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Habitat Destruction (habitat + destruction)
Selected AbstractsSpatial Tests of the Pesticide Drift, Habitat Destruction, UV-B, and Climate-Change Hypotheses for California Amphibian DeclinesCONSERVATION BIOLOGY, Issue 6 2002Carlos Davidson In California, the transport and deposition of pesticides from the agriculturally intensive Central Valley to the adjacent Sierra Nevada is well documented, and pesticides have been found in the bodies of Sierra frogs. Pesticides are therefore a plausible cause of declines, but to date no direct links have been found between pesticides and actual amphibian population declines. Using a geographic information system, we constructed maps of the spatial pattern of declines for eight declining California amphibian taxa, and compared the observed patterns of decline to those predicted by hypotheses of wind-borne pesticides, habitat destruction, ultraviolet radiation, and climate change. In four species, we found a strong positive association between declines and the amount of upwind agricultural land use, suggesting that wind-borne pesticides may be an important factor in declines. For two other species, declines were strongly associated with local urban and agricultural land use, consistent with the habitat-destruction hypothesis. The patterns of decline were not consistent with either the ultraviolet radiation or climate-change hypotheses for any of the species we examined. Resumen: Por mucho tiempo se ha sugerido que los pesticidas transportados por el viento son una causa de la declinación de anfibios en áreas sin destrucción de hábitat evidente. En California, el transporte y depósito de pesticidas provenientes del Valle Central, donde se practica la agricultura intensiva, hacia la Sierra Nevada adyacente está bien documentado y se han encontrado pesticidas en el cuerpo de ranas de la Sierra. Por lo tanto, los pesticidas son una causa verosímil de las declinaciones, pero a la fecha no se han encontrado relaciones directas entre los pesticidas y la declinación de anfibios. Construimos mapas de sistemas de información geográfica del patrón espacial de las declinaciones de ocho taxones de anfibios de California, y comparamos los patrones de declinación observados con los esperados por las hipótesis de pesticidas transportados por el viento, la destrucción del hábitat, la radiación ultravioleta y el cambio climático. En cuatro especies, encontramos una fuerte asociación positiva entre las declinaciones y la cantidad de tierras de uso agrícola en dirección contraria a los vientos, lo que sugiere que los pesticidas transportados por el viento pueden ser un factor importante en las declinaciones. Para otras dos especies, las declinaciones se asociaron contundentemente con el uso del suelo urbano y agrícola, lo cual es consistente con la hipótesis de la destrucción del hábitat. Los patrones de declinación no fueron consistentes con la hipótesis de la radiación ultravioleta ni la de cambio climático para ninguna de las especies examinadas. [source] Extinction debt on oceanic islandsECOGRAPHY, Issue 2 2010Kostas A. Triantis Habitat destruction is the leading cause of species extinctions. However, there is typically a time-lag between the reduction in habitat area and the eventual disappearance of the remnant populations. These "surviving but ultimately doomed" species represent an extinction debt. Calculating the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species,area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands, to calculate realistic and ecologically-adjusted species,area relationships. The results reveal dramatic and hitherto unrecognized levels of extinction debt, as a result of the extensive destruction of the native forest:>95%, in<600,yr. Our estimations suggest that more than half of the extant forest arthropod species, which have evolved in and are dependent on the native forest, might eventually be driven to extinction. Data on species abundances from Graciosa Island, where only a very small patch of secondary native vegetation still exists, as well as the number of species that have not been found in the last 45,yr, despite the extensive sampling effort, offer support to the predictions made. We argue that immediate action to restore and expand native forest habitat is required to avert the loss of numerous endemic species in the near future. [source] Globally threatened parrots: criteria, characteristics and curesINTERNATIONAL ZOO YEARBOOK, Issue 1 2000N.J. COLLAR Ninety (26%) of the world's parrot species are threatened with extinction. While this figure will vary with deteriorating circumstances, taxonomic insight and assessment of new evidence, the great majority (currently 93%) of threatened parrots are forest species, most (75 species, 83%) have populations estimated at less than 10 000 mature individuals, and many (37 species, 41%) have ranges %%20 000km2. Habitat destruction (notably the loss of nest-sites), trade, hunting and introduced species are significant threats. Indonesia, Australia, Brazil, the Philippines, Colombia and Mexico support two-thirds (60 species) of all threatened parrots. Conservation of sites with sympatric threatened parrots is required, alongside research and awareness programmes that enable site and species