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11.
Abstract: Most of the world's coral reefs line the coasts of developing nations, where impacts from intense and destructive fishing practices form critical conservation issues for managers. Overfishing of herbivorous fishes can cause phase shifts to macroalgal dominance, and fishers’ use of rocks as anchors lowers coral cover, giving further competitive advantage to macroalgae. Overfishing and anchoring have been studied extensively, but the role of their interaction in lowering coral reef resilience has not been quantified formally. We analyzed the combined effects of overfishing and rock anchoring on a range of reef habitat types—varying from high coral and low macroalgae cover to low coral and high macroalgae cover—in a marine park in Indonesia. We parameterized a model of coral and algal dynamics with three intensities of anchoring and fishing pressure. Results of the model indicated that damage caused by rock anchoring was equal to or possibly more devastating to coral reefs in the area than the impact of overfishing. This is an important outcome for local managers, who usually have the funds to distribute less‐damaging anchors, but normally are unable to patrol regularly and effectively enough to reduce the impact of overfishing. We translated model results into an interactive visual tool that allows managers to explore the benefits of reducing anchoring frequency and fishing pressure. The potential consequences of inaction were made clear: the likelihood that any of the reef habitats will be dominated in the future by macroalgae rather than corals depends on reducing anchoring frequency, fishing pressure, or both. The tool provides a platform for strengthened relationships between managers and conservationists and can facilitate the uptake of recommendations regarding resource allocation and management actions. Conservation efforts for coral reefs in developing nations are likely to benefit from transforming model projections of habitat condition into tools local managers can understand and interact with.  相似文献   
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13.
The Long-Term Effects of Tiger Poaching on Population Viability   总被引:4,自引:0,他引:4  
Poaching tigers, primarily for their bones, has become the latest threat to the persistence of wild tiger populations throughout the world. Anecdotal information indicates the seriousness of this new threat. It is important, however, to provide a quantitative analysis of poaching as a basis for strong policy action. We therefore created a tiger simulation model to explore the effects of realistic levels of poaching on population viability. The model is an individually based, stochastic spatial model that is based on the extensive data set from Royal Chitwan National Park, Nepal. We found that as poaching continues over time, the probability of population extinction increases sigmoidally; a critical zone exists in which a small, incremental increase in poaching greatly increases the probability of extinction. The implication is that poaching may not at first be seen as a threat but could suddenly become one. Moreover, even if poaching is effectively stopped, tiger populations will still be vulnerable and could go extinct due to demographic and environmental stochasticity. Our model also shows that poaching reduces genetic variability, which could further reduce population viability due to inbreeding depression. The longer poaching is allowed to continue, the more vulnerable a population will be to these stochastic events. At currently reported rates of poaching our analysis indicates that many wild tiger populations will be extirpated during the latter half of the 1990s.  相似文献   
14.
Indigenous, Colonist, and Government Impacts on Nicaragua's Bosawas Reserve   总被引:1,自引:0,他引:1  
Abstract:  We studied the impacts of colonists, two groups of indigenous residents (Miskitu and Mayangna), and management by the Nicaraguan Ministry of Environment and Natural Resources (MARENA) on the forest of the Bosawas International Biosphere Reserve. Indigenous people and colonists subsist on the natural resources of the reserve, and MARENA is responsible for protecting the area from colonization and illicit exploitation. Using geostatistical procedures and Landsat images at three different time periods, we compared per capita deforestation and boundary stabilization in areas with colonists and areas with indigenous peoples. We also examined whether the Mayangna deforested less than the Miskitu and whether the Nicaraguan government has effectively defended the Bosawas boundary against the advance of the agricultural frontier. In addition, we analyzed the current distribution of land uses within the reserve and its contiguous indigenous areas with a supervised classification of current land cover. Indigenous demarcations protected the forest successfully, whereas the Bosawas boundary itself did not inhibit colonization and consequent deforestation. Indigenous farmers deforested significantly less per capita than colonists, and the two indigenous groups in Bosawas did not differ significantly in their effects on the forest. Our results show that indigenous common-property institutions and indigenous defense of homeland have been powerful factors in protecting the forests of Bosawas and that the difficult evolution of a nested cross-scale governance system in Bosawas—under pressure from indigenous peoples—is probably the key to the forest ' s survival thus far.  相似文献   
15.
