Multiple ecosystem services of informal green spaces: A literature review

Informal green spaces (IGS) such as overgrown vacant lots and urban brownfields constitute a considerable amount of green resources in the city. Given that the increasingly competitive land use of the urban area, enhancing the potential ecosystem services (ES) of IGS through design and management practices is of critical importance. This literature review paper provides an overview of ES delivered by urban IGS: What types of IGS have been discussed? Which ES have been identified in IGS, what interrelationships among different types of ES have been identified, and how can the potential of IGS be enhanced by urban design practices? 112 scientific papers were analyzed for their 1) IGS terms applied, 2) ES studied, 3) current or potential ES discussed, 4) ES trade-offs, and 5) ES assessment methods. Through the review, we found that although different types of ES have been identified in IGS, most studies did not consider ES synergies and trade-offs. The few studies assessing trade-offs of ES in IGS mostly focused on large-scale IGS such as urban brownfields rather than on small-scale IGS such as vacant lands/lots. The literature review highlights two knowledge gaps for future research: the first one is to explore the design and management knowledge that integrate multiple ES in small-scale IGS based on the assessment of potential ES trade-offs and synergies; the second one is to develop the spatial assessment of ES trade-offs and synergies, which is the key to envision design and management interventions that optimize the benefits of IGS. The literature review promotes the acknowledgement of the term IGS through highlighting their value in ES provisioning and further outlines future research directions on small-scale IGS such as vacant lands/lots and patches of spontaneous vegetation.     

Using best-worst scaling to reveal preferences for retrofitting raingardens in suburban streets

Raingardens are increasingly common in sustainable stormwater management in cities around the world. Implementing raingardens will change the appearance of conventional urban streetscapes and this is especially important when retrofitting raingardens into existing streets. Raingardens need to fulfil both technical and aesthetic functions. Aesthetic function, assessed as landscape preference, must be understood to ensure that retrofitted raingardens are appropriately designed and managed. Scholars have long adopted a Likert rating scale- to determine landscape preference. Limitations of this method led market researchers to develop choice-based ranking, including best-worst scaling, to assess preference. Thus, this study uses best-worst scaling to assess landscape preference by residents for pairs of streetscapes with and without raingardens in four suburbs of Melbourne, Victoria, Australia. These preference data, and attitudes towards raingardens, stormwater harvesting and own streetscapes, inform guidelines for design and management of retrofitted raingardens. Findings revealed respondents’ overwhelming support for harvesting and reuse of stormwater, though support for fit-for-purpose stormwater reuse decreased as personal proximity increased. While attitudes towards raingardens were positive and most respondents liked the raingardens in their own street, less than one-quarter helped to maintain them. Across all respondents, maintenance of raingardens in streetscapes was regarded as the responsibility of local government. Nevertheless, many would install raingardens in their own property. Overall, streetscapes with raingardens were preferred to those without. Residency in a street with or without raingardens did not influence preference, however, residency in a particular street did. Indeed, context was important: preference for one’s own streetscape varied statistically significantly between residents of inner- and outer-Melbourne suburbs. Drawing on these results, four guidelines for design and management of retrofitted raingardens are proposed: 1. Understand context; 2. Consider how the street is used; 3. Select appropriate plants and planting style; 4. Ensure adequate maintenance.     

城市滨河区绿地景观空间的整体发展——基于上海滨河区域绿地空间结构特征的分析

运用GIS技术和Fragstats4.2景观指数分析，采用绿地面积和植被覆盖度2个空间构成指标和5个常用景观指数，从总体构成、具体河段以及主城与郊区差异比较3个方面分析滨河区主干河流周边绿地的空间格局。结果表明，整体区域植被覆盖度不高。休闲服务类绿地占比较小，分布分散，连通度低。自然形态类绿地占比相对较大，集中分布，连接度低。农业生产类占比大，集中成片，连接度高；中小型河流的公园休闲服务空间体系完善，连接度较好。区域性和流域性两级河流绿地空间功能单一，连接度需提升；主城区主体类型公园和乔木林地分布较之郊区分散，连通性更好。研究结果为城市滨河区域空间格局优化提供方法借鉴，对于提升复合生态功能非常重要。     

Enhancing pollination ecosystem service in urban green areas: An opportunity for the conservation of pollinators

