Mystery of Australia’s desert circles revealed

By Thea WilliamsSeptember 6th, 2016

They're an ecological enigma across desert country in Africa and Australia. Now, a collaboration between ecologists and indigenous rangers in Australia finds the answer to this unique desert pattern.
Wideshort of desert with bare patches of red dirt in the foreground

Near Kintore in the Northern Territory. What causes the circles and their pattern? Image: Tibor Hegedis

Australian Aboriginal people have long used them as sitting areas, walking paths, and places to grind grasses or make artefacts.

In fact, they have names in Aboriginal languages. In Manjilyjarra language they call them linyi.

These grass-fringed, bare, circular patches are widespread in the spinifex desert grasslands of Western Australia (WA) and the Northern Territory (NT). Similar-looking circles occur in Africa and have been the subject of feverish curiosity in international media in recent years. From The Atlantic to the BBC, the media has speculated about this ecological mystery dubbed ‘fairy circles’.

Fungus, gases, plant/water organisation, termites and even dragons have been posited as the cause of the bare circles.

The latest research published in a letter in the Proceedings of the National Academy of Sciences of the USA (PNAS) presents evidence that in the Australian landscape, it’s termites; countering a paper published in PNAS in March.

Excavating the evidence

map of Australia showing grasslands

The research team examined circles in four locations across WA and NT.

CSIRO’s Dr Fiona Walsh and colleagues from WA and the NT, Ashley Sparrow (CSIRO), Peter Kendrick (Dept Parks and Wildlife) and Josef Schofield (Australian Wildlife Conservancy), examined circles on satellite images and then in the field across 1,200 km from Newman in WA to Newhaven Sanctuary in the NT.

Excavations of circles at four locations revealed all circles had concreted soil and chambers made by termites of the genus Drepanotermes, whereas digging away from the circles revealed no evidence of termites.

Close up of termite chambers and termite

Soldier termites came to defend their termitaria. Image: Fiona Walsh

At one location, of the ten circles they excavated, 60 per cent of the ‘pavement termitaria’ were active, containing living termites and termite food stores.

AS the letter in PNAS states: Although we accept that water redistribution occurs between bare and vegetated areas in Australian desert grasslands, we have evidence that bare patches are subterranean termitaria, both active and inactive (abandoned).

Pavements are very hard, withstanding fire, flood, and road grader blades; on worn-down vehicle tracks, the termitaria stand as discrete walled structures. Termitaria appear long-lived even when periodically or permanently abandoned; such “ghosts of termitaria” may persist for decades or longer.

Collaborating across culture and science

Dr Walsh said her investigations with other Australian ecologists revealed what desert Aboriginal people have recognised for generations.

The circles were clear of prickly spinifex, so people could sit comfortably on them, she said, and people preferentially walked across them when travelling through the desert. Aboriginal people also swept the circular hard spots as a place to prepare foods and artefacts. Older desert people recognised these spots as a ‘normal’ feature made by termites – “as ubiquitous to them as footpath pavements are to a city-dweller”.

Dr Walsh worked with Gladys Bidu, a Kanyirninpa Jukurrpa ranger, who said pavement termites played an important role in food webs and known desert ecology.

And these linyi are a favoured place for termite-foraging bilbies and echidnas.

Animal tracks on red dirt

Echidna tracks lead to a pavement where the animal has burrowed for termites.

“It is a linyji. Hard parna (ground) made by manyjurrpa, white ants (termites),” Ms Bidu said.

Linyji is hard and flat like a claypan made by water. But they are made by manyjurrpa so different to a claypan. Ninu or Mankarr (bilby) go to the linyji to get their food. Mankarr dig linyji to eat white ants and pinga (black ants). That’s their food. Porcupine (echidna) dig the linyji too. Porcupine are looking for manyjurrpa too. White ants are their food too. ”

Dr Walsh said their research highlighted the value of Aboriginal and local people’s knowledge.

Close up of two women with red desert backdrop

Gladys Bidu and Dr Fiona Walsh have brought Aboriginal and ecological knowledge together. Image: Sophie Walter

“Scientists are interested in these plant patterns because they tell us about forces that shape plant communities and their distribution, and so help to inform projections of how desert ecosystems may respond to climate shifts and other aspects of global change,” she said.

“A deeper message from our findings is that Australian deserts are so inherently complex, variable and unpredictable that the best people to ask about how these ecosystems work may be local people.”

Dr Walsh said this research raised many ecological and cultural questions relevant to the functioning of desert grasslands and the roles of people and termites within them.


For more, view Seeing the Spots, Re-connecting the Dots, a science photo essay on people and termitaria in the Western Desert.

 

8 comments

  1. Maybe read on a little…… PNAS also published a response to the Walsh et al paper “Reply to Walsh et al.: Hexagonal patterns of Australian fairy circles develop without correlation to termitaria”, doi: 10.1073/pnas.1611877113.

  2. Very interesting…. i have followed this issue for a number of years… i am Aboriginal Elder from Anaiwon in NSW ….worked all over Australia in variious roles in Indigenous Affairs..have a keen interest in archaeology.. am custodian of rock art and site in the ranges at Moonbi NSW….

  3. Yes, according to usual PNAS practice, Getzin and colleagues have been given the right of reply. Dr Sparrow said: “In their reply, they suggest that we believe that the circles are the eroded bases of termite mounds. What we found is this genus of termites build wide, flat termitaria that are level with the soil surface. They have small, low mounds and sometimes there appear to be no mounds at all. Secondly, we are aware of the processes leading to banded mulga and other demonstrably self-organised vegetation types, but in this case we simply believe that termites are the primary cause rather than plant self-organisation.”

  4. What an incredible an interesting land we share,am so pleased to hear the oldest know living people are being heard an their knowledge of this land listened to. Thank-you.

  5. The termites eat the spinifex hence the circles.

  6. So pleased all the knowledge of our ancient land is not lost. Keep up your good work.

  7. I travelled with Dr John Read to APY Lands SA last year, I remember him stopping the car walking out and lying on the ground with a camera. This part of Australia has a Buffel grass problem and the place which interested John was an area unusually bare of the grass. Getting back into the car he explained he thought the bare area was due to termites. It would be great for APY communities if termites were able to control buffel.

  8. This work absolutely mirrors work my entomologist colleague, John L Bissett, and I undertook in Southwestern Zimbabwe in southern Africa in the early 1970s. There these otherwise inexplicable bare (often roughly circular) areas in otherwise tuft-perennial grasslands were invariably associated with the subterranean hives of the Harvester Termite Hodotermes mosambicus. The work was interrupted by the bush war and was only partly published (e.g. Macdonald, I.A.W. 1978. Pattern and process in a semi-arid grassveld in Rhodesia. Proc. Grassld Soc. Sthn. Afr. 13: 103-109.). There is also published work on “Fairy Rings” from the semi desert grassland fringes of the Namib Desert in Namibia. Good to see the South-South comparisons!

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