Abstract: Consideration of the social values people assign to relatively undisturbed native ecosystems is critical for the success of science‐based conservation plans. We used an interview process to identify and map social values assigned to 31 ecosystem services provided by natural areas in an agricultural landscape in southern Australia. We then modeled the spatial distribution of 12 components of ecological value commonly used in setting spatial conservation priorities. We used the analytical hierarchy process to weight these components and used multiattribute utility theory to combine them into a single spatial layer of ecological value. Social values assigned to natural areas were negatively correlated with ecological values overall, but were positively correlated with some components of ecological value. In terms of the spatial distribution of values, people valued protected areas, whereas those natural areas underrepresented in the reserve system were of higher ecological value. The habitats of threatened animal species were assigned both high ecological value and high social value. Only small areas were assigned both high ecological value and high social value in the study area, whereas large areas of high ecological value were of low social value, and vice versa. We used the assigned ecological and social values to identify different conservation strategies (e.g., information sharing, community engagement, incentive payments) that may be effective for specific areas. We suggest that consideration of both ecological and social values in selection of conservation strategies can enhance the success of science‐based conservation planning.  相似文献   
16.
Brazilian Protected Areas   总被引:3,自引:0,他引:3  
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17.
Wildlife crossing structures are one solution to mitigating the fragmentation of wildlife populations caused by roads, but their effectiveness in providing connectivity has only been superficially evaluated. Hundreds of grizzly (Ursus arctos) and black bear (Ursus americanus) passages through under and overpasses have been recorded in Banff National Park, Alberta, Canada. However, the ability of crossing structures to allow individual and population‐level movements across road networks remains unknown. In April 2006, we initiated a 3‐year investigation into whether crossing structures provide demographic connectivity for grizzly and black bears in Banff National Park. We collected hair with multiple noninvasive methods to obtain genetic samples from grizzly and black bears around the Bow Valley. Our objectives were to determine the number of male and female grizzly and black bears that use crossing structures; examine spatial and temporal patterns of crossings; and estimate the proportions of grizzly and black bear populations in the Bow Valley that use crossing structures. Fifteen grizzly (7 female, 8 male) and 17 black bears (8 female, 9 male) used wildlife crossing structures. The number of individuals detected at wildlife crossing structures was highly correlated with the number of passages in space and time. Grizzly bears used open crossing structures (e.g., overpasses) more often than constricted crossings (e.g., culverts). Peak use of crossing structures for both bear species occurred in July, when high rates of foraging activity coincide with mating season. We compared the number of bears that used crossings with estimates of population abundance from a related study and determined that substantial percentages of grizzly (15.0% in 2006, 19.8% in 2008) and black bear (17.6% in 2006, 11.0% in 2008) populations used crossing structures. On the basis of our results, we concluded wildlife crossing structures provide demographic connectivity for bear populations in Banff National Park. Conectividad Demográfica para Poblaciones de Úrsidos en Estructuras para Cruce de Vida Silvestre en el Parque Nacional Banff  相似文献   
18.
