Forests regenerated after clearcut harvest are often very dense and dark, with little or no light reaching the forest floor. This means few understory plants can survive to provide food and shelter for wildlife.
A variety of understory plant species and sizes found in old-growth forest provides abundant food and cover for native wildlife, including insects, small mammals, and birds.
Second-growth forests are often monocultures, with the trees all essentially the same species, age, and height, making a uniform unbroken canopy, seen on the left. This is compared with a variety of tree sizes and heights seen in the old-growth forest to the right.
Forests regenerated after clearcut harvest not only have trees that are all about the same size, but they few large snags or logs.
Large snags and logs, often completely absent in second-growth forests, are key habitat elements for species like pileated woodpeckers.
In contrast to dense second-growth forest, old-growth forest has fewer and larger trees, many large snags and logs, and abundant understory plants, providing habitat for many more wildlife species and individuals of each species.