United States Department of Agriculture

Forest 

Service

Pacific Northwest 

Research Station

General Technical Report

PNW-GTR-939

March 

2017

Climate Change Vulnerability and 

Adaptation in the Blue Mountains Region
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Editors

Jessica E. Halofsky is a research ecologist, University of Washington, College 

of the Environment, School of Environmental and Forest Sciences, Box 352100, 

Seattle, WA 98195-2100; David L. Peterson is a senior research biological 

scientist, U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Research Station, 400 N 34th St., Suite 201, Seattle, WA 98103.
Climate Change Vulnerability and 

Adaptation in the Blue Mountains Region

Jessica E. Halofsky and David L. Peterson

Editors

U.S. Department of Agriculture, Forest Service 

Pacific Northwest Research Station

Portland, Oregon

General Technical Report PNW-GTR-939

March 2017
Abstract

Halofsky, Jessica E.; Peterson, David L., eds. 2017. Climate change vulnerability 

and adaptation in the Blue Mountains. Gen. Tech. Rep. PNW-GTR-939. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station. 331 p. 

The Blue Mountains Adaptation Partnership was developed to identify climate 

change issues relevant to resource management in the Blue Mountains region, to 

find solutions that can minimize negative effects of climate change, and to facilitate 

transition of diverse ecosystems to a warmer climate. Partnering organizations 

included three national forests (Malheur, Umatilla, Wallowa-Whitman National 

Forests), the Pacific Northwest Research Station and Pacific Northwest Region of 

the U.S. Department of Agriculture, Forest Service, the University of Washington, 

and the Climate Impacts Research Consortium at Oregon State University. These 

organizations worked together over a 2-year period to conduct a state-of-the-science 

climate change vulnerability assessment and develop adaptation options for national 

forests in the Blue Mountains region. The vulnerability assessment emphasized four 

resource areas—water, fish, upland vegetation, and special habitats—regarded as 

the most important resources for local ecosystems and communities.

The vulnerability assessment indicated that effects of climate change on hydrology in the Blue Mountains will be especially significant. Decreased snowpack and 

earlier snowmelt will shift the timing and magnitude of streamflow; peak flows 

will be higher, and summer low flows will be lower. Projected changes in climate 

and hydrology will have far-reaching effects on aquatic and terrestrial ecosystems, 

especially as frequency of extreme climate events (drought) and associated effects 

on ecological disturbance (wildfire, insect outbreaks) increase. Abundance and 

distribution of spring Chinook salmon (Oncorhynchus tshawytscha Walbaum), 

redband trout/steelhead (O. mykiss gibsii Walbaum)/(O.m. Walbaum), and especially 

bull trout (Salvelinus confluentus Suckley) will be greatly reduced, although effects 

will differ by location as a function of both stream temperature and competition 

from nonnative fish species. Increasing air temperature, through its influence on 

soil moisture, is expected to cause gradual changes in the abundance and distribution of tree, shrub, and grass species throughout the Blue Mountains, with droughttolerant species becoming more competitive. Ecological disturbance, including 

wildfire and insect outbreaks, will be the primary facilitator of vegetation change. 

High-elevation forest types will be especially vulnerable to disturbance. 
Resource managers developed a detailed list of ways to address these climate 

change vulnerabilities through management actions. The large number of adaptation strategies and tactics, many of which are a component of current management 

practice, provide a pathway for slowing the rate of deleterious change in resource 

conditions. 

Keywords: Access, adaptation, Blue Mountains, Blue Mountains Adaptation 

Partnership, climate change, fire, forest ecosystems, fisheries, hydrology, roads, 

science-management partnership, special habitats, vegetation, wildlife.
Summary

The Blue Mountains Adaptation Partnership (BMAP) is a science-management 

partnership consisting of Malheur, Umatilla, and Wallowa-Whitman National 

Forests, and Pacific Northwest Research Station and Pacific Northwest Region of 

the U.S. Department of Agriculture, Forest Service; the University of Washington; 

and the Climate Impacts Research Consortium at Oregon State University. These 

organizations worked together over a period of 2 years to identify climate change 

issues relevant to resource management in the Blue Mountains region and to find 

solutions that can minimize negative effects of climate change and facilitate transition of diverse ecosystems to a warmer climate. The BMAP provided education, 

conducted a climate change vulnerability assessment, and developed adaptation 

options for federal agencies that manage 2.1 million hectares in northeast Oregon, 

southeast Washington, and a small portion of southwest Idaho.

Global climate models project that the current warming trend will continue 

throughout the 21st century in the Blue Mountains. Compared to observed historical 

temperature, average warming is projected to be 2.4 to 3.1 °C by 2050 and 3.2 to 

6.3 °C by 2100, depending on greenhouse gas emissions. Precipitation may increase 

slightly in the winter, although the magnitude is uncertain. 

The effects of climate change on hydrology in the Blue Mountains will be especially significant. Decreased snowpack and earlier snowmelt will shift the timing 

and magnitude of streamflow and decrease summer soil moisture; peak flows will 

be higher, and summer low flows will be lower. Pronounced changes in snow and 

streamflow will occur in headwater basins of the Wallowa Mountains, especially in 

high-elevation radial drainages out of the Eagle Cap Wilderness, with large changes 

occurring in the more northerly sections of the Umatilla and Wallowa-Whitman 

National Forests along the Oregon-Washington border. Mid-elevation areas where 

snow is currently not persistent (northern Blue Mountains, margins of Wallowa, 

Elkhorn, Greenhorn, and Strawberry Mountains) may become largely snow-free in 

the future.

Projected changes in climate and hydrology will have far-reaching effects on 

aquatic and terrestrial ecosystems, especially as frequency of extreme climate 

events (drought, low snowpack) and associated effects on ecological disturbance 

(streamflow, wildfire, insect outbreaks) increase. Vulnerability assessment and 

adaptation option development for the Blue Mountains conclude the following:
Water resources and infrastructure—

• Effects: Decreasing snowpack and declining summer flows will alter timing and availability of water supply, affecting municipal and public uses 

downstream from and in national forests, and other forest uses including 

livestock grazing, wildlife, recreation, firefighting, road maintenance, and 

instream fishery flows. Declining summer low flows will affect water 

availability during late summer, the period of peak demand (e.g., for irrigation and power supply). Increased magnitude of peak streamflows will 

damage roads near perennial streams, ranging from minor erosion to complete loss of the road prism, thus affecting public safety, access for resource 

management, water quality, and aquatic habitat. Bridges, campgrounds, 

and national forest facilities near streams and floodplains will be especially 

vulnerable, reducing access.

• Adaptation options: Primary adaptation strategies to address changing 

hydrology in the Blue Mountains include restoring the function of watersheds, connecting floodplains, reducing drainage efficiency, maximizing 

valley storage, and reducing fire hazard. Tactics include adding wood to 

streams, restoring beaver populations, modifying livestock management, 

and reducing surface fuels and forest stand densities. Primary strategies for 

infrastructure include increasing the resilience of stream crossings, culverts, and bridges to higher peak flows and facilitating response to higher 

peak flows by reducing the road system and disconnecting roads from 

streams. Tactics include completing geospatial databases of infrastructure 

(and drainage) components, installing higher capacity culverts, and decommissioning roads or converting them to alternative uses.

Fisheries—

• Effects: Decreased snowpack will shift the timing of peak flows, decrease 

summer low flows, and in combination with higher air temperature, 

increase stream temperatures, all of which will reduce the vigor of coldwater fish species. Abundance and distribution of spring Chinook salmon 

(Oncorhynchus tshawytscha Walbaum), redband trout/steelhead (O. mykiss 

Walbaum), and especially bull trout (Salvelinus confluentus Suckley) will 

be greatly reduced, although effects will differ by location as a function 

of both stream temperature and competition from nonnative fish species. 

Increased wildfire will add sediment to streams, increase peak flows and 

channel scouring, and raise stream temperature by removing vegetation.
• Adaptation options: Primary strategies to address climate change threats 

to cold-water fish species include maintaining or restoring natural flow 

regimes to buffer against future changes, decreasing fragmentation of 

stream networks so aquatic organisms can access similar habitats, and 

developing wildfire use plans that address sediment inputs and road failures. Tactics include using watershed analysis to develop integrated actions 

for vegetation and hydrology, protecting groundwater and springs, restoring riparian areas and beaver populations to maintain summer base flows, 

reconnecting and increasing off-channel habitat and refugia, identifying 

and improving stream crossings that impede fish movement, implementing engineering solutions to improve stream structure and flow, decreasing road connectivity, and revegetating burned areas to store sediment and 

maintain channel geomorphology.

Upland vegetation—

• Effects: Increasing air temperature, through its influence on soil moisture, is expected to cause gradual changes in the abundance and distribution of tree, shrub, and grass species throughout the Blue Mountains, with 

drought-tolerant species becoming more competitive. Ecological disturbance, including wildfire and insect outbreaks, will be the primary facilitator of vegetation change, and future forest landscapes may be dominated by 

younger age classes and smaller trees. High-elevation forest types will be 

especially vulnerable to disturbance. Increased abundance and distribution 

of nonnative plant species will create additional competition for regeneration of native plant species.

• Adaptation options: Most strategies for conserving native tree, shrub, and 

grassland systems focus on increasing resilience to drought, low snowpack, 

and ecological disturbance (wildfire, insects, nonnative species). These 

strategies generally include managing landscapes to reduce the severity and 

patch size of disturbances, encouraging fire to play a more natural role, and 

protecting refugia. Tactics include using silvicultural prescriptions (especially stand density management) and fuel treatments to reduce fuel continuity, reducing populations of nonnative species, potentially modifying seed 

zones for tree species, and revising grazing policies and practices. Rare and 

disjunct species and communities (e.g., whitebark pine, aspen, alpine communities) require adaptation strategies and tactics focused on encouraging 

regeneration, preventing damage from disturbance, and establishing refugia.
Special habitats—

• Effects: Riparian areas and wetlands will be especially vulnerable to higher 

air temperature, reduced snowpack, and altered hydrology. The primary 

effects will be decreased establishment, growth, and cover of species such 

as cottonwood, willow, and aspen, which may be displaced by upland forest 

species in some locations. However, species that propagate effectively following fire will be more resilient to climate change. Reduced groundwater 

discharge to groundwater-dependent ecosystems will reduce areas of saturated soil, convert perennial springs to ephemeral springs, eliminate some 

ephemeral springs, and alter local aquatic flora and fauna.

• Adaptation options: Primary strategies for increasing resilience of special 

habitats to changing climate include maintaining appropriate densities of 

native species, propagating drought-tolerant native species, maintaining or 

restoring natural flow regimes to buffer against future changes, and reducing stresses such as conifer encroachment, livestock grazing, and ungulate 

browsing. Tactics include planting species with a broad range of moisture 

tolerance, controlling nonnative species, implementing engineering solutions to maintain or restore flows, restoring beaver populations, reducing 

damage from livestock and native ungulates, and removing infrastructure 

(e.g., campsites, springhouses) where appropriate.

The BMAP facilitated one of the largest climate change adaptation efforts on 

federal lands to date, including participants from stakeholder organizations interested in a broad range of resource issues. It achieved specific goals of national climate change strategies for the U.S. Forest Service, providing a scientific foundation 

for resource management, planning, and ecological restoration in the Blue Mountains region. The large number of adaptation strategies and tactics, many of which 

are a component of current management practice, provide a pathway for slowing the 

rate of deleterious change in resource conditions. Rapid implementation of adaptation in sustainable resource management will help maintain critical structure and 

function of terrestrial and aquatic ecosystems in the Blue Mountains. Long-term 

monitoring will help detect potential climate change effects on natural resources, 

and evaluate the effectiveness of adaptation options that have been implemented.
Contents 

1 Chapter 1: Introduction

 Katherine Hoglund Wyatt

11 Chapter 2: Ecological, Biogeographical, and Historical Context of the 

Blue Mountains

 Katherine Hoglund Wyatt

25 Chapter 3: Climate Change and Hydrology in the Blue Mountains 

 Caty F. Clifton, Kate T. Day, Kathie Dello, Gordon E. Grant, Jessica E. 

Halofsky, Daniel J. Isaak, Charles H. Luce, Mohammad Safeeq, Brian P. 

Staab, and John Stevenson

53 Chapter 4: Climate Change, Water Resources, and Roads in the 

Blue Mountains

 Caty F. Clifton, Kate T. Day, Gordon E. Grant, Jessica E. Halofsky, 

Charles H. Luce, and Brian P. Staab

91 Chapter 5: Climate Change, Fish, and Aquatic Habitat in the 

Blue Mountains

 Daniel J. Isaak, Katherine Ramsey, John C. Chatel, Deborah L. Konnoff, 

Robert A. Gecy, and Dona Horan

149 Chapter 6: Effects of Climatic Variability and Change on Upland 

Vegetation in the Blue Mountains 

 Becky K. Kerns, David C. Powell, Sabine Mellmann-Brown, 

Gunnar Carnwath, and John B. Kim

251 Chapter 7: Climate Change and Special Habitats in the Blue Mountains: 

Riparian Areas, Wetlands, and Groundwater-Dependent Ecosystems

 Kathleen A. Dwire and Sabine Mellmann-Brown

325 Chapter 8: Conclusions

 David L. Peterson, Robyn Darbyshire, and Becky Gravenmier

1

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Chapter 1: Introduction

Katherine Hoglund Wyatt1

Introduction

The U.S. Forest Service Pacific Northwest Research Station, Pacific Northwest 

Region, and three national forests (Malheur, Umatilla, and Wallowa-Whitman) 

initiated the Blue Mountains Adaptation Partnership (BMAP) in 2013. The BMAP 

is a science-management collaboration with the goals of increasing climate change 

awareness, assessing vulnerability, and developing science-based adaptation 

strategies to reduce adverse effects of climate change and ease the transition to new 

climate states and conditions (see http://adaptationpartners.org/bmap). Developed in 

response to the proactive climate change strategies of the Forest Service (USDA FS 

2008, 2010a, 2010b), and building on previous efforts in national forests (Halofsky 

et al. 2011; Littell et al. 2012; Raymond et al. 2013, 2014; Rice et al. 2012; Swanston 

and Janowiak 2012; Swanston et al. 2011), the partnership brings together Forest 

Service scientists, University of Washington scientists, and Forest Service resource 

managers to plan for climate change in the Blue Mountains of northeastern Oregon 

and southeastern Washington. 

Climate Change Response in the Forest Service 

Climate change is an agencywide priority for the Forest Service which has issued 

direction to administrative units for responding to climate change (USDA FS 

2008). In 2010, the Forest Service provided specific direction to the National Forest 

System in the form of the National Roadmap for Responding to Climate Change 

(USDA FS 2010a) and the Performance Scorecard for Implementing the Forest 

Service Climate Change Strategy (USDA FS 2010b). The goal of the Forest Service 

climate change strategy is to “ensure our national forests and private working lands 

are conserved, restored, and made more resilient to climate change, while enhancing our water resources” (USDA FS 2010b). To achieve this goal, the performance 

scorecard contains 10 criteria grouped in four dimensions: (1) increasing organizational capacity; (2) partnerships, engagement, and education; (3) adaptation; and (4) 

mitigation and sustainable consumption. Progress towards accomplishing elements 

of the scorecard must be reported annually by each national forest and national grassland; all units were expected to accomplish 7 of 10 criteria by 2015, with at least 

1 Katherine Hoglund Wyatt is a research assistant, Natural Capital Project, Stanford 

University c/o University of Washington, School of Environmental and Forest Sciences, 

Box 352100, Seattle, WA 98195.
2

GENERAL TECHNICAL REPORT PNW-GTR-939

one “yes” in each dimension. National forests in the Forest Service Pacific Northwest Region have also completed climate change action plans that indicate how they 

will comply with the scorecard elements. 

The BMAP built on several existing efforts in ecosystem-based management 

and ecological restoration to address climate change and put these efforts in a 

broader regional context in the Blue Mountains region. There have been multiple 

restoration initiatives in the Blue Mountains over the past 20 years. In 2013, the 

Forest Service Blue Mountains Restoration Strategy Interdisciplinary Team was 

convened to coordinate restoration among the three Blue Mountains national 

forests, and this team works closely with five collaborative groups operating in the 

area. Management priorities were dry forest restoration and strategic fuel treatments, both ecological priorities considered in Hessburg et al. (2005). These efforts 

are aimed at restoring fire-adapted forests and helping to reduce wildfire severity 

(USDA FS 2013). Other restoration activities are prioritized by national forests, 

with some coordination among forests (e.g., within river basins for aquatic restoration). The BMAP works in conjunction with these management priorities to access 

the best available science on climate change effects and implement climate change 

adaptation plans. 

Science-Management Partnerships

Previous efforts in the Pacific Northwest and beyond have demonstrated the 

success of science-management partnerships for increasing climate change awareness among resource managers and adaptation planning on federal lands. Olympic 

National Forest and Tahoe National Forest initiated the first science-management 

partnerships for developing adaptation options for individual national forests 

(Littell et al. 2012). The Olympic climate change study assessed resource vulnerabilities and developed adaptation options for Olympic National Forest and Olympic 

National Park on the Olympic Peninsula in Washington (Halofsky et al. 2011). 

Similar to efforts in the Olympics, the North Cascadia Adaptation Partnership 

assessed vulnerabilities and formulated adaptation options for two national forests 

and two national parks in Washington (Raymond et al. 2014). In collaboration with 

three management units in California—Tahoe National Forest, Inyo National Forest, and Devils Postpile National Monument—the Forest Service Pacific Southwest 

Research Station held climate change education workshops and developed the Climate Project Screening Tool in order to incorporate adaptation into project planning 

(Morelli et al. 2012). In response to requests from the Shoshone National Forest in 

northern Wyoming, the Forest Service Rocky Mountain Research Station synthesized information on past climate, future climate projections, and potential effects 

Previous efforts in 

the Pacific Northwest 

and beyond have 

demonstrated the 

success of sciencemanagement 

partnerships for 

increasing climate 

change awareness.
3

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

of climate change on the multiple ecosystems within the forest (Rice et al. 2012). In 

the largest effort to date in the Eastern United States, the Forest Service Northern 

Research Station, in collaboration with the Chequamegon-Nicolet National Forest in 

northern Wisconsin and numerous other partners, conducted a vulnerability assessment for natural resources (Swanston et al. 2011) and developed adaptation options 

(Swanston and Janowiak 2012). Another joint national forest and Forest Service 

research vulnerability assessment effort focused on the vulnerability of watersheds 

to climate change (Furniss et al. 2013). The watershed vulnerability assessments, 

conducted in 11 national forests throughout the United States, were locally focused 

(at a national forest scale) and included water resource values, hydrologic reaction 

to climate change, watershed condition, and landscape sensitivity. The assessments 

were intended to help national forest managers identify where limited resources 

could be best invested to increase watershed resilience to climate change. 

The processes, products, and techniques used for several studies and other 

climate change efforts on national forests have been compiled in a guidebook 

for developing adaptation options for national forests (Peterson et al. 2011). The 

guidebook outlines four key steps to facilitate adaptation in national forests: (1) 

become aware of basic climate change science and integrate that understanding 

with knowledge of local conditions and issues (review), (2) evaluate sensitivity of 

natural resources to climate change (rank), (3) develop and implement options for 

adapting resources to climate change (resolve), and (4) monitor the effectiveness of 

on-the-ground management (observe) and adjust as needed. The BMAP is focused 

on implementation of the principles and practices in the guidebook.

The Blue Mountains Adaptation Partnership Process

The BMAP is a science-management partnership focused on vulnerability assessment and adaptation planning for the Malheur, Umatilla, and Wallowa-Whitman 

National Forests, encompassing an area of 2.14 million hectares in Oregon and 

Washington (fig. 1.1). The BMAP process includes (1) a vulnerability assessment of 

the effects of climate change on natural resources and infrastructure, (2) development of adaptation options that will help reduce negative effects of climate change 

and assist the transition of biological systems and management to a changing climate, and (3) development of an enduring partnership to facilitate ongoing dialogue 

and activities related to climate change in the Blue Mountains region.

We assessed the vulnerability of natural resources and infrastructure and developed options for adapting resources and management to a changing climate. Based 
4

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 1.1—Project area for the Blue Mountains Adaptation Partnership. 
5

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

on their importance in the region and current management concerns and challenges, 

the BMAP focused on water resources, fisheries, and vegetation (upland; riparian, 

wetland, and groundwater-dependent systems). These resources are similar to the 

resources that were the focus of the Olympic climate change assessment (Halofsky 

et al. 2011) and North Cascadia Adaptation Partnership (Raymond et al. 2014), but 

reflect different regional priorities. 

Vulnerability assessments typically involve exposure, sensitivity, and adaptive 

capacity (Parry et al. 2007), where exposure is the degree to which the system is 

exposed to changes in climate, sensitivity is an inherent quality of the system that 

indicates the degree to which it could be affected by climate change, and adaptive 

capacity is the ability of a system to respond and adjust to the exogenous influence 

of climate. Vulnerability assessments can be both qualitative and quantitative and 

focus on whole systems or individual species or resources (Glick et al. 2011). Several tools and databases are available for systematically assessing sensitivity (e.g., 

Lawler and Case 2010, Luce et al. 2014) and vulnerability of species (e.g., Potter and 

Crane 2010). 

For the BMAP, we used scientific literature and expert knowledge to assess 

exposure, sensitivity, and adaptive capacity to identify key vulnerabilities for water 

use and infrastructure, fisheries, and vegetation. The assessment process took place 

over about 4 months, and involved monthly to biweekly phone meetings for each 

of the three resource-specific assessment teams. Each assessment team refined 

key questions that the assessment needed to address, selected values to assess, and 

determined which climate change impact models best informed the assessment. In 

some cases, assessment teams conducted spatial analyses or ran and interpreted 

models, selected criteria in which to evaluate model outputs, and developed maps 

of model output and resource sensitivities. To the greatest extent possible, teams 

focused on effects and projections specific to the BMAP region and used the finest 

scale projections that are scientifically valid (Littell et al. 2011). 

By working collaboratively with scientists and resource managers and focusing on a specific region, the goal of BMAP was to go beyond general concepts to 

identify adaptation options that can be implemented in projects and plans (Peterson et al. 2011; Raymond et al. 2013, 2014; Swanston and Janowiak 2012). After 

identifying key vulnerabilities for each resource sector, a workshop was convened 

in La Grande, Oregon, in April 2014 to present and discuss the vulnerability 

assessment and to elicit adaptation options from resource managers. For each 

resource sector, participants identified strategies (general approaches) and tactics 

(on-the-ground actions) for adapting resources and management practices to climate 
6

GENERAL TECHNICAL REPORT PNW-GTR-939

change. Participants also identified opportunities and barriers for implementing 

these strategies and tactics in current projects, management plans, partnerships, 

regulations, and policies.

Participants generally focused on adaptation options that can be implemented 

given our current scientific understanding of climate change effects, but they 

also identified research and monitoring that would benefit future efforts to assess 

vulnerability and adapt management practices. Facilitators captured information 

generated during the workshops with a set of worksheets adapted from Swanston 

and Janowiak (2012). Initial results from the workshops were augmented with 

continued dialogue with Forest Service resource specialists. 

This publication contains a chapter on expected climatological and hydrological changes in the Blue Mountains, and one chapter for each of the resource sectors 

covered in the vulnerability assessment (water resources, fisheries, upland vegetation, 

and riparian wetland, and groundwater-dependent systems). Each of the latter chapters includes a review of climate change effects, sensitivities, and current management 

practices (collectively, the vulnerability assessment) and results of the adaptation 

planning discussions. Resource managers and other decisionmakers can use this 

publication in several ways. First, the synthesis of projected changes in climate and 

hydrology, and potential effects on water resources, fisheries, and vegetation is a 

state-of-science reference for addressing climate change in planning documents and 

projects. While not a comprehensive synthesis of all literature on climate change 

effects in the region, this publication does emphasize the biggest challenges for these 

resource sectors that are known at this time. Second, land managers can draw from 

the adaptation options presented in this report as they begin to implement actions in 

response to changes in climate and hydrology. We expect that over time, and as needs 

and funding align, appropriate adaptation options will be incorporated into plans and 

programs of national forests and possibly other agencies. 

Adaptation planning is an ongoing and iterative process. Implementation may 

occur at critical times in the planning process, such as when managers revise 

Forest Service land management plans and other planning documents, or after the 

occurrence of extreme events and ecological disturbances (e.g., wildfire). We focus 

on adaptation options for the Forest Service, but this publication provides information that can be used by other land management agencies as well. Furthermore, 

the BMAP process can be emulated by national forests, national parks, and other 

organizations in the Pacific Northwest and beyond, thus propagating climate-smart 

management across ever larger landscapes. 

The BMAP process 

can be emulated 

by national forests, 

national parks, and 

other organizations in 

the Pacific Northwest 

and beyond.
7

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

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Station. 60 p.

Swanston, C.W.; Janowiak, M.K., eds. 2012. Forest adaptation resources: climate 

change tools and approaches for land managers. Gen. Tech. Rep. NRS-GTR-87. 

Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern 

Research Station. 108 p.

Swanston, C.; Janowiak, M.; Iverson, L. [et al.]. 2011. Ecosystem vulnerability 

assessment and synthesis: a report from the climate change response framework 

project in northern Wisconsin. Gen. Tech. Rep. NRS-82. Newtown Square, PA: 

U.S. Department of Agriculture, Forest Service, Northern Research Station. 

142 p.
9

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

U.S. Department of Agriculture, Forest Service [USDA FS]. 2008. Forest 

Service strategic framework for responding to climate change. Version 1.0. 

http://www.fs.fed.us/climatechange/documents/strategic-framework-climatechange-1-0.pdf. (25 September 2015).

U.S. Department of Agriculture, Forest Service [USDA FS]. 2010a. National 

roadmap for responding to climate change. http://www.fs.fed.us/climatechange/

pdf/roadmap.pdf. (25 September 2015).

U.S. Department of Agriculture, Forest Service [USDA FS]. 2010b. A 

performance scorecard for implementing the Forest Service climate change 

strategy. http://www.fs.fed.us/climatechange/pdf/performance_scorecard_final.

pdf. (25 September 2015).

U.S. Department of Agriculture, Forest Service [USDA]. 2013. Eastside 

restoration strategy, update 5. Briefing Paper. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Region. http://www.fs.usda.gov/

Internet/FSE_DOCUMENTS/stelprdb5433052.pdf. (25 September 2015).
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GENERAL TECHNICAL REPORT PNW-GTR-939
11

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Chapter 2: Ecological, Biogeographical, and Historical 

Context of the Blue Mountains

Katherine Hoglund Wyatt1

Introduction

The Blue Mountains Adaptation Partnership (BMAP) includes the Wallowa-Whitman, Umatilla, and Malheur National Forests, which occupy 2.14 million hectares 

in the Blue Mountains and their subranges (referred to hereafter as the Blue Mountains) of primarily northeastern Oregon and a small portion of southeastern Washington (fig. 2.1). The area is climatologically and ecologically diverse, and although 

each national forest has a specific cultural and political context, similarities in 

geological, cultural, and ecological histories unite the Blue Mountains region. For 

example, following Euro-American settlement, the Blue Mountains experienced 

extensive sheep and cattle grazing, and later a strong timber economy (Oliver et 

al. 1994, Wissmar et al. 1994). Periodic and extensive outbreaks of mountain pine 

beetle (Dendroctonus ponderosae Hopkins), western spruce budworm (Choristoneura freemani Razowski), and Douglas-fir tussock moth (Orgyia pseudotsugata

McDunnough) occurred throughout the region in the 1900s (Rainville et al. 2008). 

As a result of this historical and biological legacy, management across the three 

national forests has sought to respond to ecological disturbances and restore fireprone ecosystems. Establishment of forest reserves for watershed protection in 

the early 1900s, development of ranching and agriculture industry through the 

20th century, and growing concerns for water quality and fisheries in the later 20th

century have refocused attention on restoring watershed and aquatic ecosystems. 

Congressional designation of seven wilderness areas within the three national 

forests (fig. 2.1) has further coalesced management objectives. In addition, the 

revised land management plan for the Blue Mountains national forests, currently in 

draft form, unites the three national forests in a joint planning framework (USDA 

FS 2014). This common historical and ecological context formed the basis of joint 

discussion on vulnerability to climate change and enabled the BMAP to identify 

common adaptation strategies that are relevant to the region as a whole. 

Ecological Setting

The complex geological history of the Blue Mountains is the foundation for the 

ecological diversity of the area. Oceanic subduction under the North American

1 Katherine Hoglund Wyatt is a research assistant, Natural Capital Project, Stanford 

University c/o University of Washington, School of Environmental and Forest Sciences, 

Box 352100 Seattle, WA 98195.

The complex geological 

history of the Blue 

Mountains is the 

foundation for the 

ecological diversity

of the area.
12

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 2.1—Wilderness areas and wild and scenic rivers in the project area for the Blue Mountains Adaptation Partnership.
13

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

plate during the late Triassic and late Jurassic periods, followed by terrestrial sedimentation and volcanic material deposition, formed the basis of the Blue Mountains 

(Brooks 1979, White et al. 1992, Wilson and Cox 1980). The region was glaciated 

20,000 to 14,000 BP (Johnson et al. 1994). Glacial deposition and volcanic ash from 

Glacier Peak 12,000 BP and Mount Mazama 6,900 BP was generally redistributed 

on north-facing slopes and broad basins (Alt and Hyndman 1995); this variation in 

deposition continues to contribute to broad differences in soil productivity (Jaindl 

et al. 1996, Johnson et al. 1994, Simpson 2007) and vegetation composition (Kelly 

et al. 2005). Mudstone, sandstone, siltstone, and shale are common throughout the 

western Blue Mountains, whereas schist, slate, argillite, tuff, chert, and intrusive 

granite are more common in the eastern Blue Mountains; limestone and portions of 

the Columbia River Basalt group are prevalent throughout the region (Jaindl et al. 

1996, Orr and Orr 1999). 

The Blue Mountains are a collection of small mountain ranges, with the highest elevations in the Eagle Caps, and the smaller Elkhorn, Greenhorn, Strawberry, 

Wenaha, and Aldrich mountain ranges. Elevation in the region ranges from 267 to 

3000 m with high points throughout the Wallowa-Whitman (Sacajawea Peak, 3001 

m), Malheur (Strawberry Mountain, 2756 m), and Umatilla (Vinegar Hill Northeast, 

2147 m) National Forests. Climatic differences, created in part by complex topography, further contribute to diversity in the Blue Mountains. The southern portion of 

the Blue Mountains, including the Strawberry subrange, is in the rain shadow of the 

Cascade Range and is most prominently affected by Great Basin climatic patterns. 

The result is warmer and drier conditions; winter minimum temperatures range 

from -5 to 5 °C, summer high temperatures from 5.5 to 18 °C, and precipitation 

from 20 to 100 cm annually (PRISM Climate Group). In the northern Blue Mountains, maritime airflows through the Columbia River Gorge, resulting in higher 

precipitation (40 to 200 cm annually) and less seasonally varied temperatures 

(Caraher et al. 1992, Heyerdahl et al. 2001, Mock 1996, Simpson 2007, Wells 2006).

Elevation gradients and ecological disturbance further define the ecological 

associations of the Blue Mountains. Historically, a low-severity fire regime at low 

elevations promoted ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. 

Lawson) and dry mixed-conifer forest dominated by ponderosa pine; these communities historically composed 20 to 50 percent of the overall landscape and 40 to 75 

percent of the forested landscape (Rainville et al. 2008). In the central and southern 

Blue Mountains, woodlands composed of western juniper (Juniperus occidentalis

Hook.), Idaho fescue (Festuca idahoensis Elmer), and bitterbrush (Purshia tridentata [Pursh] DC.), as well as shrublands composed of mountain big sagebrush 
14

GENERAL TECHNICAL REPORT PNW-GTR-939

(Artemisia tridentata ssp. vaseyana [Rydb.] Beetle), scabland sagebrush (A. rigida

(Nutt.) A. Gray), and curl-leaf mountain-mahogany (Cercocarpus ledifolius Nutt.) 

are also common at low elevation (Jaindl et al. 1996, Johnson et al. 1994). At mid 

elevation, a mixed-severity fire regime, in conjunction with moderate environmental conditions, supports lodgepole pine (Pinus contorta var. latifolia Engelm. ex 

S. Watson), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies 

grandis (Douglas ex D. Don) Lindl.), and western larch (Larix occidentalis Nutt.). 

Although it occurs as only a scattered component in other stands, these mid-elevation stands often include western white pine (Pinus monticola Douglas ex D. Don). 

At high elevations, subalpine fir (A. lasiocarpa (Hook.) Nutt.) and whitebark pine 

(P. albicaulis Engelm.) transition to alpine meadows of sedge and fescue (Jaindl et 

al. 1996, Johnson et al. 1994). In the northern Blue Mountains, the woodland zone 

supports tall shrublands (with, for example, western serviceberry (Amelanchier 

alnifolia (Nutt.) Nutt. ex M. Roem.), black hawthorn (Crataegus douglasii Lindl.), 

and western chokecherry (Prunus virginiana var. demissa (Nutt.) Torr.) rather than 

juniper and sagebrush. 

Decades of fire exclusion, livestock grazing, and timber harvest have heavily altered historical vegetation, in turn increasing the likelihood of severe fire 

and insect outbreaks (Hessburg et al. 2005, Hessburg and Agee 2003, Langston 

1995, Lehmkuhl et al. 1994, Mutch et al. 1993, Rainville et al. 2008); many of the 

most profound changes have been in lowland ponderosa pine stands, which have 

increased in density and true fir composition (Harrod et al. 1999, Hessburg et al. 

2005). Beyond fire disturbance, severe wind events, insect outbreaks, drought, 

flooding, and landslides interact to affect vegetation. These disturbance agents, in 

conjunction with variation in soils and microclimate, create mosaics and heterogeneity throughout all dominant vegetation associations (Jaindl et al. 1996, Johnson 

1994, Johnson et al. 1994). 

The diversity of vegetation in the Blue Mountains supports abundant and 

diverse fauna. Mule deer (Odocoileus hemionus Rafinesque), pronghorn (Antilocarpa americana Ord), whitetail deer (O. virginianus Zimmermann), Rocky 

Mountain elk (Cervus elaphus L.), bighorn sheep (Orvis canadensis Shaw), Rocky 

Mountain goat (Oreamnos americanus Blainville), black bear (Ursus americanus

Pallas), wolverine (Gulo gulo L.), badger (Taxidea taxus Schreber), mountain lion 

(Felis concolor L.), coyote (Canis latrans Say), pine marten (Martes martes L.), 

mink (Neovison vison Schreber), and American beaver (Castor canadensis Kuhl) 

are all found within the region (Jaindl et al. 1996). Avian diversity is even greater 
15

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

(263 species total) and includes ruffed grouse (Bonasa umbellus L.), blue grouse 

(Dendragapus obscurus Say), pileated woodpecker (Dryocopus pileatus L.), sharpshinned hawk (Accipiter striatus Vieillot), and American bald eagle (Haliaeetus 

leucocephalus L.) (Jaindl et al. 1996, Tiedemann et al. 1998). 

The Blue Mountains encompass over 16 000 km of perennial streams, almost 

2,000 lakes and ponds, and thousands of springs. Twenty-two fish species are found 

in the area, including Chinook salmon (Oncorhynchus tshawytscha Walbaum in 

Artedi), steelhead (O. mykiss Walbaum), interior redband trout (O. m. gibsii Walbaum), bull trout (Salvelinus confluentus Suckley), and Dolly Varden (S. malma 

Walbaum in Artedi) (Jaindl et al. 1996).

Cultural History of the Blue Mountains

American Indians, including the Nez Perce, Cayuse, Walla Walla, Shoshone, Bannocks, Wasco, Burns Paiute, Umatilla, and Warm Springs Tribes, have long inhabited the Blue Mountains region (Heyerdahl et al. 2001, Robbins and Wolf 1994). 

Currently, the Confederated Tribes of the Umatilla Indian Reservation (Cayuse, 

Walla Walla, and Umatilla tribes), Confederated Tribe of Warm Springs (Wasco, 

Paiute, and Warm Springs), and the Burns Paiute Reservations are in the vicinity 

of the Blue Mountains. Many of these tribes continue to have relationships with the 

national forests in the Blue Mountains. 

American Indians used the Blue Mountains for hunting and gathering. The 

Eagle Cap Wilderness was the summer home of the Chief Joseph Band of the Nez 

Perce, who hunted bighorn sheep and deer throughout the area (USDA and USDI 

1982). Hunting, as well as berry and root collection, likely occurred throughout 

the Blue Mountains region (Heyerdahl et al. 2001, Richards and Alexander 2006, 

Robbins and Wolf 1994). Fire was used to promote desired plant species as well 

as improve rangeland and hunting grounds (Heyerdahl et al. 2001, Johnson 1994, 

Robbins and Wolf 1994). 

Lewis and Clark came through the Blue Mountains between 1804 and 1806, 

and were followed in the subsequent three decades by trappers, missionaries, 

naturalists, and government scientists. Oregon Trail emigrants settled in the area 

beginning in 1843, spurring conflict and war with the Cayuse Indians (Oliver et 

al. 1994). From 1850 to 1890, the Euro-American population grew from 13,000 to 

357,000 (Robbins and Wolf 1994). The discovery of gold in the John Day area in 

1862, the Homestead Act of 1862, and 1880s railroad construction further increased 

settlement and settler-Indian conflict (Robbins and Wolf 1994, Wissmar et al. 1994). 
16

GENERAL TECHNICAL REPORT PNW-GTR-939

Following initial settlement, sheep and then cattle grazing shaped the Blue 

Mountains landscape. As the last two states to implement grazing regulations, 

Oregon and Washington faced overgrazing through the late 1800s. Sheep grazing 

began in 1860, increased steadily from 1890 to 1920, and then gradually declined; 

at its peak, there were 225,000 sheep and lambs in the Umatilla National Forest 

alone (Oliver et al. 1994). Cattle grazing was most prolific from 1940 to 1980, 

reaching almost 350,000 cattle and calves in the Blue Mountains region (Irwin et 

al. 1994). Although increased rangeland regulation and management through the 

1970s reduced overgrazing, the effects of a century of grazing persists, especially 

on vegetation, fuels, and riparian areas (Camp 1999, Irwin et al. 1994, Oliver et al. 

1994).

Following the opening of the first mill in John Day, Oregon, in 1862, the 

cultural and ecological importance of logging steadily increased. Starting in 1908, 

schools and public roads received 25 percent of timber receipts, increasing incentives for logging. Following World War II, increased vehicle capacity and improved 

chainsaws spurred increasing logging activity. The maximum annual volume was 

92 000 m3 in the 1940s and 210 000 m3 in the 1950s, increasing to 520 000 m3 in 

1973 (Oliver et al. 1994, Wissmar et al. 1994). Across Baker, Grant, Harney, Union, 

Wallowa, and Wheeler Counties production peaked between 1985 and 1992, with 

an annual output of over 1.4 million m3 (Rainville et al. 2008). 

Starting in the 1970s, restoration efforts began to repair damage to watersheds 

and fisheries, and restoration efforts expanded in the 1990s with state and federal 

listing of fish species. Recent logging efforts have focused on forest restoration 

rather than large-scale timber sales. Annual output has been below 240 000 m3

since 1997 (for Baker, Grant, Harney, Union, Wallowa, and Wheeler Counties 

combined). From 1988 to 1995, 60 percent of the timber area consisted of clearcuts 

and seed-tree harvests, decreasing to less than 30 percent after 1997 and less than 

10 percent after 2000. By 2001, over 50 percent of the timber area consisted of 

commercial thinning projects. Of land administered by the Forest Service in the 

Blue Mountains, 29 percent is open to active forestry (Rainville et al. 2008). Other 

restoration efforts, begun in the 1970s to repair damage to watersheds and fisheries, 

expanded in the 1990s with state and federal listing of fish species. 

Geography, History, and Management

National Forests and Wilderness Areas

Wallowa-Whitman National Forest covers 968 214 ha in the northeast corner of 

Oregon and a sliver of Idaho, and includes four wilderness areas totaling 237 024 

ha: the Eagle Cap, Hells Canyon, North Fork John Day, and Monument Rock 

Although increased 

rangeland regulation 

and management 

through the 1970s 

reduced overgrazing, 

the effects of a century 

of grazing persists.
17

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

(fig. 2.1). The North Fork John Day Wilderness is composed of four separate units, 

one of which is on the Wallowa-Whitman National Forest and three of which are on 

the Umatilla National Forest. Similarly, Monument Rock Wilderness is shared with 

the Malheur National Forest. Protected for scenery, recreation, fisheries, wildlife, 

and historical cultural resources, 10 rivers within the Wallowa-Whitman National 

Forest are designated in the Wild and Scenic Act of 1988 (fig. 2.1). 

Umatilla National Forest, located to the west of the Wallowa-Whitman National 

Forest, covers 566 560 ha in northeastern Oregon and southeastern Washington 

(approximately 78 percent is in Oregon and 22 percent is in Washington), and it 

includes three wilderness areas totaling 128 858 ha: the Wenaha-Tucannon, North 

Fork Umatilla, and North Fork John Day (three of four units; fig. 2.1). Wild and 

scenic rivers cover 93 km, protecting anadromous fish runs, especially steelhead 

trout, Chinook salmon, and migratory bull trout. 

Malheur National Forest covers 607 028 ha and includes four specially designated areas. Two wilderness areas, Monument Rock (shared with the WallowaWhitman National Forest) and Strawberry Mountain, cover 35 742 ha (fig. 2.1). 

Vinegar Hill Indian Rock Scenic Area contains the highest point in the forest, and 

the Cedar Grove Botanical area has the only stand of Alaska cedar (Callitropsis 

nootkatensis [D. Don] D.P. Little) east of the Cascade Range. The Malheur River 

and North Fork Malheur River are protected as wild and scenic for their scenic 

value, fisheries, geology, and wildlife. 

History and Management of the Blue Mountains

The Wallowa-Whitman, Umatilla, and Malheur National Forests are separate 

administrative units but share a common management history. The Blue Mountains Forest Reserve was informally removed from the public domain in 1902 and 

formally established in 1906. In 1908, all three national forests were designated to 

protect water, timber resources and rangeland (USDA FS 1997). The Wilderness 

Act of 1964, National Environmental Policy Act of 1969, Endangered Species Act 

of 1973, National Forest Management Act of 1976, and Oregon Omnibus Wild and 

Scenic Rivers Act of 1988 guide the three units. The Blue Mountains draft revised 

land management plan (USDA FS 2014) will provide overarching guidance for all 

resource management activities, succeeding existing land management plans for the 

national forests. 

A shared history of periodic and extensive insect outbreaks further unites 

the three administrative units. To various degrees, insect outbreaks have been 
18

GENERAL TECHNICAL REPORT PNW-GTR-939

attributed to fire exclusion and subsequent high stand density and conversion from 

pine to fir (Rainville et al. 2008, Wickman 1992). Mountain pine beetle outbreaks 

occurred in 1905, 1932, and throughout the 1940s, 1950s, and 1960s, affecting 263 

045 ha from 1955 to 1966 (Burke and Wickman 1990, Oliver et al. 1994). Western 

pine beetle (Dendroctonus brevicomis LeConte) outbreaks from 1953 to 1980 

affected 4000 to 35 000 ha annually (Rainville et al. 2008). From 1944 to 1958, 

western spruce budworm contributed to tree mortality on 364 217 ha in the Umatilla National Forest alone. Additional budworm outbreaks occurred from 1980 to 

1992 (Oliver et al. 1994). Douglas-fir tussock moth outbreaks (1946 to 1948, 1963 

to 1965, 1971 to 1975, 1991 to 1995) were the most prolific and damaging, with 

the 1970s outbreak affecting 255 000 ha (Mason et al. 1998, Rainville et al. 2008). 

Restoration efforts continue to address forest conditions affected by historical and 

potential future insect outbreaks. 

The Blue Mountains are currently managed for a wide range of ecosystem 

services, including timber, water, livestock grazing, and recreation. Whereas 

timber, grazing, and mining have been historically prominent, recreation and 

tourism are increasingly important in terms of number of users and economic 

value. The Wallowa-Whitman National Forest has 4667 km of trails and five scenic 

byways, and 20,000 hunters annually visit the Umatilla National Forest. In counties 

where employment was historically dominated by timber jobs, diverse management 

objectives including small-scale timber work have alleviated high unemployment 

experienced in the 1990s (Jaindl et al. 1996, Rainville et al. 2008).

Current restoration efforts in the Blue Mountains focus on improving the vigor 

of low-elevation dry forests, reducing fire hazard, restoring functional fish passages, improving habitat for several animal species, and improving riparian and 

stream conditions. The national Watershed Condition Framework (Potyondy and 

Geier 2011) and regional aquatic restoration strategies guide forest watershed and 

aquatic restoration programs, which include controlling invasives and restoring 

native plant communities. Addressing a long legacy of fire exclusion and timber 

practices that have created densely stocked stands, mostly at lower elevations, forest 

restoration seeks to improve forest vigor and strategically reduce fuel loads. These 

efforts also seek to limit insect outbreaks, reduce wildfire severity, and encourage 

prescribed fire use (Rainville et al. 2008, USDA FS 2013). Whitebark pine is being 

protected in the face of multiple stressors, and quaking aspen (Populus tremuloides

Michx.) regeneration is being augmented where possible. Stewardship contracting, 

which allows timber receipts to stay within the forest to fund unprofitable restoration efforts, has been widely used in the area (Rainville et al. 2008). 
19

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

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U.S. Department of Agriculture, Forest Service [USDA FS]. 2014. Draft revised 

land management plan for the Blue Mountains National Forests. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Region. http://www.fs.usda.gov/detail/wallowa-whitman/landmanagement/

planning/?cid=stelprdb5247447. (25 September 2015).

U.S. Department of Agriculture, Forest Service [USDA FS]. [N.d.]. Malheur 

history and culture. Portland, OR, U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Region. http://www.fs.usda.gov/main/malheur/

learning/history-culture. (25 September 2015).
23

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Wells, A.F. 2006. Deep canyon and subalpine riparian and wetland plant 

association of the Malheur, Umatilla, and Wallowa-Whitman National Forests. 

Gen. Tech. Rep. PNW-682. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station. 45 p. 

White, J.D.L.; White, D.L.; Vallier T. [et al.]. 1992. Middle Jurassic strata link 

Wallowa, Olds Ferry, and Izee terrances in the accreted Blue Mountains island 

arc, northeastern Oregon. Geology. 20: 729–732.

Wickman, B.E. 1992. Forest health in the Blue Mountains: the influence of insects 

and disease. Gen. Tech. Rep. PNW-GTR-295. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 15 p. (Quigley, 

T.M., ed; Forest health in the Blue Mountains: the influence of insects and 

diseases).

Wild and Scenic Rivers Act of 1968; 16 U.S.C. 1271–1287.

Wilderness Act 1964; 16 U.S.C. 1121, 1131–1136.

Wilson, D.; Cox, A. 1980. Paleomagnetic evidence for tectonic rotation of Jurassic 

plutons in Blue Mountains, eastern Oregon. Journal of Geophysical Research. 85: 

3681–3689. 

Wissmar, R.C.; Smith, J.E.; McIntosh, B.A. [et al.]. 1994. A history of resource 

use and disturbance in riverine basins of eastern Oregon and Washington 

(1800s–1990s). Northwest Science 68 (Special issue): 1–35.
24

GENERAL TECHNICAL REPORT PNW-GTR-939
25

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Chapter 3: Climate Change and Hydrology in the 

Blue Mountains

Caty F. Clifton, Kate T. Day, Kathie Dello, Gordon E. Grant, Jessica E. Halofsky, Daniel J. Isaak, 

Charles H. Luce, Mohammad Safeeq, Brian P. Staab, and John Stevenson1

Current and Historical Climate in the Blue Mountains

The dominant influences on climatic patterns in the Pacific Northwest are the 

Pacific Ocean and the Cascade Range. The diurnal temperature range is higher 

east of the Cascade crest, further inland from the Pacific Ocean. More precipitation 

falls west of the Cascade Mountains crest, and a strong rain shadow greatly reduces 

precipitation east of the crest. The southern portion of the Blue Mountains, including the Strawberry subrange, is in the rain shadow of the Cascade Mountains and 

is predominantly influenced by Great Basin climatic patterns, resulting in warmer 

and drier conditions. In the northern Blue Mountains, maritime air flows through 

the Columbia River Gorge, resulting in higher precipitation and more moderate 

temperature variations (Western Regional Climate Center 2015).

It is important to establish a baseline of historical climate in the Blue Mountains before considering future change. The Blue Mountains area aligns closely 

with the National Climatic Data Center’s (NCDC) Northeast Oregon climate 

division (Oregon Climate Division 8), which is the area for which we consider 

current and historical climate. Note that the NCDC information consists of lowelevation climate data, and high-elevation climate patterns may differ from those at 

low elevations (Luce et al. 2013). The topography of the Blue Mountains results in 

orographically enhanced local precipitation totals despite being in the lee of the 

1 Caty F. Clifton is the regional water quality and water rights program manager, U.S. 

Department of Agriculture, Forest Service, Pacific Northwest Region, 1220 SW 3rd

Avenue, Portland, OR 97204; Kate T. Day is a hydrologist, Colville Forest Plan Revision 

Team, U.S. Department of Agriculture, Forest Service, 765 South Main Street Colville, 

WA 99114; Kathie Dello is a climatologist, and John Stevenson is a research assistant, 

Pacific Northwest Climate Impacts Research Consortium, Oregon State University, 326 

Strand Ag Hall, Corvallis, OR 97331; Gordon E. Grant is a research hydrologist, U.S. 

Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry 

Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; Jessica E. Halofsky

is a research ecologist, University of Washington, College of the Environment, School of 

Environmental and Forest Sciences, Box 352100, Seattle, WA 98195-2100; Daniel J. Isaak

is a research fish biologist and Charles H. Luce is a research hydrologist, U.S. Department 

of Agriculture, Forest Service, Rocky Mountain Research Station, 322 East Front Street, 

Suite 401, Boise, ID 83702; Mohammad Safeeq is a research scientist, Sierra Nevada 

Research Institute, University of California, Merced, CA 95343; Brian P. Staab is the 

regional hydrologist, U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Region, 1220 SW 3rd Avenue, Portland, OR 97204.
26

GENERAL TECHNICAL REPORT PNW-GTR-939

Cascade Range. The regional annual average precipitation is 44 cm (20th century 

average), with greater amounts in higher elevation areas in the region. The surrounding Columbia River Plateau and High Desert see less precipitation on an 

annual basis. The temperatures in the Blue Mountains are slightly cooler than those 

of the entire region; regionally averaged mean annual temperature is about 7.5 °C 

(1901 to 2000 average), with colder temperatures at higher elevations.

Human influence on the climate is clear (IPCC 2013), and changes in the 

climate are already being realized across the Pacific Northwest, where temperatures 

have warmed by a statistically significant amount. Mean annual temperature in 

northeast Oregon increased by 0.06 °C per decade between 1895 and 2013, consistent with the overall temperature trend of the entire Pacific Northwest (USDC 

NOAA National Centers for Environmental Information 2015) (fig. 3.1). Only 

3 years have been below the 20th century annual average temperature of 7.5 °C 

since 1990 (fig. 3.1). Precipitation in the Pacific Northwest is still dominated by 

interannual variability, such as the El Niño Southern Oscillation (ENSO) (Mote et 

al. 2013). However, the Blue Mountains region does not exhibit a clear precipitation signal in terms of ENSO phase in the winter months (USDC NOAA Climate 

Prediction Center 2015). Although there is no detectable or significant precipitation 

trend in the region, the last 30 years were generally drier than the 20th century 

average, but with a few very wet years in the mid-late 1990s; the preceding decades 

(1940 through 1980) were much wetter than recent years (fig 3.2). 

Figure 3.1—Annual historical temperature for Oregon Climate Division 8. Data are from the 

National Oceanic and Atmospheric Administration National Centers for Environmental Information 

(http://www.ncdc.noaa.gov/cag/time-series/us).

Human influence on 

the climate is clear and 

changes in the climate 

are already being 

realized across the 

Pacific Northwest.
27

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 3.2—Annual historical precipitation for Oregon Climate Division 8. Data are from the 

National Oceanic and Atmospheric Administration National Centers for Environmental Information 

(http://www.ncdc.noaa.gov/cag/time-series/us).

Future Climate Projections for the Pacific Northwest

Complex global climate models (GCMs) begin to answer questions about future 

climate. Climate modeling is mostly conducted at global to regional scales because 

of the computational power required to run GCMs. The disparity between the scale 

of GCM output and information needs for regional to subregional climate change 

planning presents some challenges. However, we consider the projections for the 

Pacific Northwest region relevant for planning in the Blue Mountains; variations in 

monthly and annual temperature are highly correlated across the Pacific Northwest 

region. 

A number of modeling groups around the world have developed and run GCM 

simulations, which project future global climate under different future scenarios. 

The Coupled Model Intercomparison Project (CMIP) is a coordinated experiment 

involving many of these modeling groups worldwide, offering many simulations 

for scientists to assess the range of future climate projections for the globe. The 

latest CMIP experiment is the fifth phase of the project, referred to as CMIP5. 

Simulations of future climate are driven by Representative Concentration Pathways 

(RCPs), a departure from the last CMIP experiment, somewhat confusingly titled 

CMIP3. CMIP3 relied on the Special Report on Emissions Scenarios to drive model 

projections of future climate (Nakićenović and Swart 2000). The RCPs do not 
28

GENERAL TECHNICAL REPORT PNW-GTR-939

define greenhouse gas emissions, but instead define future concentrations of greenhouse gases, aerosols, and chemically active gases. The RCPs encompass the range 

of current estimates regarding the evolution of radiative forcing, or the assumed rate 

of extra energy entering the climate system throughout the 21st century and beyond 

(van Vuuren et al. 2011). Although the models are run at the global scale, the following projections are for the Pacific Northwest (generally Oregon, Washington, Idaho, 

and western Montana) and are based on the analysis described in Mote et al. (2013). 

More information on CMIP can be found at http://cmip-pcmdi.llnl.gov/index.html.

For the Blue Mountains vulnerability assessment, following Mote et al. (2013), 

we considered two of the CMIP5 scenarios: RCP 4.5 (significant reduction in global 

greenhouse gases and climate stabilization by year 2100) and RCP 8.5 (increasing 

greenhouse gases to the end of the 21st century). For the Pacific Northwest, every 

GCM shows an increase in temperatures in the future, with differences depending 

on global greenhouse gas emissions (fig. 3.3). There is no plausible future climate 

scenario from any GCM in which the Pacific Northwest cools in future decades. 

For the 2041–70 period, models project warming of 1.1 °C to 4.7 °C compared to 

1970–99, with the lower end possible only if global greenhouse gas emissions are 

Figure 3.3—Observed (1950–2011) and simulated (1950–2100) Pacific Northwest regional mean 

temperature for selected global climate models under Representative Concentration Pathways (RCP) 

4.5 and 8.5. The gray (historical [HIST]), red (RCP 8.5), and blue (RCP 4.5) envelopes represent the 

range of model projections. Each individual narrow line represents a model projection, and bold lines 

are means of the model projections. Figure from Mote et al. (2013).
29

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 3.1—Summary of changes in temperature projections

for the Representative Concentration Pathways (RCPs) 4.5

and 8.5 annually and by season for the Pacific Northwest for 

the change from historical (1950–1999) to mid-21st century 

(2041–2070)a

Annual

Winter 

(DJF)

Spring 

(MAM)

Summer 

(JJA)

Autumn 

(SON)

RCP 4.5 8.5 4.5 8.5 4.5 8.5 4.5 8.5 4.5 8.5

°C

Maximum 3.7 4.7 4.0 5.1 4.1 4.6 4.1 5.2 3.2 4.6

Mean 2.4 3.2 2.5 3.2 2.4 3.0 2.6 3.6 2.2 3.1

Minimum 1.1 1.7 0.9 1.3 0.5 1.0 1.3 1.9 0.8 1.6

DJF = December, January, February; MAM = March, April, May; JJA = June, July, 

August; SON = September, October, November.

a Values are for the maximum model projection, multimodel mean, and 

minimum model projection.

significantly reduced (RCP 4.5 scenario). Through about 2040, both RCP 4.5 and 

8.5 show a similar amount of warming; regional temperatures beyond 2040 depend 

on future global greenhouse gas emissions. Similar to annual temperature, all models are in agreement that each season will be warmer in the future, with the largest 

amount of warming occurring in the summer (table 3.1). In each season, RCP 8.5 

projects warmer temperatures than RCP 4.5 (Dalton et al. 2013).

Projections for future annual precipitation do not display as clear of a signal as 

those for temperature; annual precipitation projections range from wetter to drier, 

and projections for future annual precipitation indicated small trends compared to 

natural year-to-year variability. Averaging all the model outputs for annual precipitation, the projected future precipitation is close to no change from historical, with 

a wide range of projections. There is some indication and greater model agreement 

that summers will be drier in the future, although summers in the Pacific Northwest 

are already quite dry (table 3.2) (Mote et al. 2013). 

Hydrologic Processes in the Blue Mountains

Climate change will likely affect physical hydrological processes and resource 

values influenced by hydrological processes, including water use, infrastructure, 

and fish. Specifically, climate change will affect the amount, timing, and type of 

precipitation, and timing and rate of snowmelt (Luce et al. 2012, 2013; Safeeq et 

al. 2013), which will affect snowpack volumes (Hamlet et al. 2005), streamflows 

(Hidalgo et al. 2009, Mantua et al. 2010), and stream temperatures (Isaak et al. 

2012, Luce et al. 2014b). Changes in the amount and timing of precipitation will 

Climate change will 

likely affect physical 

hydrological processes 

and resource values 

influenced by 

hydrological processes, 

including water use, 

infrastructure, and fish.
30

GENERAL TECHNICAL REPORT PNW-GTR-939

Table 3.2—Summary of changes in precipitation projections for 

Representative Concentration Pathways (RCP) 4.5 and 8.5 emission 

scenarios annually and by season for the Pacific Northwest for the change 

from historical (1950–1999) to mid-21st century (2041–2070)a

Annual

Winter 

(DJF)

Spring 

(MAM)

Summer 

(JJA)

Autumn 

(SON)

RCP 4.5 8.5 4.5 8.5 4.5 8.5 4.5 8.5 4.5 8.5

Percent change

Maximum 10.1 13.4 16.3 19.8 18.8 26.6 18.0 12.4 13.1 12.3

Mean 2.8 3.2 5.4 7.2 4.3 6.5 -5.6 -7.5 3.2 1.5

Minimum -4.3 -4.7 -5.6 -10.6 -6.8 -10.6 -33.6 -27.8 -8.5 -11.0

DJF = December, January, February; MAM = March, April, May; JJA = June, July, August;

SON = September, October, November.

a

 Values are for the maximum model projection, multimodel mean, and minimum projection.

also affect vegetation (chapters 6 and 7), which will further alter water supplies 

(Adams et al. 2011). Although climate change effects on vegetation will likely be 

important, they are not considered in the hydrological projections in this chapter. 

Here we describe hydrologic processes and regimes in the Blue Mountains, historical trends in hydrologic parameters (snowpack, peak streamflow, low streamflow, 

and stream temperatures), and projected effects of climate change on those hydrologic parameters (box 3.1).

Some of the streamflow simulations shown in this report were generated by the 

Variable Infiltration Capacity (VIC) model (Liang et al. 1994) using GCMs from 

the Intergovernmental Panel on Climate Change (IPCC 2013) AR4 assessment to 

project future climates (Elsner et al. 2009). The VIC projections were prepared 

from an ensemble of GCM models that had the best match with observations in the 

historical period (see Littell et al. [2011] for details). Projections for the “2040s” 

cover an average from 2030 to 2059, and the “2080s” cover 2070 to 2099. Historical 

metrics were based on the period 1977 through 1997 (Wenger et al. 2010). The VIC 

data were computed on a 1/16th-degree (about 6-km) grid to produce daily flow data 

that were further analyzed for metrics important to aquatic ecology (Wenger et al. 

2010, 2011b). 

Snowpack

Effects of climate change on snowpack in watersheds of the Pacific Northwest can 

be broadly distinguished by mid-winter temperatures in each basin (Hamlet and 

Lettenmaier 2007). Rain-dominated basins are above freezing most of the time in 

winter, and snow accumulation is minimal (<10 percent of October through March 

precipitation). At a relatively coarse time scale, rain-dominated basins typically 
31

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 3.1—Summary of climate change effects on

hydrology in the Blue Mountains

Broad-scale climate change effect

Warming temperatures will lead to decreased snowpack accumulation and earlier 

melt out, resulting in shifts in timing and magnitude of streamflow and decreased 

summer soil moisture. Both peak and low flows may be affected.

Habitat, ecosystem function, or species

Changes in streamflow timing and magnitude could potentially affect all aquatic 

species and riparian vegetation through either increased or decreased peak flows or 

decreased summer streamflows. Changes in soil moisture could potentially affect 

most terrestrial vegetation.

Current condition, existing stressors

Vegetation water stress varies annually under the current climatic regime but 

may become more pronounced in the future. Topography influences precipitation. 

Historical land use still affects some sites. 

Sensitivity to climatic variability and change

Because of the fundamental role of water in all ecosystems, changes in availability, 

timing, and volume of water will have ramifications for most terrestrial and aquatic 

ecosystems.

Expected effects of climate change

The most pronounced changes in snow/streamflow in the Blue Mountains are likely 

to occur in headwater basins of the Wallowa Mountains, notably the higher elevation 

radial drainages out of the Eagle Cap Wilderness, with other large changes occurring in the more northerly sections of the Umatilla and Wallowa-Whitman National 

Forests along the Oregon-Washington border.

Adaptive capacity

Variable. Key challenges posed by changes in hydrology include increased water 

stress to vegetation with consequences for fire, mortality, growth, etc. Hydrological 

changes to streamflow are likely to affect some fish species more than others (see 

chapter 5).

