Definitions and History

Robert Leverett

This book is a compilation of writings by a group of distinguished scientists, naturalists, and environmentalists about an exceedingly rare part of the natural world—the scattered remnants of the original Eastern forests. Today, such forest exists on a tiny fraction of the land, but 500 years ago it was considered inexhaustible.

Isolated pockets of old-growth forest are all that remain. As such they are the subject of intense interest to the scientific, academic, and environmental communities. This book is a measure of that interest.

Some might think that interest in Eastern old growth is an extension of forest preservation movements spawned in the West. Certainly, depletion of the old-growth rainforests of the Pacific Northwest has drawn attention to the status of all public forests. Awareness of Eastern old growth has been heightened by the furor over excessive logging in Western national forests, but most of the authors have connections to Eastern forests that predate the issues surrounding Western old growth.

The uninitiated might think that these remaining patches of original forest are well known, intensively studied, and precisely defined, but spirited debates say otherwise, especially about how old Eastern forests are defined. Consequently, we will begin our tour of Eastern old growth by investigating the problems surrounding definitions and terminology.

What Is an Old-Growth Forest?

As the reader will discover in this book, scientists and forestry professionals apply different meanings to "old growth." To make matters worse, the meanings vary within the professions. These definitional differences, combined with a scarcity of searches for old growth in the field, have led understandably to varying estimates of how much Eastern old growth remains. Current estimates vary from as little as a half million acres to as much as a million and a half. This broad range excludes mature second-growth forests (i.e., previously cut), which some ecologists argue should be included, at least at some future date. The range also excludes scattered stands of "low-quality" noncommercial timber that have survived "unnoticed." When this latter category is thoroughly inventoried, surviving old growth will probably be well above 1.5 million acres. One scientist estimates the figure to be as high as five million.

The term "old growth" implies old trees. However, two criteria, age and naturalness, drive most definitions of old-growth forests. Consequently, it is tempting to conclude that an adequate definition for old growth is a forest of mature trees that has developed naturally. But how old is old, what constitutes natural development, and is it the trees or the forest that is old? A surprising number of definitions have been developed to address these questions.

"Old growth" has been used loosely to describe a forest that has existed since presettlement times and that has experienced little or no direct disruption by Euro-Americans—whether or not the forest has experienced catastrophic natural disturbance and whether or not the trees in it now are old. In this broad sense, "old growth" is roughly equivalent to the terms "primary" or "original."

However, many researchers use "old growth" in a narrower sense. They restrict it to forests in which the trees are old, at least in relation to others of their species. For example, Charles Cogbill, in his chapter on red spruce forest in the upper Northeast, limits old growth to stands that have escaped disturbances long enough for the trees to have a mean age over 150 years. Some researchers eliminate from consideration all stands of tree species that do not live more than 120 years. Peter White counters the tendency to equate exclusively with stands of old trees rather than simply with old, chronologically continuous forests. White expresses the need for a term defining old forests, not necessarily old individual trees. White imposes the requirement that such a forest should have escaped direct anthropogenic disruption.

Researchers may answer the question of what to call old forests of relatively young trees by giving separate meanings to primary and old growth. Primary would refer to forests of any age that have experienced no or only minimal human disturbance. (Whether that definition might allow light logging or grazing or anthropogenic fire varies with the researcher.) On the other hand, old growth would refer to forests that meet certain criteria of age and/or stand development. This is consistent with Lee Frelich's approach. In his chapter, Frelich defines primary and old growth separately. For Frelich and many other researchers, a primary forest may be but is not necessarily old growth. Looking at how researchers have defined old growth, we can place most definitions in one of four categories.

Category 1 definitions are the most demanding and are subscribed to by a majority of the authors of this book. They emphasize the importance of (1) tree age, (2) the lack of human disturbance, and (3) the successional stage of the forest More specifically, they require that an old-growth forest have (1) a high percentage (usually half or more) of its canopy trees over half the maximum life spans for the represented species, (2) at least a few trees near the maximum life spans for the species, (3) no...