In northeastern Brazil, in very dry forests where trees turn pale, termites are busy working for thousands of years. The only external sign of their work is a mound of land, a landfill from their underground excavation. Dirt and rubbish usually inspire a lot of admiration like clipping nails – but this is a really extraordinary slag slag.
Conical mounds, each about 8 feet long and 30 feet wide, erupt from the ground at regular intervals, about 60 feet from each of the six neighbors. From the air, a pattern generates squares or hexagonal combs in a honeycomb. Satellite maps, through Google Earth, show bumps covering more than 88,000 square miles, a wider area of Minnesota.
"Imagine it being a city," said Stephen J. Martin, an entomologist and social insect expert at Salford University, England. "We have never built a city that big." And termites along the centimeter, Syntermes proceed, do it with grain.
Overall, the land excavated by termites is the same as the volume of 4,000 Giza Pyramids, as Martin and colleagues reported in a study published Monday in the journal Current Biology. They collected samples from 11 mound centers, and by measuring radiation in mineral grains, determined the oldest mounds tested were around 3,800 years old. Maybe others are older. Based on satellite imagery and spot checks at thousands of kilometers, scientists estimate 200 million mounds stretched the landscape.
If the forest cover disappears, exposes the mound in all their splendor, this place will be celebrated as a natural "wonder of the Earth," Martin said.
But tucked under the trees and thorn bushes, the mounds are difficult to recognize. Martin did not pay attention to them at first. He will travel to Brazil's dry forest, called caatinga, in pursuit of honeybees. Only after miles of driving, where the road cuts trees to reveal the shape of the gumdrop goiter, does he see it. This is a termite mound, locals tell Martin.
"No, that's not true – there are too many of them," he recalls thinking. Back in England, his colleagues said that the mounds were definitely lake sediments or other geological features.
Locals, of course, right, when Martin found out when he returned. Miles from any big city, while walking near the swimming hole, entomologists meet another biologist, Roy Funch.
"He walked on the river with a friend, and I walked over the river to go swimming," said Funch, a co-author on the new paper. Martin "looked like, obviously, an outsider," so Funch, who also worked as a tour guide, moseed, greeted and asked what brought Martin to Brazil. Termite bumps, said Martin, regretted that nothing appeared on Google Scholar.
"I said," Hey, you just met the only man in Brazil who worked on this mound, "" Funch recalled. "So, you know, 'coincidence' puts it lightly."
Funch traveled to Brazil in 1970 with the Peace Corps. Beautiful mountains and hiking trails persuade him to settle in the northeast of the country, he said. He also fell under a mound spell. The highest, called Funch "ancestors," reaches 15 feet into the air. (Not everything is still active.)
"I think no one has ever seen such a landscape modification on a very large scale by such small creatures," he said.
In the 1980s, Funch, who described himself as a "back wood scientist" but had a doctorate in botany, wrote about termite bumps for popular science magazines. He hopes to attract the attention of other researchers. Nothing is a little. Thirty years passed, and he decided to study it himself, until he worked with Martin.
This mound, unlike other highways, is not a nest or ventilation hole. "We think that the nest will be in the middle of the mound," said Funch. "They do not. They are not even under the mound. "A large tunnel, about 10 cm (about four inches) in diameter, rises through the center of the mound. Termites send their trash and plug tunnels at the top.
"Nobody has ever found a queen's nest. We really don't know what happened underground. Absolutely nothing, "said Funch.
The mound makes an uncooperative subject. Army termites appear when researchers disturb dirt. They will take blood, said Martin. "They have sharp jaws. They will cut the skin, "he said. Nutrient-poor soils are a nightmare to be dug up, roasted hard like concrete in heat.
Remoteness and bad soil are qualities that allow termite bumps to survive. This area has a long drought, said the University in Geography Buffalo Eun-Hye Yoo, a study writer. (Yoo also met Funch in the Brazilian tourist city. "This is a good place to meet people," he said.) The climate, although not friendly to human agriculture, is stable. In this harsh environment, the termite kingdom develops.
"These termites have exploited this area and done very well for themselves," Martin said.
The rainy season lasts about one month. Caatinga jumped from brown to green and returned again. Trees bloom, and as fast as they spill leaves. In a few weeks, the forest floor is stripped of litter leaves. Termites take everything to eat. Martin suspects that litters support them for the rest of the year. Termites elsewhere are agricultural fungi on the leaves of detritus, but no termite species grow mushrooms in South America.
Scientists do not have a definitive explanation for unique hexagonal distances. The pattern is "really striking and unusual in scale. This is a good example of large-scale self-organization," said Corina Tarnita, a mathematical biologist at Princeton University who was not involved with new work. The only pattern that is comparable in nature which is so widely distributed, he said, are African fairy circles, brushed rings that appear from Angola to South Africa.
But Martin proposes that, because these social insects are "very, very good at optimizing" a six-point system, perhaps the most efficient. Underground, as seen by fiber optic cables, is a large and interconnected tunnel system. Termites guide themselves with pheromones, insects that are equivalent to subway conductors.
"When you have enough connections, it's easy to find the closest mound," Martin said. Only if the mound is not on the edge of the megacity will they begin to build a new one.
Tarnita warned that the mounds tested in this study were carried out carelessly. "It would be very important to have a systematic age assessment that gives some understanding of the relationship between age of bumps and the age of neighbors, or neighboring neighbors," he said.
Martin agreed there was a lot of work to be done. No one knows how closely related to animals at the end of the empire. Their genetics has not been tested. And the rulers of the colony remain a mystery. "We want to go to the royal room," he said. He sacrificed extraordinary bumps or two to the backhoe, for science.