1,094 research outputs found

    Biotic Indicators for Ecological State Change in Amazonian Floodplains

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    Riverine floodplains are biologically diverse and productive ecosystems. Although tropical floodplains remain relatively conserved and ecologically functional compared to those at higher latitudes, they face accelerated hydropower development, climate change, and deforestation. Alterations to the flood pulse could act synergistically with other drivers of change to promote profound ecological state change at a large spatial scale. State change occurs when an ecosystem reaches a critical threshold or tipping point, which leads to an alternative qualitative state for the ecosystem. Visualizing an alternative state for Amazonian floodplains is not straightforward. Yet, it is critical to recognize that changes to the flood pulse could push tropical floodplain ecosystems over a tipping point with cascading adverse effects on biodiversity and ecosystem services. We characterize the Amazonian flood pulse regime, summarize evidence of flood pulse change, assess potential ecological repercussions, and provide a monitoring framework for tracking flood pulse change and detecting biotic responses

    Biotic indicators for ecological state change in Amazonian floodplains

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    Riverine floodplains are biologically diverse and productive ecosystems. Although tropical floodplains remain relatively conserved and ecologically functional compared to those at higher latitudes, they face accelerated hydropower development, climate change, and deforestation. Alterations to the flood pulse could act synergistically with other drivers of change to promote profound ecological state change at a large spatial scale. State change occurs when an ecosystem reaches a critical threshold or tipping point, which leads to an alternative qualitative state for the ecosystem. Visualizing an alternative state for Amazonian floodplains is not straightforward. Yet, it is critical to recognize that changes to the flood pulse could push tropical floodplain ecosystems over a tipping point with cascading adverse effects on biodiversity and ecosystem services. We characterize the Amazonian flood pulse regime, summarize evidence of flood pulse change, assess potential ecological repercussions, and provide a monitoring framework for tracking flood pulse change and detecting biotic responses

    A baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change

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    This report forms part of a larger research programme on 'Reinterpreting the Urban-Rural Continuum', which conceptualises and investigates current knowledge and research gaps concerning 'the role that ecosystems services play in the livelihoods of the poor in regions undergoing rapid change'. The report aims to conduct a baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. The appraisal is conducted at three spatial scales: global, regional (four consortia areas), and meso scale (case studies within the four regions). At all three scales of analysis water resources form the interweaving theme because water provides a vital provisioning service for people, supports all other ecosystem processes and because water resources are forecast to be severely affected under climate change scenarios. This report, combined with an Endnote library of over 1100 scientific papers, provides an annotated bibliography of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. After an introductory, section, Section 2 of the report defines water-related ecosystem services and how these are affected by human activities. Current knowledge and research gaps are then explored in relation to global scale climate and related hydrological changes (e.g. floods, droughts, flow regimes) (section 3). The report then discusses the impacts of climate changes on the ESPA regions, emphasising potential responses of biomes to the combined effects of climate change and human activities (particularly land use and management), and how these effects coupled with water store and flow regime manipulation by humans may affect the functioning of catchments and their ecosystem services (section 4). Finally, at the meso-scale, case studies are presented from within the ESPA regions to illustrate the close coupling of human activities and catchment performance in the context of environmental change (section 5). At the end of each section, research needs are identified and justified. These research needs are then amalgamated in section 6

    Characterising the drivers of tropical freshwater fish dynamics and abundance in the Mekong river, under environmental change

