The Fairy Circles of Namibia

About 5 min read

From the air, parts of the Namib Desert look patterned, as if someone had stamped the ground with a cookie cutter. Thousands of near-perfect circles of bare sand, each ringed by taller grass, are scattered across the sparse grassland in a regular spacing visible for kilometres. They are called fairy circles, a name that comes from folklore, not science. No fairies are required. But for decades, scientists could not agree on what was required instead.

The circles are real, and they are not rare. They occur in the arid grasslands of the Namib Desert in Namibia, southern Angola and north-western South Africa, and similar patterns have been described in the Pilbara region of Western Australia. A single circle is typically a patch of barren sandy soil, commonly 2 to 12 metres across, encircled by a ring of stimulated grass growth. In the Namib, the grasses are usually species of Stipagrostis. The bare centre is not rock or salt: it is sand, on soils with very little clay, in a landscape that receives very little rain. The question that has divided researchers is simple to state and hard to answer: what kills the grass in the middle, and keeps it dead, while the grass around the edge thrives?

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A Desert That Runs on Very Little Water

The Namib is one of the oldest and driest deserts on Earth, a narrow band along the Atlantic coast of south-western Africa. The fairy circles form on permeable, sandy soils in its eastern grasslands, where rainfall is sparse and unpredictable. In the driest areas, a year can pass with almost no rain at all.

That scarcity is the starting point for every serious explanation. In a place where water is the limiting factor, a bare patch is not just an absence of grass. It is a store of water: sandy soil lets rain infiltrate quickly, and without plants in the centre to take the water up, moisture can accumulate below the bare patch and persist through long dry periods. The ring of tall grass around the edge benefits from that stored water.

The Termite Hypothesis

The most famous explanation centres on an insect: the sand termite, Psammotermes allocerus. In 2013, the ecologist Norbert Jürgens published a prominent account in the journal Science, arguing that colonies of this termite create the circles. In Jürgens’ account, the termites eat the roots of freshly germinated grasses after rain, killing the young plants and creating a bare patch. The bare patch then stores rainwater in the soil below, and the termites benefit: the stored moisture supports the ring of perennial grass around the edge, which the termites feed on, slowly expanding the circle over time.

Jürgens reported finding the sand termite in 80 to 100 percent of the circles he examined, and in 100 percent of newly formed circles. It was an elegant story, with a clear mechanism: an animal engineer, building a water store for itself. But a mechanism is not proof, and the termite hypothesis made a testable prediction: if termites kill the young grasses by eating their roots, then the dying grasses inside a new circle should show damaged, shortened roots.

The Self-Organization Hypothesis

The rival explanation gives the central role to the grasses themselves. It is known as vegetation self-organization, and it has a longer history than the termite theory: the botanist Gretel van Rooyen had already argued in 2004 that fairy circles might be a phenomenon of vegetation self-organization, after rejecting termite activity, radioactive soil and plant toxins as explanations.

The idea is that in an arid landscape, grasses interact with each other and with soil water in ways that spontaneously produce patterns. Plants close together help each other locally by improving water infiltration; plants further apart compete through spreading roots for the same scarce water. That combination of short-range facilitation and long-range competition can create alternating zones of vegetation and bare ground — spots, stripes and rings — without any animal doing the designing. Similar patterns occur in drylands around the world, which is one reason the self-organization idea has always had supporters.

Under this hypothesis, the grasses inside a new circle die not because something eats them, but because they run out of water. The surrounding grasses, with their established root systems, draw moisture out of the soil faster than the young plants inside the circle can get it. The topsoil dries, the seedlings desiccate and die, and the bare patch is born — and then maintained, because the same competition keeps new seedlings from establishing there.

What the Field Tests Found

The two hypotheses were put to a direct test in the early 2020s, and the results shifted the balance of the debate. In 2022, a team led by Stephan Getzin published a study in Perspectives in Plant Ecology, Evolution and Systematics that systematically tested both ideas. The team excavated about 500 grasses from four regions across the Namib after rain events, and measured soil moisture continuously. Their finding was striking: the newly dying grasses inside the circles had intact roots. In the freshest study sites, the roots were not shorter than those of living grasses outside the circles; in some comparisons they were longer relative to the shoots — a sign of a plant struggling for water, not a plant being eaten.

The researchers also found that the grasses died quickly after rainfall, in an undamaged state, and that the uppermost topsoil inside the circles was significantly drier than the surrounding matrix soil. Their conclusion was that plant water stress, not termite herbivory, caused the circles — that the young grasses died of desiccation in the topsoil, while the surrounding grasses depleted the moisture.

Jürgens and his colleague Alexander Gröngröft disputed that interpretation in a 2023 response, arguing that sand termite herbivory does cause the circles. Getzin and his colleague Hezi Yizhaq replied in 2024, arguing from field water measurements and root condition that the grasses die through topsoil desiccation rather than root consumption, and that termite feeding is easier to detect after plants have already dried and died — which would make some termite presence a consequence of the dead material, rather than the original cause of death.

A separate idea — that toxins left in the soil by dead Euphorbia damarana plants cause the bare interiors — was proposed in 2008 and has been refuted by detailed fieldwork and high-resolution image analysis showing that decaying Euphorbia did not inhibit grass growth and did not form fairy circles.

Where the Debate Stands

It would be misleading to present the fairy circles as fully solved. Wikipedia’s summary is honest about this: studies have proposed various hypotheses, but none has conclusively proven how the circles are formed. The termite researchers have not conceded, and the self-organization researchers have not proven that termites play no role at all.

But the direction of the evidence is clear enough to state. The strongest systematic field evidence supports water-driven vegetation self-organization: the grasses die of thirst in the topsoil, and the pattern maintains itself through competition for water. Termites are certainly present in many circles, and they may well help maintain them. What the 2022 evidence challenges is the claim that termite herbivory is the universal, initiating cause.

What Is Documented, and What Is Not

Documented: Fairy circles are circular bare patches, commonly 2 to 12 metres across, ringed by Stipagrostis grasses, in the Namib Desert of Namibia, Angola and South Africa, and in similar form in Western Australia; Jürgens (2013) proposed the sand termite Psammotermes allocerus as the creator; Getzin and colleagues (2022) excavated about 500 grasses and found that newly dying grasses inside circles had intact roots, concluding that plant water stress, not termite herbivory, caused them; Jürgens and Gröngröft (2023) disputed this, and Getzin and Yizhaq (2024) replied defending the water-stress interpretation; the Euphorbia toxin hypothesis has been refuted by fieldwork.

Unverified or disputed: Whether termite herbivory initiates fairy circles, or only maintains or exploits them; whether a single mechanism explains all circles across the whole range; and any claim that the matter is settled. The honest status is: strong recent evidence for vegetation self-organization driven by water competition, with the termite debate still active. The folklore origin — fairies, gods, or dragons — has no scientific support.