In 1987, and again 20 years later, the United Church of Christ (UCC) presented research showing t... more In 1987, and again 20 years later, the United Church of Christ (UCC) presented research showing that 60% of African Americans lived near an unregulated toxic waste facility. We build off the original UCC study and present an analysis of minority populations in relation to superfund sites, using the geometric complexity of congressional districts (CDs) as a proxy for gerrymandering within the lower 48 states. We further the analysis by looking at different areal aggregations and find that regardless of the aggregation there is a relationship between race and distance from superfund sites. Moreover, we address the issues of inherent complexity as it relates to coastal areas, which could bias the analysis, by systematically reducing the complexity within a geographic information system (GIS). At the CD level, there is a statistically significant relationship where race becomes ''whiter'' and less ''African American'' as the Euclidean distance increases from superfund sites. While there is a strong relationship between the gerrymander coefficient and the proximity to superfund sites (R 2 = 0.58, DF = 347, p < 0.001), variables such as median income, air quality, and unemployment may account for the unexplained variance in the model. We also found a strong relationship between the percent white and a higher gerrymandering coefficient, indicating that minority populations are effectively ''gerrymandered out'' of the white and lower environmental hazard districts. This research is novel in that it suggests a calculated effort to marginalize minority populations and warrants further investigation while analyzing additional proxies for environmental hazards.
This paper addresses the economic tradeoff between pumping groundwater and maintaining a native p... more This paper addresses the economic tradeoff between pumping groundwater and maintaining a native plant community that provides an ecosystem service of dust suppression. A dynamic ecological economic simulation model was created to assess net benefits of production (i.e., economic rent) from groundwater management while requiring a producer to maintain or restore native groundwater dependent vegetation in a well-field in Owens Valley, California. Historic groundwater withdrawal during dry conditions followed by recharge during wet conditions has reduced vegetation cover, soil stability and contributed to the drying of springs and seeps. Findings indicate adaptive management that pumps less water, but high volumes in wet years and low volumes in dry years, generates greater economic rent while supplying water, sustaining alkali meadow and maintaining dust suppression. Adaptive management generates economic rent of $82.6 million (in 2011 $) compared to status quo management of $30.5 million over 50 years pumping less annual groundwater than status quo at respective levels of 73% (6830 acre-ft; baseline conditions) and 56% (4952 acre-ft; climate change scenario). Under a climate change scenario and a 2.0 m root-zone or less, it would be cost effective to cease groundwater pumping rather than incur substantial restoration costs of the native plant community.
This manuscript has been reproduced from the microfilm master. UMI films the text directly from t... more This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.
Polyphenisms are excellent models for studying phenotypic variation, yet few studies have focused... more Polyphenisms are excellent models for studying phenotypic variation, yet few studies have focused on natural populations. Facultative paedomorphosis is a polyphenism in which salamanders either metamorphose or retain their larval morphology and eventually become paedomorphic. Paedomorphosis can result from selection for capitalizing on favorable aquatic habitats (paedomorph advantage), but could also be a default strategy under poor aquatic conditions (best of a bad lot). We tested these alternatives by quantifying how the developmental environment influences the ontogeny of wild Arizona tiger salamanders (Ambystoma tigrinum nebulosum). Most paedomorphs in our study population arose from slow-growing larvae that developed under high density and size-structured conditions (best of a bad lot), although a few faster-growing larvae also became paedomorphic (paedomorph advantage). Males were more likely to become paedomorphs than females and did so under a greater range of body sizes than females, signifying a critical role for gender in this polyphenism. Our results emphasize that the same phenotype can be adaptive under different environmental and genetic contexts and that studies of phenotypic variation should consider multiple mechanisms of morph production.
Many studies have attempted to assess the ability of created wetlands to replace the ecological s... more Many studies have attempted to assess the ability of created wetlands to replace the ecological structure and functions of natural wetlands over short time periods (<5 years). Few studies have repeatedly monitored vegetative community development of created depressional wetlands over longer time frames or assessed the return on the level of initial restoration efforts. Here, the vegetation communities of 17 created freshwater marshes in two different geographic regions of the U.S., Ohio and Colorado, ranging from 5 to 19 years old, were monitored over multiple years and compared to natural reference sites.
