Time filter

Source Type

Rubio L.,University of Lleida | Bodin O.,University of Stockholm | Brotons L.,Cemfor Ctfc Center Tecnologic Forestal Of Catalonia | Brotons L.,Institute Catala dOrnitologia | Saura S.,Polytechnic University of Mozambique
Ecography | Year: 2015

One of the most widespread approaches for setting spatially-explicit priorities for connectivity conservation consists in evaluating the effects of the individual removal of each habitat patch (one at a time) from the landscape. It however remains unknown the degree to which such priorities are valid and reliable in the longer term, as subsequent habitat losses and other disruptions accumulate in the landscape. We compared the patch prioritizations and estimated connectivity losses resulting from individual patch removals and from a more exhaustive assessment accounting for the potentially synergistic impacts of multiple habitat losses by testing all possible combinations of patch removals. Habitat availability (reachability) metrics and metapopulation capacity were calculated in purposefully simulated landscapes and in habitat distribution data for three bird species (NE Spain). We found that 1) individual patch removals allowed identifying areas of low contribution to connectivity that remained so after subsequent network modifications, 2) the most important patches identified through individual removals often did not coincide with those patches whose removal would actually be most detrimental after multiple habitat losses. However, these differences were smaller for the habitat reachability metrics, as well as for very mobile species that were largely insensitive to habitat spatial arrangement. If many patch losses over time are likely, it might be a more robust and fruitful conservation strategy for managers to pinpoint those patches that, with a low negative impact on connectivity, can be converted to other land uses, instead of trying to elucidate through individual patch removals which subset of protected patches would be the most effective for conserving as much connectivity as possible in the long term. Individual patch removals provide useful but non-permanent guidelines that may need to be reassessed when substantial landscape modifications occur, which requires dynamic strategies for connectivity conservation in the face of global change. © 2014 The Authors.

Gil-Tena A.,French National Center for Scientific Research | Brotons L.,Autonomous University of Barcelona | Brotons L.,Institute Catala dOrnitologia | Fortin M.-J.,University of Toronto | And 2 more authors.
European Journal of Forest Research | Year: 2013

Woodpecker species have significantly expanded their ranges in the last decades of the twentieth century in Mediterranean Europe, which seems to be closely related to forest maturation following large-scale decline in traditional uses. Here we assess the explicit role of forest landscape connectivity in the colonization of the Great Spotted Woodpecker (Dendrocopos major) and the Black Woodpecker (Dryocopus martius) in Catalonia (NE Spain). For this purpose we combined data on breeding bird atlas (10 × 10 km; 1980-2000) and forest inventories (c. 1 × 1 km, 2000). Forest connectivity was measured through graph theory and habitat availability metrics (inter- and intra-patch connectivity) according to species median natal dispersal distances. The best regressions from a set of alternative models were selected based on AICc. Results showed that connectivity between areas of mature forests [diameter at breast height (dbh) ≥ 35 cm] affected Black Woodpecker colonization events. The probability of colonization of the Great Spotted Woodpecker was greater at localities near the sources of colonization in 1980 and with a high connectivity with other less developed forest patches (dbh < 35 cm). The spatial grain at which landscape connectivity was measured influenced the model performance according to the species dispersal abilities, with the species with the lower mobility (D. major) responding better to the forest connectivity patterns at finer spatial scales. Overall, it seems that both species could expand further in European Mediterranean forests in upcoming years but at slower rates if landscape connectivity according to species requirements does not continue to increase. Hence, a proactive and adaptive management should be carried out in order to preserve these species while considering the related major impacts of global change in Mediterranean Europe. © 2012 Springer-Verlag Berlin Heidelberg.