Geographic locations most vulnerable

Mid elevations; areas where snow is not persistent (e.g., Northern Blue Mountains, 

margins of Wallowa, Elkhorns, Greenhorn, and Strawberry Mountains)
32

GENERAL TECHNICAL REPORT PNW-GTR-939

Box 3.1 continued

Risk assessment 

Potential magnitude of climate change effects

• For those regions determined to be sensitive, as identified in the hydrological 

assessment products

• Moderate magnitude by 2040

○ High magnitude by 2080

Likelihood of climate change effects

• For those regions determined to be sensitive, as identified in the hydrological 

assessment products

• Moderate likelihood by 2040

○ High likelihood by 2080

have one broad peak in streamflows in the winter that coincides with the regional 

winter peak in precipitation. However, at a finer time scale, rain-dominated basins 

may display multiple peaks in streamflow that coincide with individual storms or 

rain events. Mixed rain and snow (also called “transient” or “transitional”) basins 

can collect substantial snowpack in winter (10 to 40 percent of October through 

March precipitation), but are typically only a few degrees below freezing on average 

in mid-winter. Mixed rain-and-snow basins typically have multiple seasonal streamflow peaks, with one primary peak in late autumn caused by rain, and another in 

late spring caused by snowmelt. Snowmelt-dominated basins are relatively cold 

in winter and capture a larger percentage (>40 percent) of their October through 

March precipitation as snow. Snowmelt-dominated basins typically have relatively 

low flows through winter and a period of streamflow peaks in spring that coincides 

with seasonal snowmelt. 

Increasing temperatures in the Pacific Northwest over the past 50 years have 

led to more precipitation falling as rain rather than snow, earlier snowmelt (Hamlet et al. 2007, Stewart et al. 2005), and reduced spring snowpack (Barnett et al. 

2008, Hamlet et al. 2005, Mote 2003, Mote et al. 2005). Snowpack in the Pacific 

Northwest is expected to be sensitive to future temperature increases with changing climate. In response to warming, shifts from snowmelt-dominant to mixed 

rain-and-snow basins, and from mixed rain-and-snow to rain-dominant basins are 

projected by the 2040s in the Pacific Northwest (Tohver et al. 2014). 
33

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Kramer2 developed a snowpack sensitivity map for the Pacific Northwest 

using data from the Snow Data Assimilation System (SNODAS) (NOHRSC 2004). 

SNODAS snow water equivalent (SWE) data from 2003 to 2012 were used to 

characterize the sensitivity of snowpack to climate variability (table 3.3). Luce et al. 

(2014a) also evaluated snow sensitivity to climate at Snowpack Telemetry sites in 

the Pacific Northwest, using a spatial analog method to make April 1 SWE projections under a future climate-warming scenario of 3 °C warmer than the past 20 

years (expected by around 2050 for the RCP 8.5 scenario [fig. 3.3]). An analysis of 

snow cover data from strongly contrasting years gives some insight about potential 

sensitivity of late-season snowpack to a changing climate (see footnote 2) (table 

3.3). Results of both studies suggest that there will likely be future declines in 

snowpack persistence and April 1 SWE throughout the Pacific Northwest, with the 

largest declines in mid-elevation and wetter locations. 

In the Blue Mountains, large areas could lose all or significant portions of 

April 1 SWE under a 3 °C temperature increase (expected by around 2050 for the 

RCP 8.5 scenario [fig. 3.3]) (fig. 3.4). Results indicate that snowpack sensitivity is 

relatively high in the Strawberry Mountains, Monument Rock Wilderness, WenahaTucannon Wilderness, and at mid-elevations in the North Fork John Day, Eagle Cap 

Wilderness, and Hells Canyon Wilderness (fig. 3.4). Snowpack sensitivity is lower 

at high elevations in the Wallowa Mountains (Eagle Cap Wilderness), Greenhorn 

Mountains (North Fork John Day Wilderness), and Hells Canyon Wilderness Area. 

However, snowpack loss may still be significant (40 to 100 percent loss) in some of 

these areas (Luce et al. 2014a).

2 Kramer, M.G. Unpublished data. On file with: M.G. Kramer, University of Florida, 

Gainesville, FL 30503.

Table 3.3—Snowpack sensitivity definitions used in chapter 3 (fig. 3.4)

Sensitivity class Definition

Persistent—least sensitive Timing of peak snowmelt differed by >30 days between the 

warmest, driest year and coldest, wettest year in >30 percent of the subwatershed.

Persistent—more sensitive Timing of peak snowmelt in the warmest, driest year (2003, 

El Niño year) occurred >30 days earlier than the coldest, 

wettest year (2011, La Niña year) in >50 percent of the 

subwatershed.

Ephemeral snow April 1 snow water equivalent was <3.8 cm during dry years 

(no snow) and >3.8 cm during wet years (snow cover) in 

>80 percent of the subwatershed.

Source: Kramer, M.G. Unpublished data. On file with: M.G. Kramer, University of Florida, Gainesville, FL 

30503.

There will likely be 

future declines in 

snowpack persistence 

and April 1 SWE 

throughout the Pacific 

Northwest.
34

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 3.4—Projected change in snow water equivalent (SWE) (a) and mean snow residence time (b) for a 3 °C increase in temperature in the Blue Mountains. Point data are projections at Snowpack Telemetry (SNOTEL) stations from Luce et al. (2014). Snowpack sensitivity classes (the same in both figures) reflect the amount of shift in snowmelt timing seen in two contrasting historical years (Kramer [see footnote 2]; summarized in table 3.3). 

A
35

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

B

Figure 3.4 continued
36

GENERAL TECHNICAL REPORT PNW-GTR-939

Similarly, the VIC model was used to project up to 100 percent loss of April 1 

SWE in parts of the Blue Mountains by the 2080s (Hamlet et al. 2013). This study 

also projected that most of the watersheds in the Blue Mountains that were historically classified as mixed rain and snow will become rain dominant by the 2080s. 

These watersheds will likely receive more rain and less snow in the winter months. 

Peak Flows

Flooding regimes in the Pacific Northwest are sensitive to precipitation intensity, 

temperature effects on freezing elevation (which determines whether precipitation 

falls as rain or snow), and the effects of temperature and precipitation change on 

seasonal snow dynamics (Hamlet and Lettenmaier 2007, Tohver et al. 2014). Floods 

in the Pacific Northwest typically occur during the autumn and winter because of 

heavy rainfall (sometimes combined with melting snow) or in spring because of 

unusually heavy snowpack and rapid snowmelt (Hamlet and Lettenmaier 2007, 

Sumioka et al. 1998). Summer thunderstorms can also cause local flooding and 

mass wasting, particularly after wildfire (e.g., Cannon et al. 2010, Istanbulluoglu et 

al. 2004, Luce et al. 2012, Moody and Martin 2009). 

Flooding can be exacerbated by rain-on-snow (ROS) events, which are contingent on the windspeed, air temperature, absolute humidity, intensity of precipitation, elevation of the freezing line, and existing snowpack when storms happen 

(Eiriksson et al. 2013, Harr 1986, Marks et al. 1998, McCabe et al. 2007). Warming 

affects future flood risk from ROS events differently depending on the importance 

of these events as a driver of flooding in different basins under the current climate. 

As temperatures warm, the ROS zone, an elevation band below which there is 

rarely snow and above which there is rarely rain, will likely shift upwards in elevation. This upward shift in the ROS zone will tend to strongly increase flooding in 

basins where the current ROS zone is low in the basin (with a large snow collection 

area above). In contrast, in basins in which the ROS zone is higher in the basin, the 

upward shift in the ROS zone may only modestly increase the fractional contributing basin area with ROS or potentially shrink the relative contribution of ROS. 

In the latter half of the 20th century, increased temperatures led to earlier runoff 

timing in snowmelt-dominated and mixed rain-and-snow watersheds across the 

Western United States (Cayan et al. 2001, Hamlet et al. 2007, Stewart et al. 2005). 

With future increases in temperature and potentially in amount of precipitation in 

the winter months, extreme hydrologic events (e.g., those currently rated as having 

100-year-recurrence intervals) may become more frequent (Hamlet et al. 2013). 

An analysis for the Blue Mountains, using VIC model output from Wenger et 

al. (2010), projects that flood magnitude will increase in the Wallowa Mountains, 
37

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Hells Canyon Wilderness Area, and northeastern portion of the Wallowa-Whitman 

National Forest by the 2080s, particularly in mid-elevation areas most vulnerable 

to ROS (fig. 3.5a). The frequency of mid-winter flood events does not change over 

much of the area (fig. 3.5b, c), but the areas showing the greatest change in flood 

magnitude (fig. 3.5a) are also showing substantial changes in the frequency of the 

largest flows in winter (fig. 3.5b, c), a measure of flood seasonality that is important 

to a number of fall-spawning fish species (Goode et al. 2013; Tonina et al. 2008; 

Wenger et al. 2011a, 2011b).

Low Flows

As a result of earlier snowmelt and peak streamflows over the last 50 years in the 

Western United States, spring, early summer, and late-summer flows have been 

decreasing, and fractions of annual flow occurring earlier in the water year have 

been increasing (Leppi et al. 2011, Luce and Holden 2009, Safeeq et al. 2013, Stewart et al. 2005). An analysis by Stewart et al. (2005) in eastern Oregon showed some 

of the largest trends toward decreasing fractional flows from March through June. 

In addition to decreased summer flows, Luce and Holden (2009) showed declines 

in some annual streamflow quantiles in the Pacific Northwest between 1948 and 

2006; they found decreases in the 25th percentile flow (drought year flows) over the 

study period, meaning that the driest 25 percent of years have become drier across 

the Pacific Northwest. 

Summer low flows are influenced not only by the timing of snowmelt but 

also by landscape drainage efficiency, or the inherent geologically mediated efficiency of landscapes in converting recharge (precipitation) into discharge (Safeeq 

et al. 2013, Tague and Grant 2009). The Blue Mountains, which have moderate 

groundwater contributions, experienced reduced summer flows of 21 to 28 percent 

between 1949 and 2010 (Safeeq et al. 2013). Safeeq et al. (2014) developed and 

applied an analytical framework for characterizing summer streamflow sensitivity to a change in the magnitude (mm mm-1) and timing (mm day-1) of recharge at 

broad spatial scales (assuming an initial recharge volume of 1 mm). This approach 

facilitates assessments of relative sensitivities in different locations in a watershed 

or among watersheds. Sensitivity, in this approach, has a very specific meaning: 

the amount of summer streamflow (at some defined point during the summer, i.e., 

July 1 or August 1) change in response to a change in either the amount of water 

that recharges the aquifer during late winter and early spring, and the timing of that 

recharge. So magnitude sensitivity relates how much summer discharge will change 

(in millimeters) with a 1-mm change in amount of recharge, and timing sensitivity 

Flows have been 

decreasing, and 

fractions of annual flow 

occurring earlier in the 

water year have been 

increasing.
38

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 3.5—(a) Percentage change in the 1.5-year flood magnitude (approximately bankfull) between 2080 and the historical period (1970 to 1999) for the Blue Mountains region; brown lines are state boundaries. (b) Historical mid-winter flooding potential. (c) Projected mid-winter flooding potential for 2080. Flooding potential is shown as the number of days that winter flow is among the highest 5 percent for the year for streams in the Blue Mountains. Comparing the historical (1970–1999) to 2080s model runs shows that although much of the Blue Mountains has frequent mid-winter flooding now, it is rare in some high-elevation areas. In the future, mid-winter flooding is expected to be widespread. All projections are from the Variable Infiltration Capacity (VIC) model, using data from Wenger et al. (2010). 

A
39

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 3.5—(continued).
40

GENERAL TECHNICAL REPORT PNW-GTR-939

indicates how much summer discharge will change (in millimeters) with a 1-day 

change in the timing of recharge. Both metrics make the simplifying assumption 

that all recharge happens on a particular day, which of course is not the case—

recharge happens throughout the rain and snowmelt season. But this approach 

allows for expressing the intrinsic landscape response to a change in either magnitude or timing of recharge. 

Snow-dominated regions with late snowmelt, such as the Wallowa Mountains, show relatively high sensitivity (fig. 3.6), especially early in summer (July), 

although they are less sensitive than the Cascade and Olympic Mountains. The rest 

of the Blue Mountains region shows moderate to low sensitivity to changes in the 

magnitude and timing of snowmelt (fig. 3.6), although sensitivity in the Wallowas 

is higher in early summer. The level and sensitivity and the spatial extent of highly 

sensitive areas were shown to diminish over time as summer progresses. 

Projections of future low flows using the VIC model (data from Wenger et al. 

2010) also show relatively minor decreases in summer streamflow (<10 percent 

decrease) for 47 percent of perennial streams across the Blue Mountains region by 

2080 (fig. 3.7). However, some portions of the region, such as the Wallowas, Greenhorn Mountains, and the Wenaha-Tucannon Wilderness show greater decreases 

(>30 percent in streamflow by 2080; fig. 3.7). 

A direct comparison of the framework developed by Safeeq et al. (2014) and 

VIC projections for the 2040 time period at the hydrologic unit code 10 watershed 

scale generally highlights the same portions of the Blue Mountains as being most 

sensitive to decreases in summer flows as the climate warms in future decades 

(fig. 3.8). However, the exponential model (Safeeq et al. 2014), which incorporates 

the role of groundwater, projects larger decreases in summer low flows across the 

Blue Mountains than the VIC model.

Water Quality

Historical trends in stream temperatures are variable among different studies. 

Isaak et al. (2010, 2012) found that temperatures at unregulated stream sites closely 

tracked air temperature trends at nearby weather stations across the Pacific Northwest from 1980 to 2009. Statistically significant stream temperature increases 

occurred during summer, autumn, and winter, with the highest rates of warming 

in the summer (reconstructed trend = 0.22 °C per decade). A statistically significant stream cooling trend occurred during the spring season in association with 

a regional trend towards cooler air temperatures (Abatzoglou et al. 2014, Isaak et 

al. 2012). Most of the variation in long-term stream temperature trends (80 to 90 

Snow-dominated 

regions with late 

snowmelt, such as the 

Wallowa Mountains, 

show relatively high 

sensitivity. 
41

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 3.6—Spatial distribution of July, August, and September streamflow sensitivities to a change in magnitude (mm/mm) and timing (mm/day) of recharge from snowmelt or rainfall in the Blue Mountains analysis area. See text for further explanation of streamflow sensitivity. From Safeeq et al. (2014).
42

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 3.7—Percentage decrease in mean summer streamflow from historical time period (1970–1999) to 2080 for streams in the Blue Mountains region. Projections are from the Variable Infiltration Capacity (VIC) hydrologic model using data from Wenger et al. (2010).
43

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 3.8—Comparison of percentage decline in summer low flows for hydrologic unit code 10 watersheds, calculated as percentage of average daily flow predicted by the Vari- able Infiltration Capacity (VIC) model (Wenger et al. 2010) and the exponential model (Safeeq et al. 2014) using historical (1915–2006) data and the A1B emission scenario for the 2040s. Low-flow calculations using the exponential model were calculated only when streamflow decline was ≥0.01 mm/day.
44

GENERAL TECHNICAL REPORT PNW-GTR-939

percent) was explained by air temperature trends and a smaller proportion by discharge trends (10 to 20 percent). Arismendi et al. (2012) examined stream data from 

a larger number of sites and different periods of record and found variable trends in 

stream temperature, concluding that stream temperatures have increased at some 

minimally altered sites in the Pacific Northwest (28 to 44 percent) and decreased 

at others (22 to 33 percent); no detectable trends were found at the remaining sites. 

Stream temperature trends were influenced by the length of record, period of 

record, and location relative to dams, with more warming trends becoming apparent 

where longer term records were available. 

Luce et al. (2014b) analyzed summer stream temperature records from forested 

streams in the Pacific Northwest and found that cold streams were generally not 

as sensitive as warm streams to climatic conditions. Thus, temperature in lowelevation, warmer streams (less shade, less cool groundwater inputs) will likely 

increase the most in the future. These results suggest that these warmer streams in 

the Blue Mountains are relatively sensitive to climate. 

The NorWeST Regional Stream Temperature Database (http://www.fs.fed.

us/rm/boise/AWAE/projects/NorWeST.html) used extensive stream temperature 

observations and spatial statistical models to characterize stream temperatures 

throughout the Blue Mountains under recent historical conditions at a 1-km resolution (Isaak et al. 2015) (fig. 3.9). Future stream temperatures were then projected 

based on these historical conditions, assessments of past sensitivity to climate, and 

projections of future climatic conditions. Results project basinwide average August 

stream temperatures in the Blue Mountains to increase by about 1 °C by 2040 and 

by nearly 2 °C by 2080 in direct response to climatic conditions (i.e., no consideration of secondary effects, such as increased fire). Warmer streams in the basin will 

likely warm to a greater degree than cooler ones (Luce et al. 2014b).

Decreasing summer water availability and warming temperatures across the 

Western United States may contribute to forest mortality in some locations (Adams 

et al. 2009, Allen et al. 2010, Breshears et al. 2005, Meddens and Hicke 2014, van 

Mantgem et al. 2009) and increased wildfire extent compared to the mid-20th

century (Littell et al. 2009, Westerling et al. 2006). Increased area burned, particularly if fire in riparian areas results in decreased shade over streams, will contribute 

further to stream temperature increases (Dunham et al. 2007, Isaak et al. 2010). 

Increases in fire have increased basin-scale sediment yields in some basins (Goode 

et al. 2012). 

Warmer streams in the 

basin will likely warm 

to a greater degree 

than cooler ones.
45

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 3.9—Recent historical (1970–1999) (a) and projected future (b) (2040, A1B Scenario) August mean temperatures for streams in the Blue Mountains region. Projections are from NorWeST Regional Stream Temperature Database and Model (http://www.fs.fed.us/rm/boise/AWAE/projects/NorWeST.html).
46

GENERAL TECHNICAL REPORT PNW-GTR-939

Conclusions

The results and map products discussed in this chapter represent our current best 

understanding of the likely effects of climate change on key hydrologic processes. 

Nevertheless, these results should be applied with caution. Key uncertainties 

include the specific climate trajectories that the Blue Mountains will experience 

in the future, critical assumptions underlying all models used, and the myriad 

uncertainties and errors attached to the calibration of each of the models. Resource 

managers wishing to apply the results of this analysis in forest planning are encouraged to read the primary literature in which the strengths and limitations of different modeling and forecasting approaches are described.

In general, projections of future trends in streamflow and related processes are 

strongest in characterizing relative sensitivities of different parts of the landscape 

rather than absolute changes. In other words, the spatial pattern of trends is more 

robust than projections associated with any particular location. Similarly, more confidence applies to the interpretation of relative, as opposed to absolute, magnitudes 

of projected changes. Differences in results between modeling approaches, such as 

the low-flow analysis, should be interpreted as bracketing likely potential changes. 

Finally, the models used here contain uncertainties related to the quantification of 

soil, vegetation, and other characteristics used to generate hydrologic dynamics.

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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Chapter 4: Climate Change, Water Resources, and Roads 

in the Blue Mountains

Caty F. Clifton, Kate T. Day, Gordon E. Grant, Jessica E. Halofsky, Charles H. Luce, and Brian P. Staab1

Introduction

Water is a critical resource in dry forest and rangeland environments of western 

North America, largely determining the distribution of plant and animal species 

across a broad range of elevations and ecosystems. Water is also essential for 

human endeavors, directly affecting where and how human communities and local 

economies have developed. The Blue Mountains of northeast Oregon and southeast 

Washington are an important source of water for forest ecosystems and human 

uses. Surrounding communities rely on water from national forest lands in the Blue 

Mountains for drinking water, industrial uses, irrigation, livestock watering, and 

recreation, among other uses. Climate change affects water supply by changing the 

amount, timing, and distribution of precipitation and runoff. These changes have 

the potential to affect water supply, roads and other infrastructure, and access to 

national forest lands in the Blue Mountains region. Reduced or less reliable water 

supply affects local economic activities, planning, and resource management. Damage to roads, bridges, and culverts creates safety hazards, affects aquatic resources, 

and incurs high repair costs. Reduced access to public lands reduces the ability of 

land managers to preserve, protect, and restore resources and to provide for public 

use of resources. Understanding vulnerabilities and the processes through which 

climate change affects hydrology will help U.S. Forest Service land managers 

identify adaptation strategies that maintain ecosystem function, a sustainable water 

supply, and a sustainable road system.

In this chapter, we (1) identify key sensitivities of water supply, roads, and 

infrastructure to changes in climate and hydrology; (2) review current and proposed 

management priorities, and share management approaches that already consider 

climate or climate change; and (3) use the latest scientific information on climate 

change and effects on hydrologic regimes (see chapter 3) to identify adaptation 

1 Caty F. Clifton is the regional water quality and water rights program manager and 

Brian P. Staab is the regional hydrologist, U.S. Department of Agriculture, Forest Service, 

Pacific Northwest Region, 1220 SW 3rd Avenue, Portland, OR 97204; Kate T. Day is a 

hydrologist, Colville Forest Plan Revision Team, U.S. Department of Agriculture, Forest Service, 765 South Main Street Colville, WA 99114; Gordon E. Grant is a research 

hydrologist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; 

Jessica E. Halofsky is a research ecologist, University of Washington, College of the 

Environment, School of Environmental and Forest Sciences, Box 352100, Seattle, WA 

98195-2100; Charles H. Luce is a research hydrologist, U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station, 322 East Front Street, Suite 401, Boise, 

ID 83702.

Climate change affects 

water supply by 

changing the amount, 

timing, and distribution 

of precipitation and 

runoff.
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GENERAL TECHNICAL REPORT PNW-GTR-939

strategies and tactics. During a workshop convened in La Grande, Oregon, in April 

2014, participants reviewed the latest science on the sensitivity of water resources 

and related water uses and infrastructure to climate change in the Blue Mountains 

(boxes 4.1 and 4.2). Workshop participants worked collaboratively to identify 

adaptation options to reduce vulnerability to climate change and facilitate transition to new conditions. The results of this vulnerability assessment and adaptation 

planning process are described in the sections below. 

Water Resources and Uses

In the predominantly dry climate of the Blue Mountains region, water is the most 

critical natural resource for human habitation and enterprises. Many streams and 

groundwater systems surrounding the Blue Mountains region originate from the 

Malheur, Umatilla, and Wallowa-Whitman National Forests, thus providing a 

valued ecosystem service to local communities and economies. There are about 

6,800 water rights on national forest lands in the Blue Mountains; 43 percent 

provide water for domestic livestock, 32 percent support instream flows, 9 percent 

are for wildlife, 5 percent are for irrigation, and 3 percent are for domestic uses 

(Gecy 2014). By volume, instream flows account for 75 percent of water rights, with 

irrigation and domestic uses each accounting for 1 percent by volume, and water 

for livestock accounting for 2 percent by volume (Gecy 2014). Six municipalities 

(Baker City, La Grande, Long Creek, Walla Walla, Pendleton, and Canyon City) 

rely directly on the national forests for municipal water supply. In addition, 20 

smaller communities rely on surface or groundwater from the Blue Mountains 

forests for drinking water. There are 320 points of diversion (under a certificated 

water right) within the boundaries of national forests in the Blue Mountains that 

provide water for domestic use (Gecy 2014; e.g., see fig. 4.1).

Water is critical for livestock on national forests and surrounding lands, and 

consumption for this purpose is broadly dispersed across different ecosystems. 

About 42 percent of national forest land in the Blue Mountains is considered suitable for sheep and cattle grazing, and grazing occurs on these lands in 455 of 552 

subwatersheds within the Blue Mountains (Gecy 2014). Water for livestock is the 

largest permitted water use on national forest land by number of certificated water 

rights.

All basins in national forests of the Blue Mountains region are fully allocated 

in terms of water available for appropriation under state law in the dry summer 

season. In national forests, water is generally available for campgrounds and 

administrative sites and for other appropriated uses (e.g., livestock and wildlife), 
55

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 4.1—Summary of climate change effects on 

water resource use in the Blue Mountains

Broad-scale climate change effect

Decreasing snowpack and declining summer flows alter timing and availability of 

water supply.

Resource entity affected

Drinking water supply for municipal and public uses both downstream from and 

on the national forests, other forest uses including livestock, wildlife, recreation, 

firefighting, road maintenance, and instream fishery flows. Change in availability 

of water supply to meet human uses increases the risk of scarcity and of not satisfying consumptive and instream needs.

Current condition, existing stressors

All basins are fully allocated in terms of water available for appropriation under state 

law. On national forests, water is generally available for campgrounds and administrative sites and for other appropriated uses (e.g., livestock and wildlife), although 

in dry years, availability may be limited at some sites, especially in late summer. In 

drought years, downstream “junior” users may not receive water for various purposes, primarily irrigation. Six municipalities rely directly on the national forests for 

drinking water supply (Baker City, La Grande, Walla Walla, Pendleton, Long Creek, 

and Canyon City). Ecological effects include the following: onforest dams for storage 

facilities and stream diversions affect stream channel function; and development of 

springs and ponds for livestock affect many groundwater-dependent ecosystems. 

Changes in water supply are expected to influence water use by vegetation, exacerbate low soil moisture, and influence fire frequency with various secondary effects 

on water supply and quality. 

Sensitivity to climatic variability and change

Regional water supplies are highly dependent on snowpack extent and duration; 

April 1 snow water equivalent is the traditional indicator of late-season water availability. Declining summer low flows will affect water availability during this period 

of peak demand (e.g., for irrigation and power supply).

Expected effects of climate change

Decreased snowpack extent and duration are expected to affect the timing and 

availability of water supply, particularly in late summer when demand is high for 

both consumptive and instream uses. Decreased summer low flows will limit water 

availability during critical times and for multiple uses.
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Box 4.1 continued

Adaptive capacity

Within-forest impacts will likely be less than downstream, although some facilities 

may see reduced water supply in late summer. Annual operating plans could be 

adjusted to limit potential for effects on streams and springs by permitted livestock 

and wildlife during dry years. Off-forest effects may be greater; although some 

municipalities have backup wells, and water supply for drinking water and other uses 

is likely to be affected. There is a need for coordination at the county and state level 

for conservation planning. There may be an increase in proposals for groundwater 

and surface storage development. 

Risk assessment

Potential magnitude of climate change effects

• For those watersheds determined to be sensitive

○ Moderate magnitude by 2040

○ High magnitude by 2080

Likelihood of climate change effects

• For those watersheds determined to be sensitive

○ Moderate likelihood by 2040

○ High likelihood by 2080
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 4.2—Summary of climate change effects on 

roads and infrastructure in the Blue Mountains

Broad-scale climate change effect

Increase in magnitude of winter/spring peak streamflows.

Resource entity affected

Infrastructure and roads near perennial streams, which are valued for public access. 

Current condition, existing stressors

Many kilometers of roads are located close to streams on the national forests, and 

these roads have high value for public access and resource management. A large 

backlog of deferred maintenance exists because of decreasing budget and maintenance capacity. Many roads are in vulnerable locations subject to high flows. 

Sensitivity to climatic variability and change

Roads in near-stream environments are periodically exposed to high flows. Increased 

magnitude of peak flows increases susceptibility to effects ranging from minor 

erosion to complete loss of the road prism, resulting in effects on public safety, access 

for resource management, water quality, and aquatic habitat. 

Expected effects of climate change

Projections for increased magnitude of peak flows indicate that more kilometers of 

road will be exposed to higher flow events and greater impacts. 

Adaptive capacity

Knowing the extent and location of potentially vulnerable road segments will help 

with prioritizing scarce funding, targeting “storm damage risk reduction” treatments, 

and communicating potential hazard and risk to the public.

Risk assessment

Potential magnitude of climate change effects

• For those watersheds determined to be sensitive

○ Moderate magnitude by 2040

○ High magnitude by 2080

Likelihood of climate change effects

• For those watersheds determined to be sensitive

○ Moderate likelihood by 2040

○ High likelihood by 2080
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 4.1—Water right points of diversions (PODs) in the name of the Forest Service 

and in the name of others on and near the Wallowa-Whitman and northern Umatilla 

National Forest. The PODs in the name of the Forest Service represent a minor percentage of consumptive water rights. Consumptive water rights in the name of others are concentrated off forest in the Umatilla, Walla Walla, Grande Ronde, and Wallowa Valleys. 

although in dry years, availability may be limited at some sites, especially in late 

summer. Dams for storage facilities, stream diversions, and development of springs 

and ponds for livestock on the national forests affect hydrologic and ecologic 

function of groundwater-dependent ecosystems (see chapter 7). In drought years, 

downstream “junior” users in the water allocation system may not receive water for 

various purposes, primarily irrigation. It is uncertain if long-term climate change or 

short-term drought will alter permitted water use in the future, although significant 

changes in water use during the next decade or so are unlikely.

Climate Change Effects on Water Uses

Warming temperatures will lead to decreased snowpack and earlier snowmelt, 

resulting in shifts in timing and magnitude of streamflow and decreased summer 

soil moisture (see chapter 3). Across the Blue Mountains, the majority of precipitation occurs during the winter months, when consumptive demand is lowest. In 

summer, when demand is highest, rain is infrequent and streams are dependent 

on groundwater to maintain low or base flows. Because water supply in the Blue 

In drought years, 

downstream “junior” 

users in the water 

allocation system may 

not receive water for 

various purposes, 

primarily irrigation.
59

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Mountains is limited, climate change may reduce water available to meet current 

demands in the summer months, especially during extreme drought years and after 

multiple consecutive drought years. Although current conflict over water use in the 

Blue Mountains is not a prominent issue, future water shortages may create social 

and political tensions as different sectors (e.g., agriculture and municipal) compete 

for scarce water.

Regional water supplies depend on snowpack extent and duration, and lateseason water availability (often characterized by April 1 snow water equivalent). 

Declining summer low flows caused by earlier snowmelt runoff could affect water 

availability during peak demand. Historical snowpack sensitivity (fig. 4.2) and 

projections of summer steamflow (fig. 4.3) across the Blue Mountains identify areas 

that may be particularly sensitive with respect to water supply. Lower elevation 

locations with mixed snow and rain will be the most vulnerable to reduced spring 

snowpack, but even the most persistent snowpacks at higher elevation are expected 

to decline by the 2080s (see chapter 3). Variable Infiltration Capacity (VIC) hydrological model runs (for natural flows, not accounting for withdrawals, use, and 

storage) suggest that the Burnt, Powder, Upper Grande Ronde, Silver, Silvies, Upper 

John Day, Wallowa, and Willow subbasins are at highest risk for summer water 

shortage associated with low streamflow by 2080 (fig. 4.3). Decreases in summer 

low flows in these areas have the greatest potential to affect agricultural irrigation 

and municipal uses. 

Water diversions and dams can also affect the resilience of watersheds to 

climate change. Although dams increase water storage during low flow, diversions 

also increase water extraction. Aging and inefficient diversion infrastructure can 

increase water loss. Engaging users within basins where water shortages can occur 

is critical for addressing water distribution and climate change effects. Clarifying 

water demand, negotiating water allocations, ensuring environmental flows in the 

water rights process, adjudicating over-allocated basins, and monitoring compliance 

can help reduce susceptibility to climate stresses. 

Water quantity is an important attribute of the Watershed Condition Framework 

(WCF) classification system used by national forests to rate overall watershed 

condition (Potyondy and Geier 2011). Most subwatersheds across the Blue Mountains were rated as “functioning” or “functioning at risk” for this attribute, based on 

the magnitude of existing flow alterations from dams, diversions, and withdrawals 

relative to natural streamflows and groundwater storage. The Burnt, Powder, Upper 

Grande Ronde, and Wallowa subbasins have the highest number of subwatersheds 

rated as having “impaired function” for water quantity on national forest lands 

(fig. 4.4). Basins with the highest off-forest consumptive uses include Walla Walla, 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 4.2—Historical snowpack sensitivity and different water uses in the Blue Mountains region. Snowpack sensitivity was classified as “no snow/ephemeral snow” if April 1 snow water equivalent was less than 3.8 cm during dry years (no snow) and greater than 3.8 cm during wet years (snow cover) in ≥80 percent of the subwatershed; “mixed snow sensitivity” if the timing of peak snowmelt in the warmest, driest years (e.g., 2003, El Niño year) occurred more than 30 days earlier than the coldest, wettest year (2011, La Niña year) in ≥50 percent of the subwatershed; and “persistent-least sensitive” if timing of peak snowmelt differed by less than 30 days between the warmest, driest years and the coldest, wettest years in ≥30 percent of the subwatershed. Locations in the mixed snow vulnerability category will likely see the greatest decrease in snowpack, but even the most persistent snowpacks (persistent least sensitive) will likely decline (see chapter 3). Areas of concern include municipal watersheds, locations with Forest Service drinking water systems, and national forest lands that are over-allocated downstream. Snowpack sensitivity information was adapted from Kramer (see footnote 2). 
61

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 4.3—Projections of risk of summer water shortage associated with low streamflows in summer for 2080. Projections were calculated using flow data from the Variable Infiltration Capacity model based on historical data for 1915–2006, and summer flow simulated for a global climate model ensemble for the A1B emission scenario (from Wenger et al. 2010). The Burnt, Powder, Upper Grande Ronde, Silver, Silvies, Upper John Day, Wallowa, and Willow Creek watersheds are at highest risk of summer water shortage.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 4.4—Magnitude of flow alteration by dams and diversions in the Blue Mountains region. Resource specialists in each national forest rated relative flow alteration of subwatersheds as part of the watershed condition classification in the Watershed Condition Framework (Potyondy and Geier 2011). A relatively high percentage of subwatersheds within the Burnt, Powder, Upper Grande Ronde, and Wallowa subbasins were rated as having impaired function for this indicator of watershed condition.
63

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Umatilla, Burnt, Powder, Malheur, Silvies, and Silver Creek (Gecy 2014). Most of 

these areas are among those expected to experience the greatest changes in summer 

flows (fig. 4.3) and thus may be the most vulnerable from a water-use perspective.

Besides projected changes in streamflows and the magnitude of existing water 

diversions, the presence or absence of backup water systems is an important factor 

affecting the vulnerability of water supplies for human uses. Those systems with 

redundant supplies will generally be less vulnerable. Development of such systems, as 

well as increasing water conservation efforts, are key opportunities for adaptation. 

Roads, Infrastructure, and Access 

Roads, trails, bridges, and other infrastructure were developed in the Blue Mountains over more than a century to provide access for mineral prospectors, loggers, 

hunters, and recreationists. The national forests in the Blue Mountains were created 

to protect water supply, timber, range resources, and wildlife, and to provide multiple uses and enjoyment by the public. Providing access to accomplish these objectives largely determined where these activities historically occurred. Today, reliable 

and strategic access is critical for people to recreate, extract resources, monitor and 

manage resources, and respond to emergencies. Access to public lands promotes 

use, stewardship, and appreciation of their value as a vital resource contributing to 

quality of life (Louter 2006). 

The three national forests combined contain 37 534 km of roads (table 4.1, fig. 

4.5). Of the existing roads, 850 km of roads are paved, 17 800 km are gravel, and 

the remaining are native surface roads. Road density is higher at low elevations 

and adjacent to mountain passes, such as near major highways (fig. 4.5). Roads 

and trails cross many streams and rivers because of the rugged topography. Most 

Table 4.1—Kilometers of road by maintenance level on national forests in 

the Blue Mountains

Operational maintenance levels (ML)

National forests

Code Description Malheur Umatilla

WallowaWhitman

Kilometers

ML 1 Basic custodial care (closed) 6059 3543 7216

ML 2 High-clearance cars/trucks 8814 3131 6719

ML 3 Suitable for passenger cars 587 545 435

ML 4 Passenger car (moderate comfort) 0 114 29

ML 5 Passenger car (high comfort) 0 132 210

Total All roads 15 460 7465 14 609

Reliable and strategic 

access is critical for 

people to recreate, 

extract resources, 

monitor and manage 

resources, and respond 

to emergencies.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 4.5—Distribution of roads and trails within the three national forests in the Blue Mountains region. The national forests cover a contiguous area of over 2 million ha and contain 37 534 km of roads. The density of roads is higher at low elevations.
65

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

(96 percent) known road-water crossings are culverts installed decades ago. Some 

crossings are being replaced, but many have not been inventoried and conditions 

are unknown. In many landscapes, the older the road, the more likely it is near or 

adjacent to streams, greatly increasing risks for road damage and degraded aquatic 

resources.

Historically, timber harvest was the primary purpose for development of the 

road system in national forests. Reduced harvesting during the past 20 years has 

decreased the need for roads for timber purposes. However, local population growth 

and tourism have increased demand for access for a diversity of recreation activities. Hiking and camping are the most popular activities, but visitors are staying 

for shorter duration, often only day use; more than 60 percent of trips to national 

forests last 6 hours or less (USDA FS 2010). Short visits concentrate human impacts 

on areas that are easily accessible. Demand is increasing for trail use by mountain 

bikes and motorized vehicles and for routes designated for off-highway vehicles, as 

well as for winter recreation (USDA FS 2010).

Road Management and Maintenance

The condition of roads and trails differs widely across the Blue Mountains, as do 

the impact of roads on watersheds and aquatic ecosystems. Culverts were typically 

designed to withstand a 25-year flood. Road construction has declined since the 

1990s, with few new roads being added to the system. Road maintenance is primarily the responsibility of the Forest Service, but county road maintenance crews 

maintain some roads. The Federal Highway Administration is also involved with 

the management, design, and funding of roads within the national forests. 

Roads vary in their level of environmental impact. They tend to accelerate 

runoff rates and decrease late-season flows, increase peak flows, and increase 

erosion rates and sediment delivery to the stream system. These impacts are generally greater from roads closer to rivers and streams; however, roads in uplands also 

affect surface and shallow groundwater flows, and erosion processes (Trombulak 

and Frissell 2000).

Each national forest develops a road maintenance plan for the fiscal year, 

primarily based on priorities by operational maintenance level, then by category 

and priority. Maintenance of forest roads subject to Highway Safety Act standards receive priority for appropriated capital maintenance, road maintenance, or 

improvement funds over roads maintained for high clearance vehicles. Activities 

that are critical to health and safety receive priority in decisions about which roads 

to repair and maintain, but are balanced with demands for access and protection of 

aquatic habitat. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Given current and projected funding levels, national forest staff are examining 

tradeoffs between providing access and maintaining and operating a sustainable 

transportation system that is safe, affordable, and responsive to public needs, and 

that causes minimal environmental impact. Management actions being implemented to meet these sometimes competing objectives include reducing road maintenance levels, storm-proofing roads, upgrading drainage structures and stream 

crossings, reconstructing and upgrading roads, decommissioning roads, converting 

roads to alternative modes of transportation, and developing more comprehensive 

access and travel management plans.

Planning for transportation and access on national forests is included in forest 

land management plans. The 2001 Road Management Rule (36 CFR 212, 261, and 

295) requires national forests to use science-based analysis to identify a minimum 

road system that is ecologically and fiscally sustainable. The Malheur, Umatilla, 

and Wallow-Whitman National Forests are currently identifying a sustainable 

road network in accordance with the rule. The goals of transportation analysis are 

to assess the condition of existing roads, identify options for removing damaged 

or unnecessary roads, and maintaining and improving necessary roads without 

compromising environmental quality. Transportation analysis has four benefits: 

(1) increased ability to acquire funding for road improvement and decommissioning, (2) a framework to set annual maintenance costs, (3) improved ability to meet 

agreement terms with regulatory agencies, and (4) increased financial sustainability 

and flexibility. Consideration of climate change is not currently a formal part of the 

analysis. 

Major road projects in national forests, such as reconstruction of roads and 

trails or decommissioning, must comply with the National Environmental Policy 

Act (NEPA) of 1969 (NEPA 1969) and require an environmental assessment and 

public involvement. Decommissioning roads is a process of restoring roads to a 

more natural state by reestablishing drainage patterns, stabilizing slopes, restoring vegetation, blocking road entrances, installing water bars, removing culverts, 

removing unstable fills, pulling back road shoulders, scattering slash on roadbeds, 

and completely eliminating roadbeds (36 CFR 212.5; Road System Management; 

23 U.S.C. 101). 

Spatial and terrain analysis tools developed to assess road risks, such as the 

Water and Erosion Predictive model (Flanagan and Nearing 1995), the Geomorphic Road Analysis and Inventory Package (GRAIP) (Black et al. 2012, Cissel et 

al. 2012), and NetMap (Benda et al. 2007), are often used to identify hydrologic 

impacts and guide management on projects. For example, the Wall Creek watershed 

GRAIP analysis on the Umatilla National Forest determined that 12 percent of the 
67

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

road system contributed 90 percent of the sediment, and focused treatment plans to 

the most critical sites (Nelson et al. 2010).

Climate Change Effects on Transportation Systems

Altered hydrologic regimes are expected as a result of climate change, especially in 

the latter half of the 21st century (see chapter 3). Specifically, climate and hydrology will influence the transportation system on Blue Mountains national forests 

through reduced and earlier runoff of snowpack, resulting in a longer season of road 

use, higher peak flows and flood risk, and increased landslide risk on steep slopes 

associated with elevated soil moisture in winter (Strauch et al. 2014). Increased 

wildfire disturbance (see chapter 6), in combination with higher peak flows, may 

also lead to increased erosion and landslide frequency.

Changes in climate and hydrology can have both direct and indirect effects on 

infrastructure and access. Direct effects are those that physically alter the operation or integrity of transportation facilities. These include effects related to floods, 

snow, landslides, extreme temperatures, and wind. Indirect effects include secondary influences of climate change on access that can increase threats to public safety 

and change visitor use patterns. For hydrologic extremes such as flooding, the 

effect on access may be more related to weather events (e.g., the effects of a single 

storm) rather than climate trends, but the expansion of future extremes outside the 

historical range of frequency or intensity will likely have the greatest impacts (e.g., 

by exceeding current design standards for infrastructure). 

Projected changes in soil moisture and precipitation form and intensity with 

climate change may locally accelerate mass wasting in the Blue Mountains. For 

example, in the deeply dissected northern Blue Mountains, shallow rapid debris 

slides may become more frequent, impacting infrastructure and access. Climate 

projections indicate that the conditions that trigger landslides will increase because 

more precipitation will fall as rain rather than snow, and more winter precipitation 

will occur in intense storms (Salathé et al. 2014). These effects will likely differ 

with elevation, because higher elevation areas typically have steeper slopes and 

more precipitation during storms. Flooding can also be exacerbated by increased 

basin size during rain events, as snow elevation is projected to move higher, and 

thus more of the basin will receive precipitation as rain rather than snow. Furthermore, reduced snowpack is expected to increase antecedent soil moisture in winter 

(Hamlet et al. 2013). Increasing trends in April 1 soil moisture have been observed 

in modeling studies as a result of warming, showing that soil moisture recharge is 

occurring earlier in spring and is now higher on April 1 than it was prior to 1947 

(Hamlet et al. 2007). 

Climate and hydrology 

will influence the 

transportation system 

on Blue Mountains 

national forests 

through reduced 

and earlier runoff of 

snowpack.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Elevated soil moisture and rapid changes in soil moisture can affect the stability of a slope and are responsible for triggering more landslides than any other 

factor (Crozier 1986). Antecedent moisture, geology, soil conditions, land cover, 

and land use also affect landslides (Kim et al. 1991, Strauch et al. 2014), and areas 

with projected increases in antecedent soil moisture (coupled with more intense 

winter storms) will have increased landslide risk. Although the VIC (see chapter 3) 

model does not directly simulate slope stability failures or landslides, projections 

of December 1 total column soil moisture from VIC can be used as an indicator of 

landslide risk. Projections from VIC indicate that December 1 soil moisture will 

likely be higher as the climate warms, and thus there will be higher landslide risk in 

winter on unstable land types at higher elevations.

The vulnerability of roads to hydrologic change (see chapter 3) varies based 

on topography, geology, slope stability, design, location, and use. To assess vulnerability of the transportation system in the Blue Mountains national forests, we 

identified the traits of the transportation system most sensitive to projected climate 

changes (box 4.3). This vulnerability assessment of the transportation system can 

inform transportation management and long-range planning. 

Box 4.3—Sensitivities of the transportation system 

in national forests in the Blue Mountains

• Aging and deteriorating infrastructure increases sensitivity to climate 

impacts, and existing infrastructure is not necessarily designed for future 

conditions (e.g., culverts are not designed for larger peak flows).

• Roads and trails built on steep topography are more sensitive to landslides 

and washouts.

• A substantial portion of the transportation system is at high elevation, which 

increases exposure to weather extremes and increases the costs of repairs 

and maintenance.

• Roads built across or adjacent to waterways are sensitive to high streamflows, stream migration, and sediment movement.

• Funding constraints, insufficient funds, or both limit the ability of agencies 

to repair damaged infrastructure or take preemptive actions to create a more 

robust system. 

• Design standards or operational objectives that are unsustainable in a new 

climate regime may increase the frequency of infrastructure failure in the 

future.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Roads and trails built decades ago have increased sensitivity because of age and 

declining condition. Many infrastructure components are at or near the end of their 

design lifespan. Culverts were typically designed to last 25 to 75 years, depending 

on structure and material. Culverts remaining in place beyond their design life are 

less resilient to high flows and bed load movement and have a higher likelihood of 

structural failure. As roads and trails age, their surface and subsurface structure 

deteriorate and less intense storms can cause more damage than a high-intensity 

storm would have when the infrastructure was new.

Advanced design of materials, alignment, drainage, and subgrade that are 

required standards today were generally not available or required when much of 

the travel network was developed in the Blue Mountains. Consequently, new or 

replaced infrastructure is likely to have increased resilience to climate change, 

especially if climate change is considered in the design. New culverts and bridges 

are often wider than the original structures to meet agency regulations and current 

design standards. In the past 15 years, many culverts across the Blue Mountains 

have been replaced to improve fish passage and stream function using open-bottomed arch structures that are less constricted during high flows and accommodate 

aquatic organism passage at a range of flows. Natural channel design techniques 

that mimic the natural stream channel condition upstream and downstream of the 

crossing are being used at these crossings. In addition, culverts on non-fish-bearing 

streams are being upgraded.

The location of roads and trails can increase vulnerability to climate change. 

Many roads and trails were built on steep slopes because of the rugged topography of 

the region, so cut slopes and side-cast material have created landslide hazards. Past 

timber harvesting and its associated road network in national forests have contributed 

to the sensitivity of existing infrastructure by increasing storm runoff and peak flows 

that can affect road crossing structures (Croke and Hairsine 2006, Schmidt et al. 

2001, Swanston 1971). Many roads and trails were also constructed in valley bottoms 

near streams to take advantage of gentle grades, but proximity to streams increases 

sensitivity to flooding, channel migration, bank erosion, and shifts in alluvial fans 

and debris cones. Most road-stream crossings used culverts rather than bridges, and 

culverts are generally more sensitive to increased flood peaks and associated debris. 

Roads that are currently in the rain-on-snow zone, typically in mid-elevation basins, 

may be increasingly sensitive to warmer temperatures.

Management of roads and trails (planning, funding, maintenance, and response) 

affect the sensitivity of the transportation system, and the condition of one road 

or trail segment can affect the function of connected segments. Major highways 

within the Blue Mountains, built to higher design standards and maintained more 
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GENERAL TECHNICAL REPORT PNW-GTR-939

frequently, will likely be less sensitive to climate change than their unpaved counterparts built to lower design standards in the national forests. Lack of funding can 

limit options for repairing infrastructure, which can affect the short- and long-term 

vulnerability of the transportation system. For example, replacing a damaged 

culvert with an “in-kind” culvert that was undersized for the current streamflow 

conditions leads to continued sensitivity to both the current flow regime and 

projected higher flows. 

Current and Near-Term Climate Change Effects

Assessing the vulnerability of the transportation network in the Blue Mountains to 

climate change (boxes 4.3 and 4.4) requires evaluating projected changes in hydrologic processes (box 4.1). The integrity and operation of the transportation network 

in the Blue Mountains may be affected in several ways. Changes in climate have 

already altered hydrologic regimes in the Pacific Northwest, resulting in decreased 

snowpack, higher winter streamflow, earlier spring snowmelt, earlier peak spring 

streamflow, and lower streamflow in summer (Hamlet et al. 2007, 2010). Ongoing 

changes in climate and hydrologic response in the short term (in the next 10 years) 

are likely to be a mix of natural variability combined with ongoing trends related 

to climate change. High variability of short-term trends is an expected part of the 

response of the evolving climate system. Natural climatic variability, in the short 

term, may exacerbate, compensate for, or temporarily reverse expected trends in 

some hydroclimatic variables. This is particularly true for strong El Niño years 

(high El Niño Southern Oscillation index) and during warm phases of the Pacific 

Decadal Oscillation (as well as years with high Pacific Decadal Oscillation index), 

which may provide a preview of future climatic conditions under climate change. 

Higher streamflow in winter (October through March) and higher peak flows, 

in comparison to historical conditions, increase the risk of flooding and impacts to 

structures, roads, and trails. Many transportation professionals consider flooding 

and inundation to be the greatest threat to infrastructure and operations because 

of the damage that standing and flowing water cause to transportation structures 

(MacArthur et al. 2012, Walker et al. 2011). Floods also transport logs and sediment 

that block culverts or are deposited on bridge abutments. Isolated intense storms 

can overwhelm the vegetation and soil water holding capacity and concentrate highvelocity flows into channels that erode soils and remove vegetation. During floods, 

roads and trails can become preferential paths for floodwaters, reducing operational 

function and potentially damaging infrastructure not designed to withstand inundation. If extreme peak flows become more common, they will have a major effect on 

roads and infrastructure.
71

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 4.4—Exposure of access to climate change in 

the Blue Mountains

Current and short-term exposures (less than 10 years)

• Roads and trails are damaged by floods and inundation because of mismatches between existing designs and current flow regimes.

• Landslides, debris torrents, and sediment and debris movement block access 

routes and damage infrastructure.

• Traffic is affected by temporary closures to clean and repair damaged roads 

and trails.

• Frequent repairs and maintenance from damage and disruption incur higher 

costs and resource demands.

Medium-term exposures (intensifying or emerging in about 

10 to 30 years)

• Flood and landslide damage will likely increase in late autumn and early 

winter, especially in mixed-rain-and-snow watersheds. 

• Current drainage capacities may become overwhelmed by additional water 

and debris.

• Increases in surface material erosion are expected.

• Backlogged repairs and maintenance needs will grow with increasing 

damage.

• Demand for travel accommodations, such as easily accessible roads and trails, 

is projected to increase, which could increase travel management costs.

• Increased road damage will challenge emergency response units, making 

emergency planning more difficult.

Long-term exposures (emerging in 30 to 100 years)

• Fall and winter storms are expected to intensify, greatly increasing flood 

risk and infrastructure damage and creating a greater need for cool-season 

repairs.

• Higher streamflows will expand channel migration, potentially beyond 

recent footprints, causing more bank erosion, debris flows, and wood and 

sediment transport into streams.

• Changes in hydrologic response may affect visitation patterns by shifting 

the seasonality of use. 

• Shifts in the seasonality of visitation may cause additional challenges to 

visitor safety, such as increased use in areas and during seasons prone to 

floods and avalanches.

• Managers will be challenged to provide adequate flexibility to respond to 

uncertainty in impacts to access.
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GENERAL TECHNICAL REPORT PNW-GTR-939

In the short term, flooding of roads and trails will likely increase, threatening 

the structural stability of crossing structures and subgrade material. Roads near 

perennial and other major streams are especially vulnerable (figs. 4.6 and 4.7), and 

many of these roads are located in floodplains and are used for recreation access. 

Increases in high flows and winter soil moisture may also increase the amount of 

large woody debris delivered to streams, further increasing damage to culverts and 

bridges, and in some cases making roads impassable or requiring road and facility 

closures. Unpaved roads with limited drainage structures or minimal maintenance 

are likely to experience increased surface erosion, requiring additional repairs or 

grading. 

Increasing incidence of more intense precipitation and higher soil moisture in 

early winter could increase the risk of landslides in some areas. Landslides also 

contribute to flooding by diverting water, blocking drainage, and filling channels with debris (Chatwin et al. 1994, Crozier 1986, Schuster and Highland 2003). 

Increased sedimentation from landslides also causes aggradation within streams, 

thus elevating flood risk. Culverts filled with landslide debris can cause flooding, 

damage, or complete destruction of roads and trails (Halofsky et al. 2011). Landslides that connect with waterways or converging drainages can transform into 

more destructive flows (Baum et al. 2007). Roads themselves also increase landslide risk (Swanson and Dyrness 1975, Swanston 1971), especially if they are built 

on steep slopes and through erosion-prone drainages. In the Western United States, 

the development of roads increased the rate of debris avalanche erosion by 25 to 340 

times the rate found in forested areas without roads (Swanston 1976), and Chatwin 

et al. (1994) and Montgomery (1994) found that the number of landslides is directly 

correlated with total kilometers of roads in an area. Consequently, areas with high 

road or trail density and projected increases in soil moisture that already experience 

frequent landslides may be most vulnerable to increased landslide risks. 

Short-term exposures to changes in climate may affect safety and access in 

the Blue Mountains. Damaged or closed roads reduce agency capacity to respond 

to emergencies or provide detour routes during emergencies. Increased flood risk 

could make conditions more hazardous for river recreation and campers. More 

wildfires (see chapter 6) could reduce safe operation of some roads and require 

additional emergency response to protect recreationists and communities (Strauch 

et al. 2014). Furthermore, damaged and closed roads can reduce agency capacity to 

respond to wildfires. 

Short-term exposures 

to changes in climate 

may affect safety and 

access in the Blue 

Mountains.
73

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 4.6—National forest roads located within 90 m of major rivers and streams. These roads, which are considered vulnerable to increased flooding, comprise 3300 km in the Blue Mountains (940 km in maintenance level (ML) 1 [basic custodial care; closed], 1915 km in ML2 [high-clearance cars and trucks], 377 km in ML3 [suitable for passenger cars], 21 km in ML4 [passenger cars; moderate comfort], and 98 km in ML5 [passenger cars; high comfort]). Note that not all vulnerable roads are represented; some roads also interrupt smaller intermittent streams and vice versa.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 4.7—Projected percentage change in bankfull flow in 2080 for roads within 90 m of a major river or stream (bankfull flow refers to the flow that just fills the channel to the top of its banks and at a point where the water begins to overflow onto a floodplain. Projections were calculated using flow data from the Variable Infiltration Capacity (VIC) model, based on historical data for 1915–2006 and the Q1.5-bankfull or channel-forming flow simulated for a global climate model ensemble for the A1B emission scenario (from Wenger et al. 2010). Note that not all vulnerable roads are represented; some roads also interrupt smaller intermittent streams and vice versa.
75

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Emerging and Intensifying Exposure in the Medium and Long 

Term

Many of the observed exposures to climate change in the short term are likely 

to increase in the medium (10 to 30 years) and long term (greater than 30 years) 

(box 4.4). In the medium term, natural climatic variability may continue to affect 

outcomes in any given decade, whereas in the long term, the cumulative effects of 

climate change may become a dominant factor, particularly for temperature-related 

effects. Conditions thought to be extreme today may be averages in the future, 

particularly for temperature-related changes (MacArthur et al. 2012).

Flooding in autumn and early winter is projected to continue to intensify in 

the medium and long term, particularly in mixed-rain-and-snow basins, but directrain-and-snow events may diminish in importance as a cause of flooding (McCabe 

et al. 2007). At mid to high elevations, more precipitation falling as rain rather than 

snow will continue to increase winter streamflow. By the 2080s, peak flows are 

anticipated to increase in magnitude and frequency (fig. 4.8; see chapter 3). In the 

long term, higher and more frequent peak flows will likely continue to increase 

sediment and debris transport within waterways. These elevated peak flows could 

affect stream-crossing structures downstream as well as adjacent structures because 

of elevated stream channels. Even as crossing structures are replaced with wider 

and taller structures, shifting channel dynamics caused by changes in flow and 

sediment may affect lower elevation segments adjacent to crossings, such as bridge 

approaches. 

Projected increases in flooding in autumn and early winter will shift the 

timing of peak flows and affect the timing of maintenance and repair of roads and 

trails. More repairs may be necessary during the cool, wet, and dark time of year 

in response to damage from autumn flooding and landslides, challenging crews to 

complete necessary repairs before snowfall. If increased demand for repairs cannot 

be met, access may be restricted until conditions are more suitable for construction 

and repairs. 

In the long term, low streamflows in summer may require increased use of 

more expensive culverts and bridges designed to balance the management of peak 

flows with providing low-flow channels in fish-bearing streams. Road design regulations for aquatic habitat will become more difficult to meet as warming temperatures hinder recovery of cold-water fish populations, although some streams may be 

buffered by inputs from snowmelt or groundwater in the medium term.

Over the long term, higher winter soil moisture may increase the risk of landslides in autumn and winter. Landslide risk may increase more in areas with tree 

mortality from fire and insect outbreaks, because tree mortality reduces soil root 
76

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 4.8—Projected percentage change in Q1.5-bankfull flow in 2080, with culvert barriers indicated based on the ratio of culvert width to bankfull width. Projections were calculated using flow data from the Variable Infiltration Capacity model, based on historical data for 1915–2006 and the Q1.5-bankfull, or channel-forming flow, simulated for a global climate model ensemble under the A1B emission scenario (from Wenger et al. 2010).
77

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

cohesion and decreases interception and evaporation, further increasing soil moisture (Martin 2006, Montgomery et al. 2000, Neary et al. 2005, Schmidt et al. 2001). 

Thus, soils will likely become more saturated and vulnerable to slippage on steep 

slopes during the wet season. Although floods and landslides will continue to occur 

near known hazard areas (e.g., because of high forest road density), they may also 

occur in new areas (e.g., those areas currently covered by deep snowpack in midwinter) (MacArthur et al. 2012). Thus, more landslides at increasingly higher elevations (with sufficient soil) may be a long-term effect of climate change. Coinciding 

exposures in space and time may be particularly detrimental to access. 

Climate change effects on access may create public safety concerns for national 

forests. A longer snow-free season may extend visitor use in early spring and late 

autumn at higher elevations (Rice et al. 2012). Lower snowpack may lead to fewer 

snow-related road closures for a longer portion of the year, allowing visitors to 

reach trails and campsites earlier in the season. However, warmer temperatures 

and earlier snowmelt may encourage use of trails and roads before they are cleared. 

Trailheads, which are located at lower elevations, may be snow-free earlier, but hazards associated with melting snow bridges, avalanche chutes, or frozen snowfields 

in shaded areas may persist at higher elevations along trails. Relatively rapid warming at the end of the 20th century coincided with greater variability in cool season 

precipitation and increased flooding (Hamlet and Lettenmaier 2007). If this pattern 

continues, early-season visitors may be exposed to more extreme weather than 

they have encountered historically, creating potential risks to visitors. In summer, 

whitewater rafters may encounter unfavorable conditions from lower streamflows 

in late summer (Mickelson 2009) and hazards associated with deposited sediment and woody debris from higher winter flows. Warmer winters may shift river 

recreation to times of year when risks of extreme weather and flooding are higher. 

These activities may also increase use of unpaved roads in the wet season, which 

can increase damage and associated maintenance costs.

Climate change may also benefit access and transportation operations in the 

Blue Mountains over the long term. Lower snow cover will reduce the need for and 

cost of snow removal, and earlier snow-free dates projected for the 2040s suggest 

that low- and mid-elevation areas will be accessible earlier. Earlier access to roads 

and trails will create opportunities for earlier seasonal maintenance and recreation. 

Temporary trail bridges installed across rivers may be installed earlier in spring 

as spring flows decline. A longer snow-free season and warmer temperatures 

may allow for a longer construction season at higher elevations. Less snow may 

increase access for summer recreation, but it may reduce opportunities for winter 

recreation particularly at low and moderate elevations (Joyce et al. 2001, Morris and 

More landslides at 

increasingly higher 

elevations (with 

sufficient soil) may be 

a long-term effect of 

climate change.
78

GENERAL TECHNICAL REPORT PNW-GTR-939

Walls 2009). The highest elevations of the Blue Mountains may retain relatively 

more snow than other areas, which may create higher localized demand for winter 

recreation and river rafting in summer over the next several decades. 

Adapting Management of Water Use and Roads in a 

Changing Climate 

Through a workshop and subsequent dialogue, scientists and resource managers 

worked collaboratively to identify adaptation options that can reduce the adverse 

effects of climatic variability and change on water use and roads in the Blue Mountains. The workshop included an overview of adaptation principles (Peterson et al. 

2011) and regional examples of agency efforts to adapt to climate change. Options 

for adapting hydrologic systems, transportation systems, and access management 

were identified, as well as potential barriers, opportunities, and information needs 

for implementing adaptation. 

Adaptation Options for Water Use

Climate change adaptation options for water use on national forests must be considered within the broader context of multiownership watersheds, where most of 

the traditional consumptive uses occur off the forest but the forests are relied on for 

a majority of the supply. Many of the resource sensitivities addressed here already 

exist to some extent, but are expected to intensify as the climate warms. Adaptation 

options focusing on national forests were developed after consideration of the collective effects of several climate-related stressors: lower summer streamflow, higher 

winter peak streamflow, earlier peak streamflow, lower groundwater recharge, and 

higher demand and competition for water by municipalities and agriculture (table 

4.2). The following adaptation strategies were developed to address these stressors: 

(1) restore function of watersheds, (2) connect floodplains, (3) support groundwaterdependent ecosystems, (4) reduce drainage efficiency, (5) maximize valley storage, 

and (6) reduce fire hazard (table 4.2). The objective of most of these adaptation 

strategies is to retain water for a longer period of time at higher elevations and in 

riparian systems and groundwater of mountain landscapes. These strategies will 

likely help maintain water supplies to meet demands, especially during the summer, 

and reduce loss of water during times when withdrawals are low. This diversity of 

adaptation strategies requires an equally diverse portfolio of adaptation tactics that 

address different biophysical components of hydrologic systems and timing of uses, 

among other considerations (table 4.2). 

