National Park Service

U.S. Department of the Interior

Natural Resource Program Center

Observed and Projected Ecological Response to 

Climate Change in the Rocky Mountains and 

Upper Columbia Basin

A Synthesis of Current Scientific Literature

Natural Resource Report NPS/ROMN/NRR—2010/220
ON THE COVER

Rocky Mountain National Park

NPS photo by B. Schweiger
Observed and Projected Ecological Response to 

Climate Change in the Rocky Mountains and 

Upper Columbia Basin

A Synthesis of Current Scientific Literature

Natural Resource Report NPS/ROMN/NRR—2010/220

Isabel W. Ashton

National Park Service

Rocky Mountain Inventory & Monitoring Network

1201 Oakridge Dr, Suite 200

Fort Collins, CO 80525

isabel_ashton@nps.gov

with contributions from:

Stacey Ostermann-Kelm

Tom Rodhouse

Kathy Tonnessen

Ellen Porter

Dave McWethy

June 2010

U.S. Department of the Interior

National Park Service

Natural Resource Program Center

Fort Collins, Colorado
ii

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

The National Park Service, Natural Resource Program Center publishes a range of reports that address natural 

resource topics of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. 

The Natural Resource Report Series is used to disseminate high-priority, current natural resource management 

information with managerial application. The series targets a general, diverse audience, and may contain NPS 

policy considerations or address sensitive issues of management applicability.

All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published 

in a professional manner. 

This report received formal peer review by subject-matter experts who were not directly involved in the collection, analysis, or reporting of the data, and whose background and expertise put them on par technically and 

scientifically with the authors of the information.

Views, statements, findings, conclusions, recommendations, and data in this report do not necessarily reflect 

views and policies of the National Park Service, U.S. Department of the Interior. Mention of trade names or 

commercial products does not constitute endorsement or recommendation for use by the U.S. Government.

This report is available from Rocky Mountain Inventory and Monitoring Network (http://science.nature.nps.gov/

im/units/romn/index.cfm) and the Natural Resource Publications Management Web site (http://www.nature.nps.

gov/publications/NRPM) on the Internet. 

Please cite this publication as:

Ashton, I. W. 2010. Observed and projected ecological response to climate change in the Rocky Mountains 

and Upper Columbia Basin: A synthesis of current scientific literature. Natural Resource Report NPS/ROMN/

NRR—2010/220. National Park Service, Fort Collins, Colorado.

NPS 960/104295, June 2010
iii

Contents Contents

Figures ..........................................................................................................................................vi

Tables ...........................................................................................................................................vii

Executive Summary .....................................................................................................................ix

Acknowledgments.......................................................................................................................xi

Chapter 1: Introduction................................................................................................................1

Chapter 2: Physical Environment ................................................................................................3

2.1 Climate ..............................................................................................................................3

2.1.1  Observed trends ..........................................................................................................3

2.1.2  Projected trends ..........................................................................................................4

2.1.3  Summary .....................................................................................................................4

2.2 Air quality and deposition ...................................................................................................4

2.2.1  Observed trends...........................................................................................................5

2.2.2  Projected trends...........................................................................................................5

2.2.3  Summary .....................................................................................................................6

Chapter 3: Ecosystem Properties and Processes.........................................................................7

3.1 Biodiversity .........................................................................................................................7

3.1.1  Observed trends ..........................................................................................................7

3.1.2  Projected trends ..........................................................................................................7

3.1.3  Summary ....................................................................................................................7

3.2 Productivity .........................................................................................................................8

3.2.1  Observed trends...........................................................................................................8

3.2.2  Projected trends ..........................................................................................................8

3.2.3  Summary .....................................................................................................................8

3.3 Phenology...........................................................................................................................8

3.3.1  Observed trends ..........................................................................................................9

3.3.2  Projected trends ..........................................................................................................9

3.3.3  Summary .....................................................................................................................9

3.4 Connectivity and animal and plant movement...................................................................10

3.4.1  Observed trends ........................................................................................................10

3.4.2  Projected trends ........................................................................................................11

3.4.3  Summary ...................................................................................................................12

3.5 Wildland fire .....................................................................................................................12

3.5.1  Observed trends ........................................................................................................13

3.5.2  Projected trends.........................................................................................................13
iv

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

3.5.3  Summary ...................................................................................................................14

3.6 Insect infestations .............................................................................................................14

3.6.1  Observed trends ........................................................................................................14

3.6.2  Projected trends ........................................................................................................15

3.6.3  Summary ...................................................................................................................15

3.7 Plant and wildlife disease ..................................................................................................15

3.7.1  Observed trends ........................................................................................................16

3.7.2  Projected trends ........................................................................................................17

3.7.3  Summary ...................................................................................................................17

3.8 Invasion dynamics.............................................................................................................17

3.8.1  Observed trends.........................................................................................................18

3.8.2  Projected trends ........................................................................................................18

3.8.3  Summary ...................................................................................................................19

Chapter 4: Communities.............................................................................................................21

4.1 Alpine ...............................................................................................................................22

4.2 Observed trends................................................................................................................23

4.2.1  Projected trends.........................................................................................................23

4.2.2  Summary ...................................................................................................................24

4.3 Forests and woodlands......................................................................................................25

4.3.1  Observed trends.........................................................................................................25

4.3.2  Projected trends.........................................................................................................26

4.3.3  Five-needle pines........................................................................................................26

4.3.3.1 Observed trends ...........................................................................................................27

4.3.3.2 Projected trends ............................................................................................................28

4.3.3.3 Summary.........................................................................................................................28

4.3.4  Aspen ........................................................................................................................28

4.3.4.1 Observed trends ............................................................................................................28

4.3.4.2 Projected trends.............................................................................................................29

4.3.4.3 Summary.........................................................................................................................29

4.3.5  Summary ...................................................................................................................29

4.4 Sagebrush and grasslands.................................................................................................29

4.4.1  Observed trends.........................................................................................................30

4.5 Projected trends................................................................................................................31

4.5.1  Summary ...................................................................................................................32

Chapter 5: Aquatic Systems .......................................................................................................35

5.5.1  Observed trends ........................................................................................................35
v

Contents

5.5.2  Projected trends ........................................................................................................36

5.1 Wetlands ..........................................................................................................................37

5.1.1  Summary ...................................................................................................................38

Chapter 6: Wildlife......................................................................................................................41

6.1.1  Observed trends ........................................................................................................41

6.1.2  Projected trends ........................................................................................................41

6.1 Fish ..................................................................................................................................43

6.2 Amphibians.......................................................................................................................43

6.3 Invertebrates.....................................................................................................................45

6.4 Birds .................................................................................................................................46

6.5 Pika...................................................................................................................................47

6.6 Ungulates .........................................................................................................................48

6.7 Grizzly bears ....................................................................................................................49

6.7.1  Summary ...................................................................................................................49

Chapter 7: Conclusions ...............................................................................................................51

Chapter 8: Literature Cited.........................................................................................................55
vi

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Figure 1. The geographic scope of this synthesis includes the Upper Columbia Basin and Northern, 

Central, and Southern Rockies................................................................................................................. 1

Figure 2. Average minimum temperature, maximum temperature, and total annual precipitation 

during 1980 to 1997 in the northern Rockies (including the Upper Columbia Basin), the central 

Rockies, and the southern Rockies........................................................................................................... 3

Figure 3. Annual variations in the area burned by wildland fires in Montana, Idaho, Wyoming, and 

Colorado, 2002–2009. ............................................................................................................................. 12

Figure 4. Major community types in the Rocky Mountains and Upper Columbia Basin based on 

LANDFIRE classification........................................................................................................................... 21

Figure 5. Model of simulated vegetation changes assuming unsuppressed fire during 1971 to 2000 

(USF-HIST) and two scenarios for 2070 to 2099: a high level of CO2 emissions (USF-A) and a relatively low level (USF-B). ................................................................................................................................ 22

Figure 6. Conceptual diagram of alpine/subalpine response to climate change. .............................. 24

Figure 7. Conceptual diagram of projected changes for forests and woodlands. ............................. 27

Figure 8. Conceptual diagram describing projected changes to sagebrush and grassland ecosystems.

32

Figure 9. Projected climate changes to the hydrological cycle in the Rocky Mountains and Upper 

Columbia Basin........................................................................................................................................ 37

Figure 10. Documented terrestrial wildlife response to observed changes in climate, based on 189 

studies within the United States............................................................................................................ 42

Figures
vii

Contents

Tables

Table 1. Summary of Projected Climate Changes in the Rocky Mountains and Upper Columbia Basin 

(based on McWethy et al. in press)................................................................................................................4

Table 2. Inventory, monitoring, and research needed to better understand ecological responses to 

climate change in the Rocky Mountains and Upper Columbia Basin. ......................................................51

ix

Climate change is having significant effects 

on organisms and ecosystems worldwide, 

but changes in the western United States 

have been particularly rapid over the last 30 

years. Resource managers in the West are being asked to manage for ecological responses 

to climate, but they have limited access to regional or local information on the observed 

and projected effects of climate change. In 

this report we synthesize information on the 

observed and projected responses of selected ecosystem properties and processes, organisms, and communities within the Rocky 

Mountains and Upper Columbia Basin 

(ROCO). As defined by climate and geopolitical boundaries, this region encompasses 

the Greater Yellowstone Area, the Crown 

of the Continent ecosystem, the Colorado 

Front Range, the Upper Columbia Basin, and 

12 high-elevation units of the National Park 

System, and most of the US portion of the 

Great Northern Landscape Cooperative.

Our goals are to: (1) highlight common 

themes in response to climate change so that 

resource managers can better identify system 

vulnerabilities, determine resource program 

needs, and develop conservation targets, and 

(2) inform the development of the monitoring systems needed to assess climate change 

impacts and possible management actions.

We focus on physical and ecological properties and processes, and resources (communities and species) that are relevant to land 

managers in the ROCO region, including

● air quality; 

● ecological processes and properties, 

including biodiversity and productivity; 

phenology, connectivity, wildland fire, 

insect infestations, plant and wildlife disease, and invasion dynamics;

● communities of interest, including alpine 

and tree line, forests and woodlands, 

five-needle pines, aspen, sagebrush and 

grasslands, aquatic systems and wetlands;

● animal species, including grizzly bears, 

fish, amphibians, invertebrates, birds, pika, 

and ungulates. 

We found that some ecosystem properties, 

processes, and resources are being affected 

by warming temperatures and changes in 

precipitation patterns; this is supported by 

published evidence of observed responses 

to climate change within the last century and 

well-developed hypotheses and models that 

project a continued response during the next 

decade. The magnitude and direction of response varies, but these sensitive ecosystem 

properties, processes, and resources may 

provide strong indicators of climate change. 

Climate change indicators for the ROCO 

region include freshwater resources such as 

glaciers, wetlands, and fishes; wildlife and 

plant disease; wildland fire; insect infestations; alpine vegetation; phenology; butterflies; elk; and birds. 

For other ecosystem properties, processes, 

and resources, evidence of climate change 

has not been found and in many cases other 

stressors are likely to drive changes over 

the next century. For instance, grasslands 

and sagebrush are extremely vulnerable 

to changes in fire regimes and biological 

invasions. In other cases, we lack published 

evidence that links recent trends to climate 

change, but well-developed hypotheses suggest that the resource may be vulnerable in 

the future. For example, bats and mountain 

ungulates are expected to be sensitive to 

climate change. 

As temperatures and precipitation patterns 

change over the coming decades, a better 

understanding of how climate change affects 

resources will become critical to effective 

mitigation and management. Climate change 

will interact with multiple stressors, such as 

land-use change, atmospheric pollution, and 

invasive species, many of which are more 

proximate than climate change, making it difficult to predict changes. The only certainty 

is that ecosystem properties, processes, and 

resources will continue to change over the 

next century. Species will be lost, others will 

be gained, and disturbances will increase and 

alter the structure and function of ecosystems. Future management, monitoring, and 

research efforts will need to embrace these 

changing conditions. 

Executive Summary

xi

Contents Acknowledgments

We would like to acknowledge all the participants of the 2009 National Park Service 

(NPS) Rocky Mountain Inventory & Monitoring Technical Committee Meeting. An 

steering committee including Judy Visty 

(NPS), Kathy Tonnessen (NPS), Lisa Garrett (NPS), Tom Rodhouse (NPS), Tom Olliff 

(NPS), David McWethy (Montana State 

University), Stacey Ostermann-Kelm (NPS), 

Bruce Bingham (NPS), and Penny Latham 

(NPS) provided useful comments throughout the process. An inter-agency committee organized through the Great Northern 

Landscape Cooperative also provided 

guidance and advice throughout the writing 

and development process. This committee 

included: Yvette Converse (FWS), Mike Britten (NPS), Tom Olliff (NPS), Molly Cross 

(Wildlife Conservation Society), Steve Gray 

(WY state climatologist), Beth Hahn (USFS), 

Virginia Kelly (Greater Yellowstone Coordinating Committee), Tim Mayer (FWS), Jim 

Morrison (USFS), Stacey Ostermann-Kelm 

(NPS), Greg Pederson (USGS), David Wood 

(BLM), Andrea Ray (NOAA), and Lou 

Pitelka (NEON). 

Funding was provided by the Greater Yellowstone Coordinating Committee and 

the NPS Inventory & Monitoring Program. Conceptual models were developed 

by Stacey Ostermann-Kelm (NPS), Dave 

McWethy (Montana State University), Tom 

Rodhouse (NPS), and Isabel Ashton (NPS), 

and designed by Robert Bennetts (NPS). 

Maps were created by Meghan Lonneker 

(NPS). We acknowledge and thank Mary 

Ann Franke (NPS), Emily Yost (Utah State 

Univeristy), and Tami Blackford (NPS) for 

assistance with formatting and editing this 

document.

