Abstract
Widespread farmland abandonment has led to significant landscape transformations of many European mountain areas. These semi-natural multi-habitat landscapes are important reservoirs of biodiversity and their abandonment has important conservation implications. In multi-habitat landscapes the adaptation of communities depends on the differential affinity of the species to the available habitats. We use nested species-area relationships (SAR) to model species richness patterns of bird communities across scales in a mountain landscape, in NW Portugal. We compare the performance of the classic-SAR and the countryside-SAR (i.e. multi-habitat) models at the landscape scale, and compare species similarity decay (SSD) at the regional scale. We find a considerable overlap of bird communities in the different land-uses (farmland, shrubland and oak forest) at the landscape scale. Analysis of the classic and countryside SAR show that specialist species are strongly related to their favourite habitat. Farmland and shrubland have higher regional SSD compared to oak forests. However, this is due to the opportunistic use of farmlands by generalist birds. Forest specialists display significant regional turnover in oak forest. Overall, the countryside-SAR model had a better fit to the data showing that habitat composition determines species richness across scales. Finally, we use the countryside-SAR model to forecast bird diversity under four scenarios of land-use change. Farmland abandonment scenarios show little impact on bird diversity as the model predicts that the complete loss of farmland is less dramatic, in terms of species diversity loss, than the disappearance of native Galicio-Portuguese oak forest. The affinities of species to non-preferred habitats suggest that bird communities can adapt to land-use changes derived from farmland abandonment. Based on model predictions we argue that rewilding may be a suitable management option for many European mountain areas.
Highlights
Changes and loss of biodiversity can directly influence ecosystem structure and functioning [1], reduce ecosystem resilience to disturbances such as global warming [2], and jeopardize vital ecosystem services that support human well-being [3]
We found significant species-area relationships for all species groups in each of the three land-uses (Figure 4)
In farmland this pattern is primarily due to the decay of generalist and shrubland specialists, as farmland specialists do not display a pattern of regional species turnover (p-value n.s.)
Summary
Changes and loss of biodiversity can directly influence ecosystem structure and functioning [1], reduce ecosystem resilience to disturbances such as global warming [2], and jeopardize vital ecosystem services that support human well-being [3]. In Europe, during the last decades, agricultural intensification and industrialization of former extensively managed arable lands have promoted land abandonment and marginalization of many remote mountain areas [5]. This socio-ecological trend is mostly driven by human migration to urban areas [6], reflects the generalized demand for better life conditions (namely material well-being; [7]) and exhibits high chances of irreversibility [8]. Vegetation disturbance is highly reduced and secondary succession takes place, allowing the regeneration of native vegetation. The secondary expansion of shrubs and the regeneration of forest on former farmland and pastures lead to a simplification of the traditional landscape mosaic [5,9], which affects regional biodiversity [10,11]
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