Application of land suitability analysis and landscape ecology to urban greenspace planning in hanoi, vietnam

ARTICLE IN PRESS Urban Forestry & Urban Greening (2008) 25–40 www.elsevier.de/ufug Application of land suitability analysis and landscape ecology to urban greenspace planning in Hanoi, Vietnam Pham Duc Uy, Nobukazu Nakagoshià Graduate School for International Development and Cooperation, Hiroshima University, 1-5-1 Kagamiyama, Higashi-Hiroshima 739-8259, Japan Abstract Urban green spaces, an important component of urban ecosystems, provide many environmental and social services that contribute to the quality of life in cities One of the key tasks of planners is how to optimize the benefits of urban green spaces This study introduces a program for developing green spaces in urban areas through (1) land suitability analysis based on GIS; (2) quantifying green areas based on the ecological factor threshold method to maintain ecological balance; and (3) applying landscape-ecology principles in organizing green spaces in urban areas A case study was made for Hanoi, Vietnam and its results show that most of the planned green spaces in the 2020 Hanoi Master Plan are suitable for development However, the recommended 18 m2 green area per capita seems not to be enough to maintain ecological balance and organization of the green spaces in the 2020 plan seems to lack a theoretical basis, or a holistic framework, at different scales From this perspective, we propose that Hanoi should set aside an extra green area from 6842 to 10,228 ha, and that the 2020 Hanoi green structure plan at regional, city and neighborhood scales includes three green wedges, one green belt, various parks and other green ways to create a green network ecologically more effective than the sum of the individual green spaces This green structure and the combined data approaches used here will form a base for building a garden city or an eco-city in the future r 2007 Elsevier GmbH All rights reserved Keywords: Greenbelts; Greenways; Green wedges; Land suitability analysis; Landscape-ecology principles Introduction The roles and benefits of green spaces for urban dwellers cannot be denied Urban green spaces can be defined and classified in many ways depending on their demands and specific requirements Urban green spaces are outdoor places with significant amounts of vegetation (Bonsignore, 2003), which exist mainly as semi-natural areas (Jim and Chen, 2003), or are ÃCorresponding author Tel.: +81 824 24 6511; fax: +81 824 24 6904 E-mail addresses: ducanhy2000@yahoo.com (P.D Uy), nobu@hiroshima-u.ac.jp (N Nakagoshi) 1618-8667/$ - see front matter r 2007 Elsevier GmbH All rights reserved doi:10.1016/j.ufug.2007.09.002 viewed as last remnants of nature in urban areas (Beatley, 2000) Urban green spaces, an important part of urban ecosystems, play a pivotal role in preserving biodiversity in urban areas Moreover, green spaces sequester CO2 (Nowak, 1993; Nowak and Crane, 2002; McHale et al., 2007) and produce O2 (Jo, 2002); they reduce air pollution (Yang et al., 2005); and noise (Fang and Ling, 2003); regulate microclimates, reduce the heat island effect in cities (Shin and Lee, 2005); affect house prices (Kong et al., 2007); maintain diversity; have recreational and social values (Tarrant and Cordell, 2002); and produce a vitamin ‘‘G’’ for health, well-being and social safety (Groenewegen et al., 2006) Gilbert (1989) said ARTICLE IN PRESS 26 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 that factors such as the size, shape, diversity, history, and distribution of green spaces within a city as well as the design and management of the green spaces individually, play a decisive role in defining the functions of them Therefore, identifying suitable sites for conserving and developing green spaces is the first important step to ensure their roles and functions Site information can be gained by using land suitability analysis (LSA) based on GIS which is a strong, efficient and effective application within land-use planning, habitat analysis, etc (Miller et al., 1998; Kalogirou, 2002; Malczewshi, 2004; El-Nahry and Khashaba, 2006; Gillenwater et al., 2006) Applying the ecological factor threshold method will help quantify how much green area is necessary to maintain an ecological balance in urban areas (Zhang et al., 2007), and using an urban forest effects model (UFORE) will help quantify key values of urban green spaces such as carbon storage and sequestration (Nowak et al., 2003; United States Department of Agriculture, 2006) More importantly, the roles and functions of urban green spaces can be enhanced if they are organized by combining a variety of green space types for multiple purposes called a green network or urban green structure Urban green structure is a concept used in most Nordic countries with varying interpretations and legal status Green structure is the arrangement of green spaces in terms of their composition and configuration The composition of green spaces expresses what kind of green spaces exist and their configuration encompasses