management. [source] Major histocompatibility complex class II variation in the giant panda (Ailuropoda melanoleuca)MOLECULAR ECOLOGY, Issue 9 2006QIU-HONG WAN Abstract Habitat destruction and human activity have greatly impacted the natural history of the giant panda (Ailuropoda melanoleuca). Although the genetic diversity of neutral markers has been examined in this endangered species, no previous work has examined adaptive molecular polymorphisms in the giant panda. Here, the major histocompatibility complex (MHC) class II DRB locus was investigated in the giant panda, using single-strand conformation polymorphism (SSCP) and sequence analysis. Comparisons of DNA samples extracted from faecal and blood samples from the same individual revealed that the two materials yielded similar quantities and qualities of DNA, as well as identical SSCP patterns and allelic sequences, demonstrating the reliability of DNA isolation from panda faeces. Analysis of faecal samples from 60 giant pandas revealed relatively low number of alleles: seven alleles. However, the alleles were quite divergent, varying from each other by a range of 7,47 nucleotide substitutions (4,25 amino acid substitutions). Construction of a neighbour-joining tree and comparisons among DRB alleles from other species revealed that both similar and highly divergent alleles survived in the bottlenecked panda populations. Despite species-specific primers used and excellent faecal DNA isolated, a lower level of heterozygosity than expected was still observed due to inbreeding. There were three types of evidence supporting the presence of balancing selection in the giant panda: (i) an obvious excess of nonsynonymous substitutions over synonymous at the antigen-binding positions; (ii) trans -species evolution of two alleles between the giant panda and other felids; and (iii) a more even distribution of alleles than expected from neutrality. [source] Suitability of Golf Course Ponds for Amphibian Metamorphosis When Bullfrogs Are RemovedCONSERVATION BIOLOGY, Issue 1 2008MICHELLE D. BOONE charcas en campos de golf; competencia; depredación; metamorfosis de anfibios; Rana catesbeiana 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. Resumen:,El manejo de áreas diseñadas para la recreación humana de manera que sean compatibles con las poblaciones naturales de anfibios puede reducir los impactos negativos de la destrucción del hábitat. Examinamos el potencial de anfibios para completar el desarrollo larvario en lagos en campos de golf en presencia o ausencia de renacuajos de Rana catesbeiana, que frecuentemente son encontrados en charcas artificiales permanentes. Criamos sapos (Bufo americanus), ranas (R. sphenocephala) y salamandras manchadas (Ambystoma maculatum) con cero o cinco renacuajos de R. catesbeiana en encierros localizados en charcas en campos de golf o en humedales experimentales en un sitio de referencia. La supervivencia hasta la metamorfosis de B. americanus, R. sphenocephala y A. maculatum fue mayor en los campos de golf que en los sitios de referencia. Atribuimos este incremento en la supervivencia a la baja abundancia de insectos depredadores en las charcas de los campos de golf. Sin embargo, la presencia de renacuajos de R. catesbeiana redujo la supervivencia de B. americanus, R. sphenocephala y A. maculatum en los campos de golf, indicando que el beneficio de los hábitats acuáticos para estas especies dependía parcialmente de la comunidad biótica presente. Nuestros resultados sugieren que las charcas en áreas recreativas deberían ser manejadas manteniendo hidroperíodos intermedios, que reducirían la presencia de renacuajos de R. catesbeiana y de depredadores, como peces, y que permitirían que florezcan ensambles de anfibios nativos. [source] Spatial Tests of the Pesticide Drift, Habitat Destruction, UV-B, and Climate-Change Hypotheses for California Amphibian DeclinesCONSERVATION BIOLOGY, Issue 6 2002Carlos Davidson In California, the transport and deposition of pesticides from the agriculturally intensive Central Valley to the adjacent Sierra Nevada is well documented, and pesticides have been found in the bodies of Sierra frogs. Pesticides are therefore a plausible cause of declines, but to date no direct links have been found between pesticides and actual amphibian population declines. Using a geographic information system, we constructed maps of the spatial pattern of declines for eight declining California amphibian taxa, and compared the observed patterns of decline to those predicted by hypotheses of wind-borne pesticides, habitat destruction, ultraviolet radiation, and climate change. In four species, we found a strong positive association between declines and the amount of upwind agricultural land use, suggesting that wind-borne pesticides may be an important factor in declines. For two other species, declines were strongly associated with local urban and agricultural land use, consistent with the habitat-destruction hypothesis. The patterns of decline were not consistent with either the ultraviolet radiation or climate-change hypotheses for any of the species we examined. Resumen: Por mucho tiempo se ha sugerido que los pesticidas transportados por el viento son una causa de la declinación de anfibios en áreas sin destrucción de hábitat evidente. En California, el transporte