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  • 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.
1

Desafios para conservação de elefantes na África / Challenges to the conservation of african elephants

Zacarias, Daniel Augusta 15 December 2017 (has links)
Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-01-16T10:46:45Z No. of bitstreams: 2 Tese - Daniel Augusta Zacarias - 2017 (1).pdf: 10564997 bytes, checksum: 3beb8a6a9c5b45ffef1c47b91fb5ee3c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-01-16T10:47:18Z (GMT) No. of bitstreams: 2 Tese - Daniel Augusta Zacarias - 2017 (1).pdf: 10564997 bytes, checksum: 3beb8a6a9c5b45ffef1c47b91fb5ee3c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-01-16T10:47:18Z (GMT). No. of bitstreams: 2 Tese - Daniel Augusta Zacarias - 2017 (1).pdf: 10564997 bytes, checksum: 3beb8a6a9c5b45ffef1c47b91fb5ee3c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Biodiversity conservation is in crisis and urgent responses are needed to reverse the extinction of species, the proliferation of invasive species and the fragmentation of habitats. Among several approaches being implemented, the protection of species with great dispersal capacity and that play important ecological role has been advocated as a solution, since the protection of their habitat in parallel contributes to the protection of other species and habitats. The elephant, a megagardener of forests and savannahs, represents this type of species in the sense that it inhabits vast areas, has a high dispersal capacity and guarantees the dispersion and growth of plant species in extensive areas. Unfortunately, the current situation of the elephant is not positive and international efforts have been developed to reverse the current scenarios of reduction of its abundance and the protection of its habitat. This thesis focuses on African elephant species (Loxodonta africana and Loxodonta cyclotis) and aims to contribute to the knowledge of the main challenges that must be embraced for their protection, using an interdisciplinary approach involving scientometric analysis, climate niche modelling, multi-scale modelling of habitat connectivity, quasi-linear regression models and structural equations and knowledge syntheses. Chapter I presents a systematic review of conservation genetics studies of the African savannah elephant and discusses the main research areas, the elephant populations involved and the main lines of research addressed. Chapter 2 presents the modelling of the climatic niche response to multi-temporal climate change and determines the potential for connectivity between remaining elephant habitats and chapter 3 presents the interaction between environmental, socioeconomic and governance indicators to explain abundance of elephants in Africa, based on the most recent IUCN estimates. The fourth chapter discusses the main challenges associated with the introduction of African elephants as a strategy for the recovery of lost ecological functions with the extinction of megafauna in the Pleistocene, and the fifth chapter, which concludes, presents the synthesis of challenges and opportunities for the conservation of African elephants. / A conservação da biodiversade está em crise e são necessárias respostas urgentes para reverter a extinção de espécies, a proliferação de espécies invasoras e a fragmentação de habitats. Dentre as várias abordagens sendo implementadas, a proteção de espécies com grande capacidade de dispersão e que desempenham papel ecológico importante tem sido advogada como solução, na medida em que a proteção de seu habitat paralelamente contribui para a proteção de outras espécies e habitats. O elefante, megajardineiro das florestas e savanas, representa este tipo de espécies, no sentido em que habita vastas áreas, tem elevada capacidade de dispersão e garante a dispersão e crescimento de espécies vegetais por vastas áreas. Infelizmente a situação actual do elefante não é positiva e esforços internacionais têm sido desenvolvidos no sentido de reverter os atuais cenários de redução de sua abundancia e a proteção do seu habitat. Esta tese debruça-se sobre as espécies de elefante africano (Loxodonta africana e Loxodonta cyclotis) e procura contribuir para o conhecimento dos principais desafios que devem ser abraçados para a sua proteção, servindo-se de uma abordagem interdisciplinar envolvendo análise cienciométrica, modelagem de nicho climático, modelagem multi-escala de conectividade de habitats, modelos de regressão quasi-linear e de equações estruturais e sínteses de conhecimento. O capítulo 1 apresenta faz a revisão sistemática dos estudos de genética de conservação do elefante africano de savana e discute os principais eixos de pesquisa, as populações de elefantes envolvidas e as principais linhas de pesquisa abordadas. O capítulo 2 apresenta a modelagem da resposta do nicho climático em função de alterações climáticas multi-temporais e determina o potencial de conectividade entre os habitats remanescentes de elefantes e o capítulo 3 apresenta a interação entre indicadores ambientais, socioeconômicos e de governança para explicar a abundância de elefantes em África, tomando como base nas mais recentes estimativas da IUCN. O quarto capítulo discute os principais desafios associados à introdução de elefantes africanos como estratégia para a recuperação de funções ecológicas perdidas com a extinção da megafauna no Pleistoceno e o quinto capítulo, que faz de conclusão, apresenta a síntese dos desafios e oportunidades para a conservação dos elefantes africanos.
2

