Improving longitudinal habitat connectivity in major river restoration projects through farmland re-allocation

River restoration projects are often accompanied by major land consolidation operations, notably the re-allocation of adjacent farmland, which offers the opportunity to create an extensively-managed buffer zone outside the levees where specific habitat features are installed for endangered terrestrial and semi-aquatic biodiversity. Modern, enrivonmentally-friendly land consolidation operations might thus not only contribute to better integrate the newly restored river into the adjacent landscape, but also to reinstate the longitudinal ecological connectivity that crudely lacks along channelized rivers. Based on a theoretical re-allocation of agricultural land via land consolidation, we simulated the creation of a longitudinal biodiversity-friendly grassland buffer along a stretch of the Rhone River (SW Switzerland) where a major revitalisation project is under development. We selected a series of focal species depending on a palette of complementary habitat features, and combinations thereof, to be created for reaching these biodiversity targets. Estimations of species-specific habitat patch size requirements as well as dispersal abilities were used to analyse what would be an optimal spatial connectivity for these habitat features. Since such a buffer zone will necessarily stretch along the riverbed, which implies different spatial contraints and consequential planning strategies, we tested two scenarios via a metapopulation model: (i) arranging key habitat features longitudinally or (ii) positioning them in an isotropic context. Simulations showed that differences in metapopulation connectivity between scenarios were negligible at the foreseen scale. We conclude that land consolidation via targeted farmland re-allocation could be instrumental to restoring ecological connectivity in major river revitalisation projects. We also provide concrete quantitative values for restoring an optimal ecological buffer along the Rhˆone that will promote locally endangered biodiversity

Open forest successional stages and landscape heterogeneity promote wild bee diversity in temperate forests

Recent studies have emphasized forests as crucial habitat for wild bees. In Europe, most forests are managed following the principles of close-to-nature silviculture, which combine timber production and nature conservation. How- ever, open late and early successional stages within these forests are largely missing, which could be important for wild bees. This highlights that close-to- nature silviculture alone might not be sufficient to conserve bees within tem- perate forests. Open structures such as canopy gaps and road verges in forests could improve habitat for bees. To provide management recommendations for wild bee conservation in temperate forests, we analyzed how components of bee beta diversity varied between forest management types and tested how open structures, namely clear-cuts, canopy gaps, and forest road verges influ- enced bee abundance, richness, and diversity. In addition, we analyzed the abundance and percent of red-listed bee species at different scales. Bees were sampled using 90 pan traps on 45 (1 ha) plots in 2019 and 2020 in the Black Forest, Germany. Plots were selected in 15 triplets each consisting of three management types related to different successional stages: unmanaged, close- to-nature, and small clear-cut. Beta diversity was not consistently nested highlighting the importance of different management and successional stages within the landscape to support bees in forests. Abundance, species richness, and Shannon diversity of bees were highest on clear-cuts, compared to unmanaged- and close-to-nature plots. At landscape scale, wild bee abundance increased with canopy openness while wild bee diversity increased with land- scape heterogeneity. Abundance- and percent of red-listed bee species increased with the length of forest road verges. We advocate creating habitats at local scales which offer flowering and nesting resources by providing canopy gaps. At landscape scale, heterogeneity created through different forest succes- sional stages is needed to conserve the entire community of wild bees

Present in the western European Alps but absent in the eastern part: Can habitat availability explain the differences in red-billed chough occurrence?

The absence of a species in apparently suitable regions is often attributed to habitat deterioration, which, according to the IUCN-guidelines, would preclude reintroduction unless the habitat is sufficiently restored. The crux is therefore to determine species’ key habitat requisites and to localize potentially restorable sites based on the habitat selection of thriving populations in similar environments. The distribution of the red-billed chough Pyrrhocorax pyrrhocorax in the Alpine arch is currently restricted to its western side. The eastern Alps have only been occupied sporadically during past centuries, which triggered a discussion around reintroduction. The fact that the last confirmed pairs bred at middle elevation, in derelict buildings instead of alpine cliffs, suggested a lack of habitat suitability in the uplands. To test this hypothesis, we modelled seasonal foraging habitat (during winter, breeding and dispersal) and nest site-selection in the western Swiss Alps using long-term observation data together with a wide palette of environmental predictors. The models were extrapolated to eastern Switzerland to estimate the quality and extent of the available habitat. Both foraging and nesting habitats were predicted with a high level of accuracy (AUC > 0.8). Despite variation between seasons, south-exposed dry meadows and extensively grazed pastures were always preferred as foraging habitat, while forested and snow-covered areas were avoided. Availability of, and distance to suitable foraging habitats were the main determinants of nest-site selection, probably reflecting strong energetic constraints during reproduction. However, the extrapolation to eastern Switzerland revealed an even higher overall amount and relative percentage of all habitat types. One explanation could be that our predictors were too coarse to encapsulate qualitative, structural or compositional differences of the grasslands. However, the results could also point to an alternative hypothesis, namely that post-glacial recolonization patterns, in particular the absence of nearby source populations, precluded the occupation of the eastern Alps