The rapid growing urbanization is one of the main threats to urban biodiversity and the ecosystem services (ES) that they provide. Pollination is one of the most affected ES in urban areas mainly due to the decline in urban green areas (UGAs) and other factors derived from urbanization itself. Considering this and the already existing global pollinator crisis, the aim of this work is the evaluation of urban green infrastructure as an opportunity for pollinator conservation. For that purpose, the ornamental vegetation of a medium-sized Mediterranean city (Granada, south-eastern Spain) was determined. The floral origin, phenology and floral traits of the conforming species and the pollinator species that they attract were analysed. Additionally, NMDS analysis were performed in order to determine if the “Pollination Syndromes” are a useful tool to actually predict the pollinator group attracted to a certain plant species. It was found that UGAs have huge potential for pollinator conservation as the major part of its ornamental species have an entomophilic pollination strategy. However, there is an imbalance in the availability of flower resources throughout the year. Hence, the addition of species flowering out of the main flowering season would be advisable in order to get a continuous supply of floral resources for pollinators. A current disproportion in the potentially attracted pollinator groups was also found out, being bees the predominantly attracted ones. However, results showed that the “Pollination Syndromes” are a tool with limitations at the moment and needs to be used with considerations. Thus, the specific plant-pollinator relationship should be determined through field work in each case-study. Further studies considering key factors such as urban connectivity and fragmentation would be desirable to ensure a comprehensive management for urban pollinators.     

Needs and expectations of German and Chinese children for livable urban green spaces revealed by the method of empathy-based stories

One of the important features of cities is to provide high-quality outdoor environments for various groups of citizens. Although children are frequent users of green spaces, the knowledge and perspectives applied in planning and design of urban green spaces are mostly defined by adults. This results in spaces and practices that may limit the daily lives and creativity of urban children. Promoting child-friendly cities benefits from knowledge produced by children themselves, regarding their perceptions and experiences, as well as ideas and suggestions. This study provides empirical results concerning children’s needs and mental images for urban green spaces in two urban areas in two countries (Chengdu, China, and Ruhr Region, Germany). 765 children, ages 8–10 were surveyed through the method of empathy-based stories (MEBS). Participants were asked to use their imagination to write stories according to given scenarios. Our study shows that MEBS can be used to gather meaningful data with children, and that children are an important stakeholder group in urban planning, landscape design and management with an ability to express their diverse needs and preferences towards green spaces. Both designed green spaces (e.g. gardens, parks) and wild nature (e.g. forests, meadows) can offer a range of activities and experiences for children in their everyday lives: opportunities for play, socializing, contact with nature, aesthetic and restorative experiences, learning and exploration. Our findings include indications of children’s awareness of the diverse ecosystem services that green spaces provide, as well as of urban sustainability and livability. While we found German and Chinese children to have corresponding needs and expectations regarding urban green spaces and nature, we also found some variation. We suggest that the use of, and experiences in green spaces are linked not only to the landscape but also to conceptual-cultural contexts.     

Street trees and Urban Heat Island in Glasgow: Mitigation through the ‘Avenues Programme’

Glasgow, Scotland, is embarking on an ambitious plan to convert all city centre thoroughfares into tree-lined streets (the ‘Avenues Programme’) to make the city centre more people-friendly, attractive, greener, sustainable and economically competitive. While it is well-known that urban green infrastructure (UGI) is a promising strategy to address overheating in urban areas, evidence for the surface temperature, air temperature and thermal comfort effects of street trees is contradictory. In the context of a city-centre-wide ‘Avenues Programme’ in Glasgow, we explore its co-benefits in terms of temperature and thermal comfort. We used a multi-method approach, combining GIS-based spatial analysis with fieldwork, microclimate modelling and statistical analysis to determine the scale of the overheating problem and the likely role of its mitigation based on the ‘Avenues Programme’ case study. We show that the Surface Urban Heat Island (SUHI) differences within the city are of the same magnitude as the urban-rural anomaly and “hot” spots are localized in the city centre area and are clustered in different patterns depending on the severity of background temperatures. Therefore, small, isolated patches of vegetation would not be effective for cooling the clusters of overheated areas. Air temperature showed non-linear relationship with tree canopy cover and the relationship is stronger at medium scale. The ‘Avenues Programme’ as a whole, could eliminate the UHI effect in the city centre, with some tree species completely eliminating the UHI in the city centre. Once complete, the ‘Avenues Programme’ could significantly improve thermal comfort during heatwaves from the current ‘hot’ category to ‘slightly warm’ across the city centre.     

Effect of green infrastructures supported by adaptative solar shading systems on livability in open spaces

Lack of thermal comfort in the existing building stock in many warm summer climates and the COVID-19 pandemic have increased residents' temporary occupation of urban open spaces. However, climate change and other effects such as urban heat islands are also negatively affecting the livability of these spaces. Therefore, strategies are needed to improve the thermal conditions in these areas. In this context, the research designs, simulates and assesses an urban green infrastructure supported by an adaptative solar shading system. For this purpose, a public square to be renovated in Seville (Spain) is chosen. After an analysis of the current situation, more vegetation is added. However, trees are not planted fully grown, so their cover is not enough in the short term and an artificial system that protects from the sun by casting shade and that adapts to both their growth and the seasons is included. The urban space is characterized by on-site measurements, proposing four (initial, intermediates and final) scenarios using computational fluid dynamics simulations in an holistic microclimate modelling system. In turn, changes in thermal comfort are analyzed using the COMFA model. Results show that the air and surface temperature are decreased, reducing the number of hours in discomfort by 21% thanks to incorporating the green structure and by 30% due to the vegetation. It can be concluded that the use of these temporary urban prostheses enables urban spaces regenerated with vegetation to be enjoyed without waiting 20 or 30 years for the trees to mature, encouraging people to spend more time outdoors from the start of the intervention.     