The content of the manuscript was greatly 

improved by comments from Julio Betancourt (USGS), John Gross (NPS), Mike Britten (NPS), Stacey Ostermann-Kelm (NPS), 

Frank Rahel (University of Wyoming), 

Geneva Chong (USGS), George Malanson 

(University of Iowa), Dan Binkley (Colorado State University), Anne Schrag (World 

Wildlife Fund), Tom Rodhouse (NPS), Tom 

Olliff (NPS), David Cooper (Colorado State 

University), David Wood (BLM), Rick Sodja 

(USGS), Virginia Kelly (Greater Yellowstone 

Coordinating Committee), Ellen Porter 

(NPS), Clint Mulfield (USGS), Jason Sibold 

(Colorado State University), Kathy Tonnessen (NPS), Molly Cross (Wildlife Conservation Society), Beth Hahn (USFS), Lou Pitelka 

(NEON), and Penny Latham (NPS). 

1

Chapter 1: Introduction

Climate change is having significant effects 

on organisms and ecosystems worldwide. 

Changes in the western United States have 

been particularly noticeable in the last 

century, with increases averaging 0.5–2 ̊C 

(0.9–3.6 ̊F) in mean annual temperatures, 

depending on elevation (Diaz and Eischeid 

2007, Pederson et al. 2010). Warmer winters 

and springs have resulted in more precipitation falling as rain instead of snow, reduced 

snowpack, earlier snowmelt, earlier streamflow from snowmelt, an 8 to 10 day advance 

in the onset of spring on average across the 

West, more frequent large fires, and possibly 

an increase in insect outbreaks and plant 

mortality (Cayan et al. 2001, Stewart et al. 

2005, Breshears et al. 2005, Mote et al. 2005, 

Knowles et al. 2006, Westerling et al. 2006, 

Raffa et al. 2008, Pederson et al. 2010). The 

preponderance of evidence suggests that

the magnitude of these changes has been 

influenced by human activity. Barnett et al. 

(2008) used nested climate and hydrological 

models to attribute most of these changes in 

the West to greenhouse gas emissions and 

their impact on global and regional climate. 

Another modeling study suggests that these 

changes are caused by a blend of anthropogenic forcing and Pacific and Atlantic 

decadal variability (Wang et al. 2008). 

Resource managers in the West are being 

asked to manage for ecological responses to 

climate trends, but they have limited access 

to regional or local information about the 

observed and projected effects of climate 

change (Lawler et al. 2010). This report and 

a companion report focused on climate 

(McWethy et al. in press) are meant to fill 

this gap by providing land managers with 

a summary of past, current, and projected 

climate changes and a description of some 

of the ecological consequences of climate 

change in the Rocky Mountains and Upper 

Columbia Basin. Here, we focus on known 

and predicted ecological effects and the uncertainties associated with these predictions. 

Our coverage of topics is not comprehensive; 

we chose to focus on ecosystem properties 

and processes, species, and communities 

Figure 1. The 

geographic scope 

of this synthesis 

includes the Upper 

Columbia Basin and 

Northern, Central, 

and Southern Rockies. These regions 

encompass most of 

the Great Northern 

Landscape Conservation Cooperative, 

the Greater Yellowstone Area and 12 

high-elevation units 

of the National Park 

System. 
2

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

that are especially relevant to land managers 

in the area as indicated by the NPS Inventory & Monitoring Vital Signs Plans for the 

Greater Yellowstone, Upper Columbia Basin, 

and Rocky Mountain networks (Jean et al. 

2005, Britten et al. 2007, Garrett et al. 2007) 

and discussions with an interagency panel of 

advisors.

Defined by geopolitical and climate boundaries, the geographic scope of this report 

includes four regions: the northern US 

Rockies, the central US Rockies and Greater 

Yellowstone Area, and the southern US 

Rockies (fig.1). We refer to this area as the 

Rocky Mountain and Upper Columbia Basin 

region (ROCO). It includes most of the US 

portion of the Great Northern Landscape 

Cooperative and 12 high-elevation units of 

the National Park System that are at particular risk with climate change. The area 

overlaps the National Ecological Observatory Network’s (NEON) Northern Rockies Domain and includes portions of the 

Southern Rockies–Colorado Plateau and the 

Great Basin domains. The area also includes 

numerous units within the USDA Forest 

Service’s Northern, Rocky Mountain, and 

Intermountain regions. 

We have two goals for this ecological synthesis: (1) to highlight common themes in 

response to climate change so that resource 

managers can better identify system vulnerabilities, determine resource program needs 

and develop conservation targets, and (2) 

to inform the development of the monitoring systems needed to assess climate change 

impacts and possible management actions. 

Options for managing ecosystems in the face 

of global environmental change are not discussed in this document and we recommend 

turning to some of the exceptional resources 

for guidance (e.g., Millar et al. 2007, Williams 

et al. 2007, Baron et al. 2008a, Baron et al. 

2008b, Galatowitsch et al. 2009, Joyce et al. 

2009, Mawdsley et al. 2009).
3

Physical Environment Chapter 2: Physical Environment 

2.1 Climate 

A review of the currently available information on paleoecological, historical, and 

projected climate trends in the ROCO region 

has been produced as a companion document by McWethy and colleagues (in press). 

Here, we briefly describe the regional climate 

and observed and projected trends in climate to provide context for possible ecological responses. 

At present, the climate becomes warmer and 

drier when moving south from the northern Rockies and Upper Columbia Basin to 

the southern Rockies (fig. 2). Climate in the 

ROCO region is influenced by the Rocky 

Mountains, which present a barrier to the 

westerly flow of the atmosphere carrying 

moisture from the Pacific Ocean (fig. 1). On 

the east side of the Rockies, winter precipitation is generated from polar continental air 

flows and warmer maritime air from the Gulf 

of Mexico colliding with the mountains. 

In the summer, the northern Rockies may 

continue to receive moist Pacific air, but the 

southern and central Rockies receive dry 

continental air or monsoonal flows from 

the Gulf of Mexico and Gulf of California 

(Kittel et al. 2002). Total annual precipitation and January precipitation are greater in 

the northern Rockies than in the central and 

southern Rockies (fig.2). January temperatures in the northern Rockies and Upper 

Columbia Basin tend to be slightly warmer 

than those of the central Rockies (fig. 2) (Kittel et al. 2002). 

2.1.1  Observed trends

Since 1900, temperatures have increased 

0.5–2 ̊C (0.9–3.6 ̊F) in most areas of the 

western United States (Pederson et al. 2010, 

Mote 2003, Ray et al. 2008) but cooling has 

occurred at some sites (Ray et al. 2008, CIG 

2010). The rate of change varies by location 

and elevation but is typically a 1oC (2°F) increase since the early 20th century (Hamlet 

et al. 2007). Temperature increases are more 

pronounced during the cool season (Hamlet 

and Lettenmaier 2007). In the northern US 

Rockies, annual rates of increase are roughly 

2–3 times that of the global average (Vose et 

al. 2005, Bonfils et al. 2008, Pederson et al. 

2010, Hall and Fagre 2003), a pattern that is 

evident at northern latitudes and higher elevation sites throughout the West (Diaz and 

Eischeid 2007, National Assessment 2001). 

Rises in temperature appear to be accelerating where mean regional spring and summer 

temperatures for 1987 to 2003 were 0.87 ̊C 

(1.57°F) higher than those for 1970 to 1986, 

and were the warmest since 1895 (Westerling 

et al. 2006). 

Trends in precipitation in the ROCO region 

are far less clear. Instrumental data from the 

last century show modest increases for much 

of the northwestern United States (Mote et 

al. 1999, Mote 2003, Mote et al. 2005), but no 

directional trends for parts of the southern 

Rockies (Ray et al. 2008). Natural variability 

in precipitation is evident in the instrumental record for all of the climate regions, and 

long-term drought conditions during the 

last century impacted large areas within the 

region. Although 20th century droughts had 

substantial socioeconomic and ecosystem 

impacts, there is ample evidence that they 

were not as severe, in terms of duration and 

magnitude, as a number of drought events 

Figure 2. Average 

minimum temperature, maximum 

temperature, and 

total annual precipitation during 1980 

to 1997 in the 

northern Rockies (including the 

Upper Columbia 

Basin), the central 

Rockies, and the 

southern Rockies. 

Bars indicate means 

±1 interannual 

standard deviation. 

Data from Kittel et 

al. 2002. 
4

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

that occurred during the last millennium 

(Cook et al. 2007, 2004; Meko et al. 2007). 

2.1.2  Projected trends

Temperatures in the region are generally 

expected to increase by approximately 1–2°C 

(2‍–‍‍4‍ ̊F) during the next 50 years with n

variation over years to decades. Precipitation 

is less well understood, but the projection 

for total annual precipitation suggests that 

the dominant pattern in North America will 

be a wetter climate in the northern tier and 

a drier climate in the southwestern United 

States. These and other predicted changes 

for the Rocky Mountains and Upper Columbia Basin are outlined in Table 1. 

2.1.3  Summary

Temperatures in the region have generally increased since 1900 and this trend is 

predicted to continue. It is estimated that 

temperature will increase by approximately 

1–2°C (2‍–‍‍4‍ ̊F) in the next 50 years. Precipitation patterns are less clear, but winte

projected to be wetter and summers drier in 

the future. These climate changes will continue to affect ecological processes, properties, and resources throughout the ROCO 

region. 

2.2 Air quality and deposition

Air pollution is determined by the amount 

of emissions, atmospheric processes, and 

weather in a region. Through its effects 

on emissions, atmospheric and ecological 

processes, and weather patterns, climate 

change may have large effects on air quality (Jacob and Winner 2009). The Clean Air 

Act regulates six major classes of air pollutants: ground-level ozone, particulate matter, 

carbon monoxide, sulfur dioxide, nitrogen 

(N) dioxide, and lead (USEPA 2008a). Of 

these, ozone and particulate matter are of 

the greatest concern to human health and 

visibility. Particulate matter includes the very 

fine dust, soot, smoke, and droplets that 

are formed from atmospheric reactions. It 

is produced by dust from roads, aridification, and erosion and when fuels such as 

coal, wood, or oil are burned. Ground-level 

ozone is formed when volatile organic compounds react with N oxides in the presence 

of sunlight. Volatile organic compounds are 

released from vegetation, fuels, and industrial processes, while N oxides are emitted 

from any combustion process, including the 

burning of fuels in cars, power plants, and 

industrial boilers. In addition to impairing 

human health, ground-level ozone can cause 

foliar damage and decreased photosynthesis 

and growth in plants.

The major components of acid precipitation 

and deposition are sulfur dioxide, emitted 

primarily from power plants burning coal, 

Table 1. Summary of Projected Climate Changes in the Rocky Mountains and Upper Columbia Basin (based on McWethy et 

al. in press).

Climate Variable General Change 

Expected Range of Change Expected General pattern Confidence

Temperature Increase 1.5–2.1oC (2.7°–3.4°F) Increases slightly 

greater in the summer High

Precipitation No change 2–5% increase in winter, 0–4% 

decrease in summer

Increase in winter, 

decrease in summer

Moderate for 

winter; low for 

summer

Drought Increase in frequency and 

severity

Varies with magnitude of 

temperature and evaporation 

change

Greatest impact in 

summer High

Temperature

Extreme Events

Increase of warm events, 

decrease of cold events

Varies with magnitude of temperature change

Increase in frequency 

and length of hot 

events

High

Precipitation

Extreme Events

Potential for decreased 

frequency coupled with 

increased intensity

Uncertain

Potential for more 

intense spring and 

summer floods 

Uncertain
5

Physical Environment

and N dioxide, emitted from cars and power 

plants. Both can cause the acidification of 

soils, streams, and lakes. Since N is a limiting 

resource in many communities, N deposition can also cause unnatural fertilization, 

with cascading effects on ecosystem health 

(Galloway et al. 2003). Excess N often favors 

invasive plant species, enabling them to outcompete native species. In Rocky Mountain 

National Park, N from atmospheric deposition has caused increased nitrate in lakes, 

increased N in vegetation and soils (Baron 

et al. 2000a; Baron et al. 2003), and changes 

in aquatic biota (Baron 2006). Current levels 

of N deposition in the park are sufficient to 

alter alpine plant community composition 

(Bowman et al. 2006). In the Upper Columbia Basin Network, N deposition may be 

contributing to the invasion of cheatgrass, 

which is known to be responsive to elevated 

soil N (Chambers et al. 2007, Lowe et al. 

2003, Monaco et al. 2003).

Toxics such as mercury, which is emitted primarily by coal-burning power plants, can accumulate in the environment, posing severe 

threats to human and wildlife health. The 

Western Airborne Contaminants Assessment 

Project found elevated levels of mercury in 

fish in some western parks. In Rocky Mountain National Park, mercury concentrations 

in some fish exceeded contaminant health 

thresholds for some piscivorous mammals 

(otter and mink) and birds (kingfishers). 

Concentrations of other airborne toxics, 

including dieldrin, dacthal, and endosulfan, 

were also elevated in fish, and some fish 

showed symptoms of endocrine disruption 

(e.g., poorly developed testes and intersex 

male trout) (Landers et al. 2008). 

2.2.1  Observed trends

From 1970 to 1997, aggregate criteria air 

pollutant emissions decreased 31% across 

the United States while the US population, 

the number of vehicle miles traveled, and the 

gross domestic product increased (USEPA 

1998). Since 1990, air quality has improved 

significantly for all major classes of pollutants; the greatest reductions occurred in 

sulfur dioxide, carbon monoxide, and lead 

(USEPA 2008b). Reductions in emissions are 

primarily a result of increased regulation and 

are independent of climate effects. As with 

the rest of the nation, sulfur dioxide emissions from power plants have generally been 

reduced in the ROCO region, but emissions 

of N oxides and volatile organic compounds 

from oil and gas production have increased. 

