Browsing by Subject "Climate change"

Now showing 1 - 20 of 55
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    Assessing Impacts of Climate Change on Vulnerability of Brook Trout in Lake Superior’s Tributary Streams of Minnesota
    (University of Minnesota Duluth, 2013) Johnson, Lucinda B; Herb, William; Cai, Meijun
    Water temperature is generally considered one of the primary physical habitat parameter determining the suitability of stream habitat for fish species, with effects on the mortality, metabolism, growth, behavior, and reproduction of individuals. In this study we assessed the potential threats of climate change on stream temperatures and flow regimes in Lake Superior tributary streams in Minnesota, USA. The study included deterministic models for stream flow and temperature of three study streams (Amity Creek, Baptism River, Knife River), and regional (empirical) models for specific flow and temperature parameters to give better spatial coverage of the region. Information on stream flow, stream temperature, and land cover was used to develop a brook trout presence/absence model to understand the current pattern of distribution of brook trout and predict future distributions under future climate. The hydrology of north shore streams is mainly driven by air temperature and precipitation. Historical air temperatures in the region have a significant upward trend, particularly since 1980. Global climate model (GCM) outputs project a continued increasing trend in air temperature, with an increase in mean annual air temperature of 2 to 3 °C by 2089. The historical precipitation data shows an increasing trend for total annual precipitation at Duluth and Two Harbors between 1900 and 2010, whereas Grand Marais and Grand Portage do not have a clear trend. Based on an analysis of daily precipitation totals, there is some indication of an increasing trend in the number of days in summer with high precipitation (10-20 cm). Both the GENMOM and the ECHAM5 GCMs project overall increases in precipitation of about 15%, but differ with respect to the seasonal distribution of the precipitation changes. A significant and relatively certain impact of climate change is a projected shift in precipitation from snowfall to rainfall. While an increasing trend in precipitation leads to increasing streamflow, the increasing trend in spring and summer air temperature tends to reduce streamflow (by increasing evapotranspiration). Available streamflow records for north shore streams suggest there may be a decreasing trend in mean annual flow and summer low flow, but the trends are not statistically significant. Future projections of streamflow based on the GCM output were mixed, with the deterministic models projecting moderate increases in average stream flow and summer low flow, while the regression models for project a moderate decrease in low flow. Stream temperature analyses for the three study streams based on GCM climate output give the result of fairly uniform seasonal increases in stream temperature to 2089 ranging from 1.3 to 1.9 °C for the GENMOM model to 2.2 to 3.5°C for the ECHAM5 model. Application of the GENMOM climate data to the deterministic stream temperature models produced fairly similar stream temperature changes for the three study sites. The empirical stream temperature study found stream temperature in the north shore region to be influenced by air temperature, catchment size, percentage of woody wetlands, latitude, and soil permeability rate. In response to climate change projected by the GENMOM GCM, the regional stream temperature model projects July mean water temperature to rapidly increase by approximately 1.2oC from 1990s to 2060s, followed by a slight decrease to 2089. The temperature increase was predicted to be the largest in the coastal area of middle north shore region. The brook trout presence/absence model found water temperature to have the strongest influence on trout presence. Brook trout were predicted to be at risk for water temperatures above 18.7oC and be extirpated from streams for temperatures over 20oC. Stream flow was shown to have a negative effect on trout presence, though not as strong as water temperature. Overall, these data predict that brook trout may be extirpated from lower shore area, be exposed to increasing risk in middle shore region, and remain present in upper shore streams from the present to 2089. This work would benefit greatly from a number of modifications to the GCM’s, the spatial data used in the development of both the deterministic and empirical models, and implementation of a more detailed, spatially explicit, hydrologic model. Finally, additional fish data, including cool and warm water assemblage data, along with descriptors of landscape structure (i.e., connectivity) would allow us to assess the areas where cold water species may be threatened by the presence or potential presence of coolwater competitors.
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    An Assessment of land use impacts on channel morphology in a Western Minnesota watershed.
    (2009-12) Christner Jr., William Thomas
    This research is a comprehensive investigation encompassing land use changes in an agricultural watershed and corresponding changes to the rainfall-runoff relationship and stream channel morphology. The Lac qui Parle (LqP) watershed is one of eleven major watersheds within the Minnesota River Basin (MRB). Agriculture is the dominant land use within the MRB occurring on more than 90-percent of the landscape. This research investigates the spatial and temporal changes in channel morphology and land use between 1965/66 and 2002/03. Historical data were obtained from the US Army Corps of Engineers for the South Fork Lac qui Parle (SF LqP) River. Sixty-five cross-section sites were re-surveyed and evaluated. Current channel morphology was assessed through a second year of data collection. Additional data were collected and analyzed for crop history, riparian vegetation, agricultural drainage, annual discharge, annual peak discharge, and monthly and annual precipitation. Results indicate crop diversity within the SF LqP River has diminished and is currently dominated by corn and soybean. Surface and subsurface drainage of agricultural lands was documented on 37-percent of the sub-watershed area evaluated. Analysis of the discharge and precipitation records indicates an increase in the Q/P ratio and average annual runoff volume post-1960. The analysis indicates land use changes within the SF LqP watershed have impacted the channel morphology of the SF LqP River post-1965/66. Significant changes in channel cross-sectional area were noted in the Middle and Upper watersheds. Results corresponds to a channel enlargement ratio (CER) of 1.02 - 1.30. Changes in cultivation practices and drainage activities correspond with higher CER of 2.32 - 2.6. Similar increases were noted for peak discharge (1.30 - 1.35). CERs match values developed for storm sewered streets in urbanized areas. All changes were significant at the 95-% confidence level. A separate investigation evaluated the use of natural channel design for agricultural ditches. Results indicate natural channel design provides more efficient sediment transport, increased channel diversity/complexity, and may reduce channel maintenance costs.
