What if you could build a brick fence in your backyard that would offset a portion of your daily carbon dioxide emissions, such as those produced on your drive home from work? Would you do it?
Ronald Dorn, professor of geography at Arizona State University in Tempe, would. Except the fence he has in mind wouldn’t be just constructed from any old brick. It would be coated with calcium or magnesium and inhabited by a colony of ants.
If this idea sounds bizarre to you, that’s probably because—as Dorn himself would admit—it is. Yet, he says, it is conceivable that people all over the world could one day use their own version of this mineral/ant–based method of CO2 capture to limit the gas in the atmosphere and thereby help control its global heating effects.
CO2 is currently the primary greenhouse gas emitted via human activities, according to the U.S. Environmental Protection Agency’s Overview of Green House Gases. And the volume released has only increased since the industrial revolution, contributing to global warming.
Using ants to help capture CO2 and help fight global warming stems from a study Dorn published recently in Geology linking ants to the acceleration of natural carbon dioxide absorption in rock by up to 335 times, compared with absorption in ant-free areas.
Responding to the study, David Schwartzman, emeritus professor of biogeochemistry at Howard University who reviewed but was not a part of the research, said that encouraging ant colonization “will be important in carbon sequestration” from the atmosphere.
Of course, both he and Dorn note, the ants themselves may not always be necessary once researchers learn more about how the insects promote carbon sequestration. “I don’t know if you can just have massive ant colonies hanging around a power plant. But if we know what particular secretion of an ant gland is doing this trick, or combinations of secretions,” Dorn says, then those substances could potentially be produced in quantity.
How rock captures carbon
Dorn himself is not sure how ants perform their “magic,” but he does have a good handle on how certain rocks absorb carbon on their own.
He says that rock containing calcium and magnesium naturally absorbs carbon dioxide, which in turn transforms it into carbon-rich limestone, or dolomite. This carbon capture by rock has been happening for a very long time. In fact, over geologic time it probably helped to keep the planet’s atmospheric CO2 levels and its temperature from rising too high for life to survive. Dorn’s new research suggests ants could have been responsible for helping accelerate this process.
Overall Dorn says this chemical activity really is essential to making Earth habitable. It is so important that he has his students do a rather unusual ceremony when working out in the field for research projects. “When I take students on field trips, I make them kiss the limestone, because that limestone is just CO2 that’s just locked up in rocks and how Earth has remained habitable.”
From annoyance to anomaly
Dorn discovered the contribution ants can make almost by accident. In the 1990s, as part of studying the weathering of minerals, he stuck minerals in all sorts of different areas—in soil, in bare ground, in crusts ripe with microorganisms, in ground next to roots and in a plastic tube used as a control. You name it, he did it—he wanted a baseline from which to track changes over time, he says.
At first, the ants were mainly an annoyance. “I’d drill holes and they’d bite you,” he says. It wasn’t until after putting up with them for 25 years while taking measurements of the minerals’ weathering over time that he got his first inkling of their carbon-sequestering prowess. “It was pretty clear when I started processing samples of the minerals from the different areas that the ants were incredibly anomalous,” he says, referring to just how much the ants sped up the carbon-capture process. Follow-up work then quantified the amount of carbon stored in rocks visited by ants.
And although he still isn’t sure whether it’s the ants licking the rock, their microbes, their gland secretions or something else that accounts for the carbon enhancement in rocks, he does understand further insight into the process could potentially help people do a better job of capturing carbon from the atmosphere. “I don’t understand how the ants are doing the processes,” he says. “I would love to get funding to figure this out.... Then we could move forward to work with the chemical engineers or somebody to figure out if this magic trick can be efficiently and economically used. That would be a dream.”
Schwartzman agrees and says that such carbon sequestration will be imperative in bringing down the atmospheric level of CO2 to below 350 parts per million (it is now 400 ppm) “to avoid the worst consequences of ongoing climate change induced by anthropogenic releases of CO2 to the atmosphere.” Although he added that this carbon release must also be radically and rapidly curbed as well.
Regardless, there are over 10 trillion ants on Earth, according to some estimates. So, “clearly, more studies on the role of ants and other animals populating soils are needed to broaden our understanding of their significance,” Schwartzman says.