• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 40
  • 13
  • 6
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 91
  • 91
  • 25
  • 22
  • 21
  • 21
  • 19
  • 19
  • 16
  • 14
  • 14
  • 13
  • 12
  • 10
  • 10
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Modelling and Evaluating Suitability of Esocid Habitat in Response to Changes in Water Levels of Georgian Bay (Lake Huron) / Evaluating Suitability of Esocid Habitat in Georgian Bay

Weller, Joseph Daniel January 2019 (has links)
Muskellunge (Esox masquinongy) and Northern Pike (E. lucius) are ecologically and economically important fish species that rely on coastal habitats in Georgian Bay, especially coastal marshes. These habitats have adapted to the high natural water-level fluctuations of Lake Huron but are threatened by changing water-level conditions associated with global climate change. The overall goals of this thesis were to identify important esocid habitats and understand how their suitability will be affected by changing water levels. First, I used tracking information from radio telemetry studies of esocid populations in spatially distinct regions of Georgian Bay to identify important habitats during breeding and non-breeding seasons. I documented the strong affinity of Muskellunge to re-use specific spawning grounds close to known nursery habitat in coastal marshes. Both Muskellunge and Northern Pike used coastal marshes during the non-breeding season, and physical habitat structure was a more important driver of habitat use in the summer months than water temperature. Next, I created a GIS model using only hydrogeomorphic features (depth, slope, and wave exposure) to map the extent of coastal marshes throughout eastern and northern Georgian Bay to assess how habitat would shift under a range of possible lake elevations scenarios (175.5 – 177.5 m). The geomorphology at low lake levels favoured large areas of shallow (< 0.5 m) habitat at the expense of deeper habitats (0.5 – 1.5 m) that can support an aquatic vegetation community more suitable for young esocids. I used a similar approach to develop a Resilience Index to rank coastal marshes according to their resilience/vulnerability to stable low water levels, for use as a regional screening tool to identify critical esocid habitat. This research advances the understanding of the effects of water levels on coastal marshes and provides applicable tools to assist in conservation and management of these important recreational fisheries. / Thesis / Doctor of Philosophy (PhD) / This Ph.D. thesis describes how changes in water levels may affect habitats used by Muskellunge and Northern Pike, two important species of sport fish, in Georgian Bay (Lake Huron). Coastal wetlands were identified as critical habitats, especially for early-life stages, and are directly influenced by water levels of the Great Lakes. I developed several tools to assist in identification, evaluation, and management of coastal wetlands in Georgian Bay, a relatively undisturbed coastal region in Ontario. These tools use physical features of the landscape to predict how wetlands will respond to different lake-level conditions and influence habitat suitability for Muskellunge and Northern Pike, as well as Great Lakes fish communities in general. My thesis provides tools for environmental agencies to adaptively manage important fish habitat in a period of unpredictable water levels associated with global climate change.
12

Potential Silvicultural Effects on Bald Eagle Nesting Substrate and Economic Yields at a Navy Installation in the Chesapeake Bay: An Approach Using the Forest Vegetation Simulator and Mahalanobis Distance

Wilburn, John D. 19 March 2012 (has links)
In the interest of maintaining lands to fully support the military mission, Department of Defense (DOD) installations must manage competing objectives under constraints related to mission operations, regulation and compliance requirements, and budget reductions. Silviculture offers promise for ecosystem management while providing financial means through the sale of forest products. This study used forest inventory and bald eagle nest site data to investigate the potential effects of silviculture on bald eagle nesting habitat at Naval Support Facility Indian Head. Mahalanobis distance was used to define and classify preferred nesting substrate. Silviculture was simulated using the Forest Vegetation Simulator (FVS) to assess forest nesting substrate, economic yields and the tradeoffs between these two objectives. An alternative substrate model based on cumulative distribution functions (CDFs) and Boolean logic allowed evaluation of the strengths and weaknesses of the Mahalanobis distance method. The Mahalanobis distance model provided greater relative fit to the sample of nest sites compared to the CDF model but had lower discriminating power between presence and absence data. Simulation results indicate that top performing silvicultural treatments resulted in greater substrate availability compared to no-action over equal time periods. Uneven-age management was shown as the best system for providing nesting substrate as well as favorable economic yields in hardwood stands. Results also stress the importance of thinning in providing future nesting substrate and maintaining preferred substrate late in the rotation. Economic and habitat tradeoffs varied by treatment, suggesting that optimum prescriptions could be identified to provide for both objectives and minimize tradeoffs. / Master of Science
13

