A Meta‐Analytic Review of Corridor Effectiveness

Abstract: Using corridors for conservation is increasing despite a lack of consensus on their efficacy. Specifically, whether corridors increase movement of plants and animals between habitat fragments has been addressed on a case‐by‐case basis with mixed results. Because of the growing number of well‐designed experiments that have addressed this question, we conducted a meta‐analysis to determine whether corridors increase movement; whether corridor effectiveness differs among taxa; how recent changes in experimental design have influenced findings; and whether corridor effectiveness differs between manipulative and natural experiments. To conduct our meta‐analysis, we analyzed 78 experiments from 35 studies using a conservative hierarchical Bayesian model that accounts for hierarchical and sampling dependence. We found a highly significant result that corridors increase movement between habitat patches by approximately 50% compared to patches that are not connected with corridors. We found that corridors were more important for the movement of invertebrates, nonavian vertebrates, and plants than they were for birds. Recent methodological advances in corridor experiments, such as controlling for the area added by corridors, did not influence whether corridors increased movement, whereas controlling for the distance between source and connected or unconnected recipient patches decreased movement through corridors. After controlling for taxa differences and whether studies controlled for distance in experimental design, we found that natural corridors (those existing in landscapes prior to the study) showed more movement than manipulated corridors (those created and maintained for the study). Our results suggest that existing corridors increase species movement in fragmented landscapes and that efforts spent on maintaining and creating corridors are worthwhile.     

Value of Semi-Open Corridors for Simultaneously Connecting Open and Wooded Habitats: a Case Study with Ground Beetles

Abstract:  To counteract habitat fragmentation, the connectivity of a landscape should be enhanced. Corridors are thought to facilitate movement between disconnected patches of habitat, and linear strips of habitat connecting isolated patches are a popular type of corridor. On the other hand, the creation of new corridors can lead to fragmentation of the surrounding habitat. For example, heathland corridors connect patches of heathland and alternatively hedgerows connect patches of woodland. Nevertheless, these corridors themselves also break up previously connected patches of their surrounding habitat and in so doing fragment another type of habitat (heathland corridors fragment woodlands and woodland strips or hedgerows fragment heathlands). To overcome this challenge we propose the use of semi-open habitats (a mixture of heathland and woodland vegetation) as conservation corridors to enable dispersal of both stenotopic heathland and woodland species. We used two semi-open corridors with a mosaic of heathland and woody vegetation to investigate the efficiency of semi-open corridors for species dispersal and to assess whether these corridors might be a suitable approach for nature conservation. We conducted a mark-recapture study on three stenotopic flightless carabid beetles of heathlands and woodlands and took an inventory of all the carabid species in two semi-open corridors. Both methodological approaches showed simultaneous immigration of woodland and heathland species in the semi-open corridor. Detrended correspondence analysis showed a clear separation of the given habitats and affirmed that semi-open corridors are a good strategy for connecting woodlands and heathlands. The best means of creating and preserving semi-open corridors is probably through extensive grazing .     

Use of Empirically Derived Source-Destination Models to Map Regional Conservation Corridors

Abstract:  The ability of populations to be connected across large landscapes via dispersal is critical to long-term viability for many species. One means to mitigate population isolation is the protection of movement corridors among habitat patches. Nevertheless, the utility of small, narrow, linear features as habitat corridors has been hotly debated. Here, we argue that analysis of movement across continuously resistant landscapes allows a shift to a broader consideration of how landscape patterns influence connectivity at scales relevant to conservation. We further argue that this change in scale and definition of the connectivity problem improves one's ability to find solutions and may help resolve long-standing disputes regarding scale and definition of movement corridors and their importance to population connectivity. We used a new method that combines empirically derived landscape-resistance maps and least-cost path analysis between multiple source and destination locations to assess habitat isolation and identify corridors and barriers to organism movement. Specifically, we used a genetically based landscape resistance model for American black bears ( Ursus americanus ) to identify major movement corridors and barriers to population connectivity between Yellowstone National Park and the Canadian border. Even though western Montana and northern Idaho contain abundant public lands and the largest wilderness areas in the contiguous United States, moving from the Canadian border to Yellowstone Park along those paths indicated by modeled gene flow required bears to cross at least 6 potential barriers. Our methods are generic and can be applied to virtually any species for which reliable maps of landscape resistance can be developed.     

