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At least 559 records · Page 31Linked to original sources

Fate of geothermal mercury from Yellowstone National Park in the Madison and Missouri Rivers, USA

Mercury is a worldwide contaminant derived from natural and anthropogenic sources. River systems play a key role in the transport and fate of Hg because they drain widespread areas affected by aerial Hg deposition, transport Hg away from point sources, and are sites of Hg biogeochemical cycling and bioaccumulation. The Madison and Missouri Rivers provide a natural laboratory for studying the fate and transport of Hg contributed by geothermal discharge in Yellowstone National Park and from the atmosphere for a large drainage basin in Montana and Wyoming, United States of America (USA). Assessing Hg in these rivers also is important because they support fishery-based recreation and irrigated agriculture. During 2002 to 2006, Hg concentrations were measured in water, sediment, and fish from the main stem, 7 tributaries, and 6 lakes. Using these data, the geothermal Hg load to the Madison River and overall fate of Hg along 378 km of the Missouri River system were assessed. Geothermal Hg was the primary source of elevated total Hg concentrations in unfiltered water (6.2–31.2 ng/L), sediment (148–1100 ng/g), and brown and rainbow trout (0.12– 1.23 µg total Hg/g wet weight skinless filet) upstream from Hebgen Lake (the uppermost impoundment). Approximately 7.0 kg/y of geothermal Hg was discharged from the park via the Madison River, and an estimated 87% of that load was lost to sedimentation in and volatilization from Hebgen Lake. Consequently, Hg concentrations in water, sediment, and fish from main-stem sites downstream from Hebgen Lake were not elevated and were comparable to concentrations reported for other areas affected solely by atmospheric Hg deposition. Some Hg was sequestered in sediment in the downstream lakes. Bioaccumulation of Hg in fish along the river system was strongly correlated (r 2 =0.76–0.86) with unfiltered total and methyl Hg concentrations in water and total Hg in sediment.

Montana, Wyoming↗

Bioactive contaminants of emerging concern in National Park waters of the northern Colorado Plateau, USA

Pharmaceuticals and personal care products (PPCPs), wastewater indicators (WWIs), and pesticides (herein, Contaminants of Emerging Concern [CECs]) have been documented in surface waters throughout the world and have associated risks to aquatic life. While much research has focused on temperate and urbanized watersheds, less is known about CEC presence in semi-arid landscapes, where water availability is limited and populations are low. CEC presence in water and sediment is reported for 21 sites in eight U.S. national parks in the northern Colorado Plateau region. From 2012 to 2016, at least one PPCP and/or WWI was detected at most sites on over half of sampling visits, indicating that CECs are not uncommon even in isolated areas. CEC detections were generally fewer and at lower concentrations than in urbanized or agricultural watersheds. Consistent with studies from other U.S. regions, the most frequently detected CECs in this study include DEET, caffeine, organophosphorus flame retardants, and bisphenol A in water and fecal indicators and polycyclic aromatic hydrocarbons in sediment. Maximum concentrations in this study were generally below available water quality benchmarks, sediment quality guidelines, and risk assessment thresholds associated with vertebrates. Additional work is needed to assess the potential activity of hormones, which had high reporting limits in our study, and potential bioactivity of environmental concentrations for invertebrates, microbial communities, and algae. Potential sources of CEC contamination include upstream wastewater effluent discharges and National Park Service invasive-plant-control herbicide applications. CEC occurrence patterns and similarities between continuous and isolated flow locations suggest that direct contamination from individual visitors may also occur. While our data indicate there is little aquatic health risk associated with CECs at our sites, our results demonstrate the ubiquity of CECs on the landscape and a continued need for public outreach concerning resource-use ethics and the potential effects of upstream development.