Abstract: The importance of biodiversity as natural capital for economic development and sustaining human welfare is well documented. Nevertheless, resource degradation rates and persistent deterioration of human welfare in developing countries is increasingly worrisome. Developing effective monitoring and evaluation schemes and measuring biodiversity loss continue to pose unique challenges, particularly when there is a paucity of historical data. Threat reduction assessment (TRA) has been proposed as a method to measure conservation success and as a proxy measurement of conservation impact, monitoring threats to resources rather than changes to biological parameters themselves. This tool is considered a quick, practical alternative to more cost‐ and time‐intensive approaches, but has inherent weaknesses. I conducted TRAs to evaluate the effectiveness of Kruger National Park (KNP) and Limpopo Province, South Africa, in mitigating threats to biodiversity from 1994 to 2004 in 4 geographical areas. I calculated TRA index values in these TRAs by using the original scoring developed by Margoluis and Salafsky (2001) and a modified scoring system that assigned negative mitigation values to incorporate new or worsening threats. Threats were standardized to allow comparisons across the sites. Modified TRA index values were significantly lower than values derived from the original scoring exercise. Five of the 11 standardized threats were present in all 4 assessment areas, 2 were restricted to KNP, 2 to Limpopo Province, and 2 only to Malamulele municipality. These results indicate, first, the need to integrate negative mitigation values into TRA scoring. By including negative values, investigators will be afforded a more accurate picture of biodiversity threats and of temporal and spatial trends across sites. Where the original TRA scoring was used to measure conservation success, reevaluation of these cases with the modified scoring is recommended. Second, practitioners must carefully consider the need and consequences of generalizing threats into generic categories for comparative assessments. Finally, continued refinement of the methodology and its extension to facilitate the transfer of successful conservation strategies is needed.  相似文献   
19.
Abstract:  Tanzania is a premier destination for trophy hunting of African lions (Panthera leo) and is home to the most extensive long-term study of unhunted lions. Thus, it provides a unique opportunity to apply data from a long-term field study to a conservation dilemma: How can a trophy-hunted species whose reproductive success is closely tied to social stability be harvested sustainably? We used an individually based, spatially explicit, stochastic model, parameterized with nearly 40 years of behavioral and demographic data on lions in the Serengeti, to examine the separate effects of trophy selection and environmental disturbance on the viability of a simulated lion population in response to annual harvesting. Female population size was sensitive to the harvesting of young males (≥3 years), whereas hunting represented a relatively trivial threat to population viability when the harvest was restricted to mature males (≥6 years). Overall model performance was robust to environmental disturbance and to errors in age assessment based on nose coloration as an index used to age potential trophies. Introducing an environmental disturbance did not eliminate the capacity to maintain a viable breeding population when harvesting only older males, and initially depleted populations recovered within 15–25 years after the disturbance to levels comparable to hunted populations that did not experience a catastrophic event. These results are consistent with empirical observations of lion resilience to environmental stochasticity .  相似文献   
20.
The delay in receiving authorisation for the despatch of SMART significantly reduced our overall effectiveness. The majority of injured survivors were extracted during this time and our special expertise could have saved a significant number of lives. The episode has provided SMART with unique experience for a British medical team and this knowledge should not be wasted. In contrast to other major western countries the British response was fragmented. We have no central stockpile of equipment and no official response team. The British who responded were independent of each other even when from the same service. The quality of the individual British teams was as good as any and often better. However, the ability of other nations to coordinate their response centrally and draw from a pool of workers already used to working together, improved both their efficiency and effectiveness. There are great difficulties in communication during any disaster and these increase with the scale of the disaster. Incoming rescue workers were given false or misleading information and rumour was widespread. Even when few people were found alive rescue workers expressed a strong need for a medical presence in case they discovered an injured person or they them selves became ill or injured. We were told repeatedly by experienced rescuers that we were the first team of British senior doctors they had met at the front line of a disaster and they were extremely pleased to see us. Transport was a major problem both in terms of vehicles and local knowledge. It was not thought to be within the remit of a medical team to make provision for food and shelter and this was confirmed in Moscow prior to departure for Yerevan. In retrospect this was a mistake and reduced the time we could stay at the front line. If we had not equipped ourselves with special clothing we could not have gone to the front line. A medical team must be part of larger team of rescue workers. Within this unit there will be provision for food, shelter, transport and communication as well as medical and surgical equipment.  相似文献   
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