Birds biodiversity in urban and periurban forests: environmental determinants at local and landscape scales

A significant decline in biodiversity is associated with the current and upcoming degree of urbanization. A challenging strategy to address this conflict is to make urban growth compatible with biodiversity protection and in this context urban parks can play a crucial role. Urban systems are highly dynamic and complex human-shaped ecosystems, where the relationship between species and environment may be altered and make the preservation of biodiversity within them a challenging goal. In this study, we analysed how different environmental features affect bird biodiversity in one of the most urbanized areas of Italy (the metropolitan area of Milan) at different spatial scales. Bird surveys were conducted in fifteen urban and peri-urban parks and environmental variables at landscape and local scale recorded. Results showed that a mixture of land covers and the presence of water bodies inside urban parks favoured species occurrence and abundance at landscape scale, but a surrounding dense urban matrix deflated biodiversity. At local scale, woodland cover and presence of water bodies were key determinants in ensuring overall high biodiversity but local-specific vegetation management produced an unusual pattern for forests species. In particular, the maintenance of large trees may not result in biodiversity support for forest bird species if large trees are not located in woodland areas with a significant tree density. To understand biodiversity patterns and provide useful information for urban planning and design, we need to provide insights into species/environment relationships at multiple scales in the urban environment.     

Ecological lands for conservation of vascular plant diversity in the urban environment

Conservation of biodiversity in urban areas has become crucial to urban green area management. There are several legislative solutions for preservation of species and habitats in cities. One of them is ‘ecological lands’ – a low-restrictive form of protected areas in Poland. We aimed to assess their efficiency in vascular flora biodiversity conservation in the urban environment in Poznań (W Poland; 550,000 inhabitants). We hypothesized that ecological lands which cover <2% of the city area comprise over 50% of taxonomic diversity and over 90% of functional trait-level range of the vascular flora. Analysis of five ecological lands, which covered 1.8% of the whole city area confirmed our hypothesis. In ecological lands studied, we found 564 species of vascular plants, which is 52.9% of the whole city flora. These species belonged to 23 of 29 phytosociological classes represented in the whole city (73.9%). Functional trait distributions in ecological lands studied comprised from 95.8 to 100% of trait distributions in the flora of the whole city. Ecological lands seem to be a good way for conservation of biodiversity in urban areas. The legislative simplicity and low restrictiveness for both land management and recreational utility make ecological lands a much easier form of nature conservation which may be adapted to other cities for more efficient biodiversity management.     

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.     

The role of dispersal and local environment in urban land snail assemblages: an example of three cities in Central Italy

Ecologists increasingly appreciate the central role that urban biodiversity plays in ecosystems, however much urban biodiversity is neglected, especially some very diverse groups of invertebrates. For the first time in southern Europe, land snail communities are analysed in four urban habitats along a geographical gradient of three cities, using quantitative methods and assessing the relative roles of local environmental conditions (“distance from sea”, “distance from city centre”, “vegetation cover”) and spatial effects by principal coordinate analysis of neighbour matrices, redundancy analysis and variation partitioning. A total of 53 species was recorded, a richness similar to that of natural areas. At habitat level, species richness did not show a clear increasing trend from more to less urbanized habitats, but rather a homogeneous pattern. At city level, study areas hosted rather heterogeneous species assemblages and biotic homogenization did not seem to have any impact; indeed, only three species could be considered alien. Variation partitioning showed that land snail communities were mostly structured by environmental factors, even when spatial structures independent of measured environmental variables were included: “vegetation cover” and “distance from city centre” were the environmental variables that explained most of the variation in species composition. The lack of strong spatial structure also unexpectedly suggested that transport by humans aids dispersal of organisms with low mobility, which are usually limited by spatial constraints in natural environments. These results provide ecological and conservation implications for other invertebrate groups, suggesting to set priorities in management strategies that include habitat conservation at local scale.     