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    Biological indicators of climate change: trends in fish communities and the timing of walleye spawning runs in Minnesota.
    (2010-06) Schneider, Kristal N.
    I conducted research on two projects to examine effects of climate change on Minnesota’s aquatic communities. I used walleye egg-take records from the Minnesota Department of Natural Resources for 12 spawning locations and historical ice-out data to determine if the timing of these events is changing. I used ice-out data instead of temperature for our analyses because historical temperature data is not available and ice-out has been previously related to climate change. Because ice-out has been previously related to climate change, I regressed the dates of first egg-take against ice-out dates to determine if the timing of walleye spawning runs could be a useful biological indicator of climate change. For the second project to determine if fish species abundances are changing in response to climate change, I used historical lake survey records for 34 lakes, each with 15 to 43 years of data, and regressed catch-per-unit-effort (CPUE) against year. I examined species distributions by regressing mean latitude against year. I regressed slopes of CPUE over time against 5 local air temperature variables to determine if changes in abundance were associated with air temperature. I also used stepwise regressions (forward and backward selection) and one-way analysis of variance (ANOVA) to determine if variability in trends could be explained by lake physical and chemical characteristics. Results were reported for 7 species with the strongest trends: Centrarchids (Micropterus salmoides, Micropterus dolomieu, and Lepomis macrochirus); Ictalurids (Ameiurus melas and Ameiurus natalis); Whitefish (Coregonus artedi and Coregonus clupaeformis).For the walleye spawning analyses I found that spawning runs and ice-out are occurring earlier in some lakes but not all. However, there was a strong relationship between first eggtake and ice-out dates, and walleye egg-take appears to provide a good biological indicator of climate change. For the lake survey analysis, centrarchid abundance in lakes was increasing over time, black bullhead abundance was decreasing, and other species were increasing in some lakes and decreasing in others. Slopes of CPUE versus year increased more quickly over time in smaller lakes and more quickly moving east across the state than in larger lakes toward the west. All species’ ranges were significantly advancing northward except smallmouth bass and whitefish. Regressions of CPUE versus air temperature showed that centrarchids are increasing in lakes as summer air temperatures increase, and whitefish are decreasing in lakes as air temperatures increase. In summary, the abundances and distributions of these 7 species over time may be responsive to climate change, and trends for species abundances may be influenced by lake characteristics. Centrarchids and bullhead may be good indicators, and thus, further research is warranted. Also, because there is a strong relationship between dates of first egg-take and ice-out, and because ice-out has previously been related to climate change, the timing of walleye spawning runs may be a useful biological indicator of climate change.
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    Change we can believe in? the role and implications of culture and environmental values on climate change perceptions.
    (2012-08) Heeren, Alexander
    Climate change poses many ecological and social challenges to natural resource agencies. One great challenge that resource managers face is how to manage, or adapt, to climate change in a socially acceptable way. To meet this challenge, it is necessary to understand how public perceptions about climate change are formed and whether the public will support climate change management strategies. This issue was examined at the regional level (northeast Minnesota) using a conceptual framework tested with the results of focus groups and a mail survey. Chapter 1 of this thesis provides an introduction to the framework. The second chapter discusses the results of the focus groups examining how individuals talk about climate change. Chapter 3 tests the conceptual framework quantitatively using the results of a region wide mail survey. Finally, Chapter 4 provides a summary of the project and discusses directions that future research can take.
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    Climate Adaptation and Local Narratives: Using qualitative inquiry to inform adaptive management on the North Shore of Lake Superior Minnesota, USA
    (2018-02) Shepard, Jennifer
    Adaptive approaches to local climate change impacts primarily focus on finding the best fit between the scale of ecological systems and the scale of existing management systems. This paper argues that a third scale, the scale at which the community perceives the problem of climate change, is essential to constructing best-fit management practices. To understand community perceptions, qualitative interviews of key stakeholders on the North Shore of Lake Superior, Minnesota were collected. Analysis of the interviews was developed into a narrative visualization framework, providing local decision makers with climate narratives in an accessible format. The narrative frameworks detailed convergence around the attribution of changes in forest health and wildlife populations to climate change, but divergence around when to be concerned for local impacts. Findings indicate the need to ground local adaptation in observable changes, and the importance of facilitating stakeholder engagement with the range of narratives present in the community.
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    Climate Change and Energy Security
    (2008-09-01) Jacobs, Lawrence R.
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    Climate Change Impacts on the Water Resources of American Indians and Alaska Natives in the U.S.
