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Habitat restoration is an effective method for improving landscape connectivity, which can reduce habitat fragmentation. Maintaining landscape connectivity could promote connections between habitat, which is extremely essential to preserve gene flow and population viability. This study proposes a methodological framework to analyze landscape connectivity for Asian elephant habitat conservation, aiming to provide practical options for reducing habitat fragmentation and improving habitat connectivity. Our approach involved combining a species distribution model using MaxEnt and landscape functional connectivity models using graph theory to assess the impact on connectivity improvement via farmland/plantation restoration as habitat. The results showed that: (1) there were 119 suitable habitat patches of Asian elephant covering a total area of 1952.41 km2. (2) The connectivity between habitats improved significantly after vegetation restoration and the gain first decreased and then increased with the increase of dispersal distance. (3) The first few new habitat patches that were identified played an important role in improving connectivity, and the variation rate of connectivity gradually leveled off as the number of new habitats increased. (4) Prioritization of the 25 best new habitat patches increased connectivity from 0.54% to 5.59% as the dispersal distance increased and mainly was located between two Asian elephant distribution regions and two components. Establishment of new habitat patches was effective for improving or restoring connectivity. Our findings can be used as guidance for improving the studied fragmented Asian elephant habitats, and they can also be used as a reference for the habitat restoration of other endangered species heavily affected by habitat fragmentation. [ABSTRACT FROM AUTHOR]

Habitat connectivity is a key objective of current conservation policies and is commonly modeled by landscape graphs (i.e., sets of habitat patches [nodes] connected by potential dispersal paths [links]). These graphs are often built based on expert opinion or species distribution models (SDMs) and therefore lack empirical validation from data more closely reflecting functional connectivity. Accordingly, we tested whether landscape graphs reflect how habitat connectivity influences gene flow, which is one of the main ecoevolutionary processes. To that purpose, we modeled the habitat network of a forest bird (plumbeous warbler [Setophaga plumbea]) on Guadeloupe with graphs based on expert opinion, Jacobs' specialization indices, and an SDM. We used genetic data (712 birds from 27 populations) to compute local genetic indices and pairwise genetic distances. Finally, we assessed the relationships between genetic distances or indices and cost distances or connectivity metrics with maximum‐likelihood population‐effects distance models and Spearman correlations between metrics. Overall, the landscape graphs reliably reflected the influence of connectivity on population genetic structure; validation R2 was up to 0.30 and correlation coefficients were up to 0.71. Yet, the relationship among graph ecological relevance, data requirements, and construction and analysis methods was not straightforward because the graph based on the most complex construction method (species distribution modeling) sometimes had less ecological relevance than the others. Cross‐validation methods and sensitivity analyzes allowed us to make the advantages and limitations of each construction method spatially explicit. We confirmed the relevance of landscape graphs for conservation modeling but recommend a case‐specific consideration of the cost‐effectiveness of their construction methods. We hope the replication of independent validation approaches across species and landscapes will strengthen the ecological relevance of connectivity models. [ABSTRACT FROM AUTHOR]

Urban green spaces are key for maintaining and restoring habitat connectivity within cities. Despite substantial investigations on the contribution to connectivity of different types of urban green spaces, the specific contribution of green spaces located in multifamily residential (MFR) plots has yet to be assessed. Estimating this contribution is crucial given the multiple roles fulfilled by these green spaces in urban planning. To achieve this goal, we focused on four taxa: the European hedgehog (Erinaceus europaeus), the Red squirrel (Sciurus vulgaris), forest passerine birds and moths. We assessed the potential habitat connectivity for each taxon across the metropolitan urban area of Lyon (France), with landscape graphs built using 1-metre resolution land cover maps. Considering the current state as a reference, we then designed five land cover change scenarios affecting habitat distribution in the MFR plots: (i) maximum and (ii) minimum theoretical connectivity (references), (iii) improve quality of existing green spaces, (iv) improve quantity of green spaces with sub-optimal quality and, (v) maximum restoration (management scenarios). The taxon- and scenario-specific impacts highlight the crucial contribution of private spaces to habitat connectivity. For all taxa, while the MFR only cover 8 % of the study area, connectivity would increase by up to 60 % if these plots were greened. In contrast, sealing these plots could reduce overall connectivity by up to 40 %. The interpolation of local connectivity metrics for each habitat patch and each MFR plot allowed us to identify the most relevant plots for urban greening. Because our approach can improve habitat connectivity at different scales, from neighbourhoods to entire urban areas, it could prove useful for landscape planning in most urban settings. • Urban green spaces are crucial to habitat connectivity but the contribution of green areas located in multi-family residential plots is all too often overlooked/under-appreciated. • We modelled the habitat networks of four taxa with landscape graphs, using a 1-metre resolution land cover map. • Five land-cover change scenarios affecting multi-family residential plots were compared: two references (maximum and minimum theoretical connectivity) and three management scenarios (improve quality of existing green spaces, improve quantity of green spaces with sub-optimal quality and maximum restoration). • The city-level and plot-level connectivity metrics computed for each scenario and taxon highlight the key contribution to connectivity of urban green spaces included in multi-family residential plots. • Interpolated maps of connectivity metrics can support citizen commitment and help planners prioritise (re)greening actions. [ABSTRACT FROM AUTHOR]

