Connectivity Corridors Research Articles

Genetic variation and population structure in a threatened species, the Utah prairie dog Cynomys parvidens: the use of genetic data to inform conservation actions.

The Utah prairie dog (Cynomys parvidens), listed as threatened under the United States Endangered Species Act, was the subject of an extensive eradication program throughout its range during the 20th century. Eradication campaigns, habitat destruction/fragmentation/conversion, and epizootic outbreaks (e.g., sylvatic plague) have reduced prairie dog numbers from an estimated 95,000 individuals in the 1920s to approximately 14,000 (estimated adult spring count) today. As a result of these anthropogenic actions, the species is now found in small isolated sets of subpopulations. We characterized the levels of genetic diversity and population genetic structure using 10 neutral nuclear microsatellite loci for twelve populations (native and transplanted) representative of the three management designated "recovery units," found in three distinct biogeographic regions, sampled across the species' range. The results indicate (1) low levels of genetic diversity within colonies (H e=0.109-0.357; H o=0.106- 0.313), (2) high levels of genetic differentiation among colonies (global F ST=0.296), (3) very small genetic effective population sizes, and (4) evidence of genetic bottlenecks. The genetic data reveal additional subdivision such that colonies within recovery units do not form single genotype clusters consistent with recovery unit boundaries. Genotype cluster membership support historical gene flow among colonies in the easternmost West Desert Recovery Unit with the westernmost Pausaugunt colonies and among the eastern Pausaugunt colonies and the Awapa Recovery unit to the north. In order to maintain the long-term viability of the species, there needs to be an increased focus on maintaining suitable habitat between groups of existing populations that can act as connective corridors. The location of future translocation sites should be located in areas that will maximize connectivity, leading to maintenance of genetic variation and evolutionary potential.

Connectivity among jaguar populations in the Sierra Madre Oriental, México

Introduction: The jaguar (Panthera onca) is an apex carnivore that is vulnerable to habitat fragmentation, and some of its populations are believed to be isolated in Mexico where it is classed as endangered. The main the objective of our study was to evaluate connectivity of available jaguar habitat from the Sierra Madre Oriental of Mexico (SMO) towards southern Mexico. Methods: We determined least-cost pathways for jaguar movements among habitat patches in the SMO and identified potential corridors from the SMO. We used recent jaguar presence data and maximum entropy modeling to identify habitat patches in the SMO. We then used the Analytical Hierarchy Process to generate input values for a resistance (landscape permeability) matrix for jaguar movements that we generated using Multi-Criteria-Evaluation with a weighted linear combination. We then modeled least-cost pathways for both dispersal and local movements of jaguars. Results: We identified 581 potential highly suitable habitat patches for the jaguar. Of these, three were > 100 km2 and thus met the criteria for fundamental (i. e. capable of supporting a viable jaguar population) patches. The resistance matrix contained 3 % of low cost and 49 % intermediate cost areas for jaguar movements. Least-cost pathways analysis showed 61 dispersal routes totaling > 2,000 km and > 200 travel routes, with the largest number of both route types in Hidalgo. We also identified potentially five significant corridors for jaguar movement within the SMO and south towards southern Mexico populations. Discussion and implications: We determined that the SMO contains significant jaguar habitat with multiple biological corridors for connectivity with more southern populations of jaguar in Mexico. Based on this, we recommend development of management strategies to facilitate exchange of individuals from the SMO with other known jaguar populations in southern states (i. e. Oaxaca, Tabasco, Guerrero). Principal strategies may focus on habitat management of fundamental patches and habitat restoration between or around stepping-stones. Promoting connectivity among patches and populations which inhabit the SMO will increase its potential as a biodiversity conservation area.

