In this study, we (a) formulated a general hypothesis about how wetland (functional and structural) traits influence avian diversity, (b) turned this hypothesis into a non-parametric Bayesian ...network, (c) disentangled the direct and indirect effects of the variables influencing waterbird species, and (d) simulated the changes expected to the levels of avian diversity as a result of numerous counterfactual and management scenarios. We applied our framework to the Sicilian wetlands as a whole; then, we downscaled simulations locally to a wetland of particular interest (Pantano Bruno). We found that (1) waterbird species are highly sensitive to wetland traits; (2) wetland traits have both direct and indirect effects upon alpha avian diversity; (3) the direct and indirect effects of wetland traits can be contrasting; (4) water level fluctuations (benefit), diversions (cost), and salinity (cost) are key factors for waterbird conservation; (5) these wetlands have the potential for hosting a level of alpha avian diversity that is double the baseline (from 19 to 38 species); (6) these wetlands are prone to ecological collapse if all traits deteriorate (from 19 to 6 species per wetland); and (7) the ecological information gained at the regional scale can be properly downscaled to the local scale to make inferences on single wetlands.
The Sardinian wetlands (Italy) act as stopover sites for many migratory birds along the central eastern Mediterranean bird flyway. These wetlands are now severely threatened by human activities and ...climate change. Accordingly, we built a simulation framework to predict the effects of several counterfactual and management scenarios on the level of avian diversity in the coastal wetlands of Sardinia. We found that the alpha avian diversity (i.e., the mean number of avian species per wetland) is destined to (a) decrease due to the most likely increase in water salinity, water discharges, and tourism pressure; and (b) halve (from 14.9 to 7.4, with 9 wetlands out of 22 predicted to host only between two and five waterbird species) in the worst possible scenario. However, the results also showed that proper management strategies could prevent and reverse such outcomes. Restrictions on tourism activities, water desalination, prevention of future saltwater intrusions, and the prohibition of water discharges could markedly favor the avian diversity in these wetlands, with an expected increase in the alpha avian diversity from 14.9 to 24.8 (and 10 wetlands out of 22 predicted to host from 29 to 32 waterbird species) in the best possible scenario. The importance of our results could be emphasized in the management plans of these important wetlands, most of which belong to the Natura 2000 network.
Our study shows that the current levels of anthropogenic exploitation of the Sicilian wetlands (Italy), combined with the likely exacerbation of climate-driven variables, are unsustainable and could ...soon exclude many bird species from this metacommunity. Sicily is the largest island in the Mediterranean Sea, and its wetlands represent a network of unreplaceable stopover sites that allow waterbirds to rest and refuel during migratory journeys along the central-eastern Mediterranean bird flyway. During the summer period, these species experience higher levels of environmental stress as water scarcity and anthropogenic pressure are at their peak. Through field surveys, geoprocessing and statistical analyses, we investigated: (a) the structure of the avian metacommunity of the largest Sicilian wetlands during July–September and (b) the effects of 10 (geographic, hydrological and anthropogenic) wetland attributes on avian diversity. We sampled 73 bird species, of which 30 are listed in annex I of the Birds Directive. The avian metacommunity was significantly nested and non-modular; in addition, it presented elevated beta diversity and random species assemblage. Environmental filtering superseded biotic interactions in determining species composition. Avian diversity was significantly favored by higher water levels, water-level fluctuations and water discharges, and disfavored by water diversion, salinity and tourism pressure. The knowledge concerning the particular structure of the avian metacommunity of the Sicilian wetlands can facilitate the implementation of conservation policies that could mitigate and compensate the effects of short- and mid-term risks.
Biodiversity loss has multiple causes, but habitat degradation through land-use change is the predominant driver. We investigated the effectiveness of the Natura 2000 network in preserving the main ...wetlands of the two largest islands of the Mediterranean region, whose conservation is critical for many avian species at European and global level, in a 23-year period (1990–2012). In Sardinia, the surroundings of 22 wetlands were affected by an increase in artificial areas (+64 ha/year) and decrease in agricultural (−54 ha/year) and natural (−17 ha/year) ones. In Sicily, the surroundings of 16 wetlands were impacted by an increase in agricultural areas (+50 ha/year) and decrease in natural and semi-natural ones (−62 ha/year). Results show that the Natura 2000 policies were effective in preserving wetlands (no shrinkages detected in both regions), but their surroundings experienced intense processes of degradation and artificialization in all the sub-periods considered (1990–2000, 2000–2006, 2006–2012), whose effects are now threatening waterbirds and wetland integrity. The enlargement of the existing Natura 2000 sites, the creation of new ones and the speedup of the application of the rules of the Habitats and Birds Directives seem necessary to counteract the rapid land-use changes around these important stopover sites.
