Do bird spatial distribution patterns reflect population trends in changing landscapes (original) (raw)
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Ecography, 2008
Animal community dynamics in changing landscapes are primarily driven by changes in vegetation structure and ultimately by how species respond to these changes and at which spatial scale. We consider two major components of local community dynamics, species colonisation and extinction. We hypothesise that (1) the optimal spatial extent needed to accurately predict them will differ between these two processes; (2) it will also likely differ from species to species as a result of life history traits differences related to differences in habitat selection and (3) that a species' primary habitat will determine the spatial extent at which it perceives change in vegetation structure. We used data collected over 25 yr in a changing Mediterranean landscape to study bird species local colonisation and extinction patterns in two groups of species typical from two habitats: open farmland and woodland. Vegetation changes were measured at spatial extents ranging from 0.2 to 79 ha. Local species colonisation and extinction estimates were computed using a method accounting for heterogeneity in detection probability among species. We built linear models between local species colonisation/extinction estimates and vegetation changes and examined variations in model quality with respect to the spatial extent at which vegetation changes had been measured. Models for open habitat species showed that colonisation processes operated at the landscape scale (79 ha), while extinction was more tightly linked to local habitat requirements (0.2 ha). Models for woodland species presented a low and constant model quality whatever the spatial extent considered. Our results suggest that the dynamics of the woodland species considered responded to a combination of vegetation changes at several scales and, in particular, to changes in the vertical structure of the vegetation. We highlight the need to explicitly consider spatial extent in studies of habitat selection and of habitat and population dynamics to improve our understanding of the biological consequences of land use changes and guide more effective conservation efforts.
Erratum to: Do bird spatial distribution patterns reflect population trends in changing landscapes
Landscape Ecology, 2010
Erratum to: Landscape Ecol (2009) 24:893–906 DOI 10.1007/s10980-009-9365-5The authors regret that there was a mistake in Table 2 in the above paper. This mistake affects the results presented in the paragraph Landscape changes but does not affect the general conclusion.ResultsLandscape changesOpen habitat was associated with a low overlap of polygons between years (RAO) and a high percentage of existing polygons that disappeared (RAD; Table 2). The number of Open habitat polygons decreased while the median of their size increased (Table 2) due to the disappearance of the smallest polygons (Fig. 2). Shrubland also showed a low overlap of polygons between years as well as a high percentage of both disappearance of existing polygons and generation of new polygons (Table 2). The number of Shrubland polygons increased and the median of their size decreased (Table 2) due to the fragmentation of existing polygons and the appearance of small polygons in former open habitat (Fig. 2). Woodland w ...
Assessing the response of open-habitat bird species to landscape changes in Mediterranean mosaics
Biodiversity and Conservation, 2008
In Mediterranean landscapes, wildfires and land abandonment lead to major landscape modifications primarily by favouring the presence of open, shrub-like habitats. At present, we know very little of how these changes affect patterns of species occurrence at the landscape scale. In this work, we analyse the impact of these landscape changes on the occurrence patterns of eight open-habitat species by using presence/absence data collected in the Catalan Breeding Bird Atlas (NE Spain). We compared the species occurrence patterns along habitat gradients for three different landscape settings: a semi-permanent farmland-forest landscape (i.e. with variable proportions of farmland and forests) and two landscape settings which mimic those favoured by land abandonment and fire: farmland-shrubland landscapes and mosaic landscapes (i.e. variable proportions of farmland and forest coexisting with a shrubby matrix). In the forest-farmland landscape, we found a dominant negative effect of adjacent forest on species occurrence rates. This overall effect mostly disappeared in farmland-shrubland landscapes composed by two habitats with more similar vegetation structure. In mosaic landscapes, the general negative effect of forest habitats also appeared to be partially compensated by the presence of a shrubby matrix. Our results suggest that landscape gradients induced by fire and to some degree also land abandonment, mainly favouring availability of shrublands may potentially enhance the resilience of threatened open-habitat species at the landscape scale by increasing the range of potential habitats used. The analysis of species-occurrence patterns along predefined habitat gradients appears as a useful tool to predict potential species responses to land use change.
Temporal changes in Mediterranean bird communities across fragmented and continuous forests
Ecological Research, 2015
Habitat loss and fragmentation are recognized as the main causes for the global biodiversity crisis. Most of the studies investigating the issue of habitat fragmentation in vertebrates are cross-sectional, whereas long-term studies are least available. We surveyed bird communities in 17 forest fragments (FF) and a single continuous forest stands (CF) in central Italy twice, 10 years apart (i.e. in 1996 and in 2006). All community parameters showed a contrasting pattern between 1996 and 2006, i.e. an increase of abundance and diversity measures in CF and a decrease or a stability of the same parameters in FF. Insectivorous and migratory bird species were the most prone to population declines associated with fragmented landscapes. Differences in species turnover between CF and FF were due to a higher extinction rate in the latter forest type. There was substantial population increase between 1996 and 2006, especially in FF, of opportunistic predator species like corvids. This fact may be responsible for the observed dropping in species number, evenness and diversity in FF. Hence, we conclude that, in FF, the bird community is far from being either stabilized or resilient, as it is rapidly evolving into a more simplified assemblage, dominated by generalist species.
