A stream bed is a patchwork of stone and sand. The cobbles and gravel interlock together under the force of water, laying like shingles on a roof. Where the water flows swiftly, sand and fine silts are washed away in seconds. In slower moving portions of the stream, behind obstructions or in over widened reaches, sand and silt can use gravity to overcome the energy of the water and deposit on the bottom.
Within the matrix of the stream bed, an unseen world exists. This is the benthic world, an area occurring at the bottom of a body of water. Under the water and the waves and overhanging vegetation there is an ecosystem supported by a complex food web. One of the important components of that food web to a fly angler are the aquatic macroinvertebrates. The bugs. Chironomids, mayflies, caddisflies, stoneflies, crane flies, beetles are a few of the insects that inhabit the benthic world. They cling to the bottom of rocks and scrape algae, build cases, filter the water and they hunt other insects.
This weekend while on the stream I picked up a few rocks and turned them over. I waded into the benthic world and discovered dozens of insects on several of the streambed cobbles. The insects’ bodies are shaped to fit against the rocks, streamlined so the flowing water won’t lift them and send them tumbling downstream. When they do become dislodged (maybe when their rock is lifted out of the water by a clumsy interloper), they are put at risk. The insects are designed for clinging to the rock, not swimming in the water column. The water column is the domain of the fish and other aquatic vertebrates. The insects can become food in the water column. They can also disperse downstream, finding new rocks, expanding the footprint of the habitat, giving future generations more space to explore and to find hospitable places to live. This is drift, where they can be food, or they can grow and expand their habitats.
If every insect stayed on the same rock where it emerged from an egg, species would not be present throughout so many stream systems. Sometimes I feel like that insect. I cling to my safe and comfortable rock. I don’t want to risk becoming food or even losing my place on the rock. My rock can be my perspective, my ego, my comfort, or even an old habit. I’ve also had a few instances recently witnessing conflicts where people were holding onto their rocks, defending their positions and perspectives, unwilling to let go.
Feeling at risk or challenged from our position can produce fear and defensiveness. We protect ourselves and limit our exposure. Each of us has developed on our rocks, adapted to fit those spaces and the conditions that continually shape them. However, if we just hold on clinging to our rocks, we won’t be able to drift, explore, and expand.