Modelling the habitat selection of the bearded vulture to predict areas of potential conflict with wind energy development in the Swiss Alps

Global warming impels countries to dramatically reduce their release of greenhouse gas emissions and increase their reliance on green energy, notably wind power. Yet, without cautious planning, the sprawl of wind turbines could negatively impact biodiversity, especially flying vertebrates that are otherwise already threatened. Inherent risks for vulnerable and endangered species are usually mitigated by banning constructions within buffer areas around nesting locations. This approach, however, neglects species’ range dynamics and particularly falls short of protecting expanding populations, as in the case of natural returns or reintroduction programmes. We present here an alternative approach to mitigate wildlife-infrastructure conflicts, applying it to the bearded vulture, a species reintroduced in the European Alps. Combining casual observations and GPS locations of tagged individuals, we built several predictive distribution models with respect to bearded vulture age class and season and tested for models’ ability to correctly predict its future expansion in the Alps. Although immature and adult birds showed different habitat selection patterns, both in summer and winter, wide areas of the Swiss Alps (40%) offer suitable habitat. The above combined information enabled correctly predicting today’s use by breeding bearded vultures of previously unused areas. This study not only provides a detailed analysis of the bearded vulture’s ecological requirements in the Alps but also helps delineating areas where conflicts with wind energy production and other aerial infrastructure will likely occur in Switzerland. The resulting maps provide a large-scale planning tool that companies, landscape planners and wildlife managers can use in any environmental risk assessments

New vineyard cultivation practices create patchy ground vegetation, favouring Woodlarks

Intensive agriculture, in which detrimental farming practices lessen food abundance and/or reduce food accessibility for many animal species, has led to a widespread collapse of farmland biodiversity. Vineyards in central and southern Europe are intensively cultivated; though they may still harbour several rare plant and animal species, they remain little studied. Over the past decades, there has been a considerable reduction in the application of insecticides in wine production, with a progressive shift to biological control (integrated production) and, to a lesser extent, organic production. Spraying of herbicides has also diminished, which has led to more vegetation cover on the ground, although most vineyards remain bare, especially in southern Europe. The effects of these potentially positive environmental trends upon biodiversity remain mostly unknown as regards vertebrates. The Woodlark (Lullula arborea) is an endangered, short-distance migratory bird that forages and breeds on the ground. In southern Switzerland (Valais), it occurs mostly in vineyards. We used radiotracking and mixed effects logistic regression models to assess Woodlark response to modern vineyard farming practices, study factors driving foraging micro-habitat selection, and determine optimal habitat profile to inform management. The presence of ground vegetation cover was the main factor dictating the selection of foraging locations, with an optimum around 55% at the foraging patch scale. These conditions are met in integrated production vineyards, but only when grass is tolerated on part of the ground surface, which is the case on ca. 5% of the total Valais vineyard area. In contrast, conventionally managed vineyards covering ≥95% of the vineyard area are too bare because of systematic application of herbicides all over the ground, whilst the rare organic vineyards usually have a too-dense sward. The optimal mosaic with ca. 50% ground vegetation cover is currently achieved in integrated production vineyards where herbicide is applied every second row. In organic production, ca. 50% ground vegetation cover should be promoted, which requires regular mechanical removal of ground vegetation. These measures are likely to benefit general biodiversity in vineyard

Saproxylic beetles respond to habitat variables at different spatial scales depending on variable type and species’ mobility: the need for multi-scale forest structure management

