Spatio-temporal monitoring of urban street-side vegetation greenery using Baidu Street View images

Street-side vegetation greenery contributes substantial health benefits for pedestrians. Multi-year street view images are expected to enable the monitoring of dynamic street-side vegetation greenery changes and the development of targeted urban landscape plans. However, the potential of multi-year street view images used for the assessment of street-side vegetation greenery has not been evaluated yet. Besides, complicated urban landscapes may make it difficult to accurately quantify vegetation greenery. This study developed a framework to assess the spatio-temporal variation of street-side vegetation greenery using the Baidu Street View images and a new Vegetation Greenery Index (VGI). The proposed analytical framework was applied to Tai’an city, a highly populated city where urbanization has been rapid in China. The level of vegetation greenery estimated using the proposed framework was compared with ground truths randomly collected at sampling sites along the road networks in 2014 and 2019 to assess the applicability. Results demonstrated that the proposed VGI method could accurately quantify street-side vegetation greenery. The comparison of multi-year VGI layers could identify locations where vegetation greenery substantially changed and quantify the overall change in urban greenery. Vegetation greenery estimates were well agreed with the ground truths. Spatio-temporal variations in the urban vegetation greenery were attributed to trees that were newly planted or removed, the natural growth of the existing vegetation, and new building construction. The proposed framework is expected to be a useful tool to evaluate urban vegetation greenery and help urban landscape planning.     

Public perception of spontaneous vegetation on brownfields in urban areas—Results from surveys in Dresden and Leipzig (Germany)

Urban brownfields are found in all parts of the world. They suffer from a negative image, generally being viewed as problem areas. However, urban brownfields also offer potentials for new uses as well as for the ecological regeneration of cities. Especially urban brownfields with spontaneous vegetation can contribute to biodiversity and ecosystem services in dense urban environments. Whether and how this potential is exploited depends on the perception and preferred uses of brownfields by local residents.Through surveys undertaken in Dresden and Leipzig, this paper examines the perception and use of brownfields and their spontaneous vegetation by the urban population. Results show a range of views on brownfields with spontaneous vegetation from negative to positive evaluations. Many residents make use of brownfields, have concrete ideas about how such areas should be utilized or designed and are even prepared to take part in the transformation. The paper suggests that the use and design of green space should be rethought in unconventional ways, and discusses how the ecological and social potential of brownfields with spontaneous vegetation can be best exploited for urban residents.     

The value of vegetation cover for ecosystem services in the suburban context

Latin-American cities can be characterized by dynamic processes of urbanization that encroach upon the natural and semi-natural surrounding landscapes. Our study presents the effects of landscape development, transformed from semi-natural conditions into a mostly disperse suburban settlement. We explore the impact that this transformation has had on this context by three ecosystem services that regulate rainwater runoff, enhance microclimate conditions and help to improve air quality by monitoring vegetation cover. We have designed a spatio-temporal hierarchical analysis which employs remote sensing techniques to capture the structural changes of this landscape over long, medium and short term scales on two spatial levels. This methodological approach was tested in the Metropolitan Area of Santiago (MAS) as case study area. Despite of the increase in impervious surfaces due to urban processes, there has also been an increase in vegetation cover, which has led to an improvement in the provision of the above-mentioned ecosystem services. Hence, if diverse urbanization processes continue and they are coupled with an increase in vegetation cover, the provision of ecosystem services could also expand. This phenomenon can be observed in some areas, where public and private green spaces are created and maintained. Our data analyses give evidence that certain types of suburban areas which increase the share of vegetation cover can provide daily ecological benefits for urban neighborhoods, and beyond, for adjacent areas. Moreover, suburban development can successfully provide ecological benefits to citizens. Such processes can only be ecologically sustainable if the composition of vegetation is well-adapted to the regional climatic conditions.     

