350 research outputs found
Hydrodynamics and modelling of water flow in mangrove areas
No full textMangrove forests cover wide tropical and subtropical intertidal areas, and they are very important for their role in maintaining biodiversity, for sustainable livelihood
(e.g., wood and food resources) and for coastal protection (Robertson and Alongi, 1992; Wolanski et al., 2001, 2004; Mazda et al., 2002; Wolanski, 2006a). Human activities since the late 19th century have led to the reduction of mangrove forests around the globe (Spalding et al., 1997). This degradation seriously threatens the sustainability of mangrove ecosystems worldwide, and has also adversely affected human populations (Hong and San, 1993; Mazda et al., 2002; Hong, 2006).
Managing mangroves requires understanding the natural mechanisms that form and maintain this environment. This requires using quantitative, process-based, models. In temperate coastal environments, such models have been developed based on a two-step procedure, namely,
Step 1; A hydrodynamic model is used to calculate water flows, which transport and disperses chemical/biological materials.
Step 2: Based on the hydrodynamic model, an ecosystem model is driven to calculate the flows of biomass and energy in the food web
Great Barrier Reef Biophysics
No full textThe Great Barrier Reef (GBR; Figure 1), together with its 424,000 km2 catchment comprising 35 rivers, is enormous. It is nearly 2,000 km long, it has about 2,500 reefs of various sizes and shapes, and these reefs are scattered in diverse ways in different regions of the continental shelf. The shelf width and depth vary with latitude between 30 and 200 km, and its mean depth also varies with latitude between 30 and 100 m. It borders the Coral Sea with depths of 2,000–4,000 m
The Emergence of Biophysical Sciences for the Great Barrier Reef
No full textThe Great Barrier Reef (GBR; Figure 1), together with its 424,000 km2 catchment comprising 35 rivers, is enormous. It is nearly 2,000 km long, it has about 2,500 reefs of various sizes and shapes, and these reefs are scattered in diverse ways in different regions of the continental shelf. The shelf width and depth vary with latitude between 30 and 200 km, and its mean depth also varies with latitude between 30 and 100 m. It borders the Coral Sea with depths of 2,000–4,000 m
Coastal Wetlands: A Synthesis
No full textWhat are coastal wetland ecosystems, what are their limits of distribution, and where dothey exist in the overall coastal landscape? There are several general definitions for wetlands,but the Ramsar definition is likely the most broadly encompassing (http://www.ramsar.org/), whereas others are more focused definitions tailored to country-specific protectionand management policies (Mitsch and Gosselink, 2006). We offer a very general approachrather than a precise definition: coastal wetlands are ecosystems that are found within anelevation gradient that ranges between subtidal depths where light penetrates to supportphotosynthesis of benthic plants to the landward edge where the sea passes its hydrologicinfluence to groundwater and atmospheric processes. At the seaward margin, biofilms,benthic algae, and seagrasses are representative biotic components. At the landward margin,vegetation boundaries range from those located on groundwater seeps or fens in humidclimates to relatively barren salt flats in arid climates.Fil: Hopkinson, Charles S.. University of Georgia; Estados UnidosFil: Wolanski, Eric. James Cook University; Australia. Australian Institute of Marine Science; AustraliaFil: Brinson, Mark M.. Brinson East Carolina University; Estados UnidosFil: Cahoon, Donald R.. United States Geological Survey; Estados UnidosFil: Perillo, Gerardo Miguel E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentin
Coastal wetlands: A Synthesis
No full textThis book and this synthesis address the pressing need for better management of coastal wetlands worldwide because these wetlands are disappearing at an alarming rate; in some countries the loss is 70%–80% in the last 50 years. Managing requires understanding. Although our understanding of the functioning of coastal wetland ecosystems has grown rapidly over the past decade, still much remains to be learned and understood. We have gained insight into the roles of geomorphic processes, hydrologic dynamics, biotic feedback, and disturbance agents in creating and molding a variety of coastal wetland ecosystems across climatic gradients. The variety is expressed not so much in the more obvious differences in vegetation cover, but rather how physical processes both facilitate and constrain a diversity of plant and animal communities. At one level, coastal wetlands are the product of tidal forces and freshwater inputs at the margin of continents. At another level, the plants control the water currents in the tidal creeks draining the wetlands by generating a tidal current asymmetry that controls sediment transport and results in a deep tidal creek surrounded by shallow vegetated wetlands. The vegetation also influences the physics of water and sediment through several other processes including biofilms, bioturbation of sediments, the buffeting of currents and waves, organic enrichment of sediments, and the closing of nutrient cycles. Few ecosystems provide us with so many clear examples of such feedback controls. What we do understand about the structure and functioning of coastal wetlands should provide the theoretical underpinnings for effective management in protecting them for their many contributions to ecosystem goods and services. What we do not understand should compel us to focus our attention and energies toward seeking optimal solutions to some of the most perplexing and urgent problems facing natural resource management.Fil: Hopkinson, Charles S.. University of Georgia; Estados UnidosFil: Wolanski, Eric. James Cook University; Australia. Australian Institute of Marine Science; AustraliaFil: Cahoon, Donald R.. Patuxent Wildlife Research Center; Estados UnidosFil: Perillo, Gerardo Miguel E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Brinson, Mark M.. No especifíca;Fil: Hopkinson, Charles S.. University of Georgia; Estados Unido
