National Park Units Research Articles

A spatiotemporal comparison of interobserver error in vegetation sampling

AbstractQuestionsWe asked how interobserver error in sampling vegetation (excluding trees) varied over time, space and habitat type; determined whether there were any obvious correlates of observer error; and evaluated evidence of bias among observers.LocationNine national park units in the Midwestern USA.MethodsWe quantified observer error in the context of a long‐term monitoring program employing three observers, evaluating interobserver error across 11 locations in the Midwestern USA over five years. The vegetation (excluding trees) was sampled independently by two teams of observers at prairie and woodland locations (n = 94 plots total).ResultsTotal pseudoturnover ranged between 20.2% and 22.1% at prairie locations, and between 16.8% and 28.6% at woodland locations. The overlooking component of pseudoturnover accounted for 75% or more of total pseudoturnover, with misidentification and cautious components each contributing 19% or less of the total, depending on location. The percentage of comparisons in which both observers recorded the same cover class ranged from 71.3% to 78.5% at the prairie locations and 56.9% to 85.6% at woodland locations. When observers did not agree on cover class, they were off by more than one class less than 6% of the time. Overlooking error was more likely to occur for species with less cover, while estimation error was more likely to occur for species with greater cover. A bias existed among observers, as the least experienced observer recorded 6.2%–11.8% more species than the other two observers. Interobserver bias also existed for rates of estimation error, as one observer consistently recorded higher cover classes.ConclusionsObserver error is a pervasive aspect of vegetation sampling. Continued training and experience yielded limited increases in precision. Elements of the sampling design probably reduced observer error to a certain degree, although some level of interobserver error in vegetation surveys is unavoidable.

Sunscreen pollution is abated during the COVID-19 “Anthropause” of 2020 in two U.S. National Parks: Cape Lookout National Seashore and Kaloko-Honokōhau National Historical Park

From March to June 2020, governments across the world imposed lockdowns in an attempt to reduce the transmission of COVID-19 during the early phase of the pandemic. This period of time in which human activity slowed worldwide has been coined the “Anthropause”. The goal of this study was to determine if sunscreen pollution abated during the Anthropause and to identify the severity of the pollution when tourism/recreation recovered at two coastal units of the U.S. National Park System: Kaloko-Honokōhau National Historical Park in Hawaiʻi, U.S.A. and Cape Lookout National Seashore in North Carolina, U.S.A. Active ingredients of sunscreen products were measured in water and sand samples at both locations, including oxybenzone, octinoxate, octocrylene, octisalate, homosalate, and relevant breakdown products of some of these ingredients. A risk assessment was conducted on Anthropause and post-Anthropause contaminant levels for both locations to determine if there was a threat reduction during the Anthropause, and whether tourism recovery in the post-Anthropause period served as a threat to coastal wildlife. Both national park units exhibited an almost absolute reduction in the levels of sunscreen contamination during the Anthropause period, a striking commonality considering the geographic expanse separating the parks. Once travel restrictions were lifted, a large influx of tourists ensued at both locations, resulting in a relatively sudden and dangerous increase in the levels of sunscreen chemical pollution. This study supports the argument that unmanaged tourism is a source of coastal sunscreen pollution that poses a threat to the localized continuity of species populations and biodiversity, especially to coral reefs and fisheries.

National Park Service Internal Structures Toward Agency Resilience: A Mixed-Methods, Multi-Site, Mesoscale Investigation

