Exploring structural habitat heterogeneity in sustainable urban drainage systems (SUDS) for urban biodiversity support

Implementation of sustainable urban drainage systems (SUDS) as part of cities’ transition towards climate resilience encompasses unique opportunities to enhance urban nature qualities. SUDS include individual elements integrated in the urban landscape, e.g. rain gardens or wet basins, which are usually constructed with low structural heterogeneity. Structural heterogeneity of habitats is, however, associated with a high degree of biodiversity. This study explored potentials of habitat heterogeneity enhancement in SUDS using structural heterogeneity as a proxy for biodiversity potential. In an interdisciplinary workshop, landscape architects and urban ecologists designed individual SUDS elements with enhanced structural habitat heterogeneity, hereafter bio-SUDS. The redesigned SUDS elements were infiltration trench, curb extension, rain garden, swale, wet basin, and dry basin. To evaluate the bio-SUDS designs, we developed an index of habitat heterogeneity in SUDS based on registration of 45 structurally important components. The conversion from standard SUDS to bio-SUDS entailed substantial increases in structural heterogeneity ranging from 4 to 18 additional components within elements. Larger bio-SUDS elements returned higher index scores, but the relative score increases were substantial for all bio-SUDS and in the range of a factor of 2–5.5. Increased terrain differences, meandering edges, stones, gravel, boulders, deadwood, and brown roof-like vegetation were the components most often employed in the bio-SUDS designs. In conclusion, implementation of bio-SUDS has potential to increase structural habitat heterogeneity thereby providing habitat for biodiversity in urban green areas. The developed bio-SUDS index can assist in future assessments of ecological qualities in designs and real-world SUDS elements.     

What shapes plant and animal diversity on urban golf courses?

Recent concern over increasing loss of biodiversity has prompted considerable interest in the role of urban green spaces as reservoirs of local biodiversity. This study assessed the diversity of three indicator taxa - plants, ants and birds - on golf courses spanning a wide range of environmental variation in terms of climate, elevation, course age, size and connectivity to native woodland. Species richness and community composition was further compared between contrasting on-course habitat types that reflect different management intensities. We identified a set of taxon-specific environmental correlates indicating an intricate interplay of landscape- and local-scale variables that affect local species diversity. Our results show that floristic diversity is positively associated with the amount of rainfall, whereas ant and bird diversity are related to local-scale factors, particularly the number of trees and the size of water features on a site. The amount of on-course native habitat was a strong predictor of plant and ant diversity and was also associated with the number of unique species at the site level; this reinforces the value of remnant habitat patches as local biodiversity reservoirs that represent mini hot-spots in an otherwise species-poor urban landscape. Community composition for all three taxa differed markedly between non-playing and playing areas, with boundary and remnant habitats generally having more diverse, species-rich communities. Our results suggest that local floral and faunal biodiversity on urban golf courses can be enhanced by creating woody non-playing areas and, especially, by preserving, restoring or expanding remnant habitats.     

Both semi-natural and ruderal habitats matter for supporting insect functional diversity in an abandoned quarry in the city of Kraków (S Poland)

Urban areas are beginning to be recognized as having potential for biodiversity conservation because of the relatively high richness of some taxa. However, little is known about what functional groups of organisms constitute this richness. We investigated biodiversity patterns in an abandoned quarry using the Rapid Biodiversity Assessment method based on insect groups according to their trophic guilds. We assessed the value of semi-natural and ruderal habitats. The ruderal sites were characterized by a higher diversity and abundance of phytophagous beetles and, unexpectedly, of parasitoids and predatory beetles, whereas the reverse was true for Hemiptera and Aculeata. Patterns of α-diversity were impacted by different factors than β-diversity: these primarily acted in opposite directions, depending on the habitat type. Species richness was positively related to the woody surroundings of habitat patches on semi-natural sites, but negatively related on ruderal sites. The Dominance index was negatively affected by human impact. Insect assemblages were diversified by taller vegetation, higher nutrient content, lesser human impact and a lower level of insolation in the grasslands with ruderal vegetation than in the semi-natural grasslands. A particular habitat type may constitute a source for some insect groups but a sink for others. Ruderal habitats utilized as a substitute for loss of the semi-natural vegetation are essential for the preservation of insect functional diversity and are suitable for vulnerable groups such as Parasitica. Post-industrial areas with a habitat mosaic of semi-natural and ruderal sites may enrich biodiversity in the urban landscape.

