United States Department of Agriculture

NORTHWEST

FOREST PLAN

Synthesis of Science to Inform Land 

Management Within the Northwest 

Forest Plan Area

Volume 2

Forest 

Service

Pacific Northwest

Research Station

General Technical Report

PNW-GTR-966 Vol. 2

June

2018
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Technical Coordinators

Thomas A. Spies is a senior scientist, U.S. Department of Agriculture, Forest Service, 

Pacific Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR 97331; Peter 

A. Stine is a research program manager and biogeographer (retired), U.S. Department of 

Agriculture, Forest Service, Pacific Southwest Research Station, and is a research associate, John Muir Institute for the Environment, University of California–Davis, 1 Shields 

Avenue, Davis, CA 95616; Rebecca Gravenmier is a science coordinator, U.S. Department 

of Agriculture, Forest Service, Pacific Northwest Research Station, 1220 SW 3rd Avenue, 

Portland, OR 97204; Jonathan W. Long is an ecologist, U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, 1731 Research Park Drive, Davis, CA 

95618; and Matthew J. Reilly is a postdoctoral researcher, Humboldt State University, 

Department of Biological Sciences, 1 Harpst Street, Arcata, CA 95521.

Cover photos: Upper left: coho spawning on the Salmon River; photo by Bureau of Land 

Management. Upper right: a typical stream in the Cispus River watershed, Washington; 

photo by Alanna Wong. Lower right: an adult captive red tree vole mechanically removing 

one of two unpalatable resin ducts in a Douglas-fir needle before eating the rest of the 

needle; photo by Michael Durham. Lower middle: orange coral fungus, Olympic National 

Forest; photo by USDA Forest Service. Lower left: centipede, one component of the wide 

array of soil invertabrates found in late-successional and old-growth forests of the Northwest Forest Plan region; photo by Bruce Marcot.
Synthesis of Science to Inform 

Land Management Within the 

Northwest Forest Plan Area

Volume 2

Thomas A. Spies, Peter A. Stine, Rebecca Gravenmier, 

Jonathan W. Long, and Matthew J. Reilly, Technical Coordinators

U.S. Department of Agriculture

Forest Service

Pacific Northwest Research Station

Portland, Oregon

General Technical Report PNW-GTR-966 Vol. 2

June 2018
Abstract 

Spies, T.A.; Stine, P.A.; Gravenmier, R.; Long, J.W.; Reilly, M.J., tech. coords. 2018.

Synthesis of science to inform land management within the Northwest Forest Plan area. 

Gen. Tech. Rep. PNW-GTR-966. Portland, OR: U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station. 1020 p. 3 vol.

The 1994 Northwest Forest Plan (NWFP) was developed to resolve debates over oldgrowth forests, endangered species, and timber production on federal forests in the range 

of the northern spotted owl. This three-volume science synthesis, which consists of 12 

chapters that address various ecological and social concerns, is intended to inform forest 

plan revision and forest management within the NWFP area. Land managers with the U.S. 

Forest Service provided questions that helped guide preparation of the synthesis, which 

builds on the 10-, 15-, and 20-year NWFP monitoring reports and synthesizes the vast 

body of relevant scientific literature that has accumulated in the 24 years since the NWFP 

was initiated. It identifies scientific findings, lessons learned, and uncertainties and also 

evaluates competing science and provides considerations for management. 

This synthesis finds that the NWFP has protected dense old-growth forests and 

maintained habitat for northern spotted owls, marbled murrelets, aquatic organisms, and 

other species despite losses from wildfire and low levels of timber harvest on federal lands. 

Even with reductions in the loss of older forests, northern spotted owl populations continue 

to decline. Moreover, a number of other goals have not been met, including producing a 

sustainable supply of timber, decommissioning roads, biodiversity monitoring, significant 

levels of restoration of riparian and dry forests, and adaptation and learning through 

adaptive management. 

New conservation concerns have arisen, including a major threat to spotted owl 

populations from expanding populations of the nonnative barred owl, effects of fire 

suppression on forest succession, fire behavior in dry forests, and lack of development of 

diverse early-seral vegetation as a result of fire suppression in drier parts of moist forests. 

Climate change and invasive species have emerged as threats to native biodiversity, and 

expansion of the wildland-urban interface has limited the ability of managers to restore fire 

to fire-dependent ecosystems. 

The policy, social, and ecological contexts for the NWFP have changed since it was 

implemented. The contribution of federal lands continues to be essential to the conservation 

and recovery of fish listed under the Endangered Species Act and northern spotted owl 

and marbled murrelet populations. Conservation on federal lands alone, however, is likely 

insufficient to reach the goals of the NWFP or the newer goals of the 2012 planning rule, 

which emphasizes managing for ecosystem goals (e.g. ecological resilience) and a few 

species of concern, rather than the population viability of hundreds of individual species. 
The social and economic basis of many traditionally forest-dependent communities 

have changed in 24 years, and many are now focused on amenity values. The capacities 

of human communities and federal agencies, collaboration among stakeholders, the 

interdependence of restoration and the timber economy, and the role of amenity- or recreation-based communities and ecosystem services are important considerations in managing 

for ecological resilience, biodiversity conservation, and social and economic sustainability. 

A growing body of scientific evidence supports the importance of active management 

or restoration inside and outside reserves to promote biodiversity and ecological resilience. 

Active management to promote heterogeneity of vegetation conditions is important to 

sustaining tribal ecocultural resources. Declines in agency capacity, lack of markets for 

small-diameter wood, lack of wood processing infrastructure in some areas, and lack of 

social agreement have limited the amount of active management for restoration on federal 

lands. All management choices involve social and ecological tradeoffs related to the goals 

of the NWFP. Collaboration, risk management, adaptive management, and monitoring are 

considered the best ways to deal with complex social and ecological systems with futures 

that are difficult to predict and affect through policy and land management actions.

Keywords: Northwest Forest Plan, science, management, restoration, northern spotted 

owl, marbled murrelet, climate change, socioeconomic, environmental justice.
Preface

In 2015, regional foresters in the Pacific Northwest and Pacific Southwest Regions of the 

USDA Forest Service requested that the Pacific Northwest and Pacific Southwest Research 

Stations prepare a science synthesis to inform revision of existing forest plans under the 

2012 planning rule in the area of the Northwest Forest Plan (NWFP, or Plan). Managers 

provided an initial list of hundreds of questions to the science team, which reduced to them 

to 73 questions deemed most feasible for addressing through a study of current scientific literature. The stations assembled a team of 50 scientists with expertise in biological, ecological, and socioeconomic disciplines. At the suggestion of stakeholders, a literature reference 

database was placed online so the public could submit additional scientific literature for 

consideration. By spring 2016, writing was underway on 12 chapters that covered ecological and social sciences. 

The draft synthesis, which was ready for peer and public review by fall 2016, went 

through a special review process because it was classified as “highly influential science” in 

accordance with the Office of Management and Budget’s 2004 “Final Information Quality 

Bulletin for Peer Review.” The synthesis was classified as such because it fit the category of 

a scientific assessment that is novel, controversial, or precedent-setting, or has significant 

interagency interest. Per the bulletin, the two research stations commissioned an independent entity, the Ecological Society of America (ESA), to manage the peer-review process, 

including the selection of peer reviewers. 

The bulletin also stipulates that such an assessment be made available to the public 

through a public meeting to enable the public to bring scientific issues to the attention of 

peer reviewers. Accordingly, a public forum was held in Portland, Oregon, in December 

2016. For those who could not travel to Portland, the forum was accessible via live Web 

stream, and multiple national forests within the NWFP area hosted remote viewing. Written 

comments on the draft synthesis were collected for 2 months. This generated 130 public 

comments, totaling 890 pages, which were given to the peer reviewers for consideration 

in their review, as they deemed appropriate. The OMB guidelines further direct that the 

peer-review process be transparent by making available to the public the ESA’s written 

guidance to the reviewers, the peer reviewer’s names, the peer review reports, and the 

responses of the authors to the peer reviewer comments—all of which are available at 

https://www.fs.fed.us/pnw/research/science-synthesis/index.shtml. 

The peer reviewer comments, which were received in spring 2017 and informed by 

public input, resulted in substantive revisions to chapters of the synthesis. The result is this 

three-volume general technical report (an executive summary of the synthesis is available 

as a separate report). This document is intended to support upcoming management planning on all public lands in the Plan area, but is expected to serve primarily lands managed 

by the U.S. Forest Service. We hope it will be a valuable reference for managers and others 

who seek to understand the scientific basis and possible tradeoffs associated with forest 

plan revision and management decisions. The synthesis also provides an extensive list of 

published sources where readers can find further information.
We understand that the term “synthesis” can have many different meanings. For our 

purposes, it represents a compilation and interpretation of relevant scientific findings that 

pertain to key issues related to the NWFP that were identified by managers and by the 

authors of the document. Such a compilation not only summarizes science by topic areas 

but also interprets that science in light of management goals, characterizes competing 

science, and makes connections across scientific areas, addressing multilayered and interacting ecological and socioeconomic issues. In a few cases, simple analyses of existing data 

were conducted and methods were provided to reviewers. 

The synthesis builds upon the 10-, 15-, and 20-year NWFP monitoring reports, and 

authors considered well over 4,000 peer-reviewed publications based on their knowledge 

as well as publications submitted by the public and others suggested by peer reviewers. For 

some of the questions posed by land managers, there was ample scientific research from 

the Plan area. For many of the questions, however, little research existed that was specific 

to the area. In such cases, studies from other regions or current scientific theory were used 

to address the questions to the extent possible. In many cases, major scientific uncertainties 

were found; these are highlighted by the authors. 

The synthesis chapters characterize the state of the science but they do not develop 

management alternatives, analyze management tradeoffs, or offer recommendations as to 

what managers should do. The synthesis does identify ideas, facts, and relationships that 

managers may want to consider as they develop plans and make management decisions 

about particular issues. The final chapter attempts to integrate significant cross-cutting 

issues, e.g., ecological and socioeconomic interdependencies, compatibility of different 

management goals, and tradeoffs associated with different restoration actions. All the 

chapters identify where more research is needed to fill critical information gaps. 

We would like to acknowledge the peer reviewers who considered hundreds of public 

comments as part of the process of reviewing our lengthy draft manuscripts. We also thank 

the many contributors to the development of the synthesis in draft and final form, including 

those who provided editing, layout, database, and other support services. 
Contents

Volume 1

1 Chapter 1: Introduction

Peter A. Stine and Thomas A. Spies 

29 Chapter 2: Climate, Disturbance, and Vulnerability to Vegetation Change in the 

Northwest Forest Plan Area

Matthew J. Reilly, Thomas A. Spies, Jeremy Littell, Ramona Butz, and John B. Kim 

95 Chapter 3: Old Growth, Disturbance, Forest Succession, and Management in the 

Area of the Northwest Forest Plan

Thomas A. Spies, Paul F. Hessburg, Carl N. Skinner, Klaus J. Puettmann, Matthew J. 

Reilly, Raymond J. Davis, Jane A. Kertis, Jonathan W. Long, and David C. Shaw 

245 Chapter 4: Northern Spotted Owl Habitat and Populations: Status and Threats 

Damon B. Lesmeister, Raymond J. Davis, Peter H. Singleton, and J. David Wiens 

301 Chapter 5: Marbled Murrelet

Martin G. Raphael, Gary A. Falxa, and Alan E. Burger

Volume 2

371 Chapter 6: Other Species and Biodiversity of Older Forests

Bruce G. Marcot, Karen L. Pope, Keith Slauson, Hartwell H. Welsh, Clara A. Wheeler, 

Matthew J. Reilly, and William J. Zielinski 

371 Introduction

372 Setting and Background

373 New Learning and Recent Issues

373 Guiding Questions

374 Agency Programs on Other Species and Biodiversity of Older Forests

374 Survey and Manage Program

378 Interagency Special Status and Sensitive Species Program

378 Implications of Forest Service and BLM Planning Directions

379 Key Findings

379 New Information on Other Species and Biodiversity of Older Forests

408 Recent Research and Development on New Tools and Data

409 Recent and Ongoing Issues Adding Challenges and Opportunities

416 Uncertainties and Research Needs

416 Indicators and Surrogates 

417 Climate Change 

418 Conclusions and Management Considerations

418 Summary of Key Management Considerations

422 Issues of Species Conservation

425 Main Findings

426 Acknowledgments

427 Metric Equivalents

427 Literature Cited
461 Chapter 7: The Aquatic Conservation Strategy of the Northwest Forest Plan—A 

Review of the Relevant Science After 23 Years

Gordon H. Reeves, Deanna H. Olson, Steven M. Wondzell, Peter A. Bisson, Sean Gordon, 

Stephanie A. Miller, Jonathan W. Long, and Michael J. Furniss 

461 Introduction

463 Guiding Questions 

463 Key Findings

463 Status of Species and Population Units Listed Under the Endangered Species Act on 

Federal Lands in the Northwest Forest Plan Area

468 Monitoring—Aquatic and Riparian Effectiveness Monitoring Program 

483 Components of the Aquatic Conservation Strategy

483 Riparian Reserves

498 Key Watersheds

499 Watershed Analysis 

499 New Perspectives on Conservation of Riparian and Aquatic Ecosystems 

504 Non-Fish-Bearing Streams

506 Continuing and Emerging Topics of Concern

506 Water

506 Roads

510 Climate Change

531 Research Needs, Uncertainties, Information Gaps, and Limitations

533 Conclusions and Management Considerations

533 Guiding Questions

534 Science Foundation for the ACS (Question 1)

535 Monitoring of the ACS (Question 2)

536 Aquatic and Riparian Ecosystems (Questions 3–6)

537 Water Contributions From Federal Lands (Question 7)

537 Climate Change (Question 8)

537 Literature Cited

582 Appendix 1: Aquatic-Riparian Invasive Species of the Northwest Forest Plan Area

 Deanna H. Olson and Rebecca L. Flitcroft 

582 Priority Aquatic Invasive Species

586 Taxonomic Summaries

586 Pathogens and Parasites

586 Aquatic Plants

587 Riparian-Terrestrial Plants

587 Aquatic Invertebrates

587 Aquatic Vertebrates

588 Riparian-Terrestrial Vertebrates

588 Research and Development, Monitoring, and Management

588 Research and Development
590 Monitoring and Management 

593 Future Considerations

594 Other Nonnative Species on the Radar in the Northwest

594 Climate Change Projections

595 Research and Monitoring Priorities

596 Appendix 2: Influence of Climate Change on Life Stages of Pacific Salmon 

Peter A. Bisson, Gordon H. Reeves, Nate Mantua, and Steven M. Wondzell 

596 Adults

598 Eggs and Alevins

600 Juveniles

603 Smolts

608 Glossary

624 Acknowledgments

Volume 3

625 Chapter 8: Socioeconomic Well-Being and Forest Management in Northwest 

Forest Plan-Area Communities

Susan Charnley, Jeffrey D. Kline, Eric M. White, Jesse Abrams, Rebecca J. McLain, 

Cassandra Moseley, and Heidi Huber-Stearns 

717 Chapter 9: Understanding Our Changing Public Values, Resource Uses, and 

Engagement Processes and Practices

Lee K. Cerveny, Emily Jane Davis, Rebecca McLain, Clare M. Ryan, Debra R. 

Whitall, and Eric M. White 

809 Chapter 10—Environmental Justice, Low-Income and Minority Populations, and 

Forest Management in the Northwest Forest Plan Area

Susan Charnley, Delilah Jaworski, Heidi Huber-Stearns, Eric M. White, Elisabeth 

Grinspoon, Rebecca J. McLain, and Lee Cerveny 

851 Chapter 11: Tribal Ecocultural Resources and Engagement

Jonathan Long, Frank K. Lake, Kathy Lynn, and Carson Viles 

919 Chapter 12: Integrating Ecological and Social Science to Inform Land Management in the Area of the Northwest Forest Plan

Thomas A. Spies, Jonathan W. Long, Peter Stine, Susan Charnley, Lee Cerveny, Bruce 

G. Marcot, Gordon Reeves, Paul F. Hessburg, Damon Lesmeister, Matthew J. Reilly, 

Martin G. Raphael, and Raymond J. Davis 

ccclxxxiv

GENERAL TECHNICAL REPORT PNW-GTR-966

Table Rock Wilderness, Oregon.

Photo by USDI Bureau of Land Management, Oregon-Washington State Office.
371

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Chapter 6: Other Species and Biodiversity 

of Older Forests

Bruce G. Marcot, Karen L. Pope, Keith Slauson, 

Hartwell H. Welsh, Clara A. Wheeler, Matthew J. Reilly, 

and William J. Zielinski1

Introduction

This chapter focuses mostly on terrestrial conditions of species and biodiversity associated with late-successional and 

old-growth forests in the area of the Northwest Forest Plan 

(NWFP). We do not address the northern spotted owl (Strix 

occidentalis caurina) or marbled murrelet (Brachyramphus 

marmoratus)—those species and their habitat needs are 

covered in chapters 4 and 5, respectively. Also, the NWFP’s 

Aquatic and Riparian Conservation Strategy and associated 

fish species are addressed in chapter 7, and early-successional vegetation and other conditions are covered more in 

chapters 3 and 12. 

We begin by summarizing a set of questions provided 

by management. We then review the state of knowledge 

of species, biodiversity, and ecosystem conditions gained 

from studies conducted since the 10-year synthesis of monitoring and research results (Haynes et al. 2006). We review 

agency programs on other species and biodiversity of older 

forests of the Pacific Northwest, including implementation 

of the NWFP Survey and Manage standards and guidelines, the Interagency Special Status and Sensitive Species 

Program (ISSSSP), and other biodiversity consortia. We 

then review new findings on selected individual species 

and groups of species including fungi, lichens, bryophytes, 

and plants, as well as invertebrates. We also summarize 

findings on amphibians, reptiles, and birds, and on selected 

carnivore species including fisher (Pekania pennanti), 

marten (Martes americana), and wolverine (Gulo gulo), 

and on red tree voles (Arborimus longicaudus) and bats. 

We close the section with a brief review of the value of 

early-seral vegetation environments. We next review recent 

advances in development of new tools and datasets for 

species and biodiversity conservation in late-successional 

and old-growth forests, and then review recent and ongoing 

challenges and opportunities for ameliorating threats 

and addressing dynamic system changes. We end with a 

set of management considerations drawn from research 

conducted since the 10-year science synthesis and suggest 

areas of further study. 

The general themes reviewed in this chapter were 

guided by a set of questions provided by the U.S. Forest 

Service Pacific Northwest Region (Region 6) and Pacific 

Southwest Region (Region 5). The scientific publications 

we review were selected based on the specific subjects 

listed above, as pertinent to science findings on other 

species and biodiversity of late-successional and old-growth 

forest ecosystems in the area of the NWFP in the Pacific 

Northwest, United States. We include selected references 

on studies outside the NWFP and Pacific Northwest and 

references dating prior to the previous NWFP science 

synthesis, when such studies are nonetheless pertinent to 

understanding biological and ecological topics within the 

NWFP and Pacific Northwest. We also address selected 

topics such as early-successional forest ecosystems and 

effects of wildfire, fire suppression, and climate change, 

as guided by the availability of recent literature on NWFP 

species and biodiversity; these topics, raised by managers, 

are also covered more fully in other chapters of this science 

synthesis. The final chapter of this synthesis discusses 

the conceptual and practical implications of new science 

findings, remaining scientific uncertainties and research 

needs, and overall conclusions. 

1 Bruce G. Marcot is a research wildlife biologist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station, 620 SW Main St., Suite 400, Portland, OR 97205; Karen 

L. Pope is a research wildlife biologist, Keith Slauson is a 

research fellow, Hartwell H. Welsh is a research wildlife biologist 

emeritus, Clara A. Wheeler is an ecologist, and William J. 

Zielinski is a research ecologist, U.S. Department of Agriculture, 

Forest Service, Pacific Southwest Research Station, 1700 Bayview 

Drive, Arcata, CA 95521; Matthew J. Reilly is a postdoctoral 

researcher, Humboldt State University, Department of Biological 

Sciences, 1 Harpst Street, Arcata, CA 95521.
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GENERAL TECHNICAL REPORT PNW-GTR-966

Setting and Background

Originally, the NWFP was developed as an ecosystem

management plan to provide for the full suite of biodiversity at all taxonomic and functional levels, particularly

in late-successional and old-growth environments, under

an adaptive learning and management approach. The

first decade of the NWFP, however, focused on the status

of species; no biodiversity monitoring program per se

was instituted under the NWFP (Marcot and Molina

2006). Since then, a broad assumption has been made

that older-forest biodiversity in its full capacity would be

provided by two complementary approaches of managing

for “coarse filter” elements such as the dispersion and

distribution of late-successional forest reserves and

aquatic and riparian corridors, along with managing for

“fine filter” elements of habitat needs of selected, individual late-successional and old-growth-associated species.

The combined coarse- and fine-filter approach is intended

to provide the same level of protection as would management and monitoring directed at specific biodiversity

elements such as ecosystem processes of nutrient cycling,

species’ ecological functions, and population genetics and

viability (e.g., Noss 1990). A current challenge is to test

this assumption within the changing tapestry of ecological processes and disturbance-influenced ecosystems of

the Northwest.

The 2012 planning rule for guiding land and resource 

management plans on national forests differs from the 1982 

rule that was in place when the NWFP was first instituted 

and that guided the NWFP. The 2012 planning rule puts 

more weight on coarse-filter approaches and on ecological 

integrity (based in part on natural range of variation) but 

still calls for both coarse- and fine-filter approaches. In the 

Forest Service’s evaluations of the alternatives to the 

planning rule (USDA FS 2012), the terms coarse filter and 

fine filter are referred to extensively as “well-developed 

concept[s] in the scientific literature [with] broad support 

from the scientific community and many stakeholders.” 

However, the debate continues on an appropriate balance 

between coarse-filter (ecosystem and biodiversity) and 

fine-filter (species-specific) planning direction (Hayward et 

al. 2016,2

 Schultz et al. 2013). 

Also, although not part of the NWFP per se, some 

previous elements of the U.S. Forest Service’ Forest Inventory and Analysis (FIA) program3—which have since been 

drastically reduced or are no longer being carried out—provided much-needed information for monitoring biodiversity 

of trees, vegetation, and lichens.4 The FIA program has 

become a de facto biodiversity monitoring program, at least 

for selected vegetation and floral elements. 

In the previous science synthesis, Marcot and Molina 

(2006) concluded that NWFP directions for establishing 

effectiveness monitoring of forest biodiversity elements 

for other than selected species remained mostly unmet 

(beyond the FIA-identified biodiversity indicators). 

This remains true today, but much information has 

been provided by research studies and gathered by 

agency programs on basic occurrence, distribution, and 

ecology of rare and poorly known late-successional and 

old-growth-associated species. The 2006 synthesis also 

provided the following suggestions:

• Engage research partnerships to fill key information

gaps on rare and little-known late-successional and

old-growth species.

• Clarify objectives and expectations of implementing a

coarse- and fine-filter conservation approach to managing for viable and persistent species populations.

• Validate the use of surrogates (e.g., indicator and

focal species) for species and conservation objectives.

• Develop and maintain databases from ongoing

inventory, survey, and any monitoring programs.

2

 Hayward, G.D.; Flather, C.H.; Rowland, M.M.; Terney, R.; 

Mellen-Mclean, K.; Malcolm, K.D.; McCarthy, C.; Boyce, D.A. 

2016. Applying the 2012 planning rule to conserve species: a 

practitioner’s reference. Unpublished paper. On file with: Bruce 

Marcot, Forestry Sciences Laboratory, 620 SW Main, Portland, 

OR 97205. 78 p.

3 http://www.fia.fs.fed.us/. 4

 McCune, B. Personal communication. Professor, Department of 

Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall Corvallis, OR 97331-2902. http://bmccune.weebly.com/.
373

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

• Develop, test, and implement species survey designs. 

• Explore habitat modeling and decision-support tools 

to meet some conservation objectives. 

• Develop and implement an effectiveness monitoring 

framework. 

The current synthesis determines the degree to which 

these suggestions have been met. 

New Learning and Recent Issues

Much has been learned since the 2006 synthesis (Haynes 

et al. 2006) about conditions and dynamics of forest 

ecosystems and their organisms in the Pacific Northwest 

and throughout the West. The issue of climate change and 

its known and projected impacts on systems has become 

a foremost research topic (Bagne et al. 2011, Vose et al. 

2012). Occurrence and effects of large-scale wildfire have 

become major issues of research and management focus 

(Sheehan et al. 2015, Wimberly and Liu 2014). Studies on 

the effect of fire suppression on vegetation succession are 

needed, however, as are studies examining how suppression activities affect subsequent fire behavior but also 

how it changes vegetation conditions as habitat for many 

species (see chapter 3). Concern over invasive species also 

has elevated (Jones et al. 2010, Wilson et al. 2009; also see 

chapter 3). We address these and other issues in sections 

that follow.

Additionally, of increased focus is how early-successional vegetation provides habitats for many species 

(Hagar 2007, Swanson et al. 2011). Another topic of continued interest is the importance of conditions in the managed-forest matrix and connectivity of late-successional 

and old-growth forests and late-successional reserves 

(LSRs) in the face of fire, climate change, and increased 

pressure on matrix-land resources (Suzuki and Olson 

2008, Wilson and Puettmann 2007). As well, the roles 

and conditions of rare and little-known species have been 

addressed (Raphael and Molina 2007). In general, much 

more detailed information is now available on vertebrates 

than on most other species groups. 

Guiding Questions

This chapter reviews the scientific understanding of the 

ecology and conservation of species associated with 

late-successional and old-growth forests. We summarize 

science findings on the conservation strategy of the NWFP 

and its provision for these species; scientific progress 

since the previous NWFP evaluations (Diaz and Haynes 

2002, Haynes and Perez 2001, Haynes et al. 2006); and the 

outcome of the NWFP Survey and Manage program. 

We review advancements on science and conservation 

through the following questions:

• What is the current scientific understanding of the 

rarity of late-successional and old-growth-associated species?

• Is forest management under the NWFP providing 

habitat for rare and uncommon species as planned? 

Are rare and uncommon species maintaining populations under NWFP management? How effective 

are the management recommendations for habitat conservation in retaining these species across 

treated landscapes?

• Have we accumulated enough information to change 

the management status of these species? Are there 

species originally ranked as having low potential for 

persistence that are now of less concern, particularly 

with the reduction in harvest levels of late-successional and old-growth forest that has occurred under 

the NWFP? Are there late-successional and oldgrowth species originally ranked as high persistence 

or not initially identified as conservation concerns 

that have been added to lists of species of concern?

• What are results of research on the effects of prescribed fire and wildfire on rare and uncommon 

late-successional and old-growth species?

• What are results of research on the effectiveness 

of site buffers as compared with landscape-scale 

habitat management for ensuring late-successional 

and old-growth species persistence, dispersal, and 

habitat connectivity? 

• How has the ISSSSP served to provide information 

on late-successional and old-growth-associated species under the NWFP? 
374

• Does the current list of special status and sensitive 

species adequately represent rare late-successional 

and old-growth species with risks to population 

persistence?

• What are new issues related to conservation of biodiversity in the NWFP area?

Agency Programs on Other Species and 

Biodiversity of Older Forests

Survey and Manage Program

Following the 1993 report of the Forest Ecosystem Management Assessment Team or FEMAT (1993), and as part of the 

initial creation of the NWFP, the NWFP Survey and 

Manage program was instituted in 1993 as part of a final 

environmental impact statement and record of decision for 

amendments to U.S. Department of Agirculture (USDA) 

Forest Service and U.S. Department of the Interior (USDI) 

Bureau of Land Management (BLM) planning documents 

for federal public lands within the range of the northern 

spotted owl. The Survey and Manage program was then 

amended by a 2001 record of decision for amendment to the 

Survey and Manage, protection buffer, and other mitigation 

measures standards and guidelines. The amendment 

established (1) an annual species review panel process to 

evaluate monitoring and research findings and to recommend to the regional forester of Region 6 appropriate 

conservation categories for all late-successional and 

old-growth-associated species not otherwise provided for by 

the NWFP guidelines, and (2) a set of site survey protocols5

and management recommendations for detecting and 

conserving sites with rare and little-known species under the 

NWFP. The annual species review sessions were designed 

as rigorous, 10-person panels consisting of 5 biologists and 5 

managers and used a Bayesian network decision modeling 

construct to help evaluate knowledge and explicitly represent uncertainty of each species in documented, repeatable 

procedures (Marcot et al. 2006). Mostly because of high 

costs and administrative complexities, no formal annual 

species review has been conducted since 2003. 

5 http://www.blm.gov/or/plans/surveyandmanage/protocols/.

The Survey and Manage program was established 

under the NWFP as a means of collecting information on, 

and providing appropriate conservation direction for, rare 

and poorly known late-successional and old-growth-associated species under the precautionary principle (resisting 

implementation of untested or disputed activities that may 

have adverse effects) and an adaptive management process 

(Marcot et al. 2006, Molina et al. 2003, USDA and USDI 

2001). From the initial list of 1,120 late-successional and 

old-growth-associated species evaluated by FEMAT (1993), 

various mitigation means under the NWFP Survey and 

Manage program narrowed the list in 2001 to 296 individual species and 4 arthropod species groups. The Survey 

and Manage program was then abolished, and, under a 

management policy decision of the agencies, 152 of the 296 

species were moved to the USDA Forest Service Sensitive 

Species program and the USDI BLM Special Status Species 

program, but the court then mandated that the Survey 

and Manage record of decision be reinstated. Eventually, 

the two agencies’ species programs were merged into 

the ISSSSP, discussed more fully below, which has since 

held the responsibility for evaluation of late-successional 

and old-growth species in the region. Also in the interim, 

a set of new national forest planning regulations have 

been instituted that provide impetus for considering other 

species, biodiversity, ecosystems, dynamics, and functions 

of both older and early-seral forests (Schultz et al. 2013). We 

discuss these updates to Forest Service and BLM planning 

guidelines and regulations further below.

The Survey and Manage program has had an unstable 

existence, having been established in 1994 (USDA and 

USDI 1994) with corrections to its standards and guidelines 

published in 2001 (USDA and USDI 2001), abolished by 

the agencies in 2004 (USDA and USDI 2004), reinstated by 

the court in 2006, again abolished by the agencies in 2007, 

challenged in 2008, and with a court ruling in 2009 that the 

2007 Forest Service environmental impact statement was 

flawed and the court subsequently approving a settlement 

agreement in 2011. The timber industry then challenged the 

settlement agreement in 2011 (and subsequently dropped 

their appeal in 2015), the Ninth Circuit Court of Appeals 

reversed and remanded the approval of the settlement 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

agreement in 2013, and then in 2014, the 2007 records of 

decision were vacated. 

Vacatur of the two 2007 records of decision (in 2007, 

BLM and the Forest Service each issued separate records of 

decision) has had the effect of returning the agencies to the 

status quo in existence prior to the 2007 records of decision. 

The status quo existing before the 2007 records of decision 

was defined by three previous court rulings, as follows. First 

is the 2006 court order reinstating the 2001 record of decision, including any amendments or modifications that were 

in effect as of March 21, 2004. This ruling incorporated the 

2001, 2002, and 2003 annual species review changes. Second was the 2006 court-ordered categories of activities that 

could proceed without conducting predisturbance surveys or 

site management for species: (1) thinning in forests less than 

80 years old; (2) replacement or removal of water culverts; 

(3) activities for improvement of riparian and stream areas; 

and (4) treatment of hazardous fuels, including use of prescribed fire; these reinstatements were retained in the later 

court rulings mentioned above. Third was the 2006 court 

ruling that vacated the 2001 and 2003 annual species review 

category change and subsequent removal of reference to the 

red tree vole in a portion of its range, returning the species 

to its prior monitoring status throughout its range.

At present, oversight of the Survey and Manage 

standards and guidelines implementation is consigned to 

staff members within the ISSSSP (Region 6 and Oregon 

BLM) and the Region 5 regional wildlife program manager 

within the Ecosystem Conservation staff. These individuals 

coordinate revision of management recommendations and 

survey protocols, assist field specialists in implementing 

the standards and guidelines, resolve issues between 

Survey and Manage species management and meeting other 

resource objectives, coordinate data management between 

the agencies preparing for an Annual Species Review, stay 

abreast of taxonomic updates, and coordinate methods for 

filling information gaps. To clarify, Forest Service Region 

5 is not formally a part of the ISSSSP, which is unique to 

Forest Service Region 6 and Oregon-Washington BLM. 

The list of late-successional and old-growth-associated 

species as provided by FEMAT (1993) had been evaluated 

by the Forest Service and BLM under the Survey and 

Manage program’s annual species reviews, using a set 

of published guidelines (table 6-1) to determine species’ 

potential need for more specific and additional conservation. 

Based on an evaluation of the occurrence of, and scientific 

knowledge on, the species, about 400 species of amphibians, 

bryophytes, fungi, lichens, mollusks, vascular plants, arthropod functional groups, and one mammal were deemed to be 

potentially at-risk, and the rest of the species were deemed 

to be adequately provided under the NWFP guidelines; the 

genealogy through 2006 of the many species lists are covered by Marcot and Molina (2006) and Molina et al. (2006). 

The annual species reviews developed and adopted use of a 

Bayesian network decision modeling approach to help wade 

through the complex evaluation guidelines (table 6-1) and to 

document results on each species (Marcot et al. 2006). 

Under the Survey and Manage program, about 68,000 

sites with presence of Survey and Manage species were 

identified by surveys, and new ecological knowledge was 

gained on about 100 species leading to their being removed 

from the protection list (Molina et al. 2006). Additionally, a 

set of field and management guides were produced on 

aquatic and terrestrial mollusks and fungi,6 and guidelines 

were published on assessing rare species of lichens (Edwards 

et al. 2004), fungi (Castellano et al. 2003, Molina 2008), and 

other taxa. Eventually, the high cost of maintaining the 

Survey and Manage program, running into several tens of 

millions of dollars, with its annual species reviews and all 

other activities associated with compiling scientific and 

monitoring information on late-successional and 

old-growth-associated species, was a factor considered by 

managers in their decision to abolish the program and enfold 

it into the ISSSSP.

Understanding the distributions and disturbance 

responses of rare species is a perennial problem in ecology, 

the main issues of which include securing adequate sample 

sizes for statistical analyses (Cunningham and Lindenmayer 

2005). Methods for increasing confidence in such studies 

include stratifying samples, such as demonstrated by 

Edwards et al. (2005) with five rare epiphytic macrolichens 

in the Pacific Northwest United States. 

6 http://www.blm.gov/or/plans/surveyandmanage/field.php.
376

Table 6-1—Guidelines for determining whether late-successional and old-growth forest (late-successional 

and old-growth)-associated species under the Northwest Forest Plan (NWFP) may need additional 

conservation consideration, as required under the Survey and Manage program 2001 record of decision 

(USDA and USDI 2001) (continued)

Evaluation categorya Description in record of decision (USDA and USDI 2001)

1. Geographic range The species must occur within the NWFP area or near the NWFP area and have potentially 

suitable habitat within the NWFP area.

2. Late-successional and 

old-growth association

A species is considered to be closely associated with late-successional and old-growth forests if it 

meets at least one of the following criteria:

• The species is significantly more abundant in late-successional and old-growth forest than in 

young forest, in any part of its range.

• The species shows association with late-successional and old-growth forest and may reach 

highest abundance there, and the species requires habitat components that are contributed by 

late-successional and old-growth forest.

• The species is associated with late-successional and old-growth forest, based on field study, and 

is on a federal U.S. Fish and Wildlife Service (USFWS) list or state threatened or endangered 

list; the USFWS candidate species list; a Bureau of Land Management or Forest Service special 

status species list in California, Oregon, or Washington; or is listed by the states of California, 

Oregon, or Washington as a species of special concern or as a sensitive species.

• Field data are inadequate to measure strength of association with late-successional and 

old-growth forest; the species is listed as a federal USFWS threatened and endangered 

species; and the Forest Ecosystem Management Assessment Team suspected, or the panel 

doing the final placement in Species Review Process suspects, that it is associated with latesuccessional and old-growth forest.

3. Plan provides for 

persistence

The reserve system and other standards and guidelines of the NWFP do not appear to provide for 

a reasonable assurance of species persistence. Criteria indicating a concern for persistence, i.e., 

one or more of the following criteria must apply:

• Low to moderate number of likely extant known sites/records in all or part of a species range.

• Low to moderate number of individuals.

• Low to moderate number of individuals at most sites or in most populations.

• Very limited to somewhat limited range.

• Distribution within habitat is spotty or unpredictable in at least part of its range. 

• Very limited to somewhat limited habitat.

Criteria indicating little or no concern for persistence, usually, most of the following criteria 

must apply:

• Moderate to high number of likely extant sites/records.

• Sites are relatively well distributed within the species range.

• High proportion of sites and habitat in reserve land allocations; or limited number of sites 

within reserves, but the proportion or amount of potential habitat within reserves is high and 

there is a high probability that the habitat is occupied. 

• Matrix standards and guidelines or other elements of the NWFP provide a reasonable 

assurance of species persistence.

4. Data sufficiency Information is insufficient to determine whether Survey and Manage basic criteria are met, or to 

determine what management is needed for a reasonable assurance of species persistence.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Table 6-1—Guidelines for determining whether late-successional and old-growth forest (late-successional 

and old-growth)-associated species under the Northwest Forest Plan (NWFP) may need additional 

conservation consideration, as required under the Survey and Manage program 2001 record of decision 

(USDA and USDI 2001) (continued)

Evaluation categorya Description in record of decision (USDA and USDI 2001)

5. Practicality of survey Surveys are considered “practical” if all of the following criteria apply:

• The taxon appears annually or predictably, producing identifying structures that are visible 

for a predictable and reasonably long time.

• The taxon is not so minuscule or cryptic as to be barely visible.

• The taxon can authoritatively be identified by more than a few experts, or the number of 

available experts is not so limited that it would be impossible to accomplish all surveys 

or identifications for all proposed habitat-disturbing activities in the NWFP area needing 

identification within the normal planning period for the activity.

• The taxon can be readily distinguished in the field and needs no more than simple laboratory 

or office examination to confirm its identification.

• Surveys do not require unacceptable safety (5a) or species risks.

• Surveys can be completed in two field seasons (about 7 to 18 months).

• Credible survey methods for the taxon are known or can be developed within a reasonable 

time period, i.e., about 1 year.

6a. Relative rarity The species is relatively rare and all known sites or population areas are likely to be 

necessary to provide reasonable assurance of species persistence, as indicated by one or 

more of the following:

• The species is poorly distributed within its range or habitat.

• Limited dispersal capability on federal lands.

• Reproduction or survival not sufficient.

• Low number of likely extant sites/records on federal lands indicates rarity.

• Limited number of individuals per site.

• Declining population trends.

• Low number of sites in reserves or low likelihood of sites or habitat in reserves.

• Highly specialized habitat requirements (narrow ecological amplitude).

• Declining habitat trend.

• Dispersal capability limited relative to federal habitat.

• Habitat fragmentation that causes genetic isolation.

• Microsite habitat limited. 

• Factors beyond management under the NWFP affect persistence, but special management 

under the NWFP will help persistence.

6b. Relative 

uncommonness

The species is relatively uncommon rather than rare, and not all known sites or population areas 

are likely to be necessary for reasonable assurance of persistence, as indicated by one or more of 

the following:

• A higher number of likely extant sites/records does not indicate rarity of the species.

• Low to high number of individuals/site.

• Less restricted distribution pattern relative to range or potential habitat.

• Moderate to broad ecological amplitude.

• Moderate to high likelihood of sites in reserves. 

• Populations or habitats are stable.

a

 If criteria for any evaluation category were met, then the species may be further considered for needing additional conservation beyond what the NWFP 

generally provides; such further consideration was addressed during annual species reviews under the NWFP Survey and Manage program.
378

Interagency Special Status and Sensitive 

Species Program

The ISSSSP7 was formed in 2005 as an interagency Forest 

Service Region 6 and BLM Oregon/Washington program 

for regional-level approaches for conservation and management of rare (but neither federally listed threatened nor 

endangered) species that would meet criteria for the two 

agencies’ lists of special status species and sensitive species. 

Its geographic and ecological scope includes and exceeds 

that of the NWFP and late-successional and old-growth 

forests in Washington and Oregon. The ISSSSP is not a 

reformulation of the NWFP Survey and Manage program, 

although it has taken on some of those functions pertaining 

to evaluation of the conservation status of species, development of some species survey and monitoring protocols, and 

other items. The ISSSSP addresses species across Forest 

Service and BLM lands in Oregon and Washington (but 

not California), implementing the Forest Service sensitive 

species policy (FSM 2670) and BLM special status species 

policy (BLM 6840) and providing oversight of the Survey 

and Manage standards and guidelines. Criteria for determining Forest Service sensitive species are quite different 

from the Survey and Manage species criteria discussed 

above (also see table 1). 

California, particularly northwest California within 

the NWFP area, does not have an organization equivalent 

to the ISSSSP, which is a collaboration unique to Washington and Oregon. In California, instead, the Forest Service 

Region 5 implements the national Forest Service sensitive 

species policy (FSM 2670) and results are overseen by 

various Forest Service regional office staff for the entire 

state, not just for the NWFP area and the six national 

forests therein. California BLM includes lands within the 

NWFP area, and those are overseen by the BLM Redding 

Resource Area, Arcata Resource Area, and the Kings 

Range National Conservation Area, all within the BLM 

Ukiah District. 

The ISSSSP has produced a wide array of products 

related to conservation of rare, nonlisted species. Products 

include species fact sheets, conservation assessments, 

conservation strategies, inventory reports, inventory and 

survey protocols and methods workshops, and results of 

studies. The most recent program update8

 (June 2015) 

mentions reorganization of the program’s conservation 

and inventory information on bats and fungi (covered 

below). The ISSSSP partners with and supports a variety of 

research and academic institutions to provide key information on rare species of conservation concern within its 

geographic venue. 

Unique among federal land management agencies, the 

ISSSSP has developed criteria used in common with Forest 

Service and BLM for including species on sensitive and 

special status lists. The ISSSSP considers species for such 

listing by using independent information from the Oregon 

Biodiversity Information Center9 Washington Natural 

Heritage Program10 and NatureServe. 11

The current list of Survey and Manage species12 dates 

to December 2003 and includes 298 species: 189 fungi, 15 

bryophytes, 40 lichens, 12 vascular plants, 36 snails and 

slugs (mollusks), 4 amphibians, 1 mammal (red tree vole, 

treated below), and 1 bird (great gray owl, Strix nebulosa). 

Implications of Forest Service and BLM 

Planning Directions

The current planning rule for the U.S. Forest Service (2012: 

21174)13 states that its intent is 

... to provide for the diversity of plant and animal 

communities, and keep common native species 

common, contribute to the recovery of threatened 

and endangered species, conserve proposed and 

candidate species, and maintain species of conservation concern within the plan area, within Agency 

authority and the inherent capability of the land. 

8 http://www.fs.fed.us/r6/sfpnw/issssp/documents3/

update-2015-06.pdf. 9

 http://inr.oregonstate.edu/orbic. 10 http://www.dnr.wa.gov/natural-heritage-program. 11 http://www.natureserve.org/. 12 http://www.blm.gov/or/plans/surveyandmanage/files/sm-fsenc3-table1-1-dec2003wrtv.pdf. 13 http://www.fs.usda.gov/detail/planningrule/home/?cid=stelprdb5359471. 7 http://www.fs.fed.us/r6/sfpnw/issssp/.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

The rule establishes guidelines and mandates for ecological sustainability, particularly for ecosystem integrity 

defined as the maintenance or restoration of terrestrial and 

aquatic ecosystems and watersheds, and their structure, 

function, composition, and connectivity. The rule also 

explicitly adopts a coarse- and fine-filter approach (further 

discussed below) to managing for diversity of plant and animal communities beginning with maintaining or restoring 

the diversity of ecosystem and habitat types including rare 

aquatic and terrestrial plant and animal communities, as 

well as identifying species of conservation concern to be 

designated by the responsible official, in coordination with 

the regional forester, based on scientific information. In the 

Pacific Northwest, the Forest Service is currently producing 

a draft list of potential species of conservation concern 

to facilitate efficiencies when the region undergoes plan 

revision under the 2012 planning rule.

Additional parts of the 2012 planning rule for the Forest 

Service provide guidance on monitoring, which it defines as 

“a systematic process of collecting information to evaluate 

effects of actions or changes in conditions or relationships” 

(USDA FS 2012:21271). The planning rule also provides 

guidance on managing ecological systems at the broad scale 

and for specific ecosystem elements, such as individual 

species, at finer scales. As such, specifically, the planning 

rule refers to coarse-filter management as “designing 

ecosystem ... connectivity based on landscape patterns of 

forests, grasslands, rangelands, streams, and wetlands that 

were created under ecological processes and landscape 

disturbance regimes that occurred before extensive human 

alteration” (section 23.11b: Ecosystem Integrity), and 

fine-filter management as “species-specific plan components, including standards and guidelines, for each of those 

species” (section 23.13: Species-Specific Plan Components 

for At-Risk Species). 

Schultz et al. (2013) recommended directly monitoring selected species of conservation concern and focal 

species because of inconsistencies in the 2012 planning 

rule between its operational requirements and its generous 

discretionary allowances. They suggested that monitoring 

should evaluate viability of such species and that management should do no harm to species for which viability 

cannot be provided solely on Forest Service lands; and that 

monitoring should specify trigger points to spark reviews of 

management activities affecting species conservation. 

As a point of history, BLM proposed a new rule for 

resource management planning nationally on BLM lands 

(USDI BLM 2016), but in February 2017, Congressional 

action nullified the regulations. In the NWFP area, BLM 

Resource Management Plans (RMPs) are in effect from 

records of decision signed in August 2016.14 The new RMPs 

are intended to provide protection for northern spotted owls, 

listed fish species, and water resources, and provide for 

jobs, recreation, and timber harvest. At this point, it is 

unclear if the RMPs will provide additional guidelines for 

conservation of other old-forest species and biodiversity 

under the NWFP in addition to guidelines provided by 

ISSSSP. 

Key Findings

New Information on Other Species and 

Biodiversity of Older Forests

In this section, we review new research information on 

individual species and species groups under the NWFP 

and in old-forest environments, conducted mostly since the 

previous science synthesis (Haynes et al. 2006). 

Fungi— 

Fungi are an important part of forest ecosystems. Fungi 

have always been a conservation challenge in terms of 

species identification, taxonomic designation, inventory and 

monitoring of furtive and seldom-appearing species, and 

understanding of their key ecological roles in late-successional and old-growth forest ecosystems. Many fungi are 

rare or little known, but much has been learned about some 

aspects of species occurrence and distribution since the 

previous science synthesis. Some of this work is presented 

in peer-reviewed publications, and other work is available 

through an agency peer review process. Recent regional 

work provides information on California fungal species. 

Other work provides a better understanding of the status of 

fungal species in the NWFP area. 

14 https://www.blm.gov/or/plans/rmpswesternoregon/.
380

Occurrence of fungal species is influenced, at least in 

part, by the type and intensity of disturbances, time since 

disturbance, and vegetation development, and by forest 

stand management and forest age class (Heithecker and 

Halpern 2006, Trofymow et al. 2003). Studies by Hebel et 

al. (2009) suggested that high-severity wildfire can reduce 

or prevent colonization of, and can kill, beneficial arbuscular mycorrhizal fungi. As noted in chapter 3 and in Reilly 

et al. (2017), current rates of high-severity fire in the NWFP 

area are very low even in the moist forests where fire was 

historically infrequent. In the dry forests, where fires were 

historically frequent, recent fire rotations have been well 

below the historical levels; however, in forests that historically had low-severity fire and little high-severity fire, the 

recent amounts of high-severity fire appear to be higher. 

It is unclear how current fire regimes might affect forest 

structure, age class, and disturbance intensity. 

Presumably, native fungi species were able to persist 

across landscapes with frequent to very frequent fire (<50 

years) and in landscapes with occasional, moderately 

frequent, mixed-severity fire (50 to 200 years). Fire suppression has affected the various forest ecosystems of the 

NWFP area in different ways (chapter 3), although little 

is known about effects of fire suppression activities on 

fungi. Luoma and Eberhard (2005) urged the conservation 

of rare truffle and mushroom species “... in a manner that 

recognizes their different responses to forest disturbance.” 

They also hypothesized that fire suppression activities may 

have favored mushroom production over truffle production, 

and that presence of fire is a factor in the reproductive 

evolution of ectomycorrhizal fungi. Thus, they concluded 

that providing for ectomycorrhizal fungi would include 

restoring forest health from the adverse effects of decades 

of fire suppression. 

Many fungi species are soil dwellers and mostly 

subterranean, and, with intermittent fruiting cycles, they are 

not easy to detect and collect. Determining presence can be 

difficult, but they can play major roles in nutrient uptake by 

trees and other plants and in aiding coarse-wood decomposition, contributing to soil organic matter, and maintaining 

overall forest health. 

Luoma (2001)15 found that retention of green trees in 

late-successional forests helped retain Arcangeliella 

camphorata, a rare truffle fungus, as compared to the 

species’ loss in clearcuts. Trappe et al. (2009) provided an 

extensive study of the distribution, ecology, and conservation of truffle species in the Pacific Northwest. In southwest 

Oregon, Clarkson and Mills (1994) and Amaranthus et al. 

(1994) also had previously demonstrated that clearcuts 

ranging from 4 to 27 years since harvest nearly eliminated 

truffle production and that retention of mature trees and 

coarse woody debris promote their diversity and abundance. 

Marcot (2017) reviewed the role of fungi in wood decay of 

forest ecosystems of the Pacific Northwest. 

Some fungi are dispersed in unusual ways, such as on 

the beaks of foraging and cavity-excavating woodpeckers 

(Jusino et al. 2016). Fungi such as truffles and their ectomycorrhizal sporocarps are key food resources for northern 

flying squirrels (Glaucomys sabrinus) (Lehmkuhl et al. 

2004); in turn, flying squirrels are a key prey species of 

northern spotted owls in parts of the owl’s range. Deliberate 

introduction of fungi in live trees is a management tactic 

sometimes used to induce wood decay and create partially 

dead trees and snags for wildlife use such as in western 

Washington (Bednarz et al. 2013). 

In 1994, the Survey and Manage program listed some 

234 rare fungi species associated with late-successional and 

old-growth forests (Molina 2008). Molina’s (2008) review of 

mycology herberia eventually yielded 14,400 records of these 

species, with 55 percent of the species found at 20 or fewer 

sites and 42 percent found at 10 or fewer sites; it is unclear 

which of the 42 percent are rare or undersurveyed. Some 90 

percent of the species had some fraction of their locations 

occurring within reserves, but only a third of the species had 

all their locations within reserves. This led Molina (2008) to 

conclude that fine-filter conservation of rare species outside 

reserves was needed to help ensure conservation of the entire 

late-successional and old-growth-associated fungal biota. 

15 Luoma, D.L. 2001. Monitoring of fungal diversity at the Siskiyou integrated research site with special reference to the survey 

and manage species Arcangeliella camphorata (Singer & Smith) 

Pegler & Young. Unpublished report. On file with: Chetco Ranger 

District, Siskiyou National Forest, Brookings, OR 97415.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Overall, although this work has provided much information 

on presence and distribution of rare fungi, in general their 

species-specific status and trends are still not well known.

The ISSSSP Fungi Work Group has compiled an 

annotated bibliography on rare fungi species on the Special 

Status Species list for California, Oregon, and Washington.16 This work includes 174 references, each with annotated findings and indexed to keywords pertaining to 

ecological and management topics. 

Mushroom collection for individual use is a popular 

recreational activity in forests of the Pacific Northwest 

(Trappe et al. 2009). Individual national forests in the 

NWFP area may have specific regulations on commercial 

mushroom harvests. For example, Siuslaw National Forest 

(2007) sells individual commercial collection permits, up 

to 1,000 permits per year, with permits being unlimited by 

weight or amount of mushrooms collected. Alexander et 

al. (2002) compared the economics of timber harvest with 

16 http://www.fs.fed.us/r6/sfpnw/issssp/documents3/cpt-fueffects-guidelines-att3-annotated-bibliography-2013-10.docx.

mushroom harvest in the Pacific Northwest and found that 

some mushrooms (e.g., chanterelles, morels) have lower 

value and some (matsutake) have about the same value as 

commercial timber, as measured by soil expectation value 

analysis. At present, though, we have encountered no studies on the impacts of mushroom collection on these species’ 

populations in the NWFP area. 

Lichens—

Much has been learned over the past decade about the 

occurrence and rarity of forest lichens (table 6-2) and the 

effects of forest management in the Pacific Northwest. 

Lichens play important ecological roles in late-successional 

and old-growth forests of the Pacific Northwest (chapter 3). 

Epiphytic macrolichens, because of their complete reliance 

on atmospheric sources of water and nutrients, are useful 

for monitoring air quality and climate (fig. 6-1) (Geiser and 

Neitlich 2007; similar work by Root et al. 2015 followed 

Table 6-2—Selected recent findings on lichen species associated with late-successional and old-growth 

forest conditions within the Northwest Forest Plan area

Lichen taxa Topic Source

Bryoria subcana to 

B. fuscescens

Taxonomy of Bryoria section Implexae Velmala et al. 2014

Dermatocarpon Dermatocarpon luridum now found to not occur in the United 

States. The species in the Pacific Northwest (PNW) is D. 

meiophyllizum.

Glavich 2009, Glavich and 

Geiser 2004 

Fuscopannaria Fuscopannaria saubinetii (misidentification) does not occur in the 

PNW. Previous records were misidentifications of F. pacifica, a 

common species in the PNW.

Jørgensen 2000

Leptogium Leptogium burnetiae var. hirsutum is now a synonym of L. 

hirsutum, which does not occur in the PNW. The taxon of 

conservation concern is L. burnetiae.

Esslinger 2015

Leptogium Leptogium rivale is changed to Scytinium rivale.

L. teretiusculum is changed to S. teretiusculum.

Otálora et al. 2014

Usnea Usnea hesperina is changed to U. subgracilis. Previously, U. 

hesperina and U. subgracilis were both considered synonyms of

U. schadenbergiana; U. schadenbergiana is distinct from

U. hesperina and U. subgracilis.

Truong et al. 2013
382

mostly east of the NWFP area).17 Trofymow et al. (2003) 

found that arboreal lichen abundance and species richness 

differed between mature (75 to 95 years old) and oldgrowth (>240 years old) conifer forest stands on Vancouver 

Island, and thus can serve as indicators of late-successional 

and old-growth forest conditions. Arsenault and Goward 

(2016) reported that, in inland wet conifer forests of British 

Columbia, some macrolichens, such as Lobaria pulmonaria, are good indicators of old-growth forests in some 

ecological conditions but not in others, highlighting the 

17 Also see: http://people.oregonstate.edu/~mccuneb/epiphytes.htm

and http://people.oregonstate.edu/~mccuneb/biblio.htm.

need for caution when determining species’ association 

with, and dependence on, old-growth forest conditions. 

Sillett et al. (2000) showed that dispersal can limit the 

development of some lichens (e.g., Lobaria oregana) in 

late-successional and old-growth forests, as well as in 

young forest plantations. 

Bokhorst et al. (2015) reported that lichen species 

in southern Norway have a large impact on associated 

invertebrate communities, varying with lichens that differ 

in nitrogen fixation and nutrient concentration, thallus 

structure, and terricolous versus arboreal or epiphytic 

habitat. Whether such contributions of lichen diversity 

to overall lichen-invertebrate communities occur within 

Figure 6-1—Some arboreal, epiphytic lichens, such as this Alectoria in Wind River Experimental Forest in the south Washington Cascade Range, are fully dependent on atmospheric sources of water and nutrients, and thus can serve as sensitive indicators for monitoring 

of air pollution and climate change.

Bruce G. Marcot
383

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

late-successional and old-growth forests of the Pacific 

Northwest is apparently unstudied.

Effects of wildfire and fire suppression activities on 

late-successional and old-growth-associated lichens have 

been poorly studied. Large-scale, stand-replacing fires will 

likely reduce distribution and biomass of late-successional 

and old-growth-associated lichens over decades to centuries, as a function of the species’ dispersal mechanisms and 

limitations (Sillett et al. 2000). 

Recent studies suggest that variable-density thinning 

treatments in young forests of Douglas-fir (Pseudotsuga 

menzeisii) and western hemlock (Tsuga heterophylla) can 

provide habitat for a variety of lichen species (Root et al. 

2010) that could complement lichen assemblages found in 

unthinned late-successional and old-growth forest environments. Earlier studies suggested that uniform thinning 

of dense forest stands provides only minor improvement 

of habitat of lichens and bryophytes, whereas some variable-density thinning can help promote development of 

tree branches lower in the canopy profile as substrates for 

lichens and bryophytes. Earlier studies (e.g., Neitlich and 

McCune 1997) also revealed that forest structure may play 

a greater role in determining lichen diversity and biomass 

than forest age per se from observations that lichen biomass 

can be greater in structurally diverse young forests with 

gaps and older remnant trees than in some old-growth 

forests. Neitlich and McCune (1997) suggested, for conserving epiphytic macrolichens, to protect forest gaps, wolf 

trees (large trees with wide-spreading crowns), and old 

remnant and legacy trees. Retention of propagule sources, 

such as old legacy trees in younger stands, and older-forest 

patches in cutting units, can be critical to providing for 

old-growth-associated epiphytes (Sillett et al. 2000) and 

cryptogams (Hofmeister et al. 2015). 

Much work has also been done over the past decade 

on riparian lichens. Three groups of lichens depend on 

riparian areas:18 (1) nonepiphytic, instream species (e.g., 

Dermatocarpon meiophyllizum, Leptogium rivale, and 

Peltigera hydrothyria); (2) epiphytic species occurring in 

streamside and lakeshore forest and woodland environments 

(e.g., Leptogium polycarpum, Ramalina thrausta, Sticta 

fuliginosa, Usnea wirthii, and many cyanolichen species); 

and (3) epiphytic species in forested wetlands, particularly 

in Oregon ash (Fraxinus latifolia) swamps (e.g., Fuscopannaria mediterranea, Hypotrachyna riparia, and many 

cyanolichens). A number of these riparian lichens are likely 

afforded habitat under the NWFP’s Aquatic and Riparian 

Conservation Strategy. For further information on riparian 

lichens in the Pacific Northwest, see McCune et al. (2002) 

and Ruchty (2000).

As with fungi, many species of lichens and other rare 

and poorly known species in the Pacific Northwest are difficult to detect, inventory, monitor, and study because they 

require specialized expertise in the field and the laboratory. 

To address such problems, the Survey and Manage program spurred the development of methods for statistically 

determining the occurrence and frequency of rare species of 

lichens (Edwards et al. 2004, 2005). A guide was produced 

under the Survey and Manage program on natural history 

and management considerations of selected lichen species 

under the NWFP (Lesher et al. 2003). 

Additionally, Miller et al. (2017) tested techniques for 

surveying Lobaria oregana, a rare canopy lichen, at the 

southern edge of its range in northwest California within the 

NWFP area. They found the species on branches of large 

trees in the mid-crown, and on boles of small trees near 

ground level, suggesting that the species benefits from cool, 

wet microclimates, and that maintaining such microhabitats 

is key to its long-term viability. They also concluded that 

ground surveys are useful for detecting abundant lichen 

species, but that tree-climbing to conduct canopy surveys 

also may be needed to detect low-abundance species associated with mid- or upper-canopy conditions. 

Bryophytes—

Bryophytes—including hornworts, liverworts, and mosses 

(in general, nonvascular plants)—are a conspicuous component of many late-successional and old-growth forests of 

the Pacific Northwest, and many species have been part of 

the Survey and Manage program. Many late-successional 

and old-growth-associated bryophytes may be sensitive to 

disturbance and may require old-forest stands larger than 

18 McCune, B. Personal communication. Professor, Oregon State 

University, Corvallis, OR 97331.
384

2.5 ac (1 ha) (Halpern et al. 2012) or with more than 15 

percent retention of older green trees in dispersed retention 

harvests (Heithecker and Halpern 2006). 

Mölder et al. (2015) reported that 31 bryophyte species 

in north Germany can serve as ancient woodland indicators; 

a number of bryophyte species of the Pacific Northwest can 

serve similar functions (Rambo and Muir 1998, 2002). In 

an older study, Ryan et al. (1998) found that cryptogams in 

mixed-conifer forests of southern Vancouver Island were 

largely associated with humus, and especially coarse woody 

debris and rock substrates, and that old-growth forests 

variously excluded shade-intolerant species and selected for 

shade-tolerant species. 

A recent taxonomic update has changed Diplophyllum 

plicatum to Douinia plicata (Konstantinova et al. 2013). 

Pacific Northwest forests are the main source of commercially harvested moss in North America with dozens of 

species likely affected by the practice (Peck 2006, Peck and 

Christy 2006). The main mosses collected are epiphytes 

that require 15 to 25 years to recover, and which are most 

abundant in riparian and low-elevation forests and absent or 

much less abundant in young (<70 years) Douglas-fir plantations (Peck 2006). Commercial harvest methods of stripping 

entire moss mats can greatly impede recovery of the species 

(Peck and Frelich 2008) and may be a major, local threat 

to this group.19 Peck and Moldenke (2011) reported a wide 

array of invertebrates (205 morphospecies) associated with 

subcanopy epiphytic bryophyte mats subject to commercial 

harvest in the Coast and Cascade Ranges of the Pacific 

Northwest, where more than 8.2 million lbs (3.7 million kg) 

of bryophytes are harvested per year. However, the impact 

of moss harvest on populations of these invertebrate species 

is undetermined. 

Overall, few studies are available on the status and 

trends of the full suite of bryophyte species (and associated 

other taxa) considered under the NWFP and ISSSSP. In the 

NWFP area, some individual national forests in Region 

6 (Washington and Oregon) have their own direction 

regarding commercial moss collection, although there is no 

overall regional direction. For example, Siuslaw National 

Forest and Willamette National Forest may have instituted 

local direction of moss collection under their special forest 

products or nontimber forest products regulations (e.g., 

Siuslaw National Forest 2007). Siuslaw National Forest’s 

direction, for instance, permits commercial moss harvests 

to be limited to 16,000 lb (7258 kg) per year, from harvest 

areas that would be open for 12 years, with only one harvest 

area open at a time and rotated every 12 years, and harvest 

areas consisting of forest stands <110 years old (Siuslaw 

National Forest 2007). 

Vascular plants—

Vascular plants are a conspicuous and important component 

of late-successional and old-growth forests in the NWFP 

area. The diversity of vascular plants tends to increase 

during structural development following logging in western 

hemlock-Douglas-fir, and to peak in old-growth forest 

conditions (Halpern and Spies 1995), but less is known in 

other vegetation zones of the area. Late-successional and 

old-growth-related vascular plants in the Pacific Northwest 

are generally considered to be protected under the NWFP 

guidelines and within LSRs, and have constituted only a 

small fraction of all Survey and Manage species thought to 

be closely associated with late-successional and old-growth 

forests (Marcot and Molina 2006). 

Most studies of changes in plant communities over 

seral development have used a chronosequence (space-fortime) approach and compared composition or abundance 

in young logged stands with naturally regenerated stands 

in middle or later stages of development. These studies 

generally agree that understory plant species diversity 

increases following disturbance then decreases during 

canopy closure, and subsequently increases again and 

sometimes peaks in old-growth conditions (Halpern and 

Spies 1995, Jules et al. 2008). Few perennial understory 

plant species are either absent from, or restricted to, any 

specific stage of successional development, although 

the abundance of individual species changes over time 

(Halpern and Spies 1995). Some species are most abundant 

in old growth or are closely associated with old growth 

(table 6-3), but none of these species is on the current 

Survey and Manage species list and might be candidates 

19 For a compendium of literature on moss harvesting, see: http://

bryophytes.science.oregonstate.edu/MossHarvest.htm.
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Table 6-3—Vascular plant species found to be associated with late-successional 

and old-growth forests in the Northwest Forest Plan areaa (continued)

Species

Halpern and 

Spies 1995b

Lindh and 

Muir 2004c Jules et al. 2008d

Trees/shrubs:

Abies amabilis 

Acer circinatum 

Taxus brevifolia 

Tsuga heterophylla 

Rhododendron macrophyllum 

Vaccinium alaskaense 

Vaccinium membranaceum  

Vaccinium parvifolium 

Ribes lacustre 

Low/subshrubs:

Berberis nervosa 

Chimaphila menziesii

Chimaphila umbellata  

Cornus canadensis 

Gaultheria ovatifolia 

Goodyera oblongifolia  

Linnaea borealis  

Herbs, forbs, and fern allies:

Achlys triphylla   

Adenocaulon bicolor  

Anemone oregana 

Coptis laciniata  

Clintonia uniflora  

Disporum hookeri 

Galium spp. 

Lycopodium clavatum 

Osmorhiza chilensis 

Pyrola asarifolia  

Senecio bolanderii 

Smilacena stellata 

Synthyris reniformis 

Tiarella trifoliata  

Trillium ovatum 

Vancouveria hexandra 
386

for such consideration. Bailey et al. (1998) suggested that 

understory communities are relatively resilient to past 

cutting as few species differed in frequency of occurrence 

between young- and old-growth forests in the Oregon 

Coast and western Cascade Ranges. These results contrast 

with those of Halpern and Spies (1995) but are based on 

a much smaller sample size (9 vs. 196 plots) and are only 

from the drier part of the moist forest region.

The affinity of some species of vascular plants to 

old-growth forest conditions has been attributed to multiple 

mechanisms including the presence of canopy gaps and 

unique microclimatic conditions, greater heterogeneity in 

resources, and sensitivity to disturbance (e.g., logging and 

fire) coupled with low rates of growth and reestablishment 

(Halpern and Spies 1995). Jules (1998) found that ~97 

percent of Trillium ovatum were eliminated following clearcutting and planting of conifers. Furthermore, fragmentation of habitat had negative demographic consequences 

including decreased recruitment and seed production in 

this species (Jules and Rathcke 1999). Slow recovery rates 

of dispersal-limited, perennial herbs (e.g., Trillium spp., 

Cornus canadensis, Clintonia uniflora, Disporum hookeri

var. hookeri) may take centuries for populations to recover 

following clearcutting (Kahmen and Jules 2005). Halpern 

and Spies (1995) suggested that long-term rotations (150 to 

300 years) may be needed to maintain understory plant species that require long recovery times following disturbance. 

Observations are lacking on how these dynamics differ 

from historical dynamics following natural disturbance 

(e.g., fire).

 The response of understory vascular plants to management is known primarily from western hemlock-Douglas-fir forests (e.g., Halpern et al. 1999, Puettmann et al. 

2013) and generally suggest that certain management 

activities can increase later seral species in previously 

managed stands (i.e., clearcuts). Precommercial thinning 

can increase compositional similarity of shrubs and herbs 

between young- and old-growth stands and increase the 

abundance of late-seral herbs (Lindh and Muir 2004). Conversely, thinning in 60- to 80-year-old stands can increase 

diversity and the abundance of early-seral species but have 

little effect on late-seral species (Puettmann et al. 2013). 

North et al. (1995) found that richness of herb and shrub 

species was greater in a green tree retention harvest than in 

an adjacent clearcut and in an intact 65-year stand (also see 

Halpern et al. 2005). 

Retention patches of late-successional and old-growth 

forest scattered between late-successional forest reserves 

might serve as conservation centers for some understory 

vascular plants. Nelson and Halpern (2005) studied the 

short-term (1 and 2 years) response of understory plants 

to patterns of aggregated retention harvest and found that 

Table 6-3—Vascular plant species found to be associated with late-successional 

and old-growth forests in the Northwest Forest Plan areaa (continued)

Species

Halpern and 

Spies 1995b

Lindh and 

Muir 2004c Jules et al. 2008d

Saprophytes/root parasites: 

Corallorhiza maculata 

Corallorhiza mertensiana 

Hemitomes congestum

Hypopitys monotropa

Monotropa uniflora

Pterospora andromedea

a None of these species is on the current Survey and Manage species list.

b

 Oregon Coast Range and Oregon and Washington Cascade Range.

c

 H.J. Andrews Experimental Forest, western Cascade Range, Oregon.

d

 California Klamath Province.
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old-forest patches larger than 2.5 ac (1 ha) helped retain 

populations of late-seral plant species, although disturbance 

within 33 ft (10 m) of the stand edge (“depth of edge” 

influence) was evident by the incursion of early-seral plant 

species. Late-seral herbs were more frequently extirpated in 

harvested portions of aggregated treatments as opposed to 

dispersed treatments

Fire exclusion may have affected understory communities in late-successional and old-growth forests in 

vegetation zones where fire was frequent historically 

(Loya and Jules 2008), but these effects are poorly 

understood and more research is needed. Some evidence 

suggests increases in shrub cover may be associated with 

fire exclusion (Loya and Jules 2008). Loss of bear grass 

(Xerophyllum tenax) in anthropogenically maintained 

savannahs has also been attributed to fire exclusion (Peter 

and Shebitz 2006). Studies from mixed-conifer forests 

in the eastern Washington Cascades and from ponderosa 

pine (Pinus ponderosa) forests suggest that a single 

application of prescribed fire can reduce shrub cover, but 

effects on understory response were minor and limited to 

slight increases in vegetation cover (Dodson et al. 2008) 

and diversity (Busse et al. 2000). Donato et al. (2009) 

found that almost all species in mature and old-growth 

stands were present following high-severity fire in the 

Biscuit Fire. There is some evidence that reintroduction of wildfire to dry forests of the Sierra Nevada had 

little effect on diversity of vascular plant species but 

may increase the distribution of species that may have 

been negatively affected by fire exclusion (Webster and 

Halpern 2010).

Invertebrates—

The ISSSSP provides a series of products on selected invertebrate species.20 Range maps are provided on a number of 

mollusks species21and conservation assessments and species 

fact sheets are provided for all sensitive invertebrates 

including bumblebees, beetles, true bugs, butterflies and 

moths, damselflies and dragonflies, amphipods, and other 

taxa. The following sections summarize other recent studies 

on various invertebrate taxa including soil invertebrates, 

mollusks, and other insects and arthropods. 

Soil invertebrates—Soil invertebrates constitute a wide 

array of taxa, including microorganisms, nematodes, 

mites, springtails, microspiders, centipedes, millipedes, 

earthworms, and others, with an equally diverse set of 

ecological functional roles as comminutors (chewers), 

detritivores and saprophages (detritus-feeders), fungivores 

(fungi-eaters), prey, predators, parasites, and more (Berg 

and Laskowski 2005). In addition, there are four functional groups of arthropods—litter- and soil-dwelling species, 

coarse wood chewers, understory and forest gap herbivores, and canopy herbivores—that are listed as Survey 

and Manage species in the Oregon and California Klamath, 

California Cascade, and California Coast Range physiographic provinces. 

Some functional roles of soil invertebrates are yet to be 

discovered and may be surprising. As an example, Duhamel 

et al. (2013) reported that fungivorous springtails may play 

the ecological role of transferring secondary metabolites 

(catalpol) from host plants to arbuscular mycorrhizal fungi 

that then helps prevent the mycorrhizae from being grazed, 

thus protecting the host plant that uses the symbiotic fungi 

as a source of soil nutrient update. 

Soil microorganisms include protozoa, rotifers, 

bacteria, and others that also play key ecological functions 

contributing to forest health, resilience, and productivity 

(Luo et al. 2016). Overall, soil invertebrates, including 

microorganisms, of late-successional and old-growth 

forests in the Pacific Northwest have been little studied but 

likely include species that are undescribed and some that 

closely associate with closed-canopy, late-successional, and 

old-growth forest conditions (see chapter 3 for a discussion 

of closed-canopy and open-canopy late-successional and 

old-growth forests and associated degree of shade-tolerant 

understory plants). Several older identification guides and 

species lists for the Pacific Northwest or selected sites 

therein are available such as on oribatid mites (Moldenke 

and Fichter 1988), arthropods (Parsons et al. 1991), and 

spiders (Moldenke et al. 1987). 

20 http://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-invertebrates.shtml. 21 http://www.fs.fed.us/r6/sfpnw/issssp/planning-tools/species-distribution-maps.shtml#invertebrates.
388

Forest invertebrate species vary in their sensitivity to 

disturbance and to forest canopy closure and tree density 

conditions. For example, Brand (2002) found that species 

richness, frequency, and density of epigeic (litter-dwelling) 

springtails in the Midwest are sensitive to fire; findings 

included the springtail Tomocerus flavescens, which is also 

a component of Pacific Northwest forests. Brand suggested 

using scattered refuges to maintain survival of fire-sensitive 

invertebrates in the face of fires; whether this is practical in 

the face of increasing rates of fire in the drier forests of the 

NWFP area is untested. Within the NWFP area, Moldenke 

and Fichter (1988) documented that oribatid mites, which 

are diverse and numerically dominant in ecosystems worldwide, occurred in very different species groups in open- and 

closed-canopy forests. The closed-canopy species were 

found throughout all stages of closed-canopy succession but 

differed markedly in relative abundance between young and 

old forests. 

Milcu et al. (2006) found various responses of earthworms, springtails, and soil microorganisms—all decomposers—to grass and herb species diversity, functional 

group diversity, and growth form, but that the response of 

the decomposers did not correlate with plant productivity. 

Niwa and Peck (2002) found variable responses to time 

since prescribed fire burning in the occurrence and abundance of species of spiders (Araneae) and beetles (Carabidae) in southwest Oregon.

Some late-successional and old-growth-associated 

invertebrates, particularly dispersal-limited species, can 

serve as indicators of biodiversity and climate change 

risk (Ellis 2015, Homburg et al. 2014), and indicators of 

response of species groups to thinning (Yi and Moldenke 

2005). Such potential indicator species include flightless 

terrestrial carabid beetles (e.g., Brumwell et al. 1998, 

Driscoll and Weir 2005, Eggers et al. 2010), which are 

a component of the entomofauna of LSRs in the Pacific 

Northwest, and flightless saproxylic weevils (Coleoptera: 

Curculionidae) (Buse 2012), which are also found in 

late-successional and old-growth reserves in the Pacific 

Northwest. 

Yi and Moldenke (2005) studied the effects of thinning 

in 40- to 60-year-old Douglas-fir forest and associated 

changes in forest floor environmental conditions in Willamette National Forest in the Oregon Cascade Range. They 

reported that Formicidae ants preferred heavy thinning 

intensities; Araneae spiders, Carabidae ground beetles, and 

Polydesmida millipedes positively correlated with litter moisture, which in turn was sensitive to season and negatively 

correlated with thinning intensity; and Gryllacrididae camel-crickets were negatively associated with litter moisture. 

Rykken et al. (2007) found that invertebrates associated 

with headwater streams on the Willamette National Forest 

of Oregon, within the NWFP area, constitute spatially 

constrained but extremely species-rich communities. This 

occurred particularly within 3 ft (1 m) of the stream edge in 

mature forests and in 100-ft (30-m) riparian buffers within 

managed landscapes, such as may be provided as part of the 

Aquatic and Riparian Conservation Strategy of the NWFP 

(see chapter 7). 

Caesar et al. (2005) assessed the genetic structure of 

a soil-inhabiting beetle (Acrotrichis xanthocera: Ptiliidae) 

in LSRs in the Klamath-Siskiyou ecoregion of northern 

California within the NWFP area. They concluded that the 

reserve system currently maintains high genetic variation 

for the species and suggested that intervening habitat gaps 

among the reserves should be reduced to maintain connectivity among the beetle populations within the reserves, 

apparently under the tacit assumption that the LSR system 

would continue in its current form under its current fire 

and fuels management approach (e.g., Fire suppression and 

limited use of prescribed fire) (see chapter 3). 

Of concern for the conservation of invertebrates in 

LSRs is the incursion by invasive species. Of high concern 

are exotic earthworms (Ewing et al. 2015), e.g., Lumbricus 

terrestris, and about two dozen related species of Lumbricidae, introduced from Europe and currently found 

throughout North America including the Pacific Northwest although not yet in natural conifer stands. Exotic 

earthworms have been shown to reduce germination of 

tree seeds and survival of seedlings in southern Quebec, 

Canada (Drouin et al. 2014). In greenhouse and laboratory 

experiments, Eisenhauer and Scheu (2008) and Gundale 

(2002) found that exotic earthworms aid establishment of 

invader plants. In northern hardwood forests of Michigan 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

and New York, Gundale et al. (2005) and Eusenhauer and 

Sheu (2008), respectively, found that exotic earthworms 

reduce nitrogen retention. Hendirx and Bohlen (2002) 

reported that exotic earthworms, in general, can adversely 

affect soil processes and can introduce pathogens. In 

northern temperate forests of North America, Bohlen et al. 

(2004a, 2004b) reported that invasive exotic earthworms 

can adversely alter soil nutrient content (total carbon 

and phosphorus, and carbon-nitrogen ratios) and soil 

food webs. In the Northeastern United States, increased 

abundance of white-tailed deer (Odocoileus virginianus) 

can facilitate the spread of invasive earthworms; the deer’s 

herbivory promotes the spread of nonnative understory 

vegetation that, in turn, fosters less acidic soils that 

are more favorable to the invasive earthworm species 

(Dávalos et al. 2015). Ziemba et al. (2015) reported that 

invasive Amynthas earthworms are altering detrital soil 

communities in North America, adversely affecting 

eastern red-backed salamanders (Plethodon cinereus) (also 

see Ransom 2012). Other invasive invertebrates occur 

throughout the Western United States (e.g., Chen and 

Seybold 2014) but are largely unstudied within the NWFP 

reserve system. 

Few such studies of the specific impacts of exotic earthworms have been conducted in the NWFP region. Bailey et 

al. (2002) compared the influence of native and exotic earthworm species on soil and vegetation in remnant forests in 

the Willamette Valley of western Oregon. They discovered 

two genera of native earthworms and the exotic earthworms 

were present in all five forest study sites, and reported that 

although there was no direct evidence that exotic species 

were affecting native species, they did not detect numerous 

native species presumed present in the region. They further 

suggested experimental studies to more clearly identify 

impacts of exotic species on native fauna. 

Mollusks—Mollusks of the Pacific Northwest—particularly 

slugs and snails—have been the earlier focus of inventory, 

monitoring, and taxonomic study under the NWFP. Field 

guides have been produced under the Survey and Manage 

program for freshwater mollusks (Frest and Johannes 1999) 

and terrestrial mollusks (Kelley et al. 1999). Recent findings 

on mollusk species taxonomy are presented in table 6-4. 

In a study in northern California, Dunk et al. (2004) 

sampled five species of terrestrial mollusks (Ancotrema 

voyanum, Helminthoglypta talmadgei, Monadenia churchi, M. fidelis klamathica, and M. f. ochromphalus). In 

a comparison across randomly selected sample plots of 

various forest conditions, they found that A. voyanum was 

associated with late-successional and old-growth forests, 

M. churchi was a habitat generalist, and data were insufficient to determine habitat associations of the remaining 

three species. As a result of the information on M. churchi

being a habitat generalist, the species was removed from 

the Survey and Manage species list owing to not being 

specifically associated with late-successional and oldgrowth forests.

Table 6-4—Selected recent findings on taxonomy of mollusk species associated with late-successional and 

old-growth forest conditions within the Northwest Forest Plan area

Mollusk taxa Topic Source

Fluminicola (aquatic snail) Updated taxonomy in northern California:

F. n. sp. 14 = F. potemicus

F. n. sp. 15, 16, & 17 = F. multifarious

F. n. sp. 18 = F. anserinus

F. n. sp. 19 & 20 = F. umbilicatus

Hershler et al. 2007

Lyogyrus (aquatic snail) Lyogyrus n. sp. 1 is now described as Colligyrus greggi. The genus 

was transferred and then the species fully described.

Hershler 1999, 

Liu et al. 2015

Deroceras Deroceras hesperium is now considered D. leave, a common and 

widespread slug in North America

Roth et al. 2013

Pristiloma P. arcticum crateris is now changed to P. crateris Roth 2015
390

In a study of species in old-forest leave islands (up to 1 

ac or 0.4 ha) in western Oregon, Wessell (2005) found that 

leave island size positively correlated with overall slug and 

snail density, and density of three mollusk species groups. 

Studies conducted beyond the Pacific Northwest also 

indicate that mollusk species richness is related to habitat 

area (Horsák et al. 2012) or hardwood forest stand age 

(Moning and Müller 2009). Other studies elsewhere (Moss 

and Hermanutz 2010) suggest the importance of monitoring 

for nonnative gastropods, particularly slugs, and especially 

along the margins of disturbed (burned) areas. Invasive 

slugs can negatively affect native slug diversity and plant 

regeneration and should be included in the monitoring of 

protected areas (Moss and Hermanutz 2010). 

Jordan and Black (2015) provided a conservation 

assessment and finding of a potential threat for the mollusk 

Cryptomastix devia, otherwise known as the Puget Oregonian (Jordan and Black 2015). This terrestrial Gastropoda 

snail is strongly associated with large, old bigleaf maples 

(Acer macrophyllum) (fig. 6-2) growing among conifers, 

typically Douglas-fir, western hemlock, and western redcedar (Thuja plicata), or among other hardwoods such as black 

cottonwood (Populus trichocarpa ssp. trichocarpa and 

red alder (Alnus rubra). A primary threat identified in the 

conservation assessment for this species is reduction or loss 

of large, old bigleaf maples through suppression by Douglas-fir and other conifers, and through selective commercial 

thinning of hardwoods. Further, over the past 10 to 15 years, 

Figure 6-2—Large, old bigleaf maples are important hosts for the terrestrial gastropod snail known as the Puget Oregonian. Loss of 

maples in the southern Washington Cascade Range from commercial thinning of hardwoods, suppression by conifers, and disease may 

be threatening this snail. 

Bruce G. Marcot
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

there has been widespread mortality of bigleaf maples in 

the Upper Cowlitz and Cispus River drainages of the south 

Washington Cascades,22 the area with the vast majority of 

known locations of this mollusk. Other threats may include 

vertebrate and invertebrate predators (predatory snails, 

and beetles), and the occurrence of invasive slugs. As with 

nearly all Survey and Manage species, there is no ongoing 

research and monitoring program for this mollusk. 

Other insects and arthropods—Studies of macromoths 

in H.J. Andrews Experimental Forest in Oregon (and in 

companion study sites in Mount Jirisan National Park in 

South Korea) revealed that most species consisted of the 

families Noctuidae and Geometridae, and that more than 

3 years of sampling are needed to determine 90 percent of 

species richness (Choi and Miller 2013). Miller et al. (2003) 

studied 15 species of uncommon to rare moths (Noctuidae: 

Plusiinae) in the Cascade Range and identified three guilds 

of conifer, hardwood tree and shrub, and herbaceous-feeding species. They concluded that uncommon and rare species with special or restricted habitat requirements add to 

overall biodiversity, and that diverse environments such as 

meadows and early-successional vegetation contribute to the 

species’ diversity. 

A number of regional species identification guides 

have been recently produced on insects (Acorn and Sheldon 

2001, Haggard and Haggard 2006), lepidoptera (Miller 

and Hammond 2003), macromoths (Miller and Hammond 

2000), butterflies (Pyle 2002), bumblebees (Koch et al. 

2012), dragonflies and damselflies (Kerst and Gordon 2011), 

and others, adding to previous identification keys such as on 

arboreal spiders (Moldenke et al. 1987). 

Additional arthropods of late-successional and oldgrowth forests of the Pacific Northwest include millipedes 

and centipedes. Taxonomy, ecology, and habitat elements 

of many of these species remain poorly known. A study of 

riparian-associated millipedes in southwest Washington 

by Foster and Claeson (2011) revealed 15 species among 

10 families, and that millipede species assemblages varied 

between spring and fall and among sites. The authors urged 

further study on taxonomy and habitats and emphasized the 

importance of the ecological role of millipedes as detritivores in the forest ecosystem. 

We did not find any recent autecology studies on 

centipedes in late-successional and old-growth forests of 

the Pacific Northwest. Insights into habitat associations of 

centipedes from studies elsewhere only suggest that some 

native species may be more closely associated with interior 

forest habitat conditions, and exotic species more associated with edge and disturbed habitat conditions (Hickerson 

et al. 2005). 

A fairly recent management concern is the reduction 

in populations of pollinators on federal lands. In the Pacific 

Northwest, native bee populations are declining because 

of parasites, pathogens, pesticides, and invasive species 

(Spivak et al. 2011). Recent research has aimed at providing 

methods for restoring and conserving habitat for honeybee 

(Apis spp., nonnative species), bumblebees (Bombus spp.), 

and other pollinators (Decourtye et al. 2010, Wratten et 

al. 2012). The work highlights the economic benefit and 

ecosystem services provided by pollinating insects (Losey 

and Vaughan 2006). 

Amphibians and reptiles—

Amphibians and reptiles of forest systems—Recent studies 

on the distribution, movement, and habitat relationships 

of forest amphibians and reptiles help assess how well the 

NWFP has served to provide habitat for late-successional 

and old-growth forest-associated amphibians and reptiles. 

Old-growth forest-associated amphibians and reptiles 

are often described as secretive because most are fossorial 

and only seasonally encountered on the ground surface 

under down wood, rocks, leaves, and moss. Nonetheless, creative study approaches and modern landscape 

modeling and genetics techniques have furthered our 

understanding of the distribution, life history, and status 

of these species in the Pacific Northwest. For example, 

genetics were used to identify two new species: Scott Bar 

salamander (Plethodon asupak) and forest sharp-tailed 

snake (Contia longicaudae). The Scott Bar salamander 

is associated with cool, moist forests and talus slopes 

22 Kogut, T. Personal communication. Wildlife biologist (retired), 

P.O. Box 258, Packwood, WA 98361.
392

of an extremely restricted range in northern California; 

and, similar to other plethodontid salamanders (lungless 

salamanders of the family Plethodontidae), it is likely 

sensitive to changes in its habitat and in microclimate 

conditions (DeGross and Bury 2007, Mead et al. 2005). 

The forest sharp-tailed snake is associated with mesic 

and dense canopied forests of northern California 

and southwestern Oregon (Feldman and Hoyer 2010). 

Although little is known about this new species, the more 

wide-ranging species, C. tenuis, displays life history 

characteristics such as slow growth, late maturity, and low 

fecundity that are consistent with functional rarity and 

intrinsic vulnerability to population declines (Govindarajulu et al. 2011). 

However, in an analysis of conservation risk of wildlife, 

including amphibians and reptiles, of Washington and 

Oregon, Lehmkuhl et al. (2001) determined that although 

life history traits can be used to qualitatively determine 

potential vulnerability, alone they are not an adequate 

quantitative predictor of vulnerability without additional 

information on species’ habitat selection, habitat breadth, 

demography, and other factors. Clearly, additional survey 

and monitoring efforts and research are needed to better 

delineate species ranges and to improve our understanding 

of species’ distributions, status, habitat requirements, and 

potential vulnerability (Gibbs 1998). 

Another example of a furtive species yielding surprises 

upon study is the Shasta salamander (Hydromantes shastae) 

that, prior to 2012, was thought to be endemic to limestone 

outcroppings in the Shasta Lake watershed (Mooney 2010). 

Management decisions and land use project planning were 

based on this assumed association. Yet, Shasta salamanders 

subsequently have been found at sites lacking limestone 

outcrops and in an adjacent watershed (Lindstrand et al. 

2012, Nauman and Olson 2004).

The Survey and Manage program and the ISSSSP have 

greatly increased scientific knowledge of forest-dwelling 

salamanders and their relationships with environments in the 

Pacific Northwest. Conservation Assessments for seven terrestrial salamanders (Aneides flavipunctatus, Batrachoseps 

attenuatus, B. wrighti, Plethodon larselli, P. stormi, P. vandykei, and P. asupak) have been completed since 2005.23 The 

Density Management and Riparian Buffer Study of western 

Oregon (Anderson et al. 2007, Burton et al. 2016, Olson 

and Burton 2014) was initiated in 1994 when the NWFP 

implemented riparian buffers along non-fish- bearing streams 

(Cissel et al. 2006). This study assessed the long-term effects 

of thinning and differing riparian buffer widths on the distribution, abundance, and movement of terrestrial and aquatic 

amphibians. It showed that terrestrial salamanders are more 

abundant and more mobile in unthinned, densely canopied 

(with visible sky ranging 5 to 7 percent) (Anderson et al. 

2007) riparian buffers as compared to nearby upland thinned 

forest (with visible sky ranging 9 to 12 percent) (Anderson et 

al. 2007; Kluber et al. 2008; Olson et al. 2014a, 2014b). This 

work highlights the importance of maintaining areas of dense 

canopies within at least 50 ft (15.2 m) of perennial streams in 

managed forests to serve as habitat for terrestrial species and 

as corridors for their dispersal (Olson et al. 2014b). 

Recent studies have determined that the assumed 

dependence of terrestrial salamanders to late-successional 

and old-growth forests is more nuanced than previously 

thought (Bosakowski 1999). Some species have been found 

to be more abundant or occur more frequently in late-successional and old-growth forests (B. attenuatus, Ensatina 

eschscholtzii, Welsh and Hodgson 2013; P. elongatus, Welsh 

et al. 2008), but studies are inconsistent (e.g., P. stormi, 

Bull et al. 2006, Suzuki et al. 2008, Welsh et al. 2008). 

Relationships between plethodontid salamanders and cool, 

moist microhabitat conditions characteristic of late-successional and old-growth forests have been identified, but these 

conditions can be provided by other environmental features 

such as proximity to streams, talus slopes, and shading by 

vegetation, aspect, or topography (P. stormi, Suzuki et al. 

2008; Welsh et al. 2007; P. larselli, Crisafulli et al. 2008). For 

species associated with forest floor attributes such as amount 

of down wood, a high volume of down wood may mediate 

the otherwise adverse effects of changes to the microhabitat 

conditions after thinning (E. eschscholtzii, Welsh et al. 2015; 

E. eschscholtzii and P. vehiculum, Kluber et al. 2008, Rundio 

and Olson 2007; B. wrighti, Clayton and Olson 2009). 

23 http://www.fs.fed.us/r6/sfpnw/issssp/species-index/faunaamphibians.shtml.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Substrate type and availability are important correlates 

of some species (P. vehiculum, Kluber et al. 2008; P. 

larselli, Crisafulli et al. 2008; H. shastae, Mooney 2010; P. 

vandykei, McIntyre et al. 2006, Olson and Crisafulli 2014), 

and down logs may provide thermal refugia for salamanders 

in thinned upslope zones (Kluber et al. 2009). In areas 

deficient in preferred substrates that provide cool refugia, 

salamanders may be associated with old-growth forest and 

related microhabitat conditions (e.g., P. larselli, Crisafulli 

et al. 2008). Maintaining cool and humid refugia may be 

central in protecting populations in areas that may experience disturbances. 

Recent studies have started to unravel the complex 

trophic relationships of amphibians in forest and woodland 

food webs. Best and Welsh (2014) noted that plethodontid 

salamanders serve as predators of invertebrates, and as 

prey for carnivores. In an experiment, the authors found 

that E. eschscholtzii predation on diverse invertebrate prey 

suppressed some invertebrate taxa and released others 

resulting in increased retention of leaf litter and increased 

carbon sequestration, although such functions varied by 

the timing and amount of precipitation. We expect many 

other species of reptiles and amphibians play ecological 

roles influencing the trophic and nutrient dynamics of 

forest ecosystems to varying degrees, although quantitative 

studies are few and wanting. 

Amphibians of stream systems—

The Aquatic Conservation Strategy under the NWFP 

provides for conservation and restoration of selected stream 

and riparian systems of the Pacific Northwest (Reeves et 

al. 2006). Although most protections are for fish-bearingstreams, the importance of protecting non-fish bearing 

headwater streams and associated riparian environments 

has been increasingly recognized (Sedell and Froggatt 

1984, Wilkins and Peterson 2000). First- and second-order 

headwater channels comprise the majority of stream miles 

(kilometers) within the Pacific Northwest and serve as 

cold water refugia in a warming climate (Isaak et al. 2016). 

In addition, they serve as headwater linkages between 

watersheds that provide important dispersal corridors for 

aquatic and terrestrial species, alike (Olson and Burnett 

2009, Richardson and Neill 1998). Within stream networks, 

amphibians occur from the headwaters to the alluvial flood 

plains, and their community structure is closely tied to 

channel types and within-channel attributes (Welsh and 

Hodgson 2011). For this reason, combined with their sensitivity to environmental perturbations, stream amphibians 

have been recognized as biometrics of stream health (Welsh 

and Hodgson 2008). In a study predating the NWFP, in the 

Oregon Cascades and Coast Range, Corn and Bury (1989) 

found that four species of aquatic amphibians—coastal 

giant salamander (Dicamptodon tenebrosus), Olympic salamander (R. olympicus), coastal tailed frog (Ascaphus truei), 

and Dunn’s salamander (P. dunni)—had greater occurrence 

and abundance in streams flowing through uncut forests 

than in forests logged 14 to 40 years ago, and that tailed 

frogs and Olympic salamanders may be extirpated from 

headwaters in clearcuts. More recently, Olson et al. (2014a, 

2014b) found that streambank amphibian species, including 

Dunn’s salamander and western red-backed salamander, 

were sensitive to forest thinning within 20 to 49 ft (6 to 15 

m) of small streams including headwaters. 

Research has greatly advanced in the Pacific Northwest 

to incorporate amphibians to answer questions about the 

role of riparian buffers in the retention of aquatic ecosystem 

services. Studies have addressed how wide no-entry buffer 

zones should be to retain sensitive amphibian species 

or their critical habitat conditions and whether no-entry 

buffers are needed under differing upslope ecological 

forestry approaches. They are also asking whether or not it 

is appropriate to thin riparian zones to accelerate riparian 

restoration to achieve biodiversity goals in some cases. 

Using a meta-analysis to test the effectiveness of riparian 

buffers for conserving terrestrial fauna, Marczak et al. 

(2010) reported that riparian buffers, in general, maintain 

fewer amphibians compared to riparian forests in unharvested areas. Stream-associated amphibians such as coastal 

tailed frog and torrent salamanders are highly sensitive 

to timber harvest and the associated instream effects of 

increases in water temperature and sedimentation rates 

(Ashton et al. 2006, Bury 2008, Emel and Storfer 2015, 

Olson et al. 2007a, Pollet et al. 2010, Welsh and Hodgson 

2011). Coastal giant salamanders appear to be more resilient 

to timber harvest practices than are other stream-associated 
394

amphibians of the Pacific Northwest (Leuthold et al. 2012, 

Pollet et al. 2010). While the general findings that certain 

species are more sensitive to timber harvest than others 

holds relatively consistent in the literature, alternative 

findings in some areas (e.g., Raphael et al. 2002) highlight 

the importance of recognizing that abiotic and biotic factors 

interact with management actions in complex ways to 

influence the distribution and density of stream amphibians 

(Kroll et al. 2009).

The preponderance of evidence suggests that streams 

with riparian buffers within harvested landscapes do help 

to ameliorate some of the adverse effects of timber removal 

on instream conditions (Olson et al. 2014a, Pollet et al. 2010, 

Stoddard and Hayes 2005. In a replicated field experiment, 

Olson et al. (2014a) concluded that the NWFP Aquatic 

Conservation Strategy riparian buffers of ~230 to 476 ft 

(~70 to 145 m) seem to protect the headwater amphibian 

biota, and in a multiscaled survey, Stoddard and Hayes 

(2005) found that presence of a 150-ft (46-m)-wide riparian 

buffer predicted increased occurrence of tailed frogs and 

two species of torrent salamanders in a managed landscape. 

In the Oregon Coast Range, Kluber et al. (2008) found that 

ground surface attributes such as amount of rock or fine 

substrate determined the response of riparian and upland 

amphibian species to forest thinning along headwater 

streams, and that variable-width riparian buffer retention 

can provide for such microhabitat conditions. Olson and 

Burton (2014) examined the effects of alternative riparian 

management approaches including three no-harvest buffer 

treatments (site-potential tree-height (~230 ft [~70 m]), 

variable width with a 49-ft (15-m) minimum buffer on each 

side of the stream, and streamside retention (~20 ft [~6 m]) 

and a thin-through treatment whereby overstory tree density 

in a ~476-ft (~145-m) buffer treatment was reduced from 430 

to 600 trees per acre (hectare) to ~150 trees per acre. They 

found that densities of torrent salamanders decreased along 

streams with the narrowest buffer, ~20 ft (~6 m), and that 

densities of Dunn’s salamanders and coastal giant salamanders decreased in thin-through buffers (Olson and Burton 

2014). The authors recommend the use of a 49-ft (15-m) or 

wider buffer to retain headwater stream amphibians (Olson 

and Burton 2014).

Riparian buffers can also maintain habitat connectivity 

and headwater linkage areas for dispersing amphibians. 

Using landscape genetics, Emel and Storfer (2015) found 

that gene flow among populations of the southern torrent 

salamander (R. variegatus) becomes restricted in streams 

with low canopy cover and high heat loads. The authors 

suggest that maintaining stream corridors with continuous 

riparian buffers may increase connectivity in managed landscapes. Coastal tailed frogs disperse more readily through 

intact forests than clearcuts (Wahbe et al. 2004) and, thus, 

may benefit from headwater management for connectivity 

across ridgelines, or the creation of “headwater linkage 

areas” (Olson and Burnett 2009). Olson and Burnett (2009) 

recommend linking headwater drainages across 7th-code 

hydrologic units to maintain landscape connectivity for 

headwater species. They propose extending buffers or alternative forest management practices that maintain canopy 

structure and shading to link neighboring watersheds over 

ridgelines (Olson and Burnett 2009, Olson et al. 2007).

Amphibians of still-water systems—In the Pacific 

Northwest, still-water (lentic) environments such as lakes, 

ponds, and wet meadows, and their adjacent riparian and 

terrestrial environments, also provide for species diversity. 

Many such sites do not provide habitat for fish, however, if 

they are impermanent. Lentic breeding amphibians such as 

red-legged frogs (Rana aurora), Oregon spotted frogs (R. 

pretiosa), Columbia spotted frogs (R. luteiventris), Cascades 

frogs (R. cascadae), northwestern salamanders (Ambystoma 

gracile), western toads (Anaxyrus boreas), and Pacific 

chorus frogs (Pseudacris regilla) flourish in these environments. Yet modifications and disturbances to these species’ 

habitats (e.g., damming to increase water storage, ditching 

to increase drainage, siltation owing to timber harvest in the 

watershed, and overgrazing), combined with diseases and 

the spread of invasive species such as American bullfrogs 

(Lithobates catesbeianus) and brook trout (Salvelinus fontinalis), have resulted in some population declines (Adams 

1999, Fisher and Shaffer 1996, Pearl et al. 2007). 

The Oregon spotted frog is one of the most threatened 

amphibians in the Pacific Northwest; much information on 

this species can be found from the U.S. Fish and Wildlife 

Service Federal Register of notice of threatened status for 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

this species (USDI FWS 2014). Blouin et al. (2010) found 

that low connectivity between populations has resulted in 

decreased genetic diversity, and they recommended maintaining habitat connectivity and expanding the availability 

of appropriate wetlands. 

Whereas palustrine wetlands and the amphibians that 

depend on them are not directly protected under the NWFP, 

riparian buffers likely benefit these species. In a literature 

survey of the use of wetland buffers by reptiles and amphibians, Semlitsch and Bodie (2003) found that core habitat of 

wetlands, as used by breeding populations, ranged from 522 

to 951 ft (159 to 290 m) for amphibians and 417 to 948 ft 

(127 to 289 m) for reptiles from the edge of the aquatic site, 

and thus that adjacent terrestrial environments also were 

essential for population persistence. 

Recent and ongoing issues for amphibians: fire and timber harvest—For most of the species discussed, effects of 

large disturbances such as wildfire and broad-scale timber 

harvest on populations, have not been adequately studied, 

and monitoring programs are not in place to assess the status of species and effectiveness of the NWFP in protecting 

these species. With recent decades of fire suppression in 

the Pacific Northwest, most of the forests have experienced 

much less fire than they did historically (see chapters 2 and 

3). The effect of this change on habitats and populations of 

wildlife, including amphibians that require shaded, cool, 

moist microsites, is not known. 

For the Larch Mountain salamander (P. larselli), 

Van Dyke’s salamander (P. vandykei), California slender 

salamander (B. attenuatus), and Shasta salamander (H. 

shastae), a high proportion of known occurrences are within 

federal reserves associated with the NWFP where timber 

harvest is minimal compared to on nonreserve lands and 

thus these species are more protected, at least from timber 

harvest, under the NWFP. Species with a significant portion 

of their range on nonreserve land allocations (Siskiyou 

Mountains salamander (P. stormi) and Scott Bar salamander (P. asupak), Clayton et al. 2005, Nauman and Olson 

2008; Oregon slender salamander (B. wrighti), Clayton and 

Olson 2009; black salamander (A. flavipunctatus), Olson 

2008), however, might still be negatively affected by future 

land management activities if they deviate from the LSR 

standards, and management of these lands may be crucial 

to protect these species. Furthermore, much of the range 

of many plethodontids is on nonfederal forest land (Suzuki 

and Olson 2008). Adaptive management areas (AMAs) and 

matrix lands were expected to function as experimental 

areas to address unresolved questions and to conduct 

long-term studies on timber harvesting and fire effects on 

forest salamanders and their response to these disturbances 

(Stankey et al. 2006, Suzuki and Olson 2008). However, the 

AMA program was never fully instituted under the NWFP, 

although AMAs were designated. 

Recent and ongoing issues for amphibians: climate 

change—Climate change models for the Pacific Northwest 

region predict a warming of 0.2 to 1.1 °F (0.1 to 0.6 °C) per 

decade, with wetter autumns and winters, but drier summers 

(Mote and Salathe 2010). Significant warming is projected 

for the Pacific Northwest by the end of the 21st century, with 

simulation results projecting an increase in warming of 5.9 

to 17.5 °F (3.3 to 9.7 °C) in Washington and Oregon and 2.7 

to 8.1 °F (1.5 to 4.5 °C) in northern California, with generally increasing aridity but with higher uncertainty about 

specific precipitation levels (see chapter 2). 

Changes in the climate can affect amphibians by 

altering habitat features such as vegetation, soil, and 

hydrology directly or via interactions with other threats 

such as timber harvest, wildfire, and disease (Blaustein et al. 

2010). Plethodontid salamanders are particularly vulnerable 

to climate warming because they are specialized to cool 

microclimates, have limited dispersal capabilities, and 

may lack physiological tolerance to warm-induced stresses 

(Bernardo and Spotila 2006, Velo-Antón et al. 2013). 

Climate change may influence the distribution of suitable 

environments, which can result in fragmenting populations 

and shifting or retracting species ranges (Blaustein et al. 

2010). More precipitation during the autumn and winter 

may lengthen the period of surface activity, but warmer and 

drier summers could result in fewer available surface and 

subsurface refugia that prevent desiccation. Forest management practices that retain canopy cover, and maintain 

or supplement surface refugia such as down wood and logs 

may help to ameliorate the effects of climate change (Shoo 

et al. 2011).
396

Recent and ongoing issues for amphibians: pests and 

pathogens—Minimal research has been conducted on the 

effects of nonnative animals or plants on amphibians in 

the Pacific Northwest, and the degree to which the NWFP 

influences establishment and spread of such invasives. 

Introduced American bullfrogs (L. catesbeianus) have 

become widely established in lentic environments in the 

Pacific Northwest and are considered an important predator of native pond-breeding amphibians. Most documented 

effects are from lowland areas (<0.2 mi [<240 m]) such 

as the Willamette Valley where Pearl et al. (2004) found 

greater effects of bullfrogs on Oregon spotted frogs compared to northern red-legged frogs. Breeding bullfrog populations have been documented from the Oregon Cascades 

(Garcia et al. 2009), but environmental conditions such as 

high UV-B levels (Garcia et al. 2015) may preclude extensive colonization. 

As noted previously, the invasive Asian earthworm 

Amynthas that has invaded much of North America has 

been found to alter the behavior of eastern red-backed 

salamanders, but similar studies have not been conducted 

with salamander species found in the Pacific Northwest. 

The threat of novel diseases entering populations of 

amphibians of the Pacific Northwest appears increasingly 

pressing. The deadly amphibian disease, chytridiomycosis, 

emerged in the 1970s and has become a prominent threat 

to amphibian biodiversity worldwide (Olson et al. 2013, 

Skerratt et al. 2007). Chytridiomycosis is caused by the 

fungus Batrachochytrium dendrobatidis (Bd) and has 

been identified as causing decline or extinction of over 

200 amphibian species globally (Skerratt et al. 2007). It 

affects a broad host-range among amphibians, including 

salamanders, and has been reported in 516 (42 percent) 

of 1,240 amphibian species evaluated (Olson et al. 2013). 

Bd is widespread in the Pacific Northwest and has been 

found in northern red-legged frog, Columbia spotted frog, 

Oregon spotted frog, and Cascades frog (Pearl et al. 2007, 

2009). Although the risk posed by Bd to these species is 

mostly unclear, evidence suggests that Cascades frogs at the 

southern extent of their range in northern California have 

experienced severe declines owing to chytridiomycosis (De 

León et al. 2016, Piovia-Scott et al. 2014, Pope et al. 2014). 

More recently, in 2010, a second infectious chytrid pathogen, B. salamandrivorans (Bsal), emerged in Europe where 

it has decimated fire salamanders (Salamandra salamandra) 

(Martel et al. 2014). Unlike Bd, Bsal appears to affect only 

salamanders, not anurans (Van Rooij et al. 2015). As Bsal is 

not yet known to occur in North America, amphibian disease 

specialists are bracing for its arrival, which will probably 

occur through international pet trade routes (Grant et al. 

2016, Gray et al. 2015, Martel et al. 2014). Models of amphibian habitat suitability predict that the Pacific Northwest is 

among the highest risk areas in North America (Richgels et 

al. 2016, Yap et al. 2015). The Pacific Northwest represents a 

hotspot for salamander biodiversity and contains numerous 

species from the two most Bsal-susceptible families, Plethodontidae and Salamandridae (Martel et al. 2014). In January 

of 2016, the U.S. Fish and Wildlife Service responded to the 

threat of Bsal by enacting a temporary rule restricting the 

importation of 201 species of salamanders for the pet trade 

(USFWS 2016). Although a critical step, the risk of spread of 

Bsal to North America, home to the world’s richest salamander fauna, is still great and surveillance, research, and 

management actions are mandatory for successful mitigation 

of spread and response to this emerging infectious disease 

(Grant et al. 2016, Gray et al. 2015, Yap et al. 2015). 

Recent and ongoing issues for amphibians: connectivity—

The movement capabilities of most Pacific Northwest amphibians, especially plethodontid salamanders, are presumed to be 

limited, and fragmentation of their habitats may inhibit gene 

flow, and thus could isolate subpopulations. In forest watersheds with harvested upland areas, amphibians may disperse 

along riparian corridors that provide cooler, humid conditions 

(Olson et al. 2007a, 2014b). Stream buffers, riparian corridors, and down wood “chains” may provide connectivity for 

terrestrial species between their riparian and upland habitats, 

their adjacent stream and terrestrial habitats, and over ridges 

(Olson and Burnett 2009, 2013; Olson et al. 2014b). Providing 

linkage areas between adjacent watersheds and using various 

combinations of alternative management approaches (riparian buffers, thinning, down wood, leave islands, and uncut 

blocks) to retain forested areas along headwater ridgelines 

may facilitate upland dispersal and connectivity between subpopulations (Olson and Burnett 2009, 2013).
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

New methods for amphibians—Recently, environmental 

DNA has been applied to identifying the presence of endangered freshwater biodiversity including amphibians in lakes, 

ponds, and streams (Thomsen et al. 2012). Environmental 

DNA originates from cellular material shed by organisms 

(via skin, excrement, etc.) into aquatic environments that can 

be sampled, sequenced, and assigned back to the species of 

origin. Such methodology is important for the early detection of invasive species as well as the detection of rare and 

cryptic species. Environmental DNA approaches have been 

applied to imperiled aquatic amphibians in the Southeastern 

United States (McKee et al. 2015); an invasive salamander 

in Australia (Smart et al. 2015); and the trematode Ribeiroia 

ondatrae, a pathogenic parasite on North American amphibians (Huver et al. 2015). They have recently been applied 

to amphibians of aquatic systems in the NWFP area (e.g., 

Welsh and Cummings).24

Birds—

Bird species pertinent to the development of the LSRs and 

late-successional and old-growth forests of the NWFP are 

covered elsewhere (see chapters 4 and 5). Many other bird 

species live in or migrate through the NWPF area, contributing to the region’s biodiversity; here we address new 

science since the 10-year synthesis.

Recent studies have addressed various aspects of avian 

ecology in late-successional and old-growth forests, for 

example on pileated woodpecker (Dryocopus pileatus) 

(Aubry and Raley 2002a, Raley and Aubry 2006) and 

its role as a keystone species providing such ecosystem 

engineering functions as cavity excavation (Aubry and 

Raley 2002b). Other studies have provided information 

on forest habitat selection by white-headed woodpeckers 

(Picoides albolarvatus) (Lorenz et al. 2015), black-backed 

woodpeckers (P. arcticus) (Bonnot et al. 2009), and others. 

These studies suggest the role of disturbance (fire and forest 

pathogens) in providing habitat for these species. 

For example, white-headed woodpeckers were found 

to establish home ranges within forest patches that had 

undergone recent disturbance including small patches 

of prescribed burning and incidence of disease. Other 

studies have suggested that habitat associations of whiteheaded woodpeckers may differ by location and condition. 

Latif et al. (2015) found that the species in dry conifer 

forests on the east side of the Cascade Range in Oregon 

was closely associated with canopy openings adjacent to 

closed-canopy forests. In unburned, dry conifer forests of 

central Oregon, Hollenbeck et al. (2011) found that nest 

sites of white-headed woodpeckers were associated with 

low elevation, high density of large trees, low slope, and 

interspersion–juxtaposition of low- and high-canopy cover 

ponderosa pine patches. In postfire ponderosa pine forests 

of south-central Oregon, Wightman et al. (2010) found that 

low nest survival of white-headed woodpeckers was due to 

predation and was not correlated with habitat and abiotic 

features, and that survival in recently burned forests is 

likely enhanced with mosaic burn patterns with retention 

of larger, decayed snags. 

Fontaine et al. (2009) studied response of bird communities to single fires (2 to 3 and 17 to 18 years following 

fire), repeated high-severity fire (2 to 3 years after fires 

repeated at 15-year intervals), and stand-replacement 

fire (>100 years following fire) in mature and old-growth 

mixed-evergreen forests of the Klamath-Siskiyou region 

of southwest Oregon. They reported that bird species 

richness (number of bird species) did not differ significantly 

among the various postfire conditions; that bird density 

was lowest 2 years after fire and highest 17 to 18 years after 

fire; and that repeat-fire conditions favored shrub-nesting 

and ground-foraging species, and unburned mature forests 

favored conifer-nesting and foliage-gleaning species. In 

that ecoregion, the researchers reported that bird communities were structured mostly by conditions of broadleaf 

hardwoods and shrubs, by extended periods of early-seral 

broadleaf dominance and short-interval high-severity fires. 

Natural disturbance patterns, including fire, windthrow, and other forces, can leave remnant and legacy 

elements of older forests such as old-forest patches, 

large-diameter green trees and snags, and large-diameter 

down wood, as key habitat elements for a variety of 

species. Subsequent regrowth of the vegetation through 

secondary succession then creates early-seral structures 24 Unpublished data.
398

more complex than those resulting from final timber 

harvests such as clearcuts. The complexity of naturally 

regenerating vegetation following natural disturbances can 

often contain habitat for a wide variety of birds and other 

wildlife associated with early-successional environments 

(Marcot 1983, 1985; Swanson et al. 2011). 

Vogeler et al. (2013) adopted the use of light detection 

and ranging to evaluate forest structure conditions for 

brown creepers (Certhia americana), an old-forest associate. 

In the Eastern United States, Poulin and Villard (2011) 

determined that brown creeper nest survival was greater in 

forest interiors at least 328 ft (100 m) from the forest edge, 

and that young forest conditions—plantations from previous management—in the managed matrix can adversely 

influence productivity of the species. 

In a study of the influence of forest land ownership 

on focal species, McComb et al. (2007) projected habitat 

decreases for warbling vireo (Vireo gilvus) and increases 

for pileated woodpecker, as early-successional vegetation 

is projected to decline in area and older forests to increase. 

They also noted that land ownership patterns affected dispersion of habitat for both species, and that, for wide-ranging species, public lands provided habitat less available or 

not present on adjacent private lands. 

On southeastern Vancouver Island, British Columbia, 

Canada, just outside the NWFP area, Hartwig et al. (2003) 

noted that pileated woodpeckers selected for largest diameter trees and for patches of older forests for nest cavities in 

coastal forests of Douglas-fir and western hemlock. They 

recommend retaining large live and dead grand fir, Douglas-fir, and red alder for pileated woodpecker nest sites, and 

to provide mature climax stands with greater proportions of 

bigleaf maple and grand fir. 

On the Washington Pacific coast, Aubry and Raley 

(2002a) found that pileated woodpeckers selected Pacific 

silver fir (Abies amabilis) for nesting and western redcedar 

for roosting, and selected against western hemlock for 

both activities; that trees used for just nesting ranged from 

26 to 61 inches (65 to 154 cm) diameter at breast height 

(d.b.h.), and trees used for just roosting ranged from 61 to 

122 inches (155 to 309 cm) d.b.h.; that trees used for both 

nesting and roosting were at least 90 ft (27.5 m) tall; and 

that trees less than 49 inches (125 cm) d.b.h. or less than 

57 ft (17.5 m) tall were generally selected against. The 

authors suggested that habitat management for the species 

may need to also consider roost trees by providing snags 

and decadent live trees with heart-rot decay fungi. Raley 

and Aubry (2006) further reported that pileated woodpeckers in coastal forests foraged almost exclusively in 

closed-canopy stands, that they selected for relatively tall, 

large-diameter snags in early to moderate decay stages, 

and that they did not appear to use down logs for foraging 

because down logs did not support their primary prey of 

carpenter ants. 

Great gray owls are considered late-successional and 

old-growth forest associated within the NWFP area and 

are still a Survey and Manage species. A conservation 

assessment was developed for the species in 2012, and the 

most recent survey protocol is from 2004, as posted on the 

ISSSSP site. 

Carnivores—

This section summarizes new science associated with the 

taxa of mammalian carnivores that were either ranked as 

“not likely to remain well distributed” by the FEMAT or 

that had state or federal listing status. One species and one 

subspecies met both criteria (the fisher and the coastal population of the Pacific marten), and two species met the latter 

criterion only (the lynx [Felis lynx] and wolverine). 

Taxonomic and listing updates of carnivores—Recent 

phylogenetic studies have changed the relationships of several of the species considered here. Within the Mustelidae, 

the fisher—formerly recognized as Martes pennanti—has 

been shown to be more closely related to the wolverine and 

tayra (Eira barbara) than to martens (Martes sp.) (Koepfli 

et al. 2008, Sato et al. 2012). Consequently, the fisher is 

now recognized as being the sole extant member of its own 

genus—Pekania—and is now recognized as P. pennanti. In 

April 2016, the U.S. Fish and Wildlife Service determined 

that the West Coast Distinct Population Segment of fisher 

does not warrant federal listing status. No other federal listing pertains to the species in the NWFP area. 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Dawson and Cook (2012) evaluated phylogenetic and 

morphological evidence across the distribution of the American marten (M. americana) in North America and agreed 

with previous work (Carr and Hicks 1997) that there are 

two species of martens in North America. The American 

marten occurs east of the crest of the Rocky Mountains and 

across northern Alaska, and the Pacific marten (M. caurina) 

occurs west of the Rocky Mountains and includes the 

NWFP region. Dawson and Cook (2012) found significant 

genetic substructuring consistent with existing subspecific 

designations in the Pacific marten, and Slauson et al. (2009) 

agreed with these designations except in coastal California 

and coastal Oregon. Populations of the Pacific marten in 

coastal Oregon and coastal California appear to be a single 

evolutionary unit and have been proposed to be referred to 

collectively as the Humboldt marten (M. c. humboldtensis), 

a taxon formerly described as occurring only along the 

coast in northern California (Grinnell and Dixon 1926, 

Slauson et al. 2009). As of this writing, the U.S. Fish and 

Wildlife Service has determined that there is insufficient 

data to warrant federal listing of the Humboldt marten, but 

this decision is being appealed. The Humboldt marten is a 

state candidate species in California and is under a 1-year 

review for listing there. 

The contiguous U.S. Distinct Population Segment of 

Canada lynx is currently listed as threatened in Washington, Oregon, and beyond25

 (USFWS 2000). On August 13, 

2014, the Fish and Wildlife Service withdrew a proposal to 

list the North American wolverine in the contiguous United 

States as a threatened species under the Endangered Species 

Act; but then on April 4, 2016, the U.S. District Court for 

the District of Montana ordered U.S. Fish and Wildlife 

Service to reconsider whether to list the wolverine as a 

threatened species, and it currently sits as proposed threatened status.26 A proposed rule for listing of wolverine will 

be finalized in the future (Further, recent information on 

life history of each species is available through Web sites 

noted above).

25 http://ecos.fws.gov/ecp0/profile/speciesProfile?sId=3652. 26 http://ecos.fws.gov/ecp0/profile/speciesProfile?sId=5123.

Current distribution of carnivores—In the NWFP area, 

the fisher continues to be restricted to a single native 

population in northwestern California and southwestern 

Oregon (Lofroth et al. 2010), a single small introduced 

population in the southern Oregon Cascades from source 

populations in Canada and Minnesota (Aubry and Lewis 

2003), and recently reintroduced populations on the 

Olympic peninsula (Lewis 2014) and in the Washington 

Cascades (Lewis 2013). 

The Pacific marten appears to remain fairly well distributed in the high-elevation forests of the inland mountain 

ranges but occupies less than 5 percent of its historical 

range in the coastal forests of California and less than 10 

percent of its historical range in Oregon (Slauson et al., in 

press), and it is known from a single recent verifiable record 

from the Olympic peninsula.27

In the NWFP area, lynx are known only from high-elevation (>4,600 ft [1400 m]) spruce (Picea spp.) and lodgepole pine (Pinus contorta) forest habitats of Washington in 

the northern Cascades, and from disjunct mountain ranges 

in the counties bordering Canada. 

Verifiable wolverine occurrences in the NWFP area 

continue to be limited to high-elevation alpine and subalpine habitats in the central and northern Cascades of 

Washington (Aubry et al. 2007). However, recent detections in northeastern Oregon28 and of a single male in the 

northern Sierra Nevada (Moriarty et al. 2009) suggest that 

wolverines have the potential to occur in the Cascades of 

Oregon but have yet to be detected there. 

Habitat and feeding ecology of carnivores—We summarize here the new insights on habitat relationships of 

each species, and how these relate to each species’ key life 

history needs for feeding, resting, and reproducing. Where 

possible, we link these new insights to management actions 

that may benefit each species. Our emphasis is primarily on 

martens and fishers, which occur across a larger proportion 

of the NWFP area than do lynx and wolverine. 

27 K. Aubry, personal communication, Emeritus scientist, Pacific 

Northwest Research Station, 3625 93rd Ave., Olympia, WA 98512. 28 A. Magoun, personal communication, Wildland Research and 

Management, 3680 Non Road, Fairbanks, AK 99709.
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Fisher—In the NWFP area, fisher home ranges vary from 

2.9 to 24.5 mi2 (7.4 to 63.5 km2) for males and 0.7 to 49.5 

mi2 (1.7 to 128.3 km2) for females (Lewis 2014, Lofroth et 

al. 2010), with home ranges decreasing in size from north 

to south. Overall, home ranges tend to be composed of 

mosaics of forest stand types and seral stages, but still include high proportions of mid- to late-seral forest (Raley et 

al. 2012). Notable exceptions exist in the coastal forests in 

northwestern California, where fishers occur both in areas 

with mosaics of young regenerating forest and residual mature forest (Matthews et al. 2013), as well as in areas with 

high proportions of young regenerating forest (Thompson et 

al. 2008). Higher use of young regenerating forest in these 

areas is related to the abundance of dusky-footed woodrats 

(Neotoma fuscipes), which are an important prey species 

(Lofroth et al. 2010) and which reach peak densities in 

young even-aged stands 5 to 20 years postharvest (Hamm 

and Diller 2009). Fishers typically avoid entering open areas 

devoid of or with significantly reduced overhead cover and 

escape cover, and exhibit avoidance by positioning home 

ranges to minimize overlap with large open areas (Raley 

et al. 2012) or by moving within home ranges to avoid such 

large open areas. 

Fishers are dependent on large-diameter live and 

dead trees and downed logs with features such as cavities, 

platforms, and chambers as daily resting sites and seasonal 

den sites for females raising young (Raley et al. 2012). 

Female fishers are obligate cavity users for reproduction, 

with cavities in trees and snags providing secure environments for kits by regulating temperature extremes and 

providing protection from predators (Raley et al. 2012). 

These structures take hundreds of years to develop (Raley 

et al. 2012), emphasizing the critical importance of retaining 

these features for conservation of the species. 

Rest structures for fishers primarily include large 

deformed or deteriorating live trees and secondarily include 

snags and logs (Raley et al. 2012, Weir et al. 2012). The species of trees and logs used for resting appear less important 

than the presence of a suitable microstructure, such as a 

cavity or platform. A meta-analysis by Aubry et al. (2013) of 

resting site selection by fishers across the NWFP area and 

adjacent areas found that rest site characteristics selected by 

fishers were consistent across the Pacific States and British 

Columbia, and occurred on steeper slopes, in cooler microenvironments, with denser overhead cover, greater volumes 

of logs, and a greater prevalence of large-diameter trees 

and snags than were generally available. This meta-analysis 

provides managers with empirical support for managing for 

these conditions where maintenance or restoration of resting 

habitat conditions is an objective, even in locations where 

fishers have not been studied. Cavities used by female 

fishers for birthing and preweaning periods of kits were 

most often created by heart rot in older trees, and most often 

in the largest diameter trees available (Raley et al. 2012). 

During the postweaning period, female fishers continue to 

use tree cavities but also make use of downed logs.

Truex and Zielinski (2013) studied the influence of 

fuel treatments in forests of the Sierra Nevada, California, 

and found that mechanical treatments and fire treatments 

together, but not separately, reduced resting sites for fishers. 

Also, late-season burns adversely affected resting sites, 

but early-season burns did not. The authors suggested 

evaluating the effects of fuel treatment activities at various 

scales—fisher resting sites, home range, and landscape—to 

best balance fuel reduction with restoration and maintenance of fisher habitat. 

Marten—In the NWFP area, martens occur in two distinct 

forest regions: (1) high-elevation forests of the inland mountain ranges, such as the Cascades of California, Oregon, and 

Washington and the Marble-Salmon-Trinity Mountains of 

California, that receive significant snowfall and (2) low- to 

mid-elevation coastal forests in Oregon and California that 

receive little snowfall. In mesic west-slope forest types in 

inland mountain ranges, martens select riparian areas and 

avoid landscapes with large patches of young forest; in contrast, in xeric east-side forests in inland mountain ranges, 

martens select sites with higher tree canopy cover and avoid 

fragmented forests (Shirk et al. 2014). 

Pacific martens have recently been located in forests 

of the central and south coast regions of coastal Oregon 

(Moriarty et al. 2016a). In coastal California and Oregon, 

they occur in three environmental conditions: productive 

soil types where Douglas-fir, hemlock, and redwood forest 

associations occur; and two restricted environments on 
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low-productivity soils, including near-coast serpentine 

forest environments restricted to south coast Oregon and 

north coast California, and shore pine (Pinus contorta 

var. contorta) forest associations found in stabilized dunes 

in central coastal Oregon (Slauson et al. 2007, in press). 

Although the tree composition and vegetation structure vary 

among these three environmental conditions, they have one 

feature in common: a dense (more than 60 percent cover) 

shrub understory dominated by ericaceous species such as 

salal (Gaultheria shallon) or evergreen huckleberry (Vaccinium ovatum) (Slauson et al. 2007). In coastal forests at 

the home-range scale, martens select for large patches (more 

than 250 ac or 100 ha) of old-growth and late-mature forest 

or serpentine areas (Slauson et al. 2007). 

Complex vertical and horizontal forest structure is 

an important characteristic of marten habitat, providing 

features used to meet daily resting and seasonal denning 

needs as well as providing food and cover for prey species. 

Just outside the NWFP area in north-central California, 

Moriarty et al. (2016b) found that martens strongly selected 

complex-structured forest stands over simple stands and 

openings. Stand structure influenced martens’ movement 

patterns, being quicker and more erratic and linear in simple 

stands and openings, likely related to predator behavior; and 

more sinuous and slower in complex stands, likely related to 

foraging under cover from predators. 

In coastal California, the summer and fall diet of 

martens is dominated by sciurid and cricetid rodents 

(chipmunks [Tamias sp.], Douglas squirrels [Tamaisciurus 

douglasii], and red-backed voles [Myodes californicus]) 

and medium-sized birds. During winter, martens shift to 

larger bodied prey species such as medium-sized birds and 

northern flying squirrels (Glaucomys sabrinus) (Slauson et 

al., in press). Many of these key prey species of the Humboldt marten reach their highest densities in forest stands 

with mature and late-successional structural features (e.g., 

Carey 1991, Carey and Johnson 1995, Hayes and Cross 1987, 

Rosenberg et al. 1994, Waters and Zabel 1995) where their 

key food resources—conifer seed crops, truffles (the fruiting bodies of ectomycorrhizal fungi), and late-successional 

and old-growth-associated pendant lichens—typically reach 

their greatest abundances (Luoma et al. 2003, Smith et al. 

2002). Dense ericaceous shrub layers are also positively 

associated with key prey species including chipmunks 

(Hayes et al. 1995), northern flying squirrels (Carey 1995), 

and small mammals in general (Carey and Johnson 1995). 

Coarse woody debris also has been shown to positively 

influence foraging efficiency for martens by making prey 

more vulnerable to capture; where it has been reduced 

from timber harvest, marten foraging efficiency declines 

(Andruskiw et al. 2008). 

Like fishers, martens also depend on large decadent 

woody structures including live and dead trees and downed 

logs with features such as cavities, platforms, and chambers 

for daily use as resting sites and as seasonal den sites for 

females raising young (Raphael and Jones 1997, Slauson 

and Zielinski 2009, Thompson et al. 2012). In summer 

and fall, martens in coastal forests rest predominantly in 

large-diameter snags, downed logs, and live trees, and 

less commonly in slash piles, boulder piles, and shrub 

clumps (Slauson and Zielinski 2009). Use of the sizes of 

trees, snags, and downed logs is similar between coastal 

and inland mesic forests, but tree diameters are larger than 

reported for inland xeric forest (Raphael and Jones 1997). 

Female martens are also obligate cavity users for reproduction, with cavities in trees and snags providing secure 

environments for kits by regulating temperature extremes 

and providing protection from predators (Raphael and Jones 

1997, Slauson and Zielinski 2009, Thompson et al. 2012). 

Reproductive den structure types are more restricted than 

are rest sites (Ruggiero et al. 1998), and all natal dens have 

occurred in aerial cavities in large-diameter hardwoods, and 

maternal dens have included cavities and platforms in both 

large-diameter hardwoods and broken top live and dead 

conifers (Slauson and Zielinski 2009; Slauson, in press). 

In contrast to inland forest types, the dens found to date in 

coastal forests have been predominantly in hardwoods. 

Lynx—In northern Washington, Koehler et al. (2008) found 

that lynx exhibited the strongest selection for Engelmann 

spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) forest on moderate slopes, and to a lesser degree, 

forests with moderate canopy cover, at elevations of 5,000 

to 6,000 ft (1525 to 1829 m), and either avoided, or used 

proportional to their availability, the following cover types: 
402

lower elevation Douglas-fir, ponderosa pine forests, forest 

openings, and recently burned areas with sparse canopy 

and understory cover. Lynx in Washington spend more 

time hunting in patches of Engelmann spruce and subalpine 

fir where their predominant prey, snowshoe hare (Lepus 

americanus), occur at their highest densities (Maletzke et 

al. 2008). Lynx den sites typically occur in sheltered spaces 

most often created by downed logs, root wads of fallen trees 

and less often by boulder fields, slash piles, and live trees 

(Moen et al. 2008, Squires et al. 2008). In Montana, lynx 

den sites typically occurred in mature and mid-seral conifer 

stands with abundant woody debris, located in drainages or 

drainage-like basins (Squires et al. 2008).

Wolverine—The combination of historical records (Aubry 

et al. 2007) and contemporary studies of wolverines 

(Copeland et al. 2007, 2010) reveals that, during the denning 

and nondenning periods of the year, the species is closely 

associated with persistent spring (April to May) snow cover, 

and that this represents an obligate association with this 

bioclimatic feature. Wolverine habitat selection is strongly 

influenced by the distribution of seasonal prey resources, 

which tend to be dominated by large ungulates (e.g., moose, 

deer, elk, and caribou) (Copeland 1996, Lofroth et al. 2007) 

and large rodents (e.g., beaver, hoary marmots, and porcupine) (Lofroth et al. 2007). 

Female wolverines have been shown to be more 

sensitive than males to predation risk and human disturbance. Females make greater use of rugged terrain to avoid 

predators and avoid areas with winter ski recreation and 

higher road densities within their home ranges (Krebs et 

al. 2007). Wolverine den sites tend to occur in areas with 

persistent spring snow cover and with large boulders and 

downed trees where females find secure sites for giving 

birth to and raising kits (Dawson et al. 2010, Magoun and 

Copeland 1998). 

Landscape habitat suitability and connectivity for carnivores—Studies and habitat modeling of carnivores conducted at the landscape scale primarily address issues related to 

population processes, such as dispersal, gene flow, habitat 

connectivity, and population persistence. Regional landscape habitat models have been developed for the fisher 

in various portions of the NWFP area (Carroll et al. 1999, 

Davis et al. 2007, Halsey et al. 2015, Lewis 2013, Zielinski 

et al. 2010). Collectively, the most important predictors of 

suitable fisher habitat measured at various scales include 

areas with higher annual precipitation, moderate to dense 

tree canopy cover, higher basal area and diameter classes of 

hardwoods and conifers, and topographically complex areas 

at mid to low elevations. 

The southern portion of the NWFP area supports the 

largest extant fisher population in the Pacific Northwest. 

Modeled suitable habitat for fishers in the southern portion 

is projected to be well distributed and well connected, and 

the habitat models provide managers with a tool for planning activities and for monitoring habitat changes. 

In the coastal forests of California and Oregon, Slauson 

et al. (n.d.)29 modeled landscape habitat suitability for the 

Humboldt marten where the most important predictors, at 

various scales, were old-growth forest structure, amount of 

serpentine environment, and areas of higher precipitation, 

all positively correlated with marten detection locations 

versus nondetection locations. This model predicted that less 

than 15 percent of the historical habitat of this subspecies in 

the NWFP area is currently suitable. In the southeastern 

portion of the NWFP area, Kirk and Zielinski (2009) 

modeled landscape habitat suitability for martens in inland 

forest areas and found that marten occurrence was best 

predicted by a large amount of the biggest size classes of 

mesic forest types, by landscape configuration (more habitat 

patches), and by more habitat in public land management. 

Moriarty et al. (2015) used new methods for evaluating functional connectivity of Pacific martens across 

fragmented forest landscapes: use of food incentive experiments, and nonincentive locations of martens collected 

with global positioning system telemetry. They found 

that Pacific martens selected complex stands and crossed 

open areas in the winter when enticed by bait, and without 

bait they avoided openings and simple-structured forest 

29 Slauson, K.M.; Zielinski, W.J.; Laplante, D.; Kirk, T. [N.d.]. 

Landscape habitat suitability model for the Humboldt marten 

(Martes caurina humboldtensis). Manuscript in preparation. On 

file with: Keith Slauson, U.S. Forest Service, Pacific Southwest 

Research Station, 1700 Bayview Drive, Arcata, CA 95521. 

kslauson@fs.fed.us. 
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stands. Pacific martens also selected complex stands 

during summer and winter alike. Baiting can induce 

movements and introduce bias in habitat selection analysis 

intended to represent bait-free conditions. Dispersal 

and connectivity of Pacific martens thus seemed to be 

afforded partially by snow cover across open areas, and 

more fully by networks of complexly structured forest 

stands during summer. 

Koehler et al. (2008) developed a model of lynx habitat 

suitability from snow tracking and estimated that 1,467 

mi2 (3800 km2) of habitat suitable for lynx is present in the 

NWFP region, far less than prior estimates based on the 

correlation of historical records to vegetation types 

(McKelvey et al. 2000). Most lynx habitat identified by 

Koehler et al. (2008) occurs in western Okanogan County, 

Washington, and it was estimated that this amount of 

habitat could support a population of 87 lynx. Murray et al. 

(2008) assessed the state of lynx research and conservation 

in the species’ southern range, including the NWFP area, 

and concluded based on their review of the existing science 

that successful lynx conservation will require protection 

and management of large tracts of lynx and snowshoe hare 

habitat, and ensuring connectivity between lynx populations at the core and periphery of the species’ range. 

The global distribution of wolverines is closely associated with areas of persistent spring snow cover (Copeland 

et al. 2010). In the NWFP area, the most significant areas 

with persistent spring snow cover are high elevations of the 

north-central Washington Cascades, where most records 

of wolverines occur. Although smaller areas with these 

conditions occur in the Oregon and California Cascades, 

limited connectivity to areas known to be occupied by wolverines may impede the ability for wolverines to reoccupy 

these areas. Other than models of areas with persistent 

spring snow cover across the NWFP area (Copeland et al. 

2010), no additional habitat suitability models have been 

developed for wolverine. Similar to the lynx, ensuring 

connectivity between the largest areas of suitable habitat 

for the wolverine in the NWFP area with areas occupied 

by wolverines in British Columbia will be one of the most 

critical requirements to help ensure wolverine conservation 

in the NWFP area. 

Landscape-scale habitat connectivity is a significant 

requirement for the carnivores considered here. For lynx 

and wolverine, connectivity to population source areas 

outside the NWFP is essential for population persistence 

(Aubry et al. 2007, Murray et al. 2008, Schwartz et al. 

2009). For the fisher in the Washington Cascades (Lewis 

and Hayes 2004), and for lynx (Koehler et al. 2008), 

a current lack of connectivity likely is a main factor 

inhibiting the recolonization of suitable habitat in the 

northern portions of the NWPF area. For species that 

occupy high-elevation areas, particularly in the Cascades 

(i.e., lynx, wolverine, marten), climate change will likely 

reduce the amount and connectivity of habitat (Lawler and 

Safford 2012, McKelvey et al. 2011). In the coastal forests of 

northwestern California, the lack of connectivity of habitat 

for the Pacific marten is likely inhibiting the recolonization 

of suitable habitat patches within their dispersal capability 

(Slauson, in press). 

In general, current and future problems of habitat 

connectivity for carnivores include wide distances among 

patches of suitable habitat, low quality of intervening 

habitat, and adverse effects of natural and anthropogenic 

movement filters and barriers such as rivers and roads on 

dispersal behavior and survival (Crooks et al. 2011). Owing 

to the high cost of creating habitat corridors and enhancing 

connectivity such as by constructing wildlife crossings 

on highways, or the long time necessary for regenerating 

late-successional forests where they have been lost, connectivity enhancements that can benefit multiple species (e.g., 

Singleton et al. 2002) could be most efficient at achieving 

objectives for carnivore conservation. 

New threats to carnivores: predation—Studies in the 

NWFP area, as well as studies from adjacent areas in the 

Pacific States (Bull et al. 2001), have identified the bobcat (Lynx rufus) as a major predator of fishers (Wengert et 

al. 2014) and martens (Slauson et al., in press). Whereas 

predation is a natural mortality factor, its magnitude may 

have increased from historical times owing to the increase 

in early- to mid-seral forests in the NWFP area, which 

provide conditions suitable for predators such as bobcats 

and coyotes (Canis latrans) that have general habitat needs. 

In the NFPW area, studies of bobcat habitat use and diet in 
404

coastal forests indicate that they select for young regenerating stands (Slausonet al., in press; Wengert 2013) where 

they find key prey species such as lagomorphs, woodrats, 

and mountain beavers (Aplodontia rufa) (Knick et al. 1984; 

Slauson et al., in press). Halsey et al. (2015) modeled bobcat 

habitat to account for predation risk in evaluating reintroduction locations for fishers in the southern Washington 

Cascades, and found that reintroduction sites at middle to 

higher elevations rather than at lower elevation would likely 

reduce risk of predation by bobcats.

New threats to carnivores: rodenticides—The widespread 

use of rodenticides and other toxic chemicals found at illegal marijuana-growing operations has emerged as a major 

new threat. In California, most [dead] fishers tested for toxicant exposure tested positive for one or more anticoagulant 

rodenticides, which were ingested when the fishers consumed contaminated rodent prey. Several fishers recently 

have been confirmed to have died from acute rodenticide 

poisoning on the Hoopa Valley Indian Reservation located 

in the southern portion of the NWFP area (Gabriel et al. 

2012, 2015). Exposure rates of Humboldt martens to rodenticides is less well understood, but in California, rodenticide exposure has been confirmed in one of six (17 percent) 

[dead] martens tested (Slauson et al., in press). This threat 

may be limited to the southern portion of the NWFP area 

where cultivation of marijuana is illegal on federal land but 

common, and where most suspected use of rodenticides is 

at such illegal growing sites on public, tribal, and private 

land alike.

New threats to carnivores: wildfire and fuels treatments—

In 2007, the Fisher Conservation Strategy Biology Team held 

an expert panel workshop to conduct a threats analysis on 

fishers within the West Coast Distinct Population Segment 

and British Columbia portions of the species’ range in the 

Pacific Northwest. The team evaluated 20 types of potential 

threats and ranked four equally as the greatest threats: uncharacteristically severe wildfire, forest canopy and overstory reduction, reduction of forest structural elements, and 

forest habitat fragmentation (Marcot et al. 2012a). 

Wildfire is a natural process that can alter environments in various ways, including leaving behind remnants 

of older forest stands and large wood components that can 

serve as legacy structures as the vegetation subsequently 

regenerates. However, major loss or degradation of forests, 

especially from extensive high-intensity wildfire, can 

significantly affect habitat for the carnivores considered 

here. Effects of wildfire will be the most severe where fire 

suppression has resulted in the unnatural buildup of fuels. 

Severe wildfire occurrence is primarily in the southern 

portion of the NWFP region and at lowest elevations, 

putting the fisher at greater risk to loss of habitat than the 

other carnivores considered here. These are also the areas 

where fuels treatments such as mechanical thinning, which 

can potentially negatively affect fisher habitat, are most 

commonly prescribed. High-severity wildfire can have positive effects on some prey species, particularly herbivorous 

species such as Leporids (Lepus americanus and Sylvilagus 

bachmani) and dusky-footed woodrats (Neotoma fuscipes), 

by creating early-seral conditions that favor these populations. The degree to which high-severity wildfire can benefit 

the carnivores considered here depends on their reliance on 

these species as important components of their diets and 

the degree to which fires result in landscape patterns (e.g., 

mixed severity in the range of the fisher) compatible with 

supporting the rest of their life history needs.

The effects of fire suppression on carnivore forest 

habitat in the Pacific Northwest have received little study. 

Fire suppression activities often result in denser forests with 

more canopy layers and more dead wood from shade-tolerant trees. Whether these outcomes increase habitat quality 

or amount for forest carnivores is unstudied. 

Initial research on the effects of fuels treatments on 

fishers outside the NWFP area suggests that treatments have 

significant indirect benefits by protecting fisher habitat from 

wildfire (Scheller et al. 2011) and that some types of fuels 

treatments may be compatible with fisher occupancy as long 

as they do not exceed a particular rate and extent (Sweitzer 

et al. 2016a, Zielinski et al. 2013) and they do not affect the 

density of large structures (logs, snags, live trees) used by 

fishers for foraging, resting, and denning. 

Loss of habitat from wildfire was ranked as one of the 

top threats to the Humboldt marten in coastal California 

(Slauson et al., in press). In the last two decades, several 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

fires have burned in marten-occupied areas with unknown 

effects on the population. Fuels treatments are typically 

used to minimize the severity of wildfire in these situations, 

but to avoid reducing marten habitat, they could be carefully 

planned and monitored. Fuels treatments that reduce surface 

and ladder fuels produce stand structures that martens 

either avoid or travel through quickly (Moriarty et al. 2016), 

similar to how marten respond to open linear features such 

as ski runs (Slauson et al 2017) and seismic lines (Tigner 

et al. 2015). Therefore to minimize impacts to martens 

from fuels treatments, they could be carefully designed to 

minimize their overlap with habitats supporting important 

aspects of marten life history such as denning and have a 

spatial arrangement that most likely represents a tradeoff 

between affecting fire behavior and minimizing negative 

effects on connectivity and foraging for martens (Moriarty 

et al. 2015, 2016b). Since 1985, fires have burned more than 

386 mi2 (1000 km2) of forest habitat in Okanogan County, 

the only region in Washington where lynx has been verified 

recently; this loss of forest habitat from fire, coupled with 

the naturally fragmented distribution of suitable habitat, 

represent a present, significant threat for lynx conservation 

where they persist in the NWFP area (Koehler et al. 2008). 

The effect of wildfire and fuels treatments on wolverines has not been directly studied. 

New monitoring methods for carnivores—New developments in methods for monitoring carnivores include methods of detection, improvement of statistical survey designs, 

and advances in statistical analyses of carnivore survey data. 

Once the objectives of monitoring are identified, a suite of 

survey designs can be considered (Long and Zielinski 2008, 

O’Connell et al. 2011). Statistical advances in occupancy 

modeling (MacKenzie et al. 2006, Royle et al. 2008, Slauson 

et al. 2012) and spatially explicit capture-recapture analysis 

(Royle et al. 2014) provide two new statistical frameworks 

to conduct carnivore monitoring. Because of the importance 

of designing surveys capable of reliably detecting a species, 

detecting magnitudes of change as specified in the monitoring objective, and optimizing the costs of such designs, Ellis 

et al. (2014) developed a power-analysis tool to evaluate the 

effects of alternative design elements for monitoring wolverines that has also been evaluated for fishers (Tucker 2013). 

Monitoring population status via sampling DNA from noninvasively collected hair samples is an increasingly realistic 

goal for carnivores (Kendall and McKelvey 2008, Pauli et 

al. 2011, Schwartz and Monfort 2008). Recent advances also 

have been made in the use of camera-trap sampling of carnivores (Mcfadden-Hiller and Hiller 2015), including fishers 

(Sweitzer et al. 2016b), and mountain lions (Puma concolor) 

(Caruso et al. 2015), and carnivores elsewhere (e.g., Herrera 

et al. 2016, LaPoint et al. 2013) including arboreal situations 

(Cotsell and Vernes 2016). 

Red tree vole and Arborimus allies—

Since the 2006 synthesis (Haynes et al. 2006), much work 

has taken place on the morphology, genetics, and taxonomy 

of red tree voles and related species (Bellinger et al. 2005; 

Miller et al. 2006, 2010). Three species of Arborimus forest 

voles are now recognized to occur within the NWFP area. 

The white-footed vole (A. albipes) occurs in the Coast 

Range, Willamette Valley, and a portion of the western 

Cascades, from northwestern California north through 

Oregon to the Columbia River border with Washington. The 

red tree vole (A. longicaudus) occupies a subset of the range 

of the white-footed vole but does not extend as far into California, is absent in extreme northwest Oregon, and extends 

into the Cascades east of Portland, still constrained by the 

Columbia River to the north. The Sonoma tree vole (or 

California red tree mouse; A. pomo) is found only in coastal 

northern California, extending northward to where the red 

tree vole’s range ends. Red tree voles and Sonoma tree voles 

are arboreal, making nests and using movement runways in 

canopies of late-successional and old-growth forests; whitefooted voles, however, are only partially arboreal. 

Red tree voles and Sonoma tree voles are particularly 

ecologically interesting for their arboreal life history and 

their reliance on needles and twigs of conifers as food 

sources. Chinnici et al. (2012) documented association of 

Sonoma tree voles with unharvested and partially harvested 

old-growth Douglas-fir forest in California. Genetics analyses by Blois and Arbogast (2006) revealed that, although 

Sonoma tree voles consist of one panmictic (interbreeding) 

population, some genetic evidence suggests that southern 

Sonoma tree voles may occur as a distinct management unit 

within the species. 
406

Swingle and Forsman (2009) found that red tree voles 

occasionally moved short distances across small forest 

openings or across small logging roads less than 82 ft 

(25 m) wide. However, they saw no evidence of tree voles 

moving across large nonforest areas and thereby speculated 

that such areas are barriers to dispersal, and that long-term 

persistence of red tree voles depends on size and connectivity of forest cover and structure of the forest canopy. 

Dunk and Hawley (2009) recognized threats to red tree 

vole populations, including fire and recent historical conversion of forests to nonforest uses. They developed habitat 

association models, and their most statistically significant 

model identified the best habitat correlates as site percentage of slope, basal area of trees 18 to 35 inches (45 to 90 

cm) d.b.h., maximum tree height, and variation in diameters 

of conifers. They applied the model to the distribution of 

the species and determined that reserves have significantly 

higher quality habitat than do nonreserved lands. 

Studies by Wilson and Forsman (2013) noted that 

silvicultural thinning of young forest stands to promote lateseral forest conditions can provide habitat for a number of 

vertebrate species, but thinning can delay the development of 

a mid-story layer of trees, which is an important habitat component for red tree voles (and also of northern flying squirrels, 

Glaucomys sabrinus). The authors suggested that long-term 

forest and habitat management goals should include developing more structurally and biologically complex forests across 

the landscape at scales appropriate to the species’ ecologies. 

Other recent research on red tree voles includes determining their distribution and abundance based on occurrence 

in pellets regurgitated by a principal predator, northern 

spotted owls (Forsman et al. 2004). Working in Oregon, the 

authors found that the incidence of red tree voles in the owl 

pellets occurred most commonly in the central and south 

coastal regions, were relatively sparse in the northern Coast 

Range and Cascades areas of the state, and were absent from 

pellets on the east slope of the Cascade Mountains and most 

of the dry forest area in south central Oregon. Incidence also 

declined by elevation in the Cascades, being most common 

in owl pellets below 3,200 ft (975 m) and rare above 4,000 

ft (1220 m) elevation. The authors also speculated that red 

tree vole populations have declined in landscapes dominated 

by young forests and with increased occurrence of logging, 

fire, and human development. Their finding of low incidence 

of red tree voles in spotted owl pellets along the north coast 

area of Oregon was also supported by direct surveys there in 

Tillamook and Clatsop State Forests by Price et al. (2015) who 

found 33 tree vole nests at only 4 out of 86 randomly selected 

sites. They speculated that the dearth of nests there is because 

of logging or burning in the early 1900s and subsequent intensive forest management, and suggested that remnant old-forest 

stands on BLM and state lands serve as source populations. 

Rosenberg et al. (2016) presented models of red tree 

vole habitat, comparing and combining their best performing model with previously published models. They concluded that the ensemble combination of models provided 

the most accurate predictions of red tree vole occurrence 

and habitat suitability, and that it could be used to reduce 

survey costs and to guide management decisions and habitat 

conservation strategies for the species. 

Swingle et al. (2010) discovered that a key predator of 

red tree voles in western Oregon is weasels (Mustela spp.). 

Activity behavior and dispersal timing of red tree voles were 

studied by Forsman et al. (2009) using video cameras at nest 

sites, and additional studies of red tree vole home ranges and 

activity patterns were conducted by Swingle and Forsman 

(2009). At present, a major review has been completed 

on the distribution, habitat, and diet of red tree voles and 

Sonoma tree voles (Forsman et al. 2016), and an annotated 

bibliography has been compiled on all three Arborimus

species discussed here (Swingle and Forsman 2016).

The ISSSSP’s 2016 Red Tree Vole High Priority Site 

Management Recommendations30 provides guidance to 

field personnel for identifying land use allocations consistent with red tree vole conservation, high-priority sites outside of those allocations, and connectivity areas for linking 

sites, as well as nonpriority sites and key information gaps. 

On the International Union for Conservation of Nature 

and Natural Resources Red List, although relatively rare, 

white-footed voles are listed as of “least concern,” whereas 

red tree voles and Sonoma tree voles are both listed as “near 

30 http://www.blm.gov/or/plans/surveyandmanage/files/RTV-HPSMR-201604-final.pdf.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

threatened” because of their restriction to mature forests—

old-growth forests for the red tree vole—and from threats of 

logging and fragmentation of their forest habitats. In 2009, 

the U.S. Fish and Wildlife Service evaluated whether red 

tree voles in the North Coast Range of Oregon—sometimes 

referred to as “dusky tree voles” that seem to differ in diet 

and other aspects from other red tree voles—deserve designation as a distinct population segment under the Endangered 

Species Act. The Fish and Wildlife Service convened a panel 

of species experts and managers to evaluate the evidence 

(Marcot and Livingston 2009), and ultimately announced 

that the north Oregon Coast Range population warrants 

listing as a distinct population segment but is precluded from 

development of a proposed listing rule because of higher 

priority actions (USFWS 2011). Morphological study of the 

dusky tree vole (putatively A. longicaudus silvicola) did not 

find evidence to support the proposed, separate subspecies 

designation (Miller et al. 2010). The current listing status of 

red tree vole is Continuing Candidate; the Fish and Wildlife 

Service’s species assessment31 also provides a summary of 

recent biological and ecological information on the species. 

Bats—

At least 14 species of bats are found within the NWFP 

area. Some of these species are late-successional and 

old-growth associated, and their forest habitats are likely 

provided by NWFP reserve guidelines, although studies 

are incomplete. 

Kroll et al. (2012) reviewed the state of knowledge on 

birds and bats dependent on cavities and snags (dead standing trees) in the Pacific Northwest. They concluded that relatively little is known about how the viability of populations 

of these species is affected by distributions of snags and by 

the proximity and amount of mature and late-successional 

forests across the landscape. Rodhouse et al. (2012) provided 

models of the distributions of little brown bats (Myotis 

lucifugus) in the Northwestern United States, finding a link 

of the species with forest cover and productivity. 

