984 resultados para Steamboats -- Great Lakes (North America) -- History.


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In northern regions where observational data is sparse, lake ice models are ideal tools as they can provide valuable information on ice cover regimes. The Canadian Lake Ice Model was used to simulate ice cover for a lake near Churchill, Manitoba, Canada throughout the 2008/2009 and 2009/2010 ice covered seasons. To validate and improve the model results, in situ measurements of the ice cover through both seasons were obtained using an upward-looking sonar device Shallow Water Ice Profiler (SWIP) installed on the bottom of the lake. The SWIP identified the ice-on/off dates as well as collected ice thickness measurements. In addition, a digital camera was installed on shore to capture images of the ice cover through the seasons and field measurements were obtained of snow depth on the ice, and both the thickness of snow ice (if present) and total ice cover. Altering the amounts of snow cover on the ice surface to represent potential snow redistribution affected simulated freeze-up dates by a maximum of 22 days and break-up dates by a maximum of 12 days, highlighting the importance of accurately representing the snowpack for lake ice modelling. The late season ice thickness tended to be under estimated by the simulations with break-up occurring too early, however, the evolution of the ice cover was simulated to fall between the range of the full snow and no snow scenario, with the thickness being dependant on the amount of snow cover on the ice surface.

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This research explores whether civil society organizations (CSOs) can contribute to more effectively regulating the working conditions of temporary migrant farmworkers in North America. This dissertation unfolds in five parts. The first part of the dissertation sets out the background context. The context includes the political economy of agriculture and temporary migrant labour more broadly. It also includes the political economy of the legal regulations that govern immigration and work relations. The second part of the research builds an analytical model for studying the operation of CSOs active in working with the migrant farmworker population. The purpose of the analytical framework is to make sense of real-world examples by providing categories for analysis and a means to get at the channels of influence that CSOs utilize to achieve their aims. To this end, the model incorporates the insights from three significant bodies of literature—regulatory studies, labour studies, and economic sociology. The third part of the dissertation suggests some key strategic issues that CSOs should consider when intervening to assist migrant farmworkers, and also proposes a series of hypotheses about how CSOs can participate in the regulatory process. The fourth part probes and extends these hypotheses by empirically investigating the operation of three CSOs that are currently active in assisting migrant farm workers in North America: the Agricultural Workers Alliance (Canada), Global Workers’ Justice Alliance (USA), and the Coalition of Immokalee Workers (USA). The fifth and final part draws together lessons from the empirical work and concluded that CSOs can fill gaps left by the waning power of actors, such as trade unions and labour inspectorates, as well as act in ways that these traditional actors can not.

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The softshell clam Mya arenaria (L.) is currently widespread on the east and west coasts of North America. This bivalve also occurs on western European shores, where the post-Pleistocene origin of the species, whether introduced or relict, has been debated. We collected 320 M. arenaria from 8 locations in Europe and North America. Clams (n = 84) from 7 of the locations were examined for mitochondrial DNA variation by sequencing a section of the cytochrome oxidase 1 (COX1) gene. These were analysed together with 212 sequences, sourced from GenBank, from the same gene from 12 additional locations, chiefly from eastern North America but also 1 site each from western North America and from western Europe. Ten microsatellite loci were also investigated in all 320 clams. Nuclear markers showed reduced levels of variation in certain European samples. The same common COX1 haplotypes and microsatellite alleles were present throughout the range of M. arenaria, although significant differences were identified in haplotypic and allelic composition between many samples, particularly those from the 2 continents (Europe and North America). These findings support the hypothesis of post-Pleistocene colonisation of European shores from eastern North America (and the recorded human transfer of clams from the east to the west coast of North America in the 19th century).

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The netcdf files in this archive comprise climate model output from Community Earth System Model for experiments looking at forest loss over Western North America and the Amazon. For further description of the model and configuration for these experiments please see the accompanying manuscript: Synergistic ecoclimate teleconnections from forest loss in different regions structure global ecological responses Elizabeth S. Garcia, Abigail L. S. Swann, Juan C. Villegas, David D. Breshears, Darin J. Law, Scott R. Saleska, and Scott C. Stark published in PLOS ONE, 2016. Contact information in README.txt

