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Habitat Loss (habitat + loss)

Distribution by Scientific Domains

Life Sciences	85%
Earth and Environmental Science	7%

Distribution within Life Sciences

Conservation Science	21%
Ecology & Organismal Biology	15%
Animal Science & Zoology	5%
Ornithology	3%
16 Other Subdomains	56%

Selected Abstracts

Habitat Loss and Extinction in the Hotspots of Biodiversity

CONSERVATION BIOLOGY, Issue 4 2002
Thomas M. Brooks
None of these hotspots have more than one-third of their pristine habitat remaining. Historically, they covered 12% of the land's surface, but today their intact habitat covers only 1.4% of the land. As a result of this habitat loss, we expect many of the hotspot endemics to have either become extinct or,because much of the habitat loss is recent,to be threatened with extinction. We used World Conservation Union [ IUCN ] Red Lists to test this expectation. Overall, between one-half and two-thirds of all threatened plants and 57% of all threatened terrestrial vertebrates are hotspot endemics. For birds and mammals, in general, predictions of extinction in the hotspots based on habitat loss match numbers of species independently judged extinct or threatened. In two classes of hotspots the match is not as close. On oceanic islands, habitat loss underestimates extinction because introduced species have driven extinctions beyond those caused by habitat loss on these islands. In large hotspots, conversely, habitat loss overestimates extinction, suggesting scale dependence (this effect is also apparent for plants). For reptiles, amphibians, and plants, many fewer hotspot endemics are considered threatened or extinct than we would expect based on habitat loss. This mismatch is small in temperate hotspots, however, suggesting that many threatened endemic species in the poorly known tropical hotspots have yet to be included on the IUCN Red Lists. We then asked in which hotspots the consequences of further habitat loss (either absolute or given current rates of deforestation) would be most serious. Our results suggest that the Eastern Arc and Coastal Forests of Tanzania-Kenya, Philippines, and Polynesia-Micronesia can least afford to lose more habitat and that, if current deforestation rates continue, the Caribbean, Tropical Andes, Philippines, Mesoamerica, Sundaland, Indo-Burma, Madagascar, and Chocó,Darién,Western Ecuador will lose the most species in the near future. Without urgent conservation intervention, we face mass extinctions in the hotspots. Resumen: Casi la mitad del total de plantas vasculares del mundo y un tercio de los vertebrados terrestres son endémicos en 25 "áreas críticas" para la biodiversidad, cada una de las cuales tiene por lo menos 1500 especies de plantas endémicas. En ninguno de estos sitios permanece más de un tercio de su hábitat prístino. Históricamente, cubrían 12% de la superficie terrestre, pero en la actualidad su hábitat intacto cubre solo 1.4% del terreno. Como resultado de esta pérdida de hábitat esperamos que muchas de las especies endémicas a estos sitios estén extintas o , porque la pérdida de hábitat es reciente , se encuentren amenazadas de extinción. Utilizamos Listas Rojas de UICN para comprobar esta predicción. En general, entre la mitad y dos tercios de las plantas amenazadas y el 57% de los vertebrados terrestres amenazados son endémicos de áreas críticas para la biodiversidad. Para aves y mamíferos en general, las predicciones de extinción en las áreas críticas para la biodiversidad, basadas en la pérdida de hábitat, coinciden con el número de especies consideradas extintas o amenazadas independientemente. En dos clases de áreas críticas para la biodiversidad la coincidencia no es muy grande. En islas oceánicas, la pérdida de hábitat subestima la extinción porque las especies introducidas han causado más extinciones que las producidas por la reducción del hábitat. Por lo contrario, la pérdida de hábitat sobrestima la extinción en áreas críticas para la biodiversidad extensas, lo que sugiere una dependencia de escala (este efecto también es aparente para plantas). Para reptiles, anfibios y plantas mucho menos especies endémicas son consideradas amenazadas o extintas por pérdida de hábitat. Sin embargo, esta discordancia es pequeña en áreas críticas para la biodiversidad en zonas templadas templadas, lo que sugiere que muchas especies endémicas amenazadas en las poco conocidas áreas críticas para la biodiversidad en zonas tropicales aun están por incluirse en las Listas Rojas. Posteriormente nos preguntamos en que áreas críticas para la biodiversidad serían más serias las consecuencias de una mayor pérdida de hábitat (absoluta o con las tasas actuales de deforestación). Nuestros resultados sugieren que el Arco Oriental y los Bosques Costeros de Tanzania/Kenia, Filipinas, Polinesia/Micronesia no pueden soportar mayores pérdidas y que, si continúan las tasas de deforestación actuales, el Caribe, Andes Tropicales, Filipinas, Mesoamérica, Sundaland, Indo-Burma, Madagascar y Chocó/Darién/Ecuador Occidental perderán más especies en el futuro. Sin acciones urgentes de conservación, habrá extinciones masivas en las áreas críticas para la biodiversidad. [source]

Recognising the necessity for Indo-Pacific seagrass conservation

CONSERVATION LETTERS, Issue 2 2010
Richard K.F. Unsworth
Abstract Seagrass meadows are declining globally at an unprecedented rate, yet these valuable ecosystem service providers remain marginalized within many conservation agendas. In the Indo-Pacific, this is principally because marine conservation priorities do not recognize the economic and ecological value of the goods and services that seagrasses provide. Dependency on coastal marine resources in the Indo-Pacific for daily protein needs is high relative to other regions and has been found in some places to be up to 100%. Habitat loss therefore may have negative consequences for food security in the region. Whether seagrass resources comprise an important contribution to this dependency remains largely untested. Here, we assemble information sources from throughout the Indo-Pacific region that discuss shallow water fisheries, and examine the role of seagrass meadows in supporting production, both directly, and indirectly through process of habitat connectivity (e.g., nursery function and foraging areas). We find information to support the premise that seagrass meadows are important for fisheries production. They are important fishery areas, and they support the productivity and biodiversity of coral reefs. We argue the value of a different paradigm to the current consensus on marine conservation priorities within the Indo-Pacific that places seagrass conservation as a priority. [source]