Keil P.,Yale University | Keil P.,Academy of Sciences of the Czech Republic | Schweiger O.,Helmholtz Center for Environmental Research | Kuhn I.,Helmholtz Center for Environmental Research | And 14 more authors.
Journal of Biogeography | Year: 2012

Aim We test the prediction that beta diversity (species turnover) and the decay of community similarity with distance depend on spatial resolution (grain). We also study whether patterns of beta diversity are related to variability in climate, land cover or geographic distance and how the independent effects of these variables depend on the spatial grain of the data. Location Europe, Great Britain, Finland and Catalonia. Methods We used data on European birds, plants, butterflies, amphibians and reptiles, and data on British plants, Catalonian birds and Finnish butterflies. We fitted two or three nested grids of varying resolutions to each of these datasets. For each grid we calculated differences in climate, differences in land-cover composition (CORINE) and beta diversity (β sim, β Jaccard) between all pairs of grid cells. In a separate analysis we looked specifically at pairs of adjacent grid cells (the first distance class). We then used variation partitioning to identify the magnitude of independent statistical associations (i.e. independent effects in the statistical sense) of climate, land cover and geographic distance with spatial patterns of beta diversity. Results Beta diversity between grid cells at any given distance decreased with increasing grain. Geographic distance was always the most important predictor of beta diversity for all pairwise comparisons at the extent of Europe. Climate and land cover had weaker but distinct and grain-dependent effects. Climate was more important at relatively coarse grains, whereas land-cover effects were stronger at finer grains. In the country-wide analyses, climate and land cover were more important than geographic distance. Climatic and land-cover models performed poorly and showed no systematic grain dependence for beta diversity between adjacent grid cells. Main conclusions We found that relationships between geographic distance and beta diversity, as well as the environmental correlates of beta diversity, are systematically grain dependent. The strong independent effect of distance indicates that, contrary to the current belief, a substantial fraction of species are missing from areas with a suitable environment. Moreover, the effects of geographic distance (at continental extents) and land cover (at fine grains) indicate that any species distribution modelling should take both environment and dispersal limitation into account. © 2012 Blackwell Publishing Ltd.

Zozaya E.L.,Center Tecnologic Forestal Of Catalonia | Brotons L.,Center Tecnologic Forestal Of Catalonia | Brotons L.,Institute Catala dOrnitologia | Saura S.,Center Tecnologic Forestal Of Catalonia | Saura S.,Technical University of Madrid
Landscape Ecology | Year: 2012

Mediterranean landscapes are suffering two opposing forces leading to large-scale changes in species distribution: land abandonment of less productive areas and an increase in wildfire impact. Here, we test the hypothesis that fires occurred in recent decades drive the pattern of expansion of early-successional, open-habitat bird species by aiding in the process of colonisation of newly burnt areas. The study was carried out in Catalonia (NE Spain). We selected 44 burnt sites occurring between 2000 and 2005 to model colonisation patterns under different assumptions of potential colonisers' sources and evaluated the colonisation estimates with empirical data on six bird species especially collected for this purpose. We first defined three landscape scenarios serving as surrogates of potential colonisers' sources: open-habitats created by fire, shrublands and farmlands. Then, we used a parameter derived from a functional connectivity metric to estimate species colonization dynamics on the selected sites by each particular scenario. Finally, we evaluated our colonisation estimates with the species occurrence in the studied locations by using generalized linear mixed models. The occurrence of the focal species on the newly burnt sites was significantly related to the connectivity patterns described by both the recent fire history and the other open-habitat types generated by a different type of disturbance. We suggest that land use changes in recent decades have produced a shift in the relative importance of habitats acting as reservoirs for open-habitat bird species dynamics in Mediterranean areas. Before the middle of the twentieth century species' reservoirs were probably constituted by relatively static open habitats (grassland and farmland), whereas afterwards they likely consist of a shifting mosaic of habitat patches where fire plays a key role as connectivity provider and largely contributes to the maintenance of species persistence. © 2011 Springer Science+Business Media B.V.

Brotons L.,Center Tecnlogic Forestal Of Catalonia Ctfc | De Caceres M.,Institute Catala dOrnitologia | Fall A.,Simon Fraser University | Fortin M.-J.,University of Toronto
Ecography | Year: 2012

