Tree density and diversity in Hong Kong’s public housing estates: From provision injustice to socio-ecological inclusiveness

Abstract

Socio-economically underprivileged urban communities might suffer from restricted access to urban forests. Environmental injustice research on urban greenery in Asian cities is lacking. Public housing estates in Hong Kong, accommodating low-income households and over half of the 7.45 million population, were investigated for injustice in tree provision. Two clustering schemes used socio-economic and ecological characteristics to classify 93 estates. Factor analysis of 14 socio-economic variables identified four factors related to deprivation, namely ageing population, overcrowding, working poor with high academic qualifications, and marginalised language minorities. Principal component analysis of six ecological indices returned two components related to tree density and diversity. Estates with ageing population and more language minorities had the least urban tree provision indicated by low tree density. However, estates beset by overcrowding and working poor with high academic qualifications had the highest tree diversity indicated by the highest species evenness. Estates with the lowest language minorities had the densest but the least diverse tree stands. An alternative clustering scheme delineating ecological clusters substantiated the observed urban-tree patterns with respect to socio-economic characteristics. Estates with higher tree density and diversity had higher population density indicating overcrowding. Estates with lower tree density and diversity had more ageing population language minorities. The results highlighted the need to modify tree provision in response to changing estate demographics. From the research findings, five strategies were developed to adjust the amount and composition of the estate tree stocks to achieve greater social inclusion.