How old is the world’s oldest desert? Investigating the coevolution of landscape and climate in the development of the Namib Desert

The Namib Desert in Southern Africa is likely the world’s oldest desert, experiencing arid to hyperarid conditions for most of the Cenozoic. The desert is inhabited by a unique flora and fauna, some of which has adapted to obtain water from fog, which develops along the Namibian coastline. However, our knowledge of the climatic history of this desert is fragmentary, based on evidence from lithology and geochemistry. Temporal constraints are often provided by biostratigraphy based on fossilised ratite eggshells, which only gives an approximate sequence of events.

In order to test different scenarios for the development of the Namib Desert, we employ FastScape, a landscape evolution model, combined with a model of orographic rainfall. We use this framework to reconstruct Southern African landscape evolution based on different hypotheses arising from geological data, and infer consequential climatic histories, over the last 100 million years. Modern-day remote sensing and weather station data are used to tune and test the fit of the final model timeslice. This allows us to determine which landscape evolution scenarios are most likely, providing novel insights into the onset and evolution of aridity in the Namib Desert.