Multivariate correlates of extinction proneness in a naturally fragmented landscape

DIVERSITY AND DISTRIBUTIONS, Issue 4 2007
James I. Watling
ABSTRACT Habitat loss and fragmentation threaten a large proportion of terrestrial biodiversity, and identifying the ecological traits associated with extinction proneness is of widespread interest. We used a multivariate statistical approach to identify combinations of ecological traits that best allowed us to identify extinction-prone amphibians and reptiles in a fragmented landscape in north-eastern Bolivia. Extinction-prone amphibians were rare and did not utilize the savannah matrix separating forest islands, whereas extinction-prone reptiles were trophically specialized. Rarity and matrix aversion are among the most widely reported correlates to extinction proneness, and we argue that an increased understanding of their role as drivers of extinction processes is necessary. We suggest that the absence of reptilian vertebrate predators may exacerbate trophic cascades in habitat patches. [source]

Habitat loss, resource specialization, and extinction on coral reefs

GLOBAL CHANGE BIOLOGY, Issue 10 2004
Philip L. Munday
Abstract Coral reefs worldwide are being degraded because of global warming (coral bleaching) and coastal development (sedimentation and eutrophication). Predicting the risk of species extinctions from this type of habitat degradation is one of the most challenging and urgent tasks facing ecologists. Habitat specialists are thought to be more prone to extinction than generalists; however, specialists may be more susceptible to extinction because (1) they are specialists per se, (2) they are less abundant than generalists, or (3) both. Here, I show that declines in coral abundance lead to corresponding declines in the abundance of coral-dwelling fishes, but with proportionally greater losses to specialists than generalists. In addition, specialists have smaller initial population sizes than generalists. Consequently, specialists face a dual risk of extinction because their already small populations decline more rapidly than those of generalists. Corresponding with this increased extinction risk, I describe the local extinction of one specialist species and the near-global extinction of another species. I conclude that habitat specialists will be the first species lost from coral reefs because their small populations suffer the most from human-induced disturbances. [source]

Assessing the impact of deforestation and climate change on the range size and environmental niche of bird species in the Atlantic forests, Brazil

JOURNAL OF BIOGEOGRAPHY, Issue 7 2010
Bette A. Loiselle
Abstract Aim, Habitat loss and climate change are two major drivers of biological diversity. Here we quantify how deforestation has already changed, and how future climate scenarios may change, environmental conditions within the highly disturbed Atlantic forests of Brazil. We also examine how environmental conditions have been altered within the range of selected bird species. Location, Atlantic forests of south-eastern Brazil. Methods, The historical distribution of 21 bird species was estimated using Maxent. After superimposing the present-day forest cover, we examined the environmental niches hypothesized to be occupied by these birds pre- and post-deforestation using environmental niche factor analysis (ENFA). ENFA was also used to compare conditions in the entire Atlantic forest ecosystem pre- and post-deforestation. The relative influence of land use and climate change on environmental conditions was examined using analysis of similarity and principal components analysis. Results, Deforestation in the region has resulted in a decrease in suitable habitat of between 78% and 93% for the Atlantic forest birds included here. Further, Atlantic forest birds today experience generally wetter and less seasonal forest environments than they did historically. Models of future environmental conditions within forest remnants suggest generally warmer conditions and lower annual variation in rainfall due to greater precipitation in the driest quarter of the year. We found that deforestation resulted in a greater divergence of environmental conditions within Atlantic forests than that predicted by climate change. Main conclusions, The changes in environmental conditions that have occurred with large-scale deforestation suggest that selective regimes may have shifted and, as a consequence, spatial patterns of intra-specific variation in morphology, behaviour and genes have probably been altered. Although the observed shifts in available environmental conditions resulting from deforestation are greater than those predicted by climate change, the latter will result in novel environments that exceed temperatures in any present-day climates and may lead to biotic attrition unless organisms can adapt to these warmer conditions. Conserving intra-specific diversity over the long term will require considering both how changes in the recent past have influenced contemporary populations and the impact of future environmental change. [source]

Acoustic estimation of wildlife abundance: methodology for vocal mammals in forested habitats

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2010
Mya E. Thompson
Abstract Habitat loss and hunting pressure threaten mammal populations worldwide, generating critical time constraints on trend assessment. This study introduces a new survey method that samples continuously and non-invasively over long time periods, obtaining estimates of abundance from vocalization rates. We present feasibility assessment methods for acoustic surveys and develop equations for estimating population size. As an illustration, we demonstrate the feasibility of acoustic surveys for African forest elephants (Loxodonta africana cyclotis). Visual surveys and vocalizations from a forest clearing in the Central African Republic were used to establish that low-frequency elephant calling rate is a useful index of elephant numbers (linear regression P < 0.001, radj.2 = 0.58). The effective sampling area was 3.22 km2 per acoustic sensor, a dramatic increase in coverage over dung survey transects. These results support the use of acoustic surveys for estimating elephant abundance over large remote areas and in diverse habitats, using a distributed network of acoustic sensors. The abundance estimation methods presented can be applied in surveys of any species for which an acoustic abundance index and detection function have been established. This acoustic survey technique provides an opportunity to improve management and conservation of many acoustically-active taxa whose populations are currently under-monitored. Résumé La perte d'habitat et la pression de la chasse menacent des populations de mammifères dans le monde entier, ce qui entraîne des contraintes de temps critiques pour l'évaluation des tendances. Cette étude présente une nouvelle méthode de recherche qui échantillonne sur de longues périodes de façon constante et non intrusive et qui permet d'obtenir des estimations d'abondance à partir des taux de vocalisation. Nous présentons les méthodes d'évaluation de la faisabilité d'études acoustiques et nous développons des équations pour estimer la taille des populations. Pour illustrer ceci, nous montrons la faisabilité d'études acoustiques chez les éléphants de forêts africains Loxodonta africana cyclotis. Nous avons utilisé des études visuelles et des vocalisations d'une clairière forestière de République Centrafricaine pour établir que le taux d'appel à basse fréquence des éléphants est un indice intéressant du nombre d'éléphants (régression linéaire P < 0,001, radj² = 0,58). La superficie d'échantillonnage effective était de 3,22 km² par senseur acoustique, ce qui est une augmentation spectaculaire par rapport à la couverture des transects d'études par comptage des crottes. Ces résultats appuient le recours aux études acoustiques pour estimer l'abondance des éléphants dans de vastes zones retirées et dans des habitats variés, en utilisant un réseau de senseurs acoustiques bien répartis. Les méthodes d'estimation de l'abondance présentées peuvent être appliquées à toute espèce pour laquelle on a établi un indice d'abondance acoustique et une fonction de détection. Cette technique d'étude acoustique donne la possibilité d'améliorer la gestion et la conservation de nombreux taxons actifs au point de vue acoustique et dont les populations sont actuellement trop peu suivies. [source]

