Future climatically stable habitat of a vulnerable medicinal tree, Warburgia salutaris (Pepper-bark tree), overlaps with some protected areas in southern Africa

Abstract

Climate change will affect the distribution of medicinal plant species in sub-Saharan Africa, with potential negative consequences to especially rural and poor communities that depend on them for traditional medicines. The aim of the study was to determine future climatically stable habitat of Warburgia salutaris, a commonly used vulnerable medicinal plant species. An ensemble species distribution model (SDM) was built from eight algorithms and used to estimate the current and future distributions of the species. Six environmental variables and 146 occurrence records were used to calibrate individual SDMs before combining them into the ensemble SDM. The ensemble SDM was projected to 2041‒2060 and 2081‒2100 under two shared socioeconomic pathways (SSPs), namely SSP2-4.5 and SSP5-8.5. The projections were made under three general circulation models (GCMs), which were CanESM5, IPSL-CM6A-LR and MIROC6. Results show that the current suitable habitat of the species occurs in South Africa, Eswatini, Malawi, Mozambique and Zimbabwe. Under both time periods and SSPs, the suitable habitat of the species will markedly contract, especially under SSP5-8.5 in 2081‒2100 (CanESM5 = -79 %, IPSL-CM6A-LR = -87 %, MIROC6 = -71 %). Climate refuges that overlap with the future suitable habitat of W. salutaris were identified in protected areas (PAs), such as Malalotja Nature Reserve (Eswatini), Itala Nature Reserve (South Africa), and Nyanga National Park (Zimbabwe). The climate refuges in PAs may be priority areas to introduce the species.