Spatio-Temporal Change in Crowned (Propithecus coronatus) and Decken's Sifaka (Propithecus deckenii) Habitat in the Mahavavy-Kinkony Wetland Complex, Madagascar

The crowned sifaka (Propithecus coronatus) and Decken's sifaka (Propithecus deckenii) are Endangered lemurs endemic to west and central Madagascar. Both have suffered habitat loss and fragmentation throughout their ranges. The goal of this study, conducted in the Mahavavy-Kinkony Wetland Complex (MKWC) in northwestern Madagascar, was to assess the effects of historical change in the species' habitats, and to model the potential impact of further land-use change on their habitats. The IDRISI Andes Geographical Information System and image-processing software was used for satellite-image classification, and the Land Change Modeler was used to compare the natural habitat of the species from 1973 to 2005, and to predict available habitat for 2050. We analyzed two forests in the MKWC occupied by P. coronatus (Antsilaiza and Anjohibe), and three forests occupied by P. deckenii (Tsiombikibo, Marofandroboka and Andohaomby). The two forests occupied by P. coronatus contracted during the period 1949-1973, but then expanded to exceed their 1949 area by 28% in 2005. However, the land change model predicted that they will contract again to match their 1949 area by 2050, and will again lose their corridor connection, meaning that the conservation gains for this species in the complex are at risk of being reversed. The three forests occupied by P. deckenii have declined in area steadily since 1949, losing 20% of their original area by 2005, and are predicted to lose a further 15% of their original area by 2050. Both species are therefore at risk of becoming even more threatened if land-use change continues within the complex. Improved conservation of the remaining forest is recommended to avoid further loss, as well as ecological restoration and reforestation to promote connectivity between the forests. A new strategy for controlling agriculture and forest use is required in order to avoid further destruction of the forest.

Identification of priority conservation areas and potential corridors for jaguars in the Caatinga biome, Brazil.

The jaguar, Panthera onca, is a top predator with the extant population found within the Brazilian Caatinga biome now known to be on the brink of extinction. Designing new conservation units and potential corridors are therefore crucial for the long-term survival of the species within the Caatinga biome. Thus, our aims were: 1) to recognize suitable areas for jaguar occurrence, 2) to delineate areas for jaguar conservation (PJCUs), 3) to design corridors among priority areas, and 4) to prioritize PJCUs. A total of 62 points records of jaguar occurrence and 10 potential predictors were analyzed in a GIS environment. A predictive distributional map was obtained using Species Distribution Modeling (SDM) as performed by the Maximum Entropy (Maxent) algorithm. Areas equal to or higher than the median suitability value of 0.595 were selected as of high suitability for jaguar occurrence and named as Priority Jaguar Conservation Units (PJCU). Ten PJCUs with sizes varying from 23.6 km2 to 4,311.0 km2 were identified. Afterwards, we combined the response curve, as generated by SDM, and expert opinions to create a permeability matrix and to identify least cost corridors and buffer zones between each PJCU pair. Connectivity corridors and buffer zone for jaguar movement included an area of 8.884,26 km2 and the total corridor length is about 160.94 km. Prioritizing criteria indicated the PJCU representing c.a. 68.61% of the total PJCU area (PJCU # 1) as of high priority for conservation and connectivity with others PJCUs (PJCUs # 4, 5 and 7) desirable for the long term survival of the species. In conclusion, by using the jaguar as a focal species and combining SDM and expert opinion we were able to create a valid framework for practical conservation actions at the Caatinga biome. The same approach could be used for the conservation of other carnivores.

A Flexible Approach for Assessing Functional Landscape Connectivity, with Application to Greater Sage-Grouse (Centrocercus urophasianus)

Connectivity of animal populations is an increasingly prominent concern in fragmented landscapes, yet existing methodological and conceptual approaches implicitly assume the presence of, or need for, discrete corridors. We tested this assumption by developing a flexible conceptual approach that does not assume, but allows for, the presence of discrete movement corridors. We quantified functional connectivity habitat for greater sage-grouse (Centrocercus urophasianus) across a large landscape in central western North America. We assigned sample locations to a movement state (encamped, traveling and relocating), and used Global Positioning System (GPS) location data and conditional logistic regression to estimate state-specific resource selection functions. Patterns of resource selection during different movement states reflected selection for sagebrush and general avoidance of rough topography and anthropogenic features. Distinct connectivity corridors were not common in the 5,625 km2 study area. Rather, broad areas functioned as generally high or low quality connectivity habitat. A comprehensive map predicting the quality of connectivity habitat across the study area validated well based on a set of GPS locations from independent greater sage-grouse. The functional relationship between greater sage-grouse and the landscape did not always conform to the idea of a discrete corridor. A more flexible consideration of landscape connectivity may improve the efficacy of management actions by aligning those actions with the spatial patterns by which animals interact with the landscape.

