Restoring Landscape Connectivity Research Articles

Comparing estimates of census and effective population size in an endangered amphibian

AbstractThe field of conservation has seen a shift in focus from monitoring trends in census population size to trends in ‘effective’ population size. Numerous genetic methods exist for estimating effective population size, resulting in uncertainty among conservation practitioners as to which methods are most appropriate when conducting population assessments or evaluating recovery efforts. Demographic approaches offer a promising avenue to provide a link between census and effective population size using life‐history information, but rarely do studies have all three sources of data (genetic, demographic, life history) necessary to perform an explicit evaluation of their performance. Using data from a long‐term study of reticulated flatwoods salamanders (Ambystoma bishopi) in western Florida, USA, we assessed the magnitude of temporal variation in census population sizes and the effective number of breeders of two breeding populations to (1) document changes in the number of breeding adults over the 9‐year study duration, (2) determine whether and provide similar information about population size and trends and (3) compare alternative demographic and genetic approaches for estimating . We found that genetic estimates of , particularly if averaged across multiple estimation methods, closely tracked spatiotemporal variation in . Demographic estimates of also closely tracked but were sensitive to the assumed variance in reproductive success. In the absence of genetic information, detailed knowledge of mating systems and the environmental factors that skew reproductive contributions appear necessary for demographic to reliably inform management decisions. In these populations, appears too small (<40 individuals) to confer long‐term genetic resilience, highlighting the importance of restoring landscape connectivity and indicating that caution must be taken when sourcing animals for reintroduction efforts. More generally, our study reveals insights into the utility of alternative estimation methods in guiding recovery efforts of threatened and endangered species.

One Tree at a Time: Restoring Landscape Connectivity through Silvopastoral Systems in Transformed Amazon Landscapes

Due to the continued expansion of pastures and illicit crops, the Andes-Amazon foothills in Colombia are one of most threatened biodiversity hotspots in the country. Halting and restoring the connectivity of the landscapes transformed over the last 40 years and now dominated by extensive cattle ranching practices, represents a challenge. Silvopastoral systems (SPSs) have been proposed as a strategy to help conserve the biodiversity by improving landscape connectivity. However, understanding the contributions of SPSs to biodiversity conservation still requires additional research. At the farm scale (here called farmscape), we compared different landscape fragmentation and connectivity metrics under two SPS conditions (with and without). Overall, the adoption of SPSs increased the probability of connectivity (PC) index in all cases. However, the contributions of SPSs to landscape connectivity were not linear. Greater PC increases were observed in highly degraded farmscapes (ΔPc = 284) compared to farmscapes containing patches that were better connected and had larger habitat areas (ΔPc = 6). These variables could play a fundamental role in enhancing the landscape connectivity through restoration activities that seek to improve biodiversity conservation. Even if they are relatively small and scattered, in highly degraded cattle ranching systems, SPSs could significantly improve the landscape connectivity, which in turn could improve wildlife conservation.

Connectivity, landscape structure, and plant diversity across agricultural landscapes: novel insight into effective ecological network planning.

Natural habitats in rural and urban areas are increasingly fragmented and altered by human impacts that are limiting the animal and plant dispersal process. Fragmentation and isolation can be reversed by restoring landscape connectivity through effective Ecological Network (EN) planning. However, most of the studies analyzing the influence of connectivity and landscape structure on biodiversity are focused on animals, while the understanding of their interplaying role on plant diversity remains limited. We studied the relationships between α and β diversity pattern and landscape structure and connectivity in the nodes of an EN developed in agricultural landscapes, as a part of regional landscape planning framework in Friuli Venezia Giulia region (North-East of Italy). As an innovation, the study aims at parsing the interacting effect of landscape structure, surrounding habitats and nodes, and structural connectivity on EN plant diversity at two specific scales of investigation i.e., the habitat and the node scale. The habitat was the basic ecological unit, while the node was the basic cartographical unit for the EN mapping (multi-habitat or mono-habitat nodes). A total of 443 plant species were collected across 219 sample plots, in 14 different habitats and 87 nodes of the EN. We found that high node connectivity leads to higher species richness (α-diversity) but also increases plant community similarity (i.e., low β-diversity) at both scales. The effect of landscape structure showed differing trends depending on the habitat. In general, landscape composition of semi-natural land cover (i.e., hedgerows, watercourses) showed a positive effect on species diversity as opposed to that of the configuration of anthropogenic elements on both scales. Our results provided crucial information on the landscape processes useful to improving biodiversity conservation by EN. Our findings suggest that i) improving connectivity within ENs favors α plant diversity ii) different habitats have different sensibility to landscape structure iii) semi-natural land cover around nodes improve plant diversity; iv) planning both mono-habitat and multi-habitats nodes, increases the biodiversity conserved therein; v) nodes with more compact shapes are to be preferred.