Lacki et al. (2012) studied use of snags for roosting by 

long-legged myotis (M. volans) in the Pacific Northwest, 

and found that fir snags (Abies spp.) had the lowest persistence rates (highest falling rates) over the course of their 

5-year study (2001–2006), and that roost snags that persist 

standing the longest are larger in diameter, shorter in height, 

and with fewer branches. The authors recommend reserving 

sufficient, large-diameter leave-trees to provide for future 

use by roosting bats, given the persistence and fall rates of 

the snags they observed. Luszcz et al. (2016) studied three 

bat foraging guilds in southwest British Columbia, Canada, 

and reported that foraging activity of long-eared myotis 

increased with increasing forest age, and in general, Myotis

spp. feeding along edges and in forest gaps was greater in 

black cottonwood stands and in the interior of old Douglas-fir stands than in other types of forests.

On a far broader scale, Duchamp et al. (2007) suggested managing for bats at a landscape scale to accommodate their nocturnal foraging movements, alternative forest 

roost sites for some species, and reduce adverse effects of 

forest habitat fragmentation. The authors cite evidence that 

some bat species seem sensitive to local habitat fragmentation but also require mixes of conditions across broad 

geographic areas to meet all resource needs. 

Few studies are available on response of bats to fire. 

Buchalski et al. (2013) studied the response of bats to 

wildfire severity in a mixed-conifer forest in the Sierra 

Nevada of California and reported use in unburned, 

moderate-severity burn, and high-severity burn locations, 

with large-bodied bats showing no preference. They 

concluded there was no evidence that burn severity affected 

site selection and that bats in their region are resilient to 

landscape-scale fire that served to open up the stands and 

increase the availability of prey and roost structures. 

One issue of growing concern is the recent discovery 

(March 2016) of white-nose syndrome in a little brown bat 

(Lorch et al. 2016) 30 mi (48 km) east of Seattle, Washington.32 White-nose syndrome is caused by the fungus 

Pseudogymnoascus (prev. Geomyces) destructans (Verant 

et al. 2014) and is a major cause of mortality in a variety of 

bat species in the Eastern United States, having killed over 

6 million bats since 2006. So far, white-nose syndrome 

32 http://wdfw.wa.gov/conservation/health/wns/.

31 http://ecos.fws.gov/docs/candidate/assessments/2015/r1/

A0J3_V02.pdf. 
408

seems to exist mainly in species of bats that roost or 

hibernate in cave or cave-like environments; at least four 

species of bats in the Pacific Northwest are known to use 

such locations: little brown bat, big brown bat (Eptesicus 

fuscus), Townsend’s big-eared bat (Corynorhinus [Plecotus]

townsendii), and the poorly known long-eared myotis (M. 

evotis). Whether white-nose syndrome will spread geographically or among species in the Pacific Northwest, or to 

bat species using other roost situations such as large trees 

with sloughing bark and dense canopy foliage, is unknown. 

The 2001 amended standards and guidelines for NWFP 

implementation provided specific direction on bat conservation and management, including safety considerations for 

conducting bat surveys, survey protocols for bat surveys 

in buildings, environmental education on bat ecology and 

presence, and plans for building bat boxes. Other issues 

regarding bat conservation in the NWFP area include gating 

of caves and mines to prevent disturbance of bat colonies, 

bat mortality from wind energy installations (Rodhouse et 

al. 2015, Weller and Baldwin 2012), and concerns for human 

health and safety from bat colonies occupying buildings. 

The ISSSSP has developed a set of management and 

safety guidelines, and survey and monitoring protocols, for 

bat conservation in the Pacific Northwest.33 Forest Service 

Region 6 has also conducted bat surveys using a Bat Grid 

Monitoring design and protocol.34 The Bat Grid Monitoring 

study was conducted from 2003 to 2010 to provide a 

baseline of knowledge on bat distribution for future change 

detection, and produced predictive distribution maps of 11 

bat species in the Pacific Northwest. 

Recent Research and Development on 

New Tools and Data

Along with scientific studies specifically conducted on 

species, their habitats, and biodiversity of the NWFP area 

since the 2006 synthesis (Haynes et al. 2006), several 

advancements have been made in the development of new 

scientific tools, datasets, study methods, and assessments. 

33 http://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-mammals-bats.shtml. 34 http://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-mammals-bats-grid-monitoring.shtml.

Much work has focused on developing geographic 

models and map projections, particularly related to projected effects of climate change. The Nature Conservancy 

has assessed and mapped the degree of resilience of 

ecosystems through a broad area of western North America 

including portions of the Pacific Northwest and NWFP area 

(east Cascades, west Cascades, north Cascades, Klamath 

Mountains, California north coast, Pacific Northwest coast, 

Willamette Valley, and Puget Trough).35 They have also 

developed a mapping tool for assessing connectivity of 

“resilient terrestrial landscapes” in the Pacific Northwest 

(McRae et al. 2016). The U.S. Geological Survey has 

evaluated vulnerability of species and ecosystems to future 

climate in the Pacific Northwest.36 A number of other 

institutions, academic studies, and agencies also have 

addressed climate change impacts in the NWFP area. Other 

sources of information on biodiversity and species in the 

NWFP area include the Washington Biodiversity Council37

and the Oregon Biodiversity Information Center.38

Species and natural-area mapping studies and evaluations, specifically in the Klamath province, have been 

provided also by Sarr et al. (2015) and Olson et al. (2012). 

Sarr et al. compared three ecoregional classification 

systems and found that the top one (Omernik) served to 

map the distribution of tree species best, but the distribution 

of mammal species poorest. Olson et al. (2012) projected 

effects of climate change and determined that some oldgrowth forest conditions (“microrefugia”) were not captured 

in the existing reserve designs. These microrefugia conditions would lend to the reserve system being more resilient 

under climate change; they include old-growth and intact 

forests on north-facing slopes and in canyon bottoms, lower 

and middle elevations, wetter coastal mountains, and along 

elevational gradients. However, the degree to which these 

findings for the Klamath province can be applied beyond 

is unevaluated, and we anticipate that other patterns might 

35 https://www.conservationgateway.org/ConservationByGeography/NorthAmerica/UnitedStates/oregon/science/Pages/Resilient-Landscapes.aspx. 36 http://gec.cr.usgs.gov/projects/effects/vulnerability/index.html. 37 http://www.rco.wa.gov/biodiversity/about_the_council.shtml. 38 http://inr.oregonstate.edu/book/export/html/549.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

occur in more moist forest environments farther north in the 

NWFP area (see chapter 2) 

A number of tools for analyzing species’ habitat connectivity are available (e.g., Brost and Beier 2012). Zielinski 

et al. (2006) used MARXAN to analyze habitat of spotted 

owls and fisher in northern California under the NWFP, and 

concluded that spotted owls require a greater percentage 

of planning units with habitat than do fisher, and that the 

current location of the late-successional reserves may not be 

best to maintain habitat connections for the two species. The 

individual movement modeling shell HexSim (Schumaker 

2013) has been used in the NWFP area to assess habitat patch 

size and dispersion patterns for northern spotted owls (Marcot 

et al. 2013, Schumaker et al. 2014). Trumbo et al. (2013) used 

the modeling tool Circuitscape (McRae and Shah 2009) to 

evaluate landscape genetics relationships of Cope’s giant salamander (Dicamptodon copei). Using an example of American 

pika (Ochotona princeps), Schwalm et al. (2015) championed 

the use of species distribution models for evaluating effects of 

climate change and habitat conditions on landscape genetics. 

They found that wide local variation in pika response, ranging 

from complete extirpation in some areas to stable occupancy 

patterns in others, as well as habitat composition and connectivity, were important to include in the pika model. Many 

other simulation and modeling tools are available. 

Another recent advancement in mapping species 

distributions is the development of maps of probability of 

suitable habitat coupled with maps of uncertainty, such 

as the one produced by Rodhouse et al. (2012, 2015) and 

hosted by the ISSSSP, for bat species of the Pacific Northwest (see footnote 34), thereby providing managers with 

information on locations of habitat as well as confidence 

in the projections shown spatially. Other approaches to 

evaluating the effects of forest management on rare species 

can address the need for balanced sampling designs, 

such as using the application EstimateS (Colwell 2013) to 

statistically compare samples among various land condition 

categories (treatments).39

The modeling framework of MaxEnt (maximum 

entropy) has recently become popular, as used to map 

potential habitat in the Pacific Northwest for northern 

spotted owls (e.g., Carroll et al. 2010, Loehle et al.; also see 

chapter 4), white-headed woodpeckers (Latif et al. 2015), 

historical range of California condors (Gymnogyps californianus, D’Elia et al. 2015), fisher (Zielinski et al. 2012), and 

other species. Cautions in the use of the MaxEnt approach, 

however, have been offered by a number of researchers, 

such as Yackulic et al. (2013). 

Olson et al. (2007b) summarized the strategic surveys 

conducted under the NWFP guidelines. Strategic surveys 

(Molina et al. 2003) are designed to fill key information 

gaps on species distributions and ecologies, the basic 

criteria for Survey and Manage, to help answer three 

questions: (1) Does the species occur in or occur close to the 

NWFP area? (2) Is the species associated with late-successional and old-growth forest? (3) Does the reserve system 

and other standards and guidelines of the NWFP provide for 

a reasonable assurance of species persistence? Olson et al. 

(2007b) reported that all strategic surveys were conducted 

under the Survey and Manage program from 1994 to 2004 

and from 2006 to 2007 (other types of surveys are ongoing 

on a district-by-district basis). Survey results in the form of 

projects, publications, and reports on 10 taxa (fungi, lichens, 

bryophytes, vascular plants, arthropods, mollusks, amphibians, red tree voles, great gray owl, and bats) are now 

available in a regional repository of the ISSSSP40 that is 

currently managed for a list of sensitive species, some of 

which are Survey and Manage species.

Recent and Ongoing Issues Adding Challenges 

and Opportunities

We have raised a number of issues related to other species 

under the NWFP, in the above text. Here we summarize 

these and additional challenges and opportunities, regarding 

conservation of other species, that have emerged since the 

2006 synthesis (Haynes et al. 2006). 

40 http://www.fs.fed.us/r6/sfpnw/issssp/.

39 As suggested by D. Luoma. Personal communication. Assistant 

professor, Department of Forest Ecosystems & Society, Oregon State 

University, 239A Richardson Hall, Corvallis, OR 97331. 
410

Disturbance ecology and system dynamics—

Wildfire and fire suppression—In this chapter, we have 

reviewed the mostly adverse direct effects of severe wildfire on fungi, soil arthropods, forest salamanders, forest 

carnivores, and tree voles. Chapter 3 reviews historical fire 

regimes of moist and dry forests, effects of recent historical 

fire suppression on increasing fuel loads and current fire 

risk, fire suppression effects on reducing early-successional environments, use of fire for restoration, and how the 

role of fire in late-successional reserves varies across the 

NWFP area. 

Healey et al. (2008) reported that, since the initiation of 

the NWFP in 1994, loss of large-diameter forests to fire has 

exceeded loss from harvest across large areas of the region 

including federal and nonfederal lands (also see Davis et 

al. 2015). They also found that increased fire incidence 

is correlated with climate change and that retention of 

dry-site forests will hinge on coordinated, landscape-scale 

fire management (also see Halofsky et al. 2014, Podur and 

Wotton 2010, Sheehan et al. 2015). Healey et al. (2008: 1117) 

cited several sources for types of strategic fuel management 

approaches that “may have the potential to reduce the 

[future] impact of fire on the landscape...” 

Although severe wildfire in the NWFP area is an 

increasing threat to conservation of existing older forest 

species and ecosystems, it is likely that some dense 

late-successional and old-growth forests of the Western 

United States resulted or persisted from decades of fire 

suppression (Sollman et al. 2016), and others likely were 

maintained because of topographic positions protected from 

fire. Fire suppression may have contributed to the development and continuation of some old-forest conditions on the 

east side of the Cascade Range, such as on the Deschutes 

National Forest (also see chapter 3). Fuels reduction 

activities also have changed habitat for many NWFP 

species in the managed forest matrix, particularly in the 

dry forest types in the southern part of the NWFP region, 

by removing fuel loads that in turn reduces presence and 

amounts of fine litter fuels, and in some cases, large down 

wood used as den sites by fishers (Sweitzer et al. 2016a). 

Historically, frequent fires in dry forest types of the Pacific 

Northwest resulted in a diversity of vegetation ages and 

structures among multiple seral stages, and natural legacies 

of old-forest elements such as large trees and large down 

wood often remained postfire. But, acting as a double-edged 

sword, fires of various intensities and frequencies can either 

create standing and dead wood structures useful to wildlife, 

or burn them up, unless they are protected or unless fires 

are of generally low intensity. 

As fire regimes in the region shift location and increase 

in intensity (see chapter 3), there may arise difficult management and social choices between fire suppression and 

natural fire restoration. Wildfire in the Pacific Northwest 

is inevitable, and massive “megafires” have the potential 

of posing threats to old-forest species, such as reported on 

spotted owls in California by Jones et al. (2016). 

Prescribed fire, on the other hand, can be a valuable 

management tool for maintaining open old-growth forests, 

forest openings, and early-successional vegetation. Fuels 

management can help reduce risk of spread of large, 

high-severity fire. Management options include the use of 

fuelbreaks, managing for low fuel loading on the forest 

floor, thinning heavily stocked “doghair” and stagnant 

stands, pruning to eliminate fire ladders, and other methods. 

However, there is disagreement over the need to use such 

treatments, even in fire-prone systems (see chapter 3). 

Whereas fuel treatments and restoration management can 

affect fire behavior, these actions expose bare soil that, in 

turn, could promote invasion of exotic plant species that 

could spread into adjacent lands, and where nonnative plant 

cover is twice as high on fuel breaks as in adjacent wildlands (Merriam et al. 2006; also see chapter 3). 

Modeling by Ager et al. (2007) suggested that treating 

20 percent of the landscape as fuel breaks and for fuel 

reduction can result in a 44 percent increase in the probability of conserving late-successional and old-growth 

spotted owl habitat (see chapter 4). Moriarty et al. (2016) 

suggested that fuel treatments that simplify stand structure 

can adversely affect movement and habitat connectivity for 

martens. The authors noted that martens avoided openings 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

at landscape- and home-range scales, but thinned stands 

were avoided mostly at only the home range scale because 

such stands were uncommon in their study area of Lassen 

National Forest, in northeastern California, just outside the 

NWFP area. The authors also suggested that fuel treatments 

that would create landscape- or home range-scale openings 

be done at elevations lower than where martens typically 

occur. However, the effectiveness of such fuel-treatment 

approaches in providing for marten habitat likely varies 

with other considerations, in particular, habitat considerations for other species. Such treatments also may be more 

effective on south slopes and ridgetops, and less effective on 

north aspects and in drainage bottoms. 

Further, fuels treatments as mentioned above could 

have adverse effects on the many species, within late-successional and old-growth forest stands and other forest 

age and structure classes, that occupy litter and duff (the 

organic matter soil horizon) and down wood of various 

decay, size, and cover classes and tree species, as well as 

standing partially dead trees and snags. The flip side of 

this, however, is that species associated with open stands of 

late-successional and old-growth forest or from burn conditions might benefit from lower severity wildfire. As mentioned below, balancing reduction of fire risk with providing 

such microhabitat elements for species and biodiversity 

conservation can be the subject of a decision analysis and 

decision science process (see chapter 12). 

Early-seral vegetation environments—Early-successional 

vegetation conditions provide habitats for young-seral species and thus contribute to overall biodiversity of the region 

(Swanson et al. 2011, 2014). For example, in the KlamathSiskiyou province, early-successional vegetation, including grass- and shrub-dominated areas and areas of young 

trees and shrubs, helps support abundant populations of 

dusky-footed woodrats, which are a primary prey of northern spotted owls in that area. Lists of special status and 

sensitive species of Forest Service and BLM in Washington 

and Oregon include a few species associated with early-successional vegetation conditions, such as green-tailed towhee 

(Pipilo chlorurus).

However, natural early-successional vegetation conditions have been reduced throughout the Western United 

States, including the Pacific Northwest, from plantation 

forestry operations of tree planting, control of competing 

vegetation (typically broad-leaf or hardwood species), fire 

suppression, and some thinning (Bormann et al. 2015). 

The result is reduction in habitat for some species closely 

associated with complex, natural early-successional 

conditions and with landscape mosaics of early-successional 

and old-growth forests. For example, Betts et al. (2010) 

reported declines in bird species associated with early-seral 

broadleaf-dominated vegetation following stand-replacing 

disturbance, including timber harvest and fire, in the Pacific 

Northwest. However, variable-density thinning and heavy 

thins can promote subsequent growth of hardwood shrubs 

and trees and provide habitat for some species of lichens, 

invertebrates, and other organisms (Schowalter et al. 2003, 

Wilson and Puettmann 2007), but more study is needed 

on specific conditions and effects on late-successional and 

old-growth species (Wilson and Forsman 2013). In general, 

though, early-successional vegetation created naturally 

from fire, windstorm, or other natural disturbances usually 

differs substantially in structure and composition of plant 

and animal species from that created by timber harvest 

subsequently subject to tree planting and control of competing vegetation. 

Early-successional vegetation conditions created 

artificially also can become sources of plants, invertebrates, 

and other species that can compromise adjacent forest-interior conditions in late-successional and old-growth forest 

patches. We have noted that recent historical increases in 

artificially created early-successional vegetation have likely 

provided increased habitat for predators of mustelids, such 

as bobcats and coyotes. 

Depending on amounts and dispersion patterns, early-successional vegetation can serve to fragment otherwise 

extensive and connected late-successional and old-growth 

forest cover and impede movement, population connectivity, 

and population size of canopy-associated late-successional 

and old-growth species such as red tree voles, martens, 
412

fishers, northern flying squirrels, and brown creepers. 

Sollmann et al. (2016) found that forest thinning reduced 

local densities of northern flying squirrels which moved into 

adjacent unthinned stands; that there was no difference in 

effect from even thinning and variable thinning; and that 

their results underscore the need to consider effects of stand 

management in a broader landscape context, particularly 

regarding movement and dispersal (functional response) of 

the squirrels. 

Full range of conditions—The full suite of native species 

and biodiversity of the Pacific Northwest occurs only with a 

mix of the full range of environmental conditions, including all forest successional stages that support the full array 

of terrestrial vertebrates (e.g., Raphael 1988, Raphael and 

Marcot 1986) and geophysical conditions such as montane 

wet meadows that support associated invertebrates. The 

NWFP was designed to provide aquatic and late-successional and riparian forest environments; the most appropriate balance with other conditions (e.g., mixed of early- and 

late-successional stages) is beyond the scope of the NWFP’s 

original mandate and its guidelines under the 1982 planning rule, and is a matter of public policy informed by the 

best science. The 2012 planning rule increases emphasis on 

ecosystem approaches to conserving species and ecological integrity, based in part on the coarse-filter approach of 

providing structures and functions of ecosystems. Thomas 

et al. (2006) called for the NWFP to be recast as an integrative conservation strategy with federal forests managed as 

dynamic ecosystems. 

Climate change: indicators, tipping points, and 

thresholds—

Complicating management objectives to provide the 

full array of environmental conditions are the dynamic 

and potentially sudden influences of climate change on 

vegetation, fire, species distributions, and development 

of so-called novel ecosystems, that is, specific groups of 

species in assemblages and communities that have not 

previously occurred in those combinations (Collier 2015, 

Pace et al. 2015). The current locations of late-successional 

forest reserves under the NWFP may not be fully resilient 

to expected effects of climate change. We know little about 

how management of vegetation, fuels, and fire will be 

affected by changing climate and thus the future of late-successional and old-growth forests and associated species and 

biodiversity (Pfeifer-Meister et al. 2013, Wimberly and Liu 

2014), although some indications are that, under the NWFP, 

large reserves in moist forests have been relatively stable 

compared to smaller reserves, and that moist forests may be 

at less risk of disturbance from climate change than are dry 

forests (see chapter 3). 

Changes in climate, particularly increased temperatures 

and aridity, can adversely affect amphibians by altering 

regimes of local hydrology (see chapter 7 for more discussion of climate change effects on aquatic ecosystems), fire, 

and disease occurrence and transmission. More directly, 

it may cause physiological stress on species adapted to 

cool and moist microclimates. If climate change reduces 

availability and connectivity of higher elevation older 

forests, populations of associated carnivores such as lynx, 

wolverine, and marten might suffer, as summarized above 

(“Carnivores” section). In a study of 34 species of small 

mammals in montane environments in the Sierra Nevada 

Mountains and Lassen Volcanic National Park in California, 

Rowe et al. (2015) reported that 25 species shifted their 

ranges since the early 20th century in response to climate 

change, with high-elevation species contracting their lower 

range limits downslope and low-elevation species showing 

variable responses. 

Some lichens and bryophytes found in late-successional 

and old-growth forests could serve as useful indicators of 

changes in, and thresholds of, forest conditions and climate 

and air quality (Ellis 2015, Hofmeister et al. 2015, Mölder et 

al. 2015). Some late-successional and old-growth-associated 

invertebrates also can serve as indicators of biodiversity and 

climate change risk (Yi and Moldenke 2005). Halpern et 

al. (2012) suggested that disturbance has passed a threshold 

level for bryophyte conservation in Pacific Northwest 

forests, and that 15 percent retention of late-successional 

conifer forests—which the authors cited as the minimum 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

standard on federal forest lands in the Pacific Northwest41—

is inadequate to maintain the abundance or diversity of 

late-successional and old-growth species. 

Turner et al. (2015) developed models to simulate 

potential impacts of climate change and disturbances on 

vegetation in the Willamette River basin of Oregon. Their 

projections under climate-warming scenarios suggest 

that potential forest types will transition from evergreen 

needleleaf to a mix of broadleaf and needleleaf forms, with 

as much as a nine-fold increase in area burned by the end of 

the 21st century. Implications for lowland plants and animals 

suggest a shift to more warm-temperate and fire-tolerant 

species mixes. Research by Creutzburg et al. (2017) suggests a more modest change, as climate change will increase 

forest productivity and carbon storage capacity that will not 

be offset by wildfire under the legacy of management and 

fire suppression activities. 

Carroll et al. (2010) modeled the NWFP reserve 

network under climate change stressors. They concluded 

that using spotted owls as an umbrella species for reserve 

design, as under the NWFP, included habitat for other 

dispersal-limited (“localized”) species but will not include 

much of their core habitats, as defined in the Zonation 

model they used, under projections of climate change. Thus, 

the current array of fixed late-successional and old-growth 

reserves designed for the owls may not suffice for other species that may change locations as their habitats shift under 

climate change. The authors suggested that a fixed-reserve 

system should be designed for resilience under anticipated 

climate change by including additional areas, particularly 

by adding reserves in higher elevation sites (Carroll 2010). 

However, not all species will respond to climate change by 

migrating their distributions to higher elevations. Crimmins 

et al. (2011) reported anomalous downhill shifts of some 

plant species in California, following regional changes in 

climatic water balance rather than responding to changes 

in temperature. Tingley et al. (2012) projected effects of 

climate change on altitudinal distributions of birds in the 

Sierra Nevada of California, and found that species will 

likely respond differently and individually at their range 

margins to increasing temperature and increasingly variable 

precipitation. Similarly, variable responses by plants, birds, 

and other taxa in the NWFP area are likely. The lesson 

is that the response to changing climate and associated 

weather conditions will vary, sometimes greatly, among 

species, and such variability will likely occur in all taxa and 

species groups. 

Bagne et al. (2014) evaluated the efficacy of managing 

for special status species under climate change and its 

secondary effects on providing for overall biodiversity in 

the Southeastern United States. They concluded that 74 

percent of terrestrial vertebrates potentially vulnerable to 

climate change were not included in current lists of special 

status species, and omissions were greatest for birds and 

reptiles. Current lists of special status species—potentially 

including those of the ISSSSP in the Pacific Northwest 

under the NWFP—could be evaluated for potentially 

adding species that might be vulnerable to climate threats, 

particularly with regard to those environmental conditions 

that would exceed physiological thresholds, if such species 

were lacking. Such analyses have not been conducted across 

all taxa, although this chapter and others in this compendium (e.g., chapter 2) provide insights on some species that 

might be vulnerable to future climate change effects, such 

as marten, pika, and others.

Aside from climate change effects are questions of 

balancing conservation between biodiversity and individual species. For example, Arthur et al. (2004) modeled 

tradeoffs in western Oregon between maximizing overall 

species richness and providing for individual endangered 

species. They found that the tradeoff was nonlinear, 

whereby increasing endangered species protection from 

41 The reference here to 15 percent retention might more clearly 

pertain to the 1994 Standards and Guidelines (USDA and 

USDI 1994, page C-41) that state “Landscape areas where little 

late-successional forest persists should be managed to retain 

late-successional patches. This standard and guideline will be 

applied in the fifth field watersheds (20 to 200 mi2

 [52 to 518 km2]) 

in which federal forest lands are currently comprised of 15 percent 

or less late-successional forest.”
414

90 to 99 percent caused a decline in all-species protection 2 to 14 percent. Their risk tradeoff approach could 

be applied elsewhere throughout the Pacific Northwest 

and NWFP area to evaluate variations in proportion of 

landscapes in late-successional and old-growth reserves 

and managed matrix lands (Arthur et al. 2002). However, their model did not quantify species persistence 

or viability, and it did not evaluate endemic, rare, or 

specialized species considerations that could be added to 

their analysis. 

Matrix lands and habitat connections—

Many studies suggest that habitat connectivity, fragmentation, and isolation are among the most dire stressors 

on populations, and that, under environmental changes, 

movement barriers for many species are likely to shift 

over space and time (Caplat et al. 2016). Much has been 

written in the conservation biology literature on wildlife 

habitat corridors and connectivity among habitat patches 

and reserve areas (e.g., Beier and Brost 2010; Beier et al. 

2008, 2011). The literature has addressed the influence of 

conditions in matrix lands on arthropods (Shields et al. 

2008), butterflies (Ross et al. 2005), birds (Neuschulz et al. 

2013), and mammals (Kurek et al. 2014). Beier et al. (2008) 

suggested designing habitat linkages between wildlands to 

provide for multiple species rather than single focal species. 

Brady et al. (2009) used measures of disturbance, structure, 

and floristics in habitat core areas, habitat patch edges, and 

matrix landscapes to assess small mammal populations 

in northeast Australia. They found that small mammal 

conservation entails controlling disturbances and providing 

for habitat preservation and restoration within matrix lands. 

Wessell’s (2005) study of abundance and diversity of vascular plants, arthropods, amphibians, and mollusks in western 

Oregon suggested the value of managing forest matrix lands 

for habitat heterogeneity. 

Several studies in the Pacific Northwest have suggested a need to view the LSR system under the NWFP 

as a habitat network (Molina et al. 2006), and to provide 

further connectivity of forest reserves to account for 

anticipated climate-change shifts in habitat quality for 

sundry species (Beier and Brost 2010; Carroll et al. 2010; 

Rudnick et al. 2012; see also Spies et al. 2010). Proulx and 

Santos-Reis (2012) determined the value of conserving 

late-successional and old-growth forests and structures 

in the Pacific Northwest as habitat for Humboldt and 

Pacific martens. Habitat connectivity for organisms such 

as northern flying squirrels and red tree voles that depend 

on contiguous tree canopies can be severed with heavy 

thinning of forests designed to accelerate diameter growth 

of trees (Wilson and Forsman 2013). 

In general, these studies suggest also that the degree 

to which protection of species’ habitats in the matrix may 

contribute to population conservation is species-specific, 

and depends in part on the size and configuration of habitat 

in core areas, patches, and habitat linkages, and in the 

amount of habitat occurring in land already conserved (e.g., 

NWFP LSRs). 

Coarse and fine filters in conservation—

Since the last science synthesis, much has been written on 

sundry approaches to management of species, biodiversity, 

and ecosystems. These approaches include coarse- and 

fine-filter management; use of surrogate species such as 

indicators, umbrellas, keystones, and flagships; management of ecosystem services; management for the range of 

natural or historical variation; and much more. Much of 

this literature poses approaches with scant empirical testing 

and validation of their efficacy, however. In this section, 

we review recent literature on such topics as pertains to the 

Pacific Northwest.

A popular method for conservation assessment and 

management uses both coarse filters and fine filters (Hunter 

1991, Noss 1987). This approach first addresses coarse-level, 

spatially broad environmental conditions to meet general 

habitat associations assumedly of a large number of species, 

and next adds specific environmental components and locations to meet the needs of additional species not sufficiently 

provided by the coarse-filter level. Such an approach was 

used to craft the late-successional forest and the riparian and 

aquatic reserve system under the NWFP. Further, the Survey 

and Manage standards and guidelines and its annual species 

reviews were specifically designed to determine which 

late-successional and old-growth-dependent species would 

not be sufficiently provided by the coarse-level reserves and 

may need additional fine-filter management. Determinations 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

were made based on a rigorous, structured approach to 

evaluating new information (Marcot et al. 2006).

In the Pacific Northwest, Lehmkuhl et al. (2007) 

applied a coarse-filter approach to define the historical 

range of variability of the composition and pattern of 

forest conditions under historical fire regimes, and then a 

fine-filter approach to establish fuel reduction treatments at 

the landscape scale to provide conditions for the food web 

involving northern spotted owls and their prey of northern 

flying squirrels and bushy-tailed woodrats (Neotoma 

cinerea). Overton et al. (2006) used a coarse-filter regression approach with Gap Analysis Program information to 

evaluate use by band-tailed pigeons (Patagioenas fasciata) 

of abandoned mineral sites in western Oregon. In a more 

complex variant to the approach, Higgins et al. (2005) 

devised a four-tier spatial approach to identify areas critical 

to conservation of freshwater biodiversity in the Columbia 

River basin of the Pacific Northwest. 

Thompson et al. (2009) used a coarse-filter approach 

to define the historical range of variability of forests in the 

Oregon Coast Range as a target for biodiversity conservation, coupled with what they termed the social range of 

variability to account for resource and land use patterns. 

They found that land development, shifts in anthropogenic 

fire regimes, and climate change will likely impede the use 

of historical range of variability as a management objective, 

and that more complex planning is needed in a continuous 

process of negotiation. 

A coarse-filter approach to ecosystem management can 

also assume that emulating natural processes and disturbance dynamics, such as natural fire regimes, will provide 

for forest biota at natural population levels (Armstrong et al. 

2003). Other variants of the coarse-filter approach include 

identifying and protecting biodiversity “hot spots” under 

the assumption that most or all biota will be provided. 

Some applications of the “hot spot” approach focus not on 

overall species richness but on identifying concentrations 

of locally or regionally endemic species, which tend to be 

range restricted and perhaps extinction prone. “Endemism 

hot spots” could signal climate refugia, and protecting them 

could be a useful tool for avoiding extinction under climate 

change (e.g., Harrison and Noss 2017). 

The strength of the coarse- and fine-filter approach 

is that it can account for a wide array of species generally associated with an ecosystem condition such as 

late-successional or old-growth forests. The weakness of 

this approach is that it may require site surveys, habitat 

and ecological studies, and intensive assessments of 

individual species to determine which require fine-filter 

attention. Fine-filter management is typically viewed as 

management and conservation of species-specific habitats. This means that understanding species taxonomy 

is key to determining biological entities of potential 

conservation concern. In this chapter, we cite several 

instances of recent taxonomic findings describing 

newly identified species. Recent work on mitochondrial 

DNA (mtDNA) of flying squirrels now suggests that a 

geographically limited Pacific coastal form of northern 

flying squirrel ranges from southern British Columbia to 

southern California (Arbogast et al. 2017); the authors 

suggest the new species be designated Humboldt’s flying 

squirrel, using the previously suggested epithet Glaucomys oregonensis. Nearly all of the occurrence of flying 

squirrels in the NWFP area now pertains to this newly 

described species, although there seems to be overlap 

with the northern flying squirrel (G. sabrinus) in western 

Washington. Thus, two species of flying squirrels may 

occupy the NWFP area, and their individual conservation 

status has yet to be determined.

Hunter (2005) suggested use of an additional “mesofilter” level to complement the coarse-filter strategy for conservation of entire ecosystems in reserves and the fine-filter 

strategy for conservation of selected individual species. The 

mesofilter (“middle” filter) level would focus on conserving 

critical ecosystem components, specifically microhabitat 

attributes such as logs, snags, and pools used by invertebrates, fungi, nonvascular plants, and other species groups 

that are often overlooked in conservation planning. Hunter 

suggested that the mesofilter approach is particularly useful 

with seminatural conditions, for sustaining biodiversity and 

commodity production. In a sense, management for snags, 

down wood, riparian conditions, and other ecosystem components, as already part of agency activities in the NWFP 

area, constitutes a mesofilter approach. 
416

Assumptions of the coarse- and fine-filter approach, 

however, are seldom empirically tested in a controlled and 

rigorous manner, and their blind application may lead to 

inappropriate expectations for species conservation (Cushman et al. 2008, Hunter 2005). In one test in Oregon, Fagan 

and Kareiva (1997) found that hot spots of biodiversity 

(species richness) did not coincide with locations of rare and 

endangered butterflies. In another test in Oregon, Cushman 

et al. (2008) found that only 4 percent of the variation in 

bird species abundance was explained by using a general 

characterization of habitat as a proxy to bird species 

abundance and vegetation cover type as a proxy to habitat. 

Further, Molina (2008) found that 90 percent of fungal species has some fraction of their known sites occurring within 

LSRs in the NWFP area, but some 66 percent of all sites 

of Survey and Manage fungal species occurred outside the 

reserves, so that the coarse-filter level alone to identifying 

late-successional and old-growth forest reserves would not 

provide for many rare fungi. There may be some conservation salvation for these sites outside late-successional and 

old-growth forest reserves, insofar as the reserve strategy 

has changed, at least de facto, with little to no harvest 

of federal-land late-successional and old-growth forests 

outside the original NWFP LSRs (see chapter 12). 

Related to the coarse- and fine-filter approach to 

conservation is the application of species- and system-level 

approaches to biodiversity conservation. Species-level 

approaches include use of population viability analyses; surrogate species approaches with the use of umbrella species, 

focal species, guild surrogates, habitat assemblage surrogates, management indicator species, biodiversity indicator 

species, apex predators, and flagship species; multiplespecies approaches with use of entire guilds and entire habitat assemblages; and geographically based approaches with 

identifying locations of target species at risk and species hot 

spots or concentration of biodiversity (Marcot and Flather 

2007). System-level approaches include the use of range of 

natural variability, key habitat conditions, keystone species, 

ecosystem engineers, and approaches to emulate or provide 

for regimes of fire, herbivory, key ecological functions 

of species assemblages, and food webs (Marcot and Sieg 

2007). Much has been written about most of these speciesand system-level approaches (e.g., Branton and Richardson 

2014, Breckheimer et al. 2014, Hunter et al. 2016), including 

due caution in using them without clarity of definitions 

(Barua 2011) and empirical verification of their assumptions 

(e.g., Bifolchi and Lodé 2005). 

Each of these species- and system-level approaches carries strengths and weaknesses depending on management 

objectives. No one approach is fully effective in providing 

for species diversity, genetic diversity, and ecosystem 

diversity conservation objectives, which is why the 2012 

planning rule specifies use of both coarse- and fine-filter 

management. Raphael et al. (2007) and Raphael and Marcot 

(2007) suggested that a combination of approaches may be 

efficacious for meeting multiple conservation objectives. 

They suggested a series of steps to identify the suite of 

species- and system-level approaches for conservation of 

rare or little-known species and their habitats, and they 

emphasized the critical importance of setting clear goals, 

identifying measurable short- and long-term objectives, and 

including learning objectives to increase knowledge. 

Uncertainties and Research Needs

Indicators and Surrogates 

The debate over use of surrogate species in its many 

forms—indicators, sentinels, flagships, umbrellas, keystones, and others—bears closer scrutiny. The literature 

seems divided over cautioning against its use for more 

holistic ecosystem management, and using it with caution 

for more focused needs with clearly stated objectives. The 

Forest Service guidance on implementing the 2012 planning 

rule calls for the use of a surrogate-species approach to 

evaluating conditions contributing to viability of groups 

of species of conservation concern. In this approach, the 

viability of the surrogates is assumed to represent viability 

of the broader subset of species of conservation concern 

species with similar ecological requirements and similar 

responses to environmental conditions and changes. 

Surrogates are chosen also on the basis of their having more 

stringent ecological requirements than others of the group. 

Most important, surrogates are meant to represent ecological conditions that contribute to viability of the broader 

species group and are not meant to directly represent their 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

population dynamics per se; this qualification may add some 

uncertainty over the response of the fuller species groups 

(Wiens et al. 2008) but is truer to the concerns expressed in 

the literature over use of indicators of population viability. 

In many ways, the evolving planning and management 

framework under the NWFP has largely met earlier calls for 

conservation of forest biodiversity and other species. This 

includes viewing forests as dynamic ecosystems, explicitly 

providing for ecosystem processes, addressing little-known 

species, and attending to conditions in the managed forest 

matrix (Franklin 1993). Recent scientific publications have 

continued to suggest using management indicator species and 

umbrella species only with caution and empirical evaluation 

(Branton and Richardson 2010, 2014; Wiens et al. 2008), or 

not at all, because the terms are typically poorly defined and 

the concepts often untested. Simberloff (1998) argued that 

moving toward an ecological functional basis for species and 

biodiversity management, rather than using simpler proxies 

of indicator species, is more likely to succeed, particularly 

with application of ecological forestry approaches. Also, 

much recent scientific literature has moved beyond the 

contentious era of arguing whether species or systems should 

be the focus for conservation; the approaches are, as Lindenmayer et al. (2007) and Sergio et al. (2003) noted, complementary, including with the debate over conserving species 

versus ecosystem services (Hunter et al. 2014, Kline et al. 

2016; also see chapter 8). Ultimately, successfully combining 

species and system approaches depends on clearly articulating management objectives and determining the efficacy of 

management through monitoring and research. 

Climate Change 

Climate change is at the heart of many conservation 

concerns in the Pacific Northwest, but much empirical study 

remains to better understand its effects on species, their 

habitats, and their ecological functions, and to avoid the 

easy but potentially erroneous assumption that it is the proximate cause of most or all observed perils, such as with the 

decline of amphibians (Davidson et al. 2001, 2002). Climate 

change might act indirectly, such as by reducing snowfall 

(Corn 2003, Forister et al. 2010) and increasing evaporation, 

leading to loss of wetlands (Corn 2005); by increasing fire 

frequency and extent; and by improving environmental 

conditions for diseases or pathogens that in turn could affect 

other organisms, again such as with the decline of amphibians (Carey and Alexander 2003). 

Further, there may be higher order effects whereby 

climate change in turn alters biotic interactions among 

species, such as Preston et al. (2008) reported on an endangered butterfly and a threatened bird species in southern 

California, which led the authors to suggest that considering 

species interactions is important when designing reserve 

systems for conservation of sensitive species. How this can 

influence any redesign of reserves under the NWFP would 

require study.

Microbiota and ecosystem functioning—

There is a dearth of knowledge and understanding of 

Wilson’s (1987) “little things that run the world,” referring 

to the invertebrates, particularly soil microorganisms and 

mesoarthropods, along with the suite of poorly known fungi 

and allies, that collectively play crucial roles in organic matter breakdown, nutrient cycling, and maintenance of forest 

health (Berg and Laskowski 2005, Ulyshen 2016, Tolkkinen 

et al. 2015). There is also much to be learned about how 

biodiversity affects ecosystem functioning (Hooper et 

al. 2005, Marcot 2007). Here is where an interplay and 

complementarity of species-focused and ecological-process 

research and management can usefully provide for forest 

ecosystem conservation and restoration to meet early 

visions of achieving sustainable forestry for conservation of 

late-successional and old-growth forests and their biodiversity (Beebe 1991, Crow 1990). 

The future of other species is not written, but is 

progressively being tilted by fluctuating dynamics of fire 

regimes, shifts of forest composition and structure from 

changing climates, increasing stressors of invasive species, 

and changes in societal values with increasing needs for 

progressively scarce forest resources and their ecosystem 

services. Successfully addressing these and related issues 

for restoration and conservation of other species of late-successional and old-growth forests necessitates continuing on 

the path to whole-ecosystem research and adaptive management in a socioecological scope (Ban et al. 2013, Schmiedel 

et al. 2016; also see chapters 8 and 11). 
418

Conclusions and Management 

Considerations

Summary of Key Management Considerations

Here we apply our key findings to the set of guiding questions posed after the introduction of this chapter. We also 

address this additional question: If all late-successional and 

old-growth forests are now protected under the NWFP (and 

under designated critical habitat for the northern spotted 

owl), is there a need for additional fine-filter approaches, 

beyond those for the northern spotted owl and marbled 

murrelet, for species assumed to be associated with said 

forests? We will conclude the affirmative, that sufficient 

uncertainty exists, particularly with future changes in 

old-forest environments and species-specific habitats, 

particularly for species that are rare or poorly known or that 

are expected to be increasingly adversely affected by disturbances and changing climate. As to which species may need 

to be so studied and provided is at present unclear, although 

advances in identifying species of conservation concern 

under the 2012 planning rule will be a major step forward. 

Current scientific understanding of late-successional 

and old-growth-associated species rarity—

Although no specific analysis has been conducted to 

quantify the degree of rarity of late-successional and 

old-growth-associated species in the latest Survey and Manage species list, the general trends since the 2006 synthesis 

(Haynes et al. 2006) are:

1. Scientific understanding has greatly expanded on 

the occurrence, distribution, ecology, and potential 

threats of many of these species, as noted by the 

rich array of inventory reports and conservation 

planning documents conducted by the ISSSSP.

2. Numerous Survey and Manage species had been 

removed from that list, during the last rounds 

conducted on the annual species reviews, largely 

because predisturbance site surveys suggested that 

the species are more common or frequent than 

previously thought and because they no longer met 

the concern for the basic criteria for persistence of 

Survey and Manage species. 

3. The best scientific information to date on many of 

the remaining Survey and Manage species, as summarized by the ISSSSP, suggests continued rarity 

or potential vulnerability to habitat disturbance. It 

is true that some old-forest associated species are 

naturally rare and perhaps more vulnerable than 

are more abundant species, but neither the NWFP 

guidelines nor the 2012 planning rule state that naturally rare species are to be discounted. Although 

it may not be possible or feasible to increase the 

distribution or abundance of naturally rare species, 

their preservation or conservation is very much in 

the spirit of the NWFP. The specific lists of species 

currently considered under the ISSSSP are found 

on the web site cited above.

Planned provision of habitat for rare and uncommon 

species under the NWFP—

The NWFP was initially envisioned as providing habitats 

for late-successional and old-growth-associated species 

through a combination of LSRs, AMAs, aquatic and 

riparian reserves and buffers, and selected conservation 

of late-successional and old-growth forest stands in the 

managed forest matrix. At present, however, there is little to 

no harvest of late-successional and old-growth forest stands 

on BLM and Forest Service lands within the NWFP area, 

including within and outside reserves (see chapter 3). In this 

way, the current implementation of the NWFP is not the 

same as initially envisioned. 

Further, there has been no official effectiveness monitoring program under the NWFP, so there is limited information for determining the degree to which all old-forest 

associated species are being provided, and determining their 

habitat and population trends. Without a formal effectiveness monitoring or research program for other species and 

biodiversity under the NWFP, much has to be inferred from 

vegetation and late-successional and old-growth conditions 

and trends, although some research is available on selected 

species and taxa, as reviewed in this chapter. 

Rare and uncommon species populations under 

NWFP management—

The degree to which remaining late-successional and 

old-growth forest is adequately providing for persistent and 

sustainable populations of rare and uncommon species is 

known for only those few species for which demographic 

and monitoring studies have been conducted, such as 

with northern spotted owls and marbled murrelets. Lichen 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

sampling, if reinstituted in the Forest Service’s FIA program, 

could provide answers to this question on late-successional 

and old-growth-associated species. Otherwise, as under the 

2012 planning rule, assumptions need to be made on the 

efficacy of coarse-filter approaches to providing general 

ecosystem conditions and their adequacy to in turn provide 

habitat and resource conditions for individual species. To 

gain greater knowledge and understanding of the adequacy 

of these assumptions may entail further species-specific 

research and monitoring, perhaps including species previously deemed secure but now perhaps with uncertain futures 

from climate change and other disturbances unforeseen in 

the initial NWFP guidelines. 

Efficacy of habitat conservation management 

recommendations— 

There has been no effectiveness monitoring program for the 

bulk of Survey and Manage species. Various studies suggest 

some degree of success for specific species groups, such 

as headwater amphibians. For most species, however, no 

monitoring data are available. 

Sufficient information to change species 

management status— 

This would best be determined through an evaluation of 

recent scientific data, survey information, and other sources, 

through a structured species review process (e.g., the previously instituted annual species reviews under the Survey and 

Manage program). The ISSSSP has compiled and organized 

much survey and scientific information on the Survey and 

Manage species but has not been charged with conducting 

such species reviews per se. It is likely that significant 

information has been gathered on some species for making 

this determination, but at least some of the determination 

will not be made until or unless an adaptive learning and 

management procedure, along the lines of the annual species 

reviews (last conducted in 2003), is implemented again.

Species persistence under NWFP reduced latesuccessional and old-growth harvest—

No analysis has been conducted on threats to late-successional and old-growth-associated species, comparing threat 

levels perceived under the NWFP as initially envisioned 

with the NWFP as currently implemented. The NWFP as 

initially envisioned included late-successional and oldgrowth reserves, aquatic and riparian reserves and buffers, 

AMAs, and site-specific conservation of late-successional 

and old-growth forest stands. The NWFP as currently 

implemented includes little to no harvest of late-successional 

and old-growth forests on Forest Service and BLM lands 

within the NWFP area (see chapter 3); and provides for some 

management in LSRs in dry forests. Such a comparison 

between initial and current management conditions could 

recognize the greater roles and potential changes from shifts 

in local climate and especially in fire suppression, fuels 

management, and alternative ecological forestry approaches 

providing for the development of natural, complex early-seral and young-age forest vegetation conditions. 

Under this suite of considerations, it is likely that some 

species originally ranked as having low potential for persistence might be viewed as having higher potential, particularly if their late-successional and old-growth forest habitats 

and specific habitat elements are better provided throughout 

the matrix as anticipated over time. Other species tied to 

specific locations that are vulnerable to fire and disturbances might not fare as well, but no evaluation is currently 

available. It is likely that location data accumulated from 

predisturbance and strategic surveys might suggest adequate 

numbers by which to reduce concern for the persistence of 

some late-successional and old-growth-associated species, 

but predisturbance surveys alone do not provide information 

on whether the species survived the disturbance, only that 

they were present before the disturbance. 

Late-successional and old-growth species added to 

species-of-concern lists— 

Several “species lists” cover the NWFP area, including 

the lists of Survey and Manage species; Forest Service and 

BLM special status and sensitive species; U.S. Fish and 

Wildlife Service’s candidate, threatened, and endangered 

species under the Endangered Species Act; and various 

lists of species of conservation or vulnerability concern 

from International Union for Conservation of Nature Red 

Data Lists, state lists, Washington Natural Heritage Program, Oregon Biodiversity Information Center, and others. 

The Forest Service also is currently compiling a regional 

list of potential species of conservation concern that will 

also intersect with the NWFP area, its late-successional 

and old-growth forest-associated species, and many of the 

other lists noted here. There has been no evaluation of the 

composite set of species among all these lists, comparing 
420

to the list of late-successional and old-growth species 

originally ranked as high persistence or not identified as 

conservation concern under the NWFP. 

This report has summarized new threats or new 

scientific information revealed over the past decade, 

suggesting potentially growing conservation concern 

for late-successional and old-growth forest-associated 

bats, should white-nosed syndrome spread in the Pacific 

Northwest; highly locally endemic mollusks and other 

invertebrates, under threat of invasive invertebrate species 

or reduction in key habitat elements (e.g., large, old bigleaf 

maples for the Puget Oregonian snail); new species recently 

split taxonomically and that occupy a smaller portion of 

the former species’ range and that might associate with 

late-successional and old-growth forest environments that 

could be at risk from increasing wildfire (e.g., the new species of sharp-tail snake recently identified from northwest 

California and southwest Oregon); and other examples. For 

some species, a more extensive evaluation is in progress; 

for others, it awaits. 

In the past annual species reviews, no species was 

added to the initial Survey and Manage species list.42

42 New information to support adding a species to the Survey 

and Manage list (USDA and USDI 2001:15-16) must address the 

following three basic criteria including the specific factors used 

as a basis for determining concern for persistence, in addition to 

criteria for late-successional and old-growth association:

• The species must occur within the NWFP area, or occur close 

to the NWFP area and have potentially suitable habitat within 

the NWFP area. 

• The species must be closely associated with late-successional 

or old-growth forest.

• The reserve system and other standards and guidelines of the 

NWFP do not appear to provide for a reasonable assurance of 

species persistence.

The specific factors must apply to at least an identified portion of 

the species range, on federal lands, within the NWFP area. One 

or more of the following factors may indicate that persistence is a 

concern. These factors must be considered in the context of other 

standards and guidelines (other than those related to Survey and 

Manage) in the NWFP:

• Low to moderate number of likely extant known sites/records 

in all or part of species range.

• Low to moderate number of individuals.

• Low to moderate number of individuals at most sites or in most 

populations.

• Very limited to somewhat-limited range.

• Very limited to somewhat-limited habitat.

• The distribution of the species within habitat is spotty or 

unpredictable in at least part of its range.

Effects of fire on rare and uncommon late-successional 

and old-growth species—

Species and ecosystems of the NWFP experience diverse 

forest types and disturbance regimes (Bunnell 1995). 

Regarding effects of fire on rare and uncommon species 

associated with older forests, research results are limited 

and mixed. For example, for some species such as whiteheaded woodpecker, small patches of prescribed burning 

can be used to create or elevate the quality of their habitat. 

For other species, prescribed fire (particularly associated 

with sanitation and safety harvests) and associated fuels 

reduction activities can diminish key late-successional and 

old-growth habitat components such as large hollow trees, 

large snags, and large down logs, in turn reducing habitat 

for a wide variety of denning and cavity-using wildlife 

species, including fishers, Humboldt marten, and other 

mammalian carnivores (fig. 6-3). 

Effects of high-severity, stand-replacing wildfire are 

perceived as largely adverse to species that use dense, 

multilayered older forests, although much of the literature 

has not clarified levels of wildfire intensity, extent, and 

location when speculating or concluding on wildfire 

effects. Research suggests that (high-severity) fire can 

reduce beneficial mycorrhizal and other desirable fungi, 

but for the most part, the effects of wildfire on individual, 

rare and uncommon late-successional and old-growth 

species are largely unstudied. Insofar as atypically severe 

wildfire can reduce canopy closure and fragment dense, 

contiguous-canopy stands, it adversely affects habitat for 

red tree voles. 

Little has been studied on the direct effects of suppression of wildfire on wildlife in the Pacific Northwest. 

Efficacy of site buffers compared with landscape-scale 

habitat management for species persistence, dispersal, 

and habitat connectivity—

No studies have specifically compared site buffers with 

landscape-scale management of late-successional and 

old-growth forests, as influencing persistence, dispersal, and habitat connectivity of late-successional and 

old-growth-associated species. Similarly, little research has 

been done in the effectiveness of landscape-scale management in assuming a reasonable assurance of persistence 
421

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

of late-successional and old-growth-associated species. 

However, some studies have noted that small patches 

of late-successional and old-growth forests, and legacy 

elements of late-successional and old-growth forest such as 

large green trees, large snags, and large down wood, can 

provide limited habitat for old-forest-associated species in 

the forest matrix. Such patches can also be used as points 

of restoration of older forest. Studies of old-forest remnants 

and fragments suggest that, by themselves, they provide 

only a fraction of the original forest biodiversity. Although 

they may be valuable to conserve for that purpose, if they 

are the only remaining elements of late-successional and 

old-growth forests in an area, they cannot be counted on to 

provide for persistence, dispersal, and habitat connectivity 

of late-successional and old-growth-associated species.

In general, riparian stream buffers, including unthinned 

riparian vegetation and adjacent upland forests, have been 

shown to have immense conservation values, particularly 

for amphibians. Buffers of sufficient width along streams 

and wetlands can serve as movement corridors and landscape linkages for aquatic frogs, salamanders, reptiles, 

and birds (Perry et al. 2011, Vergara 2011). Streams with 

riparian buffers can provide for some birds (Nimmo et al. 

2016) and arthropods. Studies suggest that buffer widths 

differ to accommodate different species or species groups, 

as noted in summaries above. 

Figure 6-3—Naturally hollow Douglas-fir log in a lowland old-growth conifer forest, west Cascade Mountains of northern Oregon. 

Such logs are prime denning sites for fishers, Humboldt marten, and other mammalian carnivores. Some prescribed fire, timber salvage 

operations, and fuels reduction activities can reduce such habitat elements.

Bruce G. Marcot
422

The ISSSSP under the NWFP— 

The ISSSSP has provided a wealth of information to 

agency researchers and managers on late-successional and 

old-growth-associated species, such as conservation assessments, summaries of surveys, threats evaluations, range 

maps, survey protocols, and ecological studies. It should be 

remembered that the ISSSSP pertains only to Washington 

and Oregon; in California, the Forest Service and BLM each 

have their own species programs and lists. 

The current special status and sensitive species list—

Some Survey and Manage species also have sensitive 

or strategic species status, but the ISSSSP list does not 

include Survey and Manage species, which are maintained 

as separate lists based on different criteria. The current 

special status and sensitive species list includes those 

Survey and Manage species that qualify based on the 

ISSSSP criteria. The current ISSSSP list is broader in 

application covering all of Oregon and Washington with 

updates as recent as July 2015. The ISSSSP list includes a 

broad array of fungi, lichens, bryophytes, vascular plants, 

vertebrates, and invertebrates. Late-successional and 

old-growth species, or any species for that matter, with 

risks to persistence would likely have been included in 

the list update. No changes have been made to the Survey 

and Manage species list since 2003 owing to capacity and 

funding limitations to conduct an annual species review 

(the adaptive management process that removes or adds 

species or changes Survey and Manage category based on 

new information).

Additional fine-filter approaches for species assumed to be 

associated with late-successional and old-growth forest— 

Not all late-successional and old-growth forests are being 

protected, but surveys for Survey and Manage species 

are being conducted in stands over 80 years of age. Much 

remains to be learned about demography, persistence, 

viability, dispersal, and habitat connectivity of most 

late-successional and old-growth-associated species. The 

coarse-filter approach assumes that providing for general 

habitat conditions at a broad scale, such as through LSRs 

and aquatic and riparian reserves, will provide for many 

specific elements, but research informs on situations to 

be wary of taking that assumption at face value without 

additional information and tests. Additional knowledge 

is needed especially on many late-successional and 

old-growth-associated species still known as rare or 

uncommon, or that are little-known—such as most soil 

and canopy invertebrates, fungi, and many amphibians—and on highly locally endemic species such as some 

aquatic mollusks, before fine-filter (species-specific) 

conservation measures can be confidently replaced by 

coarse-filter guidelines.

Issues of Species Conservation

As a program to replace or complement the Survey and 

Manage program under the NWFP, the ISSSSP—spanning 

the Forest Service Region 6 and BLM Oregon and Washington—has produced much material since the 2006 NWFP 

science synthesis on a wide variety of little-known or rare 

late-successional and old-growth-associated species. Their 

products pertain directly to contributing information on 

conservation and management of Survey and Manage species under the NWFP and sensitive species across Oregon 

and Washington. The products include basic ecological 

information, field inventories and monitoring results, protocols for surveys, and conservation guidelines. Ongoing local 

monitoring efforts at district levels will continue to inform 

on the status of little-known and rare late-successional 

and old-growth-associated species, including if and when 

individual species should be of additional conservation 

concern or are doing well. 

The Survey and Manage program produced guidelines and approaches on natural history and management 

considerations for hidden, rare, or little-known species, 

including soil invertebrates and some lichens. Still, research 

is needed on their habitat associations, ecology, and degree 

of tolerance to disturbances of many rare and little-known, 

late-successional and old-growth-associated species of 

fungi, lichens, bryophtes, and vascular plant species. 

Beyond the biological sciences, successfully conserving, restoring, and managing for other species under the 

NWFP will take additional attention to social needs and 
423

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

interests (see chapters 8, 9, and 11). Fostering or retaining 

public support for conservation and restoration of rare 

and little-known species may require addressing social 

beliefs and values, and clarifying impacts and rationale of 

management policies, context, and actions (Stankey and 

Shindler 2006; see chapters 9, 10, and 11). Such was the 

case in the formulation of the initial NWFP guidelines, and 

such may be required again if the Plan is to be expanded to 

include other species, their habitats, or objectives beyond 

late-successional and old-growth forest, aquatic, and 

riparian environments. 

Accounting for dynamic systems and uncertainties—

Recent science findings suggest that successfully managing 

for the future of other species under the NWFP needs to 

explicitly account for disturbance dynamics (Odion and 

Sarr 2007) in forest ecosystems of the Pacific Northwest, 

principally fire and anthropogenic changes to species’ habitats in the managed forest matrix. Collectively, our findings 

suggest that such changes to forest age classes, structures, 

and dispersion patterns may have had greater impact on 

species metapopulation viability and on late-successional 

and old-growth forest resilience than initially thought by 

FEMAT, in large part because of increasing occurrence of 

high-severity fire in recent years. 

Recent science findings also have highlighted the 

need to consider how continuing climate change will 

affect such disturbance dynamics and landscape-level 

connectivity of habitats for late-successional and 

old-growth-associated species. Researchers have 

suggested developing adaptation planning for climate 

change effects, in large part for (1) flexing and migrating 

boundaries of LSRs (as originally intended by FEMAT 

(1993), (2) conserving habitat in higher elevations, and 

(3) providing for site-specific conservation of late-successional and old-growth forest conditions within the forest 

matrix to serve as connections between the reserves. The 

federal matrix lands are not treated as they were when 

the NWFP was implemented; rather, late-successional 

and old-growth forests in the matrix lands are generally 

not being harvested at the rate they had been previously 

(see chapter 3), which may contribute to conservation of 

old-forest habitat for some species, although the specific 

degree of contribution is unstudied. Also, the Aquatic 

Conservation Strategy, with its riparian buffers and 

headwater conservation approach, seems to be providing 

for nonfish aquatic species, particularly stream-associated 

amphibians and arthropods. 

There will always be uncertainty on species’ ecologies and conservation effectiveness. Several researchers 

have suggested use of decision science and risk analysis 

approaches to evaluating and managing for NWFP 

late-successional and old-growth-associated species under 

uncertainty (e.g., Kerns and Ager 2007). Such approaches 

might prove increasingly useful as we further enter into an 

era of climate change-induced disturbances, by presenting 

evaluations of potential changes and expected effects of 

alternative management actions as probabilities of outcomes 

in a risk analysis and risk management framework. Bormann (2004) suggested a new approach to managing forests 

under uncertainty, which they termed “options forestry” 

that would entail diversifying management operations for 

the purpose of learning under an adaptive management 

framework. Franklin and Johnson (2012) suggested a 

restoration strategy (“ecological forestry;” see also Franklin 

et al. 2007, Hanson et al. 2012) for federal public forests in 

Washington and Oregon that would produce ecological and 

economic benefits by reserving older forest stands, thinning 

plantations to encourage complex vegetation structures, and 

conducting variable-retention harvests in younger forests to 

provide diverse early-seral environments. 

Continuing the conservation of other species and 

biodiversity under the NWFP may benefit from use of 

decision science approaches including decision support 

models (Staus et al. 2010) and structured decisionmaking 

frameworks (Marcot et al. 2012b) that clearly articulate 

objectives; involve managers, decisionmakers, stakeholders, 

and analysts in all planning stages; and provide for monitoring and adaptive management to revisit, reaffirm, or 

revise management objectives and guidelines (Thompson 

et al. 2013), particularly under dynamics of changing social 

values, climates, and disturbance regimes (e.g., Jactel et al. 

2012). The topic is explored more fully in chapter 12.
424

Coarse-filter, fine-filter, and landscape-scale 

management—

We have discussed recent findings on the use and testing of 

the coarse- and fine-filter approach to management, which is 

still the prevailing framework under the NWFP, the Survey 

and Manage standards and guidelines, and the ISSSSP. 

The approach has been conflated with the use of a variety 

of species- and system-level approaches, including use of 

umbrella species, flagship species, management indicator 

species, focal species, surrogate species, guild indicators, 

indicator groups, and others (e.g., Lawler et al. 2003). The 

coarse- and fine-filter approach is a simple two-tier method 

of (1) providing general conditions, such as late-successional 

and old-growth forests in LSRs, and aquatic and riparian 

environments in the NWFP’s Aquatic Conservation Strategy, 

and (2) then testing the efficacy for conservation of all species and biodiversity attributes of interest, and devising and 

implementing additional management activities and requirements as needed to provide for the full suite of species’ 

habitats and biodiversity elements. What recent science has 

found is that the results—the combination of environmental 

conditions—will undoubtedly shift under climate change 

and disturbance dynamics, and thus might need to be at least 

intermittently reevaluated and readjusted. 

Further, the coarse- and fine-filter approach focuses on 

environmental conditions and species’ habitats except with 

the northern spotted owl and marbled murrelet, which include 

monitoring of population-level demographic status and 

trends. Whether the approach assures, to a degree acceptable 

to management, the long-term viability of all populations for 

the remaining 80 years of the NWFP is not known. 

Recent studies and evaluations of how well the NWFP 

provides for other species and biodiversity also suggest 

that the role and efficacy of late-successional (and aquatic 

and riparian) reserves needs to be put into the broader 

context of the managed forest matrix and other systems 

of the Pacific Northwest found mainly on federal public 

lands, specifically subalpine forests, rock and ice substrates, 

headwaters, complex early-successional vegetation, and 

unharvested postfire conditions. However, maintaining 

late-successional and old-growth forest ecosystems and 

their biota may not be fully achievable only with old-forest 

reserves, and only on federal forest lands, given effects of 

forest fragmentation and fire suppression and dynamics 

(e.g., Perault and Lomolino 2000, Sheehan et al. 2015). For 

these and other reasons, McAlpine et al. (2007) concluded 

that conservation of regional biodiversity under broad 

forest plans including the NWFP are better achieved with 

sustainable forest management practices implemented on—

or at least coordinated across—all ownerships and by all 

stakeholders, not just for focused forest reserves. Social and 

economic considerations for any such forest management 

are discussed in chapters 8 and 12. 

Other considerations—

Several other considerations may be pertinent and useful for 

managing for biodiversity and other species other than the 

northern spotted owl, marbled murrelet, and salmonids 

under the NWFP. One idea from recent science findings is 

the value of providing older-forest substrates and elements 

outside of LSRs that can contribute to species’ habitats and 

habitat connections in the managed forest matrix (e.g., 

Dunk and Hawley 2009). An example pertains to dead 

wood. Approximately two-thirds of Survey and Manage 

species under the NWFP are associated in some way with, 

and benefit from mitigation for, partially dead trees, snags, 

and down wood (coarse woody debris). The Forest Service 

Decayed Wood Advisor (DecAID)43 provides substantial 

information on wildlife use of snags, partially dead trees, 

and down wood, along with guidance on management of 

such elements at stand and landscape scales (Mellen et al. 

2002). 

Further, there may be an opportunity to bolster 

research, conservation, and restoration guidelines for 

providing such conditions within the managed forest matrix 

and across land ownerships. The objective would be to help 

connect LSRs, particularly now that late-successional and 

old-growth forests in the federal land matrix are currently 

being harvested at much less the rate they once were. In the 

past, thinning of plantations and young stands served to 

reduce dead wood, especially large down wood. Dead wood 

provides for a surprisingly vast array of life and its essential 

43 http://www.fs.fed.us/r6/nr/wildlife/decaid/; currently undergoing 

a major version update.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

ecological processes (Brazee et al. 2014, Seibold et al. 2015). 

Providing more naturally regenerating, structurally and 

floristically complex early-successional stands, with the aim 

of encouraging development of dead wood and large down 

wood, may be part of restoration actions. 

Protection of old-forest “legacies” such as large old 

green trees and snags and large-diameter down logs in the 

managed forest matrix has long been touted as a means of 

conserving biodiversity in Pacific Northwest old-growth 

forests following disturbances (Johnstone et al. 2016, North 

and Franklin 1990). Remnant, shade-tolerant old-growth 

trees (Thuja spp.) have been found to provide biological 

legacies and seed sources in postfire conditions in Pacific 

Northwest conifer forests (Keeton and Franklin 2005). 

However, retention of old-forest legacies may not fully 

substitute for retention of old-growth forest stands per se. 

For example, Price and Hochachka (2001) reported that 

epiphytic and alectoroid lichens were less abundant in 

mature (70- to 120-year-old) stands with structural retention 

of old-forest legacies, than in old-growth (at least 300-yearold) stands. The point here is that old-forest legacies 

retained in early-successional forests can complement but 

not fully supplant old-growth forests in providing habitat for 

old-forest species. 

There may be considerations for tradeoffs among 

the kinds of species that can be provided under different 

silvicultural activities such as different intensities of forest 

thinning. For example, in the Pacific Northwest, Pollock and 

Beechie (2014) found that different sets of wildlife species 

associated with large-diameter live trees benefited more 

from heavy thinning in riparian areas than species associated with large-diameter deadwood benefited from light or 

no thinning. The authors suggested that because far more 

vertebrate species use large deadwood than large-diameter 

live trees, riparian areas may best be left to develop naturally 

in the absence of thinning for the benefit of terrestrial and 

aquatic species. Consideration for such tradeoffs of management objectives is discussed more fully in chapter 12.

Another consideration pertains to maintaining the full 

suite of ecological functions provided by late-successional 

and old-growth-associated species. This helps provide for 

“fully-functional” ecosystems, including full food webs and 

ecosystem processes of all successional stages (Marcot 2002, 

Marcot and Sieg 2007, Marcot and Vander Heyden 2001). 

Finally, there may be efficiencies and advantages to 

continue coordination of NWFP implementation and any 

amendments or updates, with other programs including 

climate science centers, disturbance research programs, and 

other protected area network programs. 

Main Findings

Much has been learned since the 2006 synthesis (Haynes et 

al. 2006) about a wide variety of species and their occurrence, distribution, and rarity, and some on their ecology, 

reaffirming the role of LSRs and conservation of aquatic 

systems and riparian buffers in providing habitat for such 

species. Greater clarity also has been developed on the role 

of retaining old-forest components and substrates in the 

managed forest matrix to serve as connections among the 

reserves. Providing such connections is possible through 

the slowing of harvests of late-successional and old-growth 

forests in the federal matrix lands, the current critical 

habitat designation for northern spotted owls to protect all 

remaining owl habitat, and retention of old-forest structures 

in the forest matrix. Based on research on early-successional vegetation and associated biotic communities, how 

young stands in the forest matrix are managed will have a 

significant bearing on the future of older forest ecosystems 

throughout the NWFP area. 

Recent work has also called for a far more dynamic 

approach to account for shifting movement barriers, 

fire disturbance to reserves and late-successional and 

old-growth forest stands, and other anthropogenic and 

climate-mediated changes in reserves and matrix lands 

alike. Habitats and population connections of other species 

of late-successional and old-growth forests are likely more 

vulnerable to the static placement of existing LSRs than 

previously envisioned. According to the research summarized in this chapter, a dynamic approach addressing the 

long-term scheduling of forest management activities and 

additions of reserves to further connect existing reserves 

and supplement them in higher elevations could better 

account for the influence of changing fire regimes, climate, 

and use of natural resources. 
426

The Survey and Manage program, and more recently 

the ISSSSP, have provided much information on various rare 

and uncommon species associated with late-successional 

and old-growth environments. Their conservation evaluations provide evidence that the NWFP is generally providing habitat for late-successional and old-growth-associated 

species either under the late-successional, aquatic, and 

riparian buffer reserve system (coarse-filter management), or 

additionally through species-specific inventories, monitoring, and site protection (fine-filter management). Additional 

federal listing of late-successional and old-growth species 

as threatened or endangered, beyond northern spotted owl, 

marbled murrelet, and salmonids, has generally not proved 

necessary. Still, there may remain concerns for some species 

groups such as some late-successional and old-growth-associated bryophytes (Halpern et al. 2012) and other species 

groups because of the legacy of past forest harvesting 

patterns coupled with climate-change stressors (e.g., see 

section above on “Bryophytes”), but species-specific 

information is generally scant. For most of the other, rarer 

species addressed in this chapter, little to no information 

is available on population size and trend, especially their 

demographics across the managed forest matrix outside of 

reserves, although information is available on the general 

distribution or occurrence of some such species. 

The Survey and Manage program, with its annual 

species reviews, provided the basis for reducing or removing concern for conservation of many uncommon to rare 

late-successional and old-growth-associated species that 

were originally ranked as having low potential for persistence. The lowering of conservation concern was due not 

so much to lower levels of harvest of older forests, but more 

to efforts locating such species during “pre-disturbance 

surveys” before local harvests and other management activities proceeded. 

Since the 2006 synthesis (Haynes et al. 2006), no 

species have been added to the Survey and Manage species 

list; any additions would occur through a renewed annual 

species review process, and none was added during the 

reviews in 2001, 2002, and 2003. Those reviews resulted 

only in removing species from the list on the basis of new 

findings (viz., no concern for persistence, or the species 

not being late-successional and old-growth associated) or 

changing their conservation and monitoring categories 

based on new information. 

Other than the research summarized in this chapter, 

little effectiveness monitoring has been conducted on site 

buffers to confirm that they are indeed providing for species 

persistence at those sites. Limited research on riparian 

stream buffers suggest high value for protected associated 

species’ habitats. 

Acknowledgments

We thank Rob Huff and Carol Hughes of the USDA Forest 

Service and USDI Bureau of Land Management’s ISSSSP 

for information on the program’s direction and content. We 

thank Daniel Luoma, Bruce McCune, and Tom Spies for 

helpful reviews of the manuscript. We also thank Jimmy 

Swingle and Eric Forsman for providing much information 

on tree voles. Dede Olson provided helpful comments on 

the reptiles and amphibians section. Diane Ikeda and Greg 

Schroer of Forest Service Region 5, Kim Mellen-McLean 

of Forest Service Region 6, and Carol Hughes provided 

very helpful management reviews. Anne Boeder provided 

information on the current status of resource management 

plans for BLM, and Mark Skinner provided information on 

regulations of harvests of special forest products. Coauthors 

K. Pope, H. Welsh, and C. Wheeler provided text on reptiles 

and amphibians; coauthor M. Reilly provided text on 

vascular plants; and coauthors K. Slauson and W. Zielinski 

provided text on mammalian carnivores. 
427

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Metric Equivalents

When you know: Multiply by: To find:

Inches 2.54 Centimeters 

Feet (ft) .305 Meters 

Miles (mi) 1.609 Kilometers 

Acres (ac) .405 Hectares 

Square miles (mi2

) 2.59 Square feet 

Pounds (lbs) .454 Kilograms

Degrees Fahrenheit (°F) .56(°F – 32) Degrees Celsius

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Zielinski, W.J.; Dunk, J.R.; Yaeger, J.S.; Laplante, 

D.W. 2010. Developing and testing a landscape-scale 

habitat suitability model for fisher (Martes pennanti) in 

forests of interior northern California. Forest Ecology 

and Management. 260(9): 1579–1591. doi:10.1016/j.

foreco.2010.08.006.

Zielinski, W.J.; Thompson, C.M.; Purcell, K.L.; 

Garner, J.D. 2013. An assessment of fisher (Pekania 

pennanti) tolerance to forest management intensity on 

the landscape. Forest Ecology and Management. 310: 

821–826. doi:10.1016/j.foreco.2013.09.028.

Ziemba, J.L.; Cameron, A.C.; Peterson, K.; Hickerson, 

C.A.M.; Anthony, C.D. 2015. Invasive Asian 

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93(10): 805–811.
460

Molalla River, Oregon.

Photo by Jeff Clark, USDI Bureau of Land Management, Oregon-Washington State Office.
461

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Chapter 7: The Aquatic Conservation Strategy of the 

Northwest Forest Plan—A Review of the Relevant 

Science After 23 Years

Gordon H. Reeves, Deanna H. Olson, Steven M. Wondzell, 

Peter A. Bisson, Sean Gordon, Stephanie A. Miller, 

Jonathan W. Long, and Michael J. Furniss1

Introduction

The Aquatic Conservation Strategy (ACS) is a regional 

strategy applied to aquatic and riparian ecosystems across 

the area covered by the Northwest Forest Plan (NWFP, 

or Plan), encompassing broad landscapes of public lands 

administered by the U.S. Department of Agriculture Forest 

Service and the U.S. Department of the Interior Bureau of 

Land Management (BLM) (USDA and USDI 1994a). The 

ACS was developed during the analysis (FEMAT 1993) that 

led to the NWFP, but its foundation was a refinement of 

earlier strategies: the Scientific Panel on Late-Successional 

Forest Ecosystems (“The Gang of Four”) (Johnson et al. 

1991), PacFish (USDA and USDI 1994b), and the Scientific 

Analysis Team (Thomas et al. 1993). 

The ACS uses an ecosystem approach to management of 

riparian and aquatic habitats (Everest and Reeves 2007) and 

was designed to (1) protect watersheds that had good-quality 

habitat and strong fish populations at the time the Plan was 

drafted, and (2) halt further declines in watershed condition 

and restore ecological processes that create and maintain 

favorable conditions in aquatic ecosystems in degraded ecosystems (FEMAT 1993). The long-term goal (100+ years) is 

to develop a network of functioning watersheds that supports 

populations of fish and other aquatic and riparian-dependent 

organisms across the NWFP area (USDA and USDI 1994a). 

The ACS is based on preserving and restoring key ecological 

processes, including the natural disturbance regimes (USDA 

and USDI 1994a) that create and maintain habitat for native 

aquatic and riparian-dependent organisms, and it recognizes 

that periodic natural disturbances may be required to sustain 

ecological productivity. As a result, the ACS does not expect 

that all watersheds will be in favorable condition (highly 

productive for the same aquatic organisms) at any point in 

time, nor does it expect that any particular watershed will 

remain in a certain condition through time. If the ACS and 

the NWFP are effective, the proportion of watersheds in 

better condition (for native organisms) is expected to remain 

the same or increase over time (Reeves et al. 2004). 

The primary objective of the ACS is to maintain 

and restore the distribution, diversity, and complexity of 

watershed-level features and processes to which aquatic and 

riparian species are uniquely adapted. Programs and actions 

under the ACS are to maintain, not prevent, attainment of 

this goal. The ACS designates watershed analysis as the tool 

for developing baseline conditions against which to assess 

maintenance and restoration conditions, and improvements 

in biological and physical processes are to be evaluated 

relative to the natural range of variability (USDA and USDI 

1994a). ACS objectives address (1) diversity and complexity 

of watershed features; (2) spatial and temporal connectivity 

within and between watersheds; (3) physical integrity; (4) 

water quality; (5) sediment input, storage, and transport; (6) 

instream flows (e.g., both peak and low flows); (7) floodplain 

inundation; (8) riparian plant-species composition and 

structural diversity; and (9) habitat to support well-distributed populations of native, aquatic and riparian-dependent 

species of plants, invertebrates, and vertebrates.