Colorado Plateau↗

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants in water, sediment, and tissue from Rocky Mountain National Park, 2012–2013

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants (BCs) are commonly detected in surface water and bed sediment in urban and suburban areas, but these contaminants are understudied in remote locations. In Rocky Mountain National Park (RMNP), Colorado, USA, BCs may threaten the reproductive success and survival of native aquatic species, benthic communities, and pelagic food webs. In 2012–2013, 67 water, 57 sediment, 63 fish, 10 frog, and 12 quality-control samples (8 water and 4 sediment) were collected from 20 sites in RMNP. Samples were analyzed for 369 parameters including 149 pharmaceuticals, 22 hormones, 137 pesticides, and 61 other chemicals or conditions to provide a representative assessment of BC occurrence within RMNP. Results indicate that BCs were detected in water and/or sediment from both remote and more accessible locations in RMNP. The most commonly detected BCs in water were caffeine, camphor, para-cresol, and DEET; and the most commonly detected BCs in sediment were indole, 3-methyl-1H-indole, para-cresol, and 2,6-dimethyl-naphthalene. Some detected contaminants, including carbaryl, caffeine, and oxycodone, are clearly attributable to direct local human input, whereas others may be transported into the park atmospherically (e.g., atrazine) or have local natural sources (e.g., para-cresol). One or more pharmaceuticals were detected in at least 1 sample from 15 of 20 sites. Most of the 29 detected pharmaceuticals are excreted primarily in human urine, not feces. Elevated net estrogenicity was observed in 18% of water samples, and elevated vitellogenin in blood was observed in 12% of male trout, both evidence of potential endocrine disruption. Hormone concentrations in sediment tended to be greater than concentrations in water. Most BCs were observed at concentrations below those not expected to pose adverse effects to aquatic life. Results indicate that even in remote locations aquatic wildlife can be exposed to pharmaceuticals, hormones, pesticides, and other bioactive contaminants.

Colorado↗

Exposure and potential effects of pesticides and pharmaceuticals in protected streams of the US National Park Service southeast Region

Globally protected areas offer refugia for a broad range of taxa including threatened and endangered species. The United States National Park Service (NPS) manages public lands to preserve biodiversity, but increasing park visitation and development of surrounding landscapes increase exposure to and effects from bioactive contaminants. The risk (exposure and hazard) to NPS protected-stream ecosystems within the highly urbanized southeast region (SER) from bioactive contaminants was assessed in five systems based on 334 pesticide and pharmaceutical analytes in water and 119 pesticides in sediment. Contaminant mixtures were common across all sampled systems, with approximately 24% of the unique analytes (80/334) detected at least once and 15% (49/334) detected in half of the surface-water samples. Pharmaceuticals were observed more frequently than pesticides, consistent with riparian buffers and concomitant spatial separation from non-point pesticide sources in four of the systems. To extrapolate exposure data to biological effects space, site specific cumulative exposure-activity ratios (ΣEAR) were calculated for detected surface-water contaminants with available ToxCast data; common exceedances of a 0.001 ΣEAR effects-screening threshold raise concerns for molecular toxicity and possible, sub-lethal effects to non-target, aquatic vertebrates. The results illustrate the need for continued management of protected resources to reduce contaminant exposure and preserve habitat quality, including prioritization of conservation practices (riparian buffers) near stream corridors and increased engagement with upstream/up-gradient property owners and municipal wastewater facilities.

Alabama, Florida, Georgia, Kentucky, Mississippi, ↗

Decadal trends of mercury cycling and bioaccumulation within Everglades National Park