This paper explores the tradeoff between resource extraction and net carbon sequestration in mana... more This paper explores the tradeoff between resource extraction and net carbon sequestration in managing representative timber stands in the state of New Hampshire in the northeastern United States. In the absence of policies to promote forest carbon storage, land owners have incentives to employ clear-cut harvesting regimes with relatively short rotation periods. Under conservative assumptions regarding the social benefits of carbon storage, optimal rotation periods are extended by between 16 and 133 years depending on the forest type under consideration. If policy-makers pursued a cost-effective strategy to stabilize atmospheric carbon dioxide concentrations at twice the pre-industrial norm, optimal rotation periods would be extended by a full 180-347 years. The analysis suggests that partial harvesting regimes (in which approximately 35% of timber volume is removed at 15-year intervals after the timber stand reaches an initial age of 45 years) provide relatively high net benefits under a variety of circumstances. This finding is relevant because partial harvesting is an accepted and relatively common practice that could be adopted more widely.
Partnerships and co-operative environmental management are increasing worldwide as is the call fo... more Partnerships and co-operative environmental management are increasing worldwide as is the call for scientific input in the public process of ecosystem management. In Hawaii, private landowners, non-governmental organizations, and state and federal agencies have formed watershed partnerships to conserve and better manage upland forested watersheds. In this paper, findings of an international workshop convened in Hawaii to explore the strengths of approaches used to assess stakeholder values of environmental resources and foster consensus in the public process of ecosystem management are presented. Authors draw upon field experience in projects throughout Hawaii, Southeast Asia, Africa and the US mainland to derive a set of lessons learned that can be applied to Hawaiian and other watershed partnerships in an effort to promote consensus and sustainable ecosystem management.
The extent and rate to which mitigation wetlands can replace the functions of natural ones remain... more The extent and rate to which mitigation wetlands can replace the functions of natural ones remains uncertain. Further, the economic time lag costs of wetland function restoration and therefore cost-effective and efficient means of wetland mitigation have yet to be adequately addressed. In this study, 16 mitigation wetlands were assessed, comprised of eight low elevation inland freshwater emergent marshes in Ohio and eight high elevation (>2285 m) freshwater emergent marshes in a wetland complex in Colorado, USA. This research identified the ecological substitutability of mitigation inland freshwater marshes for natural ones, estimated economic restoration lag costs to society and addressed least-cost approaches to successful mitigation.
In 1987, and again 20 years later, the United Church of Christ (UCC) presented research showing t... more In 1987, and again 20 years later, the United Church of Christ (UCC) presented research showing that 60% of African Americans lived near an unregulated toxic waste facility. We build off the original UCC study and present an analysis of minority populations in relation to superfund sites, using the geometric complexity of congressional districts (CDs) as a proxy for gerrymandering within the lower 48 states. We further the analysis by looking at different areal aggregations and find that regardless of the aggregation there is a relationship between race and distance from superfund sites. Moreover, we address the issues of inherent complexity as it relates to coastal areas, which could bias the analysis, by systematically reducing the complexity within a geographic information system (GIS). At the CD level, there is a statistically significant relationship where race becomes ''whiter'' and less ''African American'' as the Euclidean distance increases from superfund sites. While there is a strong relationship between the gerrymander coefficient and the proximity to superfund sites (R 2 = 0.58, DF = 347, p < 0.001), variables such as median income, air quality, and unemployment may account for the unexplained variance in the model. We also found a strong relationship between the percent white and a higher gerrymandering coefficient, indicating that minority populations are effectively ''gerrymandered out'' of the white and lower environmental hazard districts. This research is novel in that it suggests a calculated effort to marginalize minority populations and warrants further investigation while analyzing additional proxies for environmental hazards.
This paper addresses the economic tradeoff between pumping groundwater and maintaining a native p... more This paper addresses the economic tradeoff between pumping groundwater and maintaining a native plant community that provides an ecosystem service of dust suppression. A dynamic ecological economic simulation model was created to assess net benefits of production (i.e., economic rent) from groundwater management while requiring a producer to maintain or restore native groundwater dependent vegetation in a well-field in Owens Valley, California. Historic groundwater withdrawal during dry conditions followed by recharge during wet conditions has reduced vegetation cover, soil stability and contributed to the drying of springs and seeps. Findings indicate adaptive management that pumps less water, but high volumes in wet years and low volumes in dry years, generates greater economic rent while supplying water, sustaining alkali meadow and maintaining dust suppression. Adaptive management generates economic rent of $82.6 million (in 2011 $) compared to status quo management of $30.5 million over 50 years pumping less annual groundwater than status quo at respective levels of 73% (6830 acre-ft; baseline conditions) and 56% (4952 acre-ft; climate change scenario). Under a climate change scenario and a 2.0 m root-zone or less, it would be cost effective to cease groundwater pumping rather than incur substantial restoration costs of the native plant community.