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    The Mekong river’s monsoon driven annual flood pulse creates a range of diverse habitats, with high levels of connectivity and primary productivity that support and trigger fish migratory dynamics and abundance. This abundance is reflected in the fact that the Mekong is the World’s most productive inland fisheries, supporting between 2.8-3.2 million tonnes of catch annually, underpinning the food security of over 70 million people.This thesis explores the impacts of climate change and anthropogenic activity on Mekong hydrology and system function, and the impacts these have on fish and fisheries. It combines an interdisciplinary approach utilising earth observation, historical fisheries data and hydrological records, alongside the application of hydrological modelling tools and the testing of new environmental DNA metabarcoding analyses, in order to explore how changes in Mekong hydrology will affect fish populations into the future.The results highlight a range of projected negative impacts of hydropower development, irrigation expansion and climate change on the dai fisheryresources, and in turn a range of significant impacts on regional fish protein availability, which primarily result from the blockage of key migratory routes caused by dam construction as well as changes in the timing of the flood pulse in key areas in the basin such as Tonle Sap Great Lake. The findings in this study urge a need to prioritise environmental conservation action centred on a need to maintain the historical flood pulse hydrologic regime of the Mekong river. Such a pulse is shown to be important in sustaining floodplain flood dynamics and habitat connectivity that maintains the critical dai fishery, enables migratory fish dynamics, and is thus key to overall regional food security

    TDMP-Reliable Target Driven and Mobility Prediction based Routing Protocol in Complex VANET

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    Vehicle-to-everything (V2X) communication in the vehicular ad hoc network (VANET), an infrastructure-free mechanism, has emerged as a crucial component in the advanced Intelligent Transport System (ITS) for special information transmission and inter-vehicular communications. One of the main research challenges in VANET is the design and implementation of network routing protocols which manage to trigger V2X communication with the reliable end-to-end connectivity and efficient packet transmission. The organically changing nature of road transport vehicles poses a significant threat to VANET with respect to the accuracy and reliability of packet delivery. Therefore, a position-based routing protocol tends to be the predominant method in VANET as they overcome rapid changes in vehicle movements effectively. However, existing routing protocols have some limitations such as (i) inaccurate in high dynamic network topology, (ii) defective link-state estimation (iii) poor movement prediction in heterogeneous road layouts. In this paper, a target-driven and mobility prediction (TDMP) based routing protocol is therefore developed for high-speed mobility and dynamic topology of vehicles, fluctuant traffic flow and diverse road layouts in VANET. The primary idea in TDMP is that the destination target of a driver is included in the mobility prediction to assist the implementation of the routing protocol. Compared to existing geographic routing protocols which mainly greedily forward the packet to the next-hop based on its current position and partial road layout, TDMP is developed to enhance the packet transmission with the consideration of the estimation of inter-vehicles link status, and the prediction of vehicle positions dynamically in fluctuant mobility and global road layout.Comment: 35 pages,16 Figure

    Urban Air Mobility Airspace Integration Concepts and Considerations

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    Urban Air Mobility (UAM) - defined as safe and efficient air traffic operations in a metropolitan area for manned aircraft and unmanned aircraft systems - is being researched and developed by industry, academia, and government. Significant resources have been invested toward cultivating an ecosystem for Urban Air Mobility that includes manufacturers of electric vertical takeoff and landing aircraft, builders of takeoff and landing areas, and researchers of the airspace integration concepts, technologies, and procedures needed to conduct Urban Air Mobility operations safely and efficiently alongside other airspace users. This paper provides high-level descriptions of both emergent and early expanded operational concepts for Urban Air Mobility that NASA is developing. The scope of this work is defined in terms of missions, aircraft, airspace, and hazards. Past and current Urban Air Mobility operations are also reviewed, and the considerations for the data exchange architecture and communication, navigation, and surveillance requirements are also discussed. This paper will serve as a starting point to develop a framework for NASA's Urban Air Mobility airspace integration research and development efforts with partners and stakeholders that could include fast-time simulations, human-in-the-loop (HITL) simulations, and flight demonstrations

    InundaçÔes em mĂșltiplas escalas na AmĂ©rica do Sul : de ĂĄreas Ășmidas a ĂĄreas de risco

