Towards a Sustainable Housing Environment: Ecological Landscape Principles and Practices in Large Housing Estates of Guangzhou, China
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Towards a sustainable housing environment: Ecological landscape principles and practices in large housing estates of Guangzhou, China Junyan He, Beisi Jia Department of Architecture, The University of Hong Kong [email protected] Abstract Sustainable development of housing environment is of growing concern in China’s urban de- velopment. As the capital of Guangdong Province as well as the largest city in south China, Guangzhou is now experiencing a large-scale housing development. Residential landscape is considered as the main means of creating a comfortable housing environment. Large amounts of money have been invested in residential landscape construction. This paper aims at inves- tigating the ecological landscape principles for large housing estates in Guangzhou, China in order to lead toward a more sustainable housing environment. The study is divided into two parts. The first part builds up the principle framework based on related literature review on ecology and landscape, and puts forward ecological landscape as the form that can not only minimize environmentally destructive impacts but also cultivate a harmonious people-plants relationship. The second part of this paper evaluates the validity of the claim of ‘ecological estates’ and ‘garden estates’ in the housing market. The above five principles will then be used as parameters for case evaluation and comparison. The research findings suggest that towards a sustainable housing environment, what seems to be essential to an ecological resi- dential landscape is neither the amount of finical resources that has been put into the land- scape construction, nor the green-coverage-rate of the overall housing estate; but rather the abidance with the five ecological landscape principles. Keywords Sustainability, housing environment, ecological residential landscape 1. Introduction: ecological landscape principles in housing development In 1992, the United Nations Conference on Environment and Development (UNCED) put forward the concept of sustainability, which is defined as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs”. Some years later, sustainable housing development has become a growing concern in China (Liu et al., 2001; Zhang, 1998; Ren, 2000; Jia, 1999). Landscape has a very close relationship with housing and buildings. Urban green areas, both public open spaces like parks and private planted areas around buildings, can have a marked effect on many aspects of the quality of the urban environment and the richness of life in a city (Givoni, 1998). In the residential community, landscape can affect the housing in the surroundings. Different kinds of internal courtyards and attached enclosed open spaces may affect the housing climatic characteristics. It shows that landscapes have a very close rela- tionship with housing environment. Ecological planning and design seek to make nature visible and to develop ecological char- acteristics in landscaping (Van der Ryn & Cowan, 1996). Many studies criticize the hu- man-centered tendency in landscaping where intensive human recreation and leisure activities may damage ecological processes, ecological integrity and system productivity. To move to- wards sustainable development, it is suggested that indigenous landscape patterns should be conserved, cultivated and revitalized (Platt et. al., [ed], 1994). In residential communities, ecological landscape addresses not only environmental protection but also the interrelation- ship between people and nature. Landscape planning and design principles should promote ecological integrity while forming a balanced social and physical environment. Landscaping should help to form sustainable communities that offer opportunities for participation that encourage new modes of interaction among residents. Human beings are living social groups and active participation by the residents can help to achieve sustainability (Grant et al. 1996). Planners cannot create sustainable communities without having the commitment from resi- dents to modify or adapt their behavior or attitudes towards caring for the landscape around them. Residents may take part in the design process to express themselves in the surrounding environment; work together to take care of the landscape; or obtain knowledge about planting and ecology. The formulated five principles are: 1.1 Applying indigenous plants The maximizing use of the indigenous plants is a very important idea in ecological landscape. A sustainable landscape requires minimum use of indirect solar inputs of energy, materials, and labor (Platt et al., [ed], 1994). Indigenous plants are cheaper and easier to suit the sur- roundings than the exotic ones (Greed & Roberts, 1998). They are well-suited for the local climate and easy to grow. Any virgin, untouched landscape in natural setting offers good bio-diversity models to learn from (Van der Ryn & Cowan, 1996). The quantity of the in- digenous plants should occupy a dominant percentage in the whole residential landscaping. 1.2 Minimizing energy-resource consumption and labour input in landscape maintenance During the residential landscape maintenance, energy-resource consumption becomes a big problem and should be minimized. This can be achieved by careful selection of indigenous plants, imported wildlife species and proper landscape design layout. Local plants in their natural setting effectively need no manual labor, energy or resource input except the sun, and can grow well depending on their own species competition regime (Platt et al., [ed], 1994). Comparing with the hard pavement, vegetation covering can create natural habitats and per- mit better absorption of rainfall by natural means which implies cost savings in water man- agement. Recent 20 years, ‘drought-resistant plants’ are popularized in America, for example use some beautiful drought-resistant shrub to replace the large irrigated grassland in order to save water (Makhzoumi & Pungetti, 1999). “Wildflower meadows” is defined as diverse communities of native and naturalized forbs and grasses, and it can also enhance awareness of seasonal changes and expose surrounding vistas (Platt et al, [ed] 1994). It is considered that wildflower meadows are sustainable landscape. It 2 is also suggested that wildflower meadows should be prosperous in residential community (Van der Ryn & Cowan, 1996). To our thinking, wildflower meadow can be one of the methods to build up a sustainable landscape. Because it need few manual labor input, it can support more wild insects and wildlife habitats, and it can also express the original aesthetic of the plants themselves with no artificial factors. These are the benefits called economic, ecological and aesthetic. Wildness should be permitted with wise use in the sustainable de- velopment (Grumbine, 1994) Recycling the water supply in the estate is another positive approach. There are three water resources in residential landscaping, including natural rainfall resource, underground water resource and manual irrigation. The natural rainfall resource can hardly supply the under- ground water because the hard pavement and man-made pipe in the estate. Therefore, the consideration of how to collect and apply the natural rainfall resource in the housing estate is very important. 1.3 Increasing biodiversity and micro eco-environment Ecological greenery provides good base conditions for biota to diversify and multiply. Bio- diversity allows a mixture of diversified plants and wildlife including insects and birds. In- serting and maintaining a high level of biodiversity in residential landscaping is necessary to create an authentic ecological environment (Greed & Roberts, 1998). Strengthen the rela- tionship between water and plants can help to form a good eco-environment. The green spaces which consist of monotonous plant coverage play a lower eco-efficiency than the compound green space which made up of plants and waterbody. On one hand, water vapor may bring plenty nutrients to the plants surrounded and help them to grown more flourishing. On the other hand, plants can help to purify the water body. Therefore, water-growth plant type and waterside plant type should be encouraged in the residential landscaping in order to provide the possibility of forming micro eco-environment. Wetland is a good example. It is an ideal base for biodiversity and eco-environment and should be given plenty of considera- tion in the housing construction procedure. 1.4 Continuity of the greenery McHarg wrote in his book Design with Nature that the different scaled greenery system may bring a comfortable living environment and healthy micro-climate to the whole world (McHarg, 1969). In the past 20 century, many European cities are attempting to bring nature into the city-centre and to develop physical and ecological connections between built-up ar- eas of the city and surrounding natural areas and greenspaces. Corridors and ecological con- nections can be found to various degrees in a number of these cities (Beatley, 2000). These ecological corridors intended to provide connections and migration opportunities between core areas. At the residential level, ensuring the continuity of the greenery may help to de- velop ecological corridors inside the estate and at the same time form a systematic greenery environment (Fang & Li, 2001). 1.5 Enhance the relationship between people and greenery In residential communities, ecological landscapes address not only environmental