The response of species to the environment is scale-dependent and the spatial scale at which this relationships are measured may affect conservation recommendations. Saproxylic beetles depend on decaying- and deadwood which occur in lower quantities in managed compared to natural forests. Most studies have investigated the habitat selection of saproxylic beetles at the stand scale, however depending on the species mobility, the amounts and distribution of forest attributes across the landscape may be equally important, and thus crucial to frame quantitative conservation targets. To address this gap, we evaluated the influence of environmental variables, derived from remote sensing across multiple spatial scales (50, 100, 250, 500 and 1000 m radius), on saproxylic beetles habitat selection. Focusing on four mobile and four flightless species, we hypothesized that mobile species respond to habitat variables at broader scales compared to flightless species, and that variables describing forest structure explain species presence better at smaller scales than variables describing other landscape features. Forest structure variables explained around 40% of the habitat selection, followed by variables describing forest type, topography and climate. Contrary to our expectations, mobile species responded to variables at smaller scales than flightless species. Saproxylic beetle species therefore respond to the availability of habitat features at spatial scales that are inversely related to their dispersal capacities, suggesting that less mobile species require larger areas with suitable habitat characteristics while mobile species can also make use of small, distributed patches with locally concentrated habitat features

Automated Detection of Forest Gaps in Spruce Dominated Stands Using Canopy Height Models Derived from Stereo Aerial Imagery

Forest gaps are important structural elements in forest ecology to which various conservation-relevant, photophilic species are associated. To automatically map forest gaps and detect their changes over time, we developed a method based on Digital Surface Models (DSM) derived from stereoscopic aerial imagery and a LiDAR-based Digital Elevation Model (LiDAR DEM). Gaps were detected and delineated in relation to height and cover of the surrounding forest comparing data from two public flight campaigns (2009 and 2012) in a 1023-ha model region in the Northern Black Forest, Southwest Germany. The method was evaluated using an independent validation dataset obtained by visual stereo-interpretation. Gaps were automatically detected with an overall accuracy of 0.90 (2009) and 0.82 (2012). However, a very high producers’ accuracy of more than 0.95 (both years) was counterbalanced by a user’s accuracy of 0.84 (2009) and 0.73 (2012) as some gaps were not automatically detected. Accuracy was mainly dependent on the shadow occurrence and height of the surrounding forest with user’s accuracies dropping to 0.70 (2009) and 0.52 (2012) in high stands (>8 m tree height). As one important step in the workflow, the class of open forest, an important feature for many forest species, was delineated with a very good overall accuracy of 0.92 (both years) with uncertainties occurring mostly in areas with intermediate canopy cover. Presence of complete or partial shadow and geometric limitations of stereo image matching were identified as the main sources of errors in the method performance, suggesting that images with a higher overlap and resolution and ameliorated image-matching algorithms provide the greatest potential for improvement

Improved methods for measuring forest landscape structure: LiDAR complements field-based habitat assessment

Conservation and monitoring of forest biodiversity requires reliable information about forest structure and composition at multiple spatial scales. However, detailed data about forest habitat characteristics across large areas are often incomplete due to difficulties associated with field sampling methods. To overcome this limitation we employed a nationally available light detection and ranging (LiDAR) remote sensing dataset to develop variables describing forest landscape structure across a large environmental gradient in Switzerland. Using a model species indicative of structurally rich mountain forests (hazel grouse Bonasa bonasia), we tested the potential of such variables to predict species occurrence and evaluated the additional benefit of LiDAR data when used in combination with traditional, sample plot-based field variables. We calibrated boosted regression trees(BRT) models for both variable sets separately and in combination, and compared the models' accuracies. While both field-based and LiDAR models performed well, combining the two data sources improved the accuracy of the species' habitat model. The variables retained from the two datasets held different types of information: field variables mostly quantified food resources and cover in the field and shrub layer, LiDAR variables characterized heterogeneity of vegetation structure which correlated with field variables describing the understory and ground vegetation. When combined with data on forest vegetation composition from field surveys, LiDAR provides valuable complementary information for encompassing species niches more comprehensively. Thus, LiDAR bridges the gap between precise, locally restricted field-data and coarse digital land cover information by reliably identifying habitat structure and quality across large areas