Ammonia, which is emitted from agriculture, feedlots, and automobile catalytic 

converters, also appears to be increasing, but 

because it is not a regulated air pollutant, 

emission levels are uncertain. Ground-level 

ozone has increased in areas with high levels 

of energy development due to increased traffic, road development, and diesel use. 

From 1993 to 2004, deposition and snowpack records for the ROCO region show 

a marked decrease in sulfate deposition in 

the northern, central, and southern Rockies 

(Ingersoll et al. 2008). However, ammonium 

(from ammonia) and nitrate (from N oxides) 

concentrations in snow increased during that period in the southern and central 

Rockies (Ingersoll et al. 2008). Compared to 

the rest of the United States, N deposition 

in the Intermountain West is fairly low, but 

the ecological consequences, particularly 

in alpine areas, are great (Bowman et al. 

2002; Baron et al. 2003, Baron 2006). Alpine 

ecosystems are poorly suited to assimilating 

N because of their short growing season, low 

vegetative cover, low ambient soil nutrients, 

and high rates of snowmelt flushing (Baron 

et al. 2000a, Williams and Tonnessen 2000). 

Nitrogen causes changes in alpine ecosystem 

structure and function and can contribute 

to acidification of alpine streams, lakes, and 

soils (Fenn et al. 2003). 

2.2.2  Projected trends

A warmer climate will make it more difficult 

to meet US air quality standards, particularly for ozone (Field et al. 2007, Karl et al. 

2009). Changes in climate affect air quality 

by changing wind patterns and ventilation 

rates, precipitation, dry deposition, chemical 

production and loss rates, natural emissions, 

and background concentrations (Jacob and 

Winner 2009). For instance, higher temperatures increase the oxidation of sulfur 

and N oxides, and precipitation changes will 

influence the distribution of acids deposited 

across the landscape (Bernard et al. 2001). 

Some of the better understood effects from 
6

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

a warmer climate include increased groundlevel ozone formation and increased particulate matter derived from forest fires. Ozone 

formation generally increases at higher 

temperatures due to increased gas-phase 

reaction rates (Aw and Kleeman 2003). The 

rate at which volatile organic compounds 

are produced from natural sources, such 

as trees, will also increase with increasing 

temperatures (Guenther 2002). This may be 

somewhat offset by the inhibitory effect of 

carbon dioxide (CO2) on isoprene production (Young et al. 2009), as isoprene is one 

of the more significant ozone precursors 

emitted by vegetation. Most models find that 

even with current emission rates, there will 

be a widespread increase in ground-level 

ozone during the summer over the next 

century (Jacob and Winner 2009). This is 

consistent with historical data that show a 

consistent increase in ozone with temperature in polluted areas (Jacob and Winner 

2009). In the West, however, decreases in 

background concentrations of ozone (due to 

increased water vapor) may offset increases 

in ozone due to temperature (Jacob and 

Winner 2009).

There is no consensus among models on the 

predicted effect of future climate on particulate matter (Jacob and Winner 2009). However, climate change may indirectly affect the 

concentration of particulate matter in the air 

by increasing natural sources such as wildfires and global and regional transport of 

dust (USEPA 2008b), resulting in decreased 

visibility in downwind areas. This may 

be particularly relevant in western North 

America, where 6.7 times more forested area 

burned from 1987 to 2003 than from 1970 to 

1986 (Westerling et al. 2006). 

Increased temperatures may exacerbate the 

effects of N deposition by increasing the 

rate of N cycling in soils, producing more 

available N. Increased temperatures are also 

releasing stored N from rock and ice glaciers. 

In Rocky Mountain National Park, recent 

increases in alpine stream nitrate appear to 

be related to increased melting of glaciers 

(Baron et al. 2009). Results from a modeling 

study by Civerolo and colleagues suggest that 

N deposition in eastern watersheds during 

the summer may increase 3–14% as a result of increased precipitation, while dry N 

deposition is predicted to increase because 

higher surface temperatures favor gas-phase 

nitric acid to particulate nitrate (Civerolo et 

al. 2008). However, other modeling predicts 

that planned emissions reductions will offset 

temperature-related increases in N and sulfur deposition in many parts of the country, 

with some exceptions in the West (Tagaris et 

al. 2008). 

The fate of toxics such as mercury in a 

changing climate is poorly understood, but it 

is expected that increased volatilization will 

transfer mercury between ecosystems via 

atmospheric transport, re-depositing it in a 

more mobile and potentially more toxic form 

(Jacob and Winner 2009). However, if a drier 

climate results in a loss of wetlands, aquatic 

systems may have less mercury methylation. 

Model-based predictions of air pollution in a 

changing climate are fraught with uncertainties (Bernard et al. 2001). Emission inventories vary in accuracy and unregulated pollutants like ammonia are poorly accounted for. 

While national and international emission 

regulations play a major role in regulating air 

pollution, they vary in effectiveness. There 

are additional uncertainties in our understanding of atmospheric chemistry processes, predictions of precipitation changes, and 

the role of meteorology in air quality (Jacob 

and Winner 2009). 

2.2.3  Summary

Despite uncertainties, air pollution is expected to increase in a warmer climate. 

Much evidence suggests that the frequency 

and duration of ground-level ozone events 

will increase. Remote areas may be most affected by changes in the global background 

of ground-level ozone and by increases in 

particulate matter due to increases in fire 

frequency and drought. Wet and dry deposition of N and sulfur compounds will be 

sensitive to changing precipitation patterns 

and mercury deposition may increase. 
7

Ecosystem Properties and Processes Chapter 3: Ecosystem Properties and Processes

Climate change has led to fundamental 

alterations in ecosystem properties and 

processes. In this section we summarize 

observed trends and projected responses 

to climate change for some of those that are 

likely to be affected: biodiversity, productivity, phenology, connectivity, wildland fire, 

insect infestations, plant and wildlife disease, 

and invasion dynamics. 

3.1 Biodiversity 

The Secretariat for the Convention on 

Biodiversity (2003) defines biological diversity as including all plants, animals, microorganisms, the ecosystems of which they 

are part, and the diversity within species, 

between species, and of ecosystems. Understanding and managing for the response 

of biodiversity to climate change presents 

one of the greatest challenges to land and 

resource managers in the West. The diverse 

and varied topography in the ROCO region, 

particularly in the mountains, contributes 

to high community diversity compared to 

the eastern United States, although any one 

community may have relatively few species 

(Wickham et al. 1995). Diversity is positively 

correlated with area such that larger patches 

of habitat contain more species than do 

smaller patches (MacArthur and Wilson 

1967). Habitat fragmentation and loss causes 

decreases in diversity. Other non-climate 

stressors threatening diversity include invasive species, disturbance, and pollution. On 

the global scale, it is believed that biological 

diversity will decline in response to climate 

changes (Parmesan and Yohe 2003, SCBD 

2003). Below, we describe some of the observed and predicted trends for diversity in 

the ROCO region. 

3.1.1  Observed trends

Historical and paleoecological data suggest 

that climate can drive alterations in vegetation productivity, diversity, abundance, and 

composition (e.g., Pederson et al. 2007). 

These changes in plant diversity and communities are mirrored by concurrent or subsequent changes in animal diversity. Yet there 

have been few examples of climate-driven 

extinctions or extirpations of species during 

the last century; instead the primary drivers 

have been disease, invasive species, dams 

and hydrologic alterations, hunting pressure, 

and land-use change (Tomback and Kendall 

2002). One exception is the decline of rare 

alpine plants in Glacier National Park which 

is thought to be due to warmer temperatures 

(Lesica and McCune 2004). 

3.1.2  Projected trends

With a 1°C (2°F) increase in average global 

temperature, the IPCC estimates that up to 

30% of all species will be at increased risk 

of extinction (Field et al. 2007). While such 

models and estimates include uncertainties, 

there is little or no evidence that climate 

change will slow species loss (SCBD 2003). 

The Secretariat for the Convention on Biodiversity (2003) predicted four impacts on 

biodiversity as a result of climate change: (1) 

the climatic range of many species will move 

poleward or upward in elevation; (2) many 

species that are already vulnerable, such as 

rare endemics and threatened and endangered species, are likely to become extinct; 

(3) changes in the frequency, intensity, extent, and locations of climatically and nonclimatically induced disturbances will affect 

how and at what rate existing ecosystems 

will be replaced by new plant and animal assemblages; and (4) some ecosystems, such as 

high mountain ecosystems, arid ecosystems, 

remnant native grasslands, and ecosystems 

underlain by permafrost, will be particularly 

vulnerable to climate change. Diversity will 

decline where habitats are found in small 

discrete patches, such as alpine tundra and 

lakes, and where warming contributes to 

habitat loss. 

3.1.3  Summary

Most evidence suggests that changes in 

biodiversity will occur, and that they will be 

spatially and temporally variable. Certain 

species, such as rare or threatened species, 

and certain communities, such as alpine wet 

meadows, are at particular risk of extinction or loss. Rare plants and animals with 

limited capacity to disperse are particularly 

vulnerable to loss. The rate of species loss 

and turnover will vary with the intensity of 

other stressors such as land use changes, the 
8

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

spread of invasive species, and changes in 

disturbance regimes. 

3.2 Productivity

In ecological terms, primary productivity 

refers to the rate of biomass generation by 

plants and other autotrophs and is often 

expressed in terms of growth or carbon gain. 

Experiments and latitudinal patterns suggest 

that productivity is positively correlated with 

diversity (Loreau et al. 2001); however, the 

potential mechanisms behind these patterns, 

such as increased facilitation, statistical 

biases, or niche differentiation, continue to 

be debated (e.g., van Ruijven and Berendse 

2005). Patterns of productivity are similar 

to those of diversity and are driven largely 

by precipitation, temperature, elevational, 

and soil gradients; productivity is greatest 

in warm, wet, and low elevations. Changes 

in precipitation patterns, fertilization by increased atmospheric CO2

 levels, and changing disturbance regimes make forecasting 

productivity changes difficult.

3.2.1  Observed trends

In recent decades, warmer temperatures 

and changing precipitation regimes have 

increased primary productivity on a global 

scale and particularly in the Northern 

Hemisphere (Field et al. 2007). Global daily 

satellite data indicate that the earlier onset 

of spring by 10–14 days has contributed to 

net primary production in the continental 

United States increasing nearly 10% from 

1982 to 1998 (Boisvenue and Running 2006). 

The most common measure of long-term 

trends in productivity comes from forest 

growth. It appears to be slowly accelerating 

in regions where tree growth has historically 

been limited by low temperatures and short 

growing seasons, such as boreal regions 

and eastern forests, but it is slowing in areas 

subject to drought or other large-scale disturbances such as fire and insect infestations 

(Field et al. 2007). Overall, US forest productivity has generally been increasing since 

the middle of the 20th century (Boisvenue 

and Running 2006). Where productivity has 

increased, it is difficult to determine whether 

climate is the sole cause because of the confounding effects of increased N deposition, 

increased CO2 concentrations, and successional changes.

3.2.2  Projected trends

Although primary productivity is projected 

to increase moderately due to longer growing seasons and elevated CO2 concentrations, net ecosystem and biome productivity 

may decline due to increased disturbance, 

drought, and changes in community structure. While models project that a modest 

warming will lead to greater tree growth in 

the United States (Ryan et al. 2008), there 

will be spatial and temporal variations 

depending on other factors that limit productivity at a given site (Ryan et al. 2008). 

This may result in a pattern of initial gains in 

productivity followed by declines. The areal 

extent of drought-limited ecosystems is expected to increase by 11% for each 1oC (2°F) 

of warming in the continental United States 

(Bachelet et al. 2001). For widespread species such as lodgepole pine (Pinus contorta), 

a 3oC (5°F) temperature increase would 

increase growth in the northern part of its 

range, decrease growth in the middle range, 

and decimate southern forests (Rehfeldt et 

al. 2001). Where climate change leads to conversions of vegetation type (e.g., woodland 

to grassland), this will have strong impacts 

on productivity (Izaurralde et al. 2005). 

3.2.3  Summary

Modest increases in productivity and forest growth are expected in the West with 

warmer temperatures. However, in areas 

subject to drought and decreased precipitation, productivity will likely decline. 

3.3 Phenology

Phenology is the study of the seasonal timing 

of events in the annual life cycle of plants 

and animals in relation to climate. Leaf-out, 

flowering, senescence, animal migrations, 

hibernation, and insect emergence are 

examples of phenological events. The timing 

of these events is of interest to many birdwatchers, gardeners, and other citizens, and 

they are critical to many economic activities, 

such as agriculture. The timing is sensitive to 

seasonal and interannual variations in temperature and precipitation. Thus phenology 

is considered the gateway to climatic effects 

on biota and ecosystems and is vital to the 
9

Ecosystem Properties and Processes

public interest. As a consequence, there are 

extensive phenological records from around 

the globe and across many taxa. Most of 

these records show some evidence of recent 

changes due to increasing temperatures (Parmesan 2006). At a global scale, they indicate 

that there has been a mean advance of spring 

events of ~2.3 days per decade during the last 

century (Parmesan and Yohe 2003). 

3.3.1  Observed trends

Although long-term records of phenology 

are scarce in the West compared to other 

regions, here are a few examples. 

● From 1957 to 1994, flowering of lilacs (Syringa vulgaris) and honeysuckle (Lonicera 

tatarica and L. korolkowii) have shown an 

advance of 7.5 and 10 days, respectively, 

in the West. This is most likely due to the 

1–3°C (2–5°F) increase in spring temperatures during that period (Cayan et al. 

2001). 

● In Lake Washington, near Seattle, the timing of phytoplankton blooms advanced 19 

days from 1962 to 2002 because warmer 

spring temperatures have changed the timing of stratification (Winder and Schindler 

2004). 