Determining Minimum Habitat Areas and Habitat Corridors for Cougars

I simulated population dynamics of cougars to predict the minimum areas and levels of immigration needed to avoid population extinction caused by demographic and environmental stochasticity for a period of 100 years. Under most plausible parameter values, the model predicted very low extinction risk in areas as small as 2200 km², and (in the absence of immigration) increasing risk as area decreased below 2200 km². If as few as one to four animals per decade could immigrate into a small population, the probability of population persistence increased markedly. Thus a corridor for immigration will benefit a small population in an area where further loss of habitat will occur. The model was applied to the cougar population in the Santa Ana Mountain Range of southern California (2070 km², with about 20 adults). Field data support the model’s conclusion that this population is demographically unstable. There will be a high risk of extinction if the habitat is reduced to currently protected and connected areas (1114 km²). A movement corridor allowing immigration from the adjacent population and intra-range corridors would greatly enhance the prognosis. However, the last corridor for immigration has been degraded by recent human activity. Within the mountain range, cougars recently became extinct in a 75 km² habitat fragment recently isolated by development, and cougars will become extinct in another 150 km² of habitat if a proposed housing project occludes a critical corridor. Radio tracking has confirmed use of this and other important corridors. Neither the model nor the field data alone would have much influence in the face of development pressure; together they have stimulated interest in restoring and protecting critical corridors in this range. Nonetheless, the long-term prognosis for this populations is bleak, because 22 local governments review potential impact on a case-by-case basis. Effective land-use planning must be spatially explicit and regional in scope. Because cougars need corridors and because telemetered cougars can quickly identify movement corridors, cougar research is an efficient and appropriate way to inject biological data into such planning efforts.     

Effects of Weighting Schemes on the Identification of Wildlife Corridors Generated with Least‐Cost Methods

The importance of movement corridors for maintaining connectivity within metapopulations of wild animals is a cornerstone of conservation. One common approach for determining corridor locations is least‐cost corridor (LCC) modeling, which uses algorithms within a geographic information system to search for routes with the lowest cumulative resistance between target locations on a landscape. However, the presentation of multiple LCCs that connect multiple locations generally assumes all corridors contribute equally to connectivity, regardless of the likelihood that animals will use them. Thus, LCCs may overemphasize seldom‐used longer routes and underemphasize more frequently used shorter routes. We hypothesize that, depending on conservation objectives and available biological information, weighting individual corridors on the basis of species‐specific movement, dispersal, or gene flow data may better identify effective corridors. We tested whether locations of key connectivity areas, defined as the highest 75th and 90th percentile cumulative weighted value of approximately 155,000 corridors, shift under different weighting scenarios. In addition, we quantified the amount and location of private land that intersect key connectivity areas under each weighting scheme. Some areas that appeared well connected when analyzed with unweighted corridors exhibited much less connectivity compared with weighting schemes that discount corridors with large effective distances. Furthermore, the amount and location of key connectivity areas that intersected private land varied among weighting schemes. We believe biological assumptions and conservation objectives should be explicitly incorporated to weight corridors when assessing landscape connectivity. These results are highly relevant to conservation planning because on the basis of recent interest by government agencies and nongovernmental organizations in maintaining and enhancing wildlife corridors, connectivity will likely be an important criterion for prioritization of land purchases and swaps. Efectos de los Esquemas de Ponderación sobre la Identificación de Corredores para Vida Silvestre Generados con Métodos Menos Costosos     