Agencies focused on protected areas’ conservation and recreation require internal capacity-building to enhance their organizational resilience (the ability to adapt and persist). Yet, internal capacity-building is often underemphasized as agencies attend to external relationships. This omission can lessen an agency’s ability to adapt to emergent stressors and opportunities. Specifically, relationships within an agency’s groups (i.e., divisions)—the intra-organizational mesoscale between individuals and whole organizations—can increase an agency’s ability to efficiently build resilience-enhancing adaptive capacity. The U.S. National Park Service (NPS) adopted this mesoscale in their Urban Agenda goal of One NPS, or building resilience-enhancing, agency-wide internal relationships. We investigated intra-organizational relationships in this context, examining relationships within (i.e., bonds) and across (i.e., bridges) three NPS groups: parks (physical spaces), programs (community outreach), and offices (administrative functions). Pairing qualitative interviews with quantitative social network analysis in Detroit, Tucson, and Boston, we examined internal relationship prevalence, supports, and opportunities. The NPS has program and office presence in each of these three urban areas but different proximities to national park units, which are the typical face of the NPS. Across these urban areas, we found that the parks group exhibits more bonds (park-to-park relationships), the programs group exhibits more bridges (program-to-park or program-to-office), and the offices group exhibits a mixture of bonds and bridges. To further One NPS and organizational resilience, cultivating bridges among the three groups is key. This investigation may inform a more strategic focusing of an agency’s limited resources. We highlight five directions for protected area managers’ consideration toward this aim: build bridges locally among groups; consider group composition when identifying divisions (i.e., programs appear more heterogeneous or dissimilar from each other than do the park and office groups); reflect on parks’ centrality to NPS identity and relationships; seek organizational structures supportive of relationship development; and focus on the organizational mesoscale for resilience-enhancing adaptive capacity. These directions for strategic focusing of organizational resources are based in the longstanding work of the NPS but ultimately transcend this single agency, providing targeted guidance for protected area agencies in building internal capacity toward external, public-oriented goals.

Support for management actions to protect night sky quality: Insights from visitors to state and national park units in the U.S.

Light pollution is a global phenomenon where anthropogenic light sources continue to grow unabated, affecting both social and ecological systems. This is leaving parks and protected areas as some of the last vestiges of naturally dark environments for protecting views of the night sky. Yet, even parks and protected areas have outdoor lighting. Alternative lighting practices are needed to reduce or prevent light pollution from within parks. However, making parks darker may not be desirable for some visitors if they believe it will reduce navigability, safety, or restrict how they recreate (e.g., requiring the use of red-light flashlights after dark and before dawn). How visitors will respond to alternative lighting practices that park managers can implement is still unknown. We used an on-site intercept survey at nine state and national park units in Utah, U.S., to investigate nighttime visitors' support or opposition to management actions to protect night sky quality and their interest in learning about topics related to night skies. Further, this study also segmented visitors into two groups: those ‘dependent’ on the dark sky as a resource and those whose activities did not depend on a dark sky. Defining what a ‘dark sky dependent’ visitor is, which has yet to be done in the literature, is a fundamental step to furthering night sky research and management efforts. Across nine parks and protected areas, 62% of nighttime visitors participated in dark sky dependent activities. Findings indicate broad support for management actions designed to improve night sky quality, with between 74% and 89% of all visitors supporting seven different management actions. There was stronger support from dark sky dependent visitors for some elements of alternative lighting practices, but there was still strong support for those who do not participate in dark sky dependent outdoor recreation. Additionally, between 57% and 75% of visitors were interested in learning more about topics related to night skies. This research indicates most visitors would welcome actions to preserve the quality of the rapidly dwindling naturally dark experiences offered by parks and protected areas.

Comparing Visitor Perceptions, Characteristics, and Support for Management Actions before and during a Pilot Timed Entry System at Arches National Park

Over the past decade, many national park units in the United States broke visitation records. Arches National Park (UT, USA) is no exception. Between 2011 and 2021, visitation increased 74%. As part of considering management options to address the issues from sustained and concentrated visitation, Arches implemented a pilot timed entry system from 3 April to 3 October 2022. This article compares visitor perceptions, characteristics, and support for management actions before and during the pilot timed entry system using data from visitor intercept surveys. Findings suggest visitors experience quality improved across the park and on hiking trails during the pilot timed entry system. Visitor characteristics were extremely similar, and there were no differences in local residency, group size, vehicle occupancy, race, ethnicity, first time visitation, education level, or household income. Visitors were more likely to plan for the trip further in advance and were less likely to re-enter the park during the pilot timed entry system. Lastly, visitors demonstrated more support for timed entry and lower levels of support for expanding parking, site specific reservations, and temporary closures during the pilot timed entry system. These results reflect unique insights for managers considering managed access systems like timed entry to sustainably manage visitor use in parks and protected areas.

