Evaluation of Climate and Land Use Change impacts on ecosystem services that support Food Security in Siem Reap Province, Cambodia

Nutrient delivery and water yield are key ecosystem functions that impact food security. Climate and Land use Land cover (LULC) changes are the main driving factors that affect these water related ecosystem services. By recognizing the value of ecosystem services, the efforts to manage ecosystem services have increased. One such tool to help manage ecosystem services is the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, a new but powerful ecosystem service model. However, the InVEST model still requires testing in various geographic regions. This study assessed the performance of the InVEST water yield and nutrient delivery models in Siem Reap Province, Cambodia. The climate scenarios were projected using CMIP6 for two pathways namely SSP2-4.5 and SSP5-8.5. Past, Present, and future scenarios were developed for two InVEST models including Annual water yield (AWY) and Nutrient delivery ratio (NDR) to evaluate the impacts of Climate change and LULC. In the past and present, water yield dropped by 52-69% from 2018 to 2022, with nitrogen and phosphorus exports rising by 627 and 186 tons, respectively. In future scenarios, from SSP2-4.5 to SSP5-8.5, water yield in Near Future (NF) decreased by 6-8%, while in Mid Future (MF), it increased by 10-12%, and in Far Future (FF), it decreased by 1-2%. Future nutrient delivery showed minor changes, nitrogen exports dropped by 0.42 tons for NF and increased slightly by 3 tons for MF, also increasing by 2.4 tons for FF. Phosphorus exports decreased by 0.07 tons for NF and increased slightly by 0.8 tons for MF, with a 0.7-ton increase for FF in Siem Reap province. Climate change primarily impacts water yield, with LULC governing nutrient delivery. Expanding croplands and urban areas heighten pollutants and threaten food security, while diminishing forests and vegetation reduce water yield, intensifying challenges in securing a stable food supply in Siem reap province of Cambodia.