their size, shape and distribution Pauleit and Kaliszuk (2005) have shown that the overall green structure of a city results from the interaction of natural and human processes over time including a pre-urban layer of natural and cultural landscapes, an urban layer with the distribution of these green spaces following the urban development patterns, and an infrastructure layer including roads and other linear infrastructures In the approach of urban green structure or urban green network, the important concept of the greenway is an adaptation from western countries such as Germany since the 1980s, where greenways were first established to prevent urban sprawl, separate settlements, make recreational opportunities, and improve air quality in industrialized urban areas (Haaren and Reich, 2006) Moreover, Taylor et al (1995) also showed the limitations of greenbelts in planning urban areas and described the evolution from a greenbelt approach to a more holistic greenway in Canada over a 40 year period Thus, nowadays, the greenway movement has become important in urban planning, conservation and landscape ecology all over the world For example, in Asia Yokohari et al (2006) outlined the history and future directions of greenways in Japanese New Towns, whilst Yu et al (2006) introduced the evolution of greenways in China and Tan (2006) showed a greenway network for Singapore Ahern (1995) indicated that greenways are Land suitability analysis based on GIS Finding suitable sites for developing urban green spaces Ecological element threshold method Quantifying urban green spaces Landscape ecology principles Organizing urban green spaces Fig The steps involved in the development of green spaces in Hanoi networks of land containing linear elements that are planned, designed, and managed for multiple purposes including ecological, recreational, cultural, aesthetic, or other purposes compatible with the concepts of sustainable land use Moreover, greenways are often coordinated with other planning features and purposes for example, large cities often integrate greenway concepts and the development of a green belt, thus forming a green structure in and around the city that allows movement of urban expansions in different directions All this functional knowledge can be acquired by applying landscape-ecology principles The application of landscapeecology knowledge, the principles of planning landscapes in general, and planning green structure in particular meet the requirements of sustainable developments, ecological conservation, aesthetic values, recreation, economic and environmental considerations (Leita˜o and Ahern, 2002; Jim and Chen, 2003; European Commission, 2005; Li et al., 2005) The purpose of this study is to answer the question of how to apply LSA modeling, the ecological factor threshold method, and landscape-ecology principles in planning comprehensive green structure (Fig 1), for the case of Hanoi, Vietnam The results will contribute to programming effective land use up to 2020 Data and methods Study area Hanoi – the capital of the Socialist Republic of Vietnam, is the political–economic–cultural–scientific and technological center of the whole country with a latitude from 201530 to 211230 north, and longitude from 1051440 to 1061020 east Hanoi is an ancient city with nine urban districts and five rural districts The city has been developing for almost 1000 ARTICLE IN PRESS P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 27 Fig The study area of Hanoi, Vietnam years, i.e since its establishment in 1010 It is located in the center of the Northern Delta with a population of 3,055,300 (2004), and an area of 920.97 km2 (of which downtown area: 150 km2) The downtown area of Hanoi city was selected for this study (Fig 2) There are a variety of higher plant species in Hanoi with 644 species belonging to 247 genera and 157 families In particular, there are 13 valuable and rare plant species (Yen, 2005) and 150 non-native species belonging to 78 genera and 54 families (Ninh, 2005) Method Land suitability analysis In this study, LSA for building a green space map was carried out based on air pollution maps, water body system maps, existing land-use maps, maps of valuable historical and cultural landscapes, and the Vietnamese standards for planning and designing urban and industrial areas The LSA was supported by the spatial analysis functions of GIS through steps including: identification and collection of spatial data, weighting with the analytic hierarchy process (AHP), data integration and GIS analysis, and output evaluation (Fig 3) Among the environmental functions of urban green spaces, air quality was selected because of its importance and availability of data For existing landuse systems this is a significant input because it expresses the human impact, and influences the feasibility of developing urban green spaces The existing land use, which includes basic habitat information, has been classified into real green spaces or evergreen spaces (parks, public green spaces, riverside green spaces, roadside