The adaptation tactic of using a “climate change lens” when developing plans 

and projects provides an overarching context for managing and conserving water 
79

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 4.2—Adaptation options that address climate change effects on water use in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: lower summer flows, higher winter peak flows, earlier peak flows, lower groundwater recharge, higher demand and 

competition for water by municipalities and agriculture.

Adaptation strategy: Restore function of watersheds, connect floodplains, support groundwater-dependent ecosystems, reduce drainage efficiency, maximize valley 

storage, reduce fire hazard.

• Add wood to streams and increase 

beaver populations

Collaboration with other agencies Concerns about effects of 

beavers on private property

Identification of priority areas

• Use a “climate change lens” during 

project analysis

Use the Climate Project Screening 

Tool for analysis of projects

• Improve livestock management to 

reduce water use (e.g., shutoff valve on stock ponds)

Some <10 years, 

some >30 years

Collaboration with range managers Minimal technology available for 

operations

Improved technology to reduce 

water use

• Reduce surface fuels and stand 

densities in low-elevation forest

<10 years, 

ongoing

Collaboration with fire managers Opposition to active management, prescribed burning

• Restore meadows Ongoing Interactions with roads 

Elk herbivory

Inventory and classification

of meadows

Adaptation strategy: Address demands for water (including water rights); improve water conservation.• Conduct integrated assessment of water and local effects of climate change Ongoing, opportunistic Case by case Concerns about property rights High existing workload Updated water resource use assessments at priority sites

• Implement vegetation treatments in 

high water-retention areas (e.g., snow retention)

Ongoing Enabled by national forest land 

management plan

Lack of funding for long-term 

collection of gage data

Centralized source of data and 

metadata on water resources

• Improve efficiency of drainage and 

ditches

10 to 30 years

• Encourage communication and full 

disclosure of information

Ongoing Existing management plans Identification of key messages

Communication between line 

officers and local communities

• Conduct vulnerability assessments by 

community

10 to 30 years Source water assessments in some 

cases

• Treat roads where needed to retain 

water and maintain high water quality

<10 years Collaboration with road engineers Lack of support for treatments Development of effective road 

treatments
80

GENERAL TECHNICAL REPORT PNW-GTR-939

supply (tables 4.1 and 4.2). Including climate change in decisionmaking generally 

reinforces practices that support sustainable resource management. Potential risk 

and uncertainty can be included in this process by considering a range of climate 

projections (based on different models and emission scenarios) (see chapter 3) to 

frame decisions about appropriate responses to climate change. In addition, user 

awareness of vulnerability to shortages, reducing demand through education and 

negotiation, and collaboration among users can support adaptation efforts.

Many adaptation tactics to protect water supply are current standard practices, 

or “best management practices (BMP),” for water quality protection. In 2012, the 

Forest Service implemented a national BMP program to improve management 

of water quality consistently with the Federal Clean Water Act and state water 

quality programs (USDA FS 2012; http://www.fs.fed.us/biology/watershed/BMP.

html). The BMPs are specific practices or actions used to reduce or control impacts 

to water bodies from nonpoint sources of pollution, most commonly by reducing 

the loading of pollutants from such sources into storm water and waterways. The 

BMPs are required on all activities with potential to affect water quality, including 

road management and water developments. A related tactic is improving roads and 

drainage systems to maintain high-quality water as long as possible within hydrologic systems in national forests. Although these tactics may be expensive, they 

significantly affect water retention and erosion control. Actions are typically needed 

at specific locations at key times even under normal conditions, and climate change 

will likely force more frequent maintenance and repair. 

Several adaptation tactics related to biological components of mountain landscapes can reduce the effects of climate change on water resources. Reducing stand 

density and surface fuels in low-elevation coniferous forest reduces the likelihood 

of fires that severely affect soils, accelerate erosion, and degrade water quality in 

streams. Vegetation treatments in high-snow areas may enhance snow retention and 

soil moisture, and may extend water yield into the summer, at the catchment scale, 

for a few years following treatment.

Similarly, restoration techniques that maintain or modify biophysical properties of hydrological systems to be within their presettlement historical range of 

variability can increase climate change resilience. Stream restoration techniques 

that improve floodplain hydrologic connectivity increase water storage capacity. 

Meadow and wetland restoration techniques that remove encroaching conifers can 

improve hydrologic function and water storage capacity. Adding wood to streams 

improves channel stability and complexity, slows water movement, improves 

aquatic habitat, and increases resilience to both low and high flows. Similarly, 
81

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

increasing American beaver (Castor canadensis Kuhl) populations will create more 

ponds, swamps, and low-velocity channels that retain water throughout the year.

Lower soil moisture and low flows in late summer, combined with increasing 

demand for water, will likely reduce water availability for aquatic resources, recreation, and other uses. However, water conservation measures within national forests 

can potentially reduce water use. For example, resource managers can work with 

permitees to implement livestock management practices that use less water (e.g., 

install shutoff valves on stock water troughs). Over the long term, increasing water 

conservation and reducing user expectations of water availability (e.g., through 

education) are inexpensive and complementary adaptation tactics for maintaining 

adequate water supply. 

At a broader level, it will be valuable to engage in and contribute to integrated 

assessments, such as the Oregon Integrated Water Resource Strategy, for water 

supply and availability and local effects of climate change. Vulnerability assessments for individual communities will provide better information on where and 

when water shortages may occur, leading to adaptation tactics customized for each 

location. Because discussions of water use and water rights are often contentious, 

it will be important to help foster open dialogue and full disclosure of data and 

regulatory requirements so that proactive, realistic, and fair management options 

can be developed.

Adaptation Options for Roads and Infrastructure

Climate change adaptation options for roads and infrastructure were developed 

after consideration of the collective effects of several climate-related stressors: 

sensitivity of road design and maintenance to increasing flood risk, effects of 

higher peak streamflows on road damage at stream crossings, and safety hazards 

associated with an increase in extreme disturbance events (table 4.3, box 4.2). 

The following adaptation strategies were developed to address these stressors: (1) 

increase resilience of stream crossings, culverts, and bridges to higher streamflow; 

and (2) increase the resilience of the road system to higher streamflows and associated damage by stormproofing and reducing the road system. 

The Forest Service travel analysis process (USDA FS 2005) and BMPs provide 

an overarching framework for identifying and maintaining a sustainable transportation system in national forests in the Blue Mountains, and climate change provides 

a new context for evaluating current practices (Raymond et al. 2014, Strauch et al. 

2014). Incorporating climate change in the travel-analysis process, which is already 

addressing some vulnerabilities by decommissioning and stormproofing roads, 

Vulnerability 

assessments for 

individual communities 

will provide better 

information on where 

and when water 

shortages may occur.
82

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 4.3—Adaptation options that address climate change effects on roads and infrastructure in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs Sensitivity to climatic variability and change: Road design and maintenance are sensitive to increasing flood risk; higher peak flows lead to increased road damage at stream crossings (because of insufficient culvert capacity, more culvert blockage, and low bridges); safety is compromised by more extreme events (e.g., landslides and debris flows). Adaptation strategy: Increase resilience of stream crossings, culverts, and bridges to higher peak flows. • Replace culverts with higher capacity culverts or other appropriate drainage (e.g., 

fords or dips) in high-risk locations

<10 years, 

opportunistic

Structure failures, especially 

at fish crossings

Funding Current backlog of deferred 

maintenance and upgrades

Historical use patterns

Database of projects and 

upgrades

Safety prioritiesCampground analysis

• Complete geospatial database of culverts 

and bridges

<10 years, 

opportunistic

Recording of geospatial 

locations as projects are completed

FundingIncomplete culvert survey 

information

Database of projects and 

upgrades

Adaptation strategy: Facilitate response to higher peak flows by reducing the road system and thus flooding of roads and stream crossings; disconnect roads from streams.• Continue to decommission roads with high 

risk and low access

Opportunistic, 

>30 years

Partnerships and collaboration 

with other agencies that are also disconnecting roads from waterways

High cost of 

decommissioning roads

Implementation of Geomorphic 

Road Analysis and Inventory Package for decisionmaking

• Convert use to other transportation modes 

(e.g., from vehicle to bicycle or foot)

Opportunistic, 

>30 years

Transportation planning, travel 

management plans, land and resource management plans

High cost of 

decommissioning roads

• Invoke Travel Analysis Process to prioritize 

road management

<10 to 30 

years

Travel Analysis Process and 

Minimum Roads Analysis are underway

• Use drains, gravel, and outsloping of roads 

to disperse surface water

Ongoing, 10 

to 30 years

National forest land 

management plan

High cost of road managementPriorities unclear in some cases

Implementation of Geomorphic 

Road Analysis and Inventory Package for decisionmaking
83

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

culverts, and bridges, will enhance resilience to higher streamflows. Improving and 

updating geospatial databases of roads, culverts, and bridges will provide a foundation for continuous evaluation and maintenance. If vulnerable watersheds, roads, 

and infrastructure can be identified, then proactive management (e.g., use of drains, 

gravel, and outsloping of roads to disperse surface water) can be implemented to 

reduce potential damage and high repair costs. 

National forests in the Blue Mountains have a large backlog of culverts and 

road segments in need of repair, replacement, or upgrade, even under current 

hydrologic regimes. Limited funding and staff hinder current efforts to upgrade 

the system to current standards and policies, so the additional cost of upgrades to 

accommodate future hydrological regimes could be a barrier to adaptation. However, extreme floods that damage roads and culverts can be opportunities to replace 

existing structures with ones that are more resilient to higher peak flows. These 

replacements, called “betterments,” can be difficult to fund under current Federal 

Highway Administration Emergency Relief for Federally Owned Roads program 

eligibility requirements when used to fix damage from extreme events, because the 

current policy is to replace in kind. In some cases, matching funds can be raised or 

betterments can be funded with sufficient justification and documentation of the 

environmental impacts. Justification for betterments based on the latest climate 

change science would facilitate this approach. 

Increasing resilience to higher peak flows will not be possible for all road segments because of limited funding for maintenance. Adapting road management to 

climate change in the long term may require further reductions in the road system. 

Road segments that are candidates for decommissioning are typically those with 

low demand for access, high risks to aquatic habitat, a history of frequent failures, 

or combinations of the three. National forest road managers also consider use of 

roads for fire management (fire suppression, prescribed fire, and hazardous fuel 

treatments). 

Engineers may consider emphasizing roads for decommissioning that are in 

basins with higher risk of increased flooding and peak flows, in floodplains of large 

rivers, or on adjacent low terraces. Information on locations in the transportation 

system that currently experience frequent flood damage (Strauch et al. 2014) can be 

combined with spatially explicit data on projected changes in flood risk and current 

infrastructure condition to provide indicators of where damage is most likely to 

continue and escalate with changes in climate (e.g., figs. 4.7 and 4.8). Optimization 

approaches (e.g., linear programming) can be used to compare the tradeoffs associated with competing objectives and constraints while minimizing the overall costs 

of the road system.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Reducing the road system in national forests presents both barriers and 

opportunities (table 4.3). Decommissioning roads or converting roads to trails is 

expensive and must be done properly to reduce adverse effects on water quality 

and aquatic habitat. Furthermore, reductions to the road system are often met with 

opposition from the public accustomed to using roads for recreational access, but 

public involvement in road decisions can also be an opportunity to increase awareness and develop “win-win” adaptation options. Thus, one adaptation tactic is to 

adjust visitation patterns and visitor expectations by actively involving the public 

in road decisions related to climate change. This has the added benefit of raising 

political support and possibly funding from external sources to help maintain 

access. Partnerships with recreation user groups will be increasingly important for 

raising public awareness of climate change threats to access and for identifying 

successful adaptation options.

Increased risk of flooding in some basins may require modification to current 

management of facilities and historical and cultural resources. In most cases, the 

high cost of relocating buildings and inability to move historical sites from floodplains will require that adaptation options focus on resistance through prevention of 

flood damage. Stabilizing banks reduces risk to infrastructure, and using bioengineering rather than riprap or other inflexible materials may have less environmental 

impact. In the long term, protecting infrastructure in place will be more difficult 

as flood risk continues to increase. Long-term adaptation strategies may require 

removing (or not rebuilding) infrastructure in the floodplain to allow river channels 

to migrate and accommodate the changing hydrologic regime. National forest land 

and resource management plans, which have relatively long planning horizons, are 

opportunities to implement these long-term adaptation tactics for management of 

facilities and infrastructure.

More frequent failures in the road and trail system may increase risks to public 

safety. Limited resources and staff make it difficult for national forests to quickly 

repair damage, yet the public often expects continuous access. In response to climate change, managers may consider implementing and enforcing more restrictions 

on access to areas where trails and roads are damaged and safe access is uncertain. 

Greater control of seasonal use, combined with better information about current 

conditions, especially during early spring and late autumn, before and after active 

maintenance, will ensure better public safety. Partnerships with recreation user 

groups may generate opportunities to convey this message to a larger audience, thus 

enhancing public awareness of hazards and the safety of recreation users.

In the long 

term, protecting 

infrastructure in place 

will be more difficult as 

flood risk continues to 

increase.
85

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Managers may consider adapting recreation management to changes in visitor 

use patterns in early spring and late autumn in response to reduced snowpack and 

warmer temperatures. An expanded visitor season would increase the cost of operating facilities (e.g., campgrounds), but revenue from user fees may also increase. 

Land management plans and transportation planning provide opportunities to 

address anticipated changes in the amount and timing of visitation. Limitations 

on staff because of funding or other constraints may also present obstacles to an 

expanded visitor season. Adaptive management can be used to monitor changes in 

the timing, location, and number of visitors, thus providing data on where management can be modified in response to altered visitor patterns. 

Acknowledgments

We thank Robert Gecy, David Salo, and Thomas Friedrichsen for helpful discussions and contributions. We also thank all of the participants in the hydrology group 

at the La Grande workshop for their valuable contributions to this chapter.

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Raymond, C.L.; Peterson, D.L.; Rochefort, R.M., eds. 2014. Climate change 

vulnerability and adaptation in the North Cascades region. Gen. Tech. Rep. 

PNW-GTR-892. Portland OR: U.S. Department of Agriculture, Forest Service, 

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Rice, J.; Tredennick, A.; Joyce, L.A. 2012. Climate change on the Shoshone 

National Forest, Wyoming: a synthesis of past climate, climate projections, and 

ecosystem implications. Gen. Tech. Rep. RMRS-GTR-274. Fort Collins, CO: 

U.S. Department of Agriculture, Forest Service, Rocky Mountain Research 

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Salathé, E.P.; Hamlet, A.F.; Mass, C.F. [et al.]. 2014. Estimates of twenty-firstcentury flood risk in the Pacific Northwest based on regional climate model 

simulations. Journal of Hydrometeorology. 15: 1881–1899.

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cohesion as an influence on shallow landslide susceptibility in the Oregon Coast 

Range. Canadian Geotechnical Journal. 38: 995–1024.
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Schuster, R.L.; Highland, L.M. 2003. Impact of landslides and innovative 

landslide-mitigation measures on the natural environment. In: Lee, C.F.; Tham, 

L.G., eds. Proceedings of the international conference on slope engineering. 

Hong Kong, China: University of Hong Kong: 64–74.

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and access in the North Cascade Range. In: Raymond, C.L.; Peterson, D.L.; 

Rochefort, R.M., eds. Climate change vulnerability and adaptation in the 

North Cascades region. Gen. Tech. Rep. PNW-GTR-892. Portland OR: U.S. 

Department of Agriculture, Forest Service, Pacific Northwest Research Station: 

45–112.

Swanson, F.J.; Dyrness, C.T. 1975. Impact of clear-cutting and road construction 

on soil erosion by landslides in the western Cascade Range, Oregon. Geology. 

3: 393–396. 

Swanston, D.N. 1971. Principal mass movement processes influences by logging, 

road building and fire. In: Krygier, J.T.; Hall, J.D., eds. Forest land uses and 

stream environment: proceedings of a symposium. Corvallis, OR: Oregon State 

University: 29–40.

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Congress Committtee: 251–275. http://andrewsforest.oregonstate.edu/pubs/pdf/

pub505.pdf. (29 October 2012).

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terrestrial and aquatic communities. Conservation Biology. 14: 18–30.

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Walker, L.; Figliozzi, M.; Haire, A.; MacArthur, J. 2011. Identifying surface 

transportation vulnerabilities and risk assessment opportunities under climate 

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46: W09513. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Chapter 5: Climate Change, Fish, and Aquatic Habitat

in the Blue Mountains

Daniel J. Isaak, Katherine Ramsey, John C. Chatel, Deborah L. Konnoff, Robert A. Gecy, and Dona Horan1

Introduction

National Forest System lands in the Blue Mountains region support a diversity of 

important native aquatic species that will be affected by climate change. As part of 

the Blue Mountains Adaptation Partnership, four of these species (spring Chinook 

salmon (Oncorhynchus tshawytscha Walbaum in Artedi), bull trout (Salvelinus 

confluentus Suckley), summer steelhead (O. mykiss Walbaum), and interior redband 

trout (O. m. gibbsi Suckley) were selected for climate vulnerability analysis because 

of their important role in land management planning (e.g., grazing, timber harvest, 

Endangered Species Act consultations). These species occupy a broad range of 

aquatic habitats from small headwaters tributaries to large rivers, both within and 

downstream of the Malheur, Umatilla, and Wallowa-Whitman National Forests. 

Although habitats for the selected species overlap in places, each species uses 

a unique set of aquatic habitats in the Blue Mountains national forests and their 

associated subbasins, depending on their life stage, season of the year, and available habitat conditions. These species have a diverse array of life history strategies, 

including anadromy (steelhead and spring Chinook salmon), fluvial and adfluvial 

movements (bull trout), and residency (bull trout and redband trout). 

Climate change affects the environments of these species in many ways (box 

5.1). Warming air temperatures and changing precipitation patterns are resulting in 

warmer stream temperatures (Bartholow 2005; Isaak et al. 2010, 2012b; Petersen 

and Kitchell 2001), altered stream hydrology (Hamlet and Lettenmaier 2007, Luce 

et al. 2013), and changes in the frequency, magnitude, and extent of climate-induced 

events such as floods, droughts, and wildfires (Holden et al. 2012, Littell et al. 2010, 

Luce and Holden 2009, Rieman and Isaak 2010). Fish populations have been 

1 Daniel J. Isaak is a research fish biologist, and Dona Horan is a fish biologist, U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station, 322 East 

Front Street, Suite 401, Boise, ID 83702; Katherine Ramsey is a fishery biologist, U.S. 

Department of Agriculture, Forest Service, Umatilla National Forest, 72510 Coyote Road, 

Pendleton, OR 97801; John C. Chatel is the Threatened, Endangered, and Sensitive Species program manager, U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Region, 1220 SW 3rd Avenue, Portland, OR 97204; Deborah L. Konnoff is the Ecosystem 

and Planning staff officer, U.S. Department of Agriculture, Forest Service, Mount BakerSnoqualmie National Forest, 2930 Wetmore Avenue, Suite 3A, Everett, WA 98201; Robert 

A. Gecy is a hydrologist, U.S. Department of Agriculture, Forest Service, Wallowa-Whitman National Forest, 1550 Dewey Avenue, P.O. Box 907, Baker City, OR 97814.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 5.1—Summary of climate change effects on 

fisheries in the Blue Mountains

Broad-scale climate change effects

• Water temperatures will increase. 

• Snowpack will decrease, causing a shift of peak flows from summer to 

spring, and a decrease in summer flows. 

• Peak flows will be flashier, likely resulting in channel scouring and 

increased sedimentation. 

• Wildfires will increase, creating the potential for increased erosion.

• Ocean productivity may change, affecting anadromous fish species.

Species affected

• Fish species affected will differ by location. This assessment focuses on bull 

trout, spring Chinook salmon, and redband trout/steelhead.

Current condition and existing stressors

• Altered riparian areas (from grazing, roads, recreation, etc.) lead to elevated 

water temperatures.

• Reduced resiliency of stream habitat affected by removal of woody debris, 

roads, grazing, recreation, etc. 

• Reduced summer flows—related primarily to water withdrawals.

• Invasive species—predation on spring Chinook salmon and steelhead.

• Influence of hatchery fish—spring Chinook salmon and steelhead.

• Overfishing for spring Chinook salmon.

Sensitivity to climatic variability and change

• Bull trout—Bull trout require very cold water temperatures for spawning 

and juvenile rearing, so their populations are already greatly constrained by 

the limited availability of cold habitats in the Blue Mountains. Moreover, 

these natal habitats are confined at their upstream extent by small stream 

size and channel slope, so bull trout populations are the fish world’s equivalent to terrestrial species that are trapped on “mountain-top islands.” 

Increasing temperatures will eliminate cold habitats at the downstream 

extent of these populations. Decreasing summer flows will make some 

streams too small to support fish at the upper extent, and the habitats that 

remain will be subject to increased environmental fluctuation associated 

with wildfires, debris flows, and increased winter flooding.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 5 (continued)

• Spring Chinook salmon—Adults require cool water for holding in fresh 

water prior to spawning. Juveniles could also be affected by warmer temperatures. A major impact may be changes in the size of adults and fecundity 

of females resulting from ocean acidification and warming. Spring Chinook 

salmon adults migrate upstream into low-elevation mainstem rivers and 

streams to spawn during the warmest months of the year. During especially 

warm summers, adult salmon sometimes experience direct mortality from 

thermal stress prior to spawning. These mortality events are exacerbated 

by decreases in summer flows, which confine the fish to smaller areas. 

Anticipated temperature increases will increase the frequency and severity 

of thermal stresses on spring Chinook salmon.

• Redband trout/steelhead—Most steelhead populations in the Pacific 

Northwest have reduced populations because they already have experienced 

changes in stream temperature and flow patterns as a result of land and 

water use practices. Both the resident and anadromous forms are important 

to maintain many overall populations. Both life forms have a lot of phenotypic plasticity to withstand and adapt to change, but climate change will 

likely increase competition between these life forms and will certainly affect 

populations that use lower elevations that are more susceptible to change. 

The loss or reduction in the larger anadromous form will mean fewer eggs, 

which may affect the overall population in each major population group. 

This species has a large adaptive capacity with a range of life histories and 

wide environmental tolerances, which will reduce sensitivity to the potential 

effects of climate change. Altered ocean conditions may affect the expression of the steelhead life history.

Expected effects of climate change

• Bull trout—Changes in water temperature will be an important determinant of persistence. Long-term climate patterns suggest both an expected 

decrease in the total amount of cold water stream habitat and fragmentation 

of some colder areas into disconnected “patches” of suitable habitat. Bull 

trout populations will likely increase retreat into these shrinking summer 

cold water refuges to avoid warming conditions. These restricted tributary populations may become more vulnerable to local extirpation. Many 

remaining patches will be subjected to more frequent winter peak flows 

that will scour the streambed and destroy redds or kill newly emerged fry. 

Conceivably, the combined effects of shrinking patch size and increasing 

frequency or magnitude of stream channel disturbance could chip away at 

the low resiliency of these populations, leaving them in a poorer condition to 

withstand the next series of disturbances, and accelerating the rate of local 

extirpations beyond that driven by temperature alone. Wildfire effects are 

less clear, although minimal empirical data suggest that wildfire will have 

minimal effects on bull trout. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 5 (continued)

• Spring Chinook salmon—Elevated temperatures can reduce the energy 

available for reproduction and cause mortality, particularly where there are 

sudden increases in water temperatures. Effects from higher winter floods 

will probably be minimal unless there is a very large increase. These fish 

are large, use large substrates for spawning, and spawn in areas where the 

energy of flood water can be dissipated, so the potential for increased scouring is likely to be minimal.

• Redband trout/steelhead—This species is a spring spawner and has a relatively warm thermal niche; it can move into some cold upstream areas as 

refugia. Because it spawns in the spring, eggs are not as susceptible to 

increased winter flooding as fall spawners. Shifts in the timing of peak 

flows will likely result in changes in outmigration timing, changes in survival, changes in distribution, and changes in the availability of spawning 

and rearing habitats. Increases in the temperature of cooler waters (i.e., those 

<9 o

C currently) could improve habitat for redband trout. Further temperature increases (12 to 20 oC) could lead to greater expression of the steelhead 

life history. It is less clear what the tradeoff between redband trout and 

steelhead life histories will be at water temperatures >20 oC. Altered ocean 

conditions could reduce the expression of the steelhead life history, particularly in males, and reduce the size of returning adults.

Adaptive capacity

• Bull trout—This species has very limited capacity to adapt given limited 

current habitats and restrictive ecological tolerances.

• Spring Chinook salmon—Supporting adaptive capacity is probably compromised because of low population numbers. T. Beechie, National Oceanic 

and Atmospheric Administration Fisheries, Seattle, has suggested the spring 

Chinook salmon (stream-type life history) in Puget Sound may become fall 

Chinook salmon (ocean-type life history) in response to changes of climate 

change (warmer water and lower summer flows). This could be possible in 

the Columbia Basin but is not as likely as in Puget Sound. These fish may be 

able to adjust to altered ocean conditions by reducing the time spent in the 

ocean, resulting in smaller, younger fish returning to streams.

• Redband trout/steelhead—This species has high adaptive capacity for adjusting to potential effects of climate change.

Vulnerable geographic locations

• Some spring Chinook salmon stocks (e.g., Catherine Creek stock and Upper 

Grande Ronde stock) are already in poor shape. 

• Spring Chinook salmon in Catherine Creek may lose one outmigration period 

owing to a shift in hydrograph and therefore lose species life history diversity.

• Fish of all species will be vulnerable to decreased summer flows in the 

future. Flow reductions will make some headwater streams too small to support fish. In the remainder of the network, summer flow declines will also 

reduce the overall amount of “living space” for fish. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 5 (continued)

• The nests of fall spawning fish like bull trout or spring Chinook salmon 

could be vulnerable to higher winter flows causing channel scour and egg 

mortality in channels with confined valley bottoms. This vulnerability 

would occur just upstream at higher elevations where winter high flows have 

occurred because warming will make things creep upstream.

• Places where fish distribution and abundance are currently limited by warm 

temperatures could experience fish declines with small amounts of additional warming. Bull trout distributions are limited at downstream sites 

in many streams and will have to shift upstream. Spring Chinook salmon 

adults have experienced heat stress, die-offs in a few streams, and are forced 

to cluster near cold water refuges in other streams. Additional warming will 

exacerbate these issues. 

• Fish populations that are isolated in small headwater streams could be susceptible to local extirpations caused by more environmental variation (wildfire, debris flows, droughts, floods) as climate change progresses. 

Risk assessment

Potential magnitude of climate change effects

• Bull trout—High magnitude of temperature effects by 2050 given that both 

species are already strongly and negatively affected by warm temperatures.

• Spring Chinook salmon—High magnitude of temperature effects by 2050 

given that both species are already strongly and negatively affected by warm 

temperatures. The effects of altered ocean conditions may pose the greatest risk to these fish. In fresh water, elevated summer temperatures will be 

the greatest challenge and it is likely to increase with time. The latter can be 

potentially offset with restoration of riparian areas in streams throughout the 

stream network.

• Redband trout/steelhead—This species could be less affected by altered 

ocean conditions because of the ability to express life histories that are resident in fresh water. However, the steelhead component of a population may 

decline. Steelhead exhibit high phenotypic plasticity and may shift the timing of a life stage transition to reduce the probability of exposure to changes 

in stream temperature and flow, although there is a limit to how much steelhead can shift the timing of life stages. 

• Low summer flows—Low effect on spring Chinook by 2050; moderate by 

2100. Moderate effect on bull trout by 2050; high by 2100.

• Winter flood frequency—Low effect on spring Chinook by 2050 and 2100. 

Moderate effect on bull trout by 2050; high by 2100.

• Wildfires/debris flows—Low effect on spring Chinook by 2050 and 2100. 

Moderate effect on bull trout by 2050; high by 2100.

• Invasive species—Moderate effect on spring Chinook from smallmouth 

bass (Micropterus dolomieu Lacepède) by 2050, high effect by 2100. Low 

effect on bull trout from brook trout by 2050; moderate by 2100. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 5 (continued)

Likelihood of climate change effects

• Temperature effects—High likelihood by 2050.

• Low summer flows—Moderate likelihood by 2050, but hydrology models 

need to improve for this parameter. Also need more flow data from small 

headwater streams to calibrate hydrology models.

• Winter flood frequency increase—High likelihood by 2050 because it is 

largely controlled by temperature.

• Wildfires/debris flows—High likelihood by 2050.

• Invasive species—High likelihood by 2050 because overlap with native 

species is strongly controlled by temperatures.

adapting by shifting their phenology and migration dates (Crozier et al. 2008, 2011; 

Keefer et al. 2008), using cold water refugia during thermally stressful periods 

(Keefer et al. 2009; Torgersen et al. 1999, 2012), and shifting spatial distributions 

within river networks (Comte et al. 2013, Eby et al. 2014). These changes are 

adding additional stressors to many fish populations, but many populations are 

also likely to have sufficient resilience and habitat diversity to make the necessary 

adjustments. 

In this chapter, we assess specific vulnerabilities of each of the four selected 

species to climate change in stream networks draining the Blue Mountains and 

Forest Service lands. Aiding this assessment are recently developed, high-resolution 

stream temperature and flow scenarios (Variable Infiltration Capacity [VIC] model 

ecological flow metrics—Wenger et al. 2010; NorWeST—Isaak et al. 2011; Hamlet 

et al. 2013) that translate outputs from Global Climate Models (GCMs) to reachscale habitat factors relevant to aquatic biota. The concluding section of this chapter 

discusses management strategies that can be used to help species and aquatic 

ecosystems in the Blue Mountains better adapt to climate change. No attempt is 

made to provide an exhaustive review of the climate-aquatic-fisheries literature 

because good general reviews already exist for the Pacific Northwest (ISAB 2007, 

Mantua et al. 2009, 2011; Mantua and Raymond 2014; Mote et al. 2003) and other 

geographic regions (Ficke et al. 2007; Furniss et al. 2010, 2013; Isaak et al. 2012a, 

Luce et al. 2012, Poff et al. 2002, Rieman and Isaak 2010, Schindler et al. 2008).
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Analysis Area

This chapter focuses on the 23 subbasins draining the Blue Mountains province, 

specifically the revision analysis area covered by the joint land management plan 

for the Malheur, Umatilla, and Wallowa-Whitman National Forests. The subbasins 

are distributed among four major hydrologic units or basins, referred to here as river 

basins (fig. 5.1): the middle Columbia River basin, which drains the west face of the 

Blue Mountains; the lower Snake River Basin, which drains the northern part of 

the Blue Mountains; the Middle Snake River basin, which drains the southeast face 

of the Blue Mountains; and the Oregon Closed Basins, which drains the southern 

Blue Mountains but has no hydrologic connections to either the Columbia or Snake 

Rivers.

Approximately 20 000 km of streams occur in the Blue Mountains, almost 

7000 km of which are on national forest lands. The distribution of the four selected 

fish species differs in each subbasin depending on available habitat and unique life 

history characteristics. Generally speaking, redband trout are the only species in 

Oregon Closed Basins streams, redband trout and bull trout are the only species in 

the middle Snake River basin (access to this basin by anadromous steelhead and 

spring Chinook salmon was blocked by construction of the Hells Canyon Dam 

complex), and all four species occur in the lower Snake and middle Columbia River 

basins. 

The majority of national forest lands in the analysis area is administered by the 

Malheur, Umatilla, and Wallowa-Whitman National Forests, but a small portion of 

the Ochoco National Forest is also present and administered in conjunction with 

Malheur National Forest lands. For convenience, references to the southern portion 

of the Malheur National Forest will be assumed to also include the small portion of 

Ochoco National Forest lands in the analysis area. The middle Snake River basin 

contains portions of the Wallowa-Whitman and Malheur National Forests. The 

lower Snake River basin contains portions of the Umatilla and Wallowa-Whitman 

National Forests, and the middle Columbia River basin encompasses portions of the 

three main Blue Mountains national forests.

Selected Aquatic Species

Spring Chinook Salmon

Spring Chinook salmon are a fall-spawning anadromous species. They can be 

found in medium-sized river reaches and tributaries within and downstream of 

national forest boundaries. Because they are fall spawners, they move upriver to 

spawning grounds in mid-late summer and can experience thermal barriers to 

Approximately 20 000 

km of streams occur 

in the Blue Mountains, 

almost 7000 km of 

which are on national 

forest lands.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 5.1—Analysis area and hydrologic subdomains for fisheries climate change assessment in the Blue Mountains.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

upstream movement through migratory corridors in the analysis area caused by 

sudden increases in air and water temperatures at the onset of summer, known 

in past decades to occur more quickly than salmon can adjust to physiologically. 

In some instances, sudden temperature increases have caused direct mortality of 

salmon adults.

Native spring Chinook salmon within the analysis area belong to two different 

Environmentally Significant Units (ESUs): the Middle Columbia River spring Chinook salmon ESU in the Middle Columbia River Basin, and the Snake River Basin 

spring Chinook salmon ESU in the Lower Snake River Basin (fig. 5.1). Snake River 

Basin spring Chinook salmon populations spawn and rear in subbasins forming 

the Lower Snake River hydrologic basin: Tucannon, Grande Ronde, Wallowa, and 

Imnaha subbasins. Native Middle Columbia River spring Chinook salmon spawn in 

subbasins forming the headwater forks of the John Day River: the North, Middle, 

Upper John Day and South Fork subbasins draining the west face of the Blue 

Mountains province in the Middle Columbia River Basin. Reintroduced hatchery 

stocks spawn in Walla Walla and Umatilla subbasins headwater habitats within the 

Middle Columbia River Basin in the northern Blue Mountains. For convenience, 

further discussions of native Middle Columbia River spring Chinook salmon will 

refer to these reintroduced populations as well, unless otherwise noted.

Bull Trout

Bull trout, like spring Chinook salmon, are fall spawners with eggs that overwinter 

in the gravels and fry that emerge from redds in late winter and early spring. Their 

habitat ranges from medium-sized, high-elevation tributaries to very small headwater streams. Migratory individuals are known to winter in larger rivers and tributaries but move upriver towards headwater resident tributaries as migratory corridors 

begin to warm in summer and as the fish prepare to spawn. Optimum habitats for 

bull trout provide year-round high-quality cold water and high habitat complexity.

Bull trout in the Blue Mountains exist in a variety of life history forms, including freshwater migratory (fluvial and adfluvial) and headwater year-round resident. 

Migratory bull trout move between their natal streams and larger bodies of freshwater, such as lakes, reservoirs, and mainstem rivers where they can grow much larger 

than the year-round residents that rear and mature in small colder headwaters. 

Bull trout populations are often a mix of resident and migratory individuals, an 

adaptation to infrequent but major natural disturbances in their high-elevation habitats. When such disturbances cause a small resident population to be eliminated, 

migratory individuals that were elsewhere at the time of the event can then establish 

a new population in the vacant habitat, although such recolonization may not occur 
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GENERAL TECHNICAL REPORT PNW-GTR-939

immediately. The benefits of such disturbances are that they often deliver pulses of 

large wood and streambed material that provide new spawning gravels and increase 

habitat complexity, providing resting places and cover to shelter them from predators and reduce energy demands imposed by fast streamflow. A fresh assortment 

of large streambed substrate provides spaces in the streambed where juveniles can 

hide from predators.

Columbia River bull trout are found in all subbasins except for the Burnt River 

in the Middle Snake River Basin, the Oregon Closed Basins, and the South Fork 

Crooked River subbasin in the south end of the plan area (Ochoco National Forest 

lands; Middle Columbia River Basin). The migratory life history is still present 

in most of the populations inhabiting national forest lands in the Blue Mountains 

province, but some headwater resident populations in the analysis area have become 

isolated and are very small owing to the effects of historical land use. Connectivity 

among such resident populations is no longer provided by migratory individuals, and 

these populations are considered to be at heightened risk of long-term extirpation. 

Steelhead Trout/Redband Trout

Research suggests that steelhead and redband trout are alternate life history forms 

of the same species, and often constitute the same populations, where they co-occur 

(McMillan et al 2011, Mills et al. 2012). Both steelhead and redband trout spawn at 

lower elevations and tolerate warmer temperatures in their spawning and rearing 

habitats than do fall-spawning bull trout.

Steelhead trout are a large-bodied anadromous form of O. mykiss. They spawn 

in the spring in medium rivers to headwater tributaries and rear in cool medium and 

small rivers, tributary and headwater streams, and upstream portions of large rivers 

in the analysis area, within accessible portions of the Middle Columbia River and 

Snake River Basins. Steelhead in the analysis area belong to two spatially discrete 

Distinct Population Segments (DPS): the Middle Columbia River steelhead DPS, 

and the Snake River Basin steelhead DPS in the Lower Snake River Basin. Snake 

River Basin populations spawn and rear in subbasins within the Lower Snake River 

Basin: Tucannon, Asotin, Upper and Lower Grande Ronde, Wallowa and Imnaha 

subbasins. Middle Columbia River steelhead spawn in subbasins forming the 

headwaters of the John Day River: the North, Middle, Upper and South Fork subbasins, as well as in the Umatilla and Walla Walla subbasins, all within the Middle 

Columbia River basin.

Redband trout are a much smaller bodied spring-spawning resident life form of 

O. mykiss. They represent a different range of needs both spatially and temporally 

than large-bodied spring Chinook salmon and steelhead. Redband trout inhabit 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

small and medium rivers and tributary streams year round and spawn from late 

winter into May. They are found throughout the entire analysis area, including 

several subbasins where steelhead are absent, and are considered present wherever 

steelhead are present. They occur in subbasins of the Blue Mountains where no 

spring Chinook salmon, steelhead, or other native trout species are present.

The juvenile life stages of the two forms of O. mykiss are indistinguishable 

visually where they co-occur, but juvenile individuals eventually express one of 

two life histories: they either develop physiologically into ocean-going steelhead 

or remain as freshwater resident redband trout. The likelihood that a juvenile will 

express one or the other life history is strongly influenced by environmental and 

physiological factors including water temperature, food supply, gender, growth 

rates, and body fat development that interact to determine which individuals 

out-migrate as steelhead smolts and which remain to mature in freshwater (Sloat 

and Reeves 2014). Where they co-occur, offspring of female steelhead may mature 

into resident redband trout, and offspring of female redband trout may ultimately 

out-migrate to the ocean and return to natal streams as adult steelhead (Carmichael 

et al. 2005). 

Current Status and Trend

Current Population Conditions

Snake River Basin spring Chinook salmon are currently listed as threatened under 

the U.S. Endangered Species Act within the Blue Mountains analysis area. Middle 

Columbia River spring Chinook salmon are not listed at this time. Only the anadromous (steelhead) forms of O. mykiss are listed as threatened (two steelhead DPSs); 

whereas resident redband trout remain unlisted. Bull trout are also listed as threatened (two DPSs). Each listed DPS and ESU is considered a separate species under 

the Endangered Species Act, with recovery goals both for component populations 

of each listed DPS and ESU at the subbasin scale or comparable scales and for the 

DPS/ESU as a whole.

Status reviews for listed species populations occur about every 5 years after 

they have been listed. The most recent status review for listed anadromous species was based on the criterion of self-sustainability (Ford 2011). The majority of 

the biological review team members concluded that Snake River spring/summer 

Chinook salmon ESU and both Middle Columbia River and Snake River Basin 

steelhead DPS are still high risk and should remain listed as threatened. The recent 

5-year status and trend assessment summaries (NMFS 2011a, 2011b) indicate that 
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GENERAL TECHNICAL REPORT PNW-GTR-939

although most listed spring Chinook salmon and summer steelhead populations are 

still considered nonviable, most populations are generally increasing. The National 

Marine Fisheries Service describes and monitors population viability for anadromous fish populations and major population groups at different scales by subbasin, 

major tributary watershed, or groups of adjoining subbasins, depending on the 

population of interest.

For purposes of bull trout recovery planning, core populations have been designated as population units that correspond scalewise to anadromous populations 

(Whitsell et al. 2004). These core populations have been generally defined at the 

subbasin scale, but may also be described based on groups of adjoining subbasins, 

depending on the population of interest. Core populations in the occupied subbasins 

are all part of the Columbia River bull trout DPS, which is listed as threatened. 

For the remainder of this analysis, core populations for Columbia River bull trout 

will be referred to simply as “populations,” and Columbia River bull trout will be 

referred to simply as “bull trout.” The most recent status and trend assessments for 

bull trout in the analysis area indicate that most populations are presently stable or 

increasing (USFWS 2008; http://www.fws.gov/pacific/bulltrout). 

Interagency conservation planning efforts have stratified redband trout populations in the analysis area into spatially discrete conservation population groups 

based on several geographic clusters of subbasins (May et al. 2012) within each of 

the four major hydrologic basins draining the Blue Mountains. Most of these largescale population groups were targeted for conservation efforts. 

Redband populations in the Middle Columbia River and Lower Snake River 

basins where resident populations co-occur with steelhead are generally considered 

by local biologists to be depressed. They parallel steelhead population conditions 

but to an unknown extent, because as resident individuals, redband trout do not 

experience the challenges that affect anadromous steelhead during the years spent 

outside their natal subbasins. Those challenges include adverse conditions in 

freshwater migratory corridors in the larger rivers, passage through and around 

mainstem hydropower dams, physiological transitions to and from saltwater environments in the Columbia River estuary, and additional hazards as they feed in the 

open ocean before returning to their natal streams. Interbreeding between redband 

and steelhead (Kostow 2003) may support population viability for both life histories 

where they co-occur, but the extent to which this occurs or the extent to which each 

life history supports viability of the other, is unknown.

Redband trout populations, which have long been naturally isolated from steelhead in the Oregon Closed Basin (O. mykiss newberryi), have also been separated 
103

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

from other redband populations in the Columbia and Snake River basins 

(O. m. gairdnerii) for millennia, and are especially targeted for conservation. The 

redband populations in this group of subbasins are also collectively known as the 

Great Basin DPS. Although still considered viable (USFWS 2009), these populations are believed to be declining, primarily owing to land management impacts, 

particularly downstream of national forest lands. 

Current Fish Habitat Conditions 

The majority of resident bull trout populations and spawning habitats are located 

in high-elevation habitats where management is limited. These areas are mostly 

allocated to wilderness, wild and scenic river corridors, municipal watersheds, and 

backcountry nonmotorized use where timber harvest, livestock grazing, and roaded 

access are limited. Disturbances in high-elevation spawning areas generally operate 

at natural frequencies, magnitudes, and rates to which bull trout have adapted over 

centuries. 

Habitat conditions in downstream migratory corridors, however, may affect 

fluvial bull trout adults as well as anadromous species. Current connectivity and 

habitat conditions in the Blue Mountains, especially in middle and lower elevations, 

are the result of past natural disturbances, particularly floods and wildfire, and 

past land management activities such as grazing, mining, timber harvest, irrigation 

diversion, and road construction. These disturbances have also occurred in private 

and state lands, including private inholdings that create checkerboard patterns of 

land ownership within national forest boundaries. 

This diversity of land uses interacting with natural disturbance regimes has 

contributed over time to degradation of stream channels and downcut floodplains, 

resulting in less water storage and release as baseflows during the summer season. 

Water storage behind impassible dams, water withdrawals, and irrigation diversions for downstream use also contribute to reduced baseflows and can result in 

high summer water temperatures that create thermal barriers to fish movement in 

lower river corridors. Dams and irrigation diversion structures reduce habitat and 

population connectivity wherever they occur, by partially or totally blocking fish 

passage, depending on the design and use of the individual structures. Fish habitats 

are naturally fragmented in the Oregon closed basins but are further fragmented by 

urban development and water withdrawals. 

Many kilometers of fish habitat for one or more species within national forest 

lands are blocked, or seasonally blocked, by culverts under roads. An inventory 

conducted in national forest lands in 2000 and 2001 revealed numerous passage 

Many kilometers of 

fish habitat for one or 

more species within 

national forest lands 

are blocked.
104

GENERAL TECHNICAL REPORT PNW-GTR-939

concerns created by culverts, particularly in the (1) Upper and Lower Grande Ronde 

subbasins and the upper Imnaha subbasin in the Lower Snake Basin, (2) North and 

Middle Forks John Day subbasins in the Middle Columbia River Basin, (3) Upper 

Malheur subbasin in the Middle Snake River Basin, and (4) Silvies River subbasin 

in the Oregon Closed Basins. Most of these passage barriers can impede passage 

at baseflow for juveniles of the various species, and some impede adult passage for 

one or more species like bull trout or steelhead/rainbow in headwater streams. Passage barriers generally do not exist in the larger tributaries and rivers that provide 

spawning and rearing habitat for Chinook salmon.

Although many effects from past and current management will likely continue 

for the foreseeable future, restoration efforts have been ongoing for over 20 years in 

the Blue Mountains, achieved in part by reducing land management effects under 

direction in national forest land management plans, as amended by PACFISH and 

INFISH (USDA FS 1995, USDA FS and USDI BLM 1995). Current Forest Service watershed restoration programs emphasize whole-watershed restoration, and 

strategic investment in accelerated watershed and habitat restoration are focused on 

the Blue Mountains to provide better protections from further effects of land use 

activities. Fish habitat trend analyses indicate improvements are occurring in the 

condition of aquatic and riparian habitats in national forest lands throughout the 

Blue Mountains (Archer et al. 2009, 2012). 

Analysis of Projected Climate Change Effects

To assess the potential effects of climate change on stream environments in the 

Blue Mountains, we used national geospatial data products to delineate the stream 

network. Streamflow and temperature values from high-resolution stream climate 

models were then linked to reaches in that network to create a geospatial database 

that could be queried to summarize climate effects at different time periods. 

Stream Network and Hydrology Model

To delineate a stream network for this assessment, geospatial data for the NHDPlus 1:100,000-scale national stream hydrography layer (Cooter et al. 2010) were 

downloaded from the Horizons Systems website (http://www.horizon-systems.com/

NHDPlus/index.php) and clipped to the major watershed boundaries associated with 

the Blue Mountains. The network was filtered to exclude reaches with minimum 

summer flows less than 0.034 m3 

s

-1, which approximates a low-flow wetted width 

of 1.5 m (based on an empirical relationship developed in Peterson et al. [2013]) in 

which fish occurrence is rare. For purposes of this assessment, the summer flow 
105

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

period was defined as beginning with the recession of the spring flood to September 30, and is considered to be a critical period for many fish populations because it 

coincides with maximum temperatures (Arismendi et al. 2013).

Summer flow values predicted by the VIC model (Hamlet et al. 2007, Wenger 

et al. 2010) were downloaded from the Western United States Flow Metrics website 

(http://www.fs.fed.us/rm/boise/AWAE/projects/modeled_stream_flow_metrics.

shtml) and linked to each reach in the hydrography layer through the COMID field. 

The VIC model is a distributed, physically based model that balances water and 

energy fluxes at the land surface and takes into account soil moisture, infiltration, 

runoff, and baseflow processes within vegetation classes (Liang et al. 1994). It has 

been widely used in the Western United States to study past and potential future 

changes to waterflow regimes (Hamlet et al. 2007, 2013), snowpacks (Hamlet et al. 

2007), and droughts (Luo and Wood 2007).

Application of the minimum summer flow criteria reduced the original set of 

blue-lines in the NHDPlus hydrography layer for the Blue Mountains region to 20 

123 stream km, of which 6907 km were on U.S. Forest Service lands (fig. 5.2). In 

addition to summer flows, earlier validation work (Wenger et al. 2010) suggests 

the VIC model accurately predicts several other flow metrics relevant to fish: 

center-of-flow mass (date at which 50 percent of annual flow has occurred), winter 

95 percent flow (number of days from December 1 to February 28 when flows are 

among highest 5 percent of the year), and mean annual flow (Wenger et al. 2010).

Climate Scenarios

To assess stream responses to climate change, the VIC model was forced by an 

ensemble of 10 GCMs that best represented historical trends in air temperatures and 

precipitation for the northwestern United States during the 20th century (Hamlet et 

al. 2013, Mote and Salathé 2010). We considered changes associated with the A1B 

emission scenario (moderate emissions as defined by the Intergovernmental Panel 

on Climate Change) and summarized flow characteristics during a historical baseline period (1970–1999, hereafter the 1980s) and two future periods (2030–2059 

hereafter 2040s; 2070–2099 hereafter 2080s). Within the Blue Mountain region, 

summer air temperatures were projected to increase 3.3 °C by the 2040s and 5.4 °C 

by the 2080s, with smaller increases during other seasons. Summer precipitation 

was projected to decrease 11 percent by the 2040s and 14 percent by the 2080s, but 

slight increases during other seasons meant total annual precipitation was projected 

to change less than 5 percent (Hamlet et al. 2013, Mote and Salathe 2010). 

Most GCM projections are relatively consistent until the mid-21st century and 

diverge primarily in late century owing to uncertainties about future greenhouse 
106

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 5.2—Maps showing stream reaches with mean summer flows sufficient to support fish populations for the 1980s (A) and 2080s (B) based on the A1B emissions trajectory. Red stream reaches depict locations where summer flows are projected to drop below 0.034 m3s-1 and become intermittent fish habitat. VIC = Variable Infiltration 

Capacity.
107

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

gas emissions (Cox and Stephensen 2007, Stocker et al. 2013). The climatic conditions associated with the A1B trajectory and historical period bracket that range of 

possibilities. Given uncertainties about the magnitude and timing of changes, it is 

reasonable to interpret future projections as a moderate change scenario (2040s) and 

an extreme change scenario (2080s) relative to the baseline period (1980s). 

Stream Temperature Model and Scenarios

To complement the streamflow scenarios, geospatial data for August mean stream 

temperatures were downloaded for the same A1B trajectory and climate periods 

described above from the NorWeST website (http://www.fs.fed.us/rm/boise/AWAE/

projects/NorWeST.html). NorWeST scenarios are developed by applying spatial statistical models for data on stream networks to a crowd-sourced database contributed 

by more than 70 resource agencies (Isaak et al. 2011, 2014). NorWeST scenarios 

account for differential sensitivity of streams to climate forcing through application of basin-specific parameters (Isaak et al. 2011, Luce et al. 2014b). NorWeST 

scenarios are available at a 1-km resolution and were modeled in the study area 

from more than 9,000 summers of measurement with thermographs at more than 

3,000 unique stream sites monitored intermittently with digital sensors from 1993 

to 2011. The density and spatial extent of the temperature data set, combined with 

the predictive accuracy of the NorWeST model across those sites (r

2

 = 0.94; RMSE 

= 0.90 °C) overcame the commonly cited weakness of coarse resolution in climate 

vulnerability assessments (Potter et al. 2013, Wiens and Bachelet 2010). The model 

also performed well over the wide range of climatic variation that occurred during 

the calibration period (interannual variation in August air temperatures of 5.0 °C 

and threefold variation in August flows), which is notable because the warmest and 

driest years exceeded mean conditions projected to occur by the 2040s. 

Climate Change Effects on Fish and Fish Habitat 

Streamflows–General Patterns

The broad elevation range across the Blue Mountains translates to significant spatial heterogeneity in stream hydrology. Streams in low-elevation catchments have 

rain-dominated hydrographs with peak flows occurring much earlier in the year 

than high-elevation streams dominated by snowmelt runoff. Relative to the 1980s 

baseline period, runoff timing (center of flow mass) of all streams are projected 

to advance 9 to 23 days earlier in the year, with larger changes anticipated by the 

2080s and at higher elevations (table 5.1, fig. 5.3). Similar patterns are projected 

with regards to larger changes late in the 21st century, and on national forests with 

NorWeST scenarios are 

developed by applying 

spatial statistical 

models for data on 

stream networks to 

a crowd-sourced 

database.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 5.1—Summary of streamflow statistics relevant to fish populations 

in the Blue Mountains climate change analysis area, based on changes 

associated with the A1B emission trajectory

All lands Forest Service lands

Flow metric

Climate 

period

Day of 

yeara

Days 

advance

Day of 

year

Days 

advance

Center of flow mass 1980s 181 — 189 —

2040s 172 -9 176 -13

2080s 165 -16 166 -23

Number 

of days

Days 

increase

Number 

of days

Days 

increase

Winter 95% flow 1980s 5.7 — 4.6 —

2040s 7.3 1.6 6.7 2.1

2080s 8.7 3.0 8.6 4.0

Stream 

kilometers

Percent 

change

Stream 

kilometers

Percent 

change

Stream lengthb 1980s 20 123 — 6907 —

2040s 19 130 -4.9 6362 7.9

2080s 18 681 -7.2 6070 -12.1

Cubic 

meters 

per second

Percent 

change

Cubic 

meters 

per second

Percent 

change

Mean summer flowc 1980s 0.98 — 0.68 —

2040s 0.83 -15.3 0.48 -28.9

2080s 0.77 -21.7 0.40 -41.4

Mean annual flow 1980s 1.65 — 1.09 —

2040s 1.75 5.8 1.17 7.0

2080s 1.82 10.1 1.23 12.5

— Signifies that data are not available.

a

 Refers to day of water year starting October 1.

b

 Stream reaches in network with mean summer flows greater than 0.039 m3s

-1.

c

 Average flow across all reaches in the network.
109

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 5.3—Maps showing the frequency of days when winter high flows are among the highest 5 percent of the year for the 1980s (A) and 2080s (B) based on the A1B missions trajectory. VIC = Variable Infiltration Capacity.
110

GENERAL TECHNICAL REPORT PNW-GTR-939

respect to number of winter high-flow days (fig. 5.4) and declines in average 

summer flows. 

If summer flows decline by the projected 15 to 41 percent (table 5.1), the 

linear extent of the network supporting fish (flows greater than 0.034 m3 · s

-1) 

could decrease by 5 to 12 percent, as the smallest headwater streams become more 

frequently intermittent (fig. 5.2). Summer flow reductions are predicted to be most 

prominent in the highest elevation watersheds like the Eagle Cap Wilderness where 

stream hydrologies are most dependent on winter snow accumulation. The direction 

of projected trends in stream hydrologic attributes is similar to that observed during 

the last 50 years of the 20th century across the Pacific Northwest (Isaak et al. 2012a, 

Luce et al. 2009, Safeeq et al. 2013, Sawaske and Freyberg 2014), but future changes 

and associated rates of change are expected to be larger.

Winter high-flow frequency—

As air temperatures increase, the rain-on-snow (ROS) zone will move up in elevation, increasing stream flooding where the current ROS zone is lower in a subbasin. In contrast, subbasins with an already higher elevation ROS zone will see only 

modest increased flooding risks (Hamlet and Lettenmaier 2007, Tohver et al. 2014). 

As ROS zones move higher over time, the zones themselves will shrink, reducing 

the potential contribution to peak winter runoff in some subbasins. The probability 

of ROS events occurring is also expected to decrease with warmer temperatures because of decreased snow occurrence and length of time that snow is on the ground 

(McCabe et al. 2007), especially in lower elevation subbasins in the northern Blue 

Mountains.

Most high-elevation areas under the baseline conditions (1980s) have 1 to 

6 days (mean 4.6 days) of winter high flows, with the exception of the Wallowa 

Mountains in the Eagle Cap Wilderness, which have less than a day (fig. 5.3). The 

highest elevations in the analysis area occur within the Wallowa Mountains at 3000 

m. Projections indicate that risks from mid-winter peak flows triggered by ROS 

events increase moderately by 2040 (2.1 days) and accelerate in 2080 (4 days) for 

national forest lands under the A1B emission scenario (table 5.1). By 2080, all areas, 

with the exception of the highest terrain in the Wallowa Mountains, almost double 

the number of days (mean 8.6 days) with the highest 5 percent flows (fig. 5.4). 

Increased frequency and severity of flood flows during winter can affect overwintering juvenile fish and eggs incubating in the streambed. Eggs of fall spawning 

spring Chinook salmon and bull trout may suffer higher levels of mortality when 

exposed to increased flood flows (Jager et al. 1997). Scouring of the streambed can 

dislodge eggs (Schuett-Hames et al. 2000), and elevated sediment transport caused 
111

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 5.4—Maps showing dates of the center of annual flow mass (50 percent of annual flows) for the 1980s (A) and 2080s (B) based on the A1B emissions trajectory. Cool colors indicate streams with snowmelt-dominated hydrographs, and warm colors indicate rainfall-dominated hydrographs. VIC = Variable Inflirtation Capacity.
112

GENERAL TECHNICAL REPORT PNW-GTR-939

by high flow can increase sediment deposition in redds, suffocating eggs (Peterson 

and Quinn 1996). Potential effects to fish from altered winter peak flows will likely 

vary by species and strength of each population. Eggs from smaller fall spawning 

fish (e.g., bull trout) will likely be at higher risk from winter channel scour events 

than larger fall spawning fish (e.g., spring Chinook salmon) because of shallower 

egg depths (Bjornn and Reiser 1991, Montgomery et al. 1999, Shellberg et al. 2010). 

Smaller fish also use smaller gravels that are more easily scoured than gravels used 

by larger spawning fish. 

Despite similar incubation timing, bull trout had a higher risk of scour than 

spring Chinook salmon, which bury their eggs deeper (40 cm vs. 10 to 20 cm for 

bull trout) in the Middle Fork of the Salmon River (Goode et al. 2013). The risk 

of scour was also greater for resident bull trout (10 cm egg burial depth) than for 

larger, migratory forms (20 cm egg burial depth) for identical spawning locations 

and timing. Spring Chinook salmon had lower risk of channel scour associated with 

climate change because of their spawning preference for unconfined alluvial valleys 

that are somewhat buffered from scour caused by increased winter flows (Goode 

et. al. 2013). Spring Chinook salmon redds also have lower risk because they are 

generally constructed from larger substrates that would be mobilized only during 

large flood events. 

Winter floods may increase risks to fry that are vulnerable to displacement 

during the first month after emergence (Fausch et al. 2001, Nehring and Anderson 

1993) or to juveniles with poor swimming ability in high-velocity water (Crisp 

and Hurley 1991, Heggenes and Traaen 1988). The retreat of snow level to higher 

elevations may lead to earlier fry emergence for some populations (Healey 2006). 

Individual populations have spawning times and egg development rates matched 

to the long-term environmental conditions of their spawning stream (Beacham and 

Murray 1990, Tallman 1986). Earlier emergence may expose the fry to increased 

mortality because of a lack of food or increased predation (Brannon 1987, Tallman 

and Healey 1994). 

The above potential effects are most likely to occur in years with higher ROS 

risk. However, they will not occur every year or in every subbasin across the Blue 

Mountains. Risks of winter peak flow to fish habitat will differ by habitat and 

subbasin condition, valley confinement, and frequency and intensity of each ROS 

event. Smaller watersheds with higher road densities may concentrate flows into 

streams and magnify channel scour. Habitats that offer fewer refugia (e.g., infrequent pools, shallow pools, less woody debris) from high flows may result in higher 

fish mortality from winter floods. 

Potential effects to 

fish from altered 

winter peak flows will 

likely vary by species 

and strength of each 

population.
113

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Risks from winter peak flow will almost double in some Blue Mountains 

subbasins in the future, although risk will differ at different locations. Because 

salmonids have evolved within a highly dynamic landscape (Benda et al. 1992, 

Montgomery 2000), they may have sufficient phenotypic plasticity to buffer environmental changes, assuming that such changes are within the historical range of 

variability (Waples et al. 2008). However, it is unknown if phenotypic adjustment 

can keep pace with evolving disturbance frequency induced by contemporary 

climate change (Crozier et al. 2008, 2011).

Summer flows—

As described previously, spring and early summer flows have been decreasing as 

a result of earlier snowmelt and runoff over the last 50 years (Safeeq et al. 2013, 

Stewart et al. 2005). Streamflow magnitude in the Pacific Northwest also declined 

between 1948 and 2006, including decreased 25th percentile flow (Luce and Holden 

2009), which means that the driest 25 percent of years have become drier across the 

majority of the Pacific Northwest. Overall, trends in the Blue Mountains suggest 

summer flows decreased 21 to 28 percent in the period from 1949 to 2010 (Safeeq 

et al. 2013). This trend is expected to continue because large portions of the Blue 

Mountains could lose all or significant portions of April 1 snow-water equivalent 

(SWE) in future periods because of reduced snow accumulation and increased 

ROS events that reduce snowpack SWE prior to April 1. Snowpack sensitivity differs with elevation, and risk of loss is higher where snowpack currently persists in 

higher elevation subbasins (see chapter 3). 

Effects on fish and their habitats from changes in summer low flows will differ 

by the intensity and frequency of drought and early season runoff, as a function of 

geology, drainage elevation, and fish species across the Blue Mountains. Streams 

more dependent on snowmelt with minimal groundwater contribution will be 

affected more than streams sustained by groundwater. However, even these groundwater streams will have lower baseflows in sustained droughts. 

Fish populations most affected by this change will likely be in headwater areas 

inhabited by steelhead, redband trout, and bull trout. However, all fish populations 

will be stressed as streamflows decrease over the summer. Increased intensity of 

extreme low flows reduces the probability of survival in rearing juveniles (May and 

Lee 2004), with evidence that summer and early autumn low flows cause greater 

impacts (Crozier and Zabel 2006, Harvey et al. 2006). In some stream reaches, 

riffles will become shallower and perhaps intermittent (Sando and Blasch 2015). 

This may result in disconnected stream reaches, isolated pools, overcrowding of 

fish, increased competition for food and cover, and greater vulnerability to predators in remaining deep water habitat. 
114

GENERAL TECHNICAL REPORT PNW-GTR-939

In years of extreme drought, native trout and salmon populations may retreat 

to shrinking coldwater refuges in drainages where unimpeded access allows fish to 

avoid warmer downstream conditions. Changes in low flow may reduce the likelihood of successful adult migration (Rand et al. 2006, Zeug et al. 2011) as adult fish 

return from the ocean and have difficulty negotiating waterfalls and other barriers. 

Steelhead have high phenotypic plasticity and may shift the timing of a life 

stage transition to reduce probability of exposure to changes in stream temperature 

and flow. However, steelhead are limited in their ability to shift the timing of 

their life stages. Because changes in both temperature and flow initiate transitions 

among salmon life stages (Bjornn and Reiser 1991, Quinn and Adams 1996), the 

likelihoods of a temporal disparity between life stages and a decrease in probability 

of persistence increase when temperature and flow are beyond some critical threshold (Reed et al. 2010, Schlaepfer et al. 2002).

