Home gardening in Singapore: A feasibility study on the utilization of the vertical space of retrofitted high-rise public housing apartment buildings to increase urban vegetable self-sufficiency

In land-scarce cities, high-rise apartment buildings may provide vertical spaces for natural-light home gardening along corridors, rooftops, balconies as well as façades. The vertical space can improve not only urban environmental sustainability but also food security. Using an experimental approach, we investigated the food production potential of a high-rise public housing apartment building based on different gardening systems, food crops, and sunlight availability. A gardening prototype system for building corridors was shown to increase the unit area yield of corridor gardening by fivefold compared to a commercial trough planter system. Additionally, this commercial trough planter system was mainly for leafy vegetable production, whereas the gardening prototype system for corridors is also suitable for climbing crops, such as legumes and cucurbits. Nevertheless, because of the limited space along corridors of the apartment building and the relatively low-light levels on average, corridor gardening was estimated to meet only 0.5 % of the demand for vegetables of the residents living in the apartment building. Rooftop gardening with shallow growing medium (depth < 15 cm) was estimated to meet 3 % of demand, and façade gardening 43 %, given the larger space available. Although the vegetable production potential in this study was estimated based on a particular typology of public housing apartment buildings in Singapore, our results showed that vegetable production in public housing apartment buildings is feasible, and home gardening can produce a substantial amount of vegetables for consumption if well deployed. Governments of highly urbanized cities may wish to invest in better home garden designs for high-rise public housing apartment buildings and encourage residents’ participation in home gardening, which would increase high-rise greenery coverage and improve urban food system resilience. Future studies should also investigate the environmental sustainability and food safety aspects of home gardening in highly urbanized cities.     

Assessing the potential of strategic green roof implementation for green infrastructure: Insights from Sumida ward,Tokyo

Urban green spaces, and green infrastructure more generally, provide multiple benefits that can enhance urban livability and sustainability. These range from the mitigation of air pollution and urban heat island (UHI) effect, to multi-dimensional benefits to human wellbeing and biodiversity. However, the expansion of urban green spaces is not always feasible in many cities. In such urban contexts, there have been proposals to utilize rooftops as green roofs in order to gain some of these benefits. This study spatially identifies areas where roofs have the potential to provide different types of benefits associated with urban green spaces if they are retrofitted with green roofs. Through a GIS-based approach we catalogue available roof space in Sumida ward in Tokyo for green roof implementation, and subsequenlty evaluate the potential of each roof patch to offer four types of benefits if retrofitted with a green roof, namely UHI effect mitigation, air pollution mitigation, and benefits to subjective wellbeing and biodiversity. Approximately 25% of the total roof surface in Sumida ward can potentially be used for green roof implementation. Furthermore, about 5.2% and 59% of this area has a respectively high and moderate potential to provide all four benefits if retrofitted with green roofs. This could increase the extent of green spaces by 10% and 120% respectively across the Sumida ward. In this sense, green roofs can become a major element of green infrastructure with ripple positive effects for urban livability and sustainability through the provision of UHI effect and air pollution mitigation, and benefits to subjective wellbeing and biodiversity.     

Towards an integrated garden. Gardeners of all types,unite!

Urban gardens are focal in metropolitan social-ecological infrastructure and yet they are spaces often threatened by urban development. In Berlin and Warsaw, major urban changes have prompted citizens to alter their attitudes toward the use of existing garden areas. This study tackles the socio-spatial phenomena of emerging grassroots projects and practices jointly implemented by groups of allotment and community gardeners, which are instrumental in envisioning new forms of common management and protection of garden spaces along urban transformations. The article investigates how cooperation between gardeners of different backgrounds influences allotments’ patterns of property and public accessibility. The focus is on a possible change of perspective regarding the use of closed allotment structures and the conceptualisation of a new form of hybrid urban landscape: an integrated garden. Our findings fit into the general debate on gardens as commons and new forms of green space selfgovernance.     