The construction of highways leads to several environmental and landscape impacts, including the fragmentation of natural habitats for many animal species. Highway projects are therefore generally accompanied by mobilisations from the inhabitants of the areas concerned and environmental associations. This work aims to model the potential impacts of a highway project in France on ecological networks and to study the reception of the results by the opponents of this project. We have adopted a three-step approach. First, a land-cover map of the study area was produced at a fine scale of 10 m resolution. Second, we developed a multi-species approach by defining fifteen species groups representative of different habitats of our study area. Third, the design of landscape graphs and the resulting calculation of connectivity metrics allowed mapping the impact of the highway on multi-species ecological connectivity. Reflexive feedback from comments on these results by the public during a mobilisation day against the highway project allows assessment of the relevance of such a modelling approach in this context.

National, European and international commitments have been made to maintain and restore the connectivity of natural habitats to face habitat loss and fragmentation. Meanwhile, environmental policies in different countries worldwide have proposed the mitigation hierarchy to reach the goal of "no net loss (NNL) of biodiversity". The mitigation hierarchy aims at assessing all the ecological impacts of a development project, but the impacts on landscape connectivity are not properly addressed. We propose an operational framework to assess the environmental impacts of a development project on landscape habitat connectivity. This framework is based on graph theory and the equivalent connectivity index EC of "amount of reachable habitat", which takes into account the total amount of habitat, the spatial configuration of habitat patches and the dispersal capacities of the species. We redefine the three main issues of the mitigation hierarchy regarding "no net loss of connectivity". Then, this framework was applied to a simple, virtual network case where several scenarios of impact avoidance, reduction and compensation were tested and compared. We discuss the benefits and limitations of this approach for the mitigation hierarchy and provide practical recommendations for implementation. In conclusion, we advocate and justify a better integration of the three main biodiversity conservation policies in France : the law for the recovery of biodiversity, nature and landscapes, the SRADDET and the strategy for the establishment of protected areas.

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Maintaining biodiversity is vital for ecological processes. Yet, present static protected areas seem to be inefficient in biodiversity conservation. In this study, we use a set of indicators to evaluate topological features, landscape connectivity and resilience of the current habitat conservation institution, and apply the node addition method to prioritize habitats that play roles in improving connectivity and resilience outside the protected areas. Wanzhou District, Chongqing (SW China) is selected as the study area as it is a biodiversity hotspot in Three Gorges Reservoir Area. The results show that, in current conservation institution, average clustering coefficient and average weighted degree rise with the increasing dispersal distance of species; besides, landscape connectivity is rather low, while long dispersers have larger connectivity degree and resilience compared with short ones. Furthermore, how those patches could function as connectivity providers in different aspects (e.g. stepping-stone effect) is also presented by partitioning the connectivity indicator into three parts. However, it is interesting to find that, patches with good performance in improving connectivity may not have the equal efficiency in enhancing resilience, and the possible reasons are elaborately discussed. Prioritized patches are suggested to be placed under protection, and to update the habitat conservation institution. Our indicators and method can extend the knowledge of the importance of linking protected areas with surrounding habitats, and it can serve as a supporting tool for conservation planning or land use planning. [ABSTRACT FROM AUTHOR]

Many studies have been conducted to evaluate the effects of different urban structures on landscape connectivity, and most of them rely on the comparison approach or ex-ante scenario analysis. However, we still lack an ex-post method to capture the consequences of accomplished urban structure shift (from monocentric to polycentric), which is guided by the land use planning. To fill this gap, we develop an ex-post evaluation approach which integrates counterfactual analysis and landscape graphs. Counterfactual analysis is combined with cellular automata simulation model, to uncover what the city might look like, if it had continued to expand in a monocentric structure; and the landscape graphs enable us to reveal the possible landscape connectivity in actual and counterfactual scenarios. We select Nanjing city as the study area and 4 target species, to delve into the varying impacts of the urban structure shift on different taxonomic groups. Our case study demonstrates that: (1) the impact of urban structure shift is more relevant to the long disperser; (2) the actual landscape (polycentric) would facilitate the bird's dispersal, while (3) forest mammals have higher connectivity in the counterfactual scenario (monocentric), and the possible reasons are discussed. Finally, we demonstrate that the urban structure shift might not necessarily cause the connectivity decline, on condition that the key connectivity providers are identified by integrating ecological network analysis into the land use planning, and well preserved in the shift. [ABSTRACT FROM AUTHOR]