Alien plant species do have a clear preference for different land uses within urban environments

Since neophytes can become invasive in the future, untangling their ecological preferences is of paramount importance, especially in urban areas where they represent a substantial proportion of the local flora. Studies exploring alien species assemblages in urban environments are however scarce. This study aims to unravel alien plant species preferences for five urban land uses (densely built-up areas, open built-up areas, industrial areas, broadleaved urban forests, and agricultural areas and small landscape elements). We took the city of Brussels as a model, in which we recorded all vascular species growing spontaneously in grid cells of 1 km². We tested two different ways of classifying the 1-km² cells: (1) We simply associated each cell with its dominant land cover; (2) We used a fuzzy approach for which the degree of association of a given cell to a given land cover depended on the proportion of that land cover within the cell. For both classification methods, we calculated the indicator species of the resulting land cover types based on alien species only. The crisp and fuzzy classifications identified 33 and 49 species, respectively, with a clear preference for some urban land use types (from a total of 129 alien plant species analyzed). Results showed that urban land use types having apparently similar environmental conditions can actually harbor different neophyte assemblages. Fine-tuning the categorization of urban environments in future ecological studies is therefore important for understanding spatial patterns of alien species occurrence.     

Spontaneous plant colonization and bird visits of tropical extensive green roof

Green roofs can contribute to enrichment and conservation of urban ecology. An experimental green roof was established in humid-tropical Hong Kong to monitor over two years its spontaneous colonization by plants and bird visits. Some 94 voluntary vascular plant species from 26 families and 76 genera were established, with propagules brought mainly by birds and wind and secondarily inherited from soil seed bank. Plant species composition changed dynamically during the study period. They fall into three groups, namely dominant ruderal (herbaceous and sub-shrub) as surrogate of early-stage local grassland ecosystem succession, arboreal (trees and shrubs), and hygrophilous herb. Progressive increase in vegetation cover was accompanied by changes in species diversity and evenness. In addition, 16 bird species from 8 families and 14 genera were recorded. Ten species were residents and the six migrant species were winter visitors. Their food preference was mainly omnivore and insectivore. Winter and the second year encountered higher species richness, diversity, and evenness. Most vegetation parameters correlated positively with avian community indexes, signifying provision of sustenance by green-roof ecosystem to birds. Vegetation coverage correlated negatively with avian abundance, due to shunning by the abundant ground-foraging Tree Sparrow. Both local common ruderal plant species and common urban bird species can successfully establish and reproduce on the extensive green roof, confirming potentials for urban ecology and biodiversity enhancement and conservation even in densely-developed urban areas. The successful nurturing of naturalistic green roof offers new opportunities for green roof design that deviates from the predominant cultivated-horticultural approach.     

Avian diversity in a suburban park system: current conditions and strategies for dealing with anticipated change

A growing trend towards increased urbanization emphasizes the role of suburban parks in wildlife conservation. Spatial planning aimed at maintaining biological diversity and functionality must consider how changes at landscape and more local scales will influence the biotic structure of urban areas. From May 2006 to July 2010, bird surveys were conducted in three metropolitan parks in Cleveland, Ohio, USA. Surveys were conducted with the goal of examining the effect of vegetation structure and adjacent land cover on the distribution and species richness of breeding birds within this park system. A total of 65 species were recorded throughout the study area. Avian species richness was linked to several habitat metrics, measured at both the local and landscape scale. Generally, species richness was highest at locations characterized by moderate forest cover. The proportion of canopy cover at survey sites related negatively to species richness and the density of understory vegetation showed a positive relationship with species diversity. Despite the influence of these three metrics, sensitivity analysis indicates that the density of understory vegetation is the most significant correlate to avian diversity within this suburban park system. Management actions aimed at providing habitat for the greatest diversity of breeding songbirds within the study area should allow for moderate canopy cover while retaining or improving the structural complexity of understory vegetatation.     

