The Ants Who Store Our Carbon

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As we are very rapidly discovering, living creatures have the ability to drastically alter the climate and weather systems on Earth, and the greatest changes are achieved by the species that are greatest in number. Ants may be no exception to this rule, and recent geological research suggests that ants may be providing a vital counter-balance to our CO2 emitting ways. Ants may be cooling the climate as we warm it. But are ants the solution to climate change?

Ants and Climate Change

A recent study published in Geology has begun to reveal the role ants play in keeping Earth’s atmosphere cool. They might be small, but ants are ubiquitous on Earth, found on every continent except Antarctica and numbering over 15,000 species. They have the potential to have a big impact. The study published this month showed that ants collect minerals from their environment and change them into rock, inadvertently trapping carbon dioxide gas in the rock as they do so. This process is identical to the way in which atmospheric CO2 is sequestered by the oceans, and naturally weathered on land.

To make limestone, you need CO2 and either a calcium or magnesium silicate. The formation of limestone is responsible for ‘drawdown’, a process which traps atmospheric CO2 inside rock. Drawdown is thought to have been crucial in maintaining a habitable climate during geological history. It is responsible for the carbon sequestration abilities of our oceans, and it may offer the key to tackling man-made climate change in the future.

Buried Treasure

During the course of a 25-year experiment, Dr Ronald Dorn (Arizona State University) buried basalt sand (sand formed from volcanic rock) at six sites across Arizona and Texas. Every 5 years he checked on his buried treasure, and measured the degradation of minerals olivine (a calcium silicate) and plagioclase (a magnesium silicate). These minerals naturally degrade due to water, insect activity and tree and plant roots, and he was interested in quantifying these natural processes. What he found, however, was quite a surprise. The basalt he had placed into ant nests had degraded far more than any of the other locations (bare ground, amongst tree roots, in termite nests). Ants and other insects including termites are known to enhance the weathering process by moving soil as they dig their nests, but clearly the ants were up to something else. Basalt placed in ants nests showed mineral degradation rates between 50x and 100x those for bare ground, and 5x – 10x higher than termites and plant roots. This was true across eight different species of ant, at different altitudes and in different habitats. The researchers found a build-up of limestone inside the ants’ nests indicating that they are, somehow, converting these minerals into limestone.

It remains a mystery is how the ants turn the ingredients into calcium carbonate (limestone), and whether they are doing so deliberately. Dr Dorn suggests the process may be occurring when ants stick grains of sand to the walls of their nests, gluing them in place with saliva. Alternatively, they may eat the minerals and produce a calcium carbonate excretion with the help of gut bacteria. Ants are known for their use of symbiotic bacteria to perform chemical reactions and produce useful substances. The precious fungus crop of fungus-growing ants (Atta and Acromyrmex) is vulnerable to infection by a parasitic fungus, but the ants employ symbiotic bacteria that produces antiobiotics, which are then used to clean and protect the fungus.

It isn’t clear yet how we might be able to make use of the CO2 sequestration powers of ants to help ameliorate man-made climate change, but it may provide a powerful weapon in our arsenal against global warming.

Historic Cooling

More research is needed to understand what the global impact of calcium and magnesium silicate dissolution by ants may have been historically. Ants are extremely numerous, though, making it plausible that ants may have played an important role in maintaining a relatively cool and habitable climate. The success of ants really began about 65 million years ago, during which time the Earth’s climate has cooled significantly. Ants may have been an important factor in making this happen.

The Importance of Invertebrates

This study highlights the important of insects and other invertebrates to the survival and happiness of humans. Although we often hardly even notice they are there, and are often alarmed if we do come across them, invertebrates provide us with essential ecosystem services such as nutrient and mineral cycling, pollination, seed dispersal, and climate regulation. Without them, life on Earth simply wouldn’t be possible.

Ants are especially important for their roles in ecosystems. Some ants perform seed dispersal in tropical forests, others have intricate mutualisms with plants, fungi and other insects, others are key predators, others move huge volumes of plant matter and contribute to nutrient cycling. Ants balance the ecosystems in which they live. Just think about that next time you’re about to pour boiling water down one of their nests!

It is estimated that the biomass of ants on Earth is equal to humans. Perhaps then, ants should be viewed as the ultimate balancing force to counter our destructive tendencies. Or some of them, at least. For every person on Earth, using fossil fuels and releasing greenhouse gases, there is an ant somewhere, scurrying around, busying depositing carbon dioxide into the ground again. The Yin to our Yang, if you will

Our Power Over the Planet

It is easy to feel as though we are passive recipients of the climate and weather, but the power of living things to alter the climate is remarkable. It is something that has happened throughout the history of life. The first living cells capable of photosynthesis appeared 2.4 billion years ago and released oxygen into the environment, killing most life on Earth and forever changing our atmosphere. Then, 2.3 billion years later, ants appeared on the scene and began sequestering carbon dioxide and cooling the atmosphere. Finally, around 10,000 years ago, Homo sapiens experienced a population explosion and began to alter their environment in every way imaginable. The conditions on Earth are part of an eternal feedback loop, with each other, and for the last 3.5 billion years or so, with the living things that inhabit it.

As a final point, I must add that although life altering the atmosphere has happened numerous times before, that is not to say that it’s OK for intelligent life to knowingly alter the climate. Firstly, the argument “well, somebody else already did it, so it’s OK” is a fairly childish one. Secondly, never before in evolutionary history have enormous climatic changes been caused by a sentient being. Finally, historically changes in climate have often killed the perpetrator of the change, and all our climate change projections seem to indicate that a warmer Earth does not work out well for humans.

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