The ACS sets out five components to meet its goals: 

• Riparian reserves: Riparian reserves are specifically designated portions of the watershed most 

tightly coupled with streams and rivers that provide 

1 Gordon H. Reeves is a research fish ecologist, Deanna H. 

Olson is a research aquatic ecologist, and Steven M. Wondzell 

is a research geologist, U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station, 3200 SW Jefferson 

Way, Corvallis, OR 97331; Jonathan W. Long is a research 

ecologist, U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station, 1731 Research Park, Davis, CA 

95618; Peter A. Bisson is a research fish ecologist (retired), U.S. 

Department of Agriculture, Forest Service, Pacific Northwest 

Research Station, 3625 93rd Avenue SW, Olympia, WA 98512; 

Michael J. Furniss is a hydrologist (retired), U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station, 

1700 Bayview Drive, Arcata, CA 95521-6013; Sean Gordon is a 

research assistant professor, Institute for Sustainable Solutions, 

Portland State University, 1600 SW Fourth Avenue, Portland, OR 

97204; Stephanie A. Miller is the Riparian Program lead, U.S. 

Department of the Interior, Bureau of Land Management, 20 M 

Street SE, Washington, DC 20001.
462

GENERAL TECHNICAL REPORT PNW-GTR-966

the ecological functions and processes necessary to 

create and maintain habitat for aquatic and ripariandependent organisms over time, as well as habitat 

connectivity within and between watersheds. The 

reserve boundaries were considered interim until 

a watershed analysis was completed, at which time 

they could be modified based on suggestions made in 

the watershed analysis.

• Key watersheds: 5th-code (40,000 to 250,000 ac 

[16 187 to 101 171 ha]) to 6th-code (10,000 to 40,000 

ac [4047 to 16 187 ha]) hydrologic units that were 

intended to serve as refugia for aquatic organisms, 

particularly in the short term for at-risk fish populations, and had the greatest potential for restoration, 

or to provide sources of high-quality water. At the 

time the NWFP was drafted, Tier 1 key watersheds 

had strong populations of fish, productive habitat that was in good condition, or high restoration 

potential. Tier 2 key watersheds provided sources of 

high-quality water.

• Watershed analysis: An analytical process that 

characterizes the features and processes of watersheds and identifies potential actions for addressing problems and concerns, along with possible 

management options. It assembles information necessary to determine the ecological characteristics 

and behavior of the watershed and contribute to the 

development of options to guide management in 

the watershed, including adjusting riparianreserve boundaries.

• Watershed restoration: Includes actions deemed 

necessary to restore degraded ecological processes 

and habitat. Restoration activities focus on restoring 

the key ecological processes required to create and 

maintain favorable environmental conditions for 

aquatic and riparian-dependent organisms.

• Standards and guidelines: These directives impose 

specific requirements (standards) or recommended 

approaches (guidelines) for management activities in 

riparian reserves and key watersheds.

Note that a key philosophical shift occurred in the 

development of the ACS and NWFP as compared with 

efforts prior to 1993. The ACS, along with PACFISH (USDA 

and USDI 1994b) and the riparian component of the Tongass 

Land and Resource Management Plan (USDA FS 1997), 

made two substantive changes in how riparian management 

was formulated (Everest and Reeves 2007). First, they 

addressed riparian management at the watershed scale 

(5th- to 6th-code hydrologic units), with specific emphasis 

on maintaining ecological functions over the long term. 

Second, they rejected the previous philosophy of trying to 

define and achieve the absolute minimum set of practices 

that would meet stated riparian-management goals, and the 

concept that goals could be met by implementing yet another 

set of best management practices. The new (at that time) 

management philosophy under the NWFP represented a paradigm shift in how managers viewed resource coordination. 

In previous riparian rule-sets, riparian and aquatic technical 

specialists shouldered the “burden of proof” to demonstrate 

resource damage from forestry activities and the need for 

more comprehensive forest-practices rules to meet riparian-management goals. Under the NWFP, the precautionary 

principle was invoked—the burden of proof shifted (Thomas 

et al. 2006, USDA and USDI 1994a). Forest managers who 

wanted to alter the comprehensive default prescriptions for 

riparian management under the NWFP (described above) 

to pursue other management goals were required to demonstrate through watershed analysis that changes would not 

compromise established riparian-management goals. 

This chapter focuses on the scientific literature related 

to the management and conservation of aquatic ecosystems, 

particularly as it has developed since the 10-year NWFP 

review (Reeves 2006), with particular emphasis on the area 

of the NWFP. Among the key issues considered are:

• The ecological, physical, and biological importance 

of headwater and intermittent streams.

• The contribution of periodic disturbances to the 

resilience and productivity of aquatic ecosystems.

• The inherent variation of aquatic ecosystems in 

space and time.

• A better understanding of the variation in where key 

ecological processes occur within the stream network and the development of new tools to identify 

these locations.
463

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

• An understanding of the variation in the capacity 

of aquatic ecosystems to provide habitat for various 

fish species.

• Awareness of climate change and its potential effects.

We provide an update on the status of species listed 

under the Endangered Species Act (ESA) and the components and the associated monitoring program (Aquatic and 

Riparian Effectiveness Monitoring Program [AREMP]) of 

the ACS. We also assess the implications for the potential 

evolution of the ACS in the next round of forest plans. Reeves 

(2006) provided a thorough review of the literature in the first 

10 years of the ACS, and readers should refer to that publication for a review of the relevant science during that time. 

Guiding Questions 

Federal land managers submitted many questions that they 

deemed necessary to consider in the NWFP science synthesis 

to help with any revisions of forest plans. Because there was 

substantial overlap among and duplication in the questions, 

we distilled them into categories represented by the following 

eight questions to guide our update and assessment: 

1. Is the science foundation of the ACS still valid, or 

does science developed since 1993 suggest potential changes or adjustments that could be made to 

the ACS? 

2. What is the basis of trends observed in the ACS 

monitoring program, and what are the limitations, uncertainties, and research needs related 

to monitoring?

3. What is known about the variation in characteristics 

of unmanaged streams and riparian ecosystems in 

relation to stream networks across the NWFP area? 

4. What has been learned about the effects of riparian 

vegetation on stream habitat and environments?

5. What effects have human activities had on stream 

and riparian ecosystems? 

6. What is the scientific basis for restoration management in riparian reserves, and how does restoration 

relate to the ecological goals of the ACS?

7. What is the capacity of federal lands in the NWFP 

area to contribute water for a suite of economic, 

recreational, and ecological uses?

8. What are the potential effects of climate change 

on aquatic ecosystems in the NWFP area, and are 

these adequately addressed by the ACS?

These eight questions are not answered specifically 

in sequence because of the overlap among them and the 

variety of topics they involve. They are, however, answered 

to the extent possible in different or multiple sections of the 

chapter, and are addressed in outline in the conclusions.

Key Findings

Status of Species and Population Units Listed 

Under the Endangered Species Act on Federal 

Lands in the Northwest Forest Plan Area

In 1993, only the Sacramento winter Chinook salmon 

(Oncorhynchus tshawytscha), and the shortnose sucker 

(Chasmistes brevirostris), and Lost River sucker (Deltistes 

luxatus, both native to the Klamath River system) were 

listed as threatened or endangered under the ESA in the area 

covered by the NWFP. Within a few years of the development of the ACS, 23 evolutionarily significant units of 

Pacific salmon and 3 distinct population segments of bull 

trout (Salvelinus confluentus) were listed under the ESA 

(table 7-1). There have been three additions since the 10-year 

review (Reeves 2006): the Oregon Coast coho salmon 

evolutionarily significant unit (O. kisutch), and two other fish 

species, the Oregon chub (Oregonichthys crameri) and the 

Pacific eulachon (Thaleichthys pacificus). No population 

units of Pacific salmon or bull trout have warranted delisting 

since the ACS was developed.2 However, the Oregon chub 

was delisted in 2015 (USFWS 2015), becoming the first fish 

to be delisted because of increases in numbers. Habitat on 

the Willamette National Forest contributed to its recovery.

The developers of the ACS anticipated the ESA listing 

of distinct population segments of various species of Pacific 

salmon, evolutionarily significant units, and other fish 

species. The ACS was not expected to prevent the listing 

of any species or distinct population segment because 

factors outside the responsibility and control of federal 

2

 http://www.westcoast.fisheries.noaa.gov/publications/status_

reviews/salmon_steelhead/2016_status_review.html.
464

GENERAL TECHNICAL REPORT PNW-GTR-966

Table 7-1—Evolutionarily significant units (ESUs) of Pacific salmon and trout (Oncorhynchus spp.), distinct 

population segments (DPSs) of bull trout (Salvelinus confluentus), and fish and amphibian species listed 

under the Endangered Species Act that occur in the area covered by the Northwest Forest Plan (continued)

Speciesa ESU/DPS/species

National forests (NFs) and Bureau of Land Management (BLM) 

districts in which ESU, DPS, or species occur

1. Fish

Coho salmon Lower Columbia/

southwest Washington

Gifford Pinchot and Mount Hood NFs

Oregon coast Siskiyou, Siuslaw, and Umpqua NFs; Coos Bay, Eugene, Roseburg, and 

Salem BLM districts

Southern Oregon/northern 

California

Klamath, Mendocino, Rogue River–Siskiyou, Shasta-Trinity, and Six 

Rivers NFs; Arcata, Medford, and Redding BLM districts; Kings Range 

National Conservation Area (NCA)

Central California coast Ukiah BLM district

Chinook salmon Puget Sound Gifford Pinchot, Mount Baker–Snoqualmie, and Olympic NFs

Lower Columbia Gifford Pinchot and Mount Hood NFs; Salem BLM district

Upper Columbia Okanogan-Wenatchee NF

Upper Willamette Mount Hood and Willamette NFs; Eugene and Salem BLM districts

California coastal Mendocino and Six Rivers NFs; Arcata and Ukiah BLM districts; Kings 

Range NCA

Sacramento River winter 

run

Mendocino and Shasta-Trinity NFs; Mendocino BLM district

Central Valley spring run Shasta-Trinity NF; Mendocino and Redding BLM districts

Chum salmon Hood Canal summer Olympic NF

Columbia River Salem BLM district

Steelhead Puget Sound Gifford Pinchot, Mount Baker–Snoqualimie, and Olympic NFs

Lower Columbia Gifford Pinchot and Mount Hood NFs; Salem BLM district

Mid-Columbia Gifford Pinchot, Mount Hood, and Wenatchee NFs

Upper Columbia Okanogan-Wenatchee NF

Upper Willamette Willamette NF; Eugene and Salem BLM districts

Northern California Mendocino and Six Rivers NFs; Arcata, Mendocino, and Ukiah BLM 

districts; Kings Range NCA

Central California coast Arcata BLM district; Kings Range NCA

Central Valley, California Mendocino and Shasta-Trinity NFs Mendocino BLM

Bull trout Klamath River Fremont-Winema NF

Columbia River Deschutes, Gifford Pinchot, Mount Hood, Okanogan-Wenatchee, and 

Willamette NFs; Eugene BLM district

Coastal—Puget Sound Mount Baker–Snoqualmie and Olympic NFs

Lost River sucker Fremont-Winema NF

Shortnose sucker Fremont-Winema NF

Pacific eulachon Siuslaw and Six Rivers NFs
465

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

land managers contribute to the decline and recovery of 

fish populations and will strongly influence their recovery. 

These factors include:

• Degradation and loss of freshwater and estuarine 

habitats on nonfederal lands (McConnaha et al. 

2006, NRC 1996).

• Excessive harvest in commercial and recreational 

fisheries (NRC 1996).

• Migratory impediments, such as dams (McConnaha 

et al. 2006, NRC 1996).

• Loss of genetic integrity from the effects of hatchery 

practices and introductions, combined with undesirable interactions (e.g., competition and predation) involving hatchery and naturally produced fish 

(Araki and Schmid 2010, NRC 1996).

Thus, the ACS was an attempt to develop a strategy 

to guide management of aquatic ecosystems on federal 

lands in the NWFP area that would meet potential ESA 

requirements. The ACS was expected to make significant 

contributions to the recovery of the ESA-listed fish by 

increasing the quantity and quality of freshwater habitat 

for Pacific salmon and protecting and enhancing habitats 

of other species (FEMAT 1993). Although the condition of 

habitat in aquatic ecosystems on federal lands appears to 

have improved at least slightly over the NWFP area, this has 

not been sufficient to change the status of most listed fish.

The potential of federal lands to contribute to the recovery 

of listed fish, particularly Pacific salmon, in many parts of the 

NWFP area is likely more limited than was recognized when 

the ACS was developed. The primary reason for this difference 

Table 7-1—Evolutionarily significant units (ESUs) of Pacific salmon and trout (Oncorhynchus spp.), distinct 

population segments (DPSs) of bull trout (Salvelinus confluentus), and fish and amphibian species listed 

under the Endangered Species Act that occur in the area covered by the Northwest Forest Plan (continued)

Speciesa ESU/DPS/species

National forests (NFs) and Bureau of Land Management (BLM) 

districts in which ESU, DPS, or species occur

2. Amphibians

Oregon spotted 

frog (T)

Deschutes, Fremont-Winema, Gifford Pinchot, Mount Hood, and 

Willamette NFs; Klamath Falls and Medford BLM districts; Columbia 

River Gorge National Scenic Area (NSA) (S)

Cascades frog 

(petitioned)

Deschutes, Gifford Pinchot, Mount Baker–Snoqualmie, Mount Hood, 

Okanagan-Wenatchee, Olympic, Rogue River–Siskiyou, Umpqua, and 

Willamette NFs; Medford (S), Roseburg, and Salem BLM districts

Oregon slender

salamander

(petitioned)

Mount Hood and Willamette NFs; Columbia River Gorge NSA

Cascade torrent 

salamander 

(petitioned)

Gifford Pinchot, Mount Hood, and Willamette NFs; Eugene and Salem 

BLM districts; Columbia River Gorge NSA 

Columbia torrent 

salamander 

(petitioned)

Siuslaw NF; Salem (S) BLM district 

Western pond 

turtle (petitioned)

Fremont Winema, Mount Hood, Rogue River–Siskiyou, Siuslaw, 

Umpqua, and Willamette NFs; Columbia River Gorge NSA; Coos 

Bay, Eugene, Klamath Falls, Medford, Roseburg, and Salem (S) BLM 

districts 

a

 Petitioned = under review for Endangered Species Act listing; T = threatened; S = suspected occurrence.
466

GENERAL TECHNICAL REPORT PNW-GTR-966

is that, in many situations, federal lands (figs. 7-1 and 7-2) have 

a limited capacity to provide high-quality habitat for some of 

the listed fish. Federally managed lands are generally located 

in the middle to upper portions of watersheds, which tend to 

have steeper gradients and more confined valleys and floodplains, making them inherently less productive for some fish 

(Burnett et al. 2007, Lunetta et al. 1997, Reeves et al. 2016a). 

Federal lands may, however, be important sources of wood, 

sediment (Reeves et al. 2016a), and water (Brown and Froemke 

2010, 2012) for downstream nonfederal lands, and will be 

important for the potential recovery of most populations. 

Nevertheless, their contribution to recovery may in many cases 

be insufficient without parallel contributions from nonfederal 

land ownerships elsewhere in the basin (Grantham et al. 2017).

The numbers of Pacific salmon and other anadromous 

fish returning to freshwater in the NWFP area are strongly 

influenced by ocean conditions, which are highly variable 

over time. Favorable conditions (cold water) tend to occur in 

the negative phase of the Pacific Decadal Oscillation (PDO) 

and the La Niña phase of the El Niño-Southern Oscillation 

(ENSO), when fish growth is strong and survival is high, 

resulting in strong returns of adults to freshwater (Mantua et 

al. 1997). Survival is low and numbers decline during warmer 

periods, especially during the positive phase of the PDO and 

the El Niño phase of the ENSO. Winters are cold and wet in 

the negative PDO–La Niña phase, which also creates more 

favorable conditions in freshwater (Mantua et al. 1997). A 

positive PDO–El Niño produces dry, warm winters, reducing 

streamflows, increasing water temperatures, and increasing 

the occurrence of fire (see chapter 3). The last extended period 

of high productivity was from the late 1940s to 1976 (Mantua 

et al. 1997), with brief periods of favorable conditions in 

1984–1988, 1999–2002,3 and 2010–2011 (Bond et al. 2015). 

However, beginning in 2013, abnormally warm conditions in 

the Pacific Ocean (“the Blob”) developed because of lower-than-normal heat loss from the ocean to the atmosphere, 

combined with a relatively weak mixing of the upper ocean 

layer owing to an usually high atmospheric pressure (Bond et 

al. 2015). Initial effects were most notable in the North Pacific 

Ocean off Alaska. Ocean conditions changed noticeably along 

the NWFP area in 2014 as a result, and fish returns are 

expected to decline over the next few years.

3

 Mantua, N. 2017. Personal communication. Leader Landscape 

Ecology Team, National Marine Fisheries Service–Southwest 

Fisheries Science Center, 8901 LaJolla Shores Drive, Santa Cruz, 

CA 92037. nate.mantua@noaa.gov. 

Myrtle Creek

Coquille

Applegate

North Umpqua

McKenzie

Smith/Siuslaw

Watershed

0 10 20 30 40 50 60 70 80 90 100 

Proportion of watershed area (percent)

Most ecologically sensitive fish-bearing 

streams, by ownership

Federal lands Nonfederal lands

Figure 7-1—Proportion of the length 

of fish-bearing streams categorized 

as most ecologically sensitive in the 

six study watersheds of Reeves et al. 

(2016a) in western Oregon, by ownership. Ecologically sensitive areas 

are portions of the stream network 

that (1) have moderate- to high-quality habitat potential for coho and 

Chinook salmon and steelhead, (2) 

have moderate to high potential to 

warm if the riparian ecosystem is 

modified, and (3) have moderate to 

high potential for erosion or debris 

flows. From Reeves et al. 2016a. 
467

0 5 10 20Miles 0 5 10 20 30Kilometers 

McKenzie River—stream categories

Private landsWatershed boundaryBLM adaptive management area (AMA)Bureau of Land Management (BLM) matrixBLM late-successional reserves (LSR)U.S. Forest Service (FS) matrixFS AMAFS LSR/AMA reservesFS/BLM administratively withdrawn

Land ownership and allocations

Congressionally reserved

1 = Fish-bearing, most ecologically sensitive2 = Fish-bearing, other3 = Non-fish-bearing, most ecologically sensitive4 = Non-fish-bearing, other

Stream categories

Figure 7-2—Distribution of ecologically sensitive stream reaches on federal and nonfederal lands in the McKenzie River watershed, Oregon. From 
468

GENERAL TECHNICAL REPORT PNW-GTR-966

We are unable to separate the influence of ocean conditions over the last 10 years from the influence of changes 

in the condition of freshwater ecosystems on federal lands 

that may have occurred under the NWFP and ACS. The 

actual contribution of freshwater habitats to the persistence 

and recovery of anadromous salmon and trout will be 

relatively more important when ocean conditions move into 

a less-productive phase (Lawson 1993). Improvements in 

the quantity and quality of freshwater habitat resulting from 

the ACS could result in relatively greater numbers of fish 

entering the ocean, thus increasing the likelihood of persistence of many populations during periods of low ocean 

productivity. However, as noted previously, the contribution 

of federal lands may be more limited than expected because 

their potential to provide high-quality habitat is less than 

originally recognized when the ACS was developed. 

The status of other aquatic-riparian species in the 

NWFP area is not as well monitored as that of Pacific 

salmon. The Oregon spotted frog (Rana pretiosa) was listed 

as threatened under the ESA in 2014. It is a pond-breeding 

amphibian now restricted to isolated populations that overlap 

the NWFP area in western Washington and Oregon.4 Five 

other aquatic-riparian amphibian and reptile species are 

petitioned for ESA listing and are under status review: (1) 

Columbia torrent salamander, Rhyacotriton kezeri; (2) 

Cascade torrent salamander, R. cascadae; (3) Cascades frog, 

Rana cascadae; (4) Oregon slender salamander, Batrachoseps wrighti; and (5) western pond turtle, Actinemys 

marmorata. The two torrent salamanders are headwater 

forest species, occurring predominantly in and along the 

banks of small streams, with significant portions of their 

ranges on nonfederal lands. Nevertheless, federal riparian 

reserves contribute habitat for localized populations of 

Columbia torrent salamanders and more extensive areas for 

Cascade torrent salamanders. The Oregon slender salamander is found in proximity to down wood on the forest floor in 

riparian and upland forests, and has associations with older 

forest conditions (Clayton and Olson 2007). Cascades frogs 

are pond breeders at higher elevations in the Cascade Range, 

where they may be affected by multiple stressors (Pope et al. 

4

 http://www.fs.fed.us/r6/sfpnw/issssp/agency-policy/.

2014). Similarly, multiple threats appear to affect western 

pond turtles, which may occur in stream and pond systems 

in the NWFP area (Rosenberg et al. 2009).

Monitoring—Aquatic and Riparian Effectiveness 

Monitoring Program 

Watershed conditions—

The Aquatic and Riparian Effectiveness Monitoring Program is responsible for monitoring, assessing, and reporting 

on watershed conditions on lands governed by the NWFP. 

Although NWFP implementation began in 1994, AREMP 

implementation was delayed to accommodate the time 

needed for its design. The scope of the AREMP sampling 

design includes field-data collection across 250 watersheds 

in the Plan area, with a rotation of sampling among watersheds conducted each year so that the entire population of 

watersheds selected for monitoring would be sampled over 

an 8-year period. In addition, using geographic information 

system (GIS) and remotely sensed data are used to quantify 

roads and vegetation in 1,974 watersheds with federal lands 

in the Plan area and assess the condition of upslope and 

riparian areas. 

Pilot monitoring of watershed conditions began in 

2000, and the monitoring plan was finalized in 2003 

(Reeves et al. 2004). The first full rotation of watershed 

visits was conducted in years 2002–2009, assessing initial 

status, and the second full rotation is scheduled to occur in 

2010–2018 where paired assessments of most watersheds 

were possible owing to watersheds being resampled a 

second time. Reporting is on a 5-year cycle, in synchrony 

with NWFP establishment, with the first report covering up 

to year 10 of Plan implementation (Gallo et al. 2005), the 

second report covering up to year 15 (Lanigan et al. 2012), 

and the third to year 20 (Miller et al. 2017). The 20-year 

report includes assessment of data from the first rotation 

of watershed visits (2002–2009) and the first 4 years of 

the second rotation (2010–2013), and hence includes trend 

assessments based on a subset of sampled watersheds.

Changes in data collection and aggregation procedures, 

and in application of analytical methods, were anticipated 

from the onset of the development of AREMP (Hohler et 

al. 2001). In the late 1990s, our understanding of watershed 
469

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

ecology and watershed-condition assessment approaches 

was acknowledged to be limited, and advances in both ecological and statistical disciplines were expected to contribute 

to further development of AREMP assessments. Indeed, 

both data sources and analyses have changed over time, 

with the consequence being that the results from each of the 

reports are not directly comparable. For example, relative to 

data sources, some data-collection procedures changed as 

attribute variability became apparent. Relative to analytical 

approaches, the 10- and 15-year analyses used decision 

support models (Reeves et al. 2004, Reynolds et al. 2014) 

that depended on empirical relations and expert judgment to 

evaluate data. The 20-year report employed a more statistical focus, with expert opinion and independent analysis of 

upland, riparian, and in-channel metrics. Additional discussion of adaptive processes through AREMP implementation, 

including anticipated next steps for research, is presented 

following the key 20-year findings. Although data analysis 

and assessment methods changed, each report reanalyzes the 

entire spatial and temporal dataset available at the time, and 

is intended to represent the most current understanding of 

status and trends since the beginning of the Plan. 

Key 20-year findings—

The 20-year AREMP report (Miller et al. 2017) examined 

upslope-riparian and in-channel datasets separately. This 

segregation acknowledged that the source data differed 

significantly between these two components. Upsloperiparian data were derived from remote sensing and GIS 

landscape data covering all NWFP watersheds (watersheds 

containing more than 5 percent federal ownership, a total of 

1,974 watersheds). In contrast, in-channel data were derived 

from annual field measurements, and therefore were limited 

to 213 sampled watersheds. Upslope-riparian assessments 

integrated five data types reflecting watershed processes: 

sedimentation, wood recruitment, riparian condition and 

processes, hydrology, and fish passage. In-channel analyses 

focused on three additional data types, assessed independently: physical-habitat condition, macroinvertebrate 

assemblages, and water temperature.

Upslope-riparian analyses integrated finer scaled data 

metrics reflecting indicators of key watershed processes. 

These processes included (1) stream-sediment delivery 

from landslides, based on road and vegetation disturbances, in addition to geology and climate attributes; (2) 

down-wood production and delivery, based on riparian 

and upland vegetation metrics; (3) riparian condition and 

associated processes as represented by stream temperature, 

streambank stability, and species-habitat provision based 

on riparian vegetation condition and riparian road density; 

(4) hydrology, focusing on peak flow, based on road and 

vegetation metrics; and (5) fish passage, based on stream 

gradient and assessment of barriers (e.g., dams, some road 

crossings). Using a multicriteria assessment approach, 

akin to analyses conducted in previous reports, attributes 

for a watershed were scored to a common 0 to 100 scale, 

reflecting an index of most-to-least deviation from least 

human-disturbed conditions. 

The 20-year report found little change in the average 

upslope-riparian condition, from a score of 68 in 1993 to 

69 in 2012. However, noticeable shifts were observed in 

the overall score distribution (fig. 7-3A). In particular, there 

was a noticeable increase in scores from the low to mid 

range (15 to 50) to a higher range (60 to 90), whereas the 

area with the highest scores (>90) decreased slightly. These 

patterns reflected a signature of federal land use allocations. 

The mean score in the most protected category of land 

use allocation (Congressionally reserved lands) decreased 

(−1), indicating greater disturbance, whereas averages 

for late-successional reserves and matrix lands increased 

(+2, +3), indicating less disturbance. The upward shift in 

the low-range scores is likely attributed to widespread 

vegetation regrowth and targeted road decommissioning in 

previously harvested watersheds. In contrast, the decrease 

in the high-end scores mainly followed the pattern of large 

fires during the assessment period, many of which occurred 

in wilderness areas, including the Biscuit Fire in southwest 

Oregon (2002), the B&B Complex fires in the central Oregon 

Cascade Range (2003), and numerous fires along the eastern 

edge of the North Cascade Range in Washington (2006).

It may seem counterintuitive that the most protected 

lands would show a trend toward more disturbance. 

Although this trend might be seen as negative because fire 

results in a loss of vegetation and an increase in riparianupland disturbance, it is simplistic to consider this an 
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GENERAL TECHNICAL REPORT PNW-GTR-966

Figure 7-3—Results of the 20-year assessment of watershed conditions by the Aquatic and Riparian Effectiveness Monitoring Program 

(Miller et al. 2017): (A) upslope-riparian condition, (B) in-channel condition, (C) aquatic macroinvertebrates, and (D) 7-day running 

average of maximum water temperatures. Source: Miller et al. 2017.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

adverse effect at the regional scale of forest ecosystems 

and their embedded watersheds. Wildfires are an integral 

component of long-term forest and stream ecosystem 

dynamics (e.g., Bisson et al. 2003, Franklin et at. 2017, 

Reeves et al. 1995), with direct benefits to stream habitats 

and biota resulting from fire (e.g., Flitcroft et al. 2016a) 

and related natural disturbances such as landslides (wood 

and sediment delivery to streams) (e.g., Benda and Dunne 

1997a, 1997b; May and Gresswell 2003; Reeves et al. 

2003). Aquatic-riparian ecosystems are dynamic, being 

multistate in space and time (Olson et al. 2017a, Penaluna 

et al. 2016). This recent AREMP finding highlights our 

nascent understanding of the range of historical aquaticriparian conditions in the NWFP area and the cadence and 

extent of natural disturbance events. It also brings to the 

forefront the role of both passive and active management 

of these aquatic-riparian systems in the future to maintain 

and restore the dynamics of aquatic-riparian ecosystems in 

the region, and the importance of considering whether we 

need to manage for resilience. In this framework, shaped 

by land use allocations and trends detected therein, it is 

possible that development of more nuanced evaluation 

methods is needed to assess variation in aquatic-riparian 

conditions. The problem also becomes conceptually 

challenging, given a known shifted baseline from past 

anthropogenic disturbances, including the effects of fire 

suppression, as well as from the need to develop projections of climate change, climate extremes, and related 

disturbances from fire and landslides.

In-channel watershed-condition assessments 

conducted for the 20-year report were the first such 

assessments to have enough field-site revisits (about half 

the sample) to estimate trends. Instream conditions in 

subsampled watersheds in the Plan area were assessed 

by evaluating three separate elements: physical habitat, 

macroinvertebrates, and water temperature. First, for 

physical habitat, a composite index score (on a 0 to 100 

scale, relative to unmanaged reference conditions; see 

below for more discussion on this topic) based on expert 

judgment was derived from substrate (percentage of fine 

substrates at a stream-reach scale), pool-tail fine substrates, 

and the frequency of medium- and large-size down wood. 

A small but statistically significant increasing trend (from 

46 to 49) in overall physical habitat condition was detected 

when measured both on a yearly basis with all data and 

from the subset of watersheds that had been revisited (fig. 

7-3B). Individual components of the physical habitat varied: 

reach-scale fine substrate showed an increasing trend in 

occurrence, whereas instream wood and pool-tail fine 

substrates showed no significant changes. 

Second, an index was also derived for macroinvertebrates (fig. 7-3C), which were assessed at the site level, 

then grouped into taxonomic classes and compiled into 

a score representing the ratio of expected species based 

on reference sites (E = 1) (see below) to occurrence of no 

expected species (O = 0). Site-scale scores were aggregated 

into watershed scores. A positive change in the mean score 

was detected for macroinvertebrate diversity, suggesting a 

shift toward a species composition reflective of expected 

reference conditions. 

Third, water temperature was evaluated using an 

integrated model that assessed 7-day maximum temperatures collected at low points in watersheds from June to 

September. Water temperature showed a decreasing trend, 

although temperature averages were still higher than 

federal and state standards for salmonid habitat (fig. 7-3D). 

Interestingly, water temperatures in all land use categories 

decreased, but temperatures in the most protected category 

showed the smallest decline, perhaps reflecting the upslope 

findings, which showed a signature of disturbance owing to 

vegetation loss in reserves. 

Reflection on adaptive processes through AREMP 

implementation—

Here, we outline primary changes and challenges in 

AREMP monitoring over the past 20 years, many of which 

are ongoing research-emphasis areas. These topics are 

common, foundational aspects of many aquatic-riparian 

monitoring programs, representing a larger coalition of 

scientists and managers addressing similar themes over 

diverse landscapes. The science of watershed-scale ecology 

has followed the development of the discipline of landscape 

ecology, and the challenges cited here are representative of 

a parallel course of design and analytical adaptive processes 

occurring in terrestrial forest ecosystems. 
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GENERAL TECHNICAL REPORT PNW-GTR-966

Overall, NWFP monitoring, including the AREMP 

(Hohler et al. 2001), was framed as an adaptive-management cycle (Mulder et al. 1999). For AREMP, four primary 

changes and challenges over the course of the first 20 years 

of the NWFP have included (1) redefining the overarching 

objectives of watershed-condition monitoring, shifting from 

a salmonid habitat focus to one that was more representative 

of the environmental conditions of entire watersheds, while 

retaining selected key elements of salmonid habitats; (2) 

refining the indicators used in data collection and analysis; 

(3) reconsidering approaches to using benchmarks or 

reference conditions for assessment; and (4) modifying data 

integration methods. These four topics are discussed further 

below, with comparisons to other aquatic-monitoring 

programs for a broader perspective.

Defining objectives—

The first step in designing the NWFP monitoring modules was to define the goals and objectives of monitoring 

(Mulder et al. 1999). The NWFP defined the central 

question for aquatic ecosystems as, “Is the ecological health 

of the aquatic ecosystems recovering or sufficiently maintained to support stable and well-distributed populations 

of fish species and stocks?” (USDA and USDI 1994a, E-7). 

The primary fish taxa with status of concern in the NWFP 

area were native salmonids, hence a taxonomic focus was 

present from the origin of the Plan. Although particular 

species (owls, murrelets, salmonids) have been a principle 

interest of NWFP monitoring programs, concepts developed 

in the monitoring plan also stated that “Because of the 

current wide (and justified) interest in all components of 

biological diversity, however, the species-centric approach 

is no longer sufficient” (Mulder 1999, p. 29). In this vein, 

the language of the ACS objectives (USDA and USDI 

1994a) had also included aquatic-riparian habitat conditions 

and species, but with a focus on multiple processes that 

were known to be tied to development of salmonid habitat 

conditions. At the time of the NWFP, emerging science on 

the role of disturbance in renewal of aquatic habitats also 

suggested a change in focus from the assessment of narrowly specified, in-channel habitat elements (e.g., a certain 

number of pieces of large wood per stream length) toward 

the ecosystem processes that form and maintain habitats 

(USDA and USDI 1994a). AREMP was perhaps the most 

ambitious of the monitoring modules in this regard, calling 

for monitoring a broad set of conditions in the upslope, 

riparian, and in-channel portions of watersheds that related 

to ecological processes tied to fish habitat, and evaluating 

these in comparison to broad distributions of conditions 

rather than solely on a watershed-by-watershed basis 

(Reeves et al. 2004). 

The ACS was originally envisioned as a “coarse-filter” 

conservation effort (Hunter 2005, Noss 1987) (see additional 

discussion in chapter 12). The focus of the ACS was on 

restoring and maintaining ecological processes that created 

and maintained aquatic ecosystems for a suite of organisms, 

primarily ESA-listed fish, and for clean water and other 

ecosystem services (USDA and USDI 1994a). AREMP was, 

therefore, initially directed at the habitat of native salmonids, a primary responsibility of federal land managers and 

regulators in the NWFP area (Reeves et al. 2004). Habitat 

conditions for native salmonid fishes were initially used as 

metrics for watershed condition trend assessment, owing to 

their sensitivity to changes in several habitat features (e.g., 

water temperature, sediment, down wood). As with other 

coarse-filter assessments that use biotic indicators such as 

umbrella or flagship species (e.g., Raphael and Molina 2007), 

it was assumed that other aquatic and riparian-dependent 

organisms would benefit if watershed conditions for salmonids improved. Hence, salmonids were recognized as a focal 

species group, assuming that if their habitats were sustained 

or improved in condition over time, it would infer sustainability or improvement of the greater community of biota 

and the broader watershed-scale ecosystem functions and 

processes upon which they rely. 

Development of aquatic monitoring programs requires 

a clear articulation of which biota and associated functional characteristics of habitats and ecosystems are being 

considered, and how they are likely to be altered as a result 

of the actions of interest (Carlisle et al. 2008, Palmer et al. 

2005, Pont et al. 2006). Such species-based approaches may 

not fully account for the variation in species abundance or 

community composition present, given the spatiotemporal 

heterogeneity in ecosystem conditions generated by natural 

disturbances. Further, this natural variability in species and 
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environmental conditions may make it difficult to identify 

the effects of anthropogenic disturbances and recovery from 

those disturbances, and thus make it difficult to assess and 

understand the ecological consequences of detected changes 

(Frissell et al. 2001). However, explicitly identifying the 

organism(s) of interest is essential for understanding what 

the monitoring results mean for those species and the fauna 

the species represents (Wohl 2016).

The 20-year AREMP analysis shifted from the emphasis of the 10- and 15-year analyses on evaluating habitat for 

salmonids to characterizing more general environmental 

conditions. Miller et al. (2017) used the 5th and 95th percentile values from a suite of physical attributes in reference 

sites in systems with the least human-caused disturbance 

(see later discussion) to determine the favorability of 

conditions for biota in monitored watersheds. Based on 

expert judgment, the 5th percentile was considered the most 

favorable for some attributes (e.g., pool-tail fines, reach 

fines) and the 95th for others (wood). However, Miller et al. 

(2017) did not identify which organisms these conditions 

were supposed to favor, making it difficult to understand the 

ecological validity of these values and the consequences of 

any changes detected.

This switch highlights a continuing scientific debate 

in the monitoring and assessment community on the 

merits of focusing assessments on particular flagship or 

umbrella taxa rather than on more general environmental 

processes and conditions. On the one hand, umbrella 

species serve as meaningful “endpoints” (Suter 2001) 

or “final ecosystem services” (Blahna et al. 2017) that 

provide relevance to monitoring results. On the other 

hand, in aquatic-riparian ecosystems, salmonid distributions do not reach headwater streams, which make up 

most of the stream length in NWFP watersheds (Gomi et 

al. 2002). Salmonid habitat in larger streams may not be 

representative of the condition of the entire watershed, 

unless solid ties to upstream and upslope conditions can 

be made. Further, the adequacy of salmonids as umbrella 

species has not been formally assessed (Murphy et al. 

2010, Simberloff 1998), and there are questions about 

whether one species can be an indicator of the condition 

of other species (Carlisle et al. 2008). Although these two 

objectives for watershed-condition assessments (salmonid 

habitat versus watershed environmental conditions) are 

closely related, differences in emphasis have a ripple effect 

that plays out through the monitoring and assessment process, and affects how results might be interpreted relative 

to goals of maintaining and restoring conditions.

The original AREMP design document laid out a 

conceptual model that considered the interactions between 

upslope, riparian, and in-channel processes, all within a 

variable landscape (e.g., precipitation, geology) (Reeves et 

al. 2004). No formal assessment of relationships between 

upslope/riparian/in-channel indicators in the AREMP 

conceptual model has been published, but a number of 

studies are relevant to pieces of this framework. Burnett et 

al. (2007) developed a relative ranking, Intrinsic Potential 

(IP) ranging between 0 (poor) and 1 (excellent) to determine the geomorphic potential of a reach to provide habitat 

for coho salmon in larger streams. This work was followed 

by data-driven watershed-scale models of several habitat 

attributes important for salmon that tied upland-riparian 

conditions to instream habitats, including models of debrisflow-prone areas (delivering sediment to streams: Benda 

and Dunne 1997a, 1997b; Burnett and Miller 2007); wood 

recruitment (e.g., Reeves et al. 2004); and thermal loading 

(as a proxy to represent stream temperatures; see Reeves 

et al. 2016a). Several of these studies also contributed to 

a better understanding of instream processes connecting 

lower order headwater streams to higher order streams 

occupied by salmonids. Syntheses of these multifaceted 

watershed-process models have contributed to a better 

understanding of the multistate nature of aquatic-riparian 

ecosystems (Olson et al. 2017a, Penaluna et al. 2016, 

Reeves and Spies 2017), and integration of several of these 

watershed-integration models have been used to evaluate 

potential management options (Reeves et al. 2016a). Full 

incorporation of these concepts into watershed-condition 

assessments has been indirect to date, for example, by 

implicitly supporting approaches to assess upland-riparian 

areas and full in-channel networks from headwaters downstream. This topic deserves continued attention as AREMP 

procedures continue to develop, and can potentially inform 

the overarching objectives of the program.
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GENERAL TECHNICAL REPORT PNW-GTR-966

Other aquatic-monitoring programs have incorporated 

upslope/riparian/in-channel relationships into their conceptual models, albeit in quite different ways. The National 

Rivers and Stream Survey (NRSA) (USEPA 2016) related 

four chemical and four physical habitat stressors to multimetric macroinvertebrate and fish indices using a concept of 

relative risk: the likelihood of finding poor biological conditions in a river or stream when stressor concentrations are 

high relative to the likelihood when they are low. Indirectly, 

these stressors, as well as three land-use metrics (urban land 

cover, agricultural row-crop land cover, and dam influence), 

were used in selecting the reference sites used to evaluate 

the stressor and response metrics.

PACFISH/INFISH Biological Opinion Monitoring 

Program (PIBO) approaches have not directly assessed 

upslope indicators, but have selected a set of physicalhabitat indicators based on sensitivity to land-use management intensity, using road density as a surrogate 

(Al-Chokhachy et al. 2010). A recent assessment of the 

PIBO program conceptual model by Irvine et al. (2015) 

examined correlations between upslope (grazing, road 

density, percentage forested), in-channel habitat (fine 

sediment, temperature), and a macroinvertebrate observed/

expected index. Although they found weak to no support 

for causal pathways related to effects of anthropogenic 

drivers on biological condition, they surmised that the 

conceptual model was sound, and the weak correlations 

were due to imprecision in the measurement of drivers 

(grazing, roads); stressors (sediment, measured in pool 

tails); and responses (macroinvertebrates, measured in riffles). They cited the more general issue that regional trend 

monitoring is not optimized for detecting causal mechanisms. A related and broader concern is that such surveys 

may underestimate infrequent but high-severity events 

(Suter 2001). In contrast, it was notable in the AREMP 

20-year report that the signatures of wildfire and road 

decommissioning, relatively low-frequency events, were 

detectable in the upslope-riparian assessment because it 

included a full census of watersheds, rather than a limited 

sample. Overall, scientific work in the past 20 years has 

continued to support the dynamic, disturbance-based 

ecology of aquatic-riparian ecosystems (see “Natural 

Variability” section later in this chapter). Although the 

AREMP conceptual model has not changed, there have 

been numerous refinements to the indicators used, as well 

as to their combination and interpretation.

Selection of indicators—

In-channel biotic indicators—In-channel biotic metrics 

have proven to be particularly challenging to monitor. 

Although fish populations are of principal concern to 

managers because of regulatory requirements and their 

potential as umbrella or flagship species, fish-data collection 

was dropped from AREMP protocol in 2007 because most 

in-channel watershed sample sites were above salmonid 

habitat, and the collection of meaningful salmonid-habitat 

data would have required a separate and intensive effort. 

Similarly, streambank amphibians were dropped because of 

detectability issues. Variability in detection spatially within 

watersheds as well as temporally within the year made 

streambank amphibian monitoring challenging: species 

that were present at a site early in a season could be missed 

if the site is not sampled until later in the season. Further, 

terrestrial salamanders are fossorial (live largely subsurface) and may not have been detected even if present (e.g., 

Hyde and Simons 2001).

Macroinvertebrates are the only remaining in-channel 

biotic indicator collected by AREMP. Macroinvertebrates 

have come to play a central role in many aquatic-monitoring programs because of their presumed responsiveness 

to local environmental conditions and ease of collection 

(PIBO [Al-Chokhachy et al. 2010], Oregon Department 

of Environmental Quality [Hubler 2009], NRSA [USEPA 

2016]). This commonality creates the potential for data 

sharing between monitoring programs, assuming sufficient similarity in the sampling methods used. However, 

differing results for the fish and macroinvertebrate indices 

in a recent national assessment emphasized the danger of 

relying on one taxonomic group to represent the potential 

responses or condition of other groups (USEPA 2016). 

Understanding how to reliably collect and incorporate 

data from taxa other than macroinvertebrates is a challenge for ongoing research; new multispecies environmental DNA methods are promising and are undergoing trial 

now (see app. 1).
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In-channel abiotic indicators—Measurement reliability 

has also been a challenge with abiotic in-channel indicators. 

Based on quality-control sampling, AREMP dropped the 

evaluation of pool frequency, depth, and median particle 

size from the latest 20-year assessment. Measurements 

of these parameters are still being collected, owing to the 

perceived importance of these indicators for assessment 

of habitat conditions, and the AREMP program is actively 

investigating ways to make current collections of these data 

more reliable for use in future analyses. Remaining abiotic 

indicators used in the latest report were pool-tail fine substrates, reach-scale fine substrates, down wood, and water 

temperature (Miller et al. 2017). 

Upslope-riparian indicators—The basic indicators used 

in the upslope-riparian portion of the AREMP assessments 

have changed little, but their evaluation has become more 

context sensitive. In the latest report, their combination was 

reorganized into an index with a more process-based structure. The new process-based model structure includes five 

processes that aligned it more directly with the conceptual 

model in the original AREMP plan: sediment and wood 

delivery, riparian shading, hydrology, and habitat connectivity. All these indicators are based primarily on road and 

vegetation data, the two major land-use metrics that can be 

traced backward in time to assess trends since the beginning of the NWFP. This estimation of historical data is a 

challenge that appears not to have been attempted by other 

broad-scale programs (Gordon 2014). Road and vegetation-management effects on aquatic systems continue to be 

active areas of research. 

Of particular relevance to the AREMP assessment 

is work identifying the differential effects of sediment delivery from roads, based on landscape position (Al-Chokhachy 

et al. 2016, Black et al. 2012) and the incorporation of potential fish-habitat considerations into the measure of aquatic 

connectivity (Chelgren and Dunham 2015). Advances in 

satellite data and their classification have considerably 

expanded the available vegetation metrics and the ability to 

track these through yearly time steps (Kennedy et al. 2010, 

Ohmann et al. 2011). These capabilities should be examined 

in light of the disturbance-ecology paradigm discussed 

throughout this chapter.

Examining the freshwater assessment literature more 

generally, Kuehne et al. (2017) found a shift in measures 

used from field-based responses to landscape-stressor 

metrics. The use of upslope indicators is attractive to 

managers because this is where the most extensive management activities currently occur (vegetation, roads), and also 

because these measures are more easily collected via remote 

sensing and existing GIS data, and do not require more 

labor-intensive field surveys. Measuring and understanding 

both upslope and in-channel processes, and the relationships 

between them, is critical. Taking into account the difficulties encountered by other parallel aquatic-monitoring 

programs, more formal testing of the AREMP conceptual 

model is warranted.

Benchmarks for assessment—

In the data-assessment step of analysis, indicators are 

typically compared against some benchmark (alternatively 

referred to as standards, thresholds, or evaluation criteria) 

to come up with a measure of watershed or aquatic-habitat condition. This has proven to be one of the greatest 

challenges, particularly given the expanding recognition 

of the reliance of aquatic habitats on dynamic processes of 

disturbance and renewal. Such monitoring faces the fundamental challenge of using static measurements (with limited 

temporal frequency) to measure dynamic processes. 

Stoddard et al. (2006) described a number of common 

approaches to choosing benchmarks: reference conditions, 

best professional judgment, interpreting historical condition, extrapolating from empirical models, and ambient 

distributions. The first two AREMP reports (10 and 15 

year) relied on empirical models and expert judgment to 

set evaluation criteria (Gordon and Gallo 2011). To accommodate environmental heterogeneity, separate thresholds 

were solicited for seven aquatic provinces identified in the 

NWFP area. To accommodate environmental heterogeneity, separate thresholds were solicited for seven aquatic 

provinces identified in the NWFP area. In most provinces, 

experts were unwilling to commit to standards in higher 

gradient streams for some attributes (floodplain connectivity, pool frequency, pool-tail fines, and median substrate 

diameter), so they were not included in the evaluation of 

these sites. 
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GENERAL TECHNICAL REPORT PNW-GTR-966

The most recent (20-year) AREMP report switched 

to using reference conditions to set criteria for in-channel 

conditions and upslope vegetation. Reference criteria were 

chosen using a nearest-neighbor approach, which matched a 

site to the five to seven nearest reference sites, based not on 

geographic distance but rather on similarity of largely invariant site characteristics (e.g., gradient, geology) (Bates Prins 

and Smith 2007). This approach was more empirically based 

than previous assessments; it set standards for higher gradient 

stream reaches and established a consistent method across 

the whole NWFP area. The use of the reference-condition 

approach in a monitoring program has important associated 

assumptions. The selection of reference sites should match 

the distribution of states in the ecosystem, reflecting the 

spatial and temporal dynamics at play. These values or 

thresholds are often either a direct judgment call or a chosen 

percentile of the overall disturbance distribution. In more 

highly disturbed ecoregions, few sites may qualify, as was the 

case with the Oregon/Washington Coast Range and the Franciscan provinces in the latest AREMP assessment (Miller 

et al. 2016). The nearest-neighbor approach did not rely on 

provinces/ecoregions, but rather incorporated environmental 

variability more directly through site characteristics. 

Another key consideration in development of reference 

distributions is including the entire natural range of conditions that an ecosystem can experience (Lisle et al. 2007, 

NRC 2000, Stoddard et al. 2006). Relative to the ACS and 

development of AREMP as originally conceived (Reeves 

et al. 2004), it was generally assumed that there is a given 

condition or limited set of conditions that supports aquatic 

organisms, primarily fish and macroinvertebrates (e.g., Karr 

and Chu 1998). The panel of scientists and managers who 

initially framed the ACS assumed that favorable conditions 

for fish were constrained to areas with cold water and structural heterogeneity provided by physical habitat components 

such as large down wood and coarse substrates—conditions 

often associated with old-growth forests—thus, these 

conditions and the associated old-growth forested riparian 

habitats were assumed to be most suitable for fish.

Recent studies, however, have demonstrated that 

native salmonids (Howell 2006, Rieman and Isaak 2010, 

Sestrich et al. 2011) and aquatic invertebrates (Minshall et 

al. 1989) are capable of adapting to and being productive in 

a wide range of conditions, including those following major 

disturbances such as wildfire that affect stream conditions. 

Flitcroft et al. (2016a) found that although conditions for one 

life-history stage of salmonids may be unfavorable, other 

life-history stages may find the same conditions suitable, 

and populations may respond positively. Native salmonids 

may also change life-history tactics, such as by reducing 

age or size at maturity (Rosenberger et al. 2015). Evolving 

in naturally dynamic landscapes with infrequent to frequent 

fire (see chapter 3) and occasional landslides, these species 

appear to be resilient to a broad range of disturbances 

and environments that occurred under the natural range 

of variability. It is important for monitoring programs to 

incorporate this new perspective into the development of 

benchmarks and interpretation of results to better reflect the 

responses of aquatic organisms to both management and 

natural disturbances. The range of natural conditions likely 

spans recently disturbed sites as well as areas that have been 

undisturbed for hundreds of years or longer.

However, understanding the natural range of variability 

for an ecosystem is often difficult, owing to the extent and 

magnitude of anthropogenic effects (Miller et al. 2016, NRC 

2000, Steel et al. 2016, Stoddard et al. 2006). This may 

especially be the case in dry-forest regions in the NWFP 

area where fire exclusion has altered forest and riparian plant 

composition and structure (see chapter 3); in areas where 

invasive species are now a dominant component of communities (app. 1); or where the signature of past human activities (Steel et al. 2016) and pervasive “press” disturbances 

(Yount and Neimi 1990) such as timber harvest have influenced the entire landscape so that current conditions, which 

may be a departure from the historical range, may now be 

seen as the norm (Pinnegar and Engelhard 2008), though 

they may have been rare or unknown in the past. Even areas 

that may appear to lack any sign of current or historical land 

use—areas with no discernable sign of recent human-caused 

disturbances—may no longer be considered pristine (see 

chapter 12). The Pacific Northwest moist coniferous forest 

region has recently been described as a “human-forest 

ecosystem,” because people are now a foundational element 

of the system (Olson and Van Horne 2017).
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Because pristine areas may no longer exist in many, 

if not most, ecosystems, the reference-condition approach 

sometimes has been modified to use “least-disturbed 

conditions” as a reference (Stoddard et al. 2006). But 

depending on how this approach is applied, it may not 

include the full range of potential ecosystem conditions, 

especially in naturally dynamic landscapes as described 

above, where disturbance had been excluded. Worse, in 

today’s human-influenced forest landscape, there may be no 

locations that fit even the “least-disturbed” condition (see 

discussion in chapter 3). 

Excluding the natural range of variability in the 

reference population influences the assessment of current 

conditions (NRC 2000). This issue can be illustrated by 

using the down wood data from Reeves et al. (1995), who 

examined three watersheds in the Oregon Coast Range that 

differed in the lengths of time since the last large wildfire 

(see details in “Attribute Integration Approaches” below). If 

just the values from the watersheds that were at an intermediate time point and the longest time point from disturbance 

were included as being in the population of reference conditions, wood values would vary from 12 to 24 pieces of wood 

per 100 m of stream. Twelve wood pieces per 328 ft (100 m) 

might be considered an extremely low value, and 24 a high 

value. However, if the most recently disturbed system from 

this dataset were included in the pool of reference conditions, the lower bound would be near 6 pieces of wood/328 

ft, and the score for 12 pieces of wood/328 ft would be 

much higher, relatively speaking. Clearly, use of reference 

conditions to assess monitoring trends and their ecological 

relevance can be problematic if a wide range of variation is 

not included. Articulating how reference conditions were 

determined and the range of conditions they represent is 

essential to understanding the context for comparison, 

whether least-disturbed conditions, old-growth conditions, 

or professional judgment are used. 

The relatively small number of matched sites in the 

reference pool used for the 20-year report is a potential 

drawback. Further, only one site-matching metric, quadratic 

mean diameter of conifers, reflected forest-ecosystem 

characteristics; this metric is only a limited surrogate for 

seral stage and does not reflect forest type, both of which 

may influence stream characteristics. Concerning the 

reference-site approach more generally, there is also some 

question as to whether reference sites relatively free of 

human disturbance still exist, given widespread fire suppression and now climate change (see chapter 3) (Herlihy 

et al. 2008, Stoddard et al. 2006). To the extent that these 

concerns are true, it likely creates uncertainty concerning 

monitoring results that needs to be explored.

Other recent large-scale assessments have also used 

a variation of the reference-condition approach, but none 

have incorporated much detail on surrounding vegetation 

conditions. The NRSA (USEPA 2016) incorporated environmental variability more generally into their reference 

sites by selecting a different set of sites for each ecoregion. 

Thus, their reference distribution includes a larger number 

of sites than in the AREMP analysis, but the NRSA authors 

recognized that this approach might not account for finescale variability within ecoregions and made direct comparison of results between ecoregions problematic (Herlihy et 

al. 2008, USEPA 2016). They incorporated some finer scale 

measures of environmental variability (e.g., elevation) by 

including them as covariates in the multiple linear regression (MLR) equations that defined reference expectations 

for each indicator. The PIBO analysis incorporated environmental variability by using the MLR approach, but the 

only covariate related to forest condition was the percentage 

of the 295-ft (90-m) stream buffer in forested condition 

(Al-Chokhachy et al. 2010). 

The final step in applying the reference-condition 

approach involves choosing evaluation thresholds from 

the distribution of reference values and comparing site 

values to these thresholds. AREMP and PIBO selected the 

5th/95th percentiles of their reference distributions to define 

normalized scores, assuming that more extreme values 

might be outliers that could skew the scoring process. 

They then reported these values directly, so that scores 

approximated the percentile in the reference distribution. In 

contrast, NRSA chose to place all results into three classes 

(good/fair/poor) based on the less than 5th/5th–25th/greater 

than 25th percentiles of reference. The reference-condition 

approach may appear to be more empirical, but it still relies 

on professional judgment to set evaluation thresholds. 
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GENERAL TECHNICAL REPORT PNW-GTR-966

To promote success in ACS implementation, it is 

important to know how gains in watershed condition are 

measured. Because the natural range of variability occurring in a system over large spatial and long temporal scales 

occurs across a multidimensional continuum, it can be 

difficult, if not impossible, to incorporate into assessments 

(see chapter 3). One potentially useful approach is the use 

of “state and transition” models (e.g, Wondzell et al. 2007, 

2012). Although such models can be difficult to validate, 

they can still be useful. It can be helpful to view aquatic 

ecosystems as multistate systems resulting from a variety 

of natural disturbances, as well as exogenous or anthropogenic processes that can alter habitat conditions, biota, and 

ecological processes (Penaluna et al. 2016). Having the full 

range of potential variability classified into discrete states 

provides a way to begin enumerating the ways in which 

variation is arrayed over large spatial scales and how it 

changes over long temporal scales. We suggest further 

exploration of reference conditions and their potential 

utility for analytical approaches, including consideration 

of how to use them in concert with state-transition models 

such as those developed by Wondzell et al. (2007, 2012). 

The concept of the reference condition remains 

important in land management—not because it is a goal of 

management agencies to restore systems to some previous 

reference condition, but rather because knowledge of the 

historical range of variability can help inform choices 

about desired future conditions and, thereby, help determine management and restoration goals (chapters 3 and 

12). Theoretically, departure from the reference condition 

would provide a relative measure to evaluate watershed 

conditions for managers who seek to maintain or restore 

ecosystem and species diversity (Nonaka et al. 2007, 

Safford et al. 2012). The multistate conceptual approach 

(Penaluna et al. 2016, Reeves et al. 1995) clearly shows 

that “reference conditions” are, in fact, a distribution of 

conditions from watersheds in various ecological states, 

similar to successional states in terrestrial systems (see 

discussion later in this chapter). As such, “departure from 

the reference condition” is no longer just a watershed-scale 

question, but rather a regional-scale problem that considers 

the distribution of conditions across multiple watersheds. 

Equilibrium versus spatially and temporally dynamic 

ecosystem concepts and the choice of benchmark reference 

conditions will become even greater challenges in future 

assessments given the increasing influence of climate 

change. There is growing concern about the extent to which 

ecosystems in the NWFP area, and elsewhere, have been 

affected by climate change and altered disturbance regimes, 

such as fire exclusion (Hessburg et al. 2005, Luce et al. 2012; 

also see chapter 3). We are likely seeing, or will soon see, 

the development of ecosystems that are different from the 

present and at least the near past (Hobbs et al. 2009, Luce et 

al. 2012) (fig. 7-4). Some have called this a new geological 

epoch—the “Anthropocene” (see chapter 12). The conditions 

Figure 7-4—Conceptual roles for disturbance in a changing 

climate: (A) Disturbance could continue to operate much as it 

always has, with unique disturbance/recovery patterns, or (B) it 

could become the catalyst that forces ecosystems to shift rapidly 

and via alternate and uncertain pathways in response to climate. 

Source: Luce et al. 2012.
479

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

that result from these altered ecosystem trajectories could be 

very different from those that would be found in unaffected 

systems of the past or present, and they may not necessarily 

meet social or legal expectations (Luce et al. 2012). Using 

benchmarks based on our understanding of aquatic ecosystems today may also affect assessments of ecological consequences from natural and anthropogenic factors. We rephrase 

our statement from near the top of this section: the potential 

implications of these changes merit a primary research focus, 

but in the meantime it will be important that monitoring programs, whether they use reference conditions, least-disturbed 

conditions (e.g., Miller et al. 2017), decision-support models 

(e.g., Reeves et al. 2004), or other approaches, recognize 

and acknowledge these potential concerns in the process 

of analysis and the interpretation and application of results. 

(The topic of reference conditions is discussed in different 

contexts later in this report, including an expanded treatment 

of approaches for riparian restoration.)

Attribute integration approaches—

Integration of metrics—Watersheds and streams operate as 

integrated systems, and no one indicator is likely to accurately characterize their condition. A significant scientific 

challenge remains in how to reflect this integration in their 

assessment. Early efforts and ongoing regulatory guidance 

for assessing salmonid habitat look at a number of indicators individually, without an explicit procedure for integration (NMFS 1996, USDA FS et al. 2004). NRSA, the largest 

national assessment, also primarily reports on indicators 

separately (fish, macroinvertebrates, chemical and physical 

stressors), although many of their indicators are themselves 

composite metrics. They incorporate limited integration 

through their measure of relative risk, which looks at the 

likelihood of finding poor biological conditions in a river or 

stream when stressor concentrations are high, relative to the 

likelihood when they are low (USEPA 2016).

The AREMP monitoring plan was a pioneering 

attempt to integrate indicators into a composite watershed-condition index (Reeves et al. 2004). In practice, the 

extent of integration has declined in each of AREMP’s 

reports. The 10-year AREMP report integrated all upslope 

and in-channel variables into a single score for each 

watershed (Gallo et al. 2005). Trend was calculated only 

for the upslope portion; repeated measurements of sufficient in-channel sites were not available until the 20-year 

report. The 15-year assessment separated upslope and 

in-channel metrics for two reasons. First, the upslope data 

(GIS and remote sensing) covered the whole region, so 

there was no need to restrict that analysis to the in-channel 

subsample. Second, little correlation was found between 

the upslope and in-channel results, so it was believed 

that these outputs offered fundamentally different types 

of information. In addition, the mixing of stressors and 

responses has been criticized in other watershed indices 

(Schultz 2001).

The 20-year report maintained this upslope/in-channel 

split, and also reported the in-channel elements of physical 

habitat, macroinvertebrates, and temperature separately. 

Temperature was split off because it was collected under 

a different sample design, only at the lowest point in the 

watershed rather than at each site. Macroinvertebrates 

were separated from physical habitat because they are 

often considered a qualitatively different type of indicator: 

physical habitat as a condition or stressor, and macroinvertebrates as a response. It was also believed that reporting 

these indicators separately would better identify problems 

by not obscuring high and low values in an aggregated 

average. Although macroinvertebrate, physical habitat, and 

temperature data were not integrated in the 20-year report, 

additional analyses may be useful to further assess a combined metric, especially as novel techniques emerge that can 

address issues of spatial autocorrelation along linear stream 

networks (Peterson et al. 2013, Ver Hoef et al. 2014).

Other monitoring programs have built condition indices 

by combining indicators into a more integrated value. PIBO 

averages its physical channel attributes into a single index 

score, but maintains macroinvertebrates separately (Archer 

and Ojala 2016). The state of Oregon combines a number 

of chemical metrics into an overall water-quality index 

but also reports macroinvertebrates separately (Hubler 

2009). The national Forest Service watershed condition 
480

GENERAL TECHNICAL REPORT PNW-GTR-966

class combines upslope, riparian, and in-channel biotic and 

abiotic indicators into one overall watershed-condition score 

(Potyondy and Geier 2011).

Having the metrics for watershed condition assessed 

independently begs the question as to how to interpret 

overall condition relative to findings for instream habitat, 

stream temperature, and upland/riparian condition. Miller 

et al. (2017) acknowledged that reliance on a single biological metric can lead to erroneous interpretation of the 

biological condition of a watershed (e.g., Barbour et al. 

1999), and suggested that the findings of the four separate 

stream metrics can be used as multiple lines of evidence to 

look at watershed-condition trends. So, when concordance 

among the measures differs within a given watershed, 

for example, if one or two parameters show an improving 

trend while the third does not change or declines, one can 

better understand which parameter may signal a 

potential issue and spur additional investigation. 

(See additional discussion of this issue later in 

this section.)

Interpreting long-term changes in a single 

metric can be complicated. For example, Miller 

et al. (2017) reported a broad-scale change 

in the distribution of water temperatures 

toward lower temperatures and an increase 

in watersheds with improving aquatic macroinvertebrate assemblages across the NWFP 

area. Nonetheless, 55 percent of waterbodies 

monitored by AREMP in Oregon still exceed 

state water-quality standards for these parameters (ODEQ 2012). One potential reason 

for this apparent lack of agreement between 

Miller et al. (2017) and the increase in miles 

of water-quality-impaired streams in Oregon 

(ODEQ 2012) is the lack of concordance among 

the indicators in a given watershed, as was 

shown in figure 7-5. 

One parameter may be trending in a positive direction while another is outside or moves 

outside the acceptable range. Also, the number 

of streams surveyed by ODEQ for water-quality impairment has increased over the last 10 

years, and differences in the way specific metrics are used 

may explain some of these apparent differences. More 

research is needed to fully assess whether such monitoring 

results represent favorable ecological changes over the 

long term.

Generally, analytical approaches and their interpretation for broad ecosystem assessments are still developing, 

including novel uses of individual metrics and multivariate methods. The initial NWFP monitoring strategy 

was based on identifying key stressors and a conceptual 

model that linked ecosystem and species components 

(Mulder et al. 1999). The decision-support system based 

on expert judgement used for interpretation of metrics in 

the 10-year report (fig. 7-6) is prone to subjectivity and 

uncertainty, however, there may be no real alternative 

given the needs of policymakers, the complexity of the 

Figure 7-5—Relation between scores for overall watershed condition and 

condition of the macroinvertebrate communities for watersheds in the 

Northwest Forest Plan area in the assessment by Miller et al. (2017).
481

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

ecological systems, and existing information gaps (Pielke 

2007). The movement away from expert opinion in the 

20-year report raises a new set of questions about use of 

single metrics interpreted independently and without an 

ecological framework. Carlisle et al. (2008) suggested 

that if one of the parameters of interest in a sampling 

unit (reach or watershed) is outside the threshold value 

for suitable conditions, the unit as a whole is outside the 

suitable range. A more statistically rigorous approach was 

described by Bowman and Somers (2006) and Collier 

(2009). In sum, exploration of a variety of available 

approaches is merited and timely.

Summarization over space and time—

A final consideration related to data integration is how to 

aggregate and present data over space and time. Reporting 

units over the spatial extents of land ownerships, land 

authority jurisdictions (e.g., county), and land-use allocations can address management and policy objectives, but 

the relationship of environmental conditions over space and 

time (e.g., via ecological provinces, watershed hydrological 

units) is also fundamental to our scientific understanding of 

aquatic-riparian ecosystems, particularly under the disturbance ecology paradigm (Olson et al. 2017b). Broad-scale 

aquatic assessments often report results by one or more 

aggregated spatial subunits. 

Watershed

condition,

upslope and

riparian

AVE

In-channel

condition AVE

Roads AVE

Vegetation AVE

Substrate

Landslide risk

Water temperature

Wood frequency

[If gradient ≤2%]

Pools

Biological

[If gradient ≤6%]

AVE

AVE

AVE

AVE

D50

Fines, %

Pool frequency

Pool depth

Amphibians

Macroinvertebrates

Riparian tree size, mid/late-seral

(1) Watershed density

(2) Riparian density

(1) Road crossings

Watershed-wide MIN

Terrestrial

Aquatic

AVE

EPT

Intolerants

Key

(Relative weights in parentheses)

[Context switches in brackets]

Tree size, early-seral

Canopy cover

Figure 7-6—Example of a decision process for assessing the ecological condition of a watershed (Lanigan et al. 2012). AVE = average of 

scores; MIN = minimum; D50 = median particle size; EPT = Ephemeroptera, Plecoptera, Tricoperta index. See Reeves et al. (2004) for 

details.
482

GENERAL TECHNICAL REPORT PNW-GTR-966

Two types of units are evident in AREMP and other 

efforts. The first is based on ecological conditions. Similar 

to the other NWFP monitoring modules, AREMP reports 

results by seven aquatic provinces, which are similar to the 

physiographic zones developed in the NWFP planning process (FEMAT 1993: app. V-A). Broad ecological zones were 

similarly used in NRSA, both for the definition of reference 

conditions and the reporting of results (USEPA 2016). 

Hubler (2009) took a more water-centric approach, using 

water basins (hydrologic units, in particular HUC6, mean 

area ~10,000 mi2 [~25 900 km2]) as their principal reporting 

unit. Studies focused on fish populations have developed 

units to represent genetically and demographically independent groups of fish, referred to as evolutionarily significant units (ESUs) or distinct population segments (DPS) 

(McClure et al. 2003). 

A second type of spatial aggregation common in the 

aquatic-monitoring literature is by management units. 

AREMP reports on indicators by NWFP land-use allocations, which generally correspond to land use intensities. 

The National Water-Quality Assessment targeted their 

sample by land use disturbance levels and so displays many 

of its results by urban, agriculture, and mixed-use classes 

(Carlisle et al. 2013). Hubler (2009) reported their results 

by ownerships (federal, state, private industrial, private 

nonindustrial). PIBO’s regional reports have not broken 

down their data by management classes directly, but they 

have displayed results of all sites in concert with reference 

distributions, indirectly reflecting management classes 

(Archer and Ojala 2016).

In earlier AREMP reports, the NWFP aquatic 

provinces were the basis of alternate evaluation criteria. 

However, as described above, the most recent assessment 

used neighborhoods based on in-channel characteristics, 

and upslope zones based on forest types. Because the 

aquatic provinces are no longer used to set environmental 

parameters for the assessment, other aggregations may 

prove more useful. For example, the NWFP provides a 

common set of standards and guidelines for management 

in the region; they are implemented via management plans 

developed by each agency for each of their forests and 

districts. AREMP may wish to consider reporting by these 

unit and agency boundaries to increase their relevance to 

managers. Additionally, because these plans must address 

endangered species issues, the ESU and DPS boundaries 

may now be more relevant ecological units than the 

NWFP provinces.

AREMP’s mandate is only to assess conditions on 

federal lands under the jurisdiction of the NWFP. However, 

nonfederal lands have been shown to be important, both 

for their effects on federal land conditions as well as for 

containing potentially productive fish habitat (Burnett et al. 

2007, Reeves et al. 2016a, Van Horne et al. 2017). Further 

investigation in how to link AREMP data with assessments 

covering nonfederal lands could help address this gap, for 

an all-lands approach to watershed assessments in the moist 

coniferous forest ecosystem.

Because watershed conditions differ naturally over 

time, individual watershed ratings may be truly meaningful 

only when considered in some larger aggregation (Poole et 

al. 2004, Reeves et al. 2004). Thus, the end goal of AREMP 

was to look for changes in the distribution of watershed 

conditions in the whole NWFP area over time. As a baseline 

for comparison, AREMP chose to simply use conditions in 

the first monitoring period, because the other options considered (historical conditions, simulated natural conditions) 

would have been challenging to implement. Some other 

major programs have also used initial monitoring results as 

baseline conditions (Archer and Ojala 2016, USEPA 2016), 

whereas others have simply focused on one point in time, 

for example, using their most recent data (Carlisle et al. 

2013, Hubler 2009). To our knowledge, historical conditions 

have not been estimated directly from past records, and simulation of natural conditions has been attempted only over 

considerably smaller spatial scales (Wondzell et al. 2007).

Finally, analytical approaches and their interpretation 

for broad ecosystem assessments are still developing, 

including novel uses of individual and multivariate methods. The rich AREMP dataset is ideal for comparison of 

alternative analytical approaches to assess watershed condition. Despite uncertainties and challenges faced by the 10-, 

15-, and 20-year AREMP reports, reported trends support 

the intent of the ACS to sustain and improve conditions of 

federally managed watersheds in the NWFP area.
483

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Components of the Aquatic 

Conservation Strategy

Riparian Reserves

Riparian reserves were intended to define and delineate 

the outer boundaries of the riparian ecosystem and to 

encompass the portions of a watershed most tightly coupled 

with streams and rivers (FEMAT 1993). These areas were 

assumed to provide the ecological functions and processes 

necessary to create and maintain habitat for aquatic and 

riparian-dependent organisms over time. This includes dispersal corridors for a variety of terrestrial and riparian-dependent organisms, and connectivity of streams within 

watersheds (FEMAT 1993). In 1993, the Forest Ecosystem 

Management Assessment Team (FEMAT) developed three 

management scenarios for riparian reserves along fish-bearing and non-fish-bearing streams (FEMAT 1993). Each 

scenario required a reserve width on fish-bearing streams 

of two times the height of a site-potential tree (minimum of 

300 ft [91.4 m]), defined as the average maximum height the 

dominant tree would be expected to attain given the growing conditions at that location. On non-fish-bearing streams, 

the width of the riparian reserves varied from one-sixth of 

a site-potential tree-height (minimum of 25 ft [7.6 m]) to 

one-half of a site-potential tree-height to one site-potential 

tree-height (FEMAT 1993). One scenario was integrated 

into each of the 10 landscape alternatives developed and 

evaluated by the FEMAT (1993) scientists.

The Secretaries of the Interior and Agriculture selected 

FEMAT’s Option 9 as their preferred option, which required 

a riparian-reserve network that was two site-potential 

tree-heights wide on fish-bearing streams and one-half 

of a site-potential tree-height on most non-fish-bearing 

streams. Interim boundaries of the riparian reserves were 

extended to a full site-potential tree-height on all non-fishbearing streams between the draft and final environmental 

impact statements (USDA and USDI 1994a) to increase the 

likelihood of success of the ACS, and to provide additional 

protections from timber management and road building for 

non-fish organisms that use the area in or near streams as 

habitat or migratory corridors (USDA and USDI 1994a). On 

some fish-bearing streams, two site-potential tree-heights 

from the edge of a stream may not encompass the whole 

floodplain, which can be an important source of large wood, 

making it critical to recognize and protect the entire floodplain (Latterell and Naiman 2007). This was accomplished 

in the ACS by requiring the boundary of the riparian reserve 

to extend to the edge of the 100-year floodplain (USDA and 

USDI 1994a). These boundaries were considered interim 

until a watershed analysis, which could adjust the size of the 

riparian reserve, was completed (USDA and USDI 1994a).

Depending on the degree of dissection of the forested 

landscape by streams, riparian reserves along both perennial and intermittent streams may occupy between 40 and 

90 percent of the landscape (FEMAT 1993, Hohler et al. 

2001). Interim riparian reserves of this magnitude, coupled 

with key watersheds and late-successional reserves, have 

provided a connected watershed-level reserve system for 

terrestrial, riparian, and aquatic ecosystems (Everest and 

Reeves 2007). However, the area of the forested landscape 

contained in the riparian reserves has fueled a controversy 

regarding riparian protection, resulting in new research to 

evaluate prescribed widths of riparian-management areas 

and a reexamination of existing scientific literature on the 

subject (Everest and Reeves 2007). The following sections 

summarize some of the recent key literature relating to the 

functions and size of riparian reserves. 

Ecological functions—

The scientific basis for delineation of interim riparian 

reserves in the NWFP was derived from two sets of curves 

showing the relationship between various ecological 

functions provided by riparian zones and distance from the 

channel (figs. 7-7 and 7-8). These curves were developed 

by FEMAT scientists based on the scientific literature that 

was available at the time, and on professional judgment 

when sources of information were incomplete (see table 7-2 

for original sources). The original relationships (FEMAT 

1993) that were incorporated into the NWFP (USDA and 

USDI 1994a) suggest that most ecological functions could 

be maintained by reserves equal to or less than the distance 

of one site-potential tree-height. The functions include beneficial effects of root strength for bank stability, litterfall, 

shading to moderate water temperatures, and delivery of 

coarse wood to streams (fig. 7-7A). In addition, the majority 

of moderating effects on sediment delivery to streams 
484

GENERAL TECHNICAL REPORT PNW-GTR-966

from overland erosion associated with upland activities 

generally occur within a distance of one site-potential 

tree-height (Castelle et al. 1994, Naylor et al. 2012). The 

FEMAT scientists also provided a margin for error allowing 

for incomplete science, unknown cumulative effects, or 

strategic uncertainty in defining interim riparian reserves 

prior to watershed analysis. Everest and Reeves (2007) 

concluded that science published since original development 

of the FEMAT curves has generally supported the original 

assumptions and judgments. 