Effects of long-term landscape dynamics and city growth on biodiversity in the Mediterranean: the case study of Montpellier,France

In the Mediterranean, long-term land-use changes have resulted into landscape mosaics composed of very few ancient woodland remnants scattered across extended post-agricultural woodlands. Patches of ancient woodlands are now suffering rapid urban growth that reduces their area and impact their associated biodiversity. Here we use the case study of Montpellier, one of the most dynamic cities in France, to 1) characterize temporal changes in land covers (between 1860 and 2006) in its area, and 2) using two guilds of fungal bioindicators (i.e., polypores and lichens), to compare biodiversity stakes between ancient and secondary Mediterranean woodlands. We used a combination of historical maps, archives, fungal collections and field survey in eight Quercus ilex patches (4 ancient versus 4 recent replicates) to reconstruct landscapes dynamics and assess biodiversity changes. From the 19th to the 21st century, over half (52.4%) of the ancient woodlands within Montpellier were replaced by other land covers, mainly by urban equipment, while secondary patches (16.8% of the total area) were naturally established. Remaining ancient woodlands show multi-layered vegetation made of multi-secular Pinus halepensis dominating a dynamic understorey made of Quercus ilex and various Mediterranean shrubs. Polypores, but not macrolichens, tended to differ in community composition between ancient and recent woodland patches, with the highest diversity found in ancient woodlands. This study highlights that urban woodland patches of contrasted histories harbour distinct biodiversity stakes to be included in urban planning and provide valuable areas to evaluate biodiversity patterns and dynamics.     

Urban biodiversity: comparison of insect assemblages on native and non-native trees

Trees are thought to be important for supporting urban biodiversity. However tree species differ considerably in the numbers of invertebrates they support, with potential consequences for higher trophic groups such as birds. In this study the influence of native and non-native trees on the abundance of insects (Hemiptera) and the incidence of insectivorous birds (Paridae) were investigated in the southern English town of Bracknell. The number and species of tree were recorded from each of 17 roundabout and parkland sites. Tree beating was used to sample arboreal Hemiptera and Paridae were recorded either with point counts and transect walks, depending on the size of the site. Due to the great variation between tree species, there was no overall significant difference in species richness or abundance of Hemiptera between native and non-native tree species. However, individual native trees had more species and individuals than non-natives. The proportion of native trees at Bracknell sites was positively related to the abundance of both Hemiptera and the number of Paridae observed. The consequences of vegetation type for insect abundance indicates that in order to sustain and enhance urban biodiversity, careful consideration needs to be given to species of trees present in urban areas.     

Assessing the structural heterogeneity of urban areas: an example from the Black Country (UK)

The increasing acknowledgement of the importance of urban habitats in the maintenance of biodiversity has brought with it a need to quantify this importance at a scale appropriate to the characteristic patch sizes encountered in urban areas. Taking a study area in the Black Country (UK) we used a spatially complete, rapid assessment method to evaluate habitat patches in terms of their internal structural heterogeneity. This method recognises the importance of both natural and anthropogenic processes in providing a diverse range of habitats and niches for both flora and fauna. It also recognises the key role of context in determining the ecological significance of each patch within the urban landscape.All habitats studied had a complex mix of both natural and artificial structural elements, where an element is a within-patch contributor to structural diversity, with each habitat type having a large range of element totals. Characteristic totals, reflecting the level of habitat structural diversity, were observed in some habitat types with residential areas having high values and industrial and commercial areas having low values. Certain structural elements were also associated with each habitat type allowing characteristic element assemblages to be derived. If structural diversity is linked with biodiversity, as seems to be the case in many (though not all) habitat types, then this unique method of viewing the urban landscape becomes a powerful tool for informing wildlife ecologists, nature conservationists, urban planners, environmental managers and landscape architects.     

The potential for golf courses to support restoration of biodiversity for BioBanking offsets

In golf course development there is frequently remnant vegetation on the areas unused for infrastructure. We propose that these areas, together with a whole range of other reserves including sporting fields, cemeteries, railway reserves and educational facilities may be the source of degraded remnant vegetation and associated open space that could be used to provide offsets for biodiversity. We followed the changes in vertebrate biodiversity with low key alteration to management of the Camden Lakeside Golf Course to assess if such areas had the potential for biodiversity banking offsets. Birds, bats, frogs and reptiles increased in species diversity over time. Frogs and reptiles tended to peak in species numbers during the observational period but bat and bird diversity continued to increase. We concluded that on this ‘island’ within a matrix of urbanisation and cleared agricultural lands without remnant vegetation, observed changes in diversity made such areas potential sites for biodiversity banking offsets.     

