The persistent enigma of the Namibian dessert fairy circles.

Abstract

Fairy circles is the name given to the localised bare spots which pepper the otherwise vegetated landscape of the pro-Namib transition zone to the Namib desert in western Namibia, Africa. While conjenctures on the causes of this pat- tern abound, there is no scientifc consensus about their origin. In this study we review the literature published on the subject at hand, and highlight the con- vergence of the feld to certain candidate propositions, namely the possible role of termites as ecosystem engineers, and the resource competition of plants for water leading to emergence of spatial patterns. Concomitantly, we formulate a new hypothesis on the origin of fairy circles based on differential condensation of water between the barren and vegetated areas, that could occur during night- time. As a proof of principle we demonstrate, by means of numerical simulations of a spatially explicit model, that this effect can create patterns resembling the fairy circles. We furthermore propose a simple experiment which can test this hypothesis at the field.