Although ants are well-known as being household pests, most of our terrestrial landscapes would likely be drastically different without them. Ants provide an essential ecosystem service by maintaining soil. They aerate soil by digging tunnels for their nests (which also allows water to reach plant roots), and they mix nutrients through soil.
Ants’ nest-building and foraging behaviors help soil remain fertile for plants and microorganisms to thrive. In fact, many plants would not even be able to grow where they do if ant nests didn’t exist. In a newly published study, I and two of my colleagues at the University of Boulder - Colorado have shown that factors like proximity to an ant nest and whether the nest is on a slope substantially influence the soil moisture and plants that live in the area.
We investigated patterns in the soil properties and plant communities surrounding 24 nests of the montane ant, Formica podzolica. After counting plant specimens and studying plants and soil in the lab, we found that soil moisture increases with distance from nests and that plant abundance decreases with distance from nests. We also found that the soil downhill from nests harbors more plants than soil uphill from nests, which we conclude means that nutrients and water from nests flow downhill to fertilize soil. This ant species occupies a huge geographic range from Alaska down to New Mexico, so we think they play a key role in shaping plant communities throughout much of the western U.S. and Canada.
Our study adds to a body of literature about ants as "soil ecosystem engineers." Without ants, subalpine habitats like the one in this study could be extremely different. We and other scientists continue to study how ant activity affects the soil, including the possibility of harnessing their services in both ecosystem restoration and agricultural crop production.