the population to maintain itself and have the resiliency to withstand stochastic events.
Figure 3. Core conceptual model for the Chapin Mesa milkvetch depicting the relationship between habitat and resource needs, resource functions, and demographic and distribution factors contribute to population resiliency.
2.5 Species Needs We evaluate the species’ needs in terms of the resources and/or the circumstances that support the redundancy and representation of the species. Therefore, we evaluate the redundancy of this species by the number of representative units, the size of each representative unit, and the density of Chapin Mesa milkvetch throughout each representative unit. Having multiple representative units would spread the risk of a catastrophic event, such as large-scale stand-replacing fires, affecting the whole species.
Chapin Mesa milkvetch SSA Report 13 January 2018 Representation of Chapin Mesa milkvetch is evaluated based on the presence of multiple, self- sustaining representative units within one large population across the range of the species, and their contributions to providing adaptive capacity to the species in the face of changing conditions. Each representative unit provides the same habitat characteristics that are essential for Chapin Mesa milkvetch.
In summary, in order to maintain viability, Chapin Mesa milkvetch needs multiple, self- sustaining representative units throughout its range to provide representation and redundancy.
Uncertainties Relating to Species Needs
We do not know if each Chapin Mesa milkvetch representative unit is functioning the same way; however, we do have anecdotal evidence that all representative units (except for Park Mesa) are functioning similarly. The populations on Park Mesa are smaller than in the other units, and nearby suitable habitat is not occupied. We do not know the extent of occupied habitat on the Ute Mountain Tribal Park representative unit. Therefore, we do not know precisely how many units are needed to provide sufficient redundancy and representation to the species, although we have no information that the species has ever been more widespread than it is currently.
Chapter 3. Current Condition
In this chapter, we describe the current condition of the Chapin Mesa milkvetch. We first provide a summary of potential stressors affecting the species, followed by our methodology for evaluating the current condition, and then a specific description for each factor that describes the current condition.
3.1 Stressors Affecting Chapin Mesa milkvetch and Habitat Potential stressors to the Chapin Mesa milkvetch include invasive nonnative plants, wildfires, post-fire mitigation, wildfire and fuels management, trampling and herbivory, development of infrastructure, drought, and climate change. We evaluated each potential stressor, including its source, affected resources, exposure, immediacy, geographic scope, magnitude, and impacts on individuals and populations, and our level of certainty regarding this information, to determine which stressors were likely to be drivers of the species current condition. Here, we summarize how each of these stressors may influence the current condition of the species, both individually and cumulatively; see Appendix A for our complete analysis and more detailed information on the effects of these stressors. The influence diagram in Figure 4 displays the resource needs of individuals and populations of the species, and how those needs are affected by environmental or anthropogenic stressors.
Chapin Mesa milkvetch SSA Report 14 January 2018
Figure 4. Influence diagram for the Chapin Mesa milkvetch
Invasive Nonnative Plants (including cheatgrass and invasive thistle)
Invasive nonnative plants can affect Chapin Mesa milkvetch through the indirect effects of invasion (i.e. competition for space, nutrients, and water). This invasion is facilitated by the increased frequency of burns as well as the creation of fire breaks that has occurred within Chapin Mesa milkvetch habitat (CNHP 2006, p.4). Cheatgrass, a non-native species, is just one of the many species that have been favored by burning (Floyd et al. 2006, p.1). Pinyon-juniper woodlands that have burned extensively by wildfires in the past two decades are being replaced by significant invasions of nonnative species, especially cheatgrass (Bromus tectorum), musk thistle (Carduus nutans), and Canada thistle (Cirsium arvenses) (Floyd et al. 2006, p. 1). The abundance of grasses, especially cheatgrass, western wheatgrass (Pascopyrum smithii), and smooth brome (Bromus inermis), is outside the natural range of variation; resulting in a lack of bare ground and biological soil crust (Rondeau 2017, pers. comm.). This “novel grassland” is preventing natural succession or return to the pinyon-juniper woodland habitat that Chapin Mesa milkvetch needs, and is also reducing the reproductive vigor of Chapin Mesa milkvetch (Rondeau 2017, pers. comm.). Under “normal” conditions, a post-fire area should be dominated by bunch grasses, such as mutton grass (Poa fendleriana), Indian rice grass (Oryzopsis hymenoides), and needle-and-thread grass (Hesperostipa comata), abundant forbs, and bare ground; that would then slowly succeed into a shrub/grass/ forb mix into a dense pinyon-juniper woodland (Rondeau 2017, pers. comm., Spector 2017d, pers. comm.). Grass cover, especially cheatgrass, may be inhibiting seedling emergence and survival of Chapin Mesa milkvetch
Chapin Mesa milkvetch SSA Report 15 January 2018 (Rondeau 2017, pers. comm.). Cheatgrass and other invasive nonnative plant species have already invaded different parts of the species range to varying degrees. Cheatgrass was not found in the unburned woodland monitoring plots, whereas cheatgrass invasion ranges from 8- 58% cover in the burned monitoring plots (Rondeau 2017, p. 11). We do not have percent cover information on other invasive species within Chapin Mesa milkvetch habitat at this time.
Wildfire
Five large, high intensity fires in the two decades have occurred on most of the park and a large portion of the adjacent Mesa Verde cueasta (i.e., long, sloping ridge), resulting in burns on a total of 38,704 acres (Floyd et al. 2004, p. 270, 283); and a total of approximately 760.5 acres of Chapin Mesa milkvetch habitat that has been burned in Mesa Verde National Park. Wildfire can affect Chapin Mesa milkvetch and its habitat by eliminating the fire sensitive pinyon-juniper woodlands and native understory, thereby opening up habitat to be colonized by nonnative grasses and clonal shrub species; degraded habitat is not as suitable or favorable for the species leading to species decline over time (Spector 2017a pers. comm.). Wildfires also positively influence Chapin Mesa milkvetch habitat by increasing the amount of nutrients that are available (i.e. phosphorus); however it is not known if this affects the fecundity (the ability to produce an abundance of offspring or new growth) of Chapin Mesa milkvetch (Anderson 2004, p. 39). After the 2002 Long Mesa Fire, initial monitoring showed positive effects on Chapin Mesa milkvetch; it appears that the species benefited initially from the large scale burn, resulting in a high recruitment rate (Rondeau 2017, p. i). However, by 2015-2016 the recruitment and reproductive output of the species in the burned area was far below that in the unburned woodland, suggesting that fires have an overall long-term negative impact, and that Chapin Mesa milkvetch is essentially a woodland species (Rondeau 2017, p. i). The total number of plants, or overall density (plants/m2), were similar between burned and unburned sites, but there were stark differences in age class; burned areas have been observed to have more immature and adult plants, and fewer seedlings and yearlings than unburned areas (Rondeau 2017, p. 5). On average there were 45% more immature and adult plants in burned areas, probably reflecting the reproductive flush following the 2002 Long Mesa Fire (Rondeau 2017, p.5).
In the Chapin Mesa representative unit (1980 acres), 715 acres (36.11 %) were burned in the Long Mesa and Soda Canyon fires in 2002 and 2008 respectively. In the Park Mesa representative unit (eight acres), 0.5 acres (6.63%) was burned by the Chapin 5 fire in 1996. In the West Chapin Spur representative unit (52 acres), 45 acres (85.71%) was burned by the Long Mesa fire in 2002 (see Figure 5 below). The extent of fire impacts on this species on the Ute Mountain Ute Tribal Park is not known at this time. We do not know how fire affects the seed bank at this time.
Chapin Mesa milkvetch SSA Report 16 January 2018
Figure 5. Fire History on Mesa Verde National Park
Chapin Mesa milkvetch SSA Report 17 January 2018 Drought
Drought may negatively affect Chapin Mesa milkvetch. In 2002, severe drought caused most Chapin Mesa milkvetch individuals to remain dormant (Anderson 2004, p. 4). The total annual precipitation measured at Mesa Verde in 2002 was 28 cm (11 in.), well below the average of 44 cm (17.5 in.) from 1948 to 2003. However, there were 5 years between 1948 and 1989 where Mesa Verde received less than 28 cm (11 in.) of precipitation. It is likely that drought is common enough that Chapin Mesa milkvetch can recover from its effects (Anderson 2004, p. 35), provided that severity and duration of drought does not exceed historical levels, or that nonnative plant invasion does not increase significantly as a result. Periodic drought causes Chapin Mesa milkvetch plants and seedlings to dry out during a given year, and contributes to increased fire frequency and nonnative plant invasion. We expect that short-term drought has a low-level direct impact on the species and it also indirectly facilitates cheatgrass invasion and increased fire frequency.
Droughts comparable to 2002 (precipitation 55% below average) and 2012 (precipitation 38% below average) occur on average every five years, historically. Climate change projections for the San Juan Basin, Colorado include increased temperatures, more intense and longer-lasting heat waves, and a longer fire season with greater frequency and extent of fires, and an increased probability of drought that is worsened by higher temperatures, heavier downpours, increased flooding, and increased erosion. Average annual temperatures are projected to be 3-5°F higher than the 1970-2000 average by 2035 (Rondeau et al. 2017).
The emergence of Chapin Mesa milkvetch is strongly tied to winter precipitation and its germination and successful seedling survival is strongly tied to spring precipitation. The amount of summer monsoon moisture could affect seedling survival through desiccation, depending on the development of the seedling root system earlier in the season (Anderson 2004 p. 47). Future climate projections predict lower snowpack amounts, earlier winter warming, and warmer summers, which could reduce available moisture needed for emergence, germination, and seedling survival.
Climate Change
Climate change refers to a change in the mean or variability of one or more measures of climate (e.g., temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2007, p. 78). As shown in Figure 4, climate change can influence several of the other stressors discussed in this chapter. Climate change can impact Chapin Mesa milkvetch by altering the fire regime, altering species composition, decreasing soil health and function, and elevating fire risk (Rondeau et al. 2017, p. 18). Southwestern Colorado is already experiencing higher temperatures, more frequent and prolonged drought, earlier snowmelt, larger and more intense
Chapin Mesa milkvetch SSA Report 18 January 2018 fires, more extreme storms, and spread of invasive species—these are all changes that are expected to intensify as a result of climate change putting the species at risk (Rondeau et al. 2017, p. 1). Please refer to Chapter 4. Species Future Condition and Status for more information on the climate scenarios that were used for this analysis.
Development of Infrastructure and Fire Management
Development of infrastructure
The development of infrastructure and fire management activities can both have direct and indirect impacts on Chapin Mesa milkvetch. Areas of existing park infrastructure encompass 42.65 acres (2%) of Chapin Mesa milkvetch habitat in Mesa Verde National Park; existing park infrastructure includes roads and parking lots, a wastewater treatment facility, buildings, a safety zone, fuel breaks for Chapin Mesa, and structure protection (NPS 2015b, p. 46). Park infrastructure has been centered on the premiere archeological cliff dwellings in the southern part of the park located squarely within the small geographic range of this species (NPS 2015b, p. 39). Impacts include roads, trails, parking lots, pipelines, communications systems, sewage treatment, construction of buildings for administrative, residential, and commercial use, maintenance operations, landscaping, and human activities including waling and operating vehicles and machinery (NPS 2015b, p. 40). As a result of these activities, a considerable amount of Chapin Mesa milkvetch’s habitat can no longer support the species and some adjoining areas support fewer plants than they might otherwise (NPS 2015b, p. 40). Several additional projects are planned or under consideration within Mesa Verde National Park, such as a comfort station at the park headquarters office, a wildland fire response center and helibase, a paved multi-use trail, a bike/multi-use trail, and a Fire Management plan (Spector 2017f, pers. comm) (see Fire Management, below) that would significantly impact Chapin Mesa milkvetch habitat if they are implemented.
