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31.
Abstract:  Managing areas designed for human recreation so that they are compatible with natural amphibian populations can reduce the negative impacts of habitat destruction. We examined the potential for amphibians to complete larval development in golf course ponds in the presence or absence of overwintered bullfrog tadpoles ( Rana catesbeiana ), which are frequently found in permanent, human-made ponds. We reared larval American toads ( Bufo americanus ), southern leopard frogs ( R. sphenocephala ), and spotted salamanders ( Ambystoma maculatum ) with 0 or 5 overwintered bullfrog tadpoles in field enclosures located in ponds on golf courses or in experimental wetlands at a reference site. Survival to metamorphosis of American toads, southern leopard frogs, and spotted salamanders was greater in ponds on golf courses than at reference sites. We attributed this increased survival to low abundance of insect predators in golf course ponds. The presence of overwintered bullfrogs, however, reduced the survival of American toads, southern leopard frogs, and spotted salamanders reared in golf course ponds, indicating that the suitability of the aquatic habitats for these species partly depended on the biotic community present. Our results suggest that ponds in human recreational areas should be managed by maintaining intermediate hydroperiods, which will reduce the presence of bullfrog tadpoles and predators, such as fish, and which may allow native amphibian assemblages to flourish.  相似文献   
32.
Species that are strong interactors play disproportionately important roles in the dynamics of natural ecosystems. It has been proposed that their presence is necessary for positively shaping the structure and functioning of ecosystems. We evaluated this hypothesis using the case of the world's largest parrotfish (Bolbometopon muricatum), a globally imperiled species. We used direct observation, animal tracking, and computer simulations to examine the diverse routes through which B. muricatum affects the diversity, dispersal, relative abundance, and survival of the corals that comprise the foundation of reef ecosystems. Our results suggest that this species can influence reef building corals in both positive and negative ways. Field observation and simulation outputs indicated that B. muricatum reduced the abundance of macroalgae that can outcompete corals, but they also feed directly on corals, decreasing coral abundance, diversity, and colony size. B. muricatum appeared to facilitate coral advancement by mechanically dispersing coral fragments and opening up bare space for coral settlement, but they also damaged adult corals and remobilized a large volume of potentially stressful carbonate sediment. The impacts this species has on reefs appears to be regulated in part by its abundance—the effects of B. muricatum were more intense in simulation scenarios populated with high densities of these fish. Observations conducted in regions with high and low predator (e.g., sharks) abundance generated results that are consistent with the hypothesis that these predators of B. muricatum may play a role in governing their abundance; thus, predation may modulate the intensity of the effects they have on reef dynamics. Overall our results illustrate that functionally unique and threatened species may not have universally positive impacts on ecosystems and that it may be necessary for environmental managers to consider the diverse effects of such species and the forces that mediate the strength of their influence. Efectos Positivos y Negativos de un Pez Loro Amenazado Sobre Ecosistemas Arrecifales  相似文献   
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34.
ALEX DE WAAL 《Disasters》1996,20(3):194-205
The links between certain kinds of political systems and protection against famine are investigated in this paper. The starting-point is a critique of Amartya Sen's observation that famines are unknown in countries with a free press and competitive elections. This holds true only in India because of a unique political history in which freedom from famine became a right, upon which political legitimacy was founded: an anti-famine 'social contract'.
The rise and decline of anti-famine systems in Africa is charted. Major reasons for decay include neo-liberalism and the international humanitarian system, both of which undermine relationships of domestic political accountability that underpin effective famine prevention. A number of politically regressive tendencies in 'actually existing humanitarianism' are identified that work against any nascent anti-famine social contracts in Africa. This is possible because famine prevention has not been established as a right in Africa.  相似文献   
35.
Protecting Tourists from Death and Injury in Coastal Storms   总被引:3,自引:0,他引:3  
Hurricanes, typhoons, tsunamis and other storms force thousands to flee coastal regions every year. In many cases, resort areas have been severely damaged and tourists placed in jeopardy. This article examines ways tourist businesses can and already have protected holiday-makers from coastal storm hazards through emergency evacuation and other measures. Using data from a sample of large and small hotels in New Orleans, Louisiana, we find considerable variation in protective behaviour. To explain this variation, we look at how perceptions and preparedness differ by both managerial and organisational characteristics. We then suggest a variety of measures that can be taken by hotels in coastal resort areas to reduce risk.  相似文献   
36.
6 tons C were released to the atmosphere during the period of time covered by our study, equal to approximately 34% of the 1975 vegetation C pool. The Chiapas highlands, while comprising just 0.3% of Mexico's surface area, contributed 3% of the net national C emissions.  相似文献   
37.