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    South America hosts some of the major river systems on Earth, often associated with large floodplains that are inundated every year, such as the Pantanal and many Amazon wetlands. Interfluvial wetland complexes are also found across the continent, with particular geomorphic settings and unique savanna or grassland vegetation. South American wetlands can provide distinctive ecosystem services such as biodiversity supporting, food provision and flood attenuation. On the other hand, humans have settled around wetlands for millennia, benefiting from all resources they provide, and have adapted to its flood regime as well adapted its landscape, defining what has been called human-water systems. Yet, an increasing number of South American people have been negatively affected by extreme floods. Moving from continental to local scales, this thesis invites the readers to a journey across major South American wetland systems and their unique hydrological dynamics, under the light of the satellite era and the breakthrough advances on hydrologic-hydrodynamic modeling in the last decades. This work is founded on the proposition of a continental wetland research agenda, and based on a comparative hydrology approach. Floods are studied through both natural wetland processes and hazard dimensions. The first part presents a set of studies on the Amazon basin wetlands, from the development of 1D and 2D models to simulate hydrological processes in contrasting wetland types in the Negro river basin to the basin-wide intercomparison of 29 inundation products and assessment of long-term inundation trends. While most wetland studies have been conducted over the central Amazon floodplains, major knowledge gaps remain for understanding the hydrological dynamics of interfluvial areas such as the Llanos de Moxos and Negro savannas, where the inundation is less predictable and shallower. The second part of the thesis leverages satellite-based datasets of multiple hydrological variables (water levels, total water storage, inundation extent, precipitation and evapotranspiration) to address the hydrology of 12 large wetland systems in the continent. It shows the major differences among river floodplains and interfluvial wetlands on the water level annual amplitude, time lag between precipitation and inundation, and evapotranspiration dynamics. Finally, the third part addresses the flood hazard component of human-wetland interactions through large-scale assessments of flood hazard dynamics and effects of built infrastructure (dams) on flood attenuation. The dynamics of the great 1983 floods, one of the most extreme years ever recorded in the continent, is assessed with a continental hydrological model. Then, the capabilities of continental models to simulate the river-floodplain-reservoir continuum that exists across large river basins are assessed with case studies for major river basins affected by human intervention (ItajaĂ­-Açu and upper ParanĂĄ river basins in Brazil). While this thesis enlightens some relevant hydrological processes regarding South American floods and their positive and negative effects to human societies and ecosystems in general, major knowledge gaps persist and provide great research opportunities for the near future. The launching of many hydrology-oriented satellite missions, and an ever-growing computational capacity, make the continental hydrology agenda related to wetlands and floods a great research topic for the upcoming years.A AmĂ©rica do Sul abriga alguns dos maiores sistemas hĂ­dricos do planeta, frequentemente associados a grandes planĂ­cies de inundação, como o Pantanal e vĂĄrias ĂĄreas da AmazĂŽnia. Áreas Ășmidas (AU’s) interfluviais sĂŁo tambĂ©m encontrados no continente, com caracterĂ­sticas geomorfolĂłgicas particulares, e vegetaçÔes de savana e gramĂ­neas Ășnicas. As AU’s da AmĂ©rica do Sul provĂȘm diversos serviços ecossistĂȘmicos, como suporte Ă  biodiversidade, provisĂŁo de alimento e atenuação de cheias. Humanos tĂȘm se estabelecido ao redor de AU’s por milĂȘnios, se beneficiando dos recursos providos por elas. Eles se adaptaram ao seu regime de inundação, e