y depósito de pesticidas provenientes del Valle Central, donde se practica la agricultura intensiva, hacia la Sierra Nevada adyacente está bien documentado y se han encontrado pesticidas en el cuerpo de ranas de la Sierra. Por lo tanto, los pesticidas son una causa verosímil de las declinaciones, pero a la fecha no se han encontrado relaciones directas entre los pesticidas y la declinación de anfibios. Construimos mapas de sistemas de información geográfica del patrón espacial de las declinaciones de ocho taxones de anfibios de California, y comparamos los patrones de declinación observados con los esperados por las hipótesis de pesticidas transportados por el viento, la destrucción del hábitat, la radiación ultravioleta y el cambio climático. En cuatro especies, encontramos una fuerte asociación positiva entre las declinaciones y la cantidad de tierras de uso agrícola en dirección contraria a los vientos, lo que sugiere que los pesticidas transportados por el viento pueden ser un factor importante en las declinaciones. Para otras dos especies, las declinaciones se asociaron contundentemente con el uso del suelo urbano y agrícola, lo cual es consistente con la hipótesis de la destrucción del hábitat. Los patrones de declinación no fueron consistentes con la hipótesis de la radiación ultravioleta ni la de cambio climático para ninguna de las especies examinadas. [source] Land-cover and land-use change and its contribution to the large-scale organization of Puerto Rico's bird assemblagesDIVERSITY AND DISTRIBUTIONS, Issue 1 2008Miguel A. Acevedo ABSTRACT Global biodiversity is changing rapidly driven by human alteration of habitat, and nowhere this is more dramatic than in insular habitats. Yet land-cover change is a complex phenomenon that not only involves habitat destruction but also forest recovery over different time scales. Therefore, we might expect species to respond in diverse ways with likely consequences for the reorganization of regional assemblages. These changes, however, may be different in tropical islands because of their low species richness, generalist habits and high proportion of endemics. Here, we focus on the island of Puerto Rico and ask how island-wide changes in land cover and land use has influenced the large-scale organization of bird assemblages. To address this question, we combined in a Geographical Information System (GIS) the first 6 years (1997,2002) of the Puerto Rican Breeding Bird Survey (PR-BBS) with land-cover and land-use data extracted from a published digital map derived from the classification of Landsat images. A Non-metric Multidimensional Scaling (NMS) ordination based on the composition and abundance of birds, and percentage land-use types showed that land use followed by climate could explain most of the variation observed among routes in terms of species composition and abundance. Moreover, endemic and exotic species were widely distributed throughout the island, but the proportion of endemic species is higher in closed forests while exotic species are more abundant in open habitats. However, historical accounts from the early 1900s indicate that endemic species were distributed across the entire island. Today, most of the land cover transformation in Puerto Rico occurs in the lowlands which may explain the high abundance of endemic species in cloud forests and the high abundance of exotic species in open habitats in the lowlands. [source] Nutritional consequences of a change in diet from native to agricultural fruits for the Samoan fruit batECOGRAPHY, Issue 4 2000Suzanne L. Nelson The Samoan fruit bat Pteropus samoensis Peak, an endemic flying fox that inhabits the Samoan archipelago, prefers to forage on native fruit species. This species has recently been subjected to extreme population threats including hunting and severe storms, as well as large-scale habitat degradation. If habitat destruction continues at its present rate, P. samoensis may be forced to forage more within an agricultural matrix. In this study, we analyzed sixteen species of native fruits and four species of agricultural fruits for five organic components and eight minerals to test whether native fruits provided a higher quality diet or more varied diet than agricultural fruits. Within native fruits, we also focused on four species of figs, because these fruits are often considered an important food item for tropical frugivores. Overall, native fruits provided more variation and had higher average values for several nutrients than agricultural fruits. Native fruits were especially high in biologically important minerals (calcium, iron, and sodium), and provided up to 5 times more calcium, 10.5 times more iron, and 8 times more sodium than agricultural fruits. Figs were found to be an especially rich source of many nutrients, particularly for calcium. Thus. P. samoensis. a sequential specialist, may be better able to adjust its diet to obtain higher levels of minerals when consuming a variety of native fruits than when restricted to the consumption of only agricultural fruits. These findings suggest a need to preserve native habitat and to create parks to sustain the long term health and viability of P. samoensis. [source] Spatial and temporal variations of two cyprinids in a subtropical mountain reserve , a result of habitat disturbanceECOLOGY OF FRESHWATER FISH, Issue 3 2007C.