Negative impacts of Russian-Ukrainian war on forests are overshadowed by climate-driven vegetation greening

Since the onset of the Russian-Ukrainian war in 2022, the negative impact on ecological environment has received widespread attention, but the mechanisms by which the coupling of war intensity and climatic factors drives forest vegetation dynamics remain unclear. This study developed the War Intensity Index (WI) using conflict point density and classified Ukraine into no war, weak war, and strong war. Utilizing Sentinel datasets through Google Earth Engine, we analyzed the multi-scale spatial-temporal changes in forest Normalized Difference Vegetation Index (NDVI) during the post-war (2022–2024) period compared to pre-war (2019–2021) across the growing season (April–October). We further employed geodetector, a valuable statistical tool for detecting the driving ability of various elements, to investigate the driving effects of four climatic factors. The results indicated that: 1) Overall forest NDVI in Ukraine increased by 5.29 %, but the average NDVI change rate decreased with increasing war intensity (6.20 % > 3.95 % > 1.54 %). 2) Precipitation and temperature were the dominant factors of NDVI, while WI exhibited weak independent explanatory power. The interactions between WI and climatic factors were stronger than WI alone but remained weaker than those among climatic factors. 3) The variability of climatic factors with longitude was more pronounced in strong war than weak war. These findings suggested that the war had a negative impact on forests in specific regions of Ukraine, but was overshadowed by climate-driven greening. The stronger explanatory power of climatic factors in strong war compared to weak war may be attributed to geographical differences in their spatial distribution.