    (2013) Cozzetto, K; Chief, K; Kittmer, K; Brubaker, M; Gough, R; Souza, K; Ettawageshik, F; Wotkyns, S; Opitz-Stapleton, S; Duren, S; Chavan, P
    This informative paper links the perspectives and concerns of American Indians with predictions of climate change impacts on natural resources and Native communities. The report cites current and predicted impacts on the Fond du Lac Reservation in northeastern Minnesota, referencing several local sources and tribal authorities. Extracts of key points are reproduced below. "This paper provides an overview of climate change impacts on tribal water resources and the subsequent cascading effects on the livelihoods and cultures of American Indians and Alaska Natives living on tribal lands in the U.S. A hazards and vulnerability framework for understanding these impacts is first presented followed by context on the framework components, including climate, hydrologic, and ecosystem changes (i.e. hazards) and tribe-specific vulnerability factors (socioeconomic, political, infrastructural, environmental, spiritual and cultural), which when combined with hazards lead to impacts. Next regional summaries of impacts around the U.S. are discussed. Although each tribal community experiences unique sets of impacts because of their individual history, culture, and geographic setting, many of the observed impacts are common among different groups and can be categorized as impacts on—1) water supply and management (including water sources and infrastructure), 2) aquatic species important for culture and subsistence, 3) ranching and agriculture particularly from climate extremes (e.g., droughts, floods), 4) tribal sovereignty and rights associated with water resources, fishing, hunting, and gathering, and 5) soil quality (e.g., from coastal and riverine erosion prompting tribal relocation or from drought-related land degradation). The paper finishes by highlighting potentially relevant research questions based on the five impact categories. The Midwest (MW) is the location of the five lakes comprising the Great Lakes that together form Earth’s largest surface freshwater system. Thirty federally recognized tribes live in MW states and depend on this resource. Ceremonies honoring the waters as the life-blood of Mother Earth are held throughout the region. MW Tribes depend on the waters for subsistence and commercial fishing and for water-based plant materials for traditional crafts and artwork. Additionally, most MW tribes now operate gaming facilities and other tourism enterprises that rely heavily upon water for aesthetic and recreational uses. Many MW tribes consider climate change adaptation to be one of the most important long-range environmental issues for tribal nations. Michigan tribes, for instance, have worked with the state to negotiate and sign the May 12, 2004 Intergovernmental Accord between the Federally Recognized Indian Tribes in Michigan and the Governor of the State of Michigan Concerning Protection of Shared Water Resources and the June 11, 2009 Intergovernmental Accord between the Tribal Leaders of the Federally Recognized Indian Tribes in Michigan and the Governor of Michigan to Address the Crucial Issue of Climate Change. Biannual meetings are held between the state and tribes to discuss shared responsibilities and potential cooperative efforts. Impacts on MW tribes are diverse. Key impacts are related to flora and fauna important for diet, acknowledging clan responsibilities, social and mental health, and the exercise of treaty rights. Traditional healers in the region, for instance, have noted that lack of moisture and unreliable springtime temperatures have caused significant wild and cultivated crop losses. Wild rice (manoomin) is a sacred food of great importance to the Ojibwe of the Great Lakes area and may be detrimentally affected by climate change. In the Ojibwe Migration Story, The Great Mystery foretold the coming of the light-skinned race and instructed the Ojibwe to journey westward until they found ‘the food that grows on water.’ Since the 1900s, the loss of wild rice acreage to mining, dams, and other activities has been substantial. Warmer temperatures could cause further losses by reducing seed dormancy, favoring invasive, out-competing plants, and being conducive to brown spot disease. Water levels also influence rice survival. Extremely low Lake Superior levels in 2007 forced the Bad River Band of the Lake Superior Tribe of Chippewa (WI) to cancel its annual wild rice harvest due to dramatic crop reductions. A 2012 flood led to near total wild rice crop failure on the Fond du Lac Reservation. Tribes in the Great Lakes area rely on treaty fishing, hunting, and gathering rights. The exercise of these rights requires considerable attention to environmental issues, including climate changes that affect species and habitats. These rights have been the subject of several court cases, which have resulted in decisions upholding tribal rights. Native American tribes need relevant and culturally appropriate monitoring, assessment, and research on their waters and lands and to develop or be included in the development of contingency, management, and mitigation plans. Tribes also greatly need actual implementation of projects. Although climate change preparedness can take place as a stand-alone effort, climate change considerations can be included as part of planning and implementation that is already occurring. Tribes or intertribal organizations must decide what constitutes relevant work. We propose research questions that might be significant for tribes based on the five impact categories. These include examples of science, policy, and social science questions related both to further identifying impacts and contributing climate and vulnerability factors and to identifying adaptation strategies."