Connectivity is Vitally Important in a Fragmented Forest Ecosystem to Sustain Biodiversity: An Analysis for Rize

Forests are the leading ecosystems that are under threat due to the pressure of global change. Being under pressure for a forest ecosystem means fragmented and isolated habitats, decrease in biodiversity and change in the landscape. In recent years, restoring landscape connectivity by minimising landscape fragmentation has been recognised as a key strategy to conserve biodiversity. Well-connected habitat networks are thought to both protect existing populations and help adaptation under climate change. It is therefore priority to understand how best to maintain and develop connectivity in fragmented landscapes at multiple spatial scales for effective conservation of forest biodiversity. In this study, fragmentation analysis was performed using area, edge, and isolation metrics in the forest matrix in the Rize landscape and connectivity corridors were interpreted to manage the impact of this fragmentation on species and habitats. The fragmentation analysis was carried out on 3 classes as broad-leaved, coniferous, and mixed using land cover/land use data with the years 1990-2018. The connectivity corridors between these classes were analysed using core area data and resistance maps. According to the results; it was observed that fragmentation in broad-leaved and coniferous classes and an increase in mixed forest class. In the connectivity analysis it was observed that the limiting effects arising from human activities increased more in 2018 compared to 1990. The results of this study showed that in a fragmented forest matrix, connectivity corridors can be identified and reconstructed the conditions necessary for the survival of biodiversity.

Assessing the regional landscape connectivity for multispecies to coordinate on-the-ground needs for mitigating linear infrastructure impact in Brasov – Prahova region

While many initiatives, studies and projects are focusing only on modelling wildlife connectivity movement, coordinated efforts should help to deliver adaptative solutions for the on-the-ground needs, while helping the planners and involving communities in landscape protection. Multispecies spatial models and maps allow the generalisation of findings across more significant regions and provide insights to maintain, improve or restore landscape connectivity, while individual species could contribute in establishing regions of focus in conservation efforts. Given the challenge of multispecies connectivity, we chose to build single connectivity models through circuit theory for brown bear, wolf, red deer, wild boar and roe deer. Further, we combined best-supported models in a regional cumulative spatial map, on which we identified areas of high importance for connectivity conservation to investigate and mitigate the impact of linear infrastructure. Results for carnivores and their prey species were similar to those obtained from brown bear landscape genetics modelling. Eastern slope facing was a clear preference of multispecies, and we trust this is due to abundant vegetation, food resources, and lack of fragmentation of forest regions. A vital area called Cold River corridor was validated both functional (brown bear) and structural (for carnivores and prey species) by this study and the results from previous research. However, a highway is planned to bisect the Cold River for the first time, and we advocate that the remaining conservation potential of the area should be maintained whenever possible while planning for evolutionary resilience and prioritizing management actions and effective strategies for all the species. Conservation easements could provide protections against development considered together with coordinated efforts for "smart development", and maintenance of existing forest and wildlife management and land uses preservation.