Recent studies of wood recruitment suggest that 

changes in some of the ecological function curves may 

be supported. According to the graph of the relationship 

between the cumulative effectiveness of an ecological 

process and the distance for wood recruitment from the 

immediately adjacent riparian area in fish-bearing streams, 

developed in FEMAT (1993), about 60 percent of wood 

recruitment from the immediate riparian area along 

fish-bearing streams occurs within one-half of a tree-height 

(fig. 7-7A). This graph was based on a limited number 

Cumulative effectivenes of ecological function (percent)

0 0.2 0.5 1

100

0

Shading

Coarse wood

debris to stream

Litter

fall

Root

strength

A

0 0.2 0.5 1

100

0

Distance from channel (tree-height)

Coarse wood

debris to stream

Original

Modified

B

Cumulative effectivenes of ecological function (percent)

Soil 

moisture

Soil

Radiation temperature

Air 

temperature

Wind speed

Relative

humidity

0 0.5 1 2 3

100

0

A

Relative

humidity,

from above

0 0.5 1 2 3

Relative

humidity,

adjusted

100

0

Distance from stand edge 

into forest (tree-heights)

B

Figure 7-7—(A) Relation of distance from stream channel to 

cumulative effectiveness of riparian ecological functions (FEMAT 

1993: V-27); (B) modified effectiveness curve for wood delivery 

to streams as a function of distance from the stream channel. The 

original curve was changed based on scientific literature developed since the original curve was portrayed in FEMAT (1993). 

Source: Spies et al. 2013.

Figure 7-8—(A) Relation of distance from stream channel 

to cumulative effectiveness of ecological factors influencing 

microclimate in riparian ecosystems (FEMAT 1993: V-27); (B) 

modified effectiveness curve for relative humidity as a function of 

distance from the stream channel. The curve was changed based 

on scientific literature developed since the original curve was 

portrayed in FEMAT (1993). Source: Reeves et al. 2016a.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

of studies (McDade et al. 1990, Van Sickle and Gregory 

1990) and the professional judgment of scientists involved 

with FEMAT. More recent studies on the sources of wood 

(Gregory et al. 2003, Spies et al. 2013, Welty et al. 2002) 

found that, at least in the Cascade Range of western Oregon 

and Washington, about 95 percent of the total instream 

wood inputs from the adjacent riparian area along fish-bearing streams came from distances of 82 to 148 ft (25 to 45 m) 

from the stream, representing a distance of 0.6 to 0.7 of a 

site-potential tree-height for this area (fig. 7-7B). The shape 

of this curve differs from the FEMAT curve (fig. 7-7A), 

which showed that 95 percent of the wood-recruitment 

function of the same streams occurs within a distance equal 

to about 0.95 of the height of a site-potential tree. 

A primary purpose for the extension of the boundary 

of the riparian reserve of the NWFP from one site-potential 

tree-height to two on fish-bearing streams was to protect and 

enhance the microclimate of the riparian ecosystem within 

the first tree-height (USDA and USDI 1994a). At the time 

the ACS was developed, the only research on the effects of 

clearcutting on microclimatic conditions in adjacent forests 

had been done in upland forests on level terrain (Chen 1991). 

Those studies found that the influence of recent clearcuts (10 

to 15 years old) extended from tens of yards (e.g., soil moisture and radiation) to hundreds of yards (e.g., wind velocity) 

into adjacent unharvested stands. Based on the initial work 

of Chen (1991), FEMAT (1993) hypothesized that a second 

tree-height could provide a considerable safety margin from 

negative effects of intensive management on riparian areas, 

in terms of relative humidity and other microclimatic effects 

in the riparian reserve along fish-bearing streams (FEMAT 

1993) (fig. 7-8A). 

Since the ACS and associated ecological-function 

curves were originally formulated, a number of research 

efforts have examined the effects of forest management on 

microclimate in riparian areas. The vast majority of this 

work has focused on air temperature and relative humidity 

in small, headwater streams; few studies were conducted 

along larger streams (see review by Moore et al. 2005; also 

Olson et al. 2007, 2014). The magnitude of harvest-related 

changes in microclimate in riparian areas is usually 

inversely related to the width of the riparian buffer and 

the type and extent of management activities on the outer 

(upslope) edge. Some studies failed to show any edge effect 

between clearcuts and riparian buffers composed of intact 

mature forest (i.e., the extent of change in microclimatic 

conditions resulting from the presence of a clearcut on upslope edge of the riparian area) (Anderson et al. 2007, Rykken et al. 2007). Other studies have found that edge effects 

varied from a distance of 98.5 ft (30 m) (Anderson et al. 

2007, Rykken et al. 2007) to 148 ft (45 m) (Brosofske et al. 

1997) from the stream. At the other extreme, Ledwith (1996; 

as cited by Moore et al. 2005) found that above-stream 

temperature decreased and relative humidity increased as 

buffer widths increased up to 492 ft (150 m). Rykken et al. 

(2007) attributed the lack of an edge effect to a “stream 

effect,” described by Moore et al. (2005), who noted that the 

stream can act as a heat sink and a source of water vapor 

during the day, thus keeping near-stream microclimates 

cooler and more humid than areas farther from the stream. 

Rykken et al. (2007) suggested that this stream effect might 

counteract edge effects of harvest on microclimate, thereby 

reducing the distance that harvest effects penetrate into 

riparian zones, relative to the distances measured in upland 

forest edges (e.g., from those projected by Chen et al. [1993] 

in uplands). Moore et al. (2005) also posited that cool, moist 

air might be carried by down-valley breezes, contributing to 

this stream effect. 

The FEMAT microclimate curves were based on upland 

studies of forest-edge effects and thus they do not necessarily 

Table 7-2—Literature sources used to develop the 

original curves of ecological functions in riparian 

reserves in FEMAT (1993)

Function Sources

Root strength Burroughs and Thomas 1977

Wu et al. 1986

Wood delivery Beschta et al. 1987

McDade et al. 1990

Van Sickle and Gregory 1990

Litterfall Professional judgment

Shading Beschta et al. 1987 

Steinblums 1977

Microclimate Chen 1991
486

GENERAL TECHNICAL REPORT PNW-GTR-966

apply to riparian areas with a strong stream effect, protected 

topographic position, and retention of some canopy in 

the adjacent managed stand. Reeves et al. (2016a) suggest 

that a one tree-height buffer on fish-bearing streams (fig. 

7-8B) would reduce most potential effects on microclimate 

and water temperature in near-stream environments from 

timber harvest in areas on the edge of the riparian reserve, 

particularly when some trees are retained in the harvest unit. 

In general, most studies show that microclimatic changes 

in temperature and relative humidity seldom extend farther 

than one site-potential tree-height from the clearcut edge 

into an intact riparian buffer composed of mature forest (see 

review by Moore et al. 2005 and references cited therein). 

However, the large variety of effects measured in different 

studies demonstrates that substantial uncertainties remain 

about the size and management of riparian reserves. These 

uncertainties have important implications when considering 

changes in the width of the NWFP riparian reserves. 

Increased stream temperature following forest harvest 

is one of the most frequently mentioned management 

concerns, and one that retention of riparian buffers is 

clearly designed to mitigate. Generally, the smaller the 

riparian area and the more extensive the activities, the 

greater the effect on stream temperature. Clearcut logging 

without riparian buffers usually leads to large, post-harvest 

increases in stream temperature, and the width of the 

riparian buffer needed to limit, or even eliminate, temperature increases remains uncertain (see reviews by Moore et 

al. 2005 and Leinenbach et al. 2013). Given these uncertainties, management prescriptions that reduce the width of 

the riparian reserve or allow some tree harvest within the 

reserve remain controversial. 

The NWFP area encompasses a wide array of bioclimatic conditions, across its latitudinal span, west to east with 

distance from the ocean and rain-shadow effects of mountain 

ranges, and with increasing elevation. Given this variation, 

we describe only a few broad, general patterns in riparian 

vegetation here. In subsequent sections, we contrast these patterns with present-day patterns in areas that were previously 

logged, especially where logging pre-dated the establishment 

of current forest-practices rules and allowed harvest right up 

to streambanks. Although these general trends are important 

considerations, we also emphasize that more detailed local 

knowledge will be critical for determining appropriate 

management goals and planning specific actions. 

Riparian and upland vegetation along headwater 

streams in moist or wet forest types is typically dominated 

by conifers (Nierenberg and Hibbs 2000, Pabst and Spies 

1999, Sheridan and Spies 2005) (fig. 7-9A). However, 

conifer density can be lower in riparian zones compared 

to adjacent terrestrial areas (Sheridan and Spies 2005), 

hardwoods are uncommon in both riparian and upslope 

Figure 7-9—Conceptual representation of (A) vegetative conditions in headwater and (B) mid-order streams in the Northwest 

Forest Plan area. 
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areas, and there are no clear differences in shrubs between 

the two zones (Sheridan and Spies 2005). Many mosses 

and liverworts are also found at the wetted edges of small 

streams or on wood and rock in and along the channels 

(Hylander et al. 2002). In these wet forest types, tree canopies are often dense, limiting sunlight and therefore primary productivity. As a result, headwater streams depend 

on allochthonous (coming from outside the stream) inputs 

of litter and terrestrial invertebrates from the adjacent 

riparian forests, with as much as 95 percent coming from 

within 45 to 83 ft [13.6 to 25.3 m] of the channel (Bilby and 

Heffner 2016), as the primary energy source for aquatic and 

riparian organisms in these streams and for those lower in 

the network (Baxter et al. 2005, Gomi et al. 2002, Leroy 

and Marks 2006, Richardson et al. 2005, Wallace et al. 

1997, Wipfli and Baxter 2010). Allochthonous material is 

exported to downstream areas as dissolved organic carbon, 

coarse (>1 mm, >0.04 inches) particulate organic matter, 

and to a much lesser extent, as fine particulate organic 

matter (Gomi et al. 2002, Richardson et al. 2005), which 

contribute to the productivity of fish-bearing streams. The 

structure and composition of the riparian vegetation determines the quality, quantity, and timing of the allochthonous 

input (Cummins et al. 1989, Frady et al. 2007), all of which 

influence overall stream productivity.

Forests in riparian zones and adjacent uplands become 

increasingly different as the size of streams increases 

(fig. 7-9B). In the middle portions of stream networks, the 

riparian forest is more diverse than along headwater streams 

(Acker et al. 2003, Johnson et al. 2000, Sarr and Hibbs 

2007). Riparian forests along many mid-sized streams still 

remain dominated by conifers, but they are often mixed 

with deciduous trees such as alder (Alnus spp.), big-leaf 

maple (Acer macrophyllum), willow (Salix spp.), and cottonwood (Populus spp.). Big-leaf maple and California black 

oak (Quercus kelloggii) can be common in riparian zones in 

the southern portion of the NWFP area. 

Some studies in mid-sized streams have shown that 

conifer basal area nearest the stream can be lower owing to 

reduced survival from disturbances such as flooding (Hibbs 

and Giordano 1996, Pabst and Spies 1999). Also, the availability of growing sites might be limited; conifers preferentially establish on “microtopographic ridges” created by old 

tree-falls and behind wood jams (Fetherston et al. 1995). As 

a result, tree density near the stream can be about half of that 

of upland stands (Acker et al. 2003, Rot et al. 2000, Wimberly 

and Spies 2001). In contrast, Pollock et al. (2012) suggested 

that there is little difference in tree density between upland 

and riparian stands. All these studies, however, did find that 

the basal area of conifers in streamside stands is greater than 

in stands farther from the channel or in adjacent uplands. 

Streamside trees can be among the largest in a watershed 

(Poage and Tappeiner 2002), and thus can be the source of 

the largest down trees (conifers) found in the channel (i.e., the 

key pieces) (Rot et al. 2000), which are generally recruited to 

the channel by undercutting at high water (Abbe and Montgomery 2003, Acker et al. 2003, Benda et al. 2003).

In the Oregon Coast Range, hardwoods were most 

abundant in the area closest to the channel of streams in the 

middle portion of the stream network (Pabst and Spies 1999, 

Wimblerly and Spies 2001), particularly in unconstrained 

reaches (Acker et al. 2003), and they decreased in density 

moving away from the channel. This mix of hardwoods and 

conifers is important ecologically (Sponseller and Benfield 

2001, Sponseller et al. 2001) and is frequently maintained 

by periodic flooding (Sarr and Hibbs 2007). The vegetative 

diversity provides diverse habitat for a suite of terrestrial 

and riparian organisms; hardwoods are especially important 

for riparian mollusks (Foster and Ziegltrum 2013) and 

Neotropical migrant and resident bird species (Pearson and 

Manuwal 2001). Riparian areas dominated by hardwoods, 

particularly nitrogen-fixing red alder (Alnus rubra), have the 

potential to increase primary (Cornwell et al. 2008, Kominoski and Pringle 2009, Kominoski et al. 2011, Schindler and 

Gessner 2009, Swan et al. 2009) and secondary productivity 

and invertebrate diversity in adjacent streams (Piccolo and 

Wipfli 2002, Srivastava et al. 2009, Wipfli and Musslewhite 

2004). Watersheds with mixed hardwood/coniferous riparian 

vegetation in the Oregon Coast Range received nearly 30 

percent greater influx of terrestrial invertebrate biomass than 

streams with conifer-dominated riparian areas (Romero et al. 

2005). The loss or reduction of deciduous litter could potentially influence the structure, composition, and productivity 

of riparian and aquatic biota (Wallace et al. 1997, 1999)
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GENERAL TECHNICAL REPORT PNW-GTR-966

Although these broad general patterns hold across 

much of the NWFP area, we do not mean to give the 

impression that the riparian forests and their adjacent 

uplands were uniformly forested. Rather, these forests 

were a complex, shifting mosaic of vegetation patches, 

presenting a landscape with great spatial variability 

and temporal dynamics (see more detailed discussion in 

chapter 3). Wildfire was the primary factor driving forest 

dynamics across the Oregon Coast Range (Wimberly 

et al. 2000) and other parts of the region (see chapter 

3), although windthrow, insects, and disease can also 

be important. As a consequence, upland forests, even 

when assessed at large spatial scales, showed substantial 

variation in the area and ages of forests. For example, over 

long periods, the proportion of upland forest in old-growth 

condition, when summed over areas of more than 4.9 

million ac (2 million ha), ranged from 25 to 75 percent; 

at the scale of late-successional reserves as specified in 

the NWFP (~98,842 ac [40 000 ha]), the amounts of old 

growth could range from 0 to 100 percent (Wimberley et 

al. 2000). 

In addition to the factors described above for upland 

forests, riparian forests are also influenced by fluvial and 

geomorphic processes such as floods, debris flows, and 

bank erosion. State-and-transition simulations of the natural 

disturbance regime in the Oregon Coast Range (Wondzell 

et al. 2012) showed that 51 percent of the riparian network 

was in mature forest (stand age of 66 to 200+ years). The 

simulations also showed that the long-term average forest 

composition was highly variable. Only 2 percent of the 

riparian network was in a nonforested condition, 28 percent 

was alder dominated, 40 percent was in mixed alder/conifer 

stands, and only 29 percent was in conifer-dominated stands 

(see table 5 in Wondzell et al. 2012). The specific results 

cited above pertain only to the central Oregon Coast Range, 

but it is clear that no single condition—defined by stand 

composition, structure, and tree age—can represent the full 

distribution of naturally occurring conditions over large 

areas. Rather, riparian forest conditions, when assessed over 

broad landscapes, showed a distribution of conditions that 

resulted from the combined influences of natural disturbances and plant succession.

Human impacts and restoration—

Riparian forests throughout much of the NWFP area have 

been changed by the land use activities that have taken place 

over the past century. As a consequence, the present-day 

forests may frequently differ in structure and composition 

from the presettlement forests that preceded them (McIntyre 

et al. 2015, Naiman et al. 2000, Swanson et al. 2011). This 

is particularly evident in an estimated 30 to 50 percent 

of the riparian ecosystems in the NWFP area that have 

been converted to plantations, based on the percentages 

of plantations in upland forests (see chapter 3). Riparian 

forested areas were harvested extensively, often to the edge 

of the stream, prior to the advent of current policies (Everest 

and Reeves 2007). In many cases, the riparian zones were 

subsequently planted with the most commercially valuable 

conifers, primarily Douglas-fir (Pseudotsuga menziesii), 

resulting in the development of dense, relatively uniform 

conifer stands and a decrease in hardwoods. In other cases, 

conifers were not successfully reestablished in logged 

riparian zones that are now dominated by alder with a dense 

salmonberry (Rubus spectabilis) understory, as observed 

at the reach scale by Hibbs and Giordano (1996). In watershed-scale simulations, Wondzell et al. (2012) estimated 

that, under historical conditions, 28 percent of the stream 

network in the Oregon Coast Range was in alder-dominated riparian forests, and that presently it is more than 

40 percent. Fire suppression in dry forests with high- or 

moderate-frequency fire regimes has likely altered the structure and composition of riparian vegetation in ways similar 

to those described for upslope forested areas—namely an 

increase in the density of shade-tolerant conifers and a 

reduction in hardwoods (see chapter 3). In moist forests, 

with infrequent fire regimes, fire suppression has likely 

reduced the area of early-seral conditions in uplands and 

riparian areas (see chapter 3). Similarly, the removal of large 

conifers along rivers in the coast redwood (Sequoia sempervirens) range of northern California has been associated 

with increased dominance by alder (Madej et al. 2006). 

Clearly, the direct effects of logging on the structure and 

composition of present-day riparian forest can be varied, but 

overall, the distribution of conditions has changed dramatically relative to those under natural disturbance regimes.
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Indirect effects of logging have also modified riparian 

forests. For example, rates of landslides and debris flows have 

increased in heavily roaded and logged watersheds (Goetz 

et al. 2015, Guthrie 2002, Jakob 2000), which has led to systematic changes in riparian vegetation. Debris-flow tracks are 

frequently scoured free of large wood and subsequently recolonized by red alder (Russell 2009, Villarin et al. 2009), with 

large wood deposited in runout zones. Further, the frequency 

of debris flows and landslides has contributed additional sediment to stream channels, driving more severe floods, with the 

combined effect of increasing the width of stream channels 

(Lyons and Beschta 1983). Exposed gravel bars within these 

channels are most often colonized by hardwoods, leading to 

substantial changes along the stream corridor.

Restoration challenges—

The changes to riparian forests described above create 

substantial challenges for restoration. For example, thinning 

of dense riparian Douglas-fir stands could open stands, 

allowing increased hardwood presence and thereby increasing the diversity of riparian vegetation, while also promoting 

growth of the remaining trees to decrease the time needed 

to grow trees large enough to act as key structural elements 

in the stream channel. Although such restoration treatments 

may speed the restoration of some ecological functions 

(USDA and USDI 1994a), they also may reduce dead wood 

(chapter 3), and may present risks, such as development of 

novel conditions and loss of a particular species or ecological 

condition. Concerns about the tradeoffs between potential 

gains and potential losses, or other management issues, 

appear to have limited restoration activities, particularly 

within the first site-potential tree-height of streams. Reeves 

(2006) estimated that 48,000 ac (19 400 ha) of riparian 

reserve in the matrix of the NWFP area was treated for 

restoration purposes using some form of vegetation management, primarily thinning, in the first 10 years of the Plan. 

Between 2010 and 2015, an additional estimated 38,719 ac 

(15 669 ha) in the Forest Service’s Pacific Northwest Region 

(Region 6) were commercially or noncommercially thinned 

(table 7-3). FEMAT (1993) estimated that 2.2 million ac (890 

000 ha) of riparian reserves were outside of other reserves 

and congressionally withdrawn areas in the NWFP area. 

Table 7-3—The estimated area of riparian reserves in the Northwest Forest Plan area in the 

Pacific Northwest Region of the U.S. Forest Service where active management that produced 

trees for commercial (primarily in the second tree-height of the riparian reserve) and restoration 

(noncommercial) purposes has occurred in 2010–2015

Area of riparian reserve managed 

National forest Commercial Noncommercial

Hectares Acres Hectares Acres

Deschutes 168 415 461 1,139

Fremont-Winema 0 0 0 0

Gifford-Pinchot 1031 2,548 301 744

Mount Baker–Snoqualmie 125 309 0 0

Mount Hood 674 1,665 0 0

Okanogan–Wenatchee 331 818 2150 5,313

Olympic 750 1,853 454 1,122

Rogue River–Siskiyou 142 351 616 1,522

Siuslaw 3923 9,694 203 502

Umpqua 883 2,182 622 1537

Willamette 2835 7,005 No data No data

Total 10 862 26,841 4807 11,878

Source: USDA Forest Service Pacific Northwest Region.
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GENERAL TECHNICAL REPORT PNW-GTR-966

Because this is not the total area of riparian reserves, it is 

not possible to estimate the fraction of the riparian reserve 

in the NWFP area that has undergone restoration. However, 

it is clear that the area that has been treated represents a 

relatively small proportion of the riparian reserves in total, 

and of the amount that has been altered by past activities.

Primary reasons for the limited amount of restoration 

activity are various and probably include (1) differing 

perspectives about the characterization of reference conditions, conservation, and management; (2) concerns about 

the potential effects of mechanical treatments on stream 

temperature and wood recruitment; (3) concerns about rare 

and little-known organisms that made managers reluctant to 

alter default prescriptions (Reeves 2006); and (4) trust (see 

chapter 12). We explore the potential challenges associated 

with these restoration activities below.

Reference condition versus restoring function—

Restoration activities necessarily require a “target” condition or conditions toward which the restoration activity is 

intended to move a system. One way to select a target for 

restoration goals is to identify a minimally disturbed condition and use it as a reference to which the current condition 

can be compared. The minimally disturbed condition is 

commonly called the reference condition. Although intellectually appealing, the selection of a reference condition 

is fraught with potential biases. For example, Pollock et al. 

(2012) set very stringent requirements on stand attributes that 

would be acceptable as a reference condition for Douglas-firdominated stands in riparian forests of western Washington 

state: choosing undisturbed, single-storied, conifer-dominated stands ranging in age from 80 to 200 years, and excluding 

stands dominated by hardwoods or shrubs that showed evidence of recent severe disturbance—including disturbances 

such as wildfire, insects, and disease—because these disturbances may themselves have been a product of fire exclusion 

or climate change. Also, stands with these features were 

assumed to be the successional climax forest for this size of 

stream, and such stands had been greatly reduced by logging.

The study by Pollock et al. (2012) illustrates some of 

the challenges inherent in finding reference conditions—

they are often rare and may not represent the historical 

range of conditions that existed before extensive anthropogenic modification of upland and riparian vegetation. 

Ideally, reference conditions would be identified in areas 

with similar potential vegetation and in relatively close 

proximity, or at least within the same ecoregion, so that the 

reference provides an appropriate comparison for similar 

forest stands (NRC 2000). Because of their focus on older 

conifer-dominated patches and the assumption that these 

types of stands represented the primary natural vegetation 

of streamsides in more confined terrain, Pollock et al. (2012) 

were able to identify only a small portion of the existing 

riparian forests in which stands meeting their criteria 

for dominance by older Douglas-fir trees could be found 

(only 117, or 3.3 percent, of the 3,521 potential sites met 

the filtering criteria). These stands were widely scattered, 

spanning a broad latitudinal and climatic range in western 

Washington. Further, they lumped together both upland 

stands and riparian stands, and the only riparian reference 

stands were located in the western Washington Cascade 

Range. Thus, the applicability of the results to other stand 

types and locations is very limited. Nonetheless, Pollock 

et al. (2012) illustrated that a stringent filtering approach to 

identifying reference sites could contribute to characterization of reference conditions at the patch or stand scale (e.g., 

stand density and tree size) for evaluating riparianmanagement options for Douglas-fir riparian stands in 

western Washington. The Douglas-fir patch-scale reference 

conditions could also be used in setting management goals 

for the entire landscapes of a larger riparian zone. A similar 

approach could be applied to other stand types or regions to 

provide a more complete system of reference conditions for 

riparian management in the Pacific Northwest. 

Another approach to setting reference conditions 

(although they did not call them “reference conditions” at 

the time) for riparian zones was used by Pabst and Spies 

(1999) and Nierenberg and Hibbs (2000) in the Oregon Coast 

Range. They sampled along first- through fourthorder streamsides without roads or a history of logging, and 

having no evidence of wildfire at least 80 years. Vegetation 

was sampled in transects from randomly selected starting 

points. Hence, the samples contained areas dominated by 

older conifers as well as patches of hardwoods and shrubs, in 

proportion to their occurrence in the riparian area. Smaller, 
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recent areas of geomorphic disturbances, disease, and windthrow would have been included in the samples. The studies 

focused in particular on how vegetation differed between 

streamsides and uplands at a site, controlling for differences 

in environment and disturbance history. Generally, these 

studies found that conifer dominance decreased from the 

uplands to the streamside, and that many areas within 53 

ft (16 m) of streams were typically a mosaic of conifers, 

hardwoods, and shrubs even along streams in relatively 

confined topographic settings. Conifer-snag densities were 

relatively low 17 snags/ac (6.9 snags/ha) within 53 ft (16 m) 

of streams, and about one-quarter of the densities found at 

distances of more than 53 ft (16 m) from streams (Pabst and 

Spies 1999). These studies could be used in developing management guidelines for riparian forests in the Oregon Coast 

Range. Note, however, that this approach (random samples of 

unmanaged riparian vegetation) did not sample many areas 

that had grown for several centuries since wildfire and also 

did not sample in large areas that were recently affected by 

fluvial, geomorphic, and fire disturbances, which would have 

been an important part of the historical range of variability 

in these ecosystems at watershed scales (Spies et al. 2002). 

Wondzell et al. (2012) used state-and-transition models to 

explore the range of ecological states of the riparian network 

of a large river network in the central Oregon Coast Range. 

They used GIS methods to partition the stream network and 

its valley floor into discrete reaches, which were classified into 

potential geomorphic and vegetation types. A state-and-transition model was then developed for each potential type that 

included all possible states that could result from succession, 

natural disturbance, and land use activities. Wondzell et al. 

(2012) found that the structure and composition of the current 

riparian vegetation differed from the historical; there were 

fewer conifers, particularly the largest (>30 inches [76.2 cm]), 

and more alder-dominated patches. They clearly stated that 

their simulation results “should be interpreted as hypotheses 

of likely outcomes,” and that, despite several model limitations, they can be used to “hindcast” expected historical 

distribution of riparian forest conditions.

Part of the debate about restoration needs for riparian 

areas may derive from differing views of riparian reference 

conditions (as a goal for restoration), and how they differ 

with scale and across watersheds and the NWFP region. 

Although many studies (e.g., Acker et al. 2003, Hibbs and 

Sarr 2007, Pabst and Spies 1999) have found that riparian 

vegetation and upland vegetation frequently differ in 

structure, composition, and dynamics depending on stream 

size, some have noted that differences between riparian and 

upland vegetation may be small for some stand types, and 

that in some cases upland sites can supplement riparian sites 

to increase sample size for describing target conditions for 

riparian management. For example, Pollock et al. (2012) 

noted that, for Douglas-fir-dominated stands in western 

Washington, “both forest types [upslope and riparian] are 

generally similar, but riparian stands have more live tree 

wood volumes and basal areas, suggesting they may be 

growing on sites that are more productive.” Therefore, they 

concluded that riparian restoration in Douglas-fir-dominated riparian zones should aim to produce stand characteristics with densities and sizes of live and dead trees that 

are within the range of reference conditions (both upland 

and riparian). On the other hand, others (Gregory 1997, 

Pabst and Spies 1999, Welty et al. 2002, Wimberly and 

Spies 2001) have found that the type and magnitude of 

differences in features between upslope and riparian forests 

can be large, suggesting that upslope vegetation should not 

be assumed to be a reference for designing and assessing 

managed strategies for riparian vegetation in other stand 

types, or where riparian stands differ significantly from 

upland stands (e.g., in floodplains). 

This variety of findings makes it difficult for managers 

and regulators to design and implement management 

actions in riparian reserves. We suggest that each of the 

approaches examined above—that of Pollock et al. (2012), 

Pabst and Spies (1999), Nierenberg and Hibbs (2000), and 

Wondzell et al. (2012)—offers important information that 

would contribute to building a “reference condition”-based 

strategy to examine current conditions, to project likely 

outcomes of planned management activities, and to help 

evaluate the tradeoffs between potential risks and benefits of any overall management strategy. For example, a 

modeling approach like the state-and-transition models of 

Wondzell et al. (2012) could be used to generate an expected 

historical distribution of states for the riparian vegetation 
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within a stream network. The results could be used to 

identify relatively little-disturbed watersheds across the 

ecoregion and the monitoring plots located within those 

watersheds; individual plots could then be compared to specific states in the state-and-transition model. Those states 

could be attributed with values for various metrics (e.g., 

cover, basal area, tree densities, snag densities, species composition), as was done by Pabst and Spies (1999). Because 

anthropogenically disturbed states are also included in the 

state-and-transition models, something similar could be 

done to attribute these states with empirical data. The models could then be used to hindcast the historical distribution 

of state classes, and descriptive metrics from the empirical 

data could then be linked to the historical distribution. This 

result could be compared to the current condition. Also, the 

models could be used in forward simulations, incorporating 

different land use choices, to project how the distribution 

of conditions might be expected to change over time in 

response to various management strategies. Whatever 

approach is used, it will be important for managers and 

regulators to understand the limitations of the research they 

use to design and support proposed actions, which in turn 

necessitates that researchers clearly identify the limitations 

of their research (such as how broadly or to what ecosystem 

type they can be applied), and recognize the large variation 

in the inherent structure and composition of riparian areas 

across the NWFP area. 

Riparian thinning and water temperature—Because the 

current distribution of conditions of riparian forests in many 

stream networks is far different from the historical distribution, there is substantial interest in active restoration 

treatments—especially thinning dense conifer plantations 

(Reeves et al. 2016a) or logging hardwood-dominated 

stands and replanting to convert them to conifer dominance 

(Cristea and Janisch 2007). Although these treatments are 

not inconsistent with the ACS, which generally allowed 

thinning for ecological objectives in the area beyond 120 to 

150 ft (36.6 to 45.7 m) to a distance of one site-potential treeheight, they could potentially exceed the 0.3 °C “non-degradation standard” for water-quality effects of logging. The 

0.3 °C standard is important from a regulatory perspective, 

limiting potential cumulative effects from multiple actions, 

none of which individually might be sufficient to impair water quality. Alternatively, restoration treatments might speed 

the attainment of desired future conditions. These decisions 

pose critical management challenges. Clearly, there are risks 

from any active restoration treatment, but choosing not to act 

also poses risks, not only by increasing the time needed to 

attain a desired future condition, but also leaving the riparian zone at greater risk of uncharacteristic disturbance—for 

example, dense conifer stands in dry forest zones are more 

prone to high-severity wildfire (see chapter 3). Also, there 

may be increases in primary production (Warren et al. 2016) 

and fish growth (Wilzbach et al. 2005) with the opening of 

the canopy along small and medium streams. 

Reach-scale studies clearly demonstrate that solar 

radiation is the primary factor affecting stream-water 

temperatures during summer (Leinenbach et al. 2013). 

Thus, the likely effect of forest harvest on stream temperatures will be a function of the amount of shade lost. 

The largest effects will generally be seen with clearcut 

logging right to the streambanks, whereas retention of 

forested buffers tends to reduce these effects, as does 

thinning rather than clearcutting outside the buffer. The 

actual magnitude of stream-temperature increases can vary 

greatly and is determined by factors such as discharge, 

water depth, width, flow velocity, hyporheic exchange, and 

groundwater inflows (Janisch et al. 2012, Johnson 2004, 

Moore et al. 2005). Topographic shading can also influence 

water temperatures, particularly in small streams flowing 

in narrow, steep-sided valleys, as much as or perhaps more 

than shade from streamside forests (Zhang et al. 2017). It is 

important to remember that canopy removal also results in 

nighttime long-wave radiation loss, leading to lower water 

temperatures. This effect contributes to increased thermal 

variability, with poorly understood biological consequences. 

Relatively few studies have examined the effects of 

riparian thinning on stream-water temperature. A few 

studies have examined clearcut harvesting combined with 

partial harvest of riparian buffers (Kreutzweiser et al. 2009, 

Macdonald et al. 2003, Mellina et al. 2002, Wilkerson et al. 

2006). These studies, like those cited above, suggest that the 

effect of riparian thinning on summer stream temperatures 

will be correlated positively with the amount of forest 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

canopy removed and inversely with the distance from the 

stream that the activity occurs, and thus the amount of 

shade lost (Leinenbach et al. 2013). However, the amount 

of shade lost from a given thinning treatment can be highly 

variable, and the small number of studies makes it difficult 

to draw strong generalities. The amount of shade lost can 

be smaller than the amount of tree basal area removed, 

and in one study, removal of 10 to 20 percent of the basal 

area had no measureable effect on angular canopy density 

(Kreutzweiser et al. 2009). Further, any shade loss and 

stream-temperature increases from riparian thinning are 

likely to be short lived because riparian forest canopies can 

close relatively quickly (within 3 years) after thinning (Chan 

et al. 2006, Yeung et al. 2017). The potential magnitude of 

stream-temperature increases in response to riparian thinning will be highly dependent on forest attributes outside 

the riparian buffer, the buffer size, the prethinned riparian 

forest attributes (Leinenbach et al. 2013), the thinning prescription, and the thermal sensitivity of the stream (Janisch 

et al. 2012). Further research is needed to improve our 

understanding of the impacts of thinning, but there is some 

evidence that light thinning may not substantially increase 

stream temperatures. 

Managers thus face the following question: Are there 

places in the stream network in which riparian thinning 

would help speed attainment of the reference distribution, 

and where present-day thermal regimes would suggest that 

small temperature increases would not have significant 

detrimental effects on fish (Groom et al. 2011) or other 

organisms of interest? This question tends to be investigated 

at the reach scale. For example, Pollock et al. (2012) examined the potential effects of a thinning treatment on the 

development of riparian forest-stand attributes, and Groom 

et al. (2011) looked at summer maximum temperatures 

in the treated reach. Rarely are these questions expanded 

to consider the context of the distribution of reference 

conditions across the larger watershed. If they were asked, 

the question would then become: Are the conditions of the 

treated reach overrepresented with respect to the reference 

distribution, or underrepresented? In the Oregon Coast 

Range, for example, it is clear that not all reaches would 

be maintained in conifer-dominated mature forest under 

a natural disturbance regime (Wondzell et al. 2012). If 

dense, young, conifer-dominated stands are currently more 

abundant than expected from the reference distribution, 

then should some of those stands be thinned, perhaps mimicking windthrow events that open stand canopies and allow 

development of multistoried, mixed stands? If so, how many 

should be treated to better change the long-term trajectory 

of conditions from the current distribution toward one that 

is closer to the reference distribution?

Riparian thinning and large wood—The absence or diminished quantity of wood in streams throughout the NWFP 

area is a primary concern for managers and regulators 

because wood is important for creating habitat and performing other ecological functions. Thinning and other active 

management in plantations in riparian zones can reduce the 

potential amount of wood that can be delivered to streams 

(Beechie et al. 2000, Pollock et al. 2012) and the forest 

floor (Pollock and Beechie 2014, Pollock et al. 2012) if the 

trees are removed from the site. Additionally, thinning may 

negatively affect habitat, at least in the short run, for some 

species that are favored by dense conifer cover (see chapter 3 for more details), potentially increase water temperature (Leinenbach et al. 2013), and reduce carbon storage 

(D’Amore et al. 2015). However, there are also many potential benefits to thinning, including increasing structural diversity, species richness, flowering and fruiting of understory shrubs and herbs (Burton et al. 2014, Carey 2003, Hagar 

et al. 1996, Muir et al. 2002), and faster development of mature-forest conditions, including very large trees with thick 

limbs that may be used for nesting by marbled murrelets 

(Brachyramphus marmoratus) (Carey and Curtis 1996, 

Franklin et al. 2002, Tappeiner et al. 1997) (see chapter 5). 

Furthermore, variable density thinning of the overstory in 

the second-growth riparian forest could accelerate recovery 

of old-growth characteristics by promoting dominance of 

redwood in the southern portion of the NWFP area (Keyes 

and Teraoka 2014) (see chapter 3). 

Considerable research on wood dynamics in the 

NWFP has been done in wet forests of California, Oregon, 

and Washington, but there has generally been less research 

in areas with drier forest types, including northern California. Riparian areas in redwood-dominated forests are 
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particularly distinctive owing to the exceptional productivity, low mortality, and slow decay of those trees (Benda 

et al. 2002). Benda and Bigelow (2014) compared wood volumes across four different regions of northern California, 

including the Coast Range, Klamath Mountains, Cascade 

Range, and Sierra Nevada, as well as variation associated 

with forest management. They noted that coastal streams 

had much greater wood volumes, which they attributed to 

greater forest biomass and higher growth rates of redwood 

forests, as well as slower decay of large wood pieces. 

They also observed that some second-growth forests along 

streams in that region had wood volumes comparable to 

those in old-growth forests, owing to heavy debris remaining from tractor-era logging before the 1970s. Although 

the volumes were similar, streams in old-growth areas 

had fewer but larger logs (Benda et al. 2002). Benda and 

Bigelow (2014) also found that streams in the Cascades and 

Sierras that they characterized as more heavily managed 

had larger volumes of stream wood than less intensively 

managed areas in the same regions. They conjectured that 

managed forests could have higher rates of tree mortality 

because of stem exclusion (successional phase characterized by the rapid growth and biomass accumulations of a 

particular species, and intense competition among cohorts 

[Oliver 1981]) than more mature, but not yet decadent, 

unmanaged forests with lower tree densities. 

A panel of scientists from the Forest Service and the 

National Marine Fisheries Service recently reviewed the 

published literature on the effects of thinning in riparian 

areas (Spies et al. 2013). Their major conclusions are 

summarized below: 

• Accurate assessment of thinning effects requires 

site-specific information. The effects of thinning 

regimes on dead-wood creation and recruitment (relative to no thinning) will depend on many factors, 

including initial stand conditions, particularly stand 

density, and thinning prescriptions.

• Conventional thinning generally produces fewer large 

dead trees. Thinning with removal of trees (conventional thinning) will generally produce fewer large 

dead trees across a range of sizes over the several 

decades following thinning and the lifetime of the 

stand relative to equivalent stands that are not thinned. 

• Thinning to develop old-growth structure is most 

beneficial in dense young stands less than 80 years 

old and especially those less than 50 years old. 

• Conventional thinning can accelerate the development of very large diameter trees. In stands that 

are conventionally thinned, the appearance of very 

large diameter dead trees (greater than 40 in [102 

cm]) may be accelerated by up to 20 years relative to 

unthinned plantations, depending on thinning intensity and initial stand conditions. 

• To produce down wood immediately, thinning can 

leave trees that are cut as part of the restoration program (see Benda et al. 2016 for details).

• Thinning can increase the amount of pool-forming wood only when the thinned trees are larger in 

diameter than the average diameter of pool-forming 

wood (which varies with stream size).

• Effects of thinning on instream wood need to be 

placed in a watershed context. Assessing the relative 

effects of riparian thinning on instream wood loads 

at a site and over the long term requires an estimation of the likely wood recruitment that will occur 

from both the banks and downstream movement 

from upstream sources, and the rate of decay and 

downstream transport of wood from the site.

• The ecological effects of thinning on instream habitat will vary depending upon location in the stream 

network. Riparian-management practices can be 

altered to match the ecological functions of streams.

• Variation in thinning is essential to increase species 

diversity and heterogeneity (i.e., do not use the same 

prescription everywhere). 

Since Spies et al. (2013) summarized the state of the 

science, other studies have increased our understanding of 

the effect of restoration thinning in riparian areas. Benda 

et al. (2015) simulated the idea of adding wood to channels 

during thinning by modeling the amount of instream wood 

that would result from thinning a 50- to 80-year-old Douglas-fir stand from below (i.e., removing the smallest trees 

to simulate suppression mortality) from 400 to 90 trees/

ac (988 to 222 trees/ha), which is considered a moderate 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

amount of thinning, then directionally falling or pulling 

over varying proportions of the harvested trees into the 

stream (table 7-4). This wood loading was compared to the 

amount that would be expected in the stream if the existing 

stand was not thinned. Not surprisingly, the amount of 

wood increased above the “no-thin” level immediately after 

the tipping simulation in all the wood-addition options. 

However, the cumulative total amount of wood expected in 

the stream over 100 years relative to the unthinned stand 

varied depending on the amount of wood delivered. Adding 

≤10 percent of the wood that would be removed during 

thinning resulted in less wood in the channel over time than 

the unthinned option (i.e., if the stand were not actively 

managed). When 15 to 20 percent of the volume of thinned 

trees from one side of the stream was directed to the stream 

at each entry, the total amount of dead wood in the channel 

exceeded the unthinned scenario over time (table 7-4). 

Thinning the stand again 25 years after the first thinning 

further increased wood levels (table 7-4). Carah et al. (2014) 

found that adding unanchored wood into the stream was 

less costly than securing the wood, and improved habitat 

conditions for coho salmon. Reeves et al. (2016a) included 

wood addition (tree-tipping) as a component of options for 

managing the riparian reserves on Oregon and California 

Railroad Revested lands of the BLM in western Oregon to 

accelerate attainment of restoration objectives.

Ecological tradeoffs—There are potential ecological 

consequences of limiting tree harvest (thinning) only to 

the outer portions of the riparian reserves. A myriad of 

ecological processes create and maintain the freshwater 

habitats of Pacific salmon (Bisson et al. 1997, 2009) and 

the ecological context in which they evolved (Frissell et al. 

1997). This is especially relevant to the goals of the ACS, 

which are broad and include more than aquatic conditions. 

Holling and Meffe (1996) contended that uniform management prescriptions often fail when applied to situations in 

which processes are complex, nonlinear, and poorly understood, such as in aquatic ecosystems in the NWFP area, 

and may lead to further degradation or compromising of 

the ecosystems and landscapes of interest (Dale et al. 2000, 

Hiers et al. 2016, Rieman et al. 2006). For example, managing for a single purpose (e.g., maximizing dead wood) 

may compromise or retard other ecological functions, such 

as development of hardwoods and shrubs or growing large 

trees, in areas near the stream (see previous discussion), 

and ultimately may alter the structure of the food web 

(Bellmore et al. 2013). Pollock and Beechie (2014) stated that “species that utilize large-diameter live trees will 

benefit most from heavy thinning, whereas species that 

utilize large-diameter deadwood will benefit most from 

light or no thinning. Because far more vertebrate species 

utilize large deadwood rather than large live trees, allowing 

Table 7-4—Predicted change in the estimated volume of wood in a stream channel under two different harvest 

options (single and double entry) over the simulated 100 hundred years (includes decay) when varying 

proportions of harvest wood are placed or felled into the stream channel

Change from no treatment

Scenario Single-entry thin

Double-entry thin (25 

years after first entry)

- - - - - - - - - Percent - - - - - - - - -

No treatment (reference) 0 0

Thin entire stand, no tipping -33 -42

Thin entire stand except with a buffer 32.8 ft (10 m) no-harvest buffer -7 -11

Thin with a buffer 32.8 ft (10 m) and tip 5 percent of the harvested wood -15 -15

Thin with a buffer 32.8 ft (10 m) and tip 10 percent of the harvested wood -6 +1

Thin with a buffer 32.8 ft (10 m) and tip 15 percent of the harvested wood +1 +16

Thin with a buffer 32.8 ft (10 m) and tip 20 percent of the harvested wood +6 +24

Source: Benda et al. 2016.
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GENERAL TECHNICAL REPORT PNW-GTR-966

riparian forests to naturally develop may result in the most 

rapid and sustained development of structural features.” 

We agree that tradeoffs exist and that prioritization will be 

needed (see chapter 12 for more discussion of tradeoffs). 

The choice of priority conservation targets (e.g., dead 

wood, plant-community diversity, large live trees, geomorphic disturbances) for riparian management is a difficult one 

to make, involving scientific criteria, risk assessment, and 

social values. Given the diversity of conditions in riparian 

areas at watershed and regional scales, it would make 

sense not to apply one-size-fits-all strategies, but rather to 

develop priorities based on a watershed-scale view (see “A 

context-dependent approach to riparian conservation and 

management” below). For example, Pollock and Beechie 

(2014) stated that “management strategies that seek to 

create a range of large live and dead tree densities across 

the landscape will help to hedge against uncertain outcomes 

related to unanticipated disturbances, unexpected species 

needs, and unknown errors in model assumptions.” It will 

be important to consider the full suite of ecological functions across a watershed; focusing only on one condition or 

metric may limit recovery of riparian ecosystems in ways 

that prevent full achievement of the broad objectives of the 

ACS. Given these broad objectives, a more comprehensive 

watershed- and regional-scale consideration of all ecological 

processes, and studies to develop new and more complete 

approaches, may be more fruitful than focusing on only one 

or two metrics.

A context-dependent approach to riparian 

conservation and management—

A key component of the ACS is watershed analysis 

(FEMAT 1993), which is supposed to provide the context 

of a given location for adjusting the boundaries of, and 

allowing activities within, riparian reserves. However, the 

intent of watershed analysis was never realized (Reeves 

et al. 2006), owing to a number of factors including cost 

of analysis and the need to consider a multitude of species 

and their ecological requirements. Neither FEMAT (1993) 

nor the NWFP (USDA and USDI 1994a) provided explicit 

criteria for changing the riparian reserve boundaries or 

demonstrating that proposed changes would meet or not 

prevent attainment of ACS objectives over the long term. 

In addition, at the time, credible analytical tools to aid 

decisionmaking were lacking (Reeves 2006); a fixed-width 

approach is easy to administer and apply and is less costly 

than developing site-specific recommendations (Richardson et al. 2012). As a result, adjustments have proven 

difficult for the agencies to make (Naylor et al. 2012, Richardson et al. 2012), and interim boundaries of the riparian 

reserves remained intact in the vast majority of watersheds 

(Baker et al. 2006).

Since the development of the ACS, there has been a 

call in the scientific literature to allow discretion in setting 

site-specific activities (Kuglerová et al. 2014, Lee et al. 

2004, Richardson et al. 2012), which can be economically 

beneficial (Tiwari et al. 2016). Greater flexibility in the 

management of riparian areas would depend on the “context” of the area of interest (Kondolf et al. 2006, Montgomery 2004), and the primary management objective for the 

specific area (Burnett and Miller 2007). However, development of such an approach has been limited because of the 

reliance on “off-the-shelf” and one-size-fits-all concepts 

and designs, rather than on an understanding of specific 

features and capabilities of the location of interest (Kondolf 

et al. 2003, Naiman et al. 2012). A mix of approaches could 

be undertaken, recognizing ecological and other goals such 

as timber harvest, especially if applied over larger spatial 

scales (Burnett and Miller 2007, Miller and Burnett 2008, 

Olson and Rugger 2007), and if consideration is given to 

the distribution of populations of concern and connectivity 

among them (Olson and Burnett 2009, Olson and Kluber 

2014, Olson et al. 2007). 

There have been a few attempts to design and implement a site-specific approach. Cissel et al. (1999) proposed 

a plan based on variation in the disturbance patterns (in this 

case, wildfire) in the target watershed, and called for harvest 

of some older trees and a revision of the interim riparian 

reserves for the Central Cascades Adaptive Management 

Area. Olson and Rugger (2007) proposed a two-tiered 

approach to riparian management to first identify reaches 

in which sensitive species occur, then manage their critical 

habitat elements, hence varying riparian reserve management with species distributions. Olson and Burnett (2009) 

applied sensitive-species filters to criteria for designations 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

of habitats for connectivity within and among watersheds. 

Interwatershed connections provided by riparian areas are 

critical avenues of movement to new habitats. None of these 

approaches have been implemented to date.

Reeves et al. (2016a) proposed a context-dependent 

approach for management of the riparian reserves in the 

matrix of federal lands in western Oregon that divided the 

riparian reserve into inner and outer zones, with management tailored to the specific features and characteristics 

of individual stream reaches (Option B of Reeves et al. 

2016a). The context-dependent option was informed by new 

research, tools, and concepts, including: 

• The influence of the width of riparian area on microclimate (see earlier discussion). 

• Movement of amphibians along non-fish-bearing 

streams (Olson and Burton 2014, Olson et al. 2007).

• The distance to, and sources of, wood for fish-bearing streams (Spies et al. 2013). 

• Intrinsic potential, a concept for assessing the capability of a given set of geomorphic conditions in a 

stream reach to provide habitat for selected species 

of Pacific salmon (Burnett et al. 2007). 

• NetMap (Benda et al. 2007), a geospatial platform 

for watershed analysis that can, among other things, 

identify the location of some key ecological processes that influence aquatic and riparian ecosystems on the landscape and in the stream network.

• Concepts for managing riparian ecosystems and the 

activities that affect them, such as ecological forestry (Franklin and Johnson 2012) and tree-tipping 

(Benda et al. 2016).

Under the context-dependent option, current interim 

riparian reserves of two site-potential tree-heights along 

fish-bearing streams and one site-potential tree-height along 

non-fish-bearing streams would be retained in late-successional reserves and other special land designations (Reeves 

et al. 2016a). In lands allocated as matrix under the NWFP, 

the area of interest for aquatic conservation (Reeves et al. 

[2016a] referred to this as the riparian conservation area) 

extended upslope from the stream for a distance equal to 

the height of one site-potential tree along fish-bearing and 

non-fish-bearing streams. The riparian conservation area 

was divided into an inner and an outer zone depending on 

“ecological context,” based on four characteristics of each 

stream reach—susceptibility to surface erosion, debris 

flows, thermal loading, and habitat potential for target fish 

species—to determine the width of the inner zone. The 

entire riparian conservation area of the most ecologically 

sensitive stream reaches along fish-bearing and non-fishbearing streams could be managed solely for ecological 

goals for fish and other aquatic and riparian-dependent 

biota. In other fish-bearing and non-fish-bearing streams, 

the inner zone was 100 ft (30. 5 m) and 50 ft (15.3 m) wide, 

respectively (Reeves et al. 2016a). Active management was 

limited to stands age 80 years or younger in reserves (Spies 

et al. 2013), and tree-tipping (Benda et al. 2016) was used 

throughout the riparian reserve to ensure that harvest did not 

negatively affect wood recruitment to the stream (table 7-4).

Using the matrix in BLM-managed lands in western 

Oregon to illustrate the application, Reeves et al. (2016a) 

estimated that an average of 46 percent of the riparian 

reserve in a watershed would be managed solely for ACS 

goals. Also, an estimated average of 36 percent would 

achieve ACS goals along with other potential goals, which 

could include timber production, and 18 percent could 

be managed for a variety of purposes, including wildlife 

and timber, in accordance with NWFP requirements 

(Reeves et al. 2016a). In late-successional and other reserve 

allocations, which cover approximately half of the BLM 

lands in western Oregon, interim riparian reserves would 

remain unchanged. Assuming that half of the interim 

riparian reserves on BLM lands in western Oregon would 

remain unchanged, and applying their study estimates of 

changes in matrix, Reeves et al. (2016a) estimated that 

about 72 percent of the interim riparian reserves would 

remain solely devoted to ACS goals, and 19 percent would 

likely meet ACS goals and could also provide opportunity 

for achievement of matrix goals including limited timber 

production. The reduction of the width of the riparian 

reserve along fish-bearing streams to one tree-height would 

return an estimated 9 percent of interim riparian reserves 

to matrix on these lands.

The analysis of Reeves et al. (2016a) was not intended 

to provide a single recommendation for managing riparian 
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GENERAL TECHNICAL REPORT PNW-GTR-966

ecosystems. The primary purpose was to reevaluate riparian-conservation strategies using the latest scientific evidence. This or other options should be viewed as working 

hypotheses to be tested with monitoring and adaptive-management experiments. The analysis provides an example of 

how a context- and landscape-dependent approach could 

be designed to address multiple conservation goals of the 

ACS, the commodity goals of the NWFP, and the significant 

challenges of climate change. Although new science has 

refined our understanding of the ecological processes in 

riparian ecosystems, uncertainties and information needs 

remain. Thus, an adaptive-management approach and 

further research are critical to continual improvement and 

evaluation of this and other options for meeting the goals of 

the ACS (Stankey et al. 2005).

Key Watersheds

Tier 1 key watersheds (a total of 141, covering 8,154,500 

ac (3 300 000 ha) (fig. 7-10) were intended to serve as 

refugia for aquatic organisms or to have high potential for 

restoration (USDA and USDI 1994a). Tier 2 key watersheds 

provide sources of high-quality water, and comprised 23 

watersheds covering a total of about 1,112,000 ac (405 000 

ha) (fig. 7-10). Key watersheds are aligned as closely as possible with the late-successional reserves of the NWFP (areas 

designated to protect late-successional and old-growth 

ecosystems) and other officially designated reserve areas to 

maximize ecological efficiency (USDA and USDI 1994a), 

and to minimize the amount of area in which timber-harvest 

activities were restricted. A primary objective for tier 1 key 

watersheds is to aid in the recovery of ESA-listed fishes, 

particularly in the short term (FEMAT 1993). Tier 1 key 

watersheds in good condition at the time of the Plan’s inception were assumed to serve as centers for potential recovery 

of depressed populations. Those with degraded conditions 

were expected to have the greatest potential for restoration 

and to become future sources of good habitat.

The trend in the condition of key watersheds differed 

among assessments. Gallo et al. (2005) reported that a 

greater proportion of the key watersheds had their condition 

scores improve than did non-key watersheds. Lanigan et al. 

(2012) found key watersheds to be in better condition than Figure 7-10—Location of key watersheds in the Northwest Forest 

Plan area.

P. Eldred
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non-key watersheds, primarily because more than twice as 

many miles of roads were decommissioned in key watersheds as in non-key watersheds (Gallo et al. 2005, Lanigan 

et al. 2012), suggesting that land management agencies 

appear to recognize key watersheds as priority areas for 

restoration. Miller et al. (2017), however, saw no statistical 

differences between the two groups. 

Key watersheds were originally selected based on 

the professional judgment of the scientists involved with 

the development of the ACS, in consultation with fish and 

aquatic biologists and hydrologists from the national forests 

and BLM districts covered by the NWFP. Also, they were 

tightly aligned with late-successional/old-growth reserves, 

based in part on the assumption that streams in old-growth 

forests would be most favorable for fish (FEMAT 1993). 

New techniques (e.g., NetMap, Benda et al. 2007) and 

understanding of aquatic ecosystems now provide a different perspective on aquatic ecosystems and how they operate 

in space and time. 

New concepts such as intrinsic potential of fish habitat 

(Burnett et al. 2007), projections of climate change, and new 

questions as to whether stream conditions in old-growth 

forests are actually most favorable for native salmonids 

(Bisson et al. 2009, Reeves and Bisson 2009, Reeves et al. 

1995) are pivotal concepts that reframe our understanding 

of aquatic ecology and ecosystems. No formal evaluation of 

the potential effectiveness of the network of key watersheds 

was conducted during development of the NWFP, or has 

been undertaken since it was implemented. Fish populations 

in need of attention are clearly identified now, and it would 

be useful to investigate whether the current system is beneficial to those fish in terms of the overall distribution and 

the suitability of individual watersheds. Additionally, the 

distribution of other sensitive aquatic-riparian species (e.g., 

ESA-listed or petitioned herpetofauna) could contribute to 

this assessment.

Watershed Analysis 

Watershed analysis was designed to provide the context for 

management activities in a particular sixth-field watershed 

as the basis for developing project-specific proposals and 

determining restoration needs. It was envisioned as an 

analytical and not a decisionmaking process, involving 

individuals from a variety of scientific disciplines (USDA 

and USDI 1994a). Management agencies were expected to 

complete a watershed analysis before activities (other than 

minor ones) were initiated in key watersheds or riparian 

reserves (USDA and USDI 1994a). The version of watershed 

analysis advocated in the NWFP differs from previous 

versions (e.g., Washington Forest Practices Board 1993) and 

involves multiple disciplines and issues other than those that 

are specifically aquatic. 

Baker et al. (2006) estimated that about 500 watershed 

analyses had been done by 2003, but that the quality and 

effectiveness of these analyses differed widely. No formal 

assessment of watershed analyses has been completed as of 

this writing, so it would be prudent to conduct a comprehensive review and evaluation, and consider incorporating 

new analytical tools such as NetMap (Benda et al. 2007) to 

help improve the process and reduce costs while increasing 

the usefulness of the product. The watershed analysis 

process could also be reexamined so that it is conducted 

more efficiently and considers the appropriate spatial scales, 

including the watershed of interest and its context within 

the larger basin or region. The latter could be particularly 

relevant for effective planning at a landscape scale and to 

deal with climate change.

New Perspectives on Conservation of 

Riparian and Aquatic Ecosystems 

The ACS was premised on the view that aquatic ecosystems 

were dynamic in space and time, exhibiting a range of 

potential conditions, similar to the terrestrial systems in 

which they are embedded (FEMAT 1993). Aquatic ecosystems in Pacific Northwest forests are multifaceted and 

complex, and can be conceptualized as a set of ecological 

states (Penaluna et al. 2016, Reeves et al. 1995, Rieman et 

al. 2015), each with particular abiotic and biotic conditions, 

functions, and processes at any given time. The number and 

variety of ecological states in a domain (i.e., the range of 

conditions or range of natural variability for an ecosystem) 

is in constant flux in response to changes in local conditions, stochastic processes, legacies of past disturbance, 

and time since past disturbance (Beechie et al. 2010; Benda 
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GENERAL TECHNICAL REPORT PNW-GTR-966

et al. 1998; Liss et al. 2006; Miller et al. 2003; Reeves et 

al. 1995; Resh et al. 1988; Rieman et al. 2006, 2015; Wondzell et al. 2007). Examples of the variation that aquatic 

ecosystems can experience through time are shown for the 

central Oregon Coast Range (Reeves et al. 1995) (fig. 7-11A 

and table 7-5), and eastern Oregon (Wondzell et al. 2007) 

(fig. 7-11B). Larger streams and rivers in the lower portion 

of the network are less variable through time; those in the 

upper and middle portions are more dynamic (Naiman et al. 

1992). Because of the variation in the size and asynchronous 

nature of disturbance events (Allen et al. 1982, Malard et 

al. 2002, Schindler et al. 2010, Wiens 2002), conditions will 

vary over time among watersheds, resulting in a mosaic of 

biophysical conditions across the landscape. Unmanaged 

and minimally disturbed aquatic systems may actually 

exhibit a wider range of conditions than more heavily 

managed systems (Lisle 2002, Lisle et al. 2007).

A contrasting view holds that aquatic ecosystems tend 

to be in an equilibrium or steady state, and when disturbed, 

they are expected to return to predisturbance conditions 

relatively quickly (Resh et al. 1988, Swanson et al. 1988). 

Biological (Vannote et al. 1980) and physical conditions 

(Rosgen 1994) are presumed to be relatively constant 

through time and to be “good” (barring human interference) in all systems at the same time. Conditions in aquatic 

systems with little or no human influence and natural 

Figure 7-11A—Examples of the range of conditions that aquatic ecosystems experience: (1) a stream 90 to 100 years after the last disturbance, (2) 160 to 180 years, and (3) more than 330 years (Reeves et al. 1995) (see table 5 for specific details).
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

disturbance, particularly those associated with late-successional and old-growth forest, are assumed to have the most 

favorable conditions for fish (Fox and Bolton 2007, Murphy 

and Koski 1989, Pollock and Beechie 2014, Pollock et al. 

2012) and other aquatic organisms, and are most frequently 

used as references against which the condition of managed 

streams (e.g., Index of Biotic Integrity) (Karr and Chu 

1998) and effects of management actions can be assessed. 

Systems experiencing disturbances, such as wildfire or 

floods, are often immediately “restored” by attempting 

to reduce or eliminate erosional processes. For example, 

fences were placed in headwater streams following a 

Figure 7-11B—Examples of the range of conditions that aquatic ecosystems in eastern Oregon can experience through time (Wondzell 

et al. 2007).

Table 7-5—Features of streams from the Oregon Coast Range used in figure 7-11A

Feature/stream Harvey Creek (1) Franklin Creek (2) Skate Creek (3)

Time since disturbance (years) 90–100 160–180 More than 330

Number of pieces of wood/100 m 7.9 12.3 23.5

Mean depth of pools (m) 0.9 0.35 0.1

Dominant substrate Gravel Gravel Bedrock

Percent of fish assemblage juvenile coho salmon 98.0 85.0 100.0

Percent of fish assemblage juvenile steelhead 1.0 12.5 0

Percent of fish assemblage juvenile cutthroat trout 1.0 2.5 0

Source: Reeves et al. 1995.
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GENERAL TECHNICAL REPORT PNW-GTR-966

wildfire in Colorado to reduce the potential for erosion and 

debris flows (Chin et al. 2014). However, reaches lower 

in the stream network downcut, creating other concerns. 

Although this static ecosystem view is being questioned in 

the general ecological literature (Hiers et al. 2016, Jackson 

et al. 2009, Montgomery 1999, White and Jentsch 2001, 

Wohl et al. 2014), it is still being used to guide management 

and assess effects on aquatic ecosystems, and persists in 

environmental laws and policies developed in the 1970s, 

such as the Clean Water Act (Craig 2010). 

Resilience is the capacity of an ecosystem to absorb 

change and remain within the ecosystem state and domain 

in the face of natural disturbances and human stressors 

(Desjardins et al. 2015). As ecosystems undergo larger 

shifts from human stressors, the ecosystem can be redefined, with a completely different set of characteristics and 

a compromised or altered range of conditions (Bisson et 

al. 2009, Reeves et al. 1995). Some ecosystem components 

may persist through this transition, whereas others may be 

new components arising from human or climatic alterations, 

including the development of novel states that may result in 

the loss of selected ecosystem services and conditions for at 

least some native species (Penaluna et al. 2016). 

The physical aspect of these dynamics is understood 

conceptually (see review in Buffington 2012), but few 

mechanistic models currently exist to help us understand 

the potential effects of management on dynamic ecosystems 

(but see Wondzell et al. 2007), especially under climate 

change. As a result, consideration of dynamics remains 

largely conceptual, and holistic models of basin function 

(i.e., watershed analyses) are generally lacking, limiting the 

development of process-based applications of river management and restoration (Beechie et al. 2010). Also, there 

is also a tendency to focus on mean or median conditions 

while overlooking temporal variability as “noise” and 

losing sight of the considerable inherent variability that 

characterizes riparian and aquatic ecosystems (Fausch et 

al. 2002, Montgomery 1999), which is ecologically critical 

(Hiers et al. 2016). Accounting for this variability and for 

nonstationarity of fluvial processes is central to assessing 

potential effects of climate change on riverine ecosystems 

(Buffington 2012, Miller et al. 2003, Montgomery 1999). 

However, being able to incorporate this variability into 

restoration and mitigation actions may be limited by social 

concerns (Kondolf et al. 2006) (see chapter 12). 

Consideration of large spatial and temporal scales is 

critical to the development of management and conservation 

strategies for ecosystems (Dale et al. 2000, Holling and 

Meffe 1996), including a range of conditions for aquatic 

ecosystems (Fausch 2010, Fausch et al. 2002, IMST 1999, 

Liss et al. 2006, NRC 1996). This shift requires moving 

from the current focus on relatively small spatial scales, 

with little or no consideration of the relevance of time, to a 

focus that considers large spatial scales, specifically ecosystems and landscapes, over relatively long periods (tens to 

hundreds of years) (Bisson et al. 2009, Naiman and Latterell 

2005, Poff et al. 1997, Reeves et al. 1995). An example of 

the importance of relations between scales can be seen 

in the “portfolio effect” of the behavior of populations of 

sockeye salmon (O. nerka) in Bristol Bay, Alaska, identified 

by Schindler et al. (2010). This study found large variation 

in the number of fish in any local population over time. 

However, the variation among the many populations was 

asynchronous—not all were high or low at the same time. 

As a result, the total number of fish was relatively constant 

at the landscape scale, a pattern similar to the amount of 

old growth historically found in the Oregon Coast Range 

(Wimberly et al. 2000). This pattern appears to be disrupted 

in heavily managed systems (Moore et al. 2010).

Both the NWFP and new Forest Service planning rule 

(USDA FS 2012a) require managers to consider large spatial 

scales in designing, implementing, and evaluating management actions. The new planning rule also emphasizes 

ecosystem goals based on ecological integrity. This can be 

daunting given the lack of scientifically sound examples of 

how to design and implement forest management at large 

temporal and spatial scales (North and Keeton 2008, Reeves 

and Duncan 2009, Thompson et al. 2009) and the lack of 

adequate tools and guidance. Shifting the management 

focus to the landscape level and longer time intervals 

requires recognition of the principles of hierarchy theory 

and the relation among levels of organization to increase the 

potential for success of future riparian policies and practices 

(Fausch 2010, Fausch et al. 2002). 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Regulators may recognize the need to apply policies and 

regulations across broad areas, but may be constrained by 

the regulatory framework in which they are operating, and 

generally default to single standards that are applied across 

broad areas (e.g., National Marine Fisheries Service’s matrix 

of pathway and indicators) (NMFS 1999). This premise is 

inappropriate for addressing complex, multifaceted landscapes, however (Allen and Starr 1982; O’Neill et al. 1986, 

1989); instead, it is important to recognize that a multiwatershed landscape operates differently through time than does 

a single watershed, and that smaller spatial scales tend to be 

more variable over time than larger scales (Benda et al. 1998, 

Wimberly et al. 2000). Increasing levels of aggregation, 

especially as spatial scales increase, may obscure important 

system processes (Clark and Avery 1976) and may result in 

unrealistic expectations for ecosystems and contribute to 

the contention that often surrounds large-scale management 

proposals (Allan and Curtis 2005, O’Neill et al. 1986, Shindler et al. 2002). Also, the failure to recognize the different 

levels of ecological organization and the potential response 

of each to component parts of disturbance and management 

may incur unintended economic and social costs, such as 

repeated investment in ineffective restoration and management strategies (Caraher et al. 1999, Dale et al. 2000). 

The emerging consideration of ecosystem dynamics 

and large spatial and temporal scales has implications for 

approaches to restoration of aquatic-riparian ecosystems. 

Many restoration efforts have focused mainly on improving 

habitat attributes, primarily wood placement, and to a 

lesser degree on shade improvement for water temperature. 

These efforts too often aim to bring “stability” to degraded 

systems, and are viewed as the final phase of restoration (see 

Palmer et al. 2014). The dynamic approach, not yet broadly 

practiced, focuses on restoring ecological processes (Beechie 

et al. 2009, 2010; Bernhardt and Palmer 2011), including 

periodic inputs or reoccurrences of these important habitat 

attributes. This requires a shift from reliance on striving 

only to develop a particular condition (e.g., number of pieces 

of wood per unit length) or channel classification (e.g., 

Rosgen 1994) to a quantitative approach based on ecological 

processes, theory, empirical field methods, and limited 

modeling (Kline and Cahoon 2010, Wohl et al. 2005). 

Some researchers have pointed out that although 

restoration of ecological processes, such as flow, water 

temperature, habitat complexity, and connectivity, is a critical consideration in restoring many streams, it may not be 

sufficient for degraded channels, and can even worsen the 

ecological condition of the stream (Louhi et al. 2011, Tullos 

et al. 2009). For example, in restoring floodplain overflow 

potential, if riparian trees are removed from a previously 

closed-canopy stream, the underlying energy regime may 

change from one based on allochthonous resources to one 

driven by primary production. This may shift the stream 

farther from the desired ecological state and often toward 

algae-dominated streambeds and higher temperatures 

(Robinson 2012, Sudduth et al. 2011). Similarly, if the 

hydrologic regime is restored but there is no nearby source 

of invertebrate colonists, then the instream communities 

will remain altered (Sundermann et al. 2011). Finally, an 

overreliance on an in-channel focus (small-scale) may 

not address the stressor(s) that most limit recovery of the 

aquatic ecosystem; quite often this factor is water quality, 

and thus ecological recovery will not occur until the stressor 

is addressed (Beechie et al. 2010, Kail et al. 2012, Selvakumar et al. 2010). Examples of process-focused restoration 

are presented below in the section on climate change.

In addition to considering spatial complexity, temporal 

dynamics are particularly important to understand because 

many key ecological processes such as canopy closure, 

tree-fall, and fuel loading are related to the age of trees in 

riparian areas as well as time since disturbance. Temporal 

dynamics can be examined using models, but long-term 

studies and monitoring are needed to understand how systems respond over time (Hassan et al. 2005). One strategy 

that may be appropriate is to design monitoring to focus 

more on changes following major disturbances rather than 

focusing simply on short-term trends.

The other challenge posed by a dynamic perspective 

of aquatic ecosystems is the consideration of large spatial 

scales. Restoration efforts are generally performed at small 

spatial scales, with only a relatively small percentage of any 

watershed actually treated (Ogston et al. 2014, Roni et al. 

2010). Roni et al. (2010) estimated that a minimum of 20 percent of the habitat of a given species in a watershed should 
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GENERAL TECHNICAL REPORT PNW-GTR-966

be restored to detect a 25 percent increase in smolt (salmon 

or steelhead) numbers, the minimum detection level for most 

monitoring programs. They found that floodplain restoration 

yielded greater increases than in-channel restoration. However, because of the large variability in numbers for most 

populations (Bisson et al. 1997, Schindler et al. 2010), Roni 

et al. (2010) suggested that 100 percent of the habitat should 

be restored to have a significant ecological impact.

Non-Fish-Bearing Streams

The ecological importance of headwater streams, which 

generally make up 70 percent or more of the stream 

network (Downing et al. 2012, Gomi et al. 2002), was 

not well known or understood at the time the ACS was 

developed, but it is now better established in the scientific 

literature (Leigh et al. 2016, Richardson and Danehy 

2007). Headwaters are sources of sediment (Benda and 

Dunne 1997a, 1997b; May and Lee 2004; Zimmerman and 

Church 2001; see review by MacDonald and Coe 2007) 

and wood (Bigelow et al. 2007; May and Gresswell 2003, 

2004; Reeves et al. 2003) for fish-bearing streams; provide 

habitat (Kelsey and West 1998, Olson et al. 2007) (see 

chapter 6) and movement corridors (Olson and Burnett 

2009, Olson and Kluber 2014) for several species of native 

amphibians and macroinvertebrates (Alexander et al. 2011, 

Meyer et al. 2007), including recently discovered species 

(Dieterich and Anderson 2000); and may be important 

sources of food for fish (Kiffney et al. 2000, Wipfli and 

Baxter 2010, Wipfli and Gregovich 2002, Wipfli et al. 

2007; also see reviews by MacDonald and Coe 2007 

and Clarke et al. 2008). Wood jams in small streams are 

important sites of carbon storage (Beckman and Wohl 

2014), and these streams export large amounts of carbon; 

one-third is emitted to the atmosphere and the remainder 

transported downstream (Argerich et al. 2016).

Tributary junctions of headwater streams with larger 

channels are important nodes for regulating material flows 

(Benda et al. 2004, Gomi et al. 2002, Montgomery et al. 

2003) and cold water (Ebersole et al. 2015) in a watershed, 

and are the locations where site-scale effects from management activities are often observed (Richardson and Béraud 

2014). These locations have unique hydrologic, geomorphic, 

and biological attributes and differ in the types and amount 

of materials delivered to the channel, making them sites of 

high biodiversity (Benda et al. 2004, Danehy et al. 2012) 

Headwater streams are among the most dynamic 

portions of aquatic ecosystems (Benda et al. 2005, Hassan 

et al. 2005, MacDonald and Coe 2007, Naiman et al. 1992). 

Headwater habitats may range from simple to complex, 

depending on the amount of time since disturbance (such 

as landslides and debris flows). Following evacuation by a 

debris flow, headwater depressions and channels fill with 

material from the surrounding hillslopes, including large 

wood that falls into these channels, forming obstructions 

behind which sediments and wood accumulate (Benda and 

Cundy 1990, May and Gresswell 2004), and then empty 

again with the next landslide or debris flow (fig. 7-12). As 

a result, headwater streams are likely to exhibit a range of 

conditions across the landscape at any point in time.

This cycle of filling and emptying results in a punctuated movement of sediment and wood to larger, fish-bearing 

streams (Benda et al. 1998, Naiman et al. 1992), contributing 

to the long-term productivity of many aquatic ecosystems 

(Benda et al. 2003, Hogan et al. 1998, Reeves et al. 1995). 

A common consequence of past clearcutting is an absence 

of down wood to replenish the refilling process. This lack 

of wood may result in a chronic movement of sediment to 

larger channels, which could lead to both non-fish-bearing 

and fish-bearing channels developing characteristics different from those that occurred before forest management. 

Such conditions could be outside the range of variability to 

which native biota are adapted (Beschta et al. 2004), limiting 

the effectiveness of conservation and recovery programs. 

Wood enters streams via chronic and episodic processes (Bisson et al. 1987). Chronic processes, such as tree 

mortality and bank undercutting (Bilby and Bisson 1998, 

Murphy and Koski 1989), generally introduce single trees 

or a relatively small number of trees at frequent intervals. 

Wood from headwater streams, which originates from 

within 131 ft (40 m) of the channel (May and Gresswell 

2003), is delivered to fish-bearing streams by large, infrequent events, such as windthrow (Harmon et al. 1986), wildfire (Agee 1993), severe floods, landslides, and debris flows 

(Benda et al. 2003; May and Gresswell 2003, 2004; Reeves 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

et al. 2003). Geomorphic features of a watershed influence 

the potential contribution of upslope wood sources. Steeper, 

more highly dissected watersheds will likely have a greater 

proportion of wood coming from upslope sources than 

will watersheds with lower stream densities and gradients. 

Also, there is wide variation in the potential of headwater 

streams to deliver sediment and wood to fish-bearing 

streams, depending on channel steepness and angle of entry 

along the run-out track, among other factors (Benda and 

Dunne 1997a, 1997b; Brayshaw and Hassan 2009; Burnett 

and Miller 2007; May 2007). Culverts and other stream 

crossings can also impede wood movement from smaller to 

larger streams (Trombulak and Frissell 2000).

The presence of large wood from headwater streams 

influences the behavior of landslides and debris flows and 

the response of the channel to such events. Large wood in 

debris flows and landslides influences the run-out length 

of these disturbance events (Lancaster et al. 2003). Debris 

flows without large wood move faster and farther than 

those with wood, and they are less likely to stop high in the 

stream network. A debris flow without wood is likely to be 

a concentrated slurry of sediments of various sizes that can 

move at relatively high speeds over long distances, scouring 

substrate and wood from the affected channels. These types 

of debris flows are more likely to negatively affect fish-bearing channels, as compared to the potentially favorable 

effects that result from the presence of wood. Woodless 

debris flows can further delay or impede the development 

of favorable conditions for fish and other aquatic organisms. 

In contrast, those containing wood can help store sediments 

(Bunn and Montgomery 2004) and build terraces that can 

persist for extended periods (Lancaster and Casebeer 2007, 

May and Lee 2004).

Intermittent streams, which can make up half the total 

length of the stream network (Datry et al. 2014), connected 

to larger fish-bearing streams can provide important 

seasonal habitats for spawning and rearing by fish (Boughton et al. 2009, Wigington et al. 2006). In the Oregon 

Coast Range, growth and survival of juvenile coho salmon 

was higher in intermittent streams than the perennial 

mainstem (Ebersole et al. 2006, 2009; Hance et al. 2016). 

Identification, protection, and restoration of these streams 

is important to the success of conservation efforts for native 

fish across the NWFP area.

