Thresholds in selection of breeding habitat by the Eurasian treecreeper (Certhia familiaris)

Assessment of habitat thresholds is a topical issue in ecology, both from theoretical and applied perspectives. We examined how forest structure influences selection of breeding habitat in the Eurasian treecreeper (Certhia familiaris). It is an old-growth forest passerine, which can be considered an umbrella species. Habitat selection data, covering five breeding seasons, were collected from a study area across three spatial scales: (a) territory core scale (a radius of 30 m), (b) territory scale (a radius of 200 m) and (c) large scale (a radius of 500 m). Logistic regression analyses revealed that the radii of 30 and 200 m from the nest were the most important spatial scales for the forest patch occupancy. A loss of forest habitat and a low circumference of stems within the territory decreased the probability of occupancy. There was a distinct threshold in the amount of forest cover on forest patch occupancy when the volume of timber was taken into account. At low timber volumes (0-151 m³/ha) the amount of forest cover was negatively related to the occupancy rate of forest patches. This negative relationship changed abruptly when the volume of timber exceeded 152 m³/ha, after which forest cover had a positive effect on the occupancy rate of forest patches. This is a new way to examine habitat thresholds in relation to forest cover. Furthermore, as debated in recent literature, treecreepers also tend to respond to habitat loss rather than to changes in habitat configuration, which stresses the need for habitat restoration and conservation. Moreover, our results emphasize the importance of within-territory structure over the characteristics of the habitat matrix in selection of breeding habitat.     

Soil and climate are better than biotic land cover for predicting home-range habitat selection by endangered burrowing owls across the Canadian Prairies

Statistical models that describe species-environmental relationships are important components within many wildlife conservation strategies. These models are typically developed from studies conducted on small geographic scales (hundreds of square kilometres), representing a relatively small range in environmental conditions. Such local models from local studies are often then extrapolated to predict the suitability of other unsampled regions. The value of many models would be increased by considering larger-scale processes that might be structuring spatial patterns across species distributions. We examined home-range habitat selection by burrowing owls throughout the mixed prairie grassland region of western Canada (180,000 km²) to determine whether owl selection for biotic factors changes along abiotic gradients. Specifically, we classified 37 explanatory variables into five categories (geography, grassland fragmentation, land-use, soil, and climate), created models for each set of variables, and evaluated the predictive ability of each model. We then examined interaction effects to determine if the relationship between land cover variables and the probability of owl home-range selection varied within large-scale abiotic criteria. Our results showed that soil and climate produce the most predictive models of burrowing owl home-range selection and create unique environmental conditions for owls which are independent of land cover at this scale. This study provides new insight into burrowing owl habitat requirements, and strengthens the case for considering large-scale abiotic gradients when prioritizing areas for species conservation.     

Assessment of shoreline vegetation in relation to use by molting black brant Branta bernicla nigricans on the Alaska coastal plain

To evaluate the importance of large thaw lakes on the Alaska Coastal Plain for molting Pacific black brant Branta bernicla nigricans, distribution and life form of shoreline vegetation were assessed using several scales: satellite imagery, point-intercept transects, cover quadrats, and a parameter for water regime. Brant population and distribution estimates from aerial surveys were used to classify large lakes into high, moderate, and low use. Correlations between brant and abundance of their preferred feeding site — moss flats — were best demostrated by satellite imagery. Intercepts and cover ratings were not correlated, presumably because these techniques were less efficient at assessing area. General observations suggested that the presence of islands, large ice floes, and possibly other physical attributes of the habitat, influenced brant distribution. This area is unique because of low-lying, drained-lake basins that have ideal combinations of moss flats and large water areas where brant seek protection disturbance is vital to the success of this declining species because alternate habitats may not be available elsewhere on the Coastal Plain. in water or on ice floes. Protection of the area from     

GIS-models work well, but are not enough: Habitat preferences of Lanius collurio at multiple levels and conservation implications