-C. Han Abstract,,, We investigated the variations of population of two cyprinids, Varicorhinus alticorpus and Varicorhinus barbatulus, using long-term survey data (1995,2004) in the subtropical island of Taiwan. Fish abundance data showed that at the mainstem stations, V. barbatulus which used to dominate in the higher altitude had declined significantly, while V. alticorpus that used to occupy only the lower altitude had spread upward. However, at the tributaries, trend of the populations of V. barbatulus were not significantly different over time, while populations of V. alticorpus were absent at higher altitude but began to increase at lower altitude. Environmental parameters revealed that sporadic high turbidity was observed at the mainstem stations, but not at the tributaries. Images taken before and after typhoon also showed habitat destruction by debris flow at the mainstem stations. As some models predicted that suitable fish habitats will shrink because of increasing water temperature due to global warming, we showed that fish distribution may be affected by habitat disturbance due to intensified storms sooner than the actual increase of water temperature. [source] Small and large anemonefishes can coexist using the same patchy resources on a coral reef, before habitat destructionJOURNAL OF ANIMAL ECOLOGY, Issue 5 2002Akihisa Hattori Summary 1According to meta-population models, a superior competitor and a superior disperser can coexist in a patchy environment. The two anemonefishes, a large aggressive Amphiprion clarkii Bennett and a small less-aggressive A. perideraion Bleeker, use the same host anemone Heteractis crispa Ehrenberg on a coral reef, Okinawa, Japan, where most of the hosts disappeared after the coral bleaching in 1998. Their microhabitat (host) use and coexistence, and the quality and quantity of microhabitats were investigated in 1988, 1989, 1999 and 2000 on the coral reef. Their interspecific interaction was also examined. 2Before the habitat destruction, the two species coexisted. Although A. clarkii was behaviourally dominant over A. perideraion in a cohabiting group, A. perideraion was a superior competitor in terms of site displacement, because A. perideraion could displace a microhabitat. Adult A. clarkii emigrated from a cohabiting group probably due to the high cost of interactions with adult A. perideraion . Although it is easier to defend a small area for a larger species, sharing a host with adult A. perideraion may not pay for A. clarkii because A. clarkii needs a larger area. 3A. clarkii was not only a superior disperser, which was able to find a vacated host, but also a pioneer species that was able to use newly settled small hosts. Larval A. clarkii settled on such a small host because they were able to move to larger hosts for future reproduction, while A. perideraion did not settle on a small host because of low mobility after settlement. Microhabitat (host) with various sizes might have promoted their coexistence. 4After the habitat destruction, the superior competitor A. perideraion went extinct locally due probably to lack of small host utilization ability. The present study implies that the difference in body size between the two competitors plays an important role in their coexistence, because species with different body sizes can have different mobility and require different amounts of resources. [source] GUEST EDITORIAL: The interplay of pollinator diversity, pollination services and landscape changeJOURNAL OF APPLIED ECOLOGY, Issue 3 2008Ingolf Steffan-Dewenter Summary 1Pollinators are a functional group with high relevance for ensuring cross-pollination in wild plant populations and yields in major crops. Both pollinator declines and losses of pollination services have been identified in the context of habitat destruction and land use intensification. 2This editorial synthesizes and links the findings presented in seven papers in this Special Profile, focusing on pollinator diversity and plant,pollinator interactions in natural habitats and agricultural landscapes. 3The results contribute to our understanding of local and landscape scale effects of land use intensification on pollinator densities and diversity, and pollination functions in wild plant communities and crops. 4Synthesis and applications. We emphasize the exceptional coverage in pollination ecology ranging from basic ecological relationships to applied aspects of ecosystem services and ecosystem management, and conclude with identifying gaps in current knowledge and challenging research areas for the future. [source] Effects of habitat history and extinction selectivity on species-richness patterns of an island land snail faunaJOURNAL OF BIOGEOGRAPHY, Issue 10 2009Satoshi Chiba Abstract Aim, Local-scale diversity patterns are not necessarily regulated by contemporary processes, but may be the result of historical events such as habitat changes and selective extinctions that occurred in the past. We test this hypothesis by examining species-richness patterns of the land snail fauna on an oceanic island where forest was once destroyed but subsequently recovered. Location, Hahajima Island of the Ogasawara Islands in the western Pacific. Methods, Species richness of land snails was examined in 