Integrated modelling of functional and structural connectivity of river corridors for European otter recovery

Connectivity may be structural, based on adjacency of landscape features, or functional, based on how that adjacency translates to movement of organisms. We present a modelling approach that elucidates both aspects of connectivity to identify vital corridors and conservation priorities in a river network. For the dendritic network structure of river systems, at first a graph theoretic structure is developed to model the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchical modelling of species dispersal is applied to infer the influence of riparian corridor characteristics to the species colonization.The integration of the functional and structural component is realized with a graph-theoretic connectivity measure. With this approach, the European otter colonization of the Loire river basin over 25 years is modelled on the basis of large datasets on riparian corridor land use and hydromorphological characteristics of a 17,000km river network. Channel straightening and riparian forest fragmentation are determined to be key elements to the functional connectivity. Road infrastructure is distinguished as a critical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Integration of the Bayesian model posterior colonization probability in the integrated connectivity analysis reveals the importance of the river network density to the otter colonization and locates conservation priorities mainly in the lower parts of the river basin. Synthesis and applicationsBoth functional and structural connectivity are essential elements in the contexts of ecological network identification for species conservation and recovery. We successfully developed an integrated modelling of both components of connectivity that highlighted the importance of the downstream basin for a well-connected ecological network for the otter.

Informing Program Design for Connectivity Conservation in the New South Wales Southern Highlands, Australia

Connectivity initiatives typically require conservation action on private lands as a complement to public reserve systems, so they are more likely to succeed if underpinned by knowledge of the social factors influencing landholders' participation. Using a combination of social survey and market research techniques, we identify spatially referenced landholder segments. Using a number of behavioral and attitudinal constructs, including three psychographic constructs not previously used for identifying segments—sense of place, lifestyle motives, and nature values—we identify three lifestyler and two farmer segments, and show that the characteristics of lifestyler segments are more nuanced than previously thought. Preferences for four corridor connectivity initiatives are found to differ across landholder segments, which indicates the importance using a targeted approach for designing connectivity conservation programs. The results highlight the importance for achieving corridor connectivity of the Blue Collar Lifestyler segment, a lower sociodemographic segment not previously identified in the literature.

Forest-edge utilization by carnivores in relation to local and landscape habitat characteristics in central European farmland

Rapid changes in agricultural landscape structure and composition affect many different farmland biotas, including carnivores, which are a key element of ecosystem stability, yet little is known about their distribution and habitat use. In this study, we evaluated how habitat characteristics on two different spatial scales (local and landscape scale) affected the forest-edge utilization by small and medium-sized carnivores in fragmented central European farmland. Based on an indirect method for detecting carnivores (scent stations), we sampled 212 forest fragments of different sizes (1–7864ha) during April to May from 2006 to 2009. Our results indicate that carnivore utilization of forest-edge habitats was driven by landscape rather than local characteristics even though the overall extent of explained variation was small. The most important factors that determined response of the carnivore community were the area of farmland and that of urban land on a landscape scale. The corridor connectivity between small forest fragments and other spatial elements played a crucial role in the occurrence of red fox. Our results suggest that comprehensive studies on multi-species carnivore assemblage using scent station might be useful in evaluating species-specific response to habitat characteristics, especially if large numbers of stations visited by carnivores are available.

