Floristic composition and vegetation dynamics in wadi Al-Dabab, Central Highlands of Yemen, over the last 25 years

Wadi Al-Dabab, located within the central highlands of Yemen, represents an ecologically important component of the Arabian Peninsula’s arid mountain ecosystems. This study investigated its floristic composition and long-term vegetation dynamics through comprehensive field surveys integrated with multi-temporal NDVI analysis over a 25-year period (2000–2024). The floristic survey documented 354 vascular plant species representing 233 genera and 66 families, including 21 monotypic families, eight endemic species, and 21 near-endemic taxa, highlighting the conservation and phytogeographical significance of the study area. The occurrence of pteridophytes, endemic succulents, and Afro-Arabian floristic elements reflects the diversity of habitats and microhabitats within the Yemeni central highlands and the transitional phytogeographical position of the region between paleotropical lowland and Afro-montane floristic zones. Five confirmed invasive alien species were recorded, together with several disturbance-associated taxa occurring particularly along modified drainage channels and cultivated margins. Multi-temporal NDVI analysis revealed an overall increase in vegetation cover between 2000 and 2024, characterized by a decline in sparse vegetation and increases in moderate and cultivated vegetation. However, this apparent greening should not necessarily be interpreted as ecological recovery, as it may reflect interacting effects of altered water availability and drainage patterns, agricultural expansion, anthropogenic disturbance, biological invasion, and potentially regional climatic variability. The findings demonstrate that remotely sensed increases in vegetation cover alone may provide an incomplete indication of ecosystem condition and emphasize the importance of integrating remote sensing with field-based floristic assessments for effective biodiversity conservation and long-term monitoring in arid mountain ecosystems.