Overwintering in a megacity: Urban green areas and migratory birds in Mexico City

Nearctic-Neotropical migratory birds are threatened by land-use change throughout their complex annual cycles. While urbanization is an essential driver of land-use change, it is unclear how it affects migrant birds. Although migratory birds are more diverse in non-urban patches of native vegetation than in urban areas, neotropical cities can host diverse assemblages of overwintering migrant birds. Migratory birds in neotropical cities tend to be closely associated with urban green areas (UGAs). However, how their presence and abundance are affected by the habitat elements of UGAs and the urban matrix of neotropical cities is poorly understood. In this study, we compared the migratory bird species richness and abundances among UGAs and the urban matrix of the southern section of the megacity of Mexico City and native vegetation sites outside the city. Our results show that UGAs in neotropical cities provide habitats capable of maintaining complex overwintering migratory bird assemblages with local trees as critical features. We also assess the role that UGAs' characteristics play in determining migrant bird assemblages. We conducted bird censuses and measured habitat traits to determine how migrant bird assemblages are related to the habitat features of our study sites. We measured local, buffer, and spatial habitat features of each UGA. We found 23 overwintering migrant species in the three habitats, with 22 present within UGAs. Both UGAs and urban matrix sites had higher estimated species richness of migrant birds than non-urban native vegetation sites located outside the city. Only local features of UGAs affected migrant birds. While tree abundance in UGAs was positively associated with migratory bird species richness, the proportion of tree coverage was positively related to bird abundance. Our results show that UGAs in neotropical cities can maintain complex overwintering migratory bird assemblages, with trees being the most critical habitat feature. As a result, UGA management focused on maintaining trees and increasing their numbers can improve habitat conditions for migratory birds overwintering in neotropical cities.     

Vegetation cover within and around schools in Santiago de Chile: Are schools helping to mitigate urban vegetation inequalities?

Vegetation within cities is key for urban sustainability, as it provides several ecosystem services positively influencing the urban quality of life. However, urban vegetation is often unevenly distributed within cities, typically concentrating the large proportion of vegetated areas in more affluent neighborhoods. Thus, developing strategies for reducing urban vegetation inequalities is fundamental to fostering more sustainable cities. Since schools are widely distributed in urban areas, they could be key for decreasing vegetation inequalities, in particular, if schools’ precincts in lower-income areas are managed to contain high levels of vegetation. Nevertheless, studies analyzing the potential role of schools in ameliorating vegetation inequalities in cities are largely missing in the literature. In this study we use remote sensing techniques to estimate the vegetation cover of 1579 schools and their surrounding areas in Santiago-Chile, aiming to evaluate whether vegetation within schools is helping to mitigate the high levels of vegetation inequalities characteristic of this city. We performed the analysis for public, subsidized and private schools, for the whole city and each of the 34 municipalities comprising the city. Our results show that schools are not helping to mitigate vegetation inequalities, but they tend to replicate the unequal distribution of vegetation within Santiago. This pattern holds whether the analysis is made for all schools or each of the three school types independently, and is also a prevalent pattern when the assessment is performed at the municipal level. Private schools, usually located in greener more affluent areas of the city, have significant larger proportion of vegetation, revealing that high-income students do not only live in greener neighborhoods but also have access to greener schools. These results reveal how deeply rooted in some cities are vegetation inequalities, and the urgency of modifying public policies related to how vegetation within schools is funded, planned and managed.     

A walk on the wild side: Perceptions of roadside vegetation beyond trees

Urban nature is of vital importance for human well-being in an increasingly urbanized world. Despite the wide variety of urban greenspaces, previous research has mostly focussed on parks and in particular presence of trees. Although streets are fundamental urban structures and offer an array of green elements beyond trees, the perception and valuation of other kinds of roadside vegetation by urban residents is understudied so far. This study explores the range of roadside vegetation and associated ecosystem services perceived by city dwellers in densely populated inner city districts of two German cities. Further, we explored how wild-grown roadside vegetation is valued by interviewees. Results confirmed the important role of trees but also demonstrated that city dwellers perceive a variety of cultivated and “wild” green components other than trees. Respondents attached a wide range of meanings and values to roadside greenery and showed a surprisingly high awareness of associated ecosystem services. Wild urban roadside vegetation met with high approval, although planted and maintained vegetation was preferred. Our study illustrated that trees and other elements of roadside vegetation fulfil important functions in the view of the public. For many respondents, ecological and economical functions of roadside vegetation were more important than orderliness. This indicates opportunities for enhancing the biodiversity of urban streetscapes. As public green spaces are in short supply in many cities, enhancing cultivated and wild roadside vegetation could help to deliver ecosystem services in the areas near where people move and live.     

Natural revegetation of indigenous roadside vegetation by propagules from topsoil

Road construction degrades large areas of indigenous vegetation. Better understanding of ecosystem restoration after degradation will require development and assessment of improved restoration techniques. The potential of natural revegetation based on propagules from topsoil as a restoration technique, to achieve succession towards indigenous vegetation, is not fully understood and accepted as an alternative method for vegetation establishment. The aim of this study was to evaluate this restoration technique by comparing different topsoils with respect to their potentials for revegetation and to describe the early succession on these topsoils by recording change in vegetation cover and the number of species.The study road RV23 is situated in south-east Norway and runs mainly through mixed, mostly coniferous forest. The topsoil (the upper 30 cm) was removed before road construction started, stockpiled during the construction period and then redistributed on the road verge afterwards. In 1999, 10 macroplots of 25 m² were placed randomly on selected topsoils of different qualities, to represent the soil variation in the study area. The soil quality varied from organic-rich to organic-poor soils. Each macro plot contained four 1-m² mesoplots in which the species composition was recorded in 2000 and 2001.Univariate statistical tests were applied to reveal change in vegetation cover between macroplots within 1 year and between years 2000 and 2001. Furthermore, statistical tests were used to reveal the change in single-species frequencies between the study years.Two years after deposition of topsoils, the vegetation cover was generally satisfactory from an aesthetical point of view. However, the variation in vegetation cover and species composition was considerable on different topsoils, reflecting both the local variation of the indigenous vegetation and the soil quality. A total of 121 species of vascular plants were recorded in all 10 macroplots, although not more than 59 species were found in one macroplot. Species composition and single-species frequencies changed considerably from the first year to the second. Among the 61 species that were recorded in more than five mesoplots, the frequency of 16 species increased and the frequency of 10 species decreased significantly (P<0.05). Most of the decreasing species can be considered as weed species and are not represented in the present indigenous vegetation, while most of the increasing species are. The vegetation change from 2000 to 2001 apparently represents the first steps in a succession towards an ecosystem dominated by species of the indigenous vegetation.     

Do land cover changes shape sensitivity to forest fires in peri-urban areas?

The present study assesses the spatial distribution of selected land cover classes at two years (1975 and 2000) in a Mediterranean urban area (Athens, Greece) to test the hypothesis that land cover changes determine an increase in the sensitivity of landscape to forest fires on a regional scale. While urban and agricultural areas increased, although with different rates of growth, forests and semi-natural areas decreased in the study area. These changes are reflected in a significant increase of vegetation sensitivity to forest fires measured by the forest fire risk (FR) index developed in the framework of MEDALUS project. The cover classes which contributed the most to the increase of the FR index were crop mosaic, mixed agricultural-natural areas and discontinuous, low-density settlements. Results of the present study indicate that the transformation of the fringe landscape towards low-quality agricultural and pasture areas and fragmented forest patches is potentially detrimental for environmental quality and the ecological fragility of land.     

Non-linear effects of landscape on pollination service and plant species richness in a peri-urban territory with urban and agricultural land use

Pollination contributes to both human food security and the reproduction of the majority of wild plant species, but pollinators are facing a rapid decline, a major cause of which is habitat conversion and degradation due to human activities. Urbanization is one of the major types of habitat conversion, but its influence on pollination has been surprisingly mixed, ranging from markedly negative to strongly positive effects. One hypothesis proposed to explain these discrepancies is that pollinator responses to urbanization are highly dependent on the non-urban control habitat, with negative effects when the controls are natural or semi-natural areas but positive when they are intensive agricultural areas. It was also proposed that the pollination response along an agricultural-to-urban gradient is non-linear, with maximum pollination observed at an intermediate level of urbanization due to increased environmental heterogeneity. To test these two hypotheses, we selected a group of 38 sites in a peri-urban area near Paris, France, using a semi-stratified sampling strategy that ensured that all three of the urban, agricultural and semi-natural gradients were maximized. We then estimated pollination using two approaches: we evaluated the pollination success of Lotus corniculatus, a strictly entomogamous self-sterile plant species pollinated mainly by bees, and we measured the species richness of entomogamous and non-entomogamous plants, the difference in their response being expected to relate to the pollination service provided by the overall pollinator community. We found that in our study area, pollination success of L. corniculatus responds positively to the agricultural to urban gradient but not to the semi-natural to urban gradient. The diversity of both entomogamous and non-entomogamous plants is highest at sites surrounded by intermediate proportions of urban and agricultural areas. In addition, high proportions of urban areas have a negative effect on the diversity of non-entomogamous but not entomogamous plant species, suggesting that pollinators are able to partially buffer entomogamous plant species against the negative effect of urban development. Our results show the importance of urban areas in pollination conservation plans and demonstrate that the interaction between different anthropogenic land-use is an important factor for understanding pollination.     

