Quantifying deforestation and its thermal association in a greening Singapore

Abstract Deforestation—the conversion of forested land to other land uses—has been widely examined at global and regional scales, yet its thermal implications within highly urbanized tropical cities remain insufficiently understood. Singapore, a densely developed city-state with limited land and fragmented forest remnants, provides a unique context where forest clearance is often followed by rapid land surface transformation associated with urban development. This study investigates how deforestation in Singapore has altered urban land surface temperature (LST) patterns between 2017 and 2024, and whether these thermal responses vary across daytime and nighttime conditions. It quantifies forest loss in Singapore between 2017 and 2024 using normalized difference vegetation index differencing and evaluates its thermal effects using Moderate Resolution Imaging Spectroradiometer LST data. Two complementary analytical perspectives are adopted: a time-aggregated analysis across 2017–2024 to characterize average post-deforestation thermal behaviour, and a temporal before–after control–intervention (BACI) comparisons between 2017 and 2024 to examine temporal evolution. Results reveal major clusters of vegetation decline, totalling approximately 2145.5 ha, or 3.1% of Singapore’s land area. Across both analytical perspectives, deforested areas exhibit higher daytime LST than non-deforested areas. However, with only two time periods, the parallel trends assumption underlying BACI cannot be tested; thus, this study adopts the conservative assumption of control group stability, under which the observed nighttime divergence suggests the BACI comparison may not support causal inference. These findings highlight both the thermal implications of forest loss and the analytical complexities of evaluating land-cover change in a dynamically greening city.