Comprendre et prédire l'expansion géographique des espèces végétales invasives dans les Alpes / Understand and predict the greographical spread of alpine invasive plant species

Gallien, Laure 25 June 2013 (has links)
Les invasions biologiques, deuxième menace majeure de la biodiversité, pose d'important défis pour la conservation de la biodiversité, et la recherche en éco-évolution. Les espèces invasives ont en effet été étudiées depuis plus de 150 ans, mais nos capacités à prédire leurs présences aujourd'hui et dans le futur reste rudimentaire. Ce problème est principalement dû à la difficulté d'estimer à la fois les composantes biotiques et abiotiques de la niche des espèces invasives, ainsi que leur évolution dans le temps et l'espace. L'objectif de ma thèse a été de travailler sur ces défis en améliorant les méthodes d'estimation de niche, en enrichissant notre compréhension du rôle des interactions biotiques dans le processus d'invasion, et en étudiant en détail comment les processus évolutifs peuvent affecter la dynamique spatio-temporelle des niches. Plus précisément, (1) à l'aide d'une revue de la littérature, j'ai commencé par décrire les limites des différentes approches de modélisation utilisées pour prédire la distribution des espèces invasives. (2) Ensuite, j'ai proposé un cadre de modélisation permettant d'améliorer l'estimation des niches abiotiques régionales. (3) Puis, je me suis intéressée à la caractérisation des interactions biotiques, et aux méthodes communément utilisées pour identifier les patrons de compétition symétrique en écologie des communautés. J'ai également implémenté un modèle de simulation d'assemblage de communautés pour tester la performance de ces méthodes. (4) Ces premières études m'ont permis d'étudier à la fois les composantes biotiques et abiotiques des communautés de plantes envahies dans les Alpes. (5) Finalement, j'ai étudié l'évolution de la niche environnementale chez une espèce invasive des Alpes françaises Ambrosia artemisiifolia L, à travers une approche reliant niche-trait-génétique. Dans l'ensemble, les résultats de ces études montrent à quel point les différentes facettes de l'écologie et l'évolution en invasion sont fortement intriquées. De plus, ils soulignent la nécessité d'une modélisation intégrant les processus écologiques et évolutifs pour pouvoir comprendre la dynamique des invasions et proposer des outils de protection de la biodiversité efficaces. / Biological invasions, the second major threat to biodiversity, pose significant challenges to conservation management and eco-evolutionary research. Even though invasion processes have been studied for more than 150 years, our capacity to predict their presence today and in the future is still rudimentary. This deficiency stems mainly from the difficulty involved in reliably assessing the ecological niche of an invader, i.e. those environmental and biotic conditions that allow the species to maintain viable populations. In particular, disentangling the abiotic and biotic components of the ecological niche and accounting for their changing over space and time due to evolutionary dynamics is difficult, albeit crucial for the quality of predictions. The main objective of my PhD has been to address these challenges by improving methodological approaches of niche estimation, advancing our understanding of the role of biotic interactions for invasion processes and studying in greater detail how evolution may affect spatio-temporal niche dynamics. More precisely, (1) with a comprehensive literature review, I started by describing the limits of the different modelling approaches usually applied to predict invasive species distributions. (2) Then, I provided a modelling framework for improving regional environmental niche estimations. (3) Thirdly, I focused on the identification of biotic interactions, and the methods commonly used to identify patterns of symmetric competition in ecological communities. I also implemented a simulation model of community assembly to test the efficiency of these methods. (4) In a fourth part, I studied invaded alpine plant communities and showed that characteristics of the biotic environment in these communities (e.g. symmetric vs. asymmetric competition) were good predictors of invaders' presence. (5) Finally, I provided a first example of a genetic-based, climatic niche expansion of the invasive weed Ambrosia artemisiifolia L. in the French Alps by combining information on its environmental niche, genetic structure and functional traits. Taken together, the results of these studies highlight how tightly the different facets of invasion ecology and evolution are interrelated and open the way to an integrated modelling approach that would advance both eco-evolutionary research on invasion dynamics and applied tools for biodiversity protection.
14

Planning for wildlife: an urban planning and design exploration to support Mexican free-tailed bats

