LISTENING STUDY Question 58:
What are "old growth forests"?

"Old growth" describes the fourth and final stage of stand development, following mature forest, in which the forest canopy is generally composed of scattered remaining trees that assumed dominance following natural disturbance along with newly dominant, shade-tolerant trees. Other characteristics of oldgrowth forests may include accumulated coarse woody debris, snags and canopy gaps created by fallen trees. Because of these features, and the presence of an understory, old-growth forests generally exhibit complex stand vegetation, and provide habitat for many species. Development of old-growth forest generally takes from 100 to 200 years, with variation depending on forest type. The last remaining sizable area of old-growth forest in the contiguous United States lies in the Pacific Northwest; only a few small and isolated patches of old-growth remain in eastern forests. However, as a stage in stand development, old-growth forest could also develop in eastern forests (and was present in presettlement forests). - Victoria Mills, Project Manager, Corporate Partnerships, Environmental Defense

LISTENING STUDY: Some responses reference a specific age which trees in a forest must attain to qualify as "old growth."

1. A forest stand usually at least 180-220 years old with moderate to high canopy closure
2. A multilayered, multispecies canopy dominated by large overstory trees
3. High incidence of large trees, some with broken tops and other indications of old and decaying wood (decadence)
4. Numerous large snags, and heavy accumulations of wood, including large logs on the ground - Bureau of Land Management

Old growth forest: an undisturbed forest with trees that are more than 200 years old. It is characterized by fallen trees, trees with broken tops, and mature and dying trees. - U.S. Fish and Wildlife Service

Old growth forests enrich our biodiversity and provide core habitat for wildlife, they serve as genetic repositories for future crop trees and they yield non-timber products such as medicinals. And for many people old growth forests provide unparalleled spiritual, aesthetic and recreational values.
     Old growth comprises a set of forest conditions that should not be described by the age class of trees alone. For example, in the northeast, mature hardwood trees of 80-120 years of age can satisfy many values that are ascribed to old-growth forests even though they are still vigorously growing. - Eric Palola, National Wildlife Federation, in testimony to the Senate Subcommittee on Forests and Public Land Management, October 2, 2001

The fourth and final stage of stand development, following mature forest, in which the forest canopy is generally composed of scattered remaining trees that assumed dominance following natural disturbance along with newly dominant, shade-tolerant trees. Other characteristics of old-growth forest may include accumulated coarse woody debris, snags and canopy gaps created by fallen trees. Because of these features, and the presence of an understory, old-growth forests generally exhibit complex stand vegetation, and provide habitat for many species. Development of old-growth forest generally takes from 100 to 200 years, with variation depending on forest type. The last remaining sizable area of old-growth forest in the contiguous U.S. lies in the Pacific Northwest; only a few small and isolated patches of old-growth remain in eastern forests. However, as a stage in stand development, old-growth forest could also develop in eastern forests (and was present in presettlement forests). - Environmental Defense

LISTENING STUDY: Other responses indicate that age is an important characteristic of "old growth forests" but emphasize that this varies with the individual tree species in question.

I suppose it varies by observer. I'd be comfortable with a definition of old-growth that included something about a fully functioning forest with trees exceeding 50% of maximum age for each species. - Michael Snyder, Forester

Old growth forests are those where the average age of dominant canopy trees exceeds half the mean pathological age of the species, as well as those that have not had significant human intervention (some light cutting or road building might be acceptable). - Robert R. Bryan, Forest Ecologist, Maine Audubon

An old-growth forest is a forest ecosystem where the dominant trees largely exceed the biological maturity age of the species concerned taking into account its specific environment and its geographical location. The temporal dynamic of these forests is characterised by the coexistence of living trees, senescent trees and standing dead trees as well as the presence of fallen dead trees, lying on the ground, showing different decomposition levels. Those forests show little or no evidence of human disturbance. - Canadian Forest Service

Old growth forests must be defined for each forest type, such as temperate rain forest, boreal forest, tropical rain forest, and any other major forest type. Scientists are now recognizing that within these broad forest types, there is enormous variability and that further definition is required. The definition of old growth in any kind of forest is constantly evolving as scientists get a clearer understanding of the many variables that make up any forest system. There is an excellent publication that describes the challenges in defining old growth. It's called "New Findings about Old-Growth Forests," and is a Science Update from the Pacific Northwest Research Station (Issue 4, June 2003). - Susan Hammond, Executive Director, Silva Forest Foundation

LISTENING STUDY: Some responses reference lack of human disturbance as a qualifying characteristic of "old growth."