     

Reducing management intensity and isolation as promising tools to enhance ground-dwelling arthropod diversity in urban grasslands

Urbanisation is a growing global phenomenon having multiple ecological consequences. However, the effects of urbanisation on biodiversity remain ambiguous, and some evidence exists that cities provide valuable secondary habitats for many species, possibly mitigating regional biodiversity loss. Therefore, the value of urban sites for biodiversity depends on local habitat conditions and the configuration of the surrounding landscape. We aimed to disentangle the effects of local habitat parameters (management, plant diversity) and urban matrix variables (urbanisation, isolation) on carabid beetle and spider diversity and traits in informal urban green spaces in Berlin, Germany. Habitat management and isolation were the most important influences on carabid beetle and spider species and trait compositions. Spider communities of irregular managed sites contained 2.5 times more species of conservation concern than extensive (regular) managed sites. Moreover, irregular managed sites contained larger species (both for carabid beetles and spiders) and affected the hunting mode of spiders. Isolated sites tended to have lower spider species richness and number of spider species of conservation concern. Moreover, isolated sites were characterised by small, mobile and herbivorous carabid beetles. In contrast, urbanisation and local plant diversity had no effect on carabid beetles and spiders. We conclude that urban grasslands within residential areas – even if not targeted for conservation plans – can provide important habitats for conserving biodiversity, including species of conservation concern. Reducing the intensity of habitat management and increasing the connectivity of urban grassland sites can promote diverse arthropod communities and should therefore be considered in urban planning.     

Suitability of biodiversity-area and biodiversity-perimeter relationships in ecology: a case study of urban ecosystems

Urban areas are probably the most fragmented environments with respect to the presence of semi-natural habitats and shape of these habitats may be significantly affected by urbanization. Patch perimeter in landscape or habitat studies is much less popular to study than patch area. The studied sites were situated in the industrial city of Pardubice, which is one of the ten largest cities in the Czech Republic with nearly 100,000 inhabitants. In total, 40 grasslands were studied within a circular area of 314 km². Butterflies and beetles with diurnal activity were studied during timed survey walks. A Simultaneous autoregressive model was used for test of the effect of biodiversity-area and biodiversity-perimeter relationships and for exclusion of potential bias caused by spatial autocorrelation. The models including patch perimeter performed better than those using patch area in explaining species richness, abundance and diversity of investigated organisms and were less influenced by spatial autocorrelation. The main conclusion and recommendation of the present study is that researchers should pay more attention to the possible influence of the patch perimeter as a potential predictor or co-predictor for landscape and habitat studies – especially in urban areas, where the negative effects of fragmentation might be much higher than in rural or more natural landscapes. Performing preliminary tests on comparisons between area and perimeter is highly recommended.     

Diversity patterns of alien and native plant species in Trieste port area: exploring the role of urban habitats in biodiversity conservation

Nowadays, urban areas play a crucial role in biodiversity conservation and habitat protection despite the constant pressures on which these habitats are subjected. They may even host relatively new plant communities due to the peculiar ecosystem where they vegetate. The port of Trieste (NE Italy) is characterized by a mixed mosaic of intensely human impacted areas (where commercial activities are still ongoing) flanked by abandoned areas where vegetation persists or has spontaneously recovered. In this study, we sampled the whole port area through a stratified random sampling by placing multiscalar nested plots in four different habitats (strata) previously identified by photo-interpretation. Plant species richness and abundance were assessed in each plot. Each species was then classified as native or alien and patterns of species richness and complementarity were compared among habitats. Results show that there is a significant difference in species richness patterns among habitats, while observed patterns are likely to vary at different spatial scales. As expected, urban plots account for most of the alien species in the sampling, while wooded plots cope better with invasion, accounting for a lower alien/native ratio. These results highlight how habitat diversity enhances biodiversity in urban areas and how it could provide an effective filtering effect able to reduce the spread of alien species. In addition, we provide further evidence for the use of multi-scale approaches in order to study the complex relationships between spatial heterogeneity and plant species richness.     

