67 resultados para threat


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Executive Summary: The marine environment plays a critical role in the amount of carbon dioxide (CO2) that remains within Earth’s atmosphere, but has not received as much attention as the terrestrial environment when it comes to climate change discussions, programs, and plans for action. It is now apparent that the oceans have begun to reach a state of CO2 saturation, no longer maintaining the “steady-state” carbon cycle that existed prior to the Industrial Revolution. The increasing amount of CO2 present within the oceans and the atmosphere has an effect on climate and a cascading effect on the marine environment. Potential physical effects of climate change within the marine environment, including ocean acidification, changes in wind and upwelling regimes, increasing global sea surface temperatures, and sea level rise, can lead to dramatic, fundamental changes within marine and coastal ecosystems. Altered ecosystems can result in changing coastal economies through a reduction in marine ecosystem services such as commercial fish stocks and coastal tourism. Local impacts from climate change should be a front line issue for natural resource managers, but they often feel too overwhelmed by the magnitude of this issue to begin to take action. They may not feel they have the time, funding, or staff to take on a challenge as large as climate change and continue to not act as a result. Already, natural resource managers work to balance the needs of humans and the economy with ecosystem biodiversity and resilience. Responsible decisions are made each day that consider a wide variety of stakeholders, including community members, agencies, non-profit organizations, and business/industry. The issue of climate change must be approached as a collaborative effort, one that natural resource managers can facilitate by balancing human demands with healthy ecosystem function through research and monitoring, education and outreach, and policy reform. The Scientific Expert Group on Climate Change in their 2007 report titled, “Confronting Climate Change: Avoiding the Unmanageable and Managing the Unavoidable” charged governments around the world with developing strategies to “adapt to ongoing and future changes in climate change by integrating the implications of climate change into resource management and infrastructure development”. Resource managers must make future management decisions within an uncertain and changing climate based on both physical and biological ecosystem response to climate change and human perception of and response to the issue. Climate change is the biggest threat facing any protected area today and resource managers must lead the charge in addressing this threat. (PDF has 59 pages.)

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Venomous Indo-Pacific lionfish (Pterois miles and P. volitans) are now established along the Southeast U.S.A. and parts of the Caribbean and pose a serious threat to reef fish communities of these regions. Lionfish are likely to invade the Gulf of Mexico and potentially South America in the near future. Introductions of lionfish were noted since the 1980s along south Florida and by 2000 lionfish were established off the coast of North Carolina. Lionfish are now one of the more numerous predatory reef fishes at some locations off the Southeast U.S.A. and Caribbean. Lionfish are largely piscivores that feed occasionally on economically important reef fishes. The trophic impacts of lionfish could alter the structure of native reef fish communities and potentially hamper stock rebuilding efforts of the Snapper –Grouper Complex. Additional effects of the lionfish invasion are far-reaching and could increase coral reef ecosystem stress, threaten human health, and ultimately impact the marine aquarium industry. Control strategies for lionfish are needed to mitigate impacts, especially in protected areas. This integrated assessment provides a general overview of the biology and ecology of lionfish including genetics, taxonomy, reproductive biology, early life history and dispersal, venom defense and predation, and feeding ecology. In addition, alternative management actions for mitigating the negative impacts of lionfish, approaches for reducing the risk of future invasions, and directions for future research are provided.

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An overview is presented on the M74-Syndrome of Baltic salmon which is known since 1974 and which, since 1992, has caused considerable losses of artificially produced yolk-sac larvae in Swedish and Finnish hatcheries responsible for compensatory salmon stocking programmes. The syndrome only affects offspring of wild salmon ascending the rivers for spawning and not offspring derived from salmon broodstocks permanently kept in hatcheries. The syndrome seems to be restricted to the Baltic Sea where it has been recorded in all of the remaining Swedish (except the west coast) and Finnish salmon rivers as well as in populations of Estonian rivers and the Russian River Neva. In Sweden and in Finland, the syndrome has been recorded in recent years in offspring of up to 80 % of female salmon used for spawning and resulted in a larval mortality of up to 90 %. A nutrition-associated thiamine (vitamin B1) deficiency is considered as primary cause. However, other environmental factors seem to be involved in addition. There is concern that the syndrome constitutes a major threat with respect to the survival of the few still naturally reproducing populations of Baltic salmon.

