Enriching Urban Biodiversity by Nurturing Native Woodland

Abstract

Nature can be preserved or created in cities. Hong Kong has an ultra-compact urban fabric characterized by meagre provision of urban green infrastructure, calling for mitigation by high-quality nature-in-city ingredients. Besides routine urban parks, some sites can accommodate more natural vegetation with a complex biomass structure and high leaf area index. As an alternative, the urban woodland could insert nature into the urban matrix to maximize ecosystem services and biodiversity. The eco-design was based on urban ecological concepts. It imitated the pertinent traits of the tropical native woodland, including species diversity, tree density, vegetation cover, closed canopy, vertical stratification, and interlocking crowns. Criteria were established to identify native tree species. The constituent ecosystem processes were fostered, such as energy flux, nutrient cycling and food-web formation, creating a closely-knitted and self-sustaining ecological community. The soil mix was formulated to emulate the composition and properties of local woodland soil. Environmental benefits such as urban biodiversity enhancement, cooling, air cleansing, noise abatement and groundwater recharge would improve with progressive woodland ecosystem succession. Measures were developed to overcome problems in acquiring native trees from the region’s nurseries. The knowledge exchange project furnished the experience for similar projects in tropical cities.