Corridors and barriers in biodiversity conservation: a novel resource-based habitat perspective for butterflies

Habitat loss and fragmentation, exacerbated by projected climate change, present the greatest threats to preservation of global biodiversity. As increasing habitat fragmentation and isolation of residual fragments exceeds the dispersal capacity of species, there is the growing need to address connectivity to maintain diversity. Traditionally, habitat corridors have been proposed as a solution. But, the concept of corridors (barriers) is poorly understood; typically they are defined as linear habitats linking up habitat patchwork, and are advocated without a detailed understanding of the elements making up species’ habitats and the cost-effectiveness of alternative solutions. Yet, landscapes comprise an enormous range of ‘linear’ structures that can function in different ways to promote species’ persistence and diversity. In this review, a functional definition of corridor (barrier) is developed to give prominence to connectivity as opposed to ad hoc structures purported to advance connectivity. In developing the concept, urgency to accommodate environmental changes compels a growing emphasis on organism diversity rather than a preoccupation with single species conservation. The review, in focusing on butterflies to address the issue of corridors for patchwork connectivity, draws attention to fundamental divisions among organisms in any taxon: generalists and specialists. Both groups benefit from large patches as these necessarily house species with specialist resources as well as generalists with very different resource types. But, generalists and specialists require very different solutions for connectivity, from short-range habitat corridors and gateways for specialists to habitat and resource stepping stones (nodes, surfaces) for generalists. Connectivity over extensive areas is most critical for moderate generalists and their conservation requires emphasis being placed on space–time resource heterogeneity; landscape features, of whatever dimensionality and structure, provide a vital framework for developing the variety of suitable conditions and resources for enhancing their diversity.

First Nd isotope record of Mediterranean–Atlantic water exchange through the Moroccan Rifian Corridor during the Messinian Salinity Crisis

We present the first neodymium isotope reconstruction of Mediterranean–Atlantic water exchange through the Moroccan (‘Rifian’) Corridor 8–5Ma. This covers the late Miocene Messinian Salinity Crisis (MSC); a period when progressive tectonic restriction of the Mediterranean–Atlantic seaways resulted in extreme, basin-wide Mediterranean salinity fluctuations. The Rifian Corridor was one of these seaways and until now, relatively poor age constraints existed for the timing of Corridor closure, due to the impact of uplift and erosion on the sedimentary record. The bottom water Nd isotope record from the continuous Bou Regreg Valley succession in northwest Morocco allows us to explore corridor connectivity with the Atlantic. Data from the interior and Mediterranean edge of the Rifian Corridor (respectively, the Taza–Guercif and Melilla basins, northern Morocco) provide new information on corridor shallowing and the provenance of water flowing through the seaway. As a result, we can constrain the age of Rifian Corridor closure to 6.64–6.44Ma. We also find no evidence of the siphoning of Atlantic waters through the seaway (7.20–6.58Ma). Our results cannot exclude the possibility that at times during the Messinian Salinity Crisis, Mediterranean Outflow Water reached the Atlantic.

Combining resource selection and movement behavior to predict corridors for Canada lynx at their southern range periphery

Maintaining connectivity with source populations is especially important for populations of boreal species at the southern edge of their distributions, where anthropogenic disturbance and climate change can be a threat. In the conterminous United States, Canada lynx Lynx canadensis is a federally threatened boreal species that may require connectivity with northern populations to persist. Connectivity is a function of movement between patches and the likelihood that patches are suitable for resident populations. Therefore, we combined resource selection, step selection, and least-cost path models to define empirically movement corridors for lynx in the Northern Rocky Mountains. We used telemetry data for 64 lynx monitored during 1998–2007 to create a broad-scale resource selection model that predicted probable lynx habitat across the species’ distribution in the Northern Rocky Mountains. Our model indicated that lynx selected home ranges at mid-elevations with low surface roughness and high canopy cover. Based on a subset of 37 (16 females, 21 males) adult lynx fitted with GPS collars from 2005 to 2007, we then tested the extent to which remotely-sensed indices of environmental heterogeneity, including greenness, normalized difference vegetation index, surface roughness, and a principal component that indexed stand age, could characterize landscape connectivity for lynx. We found that connectivity between lynx habitat in Canada and that in the conterminous US is facilitated by only a few putative corridors that extend south from the international border. Maintaining the integrity of these connectivity corridors is of primary importance to lynx conservation in the Northern Rockies.

