Wild Forests presents a coherreview of the scientific and policy issues surrounding biological diversity in the context of contemporary public forest management. The authors examine past and currpractices of forest managemand provide a comprehensive overview of known and suspected threats to diversity.
In addition to discussing general ecological principles, the authors evaluate specific approaches to forest managemthat have been proposed to ameliorate diversity losses. They presone such policy -- the Dominant Use Zoning Model incorporating an integrated network of "Diversity Maintenance Areas" -- and describe their attempts to persuade the U.S. Forest Service to adopt such a policy in Wisconsin.
Drawing on experience in the field, in negotiations, and in court, the authors analyze the ways in which federal agencies are coping with the mandates of conservation biology and suggest reforms that could better address these important issues. Throughout, they argue that wild or unengineered conditions are those that are mlikely to foster a return to the species richness that we once enjoyed.
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About the Author
William S. Alverson is research associate and assistant scientist in the botany departmat the University of Wisconsin-Madison.
Donald M. Waller is professor of botany and environmental studies at the University of Wisconsin-Madison.
Walter Kuhlmann practises environmental law with the Madison, Wisconsin, law firm of Boardman, Suhr, Curry & Field.
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Conservation Biology and Public Policy
By William S. Alverson, Don Waller, Walter Kuhlmann
ISLAND PRESSCopyright © 1994 Island Press
All rights reserved.
Forests Then and Now
North American forests have suffered drastic reduction since European settlement. Logging has removed more than 99% of the great virgin forests from the eastern half of the continent and still proceeds apace in the far West. Settlement has stripped most of the lower 48 states of their original large predators and hoofed mammals. How could such drastic losses occur without more public outcry? Why were sentiments for conservation so limited and ineffectual? While answers to these questions fall beyond the scope of this book, it is important to appreciate the nature, extent, and causes of these losses if we are to understand today's continuing threats to biological diversity.
Today, few of us are familiar with the unique sights, sounds, and smells of primary forests. Although many small, remnant stands still appear majestic, they lack a full complement of their original bird and mammal species. Once dominant tree and shrub species have fallen to introduced pests or are failing to regenerate. Just as scientists are beginning to appreciate more of the unique features of old-growth forests (Chapter 2), they are slipping away and becoming ecologically dysfunctional. The general public perceives very few consequences of these losses. An increasingly urban population and continuing declines in the scattered remnants of old growth suggest that fewer people every year will have the opportunity to experience old growth. Thus, we face the specter that today's and future generations will have little basis or concern for defending or restoring old-growth forests.
Many would argue that the early settlers who cleared most of the land could not afford the luxury of conserving their forests, preoccupied as they were with survival. European colonizers of a huge continent cloaked in primary forest could not imagine exhausting these forests or depleting the plants and animals they contained. For 200 years, the felling of forests and associated losses of wildlife occurred slowly relative to human life spans. Only at the end of the nineteenth century, after accelerated cutting had removed most eastern and midwestern forests, after game birds and mammals had become scarce, and after proliferating technology and transportation systems drove several species to the brink of extinction and threatened our final primeval forests, did public outcry arise to limit logging and protect wildlife. Still later came concerns to protect watersheds, re- vegetate stripped lands, and expand state and national parks, forests, and wildlife refuges.
This simplified view of nineteenth-century development obscures many of the social and commercial forces that favored agricultural settlement and deforestation (Cronon 1983, 1991). It also misleads many into believing that we have learned enough from our past mistakes to halt and reverse the destructive consequences of unbridled resource use and species declines. Early conservation measures did accomplish much in protecting soils, vestiges of remaining forests, and particular species directly threatened by overhunting. Their success, however, obscures the nature and extent of current threats to diversity and the profound failures we face as increasing numbers of species slide toward oblivion.