● At the Rocky Mountain Biological Laboratory in the southern Rockies, yellowbellied marmots (Marmota flaviventris) 

emerged from hibernation significantly 

earlier in 1999 than in 1976 (Inouye et al. 

2000). 

● Earlier emergence of flowers since 1992 

in the southern Rockies has been documented, exposing some plant species to 

increasing damage from late frosts (Inouye 

2008).

Changes in the timing of migration, hydrological events, and fire seasons are discussed 

in subsequent sections.

3.3.2  Projected trends

With continued warming, we should expect 

to see a continued advance of spring in the 

ROCO region. Compared to 1950 to 1970, 

streamflow and peak snowmelt are occurring 

1–4 weeks earlier (Stewart et al. 2005). Lack 

of good phenology data make predictions 

difficult, but changes in the timing of spring 

will likely affect the timing of reproduction, 

emergence, and migration of numerous species, which may affect community structure 

and function. On the other hand, phenological events that are tied to day length, such 

as the emergence of many plants, are not 

expected to change. 

While evolutionary adaptations to climate 

change can be rapid, it is generally thought 

that they are not rapid enough to counter 

the negative effects that climate change will 

have on many species (Parmesan 2006). 

One concern is the development of asynchronies among interacting and dependent 

species. For instance, there is the potential 

for increased stress for marmots in the early 

spring because while marmots are emerging earlier, there has been no change in the 

emergence of food plants in the area (Inouye 

et al. 2000). Mismatches in the phenology of 

birds and their prey have been documented 

in other parts of the United States and the 

globe and have been linked to population 

declines (Both et al. 2006, Wormsworth and 

Mallon 2008). 

The key uncertainties in understanding the 

response of phenology to climate change lie 

in the rate at which phenological changes 

occur and how fast species will adapt to new 

seasonal regimes. Manipulative experiments 

suggest that other global changes, such as 

changing CO2 concentrations and increased 

nutrient availability, may dampen the phenological response to warming (Cleland et al. 

2006). As a result, it will be difficult to predict 

the magnitude and direction of response for 

many species. There are also apparent contradictions between individual species and 

ecosystem level responses (Steltzer and Post 

2009). Moreover, it remains unknown how 

often and how many species interactions will 

be affected by the development of asynchronous life histories. Finally, the largest changes to date are related to earlier spring onsets; 

less is known about phenological changes to 

climatic trends in other seasons.

3.3.3  Summary

Phenological observations provide inexpensive, useful, and sensitive records on the 

ecological consequences of climate change. 
10

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Globally, there has been a trend for species 

to advance timing of many life-history events 

in concert with warming temperatures. In 

the West, records suggest that warmer spring 

temperatures have affected first flowering, 

hibernation, and lake productivity and these 

changes are expected to continue. 

3.4 Connectivity and animal and 

plant movement

Connectivity is the measure of the extent to 

which organisms can move between habitat 

patches (Taylor et al. 1993). Animal and plant 

movement is critical for migration, dispersal, 

and acquiring resources throughout a species’ home range. Plant migration and dispersal most often occur at a local scale, but 

plants can migrate long-distances via wind, 

animal, and water dispersal. The rate of 

plant migration is driven by generation time 

because it is dependent on establishment of 

seedlings and the time it takes for them to 

reach reproductive maturity (Neilson et al. 

2005). Plant migration rate can be roughly 

estimated by functional group; long-lived, 

late successional species with large seeds are 

typically slower to migrate than wind dispersed, small-seeded plants (Neilson et al. 

2005).

In the West, some of the best known animal migrations are those of birds, fish, and 

ungulates. Raptors, waterfowl, and song 

birds move between breeding grounds in the 

north and winter grounds in the south along 

the Pacific and Central Flyways following the 

spine of the Rocky Mountains (Birdnature 

1998). Some species of salmon (Oncorhynchus spp.) in the Northwest travel from the 

Pacific Ocean to the freshwaters of Idaho 

where they spawn and die, and their young 

will spend up to two years in freshwater 

prior to migrating back to the Pacific Ocean 

(Groot and Margolis 1991). Cutthroat trout 

(O. clarki bouvieri) migrate upstream into 

high-elevation lakes when barriers are not 

present (Kruse et al. 1997). Many ungulates 

in the region, such as elk (Cervus canadensis; 

e.g., Brazda 1953) and mule deer (Odocoileus 

hemionus; e.g., Sawyer et al. 2005), migrate 

between summer and winter ranges. The 

pronghorn antelope (Antilocapra americana) 

migrate seasonally throughout the ROCO 

region to access winter forage grounds 

(Hoskinson and Tester 1980, Sawyer et al. 

2005). The pronghorn migration between 

Grand Teton National Park and the Upper 

Green River Basin follows an invariant path 

spanning roughly 150 km (Berger et al. 2006) 

and is believed to be the longest remaining 

mammal migration in the continental United 

States (Berger 2004). Bats undertake significant seasonal movements at regional scales 

between winter hibernacula and summer 

pup-rearing areas (Cryan et al. 2000, Dobkin 

et al. 1995). Several bat species migrate from 

the ROCO area to the Southwest and Mexico 

(Cryan 2003, Cryan and Brown 2007).

3.4.1  Observed trends

The paleoecological and historical record 

suggests that plants can migrate in response 

to changes in climate. Fossil data suggests 

that trees may have migrated from 100 to 

1,000 meters (109–1094 yd) per year in 

response to climate warming, but these rapid 

rates are likely driven by just a few long-distance dispersal events (Higgins and Richardson 1999). Over the last century, climate 

change has driven changes in plant distribution and ranges (Parmesan and Yohe 2003). 

For instance, alpine plants have shifted 

upward in elevation in the Alps (Grabherr 

et al. 1994). In recent times, plant migration 

has been altered most by humans through 

accidental and deliberate plant introductions 

and habitat fragmentation (Pitelka 1997). In 

some cases, habitat has become so fragmented that dispersal is inhibited, driving plant 

extirpations (Fahrig 2002). 

As with other phenological events, warmer 

temperatures have driven a trend toward 

earlier spring migratory arrivals (Parmesan 

and Yohe 2003). For example, American robins (Turdus migratorius) arrived on average 

14 days earlier in 1999 than in 1981 in southern Colorado (Inouye et al. 2000), and some 

20 species of neotropical migrants arrived 

in the United States 21 days earlier in 1994 

than in 1965 (Price and Root 2005). Migratory routes, while influenced by climate, 

have been more vulnerable than migratory 

timing to widespread land-use change and 

habitat destruction. Berger (2004) estimated 

that about 75% of the migration routes in 

the Greater Yellowstone Area for pronghorn, 
11

Ecosystem Properties and Processes

bison and elk have been lost due to human 

development and agriculture.

Connectivity among habitats is essential to 

not only allow for migration, but also for 

linking and maintaining gene flow among 

disparate populations. Maintaining connectivity has been challenging as human 

populations and development in the West 

have increased. Connections between unprotected lowland source populations and 

mountain populations may be at particular 

risk. For instance, Hansen and colleagues 

(2009) showed that American robins and 

yellow warblers (Dendroica petechia) are at 

risk from human development in the Greater 

Yellowstone Area because the populations 

are dependent on breeding in lowland, unprotected areas. 

While connectivity is clearly affected by 

human development, there is less historical 

evidence from the past century that it has 

been directly impacted by climate change. 

Drying of streams and wetlands can reduce 

connectivity of aquatic habitats (Hauer et al. 

1997). Large-scale changes in vegetation patterns seen in the paleoecological record (e.g., 

Whitlock and Bartlein 1993) changed the 

structure and linkages of habitat across the 

West. More recent examples of climate altering habitat connectivity and affecting metapopulation structure may come from pikas

(Ochotona princeps) and butterflies. Beever 

et al. (2003) hypothesized that the pattern of 

pika colony extirpation in the Great Basin 

is driven by warming and increased isolation. Alpine butterfly (Parnassius smintheus) 

populations have become more isolated 

from one another in the Canadian Rockies 

due to losses of subalpine meadow habitat 

(Roland and Matter 2007). Connectivity may 

also be affected by climate change through 

changes in animal behavior. For instance, 

milder winters allow pronghorns to stay 

in their customary summer ranges and not 

migrate (e.g., Jacques et al. 2009), which may 

result in the population losing its knowledge 

of migration routes that are necessary in 

average winters.

3.4.2  Projected trends

While the fossil record suggests that plants 

can migrate rapidly in response to climate, 

it is believed that fragmentation, reduced 

source population size, and a reduction in 

animal vectors coupled with an unprecedented rate of climate change will make it 

unlikely that plant species will migrate fast 

enough to escape its consequences (Neilson 

et al. 2005). Variation in the rates and ability of plant species to migrate in the face of 

change will contribute to the formation of 

communities that have no current analogues. 

For instance, rare plants, particularly those 

with low reproductive rates and large seeds, 

may migrate more slowly than do annual 

plants. The effectiveness of plant dispersal 

and migration will strongly influence not 

only the structure and function of future 

terrestrial communities but also feedbacks 

between climate and the land surface (Higgins and Harte 2006). 

Climate change is expected to alter animal 

movement patterns through its effects on 

habitat availability and the timing of movement events. One study estimates that 

predicted climate changes will reduce migrations of neotropical birds 32% and 39% to 

the Pacific Northwest and Rocky Mountains, respectively (Price and Root 2005). It 

is expected that the general trend of earlier 

migrations will continue (Parmesan 2006).

Projected changes in vegetation cover (e.g., 

Bachelet et al. 2001), loss of snow cover, 

debris flows, seasonal floods, and declines in 

surface waters will likely impact the degree 

of connectivity among habitats. As species’ 

core habitat areas shift across the landscape, 

shrink in size, or become fragmented, those 

species’ connectivity needs are also likely to 

be altered (Cross et al. in press). Changes in 

hydrology might affect the connectedness of 

aquatic populations and habitats. Extreme 

weather events may increase the frequency 

of large-scale disturbances and these in turn 

may cause increasing fragmentation (Opdam 

and Wascher 2004). 

The more immediate threat and uncertainty 

of habitat destruction and fragmentation 

makes it difficult to predict how connectivity 

will be affected by climate change. We do not 

have a strong understanding of the connectivity needs of many species under current 

conditions in most places. Moreover, since 

the influence of climate change can vary 
12

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

dramatically across a species’ range, particularly for birds with long-distance migrations, 

understanding how climate change will affect 

migration patterns is difficult (Inkley et al. 

2004). In many cases the primary driver of 

plant dispersal and habitat alterations will 

be changes in precipitation and disturbance, 

the direction and magnitude of which is difficult to predict. Many uncertainties remain 

because different species will be affected by 

climate change at differing rates and magnitudes, and phenotypic plasticity and changes 

in behavior in response to changing environmental conditions are highly variable. 

3.4.3  Summary

It is predicted that plant and animal movements and connectivity needs will be altered 

by climate changes. However, responses will 

likely vary across species and ecosystems. 

In the paleorecord plant migration has occurred quickly in response to warming. Due 

to fragmentation and other dispersal barriers, projections estimate that plants will not 

keep pace with the current rate of climate 

change. The timing of migration events such 

as the arrival of birds and movement of ungulates between winter and summer ranges 

will likely be driven earlier as springs become 

warmer throughout the region. There remain 

large uncertainties in anticipating future 

patterns of migration due to unpredictable 

changes in habitats and the development 

of mismatches between interacting species. Connectivity of animal populations 

and habitats will decrease due to increased 

fragmentation driven by climate-induced 

disturbances or changes in vegetation. 

3.5 Wildland fire

Fire is an essential disturbance in the ROCO 

region (Keane et al. 2002), where it acts to recycle nutrients, regulate succession, maintain 

diversity, reduce biomass, control insect and 

disease populations, and regulate interactions between plants and animals (Crutzen and Goldhammer 1993). Variability in 

climate and fire regimes over the last 20,000 

years has strongly influenced forest composition and structure (Whitlock et al. 2002, 

Whitlock et al. 2003). Although fire plays a 

key role in determining the structure and 

function of most habitats in the region, it has 

less influence in alpine areas, which rarely 

burn, and in high subalpine forests, which 

have fire return frequencies of more than 200 

years (Keane et al. 2002). Long-term variations in temperature and precipitation patterns have resulted in continuously changing 

Figure 3. Annual 

variations in the 

area burned by 

wildland fires in 

Montana, Idaho, 

Wyoming, and 

Colorado, 2002–

2009. The large 

2002 Hayman fire is 

evident in Colorado 

and the 2007 Murphy complex fire in 

Idaho. Data from 

NICC 2010.
13

Ecosystem Properties and Processes

fire regimes (Whitlock et al. 2008). Historical 

records suggest that an average of 2.4 million 

hectares (5.9 million acres) burned annually in the northwestern United States prior 

to 1900, two-thirds of which was sagebrush 

and grassland vegetation (Keane et al. 2002). 

Due to fire suppression and changes in land 

cover, annual fires now typically cover less 

than half that area (Keane et al. 2002). Large 

severe fires (>300 acres, 121 ha) account for 

more than 95% of the area burned in the 

West in a given year (Peterson and McKenzie 2008). In the ROCO region, the extent 

of wildland fires varies considerably among 

years and across states, with the peak season 

occurring during the summer (Littell et al. 

2009) and the largest areas burned typically 

in Idaho and Montana (fig. 3). 

3.5.1  Observed trends

The relative influence of climate on fire 

behavior varies regionally and by ecosystem 

type, but generally current-year drought, 

low winter precipitation, wind conditions, 

and high summer temperature are positively 

associated with area burned in the Rockies 

(Westerling et al. 2006, Littell et al. 2009). In 

lower-elevation montane forests of the Colorado Front Range, large fires are commonly 

preceded by wetter than average springs 

two to four years in advance that presumably increase fine fuel loads (Veblen et al. 