Mercury (Hg) contamination has been a persistent concern in the Florida Everglades for over three decades due to elevated atmospheric deposition and the system's propensity for methylation and rapid bioaccumulation. Given declines in atmospheric Hg concentrations in the conterminous United States and efforts to mitigate nutrient release to the greater Everglades ecosystem, it was vital to assess how Hg dynamics responded on temporal and spatial scales. This study used a multimedia approach (water and biota) to examine Hg and methylmercury (MeHg) dynamics across a 76-site network within the southernmost portion of the region, Everglades National Park (ENP), from 2008 to 2018. Atmospheric Hg deposition was evaluated over time using a long-term monitoring station. Hg concentrations across matrices showed that air, water, and biota from the system were inextricably linked. Temporal patterns across matrices were driven primarily by hydrologic and climatic changes in the park and no evidence of a decline in atmospheric Hg deposition from 2008 to 2018 was observed, unlike other regions of the United States. In the Shark River Slough (SRS), excess dissolved organic carbon and sulfate were also consistently delivered from upgradient canals and showed no evidence of decline over the study period. Within the SRS a strong positive correlation was observed between MeHg concentrations in surface water and resident fish. Within distinct geographic regions of ENP (SRS, Marsh, Coastal), the geochemical controls on MeHg dynamics differed and highlighted regions susceptible to higher MeHg bioaccumulation, particularly in the SRS and Coastal regions. This study demonstrates the strong influence that dissolved organic carbon and sulfate loads have on spatial and temporal distributions of MeHg across the ENP. Importantly, improved water quality and flow rates are two key restoration targets of the nearly 30-year Everglades restoration program, which if achieved, this study suggests would lead to reduced MeHg production and exposure.

Florida↗

Naegleria fowleri detected in Grand Teton National Park hot springs

The free-living thermophilic amoeba Naegleria fowleri ( N. fowleri ) causes the highly fatal disease primary amoebic meningoencephalitis. The environmental conditions that are favorable to the growth and proliferation of N. fowleri are not well-defined, especially in northern regions of the United States. In this study, we used culture-based methods and multiple molecular approaches to detect and analyze N. fowleri and other Naegleria spp. in water, sediment, and biofilm samples from five hot spring sites in Grand Teton National Park, Wyoming, U.S.A. These results provide the first detections of N. fowleri in Grand Teton National Park and provide new insights into the distribution of pathogenic N. fowleri and other nonpathogenic Naegleria spp. in natural thermal water systems in northern latitudes.

Wyoming↗

The Western Airborne Contaminant Assessment Project (WACAP): An interdisciplinary evaluation of the impacts of airborne contaminants in Western U.S. National Parks

The concept of a nature reserve such as a National Park is to maintain a location for the enjoyment and study of a pristine environment. However, many pollutants are now known to spread far and wide from their (point[s] of) origin. To grasp the extent of pervasive and boundary-less pollution, the ambitious WACAP study evaluated contaminant data collected from Western U.S. National Parks in various media. In this Feature, Landers et al. summarize the report and speak to its utility moving forward.

Environmental Science and Technology↗

Evaluation of terrestrial and streamside salamander monitoring techniques at Shenandoah National Park

In response to concerns about amphibian declines, a study evaluating and validating amphibian monitoring techniques was initiated in Shenandoah and Big Bend National Parks in the spring of 1998. We evaluate precision, bias, and efficiency of several sampling methods for terrestrial and streamside salamanders in Shenandoah National Park and assess salamander abundance in relation to environmental variables, notably soil and water pH. Terrestrial salamanders, primarily redback salamanders ( Plethodon cinereus ), were sampled by searching under cover objects during the day in square plots (10 to 35 m 2 ). We compared population indices (mean daily and total counts) with adjusted population estimates from capture-recapture. Analyses suggested that the proportion of salamanders detected ( p ) during sampling varied among plots, necessitating the use of adjusted population estimates. However, adjusted population estimates were less precise than population indices, and may not be efficient in relating salamander populations to environmental variables. In future sampling, strategic use of capture-recapture to verify consistency of p 's among sites may be a reasonable compromise between the possibility of bias in estimation of population size and deficiencies due to inefficiency associated with the estimation of p . The streamside two-lined salamander ( Eurycea bislineata ) was surveyed using four methods: leaf litter refugia bags, 1 m 2 quadrats, 50 × 1 m visual encounter transects, and electric shocking. Comparison of survey methods at nine streams revealed congruent patterns of abundance among sites, suggesting that relative bias among the methods is similar, and that choice of survey method should be based on precision and logistical efficiency. Redback and two-lined salamander abundance were not significantly related to soil or water pH, respectively.

Texas, Virginia↗

Diapause in copepods (Crustacea) from ephemeral habitats with different hydroperiods in Everglades National Park (Florida, U.S.A.)