Stream Temperatures—General Patterns

Considerable thermal heterogeneity exists across Blue Mountain streams owing 

to the complex topography and range of elevations within the area (table 5.2, fig. 

5.5). August stream temperatures in the 1980s baseline period averaged 15.5 °C 

and ranged from 4.7 to 23.5 °C. Temperatures of streams flowing through higher 

elevation national forest lands were cooler, averaging 12.4 °C. Summer temperatures are projected to increase across the Blue Mountains by an average of 0.9 °C 

in the 2040s and 1.9 °C in the 2080s. Larger than average increases are projected to 

occur in the warmest streams at low elevations, and smaller than average increases 

are projected for the coldest streams. This differential warming occurs because 

Table 5.2—Summary of August mean stream temperatures in the Blue 

Mountains climate analysis area during the baseline period and two future 

periods associated with the A1B emission trajectory

< 8 °C 8–11 °C 11–14 °C 14–17 °C 17–20 °C > 20 °C

Stream kilometers

All lands:

1980s 448 1672 5150 8846 5000 1496

2040s 131 1122 3082 7640 7679 2959

2080s 46 770 2240 6351 8457 4752

Forest Service lands:

1980s (1970–1999) 441 1457 3237 1525 263 124

2040s (2030–2059) 131 1054 2353 2716 588 203

2080s (2070–2099) 46 739 1867 3187 923 284
115

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 5.5—Summer stream temperature map for the 1980s (A) and 2080s (B) based on NorWeST scenarios and the A1B emissions trajectory.
116

GENERAL TECHNICAL REPORT PNW-GTR-939

cold streams are usually more buffered by local groundwater contributions than 

are warm streams (Luce et al. 2014a, Mayer 2012). Those projected temperature 

increases are smaller than the 2- to 4-°C increases projected for Pacific Northwest 

streams for the same A1B trajectory (Beechie et al. 2012, Mantua et al. 2010, Wu 

et al. 2012). But previous studies modeled short-term weekly maxima that often 

changed more rapidly than mean temperature conditions (Meehl and Tebaldi 2004). 

In all cases, projections imply faster rates of stream temperature warming than 

has been observed in recent decades. Most streams in the Pacific Northwest have 

been warming 0.1 to 0.2 °C per decade (Isaak et al. 2012a, 2012b), which is slower 

than the rates of air temperature increases. Stream warming rates differ by season, 

with rates usually highest in summer and lower during winter and spring (for which 

a cooling trend has occurred in recent decades; Isaak et al. 2012a). Regional rates of 

stream warming have been dampened in recent years by a cool phase of the Pacific 

Decadal Oscillation (PDO; Mote et al. 2003; see http://cses.washington.edu/cig/

pnwc/aboutpdo.shtml), a phenomenon that will not persist indefinitely as the PDO 

continues to cycle.

Stream temperature increases will almost certainly continue, but with some 

uncertainty about site-specific rates. Fish species in Blue Mountain streams will 

respond by adjusting their spatial distributions and phenologies to the evolving 

thermal environment. Adjustments in spatial distributions will be most pronounced 

near distributional boundaries that are currently mediated by temperature. Range 

contractions and habitat losses near warm downstream boundaries are often the 

focus of climate vulnerability assessments, but upstream boundaries controlled by 

cold temperatures may be equally relevant for some species. Colonization of new 

habitats farther upstream as warming progresses could offset a portion of downstream habitat losses for some species and populations (Isaak et al. 2010). Populations may also adapt phenologically by using habitats at different times of the year 

to avoid stressful conditions. 

Evidence exists that migration dates of some salmon species have been advancing in recent decades (Crozier et al. 2008, Keefer et al. 2008, Petersen and Kitchell 

2001) and that these trends are related to warmer temperatures (Crozier et al. 2011). 

However, phenological adaptations involve tradeoffs elsewhere in the life cycle. 

In the case of salmon, earlier migrants have spent less time in the ocean and have 

smaller body sizes (Rand et al. 2006), and these fish arrive in spawning areas 

sooner where they may be more susceptible to thermal events and predation risks. 

Documentation of phenological shifts for fish species and life stages beyond adult 

migrations are limited, but the strong temperature dependencies of physiological 

Stream temperature 

increases will almost 

certainly continue, but 

with some uncertainty 

about site-specific 

rates.
117

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

and metabolic processes usually translate to earlier timing of life history events in 

most species (Parmesan and Yohe 2003, Root et al. 2004).

Spring Chinook salmon—

Populations of spring Chinook salmon in the Blue Mountains will be sensitive to 

future temperature increases because many of their primary spawning and rearing 

streams occur at low elevation and are relatively warm for this species. Moreover, 

adults in these populations already exhibit heat-related stress symptoms, including 

clustering in coldwater refugia during warm periods (Torgersen et al. 1999, 2012) and 

occasional thermally induced mortality events in the lower river migration corridors 

in the John Day River system during upriver spawning migrations. The large body 

size of salmon and preference for spawning in unconfined valleys with gravel substrates (Isaak et al. 2007) may preclude their colonization of new habitats upstream 

from historical ones, so these fish are expected to lose habitat as warming continues. 

To estimate potential habitat losses for spring Chinook salmon, a 19 °C 

temperature threshold was applied to the stream temperature scenarios described 

previously (table 5.2; fig. 5.5), and these were clipped to match the upstream 

distribution of spring Chinook salmon in the Blue Mountains. This temperature 

was chosen because streams with higher temperatures are susceptible to invasion 

by nonnative smallmouth bass that predate heavily on juvenile Chinook salmon 

(Lawrence et al. 2014). Chinook salmon populations in streams warmer than 19 °C 

also exhibit consistently higher prespawn mortality rates than populations in cooler 

streams (Keefer et al. 2010). Based on that criterion, it was estimated that 1921 

km of salmon habitat existed during the 1980s baseline across the Blue Mountains 

region, 854 km of which were on national forest lands (table 5.3, fig. 5.6). In the 

future, 24 to 38 percent of streams across the analysis area are projected to exceed 

Table 5.3—Changes in stream length (kilometers; percent 

change in parentheses) across the Blue Mountains analysis 

area with temperatures suitable for spring Chinook salmon 

spawning and rearing during three climate periods associated 

with the A1B emission trajectory

Climate period All lands

Forest Service 

lands

Kilometers <19.0 o

Ca

1980s (1970–1999) 1921 854

2040s (2030–2059) 1453 (-24.4%) 767 (-10.2%)

2080s (2070–2099) 1200 (-37.5%) 673 (-21.2%)

a

 A critical temperature threshold of 19 °C was chosen because reaches warmer than this 

are susceptible to invasion by nonnative smallmouth bass that predate on juvenile salmon 

(Lawrence et al. 2014), and because prespawn mortality rates of adult salmon are much 

higher above this threshold (Keefer et al. 2010).
118

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 5.6—Distribution of thermally suitable habitat for spring Chinook salmon downstream of Hells Canyon during the 1980s (A) and 2080s (B) based on the A1B emissions trajectory.
119

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

19 °C, but only 10 to 21 percent reductions are expected on national forest lands 

because streams are colder and farther from the temperature threshold. An earlier 

estimate of Chinook salmon habitat loss in a subset of the Blue Mountains, the John 

Day River basin, predicted larger reductions (30 to 75 percent decreases for similar 

time periods; Reusch et al. 2012), but also showed a similar pattern of larger habitat 

losses in warmer downstream areas. 

Bull trout—

Populations of bull trout in the Blue Mountains will be sensitive to future temperature increases because this species requires streams with very cold temperatures 

(Dunham et al. 2003, Mesa et al. 2013, Selong et al. 2001). Although adult bull trout 

sometimes use main-stem rivers at times of year when temperatures may be relatively warm (Howell et al. 2010, Monnot et al. 2008), spawning and juvenile rearing 

during the first few years of life occur exclusively in the coldest streams (Isaak et al. 

2010, Rieman and McIntyre 1995). Consequently, existing populations of bull trout 

in the Blue Mountains are constrained and heavily fragmented among a few small 

headwater networks. The upstream extent of bull trout in those networks is further 

limited by stream slope and small flow volumes, so colonization of new upstream 

habitats in response to climate change is not possible.

A variety of temperature thresholds have been used in bull trout climate 

vulnerability assessments (Isaak et al. 2010; Rieman et al. 2007; Ruesch et al. 2012; 

Wenger et al. 2011a, 2011b), but most focus on temperature criteria associated with 

spawning and rearing habitats because these are critical to bull trout population persistence. An 11.0 °C temperature criterion was chosen for this assessment because 

Table 5.4—Changes in stream length (kilometers; 

percentage change in parentheses) across the Blue 

Mountains analysis area with temperatures suitable for 

bull trout spawning and rearing during three climate 

periods associated with the A1B emission trajectory

All lands

Forest Service 

lands

Kilometers < 11.0 °Ca

1980s (1970–1999) 1953 1827

2040s (2030–2059) 1174 (-40%) 1129 (-38%)

2080s (2070–2099) 786 (-60%) 771 (-58%)

a Stream reaches with mean August temperatures >11.0 °C are warmer than 

optimal for bull trout spawning and rearing, so future warming will decrease 

habitat suitability in these areas. More than 90 percent of bull trout spawning 

and early juvenile rearing occurs in reaches with August temperatures <11.0 

°C, so these areas are critical to population persistence (Isaak et al. 2010, 

2014, 2015; Rieman et al. 2007).
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GENERAL TECHNICAL REPORT PNW-GTR-939

cross-referencing of extensive fish survey databases (Rieman et al. 2007; Wenger 

et al. 2011a, 2011b) with stream temperature measurements suggest more than 90 

percent of juvenile bull trout (defined as fish less than 150 mm in length) occur in 

streams at least this cold (Isaak et al. 2010, 2014, 2015). Moreover, most juveniles 

found in reaches more than 11 °C probably originated in colder, upstream areas and 

have subsequently moved downstream.

Based on that criterion, it was estimated that 1953 km of bull trout habitat 

existed during the baseline 1980s conditions across the Blue Mountains, 94 percent 

of which occurred on national forest lands (table 5.4, fig. 5.7). Future projections 

suggest that 38 percent and 58 percent of those streams will exceed 11 °C by 

mid and late 21st century, respectively. Ruesch et al. (2012) made a comparable 

estimate of bull trout habitat loss over similar time periods in the John Day River 

system that predicted larger losses (66 to 100 percent decreases), but projected a 

qualitatively similar pattern of decline as temperatures increase in the future. None 

of the available estimates accounts for reductions in habitat volume that would be 

caused by ongoing decreases in summer flows. Neither do those estimates account 

for potential negative synergies between reductions in habitat size and increased 

environmental disturbances such as wildfires, debris flows, winter high flows, and 

drought (Dunham et al. 2007, Hamlet and Lettenmaier 2007, Littell et al. 2010, 

Luce and Holden 2007). 

Steelhead trout/redband trout—

Populations of steelhead and redband trout will be affected by future temperature 

increases in the Blue Mountains, but probably less negatively than bull trout and 

spring Chinook salmon. Temperature and food availability play important roles 

in mediating the relative proportions of the two life history forms, but both have 

relatively warm thermal niches (Richter and Kolmes 1995, Rodnick et al. 2004, 

Zoellick 1999) and upstream distributions that are limited by cold temperatures in 

many streams (Isaak et al. 2015). The latter provides some flexibility as warming 

proceeds because the thermal suitability of upstream habitats will improve and may 

partially compensate for losses where streams become too warm. Several temperature categories were used to represent the breadth of the thermal niche for steelhead 

and redband trout, with temperatures less than 9 °C considered unsuitably cold, 13 

to 20 °C optimal, and greater than 25 °C unsuitably warm. 

Summaries of future stream lengths in those categories indicate that upstream 

habitat gains could occur in many streams that were too cold for this species historically, and a small net increase in the length of thermally suitable habitat may occur 

(tables 5.5, 5.6; figs. 5.8, 5.9). That result contrasts with a loss of 10 to 43 percent of 

habitat in the John Day system projected by Ruesch et al. (2012), but that estimate 

Populations of 

steelhead and redband 

trout will be affected 

by future temperature 

increases in the Blue 

Mountains.
121

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 5.7—Distribution of thermally suitable habitat for bull trout during the 1980s (A) and 2080s (B) based on the A1B emission trajectory.
122

GENERAL TECHNICAL REPORT PNW-GTR-939

Table 5.5—Changes in stream length (kilometers; percentage change in 

parentheses) with suitable temperatures for steelhead and redband trout 

downstream of Hells Canyon within the Blue Mountains analysis area during 

three climate periods associated with the A1B emissions trajectory 

Kilometer

<9 °Ca 9–13 °C 13–20 °C 20–25 °Cb

All lands:

1980s (1970–1999) 685 2684 10 630 358

2040s (2030–2059) 246 (-64%) 1724 (-36%) 11 182 (5%) 1208 (337%)

2080s (2070–2099) 105 (-85%) 1317 (-51%) 10 423 (-2%) 2512 (702%)

Forest Service lands:

1980s (1970–1999) 681 2183 2185 8

2040s (2030–2059) 246 (-64%) 1555 (-29%) 3181 (46%) 75 (937%)

2080s (2070–2099) 105 (-85%) 1262 (-42%) 3527 (61%) 163 (2,037%)

a

 Stream reaches with mean August temperatures <9 °C are too cold for redband trout, so future warming 

will increase habitat suitability in these areas.

b

 Stream reaches with mean August temperatures >20 °C are warmer than optimal for steelhead/redband 

trout so future warming will decrease habitat suitability in these areas. Temperatures >25 °C are considered 

unsuitable (Cassinelli and Moffitt 2009, Rodnick et al. 2004, Sloat and Reeves 2014).

Table 5.6—Changes in stream length (kilometers; percent change in 

parentheses) with suitable temperatures for redband trout upstream 

of Hells Canyon within the Blue Mountains analysis area during three 

climate periods associated with the A1B emissions trajectory

Kilometers

< 9 °Ca 9–20 °C 20–25 °Cb >25 °C

All lands:

1980s (1970–1999) 168 3914 71 0

2040s (2030–2059) 73 (-57%) 3516 (-10%) 565 (796%) 0

2080s (2070–2099) 34 (-80%) 3179 (-19%) 941 (1,325%) 0

Forest Service lands:

1980s (1970–1999) 158 976 0 0

2040s (2030–2059) 70 (-56%) 1062 (9%) 2 0

2080s (2070–2099) 34 (-78%) 1094 (12%) 6 0

a

 Stream reaches with mean August temperatures <9 °C are too cold for redband trout, so future 

warming will increase habitat suitability in these areas.

b

 Stream reaches with mean August temperatures >20 °C are warmer than optimal for redband 

trout, so future warming will decrease habitat suitability in these areas. Temperatures >25 °C are 

considered unsuitable (Cassinelli and Moffitt 2009, Rodnick et al. 2004, Sloat and Reeves 2014).
123

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 5.8—Distribution of thermally suitable habitat for steelhead and redband trout downstream of Hells Canyon in the 1980s (A) and 2080s (B) based on the A1B emission trajectory.
124

GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 5.9—Distribution of thermally suitable habitat for redband trout upstream of Hells Canyon and in the Oregon Closed Basins in the 1980s (A) and 2080s (B) based on the A1B emission trajectory.
125

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

was based on the assumption that unsuitably cold habitats were not upstream of current steelhead and redband trout in some streams. In a regional climate vulnerability analysis, Wade et al. (2013) indicated that steelhead migrating through the lower 

Columbia River and many large rivers and tributaries will be negatively affected 

by future temperature increases. However, the spatial resolution of the model was 

limited to the largest rivers, so their analysis could not assess effects throughout the 

full network of streams draining the Blue Mountains. Taken in combination, these 

studies suggest that although there may be some thermal effects on steelhead and 

redband trout (Ebersole et al. 2001, Torgersen et al. 2012), the species have some 

flexibility to adapt to temperature increases through different life histories, phenological adjustments, and distribution shifts. 

Climate Cycles and Ocean Effects on Fisheries

The biology and legal status of anadromous steelhead and spring Chinook salmon 

in the Middle Columbia River and Snake River basins demonstrate that anadromous fish populations are heavily influenced by many factors outside and downstream of national forest-administered lands. For example, population dynamics 

and abundance of spring Chinook salmon and steelhead are strongly affected by 

conditions in the ocean environment (Mantua et al. 1997). The productivity of that 

environment for salmon growth and survival varies through time in response to 

sea surface temperatures and strength of coastal upwelling tied to regional climate 

cycles like the El Niño Southern Oscillation (ENSO; 5- to 7-year periods) and PDO 

(20- to 40-year periods). Although ocean productivity and climate cycles most 

strongly affect anadromous fishes, these cycles are also relevant to resident species 

like bull trout and redband trout because of inland effects on temperature, precipitation, and hydrologic regimes that alter the quality and quantity of freshwater habitat 

(Kiffney et al. 2002). In the Pacific Northwest, cool (wet) phases of ENSO and PDO 

are more beneficial to fish populations than are warm (dry) phases (Copeland and 

Meyer 2011, Mote et al. 2003). 

Research summarized in the recent Intergovernmental Panel on Climate 

Change report (Stocker et al. 2013) provides little evidence to support concerns 

about climate change affecting the periodicity or magnitude of ENSO or PDO, 

either in the historical record, or in future climate projections. Therefore, we can 

expect climate cycles to periodically dampen or exacerbate the effects of climate 

change on fish populations and stream habitats. A cool PDO phase began in about 

2000 and has largely persisted to the present (see http://www.jisao.washington.edu/

pdo), but it is unknown how long this PDO phase will persist and help buffer fish 

populations against climate change. 

Population dynamics 

and abundance of 

spring Chinook salmon 

and steelhead are 

strongly affected by 

conditions in the ocean 

environment.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Adapting Fish Management to Climate Change in the 

Blue Mountains

Management strategies and tactics for increasing resilience of fish populations to 

a warmer climate in streams of the Western United States have been well documented in the scientific literature (e.g., Isaak et al. 2012a, ISAB 2007, Luce et al. 

2013, Mantua and Raymond 2014, Rieman and Isaak 2010). This documentation 

and feedback from resource specialists contributed to a summary of climate change 

adaptation options for the Blue Mountains (table 5.7). Implementation of climatesmart management actions and watershed restoration objectives will benefit from 

a strategic hierarchical approach to ensure the most important work is occurring in 

the most important places (Hughes et al. 2014). Stream restoration, which is already 

well underway in the Blue Mountains and elsewhere, will in turn need to consider 

future biophysical conditions that will be affected by a warming climate (Beechie et 

al. 2012).

Responding to Shifts in Timing and Magnitude of Streamflow

Reduced snowpack as a function of increasing temperature has already been 

documented in the Pacific Northwest, including the Blue Mountains (see chapter 3 

and previous discussion in this chapter). As this trend continues, hydrologic regimes 

will shift towards increasing dominance by rainfall and decreasing dominance by 

snow at all but the highest elevations, altering the timing and magnitude of streamflows. Specifically, winter peak flows will be higher, and extreme flows will be 

more frequent than they are now, causing considerable stress for some fish species.

Maintaining the overall integrity and functionality of stream systems will be 

critical for minimizing the effects of higher winter flows (table 5.7a). This can be 

accomplished by increasing soil water storage in floodplains and on hillslopes for 

instream baseflows, thus reducing the “flashiness” of stormflows. Decreasing fragmentation of stream networks, currently somewhat disrupted by roads and water 

diversions, will ensure that aquatic organisms have options for accessing favorable 

habitats during extreme flows. Better information about streamflow regimes will 

ensure that climate change adaptation and stream restoration will be conducted 

effectively and efficiently (Luce et al. 2012, Wigington et al. 2013).

Many management tactics are available to alter the effects of increasing winter 

streamflows, including managing upland and riparian vegetation, managing roads 

to reduce accelerated runoff, reconnecting and increasing off-channel habitat in 

side channels and wetlands, and promoting American beaver (Castor canadensis

Kuhl) populations and beaver-related overbank flow processes (Pollock et al. 2014). 

It is also desirable to identify critical downstream areas where leased water rights or 
127

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 5.7a—Adaptation responses for fisheries and aquatic environments to climate change in the Blue Mountains (continued)Adaptation tactic Timeframe

Opportunities for implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: Shift in hydrologic regime involving changes in timing and magnitude of flows. Anticipated changes include lower summer flows and higher, more frequent winter peak flows.Adaptation strategy: Maintain or restore natural flow regime to buffer against future changes.Use Watershed Analysis, Watershed 

Condition Framework, etc. to develop integrated, interdisciplinary tactics associated with vegetation and hydrology

<10 years Collaborate with nongovernmental organizations, other federal 

and state agencies, and private landowners

Competing prioritiesLack of funding

Compare Mid-Columbia River Steelhead Recovery Plan and Oregon 

Department of Fish and Wildlife climate change analysis and other products

Identify priority areas

Protect groundwater and springs <10 years Explore opportunities with range 

permittees, nongovernmental organizations, and others

Lack of information on locations 

of groundwater and springs

Lack of funds to address sites affected by livestockCompeting priorities

Identify locations of groundwater 

-dependent systems and spring influences

Restore riparian areas and beaver 

populations to maintain summer baseflows and raise water table 

<10 to 

>30 years

Collaborate with states, range permittees, and private landowners 

regarding beaver reentry

Use range allotment management, 

riparian shrub planting and protection, riparian aspen restoration and management, road infrastructure planning, and valley form analysis to assess potential sites for beaver colonies and channel migration

Effects on infrastructure (culverts 

and diversions)

Adequate food supply for growing beaver colonies and dispersing individualsPublic and private landowner 

acceptance of beaver colonies

Effects of rising water levels on 

streamside roads and camping grounds

Inventory riparian vegetationMonitor beaver populationsIdentify potential watersheds or 

stream reaches

Inventory riparian vegetation and 

stream morphology status and trends

Address water loss at water diversions and ditches <10 years Coordinate with the water district managers, water master, and 

water users

Competing priorities Lack of fundingWater law does not address ditch 

water loss and inefficiencies

Identify diversions and ditches with 

water losses or other resource issues

Reconnect and increase off-channel 

habitat and refugia in side channels and channels fed by wetlands

<10 to 

>30 years

Collaborate with partners Competing priorities 

Lack of funding

Identify potential watersheds or 

stream reaches
128

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 5.7a—Adaptation responses for fisheries and aquatic environments to climate change in the Blue Mountains (continued) Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs Revegetate, use fencing to exclude livestock <10 years Collaborate with partners on fenc- ing or acquire/lease water rights Plant in and protect riparian areas Restore aspen Competing priorities Lack of funding Difficulty of maintaining live- stock and ungulate exclosures Investigate baseline vs. desired con- ditions in riparian corridors Conduct effectiveness monitoring Acquire water rights, use low-flow channel design <10 years Collaborate with partners in ac- quiring and leasing water rights Competing priorities Lack of funding Opposition from permittees Investigate baseline vs. desired con- ditions in riparian corridors Identify water rights holders willing to collaborate Disconnect roads from streams to reduce drainage efficiency <10 to >30 years Identify areas with high drain- age efficiency, using geographic 

information system (GIS) and Netscape and Geomorphic Road Analysis and Inventory tools

Controversial from a political 

perspective

Lack of travel planCompeting prioritiesLack of fundingTime and cost for full analyses

Acquire GIS data to identify areas 

with high drainage efficiency

Identify problematic road segments 

contributing high sediment

Adaptation strategy: Decrease fragmentation of stream network so aquatic organisms can access similar habitats.Identify stream crossings that impede 

fish movements and prioritize culvert replacements 

<10 to 

>30 years

Collaborate with partners Competing priorities 

Lack of funding

Update culvert inventory

Use stream simulation design (e.g., 

bottomless arches, bridges), adjusting designs to provide low-flow thalweg

<10 to 

>30 years

Collaborate with partners to enhance skills and fundingUse GIS analyses to inform lowflow and high-flow stream design 

at specific crossings

Insufficient staff time for design, 

contracting, and effectiveness monitoring

Insufficient National Environmental Policy Act funding and 

staff time for project planning

Incorporate climate change information to ensure culvert priorities consider long-term cost-effectiveness 

and ecological effectiveness

Rebuild stream bottoms by increasing floodplain connectivity, riparian vegetation, and water tables; 

decrease road connectivity

<10 to 

>30 years

Restore beaver habitat and beaver 

colonies

Relocate streamside roads away 

from streams when possible

Manage roads, vegetation, and 

fuels to ensure large wood recruitment for in-channel potential

Hazard tree management, roadside salvage, firewood cutting, 

road proximity to stream channels and beaver colonies, developed recreation site locations

Mining claim and private land 

access obligations

Competition with livestock and 

large ungulates for limited food supply

Assess beaver habitat potentialCompare natural fire regime restoration with potential for fish habitat 

restoration

Options for alternate access routes 

for mining claims and private land access
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 5.7a—Adaptation responses for fisheries and aquatic environments to climate change in the Blue Mountains (continued)Adaptation tactic Timeframe

Opportunities for implementation Barriers to implementation Information needs

Maintain minimum streamflows 

(buy and lease water rights, install modern flow structures, monitor water use)

<10 to 

>30 years

Collaborate with partners Competing priorities

Lack of funding and personnelFew opportunities to acquire 

senior water rights

Identify areas of concern and opportunities for return on investment

Design channels at stream crossings 

to provide a deep thalweg for fish passage during low-flow periods 

<10 to 

>30 years

Competing priorities Lack of funding

Identify and prioritize channels and 

crossings of high concern

Design stream crossings to 

accommodate higher peak flows

<10 to 

>30 years

High costsCompeting priorities

Update stream crossing inventory

Adaptation strategy: Develop better information about streamflow regimes.Increase flow data collection and 

monitoring to better describe patterns in flow and improve hydrologic models

<10 to 

>30 years

Collaborate with U.S. Geological 

Survey, watershed councils, etc.

Competing prioritiesLack of funding and personnel

Identify and prioritize areas to 

monitor
130

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 5.7b—Adaptation responses for fisheries and aquatic environments to climate change in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: Streams and other water bodies (e.g., springs) will be affected by more wildfires and disturbances

associated with sediment pulses and debris-flow torrents.

Adaptation strategy: Develop wildfire-use plans that address sediment inputs and road failures; reduce sediment input from roads and management activities.Restore and revegetate burned areas 

to store sediment and maintain channel geomorphology

<10 years Collaborate with fire management 

program

Lack of funding if outside 

of Burned Area Emergency Rehabilitation

Competing priorities

Develop a geospatial layer of debrisflow potential for prefire planning <10 years Collaborate with soils and geology programs Lack of funding and personnel Competing prioritiesUse Montgomery-Buffington classification and other tools to calculate 

runout distance and woody debris source areas

<10 years Lack of funding 

Competing priorities

Adaptation strategy: Identify hillslope landslide hazard areas and at-risk roads prior to wildfires and as part of fire planning.Link stream inventory with topographic, geomorphic, and vegetation 

layers to assess existing hazard and risk

<10 years Collaborate with soils and 

geology programs

Lack of funding Competing priorities

Identify hillslope landslide hazard areas and at-risk roads

Develop a process to prioritize tactics 

needed to protect multiple fish species and populations

<10 years Collaborate with fisheries at multiple levels Competing forest priorities Lack of funding Need updated fish distribution layer
131

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 5.7c—Adaptation responses for fisheries and aquatic environments to climate change in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: Stream temperatures will increase, owing to rising air temperatures and declining summer flows, which will affect many 

life stages of aquatic organisms.

Adaptation strategy: Maintain or restore natural thermal conditions to buffer against future climate changes.Maintain or restore riparian vegetation to ensure channels are not 

exposed to increased solar radiation 

<10 to 

>30 years

In project analysis, consider departure from desired conditions/

natural range of variability

Competing priorities Lack of funding

Conduct ecologically based investigations into appropriate vegetation for 

restoration

Manage livestock grazing to restore 

ecological function of riparian vegetation and maintain streambank conditions 

<10 to 

>30 years

Work with range permittees, watershed councils, and other partners 

to fund or install fencing

Reluctant permittees do not 

want to do more fence maintenance

Competing prioritiesLack of funding

Identify streams within range allotments, then prioritize streams based 

on fish population status

Work with vegetation managers to 

identify interdisciplinary tactics for restoring riparian function and hydrologic processes

<10 to 

>30 years

Vegetation management is a 

high priority for resource management

Project planning and objectives 

are largely limited to timber products

Identifying how to pay for additional 

riparian treatments

Increase floodplain connectivity, 

diversity, and water storage to improve hyporheic and baseflow conditions 

<10 to 

30 years

Can identify treatment areas during 

project planning

High cost or social barriers to 

restoration

Identify and prioritize areas for 

treatment

Adaptation strategy: Increase connectivity within stream networks so aquatic organisms can access cold water refugia when needed.Same as above in table 4.7c Same as in 

table 4.7c

Same as in table 4.7c Same as in table 4.7c Same as in table 4.7c

Adaptation strategy: Develop better information about stream temperature regimes.Increase temperature data collection 

and monitoring to better describe patterns in thermal regimes and improve hydrologic models

<10 to 30 years Collaborate with federal and other 

partners 

Competing priorities Lack of funding

Identify and prioritize areas for data 

collection
132

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 5.7d—Adaptation responses for fisheries and aquatic environments to climate change in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs Sensitivity to climatic variability and change: Headwater and other intermittent streams and water bodies (e.g., springs) will be vulnerable to increasing wildfire; sediment pulses and altered flood patterns and magnitudes will increase with increasing fire frequency. Adaptation strategy: Develop wildfire-use plans that address sediment delivery. Restore and revegetate burned areas to store sediment and maintain channel geomorphology <10 years Burned Area Emergency Rehabili- tation (BAER) and fire-restora- tion planning for road decommis- sioning Fire-killed timber management can provide large wood for slope sta- bilization per natural fire regime 

characteristics

Other fire-restoration needs can be 

included in fire salvage National Environmental Policy Act (NEPA)

Public/internal desire to provide 

useable wood to local mills and support local employment and economy

Tight timelines for NEPA to conduct fire salvageLack of funding to conduct nonBAER fire-restoration opportunities identified in fire salvage 

NEPA documents

Identify trees likely to live 

beyond 10 years postfire

Assess how to balance ecological values and community 

economic needs

Develop a geospatial layer of debris 

flow potential for prefire planning

<10 years Hydrologists and soil scientists 

can provide data and criteria to geospatial analyst

Competing prioritiesMay not be a big concern, depending on current availability 

of data

Identify geology/topography/

soil maps/locations of known slide areas and their characteristics

Use Montgomery-Buffington classification and other tools to calculate 

runout distance and woody debris source areas

<10 years Runout distance matters only if 

debris-flow potential is an actual concern

Minimal concerns Identify geology/topography/

soil maps/locations of known slide areas and other areas of concern

Adaptation strategy: Identify hillslope landslide hazard areas and at-risk roads prior to, and as part of, fire planning.Link stream inventory with topographic, geomorphic, and vegetation layers to assess existing hazard 

and risk

<10 years Hydrologists and soil scientists 

can provide data and criteria to geospatial analyst

Minimal concerns Identify geology/topography/

soil maps/locations of known slide areas and other areas of concern

Develop a process to prioritize tactics 

needed to protect multiple fish species and populations

<10 years Convene interdisciplinary fisheries, 

hydrology, soils, and roads discussions as part of development of watershed action plans, watershed restoration action plans, and water quality restoration plans

Staff time to integrate concerns 

and information
133

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

short-term water swaps under low-flow conditions would benefit migrating spring 

Chinook populations subject to thermal stress, and where such actions would help 

sustain critical headwater areas for bull trout spawning and rearing. These adaptation tactics will be most efficient if they can be coordinated with existing stream 

management and restoration efforts conducted by the Forest Service and other 

landowners and stakeholders (Rieman et al. 2015).

Responding to the Effects of Increased Disturbance on Sediment 

and Debris Flows 

Climate change may increase the frequency of extreme events, which in turn would 

affect streams and aquatic habitat. Increased frequency of wildfire and annual area 

burned are a near certainty in the Blue Mountains region (see chapter 6). Increased 

area burned, especially if it includes increased fire intensity, will cause increased 

sediment removal from hillslope locations and higher episodic and chronic delivery 

of sediment to stream channels. Depending on the timing and magnitude of sediment delivery, some life-history stages of anadromous fish can be greatly affected. 

Large debris flows can be especially damaging to aquatic habitat.

Developing wildfire-use plans that specifically address postfire effects on 

streams and aquatic habitat can help reduce disturbance-related sediment input 

from roads and timber harvest (table 5.7b). Identifying hillslope landslide hazard 

areas and susceptible roads prior to the occurrence of wildfire, and as part of fire 

planning, will be critical to mitigating the effects of erosion. 

Restoring and revegetating burned areas, often a component of Burned Area 

Emergency Rehabilitation programs, can help to store sediment and maintain channel geomorphology following large wildfires. Effective implementation will require 

thorough prefire assessment of geomorphic hazards, especially areas prone to 

debris flows. Fortunately, analytical and decision support tools are readily available 

to calculate debris-flow-runout distance and other parameters, and to map the location of hazards. Coordination with resource specialists and programs in vegetation, 

fire, hydrology, geology, and soils will ensure accuracy and efficiency in protecting 

multiple resources. Prioritizing the tactics needed to protect multiple fish species 

and populations in the face of increasing disturbance will be challenging but necessary for guiding implementation of management actions.

Responding to Increased Stream Temperatures 

Increasing stream temperatures, combined with decreasing summer flows, will 

be one of the most obvious effects of climate change for several fish species in the 

Blue Mountains region, as detailed earlier in this chapter. Increased temperatures 

are expected to be widespread, especially at lower elevations where some species 

Increased frequency 

of wildfire and annual 

area burned are a near 

certainty in the Blue 

Mountains region.
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GENERAL TECHNICAL REPORT PNW-GTR-939

may already be at the limit of their thermal tolerance during the summer. Considerable variation exists in thermal regimes as a function of water sources (Ebersole 

et al. 2003, 2015; Fullerton et al. 2015), topography, aspect, and other factors, 

influencing where and how management actions might be implemented to reduce 

deleterious effects.

Maintaining and restoring natural thermal conditions will be the most effective 

strategy for buffering future increases in stream temperatures (table 5.7c). It will be 

especially important to increase connectivity within stream networks, so aquatic 

organisms can have year-round access to cold water, especially during stressful 

summer periods. An effective, climate-smart approach to managing for cold-water 

refugia will be possible only if stream temperature regimes are well understood. 

Fortunately, the expanding NorWeST stream temperature network, including in 

the Blue Mountains, is helping to provide a scientific foundation for site-specific 

adaptation tactics.

Increasing resilience of fish populations to higher stream temperature focuses 

primarily on maintaining existing cold-water refugia and improving the condition 

of streams that are vulnerable to increasing air temperature. Riparian function and 

hydrologic processes can be maintained by restoring riparian vegetation to ensure 

that exposure of stream channels to solar radiation is minimized. Increasing floodplain connectivity, diversity, and water storage will improve hyporheic and baseflow conditions. Reducing damage by livestock grazing on riparian vegetation and 

streambanks can result in rapid improvements but may also face opposition from 

those who access national forests for grazing. All of these adaptation tactics will 

be more effective if informed by stream temperature data collection and long-term 

monitoring.

Responding to Changes in Headwater and Intermittent Streams

Headwater and other intermittent streams and water bodies (e.g., springs, ponds) are 

vital for local and seasonal aquatic habitat. Although they may be transient, these 

water sources influence stream temperature and downstream water quantity and 

quality (Ebersole et al. 2015). Intermittent streams will be especially vulnerable to 

the effects of increasing wildfire on sediment pulses and altered flood patterns and 

magnitudes.

As noted above, wildfire-use plans will be needed to proactively reduce the 

effects of increasing fire disturbance and to identify hillslope landslide hazard areas 

and susceptible roads (table 5.7d). Restoring and revegetating burned areas can help 

to store sediment and maintain channel geomorphology following large wildfires, 

and should be informed by prefire assessment of geomorphic hazards, especially 
135

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

areas prone to debris flows. Coordination with resource specialists and programs 

in vegetation, fire, hydrology, geology, and soils will help ensure that multiple 

resources will be protected.

Conclusions

Adapting fisheries to the environmental trends associated with climate change will 

require a diverse portfolio composed of many strategies and tactics as described 

above (table 5.7). Equally important is understanding a new concept of dynamic disequilibrium in which stream habitats will become more variable, undergo gradual 

shifts through time, and sometimes decline in quality. Some fish species and populations will retain enough flexibility to adapt and track their habitats (Eliason et al. 

2011), but others may be overwhelmed by future changes. It may not be possible 

to preserve all populations of all fish species across the Blue Mountains. However, 

as better information continues to be developed, resource managers will be able to 

identify where resource commitments are best made to enhance the resilience of 

fish and fish habitat. As many species and populations adjust their phenologies and 

distributions to track climate change, Forest Service lands will play an increasingly 

important role in providing aquatic habitats. 

Three factors will be especially important for improving and maintaining 

resilience of fish species and aquatic systems to climate change. First, it will be 

critical to restore and maintain natural thermal regimes to minimize increases in 

summer stream temperatures and effects on cold-water species. As noted above, 

many techniques can be used to promote stream shading and narrow unnaturally 

widened channels. Second, a strategic approach is critical for climate-smart fisheries management and restoration during the current period of declining budgets and 

increasing stresses. For example, it is important to identify high-priority culvert 

barriers to fish movements, especially in areas with the potential to provide highquality refugia for cold-water species in the future. These types of tactics need to be 

considered at both the reach and watershed scales. Finally, long-term monitoring is 

the only means by which the effectiveness of climate-smart resource management 

can be determined, thus reducing uncertainties and informing the broader mission 

of sustainable fisheries management. More and higher quality data are needed for 

streamflow (more sites), stream temperature (annual data from sensors maintained 

over many years), and fish distributions. These data will improve status and 

trend descriptions, while also contributing to models that more accurately predict 

responses to climate change and land management.
136

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Chapter 6: Effects of Climatic Variability and Change on 

Upland Vegetation in the Blue Mountains 

Becky K. Kerns, David C. Powell, Sabine Mellmann-Brown, Gunnar Carnwath, and John B. Kim1

Introduction

The Blue Mountains ecoregion (BME) extends from the Ochoco Mountains in 

central Oregon to Hells Canyon of the Snake River in extreme northeastern Oregon 

and adjacent Idaho, and then north to the deeply carved canyons and basalt rimrock 

of southeastern Washington (see fig. 1.1 in chapter 1). The BME consists of a series 

of mountain ranges occurring in a southwest to northeast orientation, allowing the 

BME to function ecologically and floristically as a transverse bridge between the 

Cascade Mountains province to the west, and the main portion of the middle Rocky 

Mountains province to the east. 

Powell2

 defines six vegetation zones within the BME, which range from lowelevation grasslands to high-elevation alpine areas, and Johnson (2004), Johnson 

and Clausnitzer (1995), Johnson and Simon (1987), and Johnson and Swanson 

(2005) described upland plant associations. The lowest elevation plains zone 

contains grasslands and shrublands because moisture is too low to support forests 

except along waterways. The foothills zone is usually dominated by western juniper 

(Juniperus occidentalis Hook.), often with a mixture of curl-leaf mountain-mahogany (Cercocarpus ledifolius Nutt.) and antelope bitterbrush (Purshia tridentata

[Pursh] DC.) shrublands. In the northern Blue Mountains, the foothills zone generally supports tall shrublands (with, for example, western serviceberry [Amelanchier 

alnifolia [Nutt.] Nutt. ex M. Roem.], black hawthorn [Crataegus douglasii Lindl.], 

and western chokecherry [Prunus virginiana var. demissa [Nutt.] Torr.]), rather than 

western juniper, curl-leaf mountain-mahogany, and antelope bitterbrush. Located 

just above the western juniper woodlands is the lower montane zone, which

1 Becky K. Kerns is a research ecologist and John B. Kim is a biological scientist, U.S. 

Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry 

Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; David C. Powell was 

a forest silviculturist, U.S. Department of Agriculture, Forest Service, Umatilla National 

Forest, 72510 Coyote Road, Pendleton, OR 97801; Sabine Mellmann-Brown and Gunnar 

Carnwath are ecologists, U.S. Department of Agriculture, Forest Service, WallowaWhitman National Forest, 1550 Dewey Avenue, P.O. Box 907, Baker City, OR 97814. 

2 Powell, D.C. 2012. Active management of dry forests in the Blue Mountains: silvicultural 

considerations. White Paper F14-SO-WP-Silv-4. Unpublished report. Pendleton, OR: U.S. 

Department of Agriculture, Forest Service, Umatilla National Forest.
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contains dry conifer forests characterized by ponderosa pine (Pinus ponderosa

Lawson & C. Lawson), Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), and 

grand fir (Abies grandis [Douglas ex D. Don] Lindl.). Although some of these 

forests are mixed conifer, many of the warm, dry forests are composed almost 

exclusively of ponderosa pine. 

Warm, dry forests tend to be the most common forest zone in the Blue Mountains, and because they occur at lower and moderate elevations, they have a long 

history of human use both for commodity purposes (e.g., livestock grazing) and as 

an area where effective fire exclusion occurred and led to well-documented changes 

in species composition, forest structure, and stand density. The upper montane 

zone includes moist forests characterized by Douglas-fir, grand fir, and subalpine 

fir (A. lasiocarpa [Hook.] Nutt.). The upper montane zone may be very narrow or 

nonexistent in the southern portion of the Blue Mountains. High elevations support 

a subalpine zone with Engelmann spruce (Picea engelmannii Parry ex Engelm.), 

subalpine fir, and whitebark pine (Pinus albicaulis Engelm.) or an alpine zone near 

mountain summits where trees are absent. Subalpine and alpine environments 

are mostly confined to the high ridges of the Strawberry Mountains, the Elkhorn 

Crest, the Wallowa Mountains, and the Seven Devils in eastern Oregon and western 

Idaho. 

This chapter assesses potential climate change effects on upland vegetation in 

the BME using information from the literature and output from simulation models. 

The focus is on the BME in general, but emphasis is placed on the Malheur, Umatilla, and Wallowa-Whitman National Forests (see fig. 1.1 in chapter 1). First, we 

review information sources that were used as the basis of this assessment. Then we 

present the vegetation assessment, which is organized around an established vegetation classification system, followed by a brief conclusion.

Understanding Climate Change Effects 

Climate change is expected to profoundly alter vegetation structure and composition, terrestrial ecosystem processes, and the delivery of important ecosystem 

services over the next century. Climate influences the spatial distribution of major 

vegetation biomes, the abundance of species and communities within biomes, biotic 

interactions, and the geographic ranges of individual species. Climate also influences the rates at which terrestrial ecosystems process water, carbon, and nutrients 

and deliver ecosystem services like fresh water, food, and biomass. Finally climate 

influences disturbance processes that shape vegetation structure and composition, and altered disturbance regimes will likely be the most important catalyst for 

vegetation change (box 6.1). Climate-induced vegetation changes have important 

Altered disturbance 

regimes will likely be 

the most important 

catalyst for vegetation 

change.
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Box 6.1—Ecological Disturbance and Climate 

Change

Ecological disturbances include fires, floods, windstorms, and insect outbreaks, 

as well as human-caused disturbances such as forest clearing and the introduction 

of nonnative species. Disturbances are part of the ecological history of most forest 

ecosystems, influencing vegetation age and structure, plant species composition, productivity, carbon storage, water yield, nutrient retention, and wildlife habitat. Natural 

disturbances, which are influenced by climate, weather, predisturbance vegetation 

conditions, and location, can have profound and immediate effects on ecosystems 

across large spatial and temporal scales. 

Climate (and weather at a shorter time scale) influences the timing, frequency, 

and magnitude of disturbances in any particular location. For example, a 1-year 

drought may not have significant direct effects on a forest, but it can reduce tree 

resistance to insect attack and can desiccate living and dead vegetation sufficiently to 

increase fire hazard. As climate continues to warm during the 21st century, the most 

rapidly visible and significant short-term effects will be caused by altered disturbance, often occurring with increased frequency and severity. Increased disturbance 

will be facilitated by more frequent extreme droughts, amplifying conditions that 

favor wildfire, insect outbreaks, and invasive species (Adams et al. 2010, Allen et 

al. 2009, Anderegg et al. 2012). The type and magnitude of disturbances will differ 

regionally and will pose significant challenges for resource managers to mitigate 

damage to resource values and transition systems into new disturbance regimes. 

A warmer climate will cause an increase in the frequency and extent of wildfire 

in most dry forest and shrubland ecosystems (e.g., Westerling et al. 2006, 2011). By 

around 2050, the annual area burned in most of the Western United States is projected 

to be at least two to three times higher than it is today (Littell et al. 2010; Littell, n.d. 

cited in Ojima et al. 2014; McKenzie et al. 2004). The Blue Mountains ecoprovince 

is also expected to experience increased area burn by the mid 21st century (fig. 6.1). 

Recent research shows that the occurrence of large fires in the Western United States 

has increased since around 1980 (Dennison et al. 2014). Many dry forests that have 

not burned for several decades have high fuel accumulations, and initial fires may 

cause uncharacteristic tree mortality compared to low levels of mature tree mortality 

associated with historical surface-fire regime. If these areas recover as forested ecosystems, recurrent fires (if allowed to burn, and are not suppressed) may more closely 

resemble the frequency characteristic of presettlement, low-severity fire regimes. 

However, in the driest portions of the Blue Mountains, it is possible that these 

areas will not recover to forested conditions, and uncharacteristic fires combined 

with climatic warming could initiate a transition to shrub- or herb-dominated 

ecosystems.

Critical thresholds in ecosystem structure and function may be exceeded in a 

warmer climate. Warmer temperatures may increase the potential for insect and 

disease outbreaks, particularly as a transient response in colder temperate zones 

where insect and pathogen vigor has been limited by suboptimal temperatures (Bentz 

et al. 2010). Higher warm-season temperatures should also increase growth rates for 

temperate insect herbivores, although the rate of increase will vary by species (Bale 

et al. 2002). For some species, faster growth rates and reduced development time 

could enhance juvenile survivorship by reducing predation rates during the larval and 

nymphal feeding stages (Bernays 1997, cited by Bale et al. 2002). Increased growth 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 6.1—Projected increase in area burn by wildfire as associated with a mean annual temperature increase of 1 °C, shown as the percentage change relative to the median annual area burned during 1950–2003 (Littell, n.d. cited in Ojima et al. [2014]). Results are aggregated to ecoprovinces of the Western United States based on Bailey (1995).

Box 6.1 (continued)
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.1 (continued)

rates could reduce generation times for some species, which could significantly 

increase population growth rates (Bale et al. 2002, Mitton and Ferrenberg 2012). 

Increasing population success increases the potential for insect outbreaks to develop, 

although outbreaks can be limited by host and predator constraints as well (Bale et 

al. 2002, Boone et al. 2011). Increasing temperatures may also facilitate migration of 

insects and diseases toward higher elevations and latitudes (Bale et al. 2002, Bentz 

et al. 2010). Similarly, species ranges could contract at lower elevations and latitudes 

if warm-season temperatures exceed tolerance levels during the juvenile (or other) 

growth stages (Bale et al. 2002). Depending on the future scenario, some research 

indicates that western spruce budworm (Christoneura occidentalis Freeman) defoliation in Oregon would decrease under climate change scenarios that do not have an 

increase in both temperature and precipitation (Williams and Liebhold 1995). Warmer 

temperatures could also increase host stress levels and the ability to defend against 

insect attacks (Boone et al. 2011).

The recent proliferation of mountain pine beetles (Dendroctonus ponderosae

Hopkins, 1902) in lodgepole pine forests in western North America is a good example 

of how a warmer climate can propagate widespread disturbance (Bentz et al. 2009, 

Kurz et al. 2008, Raffia et al. 2008). Mountain pine beetles have affected 36 

million ha of forests in the Western United States and British Columbia over 

the last two decades, largely as a consequence of increasing temperatures in mostly 

older, low-vigor forests. Both wildfire and insect outbreaks can rapidly “clear the 

slate” in landscapes, initiating a regeneration phase in which species will compete, 

allowing for a potential change in dominant species. A rapid change in dominant 

vegetation suggests that a threshold has been crossed, at least temporarily, and that 

new conditions established in a warming climate may be difficult to reverse. Higher 

atmospheric carbon dioxide levels could reduce insect impacts by increasing carbon 

availability for defenses in plants and reducing substrate quality in host plants (Stiling 

and Cornelissen 2007). However, the inhibitory effects of increasing carbon dioxide 

concentrations may be offset by the stimulatory effects of warmer temperatures on 

insect activity (Zvereva and Kozlov 2006).

Interacting disturbances and other stressors, termed stress complexes, are a 

normal component of forest ecosystems, affecting species composition, structure, 

and function. Altering one particular factor can potentially magnify the effects of 

other stressors, leading to a rapid and possibly long-lasting change in forest ecosystems. The effects of disturbance across large geographic areas are especially pronounced where forest regeneration is slow or delayed, leading to a potential change 

in dominant vegetation. A warmer climate is expected to alter and often exacerbate 

the effects of stress complexes (McKenzie et al. 2009). To examine the intersection 

of multiple stressors that affect Oregon and Washington, Kerns et al. (n.d.) examined 

spatial data regarding wildfire potential, insect and disease risk, projected urban and 

exurban development, and a warmer climate. They mapped where these stressors 

occur in concentrated places on the landscape and where they occur in combination 

(Kline et al. 2013) (fig. 6.2). For the Blue Mountains, insect and disease risk is the 

most spatially extensive stressor.

Forest resource managers are tasked with assessing the risk of disturbances and 

opportunities for mitigation. Most federal lands have fire management plans that 

describe current fuel conditions, potential fire occurrence, likely effects of wildfire,
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 6.2—Results from a neighborhood analysis for concentrated exposure across Oregon and Washington to four stressors and their combinations.

Box 6.1 (continued)
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.1 (continued)

fire suppression strategies, and often postfire activities designed to reduce secondary damage such as erosion. Similarly, plans assessing the management of insects 

and nonnative plants evaluate the risk of their occurrence as the basis for developing 

appropriate responses. In some cases, the effectiveness of predisturbance and postdisturbance actions may be limited. For example, many nonnative species are 

so well established that it is not feasible to remove them from a particular location; 

therefore, prevention or rapid response is usually the best approach. Following large, 

intense wildfires, it may be impractical and expensive to install erosion control across 

a mountainous landscape with minimal access. Active management on certain public 

lands—wilderness, riparian habitat conservation areas, designated old growth, lands 

with endangered species—may be severely restricted owing to regulations or lack of 

social license, thus limiting mitigation of known risks. 

Disturbances, which have always been a dominant influence on the dynamics of 

forest ecosystems in western North America, will be even more important if climate 

change leads to increased frequency and magnitude of extreme weather. In most 

cases, it will be advisable to develop strategies that allow us to live with increasing 

disturbance and stress in forests, especially as the climate continues to warm. Active 

management and planning in anticipation of these changing conditions can reduce 

risk and the severity of short- and long-term hazards.

implications for wildlife habitat, biodiversity, hydrology, future disturbance 

regimes, ecosystem services, and the ability of ecosystems to absorb and sequester 

carbon from the atmosphere. 

Several information sources are useful for assessing potential climate change 

impacts on vegetation and future forest composition and structure, including longterm paleoecological records; evidence from climate, carbon dioxide, and other 

experimental and observational studies; and model predictions for the future. We 

use these sources to conduct our assessment of potential effects of climate change 

on vegetation. When different lines of evidence are in conflict, we often rely on 

our ecological and local knowledge and derived logical inference to weigh different lines of evidence. For example, we emphasize the importance of interactions 

between climate change and disturbance, which many agree is likely to be the most 

important driver of change in the next few decades (see box 6.1). However, these 

disturbances are not included in many of the models that we discuss. In addition, 

paleoecological evidence or empirical evidence from highly relevant studies is often 

given greater weight than model output. 

Paleoecological Records

Paleoecology uses data from some form of preserved plant material, or fossils 

and subfossils, to reconstruct vegetation of the past. More recent records (e.g., the 

Holocene or last 11,700 years) are commonly reconstructed by using plant materials 
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GENERAL TECHNICAL REPORT PNW-GTR-939

such as pollen and phytoliths. For example, pollen grains that are washed or blown 

into lakes can accumulate in sediments and provide a record of past vegetation. 

Different types of pollen in lake sediments reflect the vegetation that was present 

around the lake and, therefore, the climate conditions favorable for that vegetation. 

Phytoliths are morphologically distinct silica bodies from plants that can exist in 

soil, sedimentary deposits, or in archaeological material. In addition, much historical vegetation information can be obtained from biological remains in nests and 

middens (waste accumulation) created by several species of birds and small mammals, and they may be preserved for thousands of years, providing a detailed fossil 

record of past environmental conditions (Betancourt et al. 1990, Rhode 2001).

Global paleoecological records indicate that during warm periods of the past, 

tree species tended to move poleward and upward in elevation. A species “leading 

edge” is fundamentally important under global change, as it is commonly accepted 

that range expansions depend mostly on populations at the colonization front. The 

leading edge is also seen as controlled by rare long-dispersal events followed by 

exponential population growth (Hampe and Petit 2005). Unfortunately, existing 

environmental reconstructions of the Pacific Northwest are based mostly on pollen 

records obtained from lakes in forested areas west of the Cascade Range, as fewer 

of these sites exist in the the dry interior of the region. However, important insights 

can be derived from the existing literature (Blinnikov 2002, Hansen 1943, Mehringer 1997, Whitlock 1992, Whitlock and Bartlein 1997). In particular, as recent 

glaciation waned during the early Holocene period, a warmer and drier climate 

than today is inferred (Anderson and Davis 1988). Thus, inferred vegetation during the early to mid-Holocene (9,000 to 6,000 BP) is used in this assessment as 

one line of evidence with respect to potential future changes. However, early and 

mid-Holocene conditions may be drier than current projections from global climate 

models (GCMs). 

The rate of future climate change may be faster than any period in the Holocene record (500 to 1,000 years) (Whitlock 1992). Hansen (1943) reports on pollen 

profiles from a peat deposit located at Mud Lake, one of the Anthony Lakes that lie 

near the crest of the Blue Mountains. The site is at 2134 m elevation in a subalpine 

forest. The author reports on a cursory survey of the area surrounding the peat 

deposit: 50 percent lodgepole pine (Pinus contorta Douglas ex Loudon), 25 percent 

alpine fir (assumed to be subalpine fir), and 25 percent Engelmann spruce. Two 

peat cores were removed above a layer of impenetrable ash. Hansen states that they 

probably represent most, if not all, of the post Pleistocene (Holocene), but no radiocarbon dates were obtained. The source of the ash layer is unknown. A rapid gain 

in ponderosa pine pollen roughly mid-profile is one of the more important climate 

Global paleoecological 

records indicate that 

during warm periods of 

the past, tree species 

tended to move 

poleward and upward 

in elevation.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

indicator trends identified, signifying a warmer and drier climate as the influence 

of recent glaciation waned. This trend is consistent with early to mid-Holocene 

warming. A western larch (Larix occidentalis Nutt.) maximum suggests that fire 

slowed this trend, but as fires decreased, ponderosa pine continued to increase, 

again suggesting that warmer and drier conditions prevailed. A general decline in 

whitebark pine from the bottom of the profile to the level of ponderosa pine maximum is substantiating evidence for this climatic trend. Ponderosa pine pollen then 

declines from its peak to proportions that are generally maintained to the surface, 

marking the shift to a cooler and wetter climate (compared to the earlier warm and 

dry period) and present-day conditions. Today, ponderosa pine is not within the 

vicinity of the Anthony Lakes area (it is found at much lower elevations).

Mehringer3 reports on a pollen and macrofossil record from Lost Lake, which 

is located in the Umatilla National Forest on the edge of the Vinegar Hill-Indian 

Rock Scenic Area about 50 km southeast of Dale, Oregon, and only 3 km north of 

the Malheur National Forest border. At 1870 m elevation, the surrounding slopes 

of the lake are within a mixed-conifer forests above the elevation of the ponderosa 

pine zone. Grand fir, Douglas-fir, western larch, and lodgepole pine are common. 

Engelmann spruce is restricted to cold area drainages and moist areas around the 

lake. A 3.8-m core located above the Mazama ash tephra layer was examined, 

thus the record spans the last 7,600 years. The record reveals that lodgepole pine, 

Douglas-fir, and western larch have been the dominant conifers at Lost Lake for the 

past 7,600 years. However, a transition at about 4,000 years BP is noted. Relatively 

more pine, spruce, and fir pollen, and less Douglas-fir and western larch pollen 

are noted at that point in the record. This change is attributed to an increase in 

effective moisture, coinciding with a transition from open woodland conditions 

to closed-canopy forests. Although the author does not specifically discuss midHolocene warming, this change in vegetation conditions probably relates to the end 

of mid-Holocene warming and the development of present-day cooler and wetter 

conditions. This change brought an episode of intense wildfires starting about 3,600 

years BP and concluding around 1,860 years BP; sagebrush pollen is also a more 

important component of the pollen profile 9,000 to 5,600 years BP. 

Whitlock and Bartlein (1997) present a pollen record from Carp Lake, located 

at 714 m elevation in the eastern Cascades. Presently, the site is dominated by 

ponderosa pine. The Carp Lake record indicates the development of a pine-oak 

woodland at 9,000 BP. Blinnikov et al. (2002) presents a phytolith record in loess 

3 Mehringer, P.J., Jr. 1997. Late Holocene fire and forest history from Lost Lake, 

Umatilla National Forest, Blue Mountains, Oregon. Unpublished report. On file with: 

U.S. Department of Agriculture, Forest Service, Malheur National Forest. John Day, OR.
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GENERAL TECHNICAL REPORT PNW-GTR-939

from four different sites in the interior Columbia Basin, two of which were located 

in the Blue Mountains, using the Carp Lake record and the phylioth sites to infer 

vegetation in the Columbia Basin during the last 21,000 years (fig. 6.3). 

Climate, Carbon Dioxide, and Other Studies

Dendroecological records (tree rings) from the past several hundred years also 

provide evidence about changes in tree growth with climatic variability. Experimental studies involving altered temperature, water availability, and carbon dioxide 

concentration provide information about how individual species may respond to 

climate change. Observational studies regarding response of species to current 

warming trends also provide clues to potential future responses of vegetation to 

climate. For example, van Mantgem et al. (2009) note that unmanaged old forests in 

the Western United States showed that background mortality rates have increased 

in recent decades. Increases occurred across elevations, tree sizes, dominant genera, 

and past fire histories, and the authors attributed elevated mortality to regional 

warming and consequent increases in water deficits. 

Much of the evidence from climate, carbon dioxide, and other studies cited 

in this chapter is covered in greater detail in Peterson et al. (2014), which documents that climatic warming during the 20th century has led to a variety of plant 

responses, including altered phenology and geographic distributions of species 

(Crimmins et al. 2011, Kullman 2002, Parmesan 2006, Walther et al. 2005, 2012). 

Results from these types of studies are more appropriately discussed within the 

relevant vegetation type in the assessment section below. 

Model Output

Many vegetation models have the ability to simulate the effects of climate change on 

vegetation, including altered productivity, distribution shifts, and disturbance regimes. 

These climate-aware vegetation models can be divided into three classes: species 

distribution (also called empirical, correlative, statistical, bioclimatic envelope, or 

niche), process based (also called mechanistic), and landscape (Littell et al. 2011).

Species distribution models (SDMs) use historical correlations of climate and 

historical species distributions to develop relationships and then project future suitable habitat under climate change scenarios (Hamann and Wang 2006, Iverson et al. 

2008, Kerns et al. 2009, McKenzie et al. 2003a). These models are typically species 

specific. Model output is not the actual species range or habitat, although it is often 

presented as such; it is simply the climate and or environmental conditions that are 

correlated with the species historical presence or abundance. Many types of statistical relationships and approaches are used to make projections about the future (i.e., 

generalized linear models, machine learning, maximum entropy). 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.3—Inferred vegetation in the Columbia Basin during the last 21,000 years based on the pollen record at 

Carp Lake and phytoliths in four loess sections in the Columbia Basin. Figure from Blinnikov et al. 2002.
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Process models can be species specific, such as forest gap models (Bugmann 

2001), or they can simulate groups of species with similar form and function in 

ecosystems (plant functional types), including dynamic global vegetation models 

(DGVMs) (Prentice et al. 2007). Although some dismiss this class of model because 

it does not include species-specific information (Morin and Thuiller 2009), relevant 

information can be inferred from these models, including regionally specific and 

biome-scale information from projections based on plant functional types. Moreover, information at multiple taxonomic levels (e.g., species vs. vegetation type) 

about how climate might affect vegetation change, and the difference between 

projections and their sources, are themselves useful tools with which to assess 

uncertainty (Littell et al. 2011). Process models are parameterized from theoretical 

or experimental, and observational information; they project the response of an 

individual or a population to environmental conditions by explicitly incorporating 

biological processes (Bachelet et al. 2001, Bugmann 2001, Campbell et al. 2009, 

Cramer et al. 2001, Morin and Thuiller 2009). Some operate by using average 

climate while others use transient climate data. Vegetation or other output by the 

models is an “emergent property” in relation to key model input information (e.g., 

climate, soils, carbon dioxide emissions). Some argue that process models may be 

more robust at projecting the future given their basis in known mechanisms and 

their theoretical capability to extrapolate into nonanalog conditions (Coops and 

Waring 2011a, Thuiller 2007). 

Landscape models expand either of the first two types to explicitly simulate 

landscape change and ecological processes such as succession and fire. The models 

are often spatial but may be distributional (Baker 1989, Cushman et al. 2007), such 

as nonspatial state-and-transition simulation models (Kerns et al. 2012). These models are well suited to simulations of the effects of disturbance on vegetation, which 

can be a major limitation for some of the empirical and process models. They can 

use climate information as inputs, but climate is not always explicitly incorporated 

into landscape models (Littell et al. 2011).