2000). Wet antecedent conditions decrease 

as a contributing factor at higher elevations 

in the montane zone (Sherriff and Veblen 

2008) and are considered unimportant in 

the subalpine zone where fuels are abundant 

(Sibold et al. 2006). Other large-scale climate 

patterns such as the Pacific Decadal Oscillation (PDO; Hessl et al. 2004) and El Niño 

Southern Oscillation (ENSO; Schoennagel 

et al. 2005) are also associated with fires, but 

their strength and signal varies across the 

ROCO region, with ENSO more influential 

in the southern Rockies and PDO in the 

northern US Rockies (Morgan et al. 2008). 

Additionally, sea surface temperatures in the 

north Atlantic Ocean (Atlantic Multidecadal 

Oscillation, AMO) interact with ENSO and 

PDO to influence the severity and synchrony 

of drought and fire in the Rockies (Sibold 

and Veblen 2006; Kitzberger et al. 2007). The 

complex interactions of the tropical Pacific 

(ENSO), north Pacific (PDO) and north 

Atlantic (AMO) in shaping spatial patterns of 

drought and fire suggest that projecting the 

influences of climate change on future patterns of fire is extremely difficult.

The increasing frequency of warm spring 

and summer temperatures, reduced winter precipitation, and earlier snowmelt in 

the West during the last 20 years has led to 

an increase in the frequency of very large 

wildfires and total acres burned (Westerling 

et al. 2006). There is insufficient evidence at 

present to conclude that the increase in the 

frequency of large fires and total area burned 

in the northern Rockies since the mid-1980s 

is outside the range of variation experienced 

in the last 20,000 years (Whitlock et al. 2008).

Fire dynamics have been altered by climate 

indirectly through its effects on insect infestations and forest health. By changing the 

forest environment, bark beetles can influence the probability, extent, and behavior of 

fire events, but despite the widely held belief 

that bark beetle outbreaks set the stage for 

severe wildfires, few scientifically and statistically sound studies have been published 

on this topic (Negron et al. 2008). That fire 

promotes beetle infestations is clearer; the 

fire-caused injury changes conifers’ volatile 

emissions, increasing their susceptibility to 

bark beetles (Kelsey and Joseph 2003).

3.5.2  Projected trends

Most evidence supports that future climate changes will cause increases in the 

frequency, intensity, severity, and average 

annual extent of wildland fires (Field et 

al. 2007, Ryan et al. 2008). Models project 

that numerous aspects of fire behavior will 

change, including longer fire seasons, more 

days with high fire danger, increased natural 

ignition frequency and fire severity, more 

frequent large fires, and more episodes of 

extreme fire behavior (Brown et al. 2004, 

Bachelet et al. 2007, Westerling and Bryant 

2008). The best evidence, however, is for 

increases in the average annual area burned 

(McKenzie et al. 2004, Flannigan et al. 2006, 

Bachelet et al. 2007). For instance, McKenzie 

and colleagues (2004) predict that a mean 

temperature increase of 2.2°C (4.0°F) will 

increase the annual area burned by wildfire 

by 1.5 to 5. In another study, it is predicted 
14

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

that the median annual acres burned in the 

Upper Columbia Basin and northern Rockies would increase from about 0.5 million 

acres(0.2 million ha) in 1916 to 2006 to 0.8 

million acres (0.3 million ha) in the 2020s, 

1.1 million acres (0.4 million ha) in the 

2040s, and 2.0 million acres (1 million ha) in 

the 2080s (Littell et al. 2009). 

While there is strong evidence that climate 

change will increase the number of fires, and 

particularly the area burned each year, uncertainties remain. First, historical patterns 

of precipitation are linked to fire and synoptic weather features that drive fire growth, 

such as high pressure ridges and wind patterns, but models differ in their projections 

for these climate variables. Other factors, 

such as increases in non-native, annual grass 

invasions, may alter fire dynamics, making 

predictions based on climate alone difficult. 

Finally, and perhaps most importantly, if fires 

and other stand-replacing disturbances occur more frequently, the resulting landscape 

pattern may limit the size of future fires and 

total area burned (Collins et al. 2009).

3.5.3  Summary

Wildland fires have been increasing in frequency and size in the region and are expected to continue to increase with climate 

change. The increase will be seen most in 

the total area burned annually and risks will 

be greatest following dry winters and warm 

springs. 

3.6 Insect infestations

Although abundant in forest ecosystems, 

insect herbivores typically consume less than 

10% of primary productivity. However, the 

populations of some insect species periodically erupt and consumption increases to 

well over 50% (Perry 1994). When outbreaks 

occur, insect herbivores become important 

disturbance agents in forests, often causing 

widespread tree mortality on a landscape 

scale. Insect outbreaks also change forest 

ecosystem structure and function by regulating certain aspects of primary production, 

nutrient cycling, ecological succession, and 

the size, distribution, and abundance of trees 

(Romme et al. 1986). In 1997, the USDA estimated that insects and pathogens damaged 

20 million ha of US forests, which was more 

than all other disturbance types (e.g., hurricanes, fire, and drought) combined (Dale et 

al. 2001).

A few of the most common outbreak species in ROCO forests include western spruce 

budworm (Choristoneura occidentalis), 

Douglas fir tussock moth (Orgyia pseudotsugata), and the mountain pine beetle 

(Dendroctonus ponderosae). The western 

spruce budworm is a widely distributed 

and destructive forest defoliator favoring 

Douglas fir (Pseudotsuga menziesii), white fir 

(Abies concolor), Engelmann spruce (Picea 

engelmannii), blue spruce (Picea pungens), 

and subalpine fir (Abies lasiocarpa) (Leatherman et al. 2009b). Mountain pine beetles 

attack lodgepole (Pinus contorta), ponderosa 

(P. ponderosa), limber (P. flexilis), pinyon (P. 

edulis), sugar (P. lambertiana), whitebark (P. 

albicaulis), and bristlecone pines (P. aristata) 

(Leatherman et al. 2009a). In some cases and 

areas, outbreaks are cyclic and fairly predictable. For instance, an outbreak of Douglas fir 

tussock moths has occurred every 8–10 years 

in Idaho and British Columbia. In other 

cases, fire suppression and lack of sub-zero 

temperatures seem to drive outbreaks and 

dynamics remain unpredictable. 

3.6.1  Observed trends

Although outbreak dynamics differ among 

species and forests, climate change appears 

to be driving current insect outbreaks. Western spruce budworm outbreaks were more 

widespread and lasted longer in the 20th 

century than in the 19th century primarily 

because of fire suppression and increasing fir populations (Anderson et al. 1987). 

However, patterns of spruce budworm 

outbreaks have been tied to climate in both 

the East (Gray 2008) and the West (Swetnam 

and Lynch 1993). There was no clear change 

in infestation intensity and duration in the 

southern Rockies during the last three centuries until they became more intense in the 

1970s (Swetnam and Lynch 1993). Summer 

and spring precipitation are positively correlated with increased frequency of outbreaks 

over regional scales and long time frames, 

but experimental evidence suggests that 

drought may promote infestations (Swetnam 

and Lynch 1993). 
15

Ecosystem Properties and Processes

Although bark beetle infestations are a force 

of natural change in forested ecosystems, 

several current outbreaks occurring simultaneously across western North America 

are the largest and most severe in recorded 

history (Bentz 2008). From 2004 to 2008, 

the area of mountain pine beetle outbreaks 

increased across Wyoming from 1,000 to 

100,000 acres (405–40,469 ha) and the Forest Service has estimated that most of the 

mature, large-diameter lodgepole forests 

in southern Wyoming will be dead within 

3–5 years (USDA 2008b). In Grand Teton 

and Yellowstone national parks, mountain 

pine beetles and the exotic fungal pathogen 

white pine blister rust (Cronartium ribicola) 

killed more than a half million whitebark 

pines from 2002 to 2008 (USDA 2008b). 

The mountain pine beetle has also infested 

millions of lodgepole and limber pines in 

Colorado during the past decade and is 

currently increasing in northern Colorado 

and the Front Range (USDA 2008a). These 

outbreaks of bark beetles in the West have 

coincided with increased temperatures and 

changes in precipitation patterns, suggesting 

a response to a changing climate (Shaw et al. 

2005). Warming temperatures and the loss of 

extreme cold days reduce winter overkills of 

insects, speed up life cycles, modify damage 

rates, and lead to range expansions, particularly in the north (Logan et al. 2003). 

3.6.2  Projected trends

Climate change, and particularly warming, 

will have a dramatic impact on pest insects, 

and the recent trends of increasing outbreaks 

are expected to worsen (Volney and Fleming 2000, Logan et al. 2003). The greatest 

increase in mountain pine beetle outbreaks 

is expected to occur at high elevations, 

where models predict warmer temperatures 

will increase winter survival (Bentz 2008). 

At low elevations, however, mountain pine 

beetle populations may decrease as warmer 

temperatures disrupt the insects’ seasonality (Bentz 2008). Climate change will also 

alter host susceptibility to infestation. Over 

the short-term, trees will likely increase in 

susceptibility to pests due to stress from fires, 

drought, and high temperatures (Allen et al. 

2010); over the long-term, these stresses will 

cause tree ranges and distributions to change 

(Bentz 2008). Moreover, climate change 

and changes in CO2 and ozone may alter the 

conifers’ defensive mechanisms and susceptibility to beetles through their effects on the 

production of plant secondary compounds 

(Negron et al. 2008). 

Insect infestations are damaging millions of 

acres of western forests and there is clear 

evidence that damage is increasing. Nonetheless, future predictions of the extent 

of infestations remain uncertain because 

our understanding of insect infestations 

in incomplete. Key uncertainties include 

the influence of drought and precipitation 

changes, how altered forest/host composition will alter outbreaks, the biochemical 

response of trees and evolution of defensive 

mechanisms, regional differences, and the 

interactive effects of fire, plant disease, and 

insect outbreaks. 

3.6.3  Summary

Insect outbreaks are already the largest disturbance agent in ROCO forests and they are 

expected to increase in frequency and severity with warmer temperatures and increasing 

drought (Logan et al. 2003). Warmer temperatures will allow pests to increase their range 

northward and upward in elevation. 

3.7 Plant and wildlife disease

Plant diseases such as white pine blister rust 

and sudden oak death (Phytophthora ramorum) have had devastating impacts on native 

forests with cascading effects on wildlife and 

ecosystems. For instance, blister rust has 

reduced western white pine (Pinus monticola) to less than 5% of its early 20th century 

population in the interior Pacific Northwest 

(Harvey et al. 2008). Aspen (Populus tremuloides), considered a keystone species in 

the ROCO region, has suffered substantial 

declines as a result of fire suppression and a 

recently-described phenomenon known as 

sudden aspen decline that may be associated 

with disease and other pathogens (Worrall et 

al. 2008). 

Emerging wildlife diseases have become a 

high-priority concern throughout the world 

because of the potential for their spreading 

to humans, economic losses associated with 

livestock morbidity and mortality, and the 

harmful effects on wildlife populations and 
16

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

ecosystems. The wildlife diseases of greatest recent concern in the ROCO region are 

(1) chronic wasting disease, which affects 

ungulate populations; (2) brucellosis, which 

affects cattle, elk, and bison; West Nile virus, 

which affects bird populations; and (3) 

whirling disease, caused by a salmon parasite 

(Myxobolus cerebralis). Numerous other diseases, including rabies, hanta virus, plague, 

and giardia, threaten wildlife in the region 

and are of concern because they are zoonotic (shared between humans and animal 

hosts). Still others, such as white-nose syndrome in bats and avian malaria, are more 

prevalent elsewhere but present a large potential risk in the ROCO region. In contrast 

to plant diseases, which are usually slower 

to appear and spread, wildlife diseases can 

emerge suddenly and devastate populations. 

For instance, a recent outbreak of pneumonia in bighorn sheep (Ovis canadensis) has 

been responsible for hundreds of deaths in 

Nevada and Montana (WSF 2010).

3.7.1  Observed trends

Climate change has altered the dynamics of 

pathogens and diseases in the past century 

(Harvell et al. 2002). While a detailed account of climate-induced changes for every 

disease is beyond the scope of this review, 

some general trends have emerged.

● Numerous factors along with climate have 

contributed to disease emergence and 

increasing transmission risk to humans, 

including habitat fragmentation, land 

management practices, road construction, 

water control systems, and development 

(Patz et al. 2000). 

● Milder winters have made many wildlife 

and plant species more susceptible to 

disease because of they have increased the 

survival of pathogens and the population 

density of the host organisms (Harvell et 

al. 2002). For instance, as elk population 

and herd size has increased in the Greater 

Yellowstone Area during recent decades, 

in part due to milder winters (Creel and 

Creel 2009), so has brucellosis seroprevalence (Cross et al. 2010).

● Warmer water temperatures have increased the virulence of water-borne 

diseases such as whirling disease (Rahel 

and Olden 2008). Warmer temperatures 

may also be contributing to increased 

mortality of trees in the West (van Mantgem and Stephenson 2007). In another 

instance, West Nile virus transmissions 

during the epidemic summers of 2002 to 

2004 in the United States were linked to 

above-average temperatures (Reisen et al. 

2009). Laboratory studies are consistent 

with these trends in which pathogens 

and parasites can reproduce faster and 

are more virulent at higher temperatures 

(Harvell et al. 2002). 

● Drought, fire, temperature stress, and 

extreme weather events are making many 

host species less resistant to disease and 

increase the probability of continued 

spread. For example, mountain pine beetles are a vector for at least three strains of 

blue-stain fungi (Grosmannia clavigera)

(e.g., Rice and Langor 2009). Interactions 

between biotic (mostly fungal) and abiotic 

stressors (such as drought) may represent 

the most important effects of climate 

change on forest diseases (Frankel 2008). 

● Climate change is a suspected but not confirmed factor in some disease outbreaks. 