Fire Management
Fuels reduction activities have direct and indirect impacts to Chapin Mesa milkvetch plants and habitat (NPS 2015b, p. 46). Fuels reduction activities in Mesa Verde National Park occur in the fall and winter, when impacts to mature Chapin Mesa milkvetch plants are diminished or negligible because the seeds have matured and plants are dying back for the season (NPS 2015b, p. 46). Most fire suppression activities are expected to occur during the peak fire season (July and August) after most Chapin Mesa milkvetch seeds have matured and plant have stated to die back for the season (NPS 2015b, p. 39). Direct impacts to the plants, such as trampling during the cutting and hauling out of wood and slash, and scorching during prescribed burns, are short- term because most plants may be able to re-emerge the following spring (NPS 2015b, p. 47). Impacts to juvenile plants and seedlings are not documented, but could be greater because young plants are more delicate (NPS 2015b, p. 47). Mechanical fuels reduction activities result in a low
Chapin Mesa milkvetch SSA Report 19 January 2018 to moderate level of surface disturbance; however, fuels management activities tend to facilitate nonnative species invasion by creating disturbance favored by these species (NPS 2015b, p. 46).
Clearing for fuel reduction can impact Chapin Mesa milkvetch in the following ways: (1) above- ground stems can be directly removed; (2) plants that re-emerge the following spring can have less water available because the soil dries due to exposure to sun and wind; and (3) invasive weeds; the native grass mutton grass, and seeded native grasses can provide increased competition (NPS 2015b, p. 47). Clearing or burning for fire management may have a detrimental effect on the species when it occurs within the species’ range. As with wildfire, the indirect effect of facilitating invasion of the habitat by cheatgrass impacts the species because it increases the likelihood of more frequent fires (NPS 2015b, p 47.).
Mesa Verde National Park has completed a draft Conservation Plan for Chapin Mesa milkvetch that is still under review; this draft conservation plan provides details on how the Park intends to implement future fuels reduction and fire management activities, development of infrastructure, and conservation efforts that may impact or benefit Chapin Mesa milkvetch or its habitat (MVNP 2018, entire). Because this draft is still under review we cannot be certain if, when, or how it will be finalized or implemented, or if it will change, and as a result it is too preliminary for us to rely on. However, the draft Conservation Plan represents the most recent and best available information that we have on the Park’s intended plans for activities such as fire management.
Fuel reduction activities are proposed by the Park to be divided into 3 zones. Fuel reduction around structures would be most intense up to 30 feet in Zone 1 where vegetation would be cut to 4 inches in height (MVNP 2018, p.12). Within 30-100 feet from structures in Zone 2 cutting of vegetation would be similar to Zone 1 except that herbaceous vegetation and small clumps of woody shrubs and trees could be retained and intensity of treatment could taper off the further distance from the structure (MVNP 2018, p.12). In Zone 3 treatment at 100 to 200 feet from structures would include removal of ladder fuels, dead fuels and removal of trees to prevent canopy closure (MVNP 2018, p.12). Roadside fuel reduction will occur up to a maximum of 100 ft, and focus on removal of dead and down woody debris (MVNP 2018, p.12). Thinning will not remove more than 50 percent of canopy cover (MVNP 2018, p.12). Pile burning will be minimized in Chapin Mesa milkvetch habitat with most woody slash being hauled out by hand crews (MVNP 2018, p.12). Areas where density of Chapin Mesa milkvetch is high may not receive fuels treatment and will be left intact (MVNP 2018, p.12).
The ecological conditions for Chapin Mesa milkvetch within areas that have been cleared for fire management are different from its typical pinyon-juniper woodland habitat. Cleared areas are exposed to more sun and wind that dry the soil and the Chapin Mesa milkvetch seedlings, and cold spring season mornings expose young sprouts and blossoms to frost damage (NPS 2015b, p. 47). In addition to invasion by cheatgrass, removal of woody vegetation appears to result in
Chapin Mesa milkvetch SSA Report 20 January 2018 competitive release of native grasses. Density, reproductive effort and vigor of Chapin Mesa milkvetch are lower in these areas (Rondeau 2017, entire).
Mesa Verde National Park’s plans for fire management activities are outlined in its draft Fire Management Plan and updated in its draft Conservation Plan. If approved and implemented, these activities would alter an additional 10% (approximately 200.2 acres) of Chapin Mesa milkvetch habitat (see Table 3 and 4 below) (MVNP 2018, p. 13). The park has also been exploring a location on Chapin Mesa (within Chapin Mesa milkvetch habitat) to develop a helipad and large helibase building facility for crew and pilots. This is in addition to the other planned infrastructure development within Chapin Mesa habitat for the park (Spector 2017 pers. comm.), as discussed above.
Chapin Mesa milkvetch SSA Report 21 January 2018 Table 3. Existing and proposed impacts from fire management activities in Chapin Mesa milkvetch habitat in Mesa Verde National Park from the draft conservation plan (MVNP 2018, p. 13).
Existing Habitat Alteration Habitat Alteration (acres) Percent of CMM habitat in MEVE (2012 acres) Safety Zone 12.7 0.63 Chapin Mesa Boundary Fuel 24.9 1.24 Break Structure Protection (100 ft) 43.5 2.16
Total Existing 81.1 4.0
Proposed New Actions Proposed structure protection 43.5 2.16 (101-200 ft) Roadside treatment to 100 ft 151.2 7.5 -Zone 1 (0-30 ft ~ 68 acres) -Zone 2 (31-80 ft ~ 112 acres) -Zone 3 (81-150 ft ~ 156 acres) Soda Canyon Trail 5.5 0.3 Dead/Down Treatment to 40 ft Total Proposed 200.2 10.0
Total Proposed and 281.3 14.0 Existing
Chapin Mesa milkvetch SSA Report 22 January 2018 Table 4. Existing and proposed impacts from development of infrastructure in Chapin Mesa milkvetch habitat in Mesa Verde National Park from the draft conservation plan (MNVP 2018, p. 17)
Existing Park Infrastructure Development Percent of CMM habitat in (acres) MEVE (2012 acres) Roads/ Parking lots 38.3 1.9 Wastewater treatment 1.6 0.08 Buildings/ Water tank 2.75 0.14
Total Existing 42.65 2.1
Proposed New Actions HQ Comfort Station 0.5 0.02 Mesa Top Loop Bike Lane 6.7- 13.3 0.66 Visitor Distribution and 6 0.3 Transportation Plan Wildland Response Center 6 0.3
Total Proposed 25.8 1.3
Total Proposed and Existing 68.45 3.4
The Park’s Fire Program uses mechanical vegetation clearing around certain Park resources to mitigate for fire hazards. Much of this work focuses on areas around buildings, roads, and picnic areas on Chapin Mesa, within Chapin Mesa milkvetch habitat. Prior to vegetation removal activities, the Park’s Fire Program personnel will notify Vegetation Program personnel, who flag all emerged Chapin Mesa milkvetch plants for avoidance (NPS 2015b, p. 46). The Park is in the process of revising this draft Fire Management plan and is expecting to finalize it over the next few years (Spector 2017e, pers. comm.).
Post-fire mitigation
There have been effects to Chapin Mesa milkvetch from post-fire mitigation efforts, and future post-fire mitigation efforts may impact Chapin Mesa milkvetch. There is little information on Chapin Mesa milkvetch responses to nearby herbicide treatment and post-fire seeding as mitigation. However, the best available information does not indicate these efforts are influencing Chapin Mesa milkvetch at the population-level, therefore, we will not be carrying this forward in our analysis.
Trampling and Herbivory
Chapin Mesa milkvetch SSA Report 23 January 2018 Herbivory and trampling by feral horses, stray cattle, and mule deer can result to damage or complete loss of Chapin Mesa individuals. Feral horses can create dirt trails and large patches of disturbed bare ground within Chapin Mesa milkvetch habitat; which further encourage the spread of weedy species. Chapin Mesa milkvetch habitat overlaps with visitor access areas within Mesa Verde National Park; basic visitation activities can result in the crushing of individuals. Because these impacts have not been sufficiently studied or monitored, we do not completely understand their impacts. However, the best available information suggests that these impacts are localized and affecting individuals, but not having population-level impacts to Chapin Mesa milkvetch; therefore, we do not evaluate this stressor further in our analysis.
3.2 Metrics for Evaluating Current Condition
We have limited information on population demographics for Chapin Mesa milkvetch. Therefore, we are unable to evaluate the resiliency of Chapin Mesa milkvetch. However, we believe each unit is acting and responding to environmental conditions similarly.
Currently, there are approximately 809 ha (2,000 ac) of occupied habitat in Mesa Verde National Park and an unknown amount of occupied habitat on the Ute Mountain Ute Tribal Park; although similar habitat has been found on nearby mesas where the species has not been found. Since Chapin Mesa milkvetch is considered to consist of one large population, for the purposes of our analysis, we divided the range of Chapin Mesa milkvetch into four representative units (Chapin Mesa, West Chapin Spur, Park Mesa, and Ute Mountain Ute Tribal Park); these representative units were determined based on monitoring polygons previously established by CNHP. A large area of the Chapin Mesa unit (36.11%), the largest of the four units, was burned by a wildfire in 2002. Since ecological conditions for Chapin Mesa milkvetch vary greatly depending on whether the habitat has been recently burned, and because monitoring data are available in both burned and unburned areas on Chapin Mesa, we broke down the Chapin Mesa unit further into burned and unburned subunits. We then analyzed each representative unit under the following condition categories to determine what the current condition of each representative unit is. These categories were selected as metrics because these are some of the most important habitat and demographic factors that contribute to the resilience of Chapin Mesa milkvetch at the population level, and that we have sufficient information to analyze. Here, we describe how each of these metrics contributes to the health of Chapin Mesa milkvetch populations. Given that we do not have abundance data for each representative unit, we evaluate the current condition of the Chapin Mesa milkvetch using grass cover (non-bunch grasses), pinyon-juniper canopy cover, winter and spring precipitation, seedling survival, exotic plant species, intact native understory, and habitat loss as a proxy. We describe the current condition for the Chapin Mesa milkvetch in terms of habitat and environmental conditions for each representative unit.
Chapin Mesa milkvetch SSA Report 24 January 2018
Figure 6. Chapin Mesa milkvetch Representative Units
Chapin Mesa milkvetch SSA Report 25 January 2018 Table 5. Acreage of Representative Units
Representative Units Acres Chapin Mesa 1980 Park Mesa 8 West Chapin Spur 52 Ute Mountain Ute Tribal Unknown Park
Grass Cover (non-bunch grasses) – Grass cover refers to cheatgrass, smooth brome, and western wheat grass. We chose this category because non-bunch grasses will compete with Chapin Mesa milkvetch for space and nutrients (USFWS 2014b, in NPS 2015b, p. 47). Grass cover, especially cheatgrass, may be inhibiting seedling emergence and survival (Rondeau 2017, p. 11). Therefore, units with less non-bunch grass cover would be more conducive to healthy populations of Chapin Mesa milkvetch. We note that non-bunch grasses favor areas that have been burned.
Pinyon-juniper Canopy Cover – Pinyon-juniper canopy cover is one of many essential habitat components for Chapin Mesa milkvetch; providing shelter from direct sunlight and freezing winter conditions (Rondeau 2017, p. i). The presence of pinyon-juniper is largely a factor of the absence of large, stand replacing fires during the past centuries within a given area on the mesa tops. Temperature differences between burned and unburned areas within Chapin Mesa milkvetch habitat are most pronounced during the spring-summer growing season, with burned areas hotter than unburned (Rondeau 2017d, p.1). This is most likely due to radiation being much stronger in the burned areas, due to lack of shade from trees; the lack of trees is not as critical during the winter and fall months (Rondeau 2017d, p.1). Areas with sufficient pinyon- juniper canopy cover provide for better habitat, and therefore more resilient populations of Chapin Mesa milkvetch.