Water management practices in the Everglades have severely stressed the natural system, particularly by reducing the hydroperiods of much of the region. During the dry season of 1999, we investigated the influence of hydroperiod on the species composition and dormancy patterns of freshwater copepod communities in seasonal wetlands of Everglades National Park, Florida, U.S.A. The habitats were characterized by an annual dry season, from December through June. We sampled at two locations: the Long Pine Key area of the Rocky Glades region (short hydroperiod, ca. 4-5 months), and western Taylor Slough (intermediate hydroperiod, ca. 8-10 months). Both areas have experienced a reduction in natural hydroperiods and an increase in the frequency of dry-down. We collected weekly plankton samples from Rocky Glades solution holes to assess the potential species pool of copepods. To document the taxa capable of surviving dry-down by resting, we performed three immersion trials in which we rehydrated, in laboratory aquaria, sediment patches from solution holes and surface soils from all stations. Only a subset of the planktonic species collected emerged from the dried sediments. The cyclopoids Microcyclops rubellus and Paracyclops poppei were dominant. This is the first record of diapause for P. poppei. Species distributions from the different hydroperiod soil patches indicated that more diapausing species occurred at the sites that dried for shorter periods. Emerging individuals of M. rubellus and P. poppei were mainly ovigerous females, demonstrating a resting strategy seldom before recorded. The cyclopoid Diacyclops nearcticus had not been previously reported to diapause, but they emerged from the dried sediments in our trials. Our collections included six new records for Florida: Diacyclops nearcticus, Megacyclops latipes, Orthocyclops modestus, Elaphoidella marjoryae, Bryocamptus sp. and Bryocamptus cf. newyorkensis. Paracyclops poppei, Macrocyclops fuscus and Arctodiaptomus floridanus are new records for Everglades National Park. Clearly, diapause is an important strategy for the persistence of copepods in short-hydroperiod wetlands. The duration of the dry period appears to be inversely related to the number of species that emerge from diapause.

Conference Paper↗

Use of regression‐based models to map sensitivity of aquatic resources to atmospheric deposition in Yosemite National Park, USA

An abundance of exposed bedrock, sparse soil and vegetation, and fast hydrologic flushing rates make aquatic ecosystems in Yosemite National Park susceptible to nutrient enrichment and episodic acidification due to atmospheric deposition of nitrogen (N) and sulfur (S). In this study, multiple linear regression (MLR) models were created to estimate fall‐season nitrate and acid neutralizing capacity (ANC) in surface water in Yosemite wilderness. Input data included estimated winter N deposition, fall‐season surface‐water chemistry measurements at 52 sites, and basin characteristics derived from geographic information system layers of topography, geology, and vegetation. The MLR models accounted for 84% and 70% of the variance in surface‐water nitrate and ANC, respectively. Explanatory variables (and the sign of their coefficients) for nitrate included elevation (positive) and the abundance of neoglacial and talus deposits (positive), unvegetated terrain (positive), alluvium (negative), and riparian (negative) areas in the basins. Explanatory variables for ANC included basin area (positive) and the abundance of metamorphic rocks (positive), unvegetated terrain (negative), water (negative), and winter N deposition (negative) in the basins. The MLR equations were applied to 1407 stream reaches delineated in the National Hydrography Data Set for Yosemite, and maps of predicted surface‐water nitrate and ANC concentrations were created. Predicted surface‐water nitrate concentrations were highest in small, high‐elevation cirques, and concentrations declined downstream. Predicted ANC concentrations showed the opposite pattern, except in high‐elevation areas underlain by metamorphic rocks along the Sierran Crest, which had relatively high predicted ANC (>200 μ eq L −1 ). Maps were created to show where basin characteristics predispose aquatic resources to nutrient enrichment and acidification effects from N and S deposition. The maps can be used to help guide development of water‐quality programs designed to monitor and protect natural resources in national parks.