green spaces, attached green spaces), non-real ARTICLE IN PRESS 28 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 Maps of air pollution Maps of existing land use Maps of body water system Maps of industrial zone Maps of landscape Suitability scores and Raster Weighting based on AHP GIS analysis (Overlap) Output evaluation and comparison Fig Flowchart indicating the land suitability analysis for urban green space development in Hanoi green spaces or open green spaces (agricultural land, cultivated alluvial land), built-up areas, and water body systems (Fig 2) Regarding water body systems and valuable landscapes (historic, cultural sites such as temples, palaces, etc with reference to the traditional Vietnamese way of life), almost all green spaces such as parks and public green spaces have been developed in conjunction with water bodies or historical and cultural sites In addition, green spaces, water bodies and valuable landscapes are used in the strategic planning of Hanoi city Furthermore, Vietnamese regulations and standards also play an important part in developing urban green spaces and they decide how green spaces will be developed In LSA, determining the suitability scores for each factor is a compulsory step, and in this study they were regulated from to (Figs 4(a–e)) where a higher score indicates an area more suitable for developing green spaces In the land use map, for example, real green spaces receive the score (highest suitability), open green spaces score 2, and others are attributed score (lowest suitability) Weighting is one of the most important steps in suitability analysis, as it precisely affects the output, and is complicated by interacting of factors with each other AHP (Banai-Kashani, 1989) and pairwise comparison of the criteria are widely used to identify weighting scores, and they were applied in this study The MATLAB 5.3 software was used to solve the matrix which results from AHP and pairwise comparison; and the spatial function of the Arc GIS (Arc/Info, release version 9.1, ESRI, Redlands, CA 92373-8100, USA) platform was used to overlay the factors to make a composite map which acts as a suitable green map This was then compared with the 2020 Hanoi Master Plan The ecological factor threshold method The ecological factor threshold method is implemented based on the principles of ecological balance Thus, the purpose of this step was to quantify how much green area is needed for Hanoi in terms of maintaining ecological balance Zhang et al (2007) applied this method for planning urban green space systems based on analyzing the key ecological elements including: the population carrying capacity, carbon–oxygen balance, and the supply–demand equilibrium of the water resources As shown by Zhang et al (2007) the population carrying capacity is the largest number of people that food and energy produced by ecosystems can support based on stated production conditions, land productivity, standard of living, and so forth In Hanoi, this has been identified in the 2020 Master Plan The carbon–oxygen balance is the most influential factor It relates to the total of carbon emission by human as well as natural activities, and to absorbing carbon dioxide and releasing oxygen in photosynthesis of green plants In green space planning, the carbon–oxygen balance is carried on the basis of constant adjustment of green plants of green spaces and various kinds of oxygen consuming activities (Zhang et al., 2007) Water resources are an essential factor for all creatures to exist and develop Thus, the supply–demand equilibrium of water resources, which presents to an equilibrium of ARTICLE IN PRESS P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 29 Fig Suitability scores for existing land use in Hanoi (a), industrial zone (b), valuable landscape (c), water body system (d), and air quality (e) demands (domestic, industrial agricultural consumptions) and supplies (rainfall, groundwater, etc.) is important for sustainable development of human in general and vegetation or green spaces in particular Landscape-ecology concepts for green structure planning Landscape ecology has opened the door to and provides a basis for planning landscapes in general and green networks in particular Forman and Godron (1986) proposed the model of patch, corridor and matrix as the three basic components of any landscape, and state that landscape ecology deals with the effects of the spatial configuration of mosaics on a wide variety of ecological phenomena Landscape-ecology concepts and applied metrics (Leita˜o and Ahern, 2002) are likely to be useful in addressing the spatial dimension of sustainable planning and they provide a theoretical basis for landscape and urban planning The landscape-ecology principles used in planning land use and landscape architecture (Dramstad et al., 1996) are patch size, number and location; edge parameters (i.e the boundary with edge structure, and shape); corridors and connectivity; and network mosaics Jim and Chen (2003) who applied comprehensive green space planning to compact Nanjing