Bradley, Dale January 1900 (has links)
Master of Landscape Architecture / Landscape Architecture/Regional and Community Planning / Brent Chamberlain / Anthropocentric disturbances are often the main driver behind the population decline of wildlife species. Bat species are of particular concern recently with large declines in populations worldwide. The conservation of bat species relies on knowledge about the relationship between species-specific needs and the effect urban environments have on individual species. Mexican Free-Tailed Bats (MFTBs) are listed on the IUCN Red List and play an important role in many ecosystems within the United States. Austin, Texas is home to the largest urban bat colony in the world, including MFTBs. Austin can continue to benefit from millions of dollars from ecotourism bat viewing sites and the natural control of insect populations provided by this species if urbanization does not cause a reduction in their population. The focus of this research is to develop a quantitative habitat suitability model for the MFTBs in urban areas to increase the understanding of possible MFTB habitat in the Austin Metropolitan area. A geographical information system was used to map the suitability of habitats for MFTBs in urban areas based off a typology for the needs of the species, which was created through a literature review of expert knowledge. This study will help to quantify the relationship between urban environments and the MFTBs, showing that urban areas in the Austin Metropolitan area are suitable for the species. A predictive model, like the one described here, can act as a crucial assessment and planning tool for bat conservation by helping to eliminate challenges of tracking populations or identifying bats during nocturnal activities. This model informs the proposal of planning and design policy changes in Austin, Texas to better support MFTB’s habitat needs. Adjustments to current site plans in Austin are explored understand the effect the proposed MFTB planning policies could have on current development while exploring the application of the MFTB typology at a site scale. Application of the understanding created through habitat-suitability modelling helps to visualize how current projects in Austin, Texas can better support MFTBs to create an understanding of how these policies may affect the development of urban environments.
15

Habitat Suitability Criteria for Zuni Bluehead Sucker Catostomus discobolus yarrowi and Navajo Nation Genetic Subunit Bluehead Sucker Catostomus discobolus and Comparing Efficiency of AFS Standard Snorkeling Techniques to eDNA Sampling Techniques

Ulibarri, Roy M. January 2016 (has links)
I quantified habitat selection for the endangered Zuni Bluehead Sucker Catostomus discobolus yarrowi and the Navajo Nation Genetic Subunit (NNGS) Bluehead Sucker Catostomus discobolus - a recent taxon described from genetic information. Both taxa are found in northern Arizona and New Mexico border regions. I examined fish [≥50 millimeters (mm) total length (TL)] selection of microhabitat conditions (i.e., water velocity, substrate size, overhead cover, water depth, instream cover, and mesohabitat conditions [i.e., pool, run riffle], during summer base flow conditions for NNGS Bluehead Suckers, and during both summer base flow and high spring flow conditions for Zuni Bluehead Suckers in six streams). Electrofishing, seining, and snorkeling were used to evaluate fish occupancy. From this information, I developed stream specific habitat suitability criteria (HSC) and then generalized HSC for each taxon, and tested transferability of the generalized HSC to individual streams. Zuni Bluehead Suckers and NNGS Bluehead Suckers occupied similar habitats: low velocity pools; sand, silt, and pebble substrate; high percent of instream cover; and water temperatures ranging from 2-21°C. However, Zuni Bluehead Suckers selected for low (0-25%) overhead cover where as NNGS Bluehead Sucker selected for high (0-75%) overhead cover. This was likely due to the source of instream cover–aquatic macrophytes that required sunlight in the Zuni Bluehead Sucker streams, and large woody debris falling from overhead branches in the NNGS Bluehead Sucker streams. Suggestions for managers includes maintaining existing cover or artificially construct additional instream cover; promote overhead cover (e.g., maintaining large trees along streams) and pool mesohabitats. In addition to this work I also tested the new method of environmental DNA (eDNA) to further help conservation efforts for these taxa. Environmental DNA has typically been used to detect invasive species in aquatic environments through water samples. I compared the efficacy of eDNA methodology to American Fisheries Society standard snorkeling surveys to detect presence of a rare fish species. My study site included three streams on the Navajo Nation in northern Arizona and northern New Mexico containing Navajo Nation Genetic Subunit Bluehead Sucker Catostomus discobolus and the Zuni Bluehead Sucker Catostomus discobolus yarrowi. To determine sample sites, I first divided entire wetted area of streams into 100-m consecutive reaches. I systematically selected 10 of those reaches for snorkel and eDNA surveys. Water samples were taken in 10-m sections within each 100-m reach, and fish presence via snorkeling was noted in each 10-m section as well. Water samples were collected at the downstream starting point of each reach, and continued upstream in each section 5 to 8 m ahead of the snorkeler. A qPCR was run on each individual water sample in quadruplicate to test for sucker presence or absence. I was able to positively detect both species with eDNA sampling techniques in two out of three streams. Snorkeling resulted in positive detections of both species in all three streams. In streams where fish were detected with eDNA sampling, snorkeling detected fishes at 11-29 sites per stream, where as eDNA detected fish at 3-12 sites per streams. My results suggested that AFS standard snorkeling was more effective at detecting target fish species than eDNA. To improve eDNA sampling, the amount of water collected and tested should be increased. Additionally, filtering water on site may improve eDNA techniques for detecting fish. Future research should focus on standardizing eDNA sampling to provide a widely operational sampling tool similar to electrofishing, netting, and hydroacoustics.
16

