Preface
Maintaining viability of northern spotted owl populations in
Washington, Oregon, and California, in the face of the many
activities that take place in their habitats, especially logging, has
challenged public land managers for nearly two decades. Policies and guidelines established by the USDA Forest Service
during the late 1970s and early 1980s were challenged repeatedly, and from opposing camps. The timber industry is concerned that management of the owl's preferred habitat unnecessarily restricts commodity production, while environmental interests contend that Forest Service plans for the owl fall short of
assuring long-term viability of the bird. Although the controversy has been more hotly debated over the northern spotted
owl, the California spotted owl has recently taken part of the spotlight.
The Report and Its Origin
During most of the 1980s, the Forest Service implemented a
conservation strategy based on retention of Spotted Owl Habitat
Areas (SOHAs) capable of supporting one to three pairs of owls,
separated from each other by distances ranging from 6 to 12
miles, edge-to-edge. A recent, comprehensive assessment of
management for the northern spotted owl identified serious
weaknesses in the SOHA strategy, however, and gave rise to a
markedly different approach for conserving the owl.1 Because
the SOHA strategy is currently used to manage for the California
subspecies, in June 1991 the Forest Service and various agencies
of the State of California initiated a technical assessment of the
current status of the California spotted owl, under auspices of an
Interagency Steering Committee for the California Spotted Owl
Assessment (the "Steering Committee").
The Steering Committee formed two investigative, advisory
teams-the
Technical
Assessment
Team
and
the
Policy-Implementation Team. This report contains findings of
the Technical Assessment Team, as transmitted to the Steering
Committee on 8 May 1992. The Team's findings will be further
evaluated by the Policy-Implementation Team, which will suggest policies and guidelines for implementing recommendations
of the Technical Assessment Team. Final recommendations will
then be made by the Steering Committee.
In developing this technical assessment, we have drawn
information from many sources-the owl's biology, including
its geographic distribution, habitat associations, life history,
demography, and ecological relations; historical aspects of land
management and disturbance in the Sierra Nevada and southern
California; fuels management; principles of conservation biology; and risk analysis. This was consistent with our assignment,
as set forth in the charter that established the Technical Assessment Team. The charter also directed the Team to "follow
accepted scientific standards and practices." Accordingly, to the
extent possible, we have used the hypothetico-deductive process
to guide our assessment of available information. We sought to
falsify specific null hypotheses by using empirical data, computer models, widely accepted concepts and theories, and professional judgment (common sense!), rejecting hypotheses that
failed these tests. This does not mean that surviving hypotheses
are necessarily correct, only that they were not falsified by
present information. This is the way of science. It inevitably
leaves us with areas of uncertainty. How we deal with that
uncertainty in the end depends, of course, on society's objectives.
The next step in following accepted scientific standards and
practices was to submit a nearly final draft of our report for peer
review by five other scientists not selected by the Team. This
was accomplished by requesting that the Presidents of five
learned societies-The American Ornithologists' Union, The
Ecological Society of America, The Society of American Foresters, The Society for Conservation Biology, and The Wildlife
Society-personally select one reviewer each, at their discretion. We then sent the draft document to each of these reviewers,
whose critical comments and suggestions were taken into account in the revisions leading to this final report.
Although the report focuses on the California spotted owl,
much more is at issue here. The owl is designated as an "indicator species" for old-growth ecosystems even though, as detailed
in some of the chapters beyond, it is not restricted to just those
habitats. But owl pairs use inordinately large areas in the course
of their daily, seasonal, and annual activities, making the species
an effective "umbrella" for a host of other species that satisfy
their life requisites in the same habitats. Certainly commodity
production must figure prominently when we weigh the pros and
cons of maintaining viable populations of spotted owls. But
prudence demands that the assessment be exhaustive and extend
beyond the bottom line for the next year, or even the next
decade. For the forest ecosystems we consider, our appraisal
must look many decades, even centuries, into the future to be
certain that decisions we make today are sustainable into the
future-that they do not compromise future benefits from these
ecosystems. A truly balanced assessment, therefore, "...must
consider water quality, fisheries, recreation, soils, stream flows,
scenic values, biological diversity, and other species of wildlife.
All aspects of such a decision should be weighed in the balance.
The issues are not limited to questions of owls and timber
supply, as important as those are. The matter is not that simple-it never has been."'
1
Thomas, Jack Ward; Forsman, Eric E.; Lint, Joseph B.; Meslow, E.
Charles; Noon, Barry R.; Verner, Jared. 1990. A conservation strategy for the
northern spotted owl. Washington, DC: U.S. Government Printing Office;
427 p.