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Understanding how biodiversity spatially distribute over both the short term and long term, and what factors are affecting the distribution, are critical for modeling the spatial pattern of biodiversity as well as for promoting effective conservation planning and practices. This dissertation aims to examine factors that influence short-term and long-term avian distribution from the geographical sciences perspective. The research develops landscape level habitat metrics to characterize forest height heterogeneity and examines their efficacies in modelling avian richness at the continental scale. Two types of novel vegetation-height-structured habitat metrics are created based on second order texture algorithms and the concepts of patch-based habitat metrics. I correlate the height-structured metrics with the richness of different forest guilds, and also examine their efficacies in multivariate richness models. The results suggest that height heterogeneity, beyond canopy height alone, supplements habitat characterization and richness models of two forest bird guilds. The metrics and models derived in this study demonstrate practical examples of utilizing three-dimensional vegetation data for improved characterization of spatial patterns in species richness. The second and the third projects focus on analyzing centroids of avian distributions, and testing hypotheses regarding the direction and speed of these shifts. I first showcase the usefulness of centroids analysis for characterizing the distribution changes of a few case study species. Applying the centroid method on 57 permanent resident bird species, I show that multi-directional distribution shifts occurred in large number of studied species. I also demonstrate, plain birds are not shifting their distribution faster than mountain birds, contrary to the prediction based on climate change velocity hypothesis. By modelling the abundance change rate at regional level, I show that extreme climate events and precipitation measures associate closely with some of the long-term distribution shifts. This dissertation improves our understanding on bird habitat characterization for species richness modelling, and expands our knowledge on how avian populations shifted their ranges in North America responding to changing environments in the past four decades. The results provide an important scientific foundation for more accurate predictive species distribution modeling in future.

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This paper is based on a two year's intensive statistical data collection survey on Lake Kyoga, observations made on Lake Victoria over the last decade occasional visits on Lake Albert (Mobutu) and Lake Malawi. World over, scientists have kept doubting the fisheries statistical figures presented by various African countries. Some countries fail to present any figures. This paper, therefore, narrates most of the causes and possible solutions to those problems.

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Uganda's fish production has shown a substantial increase from a level of 61,500 tonnes in 1961 to a total of 214,302 tonnes in 1988. During this period significant changes also occurred in species composition, fishing factors, and patterns of utilisation. This paper briefly summarises the fisheries of Uganda's great lakes and reviews past and present trends in their exploitation, as reflected in available catch and effort data collected through the Fisheries Department statistical reporting system.

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The major dangers facing the resources of the Great Lakes of Africa include over exploitation, falling species diversity, accumulating pollution, and a probable decline in fishery productivity. These dangers may be viewed as accentuated by: i) Inadequate scientific knowledge on the exploited resources ii) Reluctance to apply even the limited scientific information available, by fishery administrators iii) Constant increase in the demand for fish and other aquatic resources. iv) Lack of commitment to active collaboration and co-operation by riparian states regarding development and management of the shared resources. This paper discusses the above factors in relation to the dangerous trends facing the resources of the Great Lakes of Africa. The discussion is intended to contribute to the promotion of rational and sustainable utilisation of the aquatic resources of these lakes.

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Small pelagic fish species have ultimately become important on most of the Great Lakes of Africa, especially after the depletion of the larger, initially preferred fish species. In Lake Victoria, the small pelagic cyprinid Rastrineobola argentea is now the only abundant native species supporting a fast growing light fishery. In Pilkington Bay, off Lingira Island the artisanal light fishery is well established and in the last two years this bay has witnessed a sharp increase in the fishing effort. This has been followed by a modification of fishing method and a reduction in the mesh size of nets used. R. argentea now caught from this bay consist of mainly juveniles and this could result into localized recruitment overfishing. Drawing examples from what is happening to the fishery in Pilkington Bay, it is necessary to carry out research on the stocks, gear and suitable fishing crafts before light fishing spreads to most parts of the lake.

