I could hardly believe my luck. On my morning science news from the American Academy for the Advancement of Science (AAAS) list was not one – but two articles on earth worms. I am a fan! I can’t remember the first time I picked up an earthworm from the sidewalk after a rain. Which, by the way, I still do. But there is no way that I can get them all, yet I hate seeing their little desiccated carcasses lying on the sidewalk the next day. It seems that they are often caught between a rock (the sidewalk) and a hard place (the dirt). After a rain the layer of ground which they normally inhabit can become saturated and the tunnels the worms make as they move about become flooded. Just like you and me, the earth worms cannot breathe under water. They breathe, as in taking in oxygen, through their skin, not through their mouths. So they will often come to the surface of the ground and wander onto the sidewalk. If they stay in the grass they are pretty much ok.
I decided to check some of what I thought I knew and ended up at the University of Illinois Extension Service where Herman the Worm holds forth on all things worm-ish, https://web.extension.illinois.edu/worms/anatomy/index.html . The site states that worms like moist environments as their skin must stay moist in order to be able to absorb oxygen. So, wet ground is good for their skin, so they can breathe easier. But saturated ground is not good; it does not allow air to penetrate to the levels of the worms. They will drown. They will escape to the surface. Earthworms also come to the surface to mate. Both are important functions for these little creatures.
But back to the main line. The first time my grandfather took me fishing, I wanted to look for worms. He took me out under a old sycamore tree on his farm and told me to dig. I was fascinated by the worms I uncovered in the dark moist soil. My grandfather told me to leave them alone, that he had other bait to use for the fish. So I took a parting look at the worms, and off we went to his boat on the river bank.
All of us have probably found worms when we have dug into the soil. And because they like to be moist it would make sense that they prefer shaded places where the earth is soft and not dried out. But where in the world are they all? Both of the articles in my AAAS science news link mentioned a coordinated study of scientists which included 6693 sites in 57 nations across the globe. The study asked about their work with earthworms. Personally, I have found that worms always show up to work on time.
And what an amazing amount of work they do. We all most likely remember a science class in grammar school in which we learned that worms are an important constituent in soil health. They aerate the soil as they tunnel about. Their tunnels allow the flow of water into deeper levels of the soils. Their droppings (known as castings) fertilize the soil. All of these; fertilizer, water , and air are important aspects of plant root growth for healthy and robust crop production.
We salute you, little worms, and out of respect I will continue to help you off the sidewalk.
Two sites with information about worms and agriculture:
University of Illinois: https://web.extension.illinois.edu/worms/anatomy/index.html
Pennsylvania State University: https://extension.psu.edu/earthworms
Information about extension services: