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- Blazquez-Cabrera, Sandra, et al.
(författare)
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Indicators of the impacts of habitat loss on connectivity and related conservation priorities : Do they change when habitat patches are defined at different scales?
- 2014
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 45, s. 704-716
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Tidskriftsartikel (refereegranskat)abstract
- Delivering indicators of habitat connectivity first requires identifying the habitat units that will be treated as individual entities for spatially explicit analyses. These units can be defined at different spatial scales or hierarchical levels, from single habitat patches to aggregations of multiple neighbor patches. Many studies have assessed the scale sensitivity of landscape-level pattern metrics when changing spatial resolution or extent. However, how patch-level connectivity indicators change across hierarchical levels (independently from modifications in resolution or extent) has been largely overlooked, despite the potentially strong and determinant effects on their outcomes and final uses. We evaluated how the hierarchical level at which habitat units are defined affects two types of outcomes frequently derived from connectivity indicators: (i) the importance values (or estimated amount of decrease in landscape connectivity that would be caused by the loss of certain habitat areas), and (ii) the priority ranking (key areas to conserve to minimize connectivity loss), as given by a selected set of widely used metrics (habitat availability, network centrality, metapopulation capacity). We found that importance values can largely vary depending on how habitat units are defined, suggesting that such results may be flawed by a particular a priori selection of hierarchical levels. However, the identification of which parts of the landscape contain the key connectivity providers (priority ranking) was robust, particularly for those metrics that account for the amount of connectivity within habitat units. We conclude that current connectivity indicators based on patch removals do not allow, considering their scale dependence, to consistently assess the magnitude of connectivity decrease resulting from large-scale habitat loss, but that they can be used with much more confidence for detecting those key areas that most contribute to maintain current connectivity levels.
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| 2. |
- Bodin, Örjan, et al.
(författare)
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Ranking individual habitat patches as connectivity providers : Integrating network analysis and patch removal experiments
- 2010
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 221:19, s. 2393-2405
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Tidskriftsartikel (refereegranskat)abstract
- Here we propose an integrated framework for modeling connectivity that can help ecologists, conservation planners and managers to identify patches that, more than others, contribute to uphold species dispersal and other ecological flows in a landscape context. We elaborate, extend and partly integrate recent network-based approaches for modeling and supporting the management of fragmented landscapes. In doing so, experimental patch removal techniques and network analytical approaches are merged into one integrated modeling framework for assessing the role of individual patches as connectivity providers. In particular, we focus the analyses on the habitat availability metrics PC and IIC and on the network metric Betweenness Centrality. The combination and extension of these metrics jointly assess both the immediate connectivity impacts of the loss of a particular patch and the resulting increased vulnerability of the network to subsequent disruptions. In using the framework to analyze the connectivity of two real landscapes in Madagascar and Catalonia (NE Spain), we suggest a procedure that can be used to rank individual habitat patches and show that the combined metrics reveal relevant and non-redundant information valuable to assert and quantify distinctive connectivity aspects of any given patch in the landscape. Hence, we argue that the proposed framework could facilitate more ecologically informed decision-making in managing fragmented landscapes. Finally, we discuss and highlight some of the advantages, limitations and key differences between the considered metrics.
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| 3. |
- Saura, Santiago, et al.
(författare)
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Stepping stones are crucial for species' long-distance dispersal and range expansion through habitat networks
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51:1, s. 171-182
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Tidskriftsartikel (refereegranskat)abstract
- Climate and land-use changes will require species to move large distances following shifts in their suitable habitats, which will frequently involve traversing intensively human-modified landscapes. Practitioners will therefore need to evaluate and act to enhance the degree to which habitat patches scattered throughout the landscape may function as stepping stones facilitating dispersal among otherwise isolated habitat areas. We formulate a new generalized network model of habitat connectivity that accounts for the number of dispersing individuals and for long-distance dispersal processes across generations. By doing so, we bridge the gap between complex dynamic population models, which are generally too data demanding and hence difficult to apply in practical wide-scale decision-making, and simpler static connectivity models that only consider the amount of habitat that can be reached by a single average disperser during its life span. We find that the loss of intermediate and sufficiently large stepping-stone habitat patches can cause a sharp decline in the distance that can be traversed by species (critical spatial thresholds) that cannot be effectively compensated by other factors previously regarded as crucial for long-distance dispersal (fat-tailed dispersal kernels, source population size). We corroborate our findings by showing that our model largely outperforms previous connectivity models in explaining the large-scale range expansion of a forest bird species, the Black Woodpecker Dryocopus martius, over a 20-year period. The capacity of species to exploit the opportunities created by networks of stepping-stone patches largely depends on species-specific life-history traits, suggesting that species assemblages traversing fragmented landscapes may be exposed to a spatial filtering process driving long-term changes in community composition.Synthesis and applications. Previous static connectivity models seriously underestimate the importance of stepping-stone patches in sustaining rare but crucial dispersal events. We provide a conceptually broader model that shows that stepping stones (i) must be of sufficient size to be of conservation value, (ii) are particularly crucial for the spread of species (either native or invasive) or genotypes over long distances and (iii) can effectively reduce the isolation of the largest habitat blocks in reserves, therefore largely contributing to species persistence across wide spatial and temporal scales. Previous static connectivity models seriously underestimate the importance of stepping-stone patches in sustaining rare but crucial dispersal events. We provide a conceptually broader model that shows that stepping stones (i) must be of sufficient size to be of conservation value, (ii) are particularly crucial for the spread of species (either native or invasive) or genotypes over long distances and (iii) can effectively reduce the isolation of the largest habitat blocks in reserves, therefore largely contributing to species persistence across wide spatial and temporal scales. Editor's Choice
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| 5. |
- Zetterberg, Andreas, et al.
(författare)
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Sprawl or dense? : Assessing impacts of regional development plans on landscape network connectivity
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The management of landscape connectivity has been identified as one of the most important measures to counteract negative impacts on biodiversity by habitat loss and fragmentation. Such management must be able to cross spatial and temporal administrative and ecological scales. The use of graph-theory and network-based landscape-ecological tools has gained considerable interest as a promising way forward to address these issues. However, despite urgent needs to adapt and implement network-based connectivity analysis in planning, assessment and decision-making, surprisingly little attention has been paid to developing approaches for their effective practical application. In this paper, a large-scale assessment of the Regional Development Plan for the Stockholm Region (RUFS 2010) was carried out, argued to be the first graph-theoretic assessment of landscape connectivity for real proposed planning alternatives. In addition, it is the first time where the analysis of connectivity was an integral part in the planning process. Three planning alternatives were compared with the current situation for four different habitat types and one hundred different dispersal capacities. Three families of network metrics representing different underlying processes were selected, that have previously been shown to capture the variability of a larger set of metrics. The sprawl alternative emerged as having the largest negative impact while the dense alternative had the smallest. However, when comparing the impact with the amount of habitat consumed, the sprawl alternative emerged as being the most efficient in several situations. In order to achieve a better understanding of the underlying processes, a spatial study was carried out. The analysis leads to important insights on the planning of connectivity in an urbanizing region, argued to be applicable within a broad set of urbanizing regions throughout the world.
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