DUNE FIELD ACTIVITY: WHAT IS THE ROLE OF GEOMORPHOLOGY?

A fundamental re-think of transitions in dune field activity is occurring as the role of geomorphology is clarified in unidirectional dune forms. Here, we review progress to date, highlight implications, and suggest future research priorities.

Dune fields globally vary in vegetation cover: from completely bare with mobile dunes, to fully vegetated with immobile dunes. The vegetation cover controls the habitability, economic value, environmental value, and infrastructure hazard. Previously, linear and unidirectional dunes (transverse, barchan, parabolic) were modeled with common dune mobility indices that link vegetation cover to a ratio of sediment transport and aridity. New research is demonstrating that dune field geomorphology strongly manipulates the activity and stabilization of dune fields.

In short, theories suggest that tall dunes travel slowly (more amenable for vegetation), angled arms have low deposition rates (more amenable for vegetation), and convex slipfaces have low deposition rates (more amenable for vegetation).

These simple, yet predictable relations have provocative implications. First, stabilization of unidirectional dune fields occurs with a threshold-type behaviour: once vegetation takes hold, the entire dune field is driven to stability through reformation and collisions. Second, the morphology of stabilized dune fields should exist in a situation whereby the topography is in a state just habitable for vegetation (we demonstrate this in real dune fields). Third, the topography of stabilized dune fields can be ‘read’ to measure stabilizing paleoclimate. And fourth, reformed stabilized dune fields are more resistant to reactivation. Together, these new ideas provide new predictive facility, open exciting new research directions, and arm researchers with tools to better adapt to inevitable future land cover changes in global dune fields.