Examining Vegetation Deterioration in the Carpathian Mountains Using Survival Analysis

Abstract

Vegetation condition is a key indicator of ecosystem stability and fire susceptibility in mountain landscapes. Using monthly Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) (2000-2024) for 223,811 vegetated H3 hexagons in the Carpathians, we applied survival analysis to quantify when sustained NDVI deterioration first occurs and how its timing varies with Natura 2000 protection and land cover. Amer defining a 2003-2008 mean NDVI baseline and identifying persistent deterioration as runs of negative anomalies during the growing season, we estimated Kaplan-Meier curves and log-rank tests. Across all countries, Natura 2000 sites showed higher survival probabilities and thus a lower hazard of persistent NDVI decline than non-protected areas, although the effect was dependent on land cover type and examined countries. Agricultural vegetation deteriorated later than forest and semi-natural vegetation. These time-to-deterioration metrics could provide additional insight to understand the drivers of vegetation decline in the Carpathians.