Dispersal and phylogeography of the agamid lizard Amphibolurus nobbi in fragmented and continuous habitat

MOLECULAR ECOLOGY, Issue 6 2005
D. A. DRISCOLL
Abstract Approximately 90% of native vegetation has been cleared for agriculture in central New South Wales, Australia. Habitat loss has reduced and fragmented populations of the agamid lizard Amphibolurus nobbi. We compared genetic structure of populations of this species in an unmodified landscape with those from small nature reserves and linear remnants in farming areas. We ask: Is there evidence for reduced dispersal and population fragmentation among farm populations? Using 2008 bp mtDNA sequences and allozyme electrophoresis, we found that small populations in farming areas had as much genetic variation as populations in nature reserves. Application of nested clade analysis (NCA) indicated isolation-by-distance effects among populations from uncleared areas, but not among populations within farming locations. The genetic evidence therefore implied a high level of migration in the cleared landscapes. High dispersal after fragmentation may have resulted from either a burst of movement at the time of land clearing with dragons from many sources finding refuge in a few remnants, or from ongoing rapid dispersal through unsuitable habitat. A phylogeny based on mtDNA revealed that A. nobbi populations in the study area are deeply divided into two reciprocally monophyletic groups. Although we did not sample the entire species range, one of these evolutionarily significant units was only detected in remnant vegetation in the agricultural landscape. Therefore, a substantial subclade of this species may be vulnerable to extinction. Our findings emphasize that local populations of widespread species can harbour important intraspecific genetic diversity, supporting the case for maintaining widespread species throughout production landscapes. [source]

Gap-crossing decisions of forest birds in a fragmented landscape

AUSTRAL ECOLOGY, Issue 4 2009
OLIVER J. ROBERTSON
Abstract Habitat loss and fragmentation are recognized as primary drivers of biodiversity loss worldwide. To understand the functional effects of habitat fragmentation on bird populations, data on movement across gaps in habitat cover are necessary, although rarely available. In this study, we used call playback to simulate a conspecific territorial intruder to entice birds to move through the landscape in a predictable and directional manner. We then quantified the probability of movement in continuous forest and across cleared gaps for two forest-dependent species, the grey shrike-thrush (Colluricincla harmonica) and the white-throated treecreeper (Cormobates leucophaeus). Fifty-four playback trials were conducted for each species across distances ranging from 25 to 480 m in continuous forest and 15,260 m across gaps in a forest-agricultural landscape in southern Victoria, Australia. The probability of movement was significantly reduced by gaps in forest cover for both species. Shrike-thrushes were six times more likely to move 170 m in continuous forest than to cross 170-m gaps. The mean probability that treecreepers would cross any gap at all was less than 0.5, and they were three times less likely to move 50 m across a gap than through continuous forest. Both species displayed non-linear responses to increasing gap distance: we identified a gap-tolerance threshold of 85 m for the shrike-thrush and 65 m for the treecreeper beyond which individuals were most unlikely to cross. The presence of scattered paddock trees increased functional connectivity for the shrike-thrush, with individuals crossing up to 260 m when scattered trees were present. We conclude that gaps in habitat cover are barriers to movement, and that characteristics of the intervening matrix influence landscape permeability. [source]

Tana River Mangabey Use of Nonforest Areas: Functional Connectivity in a Fragmented Landscape in Kenya

BIOTROPICA, Issue 5 2010
Julie Wieczkowski
ABSTRACT Habitat loss and fragmentation is a serious threat to biodiversity. Fragment isolation can be reduced if fragments are connected, either structurally through habitat corridors or functionally if the species can move through the surrounding matrix. One-way to evaluate landscape connectivity is to observe natural movements of animals within fragmented landscapes. The Tana River mangabey (Cercocebus galeritus) is an endangered monkey endemic to fragmented forests along the lower Tana River in Kenya, and who has been observed to move through matrix between fragments. One mangabey group moved through 1 km of matrix, while another group moved through two areas of matrix. I collected behavioral and ranging data on the latter group to describe its behavior and time spent in the matrix. Utilizing data from belt transects in the matrix and forest fragments, I characterized the vegetation structure of the matrix and compared it to the forests included in each group's home range. The group spent the majority of their time eating while in the matrix, and spent an average 36.4 min in one matrix area and 100 min in the other. The matrix is generally characterized by the highest measures for a nonforest attribute and the lowest measures for forest attributes. These results suggest that forest fragments are functionally, but not structurally, connected for the mangabey; a landscape approach to conservation, therefore, should be taken for the lower Tana River. Research investigating the limitations of the mangabey's ability to use the matrix is needed. [source]

Forest Fragment and Breeding Habitat Characteristics Explain Frog Diversity and Abundance in Singapore