Figure 7-12—Conceptual illustration of the changes in channel morphology based on the time since the previous debris flow (May and 

Gresswell 2004).
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GENERAL TECHNICAL REPORT PNW-GTR-966

A rich non-fish community inhabits headwater streams 

throughout the NWFP area. For example, Olson and Weaver 

(2007) found 3 species of fish and 12 species of amphibians 

in stream reaches in 12 western Oregon study sites ranging 

from Mount Hood to Coos Bay. In this study and Olson 

and Burton (2014), torrent salamanders (Rhyacotriton spp.) 

dominate intermittent streams and appear to be sensitive 

to thinning in narrow riparian-management areas; NWFP 

riparian reserves appear to be benefiting retention of this 

aquatic-dependent community in abundant small streams 

in the region. Nevertheless, two torrent salamander species 

are currently petitioned for listing under the ESA; both have 

ranges that include significant tracts of nonfederal lands. 

Continuing and Emerging 

Topics of Concern

Water

Federal lands are important sources of fresh water for 

human consumption, recreation, agriculture, and environmental needs in the United States. These lands produce an 

estimated 24.2 percent of the Nation’s water supply, 18 

percent and 1.5 percent from Forest Service and BLM lands, 

respectively (Brown et al. 2008). In the West,5 federal lands 

contribute 66 percent of the mean annual water supply, 51 

percent of which comes from Forest Service lands and 5.4 

percent from BLM lands (Brown et al. 2008). Management 

strives to maintain the quality and quantity of this water. 

The extent of the contribution of federal lands to regional 

5

 The West is defined here as including the states of Arizona, 

California, Colorado, Idaho, Montana, New Mexico, Nevada, 

Oregon, Utah, Washington, and Wyoming.

water supplies was not well quantified at the time the 

NWFP and ACS were developed. 

The contribution of water from federal lands specifically in the NWFP area is also important; however, exact 

estimates are not currently available and were beyond the 

scope of this review. At the state level, the majority of 

water in the three NWFP states (California, Oregon, and 

Washington) originates from federal lands (table 7-6), 

with the bulk coming from Forest Service lands. Within 

the NFWP area, the amount of water flowing from federal 

lands varies among national forests and watersheds. Some 

forests, such as the Deschutes and Willamette National 

Forests, make relatively large contributions, 40 percent or 

more, to the flow of rivers whose watersheds they include 

(figs. 7-13A and 7-13B, respectively). Contributions from 

other forests are smaller (less than 20 percent) (fig. 7-13C) 

but nonetheless important. See “Climate Change” below 

for potential future issues pertaining to water supply and 

stream temperatures.

Roads

Roads provide necessary motorized access for forest 

management, recreation, and other beneficial purposes 

(Gucinski et al. 2001), but they can also have detrimental 

effects on native biodiversity and ecosystem function. 

The focus of the NWFP and ACS has been to address the 

negative effects of roads on aquatic ecosystems through a 

broad program of road decommissioning and upgrading, 

including remediation of chronic sedimentation and barriers 

to aquatic organism movement. Several syntheses describe 

the types, causes, and effects of road networks on streams, 

and meta-analyses concerning the ecological effects of 

Table 7-6—Contribution of federal lands and agencies to the total mean annual water supply 

of states in the Northwest Forest Plan area (percentage of mean annual water supply)

State All federal lands Forest Service

Bureau of Land 

Management Other

Percent

California 61.1 46.6 5.5 9.0

Oregon 55.3 44.0 9.4 2.0

Washington 60.2 41.5 0 18.7

Source: Brown et al. 2008.
507

Figure 7-13—Contribution of selected national forests in the Northwest Forest Plan area to the mean annual flow of adjacent watersheds: (A) Deschutes NCascades; (B) Willamette National Forest, western Oregon Cascades; (C) Siuslaw National Forest, Oregon Coast Range; and (D) Six Rivers National Fornia. (https://www.fs.fed.us/rmrs/projects/national-forest-contributions-streamflow).
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GENERAL TECHNICAL REPORT PNW-GTR-966

roads in general and specifically the delivery of sediment 

from mountain roads with low maintenance standards 

have been published (Croke and Hairsine 2006, Forman 

and Alexander 1998, Jones et al. 2000, Trombulak and 

Frissell 2000). Reducing the effect of roads and associated 

infrastructure remains a challenge for federal management 

agencies and others.

The vulnerability of roads to hydrologic changes and 

the associated effects on aquatic and riparian ecosystems 

differ based on topography, geology, slope stability, design, 

location, and use. Roads can affect streams directly by: 

1. Accelerating erosion and increasing sediment loading (Allan 2004, Daigle 2010, MacDonald and Coe 

2008, Suttle et al. 2004). 

2. Imposing barriers to the migration of aquatic 

organisms, including access to floodplains and 

off-channel habitats (Clarkin et al. 2005, Daigle 

2010, Gibson et al. 2005, Sagar 2004, Trombulak 

and Frissell 2000). 

3. Increasing stream temperatures (Wenger et al. 2011). 

4. Causing changes in channel morphology (Daigle 

2010, Hassan et al. 2005). 

5. Introducing exotic species (Daigle 2010, 

McKinney 2001). 

6. Increasing harvest and poaching pressure (Lee et 

al. 1997, Trombulak and Frissell 2000).

7. Changing hillslope hydrology and resulting peak 

flows (Daigle 2010, Jones and Grant 2001).

Roads penetrating remote and otherwise intact forested 

landscapes can have particularly significant effects on 

aquatic ecosystems (Forman 2003, Havlick 2002, Trombulak and Frissell 2000). The ecological consequences of these 

effects are shown in table 7-7. 

The effects of roads differ widely depending on local 

features (Al-Chokhachy et al. 2016). Recently developed 

techniques, such as the Geomorphic Roads Analysis and 

Inventory Package (Black et al. 2012), can be employed to 

identify priority locations of sources of sediment, including 

culvert failures, landslides, and gullies. A modified version 

of this technique has been incorporated into NetMap 

(Benda et al. 2007) to reduce the amount of field time 

needed to assess roads. Evaluating the effectiveness of 

new analytical approaches and focusing on treating limited 

lengths of roads could be a research priority. 

A significant number of watershed-improvement 

actions implemented under the NWFP and other largescale forest planning efforts involve decommissioning 

roads that have a high probability of contributing to 

landslides, and that are not regarded as essential to 

meeting local forest objectives, as well as removing 

road-related impediments to upstream and downstream 

movements of aquatic organisms (Switalski et al. 2004). 

The watershed-analysis component of the ACS identified 

forest roads where (1) drainage systems hastened runoff 

from storms and promoted sedimentation of streams, (2) 

unstable fill materials concentrated water and increased 

the risk of landslides, and (3) the roadbed encroached on 

riparian zones (Kershner 1997). Since NWFP implementation, the Aquatic and Riparian Effectiveness Monitoring 

Program estimated that 6.7 percent of the road network has 

been removed or closed (5,390 out of 80,750 mi total [8674 

of 129 954 km]) in the NWFP area.6 Additionally, 10 

percent of the road crossings that impeded the movements 

of aquatic and riparian organisms (209 of 2,114) have been 

made passable on Forest Service Region 6 lands in the 

NWFP area since NWFP implementation.7

Though restoration of fish passage is often listed as a 

top priority for stream restoration in the Pacific Northwest 

(Roni et al. 2002, USGAO 2001), recent work has contributed much to our understanding of just how complex this 

issue is in practice (McKay et al. 2016). Advances have 

been made in culvert inventory and assessment (Clarkin 

et. al 2005), ecosystem-based restoration approaches 

(USDA FS 2008), and effectiveness monitoring (Heredia 

et al. 2016, Hoffmann et al. 2012). Until recently, however, 

the ecological benefit of these efforts has been difficult to 

quantify beyond the level of individual projects. A new 

6

 Miller, S. 2016. Personal communication. National riparian 

program lead, U.S. Department of the Interior, Bureau of Land 

Management, 1849 C Street NW, Washington, DC 20240.

7

 Capurso, J. 2017. Personal communication. Regional fish and 

aquatic program manager, U.S. Forest Service, 333 SW First Ave., 

Portland, OR 97204, jcapurso@fs.fed.us.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

study evaluating the effectiveness of passage restoration 

at the level of an entire forest (the Siuslaw National Forest) 

(Chelgren and Dunham 2015) found that individual culvert 

replacements successfully increased the probability of 

upstream access for all fishes in the study area. Results 

of this work also showed that the net benefit of culvert 

replacements was fairly modest across the extent of the 

forest when expressed in terms of gains in kilometers of 

stream occupied or increases in fish numbers resulting 

from restoration. The authors hastened to add that some 

limitations of the study design could have influenced these 

findings (Chelgren and Dunham 2015), but results of this 

study nonetheless point to the value of programmatic (vs. 

project-only) evaluations of culvert restoration. This echoes 

more general recommendations for following the cycle of 

adaptive management on national forests (Marcot et al. 

2012) and the recommended scales for managing watersheds (Fausch et al. 2002, Neeson et al. 2015). 

Much of the guidance for fish-passage restoration on 

federal lands in the Pacific Northwest was issued by an 

assessment in 2001 (USGAO 2001). This assessment highlighted the need for larger scale assessments, as noted above, 

as well as the economic challenges associated with passage 

restoration, which are only beginning to be addressed. For 

example, a followup to the Chelgren and Dunham (2015) 

study by Reagan (2015) evaluated costs and benefits of 

remaining culvert replacement opportunities on the Siuslaw 

National Forest in relation to multiple objectives, including 

benefits to fish (estimated from Chelgren and Dunham 

2015), maintenance of transportation networks, and the 

probability of culvert failures based on culvert size and 

influences of floods and major erosional events in streams. 

The Reagan (2015) analysis explicitly quantified economic 

costs and benefits of restoration in relation to these objectives and their relative assumed values. This work (along 

with others in the region, e.g., Chelgren and Dunham 2015) 

has demonstrated the value of a proactive, economic analysis of multiple objectives to identify priorities for restoration 

investments in a programmatic context. These new tools, 

if applied, can more completely address standing recommendations to land management agencies in the Pacific 

Northwest (e.g., USGAO 2001) to more efficiently invest 

limited resources to benefit fisheries and other management 

objectives through culvert replacements.

Because road access management must take into 

account social, economic, and environmental objectives 

(Daigle 2010), the decisionmaking process for dealing with 

roads is complex. A decision matrix for identifying actions 

is shown in figure 7-14. In many cases, limited funds or 

socioeconomic issues may preclude closing or removing 

roads identified as high priority for treatment on the basis of 

their effects on riparian ecosystems. Also, a road network 

may be needed to effectively implement landscape-scale 

restoration projects that might involve widespread thinning 

and prescribed fire (Franklin and Johnson 2012), and for 

fire management, fuel reduction, and fire control. Studies 

Table 7-7—Summary of effects of road on aquatic ecosystems and associated biota

Ecological effect Habitat loss/degradation Habitat fragmentation Direct mortality

Low population density   

Low population reproductive rates  

Area occupied restricted   

Decreased habitat connectivity  

Overharvest 

Changes in water quality  

Changes in hydrologic functions   

Change in wood and sediment recruitment   

Source: Modified from Robinson et al. 2010 and Daigle 2010.
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GENERAL TECHNICAL REPORT PNW-GTR-966

in Redwood National Park suggest that removal of logging 

roads can yield carbon-storage dividends, in particular by 

preventing soil erosion (van Mantgem et al. 2013). The vast 

road system on private and state lands that abut federal 

lands also needs to be considered in road assessments. 

Understanding how to balance fire management, recreation, 

and other needs against potential negative aspects of roads 

will require a concerted cooperative effort of managers 

and physical, biological, and social scientists, other organizations, and the public. (See next section for additional 

discussion of roads.)

Climate Change

Since 1994, our knowledge of climate change in the 

NWFP area has greatly improved, just as dealing with 

climate change has become an important aspect of environmental planning in the Forest Service and BLM. Many 

advances have come from models that forecast trends in 

temperature, precipitation, and snowpack, and associations of these trends with the habitat conditions for various 

species. Although there is general agreement about the 

direction of trends in many meteorological parameters, 

the rates and amounts of change at specific locations in the 

NWFP area differ among models (Climate Impacts Group 

2009; see also chapter 2). Further, other climate-related 

changes such as increases in forest insect and disease 

outbreaks and uncharacteristically severe wildfires may 

accentuate the undesirable effects of meteorological and 

hydrological trends, resulting in threats to the integrity 

of both terrestrial and aquatic ecosystems. Although 

developing proactive measures that would ameliorate 

undesirable effects of climate change on forest resources 

was not a centerpiece of the NWFP, one of the Plan’s 

main objectives was to restore forest ecosystems that were 

resilient in the face of natural and anthropogenic disturbances. The question is: how well does the NWFP address 

climate-related threats to native fishes and other aquatic 

biota as they are currently perceived? (See chapter 2 for 

further details.)

In this section, we focus on a review of recent 

advances in our knowledge of the likely effects of climate 

change on native fishes of the NWFP area. We examine 

climate-change effects on fish life cycles, with a principal 

focus on anadromous salmonids, a group of species that has 

received the most scientific attention, as well as significant 

conservation effort (table 7-8) (see additional discussion 

in app. 2). Watershed improvements undertaken through 

the NWFP are related to potential climate effects on fish 

life cycles, and to the capacity of populations to adapt 

and persist through time. Finally, we discuss the role that 

federally managed forests in the NWFP area play in conserving native fishes in a changing climate, when viewed 

in a broader matrix of different land ownerships and other 

landscape-scale uses.

Preventive management: Mitigate presence effects:

• perform regular maintenance

• monitor for signs of presence 

 effects

Decommission road:

• abandon

Decommission road:

• rip or obliterate

• maintain fish passage

• prevent erosion

• soften edge effects

Road importance

Low High

Ecological impact

Low High Figure 7-14—A decision matrix for identifying potential options for managing roads. 

(Modified from Robinson et al. 2010).
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Climate change in the Northwest Forest Plan area—

Projected changes in climate are usually derived from models based on historical data coupled with scenarios incorporating alternative assumptions about future greenhouse gas 

emissions. These assumptions range from high global rates 

of economic development and human population growth 

to conservative industrial and population-growth rates and 

widespread implementation of “clean” technologies. Model 

outcomes are often displayed as incremental changes in an 

environmental parameter of interest such as air temperature, sea level, or precipitation over a fixed period. Projected 

changes in climate under different scenarios are plotted to 

provide a range of outcomes at a given point in time, with 

scenarios incorporating intermediate assumptions about 

future greenhouse gas emissions generally believed to 

represent the most realistic expectations.

Air and water temperatures—

Virtually all climate models forecast a gradual rise in air 

temperature by the end of this century. Recent changes 

in climate appear to be happening more rapidly than in at 

least the past 1,000 years (IPCC 2007), and have included 

a global average warming of 1.4 °F (0.8 °C) during the past 

120 years. According to the IPCC (Intergovernmental Panel 

on Climate Change) (IPCC 2014), most general circulation 

models predict that 2 to 7 times more warming will occur 

by early in the next century, with projected increases in 

mean global surface temperatures by 2100, ranging from 

2.7 to 3.6 °F (1.5 to 2.0 °C) relative to the 1850–1900 

time frame, depending on carbon dioxide (CO2) emission 

scenarios (IPCC 2014). The 2014 IPCC synthesis report 

(IPCC 2014: 10) states: 

It is virtually certain that there will be more 

frequent hot and fewer cold temperature extremes 

over most land areas on daily and seasonal 

timescales, as global mean surface temperature 

increases. It is very likely that heat waves will 

occur with a higher frequency and longer duration. 

Occasional cold winter extremes will continue to 

occur. [emphasis theirs] 

The finding that climate change will include both 

gradual long-term temperature trends as well as increases in 

the frequency and duration of extreme events has important 

implications for aquatic ecosystems in the NWFP area.

Air-temperature changes in forests of the NWFP area 

are predicted to be generally consistent with global climate 

models, although somewhat more variable, with forecast 

increases ranging from 1 to 6.3 °F (0.5 to 3.5 °C) in the 

remainder of this century, depending on the greenhouse 

gas emission scenario used in the model and on forest 

location (Latta et al. 2010). Overall, these authors noted 

that relative temperature increases were more apparent at 

higher elevations than at lower elevations, and that proximity to the Pacific Ocean moderated the rate of change. 

Mote and Salathé (2010) examined a broad suite of IPCC 

climate models and found that, by the 2080s, average air 

temperatures in the Pacific Northwest were predicted to 

increase 2.9 °F (1.6 °C) under the coolest scenario and 

Table 7-8—Species of Pacific salmonids considered in this section and their typical freshwater and marine 

residence times

Residence time

Species Freshwater Marine

Pink salmon Oncorhynchus gorbusha Less than 30 days 2 years

Chum salmon O. keta Less than 30 days 2 to 5 years

Sockeye salmon O. nerka Few months to 2 years 2 to 5 years

Coho salmon O. kisutch 1 to 2 years 1.5 years

Chinook salmon O. tshawytscha Few months to 1 year 2 to 6 years

Steelhead O. mykiss 1 to 3 years 2 to 4 years

Coastal cutthroat trout O. clarkii clarkii 2 to 4 years Short forays into nearshore environment
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GENERAL TECHNICAL REPORT PNW-GTR-966

by 10.3 °F (5.7 °C) under the warmest scenario. In most 

models, the greatest absolute temperature increases were 

projected for summer months, although warming was 

also forecast in other seasons. Sea-surface temperatures 

showed less warming over the same period than those 

modeled over land.

Similar to air temperatures, water temperatures are 

expected to rise in much of the NWFP area as a result 

of climate change (Isaak et al. 2011 [NorWeST model]). 

Modeled water temperatures were developed primarily 

from models of the relation between air and water temperatures, and are projected to be stressful to lethal for many 

native salmonids (e.g., Isaak et al. 2012, Wade et al. 2013) 

(see app. 2 for more details). More recent studies suggest 

that the extent of temperature change may not be as great as 

originally projected, particularly at higher elevations (Isaak 

et al. 2016). However, other researchers (Arismendi et al. 

2014) have questioned the ability to project future water 

temperature from past relations between air and water temperatures. In addition, Arismendi et al. (2013a) found that 

recent trends in water temperature have been more variable 

than those reported by Isaak et al. (2012)—using empirical 

records, they found that water temperatures increased in 

some systems and decreased in others. Also, Leach et al. 

(2016) also found variability in water temperature in a 

headwater stream of the Oregon Coast Range that was not 

captured by the NorWeST model (Isaak et al. 2010), but 

noted that the model was not designed to track such smallscale effects. Although there is some uncertainty about the 

extent of temperature changes that streams in the NWFP 

area will experience, it is clear that dealing with water 

temperatures will be a major challenge for managers. 

Potential patterns of changes in water temperature are 

highly variable when examined at the local scale (Leach 

et al. 2016, Reeves et al. 2016b, Turschwell et al. 2016) 

(fig. 7-15). This variability is a result of local conditions 

such as stream orientation, topographic shading, and 

elevation, and strongly influences physical and biological 

attributes and resultant ecosystem integrity (Gomi et al. 

2002, Thorp et al. 2006). Understanding this variability 

will be crucial to developing effective restoration and 

mitigation programs and prioritizing specifically where 

to target efforts. Watershed analysis tools such as NetMap (Benda et al. 2007) can help identify areas that 

can provide thermal refugia and areas in which riparian 

restoration efforts (fig. 7-16) could help reduce water temperatures to levels less stressful or even optimal for native 

fish, despite climate change (Justice et al. 2017, Lawrence 

et al. 2014, Ruesh et al. 2012).

Hydrology—

Predicted future changes in streamflow on national forests 

in the Pacific Northwest are fundamentally tied to changes 

in the region’s climate. Predicted changes in annual precipitation are much less certain, and most models project that 

future precipitation will remain approximately the same as 

it has been for the past 50 years (Salathé et al. 2007). Most 

predictions of changing streamflows for the Pacific Northwest therefore focus primarily on the effects of changes in 

temperature. Seasonal changes in precipitation are showing 

up in the data (Safeeq et al. 2013) but are difficult to resolve 

regionally, and consequently are not as well understood.

A key factor affecting both high and low streamflows in 

the future will be the fate of snow and the seasonal snowpack. Snowpack dynamics are important to understanding 

streamflow regimes because snow represents a dominant 

form of storage on the landscape. When precipitation 

falls as snow, it is not available for runoff or groundwater 

recharge until it melts. Similarly, the rate and timing of 

snowmelt are first-order controls on both peak and low 

streamflows, as discussed below. 

A particularly crucial dimension of snowpack dynamics is the geographic location of the rain-snow transition 

on the landscape. This transition is controlled by elevation 

and determines how much of the winter precipitation falls 

as rain versus snow. Although often visualized as a fixed 

elevation, this transition is better seen as a stacked sequence 

of elevationally controlled zones or ranges with imprecise 

and regionally varying boundaries (Klos et al. 2014, Nolin 

and Daly 2006). In general, for any area, there is an elevation below which virtually all winter precipitation falls as 

rain and above which it falls as snow. Elevations in between 

are defined as the transitional snow zone (TSZ) that receives 

both rain and snow; snow and the snowpack usually will not 

persist all winter.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Figure 7-15—(A) Current and (B) 

projected (2040) summer water 

temperatures (°C) in the study 

basins in the Treaty of Olympia 

area (Reeves et al. 2016b).
514

GENERAL TECHNICAL REPORT PNW-GTR-966

The widely varying elevational gradients in the Pacific 

Northwest in general, and on national forest lands in particular, therefore impose considerable variability in the response 

of the landscape to changing climate. Depending on the 

proportion of the landscape that occupies each of these 

zones, a warming climate, hence a rising snow line, may 

transition the landscape from a zone dominated by seasonal 

snow accumulation and melt (snow zone) to one that receives 

a mixture of rain and snow (and rain-on-snow)—the TSZ. 

Or it may push the landscape out of the TSZ and into the 

rain zone (Klos et al. 2014, Luce et al. 2014a) 

The effects of a changing climate are already apparent 

in the snow data for the Pacific Northwest. As winter and 

spring temperatures have warmed over the past 50 to 70 

years, spring snowpacks have been smaller (Hamlet et al. 

2005, Mote 2003, Mote et al. 2005) and have melted out 

earlier (Hamlet and Lettenmaier 2007, Stewart et al. 2005). 

Moreover, the aforementioned zonal changes are already 

Figure 7-16—Example of 

identification of potential 

locations where riparian 

restoration could provide 

potential thermal refugia for 

native fish. Analysis from 

NetMap. (Modified from 

Benda et al. 2007.)
515

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

occurring in some landscapes as snow zones transition to 

the TSZ, and the TSZ becomes rain dominated (Tohver et 

al. 2014). These trends are expected to continue across much 

of the region (Luce et al. 2014a). 

However, snowpack dynamics alone do not determine 

what future streamflow regimes will look like on national forests in the NWFP area. Recent work has shown that another 

first-order control is the landscape-scale drainage efficiency: 

the inherent, geologically mediated efficiency of landscapes 

in converting recharge (precipitation) into discharge (Safeeq 

et al. 2013, 2014; Tague and Grant 2009). In essence, the 

drainage efficiency determines how quickly precipitation, 

either as rain or snowmelt, becomes streamflow. Although 

drainage efficiency is “hard-wired” into the landscape on 

millennial timescales, and thus is not changing with climate, 

it mediates the climate-influenced signals and therefore has to 

be considered in predicting future streamflow regimes. This 

is particularly true for low-flow regimes, but influences peak 

flows as well. Basically, the drainage efficiency of a landscape is determined by the rate at which water moves through 

the subsurface. In steep landscapes with shallow soils, water 

rapidly moves laterally through the subsurface via both 

saturated and unsaturated pathways, drainage efficiency is 

high, and streams respond quickly to recharge events. In 

flatter landscapes with deep, permeable, porous, or fractured 

bedrock, water moves slowly as deep groundwater, drainage 

efficiency is low, and streams respond slowly to recharge 

events but may have sustained high base flows. 

Effects of climate change on peak flows—Here we broadly consider how both climate and drainage efficiency can 

shape predictions of future streamflows on national forest 

lands. We distinguish between effects on peak and low 

flows, as the mechanisms of streamflow generation are different in each case. Finally, we discuss how these broad predictions can be refined for individual forests, a topic beyond 

the scope of the current analysis.

There are several hydrologic mechanisms by which 

climate could increase peak flows in rivers and thus their 

propensity to flood. More intense or frequent rainstorms 

are one mechanism, and some research has suggested that a 

warming atmosphere may result in a more northerly storm 

track for the North Pacific, potentially resulting in more 

intense precipitation (Salathé 2006). However, these results 

have large uncertainties and are not well represented in 

most global circulation models. A somewhat better-understood mechanism is the shifting potential for rain-on-snow 

(ROS) events in the Pacific Northwest as the climate warms. 

ROS events are known to be a potent flood-producing 

mechanism in steep mountain landscapes in the Pacific 

Northwest (Harr 1981, Marks et al. 1998, McCabe et al. 

2007). In general, landscape susceptibility to ROS events 

is determined by climate and topography; the effects of climate warming on ROS are similarly influenced by the same 

controls; and climate warming may increase, decrease, or 

not affect the risk, depending on whether snowpacks are 

cold or warm (i.e., near the freezing point). As summarized 

by Hamlet and Lettenmaier (2007):

Cold river basins where snow processes dominate 

the annual hydrologic cycle (<6 °C average in 

midwinter) typically show reductions in flood risk 

due to overall reductions in spring snowpack. Relatively warm rain-dominant basins (greater than 

5 °C average in midwinter) show little systematic 

change. Intermediate or transient basins show a 

wide range of effects depending on competing 

factors such as the relative role of antecedent snow 

and contributing basin area during storms that 

cause flooding. Warmer transient basins along the 

coast in Washington, Oregon, and California, in 

particular, tend to show increased flood risk.

A more recent analysis looked at a range of factors 

influencing peak flows, including ROS in Oregon and 

Washington, and developed a model of sensitivity to 

peak-flow increases based on perturbing the temperature in 

the model using warming scenarios from 2020 to 2080 and 

the A1B8

 emissions scenario (Safeeq et al. 2015). The 

analysis yielded regional sensitivity maps for Oregon and 

Washington that can be used to characterize the risk on 

individual national forests and landscapes. They concluded 

8

 This scenario assumes a future world of rapid economic growth 

and global populations peaking in the mid-21st century, then 

declining with the rapid introduction of new technology, with a 

balance between the use of fossil fuels and non-fossil-fuel sources.
516

GENERAL TECHNICAL REPORT PNW-GTR-966

that corresponding changes in snowpack dynamics may 

result in large (more than 30 to 40 percent) increases in 

peak flows, primarily in the Cascade Range and Olympic 

Mountains. The North Cascades, in particular, were most 

vulnerable (fig. 7-17). Lower elevation areas were less likely 

to be affected but were still vulnerable to larger floods 

generated from upstream reaches in vulnerable landscapes. 

These watersheds are also likely more susceptible to 

warming (Arismendi et al. 2013a, 2013b; Poole and Berman 

2001; van Vliet et al. 2011, 2013). Streams at higher elevations should retain flows; with stable, cooler water temperatures, they will be critical cool-water refugia for native fish 

(Isaak et al. 2012, 2015; Luce et al. 2014b; Lusardi et al. 

2016; Wenger et al. 2011). 

Effects of climate change on low flows—Snowpack dynamics and drainage efficiency combine to determine the 

sensitivity of individual landscapes to a warming climate 

(Safeeq et al. 2013, Tague and Grant 2009). There has been 

a general trend over the past 50 years for less snow in winter 

and earlier snowmelt, resulting in reductions of spring, early-summer, and late-summer flows in the Western United 

States (Leppi et al. 2012, Safeeq et al. 2013), with the lowest 

flows showing the greatest decreases across the Pacific 

Northwest (Luce and Holden 2009). Hydrologic models 

such as the variable infiltration capacity (VIC) model, coupled with downscaled climate simulations, have been used 

to generate predictions of future low flows across much of 

the Pacific Northwest (e.g., Hamlet et al. 2013). 

However, snowpack changes are not the only factor 

determining future low flows. Other recent work has 

shown that the drainage efficiency (slow versus fast) 

mediates the signal from climate-induced changes in 

snowpack and snowmelt. Employing a simple exponential-decay model to describe the recession behavior 

of streams, coupled with a regional-scale estimation of 

variations in aquifer-drainage characteristics, Safeeq et al. 

(2014) developed a sensitivity map for changes in summer 

streamflow across Oregon and Washington. As with the 

VIC products and peak-flow maps previously described, 

these maps provide water and landscape managers with a 

spatially explicit representation of where future changes in 

low flows are likely to be most pronounced. For example, 

these maps show that areas drained by young volcanic 

rocks with deep, slow groundwater systems, such as the 

High Cascades, may be particularly vulnerable to declines 

in summer streamflow, whereas areas with shallow subsurface aquifers and limited potential to store water are less 

sensitive to changes in low flows. Climate-change effects 

on summer low flows may be compounded by effects 

of forest-vegetation conditons. Perry and Jones (2017) 

found that average daily streamflow in smaller streams in 

summer in watersheds with 34- to 43-year-old plantations 

of Douglas-fir was 50 percent lower than streamflow from 

reference basins with 150- to 500-year-old forests. The 

change in flows is also likely to be highly variable among 

watersheds in a given area (fig. 7-18).

Assessing climate change effects on streamflow at the 

scale of individual national forests—The discussion above 

highlights how existing tools and models can be used to 

give technically sound predictions about the magnitude 

and timing of streamflow changes in specific landscapes. 

Although not a trivial exercise, any national forest can use 

the spatially explicit models already developed to make 

first-order forecasts for changes in streamflow regimes. The 

products to date cover most but not all forests in the area 

of the NWFP. Extending results to these unmapped forests 

(mostly in northern California) would require some extrapolation, but is well within the scope of the existing data. 

Tools and approaches such as the concept of “hydrologic 

landscapes” can expedite this process (Patil et al. 2014, 

Wigington et al. 2013, Winter 2001).

Furthermore, there are several examples to date of 

individual forests or groups of national forests and other 

federal and nonfederal landholders that have coordinated 

efforts to develop detailed assessments of likely hydrologic 

changes that can serve as models for other forests and 

regions. Specific examples include the Olympic National 

Forest (Halofsky et al. 2011), the Quinault Indian Nation 

on the Olympic Peninsula (Reeves et al. 2016b), the Blue 

Mountains Adaptation Partnership (Halofsky and Peterson 

2017), and the upcoming report from the South Central 

Oregon Adaptation Partnership. 
517

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Figure 7-17—Sixth-field hydrologic unit-scale average peak-flow sensitivities across all flood magnitudes (Q2, Q10, Q25, Q50, and 

Q100) under A1B emission scenario for the (A) 2020s, (B) 2040s, and (C) 2080s, in which red is more sensitive and blue is less 

sensitive. (Modified from Safeeq et al. 2014.)
518

GENERAL TECHNICAL REPORT PNW-GTR-966

Figure 7-18—Percentage of 

reduction in average (A) summer and (B) winter flow levels 

from current to 2040 in study 

basins in the Olympic Peninsula 

area (Reeves et al. 2016b).
519

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Extreme events—Increased frequency of extended, severe 

droughts and intense winter-storm events (IPCC 2014) 

will also affect aquatic ecosystems and fish populations 

in forested landscapes (Ward et al. 2015). The pattern of 

changes will differ widely within and among watersheds 

depending on local features, making it difficult to generalize the effects. However, changes in the seasonal timing 

of annual hydrographs and more frequent extremely low or 

high flows are very likely to affect native fish populations. 

Changes in flows that lead to earlier spring runoff and prolonged periods of summer low flows could have important 

implications for the habitat of (ISAB 2007) and food chains 

encompassing fish and other aquatic organisms (Power et 

al. 2008, Wooton et al. 1996) (see discussion in app. 2 for 

more details). Amphibians that inhabit ephemeral ponds and 

streams are likely to be especially vulnerable to drought and 

general climate change effects (Blaustein and Olson 1991, 

Shoo et al. 2011). 

Ocean conditions—

Over the past several decades, the importance of the marine 

environment to fish that spend part or all of their lives at 

sea has been recognized as a major factor regulating population abundance. Climate-related changes in the ocean that 

are potentially important to native fishes in the NWFP area 

include acidification (Orr et al. 2005), increased sea-surface 

temperatures (IPCC 2007), changes in wind and current 

patterns (Rykaczewski and Dunne 2010), and sea-level 

rise (IPCC 2007). Absorption of anthropogenic CO2 by the 

upper ocean decreases pH and carbonate-ion concentrations 

(Hendriks et al. 2010, Orr et al. 2005), increasing acidity 

and inhibiting the ability of planktonic organisms to form 

calcium carbonate, a key component of their exoskeleton. 

Many of these organisms form the base of the food chain 

that supports anadromous fishes during the marine phase of 

their life cycles. The subarctic Pacific Ocean has naturally 

higher carbon concentrations than most other ocean basins, 

and the effects of acidification are expected to occur sooner 

and be more pronounced there (Cooley et al. 2012).

Rising sea-surface temperatures may reduce the 

amount of preferred thermal habitat for anadromous salmonids in the ocean and potentially limit their marine distribution (Aziz et al. 2011, Welch et al. 1995). As areas with 

suitable temperatures decrease or shift northward, Pacific 

salmon could become concentrated in smaller foraging 

zones, resulting in increased competition for limited food 

resources (Grebmeier et al. 2006, Johnson and Schindler 

2009, Mantua et al. 2009, Welch et al. 1995). Salmon may 

be able to partially compensate for these changes by using 

cooler subsurface waters; however, deeper water may 

provide reduced food resources, increased competition 

with other marine species, or greater exposure to predation 

(Hinke et al. 2005, Myers et al. 1996).

Other potentially important climate-related changes 

in the marine environment include sea-level rise (IPCC 

2007) and altered patterns of coastal upwelling (Wang et 

al. 2015). The consequences of sea-level rise for nearshore 

fishes are uncertain and will be strongly influenced by local 

topography; new habitat could be created in some areas but 

lost in others (Flitcroft et al. 2013). Saltwater inundation 

may affect species that sometimes spawn immediately 

above tidewater (e.g., pink and chum salmon, Oncorhynchus 

gorbuscha and O. keta). Both positive and negative effects 

on estuaries are also possible as new land is inundated, and 

the degree to which estuarine productivity is altered will 

be influenced by the extent of human development. Where 

development of estuary and coastal shorelines is extensive, 

sea-level rise will likely result in more seawalls, channelization, and other measures to prevent flooding during storm 

surges (Neumann et al. 2015).

Changes in the patterns of coastal upwelling in the 

NWFP area could have very significant effects on anadromous fishes as well as other animals that depend on 

marine food webs. Wind-driven ocean currents regulate the 

strength of coastal upwelling along the Pacific Coast, where 

nutrients from deep-ocean waters fuel plankton blooms 

that are critical to marine food webs that support salmon 

(Francis and Sibley 1991). Long-term shifts in the timing 

and intensity of coastal currents and upwelling have accompanied climate change in the eastern Pacific Ocean, with 

winter and spring storm tracks gradually shifting northward 

(Salathé 2006) and upwelling along the coast in the NWFP 

area becoming more erratic and unpredictable (Bylhouwer et al. 2013). Anadromous salmonids are particularly 

vulnerable to changes in upwelling because survival of 
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GENERAL TECHNICAL REPORT PNW-GTR-966

fish in the first few weeks after entering the ocean depends 

heavily on their ability to feed and grow large enough to 

avoid predation (Beamish and Boullion 1993, Pearcy 1992, 

Walters et al. 1978). 

The occurrence of interdecadal shifts in sea-surface 

temperatures and related weather patterns (Pacific Decadal 

Oscillation—PDO) from cool/wet to warm/dry conditions 

(Mantua et al. 1997) further complicates the productivity of 

marine environments along fish migration routes, with more 

favorable ocean conditions occurring when the NWFP area 

is in a cool/wet phase than in a warm/dry phase. Wang et al. 

(2015) used a suite of climate models to forecast upwelling 

over the remainder of this century and found that, by the 

year 2100, coastal upwelling will likely start earlier, end 

later, and be more intense in the northern latitudes (British 

Columbia, Canada, and southeast Alaska) than in southern 

latitudes (northern California and Oregon). Wang et al. 

(2015) also noted that an intensification of upwelling could 

actually promote plankton productivity, but in extreme 

cases could also result in large swaths of anoxic conditions 

developing over broad areas, leading to massive die-offs of 

marine life where such conditions develop. Taken together, 

the new information on climate-related PDO cycles and 

trends in upwelling patterns suggest that the marine 

environment along the Pacific Coast is becoming more 

variable spatially and temporally, with northern California 

and Oregon being somewhat more likely to exhibit unpredictable ocean conditions than more northerly latitudes. 

For migratory organisms such as anadromous salmonids 

whose life cycles are adapted to being in the right place at 

the right time for feeding and reproduction, introducing 

more variability into the part of their life cycle where most 

growth occurs is likely to add to population destabilization.

Climate effects on fish life cycles—

Although the extent to which a particular fish population in 

the NWFP area will be affected by climate change depends 

to a large degree on changes that occur at the local level, 

climate-related effects, both favorable and unfavorable, can 

accumulate across multiple life-history stages. Restricting an understanding of climate influences to a single 

life-history stage may well underestimate the total effect 

on the population. Further, because of the wide geographic 

distributions of many native fishes and the heterogeneity 

of aquatic environments in which they reside, climate 

effects may be expressed differently across the range of 

a given species. Locally adapted life histories differ over 

broad landscapes and among different species; even stocks 

of the same species can exhibit dissimilar responses to 

similar climate trends (Schindler et al. 2010). A number 

of papers have investigated the potential effects of climate 

change on Pacific salmon, but these have primarily been 

overviews (e.g., Bryant 2009, ISAB 2007) or results of 

modeled effects on a given life-history stage (e.g., Crozier 

and Zabel 2006, Rand et al. 2006) and its associated habitat 

(e.g., O’Neal 2002). A comprehensive review of the effects 

of climate change on native fishes in the NWFP area across 

their ranges, including effects accumulated across multiple 

life-history stages, is lacking.

Understanding the potential consequences of altered 

future conditions, particularly where the perceived effects 

may not be lethal, requires consideration of the effects at 

each life-history stage (Fleming et al. 1997, ISAB 2007, 

Jonsson and Jonsson 2009). Changes at one life stage can 

cascade throughout the remaining stages, significantly altering population response. Focusing on anadromous Pacific 

salmonids, it is possible to examine the overall impacts of 

climate change by identifying effects at each life-history 

stage and discussing how those effects might be propagated 

through succeeding stages. These effects and potential 

management options are listed in table 7-9. It is also possible to identify attributes of Pacific salmon life cycles that 

promote their adaptive capacity to climate change, along 

with options for managers and decisionmakers to enable 

and enhance those attributes to mitigate potential effects of 

climate change in the NWFP area.

Other climate-related factors—

Climate warming will lead to an increase in the area burned 

by wildfires (IPCC 2014) (chapter 2). Wildfire trends in the 

NWFP area will be complex because the area includes a 

wide array of forest types, elevations, weather regimes, and 

forest-management histories (Hessburg and Agee 2003); 

hence risks of damage to native fish habitats are likely to 

be highly variable across the region. In addition to altering 

wildfire frequency and intensity, climate change will also 
521

Table 7-9—Potential effects of climate change on anadromous salmonids of the Pacific Northwest, by life-history stage (coLife stage and habitat

Potential effect of climate change Ecological consequences Ecological implications Potenti

Adults:

Ocean Acidification (Hendriks et al. 

2010, Orr et al. 2005) 

Reduced growth and survival Lower productivity of freshwater 

because of reduced amount of marinederived nutrients and eggs (Bilby et al. 1996, Cederholm et al. 2001, Garner et al. 2009, Gende et al. 2004, Helfield and Naiman 2001, Lang et al. 2006, Schindler et al. 2003) 

Increased sea-surface 

temperatures (Aziz et al. 2011, IPCC 2007)

Smaller size at return Reduced population reproductive 

capacity (Hankin and McKelvey 1985, Healey and Heard 1984)

Change in life-history expression 

(Oncorhynchus mykiss)

Loss of steelhead life history 

(migratory) and increase in rainbow trout life history (resident) (Benjamin et al. 2013, Quinn and Myers 2004, Rosenberger et al. 2015, Sloat and Reeves 2014)

Populat

consid

Freshwater Sea-level rise (IPCC 2007) Increased estuary habitat Increased life-history diversity (Bottom 

et al. 2005) 

Populat

consid

Loss of spawning habitat in areas close 

to coast 

Reduced population productive 

capacity

Increased flooding during surge events Reduced egg survival 

Increased water temperature 

(Isaak et al. 2010)

Increased stress Reduced survival to spawning grounds 

(Martins et al. 2011, Rand et al. 2006) and population reproductive capacity (Miller et al. 2011, Pankhurst et al. 1996)

Increased susceptibility to disease and 

parasites (Chiaramonte et al. 2016, Johnson et al. 1996, Miller et al. 2011, Ray et al. 2012)

Monitor

entire protec
522Table 7-9—Potential effects of climate change on anadromous salmonids of the Pacific Northwest, by life-history stage (co

Life stage and habitat

Potential effect of climate change Ecological consequences Ecological implications Potenti

Eggs and alevins:

Freshwater Elevated winter water 

temperatures

Increased rates of development 

(McCullough 1999, Neuheimer and Taggart 2007) 

Smaller size at emergence (Beacham 

and Murray 1990, Elliott and Hurley 1998)

Year-ro

tempe

Earlier time of emergence (Holtby 

1988)

Increased growth rates, earlier timing 

of smolting, and smaller size at ocean entry, but decreased marine survival (Holtby and Scrivener 1989, Schindler et al. 2005)

Increase 

off-ch

Increased winter flows 

(Hamlet and Lettenmaier 2007, Hamlet et al. 2005, Tague and Grant 2009)

Increased scour of redds (Battin et al. 

2007)

Reduced survival (Battin et al. 2007, 

Leppi et al. 2014, Shanley and Albert 2014)

Increase 

removrestricwood gradie

Increased landslides and flooding (Dale 

et al. 2001, Hamlet and Lettenmaier 2007, Miller et al. 2003)

Decreased habitat quality in short term 

but improved conditions in long term (Bisson et al. 2009; Flitcroft et al. 2016a; Reeves et al. 1995; Rieman et al. 2006, 2015)

Road re

in mos

Silvicul

most sof tree

Juveniles:

Freshwater Higher spring flows (Hamlet 

and Lettenmaier 2007, Hamlet et al. 2005, Tague and Grant 2009)

Increased access to floodplain and offchannel habitats Increased growth and survival if floodplains and off-channel habitats 

available (Brown and Hartman 1988, Moore and Gregory 1988, Peterson 1982a); decreases if not

Increase

off-ch

Earlier onset of low flows 

(Hamlet and Lettenmaier 2007, Hamlet et al. 2005, Tague and Grant 2009)

Reduced habitat availability (Battin 

et al. 2007, Luce and Holden 2009, Mantua et al. 2010, Stewart et al. 2005)

Reduced survival (Battin et al. 2007, 

Mantua et al. 2010)

Identify 

likely flow pconditripariatempe
523

Table 7-9—Potential effects of climate change on anadromous salmonids of the Pacific Northwest, by life-history stage (coLife stage and habitat

Potential effect of climate change Ecological consequences Ecological implications PotentiIncreased summer water 

temperatures (Isaak et al. 2010)

Reduced growth and survival if 

temperature increases are beyond favorable range (Crozier and Zabel 2006, Isaak et al. 2010, Marine and Cech 2004, Royer and Minshall 1997, Scarnecchia and Bergersen 1987) 

Smaller size and reduced survival 

(ISAB 2007, Quinn and Petersen 1996) 

Improve 

Increased growth if temperatures move 

into more favorable range

Altered outcomes of interactions with 

other species (ISAB 2007, 2012; Petersen and Kitchell 2001; Reeves et al. 1987)

Reduce growth and survival (ISAB 

2007, Petersen and Kitchell 2001, Reeves et al. 1987)

Change in structure and composition of 

fish communities (warmwater species increase) (ISAB 2012) 

Increased nonsummer water 

temperatures 

Increased growth rates (Ebersole et al. 

2006, Sogard et al. 2010)

Increased growth and survival Year-ro

tempe

Provide 

off-ch

Smolts:

Freshwater Earlier onset of low flows 

(Hamlet and Lettenmaier 2007, Hamlet et al. 2005, Tague and Grant 2009)

Altered timing and rate of ocean 

migration 

Decreased marine survival (Holtby 

1988, Rechisky et al. 2009)

Warmer water temperatures 

(Isaak et al. 2010)

Smaller size at ocean entry Reduced marine survival (Holtby and 

Scrivener 1989, Quinn and Peterson 1989, Slaney 1988) 

Improve 

Ocean Altered timing of ocean 

upwelling (Barth et al. 2007, Snyder et al. 2003)

Reduced availability of food resources 

(Nickelson 1986, Scheurell and Williams 2005)

Reduced marine survival (Holtby and 

Scrivener 1989, Quinn and Peterson 1989, Slaney 1988)
524

GENERAL TECHNICAL REPORT PNW-GTR-966

influence outbreaks of insects and forest diseases (Spies 

et al. 2010) in some cases, leading to alterations of forest 

stands that affect aquatic habitats. Wildfires, insects, and 

forest diseases should not be viewed strictly as threats to 

native fishes, however—they may also provide benefits. 

They can create openings and patches along water bodies 

that result in more complex stream channels and greater 

biodiversity (Flitcroft et al. 2016a, Reeves et al. 1995, Rieman et al. 2006). In addition, the erosional processes that 

accompany these disturbances are important for recruiting 

wood and coarse sediment that form essential habitats for 

many aquatic organisms (Benda et al. 2004). Thus, actions 

that seek to control erosion and other ecological processes 

that occur following wildfire may have long-term and 

unintended negative consequences for aquatic ecosystems 

(Chin et al. 2016, Harris et al. 2015). 

The effects of climate change on aquatic ecosystems 

in the NWFP area expressed through wildfires, insects, 

and diseases will be complex and difficult to predict, but 

it will be important to examine the current responses to 

wildfire and consider making potential changes to allow 

fire to be more ecologically beneficial. Climate change 

will likely influence the expansion of nonnative plant and 

animal species in the NWFP area, while at the same time 

either reducing or even extirpating native species (Dale et 

al. 2001, Garcia et al. 2014, Urban 2015). Nonnative species 

include undesirable invasives, species undergoing expansion of their native ranges, and nonnative species deliberately introduced for commercial, recreational, or cultural 

reasons. They can occur in both terrestrial (riparian) and 

aquatic ecosystems. Nonnative species are not always 

harmful to native fishes or their habitats, but in many 

instances they can (1) compete with, prey upon, hybridize 

with, or infect native species with novel pathogens; (2) 

greatly alter the structure of food webs; or (3) cause habitat 

changes that reduce the productivity of desirable aquatic 

organisms. See appendix 1 for a detailed discussion of 

invasive species in the NWFP area.

Sanderson et al. (2009) provided a useful summary 

of underappreciated threats to salmon posed by nonnative 

vertebrates, invertebrates, and plants. They concluded that 

threats posed by nonnative species may equal or outweigh 

threats posed by traditionally perceived causes of decline—

habitat alteration, harvest, hatcheries, and hydroelectric 

production. Many of the nonnative fishes known to harm 

native fishes of the NWFP area are warmwater fish species 

deliberately introduced from eastern North America. In 

some river basins, these forms have largely displaced native 

fishes from dominant roles in the aquatic food webs of 

low-elevation, low-gradient rivers (ISAB 2012). Continued 

warming will favor the expansion of warm-adapted species 

in western North America (Rahel et al. 2008), and shrinking headwater flows resulting from longer, drier summers 

(Moore et al. 2007) could force cool-adapted native species 

lower in drainage systems, where there will be greater 

opportunity for unwanted interactions with established 

populations of introduced game fishes. Restoration of 

riparian areas, however, can help reduce water temperatures 

and the potential negative consequences of climate change 

related to elevated water temperatures (Justice et al. 2017, 

Lawrence et al. 2014) 

Restoration and response to climate change under the 

Aquatic Conservation Strategy—

Watershed improvements implemented in the Northwest 

Forest Plan area—An important goal of the NWFP was to 

create a managed federal forest landscape in which natural 

ecological processes sustained healthy populations of native fish and wildlife (USDA and USDI 1994a). Architects 

of the ACS recognized that federally managed forests 

might anchor the recovery of imperiled native fishes, but 

because of their location relative to state and private forests as well as other types of land use (which tended to be 

located in lowland areas), they could not ensure that appropriate conservation measures would be applied throughout 

the full suite of freshwater environments to which many 

native species, particularly anadromous salmonids, were 

exposed (Sedell et al. 1997). Nevertheless, many of the 

aquatic-conservation actions that emerged from the NWFP 

were considered at the time to provide more protection to 

aquatic and riparian habitats than had ever before been implemented on multiple-use forests in the Pacific Northwest 

(NRC 1996). The region’s national parks and designated wilderness areas were also considered to possess 
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high-quality habitats in which natural ecosystem processes could operate. However, because of their scarcity and 

location (Reeves et al. 2016a, Sedell et al. 1994), such areas 

were generally believed to be inadequate to prevent species 

or their distinct population segments (evolutionarily significant units) from becoming imperiled, or to hasten recovery. Given the impact of climate change on fish life cycles 

as discussed above, how the framework and standard of 

guides of future forest plans could address these potential 

effects merits priority for future research. 

Restoration of mid- and late-seral forest stands—

Concurrent with the restoration of mid- and late-seral 

stands in the NWFP area, the region will likely see a reduction in large openings caused by regeneration harvests 

(clearcuts) and by wildfire, as a result of continuing fire 

suppression (see chapter 3). As forest stands grow older 

in the seasonally transient snow (“rain-on-snow”) zone, 

snowfall interception by branches will diminish the accumulation of ground-level snow and will prolong melting 

and runoff processes during subsequent rain events (Harr 

1986). Peak flows were found to increase by as much as 

20 percent in small watersheds and 30 to 100 percent in 

larger basins over a 50-year period in the western Cascade 

Range of Oregon in response to road building and clearcutting (Jones and Grant 2001). However, a recent synthesis 

of peak-runoff studies in western Oregon and Washington 

(Grant et al. 2008) concluded that the incremental contribution of clearcutting to peak flows in the transient snow zone 

was minor relative to other types of human disturbance, 

and would likely be confined to stream reaches possessing 

2 percent gradients with sand and gravel substrates. In areas in which climate change results in an expansion of the 

transient snow zone, restoration of late-seral stands is likely 

to reduce the frequency and possibly duration of flows that 

are capable of mobilizing substrates of some fish-bearing 

streams, which could benefit survival of developing fish 

eggs and alevins as well as the abundance of amphibians 

and benthic macroinvertebrates. 

One climate trend with important implications for 

native fishes is the lengthening of low-flow periods during 

the warm season; aquatic organisms in watersheds with 

reduced snowpack will be especially affected by lower 

summer flows. Although not thoroughly investigated, the 

capture of fog by tree branches in areas with summer fog 

can result in “fog drip” that contributes to runoff during 

times when rainfall is scarce (Harr 1982). Whether climate 

change will alter the frequency of foggy days in the NWFP 

area is poorly understood, but there is preliminary evidence 

that the intensification of wind-driven upwelling in the 

California current as a result of increased CO2 could lead 

to more fog and increased moisture flux along the Pacific 

Northwest coast during the upwelling season (Snyder et al. 

2003). However, Johnstone and Dawson (2010) reported that 

fog frequency along the northern California coast declined 

by 33 percent in the 20th century. Nonetheless, restoration of 

late-seral stands will result in taller trees with larger limbs, 

which could capture more moisture and deliver some of it to 

streams during a season when water is in short supply.

Increasing the amount and sources of large wood 

will help aquatic ecosystems and associated biota meet 

the challenges of climate change. The progressive impoverishment of large wood in Pacific Northwest streams, 

particularly large-diameter, habitat-forming tree trunks 

and rootwads, has long been recognized (Bisson et al. 1987, 

Sedell and Swanson 1984). Climate change is expected to 

change the frequency and severity of fires and the incidence of forest-pathogen outbreaks in many parts of the 

NWFP area (see chapters 2 and 3). However, the ensuing 

recruitment of large wood to streams, a key component of 

fish habitat, may be limited if landslide-prone headwalls 

that normally deliver this material to channels during and 

following natural disturbances no longer contain trees 

of the size needed to form and maintain structural fish 

habitats. The importance of wood recruited to streams from 

unstable hillslopes is often underappreciated. For example, 

Reeves et al. (2003) found that 65 percent of the large 

wood pieces and 47 percent of the large wood volume in 

an Oregon coastal stream originated from upslope sources. 

Measures that could take advantage of this source of wood 

include inventorying and mapping unstable headwall areas, 

protecting them from forestry-related disturbance, permitting natural wood-delivery processes to occur, and allowing 

late-seral stands to develop in these areas where appropriate 

(Cissel et al. 1999). 
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Reducing the effects of roads and passage barriers—

Reducing the hydrological and biological effects of forest 

roads in the NWFP area should improve watershed resilience to the adverse effects of climate change on aquatic 

ecosystems. Road cuts are known to be a major contributor to accelerated runoff during storms by intercepting 

subsurface flow and capturing it in ditches, which rapidly 

deliver water and fine sediment to streams (Wemple and 

Jones 2003). As the intensity of storms increases with 

gradual warming and, in some parts of the NWFP area, 

with greater precipitation, the risk of streambed-mobilizing 

runoff events will rise as well. Reducing the exacerbating 

effects of road drainage networks on peak flow in watersheds where roads have been decommissioned could lessen 

the potential for severe storms to scour eggs and alevins in 

stream gravels and likewise reduce the intrusion of harmful 

fine sediment into spawning substrates. In addition, eliminating road-related initiation points for landslides through 

road decommissioning will help return the frequency of 

mass wasting in watersheds to more natural levels.

Road corridors can serve as important invasion 

routes for nonnative species, especially nonnative plants 

(González-Moreno et al. 2015, Heckman 1999, Menuz and 

Kettenring 2013), and climate change is likely to favor 

continued expansion of nuisance and harmful exotic herbaceous species in watersheds (Dale et al. 2001). The effect of 

invasive plants on riparian ecosystems in federally managed 

forests has received relatively little study, but some plants 

(e.g., Asian knotweed, Polygonum spp.) are capable of 

displacing native vegetation (Urgenson et al. 2009) and 

disrupting the transfer of organic material from streamside 

vegetation to stream channels. Invasive plant-control 

programs are costly, and even in riparian zones where treatments have been applied, the long-term reestablishment of 

native plants has been difficult to achieve (Claeson and Bisson 2013). Therefore, reducing road densities in a watershed 

and across large areas should help forestall the movement of 

unwanted nonnative plants into sensitive riparian areas and 

protect the integrity of native plant assemblages.

Floodplain protection—One of the key tenets of the ACS 

was that connections between streams and rivers and their 

associated floodplain and wetland habitats should be protected and, if necessary, restored (Reeves et al. 2006). In 

valleys where rivers are unconstrained and riparian forests 

are well developed, off-channel habitats such as braided 

streams, oxbow lakes, springs, and other floodplain features provide important seasonal rearing habitats for a wide 

variety of aquatic and terrestrial species and are considered 

to be among the most biophysically complex and diverse 

systems on Earth (Bayley 1995). Additionally, they can be 

important areas of carbon storage (Sutfin et al. 2016). Flood 

pulses that redistribute sediment and organic matter create 

a dynamic mosaic of physical habitat features on floodplains (Junk et al. 1989, Stanford et al. 2005), which support 

diverse and productive biological communities. In forested 

regions of the Pacific Northwest, flood-induced channel 

migration creates a variety of aquatic habitat patches that 

differ in age and connectivity with the main channel, from 

connected side channels that reside within the active flood 

zone to disconnected side channels that become connected 

only during larger flood events. 

Flood-induced erosion and deposition of substrate also 

create dynamic and heterogeneous plant communities. 

Early-successional species such as alder, willow, and cottonwood are generally found on newly deposited sediments, 

whereas mixed-species (deciduous and coniferous) mature 

forests and old-growth coniferous forests are found on older 

and more stable floodplain surfaces (Naiman et al. 2010). 

This spatial heterogeneity can also create highly complex 

and spatially structured food webs (Bellmore et al. 2013), 

which may be important for mediating the strength of 

predator-prey interactions and promoting biodiversity and 

resilience (Bellmore et al. 2015)

In the context of large-scale environmental stressors 

such as climate change, intact floodplains may be hubs of 

ecological resilience. The biological and physical diversity 

found across floodplains may promote ecological resilience in 

river networks via at least two pathways. First, enhanced species diversity in floodplains may provide functional redundancy within species guilds, whereby individual species 

extirpations may not significantly reduce ecological function 

(e.g., primary/secondary production, nutrient cycling) until 

some critical threshold is exceeded (Walker 1992). Second, 

the physical heterogeneity or spatial complexity found 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

across floodplains may provide critical refugia for individual 

species (Boughton and Pike 2013, Sloat et al. 2017). For 

example, groundwater upwelling in floodplain springbrooks 

can provide cold-water thermal refugia when main-channel 

waters exceed thermal optimums for a particular species 

(Ebersole et al. 2003, Torgersen et al. 1999). Unfortunately, 

many river-floodplain systems have been severely altered 

by human disturbance, which has constrained the physical 

processes that create and maintain habitat heterogeneity in 

floodplains (Tockner and Stanford 2002), and the associated 

resilience these habitats may provide. Although active restoration efforts are frequently targeted at recreating specific 

floodplain habitats (e.g., side channels), the reestablishment 

of natural channel-forming processes (Beechie et al. 2013), 

such as the “natural flow regime” (Poff et al. 1997), may be 

most successful at restoring the biophysical complexity of 

floodplains throughout the stream network over the long term 

and help negate potential effects of climate change. 

Winners and losers— 

Climate change is projected to lead to changes in the distribution and abundance of native fishes and a host of other 

aquatic-riparian organisms in the NWFP area. Some species 

will be adversely affected by climate-mediated shifts in 

environmental conditions; others may actually benefit from 

the changes. Whether conditions will become more or less 

favorable for a particular species depends on physiological 

requirements, life-history and migratory patterns, habitat 

preferences, shifts in aquatic-community composition, and 

geographic location within the region covered by the NWFP. 

In general, we expect that fishes that prefer warm water and 

benefit from alterations in aquatic food webs and hydrologic 

regimes that accompany climate change will likely increase 

in abundance and expand their ranges. Other native fishes 

that prefer cool water will likely suffer losses from recently 

established predators and competitors; elements of their 

habitats that are needed at different points in their life cycles 

will likely decrease in abundance; and their ranges will 

either contract or shift northward. Population fragmentation 

in cool-water fishes is also likely to increase as favorable 

thermal conditions retreat to higher elevations, and smaller 

populations may suffer reduced genetic variability that 

threatens long-term survival (Kovach et al. 2015). 

For anadromous species, survival and growth at 

sea will depend on how climate change alters upwelling 

patterns, plankton blooms, forage-fish populations, predator 

abundance, and other potentially limiting variables. In 

the fisheries management community, there is no clear 

consensus on whether freshwater or marine environments 

are “more important” to regulating the abundance of Pacific 

salmon, but it has become apparent that both ecosystems 

can exert a strong influence on run size, and that there 

are many uncertainties about how these two ecosystems 

interact to govern population viability and resilience.

In the NWFP area, climate change will lead to freshwater alterations that will be more or less favorable for 

some fish species relative to others. In figure 7-19, we list 

life-history strategies of fish that could increase vulnerability to the types of habitat change discussed earlier in 

this chapter. These include inflexible habitat specialization; 

extended freshwater rearing (1 year or more); low movement 

and spawning stray rates; potential for extended exposure 

to high water temperatures in their preferred habitats; and 

autumn spawning, placing them at risk of exposure to flow 

extremes. We also list life-history and habitat requirements 

that are likely to fare better in future climates. These include 

being able to use many different habitat types (habitat 

generalist); an abbreviated period in fresh water prior to 

seaward migration; high movement and spawning stray 

rates; either brief exposure to high water temperatures or 

a tolerance of prolonged elevated temperatures; and spring 

spawning that occurs after peak winter flows. Fishes are 

then arrayed along a risk scale, ranging from those we 

believe to be less vulnerable to harm from climate change 

to those that may be moderately vulnerable, and finally to 

those that may be at high risk of long-term harm. No species 

possesses all life-history attributes that are well adapted to 

thriving under predicted climate regimes, just as no species 

possesses only attributes that are ill-adapted to all projected 

future conditions. However, based on what is known about 

climate-related trends in freshwater habitats and on detailed 

knowledge of the life-history requirements of native Pacific 

Northwest fishes, we suggest that there will be winners and 

losers among fish assemblages. To some extent, the NWFP 

addresses many of the habitat changes likely to be associated 
528

GENERAL TECHNICAL REPORT PNW-GTR-966

with climate-related alterations in federally managed forests 

by creating and maintaining functional riparian areas within 

a watershed and focusing on road removal. However, some 

changes (e.g., trends in marine conditions) will not be materially affected by NWFP implementation.

The geographical distribution of native fishes and the 

variation in their life histories, combined with the wide 

range of effects of climate change on freshwater environments, make it difficult to predict which species will benefit 

most from NWFP aquatic-habitat protections. In figure 

7-20, we divided the NWFP area into four zones: eastern, 

western, northern, and southern. The western zone includes 

watersheds draining coastal mountain ranges, whereas the 

eastern zone includes central lowlands of the NWFP area 

(Puget Sound, Willamette Valley, and California’s Central 

Valley) and western drainages of the Cascade Range and 

Siskiyou Mountains. The northern zone includes all river 

systems north of the Columbia River; the southern zone 

includes river systems southward into the Sacramento River. 

The zones are not mutually exclusive because the northern 

and southern zones include both eastern and western areas; 

however, some fishes occur primarily in western coastal 

systems and others are found primarily in eastern portions 

of the NWFP area.

Based on different types of improvements to aquatic 

habitats from implementation of the NWFP that mitigate 

harmful effects of climate change as discussed above, figure 

7-20 lists native salmonids that are likely to benefit in some 

way from the framework and standards and guidelines 

introduced by the NWFP. A few of the fishes (e.g., Chinook 

and coho salmon, steelhead [anadromous O. mykiss], 

and coastal cutthroat trout [O. clarkii clarkii]) are found 

throughout the NWFP area and therefore occur on each list; 

others (e.g., westslope cutthroat trout, O. clarkii lewisi) are 

limited to relatively small regions of the NWFP area. Figure 

7-20 does not include nonnative species or nonsalmonids. In 

general, nonsalmonids (e.g., native minnows and suckers) 

are likely to benefit from climate warming (although see 

Winning strategies Losing strategies

Habitat generalist

Shorter time in fresh water

High stray rate

Spring spawning

Brief exposure or high tolerance

 to high temperatures

Habitat specialist

Long freshwater rearing

Low stray rate

Fall spawning

Extended exposure 

 to high temperatures

chum salmon

pink salmon

fall Chinook salmon

winter steelhead

westslope cutthroat trout

coastal cutthroat trout

native minnows

native suckers

many nonnatives

Lower

risk

sockeye salmon

coho salmon

spring Chinook salmon

summer steelhead

bull trout

mountain whitefish

Higher

risk

Figure 7-19—Life cycle and habitat-preference strategies of freshwater fishes that are considered in this report to be favored (“winning”) 

and disfavored (“losing”) in future climates of the Northwest Forest Plan area. Beneath the lists of winning and losing strategies is a 

grouping of fishes along a gradient of low to high risk from climate effects. These groupings, which are somewhat subjective, are based 

on current knowledge of each species’ life histories, spawning and rearing locations in watersheds, and residence time in fresh water.
529

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Figure 7-20—Native salmonid fishes in the Northwest Forest Plan area that are likely to benefit in some way from environmental protections from the harmful effects of climate change, grouped by different geographical zones (see text).
530

GENERAL TECHNICAL REPORT PNW-GTR-966

Moyle et al. [2013], who suggested that this may not be 

true in California) and may or may not respond to NWFP 

aquatic-habitat improvements such as fish-passage barrier 

removal. Nonnative salmonids (e.g., introduced chars—

brook and lake trout, Salvelinus fontinalis and S. namaycush) will probably be adversely affected by climate change, 

but also may or may not benefit from NWFP actions. Other 

introduced species, especially warmwater fishes (e.g., 

sunfishes and basses, Centrarchidae and Micropterus spp.) 

will likely become more abundant and may increase the risk 

of predation, competition, and exotic disease exposure to 

native fishes. However, restoration of riparian habitats may 

reduce water temperatures and restrict expansion of these 

fish (Lawrence et al. 2014). Also, the effects of hatchery fish 

may reduce the potential of wild populations to respond to 

climate change (Quiñones et al. 2014a, 2014b).

Climate refugia can also be projected for amphibian 

species (Shoo et al. 2011), with myriad ecological consequences. For lentic-breeding amphibians in the NWFP area, 

higher-elevation-adapted Cascades frogs (R. cascadae) may 

be faced with shifts in their breeding-habitat conditions. In 

addition, they may encounter novel interactions with species 

associated with warmer, lower elevation habitats, such as 

native northern red-legged frogs (Rana aurora), which may 

spread to higher elevations with altered climate. The low- to 

mid-elevation-adapted red-legged frogs may in turn encounter invasive American bullfrogs (Lithobates catesbeianus), 

which now occur at warm, low elevations. Similarly, because 

mountain streamflows are projected to change, torrent 

salamanders (Rhyacotriton spp.) associated with intermittent 

streams, could have a truncated active season, retreating 

below ground as small streams dry earlier in the season, 

possibly affecting survival and reproduction.9

 They may also 

move downstream and be faced with new interactions with 

larger predatory salamanders or fish in perennial reaches. If 

they migrate downstream, their over-ridge dispersal to new 

watersheds may be affected, as distances between flowing 

water bodies increase. Hence their populations could become 

more isolated and vulnerable to stochastic events. For 

9

 Unpublished data. On file with: Deanna Olson, Forestry Sciences 

Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331.

terrestrial-breeding salamanders, we can project the consequence of warmer, drier conditions by examining the 

distribution of current species in the drier portion of the 

Northwest; these are species for which climate change has 

already occurred. Optimal habitat for the Siskiyou Mountains salamander (Plethodon stormi) is modeled to occur on 

the shaded side of mountain ridges and in cooler riparian 

areas in the dry and warm southern Oregon landscape 

(Suzuki et al. 2008), and the black salamander (Aneides 

flavipunctatus) appears to become a riparian associate in dry 

portions of its range (Nauman and Olson 2004). Hence for 

cool, moisture-dependent species, riparian areas and 

north-facing slopes with hill shading may become more 

important with projected changes in climate. Alternatively, 

as for torrent salamanders, their activity pattern may be 

altered, with reduced surface activities during dry times and 

possible consequences for survival. Range shifts for temperature- and moisture-dependent species have also been 

projected for pathogens of aquatic organisms, such as the 

amphibian chytrid fungus (Batrachochytrium dendrobatidis), 

which is predicted to increase in occurrence probability in 

the NWFP area with climate change (Xie et al. 2016).

Implementation of the NWFP represented a significant 

change in the approach to protection and management of 

freshwater habitats in federal forests of the Pacific Northwest. Although not directed at mitigating the negative 

effects of climate change on native aquatic organisms at 

its outset, the protections provided under the standards 

and guidelines of the NWFP will benefit populations of 

native coldwater fishes throughout their life cycles and 

will help maintain the diverse mosaic of habitat types on 

the landscape that is essential for population resilience 

(Beechie et al. 2013, Bisson et al. 2009). However, although 

many aquatic and riparian habitats in federal forests are 

likely to retain favorable conditions for aquatic-riparian 

biota or to slowly improve as watershed-restoration actions 

are undertaken, it is important to recognize that federally 

managed forests are usually embedded in a landscape that 

includes many different types of landowners and uses, and 

that the standard of environmental protection for other lands 

is quite different from ACS-based standards and guidelines 

of the NWFP (Reeves et al. 2016a). Climate-related changes 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

in aquatic and riparian habitats on nonfederal lands may be 

much less favorable for native aquatic organisms and more 

favorable for a variety of nonnative species. 

As the biological communities of whole river systems 

are transformed under a changing climate, there will be a 

continuing need to monitor the role that federal forests play 

in conserving native aquatic organisms in the NWFP area. 

It will be critical for planners to identify vulnerabilities to 

climate change, and to incorporate approaches that allow 

management adjustments as the effects of climate change 

become apparent (Joyce et al. 2009). Because of the nature 

of environmental variability, the inevitability of novelty 

and surprise, and the range of management objectives and 

situations across the NWFP area, no single approach will fit 

all situations. A range of management options could include 

practices focused on mitigating or negating the effects 

of climate change by building resistance and resilience 

into current ecosystems, and on managing for change by 

enabling ecosystems and associated biota to adapt to climate change (Joyce et al. 2009, Perry et al. 2015). Better and 

more widespread implementation of already known practices that reduce the effects of existing stressors represents 

an important “no-regrets” strategy (Joyce et al. 2009). 

These management opportunities will require consideration 

of the Forest Service’s adaptive capacity, including availability of personnel with the expertise to conduct required 

technical analyses, and being able to work cooperatively 

with the public and other federal agencies to develop and 

implement the resulting management strategies.

The marine environment is likely to be a major challenge for Pacific salmon in the NWFP area. The predicted 

effects of climate change on the oceans, including acidification and increased temperatures, and their potential 

ecological consequences, reduced survival and size of 

returning adult fish, were described earlier. Pacific salmon 

have survived climate shifts in the past (Waples et al. 2009) 

and likely have the ability to persist in many areas of their 

current range even under more pessimistic climate change 

scenarios. Salmonid populations exhibit large genetic and 

phenotypic diversity relative to many other bony fishes 

(Crozier et al. 2008, Schindler et al. 2010, Waples 1991) 

and can adapt to changing conditions rapidly (Healey and 

Prince 1995, Quinn et al. 2001). This diversity has allowed 

for persistence in highly dynamic and ecologically diverse 

environments in the past (Greene et al. 2009, Moore et 

al. 2014, Waples et al. 2009) and will be a key to future 

survival (Copeland and Vendetti 2009, Mangel 1994). 

However, we note that Gienapp et al. (2008) cautioned 

that our knowledge about the role of genetic variation and 

the ability of natural populations to respond adaptively 

to current and future environmental change is limited, 

and that assuming that adaptation can or will happen is 

risky because of the uncertain rate and extent of climate 

change, effects of invasive species, and altered ecological 

processes. The challenge to managers will be to conserve 

natural environmental complexity in space and time so it 

can provide the physical template for maintaining genotypic 

and phenotypic diversity in populations that are currently 

strong, or to restore environmental complexity where it is 

currently compromised.

Research Needs, Uncertainties, 

Information Gaps, and Limitations

The scientific basis of the ACS is still sound and is supported by new science produced since its inception by 

FEMAT in 1993. However, we have learned much about 

relationships of riparian vegetation to stream habitats 

and environments that has refined and modified some 

hypotheses that were used to develop the ACS in the early 

1990s. A major knowledge gain has related to the behavior 

of aquatic and riparian ecosystems in space and time. At 

the time the ACS was developed, it was assumed that these 

systems were relatively stable through time. However, 

recent science is suggesting that these systems may be very 

dynamic in space and time, similar to terrestrial systems, 

and that aquatic organisms are adapted to this dynamism. 

Implementing this perspective in management actions 

will be challenging. It is not consistent with many current 

regulatory approaches, which require aquatic and riparian 

ecosystems to meet a given standard. Also, a dynamic 

perspective could be incorporated into the requirements for 

range of natural variability and all lands consideration of 

the 2012 planning rule, but will likely require close coordination between managers and researchers.
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GENERAL TECHNICAL REPORT PNW-GTR-966

Emerging science also suggests that the absence of disturbance and management in upland terrestrial ecosystems, 

primarily fire, may be affecting vegetation, and combined 

with climate change, is likely altering these ecosystems (see 

chapters 2 and 3). The same trends are likely occurring in 

riparian and aquatic ecosystems in a manner that is not fully 

understood at present; this could be a useful subject for 

research conducted in an adaptive-management context to 

provide information to managers, regulators, and policymakers in a timely manner.

Climate change is expected to affect aquatic and riparian ecosystems throughout the NWFP area, though with 

much uncertainty. Effects will likely differ widely within 

and among watersheds and geographic areas, necessitating 

the development of new approaches to identify this variation and help craft strategies and programs for mitigation 

and adaptation. Much of the focus has been on individual 

species. Research that focuses on understanding potential 

effects over the life history of species and how effects may 

cascade through life-history stages, as well as consideration 

of community-level effects, is critical. Understanding the 

effects on water quantity and quality is also important, 

particularly across spatial scales within watersheds, among 

watersheds, and across seasons and years. It is likely that 

aquatic and associated terrestrial ecosystems will change in 

uncertain, and maybe unpredictable, ways under a changing 

climate, and that this change will vary widely across the 

NWFP area. Having the capacity to do the needed analysis 

will also be critical for the involved agencies to successfully 

meet this challenge in a timely and effective manner, particularly in an era when budgets and personnel for federal land 

-management agencies are declining (see chapter 8). Thus, 

development of cost-effective and scientifically sound analysis procedures performed with close collaboration between 

research and management is key to addressing this need. 

The contribution of federal lands to the conservation 

and recovery of ESA-listed fish continues to be important. 

However, federal lands alone are likely to be insufficient in 

geographic scope to reach the comprehensive goals of the 

NWFP relative to recovery of listed fish, particularly many 

evolutionarily significant units of Pacific salmon, as originally expected by FEMAT (1993) and the record of decision 

(USDA and USDI 1994a). Although the geomorphic setting 

of streams on federal lands may be as capable as originally 

expected of providing sufficient favorable habitat, particularly for salmon, streams on state and private lands may 

have a much greater potential to provide habitat in many 

watersheds. Thus, it will be important to work closely with 

adjoining landowners and other interested parties to develop 

more comprehensive efforts across species ranges. The 

development of incentive programs is likely to be important 

to build partnerships for fish-habitat management across 

land ownerships. Developing an understanding of the 

variation in the capacity of watersheds to provide favorable 

conditions for fish and other aquatic biota could be critical 

to the success of such programs. 

Monitoring the effectiveness of the ACS will continue 

to be important. Some meaningful uncertainties remain 

regarding the aquatic-riparian monitoring approaches, especially relative to whether they are capable of capturing the 

effects of the ACS on a wide range of ecological processes 

and species of aquatic and riparian ecosystems. Research is 

needed to test the ecological validity of individual metrics 

and different ways of combining metrics to represent 

different components of complex and diverse aquatic and 

riparian ecosystems and communities. It would, therefore, 

be prudent to compare alternative approaches in the face of 

the new understanding about the behavior of aquatic and 

riparian ecosystems in time and space and the yet-to-beunderstood effects of disturbance or lack of disturbance, 

climate change, and novel ecosystems. A related research 

need is to better understand the relationship of the productivity of aquatic biota, which include organisms other than 

salmonids, in the context of different upland vegetation 

and in-channel successional stages or restoration treatments. This type of information can feed into watershed 

assessments to better ensure that the effects of the ACS are 

captured more comprehensively relative to the biota that are 

a key ecosystem service of aquatic-riparian ecosystems. In 

particular, we lack information about the amount, pattern, 

and type of restoration activities that have occurred in 

upland and riparian forests. Implementation monitoring has 

not been adequate to enable a sufficient understanding of 

the consequences of restoration actions (or lack of actions), 
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especially relative to how they may have altered aquatic 

ecosystems in space and time.

