Within agricultural landscapes, linear features such as hedgerows and tree-lines provide valuable habitat for many species. We use data from 315 transects, completed as part of a national acoustic ...survey of bat distribution, to examine the incidence of four bat species adjacent to linear features in rural areas. The use of linear features was assessed in relation to hedgerow width, tree density, the presence of water and woodland proximity. To examine the effect of tree density, linear features were classified as either hedgerows without trees, hedgerows with sparse trees (comprising <50% tree canopy) or tree-lines (>50% tree canopy). The use of linear features by
Pipistrellus pipstrellus was not affected by tree density; linear features of all types were associated with a similar increase in
P. pipistrellus incidence. The use of linear features by
Pipistrellus pygmaeus was dependent on both tree density and the proximity of woodland; only linear features containing trees provided an increase in
P. pygmaeus incidence regardless of woodland proximity.
P. pipistrellus and
P. pygmaeus incidence was not affected by hedgerow width or the presence of water. Incidence of
Nyctalus noctula and
Eptesicus serotinus was unaffected by the density of linear features of any type. Many agri-environment schemes offer financial incentives for the creation and management of hedgerows. Optimising the biodiversity gain provided by linear features will maximise the effectiveness of these schemes. Agri-environment measures that encourage the provision and retention of hedgerow trees will benefit bats in agricultural landscapes.
Aim
To develop a causal understanding of the drivers of Species distribution model (SDM) performance.
Location
United Kingdom (UK).
Methods
We measured the accuracy and variance of SDMs fitted for ...518 species of invertebrate and plant in the UK. Our measure of variance reflects variation among replicate model fits, and taxon experts assessed model accuracy. Using directed acyclic graphs, we developed a causal model depicting plausible effects of explanatory variables (e.g. species' prevalence, sample size) on SDM accuracy and variance and quantified those effects using a multilevel piecewise path model.
Results
According to our model, sample size and niche completeness (proportion of a species' niche covered by sampling) directly affect SDM accuracy and variance. Prevalence and range completeness have indirect effects mediated by sample size. Challenging conventional wisdom, we found that the effect of prevalence on SDM accuracy is positive. This reflects the facts that sample size has a positive effect on accuracy and larger sample sizes are possible for widespread species. It is possible, however, that the omission of an unobserved confounder biased this effect. Previous studies, which reported negative correlations between prevalence and SDM accuracy, conditioned on sample size.
Main conclusions
Our model explicates the causal basis of previously reported correlations between SDM performance and species/data characteristics. It also suggests that niche completeness has similarly large effects on SDM accuracy and variance as sample size. Analysts should consider niche completeness, or proxies thereof, in addition to sample size when deciding whether modelling is worthwhile.
► We examine associations between bat roost location and landscape structure. ► We model six species using data from 1129 roosts distributed across the UK. ► All species positively associated with ...either broadleaved woodland extent or proximity. ► Increasing broadleaved extent has largest effect on roost location between 0% and 20% cover. ► Roost location for all species unaffected by the size of nearest broadleaved patch.
Although forest fragmentation can greatly affect biodiversity, responses to landscape-scale measures of woodland configuration in Europe have been examined for only a limited range of taxa. Almost all European bat species utilise woodland, however little is known about how they are affected by the spatial arrangement of woodland patches. Here we quantify landscape structure surrounding 1129 roosts of six bat species and a corresponding number of control locations across the UK, to examine associations between roost location and landscape composition, woodland proximity and the size of the nearest broadleaved woodland patch. Analyses are performed at two spatial scales: within 1
km of the roost and within a radius equivalent to the colony home-range (3–7
km). For four species, models at the 1
km scale were better able to predict roost occurrence than those at the home-range scale, although this difference was only significant for
Pipistrellus pipistrellus. For all species roost location was positively associated with either the extent or proximity of broadleaved woodland, with the greatest effect of increasing woodland extent seen between 0% and 20% woodland cover.