An estuarine ecohydrology model of Darwin Harbour, Australia
No full textThis publication does not have an abstract
Ecohydrology modeling: tools for management
No full textModels are recognized as important and necessary tools for understanding complex environmental processes. They allow us to test hypothesis in a systematic manner, predict the future behavior of ecosystems, and, thus, assist in better management of the environment. The modeling task can be addressed by various approaches. This chapter presents applications of ecohydrology models to coastal ecosystems, including various approaches that can be used model formulation. Theoretical (knowledge-driven), empirical (data-driven), and hybrid approaches to modeling are demonstrated in case studies focusing on quantifying the ecosystem health of the Guadiana Estuary in Portugal, the Lagoon of Venice in Italy, the Great Barrier Reef in Australia, and the Adriatic Sea
Integration of social and cultural aspects in designing ecohydrology and restoration solutions
No full textCoastal marine ecosystems worldwide are being degraded as a result of anthropogenic disturbance, including pollution, runoff, and sedimentation, which are directly tied to human activities within adjacent watersheds. While the biophysical sciences can provide critical data determining cause-and-effect relationships among human activities and resource degradation, the social sciences are essential for applying these data to developing and implementing sound policies and strategies. As most biological resources cannot truly be managed, the pragmatic approach is to manage those human activities responsible for coastal-resource degradation. Such approaches require the integration of social and cultural elements into designing ecohydrology and restoration solutions
An inhomogeneous singular perturbation problem for the p(x)-Laplacian
No full textIn this paper we study the following singular perturbation problem for the pϵ(x)-Laplacian: Δpϵ (x)uϵ:=div(|∇uϵ(x)|pϵ (x)-2∇ uϵ)=βϵ(uϵ)+fϵ,uϵ≥0, (Pϵ(fϵ, pϵ)) where ϵ>0, βϵ(s)=1/ϵβ(s/ϵ), with β a Lipschitz function satisfying β>0 in (0,1), β≡0 outside (0,1) and ∫β(s)ds=M. The functions uϵ, fϵ and pϵ are uniformly bounded. We prove uniform Lipschitz regularity, we pass to the limit (ϵ→0) and we show that, under suitable assumptions, limit functions are weak solutions to the free boundary problem: u≥0 and {Δp(x)u = f in {u>0}u=0,|∇u|=λ ∗(x)on ∂{u>0} (P(f, p, λ∗)) with λ∗ (x)=(p(x)/p(x)-1 M)1/p(x), p = lim pϵ and f = lim fϵ. In Lederman and Wolanski (submitted) we prove that the free boundary of a weak solution is a C1,α surface near flat free boundary points. This result applies, in particular, to the limit functions studied in this paper.Fil: Lederman, Claudia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Wolanski, Noemi Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentin
A synthesis: what is the future for coasts, estuaries, deltas and other transitional habitats in 2050 and beyond?
No full textWe synthesized the results of many case studies from experts worldwide on the state of the environment, sustainability, and the likely future of estuaries, lagoons, semienclosed seas, and coastal ecosystems. There is a high natural variability in these ecosystems and in their responses to historical human pressures within their catchments, the river, and the estuary, and the potential for sustainability depends on many variables including population growth, the culture, historical changes, and the involvement of the communities. The problems faced by half of the global population living near coasts are truly worldwide challenges and they give us the opportunity to study commonalities and differences and to provide solutions. Fundamental to addressing these challenges is an understanding of the biophysical constraints especially along the catchment-river-estuary ecosystem continuum. We emphasize that there is a need to better manage all these areas to ensure that we can maintain natural ecological structure and functioning while also allowing these systems to deliver services that produce societal goods and benefits, both now and in the future. By investigating the problems, we can offer solutions for specific issues graded within the framework of the socioeconomic and environmental mosaic. These challenges include fisheries, climate change, growing resource scarcity, coastal megacities, a growing population and an increaisng urbanisation and industrialisation of the coast, evolving human-nature interactions, remediation measures, and the willingness to adopt governance at the catchment scale. In these case studies, the DAPSI(W)R(M) problem-solving framework usefully allows us to assess risks and potentials for an effective response which have to be based on the use of good science. To be effective, this framework must be accompanied by the so-called 10-tenets of sustainable management, which include the ecological, economic, technological, societal, administrative, legislative, political, ethical/moral, cultural, and communication aspects. Stakeholder involvement therefore becomes central to successful management of the coasts and estuaries in accommodating changes over the coming century
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