Old growth forests are the later stages of forest succession in forested ecosystems. They are home to trees reaching their oldest growth stages and contain many biological features that have developed over hundreds of years.
Older conifer and hardwood forests once covered 51 percent of Minnesota’s forested regions. Today only remnants remain of these unique pieces of the state's natural history. Minnesota’s economy in the 1800s was fueled by harvesting the oldest and largest trees from the forests to supply the lumber needed by a growing nation. Most of the trees that went unharvested were young, poorly formed, or without high timber value. Some mature forests in hard-to-reach areas such as ravines, steep slopes, or in the middle of vast wetlands survived.
Today in Minnesota, ecologically significant old growth forests are protected from harvest and represent new values in modern forest management. Minnesota’s remaining old growth forests are important for their ecological, scientific, educational, aesthetic, and spiritual values. They provide important habitats for native plants and animals and a glimpse into what is biologically possible for tree growth. The DNR protects the highest quality remaining old growth forests in order to preserve and perpetuate these ecosystems and their multiple values.
Old growth forests include the following forest types in Minnesota: black ash, lowland hardwoods (including elm, silver maple, and ash trees), northern hardwoods (including maple and basswood trees), oak, red and white pines, white spruces, upland white cedar, and lowland conifers (including cedar, black spruce, and tamarack trees).
DNR defines old growth forests as forests that have developed over a long period of time, essentially free from catastrophic disturbances. They contain large, old trees of long-lived species that are beyond traditional rotation (harvest) age. High-quality old growth forests also have relatively complex stand structure (such as snags and woody debris), higher stand mortality, and few invasive species. They also include rare species or native plant communities,
The DNR manages a 44,000-acre network of old growth forest sites on state-administered land.
The goal of DNR’s old growth forest policy is to maintain a viable statewide network of high-quality old growth forest sites along with relatively undisturbed, natural-origin younger forests that will be managed to promote old growth characteristics in the future (i.e., future old growth). The DNR will manage this old growth forest network to ensure that its quality is maintained over time and it has the acreage necessary to:
- Adequately represent old growth forests as an element of the state’s biodiversity;
- Provide habitat needed for wildlife and plants associated with old forests;
- Maintain benchmark sites for natural processes that we are only beginning to understand; and
- Guarantee Minnesotans the opportunity to enjoy old growth forests now and in the future.
To achieve this goal, the DNR strives to maintain or restore the integrity of old growth communities. Timber harvesting is not allowed within designated old growth areas (including salvage and timber improvements); wildlife opening and browse regeneration development cannot occur; pesticides cannot be used (except to protect against serious exotic threats); metallic mineral exploration is prohibited; and new road development is not allowed (with very few exceptions).
The DNR continues to manage old growth forests and is working on completing a designation process for lowland conifer old growth forests.