Context: Land-cover changes (LCCs) could impact wildlife populations through gains or losses of natural habitats and changes in the landscape mosaic. To assess such impacts, we need to focus on landscape connectivity from a diachronic perspective. Objectives: We propose a method for assessing the impact of LCCs on landscape connectivity through a multi-species approach based on graph theory. To do this, we combine two approaches devised to spatialize the variation of multi-species connectivity and to quantify the importance of types of LCCs for single-species connectivity by highlighting the possible contradictory effects. Methods: We begin with a list of landscape species and create virtual species with similar ecological requirements. We model the ecological network of these virtual species at two dates and compute the variation of a local and global connectivity metric to assess the impacts of the LCCs on their dispersal capacities. Results: The spatial variation of multi-species connectivity showed that local impacts range from −6.4% to +3.2%. The assessment of the impacts of types of LCCs showed a variation in global connectivity ranging from −45.1% for open-area reptiles to +170.2% for natural open-area birds with low-dispersion capacities. Conclusions: This generic approach can be reproduced in a large variety of spatial contexts by adapting the selection of the initial species. The proposed method could inform and guide conservation actions and landscape management strategies so as to enhance or maintain connectivity for species at a landscape scale. [ABSTRACT FROM AUTHOR]

Linear Transport Infrastructures (LTI) contributes to the land use changes underpinning the 6th extinction. However, as the term LTI covers several types of infrastructure, the link between the presence of an LTI and the extinction increase is not always straight forward and depends on the nature of the LTI and its surrounding landscape. To limit the impact of LTI on biodiversity, the mitigation hierarchy aims at balancing biodiversity losses and gains to achieve the No Net Loss goals. Based on a scenario comparison of expected losses and gains during the conception to exploitation sequence of a gas pipeline on the protected butterfly P. alcon , we showed that the evaluation's spatial range of impacts and offsets is crucial to design the compensation measures. Indeed, using individual-based spatially-explicit model of P. alcon metapopulation functioning, we showed that at the locale scale (environmental impact assessment scope), the equivalence (population size, global flow of individuals and connectivity) is not reached after the project development. The forest opening due to the pipeline building contributes to reaching the equivalency of flow of individuals but changes in the population functioning leads to a loss of individuals. At the sub-regional scale, simulation results highlight unexpected negative effects up to 3 km from the infrastructure. The changes in the population functioning at the locale scale influence the sub-regional population functioning leading to a loss of population size, global flow of individuals and connectivity. Considering our results, we illustrate the crucial role of spatial scales to implement the mitigation hierarchy in environmental assessment. Practitioners should ensure that impacts and offset range of expected effect overlap at any impacted spatial scales. We argue that ecological modelling should be a relevant approach to test scenarios even at larger scales than current practices that can be monitored on operative environmental impact assessment. • We use IBM to compare scenarios of population dynamics. • We compare ecological equivalence at the local and sub-regional scales. • Most impacts of the pipeline occurs outside the EIA scope. • The offset gains have not a sufficient range of impact to overlap all the impacts. • We propose a model-oriented framework to define the EIA scope. [ABSTRACT FROM AUTHOR]

The impacts of urban growth on biodiversity vary according to the form and the intensity of urbanisation. However, there is a lack of knowledge about the consequences of the type of urban structure (e.g. monocentric vs polycentric), the shape of urban boundaries, the local density of residential development, on the habitats of wildlife species. In this context, this paper focuses on the relationship between forms of urbanisation and functional connectivity of ecological habitats. In the urban region of Besançon (eastern France), three emblematic protected species were selected to represent forest mammals. From the initial state describing current land cover, five prospective residential development scenarios were simulated, corresponding to the form currently most commonly found (e.g. compact development, transit-oriented development, polycentric development). For each scenario, we also simulate the volume of traffic on the road network to allow for the barrier effect of roads on habitat connectivity. Then, for each development scenario, we model the functional connectivity of habitats of the various target species using landscape graphs. Results show that compact city maintains more functional connectivity for all the species considered whereas urban sprawl leads to much more marked impacts. Moderately compact and regulated periurban scenarios have intermediate levels of impact. The transit-oriented development scenario produces specific impact values according to the species. An interesting point is that the decline in functional connectivity of forest habitats is more due to increased traffic than residential development proper. This outlines the relevance of integrated models for simulating both land use and transport at a fine scale. [ABSTRACT FROM AUTHOR]

