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61.
Veronica M. Bueno Kevin R. Burgio Carrie A. Cizauskas Christopher F. Clements Dana P. Seidel Nyeema C. Harris 《Conservation biology》2016,30(4):724-733
Parasitic species, which depend directly on host species for their survival, represent a major regulatory force in ecosystems and a significant component of Earth's biodiversity. Yet the negative impacts of parasites observed at the host level have motivated a conservation paradigm of eradication, moving us farther from attainment of taxonomically unbiased conservation goals. Despite a growing body of literature highlighting the importance of parasite‐inclusive conservation, most parasite species remain understudied, underfunded, and underappreciated. We argue the protection of parasitic biodiversity requires a paradigm shift in the perception and valuation of their role as consumer species, similar to that of apex predators in the mid‐20th century. Beyond recognizing parasites as vital trophic regulators, existing tools available to conservation practitioners should explicitly account for the unique threats facing dependent species. We built upon concepts from epidemiology and economics (e.g., host‐density threshold and cost‐benefit analysis) to devise novel metrics of margin of error and minimum investment for parasite conservation. We define margin of error as the risk of accidental host extinction from misestimating equilibrium population sizes and predicted oscillations, while minimum investment represents the cost associated with conserving the additional hosts required to maintain viable parasite populations. This framework will aid in the identification of readily conserved parasites that present minimal health risks. To establish parasite conservation, we propose an extension of population viability analysis for host–parasite assemblages to assess extinction risk. In the direst cases, ex situ breeding programs for parasites should be evaluated to maximize success without undermining host protection. Though parasitic species pose a considerable conservation challenge, adaptations to conservation tools will help protect parasite biodiversity in the face of an uncertain environmental future. 相似文献
62.
Environmental degradation, competition for resources, increasing food demands, and the integration of agriculture into the
international economy threaten the sustainability of many food production systems. Despite these concerns, the concept of
sustainable food production systems remains unclear, and recent attempts to appraise sustainability have been hampered by
conceptual inconsistencies and the absence of workable definitions. Six perspectives are shown to underpin the concept. Environmental
accounting identifies biophysical limits for agriculture. Sustained yield refers to output levels that can be maintained continuously.
Carrying capacity defines maximum population levels that can be supported in perpetuity. Production unit viability refers
to the capacity of primary producers to remain in agriculture. Product supply and security focuses on the adequacy of food
supplies. Equity is concerned with the spatial and temporal distribution of products dervied from resource use. Many studies
into sustainable agriculture cover more than one of these perspectives, indicating the concept is complex and embraces issues
relating to the biophysical, social, and economic environments. Clarification of the concept would facilitate the development
of frameworks and analytical systems for appraising the sustainability of food production systems.
LRRC Contribution No. 90–46. 相似文献
63.
Christopher S. Davies 《Environmental management》1988,12(4):479-490
Industrial dereliction is a concern to all societies. In the United Kingdom the British government is trying to make its abandoned coalfields more attractive to new industry through a combination of land reclamation and job incentive programs. The most ambitious of these projects occurs in the South Wales Coalfield, which records 200 years of land defilement and the highest unemployment amplitudes in mainland Britain. In returning this area to a semblance of its previous state, problems arise over how best to fill and cap the many derelict pit shafts and abandoned shallow mines that riddle this region. This analysis reports on the methods of treatment used to achieve this end, along with the procedures used to minimize ground subsidence, water pollution, noxious gas emission, and the potential for physical injury. These environmental controls have application to the United States and Western Europe, where pockets of industrial blight are also symptomatic of a troubled local economy. 相似文献
64.
Under the United States Clean Air Act Amendments of 1977, a class I designation safeguards wilderness areas from the negative
effects of new sources of air pollution. We monitored streamwater chemistry in the class I Lye Brook Wilderness in southwestern
Vermont from May 1994 through August 1995. Stream samples were collected biweekly at nine sampling locations throughout the
wilderness and were analyzed for major cations and anions, dissolved organic carbon, pH, and acid-neutralizing capacity. Eight
of nine sites sampled had mean annual acid neutralizing capacity values below zero. During the study period, decreases in
streamwater acid neutralizing capacity values were caused primarily by SO4
2−. At some sites, however, NO3
− and naturally occurring, weak organic acids were seasonally important. During high discharge, the low pH and high concentrations
of inorganic monomeric Al were at levels that are toxic to acid-sensitive aquatic species. Watershed mass balances were calculated
to determine annual gains or losses for measured ions. These budgets indicate that S inputs and outputs were nearly equal,
there was a net loss of base cations, and a net gain in N. How long these watersheds can continue to assimilate additional
N inputs is unknown. 相似文献
65.