Floral biodiversity of allotment gardens and its contribution to urban green infrastructure

Allotment gardens are a key feature of the urban landscape, providing numerous benefits beyond those of food production. These include ecosystem services such as local climate modification, pollination, and providing a pleasant location for socialising. The biodiversity of flora underpins many of these ecosystem services. The aims of this study are to assess the spontaneous vascular flora of urban allotment gardens and derive estimates of the species richness and diversity. In doing so, the specific position of allotment gardens within urban green infrastructure will be revealed and the role of allotment users in shaping local biodiversity determined. 358 species of spontaneous flora were recorded in 11 representative allotment garden estates (total area 150 ha) in Poznań, Poland. Fourteen biodiversity features were taken into account. The investigated areas exhibited high plant species richness, high diversity, low synanthropisation level, and contained valuable geobotanical elements, including plants of key importance for the European Community. For these reasons, allotment gardens should be considered as biodiversity hotspots for native species within urban green infrastructure. Based on an analysis of the spatial and functional organization of 110 individual plots, four types of usage, and corresponding plant diversity have been distinguished. The composition of the flora depends mostly on spatial and functional organization of allotment gardens and, to a much lesser extent, on the habitat conditions, which on individual plots varied very little. The high species richness and diversity in allotment gardens has important consequences for urban planning.     

Influence of urban landscape structure on bird fauna: a case study across seasons in the city of Valencia (Spain)

Studies on bird fauna of urban environments have had a long history, but the potential of studies mapping the distribution of birds in cities probably has not fully developed. The bird fauna of the municipality of Valencia (Spain) was studied to determine the influence of urbanization on bird species richness and abundance. Birds were censused during winter and the breeding season of years 1997–1998 in 197 squares measuring 49 ha each from a rural and an urbanized area. Across seasons the number of species decreased around 40% in the city compared with the rural landscape surrounding it. Such pattern could be attributed to the low number of farmland species capable to use the habitats inside the city, and the limited ability of urban parks in attracting woodland species. In the urban landscape, the influence of the dimensions and spatial arrangement of habitat patches was outweighed by the amount of each habitat per square. Bird richness and the abundance of most species were negatively related with the amount of built-up habitat per square and positively with the amount of urban parks, and of habitat diversity. Conversely, bird fauna was largely independent of mean park size per square especially during winter, indicating that at the landscape scale even small patches of habitat could play an ecological role. Conservation of urban bird diversity could benefit of two complementary strategies: (i) the protection of the surrounding rural landscape from urban development; (ii) habitat enhancement within the city. Particularly, a proper design and habitat management of urban parks could improve their suitability for urban bird fauna.     

Carabid beetles in green infrastructures: the importance of management practices for improving the biodiversity in a metropolitan city

Green infrastructure in urbanized areas has a dual purpose that achieves both sociological and ecological goals. To benefit society and the urban ecosystem, green infrastructure should be effectively managed. We investigated carabid diversity and assemblage structure as indicators of biodiversity in green infrastructures in a rapidly developing urban area to identify the habitat’s values. In addition, we attempted to reveal the effect of environmental variables (e.g., vegetation structure, soil, and disturbance) that strongly contribute to carabid diversity and assemblage structure. Of the collected organisms, 6,154 individuals representing 20 carabid species were identified in the green infrastructure. Those species with flight ability and that were found in dry habitats were widely distributed and dominated green infrastructures. Carabid assemblages changed significantly in response to management practices. These changes were both positive and negative, with the negative changes increasing the instability of the carabid assemblages through the destruction of their habitat. Other factors, such as the presence of original habitat, habitat age, and habitat succession, also had a considerable effect on carabid diversity. We revealed that management practices prevented habitat succession, and these interactive effects determined carabid diversity and structure in green infrastructures.     

