829 resultados para habitat destruction
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After declining steadily for several decades, the South China tiger (Panthera tigris amoyensis) is now thought to be extinct in the wild. However, there is some hope of reintroduction, with Hupingshan-Houhe and Mangshan-Nanling National Nature Reserves in southern China seeming to hold the most promise. Our study used slope, elevation, vegetation, and landcover variables to construct a rough habitat suitability index for tigers in these two parks. According to our model, there are areas of suitable habitat within both parks. However, there are some important variables that we were unable to include in our model, such as human population density and prey availability. Considerable in-depth research will be necessary to evaluate the suitability of these locations before reintroduction is considered.
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The purpose of this study was to conduct a habitat suitability analysis of the critically endangered Florida panther (Felis concolor coryi) in Florida. We gathered land cover, population and road data from the Florida Geographic Data Library and performed map algebra using ESRI’s ArcGIS to compile a suitable habitat map. We found that there is 20381.7 km² of highly suitable habitat and 557124.4 km² of less desirable but usable habitat for the Florida panther. The highest concentration of highly suitable habitat is in Big Cypress National Park, with smaller patches in Tates Hell State Forest and along the southeast portion of the Panhandle. Due to extensive fragmentation, however, and without establishment of habitat linkages to the existing southern population, there is little chance of survival of additional panther populations in much of northern Florida.
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The South China tiger, Panthera tigris amoyensis, once roamed the greater part of southern China. However, expanding human populations and other anthropogenic effects have resulted in the extinction of the wild population. The Chinese government has expressed interest in a reintroduction program for this species of tigers. Recent studies suggest that the Hupingshan preserve is potentially a good candidate for a tiger reintroduction program. Hupingshan is located on the border of the Hunan and Hubei provinces in Southern China. This study was a preliminary habitat suitability analysis, for the restoration of South China tigers in the Hupingshan reserve, China. ArcGIS 9.0 was used to develop a model that combined roads, railroads, slope, land cover, park classification, and population density. The tiger habitat suitability analysis was performed by weighting and combining the various layers. Preliminary results suggest that the Hupingshan reserve is suitable habitat for the reintroduction of South China tigers.
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The Schumpelerian model of endogeno~s growlh is generalized with lhe introduction of stochastic resislance. by agenls other Ihan producers. to lhe innovations which drive growth. This causes a queue to be formcd of innovations, alrcady discovered, bUI waiting to be adopled~ A slationary stochastic equilibrium (SSE) is obtained when the queue is stable~ It is shown that in the SSE, such resistance will always reduce lhe average growth iate hut it may increa~e wclfare in certain silualions. In an example, Ihis is when innovatiuns are small anti monopoly power great. The cont1icl hetween this welfare motive for resistance and those of rent-seeking innovalors.may well explain why growth rates differ.
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We develop and quantitatively implement a dynamic general equilibrium model with labor market matching and endogenous deterllÚnation of the job destruction rate. The mo deI produces a elose match with data on job creation and destruction. Cyelical fluctuations in the job destruction rate serve to magnify the effects of productivity shocks on output; as well as making the effects much more persistent. Interactions between the labor and capital markets, mediated by the rental rate of capital, play the central role in propagating shocks.
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This paper introduces a model economy in which formation of coalition groups under technological progress is generated endogenously. The coalition formation depends crucially on the rate of arrival of new technologies. In the model, an agent working in the saroe technology for more than one period acquires skills, part of which is specific to this technology. These skills increase the agent productivity. In this case, if he has worked more than one period with the same technology he has incentives to construct a coalition to block the adoption of new technologies. Therefore, in every sector the workers have incentives to construct a coalition and to block the adoption of new technologies. They will block every time that a technology stay in use for more than one period.
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This thesis provides information on the grouping structure, survival, abundance, dive characteristics and habitat preferences of short-finned pilot whales occurring in the oceanic archipelago of Madeira (Portugal, NE Atlantic), based on data collected between 2001-2011, and contributes for its conservation. Photo-identification methods and genetic analyses demonstrated that there is a large degree of variability in site fidelity, including resident, regular visitor and transient whales, and that they may not be genetically isolated. It is proposed that the pilot whales encountered in Madeira belong to a single population encompassing several clans, possibly three clans of island-associated (i.e. resident and regular visitor) whales and others of transients, each containing two to three matrilineal pods. Mark-recapture methods estimated that the island-associated community is composed of less than 150 individuals and that their survival rate is within the range of other long-lived cetacean species, and that around 300 whales of different residency patterns uses the southern area of the island of Madeira from mid-summer to mid-autumn. No significant trend was observed between years. Time-depth recorders deployed in adult whales during daytime revealed that they spend over ¾ of their time at the surface, that they have a low diving rate, and that transient whales also forage during their passage. The analyses of visual data collected from nautical and aerial line-transect surveys indicate a core/preferred habitat area in the south-east of the island of Madeira. That area is used for resting, socializing, foraging, breeding, calving and birthing. Thus, that area should be considered as an important habitat for this species, at least seasonally (during autumn) when the species is more abundant, and included in conservation plans. No direct threat needing urgent measures was identified, although the impact of some activities like whale-watching or marine traffic should be assessed.
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The composition of termite assemblages was analyzed at three Caatinga sites of the Seridó Ecological Station, located in the municipality of Serra Negra do Norte, in the state of Rio Grande do Norte, Brazil. These sites have been subjected to selective logging, and cleared for pasture and farming. A standardized sampling protocol for termite assemblages (30h/person/site) was conducted between September 2007 and February 2009. At each site we measured environmental variables, such as soil granulometry, pH and organic matter, necromass stock, vegetation height, tree density, stem diameter at ankle height (DAH) and the largest and the smallest crown width. Ten species of termites, belonging to eight genera and three families, were found at the three experimental sites. Four feeding-groups were sampled: wood-feeders, soil-feeders, wood-soil interface feeders and leaf-feeders. The wood-feeders were dominant in number of species and number of encounters at all sites. In general, the sites were not significantly different in relation to the environmental variables measured. The same pattern was observed for termite assemblages, where no significant differences in species richness, relative abundance and taxonomic and functional composition were observed between the three sites. The agreement between the composition of assemblages and environmental variables reinforces the potential of termites as biological indicators of habitat quality
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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The inherent complexity of natural communities is a challenge to our understanding about how the habitat influences the abundance, local distribution and species diversity. The habitat can influence community structure in multiple ways and elucidate these relationships has provoked a lot of debate in ecology. The habitat heterogeneity hypothesis states that an increase in habitat heterogeneity (number of habitats) leads to an increase in species diversity in the landscape due to an expansion in niche dimensions. This study aims to identify whether this hypothesis is valid for the spiders that inhabit a locality in the Caatinga of northeastern Brazil. Cursorial and arboreal spiders were sampled in 30 plots within an area of Caatinga together with measures of environmental complexity, habitat heterogeneity and environmental parameters related to multiple aspects of vegetation architecture and species composition of woody plants. Stepwise multiple regressions were used to define which local environmental parameters best explain the variation in arboreal and cursorial spiders richness. Then a NMDS (Nonmetric multidimensional scaling) was used to reduce the number of predictive variables to those who are the most important and best represent the variation in spiders richness associated with the environment they were sampled. The results show a clear segregation between the guilds of arboreal and cursorial spiders, both related to what kind of environmental variables best explain its variation as well as in relation to what part of the vegetation they occupy
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)