Large mammals of the Palaeo-Agulhas Plain showed resilience to extreme climate change but vulnerability to modern human impacts

Abstract

Recent evidence indicates that the now submerged continental shelf, the Palaeo-Agulhas Plain (PAP), formed a novel ecosystem during periods of low sea level. This landscape provided nutrient-rich forage and habitats to a variety of large mammals. This is in contrast to the modern faunal assemblage found in the present-day Cape Floristic Region, which is dominated by landscapes with nutrient-poor soils and unpalatable plants. We used archaeological and paleontological records for the region to reconstruct past large mammal communities. We build on this approach by using modern knowledge of ecosystems and ecosystem processes to help us understand how systems functioned in the past. We reconstruct species communities for the PAP of the last 300 ka and investigate potential gaps in the record using Hutchinson's weight ratio theory. We then compare the results to modern occurrences of mammals on the Cape South and West Coasts and the Serengeti (a comparable migratory system) using general linear models. Both sea-level and sampling effort influenced species richness in both the South and West coast regions during the last seven marine isotope stages. In the South coast we observed a decrease in species richness during intermediate sea levels which indicates patterns of use by early humans and habitat availability. Large mammals showed an extraordinary resilience to extreme habitat loss and survived as refugee species during high sea levels and low habitat availability. However the combination of habitat loss and modern human weapons were the cause of severe extinction rates during the last 400 years.