On a cloudless September morning in Buffelsrivier, a desolate corner of Namaqualand some 530km (329 miles) north of Cape Town, Stellenbosch University soil scientists Cathy Clarke and Michele Francis watch as a giant Volvo excavator tears into the dry ochre earth. Over the next five hours the excavator works hard to dig a trench, 60m (197 feet) long and 3m (10 feet) deep, through the heart of a giant, low-slung mound known locally as a heuweltjie or “little hill”. It’s all part of a university project to understand why the groundwater in the area is so salty.
Once the digger has returned to the nearby town of Springbok, population 12,790, Clarke, Francis, and a bevvy of grad students begin to explore the trench. They start at its extremities, what Francis describes as the “boring bits”, feeling the soil and looking for signs of life. As they move inwards, they start to notice small conglomerations of bewildered southern harvester termites (Microhodotermes viator) furiously trying to repair the damage done to their home.
At the centre of the trench, two metres (6.6 feet) below ground level, they encounter “this huge nest that looks like a giant alien”, Francis tells Al Jazeera. Clarke nods in agreement: “The moment I saw it I knew we were witnessing something special. It was just so obviously ancient … And alive.”
Once they’d taken some time to simply marvel at the work achieved by these 1cm (0.4 inch)-long creatures, they moved on to the business at hand: taking soil samples. “I delegated the task to a young male student with a pickaxe,” laughs Clarke. “But he couldn’t get the steel blade to penetrate the sides of the trench.” The ground was so hard, according to John Midgley – an entomologist at the KwaZulu-Natal Museum who was not involved in the project – because it was part of an “ancient mound” created by termites over thousands of years. Eventually, after lots of huffing and puffing, the grad student was able to obtain a sample the size of a soccer ball, which was sent for testing.
This kind of challenge is all in a day’s work for soil scientists, says Clarke, who describes her discipline as “a fun mix of everything from bucket science to high precision X-ray techniques”.
Francis tells me that when they got back to their hotel in Springbok at the end of the day, the cleaner reported them to the manager: “She thought we were zama zamas [South African slang for illegal miners] because our rooms were coated in orange dust,” she says, adding, “I guess she [the cleaner] had a point.”
How old is old?
The soil scientists knew instinctively that they had dug up a very old termite nest. But neither of them was prepared for quite how old it would be. They submitted samples for radiocarbon dating from the nests and soils from locations across the giant mound. These tests analysed the soil organic carbon (decomposed organic matter dragged into the nests by termites) and the soil mineral calcite (inorganic carbon in the form of calcium carbonate) to give a complete picture of the mound’s age.
The tests showed that the organic matter dragged into the nest by the termites had been there for at least 19,000 years. The mineral calcite in the nests, also a result of termite activity, was even older: It had been around for 34,000 years, since before the last Ice Age.
Francis is quick to point out that “this doesn’t mean the termites were living in ice”. As she explains, in arid parts of the world, the Ice Ages were actually a time of plenty: “The Namaqualand received abundant rainfall and was a magnet for animals of all types.”
While the entomologist Midgley has no doubt that termites have been active in the area for at least 30,000 years (fossilised nests were first found in the area in the 1930s), he says there is no way of proving that the nest has been continually inhabited for all of that time. “There is a high density of nests in the area. Recolonization seems inevitable, if not necessarily intentional,” explains Midgley.
Either way, research by Clarke and Francis shines a light on the role these misunderstood insects play as ecosystem engineers. At least 165 termite species, from 54 genera, are found in southern Africa. Although there are large differences between genera they are all characterised by a high degree of social organisation, with each species containing several distinct “castes”. Depending on their caste – reproductive (king and queen), soldier or worker – termites of the same species can look and behave completely differently.
Southern harvester termites mainly feed on sticks and twigs, which they carry down into their nests: in Afrikaans, they are called stokkiesdraers (stick carriers) or houtkappers (woodchoppers). Beyond these nicknames, most people know very little about them – in fact, they’re often confused with ants. The only time termites are typically talked about is when farmers moan about the destruction they wreak on pastures. Using pesticides to kill termites remains a common practice.
Termites may have a bad rap, but Clarke’s and Francis’ research highlights one of the long-term benefits of their stick-eating. Over millennia their redistribution of organic matter drastically alters the composition of the soil, effectively creating two different habitats in the same biome. Some plant species love the mineral-rich soil of the heuweltjies, while other plants have adapted to growing in soil that’s not inhabited by termites.
“The termites are one of the reasons for the Namaqualand’s incredible biodiversity,” says Clarke. The biome, known officially as the Succulent Karoo, is considered “the world’s most biodiverse desert region“.
