Dynamique des espaces forestiers et ses effets sur les espèces d’arbres endémiques et menacées à la périphérie ouest de Yaoundé (Cameroun)

Abstract

With the advancement of technology and the population boom, human populations, to improve their living conditions, are increasingly occupying natural spaces. The city of Yaoundé, for example, was from the start located in the middle of a forest-savannah mosaic area with a biodiversity rich in endemic species, particularly woody ones such as Monodera zenkeri Engl., Pristimera biholongi Hallé and Pristimera breteleri N Hallé among others. The city has evolved, expanded and has gradually occupied its margins. This has resulted in the transformation of space that was previously forest into urban and peri-urban space, causing the loss of animal and plant biodiversity. This study aims at evaluating the reactions of forest areas and the endemic and endangered woody species that compose them to this situation of peri - urbanization which is more still uncontrolled. Diachronic analyses were carried out using Landsat 7 ETM + satellite images through mapping and quantitative analysis of land use changes. Surveys and floristic inventories helped to evaluate the effects of the spatial extension of the city of Yaoundé on peripheral forest areas and plant species. The analyses showed that the forest areas of Yaoundé have indeed undergone a regressive dynamic from 2000 to 2022, with a net loss of 70.56% of forest area (reducing from 13820.75ha to 4068.68ha) for the benefit of buildings and farms which have respectively increased by 72.28% and 40.45%. This loss of forest area during this period nevertheless presents a double pattern. From 2000 in 2016, the forest decreased by 72.54%, but it saw a clear increase from 2016 to 2022 (+7.22%). The state and dynamics of forest fragmentation was also quantified for this period. The surveyed populations deplore the disappearance of some tree species, which provided them with services, of which 30.43% are threatened with extinction according to the red list of the International Union for Conservation of Nature (IUCN) such as Mahogany, Bubinga and Moabi among others. The conservation of the rich endemic and endangered biodiversity of the hills of Yaoundé requires the strict application of measures long proposed by researchers such as reforestation and the creation of biodiversity reserves. This must involve the total commitment of the state, local authorities and local populations.