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.     

Evaluating the distribution of invasive woody vegetation around riparian corridors in relation to land use

Invasive species have been causing important and irreversible impacts to native species and communities of ecosystems. They distort ecosystem functions by degrading forest lands, wetlands, and agricultural habitats and replace the native vegetation and reduce biodiversity, forest productivity, and suitable wildlife habitat. To address disturbances caused by invasive species occurrence, further information is needed regarding the occurrence, extent, and dispersal of invasive species and how land use may increase the spread of these species. The objective of this study was to find the frequency and dominance of three invasive species common to riparian areas of east Alabama: Ligustrum sinense (Chinese privet), Elaeagnus pungens (silverthorn), and Triadica sebifera (Chinese tallow tree). Surveys of these species in riparian forests in and around Auburn, Alabama were conducted to show the relative extent of these shrubs and their relation to urban land use. It was expected to see the highest levels of invasive species in the city center with decreasing levels radiating outward into rural areas. Another objective was how urban land use may affect the presence-absence and prevalence of these non-native plant species within study sites. The results showed that around the city center and suburban lands, cover of both Chinese privet and silverthorn tended to increase. In contrast, Chinese tallow tree density percent cover showed an opposite trend with landscapes close to city center often having slightly less cover. This study shows that urban land use may be an important association with distribution of invasive plant species.     

Riparian woody plant diversity and forest structure along an urban-rural gradient

Changes in riparian woody plant assemblages are anticipated in the southeastern United States due to increases in urbanization rates. Because riparian forests serve important roles in maintaining water quality and biodiversity, understanding how they respond to urbanization is crucial. The objective of this study was to examine forest structure and woody vegetation diversity indices of riparian communities in response to an urbanization gradient in West Georgia, USA. Measures of forest structure and diversity were compared to measures of urbanization and land cover. Although Liquidambar styracifluaand Quercus nigrawere dominant species in the forest stand and regeneration layer for all riparian communities, the invasive, non-native shrub Ligustrum sinense was the most dominant species observed in the regeneration layer for urban, developing, and agriculture communities. The proportion of non-native species in the forest stand and regeneration layer decreased and Shannon diversity of the regeneration layer increased with increasing distance from the urban center. Shifts in diversity indicate that anthropogenic disturbance may subdue the ability of diverse communities to resist non-native plant invasions.     

A systematic review of the relationship between urban agriculture and biodiversity

Urban agriculture is a unique form of agriculture that can provide fresh, local produce for urban residents, and may benefit biodiversity by decreasing the need to expand agriculture into natural areas as well as enhancing biodiversity in urban areas. However, although urban agriculture is also often cited as promoting biodiversity in urban areas, the extent of empirical evidence for such claims has not been studied. Here we systematically review the relationship between urban agriculture and biodiversity in the scientific literature. We strictly define urban agriculture as areas in cities that grow produce specifically for human consumption. We examined 148 papers from 2000 to 2017, of which only 24 studies fit our definition of urban agriculture, and of those, only 18 both involved urban agriculture and measured biodiversity. Of the studies that did measure biodiversity, some showed increases in diversity compared to urban vacant lots, but other showed no difference. Moreover, these studies were mostly focused on plants and invertebrates and were conducted almost exclusively in North America. In order to use the generalization that urban agriculture will have a positive influence on urban biodiversity, more studies will need to be conducted across a wider geographic range worldwide (particularly in developing countries in the tropics) and on a greater diversity of species and taxa (e.g., herpetiles, birds and small mammals). Such studies will likely increase in conservation importance as urban expansion and agricultural demands increase globally.     