217 0.25 × 0.25 km squares during 1990,91 and 2005,07. Associations of species richness with elevation, current habitat quality (proportion of habitat composed of indigenous trees and uncultivated areas), number of alien snail species, and proportion of forest loss before 1945 in each area were examined using a randomization test and simultaneous autoregressive (SAR) models. Extinctions in each area and on the entire island were detected by comparing 2005,07 records with 1990,91 records and previously published records from surveys in 1987,91 and 1901,07. The association of species extinction with snail ecotype and the above environmental factors was examined using a spatial generalized linear mixed model (GLMM). Results, The level of habitat loss before 1945 explained the greatest proportion of variation in the geographical patterns of species richness. Current species richness was positively correlated with elevation in the arboreal species, whereas it was negatively correlated with elevation in the ground-dwelling species. However, no or a positive correlation was found between elevation and richness of the ground-dwelling species in 1987,91. The change of the association with elevation in the ground-dwelling species was caused by greater recent extinction at higher elevation, possibly as a result of predation by malacophagous flatworms. In contrast, very minor extinction levels have occurred in arboreal species since 1987,91, and their original patterns have remained unaltered, mainly because flatworms do not climb trees. Main conclusions, The species-richness patterns of the land snails on Hahajima Island are mosaics shaped by extinction resulting from habitat loss more than 60 years ago, recent selective extinction, and original faunal patterns. The effects of habitat destruction have remained long after habitat recovery. Different factors have operated during different periods and at different time-scales. These findings suggest that historical processes should be taken into account when considering local-scale diversity patterns. [source] An ecological study of the relationship between two living fossils in Malawi: the Mulanje Tiger Moth (Callioratis grandis) and the Mulanje Cycad (Encephalartos gratus)AFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Julian Bayliss Abstract The Mulanje tiger moth (Callioratis grandis) has recently been discovered feeding solely on the Mulanje Cycad, Encephalartos gratus. In its type locality Encephalartos gratus is severely threatened through habitat destruction and human population growth. As a result the first detailed demographic survey of Encephalartos gratus on Mount Mulanje was undertaken with particular emphasis on the relationship between E. gratus and Callioratis grandis. What is unusual about C. grandis is that the males exhibit lekking behaviour, for which aposematism may be a prerequisite. Cycads were surveyed in a systematic manner. Both the biotic and abiotic parameters were recorded from 532 wild Encephalartos gratus. Results showed the morphological range of measurements differed from that of previously published literature on this species. Results also showed that the incidence of Callioratis larval damage was related to the maturity of the wild cycads , moth damage was greater on more mature plants. Approximately 50% of surveyed cycads showed evidence of Callioratis moth damage, however, there was no apparent preference from the moth to select either male or female cycads as food plants for the larvae. In some cases there was severe damage to cycad fronds, but this did not seem to affect the production of reproductive cones or even the survival of individual cycads. Résumé On a découvert récemment que le papillon du Mulanje (Callioratis grandis) ne se nourrit que sur le cycadale Mulanje Encephalartos gratus. Dans son milieu type, Encephalartos gratus est gravement menacé dans la nature à cause de la destruction de l'habitat et de la croissance de la population humaine. Par conséquent, la première étude démographique détaillée d'Encephalartos gratus réalisée sur le mont Mulanje fut entreprise en insistant particulièrement sur la relation entre Encephalartos gratus et Callioratis grandis. Ce qui est inhabituel chez C. grandis, c'est que les mâles présentent un comportement territorial (lek). Les cycadales ont été systématiquement surveillées. On a enregistré les paramètres biotiques et abiotiques pour 532 Encephalartos gratus poussant dans la nature. Les résultats ont montré que l'amplitude des mesures morphologiques différait de ce que la littérature existante décrit sur cette espèce. Ils ont aussi montré que l'incidence des dommages causés par les larves de Callioratisétait liée à la maturité des cycadales sauvages , les dégâts causés par les papillons étaient plus graves sur les plants plus matures. Environ 50% des cycadales suivis montraient des traces de dommages causés par ce papillon, mais il n'y avait pas de preuve qui aurait pu montrer que le papillon sélectionnait des cycadales mâles ou femelles pour en nourrir ses larves. Dans certains cas, il y avait des dégâts sérieux dans les feuilles de cycadales; cependant, cela ne semblait pas affecter la production de cônes reproducteurs, pas plus que la survie des individus. [source] Exploitation of Encephalartos transvenosus outside and