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    Climate change, forest composition, and outdoor recreation in northeastern Minnesota
    (2022-09) Bakshi, Baishali
    Climate change will likely result in a change in the composition of northern Minnesota forests by the end of the century, affecting outdoor recreation, which is a valuable ecosystem service as well as a key economic driver for the state with over $4 billion in annual expenditures in hunting, fishing, and wildlife viewing. Yet, the links between climate change, forest composition, and outdoor recreation have not been well studied. Current research finds that deer can also affect the links between climate change, forest composition, and outdoor recreation. In this dissertation, I examine and evaluate the links between these four main variables: climate change, forest composition, deer, and outdoor recreation, and a variety of other relevant predictors, using a combination of econometric modeling and spatial analysis applied to region-specific data in the Laurentian Mixed Forest Province (LMF) of northern Minnesota. My results improve understanding of these complex relationships to better inform Minnesota’s climate adaptation strategies and contribute to the literature on ecosystem services.
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    Climate change, the invasion of Bythotrephes longimanus, and recent changes in the zooplankton community of Lake Superior
    (2016-07) Pawlowski, Matthew
    In recent decades, average summer surface temperatures in Lake Superior have increased and the invasive predatory zooplankton, Bythotrephes longimanus, became established. While climate warming and Bythotrephes have influenced zooplankton communities in other lakes, it is unclear how either have or will influence the zooplankton community in Lake Superior. A late spring ice out in 2014 provided an opportunity to observe the response of zooplankton in Lake Superior to inter-annual variation in temperature. To evaluate this response, I compared biomass estimates, phenologies, and community compositions of the zooplankton communities in western Lake Superior during the 2014 and 2015 growing seasons. I also compared the community compositions observed in these years to published literature to determine whether the community has changed in response to climate warming or planktivory by Bythotrephes. I evaluated the possible role of Bythotrephes in zooplankton community changes using a bioenergetic model to compare the consumptive demands of Bythotrephes to the production rates of their potential prey. Annual peaks in zooplankton biomass were correlated with peaks in surface temperature. Peak biomass in 2014 occurred approximately 20 days later than in 2015 suggesting that continued warming could have long-term effects on the timing of peak zooplankton biomass in Lake Superior. The amount of biomass at the peak did not differ between years nor did overall community structure suggesting that zooplankton biomass and species composition in Lake Superior may be more constrained by food availability than temperature. However, long-term comparisons of zooplankton community composition indicate that densities of Bosmina longirostris declined and the proportional contribution of Daphnia mendotae to cladoceran biomass increased since the 1970s. These community changes are more consistent with the expected outcome of planktivory by Bythotrephes than the expected outcomes of changes in temperature, primary production, or vertebrate planktivory. The results suggest that Bosmina is the cladoceran species most vulnerable to suppression by Bythotrephes in Lake Superior, which supports the hypothesis that Bythotrephes has altered the cladoceran community in Lake Superior. While consumption by Bythotrephes did not exceed total zooplankton production in Lake Superior during 2014 or 2015, future increases in Bythotrephes density and temperature could cause the top-down effects of Bythotrephes on the zooplankton community to increase. This work helps to clarify how climate warming and Bythotrephes could influence the zooplankton community and energy flow pathway in Lake Superior in the future.
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    Communities in freshwater coastal rock pools of Lake Superior, with a focus on chironomidae (Diptera)
    (2014-05) Egan, Alexander
    Exposed freshwater shores have received little ecological attention. At Isle Royale, an archipelago in Lake Superior, coastal areas have a moderated climate due to the large, deep lake. This project was instigated because 1) little was known about coastal ecosystems at Isle Royale, 2) unique aquatic species were expected in this habitat, 3) potentially disastrous impacts from shipping accidents could cause population losses of sensitive species, and 4) long-term shifts in climate could influence communities via warming conditions and erratic precipitation. Focal habitats were pools on the open shore, formed in bedrock depressions from precipitation, ground water, overland flow, and wave wash. The focal study taxon was Chironomidae, a diverse family of aquatic flies, well-known for variable responses to pollution and ecological gradients. Results showed a surprisingly species-rich (n = 102) and diverse assemblage. Moderate to extreme range expansions and novel habitat use were documented. Distinct communities were observed between two vertical zones, based on distance from the lake. Differences in seasonal emergence occurred close to the lake, but emerging assemblages were similar across seasons above lake influence. Some evidence supported both biogeographic community variation based on distances between islands and control of emergence events by water temperature. However, there was no evidence that pool depth or potential for desiccation influenced chironomid occupancy. Nutrients (phosphorus, nitrogen, and carbon) were the most important factors driving chironomid assemblage differences. Pools higher on the shore showed nutrient input from upland habitats, while pools lower on the shore appeared to have nutrients flushed out by wave action and replaced with low-nutrient water. Comprehensive habitat mapping revealed high pool densities, with an extraordinary number on Passage Island, arguably the most threatened locality to shipping pollution. Also, Passage Island had the highest density of Pseudacris triseriata, a frog species with a remarkably narrow habitat use at Isle Royale. Overall, a diverse community was revealed in what superficially looks like unremarkable habitat. Apparent similarities to northern and western shores of Lake Superior suggest this study of basic aquatic ecology and physical structure describes reference conditions for coastal management across much of the lake.