Habitat restoration is one way of reducing landscape fragmentation, which is seen as a threat to biodiversity. It consists in renovating disused or degraded habitat patches or in creating new habitat patches in suitable areas. Currently, most restoration measures draw on the local knowledge of experts for selecting the best locations. For amphibian metapopulations like the European tree frog ( Hyla arborea ), the search for such locations must include regional-scale connectivity in order to maintain their viability. We set up a systematic and cumulative protocol for adding new habitat patches to a pond network. Graph modelling is used to include regional-scale connectivity as a criterion to be maximized. Successive locations are tested systematically and connectivity is compared before and after the virtual addition of each new pond. The location that increases connectivity most is identified. The results show that the priority areas identified by the model are similar to those suggested by local experts from a wildlife conservation association. The two approaches are complementary because they are applied on two different scales. The patch addition method can identify strategic areas for improving global connectivity by taking into account the regional scale. Experts’ knowledge can target the precise location within the identified area for creating new habitats based on local factors of the surrounding context. In addition, our method can be also used to prioritize locations already decided on by landscape managers. Consequently, this protocol appears to be a useful tool for guiding habitat restoration in the field. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present work is to assess the potential long-distance effect of a high-speed railway line on the distribution of the European tree frog (Hyla arborea) in eastern France by combining graph-based analysis and species distribution models. This combination is a way to integrate patch-level connectivity metrics on different scales into a predictive model. The approach used is put in place before the construction of the infrastructure and allows areas potentially affected by isolation to be mapped. Through a diachronic analysis, comparing species distribution before and after the construction of the infrastructure, we identify changes in the probability of species presence and we determine the maximum distance of impact. The results show that the potential impact decreases with distance from the high-speed railway line and the largest disturbances occur within the first 500 m. Between 500 m and 3500 m, the infrastructure generates a moderate decrease in the probability of presence with maximum values close to −40%. Beyond 3500 m the average disturbance is less than −10%. The spatial extent of the impact is greater than the dispersal distance of the tree frog, confirming the assumption of the long-distance effect of the infrastructure. This predictive modelling approach appears to be a useful tool for environmental impact assessment and strategic environmental assessment. The results of the species distribution assessment may provide guidance for field surveys and support for conservation decisions by identifying the areas most affected. [Copyright &y& Elsevier]

The influence of landscape features on the movement of an organism between two point locations is often measured as an effective distance. Typically, raster models of landscape resistance are used to calculate effective distance. Because organisms may experience landscape heterogeneity at different scales (i.e. functional grains), using a raster with too fine or too coarse a spatial grain (i.e. analysis grain) may lead to inaccurate estimates of effective distance. We adopted a simulation approach where the true functional grain and effective distance for a theoretical organism were defined and the analysis grains of landscape connectivity models were systematically changed. We used moving windows and grains of connectivity, a recently introduced landscape graph method that uses an irregular tessellation of the resistance surface to coarsen the landscape data. We then used least-cost path metrics to measure effective distance and found that matching the functional and analysis grain sizes was most accurate at recovering the expected effective distance, affirming the importance of multi-scale analysis. Moving window scaling with a maximum function (win.max) performed well when the majority of landscape structure influencing connectivity consisted of high resistance features. Moving window scaling with a minimum function (win.min) performed well when the relevant landscape structure consisted of low resistance regions. The grains of connectivity method performed well under all scenarios, avoiding an a priori choice of window function, which may be challenging in complex landscapes. Appendices are provided that demonstrate the use of grains of connectivity models. [ABSTRACT FROM AUTHOR]

Abstract: Graph theory has become a popular tool for modelling the functional connectivity of landscapes. We conduct a review of studies that use graph theory to model connectivity among patches of habitat (patch-based graphs), with the intention of identifying typical research questions and their associated graph construction and analysis methods. We identify and examine nine questions of conservation importance that can be answered with these types of graph models, discussing appropriate applications of these questions and presenting a guide for using graph methods to answer them. We also investigate how the connectivity predictions of patch-based graphs have been assessed and emphasize the importance of empirical evaluation. Our findings identify commonality among diverse approaches and methodological gaps with an aim to improve application and to help the integration of graph theory and ecological analysis. [ABSTRACT FROM AUTHOR]