Ecological Indicators, 2014
Developing sound indicators of biodiversity impact has been identified as a critical step towards our understanding of how global change components are affecting the environment across the globe. Land abandonment is recognized as a major component of global change in the Mediterranean basin, however, we lack adequate, quantitative, indicators of its impact on biodiversity. An appealing approach to develop biodiversity indicators is the use of large-scale bird monitoring projects, an important source of information that is already available in many countries. In this study we develop a method to quantify the impact of the two main processes associated with land abandonment in the Mediterranean region, namely the abandonment of farmland, which produces a shift from cultivated land to open natural habitats, and the encroachment by vegetation usually associated with reductions in livestock grazing and wood harvesting practices. We used data from bird atlas and monitoring schemes in Catalonia (north-east Iberian Peninsula) to characterize species' population response to these processes by means of detecting quantitative changes in relative abundances along a gradient ranging from habitats not affected by a given driving force to those that arise as a consequence of such force. We then generated multi-species indicators of the impact of these land use changes using these specific population responses to calibrate the relative contribution of each species in the composite index. The temporal patterns depicted by the two indicators in the period 2002-2011 show that vegetation encroachment did have a significant impact on bird communities, whereas any noticeable effect of farmland abandonment on bird populations was observed. The methodology proposed here could be employed to develop indicators capable to track biological impacts of land use change on an annual basis and inform decision-makers about the rate of increase or decrease on wildlife populations.
Dangers of predicting bird species distributions in response to land-cover changes
Ecological Applications, 2009
Land-cover changes from the last decades are leading to important declines in habitat quality, giving rise to changes in bird species distribution all over the world. However, land-cover changes result from a variety of different processes, and it is not clear how effective species distribution models are in capturing species responses to these changes. In this study, we evaluated our ability to predict the effects of land-cover changes on shifts in species distributions at large spatial and temporal scales using Mediterranean landscapes and earlysuccessional, open-habitat birds as study models. Based on presence-absence data from the second Catalan Breeding Bird Atlas (1999)(2000)(2001)(2002), we applied six different species distribution modeling techniques for 10 bird species using climate, topographic, and land-cover data as predictor variables. Then we back-projected the models on land-cover conditions from 1980 to evaluate the projections with field observation data from the first Catalan Breeding Bird Atlas (1975)(1976)(1977)(1978)(1979)(1981)(1982)(1983). Finally, we assessed if, in addition to changes in habitat suitability resulting from land-cover shifts, descriptors of fire impact contributed to further explain species distribution dynamics: colonization and local extinction.
Forest Fragmentation and Bird Community Dynamics: Inference at Regional Scales
Ecology, 2001
With increasing fragmentation of natural areas and a dramatic reduction of forest cover in several parts of the world, quantifying the impact of such changes on species richness and community dynamics has been a subject of much concern. Here, we tested whether in more fragmented landscapes there was a lower number of area-sensitive species and higher local extinction and turnover rates, which could explain higher temporal variability in species richness. To investigate such potential landscape effects at a regional scale, we merged two independent, large-scale monitoring efforts: the North American Breeding Bird Survey (BBS) and the Land Use and Land Cover Classification data from the U.S. Geological Survey.
Vegetation and songbird response to land abandonment: from landscape to census plot
Diversity and Distributions, 2006
While intensification of human activities and its ecological effects in many natural areas have recently received much attention, land abandonment in marginal areas is still the largely ignored side of a process rooted in the same socioeconomic context. Decreasing human impact in marginal rural areas often triggers a recovery of seminatural vegetation. Over a period of 25 years, we studied the changes in landscape and vegetation structure that followed land abandonment in a traditional Mediterranean mosaic of crops, grasslands, shrublands and woodlands, and assessed their effects on songbird occurrence and distribution. We combined an analysis of vegetation changes based on aerial photo interpretation with an analysis of bird censuses from 1978, 1992 and 2003 at two spatial scales: landscape and census plot (respectively 2800 and 3 ha). The perceived temporal changes in the vegetation were scale dependent. At the landscape scale, open habitats tended to disappear and woodlands matured. The contrasts in vegetation structure that defined habitat patches at the onset of the study tended to disappear. There was an overall shift of the bird community in favour of woodland species. At the scale of the census plot, however, the colonization by woody vegetation of patches formerly characterized by a homogeneous grass cover increased the local diversity of the vegetation, at least temporarily. Of seven species dependent on open habitats, the occurrence rate of five species significantly decreased, whereas it increased for two species: woodlark (Lulula arborea) and melodious warbler (Hippolais polyglotta). This increase was linked to the transitional increase in local vegetation diversity. In patches originally dominated by woodlands, local vegetation diversity decreased as woody vegetation expanded into clearings. The occurrence rate significantly increased for seven species relying on closed woodlands, while it decreased for two woodland species. As most species of high conservation profile in the Mediterranean are tied to open or to heterogeneous transitional habitats, these trends raise questions concerning their persistence in the future.