Satellite vs. Ground-Based Estimates of Burned Area in Greece: Validation of MODIS MCD64A1 Data Using Fire Service Reports

Abstract. Wildfires are among the most impactful natural disasters, severely affecting ecosystems, communities, and economies. Their frequency and intensity are increasing across many world regions due to human activities and climate change. In Greece, an increasing trend in catastrophic wildfires poses a major threat to ecological balance and society making effective prevention paramount. Monitoring and modelling wildfires are crucial steps for being able to predict and prevent their consequences, and therefore data of adequate quality is needed. This study compares burned area estimates derived from NASA’s MODIS MCD64A1 global product with the Hellenic Fire Service (HFS) records for 2002–2023. The analysis examines spatial and temporal agreement between these widely used datasets at national and regional scales, and evaluates how discrepancies vary across land cover types. The results of the comparison show strong interannual agreement (R² > 0.87 in five of seven regions), with agreement further strengthening in recent years, as indicated by a mean absolute deviation of only 5% over 2021–2023. At the national scale, MODIS overestimates burned area by 41% overall, but this difference drops to 12% when only natural land covers are considered, mainly reflecting MODIS detection of cropland burning in Thessaly-Central Greece, and Macedonia-Thrace, which is not included in the HFS data. These seasonal differences are most pronounced during September and October in northern and central Greece, whereas lower MODIS burned area estimates characterize Crete and the Aegean islands. These findings highlight the complementary value of satellite and ground-based fire records for the interpretation and use of MODIS burned area products in Mediterranean fire monitoring.