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    Complexity in Global Energy-Environment Governance
    (Minnesota Journal of Law, Science and Technology, 2014-05) Long, Andrew
    Thinking about energy as a complex system from which fossil fuel dominance and climate change emerge provides an analytical and policy-relevant framework for exploring pathways toward transforming that system. The linkage of issues and scales of authority, highlighted briefly above, are but two examples of how this might be operationalized. Literature since the 2009 UNFCCC negotiations in Copenhagen is beginning to explore alternatives to top-down binding international environmental agreements for catalyzing successful mitigation, but it has yet to coalesce around an analytical framework that can foster synergy and the development of a cohesive body of work identifying and testing viable options that are likely to produce solid policy recommendations. A perspective on climate change informed by an understanding of the global energy system as a complex system has the potential to provide such a framework. Further exploring the potential for an interdisciplinary perspective on energy as a complex system may provide the analytical framework needed to accelerate the learning process by uniting the somewhat disparate strands of thought that have emerged since the “dream of Rio,” characterized by an unjustified faith in global top-down environmentalism, came to a crashing halt at the end of 2009. A complexity perspective on energy as the source of climate change may unite many of the developing approaches, which include work exploring near-term approaches to climate change mitigation, detailed analysis of particular aspects of the mitigation challenge if developed outside of a unifying top-down structure, and analytical expositions of polycentric governance theories in climate-relevant ways. Viewed as a body of literature addressing facets of a global complex systems challenge, such work can be understood to contain the seeds of an approach that is sufficiently salient to garner political support while also probing for effective tools that will engage the multiple interacting threads of social, ecological, and technical components that affect the energy system across scales in order to produce an overall shift that achieves climate stabilization. There is much work to be done if we hope to bring about the kind of transformation of the global energy system necessary to reduce GHG emissions significantly and rapidly enough to avoid drastic climate change impacts. A complexity perspective strikes an appropriate balance between resigning the global population to the massive suffering and destabilization that climate change may bring, as a narrow focus on developed country adaptation would do, and the unwarranted faith in top-down global governance that much of the previous decade’s climate change analysis exhibited. In this sense, a complexity perspective on climate change urges a form of governance reflecting the nature of adaptive systems situated on the edge of chaos—advocating enough order to avert disaster, while imbuing reform with the long-term catalytic vision necessary to bring about the emergence of that which is desirable, but remains uncertain and unpredictable.
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    Consequences of elevated temperature on prairie plants: legumes, nitrogen, and phenology.
    (2012-05) Whittington, Heather Renee
    Because prairies are often nitrogen (N) limited, prairie legumes can have significant impacts on the nitrogen (N) dynamics of these communities because of their ability to add fixed N to their surroundings through symbiotic biological N2-fixation and their N-rich tissues that can stimulate net nitrogen mineralization. Predicted increases in temperature have the potential to alter legume traits and functioning, which can feedback to affect ecosystem dynamics. The goal of this dissertation was to examine the effect of elevated temperature on the growth, phenology, and N nutrition of four prairie legumes: Amorpha canescens, Dalea purpurea, Lespedeza capitata, and Lupinus perennis, using both a growth chamber experiment and a manipulative field warming experiment. In the growth chamber experiment, seedlings of Lespedeza exhibited higher biomass and shoot N content at 28°C than 25°C, while Lupinus seedlings displayed decreased nodulation and lower shoot N concentration at the higher temperature. In the field warming study, Dalea and Lupinus displayed higher biomass under warming and all species exhibited lower shoot N concentrations under warming. Neither N2-fixation nor net N mineralization were affected by warming. Warming accelerated flowering for several species, including Amorpha and Dalea, and accelerated spring green-up, as evidenced by higher normalized difference vegetation index (NDVI) values in warmed communities in May. These results indicate that prairie legumes are responsive to increases in temperature in a species-specific manner and that warming may alter N-cycling by changing legume abundance and tissue N chemistry. Additionally, significant interannual variation in many variables and in their responses to warming emphasizes the need for long term studies to better understand and predict potential consequences of elevated temperature on plants and their ecosystems.
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    Effect of Temperature on Habitat Use by Moose in Voyageurs National Park in the Summer
    (University of Minnesota Duluth, 2015) Moen, Ronald; Joyce, Michael; Windels, Steven K
    Moose (Alces alces) are an integral part of biological processes and a favorite sight of visitors to Voyageurs National Park (VNP). In the face of global climate change moose may also become a bellwether species for the persistence of northern species in VNP and the surrounding area. Climate change will affect national parks like VNP in many ways, ranging from changes in vegetation and possible loss of wildlife species to altered visitation rates by people. Minnesota is at the southern edge of moose distribution. Climate change predictions are for a 3o to 4o C increase in average summer temperatures by 2100, which would result in an increased number of summer days during which moose would be heat stressed. We deployed GPS collars on moose in VNP to evaluate changes in habitat use and activity as related to fine-scale changes in ambient temperature. We captured and radiocollared 21 moose by aerial darting or net-gunning. We measured black globe temperatures in habitats across VNP. The annual Minimum Convex Polygon home range area was about 15 km2, while seasonal home ranges were about 10 km2. Home range size was slightly less than in adjoining areas of northeast Minnesota. There was no difference in proportional cover type in the home range among annual, winter, and summer home ranges, and cover type use was similar to cover type use by moose in northeast Minnesota. Wet bog and wet marsh/fen cover types were preferred in hot summer temperatures, while open water was not used very much, with less than 1% of locations in water when temperatures were above 30 C. Use of almost all cover types was similar whether temperature, dew point, or heat index were used as the metric. For future analysis of cover type use ambient or black globe temperature should be an adequate metric. Habitats that are of most use to moose in hot temperatures have a wet substrate and some canopy cover during the day. At night moose seemed to be less limited by heat dissipation because of colder temperatures and the lack of solar radiation. Monitoring the population status of moose at Voyageurs National Park is of critical importance in order to make contrasts with the declining moose populations in other regions of Minnesota.