Habitat, ecology, and venom variation of cobras (genus Naja) and other venomous snakes of Bangladesh

Chowdhury, Mohammad Abdul Wahed 20 April 2022 (has links)
Im Fokus dieser Dissertation steht die Zerstörung des Lebensraumes von Schlangen durch anthropogene Einflüsse im Zusammenhang mit dem Auftreten von Schlangenbissen bei Menschen. Zum Schutz der Schlangen und dem Problem der Schlangenbisse wurden vier wesentliche Anforderungen erarbeitet. Mit Hilfe eines Artenverteilungsmodells wurden die ökologischen Nischen von 29 Giftschlangenarten aus Bangladesch und von zehn Kobraarten (Naja) aus Asien ermittelt. Auf lokaler Ebene wurde festgestellt, dass Überschwemmungen, Waldtypen, Ökosysteme und klimatische Parameter das Verbreitungsgebiet der Schlangenarten in Bangladesch beeinflussen. Auf regionaler Ebene sind anthropogene Faktoren wie die Zerstörung von Schlangenlebensräumen, Handel, Ausbeutung und Tötung von Schlangen wahrscheinlich die Hauptursachen für den Rückgang der Populationen der asiatischen Naja. Auf beiden Ebenen führt der Klimawandel zu einer Verkleinerung der ökologischen Nischen von Schlangenarten in Bangladesch und Asien. In Bangladesch könnten die untersuchten Arten innerhalb der nächsten 50 Jahre mehr als 90 % ihren derzeitigen Lebensraum verlieren (Asiatische Naja durchschnittlich 56 % (12 bis 100 %)). Wenn günstige Nischen nicht erhalten werden können, könnten viele Schlangenarten in einigen Ländern Asiens, darunter Bangladesch, in wenigen Jahrzehnten aussterben. Darüber hinaus wurde in der vorliegenden Studie geschätzt, dass die Zahl der jährlichen Schlangenbisse in Bangladesch mehr als doppelt so hoch sein könnte wie bisher angenommen. Da der Klimawandel zu einer geografischen Verschiebung günstiger Nischen führen kann, kann sich diese Veränderung auch auf die Häufigkeit von Schlangenbissen auswirken. Bei der Analyse von Giftvariationen und der Wirksamkeit von Antivenomen wurde festgestellt, dass isolierte Populationen deutliche intraspezifischere Giftvariationen zeigen. / Snakes are threatened by habitat degradation and anthropogenic impacts, while accidental encounters between humans and snakes may result in snakebite incidents. Thus, the conservation of snakes snakebite problem, a global public health emergency, are interconnected. I found four primary needs for a combined solution to satisfy both above causes. A species distribution model was employed to identify the ecological niches of 29 venomous snake species from Bangladesh and of ten cobra species (Naja) from Asia. At the local scale, flood events, forest types, ecosystems, and climatic parameters were found to shape the range of snake species in Bangladesh. At the regional scale, anthropogenic factors, like snake habitat destruction, trade, exploitation, and snake killings are likely to be the main causes for the decrease in populations of Asian Naja. At both levels, climate change causes shrinking and fragmenting the ecological niches of snake species in Bangladesh and Asia. In Bangladesh, the studied species may lose more than 90% of their current climatic niche within the next 50 years. In the same timeframe, Asiatic Naja may lose an average of 56% (12- 100%) of the area of suitable climatic niches. If favourable niches cannot be preserved, many snake species might go extinct from several countries in Asia in a few decades, including Bangladesh. In addition, the present study estimated that there might be more than double the amount of annual snakebite incidents in Bangladesh than previously estimated. As climate change may cause geographical shifting of favourable niches, this change may also have consequences for the frequency of snakebites, so snakebite should be considered a climate driven dynamic public health problem. While analysing venom variations and the efficacy of antivenom, I found that venom should be sampled from geographically or ecologically isolated populations of each venomous snake, because isolated populations have shown distinct intraspecific venom variations.

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