Assessing the Threat: Risk Assessment of Non-Native Plant Pests Likely to Threaten Livelihoods if Introduced in Rwanda

The lack of information on potential invasions by alien species is a major contributor to the prevalence of invasions in sub-Saharan Africa. A rapid risk assessment was conducted to prioritise high-risk species not yet reported in Rwanda that could be introduced and become invasive. The CABI Horizon Scanning Tool identified 9,155 species (including 641 invasive species) that have not yet been reported in Rwanda but are present in other likely trading countries. The 9,155 species comprised 5,860 arthropods, 319 bacteria, 174 chromists, 1,762 fungi, 34 molluscs, 261 nematodes, 10 protists, 33 viroids, and 712 viruses. The 9,155 species were reduced to 1,972 (392 arthropods, 147 bacteria, 79 chromists, 784 fungi, 21 molluscs, 134 nematodes, nine protists, 18 viroids, and 388 viruses) identified as affecting major crops grown in Rwanda. An additional 127, which included 14 from the list of regulated pests, four deemed of phytosanitary concern, 18 identified in other risk assessment studies, and species vectored by (14) or vectors (77) of assessed species were added, raising the total to 2,099. Of the 2,099, 1,081 were reported outside Africa and 1,018 within Africa, with 381 reported in a neighbouring country. The 2,099 (including 212 reported invasives) comprised 468 arthropods, 152 bacteria (including 24 phytoplasmas), 79 chromists, 810 fungi, 21 molluscs, 136 nematodes, four plants, nine protists, 18 viroids, and 402 viruses. The highest risk score was 175, recorded for 185 species, and the lowest was two, recorded for 22 species. The assessed species could be introduced as contaminants (1,385), stowaways (211), or via multiple pathways (503). A no-action management option was suggested for 1,270 species, surveillance for 356, and regulation for 563 (521 quarantine and 42 regulated non-quarantine). Additional actions included developing a contingency plan, conducting publicity, managing the pest by industry, and conducting research, which were suggested for 18, 21, 4, and 20, respectively. This study proposes a new list of regulated pests and also aligns Rwanda with Target 6 of the Kunming-Montreal Global Biodiversity Framework, which aims to reduce the impacts of IAS on biodiversity and ecosystem services.