Despite the specific strengths and weaknesses of different modeling 

approaches, there are caveats specific to all vegetation models. For example, most of 

the models do not deal with inertia (the tendency of vegetation to remain unchanged 

through various mechanisms) in vegetation, although some landscape models have 

the capacity to deal with inertia if they are parameterized to include climate change 

(Halofsky et al. 2013). Most of the models also do not incorporate disturbance 

processes, although MC2, a DGVM, does address fire (box 6.1). The inclusion of 

disturbance and extreme events in most models is still early in the developmental 

process (Keane et al. 2004, Lenihan et al. 1998, Thonicke et al. 2001). 

The inclusion of 

disturbance and 

extreme events in most 

models is still early 

in the developmental 

process.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Most models do not consider biotic interactions (although some process models 

do consider competition) and phenotypic plasticity (box 6.2), and no models deal 

with dispersal or genetic adaptation. A new generation of models incorporating 

climatic variability with many of these important processes is clearly needed. In 

addition, many models are used without being methodically calibrated and without 

careful validation of model skill or sensitivity analysis, such that model uncertainty 

is not understood. For all models, if future conditions differ greatly from conditions 

used to build and calibrate a model, then accuracy for projecting ecological phenomena will be relatively low (Williams et al. 2007). 

Multiple projections using different vegetation models can be used to assess a 

range of potential changes in climate habitat and implications for changes in species 

distribution under future climate scenarios. We assess vegetation model projections for the end of the 21st century for the BME using different types of vegetation 

models. Our goal is to summarize and discuss agreement or disagreement in the 

models regarding general trends relating to potential changes in climate habitat 

for vegetation, and implications of the changes for future vegetation distribution. 

Although climate change projections simulated by more than 20 different GCMs 

have been available in recent years, most of the models we examined used climate 

data as inputs that were derived from only a small subset of the available GCM 

output. We tried to limit our assessment to common climate projections (GCM and 

greenhouse gas emission scenario combination) among the models, although this 

was not always possible. In addition, we assessed model outputs under only the 

“business as usual” emission scenarios (A2, A1FI, and RCP 8.5), which significantly depart from other scenarios after the mid 21st century (Nakicenovic et al. 

2014, Nakicenovic and Swart 2000).

We selected species-specific model output from websites and peer-reviewed 

literature supporting the model output (table 6.1). We also used the MC2 model, 

a new version of MC1 rewritten for improved computational efficiency.4

 MC2

simulates response of plant functional types to climate change at a monthly type 

step, including plant physiology, biogeography, water relations, and interactions 

with fire. We selected four GCM outputs published by Coupled Model Intercomparison Project Phase 5 (CMIP5) for the RCP8.5 greenhouse gas emissions scenario 

using impact-relevant sensitivities as a guide (Vano et al.).5 The four selected 

4

 Kim, J.B.; Conklin, D. [N.d.]. MC2 Dynamic Global Vegetation Model: improvements 

in model structure and computational efficiency. Manuscript in prepartion. On file with: 

J. Kim, U.S. Department of Agriculture, Pacific Northwest Research Station, 3200 SW 

Jefferson Way, Corvallis, OR 97331.

5

 Vano, J.A.; Rupp, D.E.; Kim, J.B.; Mote, P.W. [N.d.]. Selecting climate change scenarios 

using impact-relevant sensitivities. Manuscript in prepartion. On file with: J. Kim, Pacific 

Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR 97331.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 6.2—Model limitations: phenotypic plasticity 

and biotic interactions 

Models that predict vegetation responses to climate change, particularly species 

distribution models, are generally unable to account for the effects of several 

important factors such as phenotypic plasticity (Nicotra et al. 2010, Valladares et 

al. 2014) or the outcomes of biotic interactions (Araújo and Peterson 2012). However, 

it is well-established that biotic interactions can profoundly influence how plants 

respond to changing environmental conditions (Tylianakis et al. 2008), and that 

competition will play moderate species distribution patterns and responses to climate 

change (Brooker 2006). Moreover, long-lived organisms, such as trees can substantially modify their ability to tolerate stress or acquire resources as a consequence of 

plastic responses to external environmental conditions experienced in their lifetimes. 

This often results in significant differences in phenotypes among individuals, resulting in individualistic responses to environmental change (Nicotra et al. 2010, Richter 

et al. 2012). Therefore, assessing the effects of climate change on vegetation requires 

understanding (1) how climate affects species distributions across landscapes, (2) how 

these relationships are modified by biotic interactions and expressions of phenotypic 

plasticity (Araújo and Guisan 2006), and (3) how management actions influence 

resilience and adaptive capacity of forest ecosystems (Choi 2007).

Phenotypic plasticity refers to the range of functional traits that can be 

expressed by a particular genotype or individual plant in response to the 

environment. Traits that can vary in response to the environment include plant 

physiological processes (e.g., respiration rates, growth phenology), morphology (e.g., 

height, allocation to roots), and reproduction (e.g., method, timing) (Peterson et al. 

2014). However, costly tradeoffs make plasticity less common than one might expect, 

given the apparent benefits to individuals and populations (Peterson et al. 2014). If 

plasticity cannot allow plants to adjust to changing environmental conditions, genetic 

adaptation or migration may be required to maintain species viability.

Phenotypic plasticity allows plants to adjust to seasonal changes in climate and 

longer term climatic variability, and helps avoid extreme vegetation responses to 

typical (historical) climatic variability. The ability to persist as a juvenile (advance 

regeneration) facilitates rapid response to increased resource availability following 

disturbance (or a favorable period of climate), whereas the ability to persist as an 

adult provides a continuing opportunity to reproduce during favorable periods of 

climate (Peterson et al. 2014). High phenotypic plasticity may be associated with ecological generalists and benefit plants as the climate changes, because high plasticity 

allows a single genotype to occupy different environments (Matesanz et al. 2010). 

Phenotypic plasticity can help plants become established and persist under low 

resource availability caused by climatic variability, biotic interactions, and management actions. Unlike most short-lived species, trees can modify their stress tolerance 

or acquire resources in response to environmental conditions, resulting in individualistic responses to environmental change. For example, the effects of long-term 

adaptations to water stress (changes in carbon allocation and hydraulic architecture) 

may influence the ability to cope with environmental variability. Altering water relations by shifting biomass allocation from leaves to woody tissue is an adaptive 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.2 (continued)

response of trees exposed to increased warming and drying (Cregg 1994, Parmesan 

2006, Zwiazek and Blake 1989).

Competition and stand dynamics affect plant communities and vegetation dynamics (Connell and Slatyer 1977, Grime 1979, Tilman 1982). Assessing the relationship 

between competition and climate sensitivity for mature trees requires information on 

the proximate effects of neighbors on resource availability and understanding how 

expressions of phenotypic plasticity and long-term adaptations to competitive stress 

may influence the ability to cope with environmental variability (Barnard et al. 2011, 

Woods 2008). At a local scale, stand density and structure, which can be modified 

through silvicultural treatments, can affect environmental conditions and create sharp 

gradients in factors that regulate tree growth (light, water, temperature) (Aussenac 

2000, Zhu et al. 2000). As a result, trees growing with high competition or in subdominant canopy positions are consistently exposed to different environmental conditions 

that affect morphological and physiological characteristics, including a lower ratio 

of leaf area to sapwood area (McDowell et al. 2006, Renninger et al. 2007), higher 

shoot-to-root ratio (Newton and Cole 1991), and reduced rooting depths (McMinn 

1963). Trees experiencing high competition have reduced allocation to roots, which 

reduces water available to support transpiring leaves and necessitates large amounts of 

sapwood for water storage. However, these adaptations could also buffer the negative 

effects of stressful years and decrease drought sensitivity. 

Differences in climate sensitivity between dominant and subdominant trees vary 

significantly among species depending on life history traits. In one study, dominant 

ponderosa pines were nearly twice as sensitive to high temperatures as ponderosa 

pines (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) growing in subdominant 

canopy positions, but sensitivity of Douglas-fir did not vary across canopy classes 

(Carnwath et al. 2012). The contrasting effects of canopy position on temperature 

responses of these two species likely reflect fundamental differences in their physiology, morphology, and hydraulic conductivity.

Biotic interactions can significantly influence species distributions and community composition at multiple scales (Araújo and Luoto 2007). For example, rising 

carbon dioxide concentrations and changing climate could alter the outcomes of biotic 

interactions if competing individuals or species respond differently to changes in 

the environment. If plants respond differently, the results could lead to increased or 

reduced relative rates of growth and reproduction. Changing climate and carbon dioxide concentrations could also alter the intensity of biotic interactions by increasing or 

reducing overall resource availability. A better understanding of the effects of climate 

on biotic interactions will assist resource managers with implementation of treatments 

that can affect those interactions (silviculture, fuel reduction, etc.). 

Facilitation, or positive interactions in community structure, is not as well 

understood as competition (Brooker et al. 2008, Callaway 1995, Callaway and Walker 

1997). Plants often rely on beneficial biotic interactions for initial establishment (e.g., 

nurse plants or logs, mycorrhizal infection), pollination, seed dispersal, and protection 

from herbivores. They also respond to or defend against detrimental biotic interactions 

such as competition for limited resources, herbivory, and seed predation. Positive
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GENERAL TECHNICAL REPORT PNW-GTR-939

 Box 6.2 (continued)

interactions can occur in all types of conditions but appear to be most important in 

stressful environments, like alpine, semiarid, and arid ecosystems (Callaway 1995, 

Callaway et al. 2002). 

Large trees and shrubs can facilitate establishment and persistence of understory 

plants (including tree seedlings) by modifying the microclimate (e.g., shading) and 

availability of soil nutrients and water (McPherson 1997, Scholes and Archer 1997). 

For example, it has been demonstrated that sagebrush (Artemisia spp.) can increase 

water availability near the soil surface by transporting water from deeper layers at 

night via “hydraulic lift” (Caldwell et al. 1998, Caldwell and Richards 1989, Richards 

and Caldwell 1987), but this may also benefit invasive species such as cheatgrass 

(Bromus tectorum L.) (Griffith 2010). Subalpine conifers can reduce snowpack 

duration and increase growing season length, thereby facilitating establishment of 

herbaceous plants and tree seedlings (Brooke et al. 1970), or can increase local soil 

moisture by altering windflow patterns and enhancing local snow deposition (Holtmeier and Broll 2005).
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 6.1—Summary of species-specific model output and scenarios examinedaModel name Scenario/GCM

End of century Citation Link

3-PG (hybrid) A2

CGCM2

2080 Coops and Waring (2011b) http://www.pnwspecieschange.info/index.html

ForeCASTS A1(A1FI)

HADCM3 no elevation

2100 Hargrove and Hoffman (2005) http://www.geobabble.org/~hnw/global/treeranges3/ 

climate_change/atlas.html

Plant hardiness HADGEM and 

Composite-AR5

2170–2100 McKenney et al. (2011) http://planthardiness.gc.ca/ph_futurehabitat.pl?lang=en

Plant species and climate 

profile projections

A2/CGCM3 and 

A2/Hadley

2090 Rehfeldt et al. (2006) http://forest.moscowfsl.wsu.edu/climate/species/index.php

a CGCM and Hadley were the common global climate models (GCMs) among the output available
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GENERAL TECHNICAL REPORT PNW-GTR-939

GCM outputs—CSIRO-MK360, HADGEM2-ES, MRI-CGCM3, and NORESM1-M—

were selected based on their performance ranking and climate representation. 

We avoided poorly performing models based on Rupp et al. (2013), then selected 

models that represented the ensemble or multimodel mean for the hottest, coolest, 

and wettest projections of all 30 available projections, respectively (fig. 6.4). The 

selected GCM outputs were downscaled to 30 arc-second spatial resolution using 

the delta method (Fowler et al. 2007) for model input. MC2 was calibrated for the 

historical period (1895–2009) using a hierarchical approach, using PRISM climate 

data (Daly et al. 2008) as input.6 We used MODIS net primary productivity data 

(Zhao and Running 2010), an internally generated potential vegetation type map, 

and fire-return interval data from LANDFIRE (Rollins 2009) as reference data sets 

for calibration. Future vegetation conditions were simulated for 2010–2100 using 

the four downscaled GCM data as input; output variables included vegetation type, 

carbon fluxes and stocks, and fire occurrence and effect.

Table 6.2 lists each species examined (from the species-specific models) and an 

overall summary of the model output. Projections indicate some loss to complete 

loss of habitat for most species. Specific model results are discussed in the vegetation assessment section below. The results in table 6.2 are typical for SDMs, showing large reductions in available climate habitat for many species. The SDMs often 

produce projections with dramatic reductions in suitable habitat for a species simply 

because future novel climates do not correspond to modern conditions under which 

the species occurs. Climate change is expected to result in substantial areas that 

have novel climates with no modern analog (“novel climates,” Williams and Jackson 2007, Williams et al. 2007). This may be especially true of the Western United 

States where almost half the land area may have novel climatic conditions by the 

end of the century (Rehfeldt et al. 2006). Furthermore, as models of modern realized niches increase in complexity (more climatic predictors and interactions), the 

less likely they are to project that species will exist under future climate scenarios. 

In some cases, a novel climate could be quite favorable for a species (e.g., Kerns 

et al. 2009). As a result, novel climates often create a bias in SDM projections 

toward reduced area for most species under future climate, without identifying 

which species would replace them. Thus, the projected complete loss of habitat 

of species may simply illustrate the widespread nature of novel future climate 

conditions in the BME. Some species have relatively broad ecological amplitudes 

6

 Kim, J.B.; Conklin, D.; Kerns, B.K. [N.d.]. A hierarchical approach to calibrating MC2 

Dynamic Global Vegetation Model. Manuscript in prepartion. On file with: J. Kim, U.S. 

Department of Agriculture, Pacific Northwest Research Station, 3200 SW Jefferson Way, 

Corvallis, OR 97331.

Climate change is 

expected to result in 

substantial areas that 

have novel climates 

with no modern analog.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.4—Projected annual change in precipitation and temperature compared to average annual 

historical Pacific Northwest climate for the global climate model (GCM) scenarios used as input to 

the MC2 model. All GCMs were run under Representative Concentration Pathway (RCP) 8.5, and the 

ensemble of all run under RCP 8.5 is shown for comparison. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 6.2—Summary of model projections and vulnerability assessment scores for some 

common upland species in the Blue Mountains 

Potential vegetation 

or species Common name Species model output summary

Vulnerability 

assessment 

scorea

Callitropsis nootkatensis Alaska cedar Complete lossc Elevatedb

Pinus flexilis Limber pine Major to complete lossc Elevatedb

Tsuga mertensiana Mountain hemlock Major to complete loss Elevatedb

Pinus albicaulis Whitebark pine Major to complete loss 74

Abies lasiocarpa Subalpine fir Moderate to complete loss, potential 

refugia in Wallowa Mountains

70

Picea engelmannii Engelmann spruce Moderate to complete loss, potential 

refugia in Wallowa Mountainsc 61

Pinus monticola Western white pine Some loss to major; other models 

show shifts and minor loss

57

Populus tremuloides Quaking aspen Major to complete loss; one model 

showed minor loss

57

Abies grandis Grand fir Some loss to almost complete loss 51

Abies concolor White fir Major to complete lossc 51

Pinus contorta var.

latifolia

Lodgepole pine Moderate to complete loss 43

Pseudotsuga menziesii Douglas-fir Minor to major loss 42

Juniperus occidentalis Western juniper Major to complete lossc 30

Larix occidentalis Western larch Minor loss, shifts to complete loss 32

Pinus ponderosa Ponderosa pine Minor to major loss; one model 

shows minor shift

22

Artemisia tridentata Big sagebrush Complete lossd NA

Cercocarpus ledifolius Curl-leaf mountainmahoganyMajor lossf NA

Purshia tridentata Antelope bitterbrush Complete losse NA

NA = not applicable.

Note: Loss or gain refers to climate habitat, not species range. Species are ordered from the highest vulnerability score to the lowest. 

Model output is summarized from all four models shown in table 6.1 unless otherwise noted.

a

 Based on Table 15 in Devine et al. (2012).

b

 These species were not offically ranked in Devine et al. (2012). However, they are considered to have an elevated vulnerability to 

climate change because they are rare in the Blue Mountains. 

c

 Based on three models. 

d

 Based on one model.

e

 Based on two models.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

(e.g., lodgepole pine, juniper; Miller et al. 2005, Miller and Wigand 1994, Pfister 

and Daubenmire 1975) and may be very competitive in a novel environment. In 

contrast, outputs from MC2 indicate that although some forest types may decrease 

in the future, increases in shrublands and grasslands might be expected (fig. 6.5). 

Agreement among the four simulation outputs is high, especially for the arid 

portions of the ecoregion (fig. 6.6). The northern portion of the Umatilla National 

Forest has considerable uncertainty in MC2 projections. 

Effects of Climate Change on Vegetation

To structure the vegetation assessment and development of adaptation options, we 

used the potential natural vegetation (PNV) concept and an existing vegetation 

classification scheme. Potential natural vegetation is defined as the plant community that would establish under existing environmental conditions in the absence of 

disturbance and without interference by humans (Chiarucci et al. 2010, Cook 1996). 

The PNV implies that over the course of time, similar types of plant communities 

will develop on similar sites, thus a potential plant association is an indicator of a 

particular biophysical condition or setting of a site. 

The PNV concept has been debated in the literature (e.g., Chiarucci et al. 

2010, Jackson 2013), and climate change effects on vegetation will probably not be 

consistent with the PNV concept. Paleoecological evidence suggests that species 

responses to climate are individualistic and no-analog plant communities should 

be expected in response to future climate change. Nevertheless, similar biophysical 

settings that support broad potential vegetation types will still exist in the future 

and occupy similar habitat types, but it is likely these habitat types will be redistributed across the landscape. For example, it is likely that some form of upland shrublands, grasslands, and dry forest types will exist in the future, although the species 

that make up these groups could be quite different. 

The PNV concept is still useful for discussing changes in future vegetation, 

and U.S. Forest Service management is largely based on publications, classification 

systems, and models that rely on PNV. We used potential vegetation groups (PVGs; 

Powell et al. 2007), a mid-scale hierarchy system typically used for planning and 

strategic assessments at large spatial scales. These PVGs are similar to the potential 

plant functional types used for global biome vegetation modeling (e.g., Prentice et 

al. 1992), and they crosswalk reasonably well to MC2 output and potential vegetation functional types (table 6.3). Although these broad vegetation groups may exist 

in the future as representations of biophysical settings, the species that comprise 

them at fine spatial scales may differ greatly. 

Although some forest 

types may decrease in 

the future, increases 

in shrublands and 

grasslands might be 

expected.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 6.5—Projected changes in potential vegetation functional types for the end of the 21st century. Data are based on output from the MC2 model and four 

future climate scenarios (see inset box). Historical data were generated from simulated MC2 data and may be different than other potential vegetation maps.
171

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 6.6—Number of projections resulting in vegetation type shift by the MC2 model from the historical period (1979–2008) to the late 21st century (2071–2100). The modeled ecoregion boundary is slightly different than the U.S. Environmental Protection Agency Level II Ecoregion (shown by the heavy black line).
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 6.3—Summary of the upland potential vegetation groups (PVGs) used in this chapter, and the 

crosswalk between these PVGs and MC2 potential vegetation functional types

PVG Typical species MC2 potential vegetation functional type

Cold Upland Forest Subalpine fir, Engelmann spruce, lodgepole 

pine, whitebark pine

Subalpine forest

Cold Upland Shrub Mountain big sagebrush, Sitka alder, shrubby 

cinquefoil

NA

Cold Upland Herb Greenleaf fescue, Idaho fescue, forbs, sedges NA

Dry Upland Forest Ponderosa pine, grand fir, or Douglas-fir Temperate and dry temperate needleleaf 

forest 

Dry Upland Herb Bluebunch wheatgrass and Sandberg bluegrass Temperate (C3) grassland

Dry Upland Woodland Western juniper, mountain big sagebrush, curlleaf mountain-mahoganyTemperate needleleaf woodland

Dry Upland Shrub Low, scabland, and threetip sagebrush Temperate (C3) shrubland

Moist Upland Forest Subalpine fir, grand fir, Douglas-fir, lodgepole 

pine, western larch

Moist temperate needleleaf forest

Moist Upland Woodland Western juniper, bluebunch wheatgrass, low and 

scabland sagebrush

Temperate needleleaf woodland

Moist Upland Shrub Mountain big sagebrush, antelope bitterbrush, 

snowberries, bitter cherry

Temperate (C3) shrubland

Moist Upland Herb Idaho fescue, bluebunch wheatgrass Temperate (C3) grassland

NA = not applicable.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

National forests in the Blue Mountains differ in their distribution of upland 

PVGs (table 6.4; figs. 6.7 through 6.9). Malheur National Forest uplands are dominated by the Dry Upland Forest (UF) PVG, and includes some Cold UF and moist 

forests. Umatilla National Forest uplands are dominated by Moist, Dry and Cold 

UF PVGs, a large amount of moist forest, and a considerable amount of Dry upland 

herbland. Wallowa-Whitman National Forest uplands are dominated by Dry, Cold, 

and Moist UF PVGs, with more Cold UFs than the other two Blue Mountains 

national forests. 

To aid our assessment, we also used Potential Soil Drought Stress maps developed by the U.S. Forest Service Pacific Northwest Region (Ringo et al.7

) (box 6.3). 

The following information, organized by PVG, was evaluated by workshop attendees to create the final assessment worksheets.

Cold Upland Forest

Cold UFs occur at moderate or high elevations in the subalpine zone, characterized 

by cold, wet winters, and mild, relatively cool and dry summers. Deep, persistent 

winter snowpacks are common, although the depth and persistence of winter snowpacks have been declining since the 1950s in response to climate change (Furniss 

et al. 2010, Karl et al. 2009, Stewart et al. 2004). Cold UFs have relatively short 

growing seasons, low air and soil temperatures, and slow nutrient cycling rates.

Late-seral stands are typically dominated by subalpine fir, grand fir, Engelmann spruce, whitebark pine, and lodgepole pine, but whitebark pine, lodgepole 

pine, and western larch are often persistent, early-seral species. Whitebark pine will 

successfully dominate late-seral stands at timberline, on low-moisture soils and 

southern exposures. Cold UFs are adjoined by a treeless alpine zone at their upper 

edge (often separated by a narrow zone of dwarf or krummholz trees), and by Moist 

UFs at their lower edge.

The Cold UF PVG consists of three plant association groups (PAGs), two in the 

cold temperature regime (Cold Moist and Cold Dry) and one in the cool temperature regime (Cool Dry). The Cold Dry UF PAG is the most widespread member of 

the Cold UF PVG and includes the more xeric of the high-elevation forested communities. Cold Dry UF plant associations occur on all aspects and many different 

substrates, often on sites with moderate to high impact from wind scour and, at 

lower elevation, in cold air pockets and drainages.

7

 Ringo, C.; Bennett, K.; Noller, J. [N.d.]. Climate change vulnerability assessment: 

resources for national forests and grasslands in the Pacific Northwest. Soil drought index. 

Unpublished report. On file with: Oregon State University, Department of Crop and Soil 

Science, 3017 Agricultural and Life Sciences Building, Corvallis, OR 97331.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 6.4—The distribution of upland potential vegetation groups (PVGs) 

among the three Blue Mountains Forestsa

Potential vegetation group

Malheur 

National Forest

Umatilla 

National Forest

WallowaWhitman 

National Forest

Percent

Cold Upland Forest 11 12 18

Cold Upland Shrub <1 1 1

Cold Upland Herb <1 1 4

Dry Upland Forest 70 29 32

Dry Upland Woodland <1 <1 <1

Dry Upland Shrub 6 1 2

Dry Upland Herb 3 11 13

Moist Upland Forest 5 38 10

Moist Upland Woodland 3 2 <1

Moist Upland Shrub <1 2 1

Moist Upland Herb <1 3 2

a Data are based on maps and boundaries shown in figures 6.12 through 6.14. Percentages do not add up to 

100 because other PVGs (e.g., riparian areas) are not included.
175

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 6.7—Potential vegetation groups (PVGs) for the Malheur National Forest (NF). Forest boundaries are proclaimed, and PVG data from small inholdings were removed. UF = Upland Forest, US = Upland Shrub, UH = Upland Herb, UW = Upland Woodland.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 6.8—Potential vegetation groups (PVGs) for the Umatilla National Forest (NF). Forest boundaries are proclaimed, and PVG data from small inholdings were removed. UF = Upland Forest, US = Upland Shrub, UH = Upland Herb, UW = Upland Woodland.
177

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 6.9—Potential vegetation groups (PVGs) for the Wallowa-Whitman National Forest (NF). Forest boundaries are proclaimed, and PVG data from small inholdings were removed. UF = Upland Forest, US = Upland Shrub, UH = Upland Herb, UW = Upland Woodland. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 6.3—Soil drought in forests of the Blue 

Mountains

One of the most important mechanisms by which climate change can influence 

vegetation composition and dynamics is through its effects on soil water availability, 

water uptake by plants, and evapotranspiration (Peterson et al. 2014). Soil water 

availability depends on precipitation inputs (form, amount, intensity, and seasonality), surface and subsurface water movement, evaporative demand, and vegetation 

structure and composition. Evapotranspiration is driven primarily by temperature and 

humidity, but can be constrained by reductions in stomatal conductance or reduced 

water uptake owing to low soil water availability. Peterson et al. (2014) reviewed the 

likely effects of projected changes in annual and seasonal mean temperature and 

precipitation on important components of the hydrologic cycle, including the fraction 

of winter precipitation received as snowfall, snowpack water storage, snowmelt rates, 

evapotranspiration, and soil water availability.

By examining soil indices related to drought throughout the Blue Mountains, 

land managers can potentially identify areas with drought-prone soils, although the 

relationship between low soil moisture in soils and vegetation vulnerability may not 

be straightforward. For example, soil parent materials that differ widely in texture 

may have little effect on mortality of trees and shrubs (Koepke et al. 2010). In addition, some experimental studies have shown that conifers preconditioned by exposure 

to water stress can actually have higher survival rates and improved water relations 

during subsequent drought events (Cregg 1994, Zwiazek and Blake 1989). Therefore, 

the existence of drought-prone soils may not necessarily imply vulnerability. 

We examined the Potential Soil Drought Stress (PSDS) index (under development by U.S. Forest Service Pacific Northwest Region) to assess soil drought stress in 

the Blue Mountains in spring (April, May, June) and summer (July, August, September). The PSDS index ranged from low (1) to high (5) and was developed using 

available water storage, soil, and modeled actual and potential evapotranspiration 

data. Methods are summarized below, based on Ringo et al. (see footnote 7). 

Available water holding capacity (AWHC) is the amount of plant-available water 

that can be held in each inch of soil if that soil is at field capacity (i.e., after free 

drainage of water following a storm has ceased). AWHC was calculated from Natural 

Resources Conservation Service soil surveys in the Soil Survey Geographic Database 

(SSURGO) at a scale of 1:24,000 and U.S. Forest Service Soil Resource Inventories 

(SRIs) at a scale of 1:63,560 where SSURGO was not available. Available water 

storage (AWS) for the entire soil profile was calculated by multiplying the AWHC 

for each inch of soil by the depth of the soil to 59 in or to a root restricting layer or 

bedrock, whichever was shallower. All calculations were for the dominant soil in the 

soil map unit. Data were classified into five AWHC categories from low to high.

Potential evapotranspiration (PET) is an estimate of the evaporation and transpiration that would occur if an adequate supply of moisture were available. Actual 

evapotranspiration (AET) measures the actual loss of moisture from soil and plant 

surfaces, and so the degree to which AET falls below PET may be interpreted as 

an indicator of moisture limitation. Modeled AET and PET data sets were derived 

from the Numerical Terradynamic Simulation Group at the University of Montana 

(http://www.ntsg.umt.edu/project/mod16). In their MODIS Global Evapotranspiration Project, they used remotely sensed land cover, leaf area index, and albedo data 

together with daily meteorological data for air temperature, air pressure, humidity, 

and shortwave radiation to model AET and PET monthly averages for the years 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.3 (continued)

2000–2012. Departure from PET was calculated and classified into one of five 

categories that ranged from low (AET/PET = 0.80 to 1) to high (AET/PET = 0.20 or 

less) (table 6.5). Inaccuracies of this approach include (1) atmospheric interference 

from aerosols and cloud cover, and reflectance from snow creates inaccuracies in the 

reflectance data and derivative products used to create the PET data set; and (2) there 

are some years in which sensors were malfunctioning and data were estimated rather 

than measured.

A map of PSDS index was created by overlaying AET/PET and AWHC data

(table 6.4). If there is little departure from PET (AET/PET is low) then vegetation 

is transpiring at full potential and there is enough moisture to allow this level of 

transpiration, then climatic factors, not soil water storage, limit available moisture 

for plant use. However, the degree to which AWHC or climatic factors are governing 

plant transpiration is not actually known.

As the departure from PET increases (e.g., AET/PET is much less than 1), then 

plant transpiration is below full potential. If AET/PET is extremely low (< 0.20 or 

close to 0), then it follows that all forms of available moisture for plants have largely 

been exhausted. However, the AET/PET spatial data describe average conditions 

across each grid cell and the AWHC data are finer scale. It is possible that even if 

AET/PET is classified as low within a grid as an average, areas that have soils with 

high AWHC within that grid cell may not be as dry as soils that have a lower AWHC. 

This means that although AET/PET may be mapped as extremely low, soils with 

higher AWHC may still have the ability to sustain growth. The PSDS index allows 

the combination of two scales of data (coarser scale AET/PET data and finer scale 

AWHC data) to provide a potentially more refined understanding of plant drought 

stress. 

The PSDS maps are shown for each national forest in the Blue Mountains in 

figures 6.10 through 6.12. The PSDS index has not yet been peer reviewed and relies 

heavily on the accuracy of the SSURGO data at a very fine scale. Additional field 

Table 6.5—Potential soil drought stress index (PSDI) categories derived 

from an overlay of departure from potential transpiration (AET/PET) and 

available water-holding-capacity data

Departure from potential evapotranspiration

Available water 

holding capacity 

(0-150 cm)

Low 

(0.8-1.0)

Medium low 

(0.60-0.80)

Medium 

(0.4-0.6)

Medium high 

(0.2-0.4)

High 

(< 0.20)

High 1 1 2 2 3

Medium high 1 2 3 3 3

Medium 1 2 3 3 4

Medium low 1 2 3 4 5

Low 2 3 4 5 5

Note: Additional details are provided in box 6.3. PSDI categories are an estimate of potential stress and 

range from 1 to 5, where 1 = low, 2 = medium low, 3 = medium, 4 = medium high, and 5 = high. AET = 

actual evapotransporation.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 6.10—Potential soil drought stress in the spring and summer for the Malheur National Forest. 

Box 6.3 (continued)
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.3 (continued)

Figure 6.11—Potential soil drought stress in the spring and summer for the Umatilla National Forest. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 6.3 (continued)

Figure 6.12—Potential soil drought stress in the spring and summer for the Wallowa-Whitman National Forest. 
183

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.3 (continued)

testing will help validate many assumptions and test data accuracy. Reliance on the 

fine-scale data could lead to an inappropriate spatial focus and assumptions about 

accuracy (“my favorite pixel”). Although the SSURGO soil data are available at 

relatively fine spatial scales, soil can be heterogeneous at even finer scales (as small 

as a few feet). Examination of the two spatial layers separately may be more appropriate. The PSDS index may simply provide an indication of where on the landscape 

vegetation may be vulnerable to drought stress, particularly across similar vegetation 

types or species. 

Malheur National Forest

• Overview—Patterns in the Malheur National Forest are distinctive from 

other areas in the Blue Mountains, owing to the southerly location, lack of 

maritime influence, and lower elevation terrain (fig. 6.10). Soils are typified 

by fewer volcanic soils and more clay-dominated soils. A substantial portion 

of the landscape (41 percent) is classified as high PSDS (table 6.6). Most of 

the nonforested PVGs cover a small spatial extent, so we might expect more 

error in classification associated with these groups.

• Spring—Seventy-one percent of the forest is classified into the two highest PSDS categories combined. Only 11 percent of the forest remains in the 

moderate PSDS category. All PVGs have substantial portions in the moderate and moderate to high PSDS categories (table 6.7). Nonforested PVGs 

have more area in the moderate-to-high categories compared to forested 

PVGs. The Dry UW, US, UH and Moist UW and US groups all have 90 

percent or more area in moderate-to-high or high PSDS categories combined. However, the Dry UF group actually has a higher proportion in the 

two highest PSDS categories (78 percent) than some of the other nonforested 

PVGs. The Dry US group has the highest spatial extent in moderate-to-high 

and high PSDS (98 percent).

Table 6.6—Potential soil drought stress index for the three national forests 

in the Blue Mountains 

Potential soil 

drought stress 

index

Umatilla National 

Forest

Wallowa-Whitman 

National Forest

Malheur National

Forest

Spring Summer Spring Summer Spring Summer

Percent

1–Low 0 0 0 0 0 0

2–Low to moderate 5 2 2 1 0 0

3–Moderate 52 29 46 22 28 11

4–Moderate to high 42 30 34 26 30 28

5–High 1 39 9 43 41 60

Note that not all percentages within a forest add up to 100 because of rounding or because some areas 

contain no data. Categories are based on mapped data in figures 6.12 through 6.14
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 6.7—Potential vegetation groups (PVGs) and their relative proportion 

of area mapped in each potential soil drought stress category for each 

national forest in spring (April, May, June) and summer (July, August, 

September) (continued) 

Potential soil 

drought stress: spring

Potential soil 

drought stress: summer

Potential vegetation group 1 2 3 4 5 1 2 3 4 5

Relative percent

Malheur National Forest:

Cold Upland Forest 0 0 70 21 10 0 0 40 39 21

Cold Upland Shrub 0 0 31 27 42 0 0 5 23 72

Cold Upland Herb 0 0 28 30 42 0 0 6 16 77

Dry Upland Forest 0 0 23 34 44 0 0 6 30 64

Dry Upland Woodland 0 0 9 51 40 0 0 1 8 92

Dry Upland Shrub 0 0 1 19 79 0 0 1 3 97

Dry Upland Herb 0 0 10 28 62 0 0 2 9 89

Moist Upland Forest 0 0 77 19 4 0 0 43 38 19

Moist Upland Woodland 0 0 4 31 65 0 0 0 5 95

Moist Upland Shrub 0 0 5 19 75 0 0 1 8 91

Moist Upland Herb 0 1 15 69 14 0 0 7 9 83

Umatilla National Forest:

Cold Upland Forest 0 1 78 21 0 0 1 46 36 18

Cold Upland Shrub 0 1 29 70 0 0 3 23 40 34

Cold Upland Herb 0 2 21 77 0 0 1 16 31 52

Dry Upland Forest 0 2 55 42 1 0 1 24 33 42

Dry Upland Woodland 0 0 4 96 0 0 0 3 1 96

Dry Upland Shrub 0 1 14 83 2 0 0 3 9 88

Dry Upland Herb 0 1 13 85 1 0 0 3 15 82

Moist Upland Forest 0 12 60 28 0 0 4 41 32 23

Moist Upland Woodland 0 0 14 73 14 0 0 5 6 89

Moist Upland Shrub 0 1 24 74 1 0 0 9 32 59

Moist Upland Herb 0 1 15 82 2 0 0 2 12 86

Wallowa-Whitman National Forest:

Cold Upland Forest 0 0 57 30 12 0 0 32 28 39

Cold Upland Shrub 0 0 7 31 61 0 0 2 13 85

Cold Upland Herb 0 0 32 51 17 0 0 2 16 81

Dry Upland Forest 0 2 58 34 5 0 1 27 33 38

Box 6.3 (continued)
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 6.7—Potential vegetation groups (PVGs) and their relative proportion 

of area mapped in each potential soil drought stress category for each 

national forest in spring (April, May, June) and summer (July, August, 

September) (continued) 

Potential soil 

drought stress: spring

Potential soil 

drought stress: summer

Potential vegetation group 1 2 3 4 5 1 2 3 4 5

Relative percent

Dry Upland Woodland 0 0 20 35 45 0 0 6 18 76

Dry Upland Shrub 0 0 14 54 32 0 0 2 10 88

Dry Upland Herb 0 0 17 68 15 0 0 2 12 85

Moist Upland Forest 0 4 73 21 2 0 2 39 41 19

Moist Upland Woodland 0 0 8 40 52 0 0 3 10 86

Moist Upland Shrub 0 1 21 51 27 0 0 8 21 72

Moist Upland Herb 0 0 22 63 16 0 0 2 14 83

Note: Values less than 0.5 percent are listed as 0. Categories are based on mapped data shown in figures 

6.12 through 6.14. Note that for Wallowa-Whitman National Forest, not all mapped PVGs had associated 

PSDS data. “Unmapped” PSDS data were removed to calculate the relative percentages.

• Summer—Sixty percent of the forest is mapped as high potential drought 

stress and 28 percent as moderate to high. Therefore, almost 90 percent of 

the forest could be under extreme drought conditions in the summer. All 

PVGs have more area classified in moderate-to-high and high PSDS categories. Nonforested PVGs have high proportions of mapped drought-prone 

soils compared to forested PVGs. Ninety-seven percent of the Dry US PVG 

and 95 percent of Moist UW are in high categories. Values are lower for the 

forested PVGs, but all forested PVGs have substantial portions in the high 

category. Ninety-four percent of the Dry UF PVG is in the moderate-to-high 

and high combined categories. 

Umatilla National Forest

• Overview—About half of the Umatilla National Forest is classified as having moderate PSDS (table 6.6, fig. 6.11); the relative percentage PSDS index 

classified within each upland PVG is shown in table 6.7. Most of the nonforested PVGs cover a small spatial extent, so we might expect more error in 

classification associated with these groups.

• Spring—Although 94 percent of the forest is in the moderate and moderate-tohigh categories combined, only 1 percent of the forest is mapped with high soil 

drought stress during this time period. Only 5 percent of the forest has lowto-moderate drought stress. All PVGs have substantial portions in moderate 

and moderate-to-high PSDS categories. All nonforested PVGs have more area 

classified in the moderate-to-high categories (70 percent or more) compared 

to forested PVGs. The Dry UW PVG has the highest spatial extent in the high 

PSDS (14 percent). The spatial extent of category 4 and 5 PSDS for the three 

Box 6.3 (continued)
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 6.3 (continued)

forested PVGs is much lower than the nonforested PVGs. As might be expected, the most drought-prone soils for the forested PVGs is for the Dry

UF group, with more than 40 percent in moderate to high. However, 28 percent of the Moist UF and 21 percent of the Cold UF are in moderate to high. 

• Summer—About 69 percent of the forest is mapped as having moderateto-high and high drought stress. All PVGs have more area classified in the 

moderate to high, and high PSDS categories. Nonforested PVGs have high 

proportions of drought-prone soils compared to forested PVGs. Ninety-six 

percent of the Dry UF PVG is in high PSDS, and even 23 percent of the Moist 

UW and 18 percent of the Cold UF are high. However, almost twice as much 

of the Dry UF group is in the high category (42 percent), and about 75 percent 

of this PVG is in the moderate-to high-and high categories combined. 

Wallowa-Whitman National Forest. 

• Overview—Similar to the Umatilla National Forest, about half of the WallowaWhitman National Forest is classified in moderate PSDS (table 6.6, fig. 6.12), 

and 80 percent is in moderate and moderate-to-high categories combined. 

• Spring—About 9 percent of the forest is in the high PSDS category, and only 

2 percent is in the low-to-moderate category. All PVGs have substantial portions in moderate and moderate-to-high PSDS (table 6.7). Unlike the Umatilla 

National Forest, substantial portions of the PVGs are in high PSDS status. This 

forest has large areas of glaciated terrain with scoured landscapes and shallow rocky soils and fewer deep ash caps as compared to the Umatilla. All of 

the nonforested PVGs have more area classified in moderate-to-high categories compared to forested PVGs. The Moist UW PVG has the highest spatial 

extent in high PSDS (>50 percent). Most of the nonforested PVGs cover a 

small spatial extent, so we might expect more error in classification associated 

with these groups. The spatial extent of categories 4 and 5 PSDS for the three 

forested PVGs is lower than for nonforested PVGs. The Cold UF PVG has the 

most drought-prone soils (30 percent) in moderate-to-high, most likely a function of shallow rocky, soils and glaciated terrain in these areas. 

• Summer—About 69 percent of the forest is mapped as moderate-to-high 

and high potential drought stress (categories 4 and 5 combined). As with the 

Umatilla National Forest, all PVGs have more area in the moderate-to-high 

and high PSDS categories. Similar to spring patterns described above, nonforested PVGs have high proportions of drought-prone soils compared to forested PVGs. Eighty-eight percent of the Dry US PVG and 86 percent of the 

Moist UW have high PSDS. Values are lower for the forested PVGs, but both 

the Cold and Dry UF PVGs have substantial portions in the high category. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Common undergrowth species include herbs and dwarf shrubs. Areas with 

physiographic and soil characteristics suitable for supporting forests with at least 

moderate canopy cover are frequently dominated by grouseberry (Vaccinium 

scoparium Leiberg ex Coville). Areas with steeper slopes or shallower soils support 

open-canopy stands and herb-dominated undergrowth, often featuring elk sedge 

(Carex geyeri Boott), Ross’ sedge (C. rossii Boott), and western needlegrass (Achnatherum occidentale ssp. occidentale [Thurb. ex S. Watson] Barkworth).

Cold UFs at the highest elevations often contain whitebark pine, and these open 

forest communities often have undergrowth similar to flora in subalpine and alpine 

meadows, including greenleaf fescue (Festuca viridula Vasey), prickly sandwort 

(Eremogone aculeata [S. Watson] Ikonn.), mountain heath (Phyllodoce empetriformis [Sm.] D. Don), and poke knotweed (Aconogonon phytolaccifolium var. phytolaccifolium [Meisn. ex Small] Small ex Rydb.).

Species of concern in this PVG include whitebark pine, limber pine (Pinus

flexilis E. James), and mountain hemlock (Tsuga mertensiana [Bong] Carrière) (box 

6.2). These forests are an important component of the landscape from a biodiversity 

perspective, and for snow retention and hydrologic function. 

Potential future changes—

At broad scales, forests of western North America can be partitioned into energylimited versus water-limited domains (Littell and Peterson 2005, Littell et al. 2008, 

McKenzie et al. 2003b, Milne et al. 2002). Energy-limiting factors are chiefly light 

(e.g., productive forests where competition reduces light to most individuals) and 

temperature (e.g., high-latitude or high-elevation forests). Tree growth in energylimited forests appears to be responding positively to warming temperatures over 

the past 100 years (McKenzie et al. 2001). Productivity is projected to increase in 

subalpine and alpine zones across the Pacific Northwest (Latta et al. 2010).

High-elevation forests may increase in productivity in response to moderate warming and elevated atmospheric carbon dioxide. Longer growing seasons, 

reduced snowpack and depth, and warmer summer temperatures (day and night) 

associated with future warming may promote increased tree growth within the 

treeline ecotone and an upward advance of treeline in some locations. However, a 

recent worldwide study concluded that there was evidence of treeline advance over 

the last century at only about half of the sites throughout the world with long-term 

measurements (Harsch et al. 2009). Upward migration of treeline must include the 

successful recruitment of tree seedlings, first within and then above the current 

treeline ecotone. This mechanism depends on microsite facilitation (Smith et al. 

2003) and may be limited by unsuitable topographic and edaphic conditions of 

High-elevation 

forests may increase 

in productivity in 

response to moderate 

warming and elevated 

atmospheric carbon 

dioxide.
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GENERAL TECHNICAL REPORT PNW-GTR-939

upslope areas, wind exposure, and patterns of snow distribution (Holtmeier and 

Broll 2012, Macias-Fauria and Johnson 2013). Zald et al. (2012) noted that the 

importance of snow, the mediation of snow by interacting and context-dependent 

factors in complex mountain terrain, and the uncertainty of climate-change impacts 

on snow creates a challenge for understanding how these ecotones may respond to 

future climate conditions.

A high-elevation site in the Blue Mountains that is presently at the transition 

between Cold UF and Moist UF and was forested (fig. 6.3) supported an Agropyron-dominated grassland/ponderosa pine parkland during early- to mid-Holocene 

warming. A rapid gain in ponderosa pine in the middle of this record indicates the 

influence of this species under drier and warmer conditions (Hansen 1943). Paleoecological evidence suggests Cold UFs may be converted to herbaceous parklands 

with ponderosa pine, or the importance of ponderosa pine may increase under 

warmer and drier scenarios. Douglas-fir woodland types, which are found in the 

Okanogan valley of southern and central British Columbia and western Montana, 

may also be a potential analog for what could happen in some areas of the Blue 

Mountains that are currently dominated by cold forest species. 

Species distribution models project that suitable climate available for most 

cold upland tree species will be moderately reduced to nonexistent in the Blue 

Mountains by the end of the 21st century (table 6.2). MC2 projects major loss of 

subalpine forest climate habitat as well (fig. 6.5). Based on model output, Cold UFs 

may be vulnerable to climate change, and high-elevation mountains (e.g., Wallowa 

Mountains, Seven Devils) may serve as refugia for subalpine species. Devine et al. 

(2012) considered subalpine fir, Engelmann spruce, and western white pine (Pinus 

monticola Douglas ex D. Don) to be highly susceptible to climate change (table 

6.2), although lodgepole pine has a lower susceptibility score. Although western 

white pine also has a high susceptibility score (Devine et al. 2012), its generalist 

life history (Rehfeldt et al. 1984) may confer phenotypic plasticity, allowing it to 

better adjust to changing environmental conditions (box 6.2). Another study, which 

suggests that subalpine species were among the most vulnerable to recent climatic 

variation, assigned lodgepole pine and western hemlock as the first and second 

most vulnerable species, respectively, in the Blue Mountains (Waring et al. 2011).

Disturbance—

Historically, large-scale disturbances have been infrequent in the subalpine and alpine zones but can still play an important role in shaping vegetation distribution and 

abundance. Smaller scale disturbances, such as windthrow, are common in the Cold 

UF (fig. 6.13). Deep snowpacks allow only a short fire season, fuels are often wet, 
189

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.13—Windthrow disturbance in a Cold Upland Forest.

and spatial discontinuities inhibit fire spread (Agee 1993). However, forest vegetation can be greatly altered by rare wildfire events, and tree establishment following stand-replacing wildfires can require decades to centuries for trees in subalpine 

forests that do not include lodgepole pine (Agee and Smith 1984, Little et al. 1994). 

In the future, wildfire events in subalpine systems may be more common as the 

summer dry period grows longer. Recovery of subalpine forests following wildfire 

requires nearby seed sources, an extended period of favorable climate, and favorable biotic and abiotic microsite conditions (Bansal et al. 2011, Stueve et al. 2009, 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Zald et al. 2012). Seral whitebark pine communities could benefit from increased 

fire occurrence but depend on Clark’s nutcracker (Nucifraga columbiana (A. 

Wilson, 1811)) for dispersal (Arno and Hoff 1990, Barringer et al. 2012, Keane et al. 

2012). However, even with warmer temperatures, most Cold UFs would continue to 

support high- and mixed-severity fire regimes. 

A warmer climate could increase the potential for insect and disease outbreaks 

(box 6.2). Insects in Cold UFs include nonnative balsam woolly adelgid (Adelges 

piceae (Ratzeburg)) in subalpine fir, spruce beetle (Dendroctonus rufipennis

[Kirby, 1837]) in Engelmann spruce, mountain pine beetle in lodgepole pine, and 

larch dwarf mistletoe (Arceuthobium campylopodum Engelm.) in western larch. 

Whitebark pine populations are currently declining owing to introduced white pine 

blister rust (Cronartium ribicola A. Dietr.) and mountain pine beetles. The status 

of limber pine, another species susceptible to white pine blister rust, is unknown. 

The balsam woolly adelgid is increasing in the Blue Mountains and may be a major 

stressor of subalpine fir in future decades. 

Synthesis—

Based on multiple lines of evidence from modeling and autecological assessment, 

climate change is likely to produce significant changes in Cold UFs over time, 

including altered growth, altered phenology, and establishment and persistence of 

trees in current meadow communities. However, results from experimental and 

observational studies are not as clear and even suggest potential contrary responses. 

Cold UFs may be converted to high-elevation herbaceous parklands or woodlands 

with ponderosa pine or Douglas-fir under warmer and drier scenarios. Remnant 

populations may persist in the highest of elevations within the Blue Mountains (e.g., 

Wallowa Mountains). The cool dry PAG may be more tolerant of future warming 

compared to the cold dry and cold moist PAGs. However, increased wildfire may 

constrain tree reestablishment in these slow-growing systems, particularly for sites 

without serotinous lodgepole pine as a common, prefire component. Increased insect and disease activity with climate change may also increase stress and mortality 

in these forests.

Cold Upland Shrub

Cold Upland Shrublands (US; fig. 6.14) occur at moderate to high elevations in 

climate conditions similar to Cold UFs. This PVG is not common in the Blue Mountains (table 6.4). The principal species characterizing these shrublands form associations that range from xeric to mesic, although this system may be associated with 

exposed sites, rocky substrates, cold air drainages, and dry conditions that limit tree 

growth. This PVG includes cold very moist, cold moist, cool dry, and cool moist 
191

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.14—An example of a Cold Upland Shrubland community from the south slope of the Greenhorn Mountains. 

US PAGs. Typical species include Sitka alder (Alnus viridis ssp. sinuata [Regel] 

Á. Löve & D. Löve), mountain big sagebrush (Artemisia tridentata ssp. vaseyana

[Rydb.] Beetle), and shrubby cinquefoil (Dasiphora fruticosa [L.] Rydb.). However 

the habitat conditions for these species are quite different. Cold moist shrublands 

are common in subalpine and alpine systems in the Wallowa Mountains at about 

2200 m elevation. Cold very moist shrublands consist of Sitka alder in snow slides 

in the northern portion of the Blue Mountains. The cooler upper shrubland PAGs 

are more common in the montane zone.

Potential future changes—

Species distribution model results for sagebrush indicate complete loss of habitat 

for this species in the future, although only one model was available for assessment. 

MC2 model results project a major loss of subalpine forest climate habitat, and 

an analogous loss of Cold US habitat might be inferred from this result (fig. 6.5). 

In contrast, the Biome-BGC model projects increased net productivity in eastern 

Oregon shrublands after 2030, including areas currently occupied by sagebrush 

(Reeves et al. 2014). Note that paleoecological studies generally suggest an increase 

in sagebrush during warmer conditions in the early to mid Holocene (fig. 6.3), providing an important context for interpretation of modeling studies.

Paleoecological studies 

generally suggest an 

increase in sagebrush 

during warmer 

conditions in the early 

to mid Holocene.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Disturbance—

Large-scale disturbances are infrequent in subalpine and alpine systems but can 

still play an important role in shaping vegetation distribution and abundance. Deep 

snowpacks produce a short fire season, fuels are often wet, and spatial discontinuities can inhibit fire spread (Agee 1993). In the future, wildfire events in subalpine 

systems may be more common, and shrub species may be able to more rapidly regenerate compared to subalpine tree species. Sitka alder and shrubby cinquefoil can 

survive low-to-moderate-intensity fires and resprout vigorously. However, mountain big sagebrush is readily killed by fire and requires at least 15 years or more to 

recover after fire (Bunting et al. 1987).

Synthesis—

Climate change is likely to produce changes in Cold US over time, including 

changes in plant growth and phenology. Although limited model data suggest that 

sagebrush may be highly vulnerable to climate change, paleoecological evidence 

does not support this inference. Warming at higher elevations and a longer growing 

season may increase productivity in Cold US. Increased future fire activity in subalpine environments may not constrain shrub establishment as much as tree establishment in these slow-growing areas, although recovery times may still be long.

Cold Upland Herb

Subalpine and alpine meadows are found at high elevations where temperatures are 

too cold or snow covers the ground too long for trees to grow. This PVG is not common in the Blue Mountains (table 6.4) but includes cold moist, cold dry, cool moist, 

and cool dry upland herb (UH) PAGs. Typical plant communities consist of grasslands with greenleaf fescue and Idaho fescue (Festuca idahoensis Elmer), elk sedge 

and Hood’s sedge (Carex hoodii Boott). Many of these high-elevation grasslands 

have been degraded from livestock and elk grazing (Irwin et al. 1994; Johnson 

2003). Partial to complete loss of vegetation cover resulted in significant erosion 

of deep, fine textured, loess soils and decreased productivity, and greenleaf fescue 

grasslands in the Wallowa Mountains are still recovering (Johnson 2003, Reid et 

al. 1991). Some sites appeared to have transitioned to stable forb communities with 

poke knotweed, Nuttall’s linanthus (Leptosiphon nuttallii ssp. nuttallii [A. Gray] 

J.M. Porter & L.A. Johnson) and alpine golden buckwheat (Eriogonum flavum

Nutt.). This PVG includes many rare and endemic meadow species (fig. 6.15). 

Potential future changes—

Snowpack melting and subsequent soil heating have been shown to influence flowering, growth phenology, and vegetation community patterns in alpine meadows 
193

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.15—Examples of rare and locally endemic species found in alpine and subalpine 

environments. On the top is Potentilla sp. from serpentine substrates in the Greenhorn Mountains. On the bottom is Greenman’s biscuitroot from Mount Howard, Wallowa County, Oregon. 
194

GENERAL TECHNICAL REPORT PNW-GTR-939

(Dunne et al. 2003, Inouye 2008). Spatial variability in snowpack persistence influences flowering and growth phenology within species and, to the extent that spatial 

patterns of snowmelt are consistent among years, also influences species composition and community types in alpine meadows (Canaday and Fonda 1974, Evans and 

Fonda 1990).

Subalpine conifers have been documented as infilling alpine tundra and 

meadows in the Pacific Northwest, a trend related to periods of warmer climate 

(Rochefort and Peterson 1996, Woodward et al. 1995). Snow-dominated meadows 

on Mount Rainier (Washington) (Rochefort and Peterson 1996) and in the Olympic 

Mountains (Woodward et al. 1995) have been infilled by subalpine fir and mountain hemlock during the 20th century in association with warm phases of the Pacific 

Decadal Oscillation. Tree establishment has also been documented in the Wallowa 

and Elkhorn Mountains (Skovlin et al. 2001) and in some locations, may have been 

aided by the heavy grazing pressures in the early 1900s. Because of the shallow, 

rocky soils that characterize this PVG, it is unlikely that tree encroachment will 

be a major problem in the future. Meadow plant species are able to colonize new 

habitat that was previously covered by ice or bare ground under more favorable 

climatic conditions, but the process of soil formation is slow. It is more likely that 

subalpine trees will establish in Cold US areas, many of which are characterized by 

deeper soils. 

The effects of climate change on alpine or subalpine meadow species have not 

been modeled. However, model results for subalpine tree species and MC2 results 

generally show loss of subalpine and alpine habitat, which may suggest loss of 

habitat for other subalpine and alpine life forms.

Disturbance—

As noted above, large-scale disturbances are infrequent in subalpine and alpine systems. In the future, wildfire events in subalpine systems may be more common, and 

herbaceous species may be able to more rapidly regenerate compared to shrubs and 

trees. Many species in cold UH communities are fire survivors because they sprout 

or sucker from roots, root crowns, corms, or rhizomes.

Synthesis—

There is considerable uncertainty about the future spatial extent of subalpine and 

alpine meadows. Continued warming in future decades could cause the geographic 

range of upland grass and forbs to contract, expand, or remain the same. Trends 

will most likely depend on the rates at which meadow species colonize exposed 

soil following disturbance. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Moist Upland Forests

Moist UFs occur at moderate elevations in the montane vegetation zone, or at low 

elevations in the subalpine zone (fig. 6.16). They are adjoined by cold forests at their 

upper edge and by dry forests at their lower edge. They are characterized by slightly 

longer growing seasons compared to the Cold UF, and have cooler temperatures 

and higher precipitation than Dry UF.

Late-seral stands are generally dominated by subalpine fir, grand fir, or 

Douglas-fir, and lodgepole pine or western larch often occur as early-seral species 

(except where lodgepole pine dominates). Douglas-fir and western white pine are 

mid-seral species (except in three potential vegetation types where Douglas-fir 

is the dominant (climax) species). Species of concern in this PVG include Alaska 

cedar (Callitropsis nootkatensis [D. Don] D.P. Little) (box 6.4) and quaking aspen 

(Populus tremuloides Michx.) (box 6.5).

For the Blue Mountains, the Moist UF PVG consists of five PAGs—three in 

the cool temperature regime (Cool Wet UF, Cool Very Moist UF, Cool Moist UF), 

and two in the warm temperature regime (Warm Very Moist UF, Warm Moist 

UF). The Cool Moist UF is the most common component of this PVG. Cool moist 

forest understories are dominated by forbs, several mid-height shrubs, and a few 

tall shrubs on the warm end of the PAG. These forests tend to occupy the most 

productive forested environments in the Blue Mountains because moisture is less 

Figure 6.16—Moist Upland Forest in the Blue Mountains.

These forests tend 

to occupy the most 

productive forested 

environments in 

the Blue Mountains 

because moisture is 

less limiting.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 6.4—Cold and moist upland conifer species of

concern: whitebark pine, limber pine, mountain

hemlock, Alaska cedar

Limber pine, Alaska cedar, and mountain hemlock in the Blue Mountains are represented by populations that are separated from the main parts of the species’ distributions. A single population of Alaska cedar occurs in eastern Oregon, the Cedar Grove 

Botanical Area in the Malheur National Forest (Frenkel 1974). This population is 

likely a relict of a time period when cooler and wetter conditions prevailed and the 

species occurred across a larger area (Devine et al. 2012). The distribution of limber 

pine is discontinuous throughout its range and two relict populations occur in the 

Eagle Cap Wilderness. Infrequent mountain hemlock stands occur in the northern 

half of the Wallowa Mountains. These rare, disjunct populations represent important 

genetic resources that may be at risk to climate change and other stressors. 

Whitebark pine and limber pine are also threatened by white pine blister rust 

(Smith et al. 2013, Tomback and Achuff 2010), a nonnative fungus that forms cankers 

of necrotic tissue that girdle tree stems. Alternate hosts for the fungus are currant 

(Ribes) or the herbs paintbrush Castilleja) and lousewort (Pedicularis) (Geils et al. 

2010). Indirect pathogen-related effects could occur if climate increasingly favors 

blister rust. Higher variability in weather conditions may create conditions conducive 

to infection, although drier summers could inhibit the formation and spread of rust 

spores and fruiting body development.

High-elevation species can also be rapidly altered by rare wildfire events, 

because recovery from stand-replacing wildfires is slow. This is especially true for 

species with limited distributions. Mountain hemlock in the Wallowa Mountains 

is favored by a lack of fire, because a stand-replacing fire here would likely favor 

lodgepole pine (Devine et al. 2012). The Alaska cedar grove in the Malheur National 

Forest burned in 2006, and most of the mature trees were killed. In 2014, wildfire 

burned through some of the limber pine habitat in the northern Wallowa Mountains, 

although the effects on the trees is unknown.

Fire effects on whitebark pine are difficult to generalize. Mixed-severity and 

stand-replacing fires are beneficial to seral whitebark pine communities, because the 

pine is better adapted to recolonize burned sites compared to more shade-tolerant 

subalpine fir that may outcompete pine in the absence of fire (Arno and Hoff 1990, 

Keane et al. 2012). With declining populations, loss of cone-bearing trees with 

potential resistance to blister rust will limit future management options. In addition, 

probability of dispersal by Clark’s nutcracker declines with diminishing cone production (Barringer et al. 2012). 

During the past two decades, warmer temperatures have allowed mountain pine 

beetles to shift upward and persist in higher elevation forests (Logan et al. 2010). 

Mountain pine beetle is the primary cause of whitebark pine mortality at Crater Lake 

National Park, presently at a rate of 1 percent annually (Murray 2010), and may have 

been facilitated by an increasing late-summer dry season (Daly et al. 2009). Longer, 

high-elevation growing seasons could enhance the growth of subalpine tree species 

(e.g., Bunn et al. 2005, Peterson and Peterson 2001). However, because whitebark pine 

grows so slowly, it may be at a competitive disadvantage compared to other species.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.5—Quaking aspen in upland forests

Because quaking aspen stands in the Blue Mountains are typically less than 1 ha 

and fragmented across the landscape, they are vulnerable to a warmer climate 

and other stressors (table 6.2). Aspen is an early seral component of forest communities, and stands have been declining in number, area, and stocking density. Current 

stressors include competition with shade-tolerant conifers, herbivory by livestock and 

native ungulates, and fire exclusion. Aspen can occur in cold, moist, and dry upland 

forest potential vegetation groups, although the only aspen potential vegetation type 

is in the Cool Very Moist plant association group in Moist Upland Forest (Swanson 

et al. 2010).

Sudden aspen death (SAD) was noted in the Rocky Mountains over a decade ago 

and has affected large areas of aspen in southwestern Colorado (Worrall et al. 2010). 

Sudden aspen death is characterized by rapid, synchronous branch dieback, crown 

thinning, and mortality of stems, without the involvement of primary pathogens and 

insects. Some affected stands may fail to produce suckers in response to crown loss 

and mortality. Worrall et al. (2008) proposed a disease model for SAD as follows: (1) 

predisposing factors include low elevations, south/southwestern aspects, physiological maturity, and low stand density, (2) inciting factors are acute drought with high 

temperatures during the growing season, and (3) contributing factors are insects and 

pathogens that tend to invade and kill stressed trees. 

A warmer climate and drier growing season could increase susceptibility to 

SAD in the Blue Mountains, because aspen requires mesic soil moisture conditions, 

and moisture stress is an underlying factor for SAD (Worrall et al. 2010). Aspen 

stands in the Dry Upland PVG are already near their soil moisture limit for survival, 

and increased loss of aspen in the Malheur National Forest might be expected at 

lower elevations. 