Species conservation largely depends on knowledge of habitat needs of target species. GIS-models are increasingly used to assess habitat preferences and distribution of target species, but their accuracy is constrained by availability of digital data layers. We developed a two-steps approach aiming at showing pros and cons of landscape (GIS)- and site-level habitat models, identifying key habitat factors for conservation of a threatened bird species, the red-backed shrike Lanius collurio. A spatially explicit GIS-model was generated using landscape variables, and a second model at site level was developed using fine-scale variables measured on the ground. The GIS-based model was then extrapolated to the entire region to obtain a map of distribution of suitable habitats. Positive associations between shrike occurrence and both hedgerow length and partial shrub cover were detected at both scales. Shrikes were also positively associated with grassland cover at landscape level and with partial cover of untilled herbaceous vegetation at the finer scale, and negatively affected by lucerne cover. The GIS-model led to an affordable map of predicted habitat suitability which should help conservationists to focus on different local priorities, but was unable to identify effects of untilled and lucerne cover. Site-level model gave fine details for habitat management, but its application elsewhere requires ground-measurements of factors. Combining the multiscale models could indicate more urgent actions at large scales (e.g. maintaining suitable habitats, or improving connectivity among isolated patches) and draw a detailed figure of the most suitable habitat for the species. Shrike occurrence was associated with a higher number of shrub and tree species: the indicator value of the species should ensure general benefits for biodiversity from dedicated management.     

Patch connectivity and genetic diversity conservation in the federally endangered and narrowly endemic plant species Astragalus albens (Fabaceae)

To evaluate the sufficiency of US federal critical habitat designations and a proposed conservation plan in promoting the long-term persistence of the endangered plant Astragalus albens, patterns of genetic diversity and landscape connectivity were examined. A. albens harbors substantial genetic variation and shows no evidence of historic bottlenecks, suggesting little risk of extinction due to genetic homogeneity (A = 2.40; P = 0.50) or inbreeding (f = −0.08) within occurrences. Low genetic differentiation among occurrences (θ_p = 0.01) indicates relatively high gene flow or little genetic drift. The 91 patches of A. albens were connected into a single network at a distance of 2100 m; 94% of patches were <1000 m from at least one other patch. Managing ecological conditions that maintain large population sizes and connectivity among populations throughout the species’ ecological and geographic ranges will most likely conserve existing diversity. Both reserve networks partially accomplish these goals by including most extant occurrences and >89% of the aerial extent of the species, including the largest populations, and capturing all detected alleles. However, both conservation networks fail to conserve occurrences from one portion of the species’ range, possibly speeding loss of unique local adaptations. In addition, connectivity of the whole network is reduced with the 65 patches designated as critical habitat being connected at a distance of 6200 m and the proposed reserve sites being connected at a distance of 9500 m. Although total network connectivity would be reduced, connectivity at scales most relevant to gene flow (e.g., <1000 m) remains sufficiently in tact to provide a relatively promising outlook for species persistence.     

Conserving ground-dwelling beetles in an endangered woodland community: Multi-scale habitat effects on assemblage diversity

Patterns of biodiversity are influenced by habitat features at multiple spatial scales, yet few studies have used a multi-scale approach to examine ground-dwelling beetle diversity patterns. We trapped and quantified ground-dwelling beetle assemblages at two spatial scales: (1) microhabitat elements, represented by open ground, ground under trees and ground next to logs and (2) macrohabitat, represented by three vegetation types in a box-gum grassy woodland in south-eastern Australia. Species richness and evenness was highest at samples from under trees and lowest at samples in the open. At the macrohabitat scale, species richness and evenness did not differ among vegetation types. Assemblage composition was significantly different between trees, logs and open elements. Assemblage composition was different only between vegetation types with contrasting high and low shrub cover. Estimation of true species richness indicated assemblages at logs may have a higher number of species compared to trees and open elements, and implied greater spatial heterogeneity in assemblages at logs. Significant spatial autocorrelation in beetle assemblages was detected for logs at up to 400 m, but not for ground under trees or in the open. In agreement with previous studies, a mix of vegetation types at the macrohabitat scale is important for beetle conservation. Assemblage composition, however, appears to be more closely linked with habitat elements at the microhabitat scale, where logs support a high diversity of beetle species. This strongly supports the idea that restoring logs to box-gum grassy woodlands would be useful for increasing beetle species richness and assemblage heterogeneity.     