P. pipistrellus,
Pipistrellus pygmaeus, Rhinolophus hipposideros, Eptesicus serotinus and
Myotis nattereri all selected roosts closer to broadleaved woodland than expected by chance, with 90% of roosts located within 440
m of broadleaved woodland. Roost location was not affected by the size of the nearest broadleaved patch (patches ranged from 0.06–2798
ha
±
126
SD). These findings suggest that the bat species assessed here will benefit from the creation of an extensive network of woodland patches, including small patches, in landscapes with little existing woodland cover.
Agri‐environment schemes (AES) have been criticized for being inadequately monitored and for not delivering the expected benefits to nature. Consequently, the Welsh Government funded a comprehensive ...programme of monitoring of AES between 2009 and 2012. The AES assessment focused on Tir Gofal (which translates as “Land in Care”) but also included the Organic Farming Scheme, and monitoring focused on a range of taxa of conservation importance: arable plants, grassland fungi, bats (six species), butterflies (three species), birds (five species), water vole and brown hare.
Field surveys were carried out on matched farms and fields within and outside of AES. Response variables were spatial trends of abundance, occurrence and species richness, and were modelled against AES status. Existing data were also available for two bird species.
Few differences were observed between AES and non‐AES farms and fields. Those that were observed were for species that use arable habitats (which are uncommon in Wales): arable plants, yellowhammers and brown hares. The lack of differences in non‐arable habitats may reflect the smaller contrast between AES and non‐AES management in these habitats. It may also reflect the original condition of habitat entered into AES prescriptions, as most non‐arable prescriptions were defined by mandatory management of existing habitats, rather than optional habitat creation or restoration, which is the case for most arable prescriptions.
Despite the lack of differences observed, AES may help to maintain populations of species, making it more likely that they will persist in the landscape. There is evidence, from this monitoring programme and elsewhere, that AES can increase the populations of species, when well targeted and implemented.
Policy implications. Our results indicate that Welsh Agri‐environment schemes (AES) have been only partly successful in achieving their stated aim of “maintaining and enhancing species abundance”. They can be used to improve AES design and management, both in Wales and more widely, by identifying and promoting effective management interventions, and by identifying ineffective management interventions and seeking alternatives. Comprehensive monitoring of AES, combined with specific targets regarding expected outcomes, is essential to determine whether AES are providing value for money.
•Land-use and habitats were broadly similar between TG and control farms.•New hedges, uncropped margins and young trees were more prevalent on TG farms.•Encounter rates of target bat species were ...high, and occurrence similar, on both TG and control farms.•Where present, the intensity of activity of N. noctula / Nyctalus group was higher on control farms.•There were no relationships between bat activity and time under TG management.
Agricultural intensification was a major driver of declines in western European wildlife populations during the twentieth century, including those of bats. Agri-environment schemes are advocated as the key government-funded mechanism to restore biodiversity, but evidence for their effects has been mixed. We examined the response of six bat species to Tir Gofal (TG), a Welsh AES that operated from 1999 to 2011. A large-scale multi-site study compared bat activity and key habitat variables on TG farms paired with control farms not in the scheme. Observations were made over three years (2009 to 2011) using three types of bat detector survey. Pipistrellus pipistrellus, P. pygmaeus, Myotis daubentonii, Rhinolophus hipposideros and R. ferrumequinum showed similar overall and foraging activity on TG and control farms (occurrence, intensity of activity where present). Occurrence of Nyctalus noctula and Nyctalus group was also similar on both farm types, but where they were present, the intensity of their activity was higher on control farms. The lack of influence of TG status on bat activity may reflect the close similarity in occurrence and condition of many key habitats on the two farm types and should be seen in the context of a mainly traditional extensively farmed landscape. Habitat prescriptions may have been insufficiently mature, implemented at too low density or lacking roosting provision to stimulate a species response, or may have had greater impact in a more intensively farmed landscape where less high quality bat habitat was available. A more targeted approach to creating and enhancing field and landscape scale roosting, foraging and commuting resources may be needed to effect positive responses in bat populations.