Promoting urban greening: Valuing the development of green infrastructure investments in the urban core of Manchester,UK

The attribution of economic value to landscape resources is fraught with technical and methodological difficulties. Little is mandated in UK planning policy explaining how economic value should be established. As a result landscape resources have been undervalued, underfunded and marginalised in favour of larger grey infrastructure development. The UK NEA however outlined for the first time a national scale economic evaluation of environmental resources. The Valuing Attractive Landscapes in the Urban Economy (VALUE) Interreg IVB project examined this issue by establishing a toolkit of economic evaluation methodologies for green investments across North-West Europe. Focussing on the returns that investments in green infrastructure can deliver to cities and city-regions, the VALUE project identified economic values that can be used to influence future policy-making. This paper presents an analysis of VALUE street tree investments in Manchester, UK. Using a contingent valuation survey preferences for green investments and associated willingness to pay (WTP) for them were generated. Analysis suggests that willingness to pay is directly related to the size and greenness of the proposed investment and participant perceptions of added value. 75% of respondents were WTP for investments in green infrastructure. Analysis indicates increased WTP and a marked preference for larger and physically greener investments. Payment values ranged from £1.46 to 2.33, a 59.5% variance, between the preferred investment option and the status quo. The paper concludes that although green investments vary in size and function, respondents consider the specific and wider value of green infrastructure resources when asked how much they willing to pay to fund and maintain such investments.     

A novel index for assessing perceived availability and public demand for urban green space: Application in a Mediterranean island

The objective benefits that humans derive from natural ecosystems and their enduring manifestation in urban green spaces (UGS) is well-know. Nevertheless, citizens’ preference, and perceived necessity of UGS is not always evident and therefore often not accounted for, especially in the context of urban planning decisions, where it could positively influence the effectiveness of greening strategies. This information is especially important in the Mediterranean islands, due to their unique character. Here we address these aspects, including the way they are affected by UGS perceived adequacy, accessibility, maintenance, distance, and other self-reported obstacles using a questionnaire completed by 703 residents of the Island of Crete, Greece. To integrate results, main covariates are compiled into the newly developed public UGS approval index. Survey results show that, 87.82 % of the participants consider public UGS highly necessary for their wellbeing, while only 69.22 % consider private UGS equally necessary. Nevertheless, private UGS were the most frequently visited green at 16.3 ± 0.7 days/month. Public UGS is considered more necessary for female respondents, under 35 years, living in an apartment in the city. However, it emerged that despite the significantly higher need for public UGS in the urban centers of the island, residents consider UGS inadequate and often inaccessible for people with mobility problems. Integration of the results in the new approval index, shows that citizens of Crete, are on average neutral or disapprove of local public UGS. The outcomes can be used for targeted interventions at existing and strategic planning in new UGS.     

A GIS-based mapping methodology of urban green roof ecosystem services applied to a Central European city

Green roofs provide a number of different urban ecosystem services (UESS), e.g. regulation of microclimate, support of air quality improvement, or stormwater retention. To estimate the spatial variation of green roof UESS across an urban area, a GIS-based mapping and spatial analysis methodology was established and applied to the city of Braunschweig, Germany. Based on the analysis of available geodata, in a first step, a quantity of 14,138 rooftops in the study area (14% of all buildings) was found to be generally suitable for greening. This resulted in a green roof area of 3 km². Based on criteria such as roof slope and minimum roof size, nearly two-thirds of these buildings (8596 buildings, 8.6% of total number of buildings) were categorised ‘appropriate’ for greening and subject to green roof UESS analysis.The spatial distribution of green roof UESS was estimated based on the categories thermal urban climate, air quality, stormwater retention and biodiversity. Due to their potential benefits in the four UESS categories an overall assessment resulted in a number of 867 roofs (0.9% of total number of buildings) categorised as ‘high benefit’ from rooftop greening. Another 3550 buildings (3.5%) and 4179 buildings (4.2%) were defined as ‘moderate benefit’ and ‘low benefit’, respectively. The inner city area of Braunschweig appears as a hot-spot of green roof UESS, i.e. higher percentage of ‘high benefit’ green roofs in comparison to residential areas. The proposed method is a simple but straightforward approach to analyse urban green roof UESS and their spatial distribution across a city but it is sensitive to the quality of the available input geodata.     

Is greening the building envelope economically sustainable? An analysis to evaluate the advantages of economy of scope of vertical greening systems and green roofs

A wide replication of green envelopes can be a good opportunity to improve urban environment conditions, as demonstrated by several studies. Greening systems increase also building envelope performances; however their economic sustainability has not been fully investigated. This study evaluates the economic sustainability of two combined greening systems installed on an office building: a vertical greening system and a green roof, and it evaluates the advantages of economy of scope. The Cost-Benefit Analysis on two different combinations of vertical greening and green roofs considers personal benefits and costs over their life cycle. The results demonstrate the advantages of economy of scope, due to the additional benefits coming from the combination of two different systems. The results show that the tax incentives and the combination of green systems can make the installation and the maintenance costs economically sustainable during the life span of a greening system; this could lead to a wider diffusion of greening systems with higher environmental and aesthetic performances.     