Winter Precipitation – Annual weather patterns are known to be important to plant density, reproductive output, and vigor, yet seldom do we know which climate attributes drive these metrics. Data collected by CNHP over 14 years of monitoring has revealed a strong correlation between winter precipitation (as snow) and the density of Chapin Mesa milkvetch plants (Rondeau 2017, p. 15). Monitoring data has shown that “wet” winters precede high Chapin Mesa milkvetch density counts, and dry winters translate to low or no emergence of Chapin Mesa milkvetch in the spring (Rondeau 2017, p. 15). This pattern was evident regardless of whether monitoring was conducted in burned or unburned habitat (Rondeau 2017, p. 15). Chapin Mesa milkvetch’s deep roots coupled with a complete die back each winter is conducive to taking advantage of the deep soil moisture that is provided by winter moisture, primarily as snow (Rondeau 2017, p. 15). We use winter precipitation as a proxy for density of Chapin Mesa
Chapin Mesa milkvetch SSA Report 26 January 2018 milkvetch adults/subadults, because year-to-year variation in density of adults/subadults is closely tracked with winter precipitation. Since a higher density of Chapin Mesa milkvetch plants would be expected to provide greater ability to withstand stochastic disturbance, and winter precipitation is a proxy for density, we use winter precipitation as a metric to indicate levels of resilience of Chapin Mesa milkvetch representative units.
Spring Precipitation – Seedling recruitment is another demographic factor that contributes to the resilience of Chapin Mesa milkvetch representative units (see Figure 3). However, we lack the information to measure seedling recruitment in each representative unit. Therefore, we use spring precipitation as a proxy for seedling recruitment. Spring precipitation is thought to be correlated with seedling recruitment, because it provides sufficiently moist soils that are adequate for seed germination and rapid development of deep taproots (Rondeau 2017, p. 16). Therefore, we expect that higher levels of spring precipitation would indicate higher levels of recruitment and therefore higher levels of resilience in Chapin Mesa milkvetch representative units.
Seedling Survival – Seedling survival is also a demographic factor that contributes to the resilience of Chapin Mesa milkvetch units. It is measured as the proportion of the population of Chapin Mesa milkvetch that is represented by seedlings and yearlings (Rondeau 2017, p. 9). Seedling survival was measured by Colorado Natural Heritage Program (CNHP) by way of 1m2 poker plots that are used to track Chapin Mesa milkvetch individuals from season to season and year to year (Rondeau 2017, p. 9). Low seedling survival rates in burned areas may be associated with a shallow soil water deficit during spring and summer, which is critical for seedling survival (Rondeau 2017d, p. 1). We expect that areas with high seedling survival would have higher resilience.
Exotic Plant Species – Exotic plant species refers to species such as musk thistle and Canada thistle (but does not include non-bunch grasses such as cheatgrass, which are already accounted for in the “Grass Cover” metric). We chose to include this metric to comprehensively encompass all invasive species within Chapin Mesa milkvetch habitat; exotic plant species will compete with Chapin Mesa milkvetch for space and nutrients. Therefore, we expect that representative units with fewer exotic plant species present would have healthier and more resilient Chapin Mesa milkvetch populations.
Intact Native Understory - Intact native understory is considered to be functional if all four components are present (biological soil crust, native wildflowers, bare ground, and duff) (Spector 2017a pers. comm.). Intact native understory is important for Chapin Mesa milkvetch because it supports pollinators and contributes to ecosystem stability. We expect that areas with all components of the native understory intact, and nonnative invasive species are absent or there is less than 5% cover (Spector 2017a pers. comm.), would provide for healthier and more resilient Chapin Mesa milkvetch populations. All three of these components do not have to be
Chapin Mesa milkvetch SSA Report 27 January 2018 present at the exact same spot but on a larger spatial scale (50 to 100 m2) (Spector 2017a pers. comm.).
Habitat Loss – For the purpose of this assessment, habitat loss refers to habitat lost due to the development of infrastructure. Visitor use areas in Mesa Verde National Park overlap with Chapin Mesa milkvetch habitat and have already experienced a significant amount of loss to Chapin Mesa milkvetch habitat; the Park is currently in the process of planning for more development, some of which will overlap with Chapin Mesa milkvetch habitat. We currently do not know the extent of habitat loss on the Ute Mountain Ute Tribal Park; however, based on verbal communications with the tribe, we expect that it is low. We expect that Chapin Mesa milkvetch representative units with less area impacted by development will have greater resiliency.
3.3 Description of Current Conditions Chapin Mesa milkvetch habitat is maintained in a state of dynamic equilibrium (ecological balance). With suitable habitat consisting of pinyon-juniper canopy cover, intact native understory, and deep reddish loess soils; changes to this vegetation condition could alter this equilibrium. Decreased pinyon-juniper canopy cover within habitat (decrease of 50% or more in pinyon-juniper cover) could result in habitat conditions that are degraded and not as suitable or favorable for Chapin Mesa milkvetch and could lead to species decline overtime in degraded areas (Spector 2017a pers. comm.). This is because loss of pinyon-juniper cover could result in a decreased insulative value (protection from extreme hot or cold temperatures) and a decrease in the shade needed by Chapin Mesa milkvetch for protection from sun exposure and desiccation (please refer to Appendix B - Current Condition Tables).
Based on our GIS analysis, an estimated 825 ha (2,040 ac) of Chapin Mesa milkvetch occupied habitat is present within the Mesa Verde National Park. Evaluation of habitat for each of the representative units indicates that 97% of the species habitat within Mesa Verde National Park is on Chapin Mesa, 2.5% of is on West Chapin Spur, and 0.5% is on Park Mesa. In addition, because the Chapin Mesa representative unit is so large, we further subdivided this unit into burned and unburned sub-units (containing 36.11% and 63.89% of the unit, respectively) because the ecological conditions for Chapin Mesa milkvetch differ across these areas. These values represent the acres of verified occupied habitat plus the acres of suitable habitat; these values were calculated from GIS shapefiles provided by the Mesa Verde National Park. We are not able to quantify the amount of habitat on the Ute Mountain Ute Tribal Park representative unit, because little data has been collected thus far on the species habitat in that unit. We consider each representative unit to be well connected because all representative units are less than 1 kilometer (km) from each other, and gene flow (through seed dispersal and pollen) is expected to be occurring between them. The Park Mesa representative unit may be separated from the Chapin Mesa representative unit by greater than 1km and a canyon, but this distance is
Chapin Mesa milkvetch SSA Report 28 January 2018 only acting as a barrier to gene flow through seed dispersal (Spector 2017 pers. comm.), and is unlikely to be a barrier to pollen dispersal.
Below, we describe our evaluation of each representative unit with respect to each of the metrics from section 3.2 (Appendix B - Current Condition Tables).
Grass cover (non-bunch grasses) – An evaluation of the amount of non-bunch grass cover in monitoring plots in the Chapin Mesa unit was provided by CNHP. CNHP uses cheatgrass as a surrogate species to measure grass cover in their monitoring plots because it is the most dominant species in burned areas. On average there was 38% cheatgrass cover in the burned plots (ranged from 8-58%) in 2016, a decrease from the 58% average cover of 2015, whereas no cheatgrass was recorded in the unburned woodlands (Rondeau 2017, p. 11). In addition, CNHP collected data on western wheat grass cover in 2016; western wheat grass had an average cover of 26% (ranged from 0-70%), resulting in a total grass cover of 64%, not including smooth brome (Rondeau 2017c, pers. comm.). We were not able to evaluate grass cover for the Park Mesa, West Chapin Spur, or Ute Mountain Ute Tribal Park representative units because no monitoring of grass cover has been done in those units. Since we do not have any quantitative information on precisely how much grass cover is compatible with Chapin Mesa milkvetch, we considered 0-5% cover of grass to constitute “good” condition for Chapin Mesa milkvetch, 6- 50% to represent “moderate” condition, and anything greater than 50% to represent “low” condition (Table 6 below). Based on these categories, the Chapin Mesa unit overall is in moderate condition with respect to grass cover, while the burned subunit is also in low condition, and the unburned subunit is in good condition. Table 7 below shows each representative unit’s overall current condition for this category.
Pinyon-juniper Canopy Cover – We calculated the percent of pinyon-juniper canopy cover as it relates to wildfire and fire management activities; pinyon-juniper has been eliminated in areas that have been burned, and thinning of pinyon-juniper woodlands has occurred in some areas for fire management activities. We calculated the percent canopy cover of pinyon-juniper woodland within each representative unit by means of spatial analysis of ArcGIS polygons provided by Mesa Verde National Park (2017). The calculated area of pinyon-juniper woodlands was comprised of: (1) ArcGIS vegetation layers within Mesa Verde National Park (2017), (2) ArcGIS layers with areas that have been burned (2017), (3) and ArcGIS layers of each polygon or representative unit. No data was available on pinyon-juniper canopy cover for the Ute Mountain Ute Tribal Park unit. We considered 40% or greater of pinyon-juniper canopy cover to constitute “good” condition for Chapin Mesa milkvetch, 20-39% to represent “moderate” condition, and anything lower than 19% to represent “low” condition (Table 6 below). We found that the Chapin Mesa representative unit as a whole has 60% pinyon-juniper canopy cover (“Good” condition), the Park Mesa unit has 93% pinyon-juniper canopy cover (“Good” condition), the West Chapin Spur unit has 15% pinyon-juniper canopy cover (“Low” condition), and we were
Chapin Mesa milkvetch SSA Report 29 January 2018 unable to calculate the percentage of pinyon-juniper canopy cover on the Ute Mountain Ute Tribal Park because we do not have ArcGIS data for that area.
Winter Precipitation – We defined “good”, “moderate”, and “low” conditions for Chapin Mesa milkvetch with respect to winter precipitation, as snow (December – February) based on the number of recent winter drought years. If there were 0-2 winter drought years over the last decade, we considered this to represent “good” conditions for Chapin Mesa milkvetch, while 3-4 drought years were considered to represent a “moderate” condition, and 5 or more drought years represented “low” condition. We measured winter precipitation by calculating the percent deviation from the 1971-2000 average over the most recent ten year period (2007-2016) for which data are available. Any year that the precipitation was 25% or more below the 1971-2000 average was considered a drought year (Table 6 below). Overall, we found that a total of two drought years occurred during the ten year period from 2007-2016. Because Chapin Mesa milkvetch is a narrow endemic, occurring only in Montezuma County, Colorado, these weather trends apply to all representative units. Therefore, we found that all units were in “good” condition with respect to winter precipitation. Precipitation data was provided by Mesa Verde National Park.
Spring Precipitation – We defined “good”, “moderate”, and “low” conditions for Chapin Mesa milkvetch with respect to spring precipitation (March – May) based on the number of spring drought years. If there were 0-2 number of spring drought years over the last decade, we considered this to represent “good” conditions for Chapin Mesa milkvetch, while 3-4 drought years were considered to represent a “moderate” condition, and 5 or more drought years represented “low” condition. We measured spring precipitation by calculating the percent deviation from the 1971-2000 average over a ten year period (2007-2016); we defined a drought year as any year that is 25% or more below the 1971-2000 average (Table 6 below). Overall, we found that a total of five drought years occurred in the ten year period from 2007-2016. Because Chapin Mesa milkvetch is a narrow endemic, occurring only in Montezuma County, Colorado, these weather trends apply to all representative units. Therefore, we found that all units were in “low” condition with respect to spring precipitation. Precipitation data was provided by Mesa Verde National Park and Colorado Natural Heritage Program.