Hydric vegetation communities across rural,peri-urban,and urban zones within the Prairie Pothole Region

Wetland and pond hydric vegetation is impacted across the rural, peri-urban, and urban zones by anthropogenic activities such as agricultural production, industrial manufacturing, and urban development. Previous studies have assessed urban and rural wetland vegetation, but have rarely explored the peri-urban zone of development. Therefore, to investigate the impacts of urbanization on hydric vegetation, thirty pond sites (10 rural, 10 peri-urban, and 10 urban) were randomly selected within each of the three zones. The vegetation community at each site was assessed using a quadrat method to compare the vegetation composition. In addition, floristic quality based on the conservatism value of each plant species was used to assess wetland vegetation. Results show plant communities of rural sites differed from both urban and peri-urban sites due partly to urbanization reducing the cover of obligate wetland species. Peri-urban sites contained the highest species richness, due to the increase in introduced plants associated with urbanization. Urban sites contained the lowest species richness, some of which is due to the use of rock riprap surrounding the edges of most sites. The plant conservatism values of vegetation were not different for rural and peri-urban sites, but were significantly lower in urban sites. Information from this study is useful to wetland professionals, environmental managers, and urban planners to predict hydric vegetation responses within peri-urban areas in the Prairie Pothole Region.     

A semantic model for assessing the experience of urban biodiversity

Biodiversity is a significant element of our everyday experience of urban environments, though it is generally only perceived subconsciously. Thus, there is a need to develop a method for defining and measuring experienced biodiversity. As a first step towards such a method, a semantic test was presented to a group of 102 participants. The test consisted of a form containing words/expressions selected as possible components of biodiversity. The participants rated the words on a five-grade scale, and the form was completed at six different study sites. Statistical analyses indicated that words with biological content were strongly correlated with biodiversity, as were words associated with wilderness and variation. Correlations with words of preference were less strong. Following factor analysis, a biodiversity experience index was calculated based on the factor loadings of words strongly correlated with biological diversity. The index was then calculated for all six sites. It was suggested that the index, by measuring words/expressions with higher linguistic codability, offers a valuable tool for assessing experienced biodiversity. It was further concluded that areas containing spontaneous vegetation and water obtained higher biodiversity index scores than did areas characterized by a short-cut lawn and more uniform vegetation.     

Site selection of urban wildlife sanctuaries for safeguarding indigenous biodiversity against increased predator pressures

Biodiversity loss in urban landscapes is a global challenge. Climate change is a major driving force behind biodiversity loss worldwide. Using Wellington, New Zealand as a research site, the aim of this research is to show how the most suitable patches of vegetation in urban landscapes can be identified, ranked, and prioritised as potential urban wildlife sanctuaries. This is in order to protect vulnerable indigenous fauna from some of the indirect impacts of climate change such as increased predator pressures and the spread of diseases among urban fauna caused by rising temperatures. A GIS-based multi-criteria analysis of spatial composition and configuration of patches of vegetation was undertaken with reference to eight factors affecting the quality of habitat patches and accordingly fauna behaviours in urban landscapes. Results show that Zealandia, the Wellington Botanic Garden, the Town Belt, and Otari-Wilton’s Bush are respectively the most important urban sites for establishing pest-free urban wildlife sanctuaries in the study area. This research reveals that patch size should not be considered as the single most important factor for the site selection of urban wildlife sanctuaries because the collective importance of other factors may outweigh the significance of patch size as a single criterion. Lessons learned in the course of this research can be applied in similar cases in New Zealand or internationally in order to facilitate the process of site selection for the establishment of urban wildlife sanctuaries in highly fragmented urban landscapes suffering from rising temperatures and other climatic changes.     