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Denna tvärvetenskapliga studie kontextualiserar den skönlitterära framställningen av hungersnöden i Irland i mitten av 1800-talet i förhållande till tre olika faser av irländsk historieskrivning ‒ den nationalistiska, den revisionistiska, och den postrevisionistiska ‒ med syfte att granska i vilken mån prosafiktionen antingen återspeglar eller motsäger historikernas tolkningar. År 1845 drabbades landet av en dittills okänd potatispest som förstörde skörden helt eller delvis under de följande fem åren. Missväxten ledde till utbredd svält och epidemiska sjukdomar som dödade åtminstone en miljon människor, medan ytterligare en och en halv miljon flydde, huvudsakligen till Förenta Staterna, England, och Kanada. I sina försök att hitta en rationell förklaring till hur potatispesten kunde utvecklas till den värsta svältkatastrofen i Europa under modern tid, har historiker påvisat ett antal bidragande faktorer, till exempel överbefolkning, de fattigaste jordlösa småbrukarnas och lantarbetarnas beroende av potatisen som sitt baslivsmedel, underutveckling inom jordbruket, det rådande jordegendomssystemet, och den dåvarande brittiska regeringens misslyckande att tillhandahålla effektiv och tillräcklig nödhjälp. Historiska förklaringar är naturligtvis nödvändiga för att vi skall kunna bilda oss en uppfattning om hungersnödens orsaker och konsekvenser, men svårigheten med att skildra offrens situation i en historiografisk analys baserad på fakta är uppenbar då deras egna vittnesmål till största delen saknas i källmaterialet. Följaktligen finns det en risk att historieskrivningen förmörkar det som onekligen var centrala realiteter för de värst drabbade, nämligen svält, vräkning, sjukdom och död. Här kan skönlitteraturen bidra till att komplettera historien. Genom att fokusera på ett specifikt (fiktivt) samhälle och dess (fiktiva) individer, kan skönlitterära verk ge en inblick i hur hungersnöden inverkade på olika samhällsskikt, vad människorna gjorde för att överleva, hur nöden och fasorna påverkade deras psyke, och vad eller vem de höll ansvariga för katastrofen. Å andra sidan kan denna fokusering innebära att författaren misslyckas med att ge en helhetsbild av hungersnödens enorma omfattning och att redogöra för alla faktorer som orsakade och förlängde den. Paul Ricoeurs teori om samspelet mellan historia och fiktion (the interweaving of history and fiction) är därför ett nyckelbegrepp för att bättre förstå denna traumatiska period i Irlands historia. Avhandlingen omfattar en textanalytisk, komparativ kritik av ett antal historiska och skönlitterära verk. Genom närläsning av dessa texter granskar jag vilka aspekter av hungersnöden (politiska, ekonomiska, sociala) de olika författarna valt att behandla, och på vilket sätt, samt hur deras synvinklar har format tolkningarna i sin helhet. I detta sammanhang tar jag också upp skillnaderna mella fakta och fiktion, och speciellt de etiska problem som är förknippade med skildringen av traumatiska händelser och mänskligt lidande. Samtidigt undersöker jag, med hänvisning till Roger D. Sells kommunikationsteori, huruvida vissa författare anslår en påstridig ton i sina verk och hur detta påverkar dialogen mellan författare och läsare. Med utgångspunkt i Ricoeurs teori argumenterar jag för att historia och fiktion inte bör ses som ömsesidigt antitetiska diskurser i skildringen och tolkningen av det förflutna, och att skönlitteraturen genom fokuseringen på offren, som ofta tenderar att reduceras till statistik i historieskrivningen, kan förmedla en bättre förståelse och en djupare känsla för den mänskliga dimensionen av den tragedi som utspelades under hungeråren.

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Scale ca. 1:9,000,000.

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Shows many roads, has "Tennassee" on sheet 3, as well as the 22 line boundaries note.

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Forests have a prominent role in carbon storage and sequestration. Anthropogenic forcing has the potential to accelerate climate change and alter the distribution of forests. How forests redistribute spatially and temporally in response to climate change can alter their carbon sequestration potential. The driving question for this research was: How does plant migration from climate change impact vegetation distribution and carbon sequestration potential over continental scales? Large-scale simulation of the equilibrium response of vegetation and carbon from future climate change has shown relatively modest net gains in sequestration potential, but studies of the transient response has been limited to the sub-continent or landscape scale. The transient response depends on fine scale processes such as competition, disturbance, landscape characteristics, dispersal, and other factors, which makes it computational prohibitive at large domain sizes. To address this, this research used an advanced mechanistic model (Ecosystem Demography Model, ED) that is individually based, but pseudo-spatial, that reduces computational intensity while maintaining the fine scale processes that drive the transient response. First, the model was validated against remote sensing data for current plant functional type distribution in northern North America with a current climatology, and then a future climatology was used to predict the potential equilibrium redistribution of vegetation and carbon from future climate change. Next, to enable transient calculations, a method was developed to simulate the spatially explicit process of dispersal in pseudo-spatial modeling frameworks. Finally, the new dispersal sub-model was implemented in the mechanistic ecosystem model, and a model experimental design was designed and completed to estimate the transient response of vegetation and carbon to climate change. The potential equilibrium forest response to future climate change was found to be large, with large gross changes in distribution of plant functional types and comparatively smaller changes in net carbon sequestration potential for the region. However, the transient response was found to be on the order of centuries, and to depend strongly on disturbance rates and dispersal distances. Future work should explore the impact of species-specific disturbance and dispersal rates, landscape fragmentation, and other processes that influence migration rates and have been simulated at the sub-continent scale, but now at continental scales, and explore a range of alternative future climate scenarios as they continue to be developed.