Showing papers by "Chi Yung Jim published in 2008"

Assessment and valuation of the ecosystem services provided by urban forests.

Abstract: Urban forests, composed of trees and other vegetation, are integral parts of urban ecosystems. Whether planted intentionally or left by default, urban forests appeared even in the earliest settlements. In urban areas, the constituent greenery provides a broad range of benefits, including opportunities for residents to have daily contact with nature, and to enjoy attractive landscapes and recreational activities (Grey and Deneke, 1986; Rowntree, 1986; Ulrich, 1986; Dwyer et al., 1992; Miller, 1997; Bolund and Hunhammar, 1999; Tyrvainen and Miettinen, 2000). In addition, vegetation in cities moderates microclimate extremes and reduces regional pollution (Botkin and Beveridge, 1997; Whitford et al., 2001). They contribute to an improved quality of urban life in many ways, even though these functions are often taken for granted by the public and some city authorities. The environmental benefits and natural functions provided by urban forests can be interpreted as ecosystem services, which are defined as benefits that the human population can derive, directly or indirectly, from ecosystem functions (Costanza et al., 1997). The urban population must rely mainly on services derived from external ecosystems, such as food and energy. However, the diversified benefits generated by urban forests, which are limited in comparison with the amount of imported ecosystem services, could be more instrumental in solving local environmental problems. They could significantly improve the quality of urban life, and play a paramount role in stabilizing and sustaining urban ecosystems (Daily, 1997; Bolund and Hunhammar, 1999; Jensen et al., 2000). Such ecosystem services, however, are not very tangible and generally not well understood or appreciated. Recent studies have generated a wealth of scientific information on the magnitude of their benefits. A more direct interpretation of these benefits for laypersons could promote their preservation and enhancement. A useful approach is to quantify these natural services, and then follow with a valuation of these nonmarket and noncommodity goods. The results could be translated into the universal language of monetary units, and be compared with alternatives to facilitate decision making related to natural resources or the environment. Valuation is inseparable from the choices and decisions humans have to make about ecosystems (Bingham et al., 1995; Costanza et al., 1997; Barbier et al., 1998; Costanza, 2000). Some studies have attempted to quantify the ecosystem services generated by urban

Opportunities and Alternatives for Enhancing Urban Forests in Compact Cities in Developing Countries

Abstract: That cities need to be greened is almost a foregone conclusion, if not de rigueur, for any plans for urban development or redevelopment. A green city is an ideal with a universal appeal that traverses temporal, spatial, and cultural divides (Hestmark, 2000). For many people, the greening of urbanized areas conjures up a deep innate desire to connect with the natural world and its diversified assemblages of organisms. It is natural for people to harbor a psychological and emotional attachment to beautiful natural objects, such as admirable amenity vegetation (Kaplan, 1984; Ulrich, 1986). Different socioeconomic strata develop similar levels of appreciation and preference for urban nature (Kuo et al., 1998). Urban greening entails introducing natural elements into the largely cultural fabric of cities. The fundamental requirement is the provision of planting spaces by design, or leaving such spaces unpaved by default. Greening is realized to different degrees in cities, and the quality and amount of green space is dictated by fashion, and so subject to changing contemporaneous societal attitudes and political will (Mumford, 1961; Attorre et al., 2000). Nature and culture make an enigmatic pair in relation to the history of urbanization. It is from nature that humans obtained sustenance and inspiration to develop our culture. Yet upon acquiring culture, in characteristic human fashion, we unthinkingly began to damage and reject nature (Jim, 2002a). Most cities customarily are dominated by cultural artifacts that overshadow nature, and in some places nature is thoroughly eradicated. Subconsciously and subliminally, humans need nature for a balanced physical and mental development (see the biophilia concept of Wilson, 1984). Yet consciously or unconsciously, we create conditions in cities that are often inhospitable to plant growth. Different cities, due to inherent natural biota and topography, and their development and redevelopment history, have engendered urban forms that can either accommodate or constrain vegetation growth. The most intense human-nature interactions and conflicts occur in cities, and densely populated, compact cities are particularly deprived of greenery. In recent years, especially in some developing cities, past excesses and paradoxical attitudes were moderated. We have renewed our partnership with nature and relearned to embrace the notable emblems of nature, such as amenity vegetation, in our attempts to reestablish our tenuous psychological link with nature.