Comparison of methods to model species habitat networks for decision-making in nature conservation: The case of the wildcat in southern Belgium

Facing the loss of biodiversity caused by landscape fragmentation, implementation of ecological networks to connect habitats is an important biodiversity conservation issue. It is necessary to develop easily reproducible methods to identify and prioritize actions to maintain or restore ecological corridors. To date, several competing methods are used with recurrent debate on which is best and if expert-based approaches can replace data-driven models. We compared three methods: knowledge-driven (expert based), data-driven (based on species distribution model), and a mixed approach. We quantified their differences in habitat and corridor mapping, and prioritizations of landscape elements in terms of importance for connectivity. Key parameters generating these differences were identified. To put this into practice, the case study of the wildcat (Felis silvestris Schreber, 1777) was chosen. The results highlighted differences and similarities between approaches used. The data-driven approach was more successful in identifying the suitable habitat with regard to wildcat ecology, while the knowledge-driven approach was better able to account for obstacles to wildcat movements in the landscape matrix. However, these two methods converged for the identification of patterns of habitat patches and corridors that are important for global landscape connectivity. For both methods, we identified adjustments that can improve the outcome. The mixed approach largely differed in that it required more inputs to be performed. In the end, conservation actions were identified and could guide nature conservation practitioners in their efforts to restore landscape connectivity.

Assessing vegetation recovery in reclaimed opencast mines of the Teruel coalfield (Spain) using Landsat time series and boosted regression trees

Opencast mining is an activity that caters to many economic sectors; however, it has a large impact on society and the environment. After mining, the major concern is to restore the previous land cover, which was generally a natural vegetation cover. Establishing permanent vegetation cover can restore landscape connectivity and previous ecosystem functions, enhance aesthetic values and prevent off-side effects associated with post-mining landscapes. Opencast mining reclamation deals with these issues with several strategies that aim to develop a vegetation cover after mining activity has stopped. However, not all reclamation actions are effective, and assessing their efficiency by monitoring vegetation development at reclaimed sites is a time-consuming task because it usually involves extensive field work. In this study, we present a semi-automatic approach based on analysing satellite data (Landsat) time series and using a machine learning technique to identify suitable conditions for vegetation development at reclaimed opencast mines. We analysed the Teruel coalfield (Aragón, central-eastern Spain). This area is a representative Mediterranean-Continental region that is of particular interest due the diversity of reclamation actions that have been applied and the increase in drier conditions during the last decades. Conditions were described with topography derived variables, technical reclamation features and drought-occurrence variables as potential explanatory factors. The implemented approach allowed us to identify the main abiotic filters for vegetation of this geographic region: the water availability and soil retention (both controlled by the topographic slope), and the proximity to seed sources. The analysis evidenced the negative influence of drought occurrence on vegetation development, and different responses were found depending on the timescale at which drought is calculated. Our results indicate that the reclamation landform model is the main key factor influencing vegetation development. A model such as the smooth berm-slope increases water availability and controls soil erosion, and hence, improves vegetation development. In addition, we found that further than 500-600 m from the mine, the effect of seed source declines dramatically. Therefore, all these issues should be considered in future reclamation designs in a Mediterranean-Continental environment. Our methodology could be adapted to other geographic regions where spatial environmental data are available.

Assembly mechanisms of dung beetles in temperate forests and grazing pastures

The role of deterministic and stochastic mechanisms in community assembly is a key question in ecology, but little is known about their relative contribution in dung beetle assemblages. Moreover, in human modified landscapes these mechanisms are crucial to understand how biodiversity can be maintained in productive agroecosystems. We explored the assembly mechanisms driving dung beetle assemblages in forests and grazed grassland patches, and assessed the role of dung availability, soil hardness and moisture, elevation and land use heterogeneity as environmental predictors of functional diversity. To determine the underlying assembly mechanisms, we estimated functional diversity metrics (functional richness, evenness and divergence) and their departure from the predicted values by null models. We also used GLMs to assess the influence of environmental variables on functional diversity. In most cases, stochastic processes prevailed in structuring dung beetle assemblages and, consequently, environmental variables were not good predictors of dung beetle functional diversity. However, limiting similarity was found as a secondary mechanism with an effect on dung beetle assemblages in grasslands. Our results highlight the importance of stochastic processes that may reflect a metacommunity dynamic. Therefore, restoring landscape connectivity might be more important than habitat quality for the conservation of these functionally diverse beetle assemblages.