But this is not the only way they benefit the planet.
An accidental discovery
The heuweltjies formed by southern harvester termites are quite unlike the dramatic pinnacles built by other species in Africa, Australia and South America. But this does not make them any less fascinating. Measuring up to 40 metres (132 feet) in diameter, these raised mounds containing intricate networks of termite tunnels and nests cover up to 27 percent of the surface area of Namaqualand. Scientists are divided over whether the termites actually construct the heuweltjies – but even sceptics admit that the termites play a critical role in their formation.
The southern harvester termite has a broad distribution range, but heuweltjies – which are the result of a buildup of fine soil material, carbon and salts over centuries – only form in semi-desert regions. The southern harvester termite is also common in and around Stellenbosch (the picturesque Winelands university town, about 50km east of Cape Town, where Clarke is based), but the heavy winter rains and dense vegetation prevent mound formation. Here the presence of the termites is highlighted by large bush clumps in the scrubby fynbos (native vegetation) and in nutrient-rich patches in vineyards and fruit orchards.
Buffelsrivier, which receives around four times less rain than Stellenbosch, is a different story. Massive, dense heuweltjies dot the landscape as far as the eye can see. In springtime, they are especially easy to spot, as the heuweltjies are ringed by halos of flowers.
Clarke and Francis started investigating the Buffelsrivier heuweltjies in a bid to understand why the groundwater in the vicinity was so salty – termites were only a sideshow. “The aim was to date the groundwater,” explains Francis. “Was it very old? Or was it being recharged every time it rained?”
While dating the water, they had to date the sediments around it. This process didn’t just lead to the accidental discovery of some very old termite nests. It also confirmed that the salts and other minerals in the groundwater were the direct result of termite activity. When it rains, Francis explains, “the salts built up in the mounds over thousands of years are flushed into the groundwater system via flow paths created by the tunnelling action of the termites, pushing the dissolved minerals ever deeper.”
An overlooked carbon sink
While this provided a definitive explanation for the region’s hypersaline groundwater, it also got the scientists thinking about the role termites might play in combating climate change – something which had never been considered for this species.
By dragging sticks and twigs underground, the termites add fresh stores of organic carbon to the ground at depths greater than one metre (three feet). This deep storage of organic carbon, explains Clarke, “reduces the likelihood of the carbon being released back into the atmosphere and means that the mound acts as a long-term carbon sink”. The continual harvesting of plant matter also increases the fertility status of these mounds. Hence the halos of spring flowers.
But the termites’ powers of sequestration don’t end there. The biological breakdown of termite excrement (known as frass) triggers a cascade of biological reactions, which results in the formation of calcium carbonate – the material limestone is made of. This calcium carbonate is a very stable form of carbon that is locked in the soil for thousands of years. Some of this carbon leaches into groundwater where it may remain for centuries.
“This is the kind of long-term carbon storage [14.6 metric tonnes] method that carbon storage companies are trying to replicate,” says Clarke. “But the termites have been doing it for thousands of years.
“It’s time we stopped viewing termites as pests and started to see the important role they can play in fighting global heating.”
Midgley, the entomologist, agrees, “Termites are fascinating creatures that promote biodiversity in varied and unexpected ways. For example, we found a species of hoverfly that relies on termite frass as a larval habitat … without termites, it would go extinct. The more we explore, the more fascinating aspects of termite life will emerge.”
Clarke and Francis believe that “termite activity should be incorporated into carbon models”. These models currently focus primarily on forests and oceans, so “including termite mounds could help provide a more comprehensive understanding of global carbon dynamics”.
Only scratching the surface
Until Clarke’s and Francis’ discovery, the oldest organic matter found in a termite colony came from a 4000-year-old chicken in Brazil. That said, very few studies have used heavy machinery to penetrate the hard crust formed by the insects, so there’s a good chance there could be even older colonies out there – either in Namaqualand or elsewhere.
Despite being a soil scientist and not an entomologist, Francis admits to having fallen for the honey-hued insects and their complex societies. “I know we’re not supposed to ascribe human qualities to insects,” she says. “But I can’t help myself. If I had unlimited time and funding, I would love to excavate termite mounds all around the world.”
For now, however, she’ll have to content herself with a follow-up project that takes a more in-depth look at the mechanisms of carbon sequestration in the Namaqualand heuweltjies. Stellenbosch University initiated the project, but thanks to a multinational grant funded by the National Science Foundation (US) and the National Research Foundation (South Africa), the project now boasts a team of microbiologists, ecologists and geochemists from the US and South African scientists.
At last, these pint-sized ecosystem engineers are getting the attention they deserve.