A fine-scale lidar-based habitat suitability mapping methodology for the marbled murrelet (Brachyramphus marmoratus) on Vancouver Island, British Columbia

Clyde, Georgia Emily 18 April 2017 (has links)
The marbled murrelet (Brachyramphus marmoratus) is a Threatened seabird with very particular nesting requirements. They choose to nest almost exclusively on mossy platforms, provided by large branches or deformities, in the upper canopies of coniferous old-growth trees located within 50 km of the ocean. Due primarily to a loss of this nesting habitat, populations in B.C. have seen significant decline over the past several decades. As such, reliable spatial habitat data are required to facilitate efficient management of the species and its remaining habitats. Current habitat mapping methodologies are limited by their qualitative assessment of habitat attributes and the large, stand-based spatial scale at which they classify and map habitat. This research aimed to address these limitations by utilizing light detection and ranging (lidar) technologies to develop an object-based habitat mapping methodology capable of quantitatively mapping habitat suitability at the scale of an individual tree on Northern Vancouver Island, British Columbia (B.C.). Using a balanced random forest (BRF) classification algorithm and in-field habitat suitability data derived from low-level aerial surveys (LLAS), a series of lidar-derived terrain and canopy descriptors were used to predict the habitat suitability (Rank 1: Very High Suitability – Rank 6: Nil Suitability) of lidar-derived individual tree objects. The classification model reported an overall classification accuracy of 71%, with Rank 1 – Rank 5 reporting individual class accuracies of 90%, 86%, 74%, 67%, and 98%, respectively. Evaluation of the object-based predictive habitat suitability maps provided evidence that this new methodology is capable of identifying and quantifying within-stand habitat variability at the scale of an individual tree. This improved quantification provides a superior level of habitat differentiation currently unattainable using existing habitat mapping methods. As the total amount of suitable nesting habitat in B.C. is expected to continue to decline, this improved quantification is a critical advancement for strategic managers, facilitating improved habitat and species management. / Graduate / 2018-04-07 / 0329 / 0368 / 0478 / gclyde@uvic.ca
17

Combining species distribution modelling and environmental perceptions to support sustainable strategies for Amazon-nut (Bertholletia excelsa Bonpl.) planting and conservation / Combinando a modelagem de distribuição de espécies e percepções ambientais para fundamentar estratégias sustentáveis de plantio e conservação da Castanha-da-Amazônia (Bertholletia excelsa Bonpl.)