The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand

Christchurch, the second largest city in New Zealand is a planned city on a coastal plain on the east coast of the South Island. The birth of the city and the subsequent century of development was characterised by colonial values and tree and garden planting with familiar European species along with those from Australia, North America, and eventually all other continents. The image of an “English garden city” with classical parks of oaks and willow-lined rivers became the accepted norm and the way in which the city has been promoted to potential tourists. Gardening is one of the top two recreational activities and exotic species greatly outnumber native species in the flora and in gardens. This has had serious consequences for the highly fragmented and degraded indigenous vegetation and its co-adapted wildlife. A few hardy indigenous species continued to regenerate through this period, but since the 1970s, there has been a progressive change of attitude and interest in reclaiming the natural heritage of the city, manifest in widespread private and public planting of indigenous species and active habitat restoration. In this article we examine the indigenous and exotic shrub and tree components of the Christchurch flora as planted street trees, in domestic gardens, and in parks. We also present data on shrub and tree regeneration in parks and domestic gardens in the city. Indications are that the more sensitive, less intrusive management of urban environments, combined with the greater density of indigenous seed sources, has allowed regeneration of a wide range of indigenous species across a broad spectrum of habitats – from neglected gardens to pavement cracks to exotic plantations. This is despite the competition from the prodigious seed banks and density of exotic trees, shrubs, and ground covers and albeit minimal impacts of introduced browsing and seed eating mammals. If the present trends continue through appropriate management and facilitation, these tentative signs of native forest regeneration should eventually proliferate into a sustainable mixed origin urban forest that resurrects and preserves the natural character of the region.     

The effect of spontaneous wild vegetation on landscape preferences in urban green spaces

The use of spontaneous wild vegetation (SWV) in the plans for urban greening in many cities is beginning to be discussed. However, little is known about how it is perceived and valued by citizens. The aim of this study was to determine the effect of SWV on landscape preferences. An online questionnaire was designed and given to a sample of 708 people in Latin America. The results show that they prefer more formal green spaces to those dominated by SWV. Once informed of the benefits that SWV brings to the city, preferences change, with wild vegetation spaces being more appreciated than formal ones. However, this pattern of preferences changes after 30 days. Preferences return to their initial point, with formal green spaces being appreciated again over wild spaces. The analyses show the importance of environmental education in urban greening strategies to communicate clearly, repeatedly and participatively the benefits of using SWV in public green spaces.     

Semi-natural vegetation and its relationship to designated urban green space at the landscape scale in Leeds, UK

The species composition of semi-natural vegetation in urban areas is influenced by a diversity of factors operating at a variety of spatial scales. This study investigates relationships at the landscape scale between species numbers of semi-natural plant communities and variations in the nature of designated urban green space. Species’ records were obtained from a survey of tetrads (2 km × 2 km) across a contiguous central area of built-up landscape and nearby satellite settlements in the metropolitan borough of Leeds, northern England. Plant species were categorised into natives, archaeophytes, neophytes, casuals and conservation-designated species. The type and extent of designated urban green space within a tetrad was determined using GIS. There was more built-up and designated green space area in the central urban area than in the satellite settlements. However, this difference was not reflected statistically significantly in plant category species’ numbers. Numbers of native species correlated positively with areas of green space designated for relatively high nature conservation value. Neophytes and casuals correlated positively with semi-natural green space lacking rare native species or high native species richness but designated principally for local community accessibility. The value of such spaces and the importance of their appropriate management, not only for community benefits like individual physical health and mental well-being, but also for overall urban plant biodiversity, is highlighted.     

北京怀沙河、怀九河水生植物区系初步研究

对北京怀沙河、怀九河水生植被的种类组成、分布区类型以及植被类型进行了调查.结果表明:该区共有水生植物16科18属24种;分布区类型以世界广泛分布成分最多,其次为北温带分布;水生植被分为沉水、浮水和挺水3个植被亚型和香蒲群落、慈菇群落、满江红群落、水毛茛群落、豆瓣菜群落等13个群系.     