inside Mphaphuli Cycads Nature Reserve, Limpopo Province, South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2010A. M. Ravele Abstract This study has investigated the use and threats of Encephalartos transvenosus outside and inside Mphaphuli Cycads Nature Reserve, Limpopo Province, South Africa. Data were collected from 2005 to 2006 through social and ecological surveys. Semi-structured interviews were conducted with a total of 40 people per household, sampled from four selected villages around the reserve. E. transvenosus is used for medicinal purposes, decorations, cultural activities and as food. Youth and adult persons harvest E. transvenosus for income generation, while children and aged people mainly use it for subsistence purposes. The survival of E. transvenosus in the wild is uncertain due to various threats, such as illegal collection, habitat destruction, fire and grazing. Some conservation measures are also discussed. Résumé Cet article rapporte les recherches sur l'utilisation et les menaces sur E. transvenosus en dehors et à l'intérieur de la Mphaphuli Cycads Nature Reserve, dans la Province du Limpopo, en Afrique du Sud. Des données ont été récoltées de 2005 à 2006 via des enquêtes sociales et écologiques. Des interviews semi structurées ont été menées chez un total de 40 personnes, par ménage, pris au hasard dans quatre villages choisis autour de la réserve. E. transvenosus est utiliséà des fins médicinales, pour la décoration, des activités culturelles et l'alimentation. Jeunes et adultes récoltent E. transvenosus pour en tirer des revenus, tandis que les enfants et les vieilles personnes les utilisent beaucoup pour leur subsistance. La survie d'E. transvenosus dans la nature est incertaine en raison de diverses menaces telles que la récolte illégale, la destruction de l'habitat, les feux et le pâturage. Certaines mesures de conservation furent aussi discutées. [source] Urban ecological footprints in AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2008Joy S. Clancy Abstract Africa's rate of urbanization is the highest in the world. This is relevant to ecologists working in Africa because urban growth is strongly associated with habitat destruction, and also creates new fields of study. The ecological footprint concept is used to illustrate how urban settlements in Africa impact on rural ecosystems. At an aggregate level, African countries have the lowest ecological footprints in the world. However, there is little available data for individual cities, so evidence is fragmented making concerted policy initiatives difficult. Wood fuel continues to be a major source of energy for urban households and there is a long running debate as to what extent providing wood fuel for urban use damages forest ecosystems. Growing evidence contests the assertion that urban wood fuel markets are responsible for forest degradation. Although there are other options available, the social consequences of switching energy sources need to be taken into account. Outright bans, for example on charcoal, would lead to a loss of livelihoods in rural and urban households, and may not solve deforestation as well as increasing fossil fuel use would increase the ecological footprint. Résumé Le taux d'urbanisation de l'Afrique est le plus élevé du monde. Cela concerne les écologistes qui travaillent sur ce continent parce que la croissance urbaine est étroitement liée à la destruction des habitats, et cela ouvre aussi de nouveaux champs d'étude. Le concept d'empreinte écologique est utilisé pour illustrer comment les installations urbaines en Afrique ont un impact sur les écosystèmes ruraux. Pris tous ensemble, ce sont les pays africains qui ont la plus légère empreinte écologique du monde. Cependant, nous disposons de peu de données pour des villes individuelles, de sorte que les renseignements sont fragmentés et qu'il est difficile de prendre des initiatives politiques concertées. Le bois de feu continue àêtre une des principales sources d'énergie pour les ménages urbains, et il existe un débat de longue haleine quant à savoir dans quelle mesure l'approvisionnement en bois pour la consommation urbaine endommage les écosystèmes forestiers. Des preuves de plus en plus évidentes remettent en question l'assertion selon laquelle les marchés urbains de bois de feu seraient responsables de la dégradation des forêts. Bien qu'il y ait d'autres options possibles, il faut prendre en compte les conséquences sociales du passage à d'autres sources d'énergie. Les interdictions totales, par exemple du charbon de bois, entraîneraient la perte des moyens de subsistance de ménages ruraux et urbains, et pourraient ne pas résoudre le problème de déforestation, tout comme l'utilisation accrue des combustibles fossiles augmenterait l'empreinte écologique. [source] Floral free fall in the Swiss lowlands: environmental determinants of local plant extinction in a peri-urban landscapeJOURNAL OF ECOLOGY, Issue 4 2007IVANA STEHLIK Summary 1Local floras are being depleted by a host of human activities, including habitat destruction and fragmentation, eutrophication, and the intensification of agriculture. Species with particular ecological demands or life-history attributes are more prone to extinction than species with a broader niche. 