Caragh G. Threlfall

Influence of Landscape Structure and Human Modifications on Insect Biomass and Bat Foraging Activity in an Urban Landscape

Urban landscapes are often located in biologically diverse, productive regions. As such, urbanization may have dramatic consequences for this diversity, largely due to changes in the structure and function of urban communities. We examined the influence of landscape productivity (indexed by geology), housing density and vegetation clearing on the spatial distribution of nocturnal insect biomass and the foraging activity of insectivorous bats in the urban landscape of Sydney, Australia. Nocturnal insect biomass (g) and bat foraging activity were sampled from 113 sites representing backyard, open space, bushland and riparian landscape elements, across urban, suburban and vegetated landscapes within 60 km of Sydneys Central Business District. We found that insect biomass was at least an order of magnitude greater within suburban landscapes in bushland and backyard elements located on the most fertile shale influenced geologies (both p<0.001) compared to nutrient poor sandstone landscapes. Similarly, the feeding activity of bats was greatest in bushland, and riparian elements within suburbs on fertile geologies (p = 0.039). Regression tree analysis indicated that the same three variables explained the major proportion of the variation in insect biomass and bat foraging activity. These were ambient temperature (positive), housing density (negative) and the percent of fertile shale geologies (positive) in the landscape; however variation in insect biomass did not directly explain bat foraging activity. We suggest that prey may be unavailable to bats in highly urbanized areas if these areas are avoided by many species, suggesting that reduced feeding activity may reflect under-use of urban habitats by bats. Restoration activities to improve ecological function and maintain the activity of a diversity of bat species should focus on maintaining and restoring bushland and riparian habitat, particularly in areas with fertile geology as these were key bat foraging habitats.

Roost selection in suburban bushland by the urban sensitive bat Nyctophilus gouldi

Abstract The persistence of wildlife in fragmented landscapes is predicted to rely on the presence of critical habitat elements. In urban landscapes, the persistence of hollow-dependent bats arguably depends upon the protection of roosting habitat, yet knowledge of bat roosting requirements within these landscapes is limited. We used radiotelemetry to locate day roosts of a species considered sensitive to urbanization, Goulds long-eared bat (Nyctophilus gouldi), in suburban bushland in Sydney, New South Wales, Australia. We compared roost selection data collected for 9 individuals during the mating season (March–April 2009) and 10 individuals during the maternity season (November–December 2009). We found 41 roosts of N. gouldi under decorticating bark and in tree hollows, which were all located in 1 suburban bushland reserve (∼40 ha), with roosts rarely located elsewhere, despite the abundance of available trees in smaller patches outside of the reserve. N. gouldi displayed a clear preference for trees with a greater amount of understory and canopy cover, and only roosted where the extent of forest cover in the local landscape was greatest. Maternity roosts also were predominately located in gullies, and closer to creek lines than expected. Roost switching differed significantly between seasons, with lactating females switching roosts significantly more often than nonlactating females, where roost switching occurred after 1 day on 71% of occasions. Because competition with other fauna for hollows has been suggested as a potential threat, systematic observations of hollow-using bird species, including rainbow lorikeets (Trichoglossus haematodus), were conducted. We observed birds occupying bat roosts on days following bat occupancy, and bats roosted in trees where there were fewer hollow-using birds than randomly available trees. We recommend that further examination of hollow competition be undertaken because abundant, urban-adapted, hollow-nesting birds may render hollows a limiting resource to hollow-users such as bats in urban landscapes. Protection of a network of potential roost trees in suburban bushland remnants, particularly along creek lines, will assist in maintaining this critical resource for bats.

Increasing biodiversity in urban green spaces through simple vegetation interventions

Cities are rapidly expanding world-wide and there is an increasing urgency to protect urban biodiversity, principally through the provision of suitable habitat, most of which is in urban green spaces. Despite this, clear guidelines of how to reverse biodiversity loss or increase it within a given urban green space is lacking. We examined the taxa- and species-specific responses of five taxonomically and functionally diverse animal groups to three key attributes of urban green space vegetation that drive habitat quality and can be manipulated over time: the density of large native trees, volume of understorey vegetation and percentage of native vegetation. Using multi-species occupancy-detection models, we found marked differences in the effect of these vegetation attributes on bats, birds, bees, beetles and bugs. At the taxa-level, increasing the volume of understorey vegetation and percentage of native vegetation had uniformly positive effects. We found 30-120% higher occupancy for bats, native birds, beetles and bugs with an increase in understorey volume from 10% to 30%, and 10-140% higher occupancy across all native taxa with an increase in the proportion of native vegetation from 10% to 30%. However, increasing the density of large native trees had a mostly neutral effect. At the species-specific level, the majority of native species responded strongly and positively to increasing understorey volume and native vegetation, whereas exotic bird species had a neutral response. Synthesis and applications. We found the probability of occupancy of most species examined was substantially reduced in urban green spaces with sparse understorey vegetation and few native plants. Our findings provide evidence that increasing understorey cover and native plantings in urban green spaces can improve biodiversity outcomes. Redressing the dominance of simplified and exotic vegetation present in urban landscapes with an increase in understorey vegetation volume and percentage of n