Static Analysis of Reinforced Concrete Arch-Deck Bridge with Archaized Connective Corridors

As the requirements of traffic functions and urban landscape, a reinforced concrete arch- deck bridge is designed with archaized connective corridors. The main dimensions and drawings are introduced and the static analytical results of the bridge are discussed in this paper. The numerical model was built by the integrated solution system for bridge and civil engineering- MIDAS/Civil. The results show that the temperature of bridge and the horizontal shift at arch toes due to sedimentation play important roles sensitively influencing the bending moments and displacements of control sections. Compared numerical results of the bridge only with dead loads, the maximum bending moments and displacements would reach 3.81 times and 6.52 times respectively. The axial force of arch is mainly resulted from dead loads, which gradually increases from arch crown to arch toes. The design and numerical results would give some references to similar bridges.

‘Site’ing the right reasons: critical evaluation of conservation planning for the Asiatic lion

The resurrection of Asiatic lions (Panthera leo persica) from the brink of extinction is a remarkable conservation success story. Yet, occurrence of lions as a single population makes them vulnerable to extinction from genetic and environmental factors. Asiatic lions exist as a single free ranging population of 360 individuals in Gir Protected Area (PA; about 290 lions) and surrounding satellite areas (68 lions), namely Girnar Wildlife Sanctuary (WLS), coastal areas, hill ranges extending from Mitiyala-Savarkundla-Palitana-Shihor spreading across Junagadh, Amreli and Bhavnagar districts of Gujarat State, India. This paper traces the conservation history, current conservation pressures, and critically evaluates current conservation planning based on lion ecology and existing anthropogenic pressures. Conservation proposals for translocation of lions to alternate habitats in Kuno WLS and Barda WLS are awaiting final implementation. An alternate initiative is aimed at developing satellite lion habitats, improving corridor connectivity, and facilitating natural dispersal and expansion of lion habitats. The paper evaluates human population living within 2 km boundary of lion habitats and between Gir PA and satellite habitats to show that dispersing lions have to cross heavily populated habitations taking refuge in agriculture fields and scattered forest patches. Satellite habitats vary in size from 18 km2 (Mitiyala WLS) to 250 km2 (scattered forests Hipavadli-Savarkundla-Palitana zone along Shetrunji river) and are inadequate to maintain natural ranging and movement requirements of territorial lions. These habitats are varied in vegetation, terrain, human pressure, and distance to source population. Though satellite lion habitats are important suboptimal habitats for dispersing lions, long-term conservation planning require planned restoration of mosaic habitats for growing populations.

Breaking down fences: Recoupling social–ecological systems for biodiversity conservation in Namibia

Herero communities in northern Namibia recently formed the Ehi-rovipuka Conservancy under a national Community-Based Natural Resource Management Programme (CBNRM) that has received international acclaim for wildlife conservation and poverty alleviation. Nearly a century ago ancestors of the Herero were ousted from Etosha National Park, contiguous to the Ehi-rovipuka Conservancy. The communities have been denied access ever since. Participatory Rural Appraisal (PRA) methods were employed to elucidate relationships of the Herero and their communal conservancy with the Etosha National Park. Memory mapping and villager interviews revealed a profound sense of lost traditional territory inside Etosha and a strong desire to return to the Park, not to harvest wildlife but to restore cultural practices and reap certain benefits from the Park. We term the separation of the communities from their traditional territory as a ‘decoupling’ of people from their local environment. We further suggest that the potential benefits that villagers identify from the Park represent mechanisms for ‘recoupling’ local social–ecological systems, requiring the literal and figurative breakdown of the Park fence. We describe a model to illustrate decoupling and recoupling mechanisms, and argue that recoupled social–ecological systems are necessary for long-term conservation of biodiversity. We further suggest a collaborative landscape model for biodiversity conservation featuring institutional linkages and integration between community-conserved areas, integrated conservation corridors for connectivity, and dynamic, mobile reserves collaboratively integrated with national parks management. This model may have applicability in Namibia and similar regions elsewhere with low population densities, high species endemism and prevailing or emerging threats to biodiversity.