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    Effects of Multiple Stressors on Aquatic Communities in the Prairie Pothole Region
    (University of Minnesota Duluth, 2007) Schoff, Patrick K; Johnson, Lucinda B; Guntenspergen, Glenn R; Johnson, W. Carter
    The prairie potholes wetlands of the Great Plains comprise some of the most ecologically valuable freshwater resources of the nation, but they are also exceptionally vulnerable to anthropogenic stressors, particularly those associated with agricultural land use practices. They are also considered likely to be severely impacted by climate change. In this study we have quantified relationships among stressors associated with climate, agricultural land use and amphibian communities throughout much of the prairie pothole region.
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    Effects of throughfall reduction and snow removal on soil physical and biogeochemical properties in aspen forests of northern Minnesota, USA
    (2022-04) Stockstad, Anna
    Climate change is projected to alter precipitation patterns across northern latitudes, with decreased snow accumulation and summer rainfall predicted. These changes may alter soil physical and biogeochemical properties, which would have implications for the operability and productivity of forest soils. Reductions in summer and winter precipitation were simulated using a paired-plot design with throughfall reduction and snow removal across four drainage classes at each of three locations in northern Minnesota, USA. Soil temperature and water content were measured every fifteen minutes to a depth of 60 cm, and soil frost depth (winter) and soil strength (summer) were monitored for two years. Soil respiration and extractable nitrogen were measured during two growing seasons, and a laboratory incubation was performed to test the response of carbon and nitrogen fluxes under controlled conditions. Soil temperature and water content increased from well-drained to poorly-drained soils during the winter and growing season, respectively. Snow removal caused large declines in soil temperature and significantly deeper penetration of frost that varied by drainage class, and there were strong relationships between frost depth and freezing degree days. Throughfall reduction had no effect on soil strength, soil respiration, or extractable nitrogen concentrations. Drainage class was a significant, although limited, indicator of soil strength, soil respiration, and extractable nitrogen concentrations. The laboratory incubation confirmed the lack of treatment effect on soil carbon and nitrogen fluxes, and instead showed that drainage class and soil moisture controlled these fluxes. These findings show that the dominant response of forest soils to reduced seasonal precipitation will occur during the winter with decreased soil temperatures and increased frost depth across drainage classes, which has implications for seasonal timber harvesting in northern latitudes under a changing climate.
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    Encroaching Tides: How Sea Level Rise and Tidal Flooding Threaten U.S. East and Gulf Coast Communities over the Next 30 Years
    (2014) Spanger-Siegfried, Erika; Fitzpatrick, Melanie; Dahl, Kristina
    This recent study examined coastal flooding along the Eastern and Gulf coasts of the US, and did not include the Great Lakes. However, the report concludes that extreme weather events and floods are occurring nationwide, and that other coastal communities are also at higher risk. Coastal communities and states, and the nation as a whole, need to prepare for near-term changes in tidal flooding, while working hard to minimize longer-term losses through efforts to both adapt to these changes and limit their extent. The report outlines steps to ensure more resilient coastal communities, which are extracted and reproduced below. “BUILDING COASTAL RESILIENCE IS A LOCAL IMPERATIVE . . . Over the next few decades—the time frame of our analysis—changes set in motion by our past and present heat-trapping emissions will largely drive the pace of sea level rise. The lag of several decades between the release of carbon into the atmosphere and the response of the ocean means that more tidal flooding is virtually guaranteed, and that communities need to act with urgency. Locally, there are many things we can do to help ensure enduring coastal communities, including: • Upgrade the built infrastructure in harm’s way. With help, communities can prioritize and incentivize flood-proofing of homes, neighborhoods, and key infrastructure, such as sewer and stormwater systems. • Avoid putting anything new in harm’s way. Communities can use a range of regulatory and planning tools to curtail new development in coastal locations subject to tidal flooding now and in the future. • Consider the risks and benefits of adaptation measures. Some measures to limit the impact of coastal flooding can provide multiple benefits, while others can alter shoreline dynamics and damage neighboring areas and ecosystems. Decision makers need to ensure that a rush to protect coastal communities builds broad-based resilience, rather than helping some areas while putting others at risk. • Develop a long-term vision. Communities that create a vision for both near-term protection and long-term resilience in the face of sea level rise—and craft plans for building better, safer, and more equitably—will be best positioned to thrive in the years ahead. . . . AND A NATIONAL ONE But local communities can’t go it alone—coastal challenges are too great, the costs are too steep, and too many people are at risk. Instead, we need a coordinated, well-funded national response to our country’s coastal vulnerability involving federal, state, and local collaboration. Federal and state governments can help build local resilience by supporting, incentivizing, regulating, and even mandating action. They can: • Build and maintain a coastal monitoring and data-sharing system equal to the threat. Key federal agencies can sustain and expand efforts to monitor and project sea level rise and flooding, and ensure that local decision makers have access to the data. • Encourage or mandate the use of good scientific information. Agencies can require that communities and other applicants for state and federal funds use the best available data, and demonstrate that new development and redevelopment projects can withstand projected tidal flooding and storm surges. • Support planning. More federal support for state and local planning and collaboration can accelerate efforts to build coastal resilience. • Mobilize funding. Adapting to sea level rise will require major, sustained investment. Federal policy makers need to develop new funding sources to support resilience-building efforts at the state and local level. • Improve risk management. The true costs of living on the coast are not reflected in the price of flood insurance and other risk management tools. But big increases in the cost of insurance are hard for many to bear. Federal incentives to reduce some property owners’ risks and costs can aid the transition to a more solvent flood insurance system and better risk management. • Ensure equitable investments. Federal investments in coastal resilience can prioritize households and communities with the greatest needs. • Reduce heat-trapping emissions. A near-term increase in sea level rise and tidal flooding may be locked in, but changes later this century and beyond are not fixed. To slow the rate of sea level rise—and enable coastal communities to adapt in affordable and manageable ways— we must reduce our global warming emissions.”