Identification of strategic corridors for restoring landscape connectivity: application to the Iberian lynx

AbstractThe conservation or creation of ecological corridors is a key to support species persistence in fragmented landscapes. However, little guidance exists on where to concentrate the restoration measures to improve corridor quality and functionality. Focusing on the emblematic Iberian lynx Lynx pardinus as the target species, and using a resistance surface parameterized through detailed telemetry data for the species, we applied a modeling approach that identifies corridors whose restoration would be more beneficial for enhancing landscape connectivity. Connectivity benefits were quantified, first, as the increase in the Probability of Connectivity metric (dPC) that results for the entire population network after reducing the effective distance along a particular corridor to its minimum possible value through restoration, and second, as dPC normalized by a proxy of the total restoration effort that would be required in each corridor. Results showed that the corridor restoration benefits were related to their effective distance (accumulated cost of movement along the corridor) and network centrality (potential frequency of use by dispersing individuals) in the current landscapes. Two corridors in which restoration efforts may be more desirable for the Iberian lynx were highlighted: the one linking the Doñana‐Aljarafe population with other populations and reintroduction areas further north, and a west‐east axis connecting the different populations in Sierra Morena. In general, the applied approach is a valuable tool to estimate how landscape connectivity may be affected when changes in the landscape are planned or can be predicted. This approach can be applied to potential corridors linking future reintroduction areas of the Iberian lynx, to case studies focusing on other landscapes and animal species, or to evaluate the impacts of corridor degradation or loss due to land use changes and other pressures.

A Study of the Relationship between Ecological Network Patch metrics and Landscape connectivity; with reference to case of Colombo Wetlands

Landscape fragmentation and habitat loss are emergent issues in Sri Lanka, which is a result of rapid urban development and inadequate concern of managing Landscape connectivity. Inland Wetlands and forests are the most valuable ecosystems effected from the fragmentation. Considering those habitats, Wetlands are among the most productive, active, diverse, and beneficial ecosystems in nature threatened by the urbanization. Therefore, this study aimed to introduce spatial strategies to locate landscape developments to restore landscape connectivity; referring to Colombo wetlands. Though the fragmentation causes alteration of wetland structure, fragments does serves to landscape connectivity functioning as an ecological network. Therefore the study aims to understand how the habitat/ ecological network patch metrics contribute to landscape connectivity. Two main methods used; to calculate the patch metrics; Patch area, Total edge, Perimeter-area ratio, Core area index and Inter-patch distances; GIS data have been used. Further, GIS enables least-cost path tool to be used to measure the Landscape connectivity and calculate number of species flow paths per wetland patch. With the data analysis, the study investigated the relationship between the patch metrics and the landscape connectivity. Referring to the findings, the study discussed; increasing the patch area, maintaining a mean perimeter-area ratio or core area index, reducing the inter patch distances could enhance landscape connectivity within in the urban wetland habitat patches. At the end, the study introduces strategies for Landscape architects to select most suitable locations to implement ecological based landscape developments adjacent to the existing urban habitat in order to enhance patch metrics and to restore the landscape connectivity Keywords: Landscape fragmentation, Ecological networks, Patch metrics, Landscape connectivity

Using topographic geodiversity to connect conservation lands in the Central Yukon, Alaska

Context Alaskan landscapes are changing due to climate change impacts. Maintaining or restoring landscape connectivity is a widely suggested climate change adaptation strategy because species are shifting their distributions to align with emerging conditions. Natural resource managers in Alaska have an opportunity to proactively design connected landscapes as infrastructure networks and economic development continue to increase in the state.