Seedling Survival - Based on 2016 monitoring data from CNHP in the Chapin Mesa unit, we defined seedling survival of 25% or more to be “good”, seedling survival of 15-25% to be “moderate”, and 0-15% to be “low” (Table 6 below). CNHP documented higher seedlings for Chapin Mesa in 2016 than 2015, even though the spring of 2015 was wetter than the spring 2016 and spring temperatures were nearly equivalent, at 2.5°F warmer than the 1971-2000 average (Rondeau 2017, p. 16). Winter moisture was nearly identical in 2015 and 2016 at 22% and 20% above the 1971-2000 average, respectively. The difference was in winter temperature, with the winter of 2015 relatively hot, at 4.5°F above 1971-2000 average, while 2016 had average winter temperatures (Rondeau 2017, p. 16). It is likely that the warmer winter in 2015 reduced soil
Chapin Mesa milkvetch SSA Report 30 January 2018 moisture earlier than average, and therefore provided less soil moisture for seedling survival than in 2016 (Rondeau 2017, p. 16). It is also possible that soil temperature differed and impacted seedling germination (Rondeau 2017, p. 16). June 2016 was exceptionally dry, and nearly all the seedlings in the burned area died, for a 92% loss, while the seedlings in the unburned area fared much better with a 31% loss (Rondeau 2017, pp. 16-17). June of 2015 was exceptionally wet and seedlings continued to emerge. Seedling emergence during the monsoons was virtually non- existent in both 2015-2016 (Rondeau 2017, p. 17). In addition to a difference across years, CNHP found a difference between burned and unburned areas, with 75 total seedlings in the burned area vs 288 seedlings in the unburned area (Rondeau 2017, p. 16). In summary, the burned areas produced fewer seedlings and had a low survival rate, whereas the unburned areas produced numerous seedlings and had a high survival rate (Rondeau 2017, p. 16). Based on these data, we found that both the Chapin Mesa unit as a whole and the Chapin Mesa burned representative subunit are in “moderate” condition and the Chapin Mesa unburned subunit is in “good” condition. We could not evaluate seedling survival for the Park Mesa, West Chapin Spur, and Ute Mountain Ute Tribal Park representative units as a result of insufficient data.
Exotic Plant Species - This metric was measured qualitatively (exotic plants not present, somewhat present, and present) based on observations by National Park Service botanists, because there currently are not sufficient data to calculate percent cover of these invasive species within Chapin Mesa milkvetch habitat. We defined conditions with respect to exotic plant species as “good” if exotic species were not present, as “moderate” if exotic species were somewhat present, and as “low” if exotic species were present (Table 6 below). In the Chapin Mesa unburned subunit, exotic plant species are not present; in the burned subunit exotic plant species are present. However, in the Chapin Mesa unit as a whole, exotic plants are somewhat present; this is due to the large size of and variable conditions across this representative unit. We could not evaluate the presence of exotic plants for Park Mesa, West Chapin Spur, and the Ute Mountain Ute Tribal Park representative units as a result of insufficient data.
Intact Native Understory – We measured this metric qualitatively (not present, somewhat present, and present) based on observations by National Park Service botanists because there currently is not sufficient data to calculate percent cover of intact native understory within Chapin Mesa milkvetch habitat. We defined Intact Native Understory as “good” if it is present, as “moderate” if it is somewhat present, and as “low” if it is not present (Table 6 below). Intact native understory is composed of biological soil crust, native wildflowers, and duff. We found that the Chapin Mesa unit as a whole is in “moderate” condition, the Chapin Mesa burned subunit is in “low” condition, the Chapin Mesa unburned subunit is in “good” condition, and the Park Mesa unit is in “moderate” condition. We could not evaluate the presence of an intact native understory for the West Chapin Spur Unit or the Ute Mountain Ute Tribal Park unit as a result of insufficient data; however, it is likely that an intact native understory is not present on the West Chapin Spur unit since 85.71% of this unit has been affected by fire.
Chapin Mesa milkvetch SSA Report 31 January 2018
Habitat Loss – Currently 42.7 acres (2.1%) of Chapin Mesa milkvetch habitat on the Chapin Mesa unit has already been impacted by park infrastructure. Due to the natural isolation of Park Mesa and West Chapin Spur, there currently is no park infrastructure present in these representative units. The Ute Mountain Ute Tribal Park unit has limited road access in Chapin Mesa milkvetch habitat; however, it is not often used, except for guided tours. We considered 5% or more of habitat loss to be detrimental to Chapin Mesa milkvetch, such that it is considered “low” condition, while 1-5% is considered “moderate”, and 0% is considered “good” (Table 6 below). Therefore, we found that the Chapin Mesa unit as a whole is in “moderate” condition, the Chapin Mesa unburned subunit is in “moderate” condition, the Chapin Mesa burned subunit is in “moderate” condition, the Park Mesa unit is in “good” condition, the West Chapin Spur unit is in “good” condition, and the Ute Mountain Ute Tribal Park unit is in “good” condition.
Overall Current Condition – To assess the overall current condition for each representative unit and subunits, we took an average of the conditions in each category (Table 7 below). However, we weighted pinyon-juniper canopy cover more by counting it twice when “averaging” the overall condition; we did this because it is one of the most important habitat characteristics for Chapin Mesa milkvetch. We did not count the boxes that are marked “unknown” when “averaging” the overall current condition because we have no information on those metrics for that unit.
Table 6. Metrics used to measure current condition.
Current Condition
Grass Pinyon- Exotic Intact Cover juniper Winter Spring Seedling Habitat Condition Plant Native (non bunch Canopy Precipitation Precipitation Survival loss Species Understory grasses) Cover
0-2 drought 0-2 drought Good < 5% > 40% year in a 10 year in a 10 >25% Not Present Present 0% year period year period
3-4 drought 3-4 drought Somewhat Somewhat Moderate 5-50% 20-39% years in a ten years in a ten 15-25% 1-5% Present Present year period year period
5-10 drought 5-10 drought Low > 50% 0-19% years in a ten years in a ten 0-15% Present Not Present >5% year period year period
Unknown - No Data
Chapin Mesa milkvetch SSA Report 32 January 2018 Table 7. Overall Current Conditions
Grass Pinyon- Overall Exotic Intact Represenative Cover (non- juniper Winter Spring Seedling Habitat Current Plant Native Units bunch Canopy Precipitation Precipitation Survival Loss Condition Species Understory grasses) Cover (Resiliency) Chapin Mesa Moderate Good Good Low Moderate Moderate Moderate Moderate Moderate Chapin Mesa - Low Low Good Low Moderate Low Moderate Moderate Moderate burned subunit Chapin Mesa - unburned Good Good Good Low Good Good Good Moderate Good subunit Park Mesa Unknown Good Good Low Unknown Unknown Moderate Good Moderate West Chapin Unknown Low Good Low Unknown Unknown Unknown Good Moderate Spur Ute Mountain Ute Tribal Unknown Unknown Good Low Unknown Unknown Unknown Good Moderate Park
3.4 Current Condition - Resiliency, Redundancy, and Representation
To evaluate the current biological status of Chapin Mesa milkvetch, we assessed a range of conditions to allow us to consider the species’ resiliency, redundancy, and representation.
Resiliency – We consider the unburned Chapin Mesa subunit to be the most resilient relative to the other representative units based on the quality and quantity of habitat that is provided in this area (1,265 acres (512 hectares)). This large area of habitat and good conditions in this unit likely provides Chapin Mesa milkvetch some ability to withstand stochastic events, such as drought or wildfire (unless the entire range of the species were to be burned). Intact habitat in this subunit provides Chapin Mesa milkvetch with the ability to complete its life cycle, complete with pollinators, low competition from non-bunch grasses, seed germination and survival (Rondeau 2017c, pers. comm.). The West Chapin Spur unit is considered to be the least resilient due to its small size and the amount of habitat altered by fire (45 of 52 acres burned in the Long Mesa fire; 86%); however, we were not able to completely evaluate this unit due to insufficient data. The conditions in this unit may result in lower ability of Chapin Mesa milkvetch to withstand stochastic events. We were not able to completely evaluate the Park Mesa and Ute Mountain Ute Tribal Park units due to insufficient data; however we expect that they are in moderate condition based on the information we do have on precipitation, habitat loss, and in some areas, vegetation.
Redundancy – Like many narrow endemic species, the redundancy of Chapin Mesa milkvetch is, and has likely always been, inherently low as a result of its limited geographic area, and the fact that it comprises only one population. The species has multiple representative units spread across the species range, including 3 different mesas, which may provide some limited ability to withstand catastrophic events (i.e. large high severity wildfires and severe prolonged drought); however, the species and its habitat are not distributed equally among these units. The Chapin Mesa unit is the largest unit, encompassing 97% of the species habitat. Therefore, a catastrophic event (especially a fire) could potentially affect the entire Chapin Mesa unit.
Chapin Mesa milkvetch SSA Report 33 January 2018 Representation – We do not have any information on the genetic diversity of Chapin Mesa milkvetch. Therefore, we evaluated whether there are other types of representative diversity that could potentially indicate some ability to adapt to change, such as morphological or phenological differences, or different habitat types within the species’ range. We are not aware of any significant morphological or phenological differences across the species. Much of the habitat on the southern portion of West Chapin Spur appears to be of poor quality for Chapin Mesa milkvetch (i.e. the soil is thin and the topography is irregular and rocky); such sites do not often support large numbers of individuals on Chapin Mesa (Anderson 2004, p. 26). Historical reports have noted individuals on the side canyon bottoms where red loess has collected (CNHP 2004 in Anderson 2004, p. 27); suggesting that mesa tops may not be a habitat requirement. Some patches of Chapin Mesa milkvetch appeared to be associated with slightly more mesic microsites based on the patterns of drainage and topography observed in the vicinity (Anderson 2004, p. 33). Chapin Mesa milkvetch plants were sometimes observed in high numbers rooted under the canopy of bitterbrush (Anderson 2004, p. 33). It is possible that plants growing beneath the canopy of bitterbrush were protected from browsing and the percent soil moisture maybe been higher in these microsites due to reduced insolation (exposure to the sun’s rays) (Anderson 2004, p. 34). The ability to occupy these differing habitat types could indicate some adaptability, or representation within the species. However, these are not substantially different habitat types. It is possible that, like many narrow endemic species, Chapin Mesa milkvetch may have, and may always have had, low levels of representation.
Uncertainties Relating to Current Condition
In the absence of complete demographic monitoring data, we are not able to evaluate population trends or develop a population estimate for Chapin Mesa milkvetch, and therefore, must use habitat conditions as a proxy for population health/resilience. For many habitat conditions, we do not have information to quantify what levels are needed by Chapin Mesa milkvetch, therefore we made assumptions about what represent “good”, “moderate”, and “low” conditions for the species, and in some cases had to use qualitative assessments where quantitative data on habitat conditions was lacking. We also lack any information on genetic diversity within the species to inform our assessment of representation.
Chapin Mesa milkvetch SSA Report 34 January 2018 Chapter 4. Species Future Condition and Status
We have described the natural history and distribution of Chapin Mesa milkvetch (Chapter 2). We have considered the ecological needs for the species (Chapter 2) and its current condition (Chapter 3). In this chapter, we now evaluate the species’ expected future conditions using projections and plausible scenarios. We utilized the current condition as the baseline from which to evaluate changes to those factors considered important to Chapin Mesa milkvetch.
The viability of Chapin Mesa milkvetch depends on maintaining multiple self-sustaining representative units throughout its range into the future. Given Chapin Mesa milkvetch’s dependence on its habitat for all stages of its life cycle, we consider the presence of relatively stable, undisturbed habitat that is interconnected to be necessary to support resiliency.
Future changes in climate are one of the primary factors expected to influence the future condition of Chapin Mesa milkvetch, but there is uncertainty on how climate factors such as temperature and precipitation may change, and their effects on the species.
