Weaknesses in the plant competition hypothesis for fairy circle formation and evidence supporting the sand termite hypothesis

New research challenges the prevailing plant competition hypothesis for fairy circle formation in Namibia's Sand Sea, presenting strong evidence supporting the sand termite hypothesis. Fairy circles (FCs) are circular bare patches of land surrounded by a ring of tall grasses, primarily found in arid grasslands with annual rainfall below 120 mm. The study argues that FCs are not a result of plant competition for water but rather the activity of the subterranean sand termite Psammotermes allocerus. This hypothesis is supported by extensive field data, including long-term monitoring and soil moisture measurements, which show that FCs maintain higher soil moisture levels even during droughts. Additionally, the study demonstrates that the spatial patterns of FCs closely resemble those of social insect nests, such as termite mounds, suggesting a biological rather than environmental origin. The research also refutes the plant competition hypothesis by highlighting inconsistencies in its core assumptions and providing empirical evidence that contradicts its predictions.

JUERGENS, N., VLIEGHE, K. E. P., BOHN, C., ERNI, B., GUNTER, F., OLDELAND, J., RUDOLPH, B., & PICKER, M. D. (2015). Weaknesses in the plant competition hypothesis for fairy circle formation and evidence supporting the sand termite hypothesis. Ecological Entomology, 40(6), 661–668. Portico. https://doi.org/10.1111/een.12266