Connecting regional landscapes by ecological networks in the Greater Pearl River Delta

Landscape degradation and habitat fragmentation present one of the most pressing environmental issues associated with human development and the overuse of resources. Ecological networks are claimed to be effective for maintaining and improving landscape connectivity. Although there have been several methods of designation (such as the target species method), the present study builds a regional ecological network via a landscape ecological approach for the purpose of enhancing and restoring landscape connectivity. Using ArcGIS overlay and least-cost path algorithms, the study integrated relevant environmental and socioeconomic data into GIS projects to find optimal solutions for establishing a regional ecological network to act as a framework for improving landscape connectivity. After the addition of riparian protection areas and stepping stones, the resulting landscape configuration map depicts a potential approach to regional ecological connectivity. Further studies are needed, such as integrating this regional nature protection conceptualization with the urban development land use framework.

A three-step approach to minimise the impact of a mining site on vicuña (Vicugna vicugna) and to restore landscape connectivity.

Resource extraction projects generate a diversity of negative effects on the environment that are difficult to predict and mitigate. Consequently, adaptive management approaches have been advocated to develop effective responses to impacts that were not predicted. Mammal populations living in or around mine sites are frequently of management concern; yet, there is a dearth of published information on how to minimise the negative effects of different phases of mining operations on them. Here, we present the case study of a copper mine in the Chilean Altiplano, which caused roadkills of the protected vicuña (Vicugna vicugna). This issue led to a three-step solution being implemented: (1) the initial identification of the problem and implementation of an emergency response, (2) the scientific analysis for decision making and (3) the planning and informed implementation of responses for different future scenarios and timescales. The measures taken under each of these steps provide examples of environmental management approaches that make use of scientific information to develop integrated management responses. In brief, our case study showed how (1) the timescale and the necessity/urgency of the case were addressed, (2) the various stakeholders involved were taken into account and (3) changes were included into the physical, human and organisational elements of the company to achieve the stated objectives.

Defining and evaluating the umbrella species concept for conserving and restoring landscape connectivity.

Conserving or restoring landscape connectivity between patches of breeding habitat is a common strategy to protect threatened species from habitat fragmentation. By managing connectivity for some species, usually charismatic vertebrates, it is often assumed that these species will serve as conservation umbrellas for other species. We tested this assumption by developing a quantitative method to measure overlap in dispersal habitat of 3 threatened species-a bird (the umbrella), a butterfly, and a frog-inhabiting the same fragmented landscape. Dispersal habitat was determined with Circuitscape, which was parameterized with movement data collected for each species. Despite differences in natural history and breeding habitat, we found substantial overlap in the spatial distributions of areas important for dispersal of this suite of taxa. However, the intuitive umbrella species (the bird) did not have the highest overlap with other species in terms of the areas that supported connectivity. Nevertheless, we contend that when there are no irreconcilable differences between the dispersal habitats of species that cohabitate on the landscape, managing for umbrella species can help conserve or restore connectivity simultaneously for multiple threatened species with different habitat requirements.

A Spatially Explicit Model of Functional Connectivity for the Endangered Przewalski’s Gazelle (Procapra przewalskii) in a Patchy Landscape

BackgroundHabitat fragmentation, associated with human population expansion, impedes dispersal, reduces gene flow and aggravates inbreeding in species on the brink of extinction. Both scientific and conservation communities increasingly realize that maintaining and restoring landscape connectivity is of vital importance in biodiversity conservation. Prior to any conservation initiatives, it is helpful to present conservation practitioners with a spatially explicit model of functional connectivity for the target species or landscape.Methodology/Principal FindingsUsing Przewalski’s gazelle (Procapra przewalskii) as a model of endangered ungulate species in highly fragmented landscape, we present a model providing spatially explicit information to inform the long-term preservation of well-connected metapopulations. We employed a Geographic Information System (GIS) and expert-literature method to create a habitat suitability map, to identify potential habitats and to delineate a functional connectivity network (least-cost movement corridors and paths) for the gazelle. Results indicated that there were limited suitable habitats for the gazelle, mainly found to the north and northwest of the Qinghai Lake where four of five potential habitat patches were identified. Fifteen pairs of least-cost corridors and paths were mapped connecting eleven extant populations and two neighboring potential patches. The least-cost paths ranged from 0.2 km to 26.8 km in length (averaging 12.4 km) and were all longer than corresponding Euclidean distances.Conclusions/SignificanceThe model outputs were validated and supported by the latest findings in landscape genetics of the species, and may provide impetus for connectivity conservation programs. Dispersal barriers were examined and appropriate mitigation strategies were suggested. This study provides conservation practitioners with thorough and visualized information to reserve the landscape connectivity for Przewalski’s gazelle. In a general sense, we proposed a heuristic framework for species with similar biological and ecological characteristics.