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Climate change has rapidly emerged as a significant threat to coastal areas around the world. While uncertainty regarding distribution, intensity, and timescale inhibits our ability to accurately forecast potential impacts, it is widely accepted that changes in global climate will result in a variety of significant environmental, social, and economic impacts. Coastal areas are particularly vulnerable to the effects of climate change and the implications of sea-level rise, and coastal communities must develop the capacity to adapt to climate change in order to protect people, property, and the environment along our nation’s coasts. The U.S. coastal zone is highly complex and variable, consisting of several regions that are characterized by unique geographic, economic, social and environmental factors. The degree of risk and vulnerability associated with climate change can vary greatly depending on the exposure and sensitivity of coastal resources within a given area. The ability of coastal communities to effectively adapt to climate change will depend greatly on their ability to develop and implement feasible strategies that address unique local and regional factors. A wide variety of resources are available to assist coastal states in developing their approach to climate change adaptation. However, given the complex and variable nature of the U.S. coastline, it is unlikely that a single set of guidelines can adequately address the full range of adaptation needs at the local and regional levels. This panel seeks to address some of the unique local and regional issues facing coastal communities throughout the U.S. including anticipated physical, social, economic and environmental impacts, existing resources and guidelines for climate change adaptation, current approaches to climate change adaptation planning, and challenges and opportunities for developing adaptation strategies. (PDF contains 4 pages)

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Atlantic and Gulf Coast shorelines include some of the most unique and biologically rich ecosystems in the United States that provide immeasurable aesthetic, habitat and economic benefits. Natural coastal ecosystems, however, are under increasing threat from rampant and irresponsible growth and development. Once a boon to local economies, complex natural forces – enhanced by global climate change and sea level rise - are now considered hazards and eroding the very foundation upon which coastal development is based. For nearly a century, beach restoration and erosion control structures have been used to artificially stabilize shorelines in an effort to protect structures and infrastructure. Beach restoration, the import and emplacement of sand on an eroding beach, is expensive, unpredictable, inefficient and may result in long-term environmental impacts. The detrimental environmental impacts of erosion control structures such as sea walls, groins, bulkheads and revetments include sediment deficits, accelerated erosion and beach loss. These and other traditional responses to coastal erosion and storm impacts- along with archaic federal and state policies, subsidies and development incentives - are costly, encourage risky development, artificially increase property values of high-risk or environmentally sensitive properties, reduce the post-storm resilience of shorelines, damage coastal ecosystems and are becoming increasingly unsustainable. Although communities, coastal managers and property owners face increasingly complex and difficult challenges, there is an emerging public, social and political awareness that, without meaningful policy reforms, coastal ecosystems and economies are in jeopardy. Strategic retreat is a sustainable, interdisciplinary management strategy that supports the proactive, planned removal of vulnerable coastal development; reduces risk; increases shoreline resiliency and ensures long term protection of coastal systems. Public policies and management strategies that can overcome common economic misperceptions and promote the removal of vulnerable development will provide state and local policy makers and coastal managers with an effective management tool that concomitantly addresses the economic, environmental, legal and political issues along developed shorelines. (PDF contains 4 pages)

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Coastal storms, and the strong winds, heavy rains, and high seas that accompany them pose a serious threat to the lives and livelihoods of the peoples of the Pacific basin, from the tropics to the high latitudes. To reduce their vulnerability to the economic, social, and environmental risks associated with these phenomena (and correspondingly enhance their resiliency), decision-makers in coastal communities require timely access to accurate information that affords them an opportunity to plan and respond accordingly. This includes information about the potential for coastal flooding, inundation and erosion at time scales ranging from hours to years, as well as the longterm climatological context of this information. The Pacific Storms Climatology Project (PSCP) was formed in 2006 with the intent of improving scientific understanding of patterns and trends of storm frequency and intensity - “storminess”- and related impacts of these extreme events. The project is currently developing a suite of integrated information products that can be used by emergency managers, mitigation planners, government agencies and decision-makers in key sectors, including: water and natural resource management, agriculture and fisheries, transportation and communication, and recreation and tourism. The PSCP is exploring how the climate-related processes that govern extreme storm events are expressed within and between three primary thematic areas: heavy rains, strong winds, and high seas. To address these thematic areas, PSCP has focused on developing analyses of historical climate records collected throughout the Pacific region, and the integration of these climatological analyses with near-real time observations to put recent weather and climate events into a longer-term perspective.(PDF contains 4 pages)