In this chapter we briefly review the sweep of biological change settlement has brought to our forested landscapes. We consider this historical background essential for appreciating the number and severity of these changes and for assessing how patterns of human disturbance threatened, and continue to threaten, diversity via the mechanisms described in Part II. We begin by examining how little remains of our original primary forests and where these remnants are located. We next examine how logging and development spread across the continent, altering landscapes and restructuring biological communities. Finally, we consider how the original primary forests differ from the secondary forests that succeeded them and the prospects this presents for restoring old-growth forests.
Readers interested in further information on the distribution and biotic history of forests in eastern North America should consult Braun (1950). Cronon (1983, 1991) provides insightful and informative ecological and economic histories of New England and the upper Midwest. Williams (1989) provides a detailed analysis of how logging developed geographically across the continent in accord with changes in technology. For readers with further interests in how conservation grew under the leadership of John Muir and his successors, we recommend Fox (1981). Those interested in how forestry and the U.S. Forest Service developed should consult Pinchot (1947), Frome (1962), Shepherd (1975), Steen (1976, 1984), and Clary (1986).
How Much Primary Forest Is Left?
Surprisingly few estimates exist of how much primary, or virgin, forest remains in the U.S. (Crumpacker et al. 1988). While no map has yet been drawn to show where these forests remain in the late twentieth century, several authors have recently ventured estimates of their extent. Postel and Ryan (1991) conservatively estimate that 85% of the primary forests had disappeared by the late 1980s. Other estimates range higher, to 90% (World Resources Institute 1992) or even 95–98% (Findley 1990).
Most of the eastern forests had been cut at least once by 1920 (Fig. 1-1). Today, less than 1% (Allen and Jackson 1992) and perhaps as little as 0.05% (Leverett 1993) remains of the once expansive eastern virgin forests. Yet even if we retain only an average of one part in two thousand of our original eastern forests, the total acreage sums to nearly a million acres (400,000 hectares). Most of these stands are small and inconspicuous (Fig. 1-2), leading some to deny their importance in forest conservation efforts generally. We believe instead that these remnants represent a legacy of significant conservation value due to their scarcity on the landscape and potential for helping to restore old-growth patterns and processes at larger scales (Chapter 11).
This book focuses on the dichotomy that exists between primary and secondary forests. In keeping with Davis (1993), we follow the definition of primary forest provided by Duffy and Meier (1992):
Forests that have never been clear cut and that have little or no evidence of past human activity. Such forests may have been grazed, ... experienced limited exploitation of valuable tree species, and their floors may have been burned by Amerindians and European colonists.
Under this definition we will use the terms "primary," "original," and "old growth" synonymously in this book. In contrast, secondary forests are those that have developed after the previous forest has been extensively logged or clearcut. Given the passage of long periods of time, secondary forests may take on the characteristics of primary forests so as to become indistinguishable from them. However, a recent, much publicized study of old secondary forests in the Appalachians suggests that 80 years appear insufficient for this process to allow convergence (Duffy and Meier 1992).
Biotic Changes before Columbus
Ecological change has swept and shuffled the plant communities of North America repeatedly over the past two million years. Climatic oscillations brought glaciers from the North and dry winds from the Southwest. These shifts apparently occurred slowly enough for most plant and animal species to persist by shifting their distribution continuously (Davis 1965, 1969; Delcourt et al. 1983; Peters and Darling 1985). In addition, refugia always existed to provide appropriate climatic conditions and habitats at least somewhere in the landscape.