USDA Forest Service Gen. Tech. Rep. PSW-GTR-133. 1992.
v
Some Guidelines for Using the Report
Acknowledgments
The report consists of 13 chapters covering various aspects
of the information needed for the assessment. Chapter 1 is an
extended summary of Chapters 3-13, providing the bare essentials about key findings to establish the basis for our final
conclusions, and presenting our recommendations. It is the essence of our assessment. Chapter 2 presents the consensus of the
Technical Assessment Team's recommendations about what we
think future efforts on the California spotted owl should be, and
why. Readers can explore any or all of the remaining chapters, as
needed or desired, for details on statements and conclusions
summarized in Chapter 1. Chapter 3 presents the general background leading up to the present issue and summarizes what we
know of the owl's distribution throughout California, and how
the subspecies is being managed. The next seven chapters describe the owl's general biology and ecological relations, results
of studies on its habitat associations, its demography and projections of population stability, and its major prey species. Finally,
Chapters 11-13 consider how conifer forests in the owl's range
came to be what they are today, review the fire history and
current fuels problems in owl habitat, and identify projected
trends in the forested habitats used by the owl. Four appendices
conclude the report: Appendix A identifies the Technical Assessment Team and provides a brief chronology of Team activities leading to the report; Appendix B is a glossary of terms used
in the text; Appendix C lists the common and scientific names of
plant and animal species mentioned in the text; and Appendix D
identifies authors of the various parts of the document.
We adopted some policies in the preparation of this report
that we believe will ease the reader's task. Figures and tables are
labeled by number for the chapter in which they appear, and by
letter for their order in that chapter (for example, figure 4C is the
third figure in Chapter 4). This procedure allows us to cross
reference figures and tables from one chapter to another without
confusion. In addition, a set of color photos of owl habitat taken
during the Team's field trips are aggregated at the end of Chapter 5; these are identified as "colored photo 5-1," colored photo
5-2," and so on. We have substituted acronyms for several
entities that are mentioned frequently in the text. Some are
already familiar to most readers (for example, USDA = the
United States Department of Agriculture), but in each chapter
we define anew each acronym when it is first used. A list of
many of the common acronyms appears after the Contents pages
in this volume, for quick reference in case readers momentarily
forget what one represents. All measurements are expressed in
English units (for example, feet, acres, ounces) instead of metric
units (meters, hectares, grams). This decision was made because
English units are still used by Federal land-management agencies and by the forest industry, and because most of the general
public still thinks in terms of English units, not metric units.
To complete this assessment, we have relied upon assistance, input, information, and general cooperation from literally
hundreds of persons. To acknowledge each one is clearly not
possible. We could not even rank them in order of the importance of their contributions. Certainly our biggest debt is to the
many biologists from all the State and Federal agencies and
private entities-both in management and research-who have
spent countless hundreds of hours in the field, mostly at night,
hooting for owls, searching for their nests, measuring nest trees
and stands, locating owlets, recording data, and generally accumulating the wealth of information now available about the owl
and its habitats. In particular, we thank the Forest and District
Biologists from the National Forests within the range of the
California spotted owl who have responded, again and again, to
specific requests for information that we needed. They have met
all of our requests unfailingly, pleasantly, and quickly.
Another major group of folks that worked largely behind
the scenes, and essentially anonymously as far as we on the
Team were concerned, were persons on the National Forests
who compiled and mapped habitat information for us in electronic form. We have all learned much from this exercise, which
should result in significant improvements in the way habitat
information is collected, classified, and stored in the future.
Many others operated behind the scenes to implement data
summaries, analyses, and syntheses, particularly at the Pacific
Southwest Research Station's Redwood Sciences Laboratory in
Arcata and Forestry Sciences Laboratory in Fresno. And a special thanks to folks in the California Department of Forestry's
Forest and Range Resources Assessment Program, whose willing applications of their geographic information system made
possible the mapping of all known California spotted owl sites
and an assessment of high, medium, and low likelihoods of owls
in riparian/hardwood forests in the Sierran foothills and Coast
Ranges.
The administrative side of the Team's operation was made
possible largely through the Regional Office of the Forest Service in San Francisco, which covered nearly all of the costs, and
the Pacific Southwest Research Station in Albany, California.
We were blessed by the wisdom of a couple folks in the Regional Office who saw and met a need to provide us with
"scissors" to cut through the red tape that occasionally threatened to bring our progress to a temporary halt.
vi
Technical Coordinators:
Jared Verner, Kevin S. McKelvey, Barry R. Noon,
R. J. Gutiérrez, Gordon I. Gould, Jr., Thomas W. Beck
USDA Forest Service Gen. Tech. Rep. PSW-GTR-133. 1992.