Anthropogenic noise events perturb acoustic communication networks

Anthropogenic noise sources impact ecological processes by altering wildlife behavior and interactions with cascading impacts on community structure. The distribution and magnitude of such noise has grown exponentially over the past century, and now inundates even remote areas. Here we investigate biological responses to prolific, anthropogenic noise sources associated with the physical presence of the source (vehicle noise and human voices) and disconnected from it (aircraft overflight). Bioacoustic responses to these noise sources were documented at 103 sites in 40 U. S. National Park units. The presence of bird sounds was noted in 10-s audio samples every 2 min, for 8 days at each site and related to the presence of human voices, vehicle noise, and aircraft noise in the same and preceding samples. Generalized additive models were used to fit smoothing splines to weight the influence of noise in past samples on the probability of detecting bird sounds in the present sample. We found that the probability of hearing birds increased immediately following noise events, and decreased about 2 h after the event. The negative effects were persistent more than 3 h after a noise event. The persistence of these responses – especially for noise from jets that were many kilometers distant – raises questions about the functional significance and ecological consequences of this altered activity, particularly in light of the widespread and diverse habitats in this study and ubiquity of the noise sources evaluated.

Stable background tree mortality in mature and old-growth forests in western Washington (NW USA)

Increasing rates of tree mortality have been observed in recent decades for all major forest types worldwide. Elevated mortality has been linked to drought and high temperatures resulting from human modification of the atmosphere and climate. Older forests in the Pacific Northwest are globally significant as carbon sinks and may serve as refugia in the face of wildfires and climate change. We examined temporal patterns of tree mortality in mature and old-growth forests in national park units in western Washington, U.S.A, over the period 2008 to 2018, to evaluate whether the broader pattern of increasing tree mortality applies there. We also used individual-tree models of mortality to seek links between drought and tree mortality, while considering processes internal to forest stands such as competition. The annualized rate of tree mortality for the entire period generally did not exceed the expected, background rate of 1 %. The mean was ≤ 1.0 % for saplings (2.5 to 12.6 cm dbh) for 60 % of plots, for small trees (12.7 to 76.1 cm dbh) for 66 % of plots, and for large trees (greater than76.1 cm dbh) for 92 % of plots. 95 % confidence intervals wholly exceeded 1.0 % yr−1 only for small size classes in a minority of plots (saplings, 7 % of plots, and small trees, 11 % of plots). Comparing the first and second 5-year segments of the observation period, there were no clear trends of increasing mortality for any of the size classes. We tested generalized linear mixed-effects models based on the Gompit link function, using predictive factors related to drought, tree-to-tree competition, individual tree vigor, and tree species shade tolerance. We found only an index of tree vigor to consistently predict probability of tree mortality. In one model, anomaly of vapor pressure deficit in winter months was significant, but the sign of the effect did not implicate drought (i.e., mortality probability increased with moisture). These results show that, at least up to 2018, healthy trees within old-growth, protected forests in the Pacific Northwest may be resilient to current climatic changes, highlighting the importance of continued conservation and protection of these increasingly rare ecosystems and carbon stores. The occurrence of extreme climatic events following our study period emphasizes the need for continued observation and analysis to facilitate management for protection of refugia and migration corridors.

Observer error in grassland vegetation surveys: effects on species diversity metrics and species–abundance relationships

AbstractWe investigated the effect of observer error on four commonly used species diversity measures: species richness, Shannon–Weiner diversity, Shannon–Weiner evenness and Simpson’s index of diversity. We also evaluated how observer error affects inferences derived from multivariate analyses of species–abundance relationships as determined by non-metric multidimensional scaling (NMS) ordination. Grassland vegetation was sampled by three different botanists at two national park units in Missouri and Kansas, USA. The same plots were sampled by two of the botanists, who compiled lists of species composition and estimated foliar cover. Differences in the data records were then compared. Pseudoturnover (i.e. apparent turnover due to observer error) ranged from 17.1% to 22.1%, and differences in cover class estimation ranged from 21.5% to 30.5%. The percentage difference in species diversity measures between pairs of observers depended on how data were summarized, but were always <20%, and often <10%. Based on these results, species diversity metrics are affected to a relatively smaller extent by observer error than turnover indices. Turnover indices, however, contain more information because they track individual species, whereas species are interchangeable in most species diversity indices. Thus, less of the error is identified because of how species diversity indices are calculated. NMS ordinations revealed that while the characterizations of some plots by different observers were similar, differences between observers’ records for other plots resulted in greater separation in ordination space. Points representing one observer’s records were often shifted in ordination space in the same direction compared with the other observer.