city, China have shown that island biogeography theory (MacArthur and Wilson, 1967) and landscape ecology (Forman and Godron, 1986) provide fundamental strategies for green space system design They comprise a network of greenways, green wedges and green extensions, which linked isolated green patches within and outside the city at three scales ARTICLE IN PRESS 30 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 (metropolis, city and neighborhood) Li et al (2005) also showed that according to the principles of landscape ecology, green wedges and green corridors may comprise a suitable green network system in planning urban greening in Beijing, China Yokohari and Amati (2005) proposed that urban parks need to be regarded as core areas in the city, that an outer green belt is to surround the city; and that green corridors along rivers and streets will connect the cores and the outer areas Thus, an organization of urban green spaces based on landscape-ecology principles, in respect to using linear (e.g., greenways) and non-linear elements (e.g., parks), encompasses the connectivity and networking of green spaces in urban areas better than considering them separately In other words, ecological values of a green network are better than those of the sum of the green spaces individually, and the results of green structure planning based on landscape-ecology principles (connectivity, corridors, patch arrangement, network mosaics) are a connected green network including green wedges, green belts, green ways, green cores, green extensions, etc., which are used in this study These are more likely to resist uncontrolled urban development than individual green spaces and enhance biodiversity Moreover, applying landscape-ecology principles to green structure planning also conforms to four planning strategies (Ahern, 1999): protective, defensive, offensive or opportunistic; and to two patterns: nature in city and city in nature (Yokohari and Amati, 2005) Results Constructing a green map based on LSA Based on the AHP and pairwise comparison, with the support of MATLAB software, we acquired the weighting score for each factor and then used spatial analysis function of GIS to produce a composite map (Table and Fig 5) A comparison of the composite map and the Hanoi Master Plan showed that there is compatibility between the two maps It means that almost all the sites planned for developing green spaces in the 2020 Hanoi Master Plan (Fig 6) are suitable Table The ecological factor threshold method Regarding population capacity, according to the 2020 Hanoi Master Plan, Hanoi population will reach 4.5–5 million, of which the urban population would be around 2–2.5 million This will be considered the population carrying capacity for the city According to the Human Development Report 2006 (UNDP, 2006), the per capita carbon dioxide emission of Vietnam is 0.9 tons per year (equally: 0.6 tons of O2 consumption) Therefore, the total oxygen consumption by the urban population will reach around 1.2–1.5 million tons, with an assumption that there would be no change of this index until 2020 Regarding the supply–demand equilibrium for water resources, some studies (e.g., Ngoc et al., 1997) have shown that the total amount of water supply in Hanoi is enough to match the development of the city until the year 2020 The carbon–oxygen balance was analyzed based on the carbon dioxide consumption of trees Tung (2002) estimated that in urban areas, there were around 500,000 trees over an area of 354.52 or an equivalent of 1321 trees per The per capita green area in the 2020 Hanoi Master Plan in downtown areas is 18 m2 a total of 3600–4500 Based on an estimate of Zhang et al (2007), for ‘good’ green spaces (forests, parks, etc.), the annual per hectare O2 production of trees is around 70 tons Therefore, the total oxygen production up to 2020 equals to 252,000–315,000 tons Considering the carbon–oxygen balance, a serious imbalance is readily apparent To retain a balance, downtown Hanoi needs support from outside ecosystems with a green area from 13,542 to 16,928 At present, in the suburban areas, Hanoi has a forestry area of 6700 Therefore, Hanoi needs to develop an extra green area from 6842 to 10,228 The next step would be to consider how to organize urban green spaces to optimize their benefits by using landscape-ecology principles Application of landscape-ecology principles A review of green structure in Hanoi At present, Hanoi city resembles a hybrid of the basic forms (linear, centralized and gridiron), which express physical and cultural influences through time According to the 2020 Hanoi Master Plan, the city will be planned and developed following a centralized form The weighting score for each factor to develop the composite map Factor Air pollution Water systems Industrial zones Existing land use Valuable landscape Weighting score 0.2506 0.2555 0.1544 0.02959 0.0437 Overlaying to create the composite map ARTICLE IN PRESS P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 31 Fig The composite green map for Hanoi where the city center is marked