Up to ten quadrillion ants are estimated to live on Earth. These insects exist on every continent except Antarctica. Their relentless invasion of human dwellings is mostly viewed with frustration. Nevertheless, ants and their activities also benefit humans in a variety of ways. For example, in China, southeast Asia and Australia, weaver ants are used for pest control on fruit farms. In South Africa, black ants gather the tiny rooibos seeds used to make herbal tea and store them in their nests, where they can be harvested easily. And in South America, army ants are used as surgical sutures. The ants are encouraged to bite into the skin so that their powerful mandibles lock the wound closed. The body of the ant is then cut off and discarded, leaving the ant's head as a make-shift stitch.

Credit: © BLICKWINKEL/ALAMY

It now seems that ants might help mitigate climate change, too. Silicate weathering processes — under discussion as one form of carbon sequestration from the atmosphere — were found to be particularly efficient inside the nests of ants. Over a 25-year period, Ronald Dorn monitored the breakdown of grains of basaltic rock that he had placed at a depth of about 50 cm within ants' nests in parts of Arizona and Texas, USA (Geology http://dx.doi.org/10.1130/G35825.1; 2014). His experiments showed that these basalt grains were broken down 50 to 300 times faster than similar grains placed in isolated patches of bare ground, over the same time period.

The samples retrieved from the ants' nests also showed a gradual build-up of calcium carbonate, implying that mineral weathering and reactions involving atmospheric carbon dioxide had probably taken place: when silicate minerals break down, carbon dioxide in the atmosphere reacts with the minerals to create calcium carbonate rocks. This process strips carbon from the atmosphere, and locks it into rocks.

It is unclear precisely how the ants speed up the weathering process that converts silicate minerals and carbon dioxide into carbonate rocks. The ant's role in this conversion might come from some digestive or excretion process. However, given the sheer mass of ant colonies that exist on Earth, improved understanding of the interactions between ants and silicate minerals could provide insights on how to accelerate the consumption of atmospheric carbon dioxide.