Daiana Carolina Monteiro Tourne 30 November 2018 (has links)
The amazon ecosystems have been compromised by historical forms of occupation and land-use causing habitat loss and forest fragmentation. These anthropogenic disturbances associated to climate changes have direct consequences on the distribution of species and their in situ persistence. Currently, 76 of 14.003 plants taxonomically identified in the Amazon have been listed by the Brasilian Ministry of the Environment as threatened species, though we believe this number to be much bigger in the reality. Among them, Amazon-nut (Bertholletia excelsa), a native tree species, national and internationally known for its cultural, social-economic and nutritional value has been classified as vulnerable. For developping of public policy turned to its management and conservation is fundamental to know the percentage of habitat available, as well as the nature and scale of threats to this environments. Species distribution modelling is an increasingly important tool for predicting habitat suitability and for understanding species environmental tolerances, but has been rarely used in Brazil, especially for Amazonian species. This study aimed to model the potential distribution of B. excelsa in the Amazon biome and to know the factors that control its distribution. To enhance our analysis, case studies were carried out with stakeholders aiming to know their perceptions about the main threats to the species and potential solutions.This research project was based on two hypotheses: (i) There is a suitable habitat to Amazon-nut which require different objectives for conservation and planting; (ii) If the local people are aware of the species vulnerability, they are able to point out the factors that cause this condition. In the chapter 1, habitat was investigated using MAXENT algoritm. We collected 3,325 Amazon-nut records and organized one hundred-and-two environmental variables into climatic, edaphic and geophysical categories at a spatial resolution of 30 arcs-second (~1km). Multi-colinearity between variables was dealt with multivariate statistics associated to expert\'s knowledge, and presence data biased with the spatial filtering. The best model was selected adopting quantitative metrics and visual examination. The most importante biophysic variables we identified were: altitude (m), coarse soil fragments (<2mm) and clay (%). Finaly, the best model indicated 2.3 million km2 i.e., 32% of the Amazon basin has potential for B. excelsa to grow. In the chapter 2, the factors that affect Amazon-nut conservation and planting were discussed with local communities, public managers and researchers, totalyzing 203 participants. Focus groups, individual interviews and questionaire techniques were used to gather information. Data were categorized and the perceptions among stakeholders compared using quali-quantitative analyses. We found that there are currently 36 problems responsible for the species vulnerability and 72% of them belong to environmental and political contexts. Deforestation was the main problem mentioned, followed by fruit depreciation, control failures and lack of organization in the communities. For three groups of stakeholders, the main solutions were related to political context. The results obtained in this study contribute to increase ecological knowledge on the species, to demonstrate the complexity of sustainable use in the Amazon and to guide decisions makers in the selection of priority areas for conservation and potential planting. / Os ecossistemas amazônicos vêm sendo impactados ao longo dos anos por diversos processos de uso e ocupação do território, os quais têm resultado em perdas de habitats e na fragmentação da paisagem nativa. Essas perturbações antrópicas, associadas às mudanças climáticas, têm consequências diretas sobre a distribuição e persistência das espécies in situ. Das 14.003 plantas da Amazônia reconhecidas taxonomicamente, somente 76 estão atualmente listadas pelo Ministério do Meio Ambiente brasileiro como espécies ameaçadas, embora acredita-se que esse número seja muito maior. Entre elas, a Castanha-da-Amazônia (Bertholletia excelsa), uma espécie de árvore nativa, reconhecida nacional e internacionalmente pela sua importância cultural, socioeconômica e nutricional, encontra-se classificada como vulnerável. Para nortear políticas públicas na conservação e no plantio dessa espécie, um profundo entendimento sobre o habitat disponível para ela, bem como a origem e escala das ameaças à esse ambiente, é necessário. A modelagem de distribuição de espécies é uma ferramenta que oferece predições espaciais robustas sobre a adequabilidade de habitat e tolerância das espécies, mas tem sido pouco utilizada no Brasil, sobretudo para espécies Amazônicas. Nesse contexto, esse estudo objetivou modelar a distribuição potencial da B. excelsa no bioma Amazônia, bem como conhecer os fatores que controlam sua distribuição. Para aprofundar essas análises, estudos de caso foram realizados com o objetivo de conhecer a percepção de atores sociais envolvidos com a espécie sobre as principais ameaças e potenciais soluções. Essa tese baseou-se em duas hipóteses: (i) existem áreas com maior adequabilidade para a ocorrência da Castanha-da-Amazônia que demandam diferentes objetivos, para conservação e para o plantio; (ii) se a população local é conciente da vulnerabilidade da espécie, ela pode indicar os fatores que geram essa condição. No capítulo 1, o habitat foi investigado por meio de simulações usando o algoritmo MAXENT. Um total de 3.325 ocorrências e 102 variáveis ambientais foram obtidas, e posteriormente organizadas por categorias climática, edáfica e geofísica. A resolução espacial escolhida foi de 30 arc-segundo (~1km). A multi-colinearidade entre as variáveis foi reduzida por meio da estatística multivariada associada ao conhecimento de especialistas, e as tendências nas ocorrência foram tratadas através da filtragem espacial. O melhor modelo foi selecionado usando métricas quantitativas e examinações visuais. As variáveis biofísicas mais importantes encontradas foram altitude (m), solos com fragmentos grosseiros (<2mm) e argila (%). Por fim, o modelo indicou que 2.3 million km2 i.e., 32% da região amazônica é apropriado para B. excelsa crescer. No capítulo 2, os fatores que afetam a conservação e o plantio da espécie foram discutidos com comunidades, gestores e pesquisadores locais, totalizando 203 participantes. As técnicas de discussão em grupo focal, entrevistas individuais e questionários foram utilizadas para a coleta das informações. Os dados foram categorizados e as opiniões entre os diferentes grupos comparadas utilizando análises quali-quantitativas. Concluiu-se que atualmente existem 36 problemas responsáveis pela vulnerabilidade da espécie, dos quais 72% encontram-se no contexto ambiental e político. O desmatamento foi a principal forçante apontada, seguida pela desvalorização do fruto, falhas na fiscalização e falta de organização nas comunidades. Para os três grupos, as principais soluções foram voltadas para o contexto político. Os resultados obtidos nesse estudo contribuiem para aumentar o conhecimento ecológico da espécie, para demostrar a complexidade do uso sustentável na Amazônia, e orientar tomadores de decisão na seleção de áreas prioritárias para conservação e potenciais para o plantio.
18

Combining species distribution modelling and environmental perceptions to support sustainable strategies for Amazon-nut (Bertholletia excelsa Bonpl.) planting and conservation / Combinando a modelagem de distribuição de espécies e percepções ambientais para fundamentar estratégias sustentáveis de plantio e conservação da Castanha-da-Amazônia (Bertholletia excelsa Bonpl.)

Tourne, Daiana Carolina Monteiro 30 November 2018 (has links)
The amazon ecosystems have been compromised by historical forms of occupation and land-use causing habitat loss and forest fragmentation. These anthropogenic disturbances associated to climate changes have direct consequences on the distribution of species and their in situ persistence. Currently, 76 of 14.003 plants taxonomically identified in the Amazon have been listed by the Brasilian Ministry of the Environment as threatened species, though we believe this number to be much bigger in the reality. Among them, Amazon-nut (Bertholletia excelsa), a native tree species, national and internationally known for its cultural, social-economic and nutritional value has been classified as vulnerable. For developping of public policy turned to its management and conservation is fundamental to know the percentage of habitat available, as well as the nature and scale of threats to this environments. Species distribution modelling is an increasingly important tool for predicting habitat suitability and for understanding species environmental tolerances, but has been rarely used in Brazil, especially for Amazonian species. This study aimed to model the potential distribution of B. excelsa in the Amazon biome and to know the factors that control its distribution. To enhance our analysis, case studies were carried out with stakeholders aiming to know their perceptions about the main threats to the species and potential solutions.This research project was based on two hypotheses: (i) There is a suitable habitat to Amazon-nut which require different objectives for conservation and planting; (ii) If the local people are aware of the species vulnerability, they are able to point out the factors that cause this condition. In the chapter 1, habitat was investigated using MAXENT algoritm. We collected 3,325 Amazon-nut records and organized one hundred-and-two environmental variables into climatic, edaphic and geophysical categories at a spatial resolution of 30 arcs-second (~1km). Multi-colinearity between variables was dealt with multivariate statistics associated to expert\'s knowledge, and presence data biased with the spatial filtering. The best model was selected adopting quantitative metrics and visual examination. The most importante biophysic variables we identified were: altitude (m), coarse soil fragments (<2mm) and clay (%). Finaly, the best model indicated 2.3 million km2 i.e., 32% of the Amazon basin has potential for B. excelsa to grow. In the chapter 2, the factors that affect Amazon-nut conservation and planting were discussed with local communities, public managers and researchers, totalyzing 203 participants. Focus groups, individual interviews and questionaire techniques were used to gather information. Data were categorized and the perceptions among stakeholders compared using quali-quantitative analyses. We found that there are currently 36 problems responsible for the species vulnerability and 72% of them belong to environmental and political contexts. Deforestation was the main problem mentioned, followed by fruit depreciation, control failures and lack of organization in the communities. For three groups of stakeholders, the main solutions were related to political context. The results obtained in this study contribute to increase ecological knowledge on the species, to demonstrate the complexity of sustainable use in the Amazon and to guide decisions makers in the selection of priority areas