For instance, over one million bats of six 

different species have been killed in four 

years by white-nose syndrome, caused by 

the fungus Geomyces destructans (Blehert 

et al. 2009). As scientists work to understand the direct cause of mortality and 

whether climate change is contributing to 

the spread of the disease, it continues to 

move westward (NWHC 2010).

In summary, there is ample evidence that 

climate change has contributed to the increased prevalence and virulence of wildlife 

and plant disease as well as the increased 

susceptibility of hosts. The most detectable 

effect of climate change has been on pathogen range (Harvell et al. 2002). Many vectorborne diseases of wildlife and humans have 

increased their spread in the last decades 

with a concurrent spread of the insect vector 

(Harvell et al. 2002). For example, the spread 

of avian malaria into higher elevations and 

northern latitudes is linked to increased 

minimum temperatures (Patz et al. 2000). 
17

Ecosystem Properties and Processes

3.7.2  Projected trends

Climate change will likely increase the range, 

frequency, severity, and impact of plant and 

wildlife disease (Harvell et al. 2002). The 

IPCC states with very high confidence that 

climate change will increase the risk and 

geographic spread of vector-borne infectious 

diseases, including Lyme disease and West 

Nile virus, and changes in precipitation will 

increase water-borne disease (Field et al. 

2007). Diseases will likely move farther north 

and into higher elevations. For example, 

the tick that causes Lyme disease, Ixodes 

scapularis, is limited by cold temperature, 

and models suggest that its range limit could 

shift north by 200 kilometers (124 mi) by the 

2020s and 1,000 kilometers (621 mi) by the 

2080s (Ogden et al. 2006). In some cases, climate change may adversely affect the disease 

rather than the host. For instance, fungal 

diseases dependent on moist conditions may 

decrease in a warmer, drier future (Harvell et 

al. 2002, Frankel 2008). 

One of the key uncertainties in predicting 

the spread of disease is our lack of knowledge about how climate change will affect 

novel communities that emerge and how 

dynamics will change as species that have 

been previously isolated begin to interact. 

Many wildlife and plants will be exposed to 

new diseases, but how quickly the dynamics 

between novel hosts and diseases will evolve 

remains unknown. Another uncertainty lies 

with precipitation predictions for the region. 

Water availability and the combined effects 

of drought and temperature stress are major 

factors in forest health, susceptibility to pests 

and pathogens, and mortality (Allen et al. 

2010). 

3.7.3  Summary

Climate change will likely continue to increase the prevalence of wildlife and plant 

diseases. A number of factors are believed 

to contribute to this, including (1) the direct 

effect of temperature on the reproduction, 

spread, and virulence of diseases; (2) novel 

species interactions; and (3) increased host 

susceptibility due to temperature, drought, 

and other stressors. Vector-borne diseases 

such as West Nile virus and those that are 

currently limited by low temperatures will 

increase in elevation and move northward. 

Plant communities and wildlife that are faced 

with multiple stressors are the least likely to 

resist the emergence of novel diseases. 

3.8 Invasion dynamics

Invasive species, defined as those that are 

alien (non-native) organisms to the ecosystem under consideration and whose introduction causes or is likely to cause economic 

or environmental harm or harm to human 

health, are widespread throughout the 

United States (NISIC 2010). It is estimated 

that roughly 5% of continental species are 

alien, and the proportion of plants and freshwater fish that are alien is closer to 10% (Cox 

1999). An estimated 25% of the fish species in streams of the western United States 

are alien (Schade and Bonar 2005). Of the 

170 species of native freshwater fish in the 

western United States, over 100 are listed as 

threatened or endangered or are candidates 

for listing, and exotic fish introductions are 

implicated as a cause in 38% of these listings 

(Cox 1999). 

Approximately 10% of alien species are 

likely to be problematic invaders (Williamson and Fitter 1996), which results in an 

estimate of 600 to 700 invasive species in the 

United States (Cox 1999). The ROCO region 

is less invaded than areas such as California 

and Hawaii, but the impacts and extent of 

invasion can be vast. For instance, the native bunchgrasses of the Upper Columbia 

Basin and intermountain region have proven 

particularly vulnerable to over-grazing, allowing extensive areas to become invaded 

by cheatgrass (Bromus tectorum). Millions 

of acres are at risk of being converted to 

cheatgrass monocultures with increased 

risk of frequent wildfire (Chambers et al. 

2009). Federal lands and other protected 

areas have not provided a refuge for native 

species; 3,756 non-native plant species have 

become established in 216 US national parks 

(Allen et al. 2009). Currently, however, high 

elevations appear to be less vulnerable to 

invasion, likely as a result of environmental 

constraints and reduced human development (Pauchard et al. 2009). 

The invasive species of greatest management concern in the West fall into three 

general categories: pests and pathogens, 
18

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

aquatic invaders, and invasive plants. Pests 

and pathogens, such as whirling disease and 

the fungus responsible for white pine blister 

rust, have had devastating impacts on native 

species. Lake trout (Salvelinus namaycush), 

brook trout (S. fontinalis) New Zealand mud 

snails (Potamopyrgus antipodarum), quagga 

(Dreissena bugensis), and zebra mussels (D. 

polymorpha) are some of the most troublesome aquatic invaders. Brook trout, for 

instance, have been responsible for the loss 

of many native trout populations (Peterson 

et al. 2008). Invasive bullfrogs (Rana catesbeiana) have contributed to the decline of 

native frogs in the ROCO region (Hayes et 

al. 1986). Plants of the greatest concern are 

yellow star thistle (Centaurea solsticialis), 

cheatgrass, tamarisk (Tamarix ramosissima), 

leafy spurge (Euphorbia esula) and spotted 

knapweed (Centaurea maculosa). These and 

many other invasive species have contributed 

to loss of biodiversity, localized extinctions, 

and changes in ecosystem processes such as 

fire, hydrologic regimes, and nutrient cycling 

(e.g., Vitousek et al. 1997, Ehrenfeld 2003, 

Gurevitch and Padilla 2004). 

3.8.1  Observed trends

The spread of invasive species in the West 

has accelerated in the last decades. For 

example, from 1986 to 2008, the number of 

exotic plant species documented in Yellowstone National Park nearly doubled from 

105 to 208 (NPS 2008). Non-native annual 

grasses and forbs have spread throughout 

grasslands in the West and it is estimated 

that more than 300 rangeland weed species 

are present in the United States (DiTamaso 

2000). Many species such as quagga and zebra mussels have only recently been sighted 

in Colorado and on boat trailers in Montana, 

and are expected to continue to increase in 

numbers (USGS 2010). While there is a correlation between the spread of invasives and 

warming temperatures, it is hard to pinpoint 

climate as the cause because of the many 

other factors such as lag times, deliberate 

introductions, and dispersal vectors (Hellmann et al. 2008). Nonetheless, it is suspected that climate is a major driver of the spread 

of invasive warm-water fishes (Rahel and 

Olden 2008) and some warm-season grasses 

(Sage and Kubien 2003). 

3.8.2  Projected trends

The spread and impact of invasive species 

is driven mainly by changes in land use, 

increasing urbanization, disturbance, and 

alteration in management practices, but 

climate change may exacerbate the extent 

of invasions. Climate change is generally 

expected to increase the spread of invasive 

species through direct effects on habitat 

suitability and the indirect effects of altered 

nutrient availability and disturbance regimes 

(Dukes and Mooney 1999). The IPCC has 

very high confidence that disturbances such 

as wildfire will continue to increase and this 

will facilitate invasions (Field et al. 2007). In 

general terms, invasive species are expected 

to differ in their response to climate change 

from native species because they possess 

traits such as broad climatic tolerances and 

robust dispersal mechanisms that enable 

them to better adapt to changing conditions. 

Hellman and colleagues (2008) identified five 

consequences of climate change on invasion 

dynamics: altered invasion pathways, changes in environmental constraints, altered distribution of existing invasive species, altered 

impacts of invasive species, and a change 

in management effectiveness. An example 

of an altered invasion pathway would be an 

increase in recreational boat traffic as a result 

of warmer temperatures in previously snowcovered areas resulting in an increase in the 

spread of nuisance species. 

Here are some examples of how climate 

change is expected to alter invasion dynamics in the ROCO region. 

● Stream temperatures are expected to 

warm with warmer air temperatures and 

lower flows, increasing the amount of suitable habitat for warm-water fishes by an 

estimated 31% nationwide (Mohseni et al. 

2003). 

● Warmer temperatures may increase the 

impact of invasive species. In the Columbia River, for example, increasing 

temperatures have caused smallmouth 

bass (Micropterus dolomieu) to consume 

more native salmon (Petersen and Kitchell 

2001), and whirling disease is more virulent in warmer streams (Rahel and Olden 

2008).
19

Ecosystem Properties and Processes

● Earlier melting of snowpack will alter 

streamflows, may increase disturbance 

and flood events, and favor invasive species. It is predicted that such changing 

conditions may increase rainbow trout 

(Oncorhynchus mykiss) invasions in Colorado (Fausch et al. 2001). However, native 

species such as cottonwoods could benefit 

from larger spring flood events that facilitate establishment and recolonization 

(Scott et al. 1996).

● Bradley and colleagues (2009) examined 

the current and potential distributions 

of five problematic plant invaders in the 

West (cheatgrass, knapweed, yellow star 

thistle, tamarisk, and leafy spurge) based 

on the current climatically suitable habitat 

and maps of future habitat based on an 

ensemble of global climate models. They 

found that precipitation was the most 

important predictor of plant distribution 

and that warming temperatures alone 

may have little effect on range expansion. 

Most species were expected to expand in 

some areas while contracting in others. 

For example, they predict that the risk of 

cheatgrass invasion will increase in Montana, Wyoming, Idaho, and Colorado, but 

decrease in parts of Nevada and Utah. 

There are several uncertainties associated 

with predicting the ecological response of 

invasive species to climate change, including how land management, dispersal, and 

disturbance may obscure climate signals on 

invasion dynamics. Another challenge in 

modeling the potential spread of a species is 

that the physiological limits of many species 

and their potential to adapt to new conditions is unknown and current habitat suitability may not accurately reflect potential 

suitability. It is also unclear how climate will 

alter biotic interactions and current management practices, and how these may alter 

invasion dynamics. For instance, biocontrol 

agents may no longer be effective in a changing climate.

3.8.3  Summary

Climate change is likely to increase biological invasions. In the short-term, however, 

other factors may play a much larger role in 

the spread and impact of invasive species, including changes in land use and management 

practices and increasing urbanization and 

disturbance. Still, models suggest that the 

following will occur with a warmer climate 

in the ROCO region: 

● Plant and animal species, both native 

and invasive, will migrate upslope and 

northward.

● Changes in precipitation will likely drive 

the expansion and contraction of invasive 

plants;

● Warmer stream temperatures and a reduction in ice cover will facilitate the spread 

of aquatic invasives and may increase their 

impacts.

● Changes in the timing of snowmelt and a 

subsequent increase in disturbance caused 

by spring floods may increase the risk of 

aquatic and riparian invasions.

● Warmer temperatures may change human 

visitation patterns to natural areas and 

increase the pathways of spread for many 

invasives. 

21

Communities Chapter 4: Communities

Warming temperatures and changing precipitation regimes will likely alter plant and 

animal communities throughout the ROCO 

region. Since the timing and magnitude of 

response to climate change is certain to vary 

by species, future community assemblages 

may not have current analogs. Below, we 

present some concepts that are common 

across all communities and discuss some of 

the more specific observed and projected 

responses to climate change for alpine areas, 

forests and woodlands, and sagebrush and 

grassland ecosystems. We also describe 

how aquatic resources such as glaciers and 

wetlands respond to climate changes. All of 

these community types are present within 

the ROCO region but vary in spatial extent 

and by locality (fig. 4). 

From the paleoecological record it is clear 

that communities in this region are relatively 

dynamic and have only recently become 

established (McWethy et al. in press). To 

manage terrestrial communities, they must 

be regarded as a dynamic rather than static 

assemblage of species. For instance, as many 

native species expand their range and become established in new communities, distinguishing between native and non-native 

species will become increasingly difficult.

At a landscape scale, one of the most common ways to understand how terrestrial 

communities may respond to climate change 

is through dynamic vegetation models based 

on current distribution of vegetation and 

future climate scenarios, and they can also 

incorporate management strategies, biogeography, and biogeochemistry (e.g., Bachelet 

et al. 2001). An example of such a model is 

presented in figure 5. It describes the current distribution of major community types 

for the United States and two future projections of varying CO2

 emissions and no fire 

suppression (Lenihan et al. 2008). Overall 

confidence in model predictions is low because accounting for major drivers of forest 

structure such as the spread of disease, insect 

infestations, and land use changes is difficult. 

How ecosystems will respond to climate is 

uncertain in specific details, but models are 

realistic in projecting the kinds and magnitude of changes that we can expect and some 

general patterns emerge. 

Figure 4. Major 

community types in 

the Rocky Mountains and Upper 

Columbia Basin 

based on LANDFIRE 

classification. 
22

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Most simulation models project a widespread reduction in alpine and subalpine forests in the West (fig. 5; Lenihan et al. 2008). 

The distribution of temperate conifer forests 

may expand in the northern Rockies and, 

with limited fire suppression, woodland/savanna vegetation types could replace shrubland areas in the interior West (Bachelet 

et al. 2001, Lenihan et al. 2008). We discuss 

some of the drivers and consequences of 

these changes in the sections below. 

4.1 Alpine

The alpine tundra is defined as the vegetation communities that exist above tree line. 