Increased frequency of stand-replacing fires in the future may favor aspen 

regeneration, because aspen respond to stand-replacing fire with abundant vegetative 

propagation (suckering) and rapid growth. Increased low-severity fire may benefit 

aspen if competition with conifers is reduced and soil moisture status is improved, 

although once competing conifers like ponderosa pine, Douglas-fir, and grand fir are 

relatively large, their fire tolerance exceeds that of aspen (Swanson et al. 2010). In 

addition, severe fires and reburns may kill shallow root systems and eliminate small 

clones, particularly in stressed stands.

limiting, and their temperate nature is demonstrated by high species diversity and 

closed forest structure. High species diversity pertains to both forest overstory and 

understory composition. 

Moist-forest understories are dominated by forbs, some mid-height shrubs, and 

a few tall shrubs in warmer locations. Moist-site plants such as bride’s bonnet (Clintonia uniflora [Menzies ex Schult. & Schult. f.] Kunth), twinflower (Linnaea borealis L.), false bugbane (Trautvetteria caroliniensis [Walter] Vail), western swordfern 

(Polystichum munitum [Kaulf.] C. Presl), and British Columbia wildginger (Asarum 

caudatum Lindl.) occur here, but most mesic environments in the Moist UF PVG 
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are dominated by thinleaf huckleberry (Vaccinium membranaceum Douglas ex 

Torr.). Moist forests at the warm end of the temperature spectrum (Warm Very 

Moist and Warm Moist PAGs) include mid or tall shrubs such as Rocky Mountain 

maple (Acer glabrum Torr.), mallow ninebark (Physocarpus malvaceus [Greene] 

Kuntze), and oceanspray (Holodiscus discolor [Pursh] Maxim.).

Potential future changes—

Many (but not all) productive moist upland forests at higher elevation are more 

energy limited than water limited. Light is a limiting factor in productive forests 

where competition reduces light to most individuals. Tree growth in energy-limited 

forests appears to be responding positively to warming temperatures over the past 

100 years (McKenzie et al. 2001). In the Blue Mountains, lower elevation moist 

forests may transition to being primarily water limited, particularly areas without 

much ash or loess, which would enhance water holding capacity.

Moderate warming may lead to a positive response and increased productivity. However, more extreme warming and increased drought stress, particularly at 

lower elevations and in the southern portion of the Blue Mountains (e.g., Malheur 

National Forest) will likely cause decreased tree growth and forest productivity. 

However, suitable climate habitat currently occupied by Cold UFS may offset these 

losses. 

Paleoecological evidence demonstrates that during early to mid-Holocene 

warming, areas that are currently between Cold UF and Moist UF were forested 

(fig. 6.3), supporting Agropyron-dominated grassland/ponderosa pine parkland. 

Areas currently dominated by grand fir and Douglas-fir were dominated by ponderosa pine. 

Species distribution models (table 6.1) project that the suitable climate available for most tree species characteristic of this PVG will be reduced to nonexistent 

by the end of the 21st century, although some models project minor loss of climate 

habitat for Douglas-fir. Losses were more extreme for the Malheur National Forest 

(where this PVG is currently limited in distribution) and southern portions of the 

Umatilla and Wallowa-Whitman National Forests. In contrast, MC2 projects either 

very small (three scenarios) or moderate (one scenario) increases in this forest 

type (fig. 6.5), particularly in the northern Blue Mountains. The latter scenario has 

a large projected increase in annual precipitation, including some increased precipitation in the summer, coupled with only moderate warming. None of the MC2 

scenarios project a decrease in this forest type. 

As discussed earlier, SDMs tend to produce large reductions in species climate 

habitat with future novel conditions, so the model results for these species are not 

surprising. MC2 is not constrained as much by future novel conditions. Moreover, 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

most GCM scenarios project increased precipitation for the Pacific Northwest (fig. 

6.4). Higher precipitation, coupled with warming, and the availability of climate 

habitat currently occupied by colder forest species, confirms the logic of MC2 

model output. One recent study suggests that precipitation may decrease, because 

slower westerlies associated with jet-stream changes will result in less orographic 

lifting (enhancement) of precipitation for mountainous regions (Luce et al. 2013). 

MC2 does not account for decreasing orographic effects and tends to underestimate 

the effects of decreased snowpack expected in the future. Even with these shortcomings, the MC2 projections are more robust, and it is unlikely that any future 

climate would result in a large loss of moist forest habitat. 

Disturbance—

Moist upland forests generally support mixed-severity fire regimes, although 

low- and high-severity regimes also occur (Stine et al. 2014). High levels of coarse 

woody debris, litter, and live biomass can produce occasional large, high-severity 

wildfires when fire weather and dry fuel conditions coincide. Increased frequency 

and duration of summer drought would allow wildfires to burn wetter and cooler 

sites, where high fuel loads become more available when fuel moisture is low. 

However, the primary effect of severe fire in these forests is to reduce total standing 

biomass rather than change forest composition.

Warming temperatures could increase the potential for insect and disease 

outbreaks (box 6.1). Insect and disease agents in Moist UF include western spruce 

budworm (Choristoneura occidentalis Freeman), Douglas-fir tussock moth (Orgyia 

pseudotsugata [McDunnough, 1921]), Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins, 1905), fir engraver (Scolytus ventralis LeConte, 1868), spruce 

beetle, mountain pine beetle in lodgepole pine, Douglas-fir dwarf mistletoe (Arceuthobium douglasii Engelm.), larch dwarf mistletoe, and root pathogens (particularly 

Armillaria, Annosus root rot (Heterobasidion annosum [Fr.] Bref.), and laminated 

root rot (Phellinus sulphurascens [Pilat]). 

Many Moist UFs (e.g., those not burned in recent decades) have high stand 

densities, small trees, and few large fire-tolerant trees, and are dominated by 

shade- and fire-intolerant tree species (Stine et al. 2014). Because of the increase in 

surface and canopy fuel loads, there is a greater risk of large and severe wildfires, 

particularly when fire weather conditions are severe. Increased stand densities also 

increase competition for water and nutrients, which leads to higher susceptibility to 

insect and disease outbreaks. These conditions threaten the long-term survival of 

large trees and sustainability of these forests in general.
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Synthesis—

Paleoecological and some model evidence suggest that climate change will cause 

moderate to extreme loss of Moist UFs and characteristic species. However, MC2 

model results suggest the opposite. Future warming with increased precipitation 

may lead to increased importance of this PVG across the landscape. This outcome 

is somewhat supported by recent trends in response to warming in energy-limited forests. Unlike Cold UFs, these forests may be able to adapt to future climate 

change by expanding into new available habitats. Warm and very warm moist forest 

PAGs may be able to better adapt to warming compared to cool PAGs. However, 

increased summer drought stress may make these forests more vulnerable to 

other stressors, particularly at lower elevations and on southern sites in the Blue 

Mountains. Wildfire activity and insect and disease outbreaks will most likely increase with future warming, and may reduce the distribution of this PVG.

Dry Upland Forest

Dry UFs generally occur at low to moderate elevations in the montane vegetation 

zone (fig. 6.17). Climate varies with elevation, but common features include warm, 

dry summers, with warm to hot daytime temperatures and cool nighttime temperatures, and cold, wet winters. Much of the annual precipitation falls as snow in 

winter or during spring rainstorms. Late-seral stands are dominated by ponderosa 

pine, grand fir, or Douglas-fir, and ponderosa pine or Douglas-fir also function 

as early- or mid-seral species depending on plant association. Western juniper is 

expanding rapidly into this PVG as a result of fire exclusion and climate change, 

moving upward from a foothills woodland zone located below the montane zone 

(Knapp and Soulé 1998, Miller et al. 2005). Dry UFs are adjoined by Moist UFs at 

their upper edge, and by the woodlands and shrublands of the foothills vegetation 

zone at their lower edge.

The Dry UF PVG consists of three PAGs—one from the warm temperature 

regime (Warm Dry UF), and two from the hot temperature regime (Hot Moist 

UF, Hot Dry UF). Warm, dry forests are the most common forest zone in the Blue 

Mountains (table 6.4), and they have a long history of human use for commodity 

purposes (e.g., livestock grazing and timber production; fig. 6.18). Effective fire 

exclusion has led to significant changes in species composition, forest structure, and 

stand density. Dry UF sites were historically dominated by ponderosa pine, which is 

well adapted to survive in low-severity fire regimes.

Common dry UF understory species include graminoids and mid-height shrubs. 

Elk sedge and pinegrass (Calamagrostis rubescens Buckle) are ubiquitous, and 

Future warming with 

increased precipitation 

may lead to increased 

importance of this PVG 

across the landscape.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.17—View of Dry Upland Forest from Lone Rock, Malheur National Forest.

Figure 6.18—Domestic livestock grazing is common in the Blue Mountains, particularly in dry 

upland ponderosa pine forests. 

Becky Kerns
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white spirea (Spiraea betulifolia Pall.), snowberry (Symphoricarpos spp.), mallow 

ninebark, antelope bitterbrush and curl-leaf mountain-mahogany are common 

shrubs. On hot and dry sites, mountain big sagebrush, bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] Á. Löve), and western juniper are important species.

Potential future changes—

Dry UFs in the Blue Mountains are water limited, and productivity is projected 

to decline in a warmer climate (Latta et al. 2010). Water stress during the warm 

season is the primary factor limiting tree growth at low elevations in the Pacific 

Northwest (Brubaker 1980), and negative water balances constrain photosynthesis 

(Hicke et al. 2002), although this may be partially offset if carbon dioxide fertilization significantly increases water-use efficiency in trees (Neilson et al. 2005). For 

example, Littell (2006) found that most montane Douglas-fir forests in the northwestern United States appear to be water limited, and water limitation will increase 

in warmer climate (assuming that precipitation does not increase in the summer).

Kusnierczyk and Ettl (2002) found that ponderosa pine growth is positively 

correlated with precipitation in the fall and winter prior to the growing season, 

but is not significantly correlated with temperatures, suggesting that ponderosa 

pine growth is more sensitive to changes in water balance than to temperature. 

Ponderosa pine may be able to adapt to increased summer drought stress by allocating more biomass to sapwood conducting area, reducing the ratio of leaf area 

to sapwood area and presumably reducing risks of hydraulic failure (Callaway et 

al. 1994). This is an example of phenotypic plasticity and not genetic adaptation, 

suggesting that this could be a future response to changing climate (Maherali et al. 

2002). 

Increased drought stress will likely result in decreased tree growth and forest 

productivity in Dry UFs in the Blue Mountains, particularly at the current dry 

forest-steppe ecotone. Areas with increased tree density owing to recent fire exclusion may be particularly vulnerable to future climate change because of increased 

drought stress, although suitable climate habitat currently occupied by Moist UFs 

may offset these losses.

Ponderosa pine was generally abundant during periods of major climatic change 

in the past (Whitlock 1992). Hansen (1943) documents an increase in ponderosa pine 

pollen during the past (inferred early to mid-Holocene) at a site currently dominated 

by subalpine species. Phytolith data from sites in the Blue Mountains indicate that 

the ponderosa pine forests were located at a higher elevation than today and during 

the early to mid-Holocene (fig. 6.3). Paleoecological evidence suggests that Dry UFs 

may persist but will be located farther north and at higher elevations.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Species distribution models suggest that climate habitat for ponderosa pine 

and Douglas-fir will decrease greatly, particularly in the southern Blue Mountains 

(table 6.2). Other model results suggest that Douglas-fir distribution would decrease 

only slightly or even increase. Vulnerability scores suggest that Douglas-fir might 

be more vulnerable to climate change than ponderosa pine (table 6.2). Output from 

MC2 suggests that temperate needleleaf forest and dry temperate needleleaf forest 

(both crosswalk to the dry upland PVG) will decrease in relative abundance on the 

landscape. In summary, model output suggests that dry upland forests will decrease 

somewhat in abundance across the landscape, particularly in the southwestern 

portions of the Blue Mountains. However, there is considerable model disagreement 

about the magnitude of this effect. 

Disturbance—

For dry, frequent-fire forests, present-day stand structure, species composition, fuel 

accumulation and associated risk of severe fires, and insect and disease outbreaks 

are generally regarded as historically uncharacteristic and undesirable. In the Blue 

Mountains, grand fir has recently encroached in many ponderosa pine stands, and 

ponderosa pine has moved down in elevation into adjacent woodlands. These conditions are commonly attributed to decades of fire exclusion and suppression, timber 

harvesting, historical periods of overgrazing, and shifts in climate (Hessburg et al. 

2005, Tiedemann et al. 2000, Wright and Agee 2004). The role and importance of 

fire as a disturbance process (Agee 1993, Fulé et al. 1997, Hessburg and Agee 2003) 

and disruption of fire regimes coinciding with Euro-American settlement and associated fire exclusion (Covington and Moore 1994, Hessburg et al. 2005, Swetnam 

et al. 1999) have been extensively documented. Management goals for these forests, 

such as reducing the risk of severe wildfires and sustaining and promoting biodiversity, have prompted the use of thinning and prescribed fire to reduce fuels, lower 

stand densities, and alter stand composition. Prescribed fire simulates the frequent 

low-intensity surface fires considered characteristic of the historical environment of dry, fire-prone forests throughout the interior West prior to nonindigenous 

settlement (Agee 1993, Cooper 1960, Covington and Moore 1994, Weaver 1943). 

However, prescribed fires are typically conducted mostly in the spring and autumn, 

whereas historical wildfires occurred mostly during summer and early autumn. 

The ecological implications of the current seasonal timing of prescribed burns have 

rarely been explored (but see Kerns et al. 2006). 

Dry forest sites were historically dominated by ponderosa pine because it is 

well-adapted to survive in a low-severity fire regime (Agee 1996, Hall 1976, 1980). 

Heyerdahl et al. (2001) noted that within the same plant association, fires were more 
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GENERAL TECHNICAL REPORT PNW-GTR-939

than twice as frequent at plots in the southern watersheds of the Blue Mountains 

compared to northern watersheds. Plots to the south experienced 15 and 13 fires on 

average (1687–1900), whereas plots to the north experienced only six, leading to 

mean fire-return intervals of 14 to 35 years. Heyerdahl et al. (2001) also noted that 

fire frequency varied more based on location (south versus north) rather than forest 

type. It is likely that at least some mixed- and high-severity fires also occurred 

within the matrix of primarily low-severity fire prior to Euro-American settlement 

(Hessburg et al. 2007). 

Longer summer droughts will potentially lengthen the fire season for most 

dry coniferous forest types and may increase the risk of large wildfires. Because 

of the current accumulation of live and dead fuels, large and severe wildfires may 

become the norm for these forest types. At lower elevations, these fires may cause 

conversion to shrublands or grasslands, a trend that is supported by MC2 output, 

particularly for hotter and drier scenarios. 

A warmer climate could increase the potential for insect and disease outbreaks 

(box 6.1). Insect and disease agents include western spruce budworm, Douglas-fir 

tussock moth (frequently where Douglas-fir and grand fir invaded stands historically dominated by ponderosa pine), Douglas-fir dwarf mistletoe, western dwarf 

mistletoe (Arceuthobium campylopodum Engelm.), and bark beetles (Dendroctonus

spp.). Pine white (Neophasia menapia [C. Felder and R. Felder, 1859]), or pine 

butterfly, is also important in ponderosa pine. A recent pine white outbreak in the 

Blue Mountains caused significant defoliation (Kerns and Westlind 2013) (fig. 6.19), 

although mortality from this event is not expected to be high. 

Synthesis—

Some Dry UFs may undergo undesirable changes in the face of future climate 

change. These forests have already experienced a long history of human land use. 

Many Dry UFs are already experiencing severe and uncharacteristic wildfire, and 

equally uncharacteristic insect and disease outbreaks, which will most likely increase in the future. It is likely that the hottest and driest sites will shift to woodland or steppe vegetation. Species characteristic of hot dry PAGs may be better 

adapted to future conditions and these species may become more common. Some 

model output suggests that Douglas-fir and ponderosa pine may decrease in the 

future, although paleoecological evidence conflicts somewhat with this conclusion, 

suggesting that ponderosa pine was able to adapt to warmer climate by migrating 

north or up in elevation. However, the extent to which these species can adapt under 

current and future stressors is unclear. The overall vulnerability assessment score 

for ponderosa pine is quite low, whereas Douglas-fir has a somewhat higher score 

Longer summer 

droughts will 

potentially lengthen 

the fire season for 

most dry coniferous 

forest types.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.19—Pine white butterfly defoliation is extensive in a ponderosa pine stand in the 

southern Blue Mountains (Malheur National Forest, autumn 2011).

(table 6.2). Given the strong paleoecological evidence regarding the persistence of 

ponderosa pine, coupled with its potential low vulnerability and availability of habitat currently occupied by moist forests, it is likely that this forest type will persist 

and remain an important component of the landscape, although shifts in the distribution of Dry UFs and changes in relative abundance of different PAGs might be 

expected (or the formation of novel plant associations). 

Dry and Moist Upland Woodlands

Upland woodlands (UW) in the Blue Mountains occupy the transition zone between 

shrublands at lower elevation and dry upland forests at higher elevation (fig. 6.20). 

These woodlands occupy the driest of the tree-dominated vegetation zones in the 

Blue Mountains. Summers are hot and very dry, and winters are cold and relatively 

wet. Annual precipitation in western juniper savannas and woodlands ranges from 

13 to 75 cm, but most sites fall within the range of 25 to 50 cm yr-1 (Gedney et al. 

1999). Much of this precipitation falls during the winter as rain or snow. 

There are two woodland PVGs in the Blue Mountains—Moist UW (hot moist 

UW PAG) and Dry UW (hot dry UW PAG). These two PVGs are discussed together 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 6.20—A stand with a mixture of western juniper and 

ponderosa pine. 

for this assessment, although the Dry UW PVG is the least common PVG. Western 

juniper is dominant in all of the PAGs. The Moist UW PVG is characterized by 

understory shrubs such as mountain big sagebrush, curl-leaf mountain-mahogany, 

antelope bitterbrush or the grasses Idaho fescue and bluebunch wheatgrass. The 

Dry UW PVG is characterized by understory species such as bluebunch wheatgrass, low sagebrush (Artemisia arbuscula Nutt.), and scabland sagebrush (A. rigida

[Nutt.] A. Gray). 

Western juniper has expanded its range in the interior Pacific Northwest during 

the past 130 years, invading and creating savannas and woodlands in semiarid ecosystems that were formerly shrub-steppe and grassland communities (Miller et al. 

2000). More than 90 percent of the 3.2 million ha of current juniper savannas and 

woodlands developed in the past 100 years (Miller et al. 2000). The area of juniper 

forest and woodland is estimated to have increased fivefold between 1936 and 

1988 (Gedney et al. 1999). Much of this expansion is attributed to heavy livestock 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

grazing and reduced fire frequencies (Miller et al. 2000), but woodland expansion 

may have started between 1850 and 1870 in some areas during wet, mild climatic 

conditions (Miller et al. 2005). Western junipers tolerate very dry conditions and 

can live for up to 1,000 years in the absence of disturbance (Miller et al. 2000).

Potential future changes—

Minimal experimental research has been conducted on the response of junipers to 

elevated carbon dioxide or warming temperatures. Western junipers might be expected to benefit from increasing atmospheric carbon dioxide if it reduces stomatal 

conductance and delays depletion of deep soil water, although it is unclear if improved water-use efficiency would significantly increase growth, or simply reduce 

drought stress. Increased growth of western juniper in recent decades suggests that 

elevated carbon dioxide may be increasing growth through increased water-use efficiency (Knapp et al. 2001), but such evidence is not conclusive. 

Tree-ring analyses suggest that western juniper growth is driven primarily by 

soil moisture availability and drought (Knapp et al. 2004, Knutson and Pyke 2008). 

Growth was positively correlated with winter and spring precipitation (October to 

June) and negatively correlated with spring and summer temperatures (Knutson 

and Pyke 2008). Growth sensitivity to drought was greatest at lower elevations and 

on steep, rocky sites. Cold winter temperatures also exert influence on vegetation 

communities and are almost as important as drought for limiting photosynthesis in 

juniper woodlands (Runyon et al. 1994). Extreme cold temperatures can also function as a disturbance agent (Knapp and Soule 2005). 

Juniper woodlands may increase in abundance in future scenarios associated 

with increased winter and spring precipitation. However, higher spring and summer 

temperatures may negatively affect juniper woodlands, particularly at lower elevations and for hot dry UW PAGs. Areas with increased juniper density from recent 

land use history may be particularly vulnerable to future climate change. However, 

suitable climate habitat currently occupied by dry UFs may offset these losses. 

Recent research suggests that increased precipitation intensity (the same 

amount of precipitation falling in fewer storms) can result in moisture reaching 

deeper portions of the soil profile, and that juniper and other woody plants are able 

to access the deeper moisture better than grasses and herbs. Woody plant encroachment observed over the last century could continue into the future should precipitation intensity increase (Kulmatiski and Beard 2013).

As temperatures warmed during the early Holocene, western juniper began 

migrating north into its present range in the Pacific Northwest. Since the arrival 
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GENERAL TECHNICAL REPORT PNW-GTR-939

of western juniper in central and eastern Oregon (circa 6,600 to 4,800 BP), northeastern California, and southeastern Idaho, its abundance and distribution have 

fluctuated (Miller et al. 2005). Dry climatic periods can cause regional declines of 

juniper, whereas wetter periods (wet summers, mild winters) can cause expansion. 

Paleoecological evidence suggests that juniper woodlands may increase in abundance in future scenarios associated with increased winter temperatures (virtually 

all scenarios) and increased spring and summer precipitation. The Moist UW PVG 

may become more abundant with this type of scenario. A warm, dry scenario may 

result in decreased western juniper abundance, although species characteristic of 

the Dry UW PVG may be better adapted to these conditions. Data from the Blue 

Mountains indicate that the shrub-steppe boundary was higher in elevation in the 

past during the warmer and drier Holocene (fig. 6.3), and a similar shift in the 

forest-woodland boundary might be expected. 

Model output—

Species distribution models indicate that climate habitat for western juniper, curlleaf mountain-mahogany, and big sagebrush will be almost nonexistent (table 6.2). 

However, MC2 output shows that temperate needleleaf woodlands will most likely 

increase in abundance, except for one scenario that represents the least amount 

of change (fig. 6.5). Assuming process models are more robust than species distribution models for projecting vegetation responses to climate change, we would 

expect an increase in these PVGs across the landscape, an inference that is consistent with the temperature and moisture tolerances of major species associated with 

woodland PVGs. 

Disturbance—

Historical fire regimes are not well described for juniper savannas and woodlands 

in Oregon (Agee 1993, Young and Evans 1981). Young junipers have thin bark and 

are readily killed by fires. Junipers that avoid fires early in their lifespan can subsequently escape injury and death from fire by having thicker bark and suppressing understory herbaceous fine fuels through competition for water (Agee 1993). 

Consequently, fire-scarred junipers are limited to microsites with limited fine fuel 

production. Fire scars in scattered or adjacent ponderosa pine forests might suggest 

a mixed-severity fire regime, with mean fire-return intervals of 15 years to more 

than a century and occasional large fires (Agee 1993, Miller and Rose 1999, Miller 

et al. 2005). Romme et al. (2009) noted that in many places in the West, fire-return 

intervals in juniper woodlands were very long (generally measured in centuries). 

In this predominantly fuel-limited biome, climate change effects on fire frequency 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

and severity will likely depend on changes in soil water availability and its effect on 

understory plant productivity (fuel generation).

Many of these woodlands were also homesteads at the turn of the century, have 

been subject to livestock grazing for over a century, and are still used for grazing. 

These systems are also highly changed because of exotic annual grass invasion, 

particularly after tree harvest and natural disturbances. In general, sites supporting 

moist and cooler upland woodlands and sites dominated by mountain big sagebrush 

are more resistant to invasion by juniper than sites dominated by other species or 

subspecies of sagebrush (e.g., Wyoming big sagebrush [Artemisia tridentata Nutt. 

ssp. wyomingensis Beetle & Young]) found in warmer and drier conditions 

(Miller et al. 2013).

Synthesis—

Higher spring and summer temperatures may negatively affect some very hot and 

dry juniper woodlands at lower elevations. However, it is unlikely that these PVGs 

will be greatly reduced across the landscape (although locations of juniper woodlands could shift), given the (1) adaptability of juniper to drought, (2) potential 

availability of habitat currently occupied by dry upland forests, and (3) continued 

fire suppression policies. In the future, years of wet and mild climatic conditions, 

particularly above-average spring and summer precipitation, will most likely facilitate the continued expansion of juniper. Increased fire frequency and severity associated with future warming could reverse this trend and lead to conversion of some 

of these woodlands to persistent grasslands. This disturbance-mediated effect may 

help reduce ongoing conversion of shrublands and grasslands to juniper woodlands, 

although grassland dominance may be accompanied by increasing dominance of 

nonnative annual grasses. 

Moist and Dry Upland Shrublands

Moist USs (warm moist, hot moist, very hot moist) and Dry USs (hot dry and warm 

dry) are not common in the Blue Mountains and are discussed together for this 

assessment. These PVGs tend to occupy the transition zone between woodlands at 

the upper elevation and grasslands at the lower elevation, but can also be found in 

forest openings or near ridge tops at higher elevation (e.g., snow openings, snowberry shrublands). Numerous community types differ according to the dominant 

grasses and shrubs, and species distribution largely reflects underlying gradients in 

annual mean precipitation and soil properties (Franklin and Dyrness 1973). Characteristic species for the moist US PVG include mountain big sagebrush, antelope 

bitterbrush, snowberries, bitter cherry (Prunus emarginata [Douglas] Eaton), 

Higher spring and 

summer temperatures 

may negatively affect 

some very hot and dry 

juniper woodlands at 

lower elevations.
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GENERAL TECHNICAL REPORT PNW-GTR-939

curl-leaf mountain-mahogany, and cool season (C3) bunchgrasses (e.g., Idaho 

fescue, bluebunch wheatgrass, Sandberg bluegrass [Poa secunda ssp. secunda J. 

Presl]). The dry US PVG is characterized by low, scabland, and threetip sagebrush 

(Artemisia tripartita Rydb.). The climate is classified as arid to semiarid with low 

precipitation, hot dry summers, and relatively cold winters, and these shrublands 

have often been described as cold desert or high desert (Franklin and Dyrness 

1973). Some of these sites, particularly those in the Dry US PVG, have high value 

for traditional and tribal use. Camas (Camassia spp.), bitterroot (Lewisia rediviva

Pursh), cous biscuitroot (Lomatium cous [S. Watson] J.M. Coult. & Rose), yampah 

(Perideridia spp.), and other American Indian first-food plants are often associated 

with scabland environments assigned to the Dry US PVG.

Potential future changes—

Soil moisture and winter temperature are the major limiting factors influencing 

vegetation composition and productivity in Pacific Northwest steppe communities; precipitation, temperature, soil texture, and soil depth are the primary abiotic 

determinants of soil moisture (Bates et al. 2006, Comstock and Ehleringer 1992, 

Schlaepfer et al. 2012). Winter snow and rain are important for recharging water 

storage in deep soil layers (Schlaepfer et al. 2012, Schwinning et al. 2003), and most 

precipitation in the Blue Mountains occurs during the winter and spring. However, 

high temperatures and low summer precipitation combine to produce extended 

periods of soil moisture deficits each summer. Although summers are warm and 

dry, winters can be quite cold throughout much of the steppe region in the Pacific 

Northwest (Comstock and Ehleringer 1992).

Shrubs in this PVG are generally well-adapted to both cold winter temperatures and summer drought, particularly the Dry US PVG. Sagebrush is tolerant of 

summer drought and is unresponsive to shifts in the seasonality of precipitation 

in regard to cover and density (Bates et al. 2006). Some shrubs are able to tolerate 

drought and remain photosynthetically active during periods of water and heat 

stress (Depuit and Caldwell 1975) or avoid severe drought stress by developing 

deep root systems that allow them to access deep soil water reserves throughout the 

summer (Franklin and Dyrness 1973). Schlaepfer et al. (2014) recently synthesized 

knowledge about natural big sagebrush regeneration. They noted that increases 

in temperature may not have a large direct influence on regeneration owing to 

the broad temperature optimum for regeneration. However, indirect effects could 

include selection for populations with less stringent seed dormancy. Drier conditions may have negative effects on germination and seedling survival and could 

also lead to lighter seeds, which lowers germination success further. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Moist US may be particularly vulnerable to future climate shifts, particularly at 

the lower ectone. Upland shrublands at low elevations may decrease in productivity in response to prolonged summer drought. Increased winter precipitation may 

allow soil recharge, but it is unclear if the capacity of these systems is adequate to 

avoid high stress and mortality in the summer. Paleoecological evidence suggests 

an increase in sagebrush with warming. Data from the Blue Mountains indicate that 

the shrub-steppe boundary was higher in elevation in the past during the warmer 

and drier early to mid-Holocene (fig. 6.3). 

Species distribution models project nearly complete loss of habitat for big 

sagebrush, curl-leaf mountain-mahogany, and antelope bitterbrush (table 6.2). 

Models by others suggest that sagebrush distribution may decrease, with strong 

decreases in the southern part of the range and increases in the northern parts and 

at higher elevations (Schlaepfer et al. 2012). Simulation results for big sagebrush 

from a process model (under 2070–2099 CMIP5 climate scenarios) support expectations of increased probability of regeneration at the leading edge of the current 

big sagebrush range and decreased probability at the trailing edge compared to 

current levels. MC2 projects that although temperate (C3) shrublands will decline, 

xeromorphic (C4) shrublands (shrublands with an understory C4 grass component) 

will increase markedly. Currently, C4 grasses occur only in Hells Canyon National 

Recreation Area, typically within grassland communities. It is unclear if C4 grasses 

will actually increase in this region without adequate summer precipitation, but it is 

likely that more drought-tolerant species like sagebrush will increase in dominance 

within this PVG at the expense of species adapted to moister and cooler conditions. 

Thus, model output suggests that some shrubland species may decline, but that 

shrublands overall may increase markedly across the landscape. 

Disturbance—

In productive mountain big sagebrush plant associations, such as those that include 

Idaho fescue, mean fire-return intervals ranged from 10 to 25 years, with large fires 

every 38 years (Miller et al. 2005). However, fire was much less frequent in the 

more arid plant associations such as Wyoming big sagebrush/Thurber’s needlegrass 

(Achnatherum thurberianum [Piper] Barkworth) (50 to 70 years) and low sagebrush/

Sandberg bluegrass (Miller and Rose 1999, Young and Evans 1981), where fire-free 

periods of 90 (Young and Evans 1981) and 138 years (Miller and Rose 1999) were 

reported in northern California and south-central Oregon, and fire-free periods 

probably exceeded 150 years for some sites. Baker (2006) argues that historical fire 

rotations were 70 to 200 years in mountain big sagebrush and longer in other types. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Long-term charcoal records suggest that fire regimes in these vegetation types

are climate and fuel driven; sagebrush densities and fire frequencies increased

during wet periods (decades to centuries) and declined during dry periods (Mensing 

et al. 2006).

Multiple shrub species are characteristic of these PVGs. Big sagebrush, antelope bitterbrush, and curl-leaf mountain-mahogany are fire sensitive and can be 

temporarily eliminated from a site by burning. Recovery of shrub canopy cover to 

predisturbance levels can require 10 to 50 years or more, with recruitment of new 

shrubs from soil seed banks being an important factor controlling recovery time 

(Ziegenhagen and Miller 2009). Short fire-return intervals can cause significant 

changes in species and productivity if shrub communities have not fully recovered 

between disturbances (Davies et al. 2012). 

Shrublands, particularly Dry USs, are also prone to invasion by nonnative 

annual grasses (box 6.6). In some areas, introductions of invasive plant species such 

as cheatgrass and medusahead (Taeniatherum caput-medusae [L.] Nevski) have significantly altered fire regimes by producing sufficient fine fuels to carry wildfires 

(D’Antonio and Vitousek 1992). Other important disturbances and stressors in these 

systems include juniper expansion, livestock grazing, and land conversion owing to 

agriculture or development. 

Synthesis—

Paleoecological data suggest sagebrush generally increased during warm periods 

in the past. However, in the early to mid-Holocene (warmer, drier) the shrub-steppe 

boundary was located higher in elevation, and results regarding shifts in sagebrush distribution and regeneration support this expectation. Less is known about 

other shrub species. However, species distribution models indicate highly reduced 

available climate habitat for many shrubs, but output from MC2 projects that xeromorphic shrublands will increase significantly. It is likely that increased warming 

would result in increased coverage of ecosystems better adapted to arid conditions 

ecosystems, such as shrublands. However, as wildfires and warmer conditions increase, there is a risk of conversion to nonnative annual grasslands in these systems, 

particularly for the drier PAGs.

Moist and Dry Upland Herbland

Moist UH (warm very moist, warm moist, hot moist, very hot moist) and Dry UH 

(hot dry and warm dry) are discussed together for this assessment. Dry UH is a 

more common PVG than Moist UH. Grasslands encompass numerous grass-dominated vegetation community types that differ according to the dominant grasses 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 6.6—Nonnative annual grasses

Nonnative annual grasses such as cheatgrass, medusahead, and North Africa grass 

(Ventenata dubia [Leers] Coss.) alter fire regimes and are some of the most important 

ecosystem-altering species on the planet (Brooks et al. 2004). Cheatgrass is widely 

distributed in western North America (USDA and NRCS 2013) and is abundant and 

dominant in steppe communities (Mack 1981). Following disturbance, this species is 

capable of invading low-elevation forests (Keeley et al. 2003, Keeley and McGinnis 

2007, Kerns et al. 2006) and creating surface fuel continuity between arid lowlands 

and forested uplands (fig. 6.21). Highly competitive traits enhance its ability to 

exploit soil resources after fire and to increase its status in the community (Melgoza 

and Nowak 1991, Melgoza et al. 1990), and dominance may be persistent (Zouhar 

2003). After establishment, cheatgrass tends to increase the probability of subsequent 

wildfire occurrence (D’Antonio and Vitousek 1992) because the fine, continuous, 

and highly combustible fuels dry early in the season, increasing the length of the 

fire season in some ecosystems. Aside from the potential threat to biodiversity from 

this type of change, conversion of forests and woodlands to grasslands has important 

implications for carbon cycling and feedbacks between climate and the biosphere, 

because forests sequester large amounts of carbon (Bonan 2008).

A species distribution model that assumed lower (summer) precipitation in the 

future projected expansion of cheatgrass in a warmer climate (Bradley et al. 2009). 

However, when higher precipitation is included in the model, the area of reduced 

habitat for cheatgrass was reduced as much as 70 percent. Increases in productivity in 

response to elevated carbon dioxide has been documented, and elevated atmospheric 

carbon dioxide may have already contributed to cheatgrass productivity and fuel 

loading and associated effects on fire (Ziska et al. 2005). Because of the fire and 

Figure 6.21—Cheatgrass invasion in a ponderosa pine stand after a prescribed fire that 

caused substantial overstory mortality (Malheur National Forest). 

Becky Kerns
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 6.6 (continued)

invasive grass cycle, changes in future fire regimes are important climate considerations for nonnative annual grasses. More area burned, more frequent large wildfires, 

larger extent of high-severity fire, longer wildfire durations, and longer wildfire 

seasons are expected in the future (Lutz et al. 2009, Miller et al. 2008, Nydick and 

Sydoriak 2014, Westerling et al. 2006), thus increasing the invasion risk of nonnative 

annual grass species. 

The likelihood of forest, woodlands and shrublands being invaded by nonnative 

annual grasses in a warmer climate will increase because of more disturbance, effects 

of warming on species distributions, enhanced competitiveness of nonnative plants 

from elevated carbon dioxide, and increased stress to native species (Breshears et al. 

2005, Dukes and Mooney 1999, Pauchard et al. 2009, Ziska and Dukes 2011) (fig. 6.8). 

Warming alone may increase the risk of nonnatives, because many invasive species 

have range limits set by cold temperatures, which has tended to limit their establishment in forests, particularly the higher elevation and continental western forests. Of 

particular concern in the Blue Mountains is the recent increase in North Africa grass 

and its apparent ability to outcompete and replace areas dominated by cheatgrass. The 

effectiveness of management actions to control invasive plants is decreasing in some 

areas as a result of reduced herbicide efficacy (Archambault et al. 2001, Ziska and 

Teasdale 2000), and biocontrol methods may not be as effective in a warmer climate 

(Hellmann et al. 2008).

and whose distribution largely reflects underlying gradients in annual precipitation 

and soil properties (Franklin and Dyrness 1973). The climate is classified as arid to 

semiarid with low precipitation, hot dry summers, and relatively cold winters. Most 

precipitation occurs as rain and snow in winter and spring. Moist upland grasslands 

are characterized largely by Idaho fescue and bluebunch wheatgrass (fig. 6.22). 

The absence of sagebrush suggests an improved moisture condition (Franklin and 

Dyrness 1973). Dry UHs are dominated by bluebunch wheatgrass and Sandberg’s 

bluegrass. 

Potential future changes—

Soil moisture and winter temperatures are the major environmental limiting factors influencing grassland composition, with precipitation, temperature, soil texture, 

and soil depth being the primary abiotic determinants of soil moisture (Bates et al. 

2006, Comstock and Ehleringer 1992, Schlaepfer et al. 2012). Grassland vegetation 

is generally well-adapted to both cold winter temperatures and summer drought. 

Grasses can avoid summer drought stress by concentrating growth in the spring and 

early summer, when soil water is still available and cooler temperatures promote 

high water-use efficiency (Comstock and Ehleringer 1992). Several studies also 

show that grasslands may be resistant to climate change effects (Dukes et al. 2005, 

Grasses can avoid 

summer drought stress 

by concentrating 

growth in the spring 

and early summer.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Figure 6.22—An example of a Dry Upland Herbland dominated by Idaho fescue, Umatilla 

National Forest. This site is considered to be in good condition.

Mark Darrach

Grime et al. 2008). Short-term changes in the interannual precipitation regime may 

not result in large changes in semiarid vegetation communities (Jankju 2008). 

In a warmer climate, grasslands at lower elevation may shift in dominance 

towards more drought-tolerant species (e.g., less Idaho fescue) (Blinnikov et al. 

2002) (fig. 6.5). There is essentially no model output available for individual grassland species, although Reeves et al. (2014) project that net primary productivity 

will increase in eastern Oregon grasslands in a warmer climate. MC2 projects that 

C3 grasslands will decline significantly, but that warm season (C4) grasslands will 

expand. However, the expansion of C4 grasses in the model is based on changes in 

temperature alone, and it is unlikely that C4 grasses will increase markedly in the 

future unless summer precipitation increases as well. Most GCMs project increased 

aridity in the summer. A potential shift from C3 to C4 grassland species is uncertain, although a shift in species composition to drought-tolerant species might be 

expected.

Disturbance—

Grasslands have been greatly affected by human activities, including livestock 

grazing, introduction of nonnative species, and agriculture (Humphrey 1943, 

Tisdale 1961). Grazing first became a major factor in Pacific Northwest steppe com-
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GENERAL TECHNICAL REPORT PNW-GTR-939

munities with the introduction of cattle grazing in 1834 and sheep grazing in 1860. 

Settlers also introduced numerous nonnative grasses, including cheatgrass, which 

was well-adapted to climate within parts of the steppe region, and heavy grazing 

allowed nonnative grasses to invade native communities where they became highly 

persistent (Mack 1981). In addition to grazing, many grasslands have been cultivated for dryland agricultural crops like winter wheat or irrigated to produce summer 

fruits, vegetables, and grains. Homesteading on what is now public land was common in many tributaries of the Snake River and in Hells Canyon.

Wildfire occurrence is generally limited by lack of ignitions during the fire 

season or by lack of continuous fuels in particular on scabland communities on 

shallow soils. Cold season bunchgrass communities often have continuous fuels 

to carry fire. The extensive grasslands in Hells Canyon National Recreation Area 

have experienced numerous large grassfires, and much of the area has burned at 

least once since 1980. Many of the dominant bunchgrasses recover well from fires 

by resprouting from belowground organs and can achieve prefire abundance within 

5 years. Fire-return intervals of less than 5 years have been documented only in 

isolated instances. However, in some areas, introductions of invasive plant species 

such as cheatgrass, medusahead, and North Africa grass have altered fire regimes 

by producing sufficient fine fuels to carry wildfires at higher frequencies than 

tolerated by perennial native grasses (D’Antonio and Vitousek 1992) (box 6.4).

Synthesis—

Grasslands may shift in dominance towards more drought-tolerant species, particularly at lower elevations and on more arid sites. Nonnative annual grasses may also 

increase in importance. In general, it is likely that with increased warming and fire 

occurrence, grasslands will become a bigger component of the landscape, particularly where shrublands and woodlands are no longer able to support woody species

Conclusions

Climate change is expected to alter vegetation structure and composition, terrestrial 

ecosystem processes, and the delivery of ecosystem services in the Blue Mountains. 

Climate influences the spatial distribution of major vegetation biomes, abundance 

of species and communities within biomes, biotic interactions, and geographic 

ranges of individual species. Climate also influences disturbance processes that 

shape vegetation structure and composition, which are often the catalysts for 

vegetation change. However, there is considerable uncertainty in what the actual 

effects on vegetation owing to climate change could be. Waring et al. (2011) report 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

that the Pacific Northwest has seen a significant decrease in the competitiveness of 

over 50 percent of the evergreen species in six ecoregions, with the highest concentration towards the northern and southern limits of their analysis area. However, 

these authors assigned the Blue Mountains a relatively low vulnerability score.

In a warmer, drier climate (especially in summer), the following may occur in 

the Blue Mountains by the end of the 21st century, although we note that there is 

considerable uncertainty about the future:

• The importance of pine and sagebrush species may increase.

• The forest-steppe ecotone may move north of its present position or up in 

elevation.

• Ponderosa pine may be found at higher elevations.

• Subalpine and alpine systems are potentially vulnerable, and subalpine tree 

species may be replaced by high-elevation grasslands, pine, or Douglas-fir.

• Juniper woodlands, which have been increasing in recent decades, may be 

reduced if longer and drier summers lead to more wildfire.

• Grasslands and shrublands at lower elevations may increase across the 

landscape but shift in dominance towards more drought-tolerant species.

• Nonnative species, including annual grasses, may increase in abundance 

and extent. 

In general, species with life histories tolerant of frequent disturbance and 

highly altered environments will be more dominant because they can establish and 

persist in rapidly changing environments. 

Tree growth in energy-limited portions of the landscape (high elevations, north 

aspects) may increase as the climate warms and snowpack decreases, whereas tree 

growth in water-limited portions of the landscape (low elevations, south aspects) 

will probably decrease. Some species may respond positively to higher concentrations of ambient carbon dioxide as a result of increased water-use efficiency, 

although this “fertilization” effect may diminish as other factors become limiting.

Ecological disturbance (e.g., fire, insect, and disease outbreaks), which is 

expected to increase in a warmer climate, will be extremely important in affecting 

species distribution, tree age, and forest structure, facilitating transitions to new 

combinations of species and vegetation patterns. Mountain pine beetle may be 

particularly important in lodgepole and ponderosa pine forests, and western spruce 

budworm and Douglas-fir tussock moth may also increase periodically. Annual 

area burned by wildfire is expected to increase substantially, and fire seasons will 

likely lengthen. In dry forest types where fire has not occurred for several decades, 

crown fires may result in high tree mortality. In addition, the interaction of multiple 
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GENERAL TECHNICAL REPORT PNW-GTR-939

disturbances and stressors will create or exacerbate stress complexes. For example, 

an extended warm and dry period may increase bark beetle activity, which would 

increase short-term fine fuels. 

Considerable uncertainty exists about how climate change will affect species 

distribution, forest productivity, and ecological disturbance in the Blue Mountains. 

Simulation models provide science-based projections of how a warmer climate 

could modify the growth environment of species and broad patterns of ecological 

disturbance, supplemented by studies of the paleoecology of the region. However, 

because the future climate may differ considerably from what has been observed in 

the past, it is difficult to project vegetative response accurately for specific locations 

and time periods.

Adapting Vegetation Management to Climate Change in 

the Blue Mountains

Despite the uncertainty associated with climate change, there are many proactive 

steps that land managers can take that are likely to increase ecosystem resilience 

to climate change (e.g., Halofsky et al. 2011, Raymond et al. 2015). Based on the 

vulnerability assessment information presented in this chapter, and on documented 

adaptation principles (e.g., Millar et al. 2007, Peterson et al. 2011, Swanston and 

Janowiak 2012), workshop participants identified strategies, or general approaches, 

for adapting vegetation management to climate change (table 6.8). Participants also 

identified more specific on-the-ground tactics, or actions, associated with each 

adaptation strategy and considered the implementation of those tactics, specifically 

the timeframe for implementation, opportunities and barriers to implementation, 

and information needs (table 6.8). Adaptation strategies and tactics were focused on 

addressing potential increases in fire and invasive species (table 6.8 a, b, c), insect 

outbreaks (table 6.8 d), increases in temperatures and droughts (table 6.8 e, f), and 

effects of increasing temperatures on alpine and subalpine plant communities (table 

6.8 g, h). These adaptation strategies and tactics are summarized below. 

While the strategies and tactics described here do not include all potentially 

appropriate vegetation-related actions to take under a changing climate, they do 

include those that workshop participants thought were most important. However, 

not all of these strategies and tactics are appropriate in all places and in all situations, and they should be evaluated by managers on a case-by-case basis. Many 

of these ideas will require additional thought and analysis before they can be 

implemented.

Despite the uncertainty 

associated with climate 

change, there are many 

proactive steps that 

land managers can 

take.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 6.8a—Adaptation responses for vegetation to climate change in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation

Barriers to implementation Information needs

Sensitivity to climatic variability and change: Larger and more severe fires in forest ecosystems. Adaptation strategy: Manage forest vegetation to reduce severity and patch size; protect refugia (e.g., old trees). Map fire refugia <10 years, 

opportunistic

Coordination with project planning Lack of knowledge on current location and conditions of 

fire refugia

Compilation of locations of fire

refugia with a consistent protocol

Use gaps and other methods in silvicultural prescriptions to reduce 

fuel continuity

<10 years, 

opportunistic

Coordination with project planning

Identify processes and conditions 

that create fire refugia

<10 years, 

opportunistic

Coordination with project planning Lack of knowledge on current location and conditions of 

fire refugia

Compilation of locations of fire

refugia with a consistent protocol

Adaptation strategy: Manage forest landscapes to encourage fire to play a natural role Implement fuel breaks at strategic 

locations

<10 years Coordination with roadside 

treatments

Blue Mountains restoration 

strategy

Limited capacity for National 

Environmental Policy Act analysis

Maps of lightning- and human-caused 

ignitions

Identify areas where wildland fire 

use may help to meet management objectives

<10 years Use and interpretation of the 

Wildland Fire Decision Support System

Risk aversion by fire managers Incorporation of additional information in the Wildland Fire Decision 

Support System, especially on resources that benefit from fire

Implement strategic density management through forest thinning <10 yearsIncorporate climate change in Wildland Fire Decision Support System <10 years to >30 years Public education on the benefits of fuel reduction and prescribed fire
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GENERAL TECHNICAL REPORT PNW-GTR-939 Table 6.8b—Adaptation responses for vegetation to climate change in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs Sensitivity to climatic variability and change: Higher wildfire frequency will cause increased mortality of shrub species and increased dominance of invasive species. Adaptation strategy: Increase resilience of native sagebrush-grass ecosystems. Promote the occurrence and growth of early-season native species <10 years Collaboration with range permitees Effects of a warmer climate on plant phenology

Reduce grazing in July and August 

to encourage perennial growth

10 to 30 years Collaboration with range 

permitees

Opposition by some range 

permitees; economic issues

Revise grazing policies, and review 

and evaluate grazing allotment plans

>30 years Possible in some political 

environments

Entrenched policies for grazing; economic issues; effects 

on lifestyle

Adaptation strategy: Maintain vigorous growth of native shrub, perennial grass, and other perennial species, while minimizing the spread of invasive

species

Remove encroaching conifers <10 years Collaboration with range permitees; coordination with fuel 

reduction projects; coordination with sagebrush restoration projects

Funding issues; potential 

challenges with invasive species

Synthesis of information on effects 

of conifer removal; prioritization of treatment areas

Plant seed of native species <10 years Postfire seeding; coordination 

with fuel reduction projects; coordination with sagebrush restoration projects

Low success of seeding Improved acquisition of native seed

Monitor successional patterns of 

vegetative communities

<10 years New LIDAR imaging Cost of long-term monitoring; 

difficulty of on-the-ground location accuracy

Framework for timely and efficient 

monitoring

Adaptation strategy: Maintain reproducing populations of curl-leaf mountain-mahogany, so it can expand as neededStrategically protect mountainmahogany populations to allow 

for natural reseeding after fire

<10 years to  30 years

After wildfire; during planning 

for grazing allotment management

Lack of resources; opposition 

by grazing permitees

Map of existing mountain-mahogany 

populations
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 6.8c—Adaptation responses for vegetation to climate change in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation

Barriers to implementation Information needs

Sensitivity to climatic variability and change: Higher temperatures and increased fire frequency and intensity will reduce the dominance of native grasses 

and increase dominance of nonnative annual species.

Adaptation strategy: Increase the resilience of native perennial grasses and other nontree vegetation.Apply prescribed burning in the 

spring

Ongoing Integration in existing fuels 

reduction programs

Potential increase in invasive 

species

Information on range condition 

and high-priority areas for treatment

Adaptation strategy: Manage grazing by livestock and ungulates to reduce impacts on perennial grasses.Focus grazing on nonnative species 

in spring; do not graze natives in summer

<10 years to 

30 years

Acceptance will be slow; collaboration with permitees to 

modify allotment plans

Opposition by permitees Information on range condition 

and resilient locations

Find locations where late-season 

grazing has minimal impacts

<10 years Acceptance will be slow; collaboration with permitees to 

modify allotment plans

Opposition by permitees Information on range condition 

and resilient locations

Adaptation strategy: Manage fire to avoid increase in nonnative annual species.Apply prescribed burning in the 

spring

<10 years Integration in existing fuels 

reduction programs

Potential increase in invasive 

species; small period of time for implementation

Identification of wildland-urban 

interface; seasonal fire forecasts

Adaptation strategy: Manage soil conditions to avoid increased runoff after wildfire.Maximize native vegetative ground 

cover 

<10 years Variability of local site conditions Soil mapping; erosion modeling

Adaptation strategy: Determine potential resilience of different locations, and actively restore less resilient sites.Increase resilience of native species 

where intact or productive communities exist

<10 years Monitoring of existing vegetative communities Monitoring of areas that need protection

Decrease resilience of existing nonnative species with appropriate 

management practices 

10 years to 

>30 years

Spring grazing Improved communication with 

public

Identify and promote early successional natives that may be able to 

compete with nonnatives

10 years to 

>30 years

Coordination with other 

projects that have identified suitable early successional native species and reduction in nonnatives

Improved local knowledge and 

testing of native cultivars
222

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 6.8d—Adaptation responses for vegetation to climate change in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: Uncharacteristic size and severity of ecological disturbances in forest ecosystems: insects Adaptation strategy: Recognize natural role of insect disturbances, and identify areas at high risk.Allow for natural mortality within 

the historical range of variability for specific insects

<10 years, 

depending on insect cycle

National forest land management 

plan revision

Public opposition Identify scale at which mortality 

is acceptable, relative to current objectives

In dry forest, restore low-severity 

fire to lower stand density and increase resilience to bark beetle outbreak

10 to >30 

years

Coordination with project 

planning

Inadequate resources to 

conduct restoration at large spatial scales

Adaptation strategy: In forest types where the risk of insect outbreaks is high, promote diversity of forest age and size classes.Diversify large contiguous areas of 

single-age and single-size classes 

Coordination with project 

planning

Inadequate resources; 

public opposition; internal opposition

Historical/desired conditions for 

landscape pattern and patch size
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 6.8e—Adaptation responses for vegetation to climate change in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation

Barriers to implementation Information needs

Sensitivity to climatic variability and change: A warmer climate with more droughts will reduce growth in most forests and make regeneration more 

difficult for some species.

Adaptation strategy: Protect genotypic and phenotypic diversity.Protect trees that exhibit adaptation 

to water stress, (e.g., trees with low leaf area/sapwood); collect seed for future regeneration

<10 years Coordination with project 

planning

Identification of trees with low 

leaf/sapwood area by marking crews; Identification of successful adaptation by trees to stress

Better understanding of the phenotypic adaptive capacity of different tree species

Maintain variability in species and 

in tree architecture 

10 to 30 years Coordination with project 

planning

Adaptation strategy: Maintain and enhance forest productivity regardless of tree species; focus on functional ecosystems and processes. Manage tree densities to maintain 

tree vigor and growth potential

<10 to >30 

years

Coordination with project 

planning

Prepare for species migration by 

managing for multiple species across large landscapes

10 to 30 years Coordination with project 

planning

Maintain soil productivity through 

appropriate silvicultural practices

>30 years Coordination with project 

planning

Adaptation strategy: Use judicious managed relocation of genotypes where appropriate.Push boundaries of seed zones and 

plant genotypes from warmer locations; use a variety of genotypes rather than just one

10 to 30 years, 

opportunistic

Coordination with forest 

regeneration projects

Adaptation strategy: Use tree improvement programs to ensure availability of drought-tolerant tree species and genotypes.Develop seed orchards that contain 

a broader range of tree species and genotypes than in the past

10 to >30 years Good foundation in existing 

seed orchards

Time required to develop new 

capacity

Data on tree genetics across broad 

landscapes to guide development of nursery stock and regeneration strategies
224

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 6.8f—Adaptation responses for vegetation to climate change in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers .to implementation Information needs Sensitivity to climatic variability and change: Higher temperatures and increasing drought will stress some species in moist mixed-conifer forests, especially western larch. 

Adaptation strategy: Maintain vigorous existing western larch and encourage its regeneration.Create gaps in forests to reduce 

competition and increase larch vigor

<10 years, 

opportunistic

Tree mortality of other species, 

which creates gaps for larch regeneration (after wildfire and insect outbreaks)

Public opposition to large 

forest openings

Data on current distribution of 

larch; studies on gap sizes needed for regeneration

Regenerate larch with appropriate 

site preparation (e.g., prescribed burning, followed by planting) 

<10 years, 

opportunistic

Following timber harvest, wildfire, and insect outbreaks

Table 6.8g—Adaptation responses for vegetation to climate change in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation

Barriers to implementation Information needs

Sensitivity to climatic variability and change: Higher temperatures may increase stress for some species in cold upland and subalpine forests.Adaptation strategy: Protect rare and disjunct tree species (Alaska cedar, limber pine, mountain hemlock, and whitebark pine).Plant and encourage regeneration of 

rare and disjunct species in appropriate locations

Opportunistic Following wildfire

Plant whitebark pine genotypes 

that are resistant to white pine blister rust

<10 years, 

opportunistic

Limited availability of rustresistant nursery stock
225

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 6.8h—Adaptation responses for vegetation to climate change in the Blue MountainsAdaptation tactic Timeframe

Opportunities for implementation

Barriers to implementation Information needs

Sensitivity to climatic variability and change: Higher temperatures may increase stress for some alpine plant species (including rare plants), especially in 

the Wallowa Mountains. 

Adaptation strategy: Improve our understanding of the effects of climatic variability and change on alpine plant species. Install GLORIA plots to 

monitor species distribution and abundance

<10 years

Collaborate with other federal agencies to monitor alpine species <10 years to 30 yearsGLORIA = Global Observation Research Initiative in Alpine Environments.
226

GENERAL TECHNICAL REPORT PNW-GTR-939

Responding to Increased Fire and Invasive Species 

Establishment 

Increased temperatures with climate change will likely lead to increased wildfire 

area burned (Littell et al. 2010, McKenzie et al. 2004, Westerling et al. 2006). With 

increasing fire in forested ecosystems, managing vegetation to reduce fire severity 

and decrease fire patch size could help to protect fire refugia and maintain old trees 

(Peterson et al. 2011). For example, incorporating openings in silvicultural prescriptions decreases forest density and fuel continuity, which may reduce wildfire 

severity and protect old trees (Churchill et al. 2013, Stine et al. 2014) (table 6.8a). 

Management practices that help fire to play a more natural role in ecosystems, such 

as density management, prescribed fire, and wildland fire use, may also increase 

ecosystem resilience to wildfire under a changing climate (Peterson et al. 2011, 

Stephens et al. 2010, Stine et al. 2014) (table 6.8a). 

In shrubland and grassland systems, increased area burned will likely lead to 

increased mortality of shrub species and native grasses, and increased abundance of 

nonnative species, annual grasses in particular (Creutzburg et al. 2014). Adaptation 

strategies and tactics to address these sensitivities include increasing the resilience 

of native ecosystems through grazing management (i.e., avoid grazing practices 

that promote invasive species establishment), active restoration of less resilient sites 

(e.g., plant natives on sites dominated by invasive species), and management of soil 

resources to maintain stability and productivity (e.g., establish native vegetation to 

stabilize eroded areas). 

Responding to Increased Insect Outbreaks

Native insect species have long played a role in Blue Mountain ecosystem dynamics (Oliver et al. 1994), and it will be important to recognize this role and accept 

that there will be insect-caused tree mortality under changing climate (table 

6.8d). However, there are some management actions that may increase ecosystem 

resilience to native insect outbreaks, such as mountain pine beetle outbreaks. For 

example, restoring historical fire regimes in dry forests, and increasing diversity of 

forest structure and age and size classes may help to minimize the impacts of insect 

outbreaks (Churchill et al. 2013). Increasing tree species diversity may also help to 

improve resilience to insect outbreaks (Dymond et al. 2014), particularly in lowdiversity stands (e.g., stands where ponderosa pine and western larch were removed 

and grand fir dominates). 

Increasing tree species 

diversity may also help 

to improve resilience 

to insect outbreaks, 

particularly in lowdiversity stands.
227

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Responding to Increasing Temperatures and Droughts

Increasing temperatures will likely decrease productivity in water-limited forests 

and inhibit regeneration of some species (Littell et al. 2010). Protecting trees 

that exhibit adaptation to water stress (e.g., trees with low leaf-area-to-sapwood 

ratios) and collecting seed from these individuals for future regeneration could 

help to increase resilience to water stress (table 6.8e). To ensure success of future 

revegetation efforts, seed-use plans should reflect seed needs based on projected 

climate change and disturbance trends. Managers may want to ensure that seed 

orchards contain tree species and genotypes that are well-adapted to drought and 

disturbance, and for some species, resistant to disease (e.g., white pine blister rust). 

Managers may also want to push the limits of seed zone boundaries and include 

seed from lower elevations in plantings. 

With changing climate, it will be important to promote forest productivity 

and ecosystem function (table 6.8e). In some cases, managers may want to protect 

certain species that will be susceptible to increased drought stress, such as western 

larch in moist mixed-conifer forests (table 6.8f). Silvicultural practices that maintain densities to maximize tree growth and vigor and that protect soil productivity 

will likely help to maintain ecosystem function.

Responding to Effects of Increasing Temperatures on Alpine and 

Subalpine Plant Communities

Higher temperatures are likely to increase water stress for some species in cold 

upland and subalpine plant communities. Rare and disjunct populations (e.g., 

of Alaska cedar, limber pine, whitebark pine, and mountain hemlock) may 

require protection to ensure their continued survival under changing climate 

(table 6.8g). Planting in appropriate locations could help to prevent loss of these 

populations. For whitebark pine, planting of genotypes that are resistant to 

white pine blister rust will be critical. For alpine plant species, such as those in 

the Wallowa Mountains, monitoring will be necessary to improve understanding of how climate variability and change will affect them (table 6.8h).

Acknowledgments

We appreciate input from participants in the Blue Mountains Adaptation Partnership workshop. We also thank Ray Drapek who downscaled climate data for the 

MC2 projections, and Bear Pitts, who ran the MC2 simulations. Amy Mathie, 

Michelle Day, and Danielle Bernard provided geographic information system 

support. Reviews by Larry Amell (Malheur National Forest) improved an earlier 

version of this chapter. 
228

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Chapter 7: Climate Change and Special Habitats in 

the Blue Mountains: Riparian Areas, Wetlands, and 

Groundwater-Dependent Ecosystems

Kathleen A. Dwire and Sabine Mellmann-Brown1

Introduction

In the Blue Mountains, climate change is likely to have significant, long-term 

implications for freshwater resources, including riparian areas, wetlands (box 

7.1), and groundwater-dependent ecosystems (GDEs, box 7.2). Climate change is 

expected to cause a transition from snow to rain, resulting in diminished snowpack 

and shifts in streamflow to earlier in the season (Leibowitz et al. 2014, Luce et 

al. 2012; see chapter 3). Additional effects include changes in extreme high- and 

low-flow events; alteration of groundwater recharge rates; changes in the fate and 

transport of nutrients; sediments, and contaminants, and temporal and spatial shifts 

in critical ecosystem processes and functions (Johnson et al. 2012, Raymondi et al. 

2013). Another consequence of climate change is higher frequency and severity of 

droughts (Seager et al. 2007), which will influence distribution of plant species, and 

likely increase susceptibility to insect attacks, as well as increase the frequency and 

severity of wildfires (see chapter 6). 

In this chapter, we synthesize existing information and describe the potential 

effects of climate change on riparian areas, wetlands, and groundwater-dependent 

GDEs of the Malheur, Umatilla, and Wallowa-Whitman National Forests. We begin 

by defining riparian areas, wetlands, and GDEs, highlighting the considerable 

overlap among these ecosystems, as well as the numerous definitions for them. We 

briefly describe the range of plant communities that occur in these special habitats, 

partly to highlight the existing diversity of wetland/riparian vegetation, but also as a 

basis for discussing the potential influences of climate change. Much of this chapter 

is devoted to summarizing existing information on the current condition of special 

habitats in the Blue Mountains, with focus on wetland/riparian plant communities. 