Green roofs in temperate climate cities in Europe – An analysis of key decision factors

This paper aims to identify and assess the main decision factors that are relevant for the diffusion of green roof technology in cities of temperate climate in Europe. A mixed design method was applied to identify relevant factors and to structure these along a Strengths, Weaknesses, Opportunities and Threats framework. The factors were subsequently assessed by a sample of green roof experts, using an Analytical Hierarchy Process. The results indicate that prospects for green roofs are in general rather bright, and that dissemination potential is substantial. Green roofs are particularly likely to benefit from climate change and respective counter-strategies, as they are seen as an adaptation and mitigation measure. However, current barriers to adoption need to be carefully considered. Especially the dilemmatic incentive structures, in that building owners bear most of the risks and potential disadvantages, while the public collectively benefits from green roof advantages, could be a major implementation barrier. Without supportive policies, green roofs are thus unlikely to move from niche to regime level in the near future.     

Review on the roles and effects of growing media on plant performance in green roofs in world climates

Growing media (substrate) is a fundamental part of a green roof, providing water, nutrients and support to plants. However, little research has reviewed how it affects plant performances in different climatic regions. This study aims to analyse published research on green roof growing medium across world’s climate zones. Findings are structured according to Köppen–Geiger climate classification, aiming to investigate the prevalence of research conducted in different climate zones. Results from full-scale studies and laboratory or greenhouse experiments were reviewed. The later were included as they provide systematic knowledge on the effect of individual factors on system performances although cannot provide climate specific information. Studies discussed effects of major substrate components and depths on plant survival and establishment using standard test procedures. Results showed that most research in the subject were in temperate (group C climate classification), continental (group D) and dry climates (group B), respectively. Considerable number of investigations was conducted in controlled laboratory or greenhouse environments. Based on the results, future green roof research and guidelines should consider climate specifications of the region in designing growing medium, depths and attribute of green roof substrates in order to ensure enhanced plant performance. Especially, for more fragile but less investigated dry climate, considerations should be made to tackle heat fluctuations and drought stress by enhancing water holding capacity and thermal isolation of the substrate. To move forward, sustainable building solutions as a part of future urban forms, climate-adaptive green roof systems should be included into future research, practice and guidelines.     

Development potential of sky gardens in the compact city of Hong Kong

Sky gardens have been actively studied and installed in different cities. Their development potential in compact developing cities has received little attention. Using remote sensing and GIS techniques, this study evaluates the vegetation configuration and development potential of sky gardens in urban Hong Kong, their underlying location, land use and building factors, and future planning and implementation concerns. Existing sky garden area is limited with sparse vegetation cover and low biomass. Existing podium gardens exceed roof gardens by about nine times. District development age has little effect on existing and potential sky gardens. Old towns have higher potential roof and podium gardens than new towns in most land uses. The effect of land use on potential sky gardens varies greatly by districts. Buildings with 10–20 floors have higher potential roof gardens in most districts. Building area is the main determinant of potential roof garden, and population density of potential podium gardens. Three scenarios of realization, namely minimum (20%), medium (50%) and maximum (80%), are adopted to project sky garden provision in individual districts. The projection extends to the contribution of new sky gardens to urban greening in terms of green cover and greening rate in districts. The challenges include susceptibility to typhoon damage in high-rise exposed sites, aggressive weed invasion, lack of roof-slab loading data in old buildings, and poor building maintenance. The opportunities include affordability of the new technology, enabling government policy, and establishment of scientific and research foundation in the local context. The development strategy could aim squarely at stringent technical standards and contractor skill requirement, and programme prioritization based on research findings. The study provides useful hints, approaches and recommendations for a systematic sky-garden action plan in Hong Kong and other similar compact cities.     