Evaluation of Climate Models
Using three models, three possible climate scenarios were developed by the North Central Climate Science Center in Fort Collins, Colorado for the San Juan Basin in Southwestern Colorado; Hot and Dry, Moderately Hot, and Warm and Wet, as described below (Rondeau et al. 2017, Appendix D, p. 15-21). This represents the best available scientific information on potential future climate conditions within the range of Chapin Mesa milkvetch, because it is downscaled for this specific region. We have used these models as the basis for developing three plausible future scenarios for Chapin Mesa milkvetch for the purposes of this SSA.
In the Hot and Dry scenario, annual temperatures are expected to increase approximately 5°F by 2035 (Rondeau et al. 2017, Appendix D, p. 15-21). By 2035, every summer will be warmer than 2002 and 2012 – years when the San Juan Basin experienced excessive heat waves (Rondeau et al. 2017, Appendix D, p. 15-21). Summer will expand (temperatures will remain high for a longer period of time) and annual precipitation will decline by 10% (Rondeau et al. 2017, Appendix D, p. 15-21). There will be more frequent drought years; roughly every fifth year, the San Juan Basin is projected to experience droughts similar to 2002 and 2012 (in these years, annual precipitation was 40% below average) (Rondeau et al. 2017, Appendix D, p. 15-21). The average fire season will lengthen by one month and the average total area burned in any given year will increase 16 times; not every year will be an exceptional fire season, but average fire frequency, intensity, and size will increase (Rondeau et al. 2017, Appendix D, p. 15-21).
Chapin Mesa milkvetch SSA Report 35 January 2018 In the Warm and Wet scenario, annual temperatures are expected to increase 2°F by 2035 (Rondeau et al. 2017, Appendix D, p. 15-21). Summer will expand (temperatures will remain high for a longer period of time) by a week, and annual precipitation will increase by 10% (note that soil moisture and stream flow would need a 5% increase in precipitation to offset a 2°F increase in temperature with its associated higher rate of evapotranspiration) (Rondeau et al. 2017, Appendix D, p. 15-21). Drought years, such as in 2002, will occur every 15th year, similar to today’s frequency; however, the intensity and severity of droughts will increase because of higher temperatures Rondeau et al. 2017, Appendix D, p. 15-21). The fire risk in this scenario is the lowest of the three scenarios, but fires will be present, and intermittent dry conditions may cause severe fire hazards because of high fuel loads (Rondeau et al. 2017, Appendix D, p. 15- 21).
In the Moderately Hot scenario, annual temperatures are expected to increase approximately 3°F by 2035 (Rondeau et al. 2017, Appendix D, p. 15-21). Average annual precipitation would not change; however, the San Juan Basin will experience larger year-to-year fluctuations in precipitation, with some very wet years and some intense drought years, as compared to the current San Juan Basin climate (Rondeau et al. 2017, Appendix D, p. 15-21). Once every decade, the San Juan Basin will experience a drought similar to the 2002 and 2012 droughts (years when precipitation was 40% below average) Rondeau et al. 2017, Appendix D, p. 15-21). Winter precipitation will increase, but precipitation will decline in the other seasons (Rondeau et al. 2017, Appendix D, p. 15-21). The annual fire risk is expected to be lower in this scenario than the Hot and Dry scenario. Large fluctuations between wet and dry years will increase fuel growth during wet years; so when fire does occur, the severity, intensity, and size could be very high, and in a bad fire year the average frequency will increase up to eight times and the area burned will increase up to 11 times (Rondeau et al. 2017, Appendix D, p. 15-21).
Development of Future Scenarios
Given our uncertainties regarding the future effects of climate change as well as uncertainties regarding potential future stressors to the species, we have evaluated Chapin Mesa milkvetch under three plausible future scenarios; these scenarios have been designed to capture the uncertainties regarding temperature and precipitation trends as well as other factors that influence Chapin Mesa milkvetch, such as management activities and development, to encompass the full range of plausible future conditions. These scenarios include: Scenario 1 “Optimistic” - continuation of the current land management conditions under the “Warm and Wet” future climate change model; Scenario 2 “Moderate” - slight increase in fire management actives and infrastructure development under the “Moderately Hot” future climate change model; Scenario 3 “Pessimistic” - significant increase in fire management activities and infrastructure development under the “Hot and Dry” future climate change model. Tribal management is left the same under each scenario because we have no information to indicate what level of management occurs on Tribal lands or that it will change into the future. We recognize that actual conditions in the future could include a combination of factors from any of these three
Chapin Mesa milkvetch SSA Report 36 January 2018 scenarios, or fall somewhere in between these scenarios, however, we selected these scenarios as representative of the full range of plausible conditions that could occur. Each of these scenarios was evaluated in terms of how it would be expected to impact resiliency, redundancy, and representation of the species by the year 2035.
Specifically, the future scenarios that we evaluated are as follows:
1. Scenario 1 “Optimistic” • Park does more invasive species control • Fire management activities continue at the same rate • No additional infrastructure is developed • Maintain existing closures of roads and trails • Tribal management stays the same • Climatic conditions are under the “Warm and Wet” future climate change model 2. Scenario 2 “Moderate” • Park does the same level of invasive species control as present • Slight increase in fire management activities • Slight increase in infrastructure development • Maintain existing closures of roads and trails • Tribal management stays the same • Climatic conditions are under the “Moderately Hot” future climate change model 3. Scenario 3 “Pessimistic” • Park does less invasive species control • Significant increase in fire management activities • Significant increase in infrastructure development • Existing road and trail closures are opened • Tribal management stays the same • Climatic conditions are under the “Hot and Dry” future climate change model
For each scenario, we evaluated the likely condition of each representative unit in comparison to the same metrics used in our evaluation of current condition, including grass cover, pinyon- juniper canopy cover, winter precipitation, spring precipitation, seedling survival, exotic plant species, intact native understory, and habitat loss. We categorized each unit as “improves”, “stays the same”, or “worsens” for each metric based on our judgement of how conditions are likely to change for the species by the year 2035 under each scenario, compared to how they are today (Table 8 below). Therefore, in this evaluation, these rankings represent our projection of each unit’s future condition relative to its current condition (i.e. whether each metric has improved, stayed about the same, or worsened). These results are described below.
Chapin Mesa milkvetch SSA Report 37 January 2018 Table 8. Qualitative metrics used to measure future condition
Grass Pinyon- Cover Exotic juniper Winter Spring Seedling Intact Native Habitat Condition (non Plant Canopy Precipitation Precipitation Survival Understory loss bunch Species Cover grasses) Improves Decrease Increase Increase Increase Increase Decrease Increase Decrease Stays the Stays the Stays the Stays the Stays the Stays the Stays the same Stays the same Stays the same same same same same same same Worsens Increase Decrease Decrease Decrease Decrease Increase Decrease Increase
4.1 Characterization of Species’ Resiliency, Redundancy, and Representation by Future Scenarios
Scenario 1 – Optimistic Scenario
Resiliency under Scenario 1
Under this scenario, we anticipate that all Chapin Mesa milkvetch representative units will continue to be present and stable to increasing because (1) precipitation is anticipated to increase; (2) the Park will be increasing invasive species control efforts; (3) fire management activities are not anticipated to increase; and (4) there will be no additional development of park infrastructure. Therefore, we expect the resiliency of each unit to be at least as good as it is currently, or better, such that each unit retains its ability to withstand stochastic events.
Redundancy under Scenario 1
Under this scenario, we anticipate that the existing self-sustaining Chapin Mesa milkvetch representative units will continue to be present throughout its range. Therefore, redundancy, or the ability to withstand catastrophic events, should be unchanged from current condition (i.e. redundancy will continue to be low, typical of a narrow endemic species).
Representation under Scenario 1
Under this scenario, we anticipate that the existing self-sustaining Chapin Mesa milkvetch representative units will continue to be present throughout its range due to an increase in precipitation and invasive species control and a decrease in fire management activities. Therefore, we expect similar levels of representation to what the species currently has (i.e. low representation).
Summary of Scenario 1 – Under this scenario, we would expect that each representative unit continues to be occupied and stable or increasing. We do not anticipate any significant changes in population trends during this time period for any of the representative units; although, there
Chapin Mesa milkvetch SSA Report 38 January 2018 may be an increase in density due to improved habitat and environmental conditions. These conditions are summarized in Table 9.
Table 9. Future Condition | Scenario 1 - Optimistic
Grass Pinyon- Cover Exotic Intact Overal juniper Winter Spring Seedling Habitat (non Plant Native Future Canopy Precipitation Precipitation Survival loss Representative bunch Species Understory Condition Cover Units grasses) Stays Stays the Stays the Improves Improves Improves Improves Improves the Improved same same Chapin Mesa same Stays Stays the Stays the Chapin Mesa - Improves Improves Improves Improves Improves the Improved same same burned subunit same Chapin Mesa - Stays Stays the Stays the unburned Improves Improves Improves Improves Improves the Improved same same subunit same Stays Stays the Stays the Improves Improves Improves Improves Improves the Improved same same Park Mesa same Stays West Chapin Improves Improves Improves Improves Improves Improves Improves the Improved Spur same Ute Mountain Stays Ute Tribal Improves Improves Improves Improves Improves Improves Improves the Improved Park same
Scenario 2 – Moderate Scenario
Resiliency under Scenario 2
Under this scenario, we anticipate that the existing representative units will be stable or decreasing due to an increase in fire management activities and park infrastrucuture development, invasive species control that remains the same as current control levels, and no increase in annual precipitation. An increase in winter precipitation, as rain, is expected; however, precipitation is expected to be lower in all other seasons, which could lead to decreased density and recruitment of Chapin Mesa milkvetch plants. Large fluctuations between wet and dry years will result in a high fuel load potentially creating larger and more intense fires. This could result in levels of resiliency in each representative unit that are similar or slightly lower than they are currently.
Redundancy under Scenario 2
Under this scenario, we anticipate that the existing self-sustaining Chapin Mesa milkvetch representative units will continue to be present throughout its range. However, we anticipate that the representative units may be in decline as a result of deteriorating habitat. Levels of redundancy will continue to be low, typical of narrow endemic species.
Chapin Mesa milkvetch SSA Report 39 January 2018 Representation under Scenario 2
Under this scenario, we anticipate that the existing self-sustaining Chapin Mesa milkvetch representative units will continue to be present throughout its range; however, these units may be in decline as a result of deteriorating habitat conditions. This could result in a slight decrease in representation for the species, or a slight decrease in the ability to adapt to changing conditions.
Summary of Scenario 2 – Under this scenario, we would expect that each representative unit continues to be occupied and stable to declining. We do not anticipate any significant changes in population trends during this time period for any of the representative units; although, there may be a decrease in density due to deteriorating habitat and environmental conditions. These conditions are summarized in Table 10.
Table 10. Future Condition | Scenario 2 - Moderate
Grass Pinyon- Cover Exotic Intact Overal juniper Winter Spring Seedling Habitat (non Plant Native Future Canopy Precipitation Precipitation Survival loss Representative bunch Species Understory Condition Cover Units grasses) Stays the Stays the Stays the Stays the Stays the Stays the Worsens Improves Improves Chapin Mesa same same same same same same Chapin Mesa - Stays the Stays Stays the Stays the Stays the Stays the Stays the Stays the Stays the burned same the same same same same same same same same subunut Chapin Mesa - Stays the Stays the Stays the Stays the Stays the Stays the unburned Worsens Improves Improves same same same same same same subunit Stays the Stays the Stays the Stays the Stays the Stays the Stays the Stays the Worsens Park Mesa same same same same same same same same West Chapin Stays Stays the Stays the Stays the Stays the Stays the Stays the Improves Improves Spur the same same same same same same same Ute Mountain Stays the Stays Stays the Stays the Stays the Stays the Stays the Stays the Stays the Ute Tribal same the same same same same same same same same Park
Scenario 3 – Pessimistic Scenario
Resiliency under Scenario 3
Under this scenario, we anticipate that the existing representative units will be decreasing in abundance and suitable habitat due to a significant increase in fire management activities and park infrastrucuture development, reduction in the amount of invasive species control levels, and a 10% decrease in annual precipitation. Summer will be extended (temperatures will remain high for a longer period of time) and the fire season will be extended by one month with an increase in the area burned in any given year by 16 times the current amount. The smaller representative units (Park Mesa and West Chapin Spur) may be eliminated. This could result in levels of resiliency in each representative unit that are lower than they are currently in the units that remain.
