Perpustakaan Digital ITB

Tropical forests provide a vital role in regulating ecosystem services by maintaining dynamic balance of hydrological and carbon cycles through carbon sequestration and water provision. However, these services are increasingly disrupted by deforestation, land use change, and climate variability. West Sumatra Province, Indonesia, represents this challenge, having lost significant forest cover over the past two decades, in parallel with rising CO? emissions and more than half of the province classified as low in water provision potential. This study assesses how different forest types influence carbon sequestration and water provision, evaluate the key driving factors, and analyse the interconnections between the two services in terms of synergies and trade-offs. The research applied a mixed methological framework using the Carnegie-Ames-Stanford Approach (CASA) model for quantifying carbon sequestration through Net Primary Productivity (NPP) of forest ecosystems and the InVEST Annual Water Yield model for estimating water provision. The analysis spanned the period of 2003–2023 and covered seven forest types: primary and secondary dryland forests, primary and secondary mangrove forests, primary and secondary swamp forests, and plantation forests. Results show forested areas declined by approximately 14% due to cropland and industrial plantation expansion alongside significant reduction of carbon sequestration reflected by NPP. Total carbon sequestration of forests peaked in 2008 but fell by 64% in 2013 and continued to decline, resulting in a deficit of 11 million tons of CO? sequestration required to balance emissions in 2023 which equivalent to around 8.7 km² of plantation forests. Conversely, water provision remained relatively stable with only minor fluctuations which interpreted to a weak relationship with changes in carbon sequestration. Although no outright water shortages were identified, water availability was only moderate in dryland forests as the largest occupancy. Correlation analyses identified solar radiation and photosynthetically active radiation as the principal determinants of carbon sequestration, while precipitation and reference evapotranspiration most strongly influenced water provision. The findings also indicated that climate conditions had the greatest impact on carbon sequestration, but forest type was the primary factor of water provision. Swamp and mangrove forests provided the greatest synergiesiii demonstrating high efficiency in both carbon sequestration and water provision, but the productivity level declined over time as the impact of deforestation. Plantation forests were effective in sequestering carbon but limited in providing water provision reflecting their high-water demand. Dryland forests, while spatially dominant, had low potential on both services for the primary forest and only supported to water provision for the secondary forest. Therefore, forest management strategies should be developed to optimize both carbon sequestration and water provision by considering site-specific characteristics, species composition, and management practices.