A trophic cascade can be defined as a specific food web or trophic structure where a predator preys on a herbivorous consumer which forages on a local vegetative resource; therefore, in this type of trophic structure top-down processes allow carnivorous apex predators to have indirect effects on local vegetative resources through their effects on the density or behavior/traits of the herbivores (M. Kummel, personal communication, April 8, 2019 and Ford et. al. 2015). In the case of predation on herbivorous consumers, both density and trait mediation can indirectly effect the density and growth pattern of vegetation that correlate directly to the alteration of prey populations via density and trait mediation (Ford et. al. 2015). Cougars have been identified as one of the seven apex predators that have been specifically associated with trophic cascades based on other empirical studies (Ripple et. al. 2014). Trophic downgrading follows the same pattern as alterations to trophic cascade structures: Trophic downgrading can have numerous direct and indirect ramifications on the local ecology. Trophic downgrading has similar consequences and is defined as, “the consequences of removing large apex consumers from nature (Estes et. al. 2011, 301).” Due to the unique characteristics that define the 6th mass extinction, one species has been the cause of most of the extinctions and the period has been characterized by the extinction of various large bodied animals, addressing trophic downgrading has become a prominent issue in the management of a wide array of ecological contexts globally (Estes et. al. 2011). In addition, apex predators, like cougars, facilitate ecosystem services such as carbon storage to buffer climate change, biodiversity enhancement, the reestablishment of native plant diversity, riparian restoration, and even the regulation of diseases (Estes et. al. 2011 and Ripple et. al. 2014). Thorough analyses of cougar habitat selection are rare, and have yet to be conducted in relation to the movement of elk and the growth of aspen saplings in the Pikes Peak region of Colorado U.S.A. until now. Through this study, it was observed and statistically shown that the number of aspen saplings tends to increase in areas that correspond with preferential habitat usage of cougars; whereas, the number of aspen saplings decreases in areas that correspond with a high prominence of observed elk herbivory. Therefore, in the Cougar-Elk-Aspen system within the Pikes Peak region cougars, carnivorous apex predators, are having indirect effects on local plants through top-down processes: This is a trophic cascade scenario.
This study provides preliminary qualitative groundwork for a five-year program evaluation by documenting participant-reported experiences in “Latino Family Camps/Campamentos Familiares.” Interviews with 12 members of five families who were camp participants were conducted in focus groups or individually, and coded for major themes using NVivo. Three major themes, or hypotheses, emerged from interview data. First, interviewees viewed nature as a medium for human connection. Second, interviewees reported that environmental appreciation and human-nature connection have diverse sources, including through family traditions in nature. Third, interviewees reported diverse barriers to nature that can be overcome through the Latino Family Camp program. Other notable findings were not major themes, but deserve mention: interviewees did not associate barriers to nature engagement with their ethnic identities, and no participants specifically identified practices of the camp as “inclusive” or “designed specifically for Latino communities.” Additionally, all participants reported that they enjoyed the camps and wanted to return. Positive participant responses suggest that the Latino Family Camps succeed in their goal to empower families to experience nature. However, families’ continued participation in multiple-family camps urges study of the specific benefits of community nature engagement. Program facilitators may also consider their reasoning for explicating inclusive practices for certain audiences and may include an explicit conversation with participants about historical exclusion from green spaces, diverse connections to nature, and the familial and community benefits of nature experiences.
In the context of a deepening climate crisis, bridging the divide between pro-environmental attitudes and behavior has become increasingly important. While there is a large body of research on the relation of environmental awareness and significant life experiences (SLE), outdoor programs, and adult outdoor recreation, this thesis explores the largely unstudied potential relationship between long-distance hiking and pro-environmental behavior. This qualitative study was conducted using a grounded theory approach based on 48 interviews with long-distance Pacific Crest Trail hikers collected throughout the trail. After three cycles of coding, interviews led to the emergence of four themes, which were analyzed in the context of Hungerford and Volk’s (1990) “Model for Environmental Citizenship Behavior” to develop the hypothesis that long-distance hiking will increase long-term pro-environmental behavior within the private sphere, but not the public sphere. Forty-two hikers developed precursors to pro-environmental behavior in at least one area, with particularly significant increases in environmental sensitivity, personal investment in issues and the environment, and intention to act. Implications for environmental education include possibilities for better integrating expeditionary learning and outdoor components, which may help students develop personal environmental morals in addition to the ecological backgrounds necessary for developing environmental literacy. Further research possibilities include restructuring the methodology to minimize response bias, examining the role of adult SLE, and continuing studies on long-distance hiking.
Ecotone transitions offer a rare opportunity to examine these spatial patterns along known stress gradients. This allows us to link specific patterns that exist at the different stages of bifurcation to potential mechanisms that create these complex spatial structures. This paper applied robust criticality theory the alpine forest-tundra ecotone transition to see how treelines can be understood through the framework of critical transitions, and concurrently, how robust criticality theory can be applied to an anisotropic system to predict potential threshold behavior in treeline movement upslope. Spatial structure of an abrupt treeline on Pikes Peak, CO was analyzed using Fragstats and ImageJ. The presence of robust criticality was tested using an AIC model fit test. Model analysis showed that this treeline clearly exhibits a type of robust criticality with the existence of a percolation cluster and deviations of log frequency-size distribution of patches along the elevation gradient from a strict power law. However, it did not conform to the theory perfectly. This likely points to the problem of accounting for multiple stressors that exert their influence over the dynamics of treeline to different extents in different zones. It is this complex matrix of local feedbacks created by endogenous interactions between the harsh environmental conditions and the trees that produces the dynamic spatial structure at this site along the elevation gradient. This has important implications for how the treeline will react in the future to increasing temperatures and decreasing snowpack as predicted by climate change models in the Rock Mountain West.