Using Penrose distance to identify potential risk of wildlife–vehicle collisions

Knowledge of the relationship between wildlife and roads is important for management of wildlife–vehicle collisions, which represent a serious threat to many wildlife populations and to human life and property. Effective reduction of these threats requires identification of variables influencing collision locations, and the use of these variables in spatially-explicit predictive models. We used Penrose distance modeling and 61 confirmed bobcat (Lynx rufus) road mortality locations in southern Illinois, USA, to demonstrate a rapid and accurate technique for the spatial mapping of wildlife–vehicle collision risk. We used the Penrose distance statistic to quantify the similarity between the mean multivariate habitat signature at bobcat-collision areas and road sections throughout the study area. Habitat variables assessed included road-related variables (e.g., traffic volume) and land cover characteristics (e.g., mean patch area of the landscape). Bobcat-collision areas were characterized by smaller, less-clustered habitat patches and more, large independent patches of grass cover than were study area roadway sections in general. As expected for a generalist carnivore in highly-suitable habitat, risk mapping indicated that large sections of the roaded landscape had high similarity to bobcat-collision areas. Unlike other modeling techniques used to identify risk of road mortality, our method requires little field data collection and relies on readily available digital spatial data. This technique can be used by wildlife managers and road planners, and may be particularly important in reduction of road mortality for species such as the Iberian lynx (Lynx pardinus), Florida panther (Puma concolor coryi), and Texas ocelot (Leopardis pardalus), which exist in small populations fragmented by development, and are limited by road mortalities.     

Using multi-scale modelling to predict habitat suitability for species of conservation concern: The grey long-eared bat as a case study

Although spatial scale is important for understanding ecological processes and guiding conservation planning, studies combining a range of scales are rare. Habitat suitability modelling has been used traditionally to study broad-scale patterns of species distribution but can also be applied to address conservation needs at finer scales. We studied the ability of presence-only species distribution modelling to predict patterns of habitat selection at broad and fine spatial scales for one of the rarest mammals in the UK, the grey long-eared bat (Plecotus austriacus). Models were constructed with Maxent using broad-scale distribution data from across the UK (excluding Northern Ireland) and fine-scale radio-tracking data from bats at one colony. Fine-scale model predictions were evaluated with radio-tracking locations from bats from a distant colony, and compared with results of traditional radio-tracking data analysis methods (compositional analysis of habitat selection). Broad-scale models indicated that winter temperature, summer precipitation and land cover were the most important variables limiting the distribution of the grey long-eared bat in the UK. Fine-scale models predicted that proximity to unimproved grasslands and distance to suburban areas determine foraging habitat suitability around maternity colonies, while compositional analysis also identified unimproved grasslands as the most preferred foraging habitat type. This strong association with unimproved lowland grasslands highlights the potential importance of changes in agricultural practices in the past century for wildlife conservation. Hence, multi-scale models offer an important tool for identifying conservation requirements at the fine landscape level that can guide national-level conservation management practices.     