Although we describe potential changes for different riparian/wetland vegetation 

groups, we also emphasize that there is considerable uncertainty about the rates

1 Kathleen A. Dwire is a research riparian ecologist, U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station, 240 West Prospect Road, Fort Collins, 

CO 80525-2098; and Sabine Mellmann-Brown is an area ecologist, U.S. Department 

of Agriculture, Forest Service, NE Oregon Ecology Program, Malhuer, Umatilla, and 

Wallowa-Whitman National Forests, 1550 Dewey Avenue, P.O. Box 907, Baker City, OR 

97814.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 7.1—Climate change effects on riparian areas 

and wetlands in the Blue Mountains

Broad-scale climate change effects

• Higher air temperature

• Higher frequency and severity of droughts

• Decreased snowpack

• Increased rain-snow ratio

• Altered streamflow

Habitat and species

• Cottonwood-dominated riparian communities

• Wetland and riparian aspen communities 

• Willow-dominated riparian communities

• Herbaceous-dominated riparian and wetland communities

Current condition, existing stressors

Cottonwood, aspen, and willow— 

Condition:

• Decreased area owing to conversion and development of floodplains

• Degradation of stands owing to altered flow regimes (dams, diversions) and 

changes in hydrology owing to floodplain land use

Stressors: 

• Structural simplification of channels (e.g., levee construction), roads, livestock and native ungulate browsing

• Intentional clearing/removal of native riparian woody species, e.g., to 

increase herbaceous forage or pasture area for livestock grazing

Herbaceous—

Condition: 

• High cover and frequency of nonnative pasture grasses

• High cover of grazing-tolerant native species

Stressors: 

• Heavy herbivory from livestock and native ungulates

• Increasing cover of invasive or noxious plant species

• Planting or seeding of nonnative pasture grasses
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 7.1 (continued)

Sensitivity to climatic variability and change

Cottonwood, willow, and aspen—

• Decreased establishment of willow and cottonwood

• Displacement of wetland/riparian plant species with upland species 

• Decreased riparian cover

• Decreased plant growth and increased mortality

Herbaceous—

• Further decreases in native species cover and richness

• Shift in community composition

• Increased success of nonnatives

• Loss of sensitive species

Expected effects of climate change

Cottonwood, willow, and aspen—

• Increased high flows in winter

• Decreased low flows in summer

• Increased demand for water (additional diversions, reservoir expansions)

• Increased browsing pressure

Herbaceous—

• Decreased low flows in summer

• Increased demand for water

• Increased demand for forage and grazing

Adaptive capacity

Cottonwood, willow, and aspen—

• Cottonwood and willow populations have evolved within the range of 

regional streamflow variability. They are highly dependent on natural flow 

characteristics for seed germination, seedling establishment, and stand persistence. They have limited adaptive capacity where flow regimes have been 

altered. 

• Aspen and most willow species have high vegetative regenerative capacity 

following disturbance (fires, floods), which contributes to adaptive capacity. 

However, the ability to persist depends on site conditions, particularly soil 

moisture and depth to water table. 
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Box 7.1 (continued)

Herbaceous—

• Native, herbaceous wetland species have high soil moisture requirements. 

When water table elevations decline and soil moisture conditions become 

more limiting, these species are no longer competitive against more droughttolerant species, and have limited adaptive capacity. 

• Common, dominant native species (e.g., Carex aquatilis) can occur over a 

fairly wide range of soil moisture conditions, as well as grazing pressure and 

have some adaptive capacity. Less is known about the adaptive capacity of 

many native wetland sedge and forb species, but most occur within narrow 

ranges of soil saturation/soil moisture conditions. Where these conditions are 

not met, sensitive and uncommon herbaceous species will not persist. 

Vulnerable geographic locations

Cottonwood, willow, and aspen—

• Cottonwood gallery forests along low-gradient river segments are extremely 

vulnerable, particularly in floodplains with flow diversions or groundwater 

pumping. More isolated stands along higher gradient stream segments are 

less vulnerable, but still require components of the natural flow regime for 

long-term persistence. 

• Most willow stands at lower elevations along low-gradient stream segments 

have been affected by floodplain land use and are highly vulnerable. At 

higher elevations and along smaller streams, willow stands may be less vulnerable. However, willow stands may be comprised of two to eight species, 

and the requirements for establishment, growth, and persistence are largely 

unknown for some species. Willow stands may persist, but some species 

may not survive locally. 

• Riparian aspen stands along low-gradient river segments are extremely 

vulnerable, particularly in floodplains with flow diversions or groundwater pumping. Some isolated aspen stands in uplands environments may be 

largely dependent on groundwater, so vulnerability depends on underlying 

lithology. 

Herbaceous—

• The most vulnerable herbaceous communities are those that have already 

been extensively affected by grazing and other land and water uses. 

• Alpine and subalpine herbaceous communities are highly vulnerable owing 

to decreases in amount and persistence of snow. 

• Herbaceous communities at mid elevations will experience shifts in community composition, with increased cover of nonnatives and loss of uncommon 

or sensitive species, but will likely persist.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 7.1 (continued)

Risk assessment

Potential magnitude of climate change effects

• Cottonwood-dominated riparian communities: high magnitude of effects 

along major rivers, given that cottonwood forests are currently affected and 

declining in many locations.

• Willow-dominated riparian communities: moderate-high magnitude of 

effects for some species and communities. Highest risks are for communities located along stream segments already affected by grazing and flow 

alteration. 

• Wetland and riparian aspen communities: high magnitude of effects, because 

many aspen populations are known to be declining.

• Herbaceous-dominated riparian and wetland communities: moderate magnitude of effects for communities; high magnitude of effects for rare and sensitive species that will not be competitive in drier environments.

Likelihood of climate change effects

• Cottonwood-dominated riparian communities: high likelihood of effects for 

cottonwood communities located along larger floodplains.

• Wetland and riparian aspen communities: high likelihood of effects given 

current (declining) condition. 

• Willow-dominated riparian communities: high likelihood of effects given 

predictions of changes in streamflow, increases in air temperature and 

higher frequency and severity of droughts, increased human demands for 

water. 

• Herbaceous-dominated riparian and wetland communities: moderate likelihood of effects given predictions of changes in streamflow and higher 

frequency and severity of droughts, increased human demands for water and 

other resource use.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 7.2—Summary of climate change effects on 

groundwater-dependent ecosystems (GDEs) in the 

Blue Mountains

Broad-scale climate change effects

• Higher air temperature

• Higher frequency and severity of droughts 

• Higher groundwater temperature

• Decreased snowpack, especially at lower elevations

• Possible changes in groundwater recharge quantity and levels

Habitat and systems

• Springs and associated wetlands and fens, hyporheic zones, groundwater 

contribution to streamflow (baseflow) 

Current condition, existing stressors

Current condition:

• Numerous springs developed for watering livestock

• GDEs used by livestock, and native ungulates (source of water and forage)

Stressors: 

• Continued water development

• Grazing, browsing, and trampling by livestock and native ungulates 

Sensitivity to climatic variability and change

• GDEs (springs, wetlands) and stream baseflows are supported by groundwater recharge from rain and annual snowpack, especially in more permeable 

lithologies

• GDEs may contract in size or dry out in summer 

• Increased air and water temperatures and drought will stress moisturedependent flora and fauna

• Small aquifer systems are generally more vulnerable than larger systems

• Groundwater resources may be less sensitive to climate change than surface 

water, depending on local and regional geology, and surrounding land and 

water use
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 7.2 (continued)

Expected effects of climate change

• Reduced groundwater discharge to GDEs

• Reduced areas of saturated soil 

• Perennial springs may become ephemeral 

• Ephemeral springs may disappear, except during high-snow years

• For springs discharging to streams, local cooling influence on stream temperature may be reduced 

• Increased stress from effects of grazing 

• Shifts in aquatic flora and fauna communities

• Higher groundwater temperatures

• “Gaining” reaches of streams may contribute less or become “losing” 

reaches 

Adaptive capacity

• Because GDEs and the biota they support depend on continued availability 

and volume of groundwater, they have limited adaptive capacity. 

• Current information about the role of groundwater on water budgets at different scales is very limited for wildland watersheds. Although ongoing 

research may reveal adaptive capacity in some locations, current information 

suggests that groundwater resources are declining. 

Vulnerable geographic locations

• Vulnerability largely depends on elevation and underlying lithology, which 

influence the storage and movement of groundwater.

• GDEs located at higher elevations are likely the most vulnerable, given 

predicted changes in snowpack volume and persistence. As snowpacks 

decrease, less water will infiltrate into subsurface aquifers, and the amount 

of groundwater discharge will decrease. High-elevation springs and other 

GDEs may be the first to become ephemeral, dry out, and eventually 

disappear. 

• GDEs located at mid elevations may be the least vulnerable, depending on 

underlying geology and water demands. GDEs may persist in lithologies that 

support large aquifer systems. 

• GDEs located at lower elevations, including many rheocrene springs or 

springbrooks, are extremely vulnerable to increasing water demands, pressure for increased diversion or water development, and other watershed-scale 

land use effects. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 7.1 (continued)

Risk assessment

Potential magnitude of climate change effects

• High magnitude of effects for GDEs, especially those located at higher 

elevations or occurring where underlying geology only supports small shallow aquifer systems. 

Likelihood of climate change effects

• Moderate likelihood of some GDEs disappearing by 2050, but groundwater 

research and modeling are needed to identify most vulnerable aquifers and 

GDEs.

and direction of change, which depend on the physical watershed and stream 

channel conditions, past and present land use, and the reliability of climate-change 

predictions for a given area. 

Definitions

Riparian Areas

Riparian areas have been ecologically defined as “three-dimensional zones of direct 

physical and biotic interactions between terrestrial and aquatic ecosystems, with 

boundaries extending outward to the limits of flooding and upward into the canopy 

of streamside vegetation” (Gregory et al. 1991). The first dimension of riparian 

areas is the longitudinal continuum from headwaters to the mouths of streams and 

rivers and ultimately the oceans (Vannote et al. 1980). The second is the vertical 

dimension that extends upward into the vegetation canopy and downward into the 

subsurface and includes hyporheic and belowground interactions for the length of 

the stream-riparian corridor (Stanford and Ward 1988, 1993). The third dimension 

is lateral, extending to the limits of flooding on either side of the stream or river 

(Stanford and Ward 1993). The dynamic spatial and temporal extent of each of these 

three dimensions depends on the watershed hydrologic regime, location within the 

stream network of the watershed (elevation, connectivity), and watershed physical 

characteristics and geomorphic processes, which in turn influence floodplain water 

availability and the distribution of different riparian communities. These physical 

characteristics and processes largely regulate the structure and function of riparian 

ecosystems (Gregory et al. 1991, Naiman and Décamps 1997, Naiman et al. 2005). 

In the Blue Mountains, riparian ecosystems occur along low-gradient, U- and 

trough-shaped glacial valleys in alpine, high-elevation sites; along steep-gradient, 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

low-order headwater streams; along montane channels flowing through segments of 

varying valley width; and along low-gradient, alluvial rivers in the wider reaches of 

the Grande Ronde and the John Day Rivers and their tributaries (Crowe and Clausnitzer 1997, Johnson 2004, Wells 2006). The diversity of stream sizes, landforms, 

valley widths and gradients, and hydrologic regimes determine the types of biotic 

communities that occur along streams in a given region; each of these communities 

could have distinct responses to changing climate. 

To assist in managing riparian areas, numerous administrative definitions and 

various terms have been developed (USDA FS 2012c). In the Blue Mountains, 

riparian areas, wetlands, and intermittent streams are included within Riparian 

Habitat Conservation Areas (RHCAs), which specify minimum buffers from 

each side of the channel or stream edge: intermittent streams (15 m), wetlands and 

non-fish-bearing perennial streams (46 m), and fish-bearing streams (91 m). Active 

management within these buffers must comply with a number of riparian management objectives designed to improve habitat conditions for fish species that have 

been federally listed as threatened or endangered under the Endangered Species 

Act (USDA FS 1995). Along many stream segments, the dimensions of the riparian 

buffers differ from the ecologically defined riparian area described above. 

Wetlands

Numerous definitions for wetlands have been developed for a range of administrative, academic, and regulatory delineation purposes (National Research Council 

1995). For all federal regulatory activities, wetlands are ecosystems “that are 

inundated or saturated by surface or groundwater at a frequency and duration 

sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions” (Federal 

Interagency Committee for Wetland Delineation 1989). Wetlands can be extremely 

diverse, exhibiting a wide range of vegetation, soil, and hydrologic characteristics 

(Cowardin et al. 1979, National Research Council 1995). However, all definitions 

emphasize hydrologic variables, particularly duration, seasonality, and depth of 

inundation and soil saturation, that result in distinctive hydric soils and wetland 

vegetation.

For the Blue Mountains, the Oregon Wetlands Geodatabase provides a summary map of wetlands (figs. 7.1 through 7.3), color-coded by wetland type, as classified by the U.S. Fish and Wildlife Service (http://oregonexplorer.info/wetlands/

DataCollections/GeospatialData_Wetlands) (Cowardin et al. 1979). The maps were 

compiled from existing National Wetlands Inventory data and many additional 

sources, including local surveys and academic studies. Three broad categories of 

Wetlands can be 

extremely diverse, 

exhibiting a wide 

range of vegetation, 

soil, and hydrologic 

characteristics.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 7.1—Wetlands in Malheur National Forest. Source: Oregon Wetlands Geodatabase.
261

Climate Change Vulnerability and Adaptation in the Blue Mountains Region Figure 7.2—Wetlands in the Oregon portion of Umatilla National Forest. Source: Oregon Wetlands Geodatabase.
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GENERAL TECHNICAL REPORT PNW-GTR-939

Figure 7.3—Wetlands in Wallowa-Whitman National Forest. Source: Oregon Wetlands Geodatabase.
263

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

wetlands occur in the Blue Mountains: palustrine, lacustrine, and riverine (Cowardin et al. 1979). Palustrine wetlands are freshwater wetlands that include marshes, 

wet meadows, and forested wetlands, and may be dominated by trees, shrubs, or 

emergent vegetation. Some palustrine wetlands may be associated with streams, 

particularly in headwaters, whereas many are isolated, occurring in basins, depressions, or wet meadows. Lacustrine wetlands border lake shores. Riverine wetlands 

are associated with streams and rivers, and occur along stream channels. 

In this database, most riparian areas are treated as riverine wetlands (figs. 

7.1 through 7.3), demonstrating the overlap in definitions of riparian areas and 

wetlands. This designation may result in an overestimate of wetland area, because 

some riparian areas may not qualify as jurisdictional wetlands (Federal Interagency 

Committee for Wetland Delineation 1989), but it does provide a basis for management, because all wetland and riparian areas in national forests in the Blue Mountains are managed as RHCAs (USDA FS 2012c). The mapped wetlands (shown 

in figs. 7.1 through 7.3) illustrate the extent and diversity of these resources in the 

three national forests of the Blue Mountains. 

Although the Oregon Wetlands Geodatabase is an excellent resource for 

national forests in Oregon, it covers only wetlands that occur within the state’s 

boundaries. The portion of the Umatilla National Forest in Washington is therefore 

excluded, as well as the small portion of the Wallowa-Whitman National Forest 

along the Snake River in Idaho. Wetland databases are not available for Washington 

and Idaho.

Groundwater-Dependent Ecosystems 

Groundwater is broadly defined as “all water below the ground surface, including 

water in the saturated and unsaturated zones” (USDA FS 2012c). Groundwaterdependent ecosystems are “communities of plants, animals and other organisms 

whose extent and life processes are dependent on access to or discharge of groundwater” (USDA FS 2012a, 2012b), which can greatly contribute to local and regional 

biodiversity (Murray et al. 2006). The GDEs occur at aquifer discharge locations, 

such as springs, rheic, lentic or alluvial systems (Aldous et al. 2015), which are also 

referred to as surface/terrestrial GDEs (Bertrand et al. 2012, Goldscheider et al. 

2006). Many wetlands, lakes, streams, and rivers receive inflow from groundwater, 

which can contribute substantially to maintenance of water levels, as well as water 

temperature and chemistry required by native biota (Lawrence et al. 2014, Winter 

2007). 
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Along stream segments referred to as “gaining reaches,” groundwater enters the 

stream from the banks or the channel bed, and the volume of downstream streamflow is subsequently increased (Winter 2007, Winter et al. 1996). Groundwater 

can contribute substantially to late-summer streamflow (Gannett 1984) and is the 

source for cool-water upwellings that serve as refugia for coldwater aquatic species (Lawrence et al. 2014; Torgersen et al. 1999, 2012). Springbrooks, defined as 

“runout channels from springs, which may become a stream at some distance from 

the spring source” (USDA 2012a), may also contribute to the mediation of stream 

temperature. Groundwater is important to stream and river ecosystems in the 

John Day River basin (Gannett 1984) and most watersheds in northeastern Oregon 

(Brown et al. 2009). 

In the Blue Mountains, GDEs include springs, springbrooks, certain highelevation lakes, fens, streams, rivers (Brown et al. 2009, 2010), and riparian wetlands along gaining river reaches, all of which may provide habitat for rare flora 

and fauna. Fens are wetlands supported primarily by groundwater with a minimum 

depth (usually 30 to 40 cm) of accumulated peat (Chadde et al. 1998; USDA FS 

2012a, 2012c). Springs are entirely supported by groundwater. 

Five types of GDEs have been sampled in the Blue Mountains: helocrene, hillslope, hypocrene, mound, and rheocrene (USDA FS 2012a, 2012b; modified from 

Springer and Stevens 2009). Helocrene springs emerge diffusely from low-gradient 

wetlands, often discharging from indistinct or multiple sources. Hillslope GDEs 

are springs or fens located on hillslopes, usually on 20- to 60-degree slopes, often 

with indistinct or multiple sources of groundwater. Springs associated with mounds 

actually emerge near the top of elevated surfaces, i.e., mounds composed of peat or 

mineralized carbonate, and may be located within fens or wetland complexes near 

subsurface faults. Rheocrene springs emerge directly into stream channels, and are 

also referred to as springbrooks or spring runs. Other types of GDEs may occur in 

the Blue Mountains but have not yet been described or inventoried. 

Dependence of Special Habitats on Different Water 

Sources 

In contrast to surrounding upland ecosystems, the occurrence and characteristics of 

riparian areas, wetlands, and GDEs depend on the availability of abundant water. 

The fundamental hydrologic processes that influence these special habitats are 

(1) the amount, timing, and type of precipitation (rain or snow); (2) streamflow 

variables described by magnitude, frequency, timing, duration, and rate of change 

Groundwater is 

important to stream 

and river ecosystems...

and most watersheds 

in northeastern 

Oregon. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

(Nilsson and Svedmark 2002) and other characteristics of surface water runoff; 

(3) groundwater recharge; (4) groundwater discharge; and (5) evapotranspiration 

(Lins 1997). 

Because precipitation is the ultimate source of water and directly influences 

streamflow characteristics and groundwater dynamics, it is expected that climateinduced changes in precipitation will affect riparian areas, wetlands, and GDEs. 

The availability of water to riparian areas, wetlands, or GDEs is also influenced 

by physical watershed characteristics that affect infiltration and surface and hillslope runoff, including lithology, soil depth, and topography (Jencso et al. 2009). 

However, determining how climate-induced changes in hydrologic sources and 

processes will affect special habitats is complex and has not been directly studied 

in watersheds of the Blue Mountains. Here we draw on research that has been 

conducted in other locations in the Western United States with similar plant species 

or communities and infer potential climate-induced changes in riparian and wetland 

vegetation in northeast Oregon and southeast Washington. 

Riparian ecosystems depend on the presence of flowing water, although 

streamflow may not be perennial along all stream segments and can vary considerably with season, physical features of the watershed, and water source. The 

volume of streamflow largely regulates the transport and deposition of sediment, 

influencing the creation and erosion of streambanks; floodplains; point bars; and 

meandering, braided, and abandoned channels. Depending on the physical characteristics of a given stream segment, the volume of streamflow can also drive the 

seasonal changes in water table elevation of the adjacent riparian area (Jencso et al. 

2011). These hydrologic and fluvial processes and resulting geomorphic surfaces 

are essential for the establishment, development, and persistence of riparian vegetation, and strongly influence the local distribution of different plant species and 

communities (Naiman et al. 2005). Based on long-term daily flow data (from U.S. 

Geological Survey stream gauging stations), different streams in the Blue Mountains have been characterized as supported by perennial runoff, snow plus rain, and 

super-stable groundwater (Poff 1996). 

As noted above, streamflow volume along gaining reaches increases with the 

inflow of groundwater to the channel. Stream water can also drain from the channel 

bed and banks to the groundwater system, resulting in a loss of downstream surface 

flow volume (Winter et al. 1996); these stream segments are referred to as “losing 

reaches.” The extent and location of hyporheic and groundwater exchange along a 

channel segment is influenced by valley bottom features, including width, gradient, 

substrate size, and depth to bedrock, and can determine whether a reach is gaining 
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GENERAL TECHNICAL REPORT PNW-GTR-939

or losing (Winter et al. 1996). Gaining and losing stream reaches result in different 

aquatic communities in the channels and different riparian plant communities on 

the floodplains. The extent to which specific reaches are gaining or losing may 

change in response to climate-induced changes in precipitation, streamflow characteristics, and groundwater discharge. 

Wetlands can be supported by surface water, groundwater, and precipitation, 

or frequently by combinations of these sources that differ seasonally (Goslee et 

al. 1997, Winter 2001). Fens are primarily supported by springs or local aquifers 

and can maintain fairly stable water table elevations despite changes in timing and 

amounts of precipitation (Winter 1999). Other wetlands with different or multiple 

water sources will likely respond differently to climate-induced changes and variability (Winter 1999). 

In wetlands and riparian ecosystems worldwide, hydrologic variables are 

consistently the strongest predictors of plant species distributions (Cooper and 

Merritt 2012, Franz and Bazzazz 1977, Lessen et al. 1999, Merritt and Cooper 2000, 

Shipley et al. 1991). Ordination and other analyses repeatedly show that riparian 

and wetland species and vegetation communities are distributed along gradients 

(usually elevational or microtopographic) relating to streamflow duration (Auble 

et al. 1994, 1998, 2005; Franz and Bazzazz 1977; Friedman et al. 2006); growingseason streamflow volume (Stromberg 1993); depth, duration, or timing of flooding 

(Richter and Richter 2000, Toner and Keddy 1997); inundation duration (Auble et 

al. 1994, Franz and Bazzazz 1977, Friedman et al 2006); and water table elevation 

or depth to groundwater (Busch and Smith 1995, Castelli et al. 2000, Cooper et al. 

1999, Dwire et al. 2006, Rains et al. 2004, Scott et al. 1999). In wetlands, variables 

related to water table elevation and hydroperiod are the primary determinants of 

plant species distributions (Goslee et al. 1997, Magee and Kentula 2005, Weiher and 

Keddy 1995). 

Current understanding of the water sources used by riparian/wetland plants 

is limited to a few indicator, keystone, and either highly valued or highly invasive 

species (mostly woody) (Cooper and Merritt 2012). However, it has been shown that 

riparian/wetland plant species use water from multiple sources (surface water, soil 

water, groundwater), depending on life stage and season (Busch and Smith 1995, 

Cooper et al. 1999, Goslee et al. 1997). In assessing the vulnerability of riparian/

wetland species to climate-induced changes in streamflow or groundwater, the 

availability of water at all life stages must be considered, from plant recruitment 

and establishment, to reproducing adults, to persistence at later life stages (Cooper 

and Merritt 2012). 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Lack of scientific information makes it difficult to directly infer climate change 

effects on riparian vegetation or to describe physical mechanisms regulating water 

availability to special habitats in the Blue Mountains. However, based on research 

from other locations, we assume that climate-induced changes in precipitation 

and streamflow will exert influences on the distribution of riparian vegetation via 

changes in local hydrologic regimes. Summer baseflows are predicted to decrease 

(Cayan et al. 2001, Luce and Holden 2009). If riparian water table elevation can be 

assumed to be in equilibrium with water levels in the stream, reduced baseflows 

could result in lower riparian water table elevations and subsequent drying of some 

streamside areas, particularly in wider valley bottoms. Increasing air temperature 

will result in increased evapotranspiration across the landscape, could reduce the 

hydrologic connectivity between uplands and riparian areas (Jencso et al. 2009, 

2011), and subsequently could contribute to the drying of some streamside areas. 

Dominant wetland/riparian plant communities will respond to climate-induced 

changes in hydrologic variables differently owing to differences in their species 

composition (Merritt et al. 2010, Weltzin et al. 2000). 

Current Resource Conditions

The Blue Mountains have a rich diversity of riparian and wetland plant associations 

and community types at mid-montane elevations (Crowe and Clausnitzer 1997) and 

at higher elevations and within deep canyons (box 7.3) (Johnson 2004, Wells 2006). 

Several quaking aspen (Populus tremuloides Michx.) communities and associations, which occur in upland locations as well as wetlands and riparian areas, have 

also been classified for the Blue Mountains (Swanson et al. 2010). Riparian and 

wetland aspen communities are highly valued throughout the Blue Mountains and 

are included here as special habitats. 

Past land use and management activities have affected riparian and aquatic 

resources, but in different ways and to different extents, depending on valley setting, location within the watershed, and land use (Dwire et al 1999; Kauffman et al. 

2004; Magee et al. 2008; McAllister 2008; McIntosh et al. 1994a, 1994b; Parks et 

al. 2005; Ringold et al. 2008). Streams, wetlands, and associated plant communities 

are possibly the most heavily impacted ecosystems in the Blue Mountains. In many 

cases, the effects of past land use and management activities may be considerably 

greater than the anticipated gradual influence of climate change. However, for these 

altered ecosystems, climate-induced changes will exert additional stress, possibly 

resulting in further degradation. In this section, we briefly describe the current 

condition of different riparian and wetland vegetation types and how they have been 

affected by past land use and management activities. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Box 7.3—Deep river canyons and climate change: 

the lower Snake River and its tributaries

The lower Snake River runs along the Idaho and Oregon state line and forms the 

deepest river gorge in North America, commonly referred to as Hells Canyon. From 

Hells Canyon Dam, one of three dams in the Hells Canyon Project, the river winds its 

way for 114 km to the northern boundary of Hells Canyon National Recreation Area 

(HCNRA), managed by Wallowa-Whitman National Forest. With river elevations of 

512 m at the dam to 263 m at the northern boundary of HCNRA, this river canyon 

provides the warmest and driest environments in the Blue Mountains national forests. 

The vegetation of the canyon is characterized by extensive bluebunch wheatgrass 

(Pseudoroegneria spicata [Pursh] Á. Löve) and Idaho fescue (Festuca idahoensis 

Elmer) grasslands, with stringers of conifer forests at cooler aspects and higher elevation. Riparian communities are often confined to narrow strips along river corridors 

and moisture gradients are steep. The floodplains, rocky bars and terraces at elevations below 700 m support a number of unique riparian plant communities characterized by black cottonwood, white alder, netleaf hackberry (Celtis reticula [Torr.] L.D. 

Benson), and Barton’s raspberry (Rubus bartonianus M. Peck), a narrow endemic 

shrub species of Hells Canyon and surrounding canyonlands (Wells 2006). 

With the settlement of the canyon in the early 19th century came the introduction 

of many nonnative plant species, including tree of heaven (Ailanthus altissima [Mill.] 

Swingle), false indigobush (Amorpha fruticosa L.), and Himalayan blackberry (Rubus 

armeniacus Focke). The spread of Himalayan blackberry is of particular concern for 

the endemic Barton’s raspberry, because Himalayan blackberry is able to occupy 

the same habitats but is a better competitor (Ferriel and Ferriel 2010).1 Native Rubus 

species are restricted by drought conditions during summer, whereas Himalayan 

blackberry can store more water and achieves high growth and reproductive rates 

(Caplan and Yeakley 2010). Canes can grow up to 10 m long and produce over 700 

fruits annually (Pojar and MacKinnon 1994). In Hells Canyon, Himalayan blackberry 

retains its leaves over winter, giving it an additional competitive edge over many 

native species. 

Fire exclusion has affected Hells Canyon, with steep terrain and fast fire spread 

in dry canyon grasslands, less than other areas in the Blue Mountains. From 1980 

to 2013, over 70 percent of all grass and shrublands of the HCNRA were within one 

or more mapped fire perimeters (S. Mellman-Brown, unpublished data on file at 

Wallowa-Whitman National Forest, Baker, OR). Many of these fires burned through 

riparian zones and replaced existing shrub and forest vegetation with early seral 

species. Himalayan blackberry, which resprouts readily from its root crown after fire, 

had covers of 80 percent near Pittsburg Creek one year after fire, an increase of 30 

percent compared to measurements one decade earlier. On other sites, white alder 

(Alnus rhombifolis) Nutt., a tree with poor postfire sprouting abilities, appeared to 

be replaced by blackberry thickets after high-severity fire. Increasing fire frequencies with climate change will promote fire-adapted species like tree of heaven and 

Himalayan blackberry, potentially creating widespread novel plant communities with 

few native elements. 

Warming climate with increasing fire frequencies may also facilitate the 

invasion and dominance of tamarisk in Hells Canyon (Kerns et al. 2009). Major 

population centers for tamarisk (Tamarix spp.) in the northwestern United States are 

the warmest and driest environments of the northern Basin and Range, Columbia 

Plateau, and central Snake River Plateau. Tamarisk is currently absent from the 
269

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Box 7.3 (continued)

HCNRA, but large populations exist nearby at Farewell Bend and with lower 

frequency along the Brownlee Reservoir. Large areas in the lower Snake River and 

upper John Day River drainages are also vulnerable to invasion by tamarisk (Kerns 

et al. 2009). Habitat suitability modeling by Kerns et al. (2009) suggests that tamarisk 

habitat will expand in the Northwest by the end of this century, which could dramatically change the composition and structure of many riparian corridors in the Blue 

Mountains.

1 Ferriel, J.; Ferriel, R. 2010. Rubus bartonianus status review for WallowaWhitman National Forest, and Baker Resource Area, Vale District. Unpublished 

report on file with: USDA, Forest Service; USDI Bureau of Land Management. 

Baker City, OR. 10 p.

Riparian Areas

We utilize existing vegetation classifications to highlight the diversity and complexity of riparian areas in the Blue Mountains, and as a basis for discussing how 

different vegetation types might respond to climate-induced changes. We present 

information for distinct riparian/wetland potential vegetation types (PVTs), and 

potential vegetation groups (PVGs) that have been described for the Blue Mountains 

(Crowe and Clausnitzer 1997, Powell et al. 2007, Swanson et al. 2010, Wells 2006). 

These groupings are hierarchical, aggregated from fine-scale units to mid-scale 

units, and are explained in detail in Powell et al. (2007). Potential vegetation types 

are fine-scale hierarchical classification units that include plant associations and 

plant community types (Powell et al. 2007). They are aggregated into mid-scale 

plant association groups (PAGs) representing similar ecological environments as 

characterized by temperature and moisture regimes (Powell et al. 2007). The PAGs 

are then aggregated into PVGs with similar environmental regimes and dominant 

plant species; each PVG typically includes PAGs representing a predominant 

temperature or moisture influence (Powell 2000, Powell et al. 2007). 

Potential vegetation describes the plant species composition occurring under 

existing climatic conditions and in the absence of disturbance (Powell et al. 2007), 

implies some knowledge of successional pathways, and is most useful for well-studied upland vegetation. However, riparian environments can be subject to frequent 

and unpredictable disturbances with a range of possible, but largely unstudied, 

successional trajectories. Plant associations and community types are interspersed 

along stream-riparian corridors as a mosaic, sometimes co-occurring over short 

stream lengths, responding to valley bottom width, geomorphic surfaces, and local 

differences in hydrologic variables (Naiman et al. 2005). Although successional 

Riparian environments 

can be subject 

to frequent and 

unpredictable 

disturbances with a 

range of possible, but 

largely unstudied, 

successional 

trajectories.
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GENERAL TECHNICAL REPORT PNW-GTR-939

pathways cannot be reliably determined for these riparian classifications, the plant 

community/association descriptions provide detailed floristic information and a 

basis for assessing both current conditions and future changes in species composition in response to management, natural disturbance, and climate-induced changes. 

Below, we discuss broad riparian vegetation types and note the number of PAGs 

and PVTs and other groupings that have been classified for each. 

Conifer-dominated riparian areas—

Many kilometers of streams in the Blue Mountains are bordered by conifer-dominated riparian communities. Conifer-dominated riparian areas are valued for maintenance of riparian microclimates, wildlife habitat, and a source of large wood for 

streams (table 7.1). Powell et al. (2007) describe a “cold riparian forest” PVG that 

includes three PAGs and 25 PVTs for conifer-dominated riparian areas. Depending 

on the PAG, dominant conifer species are subalpine fir (Abies lasiocarpa [Hook.] 

Nutt.), Engelmann spruce (Picea engelmannii Parry ex Engelm.), or lodgepole 

pine (Pinus contorta var. latifolia Engelm. ex S. Watson). The “warm riparian forest” PVG includes two PAGs with seven PVTs dominated by either Douglas-fir 

(Pseudotsuga menziesii [Mirb.] Franco) or grand fir (A. grandis [Douglas ex D. 

Don] Lindl.), and one PVT by western white pine (Pinus monticola Douglas ex D. 

Don). These conifer-dominated riparian vegetation types typically occur at high to 

moderate elevations, mostly along first- and second-order streams, and mostly in 

moderately to highly confined valley bottoms. Although several other PVTs have 

high cover of ponderosa pine (P. ponderosa Douglas ex P. Lawson & C. Lawson), 

grand fir, or Douglas-fir, they occur at lower elevations and are not consistently surrounded by conifer-dominated uplands (Powell et al. 2007). 

Conifer-dominated riparian vegetation types have been affected by past forest harvest, mining, grazing, road building, fire exclusion, and to a lesser extent, 

invasive species (Wickman 1992) (table 7.2). Natural disturbances include wildfire, 

infestations by forest insects and fungal pathogens, landslides, and debris flows 

(Luce et al. 2012). In some locations at lower elevations, the ponderosa pinecommon snowberry (Symphoricarpos albus [L.] S.F. Blake) community may be 

increasing in streamside areas previously dominated by deciduous woody species in 

response to channel incision and decreasing riparian soil moisture (table 7.2). 

Riparian and wetland aspen plant communities—

Stands of quaking aspen are an uncommon, valued habitat type throughout the Blue 

Mountains region, and their sustainability has been a focus for management in uplands, riparian areas, and wetlands (Swanson et al. 2010). Classification of wetland 

and riparian aspen communities for the Blue Mountains region showed the largest 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 7.1—Functions of riparian areas and key relationships to ecological servicesa (continued)Riparian functions

Indicators of riparian functions

Onsite or offsite effects of functions

Goods and services provided

Relevant riparian plant communities

Hydrology and sediment dynamicsShort-term storage of surface 

water 

Connectivity of floodplain and 

stream channel

Attenuates downstream 

flood peaks

Reduces damage from floodwaters Shrub (especially willow) and herbaceous dominated; all 

communities to some extent

Maintenance of high water table Presence of flood-tolerant, 

hydrophytic, and mesic plant species

Maintains distinct vegetation, particularly in arid 

climates

Contributes to regional biodiversity through provision 

of habitat 

Shrub (especially willow) and 

herbaceous dominated; all communities to some extent

Retention and transport of 

sediments; decreased streambank erosion 

Riffle-pool sequences, point 

bars, floodplain terraces, and bank stability 

Contributes to fluvial processes Creates predictable yet dy- namic channel and floodplain features Shrub (especially willow) and herbaceous dominated; all communities to some extent 

Biogeochemistry and nutrient cyclingRiparian vegetation provides 

source of organic carbon (allochthonous inputs to streams; organic matter inputs to soils) 

Healthy mosaic of riparian 

vegetation 

Maintains aquatic and terrestrial food webs Supports terrestrial and aquatic biodiversity Highest quality inputs are from deciduous shrubs and 

herbaceous dominated; all communities to some extent

Transformation and retention of 

nutrients and pollutants 

Water quality and biotic indicators Intercepts nutrients and toxicants from runoff; 

water quality

Improves and maintains 

water quality

Retention and interception 

most likely in shrub (especially deciduous) and herbaceous-dominated communities; all communities to some extent 

Sequestration of carbon in riparian soils Occurrence, extent, and distri- bution of organic-rich soils Contributes to nutrient retention and carbon 

sequestration 

Potentially ameliorates 

climate change; provides source of dissolved carbon to streams via subsurface flow 

Carbon sequestration in soils 

highest in herbaceous-dominated meadows; all communities to some extent
272

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 7.1—Functions of riparian areas and key relationships to ecological servicesa (continued) Riparian functions Indicators of riparian functions Onsite or offsite effects of functions Goods and services provided Relevant riparian plant communities Distinctive terrestrial and aquatic habitat Contributes to overall biodiver- sity and biocomplexity High species richness of plants and animals Provides reservoirs for genetic diversity Supports regional biodiver- sity All communities, but espe- cially those with multiple canopy strata, (e.g., cot- tonwood, aspen, and willow dominated) Maintenance of streamside mi- croclimate Presence of shade-producing canopy; healthy popula- tions of native terrestrial and aquatic biota Provides shade and thermal insulation to stream; pro- vides migratory corridors for terrestrial and aquatic species Maintains habitat for sensi- tive species (e.g., amphib- ians, cold-water fishes) All communities, but espe- cially those with multiple canopy strata, (e.g., conifer, aspen, cottonwood, and wil- low dominated)

Contribution to aquatic habitat; 

provision of large wood 

Aquatic habitat complexity (pool-riffle sequences, 

debris dams); maintenance of aquatic biota 

Maintains aquatic biota Maintains fisheries, recreation Conifer, aspen, and cotton- wood dominated

Provision of structural diversity Availability of nesting/rearing 

habitat; presence of appropriate indicator wildlife species (e.g., Neotropical migrants) 

Maintains biodiversity; provides migratory corridors 

for terrestrial and aquatic species 

Provides recreation opportunities (e.g., birding, wildlife 

enjoyment, hunting)

All woody communities, 

but especially those with multiple canopy strata (e.g., conifer, aspen, cottonwood, and shrub dominated)

a Modified from Dwire et al. (2010), Naiman et al. (2005), NRC (2002).
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 7.2—Stressors in riparian and wetland ecosystems which are likely to be exacerbated by climate changea (continued)Stressor Direct and indirect causes Potential effects

Riparian and wetland plant communities and associations most affected by climate change

Changes in flow regime 

and dewatering

Surface water: dams, diversions, land 

use changes, climate change

Groundwater: pumping, land use change, 

climate change

Water stress in vegetation Shifts in plant species compositionHomogenization of riparian area and 

simplification of biota

Isolation of floodplain from streamAltered stream-riparian organic matter 

exchange and trophic dynamics

Altered floodplain biogeochemistryAltered channel structureDecreased lateral extent of riparian area

Cottonwood, aspen, willow, and herbaceous-dominated communities located 

along low-gradient, wide valley bottoms

Channelization Bank hardening

Levee constructionStructural changes in channel-deepeningBerm developmentMeander cutoff

Isolation of floodplain from streamAltered fluvial processesAltered hydraulics (aquatic habitat and 

channel forms)

Altered floodplain biogeochemistry

Cottonwood, aspen, willow, and herbaceous-dominated communities located 

along low-gradient, wide valley bottoms

Conversion of floodplains 

to other uses

Removal of woody riparian vegetation Elimination of local populations of cottonwood, aspen, willow, and herbaceous 

communities

Reduced extent of riparian area, thus reducing ecosystem services (maintenance of 

water quality, wildlife habitat, recreation)

Cottonwood, aspen, willow, and herbaceous-dominated communities located 

along low-gradient, wide valley bottoms

Invasive species Altered physical and ecological processes that facilitate establishment and 

spread (e.g., herbivory, changes in flow regime)

Displacement of native speciesFormation of monocultureAltered site characteristics (e.g., biogeochemistry, soil properties, water balance)Shifts in community compositionAltered habitat structure

Nearly all riparian and wetland communities, especially those that occur in drier 

environments

Potential increase in tamarisk in Hells 

Canyon
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GENERAL TECHNICAL REPORT PNW-GTR-939 Table 7.2—Stressors in riparian and wetland ecosystems which are likely to be exacerbated by climate changea (continued) Stressor Direct and indirect causes Potential effects Riparian and wetland plant communi- ties and associations most affected by climate change

Changes in sediment 

delivery to channel

Offroad vehicle useRoads (drainage, gravel application)Livestock and herbivore tramplingAltered vegetative cover in watershed 

and along channel

Direct mechanical effects on channel, 

dams, and diversions

Shifts in channel and floodplain form 

(through increased or decreased delivery to channel)

Altered channel processes (e.g., incision and 

aggradation)

Nearly all riparian and wetland communities, although direct causes and severity 

will differ

Herbivory Grazing by cattle and wild ungulates Bank trampling and compaction

Altered cover and composition of vegetationStream captureNutrient inputs

Aspen, cottonwood, willow and herbaceous communities are the most heavily 

affected, but most riparian and wetland communities are affected to some extent

Wildfire and fuels, fire suppression Fuel buildup from invasive species and fire exclusion

Reduced floodingSlower decomposition of organic 

material

Increased frequency and intensity of firesLoss of fire-intolerant taxaAltered structure of riparian vegetation 

and habitat quality and distribution, with subsequent shifts in composition

Conifer-dominated riparian plant associations with dominant tree species similar 

to adjacent uplands

Insects and disease Fire exclusion and past harvest activities have resulted in susceptible stand 

structure 

Altered fuel loads and distribution associated with increased canopy mortality Conifer-dominated riparian plant associa- tions with dominant tree species similar 

to adjacent uplands 

Note: Although nearly all riparian and wetland plant associations are affected by each stressor, the most affected associations are noted in the last column.aModified from Theobald et al. (2010).
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

number of aspen community types (CT) were associated with herbaceous species in 

meadows (eight CTs), followed by associations with common snowberry (four CTs) 

and other tall shrubs (three CTs) in riparian areas (Swanson et al. 2010). One aspen 

CT was associated with Engelmann spruce, and another with tall shrub wetland 

types on slopes, likely occurring at points of groundwater emergence (Swanson et 

al. 2010).

Aspen CTs have been affected by fire suppression and herbivory by livestock 

and native ungulates (Baker et al. 1997, Bartos and Campbell 1998, Shinneman et 

al. 2013). They are currently threatened by herbivory and conifer encroachment, 

especially those occurring in meadows (Swanson et al. 2010) (table 7.2). Many 

stands are declining, without signs of regeneration, and are susceptible to a variety 

of insects and fungal pathogens (Swanson et al. 2010). Most aspen stands are less 

than 1 ha. 

Cottonwood-dominated riparian areas—

Black cottonwood (Populus trichocarpa T. & G. ex Hook.) is a keystone riparian 

species occurring along a variety of valley types in the Blue Mountains, ranging 

from high-gradient, V-shaped valleys to moderately confined or open, low-gradient 

valleys (Crowe and Clausnitzer 1997). Powell et al. (2007) classified a “warm riparian forest” PVG that includes three PAGs dominated by black cottonwood. 

Cottonwood-dominated riparian areas were among the earliest settled in the 

mid-1800s. Settlers quickly recognized the economic potential for raising livestock, 

especially along the wider valley bottoms at mid to low elevations with abundant 

forage and water resources (Dwire et al. 1999). The widespread decline of cottonwood and willows (Salix spp.) has been widely attributed to land management 

practices associated with livestock production (Beschta and Ripple 2005; McIntosh 

et al. 1994a, 1994b). Many floodplains formerly dominated by woody riparian 

species, including portions of the John Day River and its tributaries, were converted 

to cattle pastures and hay fields by modifying or relocating portions of the stream 

channels, removing woody species, and planting with introduced grasses (Dwire 

et al.1999). Other factors, such as use of cottonwood as a wood source, removal of 

streamside woody plants as “phreatophyte control,” and hydrologic modification of 

streams and rivers for agricultural production and irrigation have contributed to a 

decrease in the distribution and abundance of deciduous riparian species, including 

cottonwoods and aspen, willows, and alders (Alnus spp.). 

Several cottonwood species have been shown to depend on flood frequency 

and duration for recruitment and establishment (Mahoney and Rood 1998; Scott 

et al. 1996, 1997). Although recruitment of black cottonwood has not been studied 

Black cottonwood is 

a keystone riparian 

species occurring 

along a variety of 

valley types in the Blue 

Mountains.
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GENERAL TECHNICAL REPORT PNW-GTR-939

relative to streamflow characteristics, germination and seedling survival depend 

on continuously moist conditions (http://plants.usda.gov/plantguide/pdf/cs_pobat.

pdf), which are provided in part by high flows during spring runoff. Flow alteration of streams and rivers in the Blue Mountains may possibly have reduced the 

recruitment of new cottonwoods, thus contributing to the decline of existing stands. 

Limited recruitment has also been attributed to grazing of young cottonwood plants 

by livestock (Beschta and Ripple 2005) (table 7.2). 

Willow-dominated riparian areas—

Willow-dominated riparian areas are found across elevation ranges, but are most 

extensive at mid to lower elevations. Willows provide numerous valued ecological 

functions, including shade and organic matter for streams, increased bank stability 

and sediment retention, and wildlife habitat for many resident and migratory vertebrate species, such as Neotropical migratory birds (Kauffman et al. 2001, Kelsey 

and West 1998) (table 7.1). Willow-dominated riparian areas also maintain water 

quality through trapping sediment and pollutants from upslope and upstream areas, thus reducing the volume or concentrations delivered to streams (Johnson and 

Buffler 2008). 

Potential vegetation analysis for willow-dominated riparian areas of the Blue 

Mountains region resulted in the classification of a “cold riparian shrub” PVG 

that includes four PAGs and 10 PVTs (Powell et al. 2007). The cold riparian shrub 

PVG occurs at higher elevations or along channels with frequent cold air drainage 

at lower elevations (Crowe and Clausnitzer 1997). The dominant willow species 

include Booth’s willow (Salix boothii Dorn), undergreen willow (S. commutata

Bebb.), and Drummond’s willow (S. drummondiana Barratt). The “warm riparian 

shrub” PVG includes three PAGs with eight PVTs dominated by willow species 

that generally occur in moderately confined or open valley bottoms, including 

unconfined and glaciated valleys with low slopes (less than 3 percent) in montane 

and subalpine settings (Powell et al. 2007). These warm riparian shrub PVTs are 

also referred to as the “alluvial bar” willow group, because they frequently occur 

on coarse-textured sands, gravel, and cobble bars. They are generally dominated 

by sandbar willow (S. exigua Nutt.), dusk willow (S. melanopsis Nutt.), and Pacific 

willow (S. lasiandra Benth.) (Powell et al. 2007). 

In many streams throughout North America, the historical removal of American beaver (Castor canadensis Kuhl) has influenced the geomorphic and hydrologic 

characteristics of stream channels (Wohl 2001) as well as the distribution of woody 

riparian species, especially willows (Naiman et al. 1988). Dam building by beaver 

modifies local hydrology, thus expanding wetland area and contributing to retention 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

of sediment and organic matter (Butler and Malanson 1995; Meentemeyer and 

Butler 1999; Westbrook et al. 2006, 2011). Willows are a preferred source of food 

and dam-building material for beaver and readily establish along the edges of 

beaver ponds and beaver-influenced stream reaches. In the Blue Mountains, the 

removal of beaver likely contributed to the reduction of willow-dominated riparian 

areas and abundance of aspen (Kay 1994, McAllister 2008, Swanson et al. 2010). 

Beavers and functioning beaver dams are still infrequent in the Blue Mountains 

(Swanson et al. 2010). 

Willow-dominated riparian areas have been heavily affected by livestock use, 

including direct effects of grazing and browsing. Livestock grazing reduces cover 

and stem density of adult plants (Brookshire et al. 2002), and in many areas, has 

eliminated seedlings and saplings, thus reducing establishment of new plants. Elk 

(Cervus elaphus L.) utilize willows throughout the year (Singer et al. 1994, Zeigenfuss et al. 2002), and in floodplains with combined herbivory pressure from both 

livestock and native ungulates, willows can be highly affected. Flow alteration has 

also affected willow-dominated riparian areas; downstream of diversions, species 

composition tends to consist of more drought-tolerant species (Caskey et al. 2014). 

Other woody-dominated riparian areas (deciduous shrubs and trees)—

Geographic location, complex geology, and highly variable channel forms create 

a rich floristic diversity of woody riparian species in the Blue Mountains. Powell

et al. (2007) describe a “warm riparian forest” with seven red alder (Alnus rubra

Bong.) -dominated and two white alder (A. rhombifolia Nutt.) -dominated PVTs. In 

drier riparian areas, classified as “low soil moisture riparian shrub,” 16 additional 

PVTs are described, dominated by 13 different shrub species that occur across a 

range of valley bottom types, including steep canyons. In a “warm riparian shrub” 

PVG, they describe the following PVTs, dominated by different riparian woody 

species:

• Mountain alder (A. viridis subsp. crispa [Chaix] DC.) (16 PVTs) 

• Sitka alder (A. v. subsp. sinuata [Chaix] DC.) (3 PVTs) 

• Water birch (Betula occidentalis Hook.) (3 PVTs) 

• Red-osier dogwood (Cornus sericea L.) (3 PVTs) 

• Currant (Ribes spp.) (3 PVTs) 

• Twinberry (Lonicera involucrata [Richardson] Banks ex Spreng.) (1 PVT) 

• Shrubby cinquefoil (Dasiophora fruticosa [L.] Rydb.) (1 PVT) 

• Alderleaf buckthorn (Rhamnus alnifolia L’Hér.) (1 PVT) 

In some locations, certain woody riparian plant associations are likely the result 

of land use, particularly hydrologic modification that has caused the conversion 
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GENERAL TECHNICAL REPORT PNW-GTR-939

of willow-dominated areas to communities dominated by more dry-tolerant shrub 

species, such as shrubby cinquefoil, currant, and common snowberry. Woodydominated riparian areas, including those with cottonwood, willow, and aspen, have 

also been affected by livestock grazing, herbivory pressure from native ungulates, 

and conversion to pastures and other agricultural uses (table 7.2).

Herbaceous-dominated riparian areas— 

Several herbaceous-dominated riparian and wetland plant associations have been 

identified in the Blue Mountains, reflecting both environmental conditions and 

past land use. Herbaceous-dominated riparian and wetland communities occur 

over a wide elevation range from alpine to lower montane environments. Crowe 

and Clausnitzer (1997) identified 11 herbaceous plant associations and 17 plant CTs 

located in meadows, most of which were dominated by different sedge (Carex, 

Eleocharis, and other genera) species. In addition, they described seven herbaceous 

plant associations and six plant CTs that occurred along shaded streams or springs 

(GDEs). Herbaceous-dominated riparian areas occur most commonly in moderately 

confined to wide valley bottoms, usually along low-gradient stream segments. 

At mid elevations, herbaceous-dominated meadows have been affected by 

heavy elk grazing. At nearly all elevations, meadows have also been affected by 

livestock use (Kauffman et al. 2004), with lasting impacts in many areas (Skovlin 

and Thomas 1995). At lower elevations, changes in species composition, density, 

and cover have resulted from either the complete or partial conversion of natural 

meadows to pasture along some floodplains. As with willow-dominated communities, hydrologic modifications, including water diversions and construction of 

ditches, and stream modifications (e.g., relocation or alteration of natural channels) 

have influenced channel characteristics, seasonal water supply and water table 

elevations (McIntosh et al. 1994a, 1994b). In riparian meadows, the distribution of 

herbaceous species is largely determined by seasonal water table elevation (Castelli 

et al. 2000, Dwire et al. 2006, Loheide and Gorelick 2007), which can be influenced 

by patterns of streamflow runoff. In many meadows, a combination of hydrologic 

alteration and livestock grazing has resulted in drier conditions and increased 

dominance by nonnative grasses and grazing-tolerant native species (Johnson et al. 

1994) (table 7.2). 

Subalpine and alpine riparian areas and wetlands—

Wells (2006) described 13 wetland alpine/subalpine plant associations: 

• Three are dominated by willow species and generally occur in lowgradient, U-shaped glacial cirques, U- or trough-shaped glacial valleys, 

and higher gradient glaciated valleys. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

• Two low shrub associations are identified: 

i. “Alpine laurel (Kalmia microphylla [Hook.] A. Heller)/black alpine 

sedge (Carex nigricans C.A. Mey) plant association” that occurs in lowgradient, U- and trough-shaped valleys, and

ii. “Pink mountainheath (Phyllodoce empetriformis [Sm.] D. Don) mounds 

plant association” that occurs in the upper terminus of glacial valleys. 

• Four wet graminoid associations are described, all of which occur most 

frequently in U-shaped, low-gradient valleys. They are dominated by the 

following sedge species: 

i. Water sedge (Carex aquatilis Wahlenb.), 

ii. Northwest Territory sedge (C. utriculata Boott), 

iii. Blister sedge (C. vesicaria L.), and

iv. Few-flower spikerush (Eleocharis quinqueflora [Hartmann] O. 

Schwarz). The “few-flower spikerush plant association” is found in fens 

(GDEs) near springs at high elevations (2067 to 2348 m) in the Eagle 

Cap and Elkhorn Mountains. 

• Three moist graminoid associations are described, dominated by the following sedge species: 

i. Holm’s Rocky Mountain sedge (C. scopulorum T. Holm), 

ii. Woodrush sedge (C. luzulina Olney) and, 

iii. Black alpine sedge (C. nigricans C.A. Mey) 

• A fourth moist graminoid plant association is a sedge-forb mix, most commonly associated with headwater springs in the Strawberry Mountains. 

Referred to as the “northern singlespike sedge (C. scirpoidea Michx.)/brook 

saxifrage (Micranthes odontoloma [Piper] A. Heller)-spring plant association,” it is considered an indicator for GDEs (Wells 2006). 

Although alpine wetlands and meadows have been affected by past livestock 

grazing and ungulate browsing, they are typically in better condition than their 

low-elevation counterparts. 

PACFISH INFISH Biological Opinion Effectiveness Monitoring—

The PACFISH INFISH Biological Opinion (PIBO) Effectiveness Monitoring was 

developed as a response to declining populations of steelhead trout (Oncorhynchus 

mykiss Walbaum) and bull trout (Salvelinus confluentus Suckley) in the upper 

Columbia River basin (http://fsweb.r4.fs.fed.us/unit/nr/pibo/index.shtml). Its main 

objective is to monitor biological and physical components of aquatic and riparian habitats (Meredith et al. 2011). As part of the Columbia River Basin Project, 
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GENERAL TECHNICAL REPORT PNW-GTR-939

191 monitoring sites were established in randomly located watersheds across the 

Blue Mountains. Sites have been designated as ”reference” or ”managed” and are 

sampled on a 5-year rotation. Reference sites (18 of the 191) are located mostly in 

wilderness areas at somewhat higher elevations and with more annual precipitation. 

No reference sites are available for the Malheur National Forest, which complicates 

comparisons between reference and managed sites in the Blue Mountains. However, 

PIBO monitoring data are the primary source of quantitative information on the 

condition of riparian areas occurring along “response reaches.” 

PIBO monitoring provides a regional evaluation of the condition of riparian 

vegetation for both reference and managed sites (Archer et al. 2012a2, Meredith et 

al. 2011). At each site, plant species cover is sampled along the densely vegetated 

streamside zone, or “greenline” (Winward 2000), and along cross-sectional transects established perpendicular to the channel or valley bottom. For each site, 

“wetland ratings” are calculated based on relative abundance of wetland indicator 

species (Coles-Ritchie et al. 2007). For Blue Mountain PIBO sites, the Wilcoxon 

rank sum test was used to compare managed vs. reference sites, and the Wilcoxon 

signed rank test was used for comparisons between measurement cycles. 

Data from 2007 to 2011 showed lower total cover (p = 0.04) and woody cover 

(including conifers; p = 0.01) along the greenline for managed sites compared to reference (fig. 7.4). Nonnative species cover, however, was significantly higher at managed sites relative to reference sites (p < 0.001, fig. 7.4). A comparison of data from 

2003 to 2006 to the later sampling cycle (2007–2011) showed no detectable change 

in greenline total cover (p = 0.83), cross-section wetland rating (p = 0.30), and 

native species richness (p = 0.79). Greenline woody cover appears to have increased 

slightly at both managed and reference sites (p < 0.001 and p = 0.03, respectively) 

while nonnative cover has decreased (managed sites p = 0.03, reference sites p = 

0.002). There is evidence that wetland ratings along the greenline have decreased on 

managed sites (p < 0.001). Definitive trends in vegetation and habitat quality will 

likely take more than two 5-year sampling cycles to detect.

Invasive weed species occurred in 109 of 178 managed sites (61 percent), compared to 8 of 18 reference sites (44 percent). The five most commonly encountered 

invasive plant species for the Blue Mountains PIBO monitoring sites were Canada 

thistle (Cirsium arvense [L.] Scop.), reed canarygrass (Phalaris arundinacea L.), 

2

 Archer, E.K.; Van Wagenen, A.R.; Coles-Ritchie, M. [et al.] [N.d.]. 2012a. Effectiveness monitoring for streams and riparian areas: sampling protocol for vegetation parameters. Unpublished report. On file at: http://www.fs.fed.us/biology/fishecology/emp. 

(8 January 2015).
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

oxeye daisy (Leucanthemum vulgare Lam.), tall buttercup (Ranunculus acris L.), 

and bull thistle (Cirsium vulgare [Savi] Ten.), similar to findings for the entire 

Columbia River basin (Archer et al. 2012b). Archer et al. (2012b) concluded that 

invasive plant species are widespread across the interior Columbia River basin, 

consistent with results reported by others (Magee et al. 2008, Ringold et al. 2008). 

The continued spread of invasive species could contribute to future degradation of 

riparian plant communities. 

Wetlands

The number of wetlands in national forests of the Blue Mountains, as derived from 

the Oregon Wetlands Geodatabase, is shown in table 7.3 (wetlands for the portion 

of the Umatilla National Forest in Washington are not shown). Depending on the 

national forest, 42 to 51 percent of the mapped wetlands are classified as “riverine” 

or riparian wetlands associated with streams, indicating the overlap in definitions 

of riparian areas and wetlands (table 7.3). Riverine wetlands account for the largest area among all wetland types on the Wallowa-Whitman National Forest (table 

7.3). Other important wetland types in the Blue Mountains are: palustrine wetlands 

(freshwater wetlands including marshes and forested wetlands) and lacustrine 

wetlands (bordering lake shores). In Malheur National Forest, palustrine wetlands 

account for the largest area among all wetland types (table 7.4). The Oregon Wetlands Geodatabase also identified “potential fens” if a wetland, usually palustrine, 

occurred near a spring (tables 7.3 and 7.4; figs. 7.1 and 7.3). All fens are GDEs, 

defined and discussed in more detail below. In the National Wetlands Inventory 

database, fens are frequently classified as a type of palustrine wetland, again 

indicating overlap in definitions for riparian areas, wetlands, and GDEs. In the 

Cowardin et al. (1979) system, fens typically fall into the Palustrine Emergent Class

(PEM) with a saturated water regime. However, because characterization based on 

remotely sensed information is sometimes inaccurate, fens may remain undetected 

or be classified as other wetland types (Aldous et al. 2015, Werstak et al. 2012). 

Comparing riparian and wetland conditions— 

The current condition of riparian and wetland ecosystems differs considerably 

depending on location within the watershed, valley configuration, and past and 

current land use. The riparian and wetland communities at low to mid elevations 

have been the most altered by land use, including grazing, development of water 

infrastructure (dams, diversions), road building along floodplains, and conversion of 

floodplains to agricultural uses (Crowe and Clausnitzer 1997; McIntosh et al. 1994a, 

The continued spread 

of invasive species 

could contribute to 

future degradation 

of riparian plant 

communities. 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 7.3—Number of springs (named and unnamed) and wetlands for the Malheur, Umatilla, and 

Wallowa-Whitman National Forestsa

Springs Wetlands

National forest Named Unnamed Total Palustrine Lacustrine Riverine Total

Potential 

fens

Malheur 389 2,462 2,851 4,405 8 4,648 9,061 1,132

Umatilla 268 381 649 2,472 5 1,780 4,257 568

Wallowa-Whitman 273 1,635 1,908 5,419 77 4,886 10,382 1,037

Total 930 4,478 5,408 12,296 90 7,314 23,700 2,737

Note: The number of springs was derived from the National Hydrography Database. The number of wetlands was derived from the Oregon 

Wetlands Geodatabase, and excludes national forest land in Washington (Umatilla) and Idaho (Hells Canyon Natural Recreation Area, 

Wallowa-Whitman).

a

 This database identified “potential fens” if a wetland, usually palustrine, occurred near a spring, so overlap exists between the number of 

palustrine wetlands and number of potential fens.

Table 7.4—Area of different wetland typesa and percentage of forest area for the Malheur, Umatilla, and 

Wallowa-Whitman National Forests 

Wetland type

National forest Area Palustrine Lacustrine Riverine Potential fensb

Hectares Hectares Percent Hectares Percent Hectares Percent Hectares Percent

Malhuer 696 895 4552 0.7 62 <0.001 1963 0.3 967 0.15

Umatilla 442 428 2091 0.5 104 <0.001 1669 0.4 556 0.001

Wallowa-Whitman 914 115 3897 0.4 1447 0.01 4458 0.5 619 0.06

Total 10 540 1613 8090 2142

a

 Wetland area was derived from the Oregon Wetlands Geodatabase and excludes national forest land in Washington (Umatilla) and Idaho 

(Wallowa-Whitman, Hells Canyon National Recreation Area). 

b

 Potential fens are classified primarily as palustrine wetlands and are included in the area calculated for palustrine wetland area.

1994b) (table 7.2). Riparian and wetland communities that occur in wide, accessible valley bottoms have been more heavily affected than higher elevation, narrow, 

conifer-dominated riparian corridors. Effects of climate change on precipitation 

and streamflow, combined with agricultural and municipal demands for water, will 

continue to affect river segments and riparian areas in lower portions of watersheds 

(Theobald et al. 2010). Wetlands and riparian areas that have been affected by land 

use are more vulnerable to natural disturbances like flooding or wildfire (Dwire 

and Kauffman 2003). Less degraded wetlands and riparian areas may be more resilient to climate-related stressors (Luce et al. 2012).