for conservation and potential planting. / Os ecossistemas amazônicos vêm sendo impactados ao longo dos anos por diversos processos de uso e ocupação do território, os quais têm resultado em perdas de habitats e na fragmentação da paisagem nativa. Essas perturbações antrópicas, associadas às mudanças climáticas, têm consequências diretas sobre a distribuição e persistência das espécies in situ. Das 14.003 plantas da Amazônia reconhecidas taxonomicamente, somente 76 estão atualmente listadas pelo Ministério do Meio Ambiente brasileiro como espécies ameaçadas, embora acredita-se que esse número seja muito maior. Entre elas, a Castanha-da-Amazônia (Bertholletia excelsa), uma espécie de árvore nativa, reconhecida nacional e internacionalmente pela sua importância cultural, socioeconômica e nutricional, encontra-se classificada como vulnerável. Para nortear políticas públicas na conservação e no plantio dessa espécie, um profundo entendimento sobre o habitat disponível para ela, bem como a origem e escala das ameaças à esse ambiente, é necessário. A modelagem de distribuição de espécies é uma ferramenta que oferece predições espaciais robustas sobre a adequabilidade de habitat e tolerância das espécies, mas tem sido pouco utilizada no Brasil, sobretudo para espécies Amazônicas. Nesse contexto, esse estudo objetivou modelar a distribuição potencial da B. excelsa no bioma Amazônia, bem como conhecer os fatores que controlam sua distribuição. Para aprofundar essas análises, estudos de caso foram realizados com o objetivo de conhecer a percepção de atores sociais envolvidos com a espécie sobre as principais ameaças e potenciais soluções. Essa tese baseou-se em duas hipóteses: (i) existem áreas com maior adequabilidade para a ocorrência da Castanha-da-Amazônia que demandam diferentes objetivos, para conservação e para o plantio; (ii) se a população local é conciente da vulnerabilidade da espécie, ela pode indicar os fatores que geram essa condição. No capítulo 1, o habitat foi investigado por meio de simulações usando o algoritmo MAXENT. Um total de 3.325 ocorrências e 102 variáveis ambientais foram obtidas, e posteriormente organizadas por categorias climática, edáfica e geofísica. A resolução espacial escolhida foi de 30 arc-segundo (~1km). A multi-colinearidade entre as variáveis foi reduzida por meio da estatística multivariada associada ao conhecimento de especialistas, e as tendências nas ocorrência foram tratadas através da filtragem espacial. O melhor modelo foi selecionado usando métricas quantitativas e examinações visuais. As variáveis biofísicas mais importantes encontradas foram altitude (m), solos com fragmentos grosseiros (<2mm) e argila (%). Por fim, o modelo indicou que 2.3 million km2 i.e., 32% da região amazônica é apropriado para B. excelsa crescer. No capítulo 2, os fatores que afetam a conservação e o plantio da espécie foram discutidos com comunidades, gestores e pesquisadores locais, totalizando 203 participantes. As técnicas de discussão em grupo focal, entrevistas individuais e questionários foram utilizadas para a coleta das informações. Os dados foram categorizados e as opiniões entre os diferentes grupos comparadas utilizando análises quali-quantitativas. Concluiu-se que atualmente existem 36 problemas responsáveis pela vulnerabilidade da espécie, dos quais 72% encontram-se no contexto ambiental e político. O desmatamento foi a principal forçante apontada, seguida pela desvalorização do fruto, falhas na fiscalização e falta de organização nas comunidades. Para os três grupos, as principais soluções foram voltadas para o contexto político. Os resultados obtidos nesse estudo contribuiem para aumentar o conhecimento ecológico da espécie, para demostrar a complexidade do uso sustentável na Amazônia, e orientar tomadores de decisão na seleção de áreas prioritárias para conservação e potenciais para o plantio.
19

