Native tree species for urbanized and urbanizing landscapes: strategy for biodiversity conservation

Greening of urbanized and urbanizing landscapes in Asia Pacific region was characterized by extensive use of exotic tree species. Introductions of exotic or so-called alien tree species for economic (i.e. for timber and food) and environmental reasons had a very long history. Great similarity of exotic tree species can be observed in most countries of SEA. Many exotic species had completely adapted, naturalized already and did not cause economic and environmental harm. Moreover, they had contributed to restoration and rehabilitation of denuded forest lands, successful establishment of tree farms and plantations, augmentation of timber supply and greening of urban areas. Some exotic species, however, had been found to have: invasive characteristics; caused some economic and environmental damage; and, association with invasive, destructive insects. The need to rescue and secure threatened, endangered and near to extinction native tree species (indigenous and endemic) through conservation in their natural habitat, forest-based restoration and urban greening is now recognized. Native tree species form the very fabric of our surroundings, create our unique identity and are pride of the country. Floral diversity of most countries in the region offers huge opportunity for selection of potential species not only for rural but also for urban greening whether the aim is for economic production or for aesthetic and environmental enhancement. A lot of public, private institutions, groups and individuals have already taken the initiatives in promoting and using native species to ensure their perpetuity for the benefit of the future generations. Several requirements to further promote the use of native tree species include: research, aggressive information, education and communication program; government financial and technical support, establishment of sustained sources of seeds like seed production areas (SPAs) in natural forests and seed or clonal orchard by Department of Environment and Natural Resources, and private sectors; local government to have urban forestry unit and a comprehensive nationwide greening program.