Endemic darling or global change menace? A review of the woody encroacher Leucosidea sericea on the eastern Great Escarpment of southern Africa

Abstract

Rapid woody encroachment by native species is transforming grasslands and savannas across the world. The drivers of this encroachment are diverse, complex, and potentially interlinked, including fire exclusion, overgrazing, plant-plant interactions, extirpation of local mega-fauna, carbon fertilisation, and global warming. In southern Africa, woody encroachment is a well-studied phenomenon that has primarily been documented in savanna and woodland systems, but there has been little work on woody encroachment in southern African mountain systems. These host much of the region's exceptional endemism and provide most of the region's water, and bush encroachment may have serious impacts on both. Leucosidea sericea Eckl. & Zeyh., is a Rosaceous shrub-tree endemic to the eastern Great Escarpment (Sneeuberg, South Africa, to Nyanga, Zimbabwe) that is believed to be rapidly expanding and densifying, however, there is very limited research on this species. Accordingly, we provide the first comprehensive review of the autecology of the species, outlining a summary of past research, and highlighting research needs related to encroachment, impact, and management. In addition, we demonstrate the potential for using repeat photography to study L. sericea ecology, confirming encroachment at some sites and highlighting how run-off-run-on dynamics may influence L. sericea establishment success. Future research on: (a) how the distribution and local density of L. sericea is responding to fire regimes, climate change and recent land-use changes, (b) water use of L. sericea to predict the potential impact of the species on water provisioning at the landscape scale, (c) insect herbivory release on L. sericea due to global warming, (d) changing farming practices and restoring Southern Eland population as the original large mammal that controlled L. sericea, should be a priority to guide the management of L. sericea.