Prioritizing highway defragmentation locations for restoring landscape connectivity

SUMMARYTransport infrastructures are a major driver of global landscape change. In many areas, highways were built before environmental impact assessments required the implementation of wildlife crossing structures. A fundamental task in the development of ecological networks is identifying areas where dispersal pathways of vulnerable populations may be blocked or affected by high volume roads. Financial considerations may limit investment, thus it is vital to establish the relative contribution of each road defragmentation location to upholding habitat connectivity and availability. In this paper, recent methodological developments in habitat network analysis, derived from the probability of connectivity index, were refined and used to evaluate the role of each highway defragmentation location in restoring landscape connectivity. The forest protected area network in the Basque country (northern Spain) was selected as an illustrative case study. The proposed approach was able to quantify and effectively account for a combination of factors determining the contribution of each highway defragmentation location to upholding connectivity, which are rarely jointly considered in analyses oriented to support restoration decisions in landscapes affected by the barrier effect of transport infrastructures. The contribution to connectivity of each defragmentation location depended on its topological position in the landscape, on the relative decrease in the effective distance among habitat areas that results from the permeability restoration at that location, on the distance from the defragmentation location to other alternative wildlife crossing structures already existing in the landscape, on the amount of habitat in the areas connected by the linkages that run through the defragmentation location and on the dispersal abilities of the focal species.

Functional habitat connectivity for beach mice depends on perceived predation risk

Landscape features that promote animal movement contribute to functional habitat connectivity. Factors that affect the use of landscape features, such as predation risk, may alter functional connectivity. We identify factors important to functional habitat connectivity by quantifying movement patterns of the Santa Rosa beach mouse (Peromyscus polionotus leucocephalus) in relation to landscape features and by examining how ambient perceived predation risk, which is altered by moon phase, interacts with landscape features. We use track paths across the sand to relate the probability that beach mice cross gaps between vegetation patches to gap width, patch quality, landscape context and moon phase. Overall activity levels were lower during full versus new moon nights, demonstrating that beach mice respond negatively to moonlight. Gap crossing was more likely during new moon nights (25 % of gaps crossed vs. 7 % during full moon nights), and across narrower gaps ( 11.75 m2). This study suggests that vegetation recovery is necessary for functional connectivity in post-hurricane landscapes commonly inhabited by beach mice and provides initial guidelines for restoring landscape connectivity. More broadly, this study highlights the importance of considering predation risk when quantifying landscape connectivity, as landscape features that facilitate connectivity when predation risk is low may be ineffective if predation risk increases over time or across space.

Why dispersal should be maximized at intermediate scales of heterogeneity.