by the ancient quarter The Hanoi government will control the urban sprawl process by constraining the development of the downtown area and by developing satellite cities A review of the 2020 Hanoi Master Plan (Fig 6) uses urban population density targets set at an average of 100 m2/ person, and includes an allocation of 18 m2/person (around 4500 ha) for green spaces, parks and sporting facilities A greenbelt will be created with a width of 1–4 km for natural and ecological preservation In 2005, green structure planning was studied for a 150 km2 area of downtown Hanoi with the regional, city, and neighborhood scales These studies were projected to the 2020 The 2020 green structure plan in Hanoi is thus a combination of linear and non-linear elements Green structure at region scale Green wedges ‘‘The green wedge is composed of parks, gardens, farmlands, rivers and wetlands Green wedges and green corridors form an integrated ecological network by connecting the urban center, forest parks, mountains and the outer regional spaces’’ (Li et al 2005, p 332) Jim and Chen (2003) have shown that it is necessary to limit or prohibit the development activities inside and near green wedges Based on the 2020 Hanoi Master Plan, landform data, landscapeecology principles, and an assessment of the planned green spaces, three green wedges were proposed to connect outer green spaces and inner green spaces (Fig 7) This is regarded as an offensive strategy of green structure planning, and brings nature into the city ARTICLE IN PRESS 32 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 Fig The 2020 Hanoi Master Plan Green structure at the city scale Greenbelts Greenbelts can be understood to be narrow strips of parkland more or less encircling part of a built-up metropolitan area or large urban area (Osborn, 1969) As mentioned above, Hanoi intends to develop a greenbelt with a width from to km However, it is difficult to use one green belt to resist urbanization because it is easily encroached on by the urban sprawl process and easily breached by urban leapfog growth Li et al (2005) have pointed out the limitations of greenbelt planning in Beijing, China Taylor et al (1995) have presented the influence of greenbelts adjacent to urban area, in cases that have been ineffective in controlling urban growth outside of the greenbelt From this perspective, the green structure of Hanoi should be augmented by an inner greenbelt at the present peri-urban areas (Fig 8) This greenbelt is to be based on graph theory and gravity modeling with 33 green nodes, representing not only a zone for conservation but also a transitional zone with the function of resisting the urban sprawl, constraining the urban development, maintaining biodiversity, and enhancing recreation Moreover, almost all industrial zones in Hanoi are mainly concentrated in this belt area including Caudien, Namthanglong, Thuongdinh, Vandien, Giapbat, Vinhtuy, Saidong, and Ducgiang These industrial zones are embedded in Hanoi as a belt and make air pollution more serious Therefore, maintaining this proposed greenbelt is necessary not only for the above benefits but also for improving the ARTICLE IN PRESS P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 33 Fig The proposed green wedges for Hanoi urban environment as required in the Vietnamese standard (TCVN 4616, 1987) for planning industrial zones Parks and other public green spaces At present, there are 54 important green spaces in the Hanoi downtown area In fact, it is hard to expand them or build new ones in the built-up areas As a result, maintaining them is very important in retaining nature in the city Maintaining an inner green belt with 33 green nodes will help provide good opportunities to develop parks and other public green spaces Planning parks and other public green spaces at the city scales reflects a defensive strategy for planning green structure Such parks and public green spaces can be connected by corridors such as road greenways According to the Vietnamese standard TCXDVN 362 (2005), the per capita area for parks and flower gardens is about 7–9 and 3–3.3 m2, respectively or equivalent to a total of 2500–3075 Green structure at the neighborhood scale Attached green spaces Each part of downtown Hanoi is a mixture of residential, industrial, business and organization-owned areas where each of them is allocated a plot of land with scant space for developing green space These green spaces are distributed unevenly and are somewhat isolated Attached green spaces are composed of organization-owned green spaces, residential green spaces, etc., which play an important role in providing opportunities for residents to get in contact with nature Besides this, their function is to enhance local beauty, and to act as ecological stepping stones One solution is to restore and insert these green spaces in built-up areas such as rooftop greening, balcony greening, sidewall greening The development of this ARTICLE IN PRESS 34 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 Fig The proposed greenbelt for Hanoi green space