The arrival of humans radically altered the rate and nature of ecological change. Peoples from Asia crossed into the Americas via the Bering Sea land bridge by 11,000 years ago, bringing with them hunting techniques and weapons technology that the continent's biota had never experienced. Almost immediately (in geological terms), most of the continent's largest herbivores (camelids, horses, mastodons, giant ground sloths, giant beaver, gom-photheres, etc.), predators (e.g., dire wolves and saber-toothed tigers), and scavengers (e.g., giant condors) went extinct. Many paleontologists believe that people, directly via hunting or indirectly via their cascading effects on other animals, precipitated these cataclysmic extinctions (Martin and Klein 1984). Having not coevolved with coordinated groups of neolithic hunters, these animals were ill-equipped to tolerate their depredations. This interpretation is bolstered by the observation that similar waves of extinction have repeatedly coincided with the arrival of humans onto other continents (Australia) and islands (Madagascar, Hawaii). Thus, humans have exerted potent ecological effects for many thousands of years on this continent, greatly modifying American landscapes via hunting, fire, and perhaps other activities. Their impacts precede and anticipate the even more potent recent impacts of industrial technology and agriculture.
Early European colonists found a continent full of game and majestic timber that dwarfed remaining forests in most of their home continent. While wildlife and abundant firewood may have been the privilege of the wealthy in Europe, any early American could feast on wild game and enjoy a roaring fire. Given such bounty and aspirations, it is hardly surprising that the colonists were preoccupied with clearing the land for farms and obtaining what useful materials they could from their forests. Indeed, wilderness forests often represented danger and an obstacle to be overcome by domesticating the landscape (Cronon 1983; Merchant 1989). While their use of game, timber, and land may seem profligate in retrospect, within the context of the time it simply reflected a function of plentiful supply and limited demand. Today, many visitors from China and parts of Europe view use of lumber and paper in the U.S. as similarly profligate.
In "settling" North America, the Europeans initiated an even more extensive set of changes on the landscape than Indians had. Most immediately, hunting by settlers precipitated local, then more extensive, extirpations of many remaining predatory and game species (Gates et al. 1983). They also began to clear the great virgin forests to plant crops, tend livestock, and eventually produce timber for local and regional markets. These changes, accelerated by population growth, industry, and silviculture, drastically altered the appearance and character of the land as native forest and prairie communities dwindled.
We next consider effects on wildlife and forests sequentially, emphasizing the upper Midwest to make our descriptions more detailed and concrete. By discussing these topics separately, we do not mean to imply that logging had effects clearly separable from overhunting. The trap, the rifle, and connections to distant settlements and markets had direct and profound effects on populations of our larger mammals. Nevertheless, it would be a mistake to ignore the roles timber cutting played in fostering the spread of settlements and the application of these tools (Cronon 1983, 1991). Logging drew settlers into new regions, provided markets for the game and furs, and contributed to the need for a transportation network and dams. In turn, roads and railroads provided access to the forests for hunters and trappers while increasing edge and open habitats.
Changes in Wildlife
Hunting and trapping followed the influx of European settlers, quickly depleting populations of predators, fur bearers, and the larger game species. Woodland bison and elk were extirpated by the latter nineteenth century, echoing the earlier losses attributed to Pleistocene hunters. Hunting and habitat changes eliminated woodland caribou and moose by about 1900 in Wisconsin and Michigan, while a few caribou survived until 1939 in Minnesota (Gates et al. 1983). These species depended on lowland northern forests and probably responded as much to the widespread fires as to logging. Caribou, moose, and elk still persist in Ontario, and moose continue to thrive on Isle Royale after colonizing this island in Lake Superior earlier this century.
Although white-tailed deer populations also were decimated in the upper Midwest by 1890, their high potential rate of increase coupled with subsequent protective hunting regulations allowed them to make a spectacular comeback. Responding to the abundant forage provided by the pervasive early successional habitats of the era, deer populations quickly expanded, surging farther north than ever before. Densities soared to record levels by the 1930s and 1940s, prompting warnings by, among others, Aldo Leopold (1943), that the herd should be reduced or forest tree seedling regeneration would fail. Leopold, the father of wildlife ecology, continued to lobby for strict regulation of the deer herd until his death.