Multi-scale effect of landscape processes and habitat quality on newt abundance: Implications for conservation

Recent studies in population dynamics suggest that landscape processes and habitat quality act at different scales on population abundances, but very few have modelled their simultaneous effects. However, at a time of large declines in natural populations, it is essential to understand such multivariate components. We tested the hypothesis that natural populations of palmate newts (Triturus helveticus) are affected on three scales: breeding patch (pond), habitat complementation (terrestrial cover), and metapopulation structure (density of ponds, surrounding populations). We conducted our survey in 130 ponds from southern France (Larzac) and analysed data with generalized additive models (GAM). Two main novel results emerge from these models: (1) the three landscape scales have significant effects on newt abundance, with more newts in deep, vegetated ponds, devoid of fish and surrounded by wooded areas and inhabited ponds; (2) the quality of the surrounding breeding patches is of primary importance in determining the abundance at core sites in a complex way: high abundances are associated positively with high densities of inhabited ponds, but negatively with the number of surrounding ponds. Deforestation, invasive species and abandonment of ponds all have negative impacts on the persistence of palmate newt populations. Future studies should encompass landscapes at different scales and incorporate the habitat quality in surrounding sites to better understand population dynamics and provide adequate conservation measures.     

Overcoming the rare species modelling paradox: A novel hierarchical framework applied to an Iberian endemic plant

Rare species have restricted geographic ranges, habitat specialization, and/or small population sizes. Datasets on rare species distribution usually have few observations, limited spatial accuracy and lack of valid absences; conversely they provide comprehensive views of species distributions allowing to realistically capture most of their realized environmental niche. Rare species are the most in need of predictive distribution modelling but also the most difficult to model. We refer to this contrast as the “rare species modelling paradox” and propose as a solution developing modelling approaches that deal with a sufficiently large set of predictors, ensuring that statistical models are not over-fitted. Our novel approach fulfils this condition by fitting a large number of bivariate models and averaging them with a weighted ensemble approach. We further propose that this ensemble forecasting is conducted within a hierarchic multi-scale framework. We present two ensemble models for a test species, one at regional and one at local scale, each based on the combination of 630 models. In both cases, we obtained excellent spatial projections, unusual when modelling rare species. Model results highlight, from a statistically sound approach, the effects of multiple drivers in a same modelling framework and at two distinct scales. From this added information, regional models can support accurate forecasts of range dynamics under climate change scenarios, whereas local models allow the assessment of isolated or synergistic impacts of changes in multiple predictors. This novel framework provides a baseline for adaptive conservation, management and monitoring of rare species at distinct spatial and temporal scales.     

At which spatial and temporal scales does landscape context affect local density of Red Data Book and Indicator species?

The landscape context is crucial for forest conservation in regions where the natural forest is fragmented. The focus of practical conservation is currently shifting from local stands to a landscape perspective, but few studies have tested the relative effect of different spatial and temporal scales for occurrence and persistence of species of conservation concern. We studied Red Data Book and Indicator species (the latter proposed to indicate presence of Red Data Book species) of vascular plants, lichens, bryophytes and wood-inhabiting fungi in 22 old temperate broadleaved forests in southern Sweden. We analysed at which scales these species respond to habitat proportion in surrounding landscape. The proportion of suitable habitat was measured at two temporal scales (present-day and historic) and at two spatial scales (about 0-1 km and 1-5 km of study sites). Local density of Red Data Book species increased with increasing proportion of suitable habitat in the current landscape (within 1-5 km of study sites) while Indicator species were unaffected. The response to landscape differed between organism groups. Vascular plants (near significantly) and wood-inhabiting fungi showed a time delay of 120 years in their response, indicating a possible regional extinction debt. An appropriate minimum landscape scale for conservation of Red Data Book species in temperate broadleaved forests in Sweden seems to be about 5 km (radius), but smaller landscapes may be important for vascular plants and wood-inhabiting fungi of conservation concern. In addition, restoration is urgent to counteract the effect of time delays in species responses to recent habitat loss.     