Effects of vegetation structure and environmental characteristics on pollinator diversity in urban green spaces

With accelerating urbanization, insect pollinators in urban ecosystems face challenges such as reduced pollen sources, habitat fragmentation, and damage to the nesting environment. Urban green spaces (UGS) are essential for the stability of pollinator communities. However, little is known about the relationship between vertical layer heterogeneity and horizontal layer complexity of vegetation structure in UGS and pollinator communities. The present study aimed to assess how vegetation structure and environmental characteristics shape the insect pollinator community in UGS. To this end, this study was conducted with seven typical vegetation types which were selected according to the biotope mapping classification system (BMCS) in the ring parks around Hefei City, in Anhui province, China. A total of 11,401 pollinators belonging to 6 orders and 34 families were identified during the eight-month survey. Among the seven habitats under the BMCS, mainly successional short-cut shrub and partly open green space, trees two- or multi-layered broad-leaved mixed forest and partly closed green space, and mainly successional tall grass and partly open green space were identified as high-quality insect pollinator habitats. According to the results of the generalized linear regression, the explanatory power of the four best-fitting generalised linear models is relatively high (over 77%). In four optimal models, the effect of vegetation structure on pollinator community was greater than that of environmental characteristics. The redundancy discriminant analysis showed that the flowering abundance of nectar plants, herb richness, and shrub coverage rate were the three most important factors influencing insect pollinator communities, with a cumulative explanatory power of up to 78.8%. Pollinator abundance was positively influenced by spontaneous herbs and low-intensity management. However, high-intensity management, low diversity of plants, low nectar plant richness, ignoring seasonal nectar plant configuration, and dense tree distribution could limit pollinator reproduction and population growth. These results reflect the status of insect pollinator community in UGS in Hefei city and present a possible direction for improving urban green habitats and plant configurations.     

The green quality of urban spatial development: A multi-dimensional and multi-regional model using big data

Spatial development involves multi-dimensional and multi-regional objectives that might be competing, while few studies have examined these issues simultaneously. We proposed a comprehensive model to assess the green quality of urban spatial development (GQUSD), focusing on the synergy of multi-dimensional objectives and the balance of multi-regional interests. The metropolitan city of Hangzhou was taken as an example. We included land consumption, vegetation loss and infrastructure cost as the inputs and the density of production and living activities as the outputs of spatial development. We developed a categorical Data Envelope Analysis (DEA) using geospatial big data and stratified optimization to evaluate the synergy of inputs-outputs at the finer level of spatial grids.Resultsshow a “sandwich” structure of the GQUSD in Hangzhou when considering green space and vegetation loss, and characterize four spatial typologies of agglomerated development, limited development, blinded development and low-potential development through the Bivariate Local Indicator of Spatial Association (LISA) analysis. The “sandwich” structure is shaped by spatial processes of socio-economic agglomeration, industrial-driven sprawl, new-town development and suburbanization of high-end sectors. We also find green inequality in the spatial development of Hangzhou where vegetation costs were higher in manufactural industrial sites and low-income communities. We provide urban planning strategies to balance competing interests across regions, objectives, functions and communities for green growth and sustainable goals.     

How managers and city dwellers relate to spontaneous vegetation in cities: Towards an integrative approach

The promotion of spontaneous vegetation is recognized as a promising way to develop urban biodiversity at multiple scales. However, enhancing spontaneous vegetation in highly anthropized spaces such as cities can lead to resistance from the various urban actors who plan, manage, and use the city. An integrated approach analyzing the links between ecological, psychosocial, governance, and management issues is thus required. Here we used complementary methods (focus groups, interviews) to analyze the relationships of municipal field operatives and city dwellers to spontaneous vegetation in the streets of a French medium-sized city. We show that municipal elected officials and service director move towards a biodiversity-friendly strategy, but that the management system at all hierarchical levels must be engaged with to achieve a shared and collaborative transition to sustainability. While field operatives are rather favorable to spontaneous vegetation, their practices and their ability to change are highly dependent on psychosocial, organizational, and technical parameters that have to be aligned with ecological objectives. Concerning city dwellers, the majority holds a positive view of spontaneous vegetation, yet a considerable proportion of them seem indifferent to this vegetation. The provisioning of ecological information in situ (i.e., stickers with plant information on pavements) moderately improves their perceptions of spontaneous street vegetation. This educational approach should be accompanied by other approaches to amplify the effect for changing attitudes. These differing results are of timely interest to help devise and build an integrated socio-ecological system, and to find social and organizational levers to improve people–nature relationships in the city.