Spatial patterns and policy implications of invasive flora in the Horn of Africa

Invasive plants are fast-spreading species that pose serious and often irreversible threats to native biodiversity. This study presents a regional-scale analysis of the elevational distribution of invasive plant species, their relationship with road proximity, and their presence across different land uses. Data were synthesized following the Reporting Standards for Systematic Evidence Syntheses protocol using multiple databases, including Web of Science, Scopus, and Google Scholar. A total of 250 invasive species distributed in 63 families were documented. The dominant families were Fabaceae (16.8%), Asteraceae (9.6%) and Poaceae (6.4%). Herb was the predominant growth form, accounting for 47.6%, while liana/shrub was the least represented at just 1.2%. The native range of the species were predominantly Neotropical (30%) and African (23.1%). About 5.1% of the species were either helophytes or aquatic. Furthermore, nine (3.6%) of them were either hemiparasites or holoparasites. Kenya and Ethiopia had the highest records of invasive plant species, while Djibouti and Eritrea had the lowest. Invasive species declined significantly with increasing elevation (P < 0.001) and were declining further from roads (P < 0.008). Most occurrences were recorded in cultivated areas (33.51%), shrublands (23.1%), and urban or built-up regions (16.66%). The study highlights four main factors: (1) lack of reported protocols for assessing impact and classifying invasiveness, (2) potential 'snowball effect' in reporting, (3) paucity of data on invasive species and (4) lack of proper definition of operational terms. As a result, the number of invasive species reported in this study may not accurately represent the true extent in the region. To address this, it is recommended to develop or adopt region-specific, expert-led assessment tools and establish a collaborative framework for managing invasive plant species.