African ‘fairy circles’: Tiny insects alter vast swaths of desert [Photos]
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Humans could learn a thing or two from lowly sand termites about managing the Earth’s natural resources. Mysterious African “fairy circles,” up to 55 yards across, are created by these creatures, according to a study published in Friday’s edition of the journal Science.
Fairy circles are formations that appear along a 1,200-mile belt that stretches along the southwestern edge of Africa, from the middle of Angola to Namibia to the northern edge of South Africa. Sometimes the circles appear as bare patches of soil surrounded by grassland; more often, they look like rings of grass in otherwise empty dirt. They range in size from just a few feet across to more than half the length of a football field, and they last for decades.
Norbert Juergens, a biologist at Germany’s Hamburg University who studies biodiversity, evolution and the ecology of plants, surveyed these fairy circles over an eight-year period. He measured the water content in the soil and analyzed the various species living around — and underneath — the circles. Over time, he developed this theory of what was going on:
It all starts with a sand termite species called Psammotermes allocerus. They live underground and eat the roots of perennial grasses. That kills the grasses, creating a bare patch of soil. The termites then move on to the adjoining roots, causing the bare patch to grow into a larger circle.
If all this activity makes the termites thirsty, they’re in luck — the bare soil allows more rainwater to penetrate deeper into the ground than would be possible if plants were in the way. Indeed, his measurements of soil humidity revealed that the ground where the termites lived contained at least 5% water, which is rather wet for a desert. The conditions encourage the sand termites to keep on eating the grass roots at the edge of their habitat, expanding the fairy circle.
Of all the species Juergens encountered during his research, the P. allocerus termites were the only ones he found at every single fairy circle site. And he confirmed that they ate the roots of perennial grasses, the initial step in the fairy circle cycle.
“Ecosystem engineering is creation or modification or maintenance of habitats by organisms — well, other than humans,” Juergens said during an interview on this Science podcast. “The termites obviously create a permanent water store, and because of that, as a second step, a permanent plantation of long-lived grasses.”
That’s good for the termites, but they’re not the only ones to benefit, he added: “It turns vast landscapes from short-lived desert into permanent grassland and thereby attracts many, many species of plants and animals, expanding biodiversity enormously around these fairy circles.” These include “ants, bees, wasps, small mammals, and plants,” according to the study.
Considering their size, the landscape-altering abilities of these sand termites is arguably even more impressive than those of beavers — hailed as nature’s engineers for their propensity to build dams and turn rivers into lakes. Even humans don’t do as good a job of managing their limited resources in a sustainable way, Juergens said.
“I think there’s a lesson in what these tiny termites achieved,” he said.
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