Desert-dwelling Mountain Sheep: Conservation Implications of a Naturally Fragmented Distribution

Abstract: Mountain sheep (Ovis canadensis) are closely associated with steep, mountainous, open terrain. Their habitat consequently occurs in a naturally fragmented pattern, often with substantial expanses of unsuitable habitat between suitable patches; the sheep have been noted to be slow colonizers of vacant suitable habitat. As a result, resource managers have focused on (1) conserving "traditional" mountainous habitats, and (2) forced colonization through reintroduction. Telemetry studies in desert habitats have recorded more intermountain movement by desert sheep than was previously thought to OCCUT. Given the heretofore unrecognized vagility of mountain sheep, we argue that existing corridors of "nontraditional" habitat connecting mountain ranges be given adequate conservation consideration. Additionally, small areas of mountainous habitat that an? not permanently occupied but that may serve as "stepping stones" within such corridors must be recognized for their potential importance to relatively isolated populations of mountain sheep. We discuss the potential importance of such corridors to other large, vagile species.     

Use of Riparian Corridors and Vineyards by Mammalian Predators in Northern California

Abstract:  To address increasing fragmentation, conservation biologists have focused on protecting core habitat areas and maintaining connectivity among protected areas. Wildlife corridors, strips of relatively intact habitat designed to connect habitat fragments, may enhance connectivity, but little empirical evidence supports the idea that large mammals prefer to use corridors rather than the surrounding developed landscape. In Sonoma County, a premium wine-grape-growing region in California, we examined mammalian predator use of 21 riparian corridors classified as denuded, narrow, or wide according to the width of the remaining natural vegetation adjacent to the creek. We used unbaited, remotely triggered cameras to determine occurrence of predator species. We also monitored predator use of six vineyards, three close to core habitat and three far from core habitat, with unbaited cameras. Mammalian predator detection rates were 11-fold higher in riparian study areas than in vineyards. More native mammalian predator species were found in wide corridors than in narrow or denuded creek corridors. The number and activity level of native predators was higher in vineyards adjacent to core habitat than in vineyards farther away, where the number and activity level of non-native predators was higher. Maintaining wide and well-vegetated riparian corridors may be important in maintaining the connectivity of native predator populations to ensure their long-term survival.     

Application of least-cost path model to identify a giant panda dispersal corridor network after the Wenchuan earthquake—Case study of Wolong Nature Reserve in China

With growing levels of human-activity and frequent natural disturbances throughout the world, it is increasingly important that both research and management efforts take into account the widespread landscape fragmentation and its consequences for biodiversity conservation. The magnitude 5.12 Wenchuan earthquake in China caused dramatic impacts on giant panda (Ailuropoda melanoleuca) habitat in the nature reserves within Minshan and Qionglai mountains. With the combined stresses of the natural disaster and the extensive human activities during postquake reconstruction, giant panda habitat in this region may become more fragmented in the future. In order to preserve the giant panda population after the earthquake and protect the species against habitat fragmentation, this article explores a method of identifying giant panda migration corridors involving habitat suitability assessments and a least-cost path model. Focusing on postquake Wolong Nature Reserve, our results demonstrate that it contains 430.3 km² of suitable habitat (21.1% of total area), 463.8 km² of marginally suitable habitat (22.8%) and 1141.9 km² of unsuitable habitat (50.1%). We further show that several giant panda dispersal corridors exist in the reserve, including four corridor groups that cross the provincial highway and five corridors that do not intersect areas of human activity. This study will contribute to management and conservation efforts in Wolong Nature Reserve and beyond after the Wenchuan earthquake.     

