Fungus-farming ants have developed a way to capture atmospheric carbon dioxide and incorporate it into their exoskeletons as dolomite, a mineral that strengthens their armour and regulates nest air quality. This process, observed in species from Central and South America, occurs without the need for high temperatures or pressures that challenge lab synthesis. Researchers suggest it could inspire human carbon capture techniques.
Fungus-farming ants maintain colonies where they cultivate fungi using foraged vegetation, which in turn provides their primary food source. The dense populations of ants and fungi lead to elevated carbon dioxide levels within nests, posing a risk of toxicity.
In 2020, Cameron Currie at the University of Wisconsin-Madison and colleagues identified that ants of the species Acromyrmex echinatior integrate a carbonate biomineral into their exoskeletons through a symbiosis with Pseudonocardia bacteria. These bacteria facilitate the transformation of CO2 into rock-like material via chemical processes not fully understood.
A recent study reveals that another species, Sericomyrmex amabilis from Central and South America, achieves the same without bacterial assistance, marking the first known instance of an animal evolving this capability independently. The resulting mineral is dolomite, composed of calcium, magnesium, and carbonate. Geologically, dolomite forms over millions of years through intricate processes, as seen in Italy's Dolomite mountains. However, the ants produce it rapidly and at ambient conditions.
Hongjie Li at Zhejiang University in China notes that the ants accomplish this "quickly and effortlessly, without high temperatures." Currie explains that lab formation of dolomite is hindered because magnesium ions bind tightly to water, impeding integration into calcium carbonate crystals; scientists typically apply high temperatures and pressures to overcome this.
For the ants, this mechanism addresses dual needs: it fortifies their exoskeletons against threats and mitigates CO2 accumulation in colonies. "We have discovered a natural system that has evolved, over millions of years, to reduce the toxic accumulation of atmospheric CO2 in an ant colony," says Currie.
Scientists are investigating carbon capture methods to convert atmospheric CO2 into carbonate minerals as a strategy against global warming. Currie highlights that "these ants are the first animal shown to be engaging in such a process, offering exciting potential as a model for human efforts."
Cody Freas at the University of Toulouse, France, who was not involved in the research, calls it a "remarkable adaptation." He describes the ants as "living carbon scrubbers, converting atmospheric carbon dioxide into a protective mineral armour," which aids in nest atmosphere regulation and physical defense.