Ecosystem services from a tropical forest landscape in Southeast Asia : Assessing impacts of land-use and land-cover changes

Tropical forests are essential for global biodiversity, carbon storage, and hydrological regulation, yet accelerating land-use and land-cover change are rapidly eroding these functions across Southeast Asia. In Cambodia, forest conversion surrounding protected landscapes has intensified over recent decades, but its long-term ecological and economic consequences remain poorly quantified because few studies directly link field-based measurements of forest biodiversity with long-term land-cover change, ecosystem-service responses, and carbon value. This thesis aims to assess how land-cover change alters tropical forest biodiversity, ecosystem-service supply, and the economic value of forest carbon by integrating field measurements with satellite-based analysis in Cambodia’s protected forests. It combines field observations of forest structure, species diversity, functional traits, and soil condition with machine-learning-based land-cover mapping, time-series mapping of land-cover changes (1991–2021), hydrological modelling, and carbon stock and valuation frameworks relevant to forest carbon accounting. This integration allows consistent assessment of ecosystem changes across spatial and temporal scales. The results show that conversion from intact evergreen forest to regrowth forest and cashew plantations leads to persistent simplification of stand structure, reductions in species and functional trait diversity, and substantial reductions in aboveground biomass. These ecological changes lead to long-term declines in carbon storage and hydrological regulation, which are not compensated by forest regrowth over several decades. Regrowth forests exhibit intermediate conditions, whereas plantation systems provide only limited ecosystem services. When expressed in economic values, land-cover change results in lower biomass and carbon stocks in forests, reduces the opportunities for climate finance, and diminishes potential long-term revenues for both communities and governments. Overall, this thesis shows that land cover provides a central framework through which land-use decisions shape ecosystem functioning and what consequences this has for policy and management decisions, highlighting the critical importance of protecting intact forest.