• Ecological network modelling has been integrated in a participatory approach. • Ecological networks are modelled from multi-species landscape graphs. • Scientists and stakeholders co-constructed qualitative land-use planning scenarios. • Impacts of scenarios on multi-species landscape connectivity are estimated. • Results support a critical feedback on policy decisions and actions. This research aims at integrating ecological networks modelling in a participatory approach in order to assess impacts of land-use planning scenarios on landscape connectivity. This approach was applied to the metropolitan area of Bordeaux, a highly dynamic territory that has been modified by several decades of rapid urbanization. Whilst ecological network modelling is widely used in the academic spheres, the concept of ecological network itself also rose within operational stakeholders acting in land-use planning. However, exchanges between scientists and stakeholders about this concept and its modelling and decision-making applications remain rare and generally relate to discussions about results of analyzes carried out by scientists on their own. To our knowledge, no studies to date have involved stakeholders throughout the whole modelling process. In this purpose, we developed an adapted companion modelling approach bringing together scientists and stakeholders for co-constructing (1) a multi-species approach based on ecoprofiles, (2) a conceptual model of the territory's social-ecological functioning and (3) five land-use planning scenarios over a 15-years horizon. In parallel, we used a landscape graphs approach for modelling ecological networks of ecoprofiles, computing local and global connectivity metrics and estimating scenarios' impacts on multi-species connectivity. The results globally showed negative impacts of dystopian scenarios or anticipated trends in planning on landscape connectivity (from −20.5% to −8.1% on average, respectively), and in a lesser extent positive impacts of utopian or transformative scenarios (+1.5% and 4.5% on average, respectively). Scenarios' impacts also varied among ecoprofiles, with some ecoprofiles showing similar or antagonistic effects. These results served as a support of debates between stakeholders on the consequences of policy decisions and actions on connectivity, and on the possibilities of translating connectivity modelling in land-use planning and biodiversity conservation in an urban context. [ABSTRACT FROM AUTHOR]

Habitat restoration is one of the actions to reduce landscape fragmentation by promoting connectivity and thus biodiversity. But knowing where to implement these habitats is a major issue and planners lack guidance for answering this question, in particular when it involves multiple species and over a large area. We proposed to combine biological data, habitat suitability models and spatial graphs to improve multiscale and multispecies connectivity in Ile-de-France, a highly artificialized region of 12,000 km2. The framework consisted of i) modeling habitat suitability for eight pond-dwelling species (Alytes obstetricans, Bufo bufo, Epidalea calamita, Hyla arborea, Rana temporaria, Salamandra salamandra , Triturus cristatus, and Natrix natrix), ii) modeling the ecological network for each species, iii) prioritizing each sampling point depending on the gain in connectivity if a new pond was created there and iv) combining single-species results to identify the areas that could improve multispecies connectivity. The multivariate statistical analysis revealed that transitional forest environments appeared to be the most strategic areas for improving multispecific connectivity (at least for 5 species). Targeted addition of habitat within an ecological network can increase habitat density in deficient areas and reconnect network sub-parts. This approach is therefore promising to guide conservation actions and "no net loss" biodiversity measures, especially the final stage of offset in the mitigation hierarchy. • Habitat restoration or creation is one of the actions to reduce fragmentation. • Our goal was to improve multiscale and multispecies functional connectivity. • We modeled habitat suitability and ecological network for eight pond-dwelling species. • Forest edges appeared strategic for improving multispecific connectivity. • The results provide insights into central issues of biodiversity offset and habitat restoration. [ABSTRACT FROM AUTHOR]

We develop methods for quantifying habitat connectivity at multiple scales and assigning conservation priority to habitat patches based on their contribution to connectivity. By representing the habitat mosaic as a mathematical "graph," we show that percolation theory can be used to quantify connectivity at multiple scales from empirical landscape data. Our results indicate that connectivity of landscapes is highly scale dependent, exhibiting a marked transition at a characteristic distance and varying significantly for organisms with different dispersal behavior. More importantly, we show that the sensitivity and importance of landscape pattern is also scale dependent, peaking at scales associated with the percolation transition. In addition, the sensitivity analysis allows us to identify critical "stepping stone" patches that, when removed from the landscape, cause large changes in connectivity.

The article discusses the methods for quantifying habitat connectivity at multiple scales and assigning conservation priority to habitat patches based on their contribution to connectivity. The paper shows the use of percolation theory in quantifying habitat connectivity. Analyses revealed the dependence of the sensitivity and importance of landscape pattern on multiple scales and on the spatial distribution of habitats across a landscape. Findings also indicated that habitat loss has a highly scale-dependent effect on landscape connectivity.