Species distribution models (SDMs) have traditionally been founded on the assumption that species distributions are in equilibrium with environmental conditions and that these species-environment relationships can be used to estimate species responses to environmental changes. Insight into the validity of this assumption can be obtained from comparing the performance of correlative species distribution models with more complex hybrid approaches, i.e. correlative and process-based models that explicitly include ecological processes, thereby accounting for mismatches between habitat suitability and species occupancy patterns. Here we compared the ability of correlative SDMs and hybrid models, which can accommodate non-equilibrium situations arising from dispersal constraints, to reproduce the distribution dynamics of the ortolan bunting Emberiza hortulana in highly dynamic, early successional, fire driven Mediterranean landscapes. Whereas, habitat availability was derived from a correlative statistical SDM, occupancy was modeled using a hybrid approach combining a grid-based, spatially-explicit population model that explicitly included bird dispersal with the correlative model. We compared species occupancy patterns under the equilibrium assumption and different scenarios of species dispersal capabilities. To evaluate the predictive capability of the different models, we used independent species data collected in areas affected to different degree by fires. In accordance with the view that disturbance leads to a disparity between the suitable habitat and the occupancy patterns of the ortolan bunting, our results indicated that hybrid modeling approaches were superior to correlative models in predicting species spatial dynamics. Furthermore, hybrid models that incorporated short dispersal distances were more likely to reproduce the observed changes in ortolan bunting distribution patterns, suggesting that dispersal plays a key role in limiting the colonization of recently burnt areas. We conclude that SDMs used in a dynamic context can be significantly improved by using combined hybrid modeling approaches that explicitly account for interactions between key ecological constraints such as dispersal and habitat suitability that drive species response to environmental changes. © 2011 The Authors. Journal compilation © 2011 Nordic Society Oikos.

Clavero M.,Center Tecnologic Forestal Of Catalonia | Clavero M.,University of Girona | Brotons L.,Center Tecnologic Forestal Of Catalonia | Brotons L.,Institute Catala dOrnitologia
Global Ecology and Biogeography | Year: 2010

Aim: To test whether functional homogenization of bird communities is promoted by anthropogenic landscape transformation, using specialization and habitat preference indices that account for the multidimensionality of niches. Location: Catalonia, north-east Iberian Peninsula. Methods: We used data on bird species occurrences and landscape features in 2834 1-km2 squares. Three orthogonal landscape gradients, which were taken as niche dimensions, were defined by means of principal components analysis (PCA). Specialization and habitat preference indices were created for 103 terrestrial bird species on the basis of their frequency of occurrence variation along the landscape gradients. These indices, together with species rarity, were then averaged for bird communities. We then analysed the patterns of variation of communities' mean specialization, mean rarity and mean habitat preference values along a gradient of agricultural-forest habitat mosaics. Results: Wherever we found a significant variation in the degree of specialization along the agricultural-forest gradient, agricultural habitats held more specialized bird communities than did forest ones and bore, on average, rarer species. Thus, results contradicted our initial hypothesis that humanized areas would bear more functionally homogenized bird communities. Higher a-diversity values tended to be associated with generalist communities and with those having rarer species. Main conclusions: Estimations of bird community specialization for different niche dimensions can behave differently along certain landscape gradients, and some of these differences can be explained by the variation of mean habitat preferences. Thus, we argue that a multidimensional approach to assess average niche breadth of communities can be more informative than a unidimensional measure. Our results suggest that widespread land abandonment and current secondary forest expansion throughout the Mediterranean area are promoting functional homogenization of bird communities. It would be desirable to construct largerscale indicators of functional homogenization in order to monitor communities' responses to widespread landscape changes. © 2010 Blackwell Publishing Ltd.

Herrando S.,Institute Catala DOrnitologia | Anton M.,Institute Catala DOrnitologia
Revista Catalana d'Ornitologia | Year: 2013

The first assessment of the conservation status of breeding birds in Catalonia was conducted in 2002 on the basis of (a) population sizes and distributions and (b) the changes in these two parameters that occurred in the period from the 1980s to the beginning of the 2000s. A second more recent assessment was made that took into account population sizes and distributions in 2012 and the changes occurring in the period 2002-2012. Both assessments were made using the criteria established by the International Union for Conservation of Nature (IUCN) and it was thus possible to study the change in conservation status by applying the Red List Index, the indicator recommended by this body for this purpose. A key point in this methodology is how to determine genuine changes in status and differentiate them from changes associated with variations in the level of knowledge or with modifications in evaluation criteria. Once these factors had been taken into account, we applied the Red List Index (RLI) algorithm using 155 species (67% of bird species breeding in Catalonia) for both 2002 and 2012. The index showed an improvement of the threat status of 4% during this 10-year period. Then, we re-evaluated the 2002 status using more up-to-date criteria and knowledge and applied the same algorithm to calculate the index again (re-RLI) for 232 species (all breeding species). The re-RLI index improved by 5% during this ten-year period. The results suggest a general improvement in the overall conservation status of breeding birds in Catalonia over the last 10 years.