Habitat- and matrix-related differences in species diversity and trait richness of vascular plants,Orthoptera and Lepidoptera in an urban landscape

Urban growth is considered to be a major driver of environmental change. Urbanisation can affect urban biodiversity in different ways. So far, most studies focused on the impact of urbanisation on single taxa in one habitat type. In this study, we used data of species inventories and GIS-based landscape elements to examine the effects of habitat size and landscape composition on the species diversity of three taxonomic groups (vascular plants, Orthoptera and Lepidoptera) in meadows and ruderal sites in the urban region of Basel, Switzerland. We also related the responses of three species traits (body size, dispersal ability and food specialisation) to habitat size in Orthoptera and Lepidoptera. We found that species of the different taxonomic groups differed in their response to habitat size and landscape composition both in meadows and ruderal sites depending on the traits examined. The species richness of Orthoptera and Lepidoptera was positively related to meadow size but not to the size of ruderal sites, while the opposite was true for plants. For Lepidoptera in ruderal sites, the percentage cover of ruderal area in the closer surroundings was a better predictor of species richness than habitat size per se. To sustain high levels of urban biodiversity, we recommend that urban planners develop adequate management strategies to satisfy the different requirements of various taxonomic groups and to increase the quality of green sites surrounding the target habitat.     

Effects of habitat fragment size and isolation on the density and genetics of urban red-backed salamanders (Plethodon cinereus)

Urban expansion is creating environmental stressors through land use change, habitat fragmentation, and habitat loss. These stressors, along with a host of others, are driving precipitous declines in vertebrate taxa around the world. Amphibians, often requiring a narrow range of environmental conditions, can be especially susceptible to the stressors of environmental change. Despite habitat loss and degradation, some amphibian species continue to persist in altered urban landscapes. The red-backed salamander (Plethodon cinereus) is one such- species and in this study, we assess how habitat patch size affects population density and genetic diversity of salamander populations in and around an urban center in Ohio, United States. Further, we examined patterns of genetic differentiation and landscape connectivity to understand gene flow between populations and tested for historic demographic bottleneck effects. Populations were sampled from 9 urban forest patches ranging in size from less than 1 ha to approximately 250 ha. There was no apparent effect of contiguous habitat patch size on salamander density nor genetic diversity, but we did observe significant genetic differentiation between 97% of pairwise population comparisons. The differentiation observed was not a result of overland distance or effective distance due to landscape resistance. There was evidence of historic bottlenecks at every site. These results suggest that density is driven by within-patch heterogeneity and that genetic diversity is affected by drivers other than patch size or contemporary population density. Our study demonstrates that red-backed salamanders can persist in wooded, urban parks, but that genetic diversity remains susceptible to demographic changes.

     

Ecosystem services provided by urban spontaneous vegetation

Spontaneous vegetation colonizes large areas in and around cities. These unmanaged areas are considered to have low economic value or indicate dereliction, but recent research suggests that these can contribute valuable ecosystem services. This study evaluates indicators of ecosystem services in three habitats: urban spontaneous vegetation (USV), managed lawns, and semi-natural urban forest, in Halifax, Nova Scotia. USV had higher indicator values for habitat provisioning (plant species diversity, invertebrate abundance and taxonomic diversity) than the other habitats. Indicators of climatic regulatory services (albedo and leaf area index) in USV were similar to those in lawn habitats. Organic carbon content of the soils, an indicator of carbon storage, was lowest in USV but only marginally lower than in lawns. Standing biomass, an indicator of production services, was lowest in USV but lawn production may have been overestimated. While USV sites are usually transitory components of the urban landscape, they deserve further consideration due to their provision of ecosystem services, in some cases to a greater extent than conventionally valued urban habitats.     

Drivers of biodiversity patterns in parks of a growing South American megacity

How urban habitats contribute to biodiversity conservation is a key challenge in a rapidly urbanising world. Urban parks can provide important habitats for native species, but previous studies are geographically biased; fast growing megacities, in particular in South America, are clearly understudied. To assess habitat functions and underlying drivers in parks of Santiago de Chile, we analysed the assemblages of wild growing plant species in two ubiquitous park habitat types (grasslands, wooded areas) in 15 parks (150 plots) along an urban-rural gradient. We first used linear contrasts to compare species richness, beta diversity and the proportion of introduced species. We then tested for the explanatory value of environmental variables operating at different spatial scales (plot, park, urban matrix). Unlike in most previous studies, biodiversity patterns were not related to the position of the parks on the urban-rural gradient. Introduced species, mostly from Europe, generally dominated both habitat types (>90 %). Socio-economic (population growth or density), but not spatial, variables were retained in most models. Maintenance intensity was most influential in predicting species assemblages, complemented by park age in wooded areas. A high proportion of European grassland species indicates a trend of homogenisation in park grassland at a cross-continental scale. We conclude that habitat functions of urban parks for native species that have been mainly demonstrated for Europe cannot be generalised to South American megacities. This highlights the need for innovative and locally appropriate conservation approaches (e.g., re-introduction of native species) to foster biodiversity functions in urban parks of South American megacities.     