The alpine/tree line ecotone is found at 

approximately 3,500 meters (11,483 ft) in 

southern Colorado, 3,000 m (10,000 ft) in 

Wyoming, and 2,139 meters (7,017 ft) in 

northern Montana. The exact location and 

elevation of tree line varies with climate, 

topography, snow and debris avalanches, 

and local competition between tundra and 

trees (Malanson et al. 2007a), but it is highly 

temperature dependent and generally concurrent with the 50°F isotherm (where the 

average July temperature is above 50°, 10°C) 

(Arno and Hammerly 1984). Alpine and 

subalpine communities can be found on the 

highest peaks throughout the region, but the 

largest areas are found in the Crown of the 

Continent Ecosystem, the Greater Yellowstone Area, and the Colorado Front Range. 

The alpine environment is characterized by 

high winds, low temperatures, scouring and 

burial by snow and ice, low nutrient availability, high incident solar radiation, thin atmosphere, and a short growing season (Bowman 2001). The vegetation community is 

small in stature and dominated by perennial 

herbaceous species with species composition 

varying strongly across environmental gradients of water availability, which are driven by 

snow pack (Walker et al. 2001). The alpine 

tundra is typically dominated by graminoids 

and forbs, but nonvascular plants and woody 

shrubs are also common. Compared to other 

grassland types, the alpine tundra shows 

high local diversity (Gough et al. 2000), and 

the abundance of invasive/exotic species is 

negligible compared to other ecosystems. 

The alpine environment serves as refugia for 

certain species. For example, many Edith’s 

checkerspot butterfly (Euphydryas editha) 

populations have become extinct in the last 

century, but many fewer have been lost at 

high elevations (2,400–3,500 m) (Parmesan 

1996). Despite its small aerial extent, the 

alpine environment is considered of high 

conservation value because of its recreation 

and aesthetic values. Moreover, it supports 

numerous animals of management concern, 

including bighorn sheep, mountain goats 

(Oreamnos americanus), white-tailed ptarmigans (Lagopus leucura), and pikas. Most of 

the water resources in the West are derived 

from snowmelt, and the quality and quantity of this water is influenced by ecosystem 

Figure 5. Model of 

simulated vegetation changes 

assuming unsuppressed fire during 1971 to 2000 

(USF-HIST) and two 

scenarios for 2070 

to 2099: a high 

level of CO2 emissions (USF-A) and a 

relatively low level 

(USF-B). Figure from 

Lenihan et al. 2008. 
23

Communities

processes in the alpine tundra (Williams and 

Caine 2001). Because the alpine tundra is 

globally distributed and particularly sensitive 

to climate change and atmospheric deposition, it may provide an important indicator 

for global change (Seastedt et al. 2004). 

4.2 Observed trends

At high elevations, warming has positively 

affected the growth rate of some western 

tree species, suggesting that as temperatures 

warm the tree line will continue to move 

upward (e.g., Salzer et al. 2009). However, 

compared with the movement indicated 

by the paleoenvironmental record, direct 

evidence for upward movement of the tree 

line in the Rockies due to warming is scarce. 

In northern Montana, repeat photography 

shows that the tree line has been stable 

since the early 20th century and only the 

density of forest patches at the tree line has 

increased (Butler et al. 1994, Klasner and 

Fagre 2002). The tree line has shifted upward 

in some areas in the Canadian Rockies, but 

remained stable in others, and changes in fire 

frequency seem to have had larger effects on 

forest structure than has climate (Luckman 

and Kavanagh 2000). 

Species that persist in alpine areas have 

adapted to the extreme environment, but 

growth and reproduction are strongly 

limited by environmental conditions and 

nutrient availability. As a result, warming 

temperatures and changes in precipitation 

may strongly influence the persistence of 

alpine communities. A survey of summit 

sites in the Swiss Alps showed that vascular plants have been establishing at higher 

altitudes than recorded earlier (Grabherr 

et al. 1994). Moreover, the optimum elevation of alpine plants has increased and the 

shift upward has accelerated during the last 

century (Walther et al. 2005). Global surveys 

suggest that one consequence of warming 

temperatures in the mountains may be an 

increase in the abundance and distribution 

of exotic plants (Pauchard et al. 2009). There 

has been an increase in shrub expansion in 

the Arctic tundra as a consequence of warming and the altered precipitation of the last 

century (Sturm et al. 2001), but this has not 

been documented in the Rockies. There is 

some evidence for this from Glacier National 

Park, where four of seven indicator species 

have declined in abundance and three have 

shown no change with the increasing average summer temperatures of the last decade 

(Lesica and McCune 2004). Warming and 

changes in precipitation may have large 

effects on the timing of flowering, which in 

turn can change pollinator dynamics and 

plant community structure. Such changes 

have been seen in montane meadows in the 

Rockies (Inouye 2008) but have not been 

documented in the tundra. 

4.2.1  Projected trends

Models show that increased temperatures 

will decrease the abundance and distribution 

of subalpine trees such as Engelmann spruce 

in the Greater Yellowstone Area because of 

the limited extent of alpine area for these 

species to move into, but predictions are 

difficult because these trees are sensitive to 

concurrent changes in precipitation, insect 

outbreaks, and fire regimes (Schrag et al. 

2008). Evidence from recent and paleoecological studies suggest that tree line response 

to warming varies substantially with the 

availability of precipitation (Graumlich et al. 

2005), adding greater complexity to predictions. In summary, the tree line may shift 

upward and encroach on alpine tundra in 

the Rockies as temperatures continue to rise, 

but it may not be a clear and dramatic change 

due to variations in local geomorphology, 

plant response, and human disturbance (fig. 

6; Malanson et al. 2007b). 

Warming experiments at numerous tundra 

sites, including one in the Rockies, suggest 

that a temperature increase of 1–2°C (2–4°F) 

can increase the height and cover of deciduous shrubs and graminoids, decrease cover 

of mosses and lichens, and decrease species 

diversity and evenness (Walker et al. 2006). 

For instance, warming led to an increase in 

shrubs and a decrease in forbs in a subalpine 

meadow in the southern Rockies (Harte 

and Shaw 1995). Evidence from such experiments and historical data suggest that 

warming will likely cause changes in alpine 

community structure and communities with 

no current or past analogs may develop. 

Snow is the most important factor driving 

the current structure of vegetation within the 
24

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

alpine environment, and experiments have 

revealed that increases in snow depth and 

duration may enhance the growth of woody 

species and favor some herbaceous species 

over others (Walker et al. 2006). The direction of precipitation changes in the alpine 

and the vegetation response is one of the 

key uncertainties in describing the alpine 

response to climate change. Invariably, longterm changes in snowfall and wind deposition of snow will result in changes in the area 

of wet meadows, fell-field, and dry meadow 

communities. 

The alpine environment is also threatened by 

other global changes, including the increasing deposition of atmospheric N, ultraviolet 

radiation, dust storms, insect outbreaks, 

and fire regimes that may slow the upward 

migration of the tree line. Perhaps the greatest threat is from N deposition, which has 

increased in the Rocky Mountains in recent 

decades due to the growth of metropolitan 

areas and agriculture (Fenn et al. 2003). 

Alpine regions in the Rocky Mountains have 

a low capacity to sequester excess N because 

of short growing seasons, shallow soils, and 

steep slopes that encourage rapid run-off 

(Fenn et al. 2003). There is evidence that N 

deposition has altered alpine lake chemistry 

and biota (Baron et al. 1994) and that it can 

alter the structure of alpine communities 

(Bowman 2000). The deposition of dust 

from storms originating in the arid Colorado 

Plateau has increased in the southern Rockies (Neff et al. 2008). The dust covers the 

snow, which changes the albedo and accelerates the timing of snowmelt, which in turn 

alters alpine phenology and community dynamics (Steltzer et al. 2009). Dust events are 

also significant inputs of phosphorus and, 

as with N deposition, have the potential to 

alter water chemistry and alpine community 

structure. These multiple stressors on alpine 

systems add to the difficulty and uncertainty 

in anticipating how they will respond to 

climate change. 

4.2.2  Summary

The alpine environment is highly sensitive 

to climate change (fig. 6). From the limited 

research and monitoring efforts in the Rockies relating to tundra and climate change, it 

is known that changes will be hard to predict 

due to local variability and the large influence of precipitation and other global enviFigure 6. Conceptual diagram of 

alpine/subalpine 

response to climate 

change.
25

Communities

ronmental changes. Still, evidence suggests 

that we should expect the following changes 

with a warmer climate in the Rockies:

● The tree line may increase in elevation 

in some areas but the response will be 

complex and dependent on precipitation 

regimes, fire, and insect outbreaks. 

● Subalpine tree species may decline in 

abundance.

● The density of forests at tree line ecotones 

may increase.

● Tundra may decrease in areal extent. 

● Plant species may migrate upslope. 

● Invasive/exotic species may increase in 

abundance in alpine areas.

● Shrubs and graminoids may increase in 

abundance while mosses, lichens and 

some forbs decrease.

● Community composition may be altered 

with consequences for species that utilize 

alpine plants, such as pika, mountain 

goats, and ptarmigans.

● Changes in the alpine tundra will likely be 

driven by other global changes such as N 

deposition and dust events. 

4.3 Forests and woodlands

Forests and woodlands cover approximately 

one-third of the United States. Western 

forests are predominantly coniferous (78%) 

and in public ownership (57%) (Smith et 

al. 2001). Of the four states in the ROCO 

region, Wyoming is the least forested (11 

million acres, 4 million ha) while Colorado, 

Montana, and Idaho each contain roughly 

twice as much forested acreage (Smith et al. 

2001). The dominant forest cover types vary 

with moisture availability and elevation. At 

mid-elevations, ponderosa pine, Douglas 

fir, lodgepole pine, and aspen predominate, 

while at high elevations, forests are typically comprised of subalpine fir, Engelmann 

spruce, western white pine, and western 

larch (Larix occidentalis) (Smith et al. 2001). 

Three-quarters of US lodgepole forests are 

found in this region and they are usually 

dense, pure stands (Smith et al. 2001). 

Forests provide valuable wildlife habitat, watershed protection, carbon storage, numerous recreational opportunities, essential gas 

exchange with the atmosphere, and timber. 

Over the last century, forest composition has 

been influenced by management activities, 

introduced species, forest succession, and 

natural disturbances such as fire, drought, 

and insect outbreaks. Fire suppression has 

been routine in the region since 1900 and, 

together with planting, has played a major 

role in determining the current composition 

of western forests (Keane et al. 2002). Insect 

outbreaks affect 20 million hectares (949 

million acres) of US forest annually, approximately 44 times more area than is affected 

by fire (Dale et al. 2001). Below we describe 

some of the observed and projected trends 

in ROCO forests in response to climate 

change, then focus on aspen and five-needle 

pines, two forest types that are of particular 

management concern.

4.3.1  Observed trends

After the last glaciations ended, warm 

conditions allowed trees and shrubs to 

move northward and upslope in many areas 

(McWethy et al. in press). This suggests that 

forest composition and tree distribution 

can respond to climate alterations, but the 

rate at which these changes will occur in the 

future remains unclear. There is only limited 

evidence since 1900 that climate has directly 

caused compositional changes in forests, but 

this may be due to lag times. Trees are longlived organisms and many other factors, such 

as land management and fire, may have acted 

to obscure the climate signal. Whatever the 

cause, forests have changed in composition 

over the last 100 years. For example, in the 

Kootenai and Idaho Panhandle National 

Forests, Douglas fir and other shade tolerant 

species such as Engelmann spruce have become more abundant as the forest canopy increases while species such as ponderosa pine 

and western larch have declined (Morrison 

in prep). An outbreak of white pine blister 

rust has eliminated an estimated 90% of the 

western white pine and whitebark pine in the 

Northern Rockies (Neuenschwander et al. 

1999, Kendall and Keane 2001, Harvey et al. 
26

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

2008). Major range shifts during prehistoric 

times and rapid colonization after agricultural declines in the East suggest that certain 

traits such as high genetic mobility via pollen 

may make some tree species better suited to 

adapting to climate change than many other 

plants (Hamrick 2004). However, late-successional conifers are poor dispersers and 

slow to respond to climate change (Neilson 

et al. 2005). 

Forest composition may be slow to change, 

but many other effects of climate can be 

seen on forests around the world, including 

increased growth due to a longer growing 

season, faster growth rates particularly at 

higher elevations, increased water use efficiency, and increased growth from higher 

concentrations of CO2 in the atmosphere. 

These changes are consistent with evidence 

that US forests have become more productive in the last 55 years (Boisvenue and Running 2006). Moreover, several studies have 

documented the upward movement of the 

alpine tree line and infilling of high-elevation 

meadows in western North America during 

the 20th century (e.g., Hessl and Baker 1997, 

Luckman and Kavanagh 2000). Climate 

change may reduce forest productivity due to 

increasing drought, temperature stress, and 

evapotranspiration, and indirect effects such 

as increased insect outbreaks, increasing 

prevalence of invasive species, and increased 

fire. Higher temperatures have likely caused 

recent increases in drought stress and forest 

die-offs through their influence on transpiration, carbon storage, insect populations, and 

host susceptibility (Allen et al. 2010). Global 

patterns suggest that seasonal droughts have 

induced dieback of deciduous trees while 

multi-year droughts are more likely the cause 

of coniferous dieback (Allen et al. 2010). 

4.3.2  Projected trends

The IPCC predicts that overall forest growth 

in North America will likely increase 10–20% 

as a result of extended growing seasons and 

elevated CO2 during the next century (Morgan et al. 2001) but with important spatial 

and temporal variations (Field et al. 2007). 

Forests in the ROCO region are expected 

to have less snow on the ground, a shorter 

snow season, a longer growing season due 

to an earlier spring start, earlier peak snowmelt, and about two months of additional 

drought (fig. 7; Ray et al. 2008, Running 

2009). Increased drought stress and higher 

temperatures may increase the likelihood of 

widespread die-offs (Breshears et al. 2005, 

Allen et al. 2010). 

