The local termites create extensive subterranean labyrinths of tunnels, and they eject whatever soil they don’t need on the surface. The process is slow and gradual, but the termites have been at it for millennia. They’re more like a geological force than an organism. Just as rivers or glaciers sculpt the landscape around them, so too have these tiny insects sculpted some 90,000 square miles of Brazil into a junkyard that’s visible from space.
These mounds are known as murundus, and rather confusingly, they’re different from other mounds called campos de murundus. The latter are found in the wet, savanna-like areas of southern and central Brazil instead of the dry northeast, and it’s not clear whether they’re built by termites at all. Campos de murundus have also been well studied for decades; by contrast, the northeastern murundus, though well known by locals, have been largely neglected by scientists.
Funch first saw them three decades ago, when he arrived in Brazil as a Peace Corps volunteer. After an unsatisfying stint doing administrative work in the nation’s capital, he found a more compelling life in Lençóis, a former diamond-mining town in the east. Surrounded by forests, waterfalls, and caves, Funch became a tour guide, national-park director, and environmentalist. And wherever he went, he kept noticing the striking mounds. He wrote about them in local popular-science magazines, but never managed to stoke much interest in them.
Since then, farmers have exposed more of the mounds in an attempt to create more grazing land by clearing local plants. Their efforts were mostly futile: The local soil is too poor for crops or livestock. But they did allow Funch and other researchers to start cataloging the murundus using satellite imagery. “It used to be all green and brown, but around eight years ago, Google Earth sharpened their images, and I could see the mounds that I had known from the ground,” he says.
The honeycomb distribution of the murundus is just one example of mysterious repeating patterns in nature. The famous fairy circles of Namibia and Australia—discs of bare red soil that pockmark miles of low grassland—are another. For years, scientists have argued about the cause of these circles. Some say they’re the work of termites. Others think they’re caused by the grasses themselves, battling for water and nutrients. Still others have argued that it’s a bit of both.
Read: Visiting the mysterious fairy circles of the Namib Desert
The murundus, Funch says, are likely to be much simpler in origin. “There’s no doubt,” he says, that they’re termite-made. “I’ve seen termites building the mounds with my own eyes.”
By examining murundus that had been sliced open by road-construction teams and probing them using optic fibers, Funch and his colleague Stephen Martin realized that each one begins when a termite colony builds a vertical tube rising straight up from its underground nest. The tube isn’t a chimney—it’s mostly closed at the top except for small side-holes around the rim. As the termite workers excavate their nest, they chuck soil out of these holes, eventually creating a cone. “There’s no engineering involved,” says Funch. “They’re just throwing the stuff out.” The cones aren’t even used as portals to the surface world: When termites forage at night on the forest floor, they emerge through temporary tubes between the murundus that they then seal during the day.