34,000-year-old termite mounds in South Africa are still in use today

Inhabited termite mounds along the Buffels River in Namaqualand, South Africa, are an astonishing 34,000 years old, according to a new study.

Termites are a diverse group of insects that play an important ecological role by breaking down organic matter. They live in complex social groups, and some species create large underground nests. These can be extensive tunnels and chambers in which the termites live and store plant material. Some termite mounds can be very old; in 2018, scientists discovered termite mounds in Brazil that were 4,000 years old.

But recently Total environmental science studies have shown that termite mounds inhabited by harvest termites (Viator Mikrohodotermes) in Namaqualand they are much, much older. Using radiocarbon dating, scientists found that the mounds had been used by termites for 34,000 years, even before the last ice age. During this period, humans were busy creating cave art, while a few Neanderthals still lived in southern Europe. The world was still full of megafauna such as woolly mammoths, saber-toothed cats, and giant sloths.

The study also provides an unrivaled picture of past climate cycles in the region and highlights the previously unexplored role of termites in carbon storage, says Michele Francis, a senior lecturer at Stellenbosch University and lead author of the study.

“Our gut told us (the mounds) were special, and when we dug in and saw these old nests and termites, we thought, ‘wow,’” Francis says. “It’s like watching a movie from the past.”

Namaqualand is a semi-arid region in western South Africa, known for its abundance of spring wildflowers. The land along the Buffels River is dotted with low hills called heuweltjieswhich are about 40 meters (130 feet) in diameter, where southern harvestman termites live in underground nests. A hard layer of calcite on top of the mounds protects the termites from aardvarks (Orycteropus afer) and other insectivores.

To collect samples from the mounds, scientists first used an excavator to dig a 60 m (197 ft) wide and 3 m (10 ft) deep trench through the center. Then, in what Francis describes as hot, dusty work, they took samples from the entire section, using small metal spatulas to scrape the soil into plastic bags. Sometimes the termites would come out and frantically try to repair their nests, using balls of dirt to plug the holes the scientists had made.

Francis says she already suspected the mounds were quite old, but was still surprised when radiocarbon dating showed the carbonate was 34,000 years old. Organic material, which decays much more quickly, was also remarkably well-preserved, dating back as much as 19,000 years. Younger organic material was found lower down, showing how termites bury the carbon deep in the mound.

The analysis provides unprecedented insight into the past and suggests that termites may play a previously underappreciated role in storing carbon, Francis said.

This can happen in two ways. First, termites collect small sticks or other carbon-rich plant material on the surface and carry them more than a metre underground, where they are less likely to release carbon into the atmosphere as they decompose. Second, the tunnels created by the termites allow rainwater to flow through the mound. This rainwater can carry minerals and dissolved inorganic carbon deeper through the soil profile and into groundwater.

Termites have been shown to contribute to the global carbon cycle, as many termite species use methane-producing microbes to digest their food. But their role in carbon storage and sequestration has not been fully explored, Francis says.

Francis, along with researchers from the US and other countries, now plans to take a closer look at how the carbon in heuweltjies is stored. He says he suspects that microbes convert organic carbon into a mineral form, which would explain why the mounds are so dense with carbon. He says he hopes the new research will help quantify the value of the carbon storage potential of these and other similar mounds. Because heuweltjies cover one-fifth of Namaqualand, the benefits of protecting the mounds, as opposed to using the land for agriculture, can be significant.

“We can only do this if we know how much carbon is in it and how quickly it is accumulating,” Francis says. “So we’re trying to encourage people to study what was previously boring, so we can really understand what’s going on under our feet.”

Banner image: A four-person field research team. Photo: Michele Francis.

Madagascar lemurs and tortoises seized in Thailand reveal scale of wildlife trade

Quotations:

Francis, M. L., Palcsu, L., Molnár, M., Kertész, T., Clarke, C. E., Miller, J. A., and van Gend, J. (2024). Calcareous termite mounds in South Africa are ancient coal reservoirs. Total Environmental Science, 926171760. doi:10.1016/j.scitotenv.2024.171760

Ito, A. (2023). Global termite methane emissions are influenced by climate and land use changes. Scientific Reports, 13(1), 17195. doi:10.1038/s41598-023-44529-1