Assessment of light adequacy for vertical farming in a tropical city

The pursuit of urban agriculture as part of a city’s green infrastructure is often a challenge, particularly within compact cities, where there is a limited amount of space between buildings for urban farming and gardening. Instead, such high-rise urban developments present often under-utilized spaces on the vertical surfaces of buildings. A key unknown is the adequacy of light for plant growth. Many leafy vegetables that require high amounts of light form a significant proportion of the staple diet in many Asian countries. We report on the assessment of sunlight adequacy for growing leafy vegetables in a compact tropical city, based on the high-rise and high-density residential environment of Singapore. Leaf physiological traits of seven leafy vegetables were assessed and used to estimate plant light requirements. A survey of photosynthetically active radiation (PAR) along exposed corridors showed that the daily light integral (DLI) value ranged from 2 to 35 mol m⁻² d⁻¹ under relatively ideal weather conditions during days with abundant solar insolation, and façades that experienced a minimum of half-day direct insolation matched the light requirements of vegetables within the moderate to very high-light categories. With regard to the building form, PAR increased gradually with height, but remains highly influenced by façade orientation and configuration. Owing to the annual north–south oscillation of the sun’s path, reduced annual PAR variability and higher total annual PAR at façades, buildings with an east–west orientation will better support continuous vegetable cultivation, especially for basic building typologies without self-shading configurations. However, excessive PAR and temperatures during mid-day hours may hinder plant growth. By highlighting such patterns in levels of PAR, this study confirms the potential for high-rise and high-density conditions in the tropics to support farming using typically under-utilized vertical spaces of residential buildings.     

Perceptions of cultural ecosystem services of tree-based green infrastructure: A focus group participatory mapping in Zagreb,Croatia

Urban green infrastructure provides city dwellers numerous benefits. Among them, cultural ecosystem services (CES) are distinguished by being easily perceived and essential for people and their well-being. However, not all CES are equally easy to perceive, resulting with some of the CES categories being weakly explored. Research on CES also rarely considers elements of urban green infrastructure other than parks and forests. Therefore, there is a lack of research on different components of urban green infrastructure, especially tree-based, perceived in relation to CES. This paper presents the results of focus group participatory mapping implemented with citizens in the city districts of Zagreb on the perception of five selected CES categories in various types of urban green infrastructure. Our results show that participants perceived 13 different types of tree-based urban green infrastructure as providers of CES. We also distinguish patterns in the perception of CES categories and their connection with types of tree-based urban green infrastructure. Tree lines are perceived as providers of aesthetical experiences. Furthermore, forests and park forests are perceived in relation to place attachment and recreational activities, while parks are versatile and provide all explored CES. Other types that emerged as important were greenways, greenery around residential buildings and educational institutions, which provokes rethinking of a careful planning of the entire repertoire of urban green infrastructure.     

浅议屋顶花园的分类功能及其营造技术

屋顶花园是一种重要的园林绿化形式,在城市绿地面积逐步减少的当今社会,尤其显得颇为重要.从屋顶花园的概念出发,对屋顶花园的分类、功能及其营造技术进行了阐述,以期为推进我国屋顶花园的建设和发展提供参考.     

郑州市屋顶绿化现状及分析

屋顶绿化在城市绿化美化中占有重要作用,拥有巨大的市场潜力。通过对郑州市现有及施工中屋顶花园的调查勘测,从屋顶绿化的设计和工程两大部分进行研究分析,并对比两种屋顶绿化的建造形式(简单式屋顶绿化和花园式屋顶绿化)。总结郑州市屋顶绿化规划中存在的问题与不足,并针对这些问题和不足提出改进措施和规划意见。     

Exploring public preferences and preference heterogeneity for green and blue infrastructure in urban green spaces

Green and blue urban infrastructure (GBI) has many positive functions often not recognised by residents (e.g., microclimate regulation, water retention, etc.). The question for urban planners who are aware of these functions when planning new GBI elements or revitalising existing GBI is how much they need to account for the preference heterogeneity of locals, who typically consider only aesthetic and recreational value. This study uses data from a discrete choice experiment among residents of the medium-sized Czech city of Liberec to reveal which combinations of nature-based or semi-natural GBI and recreational facilities respondents prefer and how strong their preferences are in terms of their willingness to pay. Overall, study respondents preferred nature-based GBI to semi-natural ones. A mixed-latent class model identified two groups of respondents who differ in preferences, trade-offs, and socio-demographic characteristics: (i) mostly older educated women who prefer nature-based elements and enjoy park infrastructure; (ii) mostly less educated men who dislike urban gardens and semi-natural streams and do not value park infrastructure. Based on the results, we recommend that spatial planners and green space managers design and implement more nature-based elements in Liberec, which are in line with the respondents’ preferences.     