Chapin Mesa milkvetch SSA Report 40 January 2018 Redundancy under Scenario 3
Under this scenario, we anticipate that the largest of the existing self-sustaining Chapin Mesa milkvetch representative units will continue to be present, but the smaller representative units (Park Mesa and West Chapin Spur) may be eliminated. We anticipate that the abundance and available habitat in the remaining representative units may be in decline as a result of deteriorating habitat and environmental conditions. In this scenario, the already low levels of redundancy that the species has could be further reduced.
Representation under Scenario 3
Under this scenario, we anticipate that the largest of the existing self-sustaining Chapin Mesa milkvetch representative units will continue to be present throughout its range; however, these units may be in decline as a result of deteriorating habitat and environmental conditions. The smaller representative units (Park Mesa and West Chapin Spur) may be eliminated. This could result in a loss of a small amount of representative diversity.
Summary Scenario 3 – Under this scenario, we would expect that the largest representative unit, Chapin Mesa, will continue to be occupied but declining; the smaller representative units (Park Mesa and West Chapin Spur) may be eliminated. We do anticipate significant declines in population trends during this time period for all of the representative units. This could result in a decrease in the species’ ability to withstand stochastic and catastrophic events, and adapt to future change. These conditions are summarized in Table 11.
Table 11. Future Condition | Scenario 3 - Pessimistic
Grass Pinyon- Cover Exotic Intact Overal juniper Winter Spring Seedling Habitat (non Plant Native Future Canopy Precipitation Precipitation Survival loss Representative bunch Species Understory Condition Cover Units grasses) Chapin Mesa Worsens Worsens Worsens Worsens Worsens Worsens Worsens Worsens Worsens Chapin Mesa - Stays burned Worsens the Worsens Worsens Worsens Worsens Worsens Worsens Worsens subunit same Chapin Mesa - unburned Worsens Worsens Worsens Worsens Worsens Worsens Worsens Worsens Worsens subunit Park Mesa Worsens Worsens Worsens Worsens Worsens Worsens Worsens Worsens Worsens Stays Stays the West Chapin Worsens the Worsens Worsens Worsens Worsens Worsens Worsens same Spur same Ute Mountain Stays Stays Stays the Ute Tribal Worsens the Worsens Worsens Worsens Worsens the Worsens same Park same same
Uncertainties Relating to Future Conditions
Uncertainties remain regarding how Chapin Mesa milkvetch individuals and habitat will react to a changing climate. Uncertainties remain in regards to how the climate may change, and how
Chapin Mesa milkvetch SSA Report 41 January 2018 future management activities may change within Mesa Verde National Park and the Ute Mountain Ute Tribal Park; to account for this uncertainty, we have presented scenarios that represent this range of uncertainty. We also lack any information on how conditions may change beyond 2035.
4.2 Summary of Evaluation of Scenarios In summary, we anticipate that the largest Chapin Mesa milkvetch representative unit, Chapin Mesa, will continue to be occupied under all three scenarios (unless the entire range of the species were to be burned or invaded by nonnative plant species). Under Scenario 3 we do anticipate that there will be a reduction in resiliency, redundancy, and representation; which may put the species at an increased risk of stochastic and catastrophic events, such that the smaller representative units may no longer be occupied by Chapin Mesa milkvetch. The Chapin Mesa unit is likely the most important unit for the species survival into the future because it is the largest unit and contains the majority of the known individuals (Spector 2017d, pers. comm.). However, this species inherently has, and has likely always had, a low level of redundancy and representation due to its narrow endemism. Because there is only one large representative unit and three very small units; this species is already at some risk of catastrophic events and may have low adaptability to changing conditions.
Chapin Mesa milkvetch SSA Report 42 January 2018 Literature Cited
Anderson, D. G. (2004). Population status survey of Schmoll milkvetch (Astragalus schmolliae). Final report prepared for the National Park Service, Mesa Verde National Park. 85 pp.
Anderson, D. G. (2017). Email to Tova Spector forwarded to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from David Anderson, Colorado Natural Heritage Program, Fort Collins, CO, regarding negative survey data for Chapin Mesa milkvetch on nearby mesas within Mesa Verde National Park, Dated November 6, 2017
Barnaby, R. C. (1964). Atlas of North America Astragalus. Memoirs New York Botanical Garden, 13, 277-278.
Clow, S. (2017). Email To Dara Taylor, U.S. Fish And Wildlife Service Grand Junction, CO, From Scott Clow, Ute Mountain Ute Tribal Environmetal Office, Towaoc, CO, Regarding Identifying Chapin Mesa Milkvetch Populations on Tribal Land, Dated June, 17, 2017.
Colorado Natural Heritage Program. (2006). Element Global Rank Report. Biodiversity tracking and conservation system. Colorado State University, Fort Collins, Colorado., pp. 4.
Colorado Natural Heritage Program. (2010). Element Global Rank Report. Biodiversity tracking and conservation system. Colorado State University, Fort Collins, Colorado. p. 4.
Denver Botanic Gardens (2016). Life History and Demography of Astragalus microcymbus Barneby (Fabaceae). Population Monitoring 1995-2016. Technical Report to Bureau of Land Management. p. 2-3.
Floyd, L.M., Hanna, D., Romme, W.H., Crews, T.E. (2006). Predicting and mitigating weed invasions to restore natural post-fire succession in Mesa Verde National Park, Colorado. International Journal of Wildland Fire, 15, 247-259.
Friedlander, J. D. 1980. The Status of Rare and Endangered plant Species in Mesa Verde National Park, Colorado. Master’s thesis submitted to Department of Range Science, Colorado State University. 122 pp.
Green, T. (2012). Reproductive mechanisms in Astragalus schmolliae (Schmoll's milkvetch). Unpublished manuscript.
Intergovernmental Panel on Climate Change. (2007). Synthesis Report. Climate Change 2007.
Chapin Mesa milkvetch SSA Report 42 January 2018 Isley, D. (1998). Native and naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska And Hawaii). Monte L. Bean Life Science Museum, Brigham Young University, Provo, UT. National Science Foundation # DEB-9024537. 1007.
Karl, T.R., J.M. Melillo, and T.C. Peterson [eds]. 2009. Global Climate Change Impacts in the United States. Cambridge University Press. 196 pp.
Mesa Verde National Park (MVNP), 2018. Conservation Plan for Chapin Mesa milkvetch (Astragalus schmolliae) at Mesa Verde National Park. Research and Resource Management Division.
Morris, A.B., Baucom, R.S., Cruzan, M.B. (2002). Stratified analysis of the soil seed bank in the cedar glade endemic Astragalus vivullatus: Evidence for historical changes in genetic structure. American Journal of Botany, 89, 29-36.
National Park Service. (2015b). Fire managament plan biological assessment. Revised draft November 2015. Unpublished manuscript.
NatureServe. (2002). Element occurrence data standard. Unpublished manuscript.
Peterson, J. S. (1981). Status report on Astragalus schmolliae. Unpublished report prepared for U.S. Fish and Wildlife Service, Golden, Colorado.
Porter, C. L. (1945). Two tioid astragalus novelties from the Rocky Mountain Region.8, 100- 102.
Rondeau, R., Kuhn, B., Handwerk, J. (2016). Long term population trends of Chapin Mesa Milkvetch (Astragalus schmolliae C.L. porter) 2015 report. colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
Rondeau, R., M. Bidwell, B. Neely, I. Rangwala, L. Yung, and K. Wyborn. (2017). Pinyon- Juniper Landscape: San Juan Basin, Colorado. Social-Ecological Climate Reslilence Project. North Central Climate Center, Fort Collins, Colorado. Unpublished Manuscript.
Rondeau, R. (2017a). Email to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from Renee Rondeau, Colorado Natural Heritage Program, Hesperus, CO, Regarding the Cause and Effects of Stressors for Chapin Mesa milkvetch, Dated June 16, 2017.
Rondeau, R. (2017b). Email to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from Renee Rondeau, Colorado Natural Heritage Program, Hesperus, CO, Regarding the Life Stage of Chapin Mesa milkvetch, Dated March 31, 2017.
Chapin Mesa milkvetch SSA Report 43 January 2018 Rondeau, R. (2017c). Response to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from Renee Rondeau, Colorado Natural Heritage Program, Hesperus, CO, for the solicitation of partner review for the draft species status assessment, Dated September 20, 2017.
Rondeau, R. (2017d). Summary of Temperature at 10 centimeters Depth as it Relates to Chapin Mesa Milkvetch 2017 supplemental data. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
Rondeau, R. (2017). Long term population trends of Chapin Mesa Milkvetch (Astragalus schmolliae C.L. porter) 2016 report. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
San Miguel, G.L. 2014. Schmoll’s Milkvetch Biennial Status Report for Mesa Verde National Park: Observations, Management Actions, and Impacts from 2012 and 2013. Unpublished report. 8 pp.
Spector, T. (2017a). Email to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO from Tova Spector, Mesa Verde National Park, Mesa Verde, CO, Regarding confirmation on certain habitat characteristics, Dated September 5, 2017.
Spector, T. (2017b). Email to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO from Tova Spector, Mesa Verde National Park, Mesa Verde, CO, Regarding a Plan for Additional Park Infrastructure in Astragalus schmolliae Habitat, Dated August 7, 2017.
Spector, T. (2017c). Email to Dara Taylor, U.S. Fish And Wildlife Service, Grand Junction, CO from Tova Spector, Mesa Verde National Park, Mesa Verde, CO, Regarding the Classification of Chapin Mesa Milkvetch Populations, Dated May, 1, 2017.
Spector, T. (2017d) Response to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from Tova Spector, Mesa Verde National Park, for the solicitation of partner review for the draft species status assessment, Dated October 17, 2017.
Spector, T. (2017e). Response to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from Tova Spector, Mesa Verde National Park, regarding the draft Fire Management Plan and when it is expected to be finalized, Dated November 15, 2017.
Spector, T. (2017f). Email to Dara Taylor, U.S. Fish and Wildlife Service, Grand Junction, CO, from Tova Spector, Mesa Verde National Park, regarding the potential development on Mesa Verde National Park over the next ten years, Dated November 14, 2017.
Chapin Mesa milkvetch SSA Report 44 January 2018 U.S. Fish and Wildlife Service. (2016). USFWS Species Status Assessment Framework: and Integrated Analytical Framework for Conservation. Version 3.4 dated august 2016
Wender, B. 2012a. Astragalus schmolliae status at Mesa Verde National Park in 2011. Unpublished report. 4 pp.
Wender, B. 2012b. Astragalus schmolliae status at Mesa Verde National Park in 2012. Unpublished report. 3 pp.