The selection of relevant factors and appropriate spatial scale(s) is fundamental when modelling species response to climate change. We evaluated whether the effects of climate factors on species ...distribution/occurrence are consistently modelled over different spatial scales in birds, and used a two‐scale approach to identify species–climate correlations unlikely to represent causal effects.
We used passerine birds inhabiting mountain grassland in the Apennines (Italy) as a model. We surveyed four grassland species at 400 sampling points, and built habitat selection models (territory scale) and distribution models (seven algorithms, landscape scale). We compared the effect of climatic predictors on occurrence/distribution highlighted by models over the two spatial scales, and with the effects supposed a priori based on the climatic niche of each species.
Models at the territory level included at least one climatic predictor for three species; the observed effect of climatic predictors was seldom consistent with supposed effects. At the broadest scale, distribution models for all species included climatic predictors, with varying consistence with supposed effects and findings at the finer scale.
Despite the importance of climate for species distribution, occurrence could be more directly related to other factors, with important implications for understanding/predicting the impacts of climate/environmental changes. Our approach revealed key variables for grassland birds, and highlighted the scale‐dependent perceived importance of climate. At the local scale, climate effects were weak or hard to interpret. We found a general lack of consistence between supposed and observed effects at the territory level, and between landscape and territory models. Our results show the importance of predicting the potential effect of climatic factors prior to the analyses, carefully selecting ecologically meaningful variables and scales, and evaluating the nature and scale of climate–species links. We call for caution when predicting under future climates, especially when mechanistic effects and consistency across scales are lacking.
The distribution of seabirds at sea is influenced by physical, ecological and anthropogenic factors such as sea depth, prey distribution, intra‐specific competition and commerical fishing activities. ...We quantified the foraging habitat preferences of Scopoli's Shearwater Calonectris diomedea in the Mediterranean Sea. We analysed habitat preferences in relation to a suite of physical and ecological variables including sea depth, net primary production and distance to other colonies (as a proxy of intra‐specific competition). Since the Mediterranean is heavily impacted by commercial fisheries, we also incorporated the distance to fishing harbours in our analyses as a proxy of the availability of discards which are a potential feeding source for Scopoli's Shearwater. Foraging birds preferred shallower waters and avoided areas close to other colonies, thereby reducing interactions with conspecifics. We also found that long‐distance trips were undertaken to areas close to fishing harbours, suggesting that these represented particularly profitable locations to compensate for the greater travelling costs involved. No differences in foraging between the sexes were recorded. This study improves our understanding of the at‐sea distribution and habitat preference of a seabird inhabiting the over‐exploited Mediterranean Sea. Our results support growing evidence that seabirds exhibit complex relationships with commerical fishing activities, which must be considered when planning conservation programmes.
Wetlands provide a wide range of ecosystem services, including supplying the food and shelter for a rich assemblage of waterbirds and providing the stopover sites that allow birds to make migratory ...journeys. Human impact and the ongoing climate change are however reducing the ability of wetlands to provide such important services.
Through field surveys, GIS analyses and climate projections, we assessed the status of, and threats to, 38 largest wetlands belonging to the Mediterranean bird flyways in Sardinia and Sicily (Italy). We then combined ten decision criteria about avifaunal diversity and human/climate threats in order to prioritize the studied wetlands from most to least worthy of urgent interventions.
Results showed that the main wetlands of these two regions have distinct demands with regard to the kind of actions required, going from the mitigation of tourism pressure to the prevention of climate-induced water shortage in summer. Furthermore, clear priorities for interventions emerged in both regions.
Our study has direct implications for managers and researchers attempting to assess wetland conditions and set conservation priorities, thus offering a tool for deciding urgent interventions on the main stopover sites along the Mediterranean bird flyways.
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•Wetlands provide the stopover sites that allow waterbirds to make migratory journeys.•We evaluated and prioritized 38 main wetlands in Sardinia and Sicily (Italy).•The Sardinian wetlands resulted mainly threatened by human activities.•The Sicilian wetlands resulted primarily endangered by climate change.•We suggest urgent interventions on these sites along the Mediterranean bird flyways.