Larger ungulates suffer especially under hunting pressure because they have low intrinsic rates of population increase. (Similar levels of hunting pressure have far less effect on deer because they mature faster than caribou or moose.) Top carnivores typically share this trait of low reproductive rates. Their reduced density and large home-range needs make them especially vulnerable to overhunting. Cougar (mountain lions) were hunted out of Michigan by about 1850, Wisconsin by 1884, and Minnesota by about 1900 (Gates et al. 1983). Canadian lynx also disappeared. Wolverines persist only as mascots in Michigan, having disappeared from that state and Wisconsin by the end of the nineteenth century and from Minnesota by 1918.
Although timber wolves originally ranged across almost all of North America, they have now been reduced to two enclaves in the lower 48: northern Minnesota and the northern Rockies. Wolves are beginning to spread back into the central Rockies and northern Wisconsin and Michigan, but only as scattered individuals or packs. A population colonized Isle Royale during the winter of 1946–47, grew quickly feeding on the many moose, but has recently declined to 12 individuals, reflecting an infection by parvovirus and possibly the genetic consequence of close inbreeding (Allen 1979; Mech 1966; Wayne et al. 1991). This population's looming extinction serves to warn us of the hazards other small populations face.
Fishers (large forest-dwelling weasels), trapped out of Wisconsin by 1927, were reintroduced (Powell 1982; Pils 1983) and now number approximately 6000 in Wisconsin (B. A. Kohn, pers. commun.). This species depends on large snags and tree cavities, making it likely that logging contributed to its demise or slows its recovery. Pine martens were also extirpated in Michigan and Wisconsin then reintroduced, but they remain scarce and have not recovered to the same degree as fishers. Fur bearing mammals with higher rates of increase, such as muskrat and mink, persisted even in the face of intense trapping. Bobcats were considered vermin worth a bounty until 1963 in Wisconsin and became subject to sport hunting in 1973. The Department of Natural Resources (DNR) was petitioned in 1990 to protect the bobcat as a threatened species, and the total Wisconsin population is now estimated at 1500 (W. A. Creed, pers. commun.). Ironically, abundant fishers may be preying on bobcat kittens, contributing to their scarcity (J. Gilbert, pers. commun.).
Despite being both abundant and prolific, beaver were almost extirpated by about 1900 before they became protected (Schorger 1965). The young forest that succeeded logging and fires was empty of wolves but full of favored beaver forage (e.g., aspen and paper birch), allowing populations to bounce back and even exceed presettlement densities (Gates et al. 1983). They now pose dilemmas for forest managers in that they degrade high-quality trout streams and damage some timber, yet provide dispersed wetland habitat that support many other species. In contrast to the declines of most large mammals, rodents like the thirteen-lined ground squirrel and gray squirrel soared in abundance and extended their ranges northward (Gates et al. 1983).
Excerpted from Wild Forests by William S. Alverson, Don Waller, Walter Kuhlmann. Copyright © 1994 Island Press. Excerpted by permission of ISLAND PRESS.
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Table of Contents
ContentsAbout Island Press,
Table of Figures,
List of Tables,
PART I - Whence Biodiversity?,
1 - Forests Then and Now,
2 - Shadows in the Forest,
3 - The Myth of Heart's Content,
PART II - Ecological Mechanisms and Biotic Resources,
4 - Internal Affairs: Patch and Disturbance Dynamics,
5 - From Hero to Villain: Edge Effects,
6 - Hazards of Fragmentation: Area and Isolation Effects,
7 - Tracking Diversity: Biological Inventory, Research, and Monitoring,
PART III - Approaches to Forest Management,
8 - The Evolution of Forest Management,
9 - Multiple Use on National Forest Lands,
10 - What's New in Forest Management?,
11 - Zoning for Diversity,
PART IV - Toward a New Diversity Policy (and Twenty-First Century Old Growth),
12 - Sources of a New Diversity Policy for the National Forests,
13 - Case History: The Wisconsin National Forests,
14 - Dominant-Use Zoning and Wildlands: Forestry for the Twenty-First Century,
Glossary of Abbreviations and Acronyms,
Island Press Board of Directors,