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    Essays on optimal taxation of carbon emissions
    (2013-07) Belfiori, Maria Elisa
    This dissertation is composed of two essays and studies the optimal taxation of carbon emissions.In the first essay, I set up an economy where an externality arises from the consumption of an exhaustible resource (oil) and a technology exists to mitigate the externality. I focus on the implications for policy design of assuming social preferences differ from private preferences regarding future generations. In particular, I consider a welfare function that places direct Pareto weights on unborn generations, as opposed to future generations receiving weight only through the altruism of their ancestors. This specification delivers a social discount rate which is lower than that of private individuals. I first show that standard policies, such as price or quantity controls on the net emissions of carbon, are insufficient to achieve the social optimum: When social and private discounting differ, more sophisticated policies are necessary. The main results of the chapter characterize these sophisticated policies. I show that an optimal tax scheme requires subsidizing the mitigation technology and taxing carbon emissions, but each at different rates: the optimal subsidy for removing a ton of carbon from the atmosphere will in general not equal the optimal tax for creating a ton of carbon. I also show that an optimal cap and trade system must include a cap on carbon offset allowances.In the second essay, I study the optimal taxation of carbon emissions in an intergenerational model with imperfect altruism. This means that the current generations discount tradeoffs in the near future more than those which happen in the distant future. As a result, a problem of time inconsistency arises. I study if standard carbon policies are sufficient to control emissions in this economy. I first show that, when society can successfully resolve the inconsistency problem by committing itself to following a climate plan, standard carbon taxes coupled with a subsidy on oil reserves are enough to induce future generations to follow it. However, an initial period of sophisticated policies are required to induce the current generation to abide by it as well. When no commitment technology is available, I solve for the Markov perfect equilibrium of the dynamic game between generations and show that sophisticated policies are always required to implement the constrained social optimum.
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    Evaluation of phenotypic and physiologic characteristics of selected sources of white spruce, Picea glauca (Moench) Voss
    (2013-12) Pike, Carolyn C.
    White spruce is highly valued for its wood pulp in commercial forestry in Minnesota. Seed orchards have been developed using genotypes selected for increased volume production. I conducted three different experiments to study the variation of ecophysiologic traits among genotypes selected from the Minnesota Tree Improvement Cooperative's program to better characterize the phenotype of selected genotypes. In chapter 1, I analyzed wood specific gravity, tree volume, and leaf traits on 25-year old trees in a white spruce progeny test. Wood specific gravity was negatively correlated with tree volume. Needle traits, primarily specific leaf area (SLA), leaf area ratio (LAR) and leaf mass ratio (LMR), were positively correlated with wood volume. In chapter 2, I planted seedlings from four genotypes selected for superior volume growth and two wild sources in a common garden. I harvested ten trees from each genotype, each year for three years. I examined biomass allocation, tree allometry and assessed genetic correlations among allocation of biomass to major organs. The largest differences in biomass were found between the two wild sources that represented two different seed zones in Minnesota. Selected sources more closely resembled the southern, than the northern, wild source. The northern wild sources had slightly higher allocation to roots but otherwise no significant differences in allometry were found. In chapter 3, I set up an outdoor experiment by planting five selected- and two wild- seed sources into 1-gallon containers to test the effects of mid-winter warming on phenology and growth of white spruce. Bud-break time was delayed in plots that were warmed in February, and advanced in those warmed in March. Overall controls had the highest height growth and intermediate bud-break time. Climatic warming that takes place during winter months may delay or advance bud-break depending on the timing. Growth of white spruce is expected to decline with increased episodes of winter warming. Selected sources should be favored in reforestation across Minnesota because of the higher productivity and adaptability to local conditions.