The Sardinian wetlands belong to the Sardinia‐Corsica corridor of the central eastern Mediterranean bird flyway. They supply the food and shelter for many waterbird species and act as stopover sites ...during migratory journeys. Despite policies and laws of the European Union, the Sardinian wetlands are severely threatened by anthropic activities and ongoing climate change, making the condition of the associated avifauna critical.
We (a) inventoried the avian metacommunity of the largest coastal wetlands in Sardinia during the summer period, (b) investigated the metacommunity structure, (c) quantified the effects of wetland attributes on avian diversity at species and guild level and (d) predicted future changes in species composition of this metacommunity.
We recorded 60 bird species (of which 21 belonged to Annex I of the Birds Directive). The metacommunity structure resulted was significantly nested and non‐modular. Salinity negatively affected the presence of 48 species out of 60, followed by tourism pressure (44 species), wetland isolation (42 species) and water discharges (36 species). The mean water level resulting from artificial regulation for anthropic activities was too high for 63% of the species, which disadvantaged primarily small waders, species feeding on invertebrates and trans‐Saharan migrants. In addition, water‐level fluctuations (that would favour avian diversity) were prevented by artificial regulation during the summer period in many wetlands, producing further negative effects on the avifauna. We found 45% of the recorded bird species at risk of disappearance from this avian metacommunity.
Synthesis and applications. Our study indicates that, as things stand, the avian metacommunity of the Sardinian wetlands is destined to experience reductions in the short term and mid‐term. This decline will be accelerated by increased saltwater intrusions due to sea‐level rise. Nevertheless, the nested and non‐modular structure of this avian metacommunity would allow for pro‐active conservation measures (e.g. restriction for tourism activities, construction of artificial dune cordons to minimize saltwater intrusions, water‐level regulation that keeps into account also the ecological requirements of waterbird species) to counteract the effects of current and future threats.
Our study indicates that, as things stand, the avian metacommunity of the Sardinian wetlands is destined to experience reductions in the short term and mid‐term. This decline will be accelerated by increased saltwater intrusions due to sea‐level rise. Nevertheless, the nested and non‐modular structure of this avian metacommunity would allow for pro‐active conservation measures (e.g. restriction for tourism activities, construction of artificial dune cordons to minimize saltwater intrusions, water‐level regulation that keeps into account also the ecological requirements of waterbird species) to counteract the effects of current and future threats.
Climate and land-use change are the most severe threats to biodiversity; their effects are often intermingled, also with those of landscape/habitat management. Birds of mountain grassland are ...declining throughout Europe. Disentangling climate effects from those of land-cover and management on their occurrence is essential to identify distribution drivers, potential impacts of climate/land-use changes, and effective conservation strategies. We investigated the occurrence of water pipit (elevation specialist), skylark and red-backed shrike (elevation generalists) in Central Apennines, Italy (750–2130 m asl), using point counts. Topographic/climatic, land-cover and management fine-scale variables were considered as potential occurrence predictors in Generalized Linear Models. For all species, combining different types of predictors led to the most accurate models, but the relative importance of single-groups varied: land cover was the most important for skylark, climate/topography for water pipit, all three groups had similar support for red-backed shrike. Skylark was positively affected by solar radiation and grassland cover, and negatively by bare ground, hedgerows, rocks, shrubland, ski-pistes and buildings, confirming sensitivity to anthropic alteration of semi-natural grassland. Water pipit was favoured by grazing and negatively impacted by shrubland and average temperature (most important predictor). Red-backed shrike was affected negatively by broadleaved forest and grazing occurrence, quadratically by isolated shrubs and positively by grassland cover. Climate was a fundamental determinant of water pipit occurrence, but not for the other species. Land-cover was important for all species and also management factors were invariably included in models. Climate, habitat and management factors differently contributed to occurrence patterns in these declining species. Conservation strategies need to embrace landscape planning to preserve grassland extents/mosaics, identify climate refugia for water pipit and implement dedicated management (preventing new ski-pistes over areas suitable for birds and carefully planning grazing). It should be feasible to combine local, sustainable economies with biodiversity conservation into landscape planning for Central Apennines.
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•The effects of climate, land-use and management are crucial and often intermingled.•Disentangling them is essential to understand the decline of mountain grassland birds.•We investigated drivers of occurrence in skylark, water pipit and red-backed shrike.•Land cover, climate/topography and management had different importance across species.•Conservation strategies need to integrate climatic features, land-cover and management.
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