Optimizing Barrier Removal to Restore Connectivity in Utah’s Weber Basin

Kraft, Maggi 01 December 2017 (has links)
River barriers, such as dams, culverts and diversions are important for water conveyance, but disrupt river ecosystems and hydrologic processes. River barrier removal is increasingly used to restore and improve river habitat and connectivity. Most past barrier removal projects prioritized individual barriers using score-and-rank techniques, neglecting the spatial structure and cumulative change from multiple barrier removals. Similarly, most water demand models satisfy human water uses or, only prioritize aquatic habitat, failing to include both human and environmental water use benefits. In this study, a dual objective optimization model identified in-stream barriers that impede quality-weighted aquatic habitat connectivity for Bonneville cutthroat trout. Monthly streamflow, stream temperature, channel gradient and geomorphic condition were indicators of aquatic habitat suitability. Solutions to the dual objective problem quantify and graphically present tradeoffs between quality-weighted habitat connectivity and economic water demands. The optimization model is generalizable to other watersheds, but it was applied as a case study in Utah’s Weber Basin to prioritize removal of environmentally-harmful barriers, while maintaining human water uses. Modeled results suggest tradeoffs between economic costs of removing barriers and quality-weighted habitat gains. Removing 54 in-stream barriers increases quality-weighted habitat by about 160 km and costs approximately $10M, after which point the cost effectiveness of removing barriers to connect river habitat slows. In other words, there is decreasing benefit of removing barriers, so that after removing the first 54 barriers, it costs more to connect more high-quality habitat. Removing reservoirs or diversions that result in large economic losses did not substantially increase habitat. This suggests that removing numerous small barriers results in greater increases in habitat for the same removal costs, without significant water scarcity losses. The set of barriers prioritized for removal varied monthly depending on limiting habitat conditions for Bonneville cutthroat trout. The common barriers removed in the model were identified to communicate the most environmentally harmful barriers to local stakeholders and inform decision-making. Additionally, limiting the budget or number of barrier removal projects resulted in a different set of barriers removed. This research helps prioritize barrier removals and future restoration decisions in the Weber Basin although the model formulation is generalizable to other watersheds. Available data and a simplified approach limit the scope of this model. The modeling approach expands current barrier removal optimization methods by explicitly including economic and environmental water uses.
20

Identifying bird species as biodiversity indicators for terrestrial ecosystem management.

Alizadeh Shabani, Afshin, afshin.alizadeh@rmit.edu.au January 2006 (has links)
It is widely known that the world is losing biodiversity and primarily it is thought to be caused by anthropogenic activities. Many of these activities have been identified. However, we still lack a clear understanding of the causal relationships between human activities and the pressures they place on the environment and biodiversity. We need to know how ecosystems and individual species respond to changes in human activities and therefore how best to moderate our actions and reduce the rate of loss of biodiversity. One of the ways to detect these changes is to use indicators of ecosystem conditions. Indicators are statistics following changes in a particular factor usually over time. These indicators are used to summarise a complex set of data, and are seen as being representative of the wider situation in that field. So it can be assumed that if that particular factor is declining or improving, then the situation in general is also declining or improving. They are used to check the status and trends of biodiversity by both the public and policy makers. Indicators are also used to assess national performance and can be used to identify the actions required at the policy level. In this manner, they provide an important link between policy-makers and scientists collecting the data. The current thesis investigates the possibility of using bird species as indicators of biodiversity for better management of natural terrestrial ecosystems, by identifying their habitats according to various environmental factors. The study is established by drawing upon three main scientific areas: ecology, geographical information system (GIS), and statistical modelling. The Mornington Peninsula and Western Port Biosphere Reserve (MPWPBR) (Victoria, Australia) was chosen for the study area because of the combination of suburban and natural environments that made it optimum for this type of study. Once the study area was defined, the necessary data for the research were obtained from various sources. Birds Australia provided data on recorded observation of 271 bird species within the study area. Based on the nature of this study, seven species were selected for the study. The criteria for this selection are discussed in Chapter 3. Most literature state that the primary determinant for bird abundance is vegetation and land cover. Because of this, Ecological Vegetation Class (EVC) layer was used to determine which type(s) of vegetation have the greatest impact on habitat selection. Each species showed a relationship to a number of v vegetation types. These EVCs were combined to produce vegetation patches, and were considered as potentially suitable habitats of corresponding bird species. For each of the species, these habitat patches were analysed for the different aspects of patch characteristics (such as the level of patchiness, connectivity, size, shape, weighted distance between patches, etc.) by using the Landscape Context Tool (a GIS add-on). This process assisted the understanding of the importance of patch quality in habitat selection among different bird species by analysing the location of bird observation sites relative to habitat patches. In this way, the association between bird presence and the conditions of a habitat patch was identified by performing a discriminant function analysis. To investigate the probability of a species presence according to different environmental factors, a model of species distribution was created. Binary logistic regression was used to indicate the level of effect of each variable. The model was then successfully validated in the field. To define the indicators of environmental factors, it was essential to separate bird species based on their dependency on one or more of the studied variables. For this purpose, One-Way ANOVA was used. This analysis showed that some bird species can be considered as indicators of urban areas, while others could be good indicators of wellpreserved large forests. Finally, it must be mentioned that the type and quality of the datasets are crucial to this type of study, because some species have a higher degree of sensitivity to certain types of vegetation or land cover. Therefore, the vegetation data must be produced as detailed as possible. At the same time, the species data needs to be collected based on the presence and absence (versus presence-only) of the birds.

Page generated in 0.0718 seconds