BIOTROPICA, Issue 1 2010
David Bickford
ABSTRACT Habitat loss and fragmentation can have severe negative and irreversible effects on biodiversity. We investigated the effects of forest fragmentation on frog diversity in Singapore because of its high rates of deforestation and the demonstration that frogs are some of the most sensitive species to habitat degradation. We surveyed frog species in 12 forest fragments varying from 11 to 935 ha. We compared differences in species richness, abundance, and Shannon's index in relation to forest fragment size, connectivity (distance between fragments), and breeding habitat heterogeneity. A total of 20 species from 12 genera and five families were encountered in 12 fragments. Larger fragments and those closer to larger fragments had higher species richness. Abundance, however, was not correlated with forest area or connectivity, but we found fewer individual frogs in the larger fragments. We also found that breeding habitat heterogeneity best explained frog species diversity and abundance in forest fragments. Fragments with a high diversity of breeding habitats had more species. We found no evidence to suggest that abundance and diversity are strongly correlated, particularly in disturbed areas, but that breeding habitat heterogeneity is an under-appreciated factor that should be considered when prioritizing areas for anuran conservation. Enriching breeding habitat heterogeneity, creating corridors between fragments, and reforesting degraded areas are some of the most beneficial strategies for preserving urban frog biodiversity. [source]

One Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species Distributions

CONSERVATION BIOLOGY, Issue 6 2005
LISA A. SCHULTE
aptitud del hábitat; ecología aviar; ecología de paisaje; planificación de conservación Abstract:,Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid-1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black-throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public-land survey records represented historical habitat conditions, and a combination of forest inventory and national land-cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black-throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long-term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority. Resumen:,La evaluación de tendencias de las poblaciones de aves requiere de datos de referencia. En Norte América, los primeros datos disponibles de poblaciones son del final de la década de 1960. Sin embargo, las condiciones de los bosques en los estados de los Grandes Lagos (E.U.A.) han experimentado sucesión desde que la región fue talada en los inicios del siglo veinte, y se espera que las poblaciones de aves hayan experimentado cambios concomitantes. Proponemos que se considere al período previo a la colonización euro americana como referencia alternativa para evaluar los cambios en las poblaciones de aves. Evaluamos la cantidad, calidad y distribución del hábitat para reproducción de tres especies de aves de bosque (Dendroica pinus, D. fusca y D. virens) a mediados del siglo XIX e inicios del XX. Construimos modelos de las relaciones entre las aves y el hábitat con base en la literatura y conjuntos de datos de abundancia de aves y los aplicamos a los datos de vegetación ampliamente disponibles. Los registros topográficos de tierras públicas originales representaron las condiciones históricas del hábitat, y una combinación de datos del inventario forestal y de cobertura de suelo representaron las condiciones actuales. Evaluamos la robustez del modelo mediante la comparación de la distribución de hábitat actual con sitios de reproducción de aves registrados en el Wisconsin Breeding Bird Atlas. El modelo mostró poco cambio en la cantidad total de hábitat de Dendroica pinus, mientras que tanto D. fusca como D. virens han experimentado pérdidas sustanciales de hábitat. Para las especies examinadas, la calidad del hábitat se ha degradado desde antes de la colonización y la distribución espacial del hábitat cambió entre ecoregiones, con la expansión del rango acompañando la incursión de bosques en hábitats anteriormente abiertos o el reemplazo de bosques nativos con plantaciones de pinos. Las fuentes de pérdida y degradación de hábitats incluyen la pérdida de coníferas y de árboles grandes. Mediante la utilización de fuentes de datos ampliamente disponibles en un modelo de aptitud de hábitat, nuestro método proporciona un análisis a largo plazo de los cambios en el hábitat de aves y una referencia precolonización para evaluar prioridades de conservación actuales. [source]

Extinction-Rate Estimates for a Modern Neotropical Flora

CONSERVATION BIOLOGY, Issue 5 2002
Nigel C. A. Pitman
We present the first quantitative estimates of extinction rate in a complete Neotropical flora based on historical plant-collection records, quantitative measurements of forest loss and plant diversity, and the conservation status of endemic plant species in Ecuador. Our analyses suggest that 19,46 endemic plant species have gone extinct in Ecuador over the last 250 years, mostly because of habitat loss, and therefore are now globally extinct. An additional 282 species, nearly 7% of Ecuador's endemic flora, qualify as critically endangered. We found evidence of impending large-scale plant extinctions in the country's coastal and Andean forests, but little extinction and low potential for extinction in the Amazonian lowlands. Resumen: Las preocupaciones sobre las elevadas tasas de extinción en los trópicos son una característica común en la literatura sobre conservación, pero las mediciones directas son escasas. Presentamos las primeras estimaciones cuantitativas de la tasa de extinción en una flora neotropical completa basada en los expedientes históricos de colecciones de plantas, las mediciones cuantitativas de la pérdida de bosque y de diversidad y el estado de conservación de especies de plantas endémicas en Ecuador. Nuestro análisis sugiere que 19,46 especies de plantas se han extinguido en el Ecuador a lo largo de los últimos 250 años, debido principalmente a la pérdida de hábitat y por lo tanto son ahora extintas a nivel mundial. Además 282 especies, cerca del 7% de la flora endémica del Ecuador califica como críticamente amenazada. Encontramos indicaciones de inminentes extinciones de gran escala en el país, tanto en los bosques costeros como en los bosques de los Andes, pero poca extinción y bajo potencial de extinción en las tierras bajas del Amazonas. [source]

Habitat Loss and Extinction in the Hotspots of Biodiversity

Optimal conservation planning for migratory animals: integrating demographic information across seasons