Landscape changes caused by high altitude ski-pistes affect bird species richness and distribution in the Alps

There is a paucity of research on the wider landscape-level effects of ski-piste construction on alpine fauna. In this study, the response of alpine bird communities to the landscape changes induced by the construction of ski-pistes was investigated in the western Italian Alps. The aims were: (i) to test the hypothesis that ski-pistes have a detrimental effect on alpine grassland bird communities at a landscape-scale; and, (ii) to model local probability distributions of bird species according to different scenarios of ski-piste restoration and ski-piste proliferation above the treeline. Species richness and presence/absence data from point counts were analyzed in relation to GIS-derived landscape variables based on a 16 ha hexagon grid. Predictive variables were selected through the LASSO model selection procedure, and logistic regression was used to estimate the probability of occurrence of each species in each hexagon. Grassland species richness, and probability of occurrence of water pipit, wheatear and black redstart, significantly decreased with increasing extent of ski-piste edge. Length of ski-piste edge was in the set of best models considering a large range of habitat and landscape predictors, and are therefore clearly features that exert a strong negative effect on high alpine grassland bird communities. Predictions of species occurrence were made by applying the models to different scenarios of habitat change. These showed predicted detrimental impacts of a relatively small 10% increase in ski-piste extent, but also that grassland restoration on existing ski-pistes could result in significantly increased occurrence rates of alpine grassland species. This study suggests that ski-pistes are perceived by birds as detrimental features of the alpine landscape. To minimize their impact, new, environmentally–friendly ways of constructing pistes should be developed, which could include habitat restoration and management to obtain a level of grass cover such that edges of ski-pistes are no longer perceived by birds.     

The importance of fine-scale savanna heterogeneity for reptiles and small mammals

Tropical savannas are an important reservoir of global biodiversity. Australia’s extensive savannas, although still largely intact, are experiencing substantial declines in terrestrial biodiversity due to a variety of interrelated effects of altered fire regimes, grazing and increases in invasive species. These disturbance processes are spatially variable, combine to increase landscape to local-scale landscape heterogeneity, but rarely result in well-defined patch boundaries. We quantified the importance of this heterogeneity for native reptile and small mammal species in a tropical savanna landscape of Queensland, Australia. We used high resolution remote sensing imagery (IKONOS) to map habitat pattern at a 4 m spatial resolution and at variable extents. We found that landscapes dominated by grass or bare ground had low reptile and small mammal diversity, while landscapes with a heterogeneous mix of grass, bare ground and trees had high species diversity and relative abundance of most species. Landscape heterogeneity may increase reptile and small mammal species richness by: (i) increasing the variety and abundance of foraging resources such as seeds and invertebrates; (ii) providing cover from predators and high summer temperatures; and (iii) increasing functional connectivity and dispersal success. The importance of these resources and processes varies among individual species and at different spatial scales, reiterating the need to consider habitat requirements of multiple species in landscape management and conservation planning.     

Ecological characteristics of small farmland ponds: Associations with land use practices at multiple spatial scales

Despite their restricted surface area, small farmland ponds often have a high conservation value because they contribute significantly to regional biodiversity and contain rare or unique species. For this reason, the creation of new ponds has become a widely applied practice in many countries. Information on the effects of land use on farmland ponds is very scarce. Farmland ponds differ from larger ponds, lakes and rivers in many aspects and can therefore be expected to be affected by land use via other mechanisms operating at different spatial scales. We here present a study on 126 ponds distributed over the entire territory of Belgium (surface area: 30.500 km²). We assessed variables related to turbidity state and vegetation complexity and related them to land use variables assessed at several spatial scales ranging from the pond edge up to 32 km² circular areas. According to redundancy analysis, trampling by cattle and percentage cover of nearby crop land were positively associated with turbid state related variables. Conversely, ponds with high coverage by forest in the immediate neighbourhood tended to be more associated with the clear water state. Multiple regression analysis demonstrated a negative effect of trampling and coverage by crop land on vegetation complexity. Effects of crop lands and forest were strongest at the local scale (<200 m radius) which indicates that adverse external influences can most efficiently be mitigated at a small scale. Based on these results we suggest several recommendations for pond construction and conservation.     