We describe the development of two complementary priority species indicators (PSIs) to help the UK to report progress towards Aichi target 12 on the status of known threatened species. Based on ...species identified as national conservation priorities, the indicators present average changes in (i) 213 species for which trends in relative abundance are available from structured monitoring schemes, and (ii) 179 species for which trends in frequency of occurrence were modelled from data sets of unstructured biological records. Both indicators show substantial declines in priority species since 1970, of 67% and 40%, respectively, although the rate of decline in the relative abundance-based PSI may have lessened over the last five years (2007–2012). We discuss the biases and weaknesses of the indicators at present, and put forward suggestions as how these may be addressed, including through the development of a third PSI.
Arboreal mammals form a diverse group providing ecologically important functions such as predation, pollination and seed dispersal. However, their cryptic and elusive nature, and the heights at which ...they live, makes studying these species challenging. Consequently, our knowledge of rainforest mammals is heavily biased towards terrestrial species, limiting our understanding of overall community structure and the possible impacts of human-induced disturbance. We undertook the first in-depth appraisal of an arboreal mammal community in Southeast Asia, using camera-traps set in unlogged and logged tropical rainforest in Sabah, Borneo. Using paired canopy and terrestrial camera-traps at 50 locations (25 in unlogged forest, 25 in logged), we assessed the effectiveness of camera-trapping at characterising the arboreal versus terrestrial community, and tested the influence of strata and forest type on community structure and composition. The paired design detected 55 mammal species across 15,817 camera-trap nights (CTNs), and additional canopy sampling in a subset of trees added a further two arboreal species to the inventory. In total, thirty species were detected exclusively by terrestrial camera-traps, eighteen exclusively by canopy camera-traps, and nine by units set at both heights, demonstrating significant differences between arboreal and terrestrial communities. This pattern was strongest in unlogged forest, reflecting greater structural diversity of this habitat, but held in logged forest as well. Species accumulation curves revealed that canopy camera-trapping significantly boosted species inventories compared to terrestrial-only sampling, and was particularly effective at detecting gliding mammals, rodents and primates. Canopy inventories took longer to reach an asymptote, suggesting that a greater sampling effort is required when deploying canopy camera-traps compared to those set on the ground. We demonstrate that arboreal mammals in Borneo’s rainforest form a diverse and distinct community, and can be sampled effectively using canopy camera-traps. However, the additional costs incurred by sampling in the canopy can be substantial. We provide recommendations to maximise sampling effectiveness, while bringing down costs, to help encourage further study into one of the last frontiers of tropical forest research.
Tropical rainforest canopies are structurally complex, floristically diverse, and three-dimensionally vast. They play key roles in ecological processes such as nutrient cycling, carbon storage, and ...plant primary productivity. An ability to utilise the canopy provides wildlife with access to resources and environmental niches not available at ground level, thereby facilitating the co-existence of a very high number of species, and tropical canopies support a substantial proportion of a forest's vertebrate and invertebrate life. Mammals are a biodiverse and functionally important group and within rainforests, more than half of species are arboreal or semi-arboreal, i.e. exclusively or habitually ese the canopy space. However, due to the practical difficulties of sampling at height, tropical forest canopies remain relatively unexplored, and most arboreal taxa, with the exception of some primates, are little known to science. Arboreal mammal communities consist mainly of species that are small-bodied, cryptically coloured, elusive, and/or nocturnal; yet, traditional ground-based sampling techniques are biased towards larger-bodied, diurnal mammals that do not flee in the presence of people. Camera-trapping, widely used in terrestrial research, has started to be implemented at canopy level with promising initial results, particularly for single-species studies or those focussing on animal use of habitat features such as canopy bridges. However, the implementation of canopy camera-trapping to inventory and study arboreal communities has to date been limited to eight sites, all in the