On the minimum corridor connection problem and other generalized geometric problems

In this paper we discuss the complexity and approximability of the minimum corridor connection problem where, given a rectilinear decomposition of a rectilinear polygon into “rooms”, one has to find the minimum length tree along the edges of the decomposition such that every room is incident to a vertex of the tree. We show that the problem is strongly NP-hard and give a subexponential time exact algorithm. For the special case when the room connectivity graph is k-outerplanar the algorithm running time becomes cubic. We develop a polynomial time approximation scheme for the case when all rooms are fat and have nearly the same size. When rooms are fat but are of varying size we give a polynomial time constant factor approximation algorithm.

Climate change, biodiversity conservation, and the role of protected areas: An Australian perspective

The reality of human-forced rapid climate change presents an unprecedented challenge to the conservation of biodiversity in Australia. In this paper we consider the role of Australia's current protected area network in mitigating biodiversity loss across the continent. We do this by first examining the evolutionary history of Australia's extant fauna and flora and, specifically, the reasons why species have persisted through major changes in climate during repeated glacial cycles, and through the massive climatic changes that occurred during the Miocene and Pliocene climate change events. We then review the current major threats to Australian native species, including inappropriate fire regimes, feral mammalian predators and herbivores, invasive plants, and habitat loss, fragmentation and degradation by land use activities (especially commercial logging, water impoundment and diversion, agricultural expansion, and the intensification of pastoralism). We argue that these current threats are interfering with the natural responses to climate change that native species have relied upon in the past, thereby undermining their resilience in the face of current, human-forced climate change. We predict that the current approach to conservation planning based on accumulating small amounts of protected lands across the continent, using a set of arbitrary conservation ‘targets’, will not be effective in mitigating the impacts of human-forced climate change on Australia's biodiversity. We argue that an Australia-wide conservation strategy is needed that incorporates a larger adaptation agenda- one that recognizes the importance of protecting and restoring those natural processes and responses that have enabled species to persist through past environmental change. The following key elements are a crucial component of an effective conservation plan: identifying and protecting important climate refugia (both ecological and evolutionary); conserving the large-scale migration and connectivity corridors that operate at continent scales (including regional networks of habitat patches and habitat ‘stepping stones’); maintaining viable populations of all extant species to maximize intra-species genetic diversity and thus options for local adaptation; reducing all current threatening processes at the landscape scale across the continent; and protecting and restoring key large scale ecological processes (especially hydro-ecology and ecological fire regimes). Finally, underpinning climatic adaptation responses must be a thorough understanding of the special role Australia's extensive intact landscapes will play in the future protection of Australia's native biodiversity.

Survey of the Lynx distribution in the French Alps: 2000–2004 population status analysis

Within the SCALP framework, the status of the pan-alpine population of Eurasian Lynx is assessed every 5 years, based on the compilation of national reports and standardized classification of lynx presence signs according to data confidence levels (C1, C2, C3). From2000 to 2004, the French national network of lynx experts collected N= 393 data, out of which 224 (compared to only 69 in 1995–1999) were considered as robust enough to evidence the presence of lynx (C1 = 1%; C2 = 42%; C3 = 57%) and were used for further analysis. A majority of the signs concerned the northern part of the Alps, however, in mostly two regions (Chartreuse/Epine: 34% of the signs; Maurienne: 21%). Other data were more scattered over space, from the Cha- blais region close to Switzerland down to the Haut-Verdon close to the Mercantour mountains. A negative trend was noticed from north to south in proportions of best quality signs(C1+C2), and a positive one in low quality ones – C3 – (c² = 3.56, 1 df, p = 0.06), which could point at some methodological artefacts. Discarding C3 may however be too conservative a strategy to assess the species range and status. Using spatial recurrence and trend over time of all signs available (C1+C2+C3) could, therefore, provide the right balance between being too much versus not enough conservative. – When doing so, the area with lynx signs regularly detected sharply increased between 1996–1998 (100 km²), 1999–2001(250 km²), and 2002–2004 (1195 km²). The latter area is still quite small regarding what is required for a viable large carnivore population.A simple demographic model suggested that even a quite moderate proportion of immigrants (e.g. dispersal inflow from neighbouring coreareas – French Jura or Swiss Alps) could considerably decrease the theoretical demographic extinction risk of such a small population, but stilldepending upon adult survival rates, which also strongly influenced the extinction risk. The factors that may influence this sensitivity analysis(such as habitat connectivity and management of wooded corridors) should be evaluated within the Scalp framework.