Determining the spatial scale for conservation purposes - an example with grizzly bears

This study suggests procedures for determining the spatial scale for conservation guidelines for animals, giving an illustration with an analysis of grizzly bear habitat selection. Bear densities were sampled by identifying hairs at bait stations in British Columbia. Habitat variables were measured using remote sensing. Spatial scale was changed by varying the window size over which the variables were averaged. First, the spatial pattern of bears was studied, measuring the patchiness in bear densities at a variety of spatial scales, by calculating the correlation in bear densities between adjacent windows. This was repeated for the habitat variables. Finally, the overall interaction between bears and habitats was analysed, measuring the strength of habitat selection at different spatial scales. There are three domains of scale: at 2-4 km, bears and habitats are patchy, at 5-10 km, bears select for habitats, and at 40+ km, habitats are patchy and bears select for habitats. At scales of 40+ km, bears selected for: (i) higher slopes, or (ii) higher slopes, and some combination of more avalanche chutes, fewer roads and trees, higher elevations, and less logged land. Within 15 km areas, bears selected for 6 km areas that are either at higher elevations, or at higher elevations and had fewer trees. The relationship of conservation guidelines at different spatial scales should be determined by measuring and comparing hierarchical to non-hierarchical selection. The scales that bears select for habitats roughly correspond to the scales used in present grizzly bear conservation plans in British Columbia.     

Modeling regional-scale habitat of forest birds when land management guidelines are needed but information is limited

Conservation planning at broad spatial scales facilitates coherence between local land management and objectives set at the state or provincial level. Habitat suitability models are commonly used to identify key areas for conservation planning. The challenge is that habitat suitability models are data hungry, which limits their applicability to species for which detailed information exists, but managers need to address the needs of all at-risk species. We propose a modeling approach useful for regional-scale conservation planning that accommodates limited species knowledge, and identifies what managers should aim for at the local scale. For twenty at-risk bird species, we built models to identify potential habitat using both literature information and empirical data. Species occupancy within potential habitat depends on the presence of intrinsic elements, which we identified for each species so that managers can enhance these elements as appropriate. For most species, the estimated amount of habitat needed to meet population targets was <10% of the mapped potential habitat, with notable exceptions for Northern Goshawk (Accipiter gentilis; 100%), Brown Thrasher (Toxostoma rufum; 63.7%), and Veery (Catharus fuscescens; 17.9%). Model validation showed that interior forest species models performed best. Our modeling framework allowed us to build potential habitat models to various endpoints for different species, depending on the information available, and revealed a number of species for which basic natural history data are missing. Our potential habitat models provide regional perspective and guide local habitat management, and assist in identifying research priorities.     

The habitat requirements of the rufous treecreeper (Climacteris rufa). 1. Preferential habitat use demonstrated at multiple spatial scales

Determining the habitat requirements of a species is fundamental to effective conservation, particularly if the species is declining in areas where its habitat is being modified. Multi-scaled investigations of habitat use are essential because different selection processes may operate at different scales. I examined the habitat use of a declining woodland passerine, the rufous treecreeper (Climacteris rufa), at three spatial scales (landscape, woodland and territory) in the wheatbelt of Western Australia. Preferential habitat use was exhibited at all scales. At the landscape scale, wandoo (Eucalyptus wandoo) woodland was used at a significantly greater rate than three other common vegetation types. Territory use within woodlands was positively related to the density of hollow-bearing logs, the density of nest sites, and tree age. Within an individual territory, nest sites (hollows) were favoured if they had a spout angle of ?50° to the horizontal and an entrance size of between 5 and 10 cm. The rufous treecreeper preferentially used habitat with traits characteristic of old-growth wandoo woodland. Degradation of wandoo through habitat modification (e.g. grazing, logging, fire and removal of deadwood) represents a significant threat to the persistence of treecreepers.     

