Old growth is an advanced state of forest. Really the bulk of it is dead. In any tree only the outer inch or so of the tree is ferrying the nutrients around, the remaining inner portion is….still and old, contributing strength but not much vitality. Importantly, a ton (or more literally) of nutrients are locked up in this old growth tree. Crashing to the ground in a storm delivers all those organics back to the soil. Cutting it down and hauling it away deprives the soils of sorely needed organics, but it gives us lumber right?
Old growth is dark and gloomy and quiet. Overstory blocks out the sun so the young trees have little of the sunlight they need to grow. It’s quiet because there’s not much there. The youngish forage that tends to be in reach of browsers and other eaters of vegetation needs sunlight. When there’s little light hitting the forest floor, there’s little forage in reach and therefore few eaters. They all go where there is food. Edges, meadows, and places with enough sunlight to grow.
So, like clearcutting, old growth isn’t all it’s cracked up to be. Old growth is mostly dead and quiet. Nothing lives there hardly, except maybe a few species of birds like the spotted owl that need the old growth for nesting. Most of life moves on to other parts of the ecosystem where there is more food.
That said, old growth is a stunning place. You are small. The trees are big. You have the quiet to contemplate your spot in this primeval nature. It is an experience well worth seeking out.