Anton M.,Institute Catala DOrnitologia | Estrada J.,Institute Catala DOrnitologia | Herrando S.,Institute Catala DOrnitologia
Revista Catalana d'Ornitologia | Year: 2013

The International Union for Conservation of Nature (IUCN) recommends assessing the conservation status of species at regional level and updating it periodically. In Catalonia, the first evaluation of the threat categories of breeding birds was carried out in 2002. The present article is an update for the period 2002-2012. We applied IUCN criteria, which evaluate the risk of extinction, taking into account population estimates and the distribution of, as well as trends in, the evaluated populations. We also applied guidelines for assessing threat categories at regional level that evaluate the possibilities of rescue by neighbouring populations under the hypothetical case of local extinction. Seventy-four species were considered threatened, i.e. classified as Critically Endangered, Endangered or Vulnerable. These species represent 33% of breeding species in Catalonia. Establishing categories of threat is an important step in determining conservation priorities. However, these priorities should also take into account the status of species at a larger geographical scale, the relative importance of regional populations at global level and the true ability of environmental managers to influence the management of particular species given their habitats and the socioeconomic context.

Gil-Tena A.,University of Lleida | Brotons L.,Center Tecnologic Forestal Of Catalonia | Brotons L.,Institute Catala dOrnitologia | Saura S.,University of Lleida | And 2 more authors.
Forest Ecology and Management | Year: 2010

In the western Mediterranean region of Catalonia (NE Spain), during the last 20 years of the 20th century, the range of many forest bird species has expanded. Our objective was to characterize the roles of (a) spatial population processes (related to dispersal), (b) changes in forest structure (due to forest maturation and management), and (c) landscape composition (resulting from afforestation and fires) in the range expansion of these bird species at the landscape scale (10 × 10 km). After correcting for the differences in sampling effort, colonizations appeared to be more likely near areas in which the species had been present in the 1980s. Patterns of the range expansion were also strongly associated with forest maturation, which seems to affect the spatial arrangement of birds at multiple scales. Changes in forest landscape composition due to afforestation and fires were minor determinants of range changes, and forest management did not seem to prevent range expansion at the spatial scale studied. Colonization events appeared to be driven primarily by landscape changes occurring in nearby localities rather than within the colonized locations themselves, presumably because of source-sink dynamics and connectivity patterns. Our results showed that in Catalonia, at a landscape scale, the impact of forest management on forest bird communities is much smaller than the impact of the widespread maturation of forests following a large-scale decline in traditional uses. © 2009 Elsevier B.V. All rights reserved.

Gil-Tena A.,University of Lleida | Gil-Tena A.,Center Tecnologic Forestal Of Catalonia | Vega-Garcia C.,University of Lleida | Brotons L.,Center Tecnologic Forestal Of Catalonia | And 2 more authors.
Forest Systems | Year: 2010

For preserving biodiversity of European-Mediterranean forest ecosystems in current and future scenarios of global change by means of sustainable forest management it is necessary to determine how environment and forest characteristics correlate with biodiversity. For this purpose, neural networks were used to model forest bird species richness as a function of environment and forest structure and composition at the 1 × 1 km scale in Catalonia (NE Spain). Univariate and multivariate models respectively allowed exploring individual variable response and obtaining a parsimonious (ecologically meaningful) and accurate neural network. Forest area (with a canopy cover above 5%), mean forest canopy cover, mean annual temperature and summer precipitation were the best predictors of forest bird species richness. The resultant multivariate network had a good generalization capacity that failed however in the locations with highest species richness. Additionally, those forests with different degrees of canopy closure that were more mature and presented a more diverse tree species composition were also associated with higher bird species richness. This allowed us to provide management guidelines for forest planning in order to promote avian diversity in this European-Mediterranean region.

Loading Institute Catala dOrnitologia collaborators
Loading Institute Catala dOrnitologia collaborators