Renewable Resources and Enzymatic Processes to Create Functional Polymers: Adapting Materials and Reactions from Food Processing 总被引:1,自引:0,他引:1
Christopher M. Aberg Tianhong Chen Gregory F. Payne 《Journal of Polymers and the Environment》2002,10(3):77-84
We are exploiting materials and concepts from food science to create functionalized, environmentally friendly derivatives of the biopolymer chitosan, a byproduct of seafood processing. Functional groups are grafted onto chitosan using tyrosinase, the enzyme responsible for food browning. The functionalizing groups studied include low-molecular-weight phenols derived from natural sources and high-molecular-weight proteins. The approach of using low-molecular-weight phenols to functionalize chitosan is illustrated with arbutin, a natural phenol found in pears. Results demonstrate that tyrosinase initiates reactions that lead to the conversion of arbutin–chitosan solutions into gels. These gels can be rapidly broken by treatment with the chitosan-hydrolyzing enzyme chitosanase, demonstrating that the chitosan derivatives remain biodegradable. We briefly review other studies in which low-molecular-weight natural phenols are enzymatically grafted onto chitosan to confer functional properties. The creation of co-polymers is illustrated by results in which tyrosinase is used to couple gelatin onto chitosan. Gelatin is a proteinaceous byproduct of meat production. The tyrosinase-generated gelatin–chitosan conjugates have been observed to offer interesting rheological and thermal properties. These results demonstrate the potential for using renewable resources and enzymatic processing to create environmentally friendly polymers with useful functional properties. 相似文献
66.
This study explored whether two principles describe the relationship between the size of a pay increase (a bonus expressed as a percentage of current salary) and the attractiveness of that increase. Based on a sample of sales personnel (N = 639) and consistent with the constant proportion principle of the psychophysical law, pay increase attractiveness was unrelated to current salary level after controlling for the size of the percentage increase. In addition, at any given salary level, the relationship between the size of the increase and its attractiveness was curvilinear. The attractiveness of larger and larger bonus percentages continues to increase, but at a decreasing rate supporting the principle of diminishing returns. 相似文献
67.
Jongeun You Jill Yordy Kyudong Park Tanya Heikkila Christopher M. Weible 《Journal of Environmental Policy & Planning》2020,22(4):501-517
ABSTRACT Researchers often focus on the most intense conflicts, skewing our perception of the diversity and nature of policy conflicts. The paper examines the discourse engaged in the siting of three pipeline projects under construction, each with varying levels of conflict, and one rejected project of high conflict. We analyze over 700 newspaper articles that span the life of each proposed pipeline and supplement the news media data with interviews. Using these data, we compare differences in actor types, frames, and behaviors in natural gas pipeline siting processes characterized by high, medium, and low conflict. Comparing the characteristics of energy siting conflicts at varying intensities helps support corresponding portrayals of how people engage in the policy process. This paper offers theoretical and empirical guidance on understanding policy conflict intensity variation. 相似文献
68.
Phosphorus transfer in surface runoff from intensive pasture systems at various scales: a review 总被引:2,自引:0,他引:2
Dougherty WJ Fleming NK Cox JW Chittleborough DJ 《Journal of environmental quality》2004,33(6):1973-1988
Phosphorus transfer in runoff from intensive pasture systems has been extensively researched at a range of scales. However, integration of data from the range of scales has been limited. This paper presents a conceptual model of P transfer that incorporates landscape effects and reviews the research relating to P transfer at a range of scales in light of this model. The contribution of inorganic P sources to P transfer is relatively well understood, but the contribution of organic P to P transfer is still relatively poorly defined. Phosphorus transfer has been studied at laboratory, profile, plot, field, and watershed scales. The majority of research investigating the processes of P transfer (as distinct from merely quantifying P transfer) has been undertaken at the plot scale. However, there is a growing need to integrate data gathered at a range of scales so that more effective strategies to reduce P transfer can be identified. This has been hindered by the lack of a clear conceptual framework to describe differences in the processes of P transfer at the various scales. The interaction of hydrological (transport) factors with P source factors, and their relationship to scale, require further examination. Runoff-generating areas are highly variable, both temporally and spatially. Improvement in the understanding and identification of these areas will contribute to increased effectiveness of strategies aimed at reducing P transfers in runoff. A thorough consideration of scale effects using the conceptual model of P transfer outlined in this paper will facilitate the development of improved strategies for reducing P losses in runoff. 相似文献
69.