Diversity,abundance, and species composition of ants in urban green spaces

Urbanization threatens biodiversity, yet the number and scope of studies on urban arthropod biodiversity are relatively limited. We sampled ant communities in three urban habitats (forest remnants, community gardens, vacant lots) in Detroit and Toledo, USA, to compare species richness, abundance, and species composition. We measured 24 site characteristics to examine relationships between richness and composition and habitat patch size, vegetation, and urban features. Ant richness was higher in forests (26) than in gardens (14) and intermediate in vacant lots (20). Ant richness in gardens and vacant lots negatively correlated with abundance of an exotic ant species (Tetramorium caespitum); thus this ant may affect native ant richness in urban habitats. Ant composition differed with habitat type, and abundance was lowest in forests. Site characteristics varied with habitat type: forests were larger, had more woody plants, higher woody plant richness, more branches, and leaf litter whereas lots and gardens had more concrete and buildings. Vacant lots had taller herbaceous vegetation, and gardens had higher forb richness, density, and more bare ground. Differences in vegetation did not correlate with ant richness, but several vegetation factors (e.g. patch size, number and size of trees, leaf litter, and amount of concrete and buildings) correlated with differences in ant species composition. Additional factors relating to soil, nests, or microclimatic factors may also be important for urban ant communities. Implications for biodiversity conservation in urban ecosystems are discussed.     

Connectivity in urbanizing landscapes: The importance of habitat configuration,urban area size,and dispersal

Human activities affect both the amount and configuration of habitat. These changes have important ecological implications that can be measured as changes in landscape connectivity. I investigated how urbanization interacts with the initial amount and aggregation of habitat to change dispersal potential, restoration potential, and the risk of spatially extensive disturbances. I used a factorial set of simulated landscapes and subjected each landscape to habitat loss by overlaying 66 different US urban areas. I used a common connectivity metric, CONNECT, to assess the magnitude and direction of changes for a range of dispersal distances. My results show that the relationship between habitat loss and connectivity loss is non-linear and subject to interactions between the spatial patterns of habitat distribution, urban morphology, and dispersal capabilities. The implications of a given urban form vary widely as a function of habitat distribution and dispersal capabilities. This implies that impact assessments, restoration activities, and conservation planning should consider historical habitat distribution when evaluating observed changes in connectivity. While my results clearly show that more aggregated or continuous habitats are more vulnerable to connectivity loss, this approach can also be used to identify landscapes where restoring connectivity will be particularly effective, for example through placement of stepping stone habitats.     

Can a habitat specialist survive urbanization? the case of the viscacha (Lagidium viscacia,Chinchillidae)

Urban growth is a strong driver of habitat degradation and loss. In spite of that, a surprising diversity of native species may survive in urban areas. In the La Paz, Bolivia metropolitan area and surroundings, local populations of “viscachas” (Lagidium viscacia) currently survive in small, isolated habitat patches. We assessed 13 study sites in 1999, 2003, and 2007 to document the effects of urban growth on L. viscacia habitats. Degree of disturbance at the study sites increased more between 1999 and 2003 than it did between 2003 and 2007 due to patterns of urban expansion. Using satellite imagery we determined that the urban area increased 566 ha (from 1987 to 2001) mostly due to southward urban area expansion down the valley where the best viscacha habitats were located. Occupied patch area decreased 74 % between 1999 and 2007, accompanied by significant increases in patch edge-to-area ratios. Currently L. viscacia populations in La Paz are experiencing a habitat attrition process. If a current urban expansion plan for La Paz is approved, about 75 % of the remaining habitat may be lost to urban development in a short time, compromising the future viability of this species in the metropolitan area and surroundings. Environmental regulations to control urban growth of the La Paz metropolitan area are urgently required and constitute the only hope for the survival of L. viscacia in the city.     