Roads and their effects will continue to be a major issue 

in the NWFP area. Both research on road effects and the 

continued development of analysis tools such as Geomorphic 

Roads Analysis and Inventory Package (Black et al. 2012) 

are important. In particular, understanding the consequences 

of focusing on small segments rather than the entire network 

should be a priority. The same is true for effects of culverts 

on ecological processes and the movement of aquatic biota. 

These are current priorities given the uncertainties of climate 

change. Also, understanding how to balance fire management, recreation, and other needs against potential negative 

aspects of roads will require a concerted cooperative effort 

of managers and physical, biological, and social scientists.

A key uncertainty that has emerged from our analysis 

is how to understand and assess the effects of “no-action” 

management options and tradeoffs of managing for one 

factor (e.g., water temperature or wood recruitment) on 

other ecological processes or attributes. The assumption 

has been that focusing on one concern would not influence 

other processes or attributes, and that taking no action was 

synonymous with having no effect. However, these assumptions are questionable and deserve increased consideration 

and focus by researchers. 

Several other topics relating to the components of the 

ACS merit further research. Watershed analysis could be 

reexamined so that it is conducted more efficiently and 

considers the appropriate spatial scales, including a smaller 

watershed of interest and its context within a larger basin. 

The larger scale context is particularly relevant for effective 

landscape-scale planning. In addition, no formal evaluation 

of the potential effectiveness of the network of key watersheds was conducted during development of the NWFP, nor 

has such an evaluation been attempted since it was implemented. New concepts, tools, and emerging understandings 

about aquatic ecosystems are now available to better assess 

and increase the potential effectiveness of key watersheds. 

Our understanding of aquatic ecosystems is incomplete 

(though evolving) at this time, but because there could 

be significant implications for the productivity of these 

systems, they will continue to be a major focus of research. 

Conclusions and Management 

Considerations

The goal of the ACS was to maintain and restore aquaticriparian ecosystems on federal lands within the range of the 

northern spotted owl. A review of monitoring efforts and the 

pertinent scientific literature suggests that (1) aquatic ecosystems in the NWFP area are likely improving as expected, 

albeit slowly; (2) the fundamental tenets and ecological 

framework of the ACS are sound, and we are gaining more 

explicit understanding of several components that over time 

will have important implications for future management; and 

(3) opportunities exist for implementing parts of the ACS 

differently while continuing to achieve its goals. The third 

finding is particularly applicable to the riparian-reserve component of the ACS, where more active management may help 

to address potential concerns about the effects of the lack of 

natural disturbance (primarily wildfire), and climate change. 

The following is a detailed summary of our main 

findings and conclusions. We also note to which guiding 

questions the conclusion applies.

Guiding Questions

1. Is the scientific foundation for the ACS valid, or 

does the science developed since 1993 suggest 

potential changes or adjustments that could be 

made to the ACS?

2. What is the basis of trends observed in the ACS monitoring program, and what are the limitations, uncertainties, and research needs related to monitoring?

3. What is known about variation of characteristics of 

unmanaged streams and riparian ecosystems in relation to the stream networks across the NWFP area?

4. What has been learned about the effects of riparian 

vegetation on stream habitat and environment?

5. What effects have human activities had on stream 

and riparian ecosystems?

6. What is the scientific basis for restoration management in riparian reserves, and how does restoration 

relate to the ecological goals of the ACS?

7. What is the capacity of federal lands in the NFWP 

area to contribute water for a suite of economic, 

recreational, and ecological uses?
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GENERAL TECHNICAL REPORT PNW-GTR-966

8. What are the potential effects of climate change 

on aquatic ecosystems in the NWFP area, and are 

they adequately addressed by the ACS?

Science Foundation for the ACS (Question 1)

The scientific foundation of the ACS is generally sound.

1. It is a coarse-filter approach designed to protect 

and restore ecological processes that create and 

maintain favorable habitat conditions for native 

anadromous salmonids. This assumes that if conditions are favorable for these organisms, then they 

should be suitable for other aquatic and riparian 

associated organisms. 

a. Verifying these assumptions could be a research 

priority.

b. There is growing scientific support for larger 

scale ecological processes acting at small-to-large 

watershed scales affecting salmonid habitats and 

populations; these include landslides delivering 

sediment and wood, canopy closure, and hillshading effects on aquatic-riparian temperatures, 

and the contribution of headwaters to downstream 

conditions and populations. 

c. The ecological process and species-habitat emphasis areas of the ACS are supported, but since 1993 

additional factors have come to the forefront.

i. More aquatic species have been considered for 

listing as threatened and endangered, some 

requiring more focused attention than the 

regional scale of the ACS, and consideration of 

threats on a case-by-case basis.

ii. Aquatic invasives have emerged as an elevated 

concern because of their effects on native 

species.

iii. Anthropogenic disturbances from timber-harvest activities, including road building and 

maintenance, remain key concerns for aquaticriparian ecosystems, but new concerns about 

the extent and severity of wildfire and climate 

change have emerged as research and monitoring priorities.

iv. Reliance on federal lands alone cannot address 

the conservation need to maintain or restore 

well-distributed populations of all aquatic-riparian species; key salmonid habitats rely on 

nonfederal lands, and fragmented federal land 

ownerships affect aquatic-riparian-terrestrial 

habitat connectivity for organisms dependent 

upon aquatic-riparian ecosystems. 

2. The scientific foundation for the riparian reserve 

network is valid. The riparian reserve network 

was intended to identify the outer boundary of the 

aquatic/riparian ecosystem.

a. Since 1993, new science supports riparian buffers 

to maintain aquatic-riparian processes, habitat 

conditions, and species.

b. Our ecological knowledge about non-fish-bearing 

streams has increased tremendously since 1993, 

and the approach for protecting them is supported.

c. However, there are suggestions that the second 

site-potential tree-height on fish-bearing streams 

may not be required to maintain microclimatic 

conditions within the first tree-height.

d. There are potential options available to move away 

from fixed-width riparian buffers toward riparian 

management that considers the variability in 

ecological context within the stream network and 

specifies management depending on ecological 

importance and risk.

e. Passive restoration approaches of riparian forests 

in streamside buffers have dominated management 

choices; active restoration might be acceptable in 

some locations and could accelerate achievement 

of goals such as growth of large trees to supply key 

pieces of large wood in the future.

f. Although science has addressed reach-scale effects 

of riparian reserves, research on effects of larger 

scale management activities (e.g., small to large 

watersheds) is becoming a new research priority.

g. Implementation, effectiveness, and validation monitoring of NWFP riparian reserves has not formally 

occurred, and is an emerging priority. 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

3. The use and structure of the key watershed network are supported by recent science.

a. There is emerging evidence that the key watersheds do not have the capacity to support and

provide favorable habitat for ESA-listed fish to the

extent that was originally assumed.

b. Also, the assumption that habitat conditions in

old-growth forests are the most favorable for native

salmonids is being questioned.

c. A review of the key watershed network and the

criteria for selecting watersheds would be useful

and timely.

4. Watershed analysis remains an important process

for developing and assessing management options.

a. New analytical tools and processes are available

that could be used to improve these analyses and

make them more cost effective; this is a research

priority relative to individual watershed analysis as

well as assessment of multiple watersheds across

the region that may have differing contexts.

b. The ability of the Forest Service and other federal

land managers to conduct such analyses may be

limited by a declining workforce and technical competencey; see chapter 8 for more detailed discussion.

5. A tremendous amount of effort has been directed

at restoring degraded watersheds and the associated aquatic and riparian ecosystems.

a. The vast majority of this effort has been directed

toward fish-bearing streams. More effort could

be directed at the non-fish-bearing portions of

the stream network, which will be important to

addressing potential effects of climate change.

b. Implementation, effectiveness, and validation

monitoring is needed to assess restoration activities

and contribute to adaptive-management processes.

Monitoring of the ACS (Question 2)

The AREMP results suggest that the condition of aquatic 

and riparian ecosystems in the NWFP area is improving, 

albeit slowly, as was originally expected owing to the 

extensive amount of degradation and lengthy time needed 

for recovery. 

1. The primary reasons for improvement are likely a

reduction in the extent of roads, primarily in key

watersheds, and an increase in the number of large

trees in the riparian reserve.

2. Regionally, there is a signature of wildfire interacting with AREMP restoration criteria in some places

in the NWFP area. The ecological significance of

this interaction is unclear and merits examination.

3. Assessing watershed condition is inherently challenging, and this synthesis has highlighted a number

of areas for further research and management focus:

a. Use of multiple independent measures of watershed

attributes makes it difficult to assess the overall

condition of a watershed.

b. Development of aquatic-riparian monitoring programs requires a clear articulation of which biota

and associated functional characteristics of habitats

and ecosystems are being considered, tying these

to our understanding of patterns of change over

space and time, and how they are likely to be

altered as a result of the actions of interest.

i. It is important to clearly describe the ecological

context of aquatic-riparian monitoring, for

example, to determine to what extent AREMP

should focus on environmental parameters that

measure habitat for native salmonids or on other

aquatic and riparian-dependent organisms.

ii. Within a dynamic aquatic-riparian ecosystem

framework, change is anticipated, but a challenge for monitoring is to assess alterations in

conditions that may reflect restoration or other

trajectories of patterns in response to a variety

of human actions and other events.

c. A key consideration in development of reference distributions for comparison with current

conditions is including the entire natural range

of conditions that an ecosystem can experience

(natural range of variability). This is critical to be

able to evaluate the implications of change.

i. Reference conditions that are too narrowly or

broadly defined can skew the interpretation of

monitoring results and introduce uncertainty
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GENERAL TECHNICAL REPORT PNW-GTR-966

into the process. This is an active area of 

research for the NWFP area: Are there neighborhood, provincial, or regional patterns to 

consider? We suggest further exploration of the 

use of reference conditions and their potential 

utility for diverse analytical approaches, including consideration of how to use them in concert 

with state-transition models and the potential 

development of novel conditions in the future.

d. Refinement of the objectives and approaches of 

aquatic-riparian monitoring programs, including 

AREMP, is anticipated as our understanding 

of these ecological systems improve and new 

analytical tools are developed. Advances in 

watershed-condition assessment procedures will 

be important to ensure the validity and reduce the 

uncertainty of future results and their implications 

for management.

Aquatic and Riparian Ecosystems 

(Questions 3–6)

1. Unaltered aquatic and riparian ecosystems likely 

exhibit a wide range of conditions in space and 

time, locally and across the NWFP area, depending 

to a large degree on the magnitude and frequency 

of the associated disturbance regime. (See chapter 

3 for more details.)

a. Headwater streams tend to be dominated primarily 

by conifers much of the time.

i. The biological processing of vegetation that 

falls into the stream (allochthonous material) 

is a primary energy source for downstream 

fish-bearing streams.

b. In the middle parts of the stream network, the 

riparian zone is composed of a mixture of conifers 

and deciduous hardwoods.

i. Hardwoods are important sources of high-quality allochthonous material important for system 

productivity.

ii. Hardwoods are scarce in many areas because of 

the conversion of riparian areas to conifer-dominated plantations. There may be important 

implications to system productivity that need to 

be explored.

2. Human impacts have extensively altered riparian 

ecosystems.

a. An estimated 30 to 50 percent of the riparian 

reserve has been converted to single-species plantations, primarily conifer, as a result of past management that harvested trees to the edge of the streams 

throughout the network. In headwater streams that 

have experienced increased rates of landsliding, 

riparian zones are frequently dominated by alder.

b. The trajectory of riparian and aquatic ecosystems 

has been altered as a result, reducing ecological 

variability across the area of the NWFP.

c. Additionally, fire exclusion (see chapter 3) and climate change are likely altering aquatic and riparian 

ecosystems in ways that are not fully recognized or 

appreciated at this time.

3. Restoration activities in riparian reserves have been 

limited because of concerns about potential negative effects, particularly increased water temperatures and decreased wood-delivery potential, and 

lack of trust of the Forest Service (see chapter 12).

a. Restoration activities have primarily been 

restricted to fish-bearing streams.

i. Assessment of these activities has been 

extremely limited, so it is not possible to 

quantify the effects.

ii. More active management may be needed.

iii. The question of whether the increased risk is 

sufficiently offset by the long-term gains realized from active restoration or other activities 

within portions of the riparian buffers is a key 

research need.

b. Passive restoration has been the dominant policy in 

riparian reserves.

c. This approach assumes that “no activity equals no 

effect.” However, this assumption is questionable, 

and “no activity” may actually compromise or 

eliminate key ecological processes such as development of the largest trees.
537

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

4. Non-fish-bearing streams have received little attention in terms of restoration.

a. These streams can be important sources of large 

wood for streams lower in the network. Improving 

stand conditions is critical to maintaining this 

important ecological function.

Water Contributions From Federal Lands 

(Question 7)

The capacity of federal lands in the NWFP area to contribute water for a suite of purposes varies widely among 

forests, ranging from less than 20 percent of the total flow 

in some basins to more than 40 percent in others. 

Climate Change (Question 8)

The primary effects of climate change in the NWFP area 

will be increased water temperatures, decreased streamflows in summer, and increased winter streamflows. The 

extent of these effects will vary widely depending on 

location and local topographic features.

1. The ACS has the potential to meet these challenges, but it will take a focused effort to do so, 

including:

b. Conducting local-scale analyses.

c. Considering “all lands.”

d. Shifting the focus of management and restoration 

from increasing population sizes to increasing 

the life-history diversity of aquatic and riparian 

organisms.

e. Recognizing that there will be “winners” and 

“losers”—because of their inherent capacity to 

adapt, some organisms will increase while others 

are likely to decrease.

2. With regard to anadromous fish, changes in ocean 

conditions (water temperature, acidification, and 

timing of upwelling), which are beyond the capacity of the federal land-management agencies to 

influence, may exert a stronger influence on populations than changes in freshwater ecosystems. 

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Yap, T.A.; Koo, M.S.; Ambrose, R.F.; Wake, D.B.; 

Vredenburg, V.T. 2015. Averting a North American 

biodiversity crisis. Science. 349: 481–482.
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Yeung, A.C.Y.; Lecerf, A.; Richardson, J.S. 2017.

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Zhang, C.; Li, S.; Qi, J.; Xing, Z.; Meng, F. 2017.

Assessing impacts of riparian buffer zones on sediment 

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Appendix 1: Aquatic-Riparian Invasive Species of the Northwest Forest Plan Area

Deanna H. Olson and Rebecca L. Flitcroft1

Invasive species are generally considered novel species that 

are not native to established systems, and their introductions 

are harmful ecologically (Vitousek et al. 1997) or economically (Pimentel et al. 2000). Nuisance-species lists have 

been developed for various jurisdictions, including species 

that both have been or potentially could be introduced to an 

area with subsequent adverse effects. Priority aquatic-riparian invasive species (ARIS) include those that have the 

potential to greatly alter food webs or ecosystem structure, 

economic interests such as fisheries, and recreation opportunities or human safety—for example, by fouling waterways or affecting water transportation. Priority invasive 

species include pathogens that can trigger disease die-offs, 

predators that may restructure native communities via 

trophic cascades, ecosystem engineers that alter physical 

or biological habitat conditions, and macroinvertebrates 

and plants that may produce population booms in systems, 

altering their ecosystem structure or function. 

ARIS were not raised as a priority concern during 

development of the Aquatic Conservation Strategy 

(ACS) for the Northwest Forest Plan (NWFP, or Plan) in 

1993–1994. As described in the 10 ACS objectives (USDA 

and USDI 1994a), the focus at the time was to maintain and 

restore watershed, landscape, riparian, and aquatic habitat 

conditions to which species, populations, and communities 

are uniquely adapted—hence emphasis was placed on 

native species. More explicitly, ACS objective 10 refers 

to the maintenance and restoration of habitat to support 

well-distributed populations of native plant, invertebrate, 

and vertebrate riparian-dependent species. Since 1994, 

ARIS concerns have intensified, and several state and 

federal agency groups with species jurisdictions overlapping 

the range of the NWFP have been addressing ARIS. In particular, modifications to the Aquatic-Riparian Effectiveness 

Monitoring Program (AREMP) now address ARIS during 

the program’s annual monitoring efforts. Herein, we provide 

an overview of ARIS that are priorities for natural resource 

managers in the NWFP area, highlight key science findings 

of recent research, and describe the development of invasive 

species monitoring programs.

Priority Aquatic Invasive Species

Overall, across the Plan area, we identified 63 species and 

species groups as top regional aquatic-riparian invasive or 

nuisance-species priorities (table 7-10). Of these, 31 (49 

percent) species or species groups were designated as “high 

concern” and inventoried by AREMP in 2016. Our broader 

top-priority list of 63 taxa was derived from lists compiled 

by state government departments in the region, interagency 

collaborative groups such as state invasive species councils, 

regional U.S. Forest Service personnel, or other entities 

identifying nuisance species or emerging infectious 

diseases. Specifically, our 63 priority taxa include those 

aquatic-riparian species on Oregon’s “100 Worst List” 

(OISC 2015), Washington’s “50 Priority Species” list (WISP 

2009), a focal species list for U.S. Forest Service Pacific 

Northwest Region (Region 6) lands (Flitcroft et al. 2016b; S. 

Bautista, pers. comm.2

), and the AREMP list (Raggon 

2017). We recognize that top priorities identified by California and the U.S. Forest Service Pacific Southwest Region 

include other aquatic-riparian taxa, but upon inspection, 

species identified only in California and not by these other 

sources appeared to be of lesser immediate concern in 

northwestern California forests in the Plan area. We 

acknowledge that some other important California invasive 

species may merit consideration if our list were to be refined 

further. Lastly, some pathogens were included here because 

of their national and international priority status from other 

entities (Auliya et al. 2016, Bern Convention 2015, Conservation Institute 2013, OIE 2017, Schloegel et al. 2010, 

USFWS 2016). Note that priority species differ between 

1 Deanna H. Olson is a research ecologist and Rebecca L. 

Flitcroft is a research fish biologist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 3200 SW 

Jefferson Way, Corvallis, OR 97331.

2

 Bautista, S. 2017. Personal communication. Pesticide use & 

invasive plant coordinator, U.S. Forest Service, 1220 SW Third 

Ave., Portland, OR 97204, sbautista@fs.fed.us. 
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Table 7-10—Aquatic invasive species of concern in the Pacific Northwest states of Oregon and Washington 

and within the administrative boundaries of the U.S. Forest Service Pacific Northwest Region (continued)

Scientific name Common name Oregon Washington

Pacific 

Northwest 

Region AREMP

Pathogens and parasites:

Phytophthora alni, P. kernoviae, 

P. pluvialis, P. lateralis; P. 

ramorum

Alder root rot; Phytophthora taxon 

C; needle cast of Douglas-fir, Port 

Orford cedar root disease, sudden 

oak death

 

Batrachochytrium dendrobatidis, 

B. salamandrivorans 

Amphibian chytrid fungi (Bd, 

Bsal)

Bothriocephalus acheilognathi Asian tapeworm 

Orthomyxoviridae isavirus Infectious salmon anemia virus 

(ISAV)



Ranavirus Ranavirus

Rhabdovirus SVCV Spring viremia of carp virus 

(SVCV)



Novirhabdovirus spp. Viral hemorrhagic septicemia virus 

(VHSV) 

 

Myxobolus cerebralis Whirling disease 

Aquatic plants:

Lagarosiphon major African waterweed or African 

elodea

 

Phragmites australis Common reed   

Potamogeton crispus Curly-leaf pondweed  

Butomus umbellatus Flowering rush   

Salvinia molesta Giant salvinia  

Arundo donax Giant reed 

Hydrilla verticillata Hydrilla, water thyme    

Myriophyllum spp. including M. 

spicatum, M. aquaticum

Milfoils: Eurasian, parrotfeather   

Lythrum salicaria, Lysimachia 

vulgaris

Purple loosestrife, garden yellow 

loosestrife

  

Phalaris arundinacea; P. 

arundinacea var. picta

Reed canary grass; ribbongrass 

Didymosphenia geminata Rock snot (Didymo)   

Chondrilla juncea Rush skeletonweed  

Spartina spp. including S. 

alterniflora, S. densiflora

Spartina (cordgrass)  

Prymnesium parvum, 

Cylindrospermopsis raciborskii

Toxic algae (golden, toxic 

cyanobacteria)



Trapa natans Water chestnut (European)  
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GENERAL TECHNICAL REPORT PNW-GTR-966

Table 7-10—Aquatic invasive species of concern in the Pacific Northwest states of Oregon and Washington 

and within the administrative boundaries of the U.S. Forest Service Pacific Northwest Region (continued)

Scientific name Common name Oregon Washington

Pacific 

Northwest 

Region AREMP

Ludwigia spp. Water primrose  

Egeria densa; Elodea nuttallii, E. 

canadensis, E. canadensis × E. 

nuttallii hybrid

Brazilian elodea, western 

waterweed (Elodea)

 

Iris pseudacorus Paleyellow iris  

Nymphoides peltata Yellow floating heart   

Riparian-terrestrial plants:

Hedera helix English ivy  

Alliaria petiolata Garlic mustard  

Geranium robertianum, 

G. lucidum

geraniums (Herb-Robert, shining)  

Heracleum mantegazzianum Giant hogweed   

Rubus ulmifolius Himalayan blackberry   

Fallopia japonica var. japonica; 

Polygonum bohemicum

Knotweeds (Japanese, Bohemian)   

Pueraria lobata Kudzu   

Clematis vitalba Old man’s beard  

Hieracium aurantiacum Orange hawkweed 

Potentilla recta Sulphur cinquefoil 

Tamarix spp. Tamarix (salt cedar)   

Lamiastrum galeobdolon Yellow archangel 

Aquatic invertebrates:

Potamocorbula amurensis Asian clam   

Radix auricularia Big-eared radix  

Eriocheir sinensis Chinese mitten crab  

Cipangopaludina chinensis Chinese mystery snail  

Orconectes spp., Orconectes 

virilis, Procambarus spp.

Crayfish (red swamp, rusty, ringed, 

virile, marbled, signal, northern)

  

Carcinus maenas European green crab 

Potamopyrgus antipodarum New Zealand mud snail   

Philine auriformis New Zealand sea slug 

Bythotrephes longimanus 

[cederstroemi], Cercopagis 

pengoi

Waterfleas 

Dreissena polymorpha, D. 

rostriformis bugensis

Zebra and quagga mussels    
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Table 7-10—Aquatic invasive species of concern in the Pacific Northwest states of Oregon and Washington 

and within the administrative boundaries of the U.S. Forest Service Pacific Northwest Region (continued)

Scientific name Common name Oregon Washington

Pacific 

Northwest 

Region AREMP

Aquatic vertebrates:

Lithobates catesbeianus (Rana 

catesbeiana)

American bullfrog   

Hypophthalmichthys spp.,

Mylopharyngodon piceus

Asian carp, black carp  

Salmo salar Atlantic salmon  

Didemnum vexillum Didemnum tunicate 

Chelydra serpentina serpentina Eastern snapping turtle 

Neogobius melanostomas, 

Rhinogobius brunneus, 

Tridentiger bifasciatus

Goby 

Noteigonus crysoleucas Golden shiner 

Esox spp. Muskellunge/northern pike 

Gymnocephalus cernuus Ruffe 

Channa spp. Snakehead  

Dorosoma petenense Threadfin shad (yellow tails) 

Riparian-terrestrial vertebrates:

Sus scrofa Feral swine    

Cygnus olor Mute swan 

Myocaster coypus Nutria   

Note: Three aquatic pathogens (ranavirus, Batrachochytrium spp.) are included in this table owing to other national and international priority status 

(Auliya et al. 2016, Bern Convention 2015, Conservation Institute 2013, OIE 2016, Schloegel et al. 2010, USFWS 2016). Some species clustering within 

rows was conducted. “” denotes priority species from authority listed (above), not occurrence of species within jurisdiction.

Source: Flitcroft et al. 2016b; Bautista, S., personal communication (see footnote 2 on page 585); and Aquatic-Riparian Effectiveness Monitoring 

Program (AREMP) of the Northwest Forest Plan (Raggon 2017). 

lists created by different jurisdictions or entities because of 

their variable selection criteria or jurisdiction-specific 

habitats and issues. A species listed as a priority for one 

jurisdiction and not another may have established populations and be of concern in both areas, yet because of 

different perspectives not be considered a top priority 

everywhere. Hence, the broader species list may be important to consider as regionally representative taxa of ecological or economic concern from an all-lands perspective 

across the Plan area. A few estuarine species are included 

and may be relevant to consider here, because tidally 

influenced areas are critical ecosystems interfacing with the 

coastal forest land base. Other primarily marine-associated 

species are not included here.

Altogether, as potentially representative of the 

Plan area, Northwest taxa identified as regional ARIS 

priorities fall into six categories (table 7-10): 8 pathogens; 19 aquatic plants; 12 riparian-terrestrial plants; 

10 aquatic invertebrates; 11 aquatic vertebrates; and 3 

riparian-terrestrial vertebrates. Specifically for the Plan 

area, AREMP’s 31 invasive taxa fall into 5 categories: 

13 aquatic plants; 11 riparian-terrestrial plants; 6 aquatic 

invertebrates; 1 aquatic vertebrate; and 2 riparian-terrestrial vertebrates. 
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Taxonomic Summaries

Pathogens and Parasites

Pathogens and parasites are considered invasive when their 

spread has been documented coincident with devastating 

disease effects on host species. There is heightened concern 

for disease-causing pathogens and parasites affecting 

sensitive host taxonomic groups that provide important 

ecosystem services (goods and services that people desire) 

(Blahna et al. 2017, Penaluna et al. 2016). These host taxa 

include culturally and economically important species 

such as salmonid fishes; species with broad distributions 

that may be central to ecosystem structural integrity and 

biodiversity such as Douglas-fir (Pseudotsuga menziesii) 

and alder (Alnus spp.); and those diseases with multiple host 

taxa that could affect several native species, with consequences for the organization of wild, native communities, 

such as the fungi that cause amphibian chytridiomycosis.

Northwest aquatic-riparian pathogens of key concern 

are viruses and fungi; parasites include cnidarian and cestode worms. Aquatic invasive pathogen species infect vertebrates, for example: (1) cnidarian myxosporean parasites 

(Myxobolus cerebalis) cause whirling disease in salmonid 

fishes (first described in Germany); (2) Asian tapeworms 

infect cyprinid fishes in their native range in Asia; (3) viral 

hemorrhagic septicemia virus (VHSV) infects salmonids, 

historically known from Europe; (4) ranavirus is considered an emerging infectious disease of fishes, turtles, and 

amphibians; and (5) chytrid fungi of the genus Batrachochytrium can cause the emerging infectious disease chytridiomycosis in amphibians. Riparian pathogens of key concern 

are fungi of the genus Phytophthora (table 7-10) that infect 

trees typical of riparian zones, such as alder, Douglas-fir, 

and Port Orford cedar (Chaemaecyparis lawsoniana). 

The World Organization of Animal Health (OIE) lists 

species as notifiable because of the extent of their effects, 

the availability of diagnostic tests for detection, and the role 

of humans in disease spread. The United States is one of 

180 member nations of OIE, hence OIE listing is relevant 

for consideration here. For pathogens identified here as top 

ARIS priorities in Oregon, Washington, and Alaska, three 

are OIE notifiable (OIE 2017): VHSV, ranavirus, and B. 

dendrobatidis (Bd). Bd is also listed by the Conservation 

Institute (2013) on their world list of the Top 100 Invasive 

Species. A second amphibian chytrid fungus included on 

our Top 60 list, B. salamandrivorans (Bsal), was recently 

described in Europe (Martel et al. 2013), and early challenge experiments found numerous North American taxa to 

be vulnerable to disease effects, with rapid mortality after 

infection (Martel et al. 2014). The Bern Convention (2015) 

and others (Auliya et al. 2016) have endorsed legislation 

to forestall the spread of Bsal, and an interim rule to the 

U.S. Lacey Act (USFWS 2016) has listed host salamander species that may be susceptible to Bsal infection as 

injurious, hence restricting their transportation among 

jurisdictions. Bsal risk models (Richgels et al. 2016, Yap 

et al. 2015) show Oregon and Washington to be extremely 

vulnerable to Bsal introduction owing to the presence of 

susceptable host amphibian taxa such as the rough-skinned 

newt (Taricha granulosa), suitable Bsal habitat conditions, 

and proximity to U.S. ports of entry. The pet industry has 

placed a moratorium on some salamander trade imports to 

the United States, significantly forestalling the transmission 

of this pathogen.

Aquatic Plants

The 19 aquatic invasive plants of concern (table 7-10) 

include two algae, a diatom (rock snot or Didymo), multiple 

species of submerged aquatic plants (e.g., Elodea, Hydrilla, 

milfoils [Myriophyllum spp.]), emergent plants (e.g., reeds, 

cordgrass [Spartina spp.], loosestrife [Lysimachia spp.], 

rushes, Salvinia, reed canarygrass [Phalaris arundinacea], 

paleyellow iris [Iris pseudacorus], water primrose [Ludwigia spp.], and floating plants (e.g., curly-leaf pondweed 

[Potamogeton crispus], water chestnut [Trapa natans], 

yellow floating heart [Nymphoides peltata]). Once established, these taxa may affect ecosystems, water quality, 

human health, navigation, and recreation. Emergent plants 

can dominate wetland and floodplain areas, outcompeting 

or displacing native species, thereby reducing biodiversity 

and altering ecosystem functions. Toxic algae are a health 

concern for native vertebrates and humans because they 

create powerful toxins known to kill fish, ducks, geese, 

marine mammals, and other wildlife (Edwards 1999). The 

diatom commonly called rock snot (Didymo) is native to 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

the Pacific Northwest but is included on priority invasive 

species lists owing to a change in its growth habits in the 

mid-1980s (Bothwell et al. 2014), becoming more prolific 

in its distribution and affecting recreational experiences 

and activities. Some Northwest ARIS plants were initially 

brought to the region by the aquarium trade (the elodeas) or 

for ornamental use (reed canary grass), and then spread to 

other areas. Further, established populations may be spread 

by waterfowl as they move from one location to another, or 

by human vectors (e.g., boats and fishing gear/tackle).

Riparian-Terrestrial Plants

The 12 invasive riparian plants listed (table 7-10) are 

problematic in both upland and riparian environments. 

Species such as Himalayan blackberry (Rubus armeniacus), 

Japanese knotweed (Fallopia japonica var. japonica), 

and giant hogweed (Heracleum mantegazzianum) tend to 

shade out smaller native plants, reducing plant diversity 

and altering habitat and food resources for native wildlife. 

For example, Japanese knotweed (native to Europe and 

Asia) and giant hogweed (native to the Caucasus region 

of Eurasia) can grow as tall as 15 to 20 ft (4.5 to 6 m) and 

spread rapidly. Japanese knotweed is known globally as one 

of the world’s most destructive invasive species because 

its large underground root system can damage structures, 

walls, and architectural sites, and reduce stream-channel 

capacity. Giant hogweed is considered a public-health 

hazard because it causes a phototoxic reaction when skin 

is exposed to sap and ultraviolet radiation. Species in the 

genus Tamarix are riparian shrubs or small trees that are 

aggressively invasive and well known in the Southwestern 

United States. These riparian trees are known to decrease 

streamflows, lower biodiversity, and create salinization 

issues, among other problems. Some of the listed invasive 

riparian plants were imported to the Northwest as ornamentals and have become invasive (e.g., English ivy [Hedera 

helix] and old man’s beard [Clematis vitabla], native to the 

United Kingdom; garlic mustard [Alliaria petiolate], native 

to Europe and Asia). Garlic mustard was initially introduced 

to the east coast of North America as a medicinal herb, but 

it has spread through forest understories, where it competes 

with native species. 

Aquatic Invertebrates

The 10 invertebrates on the northwest aquatic-riparian

invasive species list (table 7-10) include several mollusks

(Asian clam [Potamocorbula amurensis], big-eared radix

[Radix auricularia], Chinese mystery snail [Cipangopaludina chinensis), New Zealand mud snail [Potamopyrgus

antipodarum), New Zealand sea slug [Philine auriformis),

zebra mussel [Dreissena polymorpha), quagga mussel [D.

rostriformis bugensis]), and crustaceans (crayfish and crab

species; waterfleas). Mollusks may spread rapidly and attain

large population sizes that displace native species. These

taxa can deplete prey resources rapidly, affecting foundation levels of food webs (algae, phytoplankton) in aquatic

systems. Along with abundant populations come abundant

waste products—in some systems, the tissues or waste

products of zebra mussels may accumulate contaminants to

300,000 times the level available in the habitat they occupy,

with subsequent effects on their environment, including

their predators (Snyder et al. 1997). Another concern is that

large numbers of some mollusks can foul human structures.

Introductions of some species are likely tied to inadvertent

human transmission, such as in ship ballast water or on boats

or fishing gear (e.g., zebra/quagga mussels, waterfleas, green 

crabs). Deliberate introduction and consequent escape of

some species is also associated with food and medical markets, biological supplies for education, and the aquarium and

bait trade (Chinese mystery snails, crayfish, mitten crabs).

Aquatic Vertebrates

One frog (American bullfrog [Lithobates catesbeianus]), 

one turtle, eight fishes, and a tunicate (Didemnum) are 

included in the priority aquatic-riparian invasive species list 

(table 7-10). These taxa are strongly tied to human introductions. For example, American bullfrogs are native to the 

Eastern United States and were brought to the West to be 

farmed for food and out of nostalgia for their calls. Bullfrogs 

are carriers of the amphibian chytrid fungus Bd but do not 

always exhibit disease symptoms and hence may serve as a 

reservoir species of the pathogen, another invasive species 

of concern. Additional concerns surround-ing bullfrog 

introductions include alterations of the native ecosystem via 

food-web changes, an issue associated with the snapping 

turtle (Chelydra serpentina) as well. 
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GENERAL TECHNICAL REPORT PNW-GTR-966

The invasive fishes include a mix of species introduced 

for human food, as bait for recreational fisheries, or from 

the aquarium or ornamental industry. Atlantic salmon 

(Salmo salar) are native to the North Atlantic Ocean, where 

they are anadromous, occurring in the ocean and returning 

to spawn in rivers. Farms in Washington and British Columbia are thought to be the origin of Atlantic salmon found 

elsewhere in the Northwest. Concerns arise in conjunction 

with their potential competition with native salmonids, 

pollution from the farms, and the potential for farm-raised 

animals to carry pathogens to native stocks. Gobies are of 

Asian origin, occurring in fresh and brackish water. They 

are thought to have been introduced in ballast water, and 

may compete with or prey upon native species. Golden 

shiners (Noteigonus crysoleucas) are from the Eastern 

United States and are pond-cultured fishes that are also 

used as bait. Where numerous, golden shiners may result in 

displacement of native species. 

Didemnum vexillum is commonly called the carpet sea 

squirt, or ascidian. It is a colonial tunicate in the chordate 

phylum, hence is included here together with vertebrates—a 

sister chordate lineage. It seems to be native to Japan, and 

has been detected along the Washington coast since 2009, 

in two Oregon bays since 2010, and near Sitka, Alaska, 

in 2010. It is a fouling organism in marine and estuarine 

systems that grows rapidly to cover vast surfaces as mats, 

displacing native biota and encrusting dock pilings and 

aquatic equipment. It can be introduced in ballast water, 

or may hitchhike on the hulls of boats or on commercial 

shellfish stock or equipment.

Riparian-Terrestrial Vertebrates

The category of terrestrial vertebrates is the smallest, with 

only three species (table 7-10), but these can have extensive 

aquatic-riparian effects, ecologically and socioeconomically. Feral swine are escaped domestic pigs with rooting 

behavior that degrades waterway habitat, provides an invasion pathway for nonnative plants, and causes damage to 

agricultural crops and lands. The mute swan was introduced 

from New York for aesthetic enjoyment. These aggressive, 

large (2- to 30-lb [0.9- to 14-kg]) birds may consume 

significant quantities of aquatic plants, competing with 

native birds for food and habitat. Nutria (Myocastor coypus) 

were initially brought to the Pacific Northwest for fur 

farming in the 1920s. After the collapse of this element of 

the fur industry, escaped and released animals subsequently 

spread throughout the region. Nutria burrow into the banks 

of streams and agricultural canals, destabilizing natural 

stream systems and human agricultural infrastructure, and 

they consume vegetable crops.

Research and Development, Monitoring, 

and Management

Research and Development

Invasive-species disturbance ecology has developed conceptually in the past few decades. Aquatic-riparian ecosystems, like their terrestrial counterparts, are heterogeneous 

in space and time, occurring in multiple states within an 

ecosystem domain (e.g., Penaluna et al. 2016). This domain 

is highly resilient to many natural disturbances, yet larger 

disturbances can push an ecosystem beyond its “tipping 

point” to a new domain, a novel ecosystem. Novel ecosystems (e.g., Hobbs et al. 2009) are developing on our planet 

from a variety of disturbances, including the effects of invasive species. As discussed above, invaders may engineer 

habitat structures and functions, or become key players in 

food webs and trophic cascades, altering the native community and ecosystem. Biotic homogenization may result 

when the variety of initial states of ecosystems becomes 

equalized as a result of domination of invasive species 

over natives (e.g., McKinney and Lockwood 1999, Olden 

et al. 2004). “The New Normal” is a pragmatic description 

of today’s ecological systems that seem to be undergoing 

irrevocable change, a newly developing status quo (Marris 

2010). However, it may be premature to characterize such 

changes as irrevocable, because there are many examples of 

restoration successes (e.g., Murcia et al. 2014). Nevertheless, 

without preempting invasions, vigilance at the early stages 

of invasion, and concerted, often-continuous restoration 

efforts, transformation to a novel ecosystem can occur. 

These concepts are playing out with aquatic invasive 

species globally. As cases of ARIS are analyzed, costs to 

native biodiversity are being claimed. For example, the 

introductions of the European brown trout (Salmo trutta) 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

into South America (Soto et al. 2006) and New Zealand 

(Townsend 1996), and the eastern mosquitofish (Gambusia 

holbrooki) into Australia (Hamer et al. 2002), have caused 

major reductions in native fishes. Similar adverse effects on 

native amphibians and other ecosystem components have 

been documented by fish-stocking practices (reviews: Dunham et al. 2004, Kats and Ferrer 2003). Despite regionwide 

efforts to control ARIS spread, some species are recognized 

as requiring continuous management, or the efficacy of 

control methods is low. As a result, some invasive species 

(e.g., bullfrogs, New Zealand mud snails, Himalayan 

blackberry) seem fully established in some watersheds; the 

specter of a pragmatic New Normal with diminished native 

aquatic biodiversity in forests may be realized, owing to our 

lack of capacity to effectively control invasions everywhere. 

Furthermore, a clear conflict exists between maintenance 

of native biodiversity and pursuit of high-value recreational 

fisheries through nonnative fish-stocking programs. 

Nevertheless, restoration tools are being applied to 

maintain habitats for key native species despite nearby invasive species occurrences (Biebighauser 2011). The solution 

appears to be purposeful management of the multistate 

ecosystem across landscapes and regions beyond that which 

has thus far occurred, in order to designate both wild and 

nonwild states, in which some places retain a semblance of 

pristine native ecosystems, whereas in other places different ecosystem services (e.g., fishing experiences) can be 

fostered. This managed multistate condition is likely part of 

our regional, if not global, future.

In the Plan area, limited research on ARIS has been 

conducted recently; several examples of case studies or syntheses follow. First, in a study of invasive fishes in the Willamette River, Oregon, LaVigne et al. (2008) documented an 

increase in invasive fish diversity and abundance since the 

1940s. They also noted the significant contribution to overall 

fish biomass in the river contributed by the top three most 

common invasive fishes (smallmouth bass [Micropterus 

dolomieu], largemouth bass [M. salmoides], and common 

carp [Cyprinus carpio]). They argued for increased river 

monitoring and the use of double-pass electrofishing as a 

means of fish capture and eradication. Carey et al. (2011) 

assessed the threat to native salmonids posed by smallmouth 

bass. They described the tension between conservation 

of native salmon and angling opportunities provided by 

invasive warm-water fishes, such as smallmouth bass. They 

argued for more specific management that targeted locations 

for native fishes only, and others in which invasive species 

would be allowed to enhance angling opportunities. This 

notion supports the wild versus nonwild ecosystem-management approach described above.

Sanderson et al. (2009) completed a comprehensive 

assessment of the potential effect of invasive species on 

Pacific salmon in the Pacific Northwest. They found that 

invasive species may pose an even greater threat to salmonid 

persistence in the region than the four traditional factors 

generally thought to affect abundance and survival of native 

salmonids (habitat alteration, harvest, hatcheries, and the 

hydrosystem). They considered invasive-species management 

to be a significant component of salmonid-recovery planning. 

Yamada and Gillespie (2008) described how initial 

assessments of the effects of European green crab (Carcinus 

maenas) invasion in the Pacific Northwest (in 1989), which 

predicted that the crabs would naturally die out, have been 

proven incorrect. Instead, they found that changing environmental conditions and coastal currents stemming from El 

Niño cycles have resulted in shifting habitat characteristics 

amenable to the crab, promoting its spread. They concluded 

that management for crab eradication is a more pressing 

issue than first thought.

Pearl et al. (2013) also showed that invasive crayfish in 

the Pacific Northwest displace native crayfish. In their work 

in the Rogue, Umpqua, and Willamette/Columbia River 

basins, they found that invasive crayfish (in particular, 

Procambarus clarkia) tended to be associated with anthropogenic effects on streams, and that these crayfish appeared 

to have a negative effect on occupancy of native crayfish. 

They argued that there is still time to control invasive 

nonnative crayfish, but that the window of opportunity for 

management to have a meaningful effect is closing.

Claeson and Bisson (2013) conducted a study of 

the efficacy of invasive knotweed removal by herbicidal 

application, and effects on the riparian plant community in 

western Washington. They found that sites where knotweed 

had been removed, followed by passive restoration, had 
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more nonnative species and vegetative cover than reference 

(no knotweed) sites, and reference sites had more native 

species. This finding was especially true for riparian areas 

along larger streams in their sample, as riparian areas 

along smaller 2nd- to 3rd-order channels had primarily 

native plant-species assemblages. They suggested active 

restoration to control secondary invaders, such as replanting native species. Also, they proposed that effectiveness 

monitoring of invasive species control projects could help to 

refine and improve restoration approaches. 

Kinziger et al. (2014) described establishment pathways of an introduced fish from a nearby source area to 

two coastal rivers of northern California. Using genetic 

techniques, they reported that the Eel River invasion of 

Sacramento pikeminnow (Ptychocheilus grandis) likely 

was the result of only three or four founding individuals, 

whereas the Elk River invasion likely came from seven 

founders. This reflects an astounding adaptive capacity 

for rapid invasion, and highlights the threat posed by such 

close-range invaders. This species is not included on our 

priority list (table 7-10).

In a study of western Oregon wetlands, Rowe and 

Garcia (2014) reported that native anuran amphibians were 

negatively associated with invasive plant cover, nonnative 

fish presence, and invasive bullfrog counts. More generally, 

Bucciarelli et al. (2014) conducted a comprehensive review 

of the effects of nonnative species on amphibians and 

broader ecosystem services, painting a complex picture of 

negative and potentially positive effects. Their conclusion 

points to the need for additional research on the interactions 

of native and nonnative species in many ecosystems. 

Globally, invasive species experts are using Webportal technologies to expedite communication among 

multiple stakeholders, including natural resource management communities, research, and the public sector. 

Web-portal information can be used to address scientific 

hypotheses, aid decisionmaking regarding surveillance 

priorities, and support local-to-regional management 

actions. To aid communication about emerging invasive 

pathogens, for example, the Pacific Northwest (PNW) 

Research Station has partnered with disease and bioinformatics experts internationally to create online data 

and mapping portals for ranavirus (https://mantle.io/grrs) 

and the amphibian chytrid fungus Bd (Olson et al. 2013) 

(https://www.Bd-maps.net). The online Bd database has 

been used in subsequent research (e.g., Grant et al. 2016, 

Xie et al. 2016). For land-management applications, the 

Bd point-locality and watershed-scale occurrence maps 

have been used during firefighting for decisions about 

which water sources might be used for water draws and 

whether water disinfection procedures may be necessary 

(NWCG 2017). A new portal is being populated now with 

data on both chytrid fungi, Bd and Bsal, including both 

planned and completed research and monitoring reports 

(www.amphibiandisease.org). In addition, EDDMapS 

(Center for Invasive Species and Ecosystem Health 2017) 

is a new, national, real-time tracking system for invasive 

species that employs global positioning system (GPS)-

based mobile applications technology to allow users to 

report invasive species occurrences. 

Monitoring and Management 

Northwest Forest Plan implementation has required ACS 

monitoring, conducted by AREMP, with adjustments and 

modifications over time to address new knowledge and 

aquatic priorities. AREMP assessments for invasive species 

began in 2007 during annual field surveys at watersheds 

across the NWFP area (Gruendike and Lanigan 2008). The 

initial focus was on 13 species of primary concern for 

Northwest national forest waterways, with an additional 14 

species considered of secondary concern (27 species total). 

The number of species assessed during annual sampling of 

watersheds in the Plan area has since fluctuated between 23 

and 41 species, with 38 total species (i.e., 31 species groups 

in table 7-10) being included in the 2017 survey season. 

Survey methods have also been modified as needed, 

examining streams and adjacent banks within the bankfull 

width of the channel during summer low-flow periods. 

Surveys now include subsampling for benthic snails, 

mussels, crayfish, and ARIS plants. Few invasive species 

have been detected annually (table 7-11), with Himalayan 

blackberry being the most common species reported. 

Because the design of the AREMP surveys revisits watersheds every 8 years, some of the detections do not represent 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

sampling of unique watersheds or sites. Taking unique sites 

and watersheds into consideration, overall, only 125 

invasive species detections of 8 species have occurred 

across 1,376 unique sites sampled in 225 unique watersheds 

for the 10 years spanning 2007 to 2016. 3 4

3

 Hirsch, C. 2017. Personal communication. Fish Program 

Manager, Siuslaw National Forest, Corvallis, OR 97331, chirsch@

fs.fed.us 

4

 Unpublished data. On file with: Aquatic and Riparian Effectiveness Monitoring Program, 3200 SW Jefferson Way, Corvallis, OR 

97331. 

ARIS monitoring is also a priority for the Aquatic 

Invasive Species Network (AISN) (AISN 2017). Initiated by 

the U.S. Geological Survey and Washington State University in 2010 as the Columbia River Basin Aquatic Invasive 

Species group (CRBAIS 2011), the network integrates 

federal, state, academic, and tribal organizations over the 

area of the Columbia River basin, which includes parts of 

seven states and British Columbia, Canada, and is roughly 

the size of France. This region overlaps the NWFP area, in 

watersheds along the western Washington-Oregon border. 

AISN objectives are to develop an integrated monitoring 

Table 7-11—Invasive species detections by the Aquatic-Riparian Effectiveness Monitoring Program (AREMP) 

of the Northwest Forest Plan, 2007–2016 

Year

Watersheds 

surveyed

Sites 

surveyed

Number 

of invasive 

species 

detections

Species detected 

(number of detections) Reference

2007 31 149 7 Himalayan blackberry (7) Gruendike and Lanigan 2008

2008 31 167 17 Himalayan blackberry (15)

reed canary grass (2)

Gruendike and Lanigan 2009

2009 28 189 17 Himalayan blackberry (14)

ringed crayfish (2)

Japanese knotweed (1)

Andersen and Lanigan 2010

2010 28 185 7 Himalayan blackberry (4)

reed canary grass (2)

Robert geranium (1)

Also reported common mullein 

(Verbascum thapsus) from the 

Region 6 invasive species list

Raggon and Lanigan 2011

2011 29 184 15 Himalayan blackberry (14)

English ivy (1)

Raggon and Lanigan 2012a

2012 28 177 10 Himalayan blackberry (9)

ringed crayfish (1)

Raggon and Lanigan 2012b

2013 28 187 4 Himalayan blackberry (2)

English ivy (1)

ringed crayfish (1)

Raggon and Lanigan 2013

2014 27 157 10 Himalayan blackberry (9)

herb Robert, geranium (1)

Raggon 2014

2015 34 177 18 Himalayan blackberry (17)

parrotfeather watermilfoil (1)

Pennell and Raggon 2016

2016 25 140 10 Himalayan blackberry(10) Raggon 2017

Overall totals 289 1,712 125 8 species total

Unique totals 225 1,376

Note: Ten-year overall totals do not represent unique watersheds and sites, as some resampling among years was conducted as per the AREMP design. 

Totals of unique watersheds and sites sampled are also provided.
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and information system, coordinate early-detection efforts, 

assess invasion pathways, and contribute to an evaluation of 

the effects of climate change on native and nonnative biota 

(CRBAIS 2011). Zebra and quagga mussels have been the 

main taxonomic emphasis; the 2016 map of monitoring sites 

shows no occurrences of zebra and quagga mussels in the 

NWFP area (AISN 2017).

In 2012, Forest Service Region 6 developed the 

Regional Aquatic Invasive Species Strategy and Management Plan (USDA FS 2012b). Its three goals were to (1) 

prevent new introductions of ARIS into waters and riparian 

areas of the region; (2) limit the spread of established 

populations of ARIS into uninfested waters; and (3) provide 

a cooperative environment that encourages coordinated 

activities among all affected parties throughout the region. 

The strategy to achieve these goals is multifaceted, including educational and training programs; implementation of 

biosecurity protocols (e.g., equipment use and cleaning, 

inspections); mapping of known invasive species occurrences to inform decisions for water draws for firefighting; 

coordination of inventory and monitoring efforts; and 

advance knowledge for eradication procedures. The 2012 

list of focal species in this document includes 26 species 

and species groups listed in table 7-10; known species 

occurrences were mapped in 2012 (USDA FS 2012b).

As part of the Region 6 ARIS strategy (USDA FS 

2012b), surveillance and management is conducted by the 

joint Region 6 and PNW Research Station dive team.5 Four 

specific incidences of invasive species establishment in the 

NWFP area have been addressed by the dive team in 

recent years. First, yellow floating heart infestation at a 

lake in Rogue River–Siskiyou National Forest, Oregon, 

was evaluated, and control measures were applied and 

monitored for efficacy. The plants were pulled out, and the 

area covered by a geotech-style (hardware weed-control) 

cloth; after 3 years, the area has remained clear of the 

plant. Second, Eurasian water milfoil was detected in 

Coldwater Lake at the Mount St. Helens National Volcanic 

5

 Hansen, B. 2017. Personal communication. Ecologist, Pacific 

Northwest Research Station, Corvallis, OR 97331, bhansen@

fs.fed.us

Monument, Washington. The plants were pulled out by the 

dive team and the lake has been monitored for 2 years. 

Third, in an estuary adjacent to the Siuslaw National 

Forest, an invasive tunicate was found. The dive team 

continues to monitor this situation, and, as yet, no control 

measures have been implemented. Fourth, the dive team 

partners with the Siuslaw National Forest to survey for 

freshwater mussels, work that includes documenting 

occurrences of the Asian clam. Additional surveillance by 

this regional dive team occurred in summer 2017 within 

the Plan area on the Deschutes National Forest, Oregon. 

The dive team also conducts half-day annual training 

sessions in aquatic-riparian invasive species identification 

and management for Region 6 personnel, to be applied as 

stream field crews conduct stream and lake inventories on 

the national forests.

Management actions implemented when there are 

known infestations of invasive species on federal lands in 

the Plan area differ depending on the species considered. 

In the best scenario, invasive species are identified when 

their population is small enough for control to be effective. 

Early Detection and Rapid Response is considered the 

cornerstone of effective invasive species management 

(USDA 2017). In situations in which identification of 

invasive species occurs before the species becomes overly 

abundant on the landscape, control techniques may be 

quite effective, as in the above examples implemented by 

the regional dive team. Additionally, across this region and 

elsewhere, biosecurity protocols are in effect for personal 

disinfection of aquatic field gear to prevent spread of 

emerging diseases and invasive organisms (e.g., Gray et al. 

2017, NWCG 2017). In riparian and upland settings, when 

invasive species have long been present in the environment 

and are ubiquitous in landscapes surrounding Forest Service land, plans for complete eradication are less feasible. 

Instead, measures are taken annually to control spread of 

invasive species, or with the understanding that additional 

treatments to combat recolonization will be necessary. 

This is particularly true of several of the invasive riparian 

and wetland plant species, including reed canary grass, 

Himalayan blackberry, and purple loosestrife. Mechanical 

means of control using masticating machines are combined 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

with pesticide applications for the most comprehensive and 

long-term control of these species.

In addition to invasive species control measures, management actions implemented by Region 6 include development of more effective monitoring frameworks, along with 

preventative measures to forestall ARIS invasion. To prevent 

the spread of invasive species, educational programs have 

been initiated, and biosecurity programs have been implemented. For example, changes have been made to fire equipment contracts that now require equipment such as water 

tanks to arrive at a fire clean and drained (see ARIS website 

at https://www.fs.fed.us/r6/fire/aquatic-invasive-species/). 

A two-pronged ARIS monitoring program has recently 

been developed by the Region 6 and the PNW Research 

Station. First, to leverage existing freshwater monitoring 

programs for ARIS detection, a review was completed of 

ongoing aquatic habitat monitoring, with particular focus 

on those programs that assess ARIS risk factors. Results 

of the evaluation found that wadeable stream sections were 

adequately represented in monitoring on lands administered 

by Region 6. However, non-wadeable river sections, lakes, 

and reservoirs that may be at highest risk for invasion by 

aquatic species were not well represented in existing survey 

programs (Flitcroft et al. 2016b). The second element was 

developed as a followup to this finding—a Pilot Monitoring 

Project of “big water,” began in the summer of 2017. The 

pilot project will implement multispecies environmental 

DNA (eDNA) methods to facilitate a consistent and rigorous sampling program. Environmental DNA refers to the 

residual DNA found in water that is shed by species present 

in (aquatic species) or near (e.g., tree fungi) the water. Water 

samples are filtered and then processed in the laboratory, 

allowing for the identification of DNA from species present 

in the water sample. Traditionally, eDNA has been used 

to identify one target species at a time. Techniques being 

developed by the PNW Research Station in collaboration 

with Region 6 will allow for up to 48 species to be identified 

per sample. This approach could provide a breakthrough for 

ARIS monitoring. 

Last, in an attempt to leverage existing resources for 

ARIS monitoring and mitigation, Region 6 has been able 

to involve forest law enforcement officers (LEOs) in AIS 

monitoring. LEOs interact regularly with users of Forest 

Service lands, making them ideal partners in ARIS monitoring. For LEOs to have authority to inspect vehicles, 

trailers, and boats, Region 6 completed a National Environmental Policy Act review in 2016 to activate two relevant 

federal regulations that prohibit the transfer of animal and 

plant invasive species across National Forest System lands. 

LEOs in the region are trained on invasive species inspection and identification. This effort parallels invasive species 

law enforcement at the state level, in which state fish and 

wildlife agencies or invasive species councils work with 

state police as the law enforcement entities to help remove 

illegal alien and invasive species. For example, in Washington state, the 2015 Report to the Legislature (http://wdfw.

wa.gov/publications/01697/) reported results from 2011 to 

2013, including (1) more than 27,000 boat inspections, with 

decontamination of 83 boats with aquatic invasive species, 

of which 19 boats had zebra or quagga mussels, and (2) six 

new infestations of New Zealand mud snails. The Oregon 

state “report card” for 2013 (http://www.oregoninvasivespeciescouncil.org/oregons-report-card) similarly reports the 

results of required boat inspections, including a 73 percent 

compliance rate, mandatory decontamination of ~4 percent 

(n = 289) of boats because of the presence of invasive plants 

or animals, including 17 boats decontaminated for quagga 

or zebra mussels. It is easy to envision how truncating the 

transmission pathway along our nation’s roadways can be an 

effective ARIS mitigation.

Future Considerations

Our focus has been on describing those invasive species that 

have become leading priorities for state or Forest Service 

management actions in the region of the NWFP, and 

summarizing recent research and management advances. 

There is a much longer list of nonnative species detected 

in western Oregon and Washington that are raising local 

to widespread concerns. Considerable attention is being 

paid to novel species in the region, with efforts to prevent 

introductions of nonnative species into new areas and to 

understand their potential effects. There are also species 

that are naturalized to the extent that they are considered 

long-term, somewhat intractable problems, and that do not 
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GENERAL TECHNICAL REPORT PNW-GTR-966

appear on state or other types of species lists; this situation 

explains why some priority species are identified in some 

Northwest states, but not others. 

Other Nonnative Species on the Radar 

in the Northwest

It is important to note that species priorities change with 

time as new knowledge or events trigger new concerns. For 

example, the 2011 earthquake and tsunami in Japan resulted 

in an alert for alien aquatic species crossing the Pacific 

Ocean and reaching the eastern Pacific shores of Oregon 

and Washington. Heightened attention to potential introductions of aquatic nuisance species has occurred, as over 300 

nonnative species have been found on debris from Japan 

that reached North America through the summer of 2016,6

with more than 100 Japanese marine species drifting across 

the Pacific on a single dock from Misawa, Japan, to Agate 

Beach, Oregon (Lam et al. 2015). The potential importance 

of estuaries for such invasions also supports our rationale 

for their inclusion here.

Barred owls (Strix varia) have naturally dispersed 

into Oregon and Washington from the south and are being 

recorded as having ripple effects through western forested 

ecosystems. In addition to interactions affecting the native 

northern spotted owl (S. occidentalis caurina), barred owls 

have been found to have a broader prey base, including 

aquatic prey such as crayfish, amphibians, and fish (Wiens 

et al. 2014). The effects of barred owls on aquatic ecosystems await further research.

Many nonnative fish species have been released in 

the Western United States for sports fisheries (Schade and 

Bonar 2005). Effects on native species have been implicated 

most frequently for amphibians in the lower 48 states (e.g., 

Knapp and Matthews 2000). Among nonnative fishes 

released in Oregon and Washington lakes and rivers are 

smallmouth bass (Micropterus dolomieu) and brook trout 

(Salvelinus fontinalis). Both are predators, and effects on 

native aquatic prey are a concern. For example, bass are 

implicated as having adverse effects on state-sensitive spe6

 Chan, S. 2017. Personal communication. Extension Watersheds 

and Aquatic Invasive Species. Oregon Sea Grant, Oregon State 

University, samuel.chan@oregonstate.edu.

cies such as the foothill yellow-legged frogs (Rana boylii) in 

Oregon (Paoletti et al. 2011). Nonnative stocked fishes are 

an example of a conflict between ecosystem services: recreation versus native species. In the NWFP area, there have 

been increasing efforts to eradicate nonnative fish from 

wild areas, such as Crater Lake National Park, Oregon. To 

date, stocking continues at some historically stocked sites 

in Oregon and Washington, and native vertebrates in these 

systems appear to be persisting—yet may have declined 

from historical numbers or distribution. This is an evolving 

issue, and monitoring may be needed for sensitive native 

species under additional stressors such as disease.

Numerous additional species could be mentioned here. 

Newly identified nonnative species can gain quick attention 

with the hope of rapid eradication, forestalling a new invasive species gaining a foothold in the region. For example, 

chemical treatment for African clawed frogs (Xenopus 

laevis) was conducted in 2016 at a pond in Lacy, Washington, (WDFW 2016). The clawed frogs were eradicated, and 

surveillance is ongoing to continue efforts as needed. The 

role of human releases of nonnative species into the wild 

focuses attention on how these animals enter the region, to 

state laws and their enforcement for alien species generally, 

and to the pet trade more specifically. 

Climate Change Projections

Climate factors (temperature and precipitation regimes) 

strongly affect seasonal conditions in upslope, riparian, and 

freshwater environments. As with native species, invasive 

species survival is also tied to these same parameters, and 

projected climate change can likewise affect them. Hence, 

the distributions of both native and invasive species are 

likely to synchronously respond to changing conditions. 

Effects on some species have not yet been modeled, but for 

many species, the effects of climate change on invasions 

can be assessed. For example, American bullfrogs require 

water temperatures greater than 20 to 21 °C (68 to 70 °F) 

for breeding (Hayes and Jennings 2005), and suitable 

breeding sites are projected to be found at higher latitudes 

and altitudes in the future. Similarly, a northward expansion of the relatively cold-water-adapted amphibian chytrid 

fungus Bd has been projected with a variety of climate 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

futures (Xie et al. 2016). Temperature and precipitation 

often constrain the range of many invasive plants and limit 

their successful establishment. With climate change, new 

habitat may become available, enabling plants to survive 

outside their historical ranges and expand beyond their 

current range. For plants, disturbances such as wildfire 

or logging can provide a “fast-track” for changes in plant 

communities or even type conversion. For aquatic-dependent species, coldwater refugia are now being considered as 

localized areas that may be used to more practically protect 

native species and assemblages from the projected increase 

in biotic homogenization that is occurring from climate 

change effects and warm-water species invasions. Finally, 

climate-related drought and flooding events are also associated with invasive species dispersal; these effects merit 

additional consideration for the Northwest and elsewhere.

Research and Monitoring Priorities

Despite their increasing recognition as a potentially 

dominant force in restructuring ecosystems, relatively few 

research studies have been conducted on Northwest ARIS; 

their effects on the composition, function, or processes 

of ecosytems; ecosystem services valued by people; and 

mitigation efficacies. As evidenced by the above selected 

studies, support is growing for the importance of invasive 

species in altering native ecosystems. For example, Sanderson et al. (2009) considered invasive species more important 

for native salmonids than four other leading concerns 

combined, including habitat alteration and overexploitation 

from fishing pressures (harvest). 

Several areas stand out as potentially meriting additional research attention. First, aquatic-riparian pathogens 

and parasites appear underrepresented on Forest Service 

regional lists of invasive concern species. None are included 

in AREMP annual surveys, and only tree fungi are included 

in the Region 6 watch list. Recognition of pathogens and 

parasites as taxa for regional monitoring could enable their 

early detection and help forestall invasions. New eDNA 

techniques could aid in this regard, as detection of cryptic 

invaders such as pathogens and parasites may otherwise 

require significant time commitment or costly laboratory 

analyses applied after disease events are large enough to 

be easily detectable. Second, only one study summarized 

above (Claeson and Bisson 2013) addressed effectiveness 

of invasive species mitigation approaches with a scientific 

study design. This is a topic that deserves research for all 

categories of invasive species in table 7-10, and likely a 

species-by-species comparison of approaches is needed. 

For example, field intervention strategies for novel species 

such as Bsal have never been attempted, and foreknowledge 

of fungicidal or other approaches could be vital to control 

spread. Nevertheless, trial of some invasive species control 

methods is ongoing via case-by-case management actions 

with monitoring, like those being conducted by the regional 

dive team. Although this adds significantly to our knowledge, it is critical to apply the rigor of hypothesis testing 

with a scientific design. Lastly, the notion of managing 

for wild and nonwild ecosystems has been broached, but 

several questions arise about how this might be developed 

into an effective long-term strategy. For example, relative 

to federal lands of the NWFP area, if reserved land use 

allocations are desired to be wild, can that goal be effectively achieved relative to aquatic-riparian ecosystems 

given that streams often are contiguous across wild and 

nonwild areas, potentially promoting invasive species 

dispersal? Furthermore, can forest restoration practices aid 

in forestalling nonnative species introductions, or altering 

the existing heterogeneity within the aquatic ecosystem to 

avoid crossing “tipping points” to establishment of a novel 

ecosystem domain (Penaluna et al. 2016)?
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Appendix 2: Influence of Climate Change on Life Stages of Pacific Salmon 

Peter A. Bisson, Gordon H. Reeves, Nate Mantua, and 

Steven M. Wondzell1

Adults

The species of anadromous Pacific salmonids found in 

the Northwest Forest Plan (NWFP) area and their freshwater and marine residence times are shown in table 7-8. 

The freshwater environment is used for both growth and 

reproduction; the marine environment is used for growth 

and the initiation of sexual maturity. Depending on species, 

fish may spend from 1 to 5 or more years in the eastern 

Pacific Ocean before returning to fresh water to spawn. An 

exception is coastal cutthroat trout (Oncorhynchus clarkii), 

which generally make limited forays into nearshore areas 

and typically do not range more than 65 mi (100 km) from 

natal rivers (Trotter 1989). Owing to marine heterogeneity, 

the disparate migration patterns of various stocks, and the 

widely varying amount of time spent at sea, the influences 

of climate change on survival and growth of different 

populations of salmon in the ocean will differ.

Although the specific effects of climate change on 

marine survival and growth of salmon will depend on the 

location of their natal rivers and their movements at sea, 

some trends seem to be common to populations along the 

Pacific Coast. Possibly as a result of decreasing pH and 

increasing temperature, salmon are becoming smaller and 

sometimes younger upon return to fresh water, and exhibit 

reduced marine survival rates. The size of returning adults 

of most Pacific salmon species has generally trended downward over the past three decades of the 20th century (Bigler 

et al. 1996), although there have been multiyear periods 

when both sizes and abundances have increased (Helle et 

al. 2007). Some populations of sockeye salmon in Bristol 

Bay, Alaska, have returned to spawn at a younger age in 

the second half of the 20th century (Hodgeson et al. 2006, 

Robards and Quinn 2002).

In the past 69 years, the size of the largest fish caught 

in a Juneau, Alaska, fishing derby for Chinook salmon (O. 

tshawytscha) has declined (fig. 7-21). Although the origin of 

these salmon is not known with certainty, it is possible that 

some originated from rivers in the NWFP area, as migratory routes for some Pacific Northwest Chinook salmon 

Figure 7-21—Winning weights of 

Juneau’s Golden North Salmon 

Derby from 1947 through 2015 

and the preceding 42-month average Pacific Decadal Oscillation 

(PDO) index. Positive deviations 

in the PDO index occur in 

warmer-than-average PDO cycles, 

and negative deviations occur 

in cooler cycles. See also Fagen 

(1988) and Reid et al. (2016).

1 Peter Bisson is a research fish ecologist (retired), U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station, 3625 93rd Ave. SW, Olympia, WA 98512; Gordon H. 

Reeves is a research fish ecologist and Steven M. Wondzell is a 

research geologist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson Way, 

Corvallis, OR 97331; Nate Mantua is a landscape ecologist, U.S. 

Department of Commerce, National Oceanic and Atmospheric 

Administration, National Marine Fisheries Service, 110 McAllister 

Way, Santa Cruz, CA 95060. 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

stocks include southeast Alaska. There are many possible 

explanations for the observed declines in fish size, but 

several previously published examinations of adult salmon 

sizes from either commercial fishing records (Helle et al. 

2007) or Alaskan fishing derbies (Fagen 1988) attributed at 

least some of the decline to increased competition, owing 

to large numbers of hatchery-produced salmon (Bigler et al. 

1996, Francis and Hare 1997). However, such relationships 

are not simple. Helle et al. (2007) analyzed data for different 

species and stocks from northern Alaska to Oregon and 

concluded that adult body size resulted from both density-dependent factors (competition) and density-independent 

factors (environmental conditions). Long-term trends in 

body size observed over time in a Juneau, Alaska, fishing 

derby are weakly correlated with the gradually warming 

42-month average Pacific Decadal Oscillation (PDO) index 

observed prior to when the fish were caught (fig. 7-21), 

suggesting a linkage between ocean conditions and fish size 

that portends future size declines under a warming climate. 

The relationship between gradual warming and shifts in the 

frequency and intensity of PDO fluctuations is unclear, but 

significant PDO regime shifts can signal major changes in 

the Earth’s biophysical systems (Reid et al. 2016).

Decreases in adult body size resulting from changing 

environmental conditions in the ocean could also lead to 

reduced reproductive success. In Pacific salmon, both the 

number of eggs (Hankin and McKelvey 1985, Healey and 

Heard 1984) and egg size (Quinn and Vøllestad 2003) are 

directly related to the weight of adult females. Reproductive 

capacity of populations could decline if females have fewer 

eggs (McElhany et al. 2000). Egg size, primarily related to 

yolk reserve, can also be an adaptation to the environment 

in which eggs develop. Fish that spawn in warmer areas 

tend to have larger eggs compared to those from cooler 

areas because the efficiency of yolk conversion to body 

tissue is reduced at higher temperatures (Fleming and Gross 

1990). The survival and body mass at hatching of eggs 

incubating at warmer future temperatures could therefore 

be compromised if egg size does not increase as well.

Food webs in aquatic and riparian ecosystems are 

supported by the influx of marine-derived nutrients from 

returning adult salmonids (Bilby et al. 1996, Schindler et al. 

2003). The productivity of many streams and rivers within 

the range of Pacific salmon is influenced by the quantity of 

marine-derived nutrients from salmon carcasses (Gende et 

al. 2004, Helfield and Naiman 2001, Willson et al. 2004). A 

reduction in the size and number of returning adult salmon 

could compromise the capacity of freshwater ecosystems 

to produce new salmon, with carryover effects on the wide 

variety of aquatic and terrestrial organisms that may also 

benefit from the consumption of eggs during the spawning 

period (Cederholm et al. 2001, Garner et al. 2009). The 

growth of juvenile salmon during the spawning season is 

important for their overwinter survival (Lang et al. 2006). 

Energy derived from eggs consumed by returning adults 

can also allow for longer migrations and extended spawning 

times (Copeland and Venditti 2009); thus fewer, smaller 

eggs could diminish this potential energy source. 

According to climate change predictions for most 

rivers in the NWFP area, returning adult salmon will face 

warmer temperatures and lower flows if migrations take 

place in summer. Some species and life-history types, such 

as stream-type (“spring”) Chinook salmon and summer 

steelhead in the southern and middle portions of the Pacific 

Coast range of Pacific salmon, return to fresh water in 

spring or early-summer months, and hold in rivers and 

streams for several months before spawning. Adults feed 

infrequently and usually rest in large pools with cool water. 

Such pools are not abundant in late summer and early 

autumn, with coolwater refuges likely to become even less 

available at those times as climate continues to warm. This 

circumstance suggests that holding and migrating adults 

may become increasingly stressed, which will diminish 

their reproductive potential and increase prespawning mortality. Beechie et al. (2006) believed that the loss of summer 

prespawn staging habitats in rivers entering Puget Sound, 

Washington, could result in the replacement of stream-type 

Chinook salmon by ocean-type Chinook salmon, whose 

autumn run timing avoids exposure to warm, low-flow summer conditions. For populations undertaking long upstream 

migrations to spawning grounds, elevated stream temperatures will incur higher metabolic costs and mortality (Rand 

et al. 2006), and fish that do arrive at spawning grounds may 

have reduced reproductive capacities (Miller et al. 2011). 
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Warmer temperatures may also limit gonadal development; 

Pankhurst et al. (1996) found that female steelhead did not 

ovulate when temperatures exceeded 70 °F (21 °C). The 

extirpation of Atlantic salmon in the southern portion of 

their distributional range is attributed to reproductive failure 

associated with elevated water temperatures in freshwater 

spawning areas (McCarthy and Houlihan 1997). 

Elevated water temperatures during migration can have 

indirect effects on returning adults. Returning adults may 

be more vulnerable to disease and parasites if conditions are 

warmer in fresh water (Johnson et al. 1996, Ray et al. 2012). 

However, Stocking et al. (2006) found no relation between 

water temperature and infection of salmonids with Ceratomyxa shasta in the Klamath River, California. Juveniles 

(Chiaramonte et al. 2016) that are unable to find coolwater 

holding areas during migration in warmer water may be 

particularly vulnerable to disease because warm water will 

favor rapid disease transmission and virulence of warmadapted pathogens that could lead to fish kills. For example, 

Miller et al. (2011) presented evidence that elevated temperatures in British Columbia’s Fraser River have likely 

contributed to the virulence of a virus that infects adult 

sockeye salmon (O. nerka) prior to entering the Fraser River, 

resulting in a high incidence of prespawning mortality.

Rising sea level (IPCC 2007) may affect the reproductive success of species that spawn close to tidewater, 

particularly some pink (O. gorbuscha) and chum (O. keta) 

salmon populations. For small populations that spawn in 

streams just above the high-tide level, elevated sea levels 

could reduce the available spawning habitat if suitable 

spawning sites upstream are inaccessible. 

The development and persistence of less favorable 

ocean conditions could potentially influence the degree of 

anadromy in populations that possess both anadromous 

and nonanadromous (fully freshwater-resident) life cycle 

options. Steelhead, the anadromous form of O. mykiss, 

persist at least in part because there is a fitness advantage 

associated with migrating to the ocean to feed and returning 

to fresh water to spawn (Quinn and Myers 2004). If this 

advantage is reduced or lost, residency could increase 

in populations, assuming that changes in the freshwater 

environment are suitable for the persistence of the freshwater life-history variant of rainbow trout (Benjamin et al. 

2013, Rosenberger et al. 2015, Sloat and Reeves 2014). Other 

Pacific Coast populations of O. mykiss maintain primarily 

resident populations in locations where the marine environment is believed to be unfavorable for survival and growth, 

as in southern California (Behnke 2002).

Eggs and Alevins

Eggs and developing embryos will likely be affected by two 

different aspects of climate change—increased temperatures during egg incubation and altered hydrographs. Under 

some climate scenarios, winter temperatures are predicted 

to increase at faster rates than are summer temperatures for 

Alaska (IPCC 2007), whereas the opposite is true for the 

more southerly NWFP region (Mote and Salathé 2010). 

Most research on climate effects on native fish has 

focused on the potential for elevated summer temperatures 

(e.g., Crozier and Zabel 2006, Isaak et al. 2010). However, the 

effect of elevated winter temperatures may be as, and perhaps 

even more, pronounced and ecologically significant than 

increases in summer temperatures. Increased winter temperatures in the NWFP area will result in more precipitation 

falling as rain rather than snow. Watersheds that historically 

developed a seasonal snowpack will experience a trend from 

snow to rain, resulting in more rapid runoff in winter and 

early spring when snow usually falls, and lower late-spring 

and early-summer flows owing to reduced snowmelt (Hamlet 

and Lettenmaier 2007, Hamlet et al. 2005, Tague and Grant 

2009). In Washington state’s transitional drainage systems 

that historically possessed both autumn/winter and spring/

summer runoff peaks, the shift to a rain-dominant hydrograph 

is expected to be the most dramatic. Substantial increases 

are anticipated in the magnitude and frequency of extremely 

high-flow events in winter, coupled with substantial reductions in summer low flows (e.g., Elsner et al. 2010, Mantua 

et al. 2010). However, because snowpack will be reduced, 

rivers with snowmelt-dominated hydrographs could likely 

see a reduction in the magnitude of high flows during spring 

runoff. Loukas and Quick (1999) predicted that floods in the 

snowmelt-dominated continental portions of British Columbia 

will decrease in magnitude by 7 percent and in volume by 

38 percent, and occur as many as 20 days earlier, as a result 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

of the snow-to-rain transition. In coastal areas, Loukas and 

Quick (1999) projected that there would be little change in the 

timing of floods, but that, on average, peak-flow magnitude 

(+14 percent), flood volume (+94 percent), frequency (+11 

percent), and duration (+44 percent) would all increase. 