adaptaram sua paisagem, definindo o que tem sido chamado de sistemas sociedade-ĂĄgua. Por outro lado, um nĂșmero crescente de pessoas tĂȘm sido negativamente afetado por cheias extremas. Da escala continental Ă  local, esta tese convida o leitor a uma jornada atravĂ©s de importantes AU’s da AmĂ©rica do Sul e suas particulares dinĂąmicas de inundação, sob a luz da era dos satĂ©lites e dos grandes avanços em modelagem hidrolĂłgica-hidrodinĂąmica das Ășltimas dĂ©cadas. Este trabalho Ă© baseado na proposta de uma escala continental de pesquisa sobre AU’s, e Ă© baseado em uma abordagem de hidrologia comparativa. InundaçÔes sĂŁo estudadas em mĂșltiplas dimensĂ”es, de processos de AU’s naturais Ă  questĂŁo do perigo para humanos. A primeira parte apresenta uma sĂ©rie de estudos sobre as AU’s da bacia amazĂŽnica, desde o desenvolvimento de modelos 1D e 2D para simular processos hidrolĂłgicos em tipos contrastantes de AU’s na bacia do Rio Negro, atĂ© a intercomparação de 29 produtos de inundação e avaliação de tendĂȘncias de inundaçÔes de longo prazo para a escala da bacia amazĂŽnica. Enquanto a maioria dos estudos de AU’s foi conduzida nas vĂĄrzeas do rio Amazonas, importantes lacunas do conhecimento permanecem para a compreensĂŁo da dinĂąmica hidrolĂłgica de ĂĄreas interfluviais como Llanos de Moxos e as savanas do rio Negro, onde a inundação Ă© menos previsĂ­vel e mais rasa. A segunda parte da tese utiliza dados oriundos de satĂ©lites relacionados a mĂșltiplas variĂĄveis hidrolĂłgicas (nĂ­veis d’água, armazenamento total de ĂĄgua, extensĂŁo de ĂĄreas inundadas, precipitação e evapotranspiração) para estudar a hidrologia de 12 grandes sistemas de AU’s do continente. SĂŁo destacadas as grandes diferenças entre planĂ­cies de inundação e AU’s interfluviais em termos de amplitude anual de nĂ­veis d’água, defasagem entre precipitação e inundação, e dinĂąmica de evapotranspiração. Por fim, a Ășltima parte da tese aborda o componente de perigo de inundação das interaçÔes sociedade-ĂĄgua atravĂ©s de avaliaçÔes em grande escala da dinĂąmica de inundação e dos efeitos de infraestruturas construĂ­das (como barragens) na atenuação de cheias. A dinĂąmica das grandes cheias de 1983, um dos anos mais extremos jĂĄ registrados no continente, Ă© avaliada com um modelo hidrolĂłgico continental. Depois, a capacidade de modelos continentais para simular o continuum entre rios, planĂ­cies de inundação e reservatĂłrios que existe em grandes bacias hidrogrĂĄficas Ă© avaliada com estudos de casos para importantes bacias afetadas pela intervenção humana (bacia dos rios ParanĂĄ e ItajaĂ­-Açu). Enquanto esta tese avança a compreensĂŁo de relevantes processos hidrolĂłgicos relacionados a inundaçÔes na AmĂ©rica do Sul em mĂșltiplas escalas, bem como seus efeitos positivos e negativos nas sociedades humanas e ecossistemas em geral, importantes lacunas do conhecimento persistem e fomentam importantes oportunidades de pesquisa futuras. O lançamento de vĂĄrias missĂ”es satelitais orientadas a hidrologia, e uma cada vez mais crescente capacidade computacional, faz da agenda continental de hidrologia relacionada a AU’s e inundaçÔes um grande tĂłpico de pesquisa para os prĂłximos anos

    The ecomics of ecosystems and biodiversity: scoping the scale

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    The G8 decided in March 2007 to initiate a “Review on the economics of biodiversity loss”, in the so called Potsdam Initiative: 'In a global study we will initiate the process of analysing the global economic benefit of biological diversity, the costs of the loss of biodiversity and the failure to take protective measures versus the costs of effective conservation. The study is being supported by the European Commission (together with the European Environmental Agency and in cooperation with the German Government. “The objective of the current study is to provide a coherent overview of existing scientific knowledge upon which to base the economics of the Review, and to propose a coherent global programme of scientific work, both for Phase 2 (consolidation) and to enable more robust future iterations of the Review beyond 2010.
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