Neotropics or Africa, and with three focussing only on medium- and large-bodied mammals. Furthermore, around half of all arboreal mammal studies utilising camera-traps deployed units at heights of ten metres or less which, in rainforests where canopies reach between 30-60 metres high, misses an extensive portion of the vertical habitat. These factors point to a clear gap in the application of the methodology, and the understanding of arboreal mammal communities, in the extremely tall and hyper-diverse rainforests of Southeast Asia.The unique height and structure of rainforests on the island of Borneo have given rise to an exceptionally high diversity of canopy-dwelling wildlife; more than half of all mammals are arboreal or semi-arboreal, and the island represents the world epicentre of gliding vertebrate diversity, including 15 gliding mammal species (14 flying squirrels and the colugo, or 'flying lemur'). Meanwhile, logging is a pervasive threat to forests globally, with some of the highest timber extraction rates in Borneo due to the dominance of commercially valuable dipterocarp trees. Many terrestrial taxa are able to persist in recovering-logged forest, but the changes in habitat structure associated with logging activities are likely to have a greater impact on species that directly depend on the complexity and connectivity of the canopy architecture. However, studies explicitly investigating arboreal mammal responses to logging are lacking, and in general, our understanding of rainforest communities is skewed towards terrestrial species and processes. We therefore risk underestimating both the diversity and potential vulnerability of arboreal wildlife, with implications for conservation, and habitat management and restoration.At our current state of knowledge, it is not clear (i) whether camera-traps set in the forest canopy are an effective sampling method for arboreal mammals in Borneo's immensely tall and biodiverse rainforests; (ii) what the outcome of this sampling would be in terms of community richness and distinctness from terrestrial mammals; and (iii) whether, and to what extent, arboreal mammals are affected by logging.In this thesis, I document the first community-wide investigation of Borneo's arboreal mammal community using camera-traps. I deployed a network of cameras in the rainforest canopy, paired with units at ground level in both unlogged and recovering-logged forest areas, to test the efficacy and cost-effectiveness of this method in Borneo. Sampling was conducted across fifty locations, divided equally between unlogged forest (N=25) and recovering-logged forest (N=25), with cameras (Reconyx Hyperfire HC500) deployed in a grid formation and spaced on average 1.26 km apart (range = 0.5-4 km). Every sampling location comprised one terrestrial camera-trap and one canopy camera-trap and, to evaluate the utility of placing more than one canopy camera per tree to maximise species detections, experimental second-canopy units were deployed at a subset of twenty locations, selected at random and divided equally between unlogged (N=10) and recovering-logged (N=10) forest areas. Total sampling thus comprised fifty terrestrial cameras and seventy canopy cameras. Terrestrial camera-traps were set approximately 0.3 m above the ground, while canopy units were set between heights of 9.8-52.3 m (mean = 25.9 m). Cameras at each location were deployed for 7-8 months except the experimental second-canopy units, which were in place for a subset of 3 months. After accounting for malfunctions, mammal detection data were obtained from 17,226 camera-trap nights (CTN): 6,661 CTN from terrestrial cameras; 9,156 CTN from canopy cameras; and an additional 1,409 CTN from experimental second-canopy units. Using these data, I quantify species diversity, community composition, and diel activity patterns, and document responses to logging, of both arboreal and terrestrial mammals, finding that differences across strata are much greater than differences between unlogged and recovering-logged forest. I further quantify relationships between mammal occurrence and a suite of remotely-sensed, high-resolution vegetation covariates, including a novel measure of canopy connectivity, and show that this is by far the most important predictor of occupancy for arboreal species among many potential covariates. My results illustrate the applicability of canopy camera-trapping to study arboreal communities in Borneo, and extend those of terrestrial studies by demonstrating that recovering-logged forests can maintain mammal diversity across strata, underscoring their value for species conservation. However, I also highlight that the arboreal community as a whole, and particular taxa within it, are more vulnerable to the effects of habitat degradation than their terrestrial counterparts.
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