Greening improvement scenarios for assessing the potential of urban carbon sinks and runoff reduction

Abstract

Two scenarios (SC1 and SC2) were developed using i-Tree Eco software to estimate carbon dioxide absorption (CO<inf>2abs</inf>) by trees and avoided runoff (AR) in improved urban green areas (increasing the sizes of these areas and planting additional trees) in Thailand for a 50-year forecast (2024–2074). Tree annual mortality rates of 1 and 3% were assigned to SC1 and SC2, respectively. The results indicated the high potential of the country’s green areas as urban C sinks if proper greening improvements are implemented. CO<inf>2abs</inf> in SC1 increased from 0.32 million metric tons-CO<inf>2</inf> equivalent (Mmt-CO<inf>2</inf>e) in 2024 to 9.24 Mmt-CO<inf>2</inf>e (a 2787.5% increase) in 2074 and is projected to increase beyond this year. In SC2, it increased from 0.32 Mmt-CO<inf>2</inf>e in 2024 to 3.66 Mmt-CO<inf>2</inf>e (a 1043.8% increase) in 2059 and is projected to gradually decline. The maximum AR (76.07 Mm³) was detected in SC1 at the end of the simulation period, but the peak AR (28.15 Mm³) in SC2 was detected in 2067, with a subsequent decline projected. Locally, CO<inf>2abs</inf> increased from the observed amounts (mainly not more than 5000 mt-CO<inf>2</inf>e) from 2019 to 2023 to more than 50,000 mt-CO<inf>2</inf>e in 65 (84.4%) of 77 provinces in Thailand in 2065.