The conflict and pest nexus drives the catastrophic decline of cactus pear ecosystem services in the Horn of Africa

The cactus pear ( Opuntia ficus-indica (L.) Mill.), or Beles, is a multi-purpose succulent vital for ecological and socio-economic survival in the arid highlands of Ethiopia and Eritrea, serving as a primary carbon sink, soil conservation tool, and seasonal source of food security and dry-season livestock forage. To systematically evaluate the dual impacts of the invasive carmine cochineal insect ( Dactylopius coccus ) and the Tigray War (2020–2022) on cactus pear ecosystems in the Horn of Africa, while assessing sustainable Integrated Pest Management (IPM) frameworks. Following PRISMA guidelines, a systematic review analyzed 170 core studies selected from 3,159 initial records across Scopus, Google Scholar, and Web of Science, utilizing cross-verification triangulation of biophysical data, socio-ecological coupling, and IPM efficacy trials. The total disruption of community-led control systems during the Tigray War triggered a conflict-pest nexus, accelerating regional infestations past 120,000 hectares by 2026, driving down ecological health indices, and causing severe humanitarian distress. Conversely, localized botanical bio-pesticides such as aqueous Tree Tobacco ( Nicotiana glauca ) mixed with soap and methanol extractions of Solanum linnaeanum achieved pest mortality rates exceeding 90% and 99.3%, respectively. The convergence of armed conflict and biological invasion has induced a terminal decline in regional Opuntia ecosystems, threatening to transform vital carbon sinks into atmospheric carbon sources. Halting this collapse requires immediate regional stability, cross-border scientific collaboration, tissue-culture propagation of clean stocks, and the large-scale deployment of conflict-resilient IPM practices.