Exploring common ground for different hypotheses on Namib fairy circles

The spatial patterns formed by thousands of red-brown fairy circles (FCs) amidst green or yellow Namib Desert grassland offer a majestic landscape view. These FCs are not simply circular gaps in the grass vegetation. Each of these bare circles forms an oasis that stores water in its soil even during extended periods of drought and over many years (Juergens 2013). Together with the surrounding belts of grass they form 'fairy circle ecosystems' that enable perennial life of many organisms thereby increasing biodiversity by one or two magnitudes if compared to the surrounding desert (Juergens 2013). At the same time they are the subject of a scientific puzzle and an ongoing debate on the causation of the circles. Presently three main lines of interpretation see the bare patches a) as a result of a damage caused by toxic gases (Naude et al. 2011), b) as a result of competition for scarce resources (Getzin et al. 2014) or c) as a result of an ecosystem design by herbivorous sand termites (Juergens 2013). All these hypotheses have strengths and weaknesses the latter ones leading to a number of open questions. This commentary explores how much common ground exists that could integrate these three quite different approaches towards a harmonized hypothesis.