High-flow events will influence egg and alevin survival, depending on the depth of the redd, the size of the 

female, and the location of spawning in the stream network. 

Eggs in shallower redds will be more susceptible to being 

scoured than will those in deeper redds, and smaller salmon 

often excavate shallower redds than larger salmon (van 

den Berghe and Gross 1989). It has been speculated that 

increased peak flows during the incubation period could 

result in decreased survival of eggs and embryos in populations exposed to hydrologic regimes that have become more 

prone to gravel-mobilizing flows (Battin et al. 2007)

Potential effects of hydrographs altered by climate 

change are likely to differ among species and life-history 

forms. In most drainages of the NWFP area, scour is likely 

to increase the most in small streams or in confined, steep 

rivers, affecting fish such as bull trout (Salvelinus confluentus) that spawn in the late autumn and early winter when 

the most severe storms tend to occur along the northwestern 

Pacific Coast (Isaak et al. 2012). Fish spawning in lower 

gradient, unconfined areas, such as coho (O. kisutch), 

Chinook, pink, and chum salmon, could be less affected. 

Studies that have examined potential effects of increased 

flows on streambed scour (Battin et al. 2007, Leppi et al. 

2014, Shanley and Albert 2014) assumed a uniform relationship between flood magnitudes and the vulnerability 

of salmon populations and their habitat. However, the 

geographic range of Pacific salmon is characterized by 

exceptional topographic complexity and watershed dynamism (Montgomery 1999), which can generate considerable 

diversity in watershed- and stream reach-scale responses of 

habitat to flood disturbance (Buffington 2012, Montgomery 

and MacDonald 2002). Thus, effects of increased flows are 

unlikely to be similar among watersheds or even among 

reaches within stream networks. 

Previous research has demonstrated that stream-channel response potential varies according to position within 

the dendritic structure of stream networks (Benda et al. 

2004), variation in valley and reach-scale confinement 

(Coulthard et al. 2000, Montgomery and Buffington 1997), 

and differences among species in their use of habitats 

created by this physiographical complexity (Goode et al. 

2013). In terms of management, floodplain connectivity may 

ameliorate the effects of future increases in discharge on 

streambed dynamics. Floodplain connectivity in unconfined 

reaches provides a “stress release valve” (McKean and Tonina 2013) that limits vulnerability of salmon spawning habitat even in large floods with return intervals of decades to 

centuries (Goode et al. 2013, Lapointe et al. 2000, McKean 

and Tonina 2013). In this regard, maintaining or restoring 

connectivity between streams and adjacent floodplains will 

mitigate near-term responses to increased flood magnitudes. 

Additionally, maintaining or restoring channel complexity 

and hydraulic roughness from large wood may further mitigate the effect of higher flows on salmon spawning habitat 

(Montgomery et al. 1996, Sloat et al. 2017).

The rate of development of eggs and the size of fish at 

emergence is related to water temperature. Egg development 

depends on the accumulation of degree days (Neuheimer 

and Taggart 2007). Even slight increases in temperature 

can accelerate rate of development and ultimately result in 

earlier time of emergence from the gravel (McCullough 

1999) (fig. 7-22). Accelerated development leads to smaller 

Figure 7-22—Changes in time of emergence of Chinook and 

coho salmon as a result of a 1 °C-increment increase in water 

temperature during egg development. From McCullough 1999.
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GENERAL TECHNICAL REPORT PNW-GTR-966

individuals at emergence because metabolic costs decrease 

the efficiency of yolk use (Beacham and Murray 1990, 

Elliott and Hurley 1998). Upon emergence, smaller fish are 

more susceptible to displacement at higher flows. Some 

fish species may be more influenced by thermal shifts 

during incubation than others; Beacham and Murray (1990) 

suggested that coho salmon are adapted for cool water 

temperatures during development and could experience 

poorer survival under warming climate scenarios.

There are important ecological implications of climate-related changes in the time and size of fish at emergence. Earlier emergence can result in an extended growing 

season, a benefit that can lead to increased fitness. Holtby 

(1988) found that an increase of 1.3 °F (0.7 °C) in winter 

water temperatures following timber harvest in Carnation 

Creek on the west coast of Vancouver Island, British Columbia, resulted in coho salmon emerging 6 weeks earlier. Size 

at age increased because of the extended growing season, 

resulting in more fish completing their freshwater-rearing 

life history in one year rather than two. Coho salmon in 

Carnation Creek also smolted and moved to sea about 2 

weeks earlier following timber harvest (which raised stream 

temperatures); however, marine survival declined, possibly 

as a result of the decoupling of the timing of smolt migration 

from marine plankton blooms (Holtby and Scrivener 1989). 

Similarly, warmer winter temperatures increased the length 

of the growing season of recently emerged sockeye salmon 

in southwest Alaska. Like coho salmon in Carnation Creek, 

sockeye salmon grew faster, and more underwent smolt 

transformation at age 1+ during warm periods rather than 

at age 2+ in cooler periods (Schindler et al. 2005). However, 

age-1+ smolts were smaller than age-2+ smolts and were 

expected to have decreased marine survival.

Juveniles

Juvenile Pacific salmon (defined here as recently emerged 

fry up to, but not including, smolts) face a number of challenges from the potential effects of climate change. These 

challenges will include elevated temperatures and altered 

streamflows, both of which can affect physical and biological aspects of stream habitats. The type and extent of flow 

effects will differ depending on the time of emergence. For 

example, fish emerging in the late winter and early spring 

may experience high flows caused by earlier snowmelt. The 

consequences of a changing hydrograph will depend to a 

large degree on the geomorphic setting in which spawning 

and emergence occurs. In some settings, increased flooding 

could improve use of floodplain habitats when fish in wide, 

geomorphically unconstrained channels have access to 

habitats where floodplain vegetation is intact and secondary 

channels are available. 

Low-gradient streams and rivers can be important areas 

for postemergent and seasonal growth (Brown and Hartman 1988, Moore and Gregory 1988, Peterson 1982a), and 

marginal areas with reduced water velocities provide refuge 

against downstream displacement. Fry that emerge at a 

smaller size if water temperature is warmer can potentially 

overcome their size disadvantage by gaining an early start 

on the growing season (Holtby 1988). Juvenile salmonids in 

rain-dominated hydrographic regimes often move into the 

lower reaches of the channel network or into off-channel 

habitats in autumn to seek refuge from unfavorable water 

velocities in the main channel (Ebersole et al. 2006, Everest 

1975, Peterson 1982b, Solazzi et al. 2000). In high-elevation 

snowfall-dominated drainage systems, however, climate 

warming might not significantly increase mid-winter flood 

flows and facilitate access to floodplain habitats if precipitation still falls as snow.

Under several climate scenarios, the onset of the lowflow period is expected to occur up to 4 to 6 weeks earlier in 

most areas as a result of warming (Hamlet and Lettenmaier 

2007, Hamlet et al. 2005, Tague and Grant 2009). An 

extended period of low discharge over the dry season would 

likely decrease the amount of habitat suitable to juvenile 

salmonids, and this effect could be most pronounced in 

small to mid-sized streams (Stewart et al. 2005), resulting 

in some reaches that formerly held surface flows throughout 

the year becoming intermittent or even drying completely. 

As noted by Battin et al. (2007), flow reductions in headwater areas during the dry season could force resident fishes 

downstream in the stream network, as well as compromise 

their ability to cope with drought, by reducing the network 

of connected, perennially flowing channels. Additionally, 

the downstream displacement of headwater-rearing fish 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

will expose them to warmer temperatures than those to 

which they are adapted, and possibly to harmful biological 

interactions with native and nonnative species inhabiting 

the lower watershed. 

The consequences of climate-induced changes in 

low flows for juvenile salmonids such as Chinook salmon 

and steelhead that often rear in rivers are likely similar to 

those in smaller streams, although the risk of river reaches 

becoming intermittent is less because drainage areas are 

larger. Mantua et al. (2010) found widespread declines in 

summer discharge for many rivers in Washington state 

under climatic warming scenarios. Likewise, Luce and 

Holden (2009) examined hydrographic records from drainage systems throughout the Pacific Northwest and found 

that summer flows in all types of hydrologic regimes have 

been declining, thus providing increasingly smaller rearing 

areas to river-dwelling species.

In addition to lower flows, elevated summer water 

temperatures will likely have strong ecological effects on 

juvenile Pacific salmon, with the direction and magnitude 

of influence varying geographically, by species, and by 

life-history type. Water temperature influences the metabolism, food consumption, and growth of an individual (Brett 

et al. 1969, Warren and Davis 1967, Wurtsbaugh and Davis 

1977). Age and size of individuals also influence thermal 

effects; younger and smaller fish are most susceptible to 

thermal extremes (Brett 1952) and to short-term thermal 

variation (Elliott 1994). There is a temperature range in 

which an individual performs best given a certain level 

of food resources, and beyond that range, metabolic costs 

increase such that growth declines (Warren 1971). Increased 

temperature could potentially affect juvenile salmonids 

in opposing ways (Li et al. 1994). Warmer water could 

enhance primary and secondary aquatic production, leading 

to greater food availability; however, if the increased metabolic demands of warmer temperatures reduce food-conversion efficiency or if the organisms benefiting from warmer 

temperatures are not preferred food items, the net effect 

of warming could be reduced growth (Bisson and Davis 

1976). In southern portions of a species’ range, elevated 

temperatures could reduce the suitability of rearing areas 

for juveniles during the summer as temperatures exceed 

the point at which gains resulting from increased aquatic 

production are offset by physiological costs, resulting in 

reduced summer growth rates (Marine and Cech 2004). In 

contrast, growth rates of juveniles in more northern areas 

could increase if projected temperature changes stimulate 

aquatic productivity while remaining within the preferred 

physiological range for the species. 

If the net effects of elevated temperatures resulting 

from climate change in southern areas reduce summer 

growth (Isaak et al. 2010, Royer and Minshall 1997, 

Scarnecchia and Bergersen 1987), juveniles will be smaller 

entering the winter (ISAB 2007), and overwinter survival 

may decrease (Quinn and Petersen 1996). However, thermal 

increases may be beneficial for growth during other seasons 

if abundant food is present. Sogard et al. (2010) found that 

juvenile steelhead on the central coast of California attained 

the most growth in the spring and autumn, and that juvenile 

coho salmon grew in the winter in coastal Oregon (Ebersole 

et al. 2006, 2009). 

Outcomes of interactions between salmonids and 

nonsalmonids can be influenced by changing water temperatures. Rearing salmonids tend to outcompete nonsalmonids for food resources and preferred feeding areas at cooler 

temperatures, whereas nonsalmonids have the advantage at 

warmer temperatures (Petersen and Kitchell 2001, Reeves et 

al. 1987). The susceptibility of juvenile salmonids to disease 

could also increase at warmer temperatures and could be 

compounded by the presence of competitors that are less 

susceptible to the pathogens infecting salmon and trout 

(Reeves et al. 1987). Additionally, warmer temperatures 

could lead to increased predation from nonnative warmwater fish (ISAB 2007, Petersen and Kitchell 2001). The aggregate results of these indirect effects are likely to be changes 

in the structure and composition of fish communities in the 

affected stream systems (ISAB 2012), particularly in the 

southern portions of the NWFP area where the potential 

for interaction with warmwater species is greatest owing 

to widespread introduction and proliferation of nonnative 

warmwater fishes.

The effects of climate change on rearing habitats for 

juvenile salmon at the local level will depend, to some 

degree, on the geomorphic features of a particular location. 
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Crozier and Zabel (2006) suggested that two climate-influenced factors—stream temperature and flow—could 

affect habitat in different ways: narrow, confined streams 

were predicted to be more responsive to flow changes, 

and geomorphically unconfined streams would be more 

sensitive to temperature changes. In addition, the future 

quantity and quality of freshwater rearing habitat of Pacific 

salmon may also be influenced by predicted increases in 

the magnitude and frequency of large disturbances. Climate 

change scenarios predict an increase in exceptional flood 

events caused by transitions from snow to rain, accelerated 

glacial melt, wildfires, and forest pathogen outbreaks (Dale 

et al. 2001, Hamlet and Lettenmaier 2007). Frequent large 

floods promote landsliding and stream sedimentation in 

many areas (Miller et al. 2003). The effects of floods and 

associated erosion events on freshwater habitat will differ 

depending on the geomorphic setting, the magnitude and 

legacy of the event, the interval between succeeding disturbances, and the extent to which the affected ecosystem has 

been altered by past human activities (Reeves et al. 1995, 

Rieman et al. 2006). 

Increased disturbance frequency and severity can 

have short-term negative consequences for fish populations, including substrate scour and fine-sediment 

intrusion that reduces egg and alevin survival and 

macroinvertebrate abundance in confined channels, 

displacement of juveniles downstream, and loss of surface 

flow in summer in reaches where porous material has been 

deposited in the channel. However, in functionally intact 

systems there is a strong potential for aquatic habitat 

complexity to improve with flooding because floodplain 

linkages can be reestablished and large wood will be 

recruited to the channel network (Bisson et al. 2009). 

Long-term changes could be favorable to rearing salmon if 

the cumulative effects of climate change on water temperature, fine-sediment levels, and surface flows remain 

within limits tolerable to juvenile salmon or exceed those 

thresholds only for a short duration. 

Population productivity after large disturbances will 

also be enhanced by the presence of adjacent fish populations that provide sources of colonizers to help initiate 

recovery and that add to the phenotypic and genetic diversity of affected populations (Schtickzelle and Quinn 2007). 

But it is also possible that in greatly altered watersheds, 

where the cumulative harmful effects of climate change 

exceed environmental tolerance limits, the damage caused 

by large-scale disturbances will be too great, and if there 

are no nearby populations to provide new colonists, local 

population extirpation will occur. 

Lakes are important rearing habitats for sockeye 

salmon and will also be affected by climate change, 

although there are relatively few drainage systems in the 

NWFP area that support sockeye salmon runs. Potential 

effects will vary greatly depending on the location and 

features of the lake, but a primary effect will be the magnitude and seasonality of warming, with epilimnetic water 

and the timing of spring and autumn turnover experiencing 

the greatest changes (Stefan et al. 2001). Slight warming of 

deep lakes could lead to increased sockeye growth rates if 

temperatures stimulate primary and secondary production 

without significantly affecting the availability of cooler 

water during periods when the epilimnion becomes too 

warm for efficient metabolism. This benefit could be offset 

during the growing season by a reduction in the delivery 

of inorganic nutrients and dissolved organic carbon from 

terrestrial systems as a result of decreased spring and 

summer flows. Reduced inputs of nutrients and dissolved 

organic carbon from the surrounding watershed could 

result in diminished algal production, which would result in 

deeper light penetration and additional warming of the lake 

(Schindler et al. 1990). 

The productivity of zooplankton, the principal food of 

juvenile sockeye salmon in lakes, will be affected by climate change, but whether or not the changes are beneficial 

will depend on ambient thermal and hydrologic regimes. In 

Alaska, warming temperatures have resulted in earlier ice 

melt, greater densities of zooplankton, and increasing sockeye growth rates (Schindler et al. 2005). In contrast, earlier 

onset of spring in western Washington’s Lake Washington 

has advanced lake stratification by 20 days in recent years, 

resulting in earlier diatom blooms and a decline in cladocerans (Daphnia spp.), important prey species for juvenile 

sockeye rearing in the lake (Winder and Schindler 2004).
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Smolts

Anadromous salmonids typically undergo the smolting 

process and move to the ocean in spring, although seaward 

migrations of some salmon stocks occur throughout the 

year. Water temperature, day length, and changes in flow 

are the principal cues influencing the timing of parr-smolt 

transformations. Environmental signals affecting smolting 

can be divided into regulating and controlling factors 

(Byrne et al. 2004). Regulating factors act on juvenile 

salmon before the migration and influence the physiological 

aspects of smolting. Controlling factors operate during 

migration and affect the speed of downstream movement. 

Water temperature and day length appear to be key regulating factors (Jonsson and Jonsson 2009). Day length is not 

influenced by climate change, but increased temperature 

will affect the onset of smoltification. For Pacific salmon, 

elevated winter temperatures can result in earlier migration 

times of smolts. Chinook salmon have been observed 

to migrate earlier in warmer years than in cooler years 

(Achord et al. 2007, Roper and Scarnecchia 1999), but 

Jonsson and Jonsson (2009) cite a suite of other studies on 

Atlantic salmon, brown trout (Salmo trutta), and steelhead 

in which water temperatures did not affect the timing 

of smolt migration. Under certain conditions, elevated 

temperatures may even inhibit parr-smolt transformation. 

Adams et al. (1973) found that smolting in steelhead held 

at 59 °F (15 °C) or warmer led to reductions of ATPase 

activity needed to initiate the smolt transformation process. 

Thus, the effect of altered temperature on timing of smolt 

migration remains unpredictable and likely will vary widely 

across populations.

To a large extent, streamflow determines the rate at 

which smolts move downstream (Connor et al. 2003, Smith 

et al. 2002). Climate model projections of stream runoff 

(Snover et al. 2003, Tague and Grant 2009) suggest that the 

onset of the low-flow period will occur 4 to 6 weeks earlier 

over much of the NWFP area in the next century. Projections of the annual cycle of elevated flows from melting 

snow for more northerly areas are not currently available, 

but we assume that they will be similar. The consequences 

of altered flows are likely to be population-specific, with 

the timing and smolt survival rates of those populations that 

tend to migrate later or are required to move long distances 

likely to be the most affected by climate change.

The survival of smolts entering the ocean depends on 

a number of factors (Pearcy 1992). Larger smolts tend to 

have higher survival rates than do smaller fish (Holtby and 

Scrivener 1989, Quinn and Peterson 1996, Slaney 1988), 

possibly because they are better able to avoid predation. The 

size of an individual at smolting is influenced by its size at 

the beginning of the previous winter. Brown and Hartman 

(1988) found that stream and groundwater warming caused 

by logging in a coastal Vancouver Island watershed resulted 

in increased overwinter growth of presmolt coho salmon, 

and Holtby and Scrivener (1989) suggested that this growth 

advantage led to higher smolt-to-adult return rates through 

improved ocean survival. 

Conditions in marine nearshore areas at the time of 

ocean entry are known to strongly influence ocean survival 

(Rechisky et al. 2009). In the coastal area influenced by 

the California current—primarily the southern half of the 

distributional range of many Pacific salmon species—

potential changes in the timing and intensity of upwelling 

have important implications for smolts (Barth et al. 2007). 

Cold, nutrient-rich waters are pushed into nearshore areas 

by northerly winds in the late spring and early summer, 

producing favorable conditions for plankton production 

(Nickelson 1986, Scheuerell and Williams 2005). Under one 

climate change scenario, upwelling is projected to intensify 

but occur later in the summer (Snyder et al. 2003), decoupling the timing of smolt migration relative to plankton 

blooms for early-entry salmon smolts. 

The abundance of predators in nearshore areas can 

also influence marine survival of smolts (Pearcy 1992). 

Coho salmon from Carnation Creek on the west coast of 

Vancouver Island, British Columbia, entered the ocean 

about 2 weeks earlier as a result of increased growth as 

juveniles (Holtby 1988), but survival declined compared to 

the timing of pre-logging smolt migration. It was believed 

that predation by mackerel (Scomber japonicus) and hake 

(Merluccius productus) contributed to the decline, as both 

species moved into Barkley Sound during periods of warm 

sea-surface temperatures. Elevated ocean temperatures 

could also result in the expansion of subtropical predators 
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GENERAL TECHNICAL REPORT PNW-GTR-966

such as the Humboldt squid (Dosidicus gigas) into Pacific 

Northwest waters, further increasing predation pressure on 

salmon smolts (Christensen and Trites 2011, ISAB 2007). 

Nearshore conditions in northern portions of the 

NWFP area will also be influenced by climate change. In 

some locations, melting glaciers could increase iron levels 

in nearshore areas (Westerlund and Ohman 1991). Iron 

levels are often considered limiting to primary production 

in the North Pacific, and increased iron levels in freshwater 

plumes could potentially enhance marine food webs (Rose 

et al. 2005) and thus improve growth and survival of 

young salmon. The projected effects of climate change on 

the ocean ecology of Pacific salmon will therefore result 

from the combined influences of several factors, notably 

predation, food resource abundance, and both intra- and 

interspecific competition.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Scientific and common names of plant species identified in this report

Scientific name Common name

Abies amabilis (Douglas ex Loudon) Douglas ex Forbes Pacific silver fir

Abies concolor (Gord. & Glend.) Lindl. ex Hildebr. White fir

Abies grandis (Douglas ex D. Don) Lindl. Grand fir

Abies lasiocarpa (Hook.) Nutt. Subalpine pine

Abies magnifica A. Murray bis California red fir

Abies procera Rehder Noble fir

Acer circinatum Pursh Vine maple

Acer macrophyllum Pursh Bigleaf maple

Achlys triphylla (Sm.) DC. Sweet after death

Adenocaulon bicolor Hook. American trailplant

Alliaria petiolata (M. Bieb.) Cavara & Grande Garlic mustard

Alnus rubra Bong. Red alder

Amelanchier alnifolia (Nutt.) Nutt. ex M. Roem. Saskatoon serviceberry

Anemone oregana A. Gray Blue windflower

Apocynum cannabinum L. Dogbane

Arbutus menziesii Pursh) Madrone

Arceuthobium M. Bieb. Dwarf mistletoe

Arceuthobium occidentale Engelm. Gray pine dwarf mistletoe

Arceuthobium tsugense Rosendahl Hemlock dwarf mistletoe

Arctostaphylos nevadensis A. Gray Pinemat manzanita

Brachypodium sylvaticum (Huds.) P. Beauv. False brome

Brodiaea coronaria (Salisb.) Engl. Cluster-lilies

Callitropsis nootkatensis (D. Don) Oerst. ex D.P. Little Alaska yellow-cedar

Calocedrus decurrens (Torr.) Florin Incense cedar

Cannabis L. Marijuana 

Carex barbarae Dewey and C. obnupta L.H. Bailey Sedges

Centaurea solstitialis L. Yellow starthistle

Chamaecyparis lawsoniana (A. Murray bis) Parl. Port Orford cedar

Chimaphila menziesii (R. Br. ex D. Don) Spreng. Little prince’s pine

Chimaphila umbellata (L.) W.P.C. Barton Pipsissewa

Clematis vitalba L. Old man’s beard

Clintonia uniflora Menzies ex Schult. & Schult. f.) Kunth Bride’s bonnet

Coptis laciniata A. Gray Oregon goldthread

Corylus cornuta Marshall var. californica (A. DC.) Sharp California hazel

Cornus canadensis L. Bunchberry dogwood

Cytisus scoparius (L.) Link Scotch broom

Disporum hookeri (Torr.) G. Nicholson var. hookeri Drops-of-gold

Fallopia japonica (Houtt.) Ronse Decr. var. japonica Japanese knotweed

Gaultheria ovatifolia A. Gray Western teaberry

Gaultheria shallon Pursh Salal
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GENERAL TECHNICAL REPORT PNW-GTR-966

Scientific name Common name

Gentiana douglasiana Bong. Swamp gentian

Geranium lucidum L. Shining geranium

Geranium robertianum L. Robert geranium

Goodyera oblongifolia Raf. Western rattlesnake plantain

Hedera helix L. English ivy

Heracleum mantegazzianum Sommier & Levier Giant hogweed

Hesperocyparis sargentii (Jeps.) Bartel Sargent’s cypress

Hieracium aurantiacum L. Orange hawkweed

Ilex aquifolium L. English holly

Iris pseudacorus L. Paleyellow iris

Juniperus occidentalis Hook. Western juniper

Lamiastrum galeobdolon (L.) Ehrend. & Polatschek Yellow archangel

Lilium occidentale Purdy Western lily

Linnaea borealis L. Twinflower

Lithocarpus densiflorus (Hook. & Arn.) Rehder Tanoak

Lonicera hispidula Pursh Honeysuckle

Lupinus albicaulis Douglas Sickle-keeled lupine

Lycopodium clavatum L. Running clubmoss

Lythrum salicaria L. Purple loosestrife

Mahonia nervosa (Pursh) Nutt. Cascade barberry

Malus fusca (Raf.) C.K. Schneid. Pacific crabapple

Notholithocarpus densiflorus (Hook. & Arn.) P.S. Manos, C.H. Cannon, & S.H. Oh Tanoak

Notholithocarpus densiflorus (Hook. & Arn.) P.S. Manos, C.H. Cannon, & S.H. Oh 

var. echinoides (R.Br. ter) P.S. Manos, C.H. Cannon & S.H. Oh

Shrub form of tanoak

Nuphar polysepala (Engelm.) Yellow pond lily

Nymphoides peltata (S.G. Gmel.) Kuntze Yellow floating heart

Osmorhiza chilensis Hook. & Arn. Sweetcicely

Phalaris arundinacea L. Reed canarygrass

Picea engelmannii Parry ex Engelm. Engelmann spruce

Picea sitchensis (Bong.) Carrière Sitka spruce

Pinus albicaulis Engelm. Whitebark pine

Pinus attenuata Lemmon Knobcone pine

Pinus contorta Douglas ex Loudon Lodgepole pine

Pinus contorta Douglas ex Loudon var. contorta Beach pine, shore pine

Pinus jeffreyi Balf. Jeffrey pine

Pinus lambertiana Douglas Sugar pine

Pinus monticola Douglas ex D. Don) Western white pine

Pinus ponderosa Lawson & C. Lawson Ponderosa pine

Populus trichocarpa L. ssp. trichocarpa (Torr. & A. Gray ex Hook) Brayshaw Black cottonwood

Potamogeton crispus L. Curly pondweed

Potentilla recta L. Sulphur cinquefoil
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Scientific name Common name

Prunus emarginata (Douglas ex Hook. D. Dietr.) Bitter cherry

Pseudotsuga menziesii (Mirb.) Franco Douglas-fir

Pteridium aquilinum (L. Kuhn) Brackenfern

Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen & S.M. Almeida ex 

Sanjappa & Predeep

Kudzu

Pyrola asarifolia Sweet American wintergreen

Quercus agrifolia Née var. oxyadenia (Torr.) J.T. Howell Coastal live oak

Quercus berberidifolia Liebm. Scrub oak

Quercus chrysolepis Liebm. Canyon live oak

Quercus douglasii Hook. & Arn. Blue oak

Quercus garryana Douglas ex hook. Oregon white oak

Quercus kelloggi Newberry California black oak

Quercus lobata Née Valley oak

Rhamnus purshiana (DC.) A. Gray Cascara

Rhododendron groenlandicum Oeder Bog Labrador tea

Rhododendron macrophyllum D. Don ex G. Don Pacific rhododendron

Ribes lacustre (Pers.) Poir. Prickly currant

Rubus armeniacus Focke Himalayan blackberry

Salix exigua Nutt. Sandbar willow

Senecio bolanderi A. Gray Bolander’s ragwort

Sequoia sempervirens (Lamb. ex D. Don) Endl. Redwood

Smilacina stellata (L.) Desf. Starry false Solomon’s seal

Synthyris reniformis (Douglas ex Benth.) Benth. Snowqueen

Taxus brevifolia Nutt. Pacific yew

Thuja plicata Donn ex D. Don Western redcedar

Tiarella trifoliate L. Threeleaf foamflower

Trapa natans L. Water chestnut

Trillium ovatum Pursh Pacific trillium

Tsuga heterophylla (Raf.) Sarg. Western hemlock

Tsuga mertensiana (Bong.) Carrière Mountain hemlock

Typha latifolia L. Cattails

Umbellularia californica (Hook. & Arn.) Nutt. California bay laurel

Vaccinium alaskaense Howell Alaska blueberry

Vaccinium membranaceum Douglas ex Torr. Thinleaf huckleberry, big huckleberry

Vaccinium ovatum Pursh Evergreen huckleberry

Vaccinium oxycoccos L. Small cranberry

Vaccinium parvifolium Sm. Red huckleberry

Vancouveria hexandra (Hook.) C. Morren & Decne. White insideout flower

Xerophyllum tenax (Pursh) Nutt. Beargrass
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Glossary

This glossary is provided to help readers understand 

various terms used in the Northwest Forest Plan (NWFP) 

science synthesis. Sources include the Forest Service 

Handbook (FSH), the Code of Federal Regulations (CFR), 

executive orders, the Federal Register (FR), and various 

scientific publications (see “Glossary Literature Cited”). 

The authors have added working definitions of terms used 

in the synthesis and its source materials, especially when 

formal definitions may be lacking or when they differ 

across sources.

active management—Direct interventions to achieve desired outcomes, which may include harvesting and planting 

of vegetation and the intentional use of fire, among other 

activities (Carey 2003).

adaptive capacity—The ability of ecosystems and social 

systems to respond to, cope with, or adapt to disturbances 

and stressors, including environmental change, to maintain 

options for future generations (FSH 1909.12.5).

adaptive management—A structured, cyclical process for 

planning and decisionmaking in the face of uncertainty and 

changing conditions with feedback from monitoring, which 

includes using the planning process to actively test assumptions, track relevant conditions over time, and measure 

management effectiveness (FSH 1909.12.5). Additionally, 

adaptive management includes iterative decisionmaking, 

through which results are evaluated and actions are adjusted 

based on what has been learned.

adaptive management area (AMA)—A portion of the federal land area within the NWFP area that was specifically 

allocated for scientific monitoring and research to explore 

new forestry methods and other activities related to meeting the goals and objectives of the Plan. Ten AMAs were 

established in the NWFP area, covering about 1.5 million 

ac (600 000 ha), or 6 percent of the planning area (Stankey 

et al. 2003).

alien species—Any species, including its seeds, eggs, 

spores, or other biological material capable of propagating 

that species, that is not native to a particular ecosystem 

(Executive Order 13112). The term is synonymous with exotic species, nonindigenous, and nonnative species (see also 

“invasive species”).

allochthonous inputs—Material, specifically food resources, that originates from outside a stream, typically in the 

form of leaf litter. 

amenity communities—Communities located near lands 

with high amenity values.

amenity migration—Movement of people based on 

the draw of natural or cultural amenities (Gosnell and 

Abrams 2011).

amenity value—A noncommodity or “unpriced” value of 

a place or environment, typically encompassing aesthetic, 

social, cultural, and recreational values.

ancestral lands (of American Indian tribes)—Lands that 

historically were inhabited by the ancestors of American 

Indian tribes.

annual species review—A procedure established under the 

NWFP in which panels of managers and biologists evaluate new scientific and monitoring information on species to 

potentially support the recommendation of changes in their 

conservation status.

Anthropocene—The current period (or geological epoch) 

in which humans have become a dominant influence on the 

Earth’s climate and environment, generally dating from the 

period of rapid growth in industrialization, population, and 

global trade and transportation in the early 1800s (Steffen et 

al. 2007).

Aquatic Conservation Strategy (ACS) —A regional strategy applied to aquatic and riparian ecosystems across the 

area covered by the NWFP) (Espy and Babbit 1994) (see 

chapter 7 for more details).

at-risk species—Federally recognized threatened, endangered, proposed, and candidate species and species of conservation concern. These species are considered at risk of 

low viability as a result of changing environmental conditions or human-caused stressors.
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best management practices (BMPs) (for water quality)—Methods, measures, or practices used to reduce or 

eliminate the introduction of pollutants and other detrimental impacts to water quality, including but not limited to 

structural and nonstructural controls and to operation and 

maintenance procedures.

biodiversity—In general, the variety of life forms and their 

processes and ecological functions, at all levels of biological 

organization from genes to populations, species, assemblages, communities, and ecosystems. 

breeding inhibition—Prevention of reproduction in 

healthy adult individuals.

bryophytes—Mosses and liverworts.

canopy cover—The downward vertical projection from the 

outside profile of the canopy (crown) of a plant measured in 

percentage of land area covered.

carrying capacity—The maximum population size a specific environment can sustain.

ceded areas—Lands that particular tribes ceded to the 

United States government by treaties, which have been catalogued in the Library of Congress.

climate adaptation—Management actions to reduce vulnerabilities to climate change and related disturbances.

climate change—Changes in average weather conditions 

(including temperature, precipitation, and risk of certain 

types of severe weather events) that persist over multiple 

decades or longer, and that result from both natural factors 

and human activities such as increased emissions of greenhouse gases (U.S. Global Change Research Program 2017).

coarse filter—A conservation approach that focuses on 

conserving ecosystems, in contrast to a “fine filter” approach that focuses on conserving specific species. These 

two approaches are generally viewed as complementary, 

with fine-filtered strategies tailored to fit particular species 

that “fall through the pores” of the coarse filter (Hunter 

2005). See also “mesofilter.”

co-management—Two or more entities, each having legally 

established management responsibilities, working collaboratively to achieve mutually agreed upon, compatible objectives to protect, conserve, use, enhance, or restore natural 

and cultural resources (81 FR 4638).

collaborative management—Two or more entities working together to actively protect, conserve, use, enhance, or 

restore natural and cultural resources (81 FR 4638).

collaboration or collaborative process—A structured 

manner in which a collection of people with diverse interests share knowledge, ideas, and resources, while working 

together in an inclusive and cooperative manner toward a 

common purpose (FSH 1909.12.05).

community (plant and animal)—A naturally occurring 

assemblage of plant and animal species living within a defined area or habitat (36 CFR 219.19).

community forest—A general definition is forest land that 

is managed by local communities to provide local benefits 

(Teitelbaum et al. 2006). The federal government has specifically defined community forest as “forest land owned in 

fee simple by an eligible entity [local government, nonprofit 

organization, or federally recognized tribe] that provides 

public access and is managed to provide community benefits pursuant to a community forest plan” (36 CFR 230.2).

community of place or place-based community—A group 

of people who are bound together because of where they 

reside, work, visit, or otherwise spend a continuous portion 

of their time.

community resilience—The capacity of a community to 

return to its initial function and structure when initially 

altered under disturbance.

community resistance—The capacity of a community to 

withstand a disturbance without changing its function and 

structure. 

composition—The biological elements within the various 

levels of biological organization, from genes and species to 

communities and ecosystems (FSM 2020).
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congeneric—Organisms that belong to the same taxonomic 

genus, usually belonging to different species.

connectivity (of habitats)—Environmental conditions 

that exist at several spatial and temporal scales that provide landscape linkages that permit (a) the exchange of 

flow, sediments, and nutrients; (b) genetic interchange of 

genes among individuals between populations; and (c) the 

long-distance range shifts of species, such as in response to 

climate change (36 CFR 219.19).

consultation (tribal)—A formal government-to-government process that enables American Indian tribes and 

Alaska Native Corporations to provide meaningful, timely 

input, and, as appropriate, exchange views, information, 

and recommendations on proposed policies or actions 

that may affect their rights or interests prior to a decision. 

Consultation is a unique form of communication characterized by trust and respect (FSM 1509.05).

corticosterone—A steroid hormone produced by many species of animals, often as the result of stress.

cryptogam—An organism that reproduces by spores and 

that does not produce true flowers and seeds; includes fungi, 

algae, lichens, mosses, liverworts, and ferns. 

cultural keystone species—A species that significantly 

shapes the cultural identity of a people, as reflected in diet, 

materials, medicine, or spiritual practice (Garibaldi and 

Turner 2004).

cultural services—A type of ecosystem service that includes the nonmaterial benefits that people obtain from 

ecosystems through spiritual enrichment, cognitive development, reflection, recreation, and aesthetic experiences 

(Sarukhán and Whyte 2005).

desired conditions—A description of specific social, economic, or ecological characteristics toward which management of the land and resources should be directed.

disturbance regime—A description of the characteristic 

types of disturbance on a given landscape; the frequency, 

severity, and size distribution of these characteristic disturbance types and their interactions (36 CFR 219.19).

disturbance—Any relatively discrete event in time that 

disrupts ecosystem, watershed, community, or species 

population structure or function, and that changes resources, substrate availability, or the physical environment (36 

CFR 219.19).

dynamic reserves—A conservation approach in which protected areas are relocated following changes in environmental conditions, especially owing to disturbance.

early-seral vegetation—Vegetation conditions in the early 

stages of succession following an event that removes the 

forest canopy (e.g., timber harvest, wildfire, windstorm), 

on sites that are capable of developing a closed canopy 

(Swanson et al. 2014). A nonforest or “pre-forest” condition 

occurs first, followed by an “early-seral forest” as young 

shade-intolerant trees form a closed canopy.

ecocultural resources—Valued elements of the biophysical 

environment, including plants, fungi, wildlife, water, and 

places, and the social and cultural relationships of people 

with those elements.

ecological conditions—The biological and physical environment that can affect the diversity of plant and animal 

communities, the persistence of native species, invasibility, 

and productive capacity of ecological systems. Ecological 

conditions include habitat and other influences on species 

and the environment. Examples of ecological conditions 

include the abundance and distribution of aquatic and terrestrial habitats, connectivity, roads and other structural 

developments, human uses, and occurrence of other species 

(36 CFR 219.19).

ecological forestry—A ecosystem management approach 

designed to achieve multiple objectives that may include 

conservation goals and sustainable forest management and 

which emphasizes disturbance-based management and 

retention of “legacy” elements such as old trees and dead 

wood (Franklin et al. 2007).

ecological integrity—The quality or condition of an ecosystem when its dominant ecological characteristics (e.g., 

composition, structure, function, connectivity, and species 

composition and diversity) occur within the natural range of 
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variation and can withstand and recover from most perturbations imposed by natural environmental dynamics or 

human influence (36 CFR 219.19).

ecological keystone species—A species whose ecological 

functions have extensive and disproportionately large effects 

on ecosystems relative to its abundance (Power et al. 1996).

ecological sustainability—The capability of ecosystems to 

maintain ecological integrity (36 CFR 219.19).

economic sustainability—The capability of society to 

produce and consume or otherwise benefit from goods and 

services, including contributions to jobs and market and 

nonmarket benefits (36 CFR 219.19).

ecoregion—A geographic area containing distinctive ecological assemblages, topographic and climatic gradients, 

and historical land uses.

ecosystem—A spatially explicit, relatively homogeneous 

unit of the Earth that includes all interacting organisms and 

elements of the abiotic environment within its boundaries 

(36 CFR 219.19).

ecosystem diversity—The variety and relative extent of 

ecosystems (36 CFR 219.19).

ecosystem integrity—See “ecological integrity.” 

ecosystem management—Management across broad 

spatial and long temporal scales for a suite of goals, including maintaining populations of multiple species and 

ecosystem services.

ecosystem services—Benefits that people obtain from 

ecosystems (see also “provisioning services,” “regulating 

services,” “supporting services,” and “cultural services”).

ectomycorrhizal fungi—Fungal species that form symbiotic relationships with vascular plants through roots, typically 

aiding their uptake of nutrients. Although other mycorrhizal fungi penetrate their host’s cell walls, ectomycorrhizal 

fungi do not. 

endangered species—Any species or subspecies that the 

Secretary of the Interior or the Secretary of Commerce has 

deemed in danger of extinction throughout all or a significant portion of its range (16 U.S.C. Section 1532).

endemic—Native and restricted to a specific geographical 

area. 

El Niño Southern Oscillation (ENSO)—A band of anomalously warm ocean water temperatures that occasionally 

develops off the western coast of South America and can 

cause climatic changes across the Pacific Ocean. The extremes of this climate pattern’s oscillations cause extreme 

weather (such as floods and droughts) in many regions of 

the world.

environmental DNA (eDNA)—Genetic material (DNA) 

contained within small biological and tissue fragments that 

can be collected from aquatic, terrestrial, and even atmospheric environments, linked to an individual species, and 

used to indicate the presence of that species.

environmental justice populations—Groups of people who have low incomes or who identify themselves as 

African American, Asian or Pacific Islander, American 

Indian or Alaskan Native, or of Hispanic origin.

ephemeral stream—A stream that flows only in direct response to precipitation in the immediate locality (watershed 

or catchment basin), and whose channel is at all other times 

above the zone of saturation. 

epicormic—Literally, “of a shoot or branch,” this term implies growth from a previously dormant bud on the trunk or 

a limb of a tree. 

epiphyte—A plant or plant ally (including mosses and 

lichens) that grows on the surface of another plant such as a 

tree, but is not a parasite. 

even-aged stand—A stand of trees composed of a single 

age class (36 CFR 219.19).

fecundity—The reproductive rate of an organism or 

population.

federally recognized Indian tribe—An Indian tribe or 

Alaska Native Corporation, band, nation, pueblo, village, or 

community that the Secretary of the Interior acknowledges 
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to exist as an Indian tribe under the Federally Recognized 

Indian Tribe List Act of 1994, 25 U.S.C. 479a (36 CFR 

219.19).

fine filter—A conservation approach that focuses on conserving individual species in contrast to a “coarse filter” 

approach that focuses on conserving ecosystems; these 

approaches are generally viewed as complementary with 

fine-filtered strategies tailored to fit particular species that 

“fall through the pores” of the coarse filter (Hunter 2005). 

See also “mesofilter.” 

fire-dependent vegetation types—A vegetative community that evolved with fire as a necessary contributor to its 

vitality and to the renewal of habitat for its member species. 

fire exclusion—Curtailment of wildland fire because of 

deliberate suppression of ignitions, as well as unintentional effects of human activities such as intensive grazing 

that removes grasses and other fuels that carry fire (Keane 

et al. 2002). 

fire intensity—The amount of energy or heat release 

during fire.

fire regime—A characterization of long-term patterns of 

fire in a given ecosystem over a specified and relatively long 

period of time, based on multiple attributes, including frequency, severity, extent, spatial complexity, and seasonality 

of fire occurrence.

fire regime, low frequency, high severity—A fire regime 

with long return intervals (>200 years) and high levels of 

vegetation mortality (e.g., ~70 percent basal area mortality 

in forested ecosystems), often occurring in large patches 

(>10,000 ac [4047 ha]) (see chapter 3 for more details).

fire regime, moderate frequency, mixed severity—A 

fire regime with moderate return intervals between 50 and 

200 years and mixtures of low, moderate, and high severity; high-severity patches would have been common and 

frequently large (>1,000 ac [>405 ha]) (see chapter 3 for 

more details).

fire regime, very frequent, low severity—A fire regime 

with short return intervals (5 to 25 years) dominated by 

surface fires that result in low levels of vegetation mortality 

(e.g., <20 percent basal area mortality in forested ecosystems), with high-severity fire generally limited to small 

patches (<2.5 ac [1 ha]) (see chapter 3 for more details). 

fire regime, frequent, mixed severity—A fire regime with 

return intervals between 15 and 50 years that burns with a 

mosaic of low-, moderate-, and high-severity patches (Perry 

et al. 2011) (see chapter 3 for more details).

fire rotation—Length of time expected for a specific 

amount of land to burn (some parts might burn more than 

once or some not at all) based upon the study of past fire 

records in a large landscape (Turner and Romme 1994).

fire severity—The magnitude of the effects of fire on ecosystem components, including vegetation or soils.

fire suppression—The human act of extinguishing wildfires (Keane et al. 2002). 

floodplain restoration—Ecological restoration of a stream 

or river’s floodplain, which may involve setback or removal 

of levees or other structural constraints.

focal species—A small set of species whose status is assumed to infer the integrity of the larger ecological system 

to which it belongs, and thus to provide meaningful information regarding the effectiveness of a resource management plan in maintaining or restoring the ecological conditions to maintain the broader diversity of plant and animal 

communities in the NWPF area. Focal species would be 

commonly selected on the basis of their functional role in 

ecosystems (36 CFR 219.19).

food web—Interconnecting chains between organisms in 

an ecological community based upon what they consume.

Forest Ecosystem Management Assessment Team 

(FEMAT)—An interdisciplinary team that included expert 

ecological and social scientists, analysts, and managers 

assembled in 1993 by President Bill Clinton to develop 

options for ecosystem management of federal forests within 

the range of the northern spotted owl (FEMAT 1993).
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forest fragmentation—The patterns of dispersion and 

connectivity of nonhomogeneous forest cover (Riitters et 

al. 2002). See also “landscape fragmentation” and “habitat 

fragmentation” for specific meanings related to habitat loss 

and isolation.

frequency distribution—A depiction, often appearing in 

the form of a curve or graph, of the abundance of possible 

values of a variable. In this synthesis report, we speak of the 

frequency of wildfire patches of various sizes.

fuels (wildland)—Combustible material in wildland areas, 

including live and dead plant biomass such as trees, shrub, 

grass, leaves, litter, snags, and logs. 

fuels management—Manipulation of wildland fuels 

through mechanical, chemical, biological, or manual means, 

or by fire, in support of land management objectives to control or mitigate the effects of future wildland fire.

function (ecological)—Ecological processes, such as energy flow; nutrient cycling and retention; soil development and 

retention; predation and herbivory; and natural disturbances 

such as wind, fire, and floods that sustain composition and 

structure (FSM 2020). See also “key ecological function.” 

future range of variation (FRV)—The natural fluctuation 

of pattern components of healthy ecosystems that might 

occur in the future, primarily affected by climate change, 

human infrastructure, invasive species, and other anticipated disturbances.

gaps (forest)—Small openings in a forest canopy that 

are naturally formed when one or a few canopy trees die 

(Yamamoto 2000).

genotype—The genetic makeup of an individual organism. 

glucocorticoid—A class of steroid hormones produced by 

many species of animals, often as the result of stress.

goals (in land management plans)—Broad statements of 

intent, other than desired conditions, that do not include expected completion dates (36 CFR part 219.7(e)(2)).

guideline—A constraint on project and activity decisionmaking that allows for departure from its terms, so long as 

the purpose of the guideline is met (36 CFR section 219.15(d)

(3)). Guidelines are established to help achieve or maintain a 

desired condition or conditions, to avoid or mitigate undesirable effects, or to meet applicable legal requirements.

habitat—An area with the environmental conditions and 

resources that are necessary for occupancy by a species and 

for individuals of that species to survive and reproduce.

habitat fragmentation—Discontinuity in the spatial distribution of resources and conditions present in an area at a 

given scale that affects occupancy, reproduction, and survival in a particular species (see “landscape fragmentation”).

heterogeneity (forest)—Diversity, often applied to variation in forest structure within stands in two dimensions: 

horizontal (e.g., single trees, clumps of trees, and gaps of no 

trees), and vertical (e.g., vegetation at different heights from 

the forest floor to the top of the forest canopy), or across 

large landscapes (North et al. 2009).

hierarchy theory—A theory that describes ecosystems at 

multiple levels of organization (e.g., organisms, populations, 

and communities) in a nested hierarchy.

high-severity burn patch—A contiguous area of highseverity or stand-replacing fire.

historical range of variation (HRV)—Past fluctuation or 

range of conditions in the pattern of components of ecosystems over a specified period of time.

hybrid ecosystem—An ecosystem that has been modified from a historical state such that it has novel attributes while retaining some original characteristics (see 

“novel ecosystem”).

hybrid—Offspring resulting from the breeding of two 

different species.

inbreeding depression—Reduced fitness in a population 

that occurs as the result of breeding between related individuals, leading to increased homogeneity and simplification of the gene pool.
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GENERAL TECHNICAL REPORT PNW-GTR-966

in-channel restoration—Ecological restoration of the 

channel of a stream or river, often through placement of materials (rocks and wood) or other structural modifications.

individuals, clumps, and openings (ICO) method—A 

method that incorporates reference spatial pattern targets 

based upon individual trees, clumps of trees, and canopy 

openings into silvicultural prescriptions and tree-marking 

guidelines (Churchill et al. 2013).

Interagency Special Status and Sensitive Species 

Program (ISSSSP)—A federal agency program, established under the U.S. Forest Service Pacific Northwest 

Region and Bureau of Land Management Oregon/

Washington state office. The ISSSSP superseded the Survey 

and Manage standards and guidelines under the NWFP and 

also addresses other species of conservation focus, coordinates development and revision of management recommendations and survey protocols, coordinates data management 

between the agencies, develops summaries of species biology, and conducts other tasks. 

intermittent stream—A stream or reach of stream channel 

that flows, in its natural condition, only during certain times 

of the year or in several years, and is characterized by interspersed, permanent surface water areas containing aquatic 

flora and fauna adapted to the relatively harsh environmental conditions found in these types of environments.

invasive species—An alien species (or subspecies) whose 

deliberate, accidental, or self-introduction is likely to cause 

economic or environmental harm or harm to human health 

(Executive Order 13112).

key ecological function—The main behaviors performed 

by an organism that can influence environmental conditions 

or habitats of other species.

key watersheds—Watersheds that are expected to serve as 

refugia for aquatic organisms, particularly in the short term, 

for at-risk fish populations that have the greatest potential 

for restoration, or to provide sources of high-quality water. 

land and resource management plan (Forest Service)—A 

document or set of documents that provides management 

direction for an administrative unit of the National Forest 

System (FSH 1909.12.5).

landform—A specific geomorphic feature on the surface of 

the Earth, such as a mountain, plateau, canyon, or valley.

landscape—A defined area irrespective of ownership 

or other artificial boundaries, such as a spatial mosaic of 

terrestrial and aquatic ecosystems, landforms, and plant 

communities, repeated in similar form throughout such a 

defined area (36 CFR 219.19).

landscape fragmentation—Breaking up of continuous 

habitats into patches as a result of human land use and 

thereby generating habitat loss, isolation, and edge effects 

(see “habitat fragmentation”).

landscape genetics—An interdisciplinary field of study 

that combines population genetics and landscape ecology to explore how genetic relatedness among individuals 

and subpopulations of a species is influenced by landscape-level conditions.

landscape hierarchy—Organization of land areas based 

upon a hierarchy of nested geographic (i.e., different-sized) 

units, which provides a guide for defining the functional 

components of a system and how components at different 

scales are related to one another.

late-successional forest—Forests that have developed after 

long periods of time (typically at least 100 to 200 years) following major disturbances, and that contain a major component of shade-tolerant tree species that can regenerate beneath a canopy and eventually grow into the canopy in which 

small canopy gaps occur (see chapter 3 for more details). 

Note that FEMAT (1993) and the NWFP also applied this 

term to older (at least 80 years) forest types, including both 

old-growth and mature forests, regardless of the shade tolerance of the dominant tree species (e.g., 90-year-old forests 

dominated by Douglas-fir were termed late successional).

leading edge—The boundary of a species’ range at which 

the population is geographically expanding through colonization of new sites.
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legacy trees—Individual trees that survive a major disturbance and persist as components of early-seral stands 

(Franklin 1990).

legacies (biological)—Live trees, seed and seedling banks, 

remnant populations and individuals, snags, large soil aggregates, hyphal mats, logs, uprooted trees, and other biotic 

features that survive a major disturbance and persist as 

components of early-seral stands (Franklin 1990, Franklin 

et al. 2002).

lentic—Still-water environments, including lakes, ponds, 

and wet meadows.

longitudinal studies—Studies that include repeated observations on the same response variable over time.

lotic—Freshwater environments with running water, including rivers, streams, and springs.

low-income population—A community or a group of individuals living in geographic proximity to one another, or 

a set of individuals, such as migrant workers or American 

Indians, who meet the standards for low income and experience common conditions of environmental exposure or 

effect (CEQ 1997).

managing wildfire for resource objectives—Managing 

wildfires to promote multiple objectives such as reducing 

fire danger or restoring forest health and ecological processes rather than attempting full suppression. The terms 

“managed wildfire” or “resource objective wildfire” have 

also been used to describe such events (Long et al. 2017). 

However, fire managers note that many unplanned ignitions are managed using a combination of tactics, including 

direct suppression, indirect containment, monitoring of fire 

spread, and even accelerating fire spread, across their perimeters and over their full duration. Therefore, terms that 

separate “managed” wildfires from fully “suppressed” wildfires do not convey that complexity. (See “Use of wildland 

fire,” which also includes prescribed burning).

matrix—Federal and other lands outside of specifically 

designated reserve areas, particularly the late-successional 

reserves under the NWFP, that are managed for timber production and other objectives.

mature forest—An older forest stage (>80 years) prior to 

old-growth in which trees begin attaining maximum heights 

and developing some characteristic, for example, 80 to 200 

years in the case of old-growth Douglas-fir/western hemlock forests, often (but not always) including big trees (>50 

cm diameter at breast height), establishment of late-seral 

species (i.e., shade-tolerant trees), and initiation of decadence in early species (i.e., shade-intolerant trees).

mesofilter—A conservation approach that “focuses on conserving critical elements of ecosystems that are important 

to many species, especially those likely to be overlooked 

by fine-filter approaches, such as invertebrates, fungi, and 

nonvascular plants” (Hunter 2005).

meta-analysis—A study that combines the results of multiple studies. 

minority population—A readily identifiable group of people living in geographic proximity with a population that is 

at least 50 percent minority; or, an identifiable group that 

has a meaningfully greater minority population than the 

adjacent geographic areas, or may also be a geographically 

dispersed/transient set of individuals such as migrant workers or Americans Indians (CEQ 1997).

mitigation (climate change)—Efforts to reduce anthropogenic alteration of climate, in particular by increasing 

carbon sequestration. 

monitoring—A systematic process of collecting information to track implementation (implementation monitoring), 

to evaluate effects of actions or changes in conditions or relationships (effectiveness monitoring), or to test underlying 

assumptions (validation monitoring) (see 36 CFR 219.19).

mosaic—The contiguous spatial arrangement of elements 

within an area. In regions, this is typically the upland vegetation patches, large urban areas, large bodies of water, and 

large areas of barren ground or rock. However, regional mosaics can also be described in terms of land ownership, habitat 
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patches, land use patches, or other elements. For landscapes, 

this is typically the spatial arrangement of landscape elements.

multiaged stands—Forest stands having two or more 

age classes of trees; this includes stands resulting from 

variable-retention silvicultural systems or other traditionally even-aged systems that leave residual or reserve 

(legacy) trees.

multiple use—The management of all the various renewable surface resources of the National Forest System so that 

they are used in the combination that will best meet the 

needs of the American people; making the most judicious 

use of the land for some or all of these resources or related 

services over areas large enough to provide sufficient latitude for periodic adjustments in use to conform to changing 

needs and conditions; that some land will be used for less 

than all of the resources; and harmonious and coordinated 

management of the various resources, each with the other, 

without impairment of the productivity of the land, with 

consideration being given to the relative values of the various resources, and not necessarily the combination of uses 

that will give the greatest dollar return or the greatest unit 

output, consistent with the Multiple-Use Sustained-Yield 

Act of 1960 (16 U.S.C. 528–531) (36 CFR 219.19).

natal site—Location of birth.

native knowledge—A way of knowing or understanding the 

world, including traditional ecological, and social knowledge 

of the environment derived from multiple generations of indigenous peoples’ interactions, observations, and experiences with their ecological systems. This knowledge is accumulated over successive generations and is expressed through 

oral traditions, ceremonies, stories, dances, songs, art, and 

other means within a cultural context (36 CFR 219.19).

native species—A species historically or currently present 

in a particular ecosystem as a result of natural migratory or 

evolutionary processes and not as a result of an accidental 

or deliberate introduction or invasion into that ecosystem 

(see 36 CFR 219.19).

natural range of variation (NRV)—The variation of ecological characteristics and processes over specified scales of 

time and space that are appropriate for a given management 

application (FSH 1909.12.5).

nested hierarchy—The name given to the hierarchical 

structure of groups within groups used to classify organisms.

nontimber forest products (also known as “special forest products”)—Various products from forests that do not 

include logs from trees but do include bark, berries, boughs, 

bryophytes, bulbs, burls, Christmas trees, cones, ferns, firewood, forbs, fungi (including mushrooms), grasses, mosses, 

nuts, pine straw, roots, sedges, seeds, transplants, tree sap, 

wildflowers, fence material, mine props, posts and poles, shingle and shake bolts, and rails (36 CFR part 223 Subpart G).

novel ecosystem—An ecosystem that has experienced large 

and potentially irreversibly modifications to abiotic conditions 

or biotic composition in ways that result in a composition 

of species, ecological communities, and functions that have 

never before existed, and that depart from historical analogs 

(Hobbs et al. 2009). See “hybrid ecosystem” for comparison.

old-growth forest—A forest distinguished by old trees 

(>200 years) and related structural attributes that often (but 

not always) include large trees, high biomass of dead wood 

(i.e., snags, down coarse wood), multiple canopy layers, 

distinctive species composition and functions, and vertical 

and horizontal diversity in the tree canopy (see chapter 3). 

In dry, fire-frequent forests, old growth is characterized by 

large, old fire-resistant trees and relatively open stands without canopy layering. 

palustrine—Inland, nontidal wetlands that may be permanently or temporarily flooded and are characterized by the 

presence of emergent vegetation such as swamps, marshes, 

vernal pools, and lakeshores.

passive management—A management approach in which 

natural processes are allowed to occur without human intervention to reach desired outcomes.

patch—A relatively small area with similar environmental conditions, such as vegetative structure and composition. Sometimes used interchangeably with vegetation or 

forest stand.
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

Pacific Decadal Oscillation (PDO)—A recurring (approximately decadal-scale) pattern of ocean-atmosphere 

—a stream or reach of a channel that flows continuously 

or nearly so throughout the year and whose upper surface 

is generally lower than the top of the zone of saturation in 

areas adjacent to the stream.

perennial stream—A stream or reach of a channel that 

flows continuously or nearly so throughout the year and 

whose upper surface is generally lower than the top of the 

zone of saturation in areas adjacent to the stream.

phenotype—Physical manifestation of the genetic makeup 

of an individual and its interaction with the environment.

place attachment—The “positive bond that develops 

between groups or individuals and their environment” 

(Jorgensen and Stedman 2001: 234).

place dependence— “The strength of an individual’s 

subjective attachment to specific places” (Stokols and 

Shumaker 1982: 157).

place identity—Dimensions of self that define an individual’s [or group’s] identity in relation to the physical 

environment through ideas, beliefs, preferences, feelings, values, goals, and behavioral tendencies and skills 

(Proshansky 1978).

place-based planning—“A process used to involve stakeholders by encouraging them to come together to collectively define place meanings and attachments” (Lowery and 

Morse 2013: 1423).

plant association—A fine level of classification in a hierarchy of potential vegetation that is defined in terms of a climax-dominant overstory tree species and typical understory 

herb or shrub species. 

population bottleneck—An abrupt decline in the size of 

a population from an event, which often results in deleterious effects such as reduced genetic diversity and increased 

probability of local or global extirpation.

potential vegetation type (PVT)—Native, late-successional (or “climax”) plant community that reflects the regional 

climate, and dominant plant species that would occur on a 

site in absence of disturbances (Pfister and Arno 1980).

poverty rate—A measure of financial income below a 

threshold that differs by family size and composition.

precautionary principle—A principle that if an action, 

policy, or decision has a suspected risk of causing harm 

to the public or to the environment, and there is no scientific consensus that it is not harmful, then the burden 

of proof that it is not harmful falls on those making that 

decision. Particular definitions of the principle differ, and 

some applications use the less formal term, “precautionary approach.” Important qualifications associated with 

many definitions include (1) the perceived harm is likely 

to be serious, (2) some scientific analysis suggests a significant but uncertain potential for harm, and (3) applications of the principle emphasize generally constraining 

an activity to mitigate it rather than “resisting” it entirely 

(Doremus 2007).

prescribed fire—A wildland fire originating from a 

planned ignition to meet specific objectives identified 

in a written and approved prescribed fire plan for which 

National Environmental Policy Act requirements (where applicable) have been met prior to ignition (synonymous with 

controlled burn).

primary recreation activity—A single activity that caused 

a recreation visit to a national forest.

probable sale quantity—An estimate of the average 

amount of timber likely to be awarded for sale for a given 

area (such as the NWFP area) during a specified period.

provisioning services—A type of ecosystem service that 

includes clean air and fresh water, energy, food, fuel, forage, wood products or fiber, and minerals.

public participation geographic information system 

(PPGIS)—Using spatial decisionmaking and mapping tools 

to produce local knowledge with the goal of including and empowering marginalized populations (Brown and Reed 2009).

public values—Amenity values (scenery, quality of life); 

environmental quality (clean air, soil, and water); ecological 
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GENERAL TECHNICAL REPORT PNW-GTR-966

values (biodiversity); public use values (outdoor recreation, 

education, subsistence use); and spiritual or religious values 

(cultural ties, tribal history).

record of decision (ROD)—The final decision document 

that amended the planning documents of 19 national forests 

and seven Bureau of Land Management districts within the 

range of the northern spotted owl (the NWFP area) in April 

1994 (Espy and Babbit 1994).

recreation opportunity—An opportunity to participate 

in a specific recreation activity in a particular recreation 

setting to enjoy desired recreation experiences and other 

benefits that accrue. Recreation opportunities include nonmotorized, motorized, developed, and dispersed recreation 

on land, water, and in the air (36 CFR 219.19).

redundancy—The presence of multiple occurrences of 

ecological conditions, including key ecological functions 

(functional redundancy), such that not all occurrences may 

be eliminated by a catastrophic event. 

refugia—An area that remains less altered by climatic and 

environmental change (including disturbances such as wind 

and fire) affecting surrounding regions and that therefore 

forms a haven for relict fauna and flora.

regalia—Dress and special elements made from a variety 

of items, including various plant and animal materials, and 

worn for tribal dances and ceremonies.

regulating services—A type of ecosystem service that 

includes long-term storage of carbon; climate regulation; 

water filtration, purification, and storage; soil stabilization; 

flood and drought control; and disease regulation.

representativeness—The presence of a full array of ecosystem types and successional states, based on the physical 

environment and characteristic disturbance processes.

reserve—An area of land designated and managed for a special purpose, often to conserve or protect ecosystems, species, 

or other natural and cultural resources from particular human 

activities that are detrimental to achieving the goals of the area.

resilience—The capacity of a system to absorb disturbance 

and reorganize (or return to its previous organization) so as 

to still retain essentially the same function, structure, identity, and feedbacks (see FSM Chapter 2020 and see also “socioecological resilience”). Definitions emphasize the capacity 

of a system or its constituent entities to respond or regrow after mortality induced by a disturbance event, although broad 

definitions of resilience may also encompass “resistance” 

(see below), under which such mortality may be averted.

resistance—The capacity of a system or an entity to withstand a disturbance event without much change.

restoration economy—Diverse economic activities associated with the restoration of structure or function to terrestrial 

and aquatic ecosystems (Nielsen-Pincus and Moseley 2013).

restoration, ecological—The process of assisting the recovery of an ecosystem that has been degraded, damaged, or 

destroyed. Ecological restoration focuses on reestablishing 

the composition, structure, pattern, and ecological processes necessary to facilitate terrestrial and aquatic ecosystems 

sustainability, resilience, and health under current and future conditions (36 CFR 219.19).

restoration, functional—Restoration of dynamic abiotic 

and biotic processes in degraded ecosystems, without necessarily a focus on structural condition and composition.

riparian areas—Three-dimensional ecotones (the transition zone between two adjoining communities) of interaction that include terrestrial and aquatic ecosystems that 

extend down into the groundwater, up above the canopy, 

outward across the floodplain, up the near slopes that drain 

to the water, laterally into the terrestrial ecosystem, and 

along the water course at variable widths (36 CFR 219.19).

riparian management zone—Portions of a watershed 

in which riparian-dependent resources receive primary 

emphasis, and for which plans include Plan components to 

maintain or restore riparian functions and ecological functions (36 CFR 219.19).

riparian reserves—Reserves established along streams and 

rivers to protect riparian ecological functions and processes 
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Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

necessary to create and maintain habitat for aquatic and riparian-dependent organisms over time and ensure connectivity 

within and between watersheds. The Aquatic Conservation 

Strategy in the NWFP record of decision included standards 

and guidelines that delineated riparian reserves.

risk—A combination of the probability that a negative outcome will occur and the severity of the subsequent negative 

consequences (36 CFR 219.19).

rural restructuring—Changes in demographic and economic conditions owing to declines in natural resource 

production and agriculture (Nelson 2001).

scale—In ecological terms, the extent and resolution in spatial 

and temporal terms of a phenomenon or analysis, which differs 

from the definition in cartography regarding the ratio of map 

distance to Earth surface distance (Jenerette and Wu 2000).

scenic character—A combination of the physical, biological, 

and cultural images that gives an area its scenic identity and 

contributes to its sense of place. Scenic character provides a 

frame of reference from which to determine scenic attractiveness and to measure scenic integrity (36 CFR 219.19).

science synthesis—A narrative review of scientific information from a defined pool of sources that compiles and 

integrates and interprets findings and describes uncertainty, including the boundaries of what is known and 

what is not known.

sense of place—The collection of meanings, beliefs, symbols, values, and feelings that individuals or groups associate with a particular locality (Williams and Stewart 1998).

sensitive species—Plant or animal species that receive 

special conservation attention because of threats to their 

populations or habitats, but which do not have special status 

as listed or candidates for listing under the Endangered 

Species Act.

sensitivity—In ecological contexts, the propensity of 

communities or populations to change when subject to 

disturbance, or the opposite of resistance (see “community resistance”).

sink population—A population in which reproductive rates 

are lower than mortality rates but that is maintained by immigration of individuals from outside of that population (see 

also “source population”). 

social sustainability—“The capability of society to support 

the network of relationships, traditions, culture, and activities that connect people to the land and to one another, and 

support vibrant communities” (36 CFR 219.19). The term is 

commonly invoked as one of the three parts of a “triple-bottom line” alongside environmental and economic considerations. The concept is an umbrella term for various topics 

such as quality of life, security, social capital, rights, sense 

of place, environmental justice, and community resilience, 

among others discussed in this synthesis.

socioecological resilience—The capacity of socioecological 

systems (see “socioecological system”) to cope with, adapt 

to, and influence change; to persist and develop in the face 

of change; and to innovate and transform into new, more 

desirable configurations in response to disturbance.

socioecological system (or social-ecological system)—A 

coherent system of biophysical and social factors defined 

at several spatial, temporal, and organizational scales that 

regularly interact, continuously adapt, and regulate critical 

natural, socioeconomic, and cultural resources (Redman et 

al. 2004); also described as a coupled-human and natural 

system (Liu et al. 2007).

source population—A population in which reproductive 

rates exceed those of mortality rates so that the population 

has the capacity to increase in size. The term is also often 

used to denote when such a population contributes emigrants (dispersing individuals) that move outside the population, particularly when feeding a sink population.

special forest products—See “nontimber forest products.”

special status species—Species that have been listed or 

proposed for listing as threatened or endangered under the 

Endangered Species Act.

species of conservation concern—A species, other than 

federally recognized as a threatened, endangered, proposed, 
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GENERAL TECHNICAL REPORT PNW-GTR-966

or candidate species, that is known to occur in the NWFP 

area and for which the regional forester has determined that 

the best available scientific information indicates substantial 

concern about the species’ capability to persist over the long 

term in the Plan area (36 CFR 219.9(c)).

stand—A descriptor of a land management unit consisting of 

a contiguous group of trees sufficiently uniform in age-class 

distribution, composition, and structure, and growing on a site 

of sufficiently uniform quality, to be a distinguishable unit.

standard—A mandatory constraint on project and activity 

decisionmaking, established to help achieve or maintain the 

desired condition or conditions, to avoid or mitigate undesirable effects, or to meet applicable legal requirements.

stationarity—In statistics, a process that, while randomly 

determined, is not experiencing a change in the probability 

of outcomes.

stewardship contract—A contract designed to achieve 

land management goals while meeting local and rural community needs, including contributing to the sustainability 

of rural communities and providing a continuing source of 

local income and employment.

strategic surveys—One type of field survey, specified 

under the NWFP, designed to fill key information gaps on 

species distributions and ecologies by which to determine 

if species should be included under the Plan’s Survey and 

Manage species list.

stressors—Factors that may directly or indirectly degrade 

or impair ecosystem composition, structure, or ecological 

process in a manner that may impair its ecological integrity, 

such as an invasive species, loss of connectivity, or the disruption of a natural disturbance regime (36 CFR 219.19).

structure (ecosystem)—The organization and physical 

arrangement of biological elements such as snags and down 

woody debris, vertical and horizontal distribution of vegetation, stream habitat complexity, landscape pattern, and 

connectivity (FSM 2020).

supporting services—A type of ecosystem service that 

includes pollination, seed dispersal, soil formation, and nutrient cycling.

Survey and Manage program—A formal part of the 

NWFP that established protocols for conducting various 

types of species surveys, identified old-forest-associated 

species warranting additional consideration for monitoring and protection (see “Survey and Manage species”), and 

instituted an annual species review procedure that evaluated 

new scientific and monitoring information on species for 

potentially recommending changes in their conservation 

status, including potential removal from the Survey and 

Manage species list. 

Survey and Manage species—A list of species, compiled 

under the Survey and Manage program of the NWFP, that 

were deemed to warrant particular attention for monitoring and protection beyond the guidelines for establishing 

late-successional forest reserves.

sustainability—The capability to meet the needs of the 

present generation without compromising the ability of future generations to meet their needs (36 CFR 219.19).

sustainable recreation—The set of recreation settings and 

opportunities in the National Forest System that is ecologically, economically, and socially sustainable for present and 

future generations (36 CFR 219.19).

sympatric—Two species or populations that share a common geographic range and coexist.

threatened species—Any species that the Secretary of the 

Interior or the Secretary of Commerce has determined is 

likely to become an endangered species within the foreseeable future throughout all or a significant portion of its 

range. Threatened species are listed at 50 CFR sections 

17.11, 17.12, and 223.102. 

timber harvest—The removal of trees for wood fiber use 

and other multiple-use purposes (36 CFR 219.19).

timber production—The purposeful growing, tending, 

harvesting, and regeneration of regulated crops of trees to 

be cut into logs, bolts, or other round sections for industrial 

or consumer use (36 CFR 219.19).

topo-edaphic—Related to or caused by particular soil 

conditions, as of texture or drainage, rather than by physiographic or climatic factors within a defined region or area.
621

Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area

traditional ecological knowledge—“A cumulative body 

of knowledge, practice, and belief, evolving by adaptive 

processes and handed down through generations by cultural 

transmission, about the relationship of living beings (including humans) with one another and with their environment” 

(Berkes et al. 2000: 1252). See also “native knowledge.”

trailing edge—When describing the range of a species, the 

boundary at which the species’ population is geographically 

contracting through local extinction at occupied sites.

trophic cascade—Changes in the relative populations of 

producers, herbivores, and carnivores following the addition 

or removal of top predators and the resulting disruption of 

the food web.

uncertainty—Amount or degree of confidence as a result 

of imperfect or incomplete information.

understory—Vegetation growing below the tree canopy in a 

forest, including shrubs and herbs that grow on the forest floor.

use of wildland fire—Management of either wildfire or 

prescribed fire to meet resource objectives specified in land 

or resource management plans (see “Managing wildfire for 

resource objectives” and “Prescribed fire”).

variable-density thinning—The method of thinning some 

areas within a stand to a different density (including leaving 

dense, unthinned areas) than other parts of the stand, which 

is typically done to promote ecological diversity in a relatively uniform stand.

vegetation series (plant community)—The highest level 

of the fine-scale component (plant associations) of potential 

vegetation hierarchy based on the dominant plant species 

that would occur in late-successional conditions in the absence of disturbance.

vegetation type—A general term for a combination or 

community of plants (including grasses, forbs, shrubs, or 

trees), typically applied to existing vegetation rather than 

potential vegetation. 

viable population—A group of breeding individuals of a 

species capable of perpetuating itself over a given time scale. 

vital rates—Statistics describing population dynamics such 

as reproduction, mortality, survival, and recruitment.

watershed—A region or land area drained by a single 

stream, river, or drainage network; a drainage basin (36 

CFR 219.19).

watershed analysis—An analytical process that characterizes watersheds and identifies potential actions for addressing problems and concerns, along with possible management 

options. It assembles information necessary to determine the 

ecological characteristics and behavior of the watershed and 

to develop options to guide management in the watershed, 

including adjusting riparian reserve boundaries.

watershed condition assessment—A national approach 

used by the U.S. Forest Service to evaluate condition of 

hydrologic units based on 12 indicators, each composed of 

various attributes (USDA FS 2011).

watershed condition—The state of a watershed based on 

physical and biogeochemical characteristics and processes 

(36 CFR 219.19).

watershed restoration—Restoration activities that focus 

on restoring the key ecological processes required to create 

and maintain favorable environmental conditions for aquatic and riparian-dependent organisms.

well-being—The condition of an individual or group in social, economic, psychological, spiritual, or medical terms.

wilderness—Any area of land designated by Congress as 

part of the National Wilderness Preservation System that 

was established by the Wilderness Act of 1964 (16 U.S.C. 

1131–1136) (36 CFR 219.19).

wildlife—Undomesticated animal species, including amphibians, reptiles, birds, mammals, fish, and invertebrates 

or even all biota, that live wild in an area without being 

introduced by humans.

wildfire—Unplanned ignition of a wildland fire (such as a 

fire caused by lightning, volcanoes, unauthorized and accidental human-caused fires), and escaped prescribed fires.
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GENERAL TECHNICAL REPORT PNW-GTR-966

wildland-urban interface (WUI)—The line, area, or zone 

where structures and other human development meet or intermingle with undeveloped wildland or vegetation fuels.

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Acknowledgments

We thank reviewers from U.S. Forest Service Regions 5 and 

6, who provided valuable input on earlier drafts of these 

chapters. We thank the many anonymous reviewers for 

their constructive comments. We also thank members of 

the public, Tribes, and other agencies who provided peer-reviewed literature for consideration, attended the public 

forums, or provided review comments for peer reviewers to 

consider. We thank Cliff Duke with the Ecological Society 

of America for organizing and coordinating the peer review 

process. We thank Lisa McKenzie and Ty Montgomery 

with McKenzie Marketing Group for coordinating and 

summarizing the extensive public input we received and for 

organizing and facilitating the public forums. We also thank 

Kathryn Ronnenberg for assisting with figures and editing 

for some chapters, as well as Keith Olsen for his work 

on figures. Sean Gordon is thanked for his creation and 

management of the NWFP literature reference database and 

for formatting all the citations in the chapters, which was a 

very large task. We really appreciate the efforts of Rhonda 

Mazza, who worked with the authors to write the executive 

summary. We appreciate the heroic efforts of the entire 

Pacific Northwest Research Station communications team 

to get the science synthesis edited and published to meet 

tight deadlines, especially editors Keith Routman, Carolyn 

Wilson, and Oscar Johnson and visual information specialist Jason Blake. Borys Tkacz and Jane Hayes are acknowledged for their diligent policy reviews of all chapters. We 

want to acknowledge the leadership of Paul Anderson and 

Cindy Miner and Yasmeen Sands for their communications 

coordination. Finally, the team wishes to thank Region 5, 

Region 6, and the Pacific Northwest and Pacific Southwest 

Research Stations for significant funding and other support 

for this effort. 
Pacific Northwest Research Station

Website http://www.fs.fed.us/pnw/

Telephone (503) 808–2592

Publication requests (503) 808–2138

FAX (503) 808–2130

E-mail pnw_pnwpubs@fs.fed.us

Mailing address Publications Distribution

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P.O. Box 3890

Portland, OR 97208–3890
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