Effectiveness of Corridors Relative to Enlargement of Habitat Patches

Abstract:  The establishment of biological corridors between two otherwise isolated habitat patches is a common yet contentious strategy for conserving populations in fragmented landscapes. We compared the effectiveness of corridors with the effectiveness of an alternate conservation strategy, the enlargement of existing habitat patches. We used a spatially explicit population model that simulated population size in two kinds of patches. One patch had a corridor that connected it to a larger "source" patch and the other patch was unconnected and enlarged at the periphery by an area the same size as the corridor. Patch isolation, corridor width, patch size, and the probability that individuals would cross the border from habitat to matrix were varied independently. In general, population size was greater in enlarged patches than in connected patches when patches were relatively large and isolated. Corridor width and the probability of crossing the border from habitat to matrix did not affect the relative benefit of corridors versus patch enlargement. Although biological corridors may mitigate potential effects of inbreeding depression at long time scales, our results suggest that they are not always the best method of conserving fragmented populations.     

Mapping legal authority for terrestrial conservation corridors along streams

Wildlife corridors aim to promote species’ persistence by connecting habitat patches across fragmented landscapes. Their implementation is limited by patterns of land ownership and complicated by differences in the jurisdictional and regulatory authorities under which lands are managed. Terrestrial corridor conservation requires coordination across jurisdictions and sectors subject to site-specific overlapping sources of legal authority. Mapping spatial patterns of legal authority concurrent with habitat condition can illustrate opportunities to build or leverage capacity for connectivity conservation. Streamside areas provide pragmatic opportunities to leverage existing policy mechanisms for riverine and terrestrial habitat connectivity across boundaries. Conservation planners and practitioners can make use of these opportunities by harmonizing actions for multiple conservation outcomes. We formulated an integrative, data-driven method for mapping multiple sources of legal authority weighted by capacity for coordinating terrestrial habitat conservation along streams. We generated a map of capacity to coordinate streamside corridor protections across a wildlife habitat gap to demonstrate this approach. We combined values representing coordination capacity and naturalness to generate an integrated legal-ecological resistance map for connectivity modeling. We then computed least-cost corridors across the integrated map, masking the terrestrial landscape to focus on streamside areas. Streamside least-cost corridors in the integrated, local-scale model diverged (∼25 km) from national-scale least-cost corridors based on naturalness. Spatial categories comparing legal- and naturalness-based resistance values by stream reach highlighted potential locations for building or leveraging existing capacity through spatial coordination of policy mechanisms or restoration actions. Agencies or nongovernmental organizations intending to restore or maintain habitat connectivity across fragmented landscapes can use this approach to inform spatial prioritization and build coordination capacity. Article impact statement: Combined mapping of legal authority and habitat condition reveals capacity to coordinate actions along streams for clean water and wildlife.     

Trade‐offs and efficiencies in optimal budget‐constrained multispecies corridor networks

Conservation biologists recognize that a system of isolated protected areas will be necessary but insufficient to meet biodiversity objectives. Current approaches to connecting core conservation areas through corridors consider optimal corridor placement based on a single optimization goal: commonly, maximizing the movement for a target species across a network of protected areas. We show that designing corridors for single species based on purely ecological criteria leads to extremely expensive linkages that are suboptimal for multispecies connectivity objectives. Similarly, acquiring the least‐expensive linkages leads to ecologically poor solutions. We developed algorithms for optimizing corridors for multispecies use given a specific budget. We applied our approach in western Montana to demonstrate how the solutions may be used to evaluate trade‐offs in connectivity for 2 species with different habitat requirements, different core areas, and different conservation values under different budgets. We evaluated corridors that were optimal for each species individually and for both species jointly. Incorporating a budget constraint and jointly optimizing for both species resulted in corridors that were close to the individual species movement‐potential optima but with substantial cost savings. Our approach produced corridors that were within 14% and 11% of the best possible corridor connectivity for grizzly bears (Ursus arctos) and wolverines (Gulo gulo), respectively, and saved 75% of the cost. Similarly, joint optimization under a combined budget resulted in improved connectivity for both species relative to splitting the budget in 2 to optimize for each species individually. Our results demonstrate economies of scale and complementarities conservation planners can achieve by optimizing corridor designs for financial costs and for multiple species connectivity jointly. We believe that our approach will facilitate corridor conservation by reducing acquisition costs and by allowing derived corridors to more closely reflect conservation priorities.     