type represents an opportunistic strategy of sheltering trees in green structure planning Road greenways Road greenways are an important component of greenway networks in urban areas In Hanoi there are some species which have been associated with some roads for a long time and have become a symbol of these roads such as Alstonia scholaris (L.) R Br in Nguyendu street or Dracontomelum duperreanum Pierre species in Phandinhphung street One of the typical characteristics of roads in Hanoi is that they are narrow with scant space for pavement, especially in the ancient quarter It is hard to plant or expand the area for trees in the available roadside settings, however the construction of new roads or reconstruction of old roads will give opportunity to develop greenways Regarding transportation planning of the Hanoi Master Plan up to the year 2020, the roads (number 1, 2, 3, 5, 6, 18, 32, Lang-Hoalac highway, and ring road 1, 2, 3) will be reconstructed or constructed As a result, greenway planning was proposed as shown in Fig 7, with the per capita roadside green space about 1.7–2 m2, or 425–500 total Riparian green spaces As a result of landform or watershed development there are many lakes, rivers, creeks and canals in Hanoi They play an important role in maintaining the urban environment, providing recreational areas, and in acting as corridors with functions that includes habitat, conduit, filter, source and sink (Forman and Godron, 1986) Riparian areas also play an important role in controlling floods and supplying an important habitat area for wildlife Therefore, the proposed riparian green spaces would follow along riverbanks or flood places of the Hong River, which are cultivated sometimes in the year as shown in ARTICLE IN PRESS P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 35 Fig The proposed greenways for Hanoi Fig In addition, in Hanoi, newly planted rows of trees and shrubbery provide ecological protection of landscapes between the banks of the rivers of Tolich, Lu, Set, Kimnguu, Hong, Nhue, Calo and Duong This is included in the 2020 Hanoi Master Plan Discussion Applying LSA based on GIS is a very useful and effective tool in identifying suitable sites for developing green spaces To reduce the subjectiveness in analyzing green space suitability, the AHP and pairwise comparison process were used with the support of MATLAB software in solving the eigenmatrix The results show that almost all planned green spaces in the 2020 Hanoi Master Plan were compatible with our analysis As shown in Miller et al (1998), this analysis is dependent on many criteria and many data and it is an extremely difficult task which should take into account natural, social, and economic factors This approach reflects green space suitability more accurately, adequately, and comprehensively Regarding ecological and environmental significances, five principal components (air environment, land use, water body system, valuable landscape, and industrial zone) were selected for this analysis More importantly, this study has introduced a useful, effective and efficient method for identifying suitable sites for developing green spaces in urban areas Quantifying green areas is necessary for urban planning and there are diverse ways to quantify such green areas depending on the specific demands and ARTICLE IN PRESS 36 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 Fig 10 The proposed comprehensive green structure for Hanoi requirements of the city concerned It was found that the ecological factor threshold method is especially suitable for quantifying green areas in the context of developing countries The results of this study show that the 18 m2 per capita green area seems not to be enough to maintain an ecological balance in Hanoi Thus, Hanoi needs to develop an extra green space area of 6842–10,228 Green structure planning in Hanoi at the regional, city, and neighborhood scales up to the year 2020 (Fig 10) was based on landscape-ecology principles and this green structure was developed as an integrated green network This network will guarantee the preservation of ecological functions and processes as well as the structure of the landscape This is a conceptual approach and no analysis of quantitative results was done for each individual green space Yet it will form basis for organizing green infrastructure and building an eco-city Continuity and connectivity of green patches, green cores or green hearts which are upheld by the creation of corridors, road greenways and river greenways are important because Hobbs and Saunders (1990) show that preserving parks is only a temporary solution, and without connections between them, isolation and loss of genetic diversity is imminent An analysis of green space organization in the 2020 Hanoi Master Plan showed that green spaces would be somewhat fragmented and isolated This would lead a reduction not only in green space area but also in the quality of ecosystem services, taking away the local inhabitants’ rights to access these green spaces, and making urban environmental issues more