Yosemite Nataional Park↗

Quantifying interdependencies in geyser eruptions at the Upper Geyser Basin, Yellowstone National Park

The Upper Geyser Basin at Yellowstone National Park (Wyoming, USA) harbors the greatest concentration of geysers worldwide. Research suggests that individual geysers are not isolated but rather are hydraulically connected in the subsurface with other geysers and thermal springs. To quantify such connections, we combined techniques from machine learning, causal inference, and dynamical systems to characterize the collective eruptive behavior of a set of 10 geysers over 18 months (April 2007 – September 2008) focusing on geyser-geyser interactions. Model predictions were up to 15 times more accurate when we sought to predict a geyser's eruption time series based on outflow channel temperatures from the network than based on its own time series alone, suggesting the existence of a complex interconnected subsurface groundwater system. On average, cone-type geysers had larger impacts on other geysers than did fountain-type geysers. Similarly, cone-type geysers were on average more insulated from other geysers. However, substantial unexplained variation remained after considering the cone versus fountain dichotomy. Distance between geysers also affected interactions: nearby geysers had stronger effects on focal geysers than did geysers located farther away. Collectively, results support the hypothesis of geyser interdependence at timescales of 5 min–10 days. Our analyses highlight the existence of quantifiable geyser-to-geyser interactions that can be resolved through pairwise and system-level analyses. These findings emphasize the subsurface interconnectedness of thermal features, provide information relevant to visitor experiences in Yellowstone National Park, and suggest strategies for exploring patterns of interdependence that may exist among other episodic geological phenomena.

Wyoming↗

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad??? AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad??? AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns. ?? The Royal Society of Chemistry and the Division of Geochemistry of the American Chemical Society 2003.

Geochemical Transactions↗

Chlorophyll maxima in mountain ponds and lakes, Mount Rainier National Park, Washington State, USA

Hypolimnetic chlorophyll maxima are common in clear lakes and often occur at depths with between 1 and 0.1% of the surface incident light. Little is known, however, about the concentrations of chlorophyll in thermally unstratified mountain ponds and how these concentrations compare to epilimnetic and hypolimnetic concentrations in mountain lakes. The objectives of this study were to document the concentrations of chlorophyll in thermally unstratified ponds and stratified lakes in Mount Rainier National Park (MORA) and to compare the results with concentrations and distributions of chlorophyll in clear-deep lakes in the Oregon Cascade Range and the Sierra Nevada Range. Thirty-two ponds (<2.5 m deep) and 14 lakes(>9.9 m deep) were sampled primarily during the summers of 1992 to 1996 at MORA. Water samples from near the surface (0.1–0.5 m) of ponds and near the surface and near the bottom of lakes were collected over the deepest part of each system. One exception, Mowich Lake, was sampled at seven depths between the surface and 50 m (Z=58.6 m). Chlorophyll concentrations were low in all systems, but higher in ponds (average 1.8 μg·L −1 ) than in lakes. Chlorophyll concentrations were higher in hypolimnetic lake samples (average 0.7 μg·L −1 ) than in epilimnetic lake samples (average 0.2 μg·L −1 ). Elevated concentrations of chlorophyll in mountain ponds, relative to those in hypolimnetic lake samples, may have been influenced by increased nutrient availability from interactions at the mud-water interface and, in this park, defecation by elk that used many of the ponds as wallows. Mowich Lake showed a chlorophyll maximum (~1.5 μg·L −1 ) near the lake bottom. Based on Secchi disk clarity readings, the depth of 1.0% incident surface solar radiation was greater than the maximum depths of the ponds and lakes. Comparative data from other clear-deep lakes in the Oregon Cascade Range and Sierra Nevada Range suggested that deep-chlorophyll maxima (~1.5 μg·L −1 ) occurred at <1.0% and > 0.1% of the incident surface solar radiation, and that the typical maximum depths ranged between 75 and 140 m during thermal stratification.

Washington↗

Accurately characterizing climate change scenario planning in the U.S. National Park Service: Comment on Murphy et al. 2023

We more accurately locate the boundary between current practice and research priorities regarding climate change scenario planning in U.S. federal land management agencies by supplementing the characterization in a recent article (“Understanding perceptions of climate change scenario planning in United States public land management agencies”) of its use in the U.S. National Park Service. Accurately reflecting the full depth and breadth of efforts to streamline and mainstream the method for climate change adaptation planning in the U.S. National Park Service provides readers helpful guidance and resources called for by Murphy et al.