Greenpeace supports the Taiga Rescue Network (TRN) definition, whereby the term old-growth forest can be applied to an area in which no forestry activities have been conducted since 1960, if the area in question measures at least ten hectares and contains at least ten cubic meters per hectare of the decomposing wood that is so vital to many animal species. It is almost impossible to find any dead trees in planted forest areas. - Oliver Salge 2003

Forests in the last stage of successional development after a long period without significant disturbance. They are generally characterized by multiple canopy layers, variety in tree sizes and species, decadent old trees, standing and dead woody material, and abundant ground-level decomposition. - Northern Forest Alliance 1999

Forest that is ecologically mature and has been subjected to negligible unnatural disturbance such as logging, mining, roading and clearing. The definition focuses on structural diversity and includes forest in which the upper stratum or overstorey is in the mature and late mature stage, and regrowth more than 120 years old produced through natural processes, ie. Wildfire or windstorm. - Native Forest Network

Perhaps the only definition of old growth that works in the context of papermaking is: Forests that have not been extensively disturbed by industrial logging in the past 150 years. - Susan Hammond, Executive Director, Silva Forest Foundation

LISTENING STUDY: Some responses reference various ecological and structural features of forests that would indicate their status as "old growth."

A community with dominant trees at or near biological maturity. The age and structure of an old-growth community varies with species and site. Old-growth stands are sometimes characterized by a multi-layered, uneven age and size class structure; a high degree of compositional and structural patchiness and heterogeneity; and significant amounts of woody debris and tip-up mounds. - United States Forest Service

Old growth is best identified by certain features of the forest. These features include increased size of trees, large standing dead trees, fallen trees, buried wood in various states of decay, thick forest floor, tree lichens and a high diversity of fungi, etc. These features all contribute to a more complicated forest structure than the earlier successional stages of the forest, and this results in a higher diversity of plants and animals. - Rainforest Action Network

Old-growth forest-forests that contain a wide range of tree sizes and ages, and often including a long-lived dominant and a shade-intolerant associate, a deep, multilayered crown canopy, large individual trees, and significant accumulations of coarse woody debris including snags and fallen logs. - Society of American Foresters 1991

Old-growth forests are the fourth and final stage of stand development, following mature forests, in which the forest canopy is generally composed of scattered remaining trees that assumed dominance following natural disturbance along with newly dominant, shade-tolerant trees. Development of an old-growth forest generally takes more than 100 years, with variation depending on forest type. An old-growth forest exhibits these characteristics:
-A watershed-level forest of 5,000 acres or more in size, that has been left undisturbed, and predominantly has trees that are 200 to 1,000 years old;
-The accumulation of coarse woody debris, snags, and canopy gaps created by fallen trees;
-The presence of an understory consisting of a multilayered combination of seedlings, mature trees, bushes, and other plants, which attribute to a complex stand vegetation pattern;
-The inclusion of numerous dead trees, both standing and fallen, that provide essential habitat and nutrients to plant and animal forest species;
-An ecosystem rich in biodiversity, providing habitat for a wide variety of indigenous plant and animal species. - Boise Cascade

Although the ages of some [Canadian] boreal larch and black spruce trees have been found to exceed 350 years, the unifying feature of Canada's boreal's old-growth is generally not age per se . . . but the set of structural characteristics shared by many forest types in the later stages of succession. Relative to younger stages, old stands have trees of many ages and sizes and often have more large canopy trees, large snags, and large downed logs. Overall, structural diversity is highest in old stands, and this is reflected in unique plant and animal communities as well as high overall species richness relative to younger stands. - Bringing Down the Boreal, ForestEthics, 2004

LISTENING STUDY: Other responses indicate that there are many definitions of "old growth forests" but little agreement on any one particular definition.

The US Forest Service has over 100 definitions for "old growth." The definition changes depending on whom you ask. The "old growth" issue was raised largely as a result of the harvesting of 1000-year-old huge towering Douglas fir trees in the rainforests of the Pacific Northwest. Visions of these majestic and relatively rare trees being harvested for wood products caused a public outcry. Today, activists are calling 100-year-old trees of interior Canada "old growth" even though the trees are 1/8 the size of the Pacific Northwest "old growth" trees and are not endangered from a biodiversity perspective. A more scientific and precise term that Conservation International uses when characterizing endangered woodlands is "forests of exceptional conservation value," or FECV for short. - International Paper

Addressing the issue of "old growth" is a challenge, given the lack of consensus on a definition for the term: researchers at the U.S. Forest Service found at least 114 definitions. "Old growth" describes not only the age of the trees, but the overall state and composition of a forest as well.
     Governmental authorities, environmental organizations and businesses worldwide share the goal of protecting ecologically rich ancient forests. Exchanging information through dialogue and scientific reporting helps to develop forest management approaches designed to conserve the biodiversity and cultural values of old growth forests. - Stora Enso

LISTENING STUDY: Other responses:

There are 100-some definitions out there, but mainly it just means that older trees are dominant in a landscape. - Partin 2004

Forests that have been able to evolve for centuries and maintain their ecological integrity. - Frank Locantore, Co-op America