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Atlantic and Gulf Coast shorelines include some of the most unique and biologically rich ecosystems in the United States that provide immeasurable aesthetic, habitat and economic benefits. Natural coastal ecosystems, however, are under increasing threat from rampant and irresponsible growth and development. Once a boon to local economies, complex natural forces – enhanced by global climate change and sea level rise - are now considered hazards and eroding the very foundation upon which coastal development is based. For nearly a century, beach restoration and erosion control structures have been used to artificially stabilize shorelines in an effort to protect structures and infrastructure. Beach restoration, the import and emplacement of sand on an eroding beach, is expensive, unpredictable, inefficient and may result in long-term environmental impacts. The detrimental environmental impacts of erosion control structures such as sea walls, groins, bulkheads and revetments include sediment deficits, accelerated erosion and beach loss. These and other traditional responses to coastal erosion and storm impacts- along with archaic federal and state policies, subsidies and development incentives - are costly, encourage risky development, artificially increase property values of high-risk or environmentally sensitive properties, reduce the post-storm resilience of shorelines, damage coastal ecosystems and are becoming increasingly unsustainable. Although communities, coastal managers and property owners face increasingly complex and difficult challenges, there is an emerging public, social and political awareness that, without meaningful policy reforms, coastal ecosystems and economies are in jeopardy. Strategic retreat is a sustainable, interdisciplinary management strategy that supports the proactive, planned removal of vulnerable coastal development; reduces risk; increases shoreline resiliency and ensures long term protection of coastal systems. Public policies and management strategies that can overcome common economic misperceptions and promote the removal of vulnerable development will provide state and local policy makers and coastal managers with an effective management tool that concomitantly addresses the economic, environmental, legal and political issues along developed shorelines. (PDF contains 4 pages)

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Beachfront jurisdictional lines were established by the South Carolina Beachfront Management Act (SC Code §48- 39-250 et seq.) in 1988 to regulate the new construction, repair, or reconstruction of buildings and erosion control structures along the state’s ocean shorelines. Building within the state’s beachfront “setback area” is allowed, but is subject to special regulations. For “standard beaches” (those not influenced by tidal inlets or associated shoals), a baseline is established at the crest of the primary oceanfront sand dune; for “unstabilized inlet zones,” the baseline is drawn at the most landward point of erosion during the past forty years. The parallel setback line is then established landward of the baseline a distance of forty times the long-term average annual erosion rate (not less than twenty feet from the baseline in stable or accreting areas). The positions of the baseline and setback line are updated every 8-10 years using the best available scientific and historical data, including aerial imagery, LiDAR, historical shorelines, beach profiles, and long-term erosion rates. One advantage of science-based setbacks is that, by using actual historical and current shoreline positions and beach profile data, they reflect the general erosion threat to beachfront structures. However, recent experiences with revising the baseline and setback line indicate that significant challenges and management implications also exist. (PDF contains 3 pages)

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The paper assessed qualitatively the threat status of nigerian freshwater fishes that are presently being exported and those that have potential in aquarium trade using such criteria as rarity, size at maturity, mode of reproduction, human population density, habitat degradation, pollution and range of each species among others. For their conservation captive breeding of these fishes were proffered with information that can assist collectors, exporter and aquaculturists that wants to breed polypterids, Butterfly fish, Knife fish, Elephantfish, Pollymyrus isidori, Arnordichthys spilopterus, Nannaethiops unitaeniatus, Killifishes, Polycentropsis abbreviatta, Cichlids, Ctenpomas, Mastacembelids and Tetraodon lineatus

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One of the supposed effects of the observed ozone depletion is the increase of solar UV-B irradiation at the seasurface. This will cause an impact on certain compartments of marine ecosystems. Especially, sensitive developmental stages of pelagic fish embryos might be affected. Embryos of dab (Limanda limanda) and plaice (Pleuronectes plalessa) were experimentally exposed 10 different amounts of UVB irradiation in a sunshine simulator. This programmable device allows the dosage of realistic solar irradiation in quality and guantity. Experiments were carried out in March 1995 and February 1996. Either artificially inserninated and reared emhryos of dab and plaice or embryos caught in the German Bight were exposed to simulated solar irradiation. The 1995 experiments served to identify the effective irradiation dosages. For the 1996 experiments irradiation applied was much lower, being dose to realistic valucs expected over the North Sea as a consequence of ozone depletion. The following end points were studied: 1. Mortality, 2. sublethal morphological effects (malformations), 3. DNA damage, 4. changes in buoyancy of embryos measured as changes in osmolarity of the perivitelline fluid. Conditions for the simulation of daylight were a c1oudless sky with a solar zenith distance of 34 % (air mass 1.2). The adopted ozone depletion was 40 % corresponding to 180 DU (Dobson Units) instead of 300 DU. In the 1995 experiments time and dosage dependent influenccs on mortality and buoyancy of embryos of dab and plaice were found. Even in those embryos which were protected from the UV-B spectral range a loss of buoyancy was registered after 12 hours in the simulator. No diffcrences in DNA integrity as determined by DNA unwinding of exposed and control embryos were found. Also with lower amounts of irradiation in the 1996 experiments dosage dependent acute mortality, malformations, and impact on the buoyancy of the emhryos was registered. Sublethal effects occurred as well in embryos protected against UV-B in the exposure chambers, but were not found in the dark controls. The impact of low dosages of UV-B on the buoyancy of pelagic fish embryos might indicate an important ecological threat and deserves further studies.

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Changes in sustainability of aquatic ecosystems are likely to be brought about by the global warming that has been widely predicted. In this article, the effects of water temperature on water-bodies (lakes, oceans and rivers) are reviewed followed by the effects of temperature on aquatic organisms. Almost all aquatic organisms require exogenous heat before they can metabolise efficiently. An organism that is adapted to warm temperatures will have a higher rate of metabolism of food organisms and this increases feeding rate. In addition, an increase in temperature raises the metabolism of food organisms, so food quality can be altered. Where populations have a different tolerance to temperature the result is habitat partitioning. One effect of prolonged high temperature is that it causes water to evaporate readily. In the marine littoral this is not an important problem as tides will replenish water in pools. Small rain pools are found in many tropical countries during the rainy season and these become incompletely dried at intervals. The biota of such pools must have resistant stages within the life cycle that enable them to cope with periods of drying. The most important potential effects of global warming include (i) the alteration of existing coastlines, (ii) the development of more deserts on some land masses, (iii) higher productivity producing higher crop production but a greater threat of algal blooms and (iv) the processing of organic matter at surface microlayers.

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Experimental stocking density of Macrobrachium rosenbergii in larval rearing was conducted in A.G. Aqua Hatchery, Chakaria, Bangladesh to study the effect of different stocking densities on growth, survival rate and diseases stress under hatchery condition. The research work was conducted using six cemented rectangular tanks having 3m3 capacity (1.5mX2mX1m) each. Stocking density were maintained in three experimental setup as 200, 150 and 100ind/L of the T1, T2 and T3 respectively with one replicate each. The larvae were fed with Artemia nauplii, Custard, Maxima and brine shrimp flakes. Water quality was maintained by exchanging 20-30% (12ppt saline water) daily. During the study period, temperature, pH, DO, salinity, nitrite-nitrogen, ammonia and alkalinity were maintained from 28.5-31.5ºC, 7.5-7.8, 5.8-5.9mg/L, 12-13ppt, 0.14-0.2 mg/L, 0.22-0.3mg/L, and 140-160mg/L respectively. The growth rates of larvae at 11th stage were recorded in terms of body length 0.115, 0.136, and 0.169 mm/day whereas body weight were observed 0.000115, 0.000180, and 0.000240g/day. The survival rate of larvae were found 21.8%, 30.4% and 51.3% in treatments T1, T2 and T3 respectively. PL was obtained as 43, 45, and 51PL/L and days required of 41, 38 and 34 days in stocking density of 200, 150, and 100ind/L respectively. It was found that the minimum of 34 days was required to attain the PL (12th stage) using the stocking density of 100 individuals/L. Cannibalism, Zoothamnium, Exuvia Entrapment Disease (EED), and Bacterial Necrosis (BN) were found to be the threat to the commercial hatchery operation that might responsible for potential larval damages which can be reduced by lowering the stocking densities in larval rearing tank that also increased the survival and growth rate.