Atmospheric mercury (Hg), an airborne heavy metal, can be deposited into aquatic and terrestrial systems, posing a risk to ecosystems and human health. It is therefore important to understand the sources, chemical cycling, and fate of atmospheric mercury. This study looks at total gaseous Hg (TGM) and total Hg (THg) concentrations collected at an urban near-road site in Colorado Springs, CO from June - August, 2016 and at a rural location in Rocky Flats National Wildlife Refuge, Louisville, CO, from June - August, 2018. Mercury concentrations at the two sites were significantly different from one another. The urban data set reveals a significant diurnal pattern, with hourly average TGM concentrations reaching a maximum at 3:00 MST (1.9 ± 0.3 ng/m3) and minimum at 13:00 MST (1.6 ± 0.2 ng/m3). In contrast, at the rural site we find that hourly-average concentrations peak at 13:00 MST (1.5 ± 0.1 ng/m3) and are lowest at 6:00 MST (1.4 ± 0.1 ng/m3). These diurnal Hg patterns are comparable to those found in other studies looking at urban/rural differences. Sources of Hg at both sites were also investigated. At the urban site, the data points to high TGM concentrations originating from local sources. Additionally, strong correlation between TGM and CO2 suggests soil evasion as a potential Hg source. The rural site, on the other hand, does not appear to be influenced by nearby Hg point sources and reflects a typical background site.
Warmer and drier conditions as a result of climate change are expected to have significant effects on closed cone conifer ecosystems, including changes in disturbance regimes, reduced plant growth, and decreased seedling recruitment. Changes in the fire regime could potentially cause localized extinction by narrowing the fire interval past the point compatible with the reproductive timeframe of the closed cone forest. The “interval squeeze hypothesis” describes the synergistic effects of changes in disturbance regimes, plant growth, and seedling recruitment, and suggests that closed cone conifer ecosystems may face extinction sooner than initially accounted for. California closed cone pine species provide a unique way to test the interval squeeze hypothesis. Their short lifespan and fire return interval allow data to be collected over the lifetime of the forest and quantify changes caused by climate change. Stand structure and composition metrics were measured at six sites in California and Colorado. The univariate comparison of metrics showed that California and Colorado pine species are similar across important aspects of stand structure and composition. As such, there is potential for California forests to serve as a model ecosystem for Colorado forests. Pinus contorta var latifolia (Lodgepole Pine) is one of the most widespread tree species across western North America. A large-scale mortality event of P. contort var latifolia forest could cause significant change to the carbon sequestration and water infiltration capacity of these forests.
Treelines can serve as model ecotones in their response to climate change. However, the role of tree architecture at treelines is poorly understood. This paper examines tree architectures at a fast-migrating diffuse treeline in a bowl on the western slope of Pikes Peak (Colorado). Investigating the spatial distribution of the allometric types, the relationship between the growth rate and height for each architecture type, and the impacts of the changing climate on the architectural spatial distribution. The study site was divided into an Upper Zone (UZ) and Lower Zone (LZ). We found multiple distinct architectures within this diffuse treeline. Unexpectedly, tree architectures did not follow a spatial distribution pattern of clustering or avoiding with like and or different architectures. Krummholz and Cone architectures were found growing in close proximity to one another, signifying that the upper climatic boundary at this site has advanced up in elevation. These multiple architectures are able to represent current and past climatic conditions. Advancement is occurring at such rapid rates that tree established architectures are not able to release from their path dependency. To my knowledge, this is the first study that examines multiple tree architectural types within a treeline and how they are distributed in space.
As terrestrial and marine ecosystems increasingly experience detrimental stress from pollution and contamination, contemporary waste management should consider wastewater as more than just trash to discard, but instead as a crucial resource to be developed. The Toxicity Identification Evaluation (TIE) is one of more comprehensive ecotoxicological methods which can evaluate and address toxic wastewater mitigation without knowledge of the specific toxic components. The aim of this study was to explore the effectiveness of TIE from a wastewater management standpoint by a) Testing the TIE method on a specific toxic aqueous effluent produced from a Danish offshore oil drilling operation, and b) assess its efficacy in the broader context of environmental management through a comparison of scientific literature on wastewater management. By applying TIE in conjunction with a MicrotoxTM equivalent toxicity test, this study found that an initial biological treatment followed by the application of activated carbon, is effective for addressing the toxic fractions of the oil produced wastewater. An analysis of the literature reveals that the strength of TIE compared to other more chemically specific techniques is in its broad application and ability to be applied to unfamiliar toxins and situations. Overall, the TIE is a critical tool to be considered and recommended for wastewater management as well as broader environmental management.