Groundwater-Dependent Ecosystems

Steep-elevation gradients, varied bedrock, and glacial landforms in the Blue 

Mountains influence the distribution, characteristics, and water chemistry of GDEs. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Although the U.S. Forest Service recognizes that groundwater is a key component 

of the water resources on National Forest Systems lands (USDA FS 2007), existing 

information on the condition and distribution of GDEs in national forests of the 

Blue Mountains is limited. Here, we again rely on data compiled by The Nature 

Conservancy (Brown et al. 2010), the National Hydrology Dataset (http://nhd.usgs.

gov), and the Oregon Wetlands Geodatabase (http://oregonexplorer.info/wetlands/

DataCollections/GeospatialData_Wetlands) to assess the current condition of GDEs 

in the Blue Mountains. 

Springs—

The number of currently mapped springs for Malheur, Umatilla, and WallowaWhitman National Forests is shown in table 7.3. The percentage of named springs, 

which implies a known perennial water source, ranges from 9 percent of mapped 

springs in Umatilla National Forest (Oregon portion) to 14 percent in both Malheur 

and Wallowa-Whitman National Forests. Most springs are unnamed, and many may 

not be perennial, especially during drier years. The number of springs is presented here to document the currently known occurrence of spring GDEs in the Blue 

Mountains. Although many more springs likely exist, such as rheocrene springs 

discharging directly to streams, they are not yet mapped. 

Springs play a key role as groundwater discharge zones that deliver cool water 

to warming streams and support late-season streamflows in summer, and may 

deliver relatively warm water during winter months (Lawrence et al. 2014, Winter 

2007). Using criteria developed by The Nature Conservancy, most streams and rivers in the Blue Mountains are at least partially groundwater dependent. Santhi et al. 

(2008) estimated that 59 percent of annual streamflow in the semiarid mountains of 

eastern Oregon is attributable to groundwater discharge. Locations of groundwater 

discharge to streams have been identified using remote sensing (Torgersen et al. 

1999) and field techniques (Torgersen et al. 2012) but have not been systematically 

mapped (see chapter 4). The focus on stream temperature in relation to salmonid 

habitat has increased awareness of the ecological relevance and importance of 

groundwater discharge to streams and rivers. 

Fens—

The Oregon Wetlands Geodatabase identified “potential fens” if a wetland, usually palustrine, occurred near a spring. To determine if these wetlands are indeed 

fens, each would require a field visit to determine that the wetland is supported (at 

least in part) by groundwater and that a minimum depth of peat (30 to 40 cm) has 

accumulated within the wetland (Chadde et al. 1998; USDA FS 2012a, 2012c). Fens 

occupy less than 1 percent of the Blue Mountains landscape (table 7.4), but they 
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GENERAL TECHNICAL REPORT PNW-GTR-939

contribute substantially to regional biodiversity of plants and animals (Blevins and 

Aldous 2011). In an otherwise arid region, perennially saturated fens are critical 

habitat for invertebrate and amphibian species. Although not explicitly differentiated as fen vegetation, several herbaceous-dominated plant associations frequently 

occur in fens. These are underlain by organic soils and dominated by different 

sedge species, including Northwest Territory sedge, Cusick’s sedge (Carex cusickii

Mack. ex Piper & Beattie), Holm’s Rocky Mountain sedge, and woodrush sedge 

(Crowe and Clausnitzer 1997). 

Current condition of groundwater-dependent ecosystems—

Since 2008, 133 GDEs, mostly springs, have been inventoried and documented 

in the Blue Mountains national forests using draft and final versions of the 

Groundwater-Dependent Ecosystems Level I and Level II inventory methods 

(USDA FS 2012a, 2012b). The Level I guide (USDA FS 2012a) describes basic 

methods for assessing GDEs within a given area (e.g. national forest, ranger district, 

or specific project area) and is intended to qualitatively document the location, size, 

and basic characteristics of each GDE site. It also presents a “management indicator 

tool,” described in more detail below. The Level II guide presents more detailed inventory (USDA FS 2012c) in addition to protocols for more comprehensive characterization of the vegetation, hydrology, geology, and soils at a given site. 

In Malheur and Wallowa-Whitman National Forests, these inventories targeted 

strategically selected sites, because of concerns about disturbance and management, 

proposals for water development, and the high value of the resource. The GDE 

inventories in Umatilla National Forest targeted portions of grazing allotments 

and watersheds with specific management concerns. Most inventories in all three 

national forests used the Level 1 inventory protocol (USDA FS 2012b). As of 2014, 

eight Level II inventories have been conducted, including collection of quantitative 

vegetation data suitable for monitoring. 

In Umatilla National Forest, Level I inventories were conducted at 102 GDEs. 

Nearly 72 percent of these GDEs were identified as rheocrene springs that discharge directly into stream channels (table 7.5). Helocrene springs were the second 

most common GDE type and typically support a larger, low-gradient wetland (0.1 

to greater than 1 ha). Water diversions that withdrew emerging water away from 

the spring habitat or adjacent stream were observed at 46 of the inventoried springs 

(table 7.5). The amount of water diverted away from the GDE was estimated at 20 

sites, averaging 93 percent of the available water at the time of sampling. Information on diverted water and other variables was not recorded at two of the 102 GDEs 

(“missing data”; table 7.5). 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 7.5—Number of different types of groundwater-dependent ecosystems (GDEs) affected by 

water diversion for 102 GDEs in Umatilla National Forest

GDEsa

Helocrene Hillslope Hypocrene Mound Rheocrene Unclassified Total

No permanent diversion 8 2 1 1 39 3 54

Permanent diversionb 5 2 0 1 33 5 46

Missing data 0 1 0 0 1 0 2

Total 13 5 1 2 73 8 102

a

 See text for definitions of GDE types.

b

 Permanent diversion includes some types of infrastructure that withdrew emerging water away from the spring habitat.

In the GDE Level I protocol (USDA FS 2012a), a series of 25 management 

indicator statements assist in identifying potential concerns and needs for management action based on observations recorded during field inventories. Information 

for the following three management indicators is presented for GDEs in Umatilla 

National Forest (table 7.6). Assessments for each of these are described in more 

detail in USDA FS (2012a): 

• Aquifer functionality—There is no evidence to suggest that the aquifer supplying groundwater to the site is being affected by groundwater withdrawal 

or loss of recharge. 

• Soil integrity—Soils are intact and functional; for example, saturation is 

sufficient to maintain hydric soils, if present, and erosion or deposition is 

not excessive.

• Vegetation composition—The site includes anticipated cover of plant 

species associated with the site environment, and upland species are not 

replacing hydric species. 

Over 56 percent of the GDEs had evidence that aquifer functionality was 

compromised in some way, usually through groundwater extraction (table 7.6). Soil 

alterations in the form of ground disturbance, soil compaction, or soil pedestaling 

affected 24 percent of inventoried sites (soil integrity; table 7.6). Upland species 

cover was higher than expected in nearly 18 percent of the GDEs, suggesting that 

hydric species may have been replaced as a result of altered local hydrology. 

Trails created by animals or people were noted in 44 percent of the sites, grazing/browsing by livestock was noted in 36 percent of sites, and grazing/browsing 

by wildlife was observed in 16 percent of sites. Thirty-one percent of the sites were 

disturbed through animal trampling. Disturbances were severe enough to question 
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GENERAL TECHNICAL REPORT PNW-GTR-939

Table 7.6—Selected management indicators for 62 groundwaterdependent ecosystem sites in Umatilla National Foresta

Management indicator No concern Issue of concern Not applicable

Aquifer functionality 20 35 7

Soil integrity 42 15 5

Vegetation composition 47 11 4

a

 Sensu USDA FS 2012c. See text for explanation of management indicators.

the long-term functioning of the most severely impacted GDEs. In summary, the 

inventoried GDEs in Umatilla National Forest showed significant resource impacts 

through water diversion, soil disturbance, and livestock impacts on vegetation 

composition (table 7.6). The GDE inventories for Malheur and Wallowa-Whitman 

National Forests documented similar trends (data not shown). 

In an assessment of GDEs in Oregon, Brown et al. (2009, 2010) examined 

existing data to determine distribution of GDEs and associated threats, focusing on 

water quantity and quality. They used the National Hydrography Dataset to identify 

locations of GDEs at the scale of hydrologic unit code 6 (HUC6), and focused their 

assessment on watersheds containing two or more types of GDEs (e.g., wetlands 

and rivers), which they termed “GDE clusters.” To evaluate threats to water quantity 

supporting GDEs, they examined the extent of water extraction or pumping through 

permitted wells used primarily for irrigation, industrial, and municipal uses, and 

unregulated (exempt) wells, which are used for livestock and domestic purposes. 

Where possible, they incorporated pending groundwater pumping permits and 

projections of residential growth to assess future threats from groundwater extraction. They found that GDE clusters in the Grande Ronde Valley, which is largely 

surrounded by Wallowa-Whitman National Forest, are threatened by diminished 

groundwater quantity (Brown et al. 2009).

To evaluate threats to groundwater quality supporting GDEs, Brown et al. 

(2009, 2010) examined contamination by nitrogen and phosphorus (high levels of 

fertilizer use), pesticides, and other toxic chemicals, using the compiled information to locate where GDEs (and GDE clusters) may be threatened by contaminated 

groundwater. Based on location and type of surrounding industrial and agricultural 

land use, they estimated that 22 to 40 percent of the GDE clusters in the John Day, 

Malheur/Owyhee, and northeast Oregon HUCs were potentially at risk by groundwater contamination from pesticides or nutrients. Although most of the threatened 

GDE clusters they identified were located in agricultural valleys, not in national 

forests, contaminated groundwater may influence water quality in other portions 

of these basins, depending on physical features of the aquifers. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Potential Climate Change Effects

Riparian Areas and Wetlands 

Changing climate in the Pacific Northwest is projected to alter streamflow in rivers 

and streams in a number of ecologically significant ways (see chapters 3 and 5). 

Warmer temperatures will influence changes in precipitation, evapotranspiration, 

and snow accumulation, timing, and rate of melt (chapter 3). Earlier spring snowmelt will affect the timing and magnitude of peak flows, leading to higher peak 

flows in winter (Mote et al. 2005). Summer low flows are projected to decrease 

throughout the West (Cayan et al. 2001, Luce and Holden 2009). 

In this section, we describe the potential effects of climate change in special 

habitats in the Blue Mountains, based on research that has examined responses 

of riparian vegetation to hydrologic alteration, primarily dams and diversions, as 

described above. However, there is considerable uncertainty in our projections, 

because empirical data are lacking on specific mechanisms through which climate 

change will influence riparian and wetland plant communities in the Blue Mountains. Climate change is likely to affect diverse riparian/wetland plant communities 

differently, depending on elevation, location within the watershed, land use, and 

species composition. Shifts in riparian vegetation and reduction in riparian area will 

probably occur in response to changes in streamflow characteristics, direct effects 

of higher temperatures, and seasonal and spatial distributions of soil moisture 

independent of streamflow (atmospheric and non-alluvial groundwater) (box 7.1). 

Reduced riparian extent could result in direct losses in quantity and quality 

of ecosystem services provided by riparian vegetation, such as wildlife habitat, 

recreational value, shade over streams, and buffer capacity for maintenance of 

stream water quality. Less quantifiable are the loss of aesthetic values associated 

with reduced riparian cover and changes in streamside species composition, vegetation and age-class structure. Reduced width of riparian areas associated with 

projected changes in streamflow characteristics (see chapter 3), increased severity 

and frequency of drought, and higher agricultural and municipal demands for water 

could result in lower buffer capacity between aquatic and upland habitats. 

Conifer-dominated riparian areas—

In headwater portions of forested watersheds, riparian areas are frequently dominated by the same species as surrounding uplands, although stands may differ in age, 

stem density, and relative proportions of different species or size classes (Dwire et 

al. 2015). With progression of climate change, conifer-dominated riparian forests 
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GENERAL TECHNICAL REPORT PNW-GTR-939

are increasingly subject to disturbances occurring in upland forests, including more 

numerous and severe fires and more frequent incidence of insect infestations. 

In the Blue Mountains, Olson (2000) compared the fire history of upland and 

riparian forests, dominated by ponderosa pine, Douglas-fir, and grand fir. In these 

dry forest types, characterized by a low-severity fire regime, fires in riparian areas 

were slightly less frequent than in uplands of the same forest types, although, 

differences were not significant. Williamson (1999) studied fuel characteristics 

and potential for crown fire initiation (torching) in paired upland-riparian stands 

of ponderosa pine, Douglas-fir, grand fir, and subalpine fir in the Blue Mountains. 

The potential for torching was high in both upland and riparian forests of all forest 

types, suggesting that high-severity fire could extend downslope into the valley 

bottoms. With projected changes in fire intensity and severity, fuel conditions in 

riparian areas may not differ sufficiently from those in uplands to stop or reduce the 

intensity of large wildfires during hot, dry weather (Luce et al. 2012). 

Recent warmer climate has been associated with frequent and extensive insect 

outbreaks, as well as outbreaks in places where historical insect activity was low 

or unknown (Logan and Powell 2009; see chapter 6). Warming temperatures are 

projected to promote insect outbreaks in forested areas by increasing water stress 

in host trees while conferring physiological advantages to insects (Bale et al. 2002). 

Riparian trees, which grow in moist soils and cool microclimatic conditions, may 

be more resistant to insect infestation. However, climate-induced increases in air 

temperature and changes in precipitation may result in drier streamside conditions, 

leading to stress in riparian trees. In addition, high insect densities may overwhelm 

local resistance to attack, making host trees vulnerable despite location along a 

stream channel. Wildfire, an important forest disturbance that is directly influenced 

by climate change (Peterson et al. 2014, Westerling et al. 2006), can reduce the 

resistance of surviving trees to insect attack. In addition, insect-caused canopy 

mortality alters the amount, composition, and arrangement of fuels (Jenkins et al. 

2008, 2012). As fire- and insect-caused mortality transform the structure of dry 

forests, effects on associated riparian forests may also become more prominent.

In a vulnerability assessment of forest trees in the Pacific Northwest, tree species were ranked by risk factors: distribution, reproductive capacity, habitat affinity, 

adaptive genetic variation, and threats from insects and disease (Devine et al. 2012). 

Each risk factor incorporated several variables evaluating the vulnerability of each 

species to climate change. Authors found that subalpine fir and Engelmann spruce, 

dominant conifer species in many high-elevation, forested riparian areas in the Blue 

Mountains, were rated as highly vulnerable to climate change (Devine et al. 2012). 

Increases in air 

temperature 

and changes in 

precipitation may 

result in drier 

streamside conditions, 

leading to stress in 

riparian trees.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Although some riparian conifer species could decline in cover, others may increase. 

For example, at lower elevations, ponderosa pine, grand fir, and Douglas-fir could 

increase in cover and density along drier floodplains. 

Riparian and wetland aspen plant communities—

Quaking aspen is one of the few broadleaf deciduous trees in northeastern Oregon, 

providing vegetative diversity in the Blue Mountains region (Swanson et al. 2010). 

Its relative rarity, high value for wildlife, and colorful autumn foliage contribute to 

its aesthetic value. Over the last 25 years, many aspen stands in the Blue Mountains 

have been declining in number, area, and stem density (Swanson et al. 2010); similar dieback has been observed in other locations in western North America (Worrall 

et al. 2013). The reasons for broad-scale decline remain uncertain but may be related to low soil moisture in severely affected stands (Worrall et al. 2013; see chapter 

6). In the Blue Mountains, aspen communities will likely continue to decrease in 

extent if climate-related changes reduce water availability, thus affecting streamflow characteristics, available groundwater, and drought conditions (see chapter 6). 

Cottonwood-dominated riparian areas—

Black cottonwood is a fairly short-lived tree (Braatne et al. 1996) that likely depends on seasonal flooding for recruitment and stand replacement (Lytle and 

Merritt 2004, Mahoney and Rood 1998, Merigliano 2005, Shafroth et al. 1998), and 

on baseflow for stand maintenance (Lite and Stromberg 2005). Relationships between streamflow and aspects of cottonwood ecology have been described for different species, geomorphic settings, and regions in western North America, mostly 

in response to dams and other flow alterations (Auble et al. 1994, Braatne et al. 

1996, Merritt and Cooper 2000). Research results have also indicated that numerous 

cottonwood populations are in serious decline, and that nonnative woody riparian 

species, notably tamarisk (Tamarix spp.), are expanding in distribution and displacing native cottonwoods throughout the Western United States, particularly along 

rivers with altered flow regimes (Friedman et al. 2005, Merritt and Poff 2010). 

Although tamarisk is not currently an issue in national forests of the Blue 

Mountains, habitat suitability modeling suggests that riparian habitat for tamarisk 

will increase throughout the Pacific Northwest over the next century (Kerns et al. 

2009), which could have negative consequences for native cottonwoods. Decreases 

in distribution and declines in the condition of cottonwood stands are likely for 

cottonwood-dominated riparian areas in the Blue Mountains in response to climaterelated changes in availability of stream and groundwater, and increased frequency 

and severity of droughts. Many cottonwood stands are already compromised by 
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GENERAL TECHNICAL REPORT PNW-GTR-939

limited recruitment, livestock grazing (Beschta and Ripple 2005), and floodplain 

conversion and development. Additional stress from climate-related changes in the 

hydrologic regime could have negative effects on the distribution and abundance of 

cottonwood.

Willow-dominated riparian areas—

Throughout the Western United States, willow-dominated riparian areas occur in 

broad valley bottoms, including unconfined and glaciated valleys with low slopes 

in montane and subalpine landscapes (Patten 1998, Rocchio 2006). Floods, streamflow, shallow subsurface drainage, and American beaver activities all contribute 

to maintenance of high water tables and willow dominance (Demmer and Beschta 

2008, Gage and Cooper 2004). The relative importance of streamflow and hillslope 

discharge for maintenance of willow ecosystems depends on elevation, geology, 

season, and other factors (Westbrook et al. 2006, 2011; Wolf et al. 2007). 

Climate-induced changes in precipitation could affect both streamflow characteristics and groundwater discharge and may result in the spatial contraction of 

willow communities and in local loss of species near limits of their distribution. 

Similar to most cottonwood species, many willow species are thought to be reproductive specialists, requiring open substrates with certain particle size distributions 

that are able to maintain soil moisture levels for germination and establishment 

(Karrenberg et al. 2002). Hydrologic modification of streams has altered flood frequency and duration along many riparian corridors, which has likely influenced the 

local recruitment and persistence of willows and contributed to the decline of some 

willow species and communities, particularly those in the “cold riparian shrub” 

PVG (table 7.2; see also Stromberg et al. 2010). Willow communities in the “warm 

riparian shrub” PVG tend to be dominated by clonal willow species that frequently 

establish and spread via vegetative propagules. However, clonal willow species 

depend on flow characteristics for creation and reworking of sand and gravel bars, 

where they frequently establish. In addition, drying of willow-dominated plant 

communities, in combination with higher air temperature and projected decreases 

in stream baseflow could reduce soil and foliar moisture and limit their ability to 

serve as fuel breaks during wildfires.

Other shrub-dominated riparian areas—

Depending on the species, some shrub-dominated riparian areas could increase in 

areal extent and displace more moisture-dependent vegetation, including willow 

communities and sedge-dominated meadow communities. Conifers could encroach 

into shrub-dominated riparian areas, particularly at lower elevations. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Herbaceous-dominated riparian areas—

Wetland herbaceous species are highly sensitive and responsive to water table 

elevation, which could become more variable and less predictable with changes 

in streamflow characteristics and increased frequency and severity of drought. In 

some locations, wet meadows could contract in area, and vegetation could shift 

from sedge-dominated communities to more drought-tolerant native and nonnative 

grasses and possibly shrubs. Changes in species composition and cover of riparian 

vegetation could have cascading effects on water quality by reducing infiltration of 

runoff, and on stream channel morphology by weakening bank stability. 

Summary—

As noted above, climate change could influence riparian and wetland vegetation in 

the Blue Mountains in various ways (box 7.1), depending on species composition 

and physical setting, specifically valley bottom width and geometry and location 

within the stream network and watershed. Some riparian plant communities and 

associations could contract in area, many could change in species composition over 

time, and others could increase in cover. The following trends are expected:

• Conifer-dominated riparian areas will become more susceptible to 

drought, wildfire, and insect infestations. Shifts in latitudinal and altitudinal distribution of dominant conifers will likely track trends in uplands (see 

chapter 6). Conifer-dominated communities will increase in cover, particularly at lower elevations, encroaching on shrub-dominated riparian areas 

and herbaceous-dominated meadows. 

• Riparian and wetland aspen plant communities will likely continue to 

decrease in extent and decline in vigor owing to drought and decreased 

water availability. Some populations (e.g., those associated with springs) 

may be lost because of altered local hydrology.

• Cottonwood-dominated riparian areas will decrease in extent. 

Reductions in late summer baseflows will likely compromise the persistence of existing stands. Changes in timing and magnitude of spring runoff 

could influence the recruitment and establishment of new individuals, thus 

affecting the replacement of existing stands. 

• Willow-dominated riparian areas will decrease in extent as riparian 

width contracts in response to changes in frequency and magnitude of 

flooding, and lower water table late in the growing season as a result of 

lower baseflows. Changes in timing and magnitude of spring runoff could 

influence recruitment and establishment of new individuals, thus affecting 
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GENERAL TECHNICAL REPORT PNW-GTR-939

replacement of existing stands. Species composition of willow communities 

will likely shift, favoring the most drought-tolerant willows and other shrub 

species.

• Other woody-dominated riparian areas will increase in extent in some 

riparian areas, displacing more mesic willow species and communities, and 

favoring more drought-tolerant species. In communities dominated by more 

drought-tolerant species, encroachment of conifers could increase, possibly 

replacing some shrub species over time. 

• Herbaceous-dominated riparian areas will decrease in extent as riparian 

width contracts in response to decreased water availability owing to lower 

baseflows, and changes in the magnitude, duration, and extent of flooding. 

Some sedge species will be replaced by more drought-tolerant (and grazing 

tolerant) native and nonnative grass species, and invasive species will likely 

increase in cover. 

Groundwater-Dependent Ecosystems 

Climatic variables affect hydrological processes, and in the Pacific Northwest, 

increased warming will influence the amount, timing, and distribution of runoff, as 

well as groundwater recharge and discharge (Elsner et al. 2010, Waibel et al. 2013). 

In the Blue Mountains, air temperatures are projected to become warmer during 

all seasons, with the largest increases occurring in summer (chapter 3), which 

will increase evapotranspiration in all ecosystems, including the special habitats 

discussed in this chapter. Snowpack is the main source of groundwater recharge in 

mountainous terrain (Winograd et al. 1998). 

Higher minimum temperatures can reduce the longevity of snowpack, and 

decrease the length of time aquifer recharge can occur, potentially leading to faster 

runoff and less groundwater recharge. Groundwater recharge has been examined 

in only a few locations (Tague and Grant 2009), and little is known about groundwater recharge processes in many watersheds, including those that may be shifting 

from snow-dominated to more rain-dominated hydrologic regimes (Safeeq et 

al. 2013, 2014; see chapter 3). Snowmelt is generally considered a more efficient 

recharge agent than rainfall, so snow-to-rain shifts could potentially drive declines 

in groundwater recharge in snow-dominated areas (Earman and Dettinger 2011). 

Depending on elevation and the hydrogeologic setting, however, slowly infiltrating 

precipitation that includes both rain and snow may recharge some groundwater 

aquifers as effectively as rapid, seasonal snowmelt runoff. Although rain-on-snow 

zones are expected to shift upwards in elevation (see chapter 3), the influence of 

these shifts on groundwater recharge is unknown. 

Increased warming will 

influence the amount, 

timing, and distribution 

of runoff, as well as 

groundwater recharge 

and discharge.
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

In the Blue Mountains, annual precipitation is projected to remain within the 

natural range of variability (see chapter 3). However, summers will be drier, the 

onset of snowmelt will be earlier (Luce et al. 2012), the rate of snowmelt will be 

more rapid, and the snow water equivalent (SWE) of snowpack will decrease (Folland et al. 2001; see chapter 3), all of which will influence snowpack volume. The 

biggest declines in snowpack persistence and April 1 SWE are projected to occur in 

mid elevations (see chapter 3). Although effects will differ considerably depending 

on local physical features and land use, these changes will likely affect groundwater recharge rates and, in turn, influence groundwater levels and the amount of 

groundwater available to support springs, groundwater-dependent wetlands, stream 

baseflows, and soil moisture (Ludwig and Moench 2009).

When assessing potential climate-induced changes to groundwater resources, 

recharge, and GDEs, it is critical to consider the hydrogeologic setting. Geologic 

units respond differently to changes in precipitation because of differences in 

hydraulic conductivity, transmissivity, primary vs. secondary porosity, and fracture 

patterns. In a study that combined examination of aerial photography (over 50 to 80 

years) and climate analysis, Drexler et al. (2013) showed that five fens in the Sierra 

Nevada (California) decreased 10 to 16 percent in area. This decrease in GDE area 

occurred over decades with documented increases in annual mean minimum air 

temperature and decreases in SWE and snowpack longevity. However, two fens in 

the southern Cascade Range, underlain by different geology than the Sierra Nevada, 

did not change in area, suggesting that the hydrogeologic setting plays an important 

role in mediating changing climate variables on GDEs. 

In the Blue Mountains, several different hydrogeologic categories can be 

delineated, including igneous/metamorphic, basalt, sedimentary, and older volcanic 

units (Gonthier 1985). Igneous and metamorphic rocks that exhibit low permeability and porosity, low-volume-groundwater discharges to GDEs, and are recharged 

only during large infrequent precipitation or snowmelt events, may not be very 

vulnerable to changes in temperature and precipitation regimes. However, aquifers 

in sedimentary or basalt formations, which generally have high permeability and 

porosity, larger volume discharges to GDEs, and are recharged more frequently, 

may be more sensitive to altered climate.

Small, unconfined aquifers, especially surficial and shallow aquifers, are more 

likely to have renewable groundwater on shorter time scales and may respond 

rapidly to changes in climate (Healy and Cook 2002, Lee et al. 2006, Sophocleous 2002, Winter 1999). Larger, deeper, and confined aquifers are more likely 

to have nonrenewable groundwater, may be less sensitive to the direct effects of 
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GENERAL TECHNICAL REPORT PNW-GTR-939

climatic variability and change, and are projected to have a slower response (Wada 

et al. 2012). Hydrogeologic units in the Blue Mountains exhibit both confined and 

unconfined conditions. The deeper basalt units and older volcanic aquifers tend to 

be more confined (Gonthier 1985). 

Groundwater storage can act as a moderator of surface water response to 

precipitation (Maxwell and Kollet 2008), and changes to groundwater levels can 

alter the interaction between groundwater and surface water (Hanson et al. 2012). 

Climate-induced changes in connectivity between groundwater and surface water 

could directly affect stream baseflows and associated wetlands and other GDEs 

(Candela et al. 2012, Earman and Dettinger 2011, Kløve et al. 2012, Tujchneider 

et al. 2012). Simulation modeling shows that short flow-path groundwater systems, including many that provide baseflow to headwater streams, could change 

substantially in the timing of discharge in response to changes in seasonality of 

recharge (Waibel et al. 2013). By contrast, regional-scale aquifer systems with 

flow paths on the order of tens of kilometers, are much less affected by shifts in 

seasonality of recharge (Waibel et al. 2013). These effects may be highly variable, 

and largely depend on local hydrogeology. In wetlands, changes in groundwater 

levels can lead to reduced groundwater inflow, leading to lower water table levels 

and altered wetland water balances. For local- and intermediate-scale systems, the 

spatial extent of some GDEs will likely contract in response to decreasing surface 

water and groundwater and increasing temperatures. Changes in groundwater and 

surface water will also vary depending on location within the watershed and stream 

network, as well as future land use. 

Effects of changing climate on the ecology of GDEs will depend on changes 

in groundwater levels and recharge rates, as influenced by the size and position 

of groundwater aquifers (Aldous et al. 2015). The GDEs supported by small, local 

groundwater systems tend to exhibit more variation in temperature and nutrient 

concentrations than regional systems (Bertrand et al. 2012). Larger systems will 

likely be more resilient to climate change. Freshwater springs are dependent on 

continuous discharge of groundwater and form ecotones between subsurfacesurface water and aquatic-terrestrial environments, which contribute to local and 

regional aquatic biodiversity (Ward and Tockner 2001). Springs and springbrooks 

are physically stable environments that support locally unique biological communities (Barquin and Death 2006). However, climate-induced changes in recharge rates 

may be reflected in decreased summertime flows with possible drying, as well as 

increased winter flow and associated flooding that could have negative impacts on 

biological communities (Green et al. 2011). 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Taylor and Stefan (2009) estimated that groundwater temperatures would rise 

by up to 4 °C in a temperate region under a doubling of carbon dioxide. Because 

many biogeochemical processes are temperature dependent, climate-induced 

changes in groundwater temperature may negatively affect the quality of groundwater and, in turn, influence aquatic communities (Figura et al. 2011). However, 

because the thermal regime of groundwater systems is less dependent on air 

temperature patterns than surface waters, the effects of rising air temperatures are 

likely to be less pronounced in springs and other GDEs. 

For fens, peat accumulating processes will be influenced by increasing temperatures and local and regional changes in hydrologic regime. Reduced groundwater 

levels tend to promote soil aeration and organic matter oxidation. Generation and 

maintenance of peat soils over time depend on stable hydrological conditions. In 

recent studies of peatlands exposed to groundwater lowering, responses such as soil 

cracking, peat subsidence, and secondary changes in waterflow and storage patterns have been observed (Kværner and Snilsberg 2011). Wetland plant species can 

respond to even slight changes in water table elevation (Magee and Kentula 2005, 

Shipley et al. 1991, Vitt et al. 1984), and shifts in composition of both vascular and 

bryophyte species could occur in fens with lowered water tables. 

Land-use changes can alter watershed conditions and generate responses in 

biological communities and ecological processes, and in some cases, may override 

hydrologic modifications caused by large-scale climate shifts. As noted above for 

wetland and riparian ecosystems, effects of land use and management activities 

may have more immediate and detectable impacts on GDEs and the species they 

support than changing climate. For example, a recent study on spring-channel water 

diversion indicated that substantial decreases in physical and aquatic habitat occur 

with relatively small (10 to 20 percent) discharge reductions (Morrison et al. 2013). 

In the Umatilla National Forest, approximately 45 percent of inventoried springs 

undergo water withdrawals from the spring habitat (table 7.5). However, some 

spring organisms appear to be resilient to human-induced disturbances. Ilmonen 

et al. (2012) showed that invertebrate communities in springs affected by logging 

about 30 years prior to sampling did not differ appreciably from those in unaffected 

reference springs.

Management Context 

Current Management Objectives and Desired Outcomes

Riparian areas and wetlands are protected under the Clean Water Act, which regulates the development and modification of floodplains; minimizes the destruction, 

loss, and degradation of wetlands; and enhances the natural and beneficial value 
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GENERAL TECHNICAL REPORT PNW-GTR-939

of wetlands. Current management objectives for riparian areas in eastern Oregon 

are mainly informed by the aquatic strategies PACFISH and INFISH (USDA FS 

1995, USDA FS and USDI BLM 1995) that were developed and adopted by the U.S. 

Forest Service and Bureau of Land Management. These strategies were considered 

short-term interim direction to protect native fish populations and their aquatic 

habitat. They will be revised by desired riparian conditions and management objectives with the adoption of new land management plans for all three national forests 

in the Blue Mountains. 

Riparian goals in PACFISH and INFISH address water quality, stream channel 

integrity, instream flow, natural timing and variability of water-table elevation, 

diversity and productivity of riparian plant communities, and other riparian and 

aquatic habitat qualities necessary to support populations of inland native and anadromous fish. Riparian vegetation is to be maintained or restored to provide instream 

and riparian large wood, thermal regulation (including stream shading), and protection of floodplain surfaces and banks against uncharacteristic erosion. PACFISH 

and INFISH interim direction establishes riparian management objectives (RMOs) 

for all watersheds that include inland native or anadromous fish. These RMOs 

describe habitat conditions as a range of features that need to be met or exceeded. 

The key feature is pool frequency that varies by channel width. Supporting features 

include maximum water temperature, instream large wood, width-depth ratios, and 

measures of bank stability and bank angle. In the absence of site-specific watershed 

analysis, the RMOs provide a benchmark for all management actions and apply 

to all Riparian Habitat Conservation Areas (RHCAs), including streams with and 

without fish, wetlands, and intermittent streams.

The U.S. Forest Service groundwater management program has made progress in increasing awareness of the importance and vulnerability of groundwater 

resources, and providing guidance on identify, assessing, and analyzing of GDEs 

(USDA FS 2012a,c). National forests in the Blue Mountains are still in the early 

stages of identifying and understanding the extent of groundwater resources, as 

well as potential threats. However, resource managers are increasingly considering 

GDEs in watershed assessments and project-level planning. 

Management Practices

The establishment of RHCAs has altered management priorities to put primary 

emphasis on riparian-dependent resources. Management activities in RHCAs are 

subject to specific standards and guidelines that limit timber harvest (including 

fuelwood cutting). Consequently, fuel management, timber sales, and forest 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

restoration projects commonly exclude RHCAs from any treatment. This management approach may be creating uncharacteristic fuel conditions within some riparian corridors (Messier et al. 2012, Meyer et al. 2012). Avoiding active management 

within RHCAs that have been altered by fire suppression and streamflow regulation 

(dams, roads, culverts, diversions) could further influence disturbance regimes and 

contribute to more uniform, late-seral forest structure, or to increased fire hazard. 

This management approach could also affect postdisturbance conditions, resulting 

in decreased riparian plant diversity over time. 

In upland forest watersheds where fuel treatments are implemented, it might 

be beneficial to include adjacent riparian areas for treatments (Meyer et al. 2012) to 

avoid concentration of fuels in streamside areas. Although treating fuels in riparian 

areas can potentially affect desired functions and ecosystem services (Dwire et al. 

2010) (table 7.1), research has indicated that effects of prescribed fire are largely 

short term (Arkle and Pilliod 2010, Béche et al. 2005). However, the effects of other 

fuel reduction treatments (e.g., mechanical thinning or various treatment combinations) on stream and riparian attributes have not been evaluated. 

The RHCA standards and guidelines require adjustment or elimination of 

grazing practices that are inconsistent with attainment of RMOs but appear to have 

a smaller effect on management practices compared to timber management. The 

requirements have resulted in increased fencing of sensitive riparian and wetland 

resources within grazing allotments. Other management actions include active 

movement of cattle out of riparian zones, and placement of cut conifers to discourage access to treated aspen stands and streamside meadows. To monitor the effects 

of grazing practices and ensure that they do not prevent the attainment of RMOs, 

national forests have implemented riparian monitoring protocols such as Multiple 

Indicator Monitoring (Burton et al. 2011) in addition to PACFISH/INFISH effectiveness monitoring. 

Adapting Special Habitats to Climate Change in the 

Blue Mountains 

Management strategies and tactics for increasing resilience of vegetation in the 

Pacific Northwest to a warmer climate are well documented (e.g., Gaines et al. 

2012; Halofsky et al. 2011; Littell et al. 2012, 2014; Raymond et al. 2013, 2014; see 

chapter 6). Although adaptation options for habitats associated with special hydrologic conditions are a small part of this knowledge base, these habitats have a disproportionately large effect on biological diversity in the region. Adaptation options 

for water resources (Dalton et al. 2013, Halofsky et al. 2011, Strauch et al. 2014; see 

In upland forest 

watersheds where 

fuel treatments are 

implemented, it might 

be beneficial to include 

adjacent riparian areas 

for treatments.
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GENERAL TECHNICAL REPORT PNW-GTR-939

chapter 4) are often synonymous with, or related to, adaptation options relevant 

for special habitats (e.g., maintaining and restoring instream flows). These sources 

of information, combined with feedback from resource specialists, contributed to 

a summary of climate change adaptation options for special habitats in the Blue 

Mountains (tables 7.7, 7.8, and 7.9). Implementation of climate-smart management 

actions and restoration objectives will benefit from a strategic approach to ensure 

that the most important work is occurring in the most important places (Hughes et 

al. 2014). Because special habitat conservation is at the interface of vegetation and 

stream restoration, opportunities exist for coordination of restoration programs and 

on-the-ground actions.

Riparian Areas and Wetlands

The productivity of wetland and riparian ecosystems could decrease in the future 

as a result of increased evapotranspiration and reduced snowpack, causing lower 

water supply during the growing season and more variable streamflow. Maintaining 

appropriate densities of native species, propagating drought-tolerant native species, 

and controlling or eliminating nonnative species are strategies that may increase 

riparian resilience to a warmer climate (tables 7.7 and 7.8). It would also be beneficial to plant species that have a broad range of moisture tolerances, such as Lewis’ 

mock orange (Philadelphus lewisii Pursh) and choke cherry (Prunus virginiana L.), 

which are resistant to variable water availability during the growing season. Finally, 

removing infrastructure (e.g., campsites, utility corridors, spring houses, and spring 

boxes) from riparian areas and wetlands will reduce soil compaction and other 

physical damage, thus allowing natural physical processes to occur and improving hydrologic function. Opposition by the public to facilities removal is likely, so 

relocation (rather than removal) of some facilities to areas with less environmental 

impact can be considered. 

Improving soil health and bank stability to reduce erosion and enhance native 

vegetation is an adaptation strategy that would improve riparian conditions (Kauffman et al. 2004). The most important measure is to reduce degradation of riparian 

areas by livestock through fencing and rest-rotation grazing. Livestock grazing has 

caused considerable damage to riparian systems over many decades, and efforts to 

repair and reduce this damage will improve resilience, although opposition from 

range permittees is likely if changes are instituted. Along stream segments with 

highly valued deciduous riparian vegetative cover, fencing to exclude native ungulates could also be considered. Elk and deer are frequently able to enter enclosures 

or riparian areas that have been fenced to exclude cows. 
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 7.7a—Adaptation responses to climate change for riparian and wetland systems in the Blue Mountains (continued)Adaptation tactic Timeframe

Opportunities for implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: Shifts in hydrologic regime include changes in timing and magnitude of flows, lower summer flows and 

higher, more frequent winter peak flows. Reduced snowpack will decrease water supply during growing season and lead to more variable streamflow, thus reducing productivity in riparian ecosystems.

Adaptation strategy: Maintain appropriate densities of native species, and propagate more drought-tolerant native species.Plant species that have a broader 

range of moisture tolerance (e.g., mock orange, choke cherry)

10 to 30 

years, >30 years

Collaborate with Idaho Power, 

range permittees, and private landowners

High costLimited availability of local 

plant material

Identify segments along streamriparian corridors with need 

for shade that meet growth requirements of desirable woody species

Eradicate and control invasive 

species where possible (especially after fire)

<10 years, 10 

to 30 years

Collaborate with range permittees, private landowners, 

counties, and Idaho Power

High cost Identify riparian areas (stream 

segments) with high cover of most noxious nonnative species; prioritize treatment areas 

Remove infrastructure where appropriate (e.g., campsites, utility 

corridors, springhouses, and spring boxes)

<10 years Various management plans High cost

Public opposition; constraints 

of existing water rights for modifying spring developments

Identify infrastructure that can be 

removed; prioritize decommissioning and removal

Adaptation strategy: Maintain or restore natural flow regime to buffer against future changes.Develop integrated, interdisciplinary tactics to maintain or restore 

natural flows; purchase and obtain instream flow rights where possible 

<10 years Collaborate with nongovernmental organizations, other 

federal and state agencies, and private landowners

Competing priorities; lack of 

funding

Using watershed analysis, watershed condition framework, 

or other approaches to identify priority watersheds and stream segments 
300

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 7.7a—Adaptation responses to climate change for riparian and wetland systems in the Blue Mountains (continued) Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs Restore riparian areas and beaver populations to maintain summer baseflows and raise water table <10 years to >30 years Collaborate with states, range permittees, and private landowners regarding beaver reentry Use range allotment manage- ment, riparian shrub planting and protection, riparian aspen restoration and management, road infrastructure planning, and valley form analysis to assess potential sites for 

beaver colonies and channel migration

Effects on infrastructure (culverts and diversions)Adequate food supply for 

growing beaver colonies and dispersing individuals

Public and private landowner 

acceptance of beaver colonies

Effects of rising water levels on 

streamside roads and camping grounds

Improve geographic information 

system (GIS) layer for distribution of riparian community types relative to valley bottom classification

Identify watersheds and stream 

reaches with highest potential for successful establishment

Monitor beaver populationsInventory riparian vegetation and 

stream morphology status and trends

Address water loss at points of water diversion and along ditches <10 years Coordinate with the water dis- trict managers, water master, 

and water users

Competing prioritiesLack of fundingWater law does not address 

ditch water loss, inefficiencies, and other impacts on forest resources

Identify diversions/and ditches 

with water losses or other impacts on forest resources

Anticipate new proposals for development of water infrastructure 

(additional diversions or reservoir expansions)

<10 years Develop approach for protection of streamflow and 

maintenance of water levels in wetlands 

Competing prioritiesConstraints of water laws

Identify priority watersheds and 

stream reaches; define flows required for sediment transport, and maintenance of riparian and wetland vegetation and aquatic habitat

Reconnect and increase off-channel 

habitat and refugia in side channels and channels supported by sideslope wetlands

<10 to >30 

years

Collaborate with partners Competing priorities 

Lack of funding

Identify potential watersheds and 

stream reaches
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 7.7a—Adaptation responses to climate change for riparian and wetland systems in the Blue Mountains (continued)Adaptation tactic Timeframe

Opportunities for implementation Barriers to implementation Information needs

Revegetate; fence to exclude livestock; acquire water rights <10 years Collaborate with partners to fence or acquire or lease water 

rights

Revegetate and protect riparian 

areas

Restore aspen

Competing prioritiesLack of fundingDifficulty of maintaining livestock and ungulate exclusions

Investigate baseline vs. desired 

conditions in riparian corridors

Conduct effectiveness 

monitoring

Identify water rights holders 

willing to collaborate

Adaptation strategy: Improve soil health (including bank stability) and increase resilience of native vegetative communities to maintain natural 

water storage.

Reduce degradation by livestock; 

fence riparian areas, and use rest rotation

Ongoing Adjust range allotment management where possible; collaborate with range permittees and 

private landowners 

Public opposition Identify stream-riparian reaches 

for fencing, or changes in grazing management

Manage fuel loads through various prescriptions (prescribed fire, 

mechanical treatments)

10 to 30 

years

Forest plans for fire and fuels 

management

High costLogistical challenges of prescribed fire use in riparian 

areas

Quantify riparian fuel loads (relative to uplands) and effectiveness of various fuel reduction 

treatments
302

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 7.7b—Adaptation responses to climate change for high-elevation riparian systems in the Blue Mountains Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs Sensitivity to climatic variability and change: Reduced snowpack will decrease water supply during growing season and lead to more variable stream- flow, thus reducing productivity in riparian systems in alpine and subalpine ecosystems. Adaptation strategy: Reduce stresses such as conifer encroachment, livestock grazing, and ungulate browsing. Consider riparian fuel reduction strategies in forested subalpine areas, including small-scale fuel breaks <10 years Coordination with other fuels management and restoration projects Logistical constraints Assessment of riparian fuel char- acteristics Identify strategic locations for fuel breaks Reduce degradation by livestock Ongoing Adjust range allotment manage- ment where possible; collaborate with range permittees and 

private landowners

Public opposition Identify stream-riparian reaches 

for fencing, or changes in grazing management
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Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Table 7.7c—Adaptation responses of groundwater-dependent ecosystems (GDEs) to climate change in the Blue Mountains (continued)Adaptation tactic Timeframe

Opportunities for 

implementation Barriers to implementation Information needs

Sensitivity to climatic variability and change: Reduced snowpack will decrease water supply during growing season, thus reducing productivity in 

groundwater-dependent systems, including springs and wetlands.

Adaptation strategy: Manage for resilience of springs and wetlands by considering the broader forest landscape including uplands.Consider impacts and potential 

benefits of vegetation management treatments (prescribed fire, 

mechanical thinning) 

<10 years Coordination with other fuels 

management and restoration projects

Lack of scientific and sitespecific information on spring 

ecology

Inventory and characterization of 

springs, other GDEs and surrounding forest conditions

Protect groundwater recharge areas <10 years Explore opportunities with 

range permittees, nongovernmental organizations, and others

Limited information on locations of springs, recharge 

areas, and groundwater input to stream channels 

Lack of funds to address sites 

affected by livestock

Competing priorities

Locate and characterize GDE 

and spring influences

Adaptation strategy: Manage water to maintain springs and wetlands; improve soil quality and stability. Decommission roads and reduce 

road connectivity to encourage interception and retention of water

<10 years Incorporate into forest plans 

as watershed improvement strategy

High costPublic oppositionCompeting priorities

Identify and prioritize project 

areas

Reduce ungulate trampling with 

fencing

<10 years Work with range permittees, 

watershed councils, and other partners to fund or install fencing

High costNeed for maintenance

Identify and prioritize springs 

and wetlands for fencing

Monitor effectiveness of fencing 

projects

Maintain water on site through 

water conservation techniques such as float valves, diversion valves, and hose pumps

<10 years Incorporate into forest plans 

as watershed improvement strategy; specify in allotment management plans

Range permittees do not like 

these practices

Identify permittees and water 

users who are willing to collaborate

Encourage spring development 

project designs that will ensure environmental flows for native species and habitat

<10 years Proposed, new, or redeveloped 

livestock watering projects

Conduct environmental flow/

level analysis
304

GENERAL TECHNICAL REPORT PNW-GTR-939 Table 7.7c—Adaptation responses of groundwater-dependent ecosystems (GDEs) to climate change in the Blue Mountains (continued) Adaptation tactic Timeframe Opportunities for implementation Barriers to implementation Information needs • Collect no more water than is sufficient to meet the intended purpose of the spring development <10 years Proposed, new, or redeveloped livestock watering projects Conduct environmental flow/ level analysis • Include implementation and effectiveness monitoring to evaluate success of the project in meeting design objectives and avoiding or minimiz- ing unacceptable impacts to spring ecology <10 years Incorporate into forest plans as watershed improvement strategy

• Use suitable measures to 

maintain desired downstream temperatures, dissolved oxygen levels, and aquatic habitats when water is released from a pond trough or impoundment.

<10 years Proposed, new, or redeveloped 

livestock watering projects

• Use float valves or other flow 

control devices to provide flow only when a demand is present

<10 years Incorporate into forest plans 

as watershed improvement strategy

• Use a flow-splitting device 

to retain as much flow in the spring and associated habitat as possible

<10 years Proposed, new, or redeveloped 

livestock watering projects

• Consider discontinuing use 

of a water resource in critical habitats 

<10 years Allotment management plan 

revision

Ecological assessment

Relocate water troughs away from 

springs and riparian areas to limit trampling. 

<10 years Proposed, new, or redeveloped 

livestock watering projects

Change the duration, season, or 

intensity of grazing if the current grazing strategy inhibits natural recovery at a given site

<10 years Allotment management plan 

revision

Determine the duration, season, 

and intensity of grazing with the least impact for a given site
305

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Riparian areas and wetlands are important components of alpine and subalpine 

ecosystems. In these systems, an important adaptation strategy is to reduce existing 

stresses, such as conifer encroachment, livestock grazing, and ungulate browsing 

(table 7.8). Specific adaptation tactics include controlling livestock grazing and 

removing nonnative species where feasible, especially following wildfire. Collaboration with range permittees, fire and fuels managers, and coordination with 

ongoing restoration activities, will enhance the effectiveness of adaptation actions.

Groundwater-Dependent Ecosystems 

Reduced snowpack could decrease water supply, potentially reducing productivity 

in all types of GDEs. The primary strategy for increasing resilience in GDEs is to 

manage for their functionality in the spatial context of the broader forest landscape 

(table 7.9), because the structure and function of GDEs are largely influenced by 

surrounding vegetation and hydrology. An adaptation strategy is to maintain GDEs 

by maintaining water supply and improving soil quality and stability. This can be 

accomplished through three different tactics. First, decommissioning roads and 

reducing road connectivity is likely to increase interception of precipitation and 

local retention of water. Second, trampling of GDEs by domestic livestock and 

native ungulates can be better managed with fencing. Third, water can be maintained at developed spring sites through improved engineering, including use of 

float valves, diversion valves, and pumps. These tactics require significant costs, 

and there may be opposition to road removal and grazing restrictions by the public 

and range permittees.

As ecosystems, GDEs are understudied, primarily because subterranean 

systems are difficult to access. The scientific community is in early stages of 

research and management of these ecosystems and faces important knowledge 

gaps. The current lack of knowledge on groundwater has limited the consideration 

of groundwater resources in integrated forest planning, inventory, monitoring, and 

permitting. A framework for managing groundwater resources in national forests is 

needed, one that includes a more consistent approach for evaluating and monitoring 

the effects of management actions on groundwater. With respect to conservation of 

GDEs, guidance on how groundwater resources are considered in agency activities 

is needed, and will require evaluation of potential effects of groundwater withdrawals on national forest resources. Guidance should also provide a strategy through 

which groundwater and vegetation can be jointly managed, thus facilitating management of riparian areas, wetlands, and GDEs in a warmer climate.
306

GENERAL TECHNICAL REPORT PNW-GTR-939

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Chapter 8: Conclusions

David L. Peterson, Robyn Darbyshire, and Becky Gravenmier1

The Blue Mountains Adaptation Partnership (BMAP) made significant progress 

on the climate change response of national forests, synthesized the best available 

scientific information to assess climate change vulnerability, developed adaptation 

options, and catalyzed a collaboration among national forests and other stakeholders 

seeking to address climate change in the Blue Mountains region. This vulnerability 

assessment and corresponding adaptation options enabled the national forests to 

address several components of the U.S. Forest Service (USFS) climate change 

response strategy as outlined in the National Roadmap for Responding to Climate 

Change (USDA FS 2010a) and the Climate Change Performance Scorecard (USDA 

FS 2010b) (see chapter 1). The BMAP process allowed the Malheur, Umatilla, and 

Wallow-Whitman National Forests to respond with “yes” to scorecard questions in 

the organizational capacity, engagement, and adaptation dimensions. 

To maintain focus on key near-term issues, the BMAP assessment emphasizes 

four resource areas—water, fish, upland vegetation, and special habitats—regarded 

as the most important resources for local ecosystems and communities. Water is 

critical because downstream users rely on snowpack and water that comes from 

national forests in the Blue Mountains. Cold-water fish species, which depend on 

that water, are critical for biological diversity, sport fishing, and food and cultural 

values for American Indians. Upland vegetation provides a multitude of ecosystem 

services in the form of forest products for local economies, wildlife habitat, shade 

for streams, soil protection, livestock forage, and scenery. Finally, special habitats 

(e.g., wetlands, groundwater-dependent ecosystems) benefit a high diversity of 

terrestrial and aquatic species even though these habitats occupy a relatively small 

proportion of the landscape. In the future, it may be possible to expand the assessment to include other systems and issues such as wildlife, recreation, and socioeconomic effects.

The BMAP built on previous science-management partnerships by creating an 

inclusive forum for resource managers and stakeholders to address issues related 

to climate change vulnerability and adaptation. This partnership was conducted 

for national forests only, so additional work is needed to achieve an “all lands” 

approach to climate change adaptation in the Blue Mountains region. The scope 

1 David. L. Peterson is a senior research biological scientist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 400 N 34th St., Suite 201, Seattle, 

WA 98103; Robyn Darbyshire is the regional silviculturist, and Becky Gravenmier is 

the science/climate change coordinator, U.S. Department of Agriculture, Forest Service, 

Pacific Northwest Region, 1220 SW 3rd Avenue, Portland, OR 97204.
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of this vulnerability assessment was to cover a range of natural resources that are 

critical for human communities and ecosystem services in the Blue Mountains. By 

exploring resources in detail, participants identified species and ecosystems that are 

sensitive to climate change. More detailed quantitative and spatially explicit vulnerability assessments would improve the scientific basis for detecting the effects 

of climate change and developing site-specific management responses and plans. 

It would also allow resource managers to prioritize locations for implementation. 

Finally, integrating carbon assessments would allow managers to develop linkages 

between adaptation and mitigation actions. 

Relevance to Forest Service Climate Change Response 

Strategies 

In this section, we summarize the relevance of the BMAP process to the climate 

change strategy of the USFS and to the forest plan revision process for national 

forests. Information presented in this report is also relevant for other land management agencies and stakeholders in the Blue Mountains. This process can be replicated and implemented by any organization, and many of the adaptation options 

are applicable beyond the Blue Mountains. Like previous adaptation efforts (e.g., 

Halofsky et al. 2011), a science-management partnership was critical to the success 

of the BMAP. For others interested in emulating this approach, we encourage them 

to pursue this partnership as the foundation for increasing climate change awareness, assessing vulnerability, and developing adaptation plans. 

Organizational capacity to address climate change, as outlined in the USFS 

Climate Change Performance Scorecard requires building institutional capacity 

in management units through training and education for employees. Training and 

education were built into the BMAP process through workshops and webinars 

that provided information about the effects of climate change on water resources, 

fisheries, and vegetation. The workshops introduced climate tools and processes for 

assessing vulnerability and planning for adaptation. 

The BMAP science-management partnership and process were as important 

as the products that were developed because partnerships are the cornerstone for 

successful agency responses to climate change. We built a partnership that included 

three national forests (Malheur, Umatilla, Wallowa-Whitman), the Pacific Northwest Regional Office, and the Pacific Northwest Research Station of the USFS; and 

two universities (Oregon State University and University of Washington), and is 

relevant for ongoing forest plan revision and restoration conducted by the national 

forests in collaboration with several stakeholders.

The BMAP sciencemanagement 

partnership and 

process were as 

important as the 

products that were 

developed.
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Elements 4 and 5 of the USFS Climate Change Performance Scorecard require 

units to engage with scientists and scientific organizations to respond to climate 

change (element 4) and work with partners at various scales across all boundaries 

(element 5). The BMAP process therefore contributed to the USFS in achieving 

unit-level compliance in their agency-specific climate responses. 

Elements 6 and 7 of the USFS Climate Change Performance Scorecard require 

units to assess the expected effects of climate change and which resources as a 

result will be most vulnerable, and identify management strategies to improve the 

adaptive capacity of the national forest lands. The BMAP vulnerability assessment 

used the best available science to identify sensitivity and vulnerability of multiple 

resources in the Blue Mountains. Adaptation options developed for each resource 

area can be incorporated into resource-specific programs and plans. The identification of key vulnerabilities and adaptation strategies can also inform the forest plan 

revision process. 

The science-management dialogue identified management practices that are 

useful for increasing resilience and reducing stressors and threats. Although implementing all adaptation options developed in the BMAP process may not be feasible, 

resource managers can still draw from the menu of options as needed. Some 

adaptation strategies and tactics can be implemented on the ground now, whereas 

others may require changes in policies and practices or can be implemented when 

forest land management plans are revised or as threats become more apparent. 

Implementation

Implementing adaptation is the most challenging next step for the BMAP. This can 

occur gradually over time, often motivated by extreme weather and large disturbances, and facilitated by changes in policies, programs, and land management plan 

revisions. It will be especially important for ongoing restoration programs to incorporate climate change adaptation to ensure effectiveness. Landowners, management 

agencies, and American Indian tribes will need to work together for implementation 

to be effective. 

In several cases, similar adaptation options were identified for more than one 

resource sector, suggesting a need to integrate adaptation planning across multiple 

disciplines. Adaptation options that yield benefits to more than one resource are 

likely to have the greatest benefit (Halofsky et al. 2011, Peterson et al. 2011). However, some adaptation options involve tradeoffs and uncertainties that need further 

exploration. Assembling an interdisciplinary team to tackle this issue will help to 

assess risks and develop risk management options. 
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Integration of the information in this assessment in everyday work through 

“climate-smart thinking” is critical, and can be reflected in resource management 

and planning, as well as for management priorities such as safety. Flooding, wildfire, and insect outbreaks may all be exacerbated by climate change, thus increasing 

hazards faced by federal employees and the public. Resource management can help 

minimize these hazards by reducing fuels, modifying forest species composition, 

and restoring hydrologic function. These activities are commonplace, demonstrating that much current resource management is already climate smart. This 

assessment can improve current management practice by helping to prioritize and 

accelerate implementation of specific options and locations for adaptation. 

Putting adaptation on the ground will often be limited by insufficient human 

resources, insufficient funding, and conflicting priorities. However, the magnitude and likelihood for some changes to occur in the near future (especially 

water resources and fisheries) are high, as are the consequences for ecosystems 

and human values, and some adaptation options may be precluded if they are not 

implemented soon. This creates an imperative for timely action for the integration 

of climate change as a component of resource management and agency operations.

The climate change vulnerability assessment and adaptation approach developed by the BMAP can be used by the USFS and other organizations in many 

ways. From the perspective of federal land management, this information can be 

integrated within the following aspects of agency operations:

• Landscape management assessments/planning: Provide information on 

departure from historical range of variability and on desired conditions 

(e.g., land management plans, watershed assessments).

• Resource management strategies: Incorporate information into conservation strategies, fire management plans, infrastructure planning, and state 

wildlife action plans. 

• National Environmental Policy Act (NEPA) analysis: Provide best available science for documentation of resource conditions, vulnerabilities of 

resources to climate change, and the development of alternatives.

• Monitoring plans: Identify knowledge gaps that can be addressed by monitoring in broad-scale strategies, plan-level programs, and project-level data 

collection.
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Agencies can use climate change vulnerability information and adaptation 

strategies and tactics within:

• The National forest land management plan revision process: Provide a foundation for understanding key resource vulnerabilities caused by climate 

change for the assessment phase of forest plan revision. Information from 

vulnerability assessments can be applied in assessments required under the 

2012 Planning Rule, describe potential climatic conditions and effects on 

key resources, and identify and prioritize resource vulnerabilities to climate 

change in the future. Climate change vulnerabilities and adaptation strategies can inform forest plan components such as desired conditions, objectives, standards, and guidelines. 

• Resource management strategies: Incorporate information into forest resiliency and restoration plans, conservation strategies, fire management plans, 

infrastructure planning, and state wildlife action plans

• Project design/implementation: Provide mitigation and design tactics at 

specific locations.

• Monitoring evaluations: Provide periodic evaluation of monitoring 

questions.

We are optimistic that climate change awareness, climate-smart management 

and planning, and implementation of adaptation in the Blue Mountains region will 

continue to evolve. We anticipate that by the end of the decade:

• Climate change will become an integral component of business operations.

• The effects of climate change will be continually assessed on natural and 

human systems, with a stronger focus on ecosystem services. 

• Monitoring activities will include indicators to detect the effects of climate 

change on species and ecosystems. 

• Agency planning processes will provide opportunities to manage across 

boundaries. 

• Restoration activities will be implemented in the context of the influence of 

a changing climate. 

• Management of carbon will be included in adaptation planning.

• Institutional capacity to manage for climate change will increase within 

federal agencies and local stakeholders. 

• Resource managers will implement climate-informed practices in long-term 

planning and management. 
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This assessment provides a foundation for addressing key climate change 

vulnerabilities by implementing adaptation options that help reduce the negative 

effects of climate change and transition resources to a warmer climate. Maintaining 

the science-management partnership that was developed as part of the BMAP process will enhance the scientific capacity of the national forests. The effectiveness 

of the partnership will be improved by collaborating with organizations focused 

on restoration and other issues, thus increasing the capacity of national forests to 

address specific issues and landscapes. We hope that the assessment and an enduring partnership will help implement climate change in resource management and 

planning throughout the Blue Mountains region. 

Acknowledgments

We thank leadership and resource managers of Malheur, Umatilla, and WallowaWhitman National Forests for their support of the BMAP. We especially appreciate the expertise of Becky Gravenmier, Robyn Darbyshire, David Powell, David 

Salo, Larry Amell, Ayn Shlisky, and John Stevenson. We thank all participants 

in the vulnerability assessment and adaptation workshop for their enthusiasm and 

contributions. The following reviewers provided insightful comments that greatly 

improved this publication: Peter Adler, Joseph Gurrieri, Michael Furniss, Guillaume Mauger, Michelle McClure, Ronda Strauch, and Steven Wondzell. Amy 

Mathie provided outstanding support with geospatial analysis and cartography. 

Funding was provided by the U.S. Forest Service Pacific Northwest Research 

Station, Pacific Northwest Region, and the Office of Sustainability and Climate 

Change, and by the National Oceanic and Atmospheric Administration. 

English Equivalents

When you know: Multiply by: To find:

Millimeter (mm) 0.0394 Inches

Centimeters (cm) .394 Inches

Meters (m) 3.28 Feet

Kilometers (km) .621 Miles

Hectares (ha) 2.47 Acres

Cubic meters (m3

) 35.3 Cubic feet

Degrees Celsius (°C) 1.8 °C + 32 Degrees Fahrenheit

We hope that the 

assessment and an 

enduring partnership 

will help implement 

climate change in 

resource management 

and planning. 
331

Climate Change Vulnerability and Adaptation in the Blue Mountains Region

Literature Cited

Halofsky, J.E.; Peterson, D.L.; O’Halloran, K.A.; Hoffman, C.H. 2011. 

Adapting to climate change at Olympic National Forest and Olympic National 

Park. Gen. Tech. Rep. PNW-GTR-844. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 130 p. 

Peterson, D.L.; Millar, C.I.; Joyce, L.A. [et al.]. 2011. Responding to climate 

change in national forests: a guidebook for developing adaptation options. Gen. 

Tech. Rep. PNW-GTR-855. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station. 109 p.

U.S. Department of Agriculture, Forest Service [USDA FS]. 2010a. National 

roadmap for responding to climate change. http://www.fs.fed.us/climatechange/

pdf/roadmap.pdf. (23 July 2015).

U.S. Department of Agriculture, Forest Service [USDA FS]. 2010b. A 

performance scorecard for implementing the Forest Service climate change 

strategy. http://www.fs.fed.us/climatechange/pdf/performance_scorecard_final.

pdf. (23 July 2015).
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