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In Europe, temporary ponds are a naturally common and widespread habitat occurring, often in abundance, in all biogeographical regions from the boreal snow-melt pools of northern Scandinavia to the seasonally inundated coastal dune pools of southern Spain. Ecological studies in Europe and elsewhere also emphasise that temporary ponds are a biologically important habitat type, renowned both for their specialised assemblages and the considerable numbers of rare and endemic species they support. They are, however, a habitat currently under considerable threat. Most temporary ponds are inherently shallow and the majority are destroyed even by limited soil drainage for agriculture or urban development. The paper gives an overview of definitions of temporary ponds and examines their formation and abundance. The authors also summarise a visit to the Bialowieza Forest in Poland to investigate the occurrence of temporary ponds.

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Signal crayfish (Pacifastacus leniusculus) have existed in the upper reaches of Broadmead Brook in Wiltshire since 200 individuals were introduced at West Kington in 1981. The population has expanded upstream and downstream since this introduction, however, giving rise to concerns that it may potentially threaten the native crayfish population further downstream. Signal crayfish can act as a vector of crayfish plague - a disease caused by the fungus Aphanomyces astaci Schikora which results in almost complete mortality to the native, white-clawed crayfish Austropotamobius pallipes. The native crayfish in Broadmead Brook have not yet succumbed to crayfish plague and are currently free of the disease. However, as signal crayfish appear to out-compete the native species, the native population could still be under threat. In this article, we highlight the findings of previous crayfish surveys on Broadmead Brook and describe work undertaken in summer 2001 to map the current distribution of native and signal crayfish. Finally, options for controlling the spread of signal crayfish are discussed.

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Amphibian declines and extinctions have been documented around the world, often in protected natural areas. Concern for this alarming trend has focused attention on the need to document all species of amphibians that occur within U.S. National Parks and to search for any signs that amphibians may be declining. This study, an inventory of amphibian species in Virgin Islands National Park, was conducted from 2001 to 2003. The goals of the project were to create a georeferenced inventory of amphibian species, use new analytical techniques to estimate proportion of sites occupied by each species, look for any signs of amphibian decline (missing species, disease, die-offs, etc.), and to establish a protocol that could be used for future monitoring efforts. Several sampling methods were used to accomplish these goals. Visual encounter surveys and anuran vocalization surveys were conducted in all habitats throughout the park to estimate the proportion of sites or proportion of area occupied (PAO) by amphibian species in each habitat. Line transect methods were used to estimate density of some amphibian species and double observer analysis was used to refine counts based on detection probabilities. Opportunistic collections were used to augment the visual encounter methods for rare species. Data were collected during four sampling periods and every major trail system throughout the park was surveyed. All of the amphibian species believed to occur on St. John were detected during these surveys. One species not previously reported, the Cuban treefrog (Osteopilus septentrionalis), was also added to the species list. That species and two others (Eleutherodactylus coqui and Eleutherodactylus lentus) bring the total number of introduced amphibians on St. John to three. We detected most of the reptile species thought to occur on St. John, but our methods were less suitable for reptiles compared to amphibians. No amphibian species appear to be in decline at this time. We found no evidence of disease or of malformations. Our surveys provide a snapshot picture of the status of the amphibian species, so continued monitoring would be necessary to determine long-term trends, but several potential threats to amphibians were identified. Invasive species, especially the Cuban treefrog, have the potential to decrease populations of native amphibians. Introduced mammalian predators are also a potential threat, especially to the reptiles of St. John, and mammalian grazers might have indirect effects on amphibians and reptiles through habitat modification. Finally, loss of habitat to development outside the park boundary could harm some important populations of amphibians and reptiles on the island.