Urbanisation and Its Effects on Bats—A Global Meta-Analysis

Urbanisation is viewed as the most ecologically damaging change to land use worldwide, posing significant threats to global biodiversity. However, studies from around the world suggest that the impacts of urbanisation are not always negative and can differ between geographic regions and taxa. Bats are a highly diverse group of mammals that occur worldwide, and many species persist in cities. In this chapter, we synthesise current knowledge of bats in urban environments. In addition, we use a meta-analysis approach to test if the general response of bats depends on the intensity of urbanisation. We further investigate if phylogenetic relatedness or functional ecology determines adaptability of species to urban landscapes and if determining factors for urban adaptability are consistent worldwide. Our meta-analysis revealed that, in general, habitat use of bats decreases in urban areas in comparison to natural areas. A high degree of urbanisation had a stronger negative effect on habitat use compared to an intermediate degree of urbanisation. Neither phylogenetic relatedness nor functional ecology alone explained species persistence in urban environments; however, our analysis did indicate differences in the response of bats to urban development at the family level. Bats in the families Rhinolophidae and Mormoopidae exhibited a negative association with urban development, while responses in all other families were highly heterogeneous. Furthermore, our analysis of insectivorous bats revealed that the adaptability of individual families, e.g. Emballonuridae and Vespertilionidae, to urbanisation is not consistent worldwide. These results suggest that behavioural and/or morphological traits of individual species may better determine species’ adaptability to urban areas, rather than phylogenetic or functional classifications, and that driving factors for species adaptability to urban areas might be regionally divergent. We thus argue that future research should focus on behavioural and morphological traits of bats, to assess if these determine urban adaptability in this species-rich group of mammals.

Soil Carbon and Carbon/Nitrogen Ratio Change under Tree Canopy, Tall Grass, and Turf Grass Areas of Urban Green Space.

Soils in urban green spaces are an important carbon (C) store, but urban soils with a high carbon to nitrogen (C/N) ratio can also buffer N eutrophication from fertilizer use or atmospheric deposition. The influence of vegetation management practices on soil C cycling and C/N ratios in urban green spaces is largely unknown. In 2013, we collected replicate ( = 3) soil samples from tree canopy, tall grass, and short turf grass areas ( = 3) at four random plot locations ( = 4) established in 13 golf courses ( = 13). At each sample point, soil was separated into 0- to 0.1-, 0.1- to 0.2-, and 0.2- to 0.3-m depths (total = 1404). Linear mixed models investigated the relationships between soil properties, vegetation attributes, and green space age. Tree canopy soil was less compacted (1.07 g cm) than grassy areas (1.32 g cm). Similarly, tree canopy soil had mean C/N ratios of 17.2, as compared with between 14.2 and 15.3 in grassy areas. Soil properties in tree canopy areas were best explained by tree basal area and understory vegetation volume. Soil C/N increased with increasing understory vegetation, and the difference in soil C/N between tree canopy and short turf grass areas increased over time. The soil properties in tree canopy areas of urban green space mean they can increasingly buffer the localized use of N fertilizers and atmospheric N deposition. Managers of urban green spaces concerned about N pollution of groundwater and waterways could consider planting trees in suitable topographic locations and promoting understory vegetation and surface litter accumulation.

Variation in Vegetation Structure and Composition across Urban Green Space Types

The ecological sustainability and function of urban landscapes is strongly influenced by the composition and structure of the local plant community. Taxonomic composition generally refers to the identity of the species comprising the community, while we define structure as the presence of multiple canopy layers, as well as stems of varying diameter and age. These aspects of urban vegetation significantly influence the ecology of cities, yet they are generally poorly quantified across the range of natural and constructed plant communities present in urban landscapes. We quantified vegetation composition and structure to i) simultaneously assess their variation across four green spaces types (golf courses, public parks, residential neighbourhoods and patches of remnant vegetation) in Melbourne, Australia, and ii) investigate the relationship between vegetation composition and structure within these green spaces. The four green space types supported distinctly different plant communities. Vegetation composition in the residential neighborhoods differed significantly from the others (p<0.05), largely due to the increased richness of shrubs and cultivated plants, and the reduced presence of large trees. Residential neighborhoods had the highest plant species richness, although a large proportion of these species occurred infrequently. The structural complexity of understorey vegetation (calculated as % volume occupied) below 0.5 m was highest in remnant patches followed by golf courses, public parks and residential neighborhoods. The structural complexity of understorey vegetation in remnant vegetation patches was very similar to that of golf courses even though some of the latter were dominated by exotic plant species. Variation in the composition and structure of urban vegetation might have great implications for the retention of faunal diversity within cities because different taxa have specific habitat requirements. Hence, further understanding of variations in the composition and structure of both natural and constructed plant communities in cities will greatly improve our ability to create urban landscapes that enhance both plant and animal biodiversity.

Odour cues influence predation risk at artificial bat roosts in urban bushland

Odours that accumulate from roosting can attract predators and increase predation risk. Consequently, selection should favour strategies that allow prey to evade detection by predators, including changing roosts. Insectivorous bats that roost in tree hollows regularly switch roosts and roost in different sized groups, strategies that would alter the accumulation of roost odours and are hypothesized to reduce predation risk. We experimentally manipulated the amount and refresh rate of roosting odour cues at 90 artificial bat roosts in Sydney, Australia, to test the hypothesis that odours increase predator visitation. Predators visited roosts with bat faeces significantly more often than untreated control roosts. Roosts with small amounts of faeces mimicking sites used by solitary bats had the greatest rate of visitation. This suggests that bats roosting alone, rather than in groups, have a greater likelihood of disturbance or predation. Roost switching probably decreases the predictability of finding occupied roosts; however, we show that all roosts (those currently or recently occupied) were visited by predators, suggesting generalist urban predators readily investigate potential roosts. This is the first demonstration that bat odours are attractive to predators that use olfactory cues, showing that bats are at risk of predation in visually cryptic roosts.

Do Green and Golden Bell Frogs Litoria aurea occupy habitats with fungicidal properties

The Green and Golden Bell frog Litoria aurea is in major decline in Australia, where its distribution is now confined mainly to the east coast of New South Wales (NSW). Infection by the newly emerged amphibian fungal pathogen Batrachochytrium dendrobatidis has been identified as one of the main threats affecting L. aurea. Surprisingly, some of the sites in NSW sustaining the largest populations of this species are industrial and urban habitats that are often disturbed and polluted, which could protect L. aurea from chytrid infection if pollution had fungicidal capacity. The aim of this study was to characterise the trace metal concentration of several L.aurea breeding sites in the Sydney and Illawarra regions of NSW and to evaluate the fungicidal efficacy of the main trace metals identified. Selected L. aurea sites were sampled throughout the breeding season (September to February) to establish the concentration of trace metals in both surface sediment and waters. Physico-chemical parameters including pH ...

Conserving herbivorous and predatory insects in urban green spaces

Insects are key components of urban ecological networks and are greatly impacted by anthropogenic activities. Yet, few studies have examined how insect functional groups respond to changes to urban vegetation associated with different management actions. We investigated the response of herbivorous and predatory heteropteran bugs to differences in vegetation structure and diversity in golf courses, gardens and parks. We assessed how the species richness of these groups varied amongst green space types, and the effect of vegetation volume and plant diversity on trophic- and species-specific occupancy. We found that golf courses sustain higher species richness of herbivores and predators than parks and gardens. At the trophic- and species-specific levels, herbivores and predators show strong positive responses to vegetation volume. The effect of plant diversity, however, is distinctly species-specific, with species showing both positive and negative responses. Our findings further suggest that high occupancy of bugs is obtained in green spaces with specific combinations of vegetation structure and diversity. The challenge for managers is to boost green space conservation value through actions promoting synergistic combinations of vegetation structure and diversity. Tackling this conservation challenge could provide enormous benefits for other elements of urban ecological networks and people that live in cities.

Green space context and vegetation complexity shape people’s preferences for urban public parks and residential gardens

Abstract Landscape preferences shape decision-making and drive the ecological outcomes of urban landscapes. We investigate how people’s landscape preferences are shaped by the green space context (public park vs private residential garden landscapes) and by physical features such as vegetation complexity. A postal questionnaire was sent to households near seven urban parks in Melbourne, Australia. Results showed that landscapes were grouped into four categories based on patterns of preference response. Landscapes with moderate vegetation complexity were placed in separate categories distinguished by green space context (parks vs gardens), while very simple and very complex landscapes were placed in different categories irrespective of green space context. Surprisingly, dense vegetation was highly preferred by respondents. As areas of dense vegetation also provide complex habitats for wildlife, this highlights the possibility of developing policies and designing landscapes that can benefit both people and nature.