Solid phase microextraction (SPME) was used for the extraction of residual coumaphos and dichlorvos in whole milk. The residues were analyzed by capillary gas chromatography equipped with nitrogen phosphorus detector (GC-NPD). A manual SPME holder with a 100-μm polyacrylate fiber was used. The optimized conditions for extraction by SPME method were: sample agitation, absorption temperature of 30°C, absorption time of 40 min, desorption time of 10 min, and sample volume was 16.0 mL in the vial. Under these conditions, the calibration graphs were linear in the range of 0.17 μgL?1 to 1.75 μgL?1 for coumaphos and 0.69 μgL?1 to 6.90 μgL?1 for dichlorvos. Precision was good with RSD values of 13% for coumaphos and 14% for dichlorvos. The detection limits (LOD) were 0.060 μgL?1 for dichlorvos and 0.052 for coumaphos. The quantification limits (LOQ) were 0.086 μgL?1 for dichlorvos and 0.066 μgL?1 for coumaphos. The results obtained in this study suggest that SPME is a suitable technique for residual pesticide analysis of milk. The data demonstrate that particular OP pesticides used in dairy farming in the region of Minas Gerais were found to contaminate cow whole milk, and the residues are not removed by treating the milk by boiling.  相似文献   
38.
北京雾霾天气期间气溶胶光学特性   总被引:17,自引:11,他引:17  
为了解北京地区雾霾天气条件下大气气溶胶的光学特性,利用2002~2008年AERONET资料分析了雾霾天气期间气溶胶光学厚度、Angstrom波长指数、粒子尺度谱分布和单次散射反照率等气溶胶光学特性参数.结果表明,北京地区雾霾天气期间气溶胶光学厚度表现出较高值,且随波长增大而减小,440 nm时平均气溶胶光学厚度达到1.34.Angstrom波长指数在雾霾天气时也表现出较高值,平均值达到1.11;其中高于0.9的波长指数出现频率达到94%,说明北京雾霾天气期间气溶胶粒子主要以细粒子为主.气溶胶体积尺度谱分布表现出双峰型结构,细模态的平均峰值半径随光学厚度增大而增大,而粗模态的平均峰值半径却随光学厚度增大表现出减小趋势;气溶胶粒子尺度谱中的主模态峰与光学厚度有关.雾霾天气期间平均单次散射反照率达到0.89,且随光学厚度增大表现出依次增大趋势,但对波长变化表现不敏感.  相似文献   
39.
A major question in global environmental policy is whether schemes to reduce carbon pollution through forest management, such as Reducing Emissions from Deforestation and Degradation (REDD+), can also benefit biodiversity conservation in tropical countries. We identified municipalities in Brazil that are priorities for reducing rates of deforestation and thus preserving carbon stocks that are also conservation targets for the endangered jaguar (Panthera onca) and biodiversity in general. Preliminary statistical analysis showed that municipalities with high biodiversity were positively associated with high forest carbon stocks. We used a multicriteria decision analysis to identify municipalities that offered the best opportunities for the conservation of forest carbon stocks and biodiversity conservation under a range of scenarios with different rates of deforestation and carbon values. We further categorized these areas by their representativeness of the entire country (through measures such as percent forest cover) and an indirect measure of cost (number of municipalities). The municipalities that offered optimal co‐benefits for forest carbon stocks and conservation were termed REDDspots (n = 159), and their spatial distribution was compared with the distribution of current and proposed REDD projects (n = 135). We defined REDDspots as the municipalities that offer the best opportunities for co‐benefits between the conservation of forest carbon stocks, jaguars, and other wildlife. These areas coincided in 25% (n = 40) of municipalities. We identified a further 95 municipalities that may have the greatest potential to develop additional REDD+ projects while also targeting biodiversity conservation. We concluded that REDD+ strategies could be an efficient tool for biodiversity conservation in key locations, especially in Amazonian and Atlantic Forest biomes. Identificación de Áreas en Brasil que Optimizan la Conservación del Carbono del Bosque, Jaguares y la Biodiversidad.  相似文献   
40.
Abstract:   We studied the conservation status of Atlantic forest birds in 43 forest fragments ranging in size from 1 to 384 ha in the Viçosa region of southeastern Brazil. We compared data from 15 years of field work with historical records from the region, mainly originating from specimens collected by João Moojen during the 1930s. We used published studies associated with museum data and current field work to assess the decline of forest birds during the last 70 years and to relate their disappearance to forest fragmentation and destruction. At least 28 bird species have become locally extinct, 43 are critically endangered, and 25 are vulnerable, representing 60.7% of the original forest bird community known to exist in the region. Vulnerability to fragmentation differed among guilds, forest strata, and endemicity status. Birds that feed on fruit and seeds, and those that feed on insects, were more threatened than omnivores and carnivores. Nectarivorous species were less threatened than other guilds. Moreover, terrestrial and understory birds or birds using only one forest stratum also were more likely to have been threatened. Finally, Atlantic forest endemics were more likely to have become extinct than nonendemic species. In general, sensitivity to environmental disturbance at the local level was similar to the predicted vulnerability to regional disturbance derived from the literature. Our results indicate that a serious decline of Atlantic forest birds is underway and that many other species of birds, not previously recognized as threatened, are of conservation concern .  相似文献   
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