CONSERVATION LETTERS, Issue 3 2010
Justin Sheehy
Abstract Conservation strategies for migratory animals are typically based on ad-hoc or simple ranking methods and focus on a single period of the annual cycle. We use a density-dependent population model to examine one-time land purchase strategies for a migratory population with a breeding and wintering grounds. Under equal rates of habitat loss, we show that it is optimal to invest more, but never solely, in the habitat with the higher density dependence to habitat cost ratio. When there are two habitats that vary in quality within a season, the best strategy is to invest only in one habitat. Whether to purchase high- or low-quality habitat depends on the general life history of the species and the ratio of habitat quality to habitat cost. When carry-over effects are incorporated, it is almost always optimal to invest in high-quality habitat during the season that produces the carry-over effect. We apply this model to a threatened warbler population and show the optimal strategy is to purchase more breeding than wintering habitat despite the fact that breeding habitat is over ten times more expensive. Our model provides a framework for developing year-round conservation strategies for migratory animals and has important implications for long-term planning and management. [source]

Integrating species life-history traits and patterns of deforestation in amphibian conservation planning

DIVERSITY AND DISTRIBUTIONS, Issue 1 2010
C. G. Becker
Abstract Aim, To identify priority areas for amphibian conservation in southeastern Brazil, by integrating species life-history traits and patterns of deforestation. Location, State of São Paulo, Brazil. Methods, We used the software Marxan to evaluate different scenarios of amphibian conservation planning. Our approach differs from previous methods by explicitly including two different landscape metrics; habitat split for species with aquatic larvae, and habitat loss for species with terrestrial development. We evaluated the effect of habitat requirements by classifying species breeding habitats in five categories (flowing water, still water permanent, still water temporary, bromeliad or bamboo, and terrestrial). We performed analyses using two scales, grid cells and watersheds and also considered nature preserves as protected areas. Results, We found contrasting patterns of deforestation between coastal and inland regions. Seventy-six grid cells and 14 watersheds are capable of representing each species at least once. When accounting for grid cells already protected in state and national parks and considering species habitat requirements we found 16 high-priority grid cells for species with one or two reproductive habitats, and only one cell representing species with four habitat requirements. Key areas for the conservation of species breeding in flowing and permanent still waters are concentrated in southern state, while those for amphibians breeding in temporary ponds are concentrated in central to eastern zones. Eastern highland zones are key areas for preserving species breeding terrestrially by direct or indirect development. Species breeding in bromeliads and bamboos are already well represented in protected areas. Main conclusions, Our results emphasize the need to integrate information on landscape configuration and species life-history traits to produce more ecologically relevant conservation strategies. [source]

New York's nature: a review of the status and trends in species richness across the metropolitan region

DIVERSITY AND DISTRIBUTIONS, Issue 1 2009
Linda M. Puth
ABSTRACT Aim, The world's population is urbanizing, yet relatively little is known about the ecology of urban areas. As the largest metropolitan area in the USA, New York City is an ideal location to study the effects of urbanization. Here, we aim to produce a better understanding of the state of the research for species richness of flora and fauna across the New York metropolitan region. Location, New York metropolitan region, USA. Methods, We conducted a review of the published and grey literature, in which we targeted studies of species richness, and categorized each study by habitat, location and taxonomic group. Results, We found 79 studies reporting location-specific species richness data, resulting in 261 location-taxonomic group records. Of these, 26 records had data from multiple time periods; 17 showed decreases in species richness, six reported increases and three showed stable species richness. Of these 26 records, most declines were attributed to anthropogenic causes, such as habitat loss/degradation and invasive species, while most increases reflected recovery from major habitat loss or increases in exotic species. Overall, most records (84) were terrestrial, followed by those in freshwater (72) and mixed habitats (61). When parsed by taxonomic group, the most commonly studied groups were plants (76) and mammals (48). Main conclusions, In general, we discovered fewer studies than expected reporting species richness, especially studies reporting species richness for more than one point in time. Most studies that did contain data over time reported declines in species richness, while several studies reporting increasing or stable species richness reflected increases in exotic species. This survey provides a crucial first step in establishing baseline ecological knowledge for the New York metropolitan region that should help prioritize areas for protection, research and development. Furthermore, this research provides insights into the impacts of urbanization across the USA and beyond and should help establish similar frameworks for ecological understanding for other metropolitan regions throughout the world. [source]

Modelling and analysing evolution of dispersal in populations at expanding range boundaries

ECOLOGICAL ENTOMOLOGY, Issue 5 2007
CLARE L. HUGHES
Abstract 1.,Species would be expected to shift northwards in response to current climate warming, but many are failing to do so because of fragmentation of breeding habitats. Dispersal is important for colonisation and an individual-based spatially explicit model was developed to investigate impacts of habitat availability on the evolution of dispersal in expanding populations. Model output was compared with field data from the speckled wood butterfly Pararge aegeria, which currently is expanding its range in Britain. 2.,During range expansion, models simulated positive linear relationships between dispersal and distance from the seed location. This pattern was observed regardless of quantity (100% to 10% habitat availability) or distribution (random vs. gradient distribution) of habitat, although higher dispersal evolved at expanding range margins in landscapes with greater quantity of habitat and in gradient landscapes. Increased dispersal was no longer evident in any landscape once populations had reached equilibrium; dispersal values returned to those of seed populations. However, in landscapes with the least quantity of habitat, reduced dispersal (below that of seed populations) was observed at equilibrium. 3.,Evolutionary changes in adult flight morphology were examined in six populations of P. aegeria along a transect from the distribution core to an expanding range margin in England (spanning a latitudinal distance of >200 km). Empirical data were in agreement with model output and showed increased dispersal ability (larger and broader thoraxes, smaller abdomens, higher wing aspect ratios) with increasing distance from the distribution core. Increased dispersal ability was evident in populations from areas colonised >30 years previously, although dispersal changes were generally evident only in females. 4.,Evolutionary increases in dispersal ability in expanding populations may help species track future climate changes and counteract impacts of habitat fragmentation by promoting colonisation. However, at the highest levels of habitat loss, increased dispersal was less evident during expansion and reduced dispersal was observed at equilibrium indicating that, for many species, continued habitat fragmentation is likely to outweigh any benefits from dispersal. [source]

Is the matrix a sea?

