Lake Ossa in Cameroon is a large wildlife reserve well-known for its important population of African manatee, which is listed as Vulnerable on the IUCN Red List. It is also an important source of food and income for the 400 local fisher households who live in the area. Since 2017, a large increase of an invasive aquatic species called Giant salvinia (Salvinia molesta) has been killing the native plants that are food for the manatees. Because Salvinia doubles in size every 7 to 10 days, it creates a dense cover that depletes the lake’s oxygen, killing the manatees main food plant and impacting the fish population and local ecosystem. Estimations now indicate that there are less than 50 manatees remaining.
This is a conservation emergency. If nothing is done to control the invasive plant, the lake, the manatees and the remaining biodiversity could disappear. This would also have a large impact on the local population, who depend on the lake for their livelihood.
The project has chosen a biological and environmentally safe approach to reducing the Giant salvinia. They will introduce Salvinia weevils, a type of beetle, which has previously been used to remove Giant salvinia successfully in other African countries. The team will test the release of the beetles in two test areas and, if successful, will scale up the project to the remaining areas of the lake impacted by Giant Salvinia.
The project is liaising closely with the local community, who are greatly impacted by the situation as fish stocks have reduced and fishing has become difficult. The local population will be involved in the mechanical removal of the Giant salvinia. Furthermore, the project plans to engage local youth by training them in how to create compost from the Giant salvinia collected.
The project aims to reduce the Giant salvinia by 50% by November 2020. This will not only directly benefit the 400 fishermen who rely on the lake for fishing, but also the many women who sell fish from the lake. It will also help the lake recover, protecting the biodiversity, including the African manatees.