Challenges of urban green space management in the face of using inadequate data

Effective urban planning, and urban green space management in particular, require proper data on urban green spaces. The potential of urban green spaces to provide benefits to urban inhabitants (ecosystem services) depends on whether they are managed as a comprehensive system of urban green infrastructure, or as isolated islands falling under the responsibility of different stakeholders. Meanwhile, different urban green space datasets are based on different definitions, data sources, sampling techniques, time periods and scales, which poses important challenges to urban green infrastructure planning, management and research. Using the case study of Lodz, the third largest city in Poland, and an additional analysis of 17 other Polish cities, we compare data from five publicly available sources: 1) public statistics, 2) the national land surveying agency, 3) satellite imagery (Landsat data), 4) the Urban Atlas, 5) the Open Street Map. The results reveal large differences in the total amount of urban green spaces in the cities as depicted in different datasets. In Lodz, the narrowly interpreted public statistics data, which are aspatial, suggest that green spaces account for only 12.8% of city area, while the most comprehensive dataset from the national land surveying agency reveals the figure of 61.2%. The former dataset, which excludes many types of green spaces (such as arable land, private and informal green spaces), is still the most commonly used. The analysis of the 17 other cities confirms the same pattern. This results in broader institutional failures related to urban green infrastructure planning, management, and research, including a lack of awareness of green space quality (e.g. connectivity) and benefits (ecosystem services), and the related political disregard for urban green spaces. Our comparison suggests that a better understanding of green space data sources is necessary in urban planning, and especially when planning urban green infrastructure.     

Role of green roofs in urban connectivity,an exploratory approach using landscape graphs in the city of Paris,France

Green roofs provide many ecosystem services, but little is known about the way they contribute to urban functional connectivity. This paper has the following four objectives: (1) to compare the potential green roofs’ role to connectivity in relation to other urban green spaces, (2) to specify the green roofs contribution’s type, (3) to explore the influence of building height integration method and finally (4) to assess the impact on connectivity of simulated greening new roofs. Using a landscape graph approach, we modeled ecological networks of three species groups with different dispersion capacities in the Paris region (France). Then, we computed several connectivity metrics to assess the potential contribution of green roofs to functional connectivity. At a large scale (metropole scale), our results show that green roofs can slightly improve the global connectivity largely through the connections rather than the addition of habitat area. More than a stepping stone function, green roofs would have a dispersion flux function at a local scale. Furthermore, when the difficulty of crossing movement is exponential to the height of buildings, green roofs over 20 m high are mostly disconnected from the ecological networks. In addition to the green roof’s height, our analysis highlights the very strong role played by buildings’ configuration. This study raises promising directions for the integration of building height into the analysis of urban connectivity. Detailed research and long-term biological data from green roofs and green spaces are needed to confirm our results.     

杭州市屋顶绿化现状调查研究

杭州市用于屋顶绿化的植物种类共计63科111属145种;从植物的观赏特性方面对应用状况进行分析,并依据园林布局形式和屋顶的开敞程度对杭州市屋顶绿化进行分类。结合实地调查,通过自身对比及与国外先进国家的屋顶绿化对比,发现杭州市屋顶绿化目前存在的问题并提出改进意见。     

重庆花园式屋顶绿化生态效益的初步研究

为了探讨屋顶绿化的生态效益,2013年7月选取重庆市园林事业管理局花园式屋顶绿化作为研究对象,以无绿化植物的屋顶水泥地作为对照,进行“乔-灌”、“灌-草”和草坪三种不同植物配置模式的气温、空气相对湿度、地表温度和空气中负氧离子含量测定。研究结果表明,屋顶绿化具有重要的生态效益,且不同植物配置模式的生态效益有较大差异。降温幅度为“乔－灌”（3．60℃）〉“灌～草”（2．68℃）〉草坪（1．43℃）,增湿幅度为草坪（29．42％）〉“乔-灌”（17．68％）〉“灌-草”（9．46％）,对地表温度的降低程度“乔－灌”（25．55℃）〉草坪（20．67℃）;屋顶绿化空气负氧离子含量此对照高33．73ions／m^3。