The search for fragmentation thresholds in a Southern Sydney Suburb

Fragmentation of habitat is recognised as the number one threat to biodiversity and as such has attracted considerable research. However, much of this research has been conducted in forestry and agricultural environments, with little research in urban areas. In this study, field surveys were conducted measuring the impact of fragmentation on bird, frog, plant and fungi species richness, within the fragmented urban landscape of southern Sydney. Of all fragmentation parameters examined, remnant area was the best and most significant predictor of species richness for all taxa studied. Remnant size thresholds, below which biodiversity declined rapidly, were observed at approximately 4 ha for bird and frog species richness and approximately 2 ha for plant and fungal species richness. A further threshold appears to exist at approximately 50 ha for the dominance of forest interior species. Further relationships were also observed for perimeter:area ratio, indicating the influence of various edge effects on all taxa. Isolation effects were observed in the form of an inverse linear relationship between distance to other large reserves and species richness for fungi, birds and frogs. Corridor connectivity also produced an overall positive relationship for birds, frogs and plants. It is concluded that the identification of fragmentation thresholds and relationships provides an important management tool for the design of networks aimed at conserving biodiversity in fragmented urban environments.

Vibration characteristics of the Bayon temple main tower, Angkor, Cambodia

Bayon temple, Angkor, built in the late 12th century to the early 13th century, is a masonry temple made of sandstone which has deteriorated possibly due to rain, plants, settlements, and so on. Strong winds blowing more than 20m/sec were observed in the rainy season, which may cause vibration of the structure either directly or via ground motion, we may add wind induced vibration to the list of deterioration causes. Proceeding to a study on the response of the masonry structure to the strong wind, we carried out a micro tremor measurement to evaluate the vibration characteristics of the main tower and surrounding sub-towers in the temple. We identified translational and torsion modes of towers with their predominant frequencies, damping factors, and base-fixed frequencies. We examined all of the sub-towers to find statistically the effects of height and corridor connectivity on their vibration characteristics. Then, we attempted to construct an FEM model for the main tower by simulating the base-fixed natural frequencies of the horizontal translational modes. The model with an elastic modulus practically used for sandstone shows much higher frequencies, which let us decrease the modulus to less than 1/10. We also find that this reduced stiffness model shows about a half the observed vertical translational frequency so as to suggest a lack of consistency with continuum modelling of basically discontinuous masonry structure.

Assessment of livestock grazing pressure in and around the elephant corridors in Mudumalai Wildlife Sanctuary, south India.

Mudumalai Wildlife Sanctuary in southern India plays an important role in biodiversity conservation, especially of large mammals, by offering habitat contiguity of about 3300 km2 with three other protected areas in the region, namely Nagarahole and Bandipur National Parks and Wynaad Wildlife Sanctuary through forest corridors between the Western Ghats and Eastern Ghats forests. The habitat linkage is crucial for large ranging animals such as elephants, which use these forest corridors for migration. Livestock grazing, a major biotic interference in forest corridors, originates from seven settlements of the Masinagudi group of villages on the eastern and the southeastern fringes of the sanctuary. Construction of a series of hydroelectric power stations, numbering about three at Singara, Marvakandy (Masinagudi) and Moyar, around the Masinagudi villages caused a rapid growth in human population (143% between 1961 and 1991), particularly the landless labourers and livestock. Free grazing by about 15 000–17 000 resident as well as migratory livestock every year in and around the forest corridors, coupled with removal of cattle dung from the forest floor, have adversely affected the forest regeneration and helped proliferation of weed species such as Lantana camara, Casia tora, C. occidentalis, Opuntia dillenii, and Ageratum conyzoides. The annual fodder production from the corridor forest could meet the demand of about two-thirds of the resident population, while the crop residues from the marginal agriculture could not support the remaining one-third livestock population. In view of such a situation, measures have been suggested to reduce livestock population and implement the ecodevelopment packages in order to ensure the corridor connectivity for the long-term conservation of the elephant population.