A priori valuation of land use for the conservation of black rhinoceros (Diceros bicornis)

The appropriateness of using carrying capacity (CC) estimates to indicate habitat utilisation for a particular species, and thus as a tool for conservation population planning, has been questioned. We argue individual fitness is driven by resource availability, and we therefore assume individuals select habitats with a higher quality, abundance, and availability of key resources. In the past such selection has been related to the CC of a habitat. We tested whether we can use CC estimates to indicate habitat selection by individuals using a selective forager, black rhinoceros Diceros bicornis, for which CC approaches underpin species conservation plans. We tested for correlation of individuals’ habitat selection with predicted CC values at three spatial scales of selection. Individual selection was not related to the value of the habitat according to our CC estimates for any of the three scales we tested at. We discuss how density-dependence, environmental variables, scale of selection, individual variation and intra- and inter-specific dynamics may have influenced these results. Following this, we question the use of a priori calculations of potential resource quality and abundance of habitats (CC estimates), which do not take into account the various factors that influence an animal’s selection of a habitat, as an indicator of species habitat selection. We raise caution regarding the use of such CC models to determine optimal population numbers for an area.     

Oil prospecting and its impact on large rainforest mammals in Loango National Park, Gabon

Resource extraction is increasingly affecting protected areas worldwide. However, aside from studies on logging, limited information is available about the effect this has on wildlife, which may be of great consequence, especially when endangered species could be affected. Specifically, the effect of intense human-induced noise during oil exploration on wildlife is poorly understood. We explore the effect of seismic oil exploration on large mammal distribution in an 80 km² area of Loango National Park, Gabon. Following the ecological theory of habitat disturbance, we predicted that changes in habitat use in response to noise disturbance would scale with the body/home range size of each species examined. Our study was conducted over six months before, during and after low-impact seismic operations. We recorded counts along transects of indirect signs of elephants (Loxondota africana cyclotis), chimpanzees (Pan troglodytes troglodytes), gorillas (Gorilla gorilla gorilla), duikers (Cephalophus spp.), and the vocalizations of five monkey species (Cercocebus torquatus,Cercopithecus cephus, C. nictitans, C. pogonias and Lophocebusalbigena) and modeled seismic impact over different spatial scales (small, intermediate and large). We found that elephants avoided seismic activity on all three spatial scales, apes avoided on the intermediate and small scales, and there was no effect for duikers and monkeys. We conclude that low-impact seismic operations can cause considerable temporary habitat loss for species with large ranges and suggest that the impact on those endangered species can be minimized by adequately spacing seismic lines and activity in space and time to enable species to move away from the progressive noise disruption.     

Conservation issues of temporary wetland Branchiopoda (Anostraca, Notostraca: Crustacea) in a semiarid agricultural landscape: What spatial scales are relevant?

Ecologists increasingly recognise the importance of spatial scale for conservation. This study focuses on threatened temporary wetland crustaceans, the fairy shrimp Branchinecta orientalis Sars (Anostraca) and the tadpole shrimp Triops cancriformis Bosc (Notostraca). Using redundancy analyses with a canonical variance partitioning approach, we studied how local habitat conditions and landscape features influence their densities at 4 spatial scales (100 m buffer strip around ponds, 1 km, 5 km and 10 km catchment scales). Branchinecta densities were negatively related with local conditions (trophic status) at all scales. Landscape effects (catchment:wetland size ratio) were only significant at the 10 km scale. However, trophic state conditions were influenced by local contamination rather than landscape conditions. Local degradation tended to be more pronounced in wetlands situated in catchments with a higher cover of natural vegetation compared to those in agricultural catchments. Triops was less influenced by local effects at all scales. The importance of landscape effects increased with landscape scale but effects were only significant at the 10 km scale, and were negatively explained by irrigated croplands. The importance of broad landscape scales and the difficulty to restore locally degraded sites challenges management. Because rationalisation of large-scale agricultural practises can conflict with socioeconomic demands, a first step to the conservation of actual Branchiopoda populations in this remnant wetland complex could benefit from the creation of vegetated buffer strips around the wetlands and/or hedgerows around agricultural fields to counteract atmosphere-mediated flux of particles and solutes from croplands to wetlands at broad landscape scales.