Defenders' Experts
Forest Biodiversity
Just consider the immense variety of things we call "trees." They can range
from seedlings to giants more than 300 feet tall, some thousands of years old.
They come in a variety of life-forms: broadleaved, needle-leaved, evergreen and
deciduous. Trees can provide important habitat benefits even after they die,
whether still standing (snags) or fallen (logs). Some estimates suggest that
about one-fourth of all forest wildlife depend on snags and logs.
The immense variety among trees is mirrored in the diversity of "forests," which the USDA Forest Service defines as lands that are at least 10 percent covered by trees and at least one acre in size. This includes areas in which trees are intermingled with other types of vegetation, such as shrubs; plantations or "tree farms;" and forests that are regenerating naturally after fire or timber harvest.
Conservation biologists often describe forests in terms of their
structure and functions, which are shaped in part by a variety of dynamic forces
- both natural and human related - collectively referred to as disturbance
regimes. But forests also encompass a largely unseen world
of species and processes that are absolutely
critical to the function of these ecosystems.
About the Forest Biodiversity section
Forests, in all their variety, provide benefits to biodiversity and management opportunities and challenges that are sufficiently different from other ecosystem types to merit separate consideration.
The material here emphasizes considerations at a landscape scale (typically of at least a few thousand acres), but many of the principles discussed can be scaled up or down, and individual landowners should be able to find some useful suggestions relevant to smaller ownerships.
Readers may detect a bias to examples from the West and Pacific Northwest, which reflects the both the authors' knowledge and the fact that much of the most innovative landscape-scale planning has occurred in these regions. We attempt to acknowledge examples from elsewhere, and believe the principles discussed here are broadly applicable. We also welcome suggestions about examples from elsewhere in the country that we can incorporate as the website is revised and updated.
In this section. . .
Forests, in all their variety, provide benefits to biodiversity and management opportunities and challenges that are different from other ecosystem types.
Natural forests are a mosaic of stands of varying sizes and ages which supports a great diversity of wildlife.
Disturbances are events and processes that kill or remove substantial portions of trees in a forest: wind, flood, landslides, insect and disease outbreaks, and fire.
Forests depend on the rich variety of tiny living things residing in or on the soil of the forest.