serious A further point is that the ARTICLE IN PRESS P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 2020 Plan seems to lack a theoretical basis or a holistic framework for organizing green structure at different scales These shortcomings will be compensated for by applying landscape-ecology principles, and the proposed comprehensive green space framework aims at fulfiling a number of fundamental landscape-ecology requirements (Jim and Chen, 2003) The combination of various green spaces to make a green network is very important in planning green structure because it is very difficult to use only one, or few different, kinds of green spaces to maintain all the benefits of greening in urbanized areas Taylor et al (1995) have shown that the reason for failure of greenbelts in Canada was that the ecological principles of maintaining connectivity by providing spatially continuous corridors (Forman and Godron, 1986) were not employed in the greenbelt approach in Ottawa Thus the approach lacked many of the features inherent in more contemporary greenways Li et al (2005) demonstrated weaknesses in the current belt in the 1992 Master Plan for Beijing As a result, the two greenbelts in Beijing have already been fragmented by extensions of settlement areas He concluded that the greenbelt areas shown in the planning documents not conform to reality and the future population increase will pose severe pressure on these green spaces Thus, there is a basic requirement that the planning and development of green structure needs a multi-functional approach The combination of many different green spaces into an integrated green framework in response to pressure from urban development is desirable In the proposed Hanoi green structure at the regional scale, three green wedges play a pivotal role in bringing nature into the city and maintaining biodiversity At the city scale, an inner greenbelt was proposed which offered the best potential for supporting an eco-network Moreover, it can be combined with the planned outer greenbelt to control the urban sprawl process more effectively and efficiently Planning green wedges and greenbelts represents offensive and defensive strategies in green structure planning, respectively At the neighborhood scale, a network of road greenways and riparian green spaces was proposed The greenways play a role as corridors in wildlife movement, and in bringing nature to move deeply into the city This reflects a defensive and opportunistic strategy of green structure planning Maintaining parks, public green spaces and attached green spaces is essential as part of a protective strategy when planning This study’s proposed comprehensive green structure development, which intend to last up to 2020, not only meets the requirements of landscape-ecology principles (Forman and Godron, 1986) but it is also feasible because a comparable number of green spaces are in the year 2020 Hanoi Master Plan The development of green wedges is based on open space and agricultural land, however the development and augmentation of other green spaces 37 such as road greenways, green cores and green links of green cores in the inner greenbelt might be difficult due to land budgeting and pressure of urban development In the other words, this green space system is facing with some obstacles such as rapid urbanization, weakness in controlling and managing urban development, land use change, and economic growth However, such pressures can be managed if planners and decision-makers, i.e Hanoi government, understand the roles and importance of these green spaces in developing a sustainable urban area Three primary green wedges have been designated to guard green spaces from encroachment, with intervening spaces allowing for urban growth It is necessary to build countermeasures to avoid ecological deterioration of sensitive areas by human development activities Li et al (2005) show that measures regarding legal, economic, institutional, social and technology aspects to protect green spaces require particular attention Besides, compensation schemes, which reflect the real value of green spaces, could become one of the most important measures and some green spaces at strategic locations should be identified and conserved For patch configuration of this proposed green network, by creating a connected network which helps enhance the size, location and number of patches the spatial configuration of patches has been improved through an improvement of the adjacency, connection or juxtaposition Moreover, with three proposed green wedges which are created from agricultural areas (introduced patches), wetlands (environmental patches) and so forth, the quality and diversity of green patches will be improved As shown by Jim and Chen (2003), the ideal landscape configuration is city patches encompassed within a green space matrix with diversified habitats to foster biodiversity It is apparent that these proposed green patches have a high perimeter-to-area ratio to maximize exchanges with the matrix environs In other words, an elongated patch with