A Case Study of Millennials’ Attitudes Toward U.S. National Parks

Visitation to some of the most popular national parks in the United States has surged in recent years, but in many national park units, attendance has declined even as the U.S. population increases. Changing demographics, patterns of visitation, maintenance needs, and inconsistent federal support raise questions about national parks’ relevance to younger generations. In particular, the attitudes of the U.S. Millennial generation are a key concern for park managers and supporters. We evaluate the views of a sample of Millennials toward America’s national parks and find that many lack basic knowledge about national parks, yet still say they value and appreciate the national park system. Land managers should respond to knowledge gaps of Millennials and pursue outreach that strategically consolidates the support of this and younger generations for a national parks system that is expected to provide ecological and cultural benefits for current and future generations.

Analyzing national parks visitor activities using geotagged social media photos

Visitor activities within national parks are important information for park management. Currently, national parks and nature-based recreation area worldwide have no systematic visitor activity data collection schemes. Traditional visitor movement or activity data collection methods used in tourism studies are often costly in money and time and difficult to implement. This paper presents a framework and formal procedure that uses geotagged photos crowdsourced from social media platforms to uncover visitor activities within national parks. First, the daily individual space-time paths are constructed from the photo geotags and timestamps for all visitors. Then the following information is derived from the space-time paths: 1) four activity types including stationary, walking, vehicle riding, and flying; 2) the total time of various visitor activities in a park; 3) visitor flow directions aggregated to a grid; 4) a graph constructed from space-time paths and the directed and undirected connections (flows) between POIs; and 5) the centrality of POIs derived from the graph. A case study of four highly visited U.S. national park units from 2008 to 2021 demonstrates the process and capabilities of the method. It also reveals a trend of increased walking time and decreased stationary time in the case study parks over the years. Although this study is only based on Flickr photos, the method can be implemented with data derived from any social media platforms as long as geotags and timestamps are available. The method may be used to monitor visitor activities and movements within national parks and other outdoor recreation areas, especially remote and unmonitored locations.

U.S. National Park visitor perceptions and behavioral intentions towards actions to prevent white-nose syndrome.

In the United States, the discovery and spread of white-nose syndrome (WNS) has drastically changed how bats and caves are managed. The U.S. National Park Service has been instrumental in the national response to WNS, as it manages extensive cave resources and has a close relationship with the public. However, managers lack information on visitor support for disease prevention measures designed to slow the spread of WNS and minimize human disturbance of vulnerable bat populations. This study utilized the Theory of Planned Behavior to determine how visitor attitudes, subjective norms, and perceived behavioral controls influenced their behavior regarding WNS preventive actions, including participation in educational programming on bats, wearing clothes or shoes in caves that have not been contaminated with the fungus that causes WNS, walking over decontamination mats, and complying with cave closures. During summer of 2019, data were collected using an on-site survey of 1365 visitors to eight U.S. national park units: Oregon Caves, Lava Beds, Carlsbad Caverns, El Malpais, Wind Cave, Jewel Cave, Mammoth Cave, and Cumberland Gap. Visitors were willing to participate in all preventative actions addressed in the survey (77.7%-96.7%). Visitors expressed that engaging in these actions was very desirable (36.0%-65.6%), and their decision to engage in these actions was most strongly influenced by park staff (39.2%-68.8%) or signage (35.5%-61.9%). Attitudes and subjective norms were positive predictors of behavioral intentions for all measures. Perceived behavioral control was not a direct predictor for behavioral intent, but its interaction with attitudes and subjective norms had a moderating influence on intention to comply with multiple WNS preventive actions. With the continued spread of WNS and emergence of other threats to bats, understanding visitor behavioral intent and underlying factors will facilitate successful implementation of preventive actions that are publicly supported and promote conservation of bat populations in U.S. national parks.