2We used an old herbarium from the municipality of Küsnacht (Swiss lowlands) as a historical record for comparison with contemporary plant diversity. This comparison revealed that 17% to 28% of all vascular plants that occurred between 1839 and 1915 were extinct by 2003. 3Species of different habitats and life-forms had significantly different rates of extinction: wetlands, disturbed sites and meadows lost most species, whereas forests and rocky habitats were least affected; aquatics and annuals were most prone to extinction, geophytes and hemicryptophytes were intermediate, and phanerophytes and chamaephytes were least affected. 4Species adapted to nutrient-poor soils suffered highest extinction in all habitats, indicating that eutrophication poses an urgent threat to species diversity. Light and soil moisture requirements also had significant effects on extinction, but the direction of the effect varied by habitat. 5When species were grouped into IUCN categories of the red list of Switzerland, the rank order of the observed extinction matched the red list assignment. 6Because many of the remaining species had high estimated extinction probabilities and because extinction is often delayed (extinction debt), a substantial part of the remaining flora of Küsnacht is likely to go extinct in the near future. This will increase the dominance of the common species that already comprise 81% of the local flora. 7The rates and patterns of extinction in Küsnacht are probably representative of surrounding Swiss lowlands and peri-urban landscapes in most developed countries. Studies such as ours can serve as a call for action and form a basis for future monitoring of biodiversity. [source] A BIOECONOMIC APPROACH TO THE FAUSTMANN,HARTMAN MODEL: ECOLOGICAL INTERACTIONS IN MANAGED FORESTNATURAL RESOURCE MODELING, Issue 4 2008JULIA TOUZA Abstract This paper develops a bioeconomic forestry model that makes it possible to take ecosystem services that are independent of the age structure of trees into account. We derive the Faustmann,Hartman optimal harvesting strategy as a special case. The bioeconomic model is then extended to account for the fact that forest harvesting decisions impact on other ecological resources, which provide benefits for the wider community. The paper focuses on impacts associated with disturbance caused by logging operations and habitat destruction due to tree removal. This enables us to explore the interactions between forest management and the dynamics of ecological resources. The optimal rotation rule is obtained as a variation on the traditional Faustmann,Hartman equation, where an additional term captures the potential benefits derived from the growth of the ecological resource valued at its shadow price. The steady-state solutions to the problem and sensitivity to model parameter are identified using numerical analysis. [source] The effects of habitat destruction in finite landscapes: a chain-binomial metapopulation modelOIKOS, Issue 2 2001Mark F. Hill We present a stochastic model for metapopulations in landscapes with a finite but arbitrary number of patches. The model, similar in form to the chain-binomial epidemic models, is an absorbing Markov chain that describes changes in the number of occupied patches as a sequence of binomial probabilities. It predicts the quasi-equilibrium distribution of occupied patches, the expected extinction time ( ), and the probability of persistence ( ) to time x as a function of the number N of patches in the landscape and the number S of those patches that are suitable for the population. For a given value of N, the model shows that: (1) and are highly sensitive to changes in S and (2) there is a threshold value of S at which declines abruptly from extremely large to very small values. We also describe a statistical method for estimating model parameters from time series data in order to evaluate metapopulation viability in real landscapes. An example is presented using published data on the Glanville fritillary butterfly, Meltiaea cinxia, and its specialist parasitoid Cotesia melitaearum. We calculate the expected extinction time of M. cinxia as a function of the frequency of parasite outbreaks, and are able to predict the minimum number of years between outbreaks required to ensure long-term persistence of M. cinxia. The chain-binomial model provides a simple but powerful method for assessing the effects of human and natural disturbances on extinction times and persistence probabilities in finite landscapes. [source] Genetic identification of source populations for an aquarium-traded invertebrateANIMAL CONSERVATION, Issue 1 2009D. A. Weese Abstract Increasingly, wildlife managers are turning to molecular genetics to aid in conservation efforts. While such approaches have been applied to large terrestrial and aquatic vertebrate species, their application to other traded organisms has not been extensively explored. Here, we examined the utility of these techniques for identifying source populations of aquarium ornamental invertebrates, using members of the Hawaiian atyid genus Halocaridina as a study system. These shrimps, restricted to anchialine habitats of the Hawaiian Islands, are popular in the aquarium trade due to their ability to survive in hermetically sealed containers for extended periods of time. However, commercial harvesting, coupled