A Strategy for Conservation of Springsnails in Nevada and Utah, USA

Abstract

The Nevada and Utah Springsnail Conservation Strategy (the Strategy) is a comprehensive and proactive 10-year plan to protect 103 species of truncatelloidean springsnails and their habitats (primarily springs). Springsnails are tiny, aquatic, and often locally endemic truncatelloidea and cerithioidean snails threatened by both local and regional stressors. A bi-state agreement (the Agreement) was forged by state and federal agencies and The Nature Conservancy (TNC) in 2018 in a manner consistent with U.S. Fish and Wildlife Service (USFWS) conservation criteria. Successful achievement of Agreement objectives will protect springsnails and their habitats in the two states, precluding the need for a federal listing of those species. The objectives of the Agreement are to: (1) compile springsnail ecology and distribution data into a single database; (2) identify, assess, and reduce threats to the taxa and their habitats; (3) maintain, enhance, and restore spring habitats; (4) develop and maintain a springsnail conservation team (SCT); and (5) create an effective education and outreach program for landowners, agencies, and the general public. The SCT held in-person and multiple virtual meetings in 2019–2020 to initiate the Strategy, introduce and clarify member roles, and pursue the integration of available information. The SCT assembled information and literature on each taxon in the two states into the Springs Online database (springsdata.org), a password-protected, easily used online information management system for archiving and reporting on springs-dependent species taxonomy, distribution, associated species, and population and conservation status data. The information gathered was used to generate conservation reports for individual species that can be readily updated as new information emerges. Within each Agreement objective, we describe issues to ensure springsnail species representation, resiliency, and redundancy, which are USFWS metrics of population integrity. We describe springsnail diversity and distribution, the threats and challenges to effective springsnail conservation, and the process the SCT is using to address those issues. Development of the Strategy enables the SCT to monitor, prioritize, and readily report on springsnail conservation progress over the decadal life of the Agreement. As one of the largest springs and springs-dependent species conservation efforts in the world, the context and development of the Strategy provide key lessons for other such efforts.

1. Introduction

Springsnails are tiny aquatic, fresh- or brackish-water gastropods in the order Neotaenioglossa and the superfamilies Truncatelloidea and Cerithioidea. More than 1000 species are likely to occur throughout the non-ice-dominated world (Tables S2 and S3 in Supplementary Materials, https://springstewardshipinstitute.org/springsnail-conservation-strategy, accessed 31 July 2022), with 182 species of springsnails described in North America and additional species described there regularly [1,2,3,4,5]. Springsnail species often are closely adapted to the geochemistry and temperature of individual springs, with many species occurring as local endemics at only one or a few water sources. Springsnails in the USA are particularly diverse in arid Nevada and Utah, where at least 103 taxa have been identified [1]. Concern over their conservation has increased because of intensifying drought, groundwater extraction, and the widespread appropriation of springs for domestic and agricultural purposes [6,7,8,9,10,11].

The contemporary status of many springs-dependent springsnail populations and their habitats has not been recently documented. Sada and Lutz [12] reported that 83% of 2,256 springs inventoried in the Great Basin and Mojave deserts between the 1980s and 2013 were impaired by human activities, results that were corroborated by Stevens et al. in the Nevada and Utah portions of the Colorado River basin [13]. The declining health of springsnail populations and their habitats has led to mandated protection of springsnails as Species of Greatest Conservation Need in the 2015 Utah State Wildlife Action Plan [14] and by the U.S. Fish and Wildlife Service (USFWS) under the federal Endangered Species Act (ESA) [15]. For example, two southwestern species were recently federally listed (i.e., Black River springsnail—Pyrgulopsis trivialis and San Bernardino springsnail—P. bernardina) in Arizona, and some populations and species have recently been reported as extinct [16]. Such state and federal protections can limit economic development but may be avoided through habitat conservation planning [17].