Root hemiparasitic plants are associated with more even communities across North America.

Root hemiparasitic plants both compete with and extract resources from host plants. By reducing the abundance of dominant plants and releasing subordinates from competitive exclusion, they can have an outsized impact on plant communities. Most research on the ecological role of hemiparasites is manipulative and focuses on a small number of hemiparasitic taxa. Here, we ask whether patterns in natural plant communities match the expectation that hemiparasites affect the structure of plant communities. Our data were collected on 129 national park units spanning the continental United States. The most common hemiparasite genera were Pedicularis, Castilleja, Krameria, and Comandra. We used null models and linear mixed models to determine whether hemiparasites were associated with changes in community richness and evenness. Hemiparasite presence did not affect community metrics. Hemiparasite abundance was positively associated with increasing evenness of herbaceous species, but not with species richness. The associations that we observed on a continental scale are consistent with evidence that the impacts of root hemiparasitic plants on evenness can be substantial and abundance dependent but that effects on richness are less pronounced. Hemiparasites mediate competitive exclusion in communities to facilitate species coexistence and merit consideration of inclusion in ecological theories of coexistence.

Integrating water quality monitoring and diatom community trends to determine landscape‐level change in protected lakes

AbstractLakes in protected or remote regions are not immune to anthropogenic impacts and face a variety of stressors ranging from atmospheric deposition of pollutants to global climate change. Monitoring programs in these lakes can be limited in scope due to sampling logistics, leaving an incomplete picture of how the systems may be impacted by environmental stressors. Here, we used diatoms as early indicators of change in relatively undisturbed lakes from five national park units in the US Great Lakes region. Surface sediment samples were collected repeatedly over more than a decade to analyze the diatom community turnover. This diatom community assemblage data were compared with the measured water quality data collected over the same period in order to identify the predominant drivers of ecological change. Even though the parks in this study span two biomes, and lake characteristics vary between and within parks, we found synchronicity in measured water quality trends and diatom responses. Changes in the thermal regime and water‐column mixing appeared to drive much of the change across parks, although much of the diatom turnover also followed a sulfate or pH gradient. Nutrients did not appear to play a major role in diatom community change. This method of using diatoms in conjunction with water quality monitoring allows for an integrated response over a number of years and provides managers with a complementary tool to determine which environmental parameters are having the biggest effect on lake ecology.

Strategies for Long-Term Monitoring of Riverscour Plant Communities to Inform Science-Based Management

Understanding the condition of natural resources in protected areas is fundamental to their management and preservation. Long-term monitoring can provide crucial data for managers to prioritize management actions and subsequently determine their effectiveness. In five national park units in the eastern United States, the National Park Service Inventory and Monitoring Program monitors rare riverscour communities—open habitats in which sun-loving plants grow over rocky substrates along high-gradient streams. Based on a decade of monitoring experience, we present recommendations for monitoring riverscour communities including sampling methodology, data collection methods, and subsequent management actions. Given increasing stressors from changing climate, invasive species, and altered hydrology, understanding how riverscour communities are changing is increasingly important to their protection.

Using ADS–B Data to Understand Overflight Altitude Characteristics at Hawai‘i Volcanoes National Park

Air tour management plans for U.S. national park units are developed by the Federal Aviation Administration (FAA) and the National Park Service (NPS). The FAA recommends pilots fly higher than 2,000 feet above ground level (AGL) over parks, wildlife refuges, and areas with wilderness characteristics. Management of air tours is important for mitigating visual and noise impacts. Understanding air tour travel patterns has been problematic because objective location data have been difficult to obtain. A newer technology, Automatic Dependent Surveillance–Broadcast (ADS–B), can be used to accurately track overflights. Prior ADS–B studies of air tours conducted limited analysis with respect to altitude characteristics. Thus, the purpose of this study was to determine how overflights spatially vary across altitudes and determine altitude trends for primary flight corridors. Results suggest overflights trend along the east side of the park and 74.59 percent of waypoints within a 0.5-mile buffer around the park boundary had altitudes less than 2,000 feet above ground level (AGL). Results revealed that as altitude increased, overflight density decreased. Using hot spot clustering analysis, overflight lateral pattern differences were determined for altitudes lower than 2,000 feet AGL compared to altitudes higher than 2,000 feet AGL. This study also identified one primary flight corridor with average altitudes mostly below 2,000 feet AGL. Managers can use these results to inform the development of air tour management plans and monitor compliance.