Chapin Mesa milkvetch SSA Report 45 January 2018 Appendix A – Cause and Effects Tables THEME: Climate Change and Drought [ESA Factor(s): A] Analysis Confidence / Uncertainty Supporting Information SOURCE(S) Climate Change Activity(ies) Prolonged drought periods, changes in timing of precipitation, changes in type of Highly Confident Karl et al, pp. 129-134, UCAR 2009, pp. 1- precipitation, increased temperatures, encouragement of invasive species 14, Floyd et al. 2006, p. 247 encroachment. STRESSOR(S) Changes in timing of precipitation, changes in type of precipitation, changes in the Highly Confident Karl et al, pp. 129-134, UCAR 2009, pp. 1- amount of evapotranspiration, changes in soil moisture, increased wildfires, increased 14, Floyd et al. 2006, p. 247, invasive species encroachment, decrease in pinyon-juniper overstory, and loss of habitat. Affected Resource(s) Periodic drought causes plants and seedlings to dry out, and contributes to increased Highly Confident Anderson 2004, p. 4 fire frequency and nonnative plant invasion. There is a direct effect on the species; severe drought can cause Chapin Mesa milkvetch individuals to remain dormant1. Exposure of Stressor(s) Prolonged periods of drought overlaps with emergence/re-emergence of Chapin Mesa Highly Confident Floyd et al. 2006, p. 247 milkvetch. Seedlings will not sprout, yearlings and adults will remain dormant if conditions are not favorable to re-emerge which will impact reproductive output and the loss of individuals. Increasing fire frequency due to dry conditions and increased fuel load will eliminate pinyon-juniper overstory that is a key habitat factor for Chapin Mesa milkvetch. However, this species can withstand and is adapted to periodic drought, we know this because there have been droughts throughout history; but if drought increases or becomes more prolonged/severe in the future it could become problematic for this species. Immediacy of Past, present, and future. Even though there are uncertainties associated with future Moderately Confident Stressor(s) projections, we expect that there will be a higher frequency of prolonged droughts. Changes in Resource(s) Loss of individuals and loss of habitat. Moderately Confident Response to Stressors: Chapin Mesa milkvetch individuals will often remain dormant during periods of Highly Confident INDIVIDUALS prolonged drought. Seeds will not have the appropriate soil moisture level to trigger germination. POPULATION & SPECIES RESPONSES Effects of Stressors: Lower reproductive rates, changes in species distribution, lower population growth Moderately Confident POPULATIONS rate. Though more research needs to be done. [RESILIENCY] GEOGRAPHIC This stressor affects the entire range of the species. Highly Confident SCOPE MAGNITUDE Short-term drought likely has a low-level direct impact on the species and it also Moderately Confident indirectly facilitates cheatgrass (and other invasive species) invasion and increased fire. Over the long-term drought has a high-level impact. SUMMARY Drought facilitates increased fire frequency and cheatgrass invasion; climate change may exacerbate this stressor. Also affects winter precipitation which is an important factor for the emergence (and reproduction) of Chapin Mesa milkvetch. This stressor will be carried forward in our analysis.
Chapin Mesa milkvetch SSA Report 46 January 2018 THEME: Development of Infrastructure [ESA Factor(s): A] Analysis Confidence / Uncertainty Supporting Information SOURCE(S) Development of infrastructure Grading and paving of roads, construction of visitor facilities, building modifications Highly Confident NPS 2015b Activity(ies) and utility upgrades. Regular maintenance and construction projects at Mesa Verde will continue to result in Highly Confident NPS 2015b a small amount of plant mortality and direct loss of habitat. Ground disturbance to STRESSOR(S) create infrastructure can increase invasive weeds and reduce forage and nest sites for pollinators. Affected Resource(s) Direct effect on the individual and habitat. Highly Confident NPS 2015b This stressor overlaps with the species specific habitat and reduced forage and nest Highly Confident Exposure of Stressor(s) sites for pollinators. Immediacy of Past, present. Future Moderately Confident Stressor(s) Loss of individuals, habitat, pollinators, and pollinator resources. Highly Confident NPS 2015b Changes in Resource(s) Response to Stressors: Death of individuals, loss to above ground growth, reduced reproductive effort from Moderately Confident INDIVIDUALS damaged individuals, decreased flower visits from pollinators. POPULATION & SPECIES RESPONSES Effects of Stressors: Declining populations, reduced population growth, loss of habitat. Moderately Confident POPULATIONS [RESILIENCY] Overall, the impact of existing development appears moderate, impacting about Highly Confident NPS 2015b 11.65% of the species' range on Mesa Verde and 8% of the species entire range. More than 10% of Chapin Mesa milkvetch habitat has been eliminated during the development of visitor facilities in Mesa Verde. Several additional projects are GEOGRAPHIC planned or under consideration within Mesa Verde National Park such as a comfort SCOPE station at the park headquarters office, a wildland fire response center and helibase, a paved multi-use trail, a bike/multi-use trail, and a fire management plan (Spector 2017x, pers. comm) that would significantly impact Chapin Mesa milkvetch habitat if they are implemented.This impact is expected to increase as more projects are planned within Chapin Mesa milkvetch habitat. Impacts from development extend beyond the footprint of the infrastructure as indirect Highly Confident MAGNITUDE effects (i.e. Pollinators, increasing suitable sites for invasive weed establishment).
Chapin Mesa milkvetch SSA Report 47 January 2018 Because Chapin Mesa milkvetch habitat overlaps with the main visitor area at Mesa Spector 2017 pers. comm. Verde National Park, the park cannot place new development outside of the species habitat. Several projects are being planned and/or considered that would significantly impact Chapin Mesa milkvetch habitat. The Fire Management Plan is in the final stages of a draft NEPA so it's highly likely to proceed. This would alter an additional 20% of Chapin mesa milkvetch habitat by thinning pinyon-juniper woodland out to SUMMARY 300 feet from infrastructure including roads. In addition, the park is considering widening the main park highway within Chapin Mesa milkvetch habitat by up to 10 feet as part of the Visitor Distribution Plan. Other impacts may be proposed as part of this plan. In summary Chapin Mesa milkvetch habitat is highly likely to be impacted by future development due to the conflict of Chapin Mesa being the most visited part of the park which also overlaps Chapin Mesa milkvetch habitat. This stressor will be carried forward in our analysis.
THEME: Herbivory and Trampling [ESA Factor(s): A, C] Analysis Confidence / Uncertainty Supporting Information Feral horse trespass, stray cattle, mule deer, insect larvae, small rodents, and SOURCE(S) park visitors. Feral horses have created dirt trails and large patches of disturbed bare ground within Chapin Mesa milkvetch habitat, which further encourage the spread of weedy species. Loss of plants to trampling and herbivory by feral horses. San Miguel 2014, p. 1; Friedlander 1980, p. Activity(ies) Highly Confident Chapin Mesa milkvetch habitat overlaps with visitor access areas within Mesa 64 Verde National Park; basic visitation activities can result the crushing of individuals. Feral horse and cattle activity creates bare patches of disturbed soil STRESSOR(S) Highly Confident encouraging the spread of weeds, loss of habitat, and loss of individuals. Loss of habitat and loss of individuals due to trampling, herbivory, and Affected Resource(s) Somewhat Confident San Miguel 2014, p. 1; Wender 2012b, p.1 invasive species encroachment. This stressor can affect the species at any time during its life cycle and anywhere in the species habitat. Seed predation by snout beetles or weevils Exposure of Stressor(s) Low Confidence caused loss of seed in about 12.5% of Chapin Mesa milkvetch plants in plots sampled in 1980. Past, present, and future. However, a Trespass Livestock Management Plan is Immediacy of Stressor(s) currently being developed and will result in the future removal of feral horses Somewhat Confident and cattle from the park. Adult plants are grazed/trampled and seedlings are destroyed. Trampling by Changes in Resource(s) feral horse trespass compacts soil and results in habitat loss for Chapin Mesa Moderately Confident milkvetch Response to Stressors: Adult plants are grazed/trampled and seedlings are destroyed. Moderately Confident INDIVIDUALS POPULATION & SPECIES RESPONSES
Chapin Mesa milkvetch SSA Report 48 January 2018 Effects of Stressors: Changes in distribution as a result of the bare ground created by the feral POPULATIONS horses that encourages the encroachment of invasive species. Lower Low Confidence Anderson 2001, p. 11 [RESILIENCY] reproductive output. We have no information on the geographic scope of this stressor. However, GEOGRAPHIC SCOPE Low Confidence the effects of this stressor are probably localized. The scope of these impacts is not large enough to be considered to be a MAGNITUDE Highly Confident population level impact to the species. Because these impacts are not large enough to be considered to be a SUMMARY population level impact to the species at this time and will not be carried forward in our analysis.
THEME: Wildfire and Fuels Management
[ESA Factor(s): A] Analysis Confidence / Uncertainty Supporting Information SOURCE(S) Wildfire and fuels management (clearing and prescribed burns) Wildfire management at Mesa Verde includes the creation of fire breaks, Highly Confident Activity(ies) fire lines, and staging areas, all of which remove or alter the mature pinyon-juniper woodland habitat where Chapin Mesa milkvetch is found. Wildfire and fuels management activities result in the loss of pinyon- Highly Confident juniper woodlands (where Chapin Mesa milkvetch is found) through mechanical means or through prescribed burns. In 2011, a survey on the STRESSOR(S) tribal fire break documented the presence of foreign mulching materials, non-native seeded plant species, and feral horse bedding areas, all of which are habitat alterations likely to impede the regrowth of Chapin Mesa milkvetch. This stressor is affecting the habitat in which Chapin Mesa milkvetch is Highly Confident Anderson 2004, p. 73 Affected Resource(s) found. Wildfire and fuels management activities result in the loss of pinyon- Highly Confident Anderson 2004, pp. 60, 73; Spector 2017 pers. juniper woodlands, which is where Chapin Mesa milkvetch is found. comm. Cleared areas are exposed to more sun and wind that dry the soil and the Chapin Mesa milkvetch seedlings, and cold spring season mornings Exposure of Stressor(s) expose young sprouts and blossoms to frost damage. Removal of woody vegetation can invite the establishment of nonnative invasive plants. This response is seen in mechanical fuels reduction areas on Chapin Mesa, where cover of muttongrass can approach 75%2. Past, present, and future. Current and future fuels reduction activities are Highly Confident NPS 2015b and will have a negative impact on 18% of the species range. An Immediacy of Stressor(s) indirect benefit is that fire breaks may help to stop fire from burning larger amounts of Chapin Mesa milkvetch habitat.
Chapin Mesa milkvetch SSA Report 49 January 2018 Above ground stems are directly removed, plants that re-sprout the Moderately Confident following spring have less water available because the soil dries due to Changes in Resource(s) exposure to sun and wind, and invasive weeds, and native grasses provide increased competition. Plants were growing among large, crowded bunches of muttongrass and Highly Confident Anderson 2004, p. 73; Response to Stressors: appeared small and unhealthy. This effect is probably due to INDIVIDUALS competition with muttongrass for water and nutrients. Also noted above that some Chapin Mesa milkvetch individuals are directly removed. POPULATION & SPECIES RESPONSES Density, reproductive effort and vigor of Chapin Mesa milkvetch Moderately Confident Effects of Stressors: appeared to be low in areas where there is removal of pinyon-juniper POPULATIONS [RESILIENCY] woodland. Clearing and prescribed burns would affect ~18% of the range of Chapin Moderately Confident NPS 2015b Mesa milkvetch if approved. Mesa Verde's draft Fire Management Plan GEOGRAPHIC SCOPE estimates that 3,837 burn piles of ~6 meters squared each would be scattered over the 163 hectare (402 acres) of proposed activities within Chapin Mesa milkvetch habitat. Current and future fuels reduction activities are and will have a negative Highly Confident Spector 2017 pers. comm. impact on 18% of the species range; however, this stressor is of less MAGNITUDE magnitude than increased wildfire and cheatgrass invasion. Clearings and burn piles will increase the risk of invasion of nonnative invasive species. Due to the amount of occupied habitat affected and the increase in SUMMARY nonnative species invasion; this stressor will be carried forward in our analysis.
THEME: Post-fire Mitigation [ESA Factor(s): A] Analysis Confidence / Uncertainty Supporting Information SOURCE(S) Post-fire mitigation Burned areas that have been sprayed and seeded, to prevent the spread of Highly Confident Kuhn and Anderson 2012, pp. 15, 28; Spector cheatgrass, have significantly lower densities of Chapin Mesa milkvetch 2017 pers. comm. than that of areas that have been burned, seeded, and unsprayed. Activity(ies) Herbicide application is considered to have a negative impact on the species. However, the park spot treats invasive species and does not treat large areas in Chapin Mesa milkvetch habitat. Direct loss of individuals that are found in areas where there is herbicide Moderately Confident application (specifically aminopyralid-which is highly active on plants in STRESSOR(S) the Fabaceae family). However, there has been no widespread herbicide treatment in Chapin Mesa milkvetch habitat.