A green infrastructure planning framework–guidance for priority,hubs and types

Green infrastructure (GI) has become an important tool to achieve sustainability and resilience in cities because of its various benefits, including stormwater management, urban heat island mitigation, air quality improvement, and carbon storage. Most existing studies have often focused on a single aspect, while few studies have incorporated the results of GI analysis into the planning process. To address this gap, we propose a planning framework to prepare the GI intervention solutions, aimed at identifying the priority actions, hubs to extract maximum multifunctionality, and preference types at the regional scale. We applied the planning framework to Wuhan city as a case study, and found an overall significant multifunctional potential. Two-thirds of the benefit pair (including spatial autocorrelation and bivariate spatial autocorrelation for benefits) relationships were found to be positive, and block areas approximately 15% of the total area were recommended as hubs to lay out the GI. Warnings should be received for evidence, revealing that industrial areas have higher requirements for GI that can alleviate the thermal environment and improve air quality. Strong positive correlations between various benefits were found in this area, especially based on a relatively large proportion of existing natural land. Further, we classified the types of GI preference by SOM (Self-organizing map neural network), and found that differentiated GI planning and strategy formulation are required by different types of regions. The planning framework provides intuitive guidance for GI intervention solution making, which can provide planners and government officials a deeper understanding of GI discourse based on clearly explained answers of important decision-making questions.     

Characterization of co-benefits of green stormwater infrastructure across ecohydrologic regions in the United States

Stormwater Green Infrastructure (SGI) systems such as rain gardens, permeable pavement and bioswales are commonly used in municipalities to reduce urban flooding and water pollution. In conjunction with these direct benefits, SGI systems provide additional social and environmental “co-benefits”. Our goal was to investigate the co-benefits of commonly used SGI systems in five cities in the United States, including Baltimore, Denver, New York City, Philadelphia, and Portland. The i-Tree Eco model was used to predict carbon storage and sequestration, air pollution removal, UV reduction, and cooling effects of trees for individual tree species and estimated SGI tree inventories across the five study cities based on observed tree characteristic data. Aspects of SGI design, environmental factors, and model inputs were assessed to understand what parameters impacted SGI co-benefits predicted by the model. We evaluated the most highly influential parameters using a global sensitivity analysis method. As expected, the type of SGI design, and the overall number of trees utilized within those designs, played a large role in determining the overall amount of co-benefits predicted by the model. However, climate also influenced estimation of benefits produced, with similar responses predicted for cities in the same climate zone (e.g. Baltimore, Philadelphia, and New York City). In particular, the global sensitivity analysis showed that variables influencing environmental conditions and tree growth also impacted final co-benefit predictions produced by i-Tree Eco. study revealed how various assumptions and prevailing equations within the i-Tree Eco model can play a major role in the final outcomes predicted by the model. Studies that use i-Tree Eco to analyze potential co-benefits of SGI projects, especially when the goal is to compare projects across climate zones, should consider what aspects of the results are simply a function of the model itself. Overall, the model predicts that more co-benefits are provided in certain climate zones, an assumption currently supported in the literature.     

Equally green? Understanding the distribution of urban green infrastructure across student demographics in four public school districts in North Carolina,USA

Green infrastructure (GI) provides a suite of ecosystem services that are widely recognized as critical to health, well-being, and sustainability on an urbanizing planet. However, the distribution of GI across urban landscapes is frequently uneven, resulting in unequal delivery of these services to low-income residents or those belonging to underserved racial/ethnic identities. While GI distribution has been identified as unequal across municipalities, we investigated whether this was true in public schoolyards within and among urban school districts. We examined schoolyards in four metropolitan areas of diverse socio-economic and demographic compositions in North Carolina, USA to determine if they provided equal exposure to GI, then compared whether this was true of the broader urban landscape. We first classified the land cover of elementary schoolyards and their neighborhoods, then used bivariate and multivariate approaches to analyze the relationships between GI (i.e. tree canopy cover and total GI) and the socioeconomic status and race/ethnicity of the schools and surrounding neighborhoods, respectively. We found that the extent of tree canopy cover and total GI in schoolyards was unrelated to the socioeconomic status and the race/ethnicity of students across the four school districts. In contrast, neighborhoods with lower socioeconomic status and larger populations of underserved race/ethnicity residents had less tree canopy cover and total GI. Although total GI was more evenly distributed in schoolyards, the extent of tree canopy cover and total GI in schoolyards was lower than that in the neighborhoods. This suggests opportunities for school districts to expand GI in schoolyards, leveraging their potential to increase ecosystem services to all children, from increased educational opportunities to improved mental, physical, and environmental well-being.