Dispersal is a fundamental biological process that results in the redistribution of organisms due to the interplay between the mode of dispersal, the range of scales over which movement occurs, and the scale of spatial heterogeneity, in which patchiness may occur across a broad range of scales. Despite the diversity of dispersal mechanisms and dispersal length scales in nature, we posit that a fundamental scaling relationship should exist between dispersal and spatial heterogeneity. We present both a conceptual model and mathematical formalization of this expected relationship between the scale of dispersal and the scale of patchiness, which predicts that the magnitude of dispersal (number of individuals) among patches should be maximized when the scale of spatial heterogeneity (defined in terms of patch size and isolation) is neither too fine nor too coarse relative to the gap-crossing abilities of a species. We call this the “dispersal scaling hypothesis” (DSH). We demonstrate congruence in the functional form of this relationship under fundamentally different dispersal assumptions, using well-documented isotropic dispersal kernels and empirically derived dispersal parameters from diverse species, in order to explore the generality of this finding. The DSH generates testable hypotheses as to when and under what landscape scenarios dispersal is most likely to be successful. This provides insights into what management scenarios might be necessary to either restore landscape connectivity, as in certain conservation applications, or disrupt connectivity, as when attempting to manage landscapes to impede the spread of an invasive species, pest, or pathogen.

Restoring Connectivity in Landscapes Fragmented by Major Roads: A Case Study Using Wooden Poles as “Stepping Stones” for Gliding Mammals

Tree‐dwelling mammals may be vulnerable to road mortality if forced to cross canopy gaps on the ground. This group of mammals has received scant attention worldwide despite major road projects potentially causing severe fragmentation to their habitat. Gliding mammals may be enabled to cross road gaps that exceed their gliding capability by the installation of tall wooden poles to act as “stepping stones.” We investigated whether such glide poles installed across two land‐bridges in eastern Australia could restore landscape connectivity for small gliding petaurid marsupials. Hair‐traps revealed repeated use of all poles at both locations over periods of 1–3 years. Camera traps at one site suggest a crossing frequency on the poles by the squirrel glider (Petaurus norfolcensis) of once every 3.8 nights. Radio‐tracked animals did not glide directly over the road but instead used the poles to cross on the bridge. Hair‐traps and camera traps installed within the middle of two reference land‐bridges that lacked glide poles failed to detect crossings by gliding mammals despite their presence in adjacent forest. These observations suggest that glide poles can facilitate road crossing and thereby restore habitat connectivity for gliding mammals. This lends support to the notion that glide poles have the potential to mitigate road‐induced habitat fragmentation for gliding mammals worldwide.

Dispersal as a limiting factor in the colonization of restored mountain streams by plants and macroinvertebrates

Summary1. Over the past centuries, European streams have been heavily influenced by humans through pollution and regulation. As a result, the quality and diversity of freshwater riparian habitats have declined strongly, and the diversity of riparian flora and fauna has decreased. Recent restoration measures have resulted in stream habitat improvements, but biodiversity improvements have failed to follow in fragmented streams. It has been suggested that dispersal limitation could play an important role in the lack of biodiversity improvement in restored streams, but to date, there is no conclusive evidence for this assumption.2. In this study, we investigated whether colonization of restored streams by plants and macroinvertebrates is limited by dispersal. We hypothesized that colonization success increases with increasing availability of (nearby) source populations and with increasing ability of species to disperse over long distances. We related species composition in seven restored stream sections to species’ abundances in the surroundings and to species’ dispersal abilities.3. For both plants and macroinvertebrates, colonization success is strongly related to the abundance of species in the local and regional species pools.4. For plants, dispersal strategy has an additional influence on colonization success: short‐lived plants with high production of small, well‐dispersed seeds colonized best within the 3‐ to 5‐year period after restoration.5. The existence of dispersal strategy constraints could not be confirmed in macroinvertebrates, possibly because these are limited by a lack of connectivity on larger spatial scales. On the landscape scale, beneficial effects of increased plant diversity might further improve habitat suitability for macroinvertebrates.6. Synthesis and applications. Dispersal appears to be a limiting factor for successful (re)colonization of restored streams in fragmented landscapes. In plants, this is attributed to limitations in seed dispersal abilities and likely to a lack of nearby source populations as well. In macroinvertebrates, lack of nearby source populations may also be a limiting factor. Hence, we suggest restoring landscape connectivity at larger spatial scales and optimizing the availability of near‐natural ‘source’ areas in the vicinity of restoration projects, at least for plants, to improve the success of biodiversity restoration in fragmented habitats.