Dynamic vegetation models project that 

suitable habitat for western larch, whitebark 

pine, lodgepole pine, and subalpine fir is 

generally expected to decrease (Morrison 

in prep). A 3oC (5°F) temperature increase 

is expected to increase the growth of lodgepole pine in the northern part of its range, 

decrease growth in the middle, and decimate southern forests (Rehfeldt et al. 2001). 

In the coming century, subalpine forests 

are projected to decline in abundance and 

woodlands may become more abundant (fig. 

5; Lenihan et al. 2008).

The key uncertainty regarding the future 

of forests lies in the interaction of multiple 

global change factors and the unpredictable 

nature of large disturbances such as fire and 

insect outbreaks. Researchers currently rely 

on models that link climate scenarios to vegetation dynamics and these are wrought with 

uncertainties. Such models are limited by the 

lack of local and accurate vegetation maps 

and appropriately scaled climate data (Allen 

et al. 2010). Moreover, it remains unclear if 

trees will keep pace with the rapidly changing climate through adaptation or by migrating to suitable habitat. Predictions are also 

hindered by an incomplete understanding 

of tree physiology, soil dynamics, and insect 

populations. Moreover, complex trophic 

interactions, which are not accounted for in 

these models, can drastically alter vegetation. 

For instance, warming may decrease predators, increase prey, and decrease the prey’s 

preferred vegetation. Such a cascading effect 

has been documented in Isle Royale with 

wolves (Canis lupus), moose (Alces alces), 

and fir trees (Schmitz et al. 2003). 

4.3.3  Five-needle pines

Five-needle pines such as limber pine and 

whitebark pine are keystone species that provide food and habitat for wildlife. Whitebark 

pine is found in upper subalpine ecosystems 

throughout the northern Rockies, where it 

often grows in areas with poor soils, high 
27

Communities

winds, and steep slopes (Arno and Hoff 

1990). The southern limit of its range is in 

the Greater Yellowstone Area (Little 1971). 

It provides food for more than 17 animal 

species, including the Clark’s nutcracker 

(Nucifraga columbiana) and grizzly bear (Ursus arctos horribilis) (Arno and Hoff 1990). 

Limber pine is more widespread and occurs 

in the subalpine areas of the southern, central, and northern Rockies and in parts of the 

Upper Columbia Basin (e.g., Craters of the 

Moon National Monument and Preserve). 

Bristlecone pine, another five-needle pine, is 

found at high altitudes in the southern Rockies (Little 1971). 

4.3.3.1 Observed trends 

Whitebark pine has declined dramatically 

in the last century due to attacks by a blister 

rust fungus, epidemics of mountain pine 

beetles, fire suppression, and successional 

replacement, mainly by subalpine fir (Keane 

and Arno 1993, Kendall and Keane 2001). In 

areas where it was once a dominant feature 

of the landscape, it has declined by more 

than 50% and most of the remaining stands 

in the ROCO region are in high-elevation 

sites that have a limited capacity to produce 

cones and regenerate (Kendall and Keane 

2001). Mortality rates of whitebark pine 

populations in western Montana averaged 

42% from the 1970s to the 1990s. With a 

large reduction in cone production and a 

decline in population size, whitebark pine is 

considered functionally extinct in more than 

a third of its range (Kendall 2010). 

The primary cause of mortality has been 

white pine blister rust, a fungus native to 

Asia and now widespread across the West. 

The low natural resistance of North American five-needle pines along with favorable 

climatic conditions enabled the disease to 

spread rapidly. The pathogen became spread 

throughout the western white pine region 

in the early part of the 20th century and to 

higher elevations and a greater number of 

pine species more recently. It is now established in limber pine in Wyoming and Colorado, and bristlecone pine in southern Colorado. It was found for the first time in limber 

pine in Craters of the Moon in 2006, triggering concerns that the unique population on 

the lava flows may be at risk. In northwestern 

Montana and southern Alberta, surveys 

found that more than one-third of the limber 

Figure 7. Conceptual diagram of 

projected changes 

for forests and 

woodlands.
28

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

pines were dead (Kendall et al. 1996).

Wind, temperature, and humidity can influence the dispersal of blister rust as can the 

availability of ribes (Ribes spp.) hosts (Van 

Arsdel et al. 2006). Generally, cool temperatures and high relative humidity favor disease 

spread and intensification. The incidence 

of pine infection may increase substantially 

during years when optimum environmental 

conditions coincide with spore production, dissemination, germination and infection (Koteen 1999). However, it is unclear 

whether climate change has had a role in 

driving blister rust because its impact does 

not seem to be constrained substantially by 

climate conditions across the Rockies. High 

humidity and warm weather provide better conditions for blister rust, but cold and 

dry conditions have not limited its spread to 

higher elevations in the Greater Yellowstone 

Area (Kendall and Keane 2001). 

4.3.3.2 Projected trends 

Regardless of climate, five-needle pines 

will likely continue to decline in the Rocky 

Mountains and the prevailing cause of death 

will continue to be blister rust. If five-needle 

pines are maintained in these ecosystems 

over the long term, they are expected to be 

very slow to respond to climate change and 

will alter their range northward or upslope. 

On the other hand, climate change may 

increase fire frequency, thereby reducing firs 

and other species that exclude five-needle 

pines, enabling expanded distributions in 

the future.

4.3.3.3 Summary

Climate is expected to play only a small role 

in the future of five-needle pines. It is likely, 

however, that widespread disease and mountain pine beetles will continue to devastate 

pine populations throughout the ROCO 

region. 

4.3.4  Aspen

Aspen is the most widespread deciduous tree 

in North America (Little 1971). Its geographic range is limited to areas below 3,700 

meters (12,139’) (Mitton and Grant 1996) 

that receive more than 400 mm (16”) of 

annual precipitation (DeByle and Winokur 

1985). Aspen stands are patchily distributed 

in the ROCO region. It occurs in pure stands 

throughout the southern Rockies, but is less 

abundant in the northern Rockies, where 

it often occurs in smaller discrete patches 

(Stohlgren et al. 2002, Shepperd et al. 2001). 

4.3.4.1 Observed trends

Aspen communities provide some of the 

most biologically diverse habitats in the intermountain West, where they help support 

an array of vascular plants in the understory as well as insects, birds, and mammals 

(Stohlgren et al. 2002). In particular, native 

ungulates use aspen as preferred forage and 

for shade and concealment. Aspen spreads 

primarily vegetatively in the West and clones 

can be very large. Individual stems within a 

clone are rarely live more than two centuries, 

and regeneration after fires is typically very 

strong (Sheppard et al. 2001a, b). Where 

aspen occurs in mixed stands, regeneration 

is limited in the shade of conifer species such 

as Douglas fir, subalpine fir, and juniper, and 

the aspen die after 100 to 150 years (Kaye 

et al. 2005). Aspen seedlings are rare but 

not uncommon after fires. One of the best 

known recruitment events was following 

the 1988 fires in Yellowstone National Park 

(Romme et al. 2005). 

Widespread mortality of older aspen stems 

has occurred in the West in recent decades 

(Bartos 2001), but this decline has not been 

consistent across the landscape and regeneration of younger stems has been strong except where livestock and wildlife browsing is 

intense (Veblen et al. 2000). Declining stands 

in the West are associated with fire suppression, conifer encroachment, increased 

herbivory from elk, fungal infection, and sustained drought (Kashian et al. 2007). Heavy 

browsing by elk has reduced regeneration by 

40–80% in Yellowstone National Park (Hart 

and Hart 2001) and by up to 90% in Rocky 

Mountain National Park (Binkley 2008). Aspen recruitment has been very limited since 

1975 in areas of Rocky Mountain National 

Park with intensive elk grazing while remaining stable in areas with fewer elk, suggesting 

that herbivory plays a larger role than climate 

change in aspen decline (Binkley 2008). 

While aspen is declining in some areas, 

other stands are persistent and increasing 

in size (e.g., Kashian et al. 2007). There has 

been a general increase in aspen in southern 
29

Communities

Colorado since 1898, but patterns vary with 

elevation and fire history (Kukalowski et al. 

2006). Aspen has been expanding upslope 

on southern exposures in the last century 

and this is thought to be due to climate 

warming (Elliott and Baker 2004). In Alberta, 

warmer temperatures and disturbance have 

led to seedling regeneration up to 200 meters 

(656’) higher than the existing mature stands 

(Landhausser 2010). 

4.3.4.2 Projected trends

As with other communities, aspen are influenced by many global changes in addition to 

warming temperatures. Experiments suggest 

that the growth of aspen is more accelerated 

by increased CO2 concentrations than are 

other tree species (Lindroth 1993). On the 

other hand, ground-level ozone, which has 

been increasing in the West over the last century (Vingarzan 2004), has been shown to 

decrease aspen growth and photosynthetic 

rate and increase susceptibility to pests, but 

these effects are moderated when CO2 is increased (Karnosky 2005). High mortality of 

lodgepole pine from mountain pine beetles 

may favor aspen growth, but this effect will 

likely only be seen in locations with existing aspen clones; it is unlikely to occur via 

seed recruitment (Romme et al. 2006). The 

future of aspen in national parks will be 

strongly dependent on elk management. 

After the 1988 fires in Yellowstone, seedling 

success was higher where ungulates were 

excluded (Romme et al. 2005). Ripple and 

Beschta (2004) have suggested a complex 

trophic relationship between wolf reintroduction, ungulates, and aspen and willow 

recovery that has implications for the longterm persistence of aspen in ROCO parks. 

Understanding and managing aspen in 

these areas will require consideration of the 

role of fire and elk browsing (Hessl 2002).

A recent paper examining sudden aspen 

decline and the impacts of global warming 

in the West forecasts that aspen will move 

upslope but will be lost from lower and drier 

areas (Rehfeldt 2009). The key uncertainties 

in forecasting the ecological response of aspen to climate change lies in our incomplete 

understanding of the causes of sudden die 

off, the long-term impacts of ungulate management, the potential appearance of nonnative insects or disease, and the interactive 

effects of other global changes.

4.3.4.3 Summary

Aspen forests are small in area but a vital 

resource in the West because of their high diversity and aesthetic appeal. While there has 

been some expansion of aspen into higher 

elevations and aspen may be positively affected by global changes such as increasing fire 

frequency, beetle outbreaks, and rising CO2, 

aspen is expected to continue to decline at 

the landscape scale. In areas without hunting 

and large predators, including some national 

parks, the most important factor determining the success of aspen is increasing herbivore pressure. Aspen stand are expected to 

recover in parks that develop and implement 

elk management plans. As described by the 

Upper Columbia Basin Network, the desired 

condition for aspen in the parks is stands 

that exhibit adequate regeneration (>1200 

stems/ha, 486/stems/acre), low levels of 

conifer encroachment, and canopy cover of 

>40%, and that do not have risks of die-off 

(Strand et al. 2009). 

4.3.5  Summary

Climate change is expected to increase forest 

growth and many species will move upslope. 

Forest composition will likely change as once 

dominant species are eliminated from the 

community by disease and insect outbreaks 

and replaced by other tree species. Wildfires are predicted to increase in severity, 

frequency, and areal extent, which will have 

large impacts on stand age and structure. 

Dynamic vegetation models project a general 

decline in subalpine forests and an increase 

in woodlands at lower elevations. 

4.4 Sagebrush and grasslands

Sagebrush and grasslands in the ROCO region include sagebrush steppe, represented 

in the western portions of the Great Northern LCC that border the Great Basin and 

in the Columbia Basin; shortgrass steppe, 

found in Colorado; Palouse grasslands, limited to eastern Washington and northwestern 

Idaho; and northern mixed grass prairie 

(Seastedt 2002). Other grasslands, such as 

subalpine meadows and those associated 

with ponderosa pine, are scattered through-
30

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

out the foothills and higher elevations of the 

region. The intermountain sagebrush steppe 

and grasslands are a heterogeneous mixture 

of true grasslands, savannah, woodlands, 

and shrublands, and are strongly controlled 

by topographic moisture gradients (West 

and Young 2000). Presettlement fire intervals 

varied across the landscape from decadal 

in some moist grasslands in Colorado and 

mesic big sagebrush communities to 100 

years or more in xeric sagebrush ecosystems 

(Bunting et al. 2002). Some of the most common native species in these communities 

are prairie Junegrass (Koeleria macrantha), 

Idaho fescue (Festuca idahoensi), bluebunch wheatgrass (Pseudoroegneria spicata), 

rough fescue (Festuca campestris), Sandberg 

bluegrass (Poa secunda), threetip sagebrush (Artemisia tripartite), big sagebrush 

(A. tridentate), and blue grama (Bouteloua 

gracilis). Sagebrush steppe and grasslands 

in the ROCO region support sensitive 

wildlife species including black-footed 

ferrets, pronghorn antelope, sage grouse, 

and numerous sagebrush/grassland obligate 

songbirds (Knick et al. 2003, Aldridge et al. 

2008). 

4.4.1  Observed trends

Over the past 25 years, more than 25 million acres (10 million ha) of shrubland and 

grassland have been eliminated in the United 

States, twice the rate of forest loss (TNC 

2009). Western shrublands and grasslands 

have been extensively modified by settlement, grazing, altered fire regimes, and 

introduced species, causing major, possibly 

irreversible, changes in ecosystem structure 

and function (e.g., Seastedt 2002, Knick et 

al. 2003). Many of the ROCO grasslands 

are currently managed as pasture. Sagebrush steppe is considered one of the most 

threatened US ecosystems (Noss et al. 1995). 

Cheatgrass is estimated to have invaded 

more than 50% of the sagebrush habitat in 

the Great Basin (Rowland 2006). One of the 

largest threats to western grasslands, particularly in Wyoming, is rapid energy development (e.g., oil, gas, and wind). Oil and 

gas development is expected to impact 3.7 

million hectares (9.1 million acres) of sagebrush and 1.1 million hectares (2.7 million 

acres)of grