A study recently published in the journal geology highlights the important role that Earth’s smallest animals, the insects, plan in global scale geologic processes. Insects might seem small, but a look at some statistics counters that view: it has been estimated that there are more than 10 quintillion (10,000,000,000,000,000,000 or 10*10^19) insects alive at any one time. That’s more than 200 million insects per human being! If this is the case, there are about 300 lbs worth of insects for each pound of humans.

The study, completed by Ronald I. Dorn, a professor at Arizona State University, focused on possible links between ants, which are ubiquitous on every continent except for Antarctica, and the global climate. It has long been known that they play a role in bioturbation – the mixing of sediments by animals. Dorn’s study, however, focuses on the role of ants in controlling the levels of CO2 in earth’s atmosphere.

To understand how ants could play such a role, we need to understand the global CO2 budget. CO2 is released into the atmosphere from a variety of sources, including volcanic eruptions, natural gas seeps, and the production and burning of fossil fuels. If there were no mechanisms in place to control CO2 levels, concentrations would just keep increasing.

Fortunately, there is a common geologic process capable of removing CO2 from the atmosphere. This process is called the Urey reaction. Here’s how it works: carbon dioxide reacts with certain minerals, primarily olivine and plagioclase feldspar, in the presence of water, forming calcium carbonate. This calcium carbonate incorporates the CO2, which is removed from the atmosphere.

The rate of the reaction depends on a variety of factors, including the length of time the water is in contact with rocks and the concentration of CO2 in the water.

What does this have to do with insects? Well, the University of Arizona study found that rates of olivine and plagioclase weathering were enhanced by up to two orders of magnitude near ant colonies. The experiment worked like this: blocks of basalt were crushed into sand sized particles. Next, the density of the sample was measured. Finally, the sand was buried in several locations, some with ants, some without. At five year intervals, the basalt grains were dug up and measured for density. Results showed that the change in density (caused by the reaction) was up to one hundred times higher at sites with ants. Given that there are over 10,000,000,000,000 ants on earth at any given time, the overall impact of ants on atmospheric CO2 levels could be astronomical!

Future studies will consider some additional questions:

How do ants actually speed up the process?

Could ants be used to slow climate change by controlling atmospheric CO2 levels?

Do other insects also play such an important role?