Covariates affecting spatial variability in bison travel behavior in Yellowstone National Park.

Understanding mechanisms influencing the movement paths of animals is essential for comprehending behavior and accurately predicting use of travel corridors. In Yellowstone National Park (USA), the effects of roads and winter road grooming on bison (Bison bison) travel routes and spatial dynamics have been debated for more than a decade. However, no rigorous studies have been conducted on bison spatial movement patterns. We collected 121 380 locations from 14 female bison with GPS collars in central Yellowstone to examine how topography, habitat type, roads, and elevation affected the probability of bison travel year-round. We also conducted daily winter bison road use surveys (2003-2005) to quantify how topography and habitat type influenced spatial variability in the amount of bison road travel. Using model comparison techniques, we found the probability of bison travel and spatial distribution of travel locations were affected by multiple topographic and habitat type attributes including slope, landscape roughness, habitat type, elevation, and distances to streams, foraging areas, forested habitats, and roads. Streams were the most influential natural landscape feature affecting bison travel, and results suggest the bison travel network throughout central Yellowstone is spatially defined largely by the presence of streams that connect foraging areas. Also, the probability of bison travel was higher in regions of variable topography that constrain movements, such as in canyons. Pronounced travel corridors existed both in close association with roads and distant from any roads, and results indicate that roads may facilitate bison travel in certain areas. However, our findings suggest that many road segments used as travel corridors are overlaid upon natural travel pathways because road segments receiving high amounts of bison travel had similar landscape features as natural travel corridors. We suggest that most spatial patterns in bison road travel are a manifestation of general spatial travel trends. Our research offers novel insights into bison spatial dynamics and provides conceptual and analytical frameworks for examining movement patterns of other species.     

The spatial links tool: Automated mapping of habitat linkages in variegated landscapes

The removal, alteration and fragmentation of habitat in many parts of the world has led to a loss of biodiversity. Within the prevailing societal limitations the process is not easily reversed. Attempts are being made to minimise the fragmentation of remaining habitat by strategically reversing or managing habitat loss. Although their relative usefulness is a topic of debate among ecologists, habitat corridors are seen as one way of maintaining spatially dependent ecological processes within landscapes where habitat has been seriously depleted. Corridors can only be effective if they significantly contribute to the species sustaining processes of gene flow, resource access or the colonisation of vacant patches. We present a spatial habitat modelling methodology for evaluating the contribution and potential contribution of connecting paths to landscape connectivity. We have developed the spatial links tool (SLT), which maps link value across a region. The SLT combines connectivity measures from metapopulation ecology with the least cost path algorithm from graph theory, and can be applied to continuously variable landscape data. Combined with expert judgement, link value maps can be used to delineate habitat corridors. The approach capitalises on some synergies between ecological relevance and computational efficiency to produce an easily applied heuristic tool that has been successfully applied in NSW Australia.     

A Comparison of Corridors and Intrinsic Connectivity to Promote Dispersal in Transient Successional Landscapes

Low-vagility organisms that specialize on transitory successional habitats may be especially dependent upon habitat connectivity to maintain population viability. We analyzed the theoretical intrinsic connectivity of successional landscapes (i.e., the natural juxtaposition of similar habitats that allows dispersal) as a function of patch geometry coupled with the disperser's habitat specificity. Habitat specialists living in poorly connected landscapes (approximating hexagonal patches) have only a 26.5% chance of colonizing a new site when their resident patch becomes unsuitable. In contrast, generalists living in well connected landscapes can virtually always colonize a new site when needed. We infer from our simulation that for some habitat specialists, such as the rare, endemic Florida scrub lizard (Sceloporus woodi), anthropogenic control of successional dynamics for commercial logging may significantly reduce intrinsic connectivity. Lizard population viability may now depend upon the extrinsic connectivity provided by artificial corridors. However, the use of corridors will not serve as a general solution to the problem of anthropogenically reduced intrinsic connectivity until key logistical design problems have been resolved. Moreover, efforts to enhance intrinsic connectivity by modifying patch geometry may produce undesirable edge effects and conflict with old-growth preservation. Future research should focus on developing spatially explicit corridor models, documenting natural levels of intrinsic connectivity, quantifying anthropogenic disruption of natural connectivity, and describing species-specific mechanisms of inter-patch dispersal.     

