1,721,177 research outputs found
Natural resource system challenge IV: oceans and aquatic ecosystems
Full text linkWater is vital for all life on earth. It is also vital for humanity's food security and health. At present at least one billion people lack access to an adequate supply of safe water, and 1.7 billion people do not adequate sanitation. Freshwater is vital, not only for drinking but also for food security; agriculture is responsible for 93 percent of total water consumed by all economic sectors. Many countries have increasing problems in providing clean water to sustain human activities. The oceans are used extensively to provide fish for human consumption, and there are already indications that this extraction of seafood is unsustainable, yet human populations are growing by 90 million per year and the demand for seafood is growing. The food security requirements of an increasing human population will exacerbate current problems with water availability and quality. Human health and economic development are threatened, or restricted, by water quality issues that limit human welfare and water uses. These include salinization of rivers and lakes, microbiological and organic pollution, and pollution by wastes from human activities (for example, heavy metals, toxic organic compounds, nutrients, and eroded soils). Human activities also exacerbate water-related diseases, especially in the tropical world where economic development is still greatly limited by illnesses such as river blindness (onchocerciasis), malaria, bacterial diarrhea, and bitharziasis (schistosomiasis). These problems may become worse in the future.
The aim of this essay is to guide the reader through the various pathways followed by surface water on earth. It will describe the dominant processes that govern how organisms interact with water and with each other, and how they in turn can modify water properties. This knowledge is important for humanity. Indeed, only by understanding our actions' impacts upon water, and the animals and plants living in it, can we learn to exploit water, marine and freshwater habitats and the living organisms, without destroying the resources on which our livelihood and very survival depend
Increasing trade and urbanisation of the Asia Pacific coast
No full textThis publication does not have an abstract
The Environment in Asia Pacific Harbours
Full text linkUrbanization has reached unprecedented levels in the estuarine and coastal zone, particularly in the Asia Pacific region where mega-cities and mega-harbours are still growing. This book demonstrates the different solutions and pitfalls, successes and failures in a large number of ports and harbours in the Asia Pacific Region, and shows how science can provide ecologically sustainable solutions that apply wherever the growth of mega-harbours occurs
Is harbour development ecologically sustainable?
No full textThis publication does not have an abstract
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
Hydrodynamics of Darwin Harbour
No full textAlthough macrotidal, Darwin Harbour is poorly flushed, especially in the dry season when the residence time in the upper reaches is of the order of 20 days. Much of the riverine fine sediment remains trapped in mud flats and mangroves with little escaping to the sea. The complex bathymetry of headlands and embayments generate complex currents comprising jets, eddies, and stagnation zones that can trap pollutants inshore. The tidally averaged circulation may control the location of the sand banks, indicating a feedback between the bathymetry and the water circulation. The environment in Darwin Harbour has the potential to degrade and the water circulation in the harbour must be considered when planning developments
Muddy coastal waters and depleted mangrove coastlines - depleted seagrass and coral reefs
No full textAlong the tropical northeastern coast of Queensland is one of the outstanding biotic ecosystems in the world, the Great Barrier Reef (GBR), attested to be the only biotic structure in the world visible from space. This complex series of reef communities is based on tiny coral polyps and deep accumulations of their carbonate skeletons over eons. The resulting barrier to ocean waves has created a vast and relatively sheltered coastal lagoon in which other complex biotic tropical ecosystems have flourished in association with coral reefs. Two types of ecosystems dominate these sheltered waters, namely, the mostly sub-tidal seagrass meadows in the extensive coastal lagoon, and mangrove and salt marsh growing along the upper intertidal zone and within all estuaries. These ecosystems are highly dependent not only on each other, but also on prevailing environmental conditions in a dynamic equilibrium
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
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
Estuarine ecohydrology modeling: what works and within what limits?
No full textThere is a practical need for models to assess the impact on estuarine ecosystems of development proposals throughout the river catchment and the effectiveness of remedial measures. Such models must link the catchment and all the human activities within it with the estuary and the coastal seas. Also they must link models of the water circulation with sediment dynamics model and with ecology models. This is because water transports waterborne matter, because sediment provides habitats, affects turbidity and thus photosynthetically active radiation, and it absorbs nutrients, and because all these processes affect the estuarine ecology. Several such models have been proposed and are reviewed. Water circulation models are the most advanced and have been extensively proven. There are still problems with those models when tackling estuarine fronts and river plumes in that they do not work well for estuarine fronts, and this is important for the ecology because such fronts are used by fish larvae in their strategy to recruit. Models of the sediment dynamics are still empirical for sand but they are better developed for mud; nevertheless, none can be reliably used without extensive field data. Fine sediment dynamics models must integrate the feedbacks between the physics and the biology; for instance, the mud dynamics themselves are closely dependent on the biology through its role in floc formation and substrate stabilization/destabilization by the benthic fauna and flora. To be of practical use, models of the ecology need to be kept “simple,” that is, restricted to the essential processes. These models require extensive field data for verification and in such cases the models appear reliable. When such data are unavailable, which is the case for many estuaries, model verification is only qualitative. Estuarine ecohydrology modeling is thus possible and practical for systems where the food web structure basically stays unchanged, provided suitable field data are available. As no two estuaries are the same, by and large this modeling is still an art more than a formal science and for each estuary the modeler needs to work closely with the physical oceanographer and the ecologist
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