Society and Natural Resources↗

The influence of gender on the relationship between wildlife value orientations, beliefs, and the acceptability of lethal deer control in Cuyahoga Valley National Park

This study examines how wildlife value orientations, attitudes, and gender influence acceptance of lethal actions to control deer in Cuyahoga Valley National Park in Ohio. Data were collected from female and male residents (n = 659) in a nine-county area, the primary service area of the park. Females and males demonstrated significant differences in their wildlife value orientations, attitudes toward lethal deer control, beliefs about the outcome of lethal deer control, and perceived personal impacts of lethal deer control. Gender also acted as a moderator of the relationship between values, beliefs and attitudes. Results indicate that a focus on understanding differences between males and females is essential to public participation in decision making concerning this and similar issues.

Society and Natural Resources↗

Evaluation of internal loading and water level changes: implications for phosphorus, algal production, and nuisance blooms in Kabetogama Lake, Voyageurs National Park, Minnesota

Hydrologic manipulations have the potential to exacerbate or remediate eutrophication in productive reservoirs. Dam operations at Kabetogama Lake, Minnesota, were modified in 2000 to restore a more natural water regime and improve water quality. The US Geological Survey and National Park Service evaluated nutrient, algae, and nuisance bloom data in relation to changes in Kabetogama Lake water levels. Comparison of the results of this study to previous studies indicates that chlorophyll a concentrations have decreased, whereas total phosphorus (TP) concentrations have not changed significantly since 2000. Water and sediment quality data were collected at Voyageurs National Park during 2008–2009 to assess internal phosphorus loading and determine whether loading is a factor affecting TP concentrations and algal productivity. Kabetogama Lake often was mixed vertically, except for occasional stratification measured in certain areas, including Lost Bay in the northeastern part of Kabetogama Lake. Stratification, higher bottom water and sediment nutrient concentrations than in other parts of the lake, and phosphorus release rates estimated from sediment core incubations indicated that Lost Bay is one of several areas that may be contributing to internal loading. Internal loading of TP is a concern because increased TP may cause excessive algal growth including potentially toxic cyanobacteria.

Minnesota↗

Challenges and solutions for applying the travel cost demand model to geographically remote visitor destinations: A case study of bear viewing at Katmai National Park and Preserve

Remote and unique destinations present difficulties when attempting to construct traditional travel cost models to value recreation demand. The biggest limitation comes from the lack of variation in the dependent variable, defined as the number of trips taken over a set time frame. There are various approaches that can be used for overcoming limitations of the traditional travel cost model in the context of remote destinations. This study applies an adaptation of the standard model to estimate recreation benefits of bear viewing at Katmai National Park and Preserve in Alaska, which represents a once-in-a-lifetime experience for many visitors. Results demonstrate that visitors to this park’s Brooks Camp area are willing to pay an average of US$287 per day of bear viewing. Implications of these findings for valuing recreation at other remote destinations are discussed.

Alaska↗

Valuing wildlife sightings at the species-wide and individual animal levels: An approach and application to bear viewing in Yellowstone National Park

Wildlife viewing is a popular recreation activity in parks and protected areas around the world, yet information on the nonmarket value that visitors derive from viewing specific species, and how that value is affected by small-scale population changes, is lacking. We devised an approach to fill the gap. First, we applied the travel cost method to obtain the value of a wildlife viewing trip. Next, we estimated a value per animal sighting, which we aggregated by the number of visitors who experienced and valued a sighting. Finally, we incorporated the probability of viewing an animal to determine an individual animal’s contribution to sighting value, which varies by species type, visibility, and seasonality. We examined bear viewing in Yellowstone National Park. For grizzly and black bears, respectively, per-sighting values are $16 and $14, aggregate annual sighting values are $6.9 and $9.7 million, and annual per-bear viewing values are $46,000 and $15,000.

Idaho, Montana, Wyoming↗