Vulnerability of baobab (Adansonia digitata L.) to human disturbances and climate change in western Tigray, Ethiopia: Conservation concerns and priorities

The increasing rate of land use intensification and the rising evidence of climate change impacts raise concerns about the viability of valued non-timber forest product (NTFP)-providing trees. This calls for the assessment of the current status and future trajectories of their populations. Using population data collected from three land-use types (e.g., grazing lands, riverine areas and natural forest) in western Tigray, we evaluated the vulnerability of the multipurpose baobab tree (Adansonia digitata L.) to human disturbances and climate change. The study was based on the premises that integrating ecological science with modeling tools and local knowledge would enhance the overall effectiveness of conservation strategies and community support. Therefore, based on field-based inventory, ecological niche modeling and a socioeconomic study, we characterized and mapped baobab current and future population distribution and documented local knowledge on the uses and management of the species. The characterization of the population structure showed that baobab stands were denser with larger-sized and taller trees in riverine areas and natural forest compared to grazing lands, suggesting adverse effects of human disturbances on its populations. Moreover, positively skewed size-class distributions with negative slopes in all land-use types indicated a low recruitment of juvenile trees to the adult stage. Climate change simulations using Maximum Entropy Algorithm (Maxent) revealed that future temperature increases would lead to significant reductions (41–100%) in baobab suitable habitats due to range contraction. The intensive harvesting of baobab leaves, branches and bark and lack of conversation practices as indicated by local communities, in combination with the risk of local extinction under future climate warming constitute serious threats for the viability of the species in western Tigray. The results suggest immediate interventions, such as planting baobab at up to 65 m higher in altitude, designing appropriate leaf and bark harvest strategies and protecting seedlings from livestock, will help guarantee the persistence of the species populations.