Pressure on urban trees in Hong Kong: Pervasive problem and possible amelioration

Abstract

Urban development in Hong Kong has left a tightly-packed town plan with little intervening space for trees. Limitation of available land in relation to a large population underscores the fundamental constraint. The planting tradition adopted since the founding of the city some 150 years ago was implemented when the urban matrix was still relatively porous. Recent intensification of development has imposed increasing pressure on the meagre tree stock. Pervasive shortage of plantable space is aggravated by its poor quality which deteriorates with land-use changes. Setting back building lots for amenity planting, if applied on a large scale, should bring permeation of greenery. Existing roadside and offroad habitats, including areas containing high-calibre specimen trees and woodland plots, are often lost to vehicular-traffic infrastructure and other community needs. Proliferation of underground utilities restricts chances for roadside trees. Frequent trenching to repair buried services and recently to install a territory-wide cable-television and communication network brings havoc to roots, and premature decline. Soils at planting sites, especially at roadsides, are beset by problems such as: shallowness, too many boulders and stones, excessively coarse texture, compaction, nutrient deficiency, alkaline reaction and pollution. Outmoded nursery practice, ineffective quality control, and lack of research on suitable cultivars have allowed widespread use of substandard planting materials. Whereas trained arboriculturists are employed by the government to look after public trees, the shortage of expertise and professionalism in the private sector degrades the quality of tree work. The poor match between species selection and planting-site conditions, and a large backlog of surgery work need to be addressed. Preservation efforts are not commensurate with the scarcity of outstanding trees, with worthwhile ones continually lost due mainly to construction activities. Transplanting, the protection of champion trees and those dwelling on old stone walls should be more earnestly adopted measures. The community needs to modify its rather apathetic attitude towards urban trees and furnish effective statutory measures to plan, plant and preserve trees to effect long-term improvement.