The pollen grains content of lacustrine sediments allowed to trace the history of mountain biomes in Cameroon during the last 90 000 years. This study, conducted by French laboratories LOCEAN and LSCE of the IPSL with the National Herbarium of Cameroon, showed that tropical mountain forests are extremely vulnerable to climate change.
Because they have forms and ornamentations that are specific to most plant species and are remarkably preserved in sediments, pollen grains are powerful tools for reconstructing the vegetation of the past and understanding biodiversity.
Bambili Lake, located on the volcanic line of Cameroon at an altitude of 2273m, has provided a unique palynological sequence in tropical Africa, the first that accurately covers such a long period, ie most of the last climatic cycle. This sequence makes it possible to precisely follow the response of mountain biomes to extreme climatic, glacial and interglacial situations.
The study shows that Cameroon’s mountain forest biome has been extremely sensitive to climate change in contrast to lowland forests that appear to have been much more stable. Its area has varied considerably over time, in particular because of the large movements of its upper limit. This ecological instability has not been a hindrance to the exceptional biodiversity of the high mountains of Cameroon, but has instead favored it.
Anne-Marie Lézine, Kenji Izumi, Masa Kageyama, Gaston Achoundong (2019) A 90,000-year record of Afromontane forest responses to climate change, Science, doi: 10.1126/science.aav6821