Spacing of point counts for grassland bird surveys in small geographical areas: Biases and tradeoffs

Point counts are the most commonly employed methodology in bird surveys. Survey points are usually spaced ≥250 m apart to prevent double counting. In cases where they are used in small (<200 ha) geographic areas, this spacing results in a very small sample size, which may substantially underestimate species richness. Alternatively, locating survey points closer together may produce more complete species lists, but result in excessive double counting of individuals, yielding biased population estimates. We investigated this tradeoff in surveys of breeding birds in predominantly grassland habitats in 5 small (73–114 ha) national park units with survey points spaced at 100 m intervals. Sampling at this distance captured 70–90% of the estimated species richness at 4 of the 5 parks. Approximately half of the species observed were rare, occurring at ≤3 sites. Approximately one-third of all birds were observed far enough from the survey point to be counted at another point. Based on rarefaction curves, increasing the distance between survey points from 100 m to 200 m would result in a 27–48% reduction of observed species. Conducting multi-species bird surveys in small geographic areas using single-visit point counts that are widely spaced (e.g., ≥250 m) will likely underestimate species richness, even with the use of statistical species richness estimators. As a result, rare species will be undersampled.

Resilience to fire and resistance to annual grass invasion in sagebrush ecosystems of US National Parks

Western North American sagebrush shrublands and steppe face accelerating risks from fire-driven feedback loops that transition these ecosystems into self-reinforcing states dominated by invasive annual grasses. In response, sagebrush conservation decision-making is increasingly done through the lens of resilience to fire and annual grass invasion resistance. Operationalizing resilience and resistance concepts requires place-based understanding of resilience and resistance variation among landscapes over time. Place-based insights allow for landscape prioritization in targeted areas of significance such as protected-area sagebrush ecosystems that exhibit inherently low resilience and are therefore at high risk of loss. We used a multi-scale approach to evaluate sagebrush resiliency and strategic planning across 1) the US National Park system, 2) a regional suite of five parks, and 3) for two specific park case studies. First, we summarized broad patterns of relative resilience to fire and resistance to annual grass invasion across all parks with sagebrush ecosystems. We found that national parks represented ~11% of US protected-area sagebrush ecosystems and reflected a similar low-resilience bias that occurs across the biome, broadly. Climate change is likely to shift both low- and high-resilience park sagebrush ecosystems towards moderate resiliency, creating new opportunities and constraints for park conservation. Approximately seventy park units include at least some sagebrush shrublands or steppe, but we identified 40 parks with substantial amounts (>20% of park area) that can be included in an agency-wide conservation strategy. Second, we examined detailed patterns of resilience and resistance, fire history and fire risk, cheatgrass (Bromus tectorum) invasion, and sagebrush shrub (Artemisia spp.) persistence in five national park units in Columbia Basin and Snake River Plain sagebrush steppe, contextualized by the broader summary. In these five parks, fire frequency and size increased in recent decades. Cheatgrass invasion and sagebrush persistence correlated strongly with resilience, burn frequency (0–3 fires since ~1940), and burn probability, but with important variation, in part mediated by local-scale topography. Third, we used these insights to assemble strategic sagebrush ecosystem fire protection mapping scenarios in two additional parks – Lava Beds National Monument and Great Basin National Park. Readily available and periodically updated geospatial data including soil surveys, fire histories, vegetation inventories, and long-term monitoring support resiliency-based adaptive management through tactical planning of pre-fire protection, post-fire restoration, and triage. Our assessment establishes the precarious importance of the US national park system to sagebrush ecosystem conservation and an operational strategy for place-based and science-supported conservation.

Assessing trends and vulnerabilities in the mutualism between whitebark pine (Pinus albicaulis) and Clark's nutcracker (Nucifraga columbiana) in national parks of the Sierra-Cascade region.

Dispersal of whitebark pine (Pinus albicaulis Engelm.), a keystone species of many high-elevation ecosystems in western North America, depends on Clark's nutcracker (Nucifraga columbiana Wilson), a seed-caching bird with an affinity for whitebark seeds. To the extent that this dependence is mutual, declines in whitebark seed production could cause declines in nutcracker abundance. Whitebark pine is in decline across much of its range due to interacting stressors, including the non-native pathogen white pine blister rust (Cronartium ribicola J. C. Fisch.). We used avian point-count data and tree surveys from four national park units to investigate whether trends in whitebark pine can explain trends in Clark's nutcracker. Spatial trends were modeled using recent data from two parks, while temporal trends were modeled using longer time-series of nutcracker and whitebark data from two additional parks. To assess the potential dependence of nutcrackers on whitebark, we linked a model of nutcracker density (accounting for detection probability) with a model of whitebark trends, using a Bayesian framework to translate uncertainty in whitebark metrics to uncertainty in nutcracker density. In Mount Rainier National Park, temporal models showed dramatic declines in nutcracker density concurrent with significant increases in whitebark crown mortality and trees infected with white pine blister rust. However, nutcrackers did not trend with whitebark metrics in North Cascades National Park Service Complex. In spatial models of data from Yosemite National Park and Sequoia-Kings Canyon National Park, nutcracker density varied not only with local cover of whitebark but also with elevation and, in Sequoia-Kings Canyon, with cover of another species of white pine. Our results add support for the hypothesis that the mutualism between whitebark pine and Clark's nutcracker is vulnerable to disruption by blister rust, and our approach integrates data across monitoring programs to explore trends in species interactions.

Exploring the effects of aircraft noise on bioacoustic activity in national parks

In the course of measuring and analyzing environmental acoustic conditions in U. S. National Park units, a large number of acoustical recordings have been aurally reviewed by trained technicians who noted the presence of a wide variety of sound sources. For this presentation, we analyzed changes in bioacoustic activity in relation to sounds from nearby people and distant aircraft. A central question for our analysis was the relevant time scale of exposure, as it is plausible that natural choruses are affected both by the immediate stimuli they experience as well as their recent history of exposure to similar stimuli. The large sample size—600 000 observations—enabled us to investigate data-driven models that document the decay of effects with increasing time lag between exposure and response.

Established and empirically derived landbird focal species lists correlate with vegetation and avian metrics.

Surrogate species are commonly used in conservation science due to the fact that it is not feasible to measure and manage each component of biodiversity independently; yet, there is much debate about their efficacy. We use long-term monitoring data from six national park units in northern California and southern Oregon to test the focal species approach, wherein a suite of species is selected whose habitat requirements collectively encompass those of co-occurring species. Specifically, we examine how well existing Partners in Flight (PIF) habitat-based focal species lists and empirically derived focal species lists represent vegetation and three avian assemblages of interest: the entire assemblage, species of concern, and common species in steep decline. Existing PIF focal species lists were significantly correlated with the three alternative matrices of avian assemblages and vegetation, but not all parks and alternate matrices performed with equal correlative strength and/or significance. For example, existing PIF focal species lists were significantly correlated to the entire assemblage at five of the six parks and had ecologically meaningful correlations (>0.70) at four. However, PIF focal species list correlations with park specific species of concern and common species in steep declined varied widely, with correlations between 0.040-0.943 and 0.210-0.556, respectively. Averaged across park units the empirical focal species lists developed to represent both vegetation metrics and species of concern improved correlation with all alternative matrices of avian assemblages and vegetation metrics. We found that the focal species approach generally represented the entire avian community, but did not adequately represent suites of species of concern or common species in decline. Empirical testing is a critical step in validating or refining suites of focal species at management relevant scales, and in some instances, a more refined focal species list may increase overall utility of the surrogate species approach.