Conservation Corridors and Contagious Disease: A Cautionary Note

Recent conservation proposals frequently include the establishment of corridors to connect isolated patches of wildlife habitat. Much attention has been focused on the potential benefits of corridors with little note given to potentially adverse consequences. A simulation model is developed here to study the effect of corridors on the survival of a metapopulation in the presence of a fatal disease that is spread by direct contact between susceptible and infected individuals. For the disease modeled here, a landscape of patches connected by corridors generally suffers fewer metapopulation extinctions than a landscape of isolated patches. However, under a narrow range of conditions, results suggest that corridors may dramatically increase the probability of metapopulation extinction. This occurs when disease-induced mortality is low enough to allow infected individuals to spread the disease, but high enough to reduce population levels to the point that random demographic and environmental events cause frequent metapopulation extinctions. This has important implications for the design and management of conservation reserve networks. Although discussion focuses primarily on conservation corridors, the model results apply to any management techniques that increase the movement of individuals among populations.     

How Corridors Reduce Indigo Bunting Nest Success

Abstract:  Corridors are a popular strategy to conserve biodiversity and promote gene flow in fragmented landscapes. Corridor effectiveness has been bolstered by the fact that no empirical field studies have shown negative effects on populations or communities. I tested the hypothesis that corridors increase nest predation in connected habitat fragments relative to unconnected fragments. I evaluated this hypothesis in a large-scale experimental system of open-habitat fragments that varied in shape and connectivity. Corridors increased nest predation rates in connected fragments relative to unconnected fragments with lower edge:area ratios. Nest predation rates were similar between connected and unconnected fragments with higher edge:area ratios. These results suggest that the increase in predator activity is largely attributable to edge effects incurred through the addition of a corridor. This is the first field study to demonstrate that corridors can negatively impact animal populations occupying connected fragments.     

Conservation Value of Remnant Riparian Forest Corridors of Varying Quality for Amazonian Birds and Mammals

Abstract:  Forest corridors are often considered the main instrument with which to offset the effects of habitat loss and fragmentation. Brazilian forestry legislation requires that all riparian zones on private landholdings be maintained as permanent reserves and sets fixed minimum widths of riparian forest buffers to be retained alongside rivers and perennial streams. We investigated the effects of corridor width and degradation status of 37 riparian forest sites (including 24 corridors connected to large source-forest patches, 8 unconnected forest corridors, and 5 control riparian zones embedded within continuous forest patches) on bird and mammal species richness in a hyper-fragmented forest landscape surrounding Alta Floresta, Mato Grosso, Brazil. We used point-count and track-sampling methodology, coupled with an intensive forest-quality assessment that combined satellite imagery and ground truthed data. Vertebrate use of corridors was highly species-specific, but broad trends emerged depending on species life histories and their sensitivity to disturbance. Narrow and/or highly disturbed riparian corridors retained only a depauperate vertebrate assemblage that was typical of deforested habitats, whereas wide, well-preserved corridors retained a nearly complete species assemblage. Restriction of livestock movement along riparian buffers and their exclusion from key areas alongside deforested streams would permit corridor regeneration and facilitate restoration of connectivity .     