Urbanization and the abundance and diversity of Prairie bats

The effects of urbanization on biodiversity are generally considered to be negative, but the potential for landscape context to modulate these effects has not been adequately examined because most urban ecology research has been conducted in one biome: the temperate forest. This bias also applies to studies of the urban ecology of bats, whose diversity is correlated with habitat heterogeneity. We investigated the hypothesis that in the fairly flat, homogeneous Prairies, urbanization, by creating structurally complex islands, benefits bats by increasing access to the vertical landscape elements (buildings and trees) in which they roost. From 2006 to 2008, we surveyed bat assemblages in and around Calgary, Alberta, using mist nets to capture them and bat detectors to record their echolocation activity. Our data supported the prediction that urbanization increases the abundance of Prairie bats, but not the prediction that it increases their diversity. Instead, the urban bat assemblage was less diverse, and exhibited decreased species evenness compared to non-urban assemblages. Although Myotis lucifugus dominated bat assemblages throughout our study area, this was most evident in the city, and this species drove the increased urban abundance of bats. Ultimately, we reject our hypothesis and conclude that urbanization in the Prairies may create attractive habitat for one synanthropic bat, but is detrimental to others.     

Urban river wall habitat and vegetation: observations from the River Thames through central London

Along heavily engineered urban rivers, river walls and embankments represent the most common habitat available to riparian vegetation. This paper presents the first study into river wall vegetation and the influence of wall surface materials on plant diversity. We were concerned with investigating the plant diversity of such wall habitats, assessing relationships between different wall surface materials and plant diversity, and determining whether river wall and embankment habitats along the River Thames through central London could support native riparian species alongside more typical urban wall flora. Fifteen sites along the River Thames through central London were surveyed to describe wall flora and establish relationships between plant diversity and wall materials. Walls were not species rich, but contained a mix of terrestrial and riparian species. Stone walls with surface fractures and heterogeneous wall surfaces were conducive to plant diversity at the local scale, while wall surface heterogeneity was also important at the landscape scale. Some stratification of vegetation was observed based on wall position relative to flow disturbance. The potential exists for walls to act as sites for habitat improvement and reconciliation ecology within urban rivers.     

Legacy effect of trees in the heritage landscape of a peri-urban golf course

Negative environmental impacts of golf courses have received more attention than positive ecological contributions. We studied the mature tree communities and their legacy effect in a historical urban-fringe golf-course site in Hong Kong covering 170-ha with well-managed natural-cum-cultural landscape. Some 44.3 % of the site is covered mainly by large trees forming a mature peri-urban forest. The 94 species in 35 families offer a high species diversity exceeding local secondary and climax fengshui woodlands with notable rare and protected species. Tree species composition, richness and legacy effects brought by anthropogenic and natural factors were investigated by three habitats with varying naturalness and three golf courses with different age. Landscape zone is remarkably heterogeneous versus other microhabitats (fairway and woodland) and the heterogeneity of tree communities amongst the three courses is relatively weak. Synergistic operation of natural regeneration (natural legacy effect) and anthropogenic management (anthropogenic legacy effect) has fostered diversity accumulation. On the one hand, temporal changes in landscape fashion through a century and variations in site management have driven and maintained species diversity. On the other hand, the founder effect of inherited and cultivated species, as well as successful invasion and establishment of native species, have imposed floristic imprint and inertia on woodland habitat. The findings suggested that urban golf courses can serve as potential hotspots for biodiversity conservation within urban ecosystems.     

Patterns of pollinator turnover and increasing diversity associated with urban habitats

The role of urban expansion on bee diversity is poorly understood, but it may play an important role in restructuring pollinator diversity observed in rural regions at the urban perimeter. We studied bee communities in two habitats essential for pollinators (residential gardens and semi-natural areas) at 42 sites situated at the edge of greater Montreal, Canada. Bee species richness, abundance and functional diversity all increased with urbanization in both habitat types, but gardens and semi-natural areas supported distinct bee communities with unique responses to urbanization in terms of species turnover. Compared to semi-natural sites, residential gardens supported bees that foraged from a greater number but a lower proportion of available plant species. Bees did not discriminate between exotic and indigenous plant species in either gardens or semi-natural sites and were attracted to flowers in either habitat irrespective of their origins. Protecting semi-natural ruderal areas and providing residential garden habitats for pollinators are both effective means of promoting regional bee diversity in urbanizing regions.