Here we summarize efforts by Nevada and Utah to reduce the need for state or federal listing of springsnails, as well as other springs-associated biota, by protecting springs that support springsnails. We present and describe the Nevada and Utah Springsnail Conservation Agreement (Agreement) [18] and the 2020 Springsnail Conservation Strategy [19] (Supplementary Materials). These two documents were developed partially in response to petitions submitted to the USFWS. Forest Guardians [20] and the Center for Biological Diversity [21] petitioned the USFWS to evaluate the listing of 47 Great Basin and Mojave Desert springsnail species under the ESA. While the USFWS subsequently concluded that none of those species in Nevada or Utah warranted federal listing [22,23,24], attention to the long-term survival and persistence of springsnail habitats is receiving increasing scrutiny [8]. Conservation of Nevada and Utah springsnails requires reducing or eliminating threats, improving degraded habitat conditions, and restoring many of the natural functions of associated springs and stream ecosystems. The Strategy was developed to collaboratively stabilize or increase at-risk springsnails by improving or protecting the hydrologic and habitat functionality of springs at which populations occur. These measures also may: benefit other threatened and sensitive species that co-occur in these ecosystems; reduce habitat degradation and downstream habitat losses; and potentially enhance agricultural and recreation opportunities, as well as property values [14,25]. This is one of the largest efforts in the world to protect springs and their dependent biota.

We describe the background of the Agreement and Strategy and the planning elements and processes, information management, monitoring protocols, and risk assessment approaches of the Strategy to assist managers in prioritizing information compilation and conservation actions. Implementation of the Strategy over the next decade is expected to improve springsnail conservation, springs habitat integrity, and the sustainability of springsnail populations.

2. Study Area

The region encompassed in this plan includes the states of Nevada and Utah (Figure 1). Except for eastern Utah and southeastern Nevada, the region falls largely into the internally draining Basin and Range geologic province. Endorheic basins in Nevada include those of the Amargosa, Truckee, Carson, Walker, Humboldt, and Owyhee rivers in the south, west, and northern parts of the state. Externally draining Nevada rivers include the White/Muddy, Virgin, and Colorado rivers in the southeastern portion of the state, and the Snake River in the northern and northwestern portions of the state, respectively. North-central and western Utah is drained by endorheic Bonneville Basin drainages; and the Sevier River occupies central and southwestern Utah. Exorheic drainage basins include the Green and Colorado in the east and south, the Virgin River in the Lower Colorado Region, and tributaries of the Snake River in the north. The Great Basin was occupied by multiple, large, endorheic Pleistocene lakes as recently as 15,000 years ago, the largest among which were 1,600 km² Lake Manly in the Amargosa River and Death Valley drainages, 22,000 km² Lake Lahontan in northwestern Nevada, and 51,000 km² Lake Bonneville in Utah 26 (e.g., [26]). Waxing and waning of aquatic habitat connectivity variably facilitated or interrupted gene flow and colonization, resulting in the many now highly endemized Great Basin populations (e.g., [27,28,29]).

Contemporary Great Basin groundwater is distributed among five major flow systems [30], including drainages into the Great Salt Lake Desert/Lake Bonneville basin, the Humboldt River/Lahontan basin, the Colorado River basin, the Death Valley/Lake Manly basin, and the Snake River basins, each of which is subdivided into major sub-basins and many local aquifers (e.g., [31,32]). Much of the landscape is underlain by the 285,000 km² Great Basin carbonate and alluvial aquifer system (GBCAAS). Some GBCAAS sub-basins extend beneath multiple surface-endorheic valleys, producing springs with flow paths hundreds of kilometers long and with groundwater residence times exceeding 100,000 years (e.g., the White-Muddy River drainage in eastern Nevada) [33,34,35,36]. In addition, minor groundwater basins with shorter flow paths exist in hundreds of mountain ranges, supporting thousands of springs throughout both states (e.g., [32]). Such montane groundwater basins are relatively small, but some of those at lower and middle elevations also support springsnails.

The regional climate is arid and continental, with hot, dry summers and wetter winters. Nevada and Utah are considered to be the first and third driest states in the USA, respectively. Elevations range from 50 to more than 4000 m, and elevation strongly influences ambient temperature, precipitation, and evapotranspiration [37]. Springsnails typically occur at elevations <2000 m; thus, the ambient climate of their habitats is typically warm and summer-dry; however, the Wasatch Front near Salt Lake City receives more moisture than other low elevation areas in the two states and supports many springsnail populations. In striking contrast to the Basin and Range province, few springsnail populations have been reported from the Colorado River drainage in eastern Utah (Figure 1) [1,38]. With relatively little private or state land, most of the two states are managed by federal agencies, primarily for ranching, agriculture, and mining, and some lands are managed by Native American Tribes. Major cities include Las Vegas, Reno, and Salt Lake City, urban areas that are placing ever-increasing demands on the region’s limited water supplies. Additional study area information is provided in the Supplementary Materials.

3. Study Organisms

Thus far, 103 Truncatelloidea and Semisulcospiridae springsnail species have been described on the bases of morphology and genetics in Nevada (86 species) and Utah (21 species), with four species occurring in both states (

Table 1. Summary of springs and springsnail diversity, distribution, and inventory history in Nevada and Utah. Data summarized from Supplementary Materials Table S3. Asterisks (*) indicates estimations.

Variable	Nevada	Utah	Total
No. Reported Springs on Federal Land	17,835	6129	23,964
No. Inventoried Springs on Federal Land	2610	832	3442
No. Springs on State or City Land	280	603	883
No. Inventoried Springs on State or City Land	12	43	55
No. Springs Tribal Land	133	354	487
No. Springs Inventoried on Tribal Land	20	2	22
No. Springs on Private Land	7221	4559	11,780
No. Springs Inventoried on Private Land	761	186	947
Total No. Reported Springs	25,469	11,645	37,114 *
Total No. Inventoried Springs	3403	1063	4466
No. Federally-owned Springs with Springsnails	399	116	515
No. State- or City-owned Springs with Springsnails	5	32	37
No. Tribally-owned Springs with Springsnails	11	1	12
No. Privately-owned Springs with Springsnails	365	164	529
Total No. Springs with Springsnails	780	313	1093
No. Species of Springsnails	86	21	103

; Table S3 in Supplementary Materials; Figure 1) [1] Springsnail families in Nevada and Utah include: Amnicolidae (Amnicola and Coligyrus), Assimineidae (Assiminea), Cochliopidae (Eremopyrgus, Tryonia), Hydrobiidae (Pyrgulopsis), Lithoglyphidae (Fluminicola), and Tateidae (non-native Potamopyrgus) in the superfamily Truncatelloidea [1]; and Semisulcospiridae (Pleuroceridae; Juga) in the superfamily Cerithioidea. Within the caenogastropod Littorinimorpha, Truncatelloidea was proposed to clarify relationships among a diverse array of species formerly assigned to the superfamilies of Rissoacea and Cingulopsoidea [39]. Representatives of this superfamily are known throughout the world (Table S2 in Supplementary Materials) [3]. Springsnail taxonomy remains the focus of considerable ongoing research, with new species described each year and taxonomic advancement continuing at all levels of systematics [1,2,4,39,40,41]. The few widespread taxa typically have been, on closer investigation, subdivided into multiple haplotypes (subspecific lineages) or cryptic species [1,42]. Thus, the bi-state list is likely to increase. All presently recognized, recently extinct, and as-yet-undescribed springsnail species occurring in the two states are included in the Strategy (Supplementary Materials). Details on springsnail evolution, taxonomy, and diversity are provided in the Supplementary Materials.

Information on springsnail ecology and population resiliency, redundancy, and representation of springsnail populations have improved through quantitative research on several individual species, providing insight into life histories and the environmental factors affecting their abundance, distribution, and habitat use [43,44,45,46,47,48,49,50,51,52,53]. While the Strategy includes consideration of 103 springsnail species, the ecology of only a few species has been studied thus far, and most life history research has not taken place in Nevada or Utah. However, such studies demonstrate that each springsnail species occupies a distinct microhabitat (niche) with species-specific attributes of current velocity, water depth, substrata, temperature, water geochemistry, and interactions with other species. Further information on the ecology of selected springsnails is provided in the Supplementary Materials.

4. The Springsnail Conservation Program: Goals, Objectives, and Strategic Elements

The overall goal of the Agreement is to conserve at least 103 springsnail species that are distributed among several thousand springs in Nevada and Utah (Supplementary Materials Table S1). Five objectives were mandated by the government signatories of the Nevada and Utah Springsnail Conservation Agreement, which address information management, threats, habitat persistence, organization, and outreach. Strategic elements were developed by the Springsnail Conservation Team (SCT) to specify how the Agreement objectives are to be achieved (Supplementary Materials Table S8), and further details and background on the Strategy are provided in the Supplementary Materials.

Objective 1: Information Acquisition and Management

The strategies for addressing this objective involve the development of a comprehensive species list, identification of data gaps, and database management. Since 2019, the SCT has made much progress toward addressing this objective, and efforts are ongoing. The SCT is presently using Springs Online (https://SpringsData.org) as the repository database for springsnail and spring habitat information [54]. It is organized to receive annual inventory and monitoring information from collaborating agencies and researchers and its programming provides automated reporting with up-to-date information upon request. These reports provide a two-page synopsis of information useful to natural resource managers (e.g., species taxonomy, listing status, number of reported populations and habitats, date of the last detection; Supplementary Materials Appendix A).

Using the information in the database, the SCT completed a draft springsnail species list in 2019 based on the best available information (Supplementary Materials Table S3; Supplementary Materials Appendix A). As the database is more completely populated, it will provide an increasingly robust means of assessing population distribution, status and trends, and threats through time. Such information can be used by state and federal agencies to update NatureServe ranks that inform Species of Greatest Conservation Need listing in State Wildlife Action Plans [14,25] and Species Status Assessments by the USFWS. Additionally, the database provides a means for identifying data gaps regarding springsnail distribution, status, and habitat quality. We also developed an easily accessed, searchable master bibliography of Nevada and Utah springsnail literature (Supplementary Materials Appendix F), to which additional literature can continue to be contributed as it emerges.

The second strategic element under Objective 1 involves ensuring that standardized, effective survey and monitoring protocols are available to SCT partners. Springsnail inventory and monitoring protocols are provided in Supplementary Materials Appendix B. and involve three tiers to be used for: (1) qualitative inventory surveys, (2) semi-quantitative surveys, and (3) quantitative effectiveness monitoring and population monitoring. This protocol was developed by Donald R. Sada based on many years of springsnail sampling across the Great Basin.

Objective 2: Identify, Assess, and Reduce Threats

Effectively addressing threats to 103 springsnail species among thousands of remote springs across the two states is no small task. Effective communication among partners, coordinated efforts, and prioritization of conservation efforts are key to SCT success in addressing threats over time. In particular, agreement on threat terminology and the development of a risk assessment tool are important to the SCT in moving forward with threat mitigation. For example, habitat protection measures at several US Fish and Wildlife Service refuges have recently resulted in the conservation of more than a dozen springsnail species (e.g., at Warm Springs-Moapa, Ash Meadows, and Pahranagat Desert Wildlife Refuge preserves in southern Nevada). Management lessons from these examples will help advance springsnail conservation throughout the Great Basin.

Identification, assessment, and reduction of stressors and threats by a diverse group of partners across two states require agreement on terminology and recognition that agency lexica and missions differ. The states of Nevada and Utah and the USFWS define threats and stressors differently [14,25,55]. This necessitated the development of a crosswalk through which different terms and definitions related to threats and stressors are related (Supplementary Materials Appendix C) and recognition of agency responsibilities and priorities (Supplementary Materials Appendix D). The crosswalk relates risk factor terms used by the Nevada Department of Wildlife to those describing the threats and stressors identified in the Utah Wildlife Action Plan [14] Levels 1 and 2 and the listing criteria used by the USFWS (below).

The SCT’s springsnail initial risk assessment approach encompasses an evaluation of the severity of potential threats and active stressors affecting a species or its habitat. It has initially been structured to accommodate comparison across species, habitats, and time for use in prioritizing conservation efforts (Supplementary Materials Appendix E). Scale can affect the severity and scope of a threat to springsnail populations, so the risk assessment identifies whether a threat is local (i.e., within the immediate locality of the spring ecosystem) or far-field (non-local; beyond the vicinity of the spring). The main threat categories covered in the risk assessment include: habitat degradation; over-use (for scientific, education, or recreation); regulatory mechanisms; and biological factors (i.e., non-native species predation and competition from Louisiana red crayfish-Procambarus clarkii [56], red-rimmed Melania-Melania tuberculata [57], growing threats of invasion by New Zealand mudsnail Potamopyrgus antipodarum [26,58], and introduction of many game and aquarium fish species [59,60,61], as well as other factors). Several specific threats (referred to as “elements”) fall under each of the five major threat categories, as explained by the SCT (Appendix E in Supplementary Materials).

The SCT will incorporate the best existing data to refine species status assessment that meets USFWS standards. Springsnails are a sensitive taxonomic group and are subject to potential federal listing, so the SCT also incorporates elements of the USFWS conservation framework (the “3 Rs”: representation, resiliency, and redundancy; [62]). Although population resiliency (ability to recover from disturbances) is sometimes relatively high, population representation across environmental gradients is often limited by extreme stenotolerance, and redundancy is limited because individual species often occur in only one or a few populations. Despite these natural limitations, USFWS springsnail species reviews have rarely resulted in federal listing in Nevada and Utah [22,23,24].

The Strategy’s risk assessment tool (Supplementary Materials Appendix E) represents the first step toward prioritization of conservation efforts based on threats, but it may not adequately integrate climate and hydrologic risks. The SCT is currently partnering with experts on climate and hydrologic risk assessment to refine modeling and better predict and determine how changes in climate and groundwater levels andhydrology will affect springsnail demography, as well as habitat quality and quantity. Additionally, while local threats are relatively easy to detect, understand, measure, and sometimes mitigate, far-field threats are more difficult to identify, quantify, and resolve. To support continued development of future versions of these tools, a geographic information system-based land use risk model that functions at various scales will help identify other far-field threats. Such tools and models also will be useful for measuring the effectiveness of conservation efforts over time.

Objective 3: Conserve Habitats to Ensure Species Persistence

Overview: Achieving this third objective will require consistent effort in surveying, data management, data analysis, and threat mitigation. Field survey data are needed on species distribution and demography over time so that managers can assess status and trends. Threat mitigation varies by spring type [13], is a concern throughout the Great Basin, and will be increasingly necessary as human populations in Nevada and Utah continue to grow. Several simple mitigation strategies can be widely implemented to make major improvements in springsnail conservation and are discussed below. Consistent monitoring is needed to ensure the effectiveness of threat mitigation projects over time.

Livestock and Wildlife Management and Fencing Practices: Many springs in Nevada and Utah are compatibly used for livestock and wildlife management. Domestic and feral livestock and wild ungulate impacts on habitat structure are common at Nevada and Utah springs but often are similar and difficult to distinguish. Threats posed by livestock and wildlife impacts on spring habitats include trampling and pedestal formation, vegetation disruption and removal, fecal contamination, surface water quality degradation, and increased embeddedness of the firm substrata often required by springsnails. Such impacts can largely or entirely eliminate springsnail populations and habitat functionality. However, many springsnail populations are resilient and can survive moderate levels of impact from large animals; thus, livestock and wildlife management can be compatible with springsnail conservation and effective management.

Local Flow Diversion: Livestock, domestic, and wildlife watering and flow regulation often stress springs ecosystem integrity, but such impacts often can be compatibly managed. For example, installing a flow splitter can allow both abstraction of flow and the continued emergence of groundwater at the source [63]. Flow diversion often is plagued by pipe leakage, the maintenance of which remains the obligation of the steward. Fencing the source while still providing livestock and wildlife with alternative water is often a compatible solution; however, monitoring is needed to ensure the effectiveness of habitat protection over time [64]. Hillslope erosion can be addressed through low-cost construction of a simple steppingstone trail to the source, allowing easier access for the steward. Although springsnail populations are resilient to minor human disturbances and can tolerate some geomorphic alteration of their habitats, monitoring and appropriate responses are required to ensure their persistence at developed springs.

Nearly all springsnail taxa require firm substrata near springs sources, habitat elements often eliminated by intensive ungulate trampling. Furthermore, many springsnails co-occur with watercress (Nasturtium officinale) and sometimes cattail (Typha spp.) Depending on the springsnail species’ habitat requirements, the addition of appropriate substrata (sand, gravel, sticks, and logs), and perhaps the addition of watercress, but not highly invasive cattail, may benefit springsnails and other near-source springs-dependent taxa. Such habitat augmentation should be experimentally determined and, if implemented, carefully monitored.

Regional Threat Reduction: At far-field scales, the mitigation, reduction, or elimination of broad-scale threats and stressors involves societal discussion and agreement, which are part of the foundation established through the Agreement. Such discussion requires consistent attention and considerable effort on the part of the SCT, its signatory agencies, and the public in the two states. While difficult to coordinate, such discussions and agreements are essential to reduce risk and threat severity to springsnails and to ensure the sustainability of groundwater resources throughout the two states.

Objective 4: SCT Organization and Coordination

The SCT organizational process has been structured to ensure, to the extent possible, achievement of Agreement objectives (Figure 2). The Agreement and Strategy are based on adaptive management, the structured process of making well-informed decisions in the face of uncertainty [65,66,67]. Adaptive management involves collaboration with stakeholders to recognize issues, implement management actions, review monitoring data on the success of those actions, provide feedback to improve management and communicate lessons learned. The SCT developed specific procedures for the timing and conduct of its semi-annual meetings, as well as the development of ad hoc committees and annual reports. These specifications are described in the Strategy and als o in a charter document (Supplementary Materials).

Objective 5: Education and Outreach for Springsnail Conservation

The ease with which springsnail populations and habitats can be conserved varies widely across the Great Basin. Degraded springs on federal lands can be relatively easily rehabilitated by SCT partners, provided administrative support is maintained. If a spring’s aquifer is relatively intact, and if stakeholders can reach a consensus on management options and actions, stewardship planning and implementation benefiting all parties and natural resources may be achieved relatively easily (e.g., [68,69,70]). However, the SCT will need to develop and maintain strong partnerships and diverse expertise. For example, USDA Natural Resources Conservation Service partners may be helpful in exploring and implementing incentives to improve springsnail conservation actions by private parties, and Bureau of Land Management partners may provide expertise in livestock and human recreation management around springs to reduce habitat degradation.

While springs are compelling conservation foci for the public, springsnails are inconspicuous and thus far have elicited limited public appreciation. Hence, promoting the ecological integrity of springs may be the most effective route toward addressing springsnail conservation. In addition to reporting on program successes (Supplementary Materials Appendix G), the phrase “What is good for springs is good for all things” can be an effective campaign slogan for the Strategy to more easily reach the private sector and help increase public enthusiasm and involvement for protection of springsnails and their habitats, as well as the many other species those springs support. Thus, the SCT will have to initiate new forms of communication, education, and outreach about springsnails and their habitats to attract support from the public and private landowners, as well as the scientific community, signatory agencies, and other states in the Great Basin and elsewhere.

5. Conclusions

The Nevada and Utah Springsnail Conservation Agreement was developed to protect springsnails and their habitats in Nevada and Utah, thereby precluding the need for a federal listing of those species. A diverse group of partners, the Springsnail Conservation Team has worked collaboratively to develop the Strategy and implement its five goals. The team has successfully advanced several Strategy objectives (e.g., administrative organization, database management, and information for improving risk assessment), but more work is required, and these efforts must continue over time to be effective. Well-monitored on-the-ground conservation actions are needed, with good communication to inform the public and other managers. Additional partnerships, including those with other states, are needed to improve inventory and habitat assessment and protection, as well as improve hydrologic and climate change modeling. It also will be important for the Strategy to remain a “living document” to better follow adaptive management practices and maximize the program’s effectiveness and efficiency over time.