This manuscript has been reproduced from the microfilm master. UMI films the text directly from t... more This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.
Polyphenisms are excellent models for studying phenotypic variation, yet few studies have focused... more Polyphenisms are excellent models for studying phenotypic variation, yet few studies have focused on natural populations. Facultative paedomorphosis is a polyphenism in which salamanders either metamorphose or retain their larval morphology and eventually become paedomorphic. Paedomorphosis can result from selection for capitalizing on favorable aquatic habitats (paedomorph advantage), but could also be a default strategy under poor aquatic conditions (best of a bad lot). We tested these alternatives by quantifying how the developmental environment influences the ontogeny of wild Arizona tiger salamanders (Ambystoma tigrinum nebulosum). Most paedomorphs in our study population arose from slow-growing larvae that developed under high density and size-structured conditions (best of a bad lot), although a few faster-growing larvae also became paedomorphic (paedomorph advantage). Males were more likely to become paedomorphs than females and did so under a greater range of body sizes than females, signifying a critical role for gender in this polyphenism. Our results emphasize that the same phenotype can be adaptive under different environmental and genetic contexts and that studies of phenotypic variation should consider multiple mechanisms of morph production.
Many studies have attempted to assess the ability of created wetlands to replace the ecological s... more Many studies have attempted to assess the ability of created wetlands to replace the ecological structure and functions of natural wetlands over short time periods (<5 years). Few studies have repeatedly monitored vegetative community development of created depressional wetlands over longer time frames or assessed the return on the level of initial restoration efforts. Here, the vegetation communities of 17 created freshwater marshes in two different geographic regions of the U.S., Ohio and Colorado, ranging from 5 to 19 years old, were monitored over multiple years and compared to natural reference sites.
This paper explores the tradeoff between resource extraction and net carbon sequestration in mana... more This paper explores the tradeoff between resource extraction and net carbon sequestration in managing representative timber stands in the state of New Hampshire in the northeastern United States. In the absence of policies to promote forest carbon storage, land owners have incentives to employ clear-cut harvesting regimes with relatively short rotation periods. Under conservative assumptions regarding the social benefits of carbon storage, optimal rotation periods are extended by between 16 and 133 years depending on the forest type under consideration. If policy-makers pursued a cost-effective strategy to stabilize atmospheric carbon dioxide concentrations at twice the pre-industrial norm, optimal rotation periods would be extended by a full 180-347 years. The analysis suggests that partial harvesting regimes (in which approximately 35% of timber volume is removed at 15-year intervals after the timber stand reaches an initial age of 45 years) provide relatively high net benefits under a variety of circumstances. This finding is relevant because partial harvesting is an accepted and relatively common practice that could be adopted more widely.
Partnerships and co-operative environmental management are increasing worldwide as is the call fo... more Partnerships and co-operative environmental management are increasing worldwide as is the call for scientific input in the public process of ecosystem management. In Hawaii, private landowners, non-governmental organizations, and state and federal agencies have formed watershed partnerships to conserve and better manage upland forested watersheds. In this paper, findings of an international workshop convened in Hawaii to explore the strengths of approaches used to assess stakeholder values of environmental resources and foster consensus in the public process of ecosystem management are presented. Authors draw upon field experience in projects throughout Hawaii, Southeast Asia, Africa and the US mainland to derive a set of lessons learned that can be applied to Hawaiian and other watershed partnerships in an effort to promote consensus and sustainable ecosystem management.
The extent and rate to which mitigation wetlands can replace the functions of natural ones remain... more The extent and rate to which mitigation wetlands can replace the functions of natural ones remains uncertain. Further, the economic time lag costs of wetland function restoration and therefore cost-effective and efficient means of wetland mitigation have yet to be adequately addressed. In this study, 16 mitigation wetlands were assessed, comprised of eight low elevation inland freshwater emergent marshes in Ohio and eight high elevation (>2285 m) freshwater emergent marshes in a wetland complex in Colorado, USA. This research identified the ecological substitutability of mitigation inland freshwater marshes for natural ones, estimated economic restoration lag costs to society and addressed least-cost approaches to successful mitigation.
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