Urban Biogeographical Analysis of Spontaneous Tree Growth on Stone Retaining Walls

Abstract: Stone retaining walls in urban Hong Kong provided vertical habitats for spontaneous colonization by a diversified humid-tropical flora with large trees. A citywide survey assessed wall and tree characteristics to understand wall-tree relationships and identify conservation candidates. Nonparametric correlations were computed between 28 wall attributes versus tree count, tree biomass, and species-vegetation factors. Most of the 245 walls, with 1275 trees, were in residential areas. Moraceae dominated the 30 tree species, predominantly genus Ficus, and especially F. microcarpa. Natives formed the overwhelming majority, largely with pioneer and ruderal traits. The positive effect of adjacent built-up land use and negative effect of wall exposure indicated sheltering from wind could facilitate tree growth. Wall height was a key determinant as taller walls furnished more surfaces free from human disturbance and conducive to seed deposition by frugivorous birds and bats. Stone width offered more horizontal micr...

Multipurpose census methodology to assess urban forest structure in Hong Kong.

Abstract: Surveys of urban forests in the compact city environment of Hong Kong were initiated in 1985 and regularly updated thereafter. Roadside trees were evaluated first in a tree census and reported in this article followed by urban parks, public housing estates, and special habitats such as old stone walls or special specimens such as heritage trees. The survey method aimed at collecting comprehensive data to echo both tree conditions and tree-environmental interactions. Detailed information was gleaned, with the help of well-trained assistants, on tree sites, tree growing space, tree structure, and tree defects and disorders. A field record form was designed, pilot-tested, and refined to solicit responses to multiple choices or direct measurements to minimize subjectivity and errors in data recording and entry. The study also identified potential planting sites, registering suitability for tree growth, site characteristics, and dimensions. Data fields were designed to be quantitative or convertible to ordinal ranks to facilitate statistical analysis. Locations of trees and planting sites were marked on large-scale maps to permit spatial analysis. Besides statistical analysis, community ecology attributes and custom-designed indices were used to assess urban forest structure. The multipurpose method could be appropriately adjusted for use in other compact city areas.

Variations of the Treescape in Relation to Urban Development in a Chinese City: The Case of Nanjing∗

Abstract: Urban trees, as prominent and pertinent landscape elements of cities, are increasingly studied by both practitioners and academics. Trees in Chinese cities have hitherto received little detailed analysis from the viewpoint of urban forestry or landscape analysis. This study attempts a comprehensive evaluation of the tree population in Nanjing, focusing on the association between urban development and treescape attributes. Six districts, covering the main built-up area of 130 km2, formed the study area. Nine land-use types with varied urban morphology and three urban zones with different development history were identified, within which subareas and trees were sampled for field study of tree dimensions, tree performance, and site characteristics. Statistical analyses on the 6,527 surveyed trees verify that tree performance is significantly associated with land use, site condition, and related human activities. Treescape is associated with housing ownership, town planning, and the history of urban ...

Assessing Natural and Cultural Determinants of Urban Forest Quality in Nanjing (China)

Abstract: This study assessed underlying natural and cultural determinants of tree health and ways to improve urban forest performance in compact Nanjing city. Two groups of factors were investigated: (1) habitat conditions, including planting site, ground-cover, land cover, and district; and (2) tree traits, including species provenance and seasonality, and tree dimensions. A stratified sampling strategy selected 6351 trees for detailed assessment. The data were analyzed by multivariate logistic regressions. Institutional, park-garden and industrial trees with more open-space sites with vegetated ground-cover performed better than roadside and residential ones. Poor trees in confined residential sites deviated from those in other cities. Park-garden sites did not always nurture meritorious, large and diversified trees. District differentiation in tree performance was related to land cover. Exotic and evergreen species grew better than indigenous and deciduous, offering hints on species-habitat matching. Detailed f...