a longer border of the proposed green network allows more interactions with the surrounding matrix, and thus linear green spaces should be incorporated into urban areas to maximize edge effects or the linearity of the network configuration suits the compact urban form (Jim and Chen, 2003) In this proposed green network, the origin of green patches is mainly introduced and environmental patches, or planted patches and habitations As shown by Forman and Godron (1986), the matrix is the most extensive and dominating landscape element Thus, in this study, it is expressed through a greater relative area of green patches, the most connected portion of the landscape, a predominant role in the dynamics of the landscape It is always somewhat heterogeneous However, the distinction between matrix and patches at the regional scale is slightly different and the rest of the matrix could be considered a patch At the city and neighborhood scales, the matrix of the green ARTICLE IN PRESS 38 P.D Uy, N Nakagoshi / Urban Forestry & Urban Greening (2008) 25–40 network has a higher porosity and irrespective degree of connectivity Finally, it is concluded that this proposed green network helps green patches enhance the connectivity and reduce fragmentation and isolation through the linked and integrated greenway system This improves different attributes of fragmentation of green patches such as density, isolation, size, shape, aggregation, and boundary characteristics, and can act as a catalyst to preserve existing green spaces and generate new ones The connections between the green enclaves can stem the tendency to eliminate small and isolated green spaces and connection increases habitat diversity and capability to support flora and fauna, which in turn enhance amenity value to humans (Jim and Chen, 2003; Li et al., 2005) It is obvious that an increase of the density of fragments of green patches leads a decrease of the isolation of green patches geometrically As mentioned before, a system of greenways within the network can be designed to improve the accessibility of green spaces with footpaths, footbridges and over or underpasses Greenways can be established along twelve selected roads equipped with widened amenity strips and roadside trees with footbridges and underpasses for uninterrupted pedestrian-movement and to maximize accessibility and connectivity of the greenways The riverside greenway can be used to create recreational open spaces for people with easy access and bring vitality to the downtown areas At the neighborhood scale, small green spaces provide to daily needs for contact with nature as Nakagoshi et al (2006) argued that even small green parts are potential elements of green networks in cities A network of greenways and green wedges is suggested to link isolated green patches within and without the city The linkage system at the neighborhood scale aims at connecting existing isolated residential green spaces with small green spaces One of important aspects in a program for developing urban green spaces is a selection of strategic positions for biodiversity conservation In Hanoi, some parks such as Lenin, Bacthao and Thule were established a long time ago, during the French colonial period They have a higher biodiversity and are considered as green cores in this green network Besides, green spaces along the Hong River and three green wedges also play an extremely important role in maintaining and conserving biodiversity for the city In the tree-planting program, it is necessary to give priority to native species which suit to urban environment This has been identified in the Vietnamese standard TCVN 362 (2005), mentioning species such as Hopea odorata Roxb, Tamarindus indica L, Shorea roxburghii G Don, Phoenix loureiri Kunth., Terminalia cattapa L., Delonix regia (Bojer ex Hook) Raf., Lagerstroemia speciosa L and so forth In Hanoi, there has recently been a growing awareness about the roles and benefits of greening in urbanized areas As a result, planners and decisionmakers propose a combination of water bodies and green areas, using cultural as well as historic values, in a strategic concept for city planning in Hanoi Thus, the time seems right to discuss the mentioned plan with them, i.e Hanoi government and Department of Planning and Architecture This comprehensive green structure plan is not only based on landscape-ecology principles and island biogeography theory but also complies with planning strategies, viz: protective, defensive, offensive or opportunistic (Ahern, 1999) The proposed green structure in this study also embraces the concept: nature in city and city in nature (Yokohari and Amati, 2005) Landscapeecology principles are useful for, and fit the requirements of, green structure planning This green network will be a basis for planning, designing and organizing green infrastructure whilst ensuring the sustainable development of Hanoi city as an ‘‘eco-city’’ in the future Acknowledgments The authors would like to thank all members of the Nakagoshi 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