ECOLOGICAL ENTOMOLOGY, Issue 1 2005
Habitat specificity in a naturally fragmented landscape
Abstract., 1. Metapopulation and island biogeography theory assume that landscapes consist of habitat patches set in a matrix of non-habitat. If only a small proportion of species conform to the patch,matrix assumptions then metapopulation theory may only describe special cases rather than being of more general ecological importance. 2. As an initial step towards understanding the prevalence of metapopulation dynamics in a naturally fragmented landscape, the distribution of beetle species in three replicates of three habitat types was examined, including rainforest and eucalypt forest (the habitat patches), and buttongrass sedgeland (the matrix), in south-west Tasmania, Australia. 3. Ordination methods indicated that the buttongrass fauna was extremely divergent from the fauna of forested habitats. Permutation tests showed that the abundance of 13 of 17 commonly captured species varied significantly among habitats, with eight species confined to eucalypts or rainforest, and three species found only in buttongrass. Approximately 60% of species were confined to forested habitat implying that metapopulation theory has the potential to be very important in the forest,buttongrass landscape. 4. Although floristically the rainforest and eucalypts were extremely distinct, the beetle faunas from eucalypts and rainforests overlapped substantially. Therefore rainforest patches connected by eucalypt forest represent continuous habitat for most species. 5. Other studies report a wide range of values for the proportion of patch-specific species in fragmented landscapes. Understanding the environmental or historical conditions under which a high proportion of species become patch specialists would help to identify where spatial dynamic theory may be especially applicable, and where habitat loss and fragmentation poses the greatest threat to biodiversity. [source]

A general framework for neutral models of community dynamics

ECOLOGY LETTERS, Issue 12 2009
Omri Allouche
Abstract Neutral models of community dynamics are a powerful tool for ecological research, but their applications are currently limited to unrealistically simple types of dynamics and ignore much of the complexity that characterize natural ecosystems. Here, we present a new analytical framework for neutral models that unifies existing models of neutral communities and extends the applicability of existing models to a much wider spectrum of ecological phenomena. The new framework extends the concept of neutrality to fitness equivalence and in spite of its simplicity explains a wide spectrum of empirical patterns of species diversity including positive, negative and unimodal productivity,diversity relationships; gradual and highly delayed declines in species diversity with habitat loss; and positive and negative responses of species diversity to habitat heterogeneity. Surprisingly, the abundance distribution in all of these cases is given by the dispersal limited multinomial (DLM), the abundance distribution in Hubbell's zero-sum model, showing DLM's robustness and demonstrating that it cannot be used to infer the underlying community dynamics. These results support the hypothesis that ecological communities are regulated by a limited set of fundamental mechanisms much simpler than could be expected from their immense complexity. Ecology Letters (2009) 12: 1287,1297 [source]

Aqueous exposure to 4-nonylphenol and 17,-estradiol increases stress sensitivity and disrupts ion regulatory ability of juvenile Atlantic salmon

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2007
Darren T. Lerner
Abstract Population declines of wild Atlantic salmon have been attributed to an array of anthropogenic disturbances, including dams, commercial and recreational fishing, habitat loss, and pollution. Environmental contaminants in particular, can act as environmental stressors on fish, typically causing disruption of ion homeostasis due to their close association with the aquatic environment. To examine the effects of the xenoestrogen 4-nonylphenol (NP) or 17,-estradiol (E2) on stress sensitivity and ion regulation, we exposed juvenile Atlantic salmon continuously for 21 d to either 10 or 100 ,g/L NP (NP-L or NP-H), 2 ,g/L E2 (positive control), or vehicle control during the parr-smolt transformation in April. After treatment, fish were sampled in freshwater (FW), transferred to 30, seawater (SW) for 24 h, or subjected to a handling stress. Estradiol and NP-H increased plasma vitellogenin in males and females, and E2 increased gonadosomatic index only in males. In FW, E2 reduced sodium potassium,activated adenosine triphosphatase activity as well as plasma levels of growth hormone, insulin-like growth factor I, and triiodothyronine. Both E2 and NP-H reduced plasma sodium in FW and increased plasma chloride in SW. Plasma Cortisol levels pre- and poststressor were significantly elevated by all treatments relative to controls, but only E2 increased plasma glucose before and after the stressor. These results indicate that exposure of anadromous salmonids to environmental estrogens heightens sensitivity to external stressors, impairs ion regulation in both FW and SW, and disrupts endocrine pathways critical for smolt development. [source]

Extinction vulnerability in marine populations

FISH AND FISHERIES, Issue 1 2003
Nicholas K Dulvy
Abstract Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa. We have compiled 133 local, regional and global extinctions of marine populations. There is typically a 53-year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical comparative methods, which suggests that marine extinctions may have been underestimated because of low-detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insufficiently conservative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large-scale dispersal characteristics. For commercially exploited species, it is often argued that economic extinction of exploited populations will occur before biological extinction, but this is not the case for non-target species caught in multispecies fisheries or species with high commercial value, especially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of fish populations have been invoked to avoid listing commercial species of fishes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee effect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence suggests that fish populations do not fluctuate more than those of mammals, birds and butterflies, and that fishes may exhibit vulnerability similar to mammals, birds and butterflies. There is an urgent need for improved methods of detecting marine extinctions at various spatial scales, and for predicting the vulnerability of species. [source]

Fluctuations in European eel (Anguilla anguilla) recruitment resulting from environmental changes in the Sargasso Sea