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.     

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.     

Components of landscape pattern and urban biodiversity in an era of climate change: a global survey of expert knowledge

There is sufficient evidence to show that both humans and fauna are profoundly affected by landscape pattern composition and configuration in relation to adaptation to climate change impacts in urban landscapes. Despite this, global-scale research that ranks which components of landscape pattern play the most pivotal roles in this process is absent. Also lacking is in-depth examination of the potential areas of conflict between biodiversity conservation targets and those that pertain to human dimensions of climate change adaptation goals in relation to landscape patterns. The research aim was to determine how to identify, rank, and weight the most important components of landscape pattern affecting urban biodiversity in the changing climate and how to address areas of conflict between biodiversity conservation and human dimensions of climate change adaptation goals in terms of the spatial patterning of land cover classes distributed across urban landscapes. To do this, a global survey of 87 participants from 69 academic centres involved in at least 325 research projects between 2000 and 2017 was conducted. Of the eight components of landscape pattern identified and ranked by participants worldwide, the three most important components are respectively patch size, connectivity and proximity, and land cover heterogeneity. This research reveals that opinions of participants with experience in conducting research in the Southern Hemisphere in general and Oceania in particular influence this ranking. While a range of recommendations from specialists have been gathered and weighted, there is still much more research required to address areas of conflict between what fauna and humans need in the face of climate change.     

Butterfly diversity,habitat and vegetation usage in Hong Kong urban parks

The conservation value of urban parks for butterfly communities remains poorly understood, particularly for tropical butterflies in Asia. We conducted point count and route transect butterfly surveys, and used them to sample four habitats located within 13 urban parks across Hong Kong. We found 1054 individuals and 58 species of butterflies recorded in 60 survey hours over 6 months. This represents approximately one quarter of the entire known Hong Kong butterfly species list. Over 30 % of the individuals counted were Catospilia sp. but six of the species identified are classified locally as rare or very rare. Tree-covered habitats and grasslands showed higher butterfly diversity than open areas. The most common butterfly behavior was “directed flight,” which we also found to be habitat-dependent and most common in ponds and open areas. We additionally observed the use of vegetation in urban parks, which included 40 species of nectar plant and four records of butterfly oviposition. The high butterfly diversity, presence of rare species and usage of vegetation (especially as a nectar resource) we documented in this study suggests that urban parks have some conservation value for Hong Kong. However, the use of pesticides and heavy vegetation clearing may limit significant butterfly reproduction and population growth. Altogether these results emphasize the diversity of uses of urban parks for butterflies in Hong Kong while also providing possible directions for improvement in habitat and vegetation management that could increase urban park value for biodiversity.     

Species richness in urban parks and its drivers: A review of empirical evidence

There is growing recognition of urban areas as hosts for innovative ways to conserve and promote biodiversity. Parks, as one specific type of urban green space, constitute particularly important biodiversity hotspots in the cityscape. We reviewed empirical findings on the species richness in urban parks across all species groups that have been studied. The aim was to assess and discuss the overall species richness of urban parks, its community attributes and drivers. Search and subsequent selection process resulted in 62 papers from 25 different countries. For all examined species groups, the findings consistently show that parks are among the most species rich types of urban green spaces, but also that exotics constitute large shares, especially of plant species. Key ecological theories like the gradient approach and the island habitat ecological theory, and fundamental ecological relationships such as the species-area relationship are valid despite the manipulated ‘nature’ of parks and the surrounding urban matrix. Most studies surveyed large number of parks and applied ‘multi-scale’ approaches in tests of confounding variables, providing methodological strength. While matrix effects are consistently found to affect species richness negatively, the diversity of habitats and microhabitat heterogeneity contained in urban parks appears as the most decisive factor for the overall species richness. However, a constraint of research to date is the limitation of individual studies to one or a few species groups, rarely bridging between flora and fauna. Adopting ‘multi-species group’ approaches in future research is needed to further advance the understanding of the overall biodiversity of urban parks, and its drivers.