I bought a bag of ‘top soil’ yesterday to mix into my raised veggie bed. Only, it wasn’t soil. When I opened the bag I saw a lot of organic material but there was no evidence of any mineral content. To make matters worse, it was dead organic material — dry and unscented.
I was hoping to see something more like the gift the ants brought me in the picture above: rich soil with a texture like chocolate cake. Healthy soil ideally is about 45% parent material: clay, silt or sand. About 1/4 should be air, 1/4 water and only a fraction of the rest should be organic stuff — about 5% in all.
No wonder the bag was so cheap to purchase and easy to lift. Making compost is easy and here where it gets so hot it takes almost no time at all. But creating mineral particles? That process is not so fast and not so cheap. In the wild, the process begins with weathering. And that weathering is sometimes helped along by the lowly ant.
Rocks break up into the tiny bits needed to create soil partly through abrasion: particles rubbing against each other. As the term weathering suggests, weather can play a key role. Rocks expand, contract and break with changes in temperature and moisture availability. The same factors that cause erosion (wind, water, pressure changes) can also cause rocks to disintegrate. If the rocks stay put it is called weathering; if the particles are dispersed it is erosion. But these physical processes take time. A lot of time.
The chemistry of air and water can speed up the disintegration of rocks a bit. Rainwater tends to be naturally acidic. Add in air pollution and that water can become greatly acidic. When rain falls on calcium rich rocks like limestone, carbonization (the fizzing found in soda pop or by using baking soda) occurs. If you are a nerd like me, try pouring vinegar on limestone for a dramatic demonstration of this process sometime. drop drop fizz fizz
Likewise, the oxygen found in our air can react with iron rich rocks such as pyrite. When exposed to air, the iron rusts away leaving a rich red parent material that looks a little like the surface of Mars.
But even with the addition of chemical weathering it takes a long time to make soil. I have heard people say it takes about 100 years to create just an inch of topsoil.
Ants and Soil Formation
Earthworms get a lot of credit for helping to speed up the process of soil formation. As worms move through the soil mineral particles rub against each other. The passage of worms opens spaces allowing the good chemistry of air and water to filter down to parent materials. Earthworms also churn the soil bringing parent material closer to the surface. But though this will sound like blasphemy — in many places earthworms are not terribly efficient at cycling soil; in some places they may even be harmful.
Ants are the true heroes though unsung and unappreciated. In some places they are even (gasp) considered pests.
Earthworms Ain’t Natural! ;)
Wherever there was glaciation in North America the native earthworms became extinct. The earthworms now commonly found in Northern regions were all introduced by settlers. These earthworms are great helpers in most people’s gardens but they are a menace for Northern forest ecosystems — destroying cover and leaving soil bare and vulnerable to erosion. In arid and hot regions of North America compost worms really struggle just to survive — for much of the year they need to go dormant.
So, if earthworms and red wigglers weren’t originally part of the soil ecosystem, how was soil cycled?
Ants. And other diggers. And plant roots. And mycorrhiza. But today I am thinking of ants. In many places, ants actually outperform worms when it comes to cycling soil.
Don’t believe it is possible? Look up ant colony art to see just how extensively ants can work their way through soil.
Ants Are Friends
Ants are also great for pest control. Did you know that ants — especially fire ants — kill fleas? Not to mention the eggs & larvae of flies, silverfish, bed bugs, and even cockroaches …
And the next time you see a volunteer wildflower growing you may want to give ants the credit for planting it. Ants are great for dispersing seeds.
Ants Even Battle Climate Change
Soil has a great reputation for its ability to sequester carbon. Ants also play an important role in helping to store carbon.
The geologist Ronald Dorn discovered just how powerful ants can be at weathering basalt sand. He found that sand worked by ants weathered up to 300 faster than sand left undisturbed on the surface. As the ants use the sand limestone is created as a byproduct. The bonus? As part of the accelerated weathering process, carbon dioxide is trapped from the atmosphere and stored in the deposits.
If you think ants are too tiny or insignificant consider that the biomass of ants is roughly equivalent to the biomass of humans. A lot of little bodies cooperating can accomplish a whole lot of good. So the next time I see ants I think I will give them a nice hurrah. As long as they stay out of the kitchen … =)