FISHERIES OCEANOGRAPHY, Issue 1 2008
SYLVAIN BONHOMMEAU
Abstract European eel decline is now widely observed and involves a large number of factors such as overfishing, pollution, habitat loss, dam construction, river obstruction, parasitism and environmental changes. In the present study, we analyzed the influence of environmental conditions in the Sargasso Sea and Atlantic ocean circulation on European glass eel recruitment success. Over a recent 11-yr period, we showed a strong positive correlation between an original index of glass eel recruitment and primary production (PP) in eel spawning area. Moreover, PP was negatively correlated with temperature in the Sargasso Sea. Therefore, we used sea temperature as an inverse proxy of marine production. A close negative relationship has been found over the last four decades between long-term fluctuations in recruitment and in sea temperature. These findings were reinforced by the detection of a regime shift in sea temperature that preceded the start of the decline in glass eel recruitment in the early 1980s. By contrast, variations in integrative indices measuring ocean circulation, i.e. latitude and strength of the Gulf Stream, did not seem to explain variations in glass eel recruitment. Our results support the hypothesis of a strong bottom-up control of leptocephali survival and growth by PP in the Sargasso Sea on short and long time scales. We argue that sea warming in the eel spawning area since the early 1980s has modified marine production and eventually affected the survival rate of European eels at early life stages. [source]

Mechanistic links between climate and fisheries along the east coast of the United States: explaining population outbursts of Atlantic croaker (Micropogonias undulatus)

FISHERIES OCEANOGRAPHY, Issue 1 2007
JONATHAN A. HARE
Abstract Climate has been linked to variation in marine fish abundance and distribution, but often the mechanistic processes are unknown. Atlantic croaker (Micropogonias undulatus) is a common species in estuarine and coastal areas of the mid-Atlantic and southeast coasts of the U.S. Previous studies have identified a correlation between Atlantic croaker abundance and winter temperatures in Chesapeake Bay, and have determined thermal tolerances of juveniles. Here we re-examine the hypothesis that winter temperature variability controls Atlantic croaker population dynamics. Abundance indices were analyzed at four life history stages from three regions along the east coast of the U.S. Correlations suggest that year-class strength is decoupled from larval supply and is determined by temperature-linked, overwinter survival of juveniles. Using a relation between air and water temperatures, estuarine water temperature was estimated from 1930 to 2002. Periods of high adult catch corresponded with warm winter water temperatures. Prior studies indicate that winter temperature along the east coast is related to the North Atlantic Oscillation (NAO); variability in catch is also correlated with the NAO, thereby demonstrating a link between Atlantic croaker dynamics, thermal limited overwinter survival, and the larger climate system of the North Atlantic. We hypothesize that the environment drives the large-scale variability in Atlantic croaker abundance and distribution, but fishing and habitat loss decrease the resiliency of the population to periods of poor environmental conditions and subsequent weak year classes. [source]

Non-optimal animal movement in human-altered landscapes

FUNCTIONAL ECOLOGY, Issue 6 2007
LENORE FAHRIG
Summary 1I synthesize the understanding of the relationship between landscape structure and animal movement in human-modified landscapes. 2The variety of landscape structures is first classified into four categories: continuous habitat, patchy habitat with high-quality matrix, patchy habitat with low-quality matrix, and patchy, ephemeral habitat. Using this simplification I group the range of evolved movement parameters into four categories or movement types. I then discuss how these movement types interact with current human-caused landscape changes, and how this often results in non-optimal movement. 3From this synthesis I develop a hypothesis that predicts the relative importance of the different population-level consequences of these non-optimal movements, for the four movement types. 4Populations of species that have inhabited landscapes with high habitat cover or patchy landscapes with low-risk matrix should have evolved low boundary responses and moderate to high movement probabilities. These species are predicted to be highly susceptible to increased movement mortality resulting from habitat loss and reduced matrix quality. 5In contrast, populations of species that evolved in patchy landscapes with high-risk matrix or dynamic patchy landscapes are predicted to be highly susceptible to decreased immigration and colonization success, due to the increasing patch isolation that results from habitat loss. 6Finally, I discuss three implications of this synthesis: (i) ,least cost path' analysis should not be used for land management decisions without data on actual movement paths and movement risks in the landscape; (ii) ,dispersal ability' is not simply an attribute of a species, but varies strongly with landscape structure such that the relative rankings of species' dispersal abilities can change following landscape alteration; and (iii) the assumption that more mobile species are more resilient to human-caused landscape change is not generally true, but depends on the structure of the landscape where the species evolved. [source]

Exploitation and habitat degradation as agents of change within coral reef fish communities

GLOBAL CHANGE BIOLOGY, Issue 12 2008
S. K. WILSON
Abstract Over-exploitation and habitat degradation are the two major drivers of global environmental change and are responsible for local extinctions and declining ecosystem services. Here we compare the top-down effect of exploitation by fishing with the bottom-up influence of habitat loss on fish communities in the most diverse of ecological systems, coral reefs. Using a combination of multivariate techniques and path analyses, we illustrate that the relative importance of coral cover and fishing in controlling fish abundance on remote Fijian reefs varies between species and functional groups. A decline in branching Acropora coral is strongly associated with a decline in abundance of coral-feeding species, and a decrease in coral-associated habitat complexity, which has indirectly contributed to reduced abundance of small-bodied damselfish. In contrast, reduced fishing pressure, brought about by declining human populations and a shift to alternate livelihoods, is associated with increased abundance of some piscivores and fisheries target species. However, availability of prey is controlled by coral-associated habitat complexity and appears to be a more important driver of total piscivore abundance compared with fishing pressure. Effects of both fishing and coral loss are stronger on individual species than functional groups, as variation in the relative importance of fishing or coral loss among species within the same functional group attenuated the impact of either of these potential drivers at the functional level. Overall, fishing continues to have an influence on Fijian fish communities; however, habitat loss is currently the overriding agent of change. The importance of coral loss mediated by climate change is expected to have an increasing contribution to fish community dynamics, particularly in remote locations or where the influence of fishing is waning. [source]

