Soil Mixing Gives Carbon Dioxide More Places to Bond to Minerals

Biological Strategy

Red harvester ant

Image: Fir0002/Flagstaffotos / Wikimedia Commons / CC BY NC - Creative Commons Attribution + Noncommercial

Regulate Climate

Individuals and ecosystems manage local atmospheric conditions, thus regulating local climates. The local scale refers to climates such as those found under a shrub or within a forest. This local climate is called a microclimate. Regulating local climate creates favorable conditions, such as increased humidity or less severe winds, and contributes to species diversity. Microclimate development occurs over time: just from their presence, a few species initially able to tolerate the local conditions start to modify those conditions, resulting in microclimates that support others. For example, plants that live in alpine areas are subject to strong ultraviolet light, drying winds, and freezing temperatures. By growing together into dense clusters, these plants create a favorable microclimate that supports survival of a diversity of species.

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Modify PH

In its liquid form, each H2O water molecule is continuously breaking apart into its constituent OH- and H+ ions and reforming. In pure water, the concentration of OH- and H+ ions is equal, but impure water can have unequal concentrations of these two ions depending on the type and concentration of impurities. A pH of 7 indicates a balance between OH- and H+ ions. Below 7 the concentration of H+ ions is greater than the concentration of OH- ions and the solution is referred to as acidic. Above a ph of 7, the OH- ion concentration is higher and the solution is referred to as basic or alkaline. The pH of a solution can have an impact on chemical reactions, so organisms have figured out how to control pH to achieve a desired outcome. For example, single-celled Foraminifera form their shells by pumping H+ ions outside internal vesicles thereby increasing internal pH which causes dissolved calcium and carbonate ions to precipitate out as solid calcium carbonate.

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Chemically Break Down Inorganic Compounds

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). For example, inorganic pyrophosphate is hydrolyzed to form two phosphate groups in the cellular degradation pathway of fatty acids.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Ants may increase carbon dioxide drawdown by enhancing mineral weathering in the soil.

Ants are ecosystem engineers that can have a large effect on the biological, chemical, and physical properties of the soil in which they live. As ants move around in the soil finding food or building underground nests, they disturb and mix up the soil around them. It’s thought that this disturbance can enhance the dissolving of minerals—known as weathering—in the soil. Studies have found that ants are one of the most effective biological enhancement weathering (BEW) agents when compared to other insects or plant roots.

In one of the most common processes of weathering, rocks rich with minerals containing calcium and magnesium come into contact with water, which breaks down the minerals. Carbon dioxide combines with these dissolved minerals to eventually form calcium or magnesium carbonate (limestone or dolomite) and clays. Because ants appear to enhance this rock dissolving process when they mix the soil, they may play a role in the drawdown of carbon dioxide from the atmosphere.

Experiments have shown that ants enhance mineral weathering 3 to 100 times more than other insect or plant agents. This increased rate of weathering due to normal ant activity may be beneficial to help keep global temperatures low by reducing carbon dioxide in the atmosphere.

Image: myrmecophile77 / CC BY NC - Creative Commons Attribution + Noncommercial

Image: Royce Milam / CC BY - Creative Commons Attribution alone

Image: Steve Shattuck/CSIRO Australia / CC BY - Creative Commons Attribution alone

Last Updated June 8, 2017

References

“25 years of in-situ measurements of Ca-Mg silicate mineral dissolution by ants, termites, root mats, bare ground, and a control reveals ants to be one of the most powerful biotic weathering agents yet recognized. Six sites in Arizona and Texas (USA) indicate that eight different ant species enhance mineral dissolution by ~50×–300× over controls. A comparison of extracted soil at a 50 cm depth in ant colonies and adjacent bare ground shows a gradual accumulation of CaCO₃ content for all eight ant species over 25 yr. Ants, thus, have potential to provide clues on how to enhance contemporary carbon sequestration efforts to transform Ca-Mg silicates and CO₂ into carbonate.” (Dorn 2014:771)

“Given observed high BEW [biotic enhancement weathering] of ant colonies, an understanding of the geobiology of ant-mineral interactions might offer a line of research of how to geoengineer accelerated CO₂ consumption by Ca-Mg silicates. Similarly, ants might also provide clues on geoengineering efficient pathways of CaCO₃ precipitation to sequester atmospheric CO₂.” (Dorn 2014:773)

Journal article

Ants as a powerful biotic agent of olivine and plagioclase dissolution

Geology | 01/01/2014 | Dorn RI

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