Travis C Obenshain KR Gunter JT Regens JL Whipple C 《Environmental science and pollution research international》2004,11(5):302-306
GOAL, SCOPE AND BACKGROUND: This paper uses two case studies of U.S. Department of Energy nuclear weapons complex installations to illustrate the integration of expedited site characterization (ESC) and multimedia modeling in the remedial action decision making process. CONCEPTUAL SITE MODELS, MULTIMEDIA MODELS, AND EXPEDITED SITE CHARACTERIZATION: Conceptual site models outline assumptions about contaminates and the spatial/temporal distribution of potential receptors. Multimedia models simulate contaminant transport and fate through multiple environmental media, estimate potential human exposure via specific exposure pathways, and estimate the risk of cancer and non-cancer health outcomes. ESC relies on using monitoring data to quantify the key components of an initial conceptual site model that is modified iteratively using the multimedia model. CASE STUDIES: Two case studies are presented that used the ESC approach: Los Alamos National Laboratory (LANL) and Pantex. LANL released radionuclides, metals, and organic compounds, into canyons surrounding the facility. The Pantex Plant has past waste management operations which included burning chemical wastes in unlined pits, burying wastes in unlined landfills, and discharging plant wastewaters into on-site surface waters. CONCLUSIONS: The case studies indicate that using multimedia models with the ESC approach can inform assessors about what, where, and how much site characterization data needs to be collected to reduce the uncertainty associated with risk assessment. Lowering the degree of uncertainty reduces the time and cost associated with assessing potential risk and increases the confidence that decision makers have in the assessments performed. 相似文献
70.
Integrated BIosphere Simulator (IBIS) yield and nitrate loss predictions for Wisconsin maize receiving varied amounts of nitrogen fertilizer 总被引:1,自引:0,他引:1
Agriculture in the U.S. Midwest faces the formidable challenge of improving crop productivity while simultaneously mitigating the environmental consequences of intense management. This study examined the simultaneous response of nitrate nitrogen (NO3-N) leaching losses and maize (Zea mays L.) yield to varied fertilizer N management using field observations and the Integrated BIosphere Simulator (IBIS) model. The model was validated against six years of field observations in chisel-plowed maize plots receiving an optimal (180 kg N ha(-1)) fertilizer N application and in N-unfertilized plots on a silt loam soil near Arlington, Wisconsin. Predicted values of grain yield, harvest index, plant N uptake, residue C to N ratio, leaf area index (LAI), grain N, and drainage were within 20% of observations. However, simulated NO3-N leaching losses, NO3-N concentrations, and net N mineralization exhibited less interannual variability than observations, and had higher levels of error (20-65%). Potential effects of 30% higher (234 kg N ha(-1)) and 30% lower (126 kg N ha(-1)) fertilizer N use (from optimal) on NO3-N leaching loss and maize yield were simulated. A 30% increase in fertilizer N use increased annual NO3-N leaching by 56%, while yield increased by only 1%. The NO3-N concentration in the leachate solution at 1.4 m below the soil surface was 30.7 mg L(-1). When fertilizer N use was reduced by 30% (from optimal), annual NO3-N leaching losses declined by 42% after seven years, and annual average yield only decreased by 8%. However, NO3-N concentration in the leachate solution remained above 10 mg L(-1) (11.3 mg L(-1)). Clearly, nonlinear relationships existed between changes in fertilizer use and NO3-N leaching losses over time. Simulated changes in NO3-N leaching were greater in magnitude than fertilizer N use changes. 相似文献