Coral bleaching, reef fish community phase shifts and the resilience of coral reefs

GLOBAL CHANGE BIOLOGY, Issue 9 2006
DAVID R. BELLWOOD
Abstract The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5,35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience. [source]

Landscape modification and habitat fragmentation: a synthesis

GLOBAL ECOLOGY, Issue 3 2007
Joern Fischer
ABSTRACT Landscape modification and habitat fragmentation are key drivers of global species loss. Their effects may be understood by focusing on: (1) individual species and the processes threatening them, and (2) human-perceived landscape patterns and their correlation with species and assemblages. Individual species may decline as a result of interacting exogenous and endogenous threats, including habitat loss, habitat degradation, habitat isolation, changes in the biology, behaviour, and interactions of species, as well as additional, stochastic threats. Human-perceived landscape patterns that are frequently correlated with species assemblages include the amount and structure of native vegetation, the prevalence of anthropogenic edges, the degree of landscape connectivity, and the structure and heterogeneity of modified areas. Extinction cascades are particularly likely to occur in landscapes with low native vegetation cover, low landscape connectivity, degraded native vegetation and intensive land use in modified areas, especially if keystone species or entire functional groups of species are lost. This review (1) demonstrates that species-oriented and pattern-oriented approaches to understanding the ecology of modified landscapes are highly complementary, (2) clarifies the links between a wide range of interconnected themes, and (3) provides clear and consistent terminology. Tangible research and management priorities are outlined that are likely to benefit the conservation of native species in modified landscapes around the world. [source]

Not seeing the ocean for the islands: the mediating influence of matrix-based processes on forest fragmentation effects

GLOBAL ECOLOGY, Issue 1 2006
John A. Kupfer
ABSTRACT The pervasive influence of island biogeography theory on forest fragmentation research has often led to a misleading conceptualization of landscapes as areas of forest/habitat and ,non-forest/non-habitat' and an overriding focus on processes within forest remnants at the expense of research in the human-modified matrix. The matrix, however, may be neither uniformly unsuitable as habitat nor serve as a fully,absorbing barrier to the dispersal of forest taxa. In this paper, we present a conceptual model that addresses how forest habitat loss and fragmentation affect biodiversity through reduction of the resource base, subdivision of populations, alterations of species interactions and disturbance regimes, modifications of microclimate and increases in the presence of invasive species and human pressures on remnants. While we acknowledge the importance of changes associated with the forest remnants themselves (e.g. decreased forest area and increased isolation of forest patches), we stress that the extent, intensity and permanence of alterations to the matrix will have an overriding influence on area and isolation effects and emphasize the potential roles of the matrix as not only a barrier but also as habitat, source and conduit. Our intention is to argue for shifting the examination of forest fragmentation effects away from a patch-based perspective focused on factors such as patch area and distance metrics to a landscape mosaic perspective that recognizes the importance of gradients in habitat conditions. [source]

Information needs to support environmental impact assessment of the effects of European marine offshore wind farms on birds

IBIS, Issue 2006
A.D. FOX
European legislation requires Strategic Environmental Assessments (SEAs) of national offshore wind farm (OWF) programmes and Environmental Impact Assessments (EIAs) for individual projects likely to affect birds. SEAs require extensive mapping of waterbird densities to define breeding and feeding areas of importance and sensitivity. Use of extensive large scale weather, military, and air traffic control surveillance radar is recommended, to define areas, routes and behaviour of migrating birds, and to determine avian migration corridors in three dimensions. EIAs for individual OWFs should define the key avian species present; as well as assess the hazards presented to birds in terms of avoidance behaviour, habitat change and collision risk. Such measures, however, are less helpful in assessing cumulative impacts. Using aerial survey, physical habitat loss, modification, or gain and effective habitat loss through avoidance behaviour can be measured using bird densities as a proxy measure of habitat availability. The energetic consequences of avoidance responses and habitat change should be modelled to estimate fitness costs and predict impacts at the population level. Our present ability to model collision risk remains poor due to lack of data on species-specific avoidance responses. There is therefore an urgent need to gather data on avoidance responses; energetic consequences of habitat modification and avoidance flights and demographic sensitivity of key species, most affected by OWFs. This analysis stresses the importance of common data collection protocols, sharing of information and experience, and accessibility of results at the international level to better improve our predictive abilities. [source]

Invertebrate diet of the Houbara Bustard Chlamydotis [undulata] macqueenii in Abu Dhabi from calibrated faecal analysis

IBIS, Issue 3 2000
BARBARA J. TIGAR
The ecology of the Houbara Bustard Chlamydotis [undulata] macqueenii is poorly known and populations are declining due to hunting and habitat loss. As wintering populations in Abu Dhabi may be limited by habitat and food, we studied the diet using calibrated faecal analysis. Prey were categorized into 16 groups and fed to captive birds under controlled conditions. We calculated the recovery rates of prey following digestion and identified consistent fragments for each group. Wild Houbara Bustard faeces were collected and examined for key fragments, and initial prey intake was calibrated. Plant remains were identified and their contribution was estimated. Fewer than 28% faeces contained >50% plant material by volume and only 12% contained 95% or more. Numerically, the most important prey were: ants (64%), large nocturnal tenebrionids (14.5%), small climbing tenebrionids (12%) and diurnal tenebrionids. However, the Tenebrionidae contributed 97% of the animal biomass. The relative proportions of prey in the diet were similar to relative abundance as assessed by pitfall trapping. Estimates of the energetic value of the prey suggested that on average Houbara Bustards must consume around 670 desert invertebrates/day to meet energy needs. The effort required to catch these prey may vary at least ten-fold seasonally. On average plants could provide a further 6.4,14% energy but more work is needed on this. Whether Houbara Bustards wintering in Abu Dhabi are prey-limited depends on prey densities and renewal rates which remain unknown. [source]