Corridor Length and Patch Colonization by a Butterfly, Junonia coenia

Abstract: Corridors have been proposed to reduce isolation and increase population persistence in fragmented landscapes, yet little research has evaluated the types of landscapes in which corridors will be most effective. I tested the hypothesis that corridors increase patch colonization by a butterfly, Junonia coenia , regardless of the butterfly's initial distance from a patch. I chose J. coenia because it has been shown to move between patches preferentially through corridors. Individuals were released 16–192 m away from open experimental patches into adjacent open corridors or forest. Neither corridors nor distance had a significant effect on patch colonization, but there was a significant interaction between the presence or absence of corridors and distance. At small distances (16–64 m), J. coenia was more likely to colonize open patches when released within forest than within open corridors, most likely because J. coenia used corridors as habitat. Nevertheless, patch colonization by butterflies released within forest decreased rapidly as distance from patches increased, as predicted by a null model of random movement. Colonization did not change with distance in the corridor, and at long distances (128–192 m), butterflies released in corridors were twice as likely to colonize open patches as those released in forest. These results suggest that one critical factor, interpatch distance, may determine the relative effectiveness of corridors and other landscape configurations, such as stepping stones, in reducing isolation in fragmented landscapes. When distances between patches are short compared to an animal's movement ability, a stepping stone approach may most effectively promote dispersal. Alternatively, the conservation value of corridors is highest relative to other habitat configurations when longer distances separate patches in fragmented landscapes.     

Evaluating the Effectiveness of Corridors: a Genetic Approach

Abstract: The effectiveness of corridors in maintaining dispersal in fragmented landscapes is a question of considerable conservation and ecological importance. We tested the efficacy of corridors as residual landscape structures in maintaining population structure in the red-backed vole ( Clethrionomys gapperi ), a closed-canopy specialist, and the deer mouse (   Peromyscus maniculatus ), a habitat generalist. In coniferous forests managed for timber production in northeastern Washington, we sampled pairs of populations in three landscape classes: (1) contiguous landscapes, in which sites were located completely within a matrix of closed-canopy forest; (2) corridor landscapes, in which sites were connected by a corridor of closed-canopy forest; and (3) isolated landscapes, in which sites were separated from one another by clearcut or young regeneration stands. For each species, we used four microsatellite loci to quantify genetic distance between population pairs. Nei's genetic distance (   D _s  ) increased from smallest to largest in the order of contiguous, corridor, and isolated landscapes for C. gapperi. For P. maniculatus, genetic distances across landscape configurations were not significantly different. The differences between the two species indicate that they respond differently to the presence of forest corridors. In managed forests, corridors between unlogged habitats appear to maintain higher population connectivity for C. gapperi than landscapes without corridors.     

Ecological Networks as Conceptual Frameworks or Operational Tools in Conservation

Abstract:  The establishment of ecological networks (ENs) has been proposed as an ideal way to counteract the increasing fragmentation of natural ecosystems and as a necessary complement to the establishment of protected areas for biodiversity conservation. This conservation tool, which comprises core areas, corridors, and buffer areas, has attracted the attention of several national and European institutions. It is thought that ENs can connect habitat patches and thus enable species to move across unsuitable areas. In Europe, however, ENs are proposed as an oversimplification of complex ecological concepts, and we maintain that they are of limited use for biodiversity conservation for several reasons. The ENs are species specific and operate on species-dependent scales. In addition, the information needed for their implementation is only available for a handful of species. To overcome these limitations, ENs have been proposed on a landscape scale (and for selected "focal" species), but there is no indication that the structural composition of core areas, corridors, and buffer areas could ensure the functional connectivity and improve the viability of more than a few species. The theory behind ENs fails to provide sufficient practical information on how to build them (e.g., width, shape, structure, content). In fact, no EN so far has been validated in practice (ensuring connectivity and increasing overall biodiversity conservation), and there are no signs that validation will be possible in the near future. In view of these limitations, it is difficult to justify spending economic and political resources on building systems that are at best working hypotheses that cannot be evaluated on a practical level.