Global Ecology and Conservation (Jun 2023)
Impact of climate patterns, land-use types and exploitation on the population structure of Bombax costatum Pellegr. and Vuillet in West African semi-arid savannas
Abstract
Some multi-purpose woody species, although currently considered as “least concern” by the International Union for Conservation of Nature (IUCN), are undergoing several disturbances resulting from human overexploitation and changes in climate conditions and land-use types. The patterns of such disturbances are likely to vary across climate regions due to changes in socio-ecological context. However, they can strongly impair the long-term viability of species. Therefore, understanding the effects of such disturbances on populations of valuable species is essential for their sustainable management. This study examines the impact of climate regions, land-use types and exploitation (pruning and debarking) on the population ecology of Bombax costatum.Human exploitation indices (intensity of debarking and pruning) and ecological characteristics of the species (tree diameter, height, crown diameter and regeneration modes) were recorded in two contrasting climate regions (Sudanian and Sudano–Sahelian) and land-use types (protected area and unprotected area) in Burkina Faso. General linear models were used for data analysis.The results showed that at least two-thirds of individuals were debarked and pruned in the unprotected (66.17 ± 6.93%) and the protected area (73.61 ± 7.37%) of the Sudano–Sahelian climate region. Contrastingly, in the Sudanian climate region, 92.78 ± 3.89% of individuals were debarked and pruned in the unprotected area but only 15.56 ± 5.28% in the protected area. Although debarking was practised with low intensity (1–25%), pruning was severely and very severely practised (56–75% and 76–100%, respectively).The species displayed a similar tree diameter, crown diameter and total height between climate regions and land-use types except in the Sudanian unprotected area, where the highest values were observed. The climate regions did not significantly influence the densities of adult or juvenile individuals (p = 0.099). On the contrary, between protected to unprotected areas, there was an increase in the density of adults (p = 0.0080) and a decrease in that of juveniles (p = 0.024). The diameter size classes distribution showed an unstable population in the protected area of the Sudano–Sahelian climate region and the unprotected area of the Sudanian climate region indicating strong anthropogenic pressures. More than 60% of the regenerations were from root suckers, indicating that the species experienced poor sexual regeneration.In synthesis, our results showed that land use impacts varied between the two climate regions and that protected areas are not always a suitable place for the conservation of multi-purpose species. The results also suggested that B. costatum is threatened in West African semi-arid savanna and that there is an urgent need to implement proper management of the species and update its global conservation status.