with habitat destruction and strong regional endemism, could lead to the depletion/extinction of unique populations. Because the land district of Kona, along the west coast of the island of Hawai'i, has the state's highest concentration of anchialine habitats, we hypothesized that commercially available Halocaridina originated from this region. To test this, mitochondrial cytochrome c oxidase subunit I gene sequences from 96 individuals, obtained from six vendors, were compared with 580 homologous sequences from previous studies covering the known distribution range of Halocaridina. Recovery of identical, regional-specific haplotypes, network analyses and statistical assignment tests identified these commercially acquired specimens as belonging to either the Kona, Ka',, (western and southern coasts, respectively, island of Hawai'i) or Kina'u (southern coast, island of Maui) genetic groups of these shrimps. Although 39 of the 96 individuals originated from the Kona genetic group as hypothesized, our finding that commercially available Halocaridina are from three genetic groups spanning two islands suggests that other populations also warrant potential management consideration. While this study represents the first application of molecular genetics in identifying source populations of aquarium ornamental species, we feel that these techniques are amenable more broadly as they are dependent on only a few caveats. [source] Local richness and distribution of the lizard fauna in natural habitat mosaics of the Brazilian CerradoAUSTRAL ECOLOGY, Issue 1 2009CRISTIANO NOGUEIRA Abstract We investigate local lizard richness and distribution in central Brazilian Cerrado, harbouring one of the least studied herpetofaunas in the Neotropical region. Our results are based on standardized samplings at 10 localities, involving 2917 captures of 57 lizard species in 10 families. Local richness values exceeded most presented in earlier studies and varied from 13 to 28 species, with modal values between 19 and 28 species. Most of the Cerrado lizard fauna is composed of habitat-specialists with patchy distributions in the mosaic of grasslands, savannas and forests, resulting in habitat-structured lizard assemblages. Faunal overlap between open and forested habitats is limited, and forested and open areas may act as mutual barriers to lizard distribution. Habitat use is influenced by niche conservatism in deep lineages, with iguanians and gekkotans showing higher use of forested habitats, whereas autarchoglossans are richer and more abundant in open habitats. Contrary to trends observed in Cerrado birds and large mammals, lizard richness is significantly higher in open, interfluvial habitats that dominate the Cerrado landscape. Between-localities variation in lizard richness seems tied to geographical distance, landscape history and phylogenetic constraints, factors operating in other well-studied lizard faunas in open environments. Higher richness in dominant, open interfluvial habitats may be recurrent in Squamata and other small-bodied vertebrates, posing a threat to conservation as these habitats are most vulnerable to the fast, widespread and ongoing process of habitat destruction in central Brazil. [source] Biogeography meets conservation: the genetic structure of the endangered lycaenid butterfly Lycaena helle (Denis & Schiffermüller, 1775)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010JAN CHRISTIAN HABEL Cold-adapted species are thought to have had their largest distribution ranges in central Europe during the glacial periods. Postglacial warming caused severe range shifts of such taxa into higher latitudes and altitudes. We selected the boreomontane butterfly Lycaena helle (Denis & Schiffermüller, 1775) as an example to demonstrate the genetic effects of range changes, and to document the recent status of highly fragmented remnant populations. We analysed five polymorphic microsatellite loci in 1059 individuals sampled at 50 different localities scattered over the European distribution area of the species. Genetic differentiation was strong among the mountain ranges of western Europe, but we did not detect similarly distinct genetic groups following a geographical pattern in the more eastern areas. The Fennoscandian populations form a separate genetic group, and provide evidence for a colonization from southern Finland via northern Scandinavia to south-central Sweden. Species distribution modelling suggests a large extension of the spatial distribution during the last glacial maximum, but highlights strong retractions to a few mountain areas under current conditions. These findings, combined with our genetic data, suggest a more or less continuous distribution of L. helle throughout central Europe at the end of the last ice age. As a consequence of postglacial warming, the species retreated northwards to Fennoscandia and escaped increasing temperatures through altitudinal shifts. Therefore, the species is today restricted to population remnants located at the mountain tops of western Europe, genetically isolated from each other, and evolved into genetically unique entities. Rising temperatures and advancing habitat destruction threaten this wealth of biodiversity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 155,168. [source] | |||||||||||||||||||||||||