Chapin Mesa milkvetch SSA Report 50 January 2018 Direct effect on individuals that have been sprayed with a specific Highly Confident Affected Resource(s) herbicide (aminopyralid). Some small trial applications of herbicide (imazapic) occurs inside of Somewhat Confident Spector 2017 pers. comm. Chapin Mesa milkvetch habitat after a fire and during plant dormancy Exposure of Stressor(s) when cheatgrass is germinating. However, this has treatment has not been regular and is restricted to a few small plots.
Immediacy of Stressor(s) Present Highly Confident Changes in Resource(s) Direct effects on individuals that have been sprayed with aminopyralid; Low Confidence Spector 2017 pers. comm. however this herbicide is not used widely in the park. Seeding as post- fire mitigation could help prevent cheatgrass from establishing and other hand seeding western wheatgrass a rhizomatus grass may also be competing with Chapin Mesa milkvetch. Direct effect on individuals that have been sprayed with a specific Highly Confident Response to Stressors: herbicide (aminopyralid). INDIVIDUALS POPULATION & SPECIES RESPONSES Effects of Stressors: Unknown Low Confidence POPULATIONS [RESILIENCY] Fires have impacted ~21% of total habitat for this species and cheatgrass Highly Confident Rondeau et al.2017, p. 11 GEOGRAPHIC SCOPE has spread to ~58% within burned areas inside of Mesa Verde National Park; resulting in the need for post-fire mitigation efforts. Uncertain. Without fully understanding the effects of post-fire Low Confidence MAGNITUDE mitigation efforts on populations of Chapin Mesa milkvetch it is difficult to determine the magnitude of this stressor. There have been effects to Chapin Mesa milkvetch from post-fire mitigation efforts, and future post-fire mitigation efforts may impact SUMMARY Chapin Mesa milkvetch. However, we have no information to suggest population-level impacts are occurring, therefore, we will not be carrying this forward in our analysis.
Chapin Mesa milkvetch SSA Report 51 January 2018 THEME: Wildfires [ESA Factor(s): A] Analysis Confidence / Uncertainty Supporting Information SOURCE(S) Lightning strikes and human induced Fire alters the habitat by removing tree canopy and increasing light and Highly Confident Floyd et al., 2006, p. 247 exposing plants to temperature extremes. Historically, small, lightning-caused fires have been frequent in Mesa Verde. Most of the fires started in the pinyon- juniper woodlands and burned less than 1 ha (2.5 ac). A recent increase in fire Activity(ies) activity is a result of severe drought conditions preceded by wet climatic conditions; increasing fuel load due to fire suppression in the pinyon-juniper woodlands, all coincide with the natural end of a long fire cycle. Lightening or human caused fire leaves bare ground as a result lost vegetation; thus leaving areas more susceptible to nonnative species invasion. Recurrent fires favor re-sprouting colonial species, and catastrophically Highly Confident (Floyd et al. 2006, p. 247); eliminate the fire-sensitive pinyon-juniper woodlands. Chapin Mesa milkvetch (Floyd et al. 2000, p. 1667, does not grow in Gambel oak-montane shrub-dominated areas, and we cannot 1677); Spector 2017 pers. STRESSOR(S) predict the long-term success of the species following the loss of the pinyon- comm. juniper due to fire and fire break construction. This species has a root crown that, if damaged, will result in mortality. Recurrent fires favor re-sprouting colonial species, and gradually eliminate the Highly Confident Floyd et al. 2000, p. 1667; fire-sensitive pinyon-juniper woodlands. Chapin Mesa milkvetch does not grow Spector 2017 pers. comm. in the shrub-dominated areas of Mesa Verde now, and we cannot predict the Affected Resource(s) long-term success of the species following the loss of the pinyon-juniper due to fire and fire break construction. In addition, the loss of canopy cover may affect the residence time of snow on the ground, which in turn would affect spring moisture. Six large wildfires burned within Mesa Verde between 1989 and 2003, and Highly Confident extensive portions of those burned areas have been invaded by nonnative plant species. Therefore, until recently, the southern half of Mesa Verde had a fire Exposure of Stressor(s) return interval of about 400 years for pinyon-juniper vegetation (Chapin Mesa milkvetch habitat). The annual average number of fires starts between 1926 and 1969 was 5 per year, which increased to 18 per year between 1970 and 1997.
Immediacy of Stressor(s) Past and future Moderately Confident Fire alters habitat by removing tree canopy and increasing light, exposing plants Highly Confident Spector 2017 pers. comm. to temperature extremes, and potentially affect the amount of snow retention thus affecting soil moisture. Chapin Mesa milkvetch individuals burn to the Changes in Resource(s) ground and then re-sprout the following spring if the fire is not too intense, but then have competition from nonnative plant species and grasses. Wildfire indirectly affects the species by facilitating invasion of cheatgrass, increasing herbivory and fluctuating temperature extremes.
Chapin Mesa milkvetch SSA Report 52 January 2018 Wildfires can burn Chapin Mesa milkvetch individuals to the ground; Highly Confident depending on the intensity the individuals may or may not grow back the Response to Stressors: following spring. Wildfires alter the habitat by removing tree canopy, which INDIVIDUALS will alter microsites light intensity and temperatures. Burning does not significantly impact plant mortality.
POPULATION & SPECIES RESPONSES Wildfire will alter post-fire environment by facilitating the invasion of Moderately Confident CNHP 2017 cheatgrass, increasing herbivory, and fluctuating temperature extremes will have effects on reproductive output, distribution, and population growth. Demography data has a strong burn effect for number of seedlings/adult, Effects of Stressors: flowers/adult, and fruits/adult. For all of these metrics, we see fewer in the POPULATIONS [RESILIENCY] burned areas compared to the unburned areas.
Historically fires have overall impacted about 21% of the total habitat for the Highly Confident species. The geographic scope of this stressor currently cover ~1/4 of the total GEOGRAPHIC SCOPE habitat for the species and is likely to increase into the future as climate changes and cheatgrass continues to invade the habitat for this species and recovery to intact habitat, if it occurs, will take at least 100 years. The current problem of cheatgrass, smooth brome and western wheatgrass is the Somewhat Confident Rondeau 2017 pers. comm. 'new' problem that Chapin Mesa milkvetch and pinyon-juniper woodlands did not evolve with. Generally the burned area would have gone to bunchgrass MAGNITUDE grassland with some shrubs. The introduction of these other grasses likely inhibits or slows the regrowth of shrubs and trees, thus it may have a negative impact on the recovery of Chapin Mesa milkvetch Due to the indirect effect of wildfire on altering the post-fire environment by facilitating invasion of cheatgrass and other nonnative bunch grasses, increasing SUMMARY herbivory, fluctuating temperature extremes and increase in fire frequency this stressor will be carried forward in the analysis.
Chapin Mesa milkvetch SSA Report 53 January 2018 THEME: Invasive Nonnative Plants [ESA Factor(s): A] Analysis Confidence / Uncertainty Supporting Information SOURCE(S) Wildfires and associated fire activities Cheatgrass has been in Mesa Verde for many years. However, it was never Romme et al. 2006, p. 3; widespread until 2000, when unusually warm dry summers and winters coupled Romme et al. 2006, pp. 2–3; with heavy fall rains allowed cheatgrass to rapidly expand its range, especially Hanna et al. 2008, p. 18; in places where fire or other disturbances have created bare ground. Cheatgrass Hanna et al. 2008, p. 9; is now a dominant species in much of the area burned in Mesa Verde and it has Floyd et al. 2006, p. 254; inundated the burned and disturbed portions of Chapin Mesa milkvetch habitat Anderson 2004, pp. 60–61; on Chapin Mesa. The highest infestation occurred in an area that burned both in Rondeau 2017 pers. comm. Activity(ies) Highly Confident the 1996 and the 2002 fires on Park Mesa. This area had been a old-growth pinyon-juniper woodland before the 1996 fire, and was seeded with native grasses. After re-burning in 2002, this area was inundated by cheatgrass. Western wheat grass and smooth brome are equally as problematic, resulting in a larger package of non-bunch grasses that may be a problem. Once mature pinyon-juniper woodland has been burned, it is highly vulnerable to post-fire weed invasion. Cheatgrass competes with seedlings and re-emerging adults for water and Highly Confident STRESSOR(S) nutrients. Cheatgrass increases fire frequency-facilitating further rapid spread.
Cheatgrass and other invasive nonnative species out competes Chapin Mesa Highly Confident Affected Resource(s) milkvetch for habitat, nutrients, and water. Cheatgrass is a winter annual that germinates in the fall, grows slowly during Highly Confident Anderson 2004, pp. 60–61; the winter, and then grows rapidly in the early spring when Chapin Mesa Floyd-Hanna et al. 1999, p. milkvetch begins to emerge. Given the season overlap of Chapin Mesa 148; Romme et al. 2003, p. milkvetch seedling growth with the peak growth of cheatgrass, it is likely that 344; Rondeau 2017 pers. the presence of cheatgrass in populations of Chapin Mesa milkvetch comm. Exposure of Stressor(s) compromises its viability1. Musk thistle is particularly invasive in burned areas of Mesa Verde by 1999 and is aggressively invading areas occupied by Chapin Mesa milkvetch. Western wheat grass and smooth brome are equally as problematic, resulting in a larger package of non-bunch grasses that may be a problem. Immediacy of Stressor(s) Present and future Highly Confident Loss of habitat as cheatgrass continues to spread, decrease in the number of Highly Confident Friedlander 1980, pp. 75-76; Changes in Resource(s) individuals, changes to the historical fire regime. Rondeau et al.2016, p. 16; Floyd et al. 2006, p. 257 Given the seasonal overlap of Chapin Mesa milkvetch seedling growth with the Moderately Confident Anderson 2004, pp. 60–61; Response to Stressors: peak growth of cheatgrass, it is likely that the presence of cheatgrass in Rondeau 2017 pers. comm. INDIVIDUALS populations of Chapin Mesa milkvetch interferes with reproduction and recruitment. POPULATION & SPECIES RESPONSES
Chapin Mesa milkvetch SSA Report 54 January 2018 Cheatgrass will out compete Chapin Mesa milkvetch for space, nutrients, and Highly Confident Friedlander 1980, pp. 75-76; Effects of Stressors: water; resulting in a reduction in population size, changes its distribution, and Rondeau et al.2016, p. 16; POPULATIONS [RESILIENCY] reduced reproductive rate. Floyd et al. 2006, p. 257; Anderson 2004, pp. 60–61 This stressor covers ~58% of burned areas within occupied Chapin Mesa Highly Confident Rondeau et al.2017, p. 11; milkvetch habitat. All burned areas are susceptible to cheatgrass invasion. Spector 2017 pers. comm. GEOGRAPHIC SCOPE Burned areas cover 37% of Chapin Mesa milkvetch habitat within the park. The extent of cheatgrass invasion on the Ute Mountain Ute Tribal park is currently unknown. The geographic scope of this stressor currently covers more than half of the burned areas that are within Chapin Mesa milkvetch habitat thus it is likely that MAGNITUDE Highly Confident the magnitude of this stressor is high in the areas where cheatgrass and other nonnative bunch grasses has spread there is no recruitment observed. Cheatgrass continues to spread into recently burned areas in Mesa Verde and for SUMMARY reasons state in "Magnitude" and will be need to be evaluated under future scenarios.
Chapin Mesa milkvetch SSA Report 55 January 2018 Appendix B - Current Condition Tables
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