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    Evolution and the climatic niche: Using genomics and niche modeling to explore how climate impacts evolutionary processes
    (2022-02) Weaver, Samuel
    Climate shapes the distributions of and interactions among species and thus influences many evolutionary processes related to the generation and maintenance of biodiversity. Oscillations in climatic regimes have played an important role in shaping the patterns of diversity by driving speciation events when previously connected populations become allopatrically isolated in different environments. Changing climates also are associated with extinction events when populations are unable to track their climatic niche or adapt to novel conditions. The rapid climate change caused by human activity emphasizes the need to understand the role climate plays in mediating species interactions and distributions. This work combines the use of climatic and genomic data across a variety of vertebrate systems to explore how climate has shaped the processes of speciation and evolution, and how climate may threaten the continued persistence of both recognized and unrecognized diversity. The evolution of a species’ climatic niche, or the climatic conditions under which a species occurs, plays a central role in generating diversity and adaptation to new environmental conditions. Faster rates of climatic niche evolution are associated with increased diversification rates, suggesting that the exploration of novel climate space can facilitate isolation and subsequent diversification. The evolution of traits that may increase or decrease rates of climate niche evolution, then, may play an important role in the colonization of novel environments and the formation of species. In my first chapter, I show that the evolution of a short aquatic larval stage in Desmognathus salamanders led to an increase in the rate of climatic niche evolution, which may have played a central role in the adaptive radiation of this group. Changes in climate have the potential to bring long-isolated species into contact with one another. Oftentimes, these species can produce viable offspring with one another and form hybrid zones. These hybrid zones often form along ecological gradients, with hybrids occurring in habitats intermediate to the climatic conditions occupied by the pure parental populations. In the Southern Appalachian Mountains, Plethodon shermani and Plethodon teyahalee hybridize extensively along an elevational gradient. P. shermani occurs on different mountaintop isolates, and P. teyahalee is distributed in between them at lower elevations. In my second chapter, I explore the genomic evidence for hybridization between these two species and whether climatic variation associated with elevation maintains species boundaries in this system. All surveyed parental P. shermani populations have experienced some degree of introgression from P. teyahalee, and multiple lines of evidence suggest that selection for P. teyahalee alleles drives asummetric introgression from P. teyahalee into P. shermani. We identify no intrinsic genetic barriers to gene flow, suggesting that these hybrid zones are regulated by ecological, rather than intrinsic factors. These findings suggest that all P. shermani populations are in danger of swamping by P. teyahalee as conditions in the Appalachians become warmer and drier. Genomics and niche modeling are powerful tools for identifying cryptic lineages of conservation concern within widespread species. In addition to identifying lineages, these approaches can inform managing agencies about threats to population persistence such as climate change-induced habitat loss and inbreeding. In my final chapter, I assess patterns of genomic and environmental differentiation among populations of Kinosternon hirtipes. Within this group, we identified multiple evolutionarily distinct lineages, many of which correspond to described subspecies. Genetic and ecological differentiation among these lineages appears to be due to vicariance associated with the Trans-Mexican Volcanic Belt. Northern populations exhibit low genetic diversity, high levels of inbreeding, and may lose over 85% of climatically suitable habitat to climate change, raising concern over their long-term viability.
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    Examining the drivers of current and future changes in Central U.S. warm-season rainfall
    (2014-09) Harding, Keith John Iliff
    Warm-season precipitation in the Central U.S. is highly variable, as severe droughts and flooding often occur in consecutive years or simultaneously. Some of the most highly productive agricultural lands are present within the region despite susceptibility to warm-season rainfall extremes. Climate change is expected to increase precipitation extremes globally, but how warm-season Central U.S. precipitation will be affected is unclear. In this study, I examine the drivers of current and future warm-season precipitation in the region as well as how the basic characteristics of summer rainfall may be affected by climate change through the use of gridded observations, reanalysis datasets, and dynamical downscaling of global climate models (GCMs). It is demonstrated that the negative phase of the Pacific-North American (PNA) teleconnection pattern enhances heavy precipitation events over the Upper Midwest by modulating the strength of the Great Plains Low Level Jet (GPLLJ), possibly enabling greater medium range prediction of Midwest heavy rain events. Similarly, I aim to reduce uncertainty in long-term projections of how precipitation may be affected by climate change by examining shortfalls in GCM-simulated warm-season precipitation and demonstrating improvement with dynamical downscaling. Using the Weather Research and Forecasting (WRF) model, two GCMs are dynamically downscaled in one historical and three future timeslices with varying anthropogenic forcing. Future warm-season precipitation in these simulations is more intense, less frequent, and occurs with more days between rain events, similar to trends in observations that show large increases in extreme rainfall events and rainfall intensity. The intensification of extreme rainfall events in future simulations is the strongest during the April-July, associated with a strengthening of the GPLLJ during those months. Heavier rainfall rates during extreme precipitation events are related to a stronger cold pool and mesohigh, which force stronger moisture convergence above the cold pool in the presence of additional low-level moisture and a drier mid-troposphere. Overall, the identification of plausible physical mechanisms that might contribute to the enhancement of heavy rainfall events in the region enables greater confidence in future projections of extreme rainfall events.