Tree species for urban parks and roadside based on carbon storage, sequestration and maintenance in Iskandar Malaysia

Abstract

Urbanisation triggers high carbon emission and exacerbates global warming. Trees play a significant role to tackle these problems as they provide vital ecosystem services including carbon storage and sequestration. However, trees vary in their ability to provide these services and there is little information on how actual carbon storage and sequestration by trees could be estimated particularly in the tropical region. Furthermore, trees with low endurance rate and unhealthy ones can be harmful to properties and human lives as well as overhanging branches can obscure streetlights, signs and traffic signals and affect road users’ vision in the vicinity. These situations contribute to the cumulative maintenance burden to the local authority. This research aims to select types of urban tree species suitable for urban parks and roadsides based on their capacity to store and sequester carbon, and ease of maintenance in Iskandar Malaysia. Field data of 2,245 urban trees were collected from two local authorities, namely Johor Bahru City Council and Pasir Gudang Municipal Council. Allometric equations were used to estimate carbon storage and sequestration. The findings showed that Pterocarpus indicus, Alstonia angustifolia, Syzygium grande, Pongamia pinnata and Hopea odorata stored (2,019, 1,531, 615, 321 and 244 kg tree-1, respectively) and sequestered (78, 61, 30, 17 and 13 kg tree-1 year-1, respectively) the highest carbon in comparison to other species. In addition, a questionnaire survey was also conducted to gain detailed information about tree maintenance from professionals including urban planners, landscape architects and certified arborists. Results showed that Pongamia pinnata had the highest score of 94, followed by Syzygium grande (91), Alstonia angustifolia (90), Hopea odorata (90) and Pterocarpus indicus (83). Hence, these are the most suitable tree species to be planted at urban parks and roadsides because of their high capacity to store and sequester carbon and their low maintenance as shown by the local authorities. This study has shown ways to assess the actual role of urban trees in reducing carbon and mitigate climate change as well as reduce the burden of maintenance for local authorities and decision makers. The implication would be better management plans for urban forestry in Malaysia for the future.