Many countries in Africa are affected by Invasive Alien Species (IAS). In 2004, the IUCN–World Conservation Union identified 81 IAS in South Africa, 49 in Mauritius, 37 in Algeria and Madagascar, 35 in Kenya, 28 in Egypt, 26 in Ghana and Zimbabwe, and 22 in Ethiopia. However, very little is known about IAS in Nigeria, with most technical reports and literature reporting fewer than 10 invasive plants in the country. Aside from plant invaders, ''Rattus rattus'' and Avian influenza virus were also considered IAS in Nigeria. The initial entry of IAS into Nigeria was mainly through exotic plant introductions by the colonial rulers either for forest tree plantations or for ornamental purposes. The entry of exotic plants into Nigeria during the post-independence era was encouraged by increasing economic activity, the commencement of commercial oil explorations, the introduction through ships, and the introduction of ornamental plants by commercial floriculturists.