Environmental Monitoring of Carbon Loss and Sequestration under Urban Expansion Pressure: A Case Study from Istanbul, Türkiye

Abstract Urban expansion in rapidly growing megacities significantly alters terrestrial carbon dynamics, often reducing carbon sequestration potential and increasing greenhouse gas emissions. This study assessed the impacts of land-use change on carbon stocks in Istanbul, Türkiye, between 2017 and 2024, using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model within a Geographic Information Systems (GIS) framework. Sentinel-2 satellite imagery and supervised classification identified six major land cover classes and quantified spatial-temporal transitions. Results revealed a 3.72% increase in built-up areas and declines in agricultural (–2.03%), forested (–0.31%), and rangeland (–0.19%) areas, leading to a net carbon loss of − 1,117,034.57 tC (approximately − 4.1 MtCO₂eq). Soil organic carbon represented the most vulnerable pool, accounting for 75.7% of total losses, particularly in agricultural lands. Aboveground and soil carbon losses in forested areas further emphasized the adverse impacts of deforestation and impervious surface expansion. The findings highlight the urgent need for stricter land-use regulations, conservation of ecological buffer zones, and integration of green infrastructure to enhance urban carbon management. The study demonstrates the applicability of the InVEST model for urban-scale carbon monitoring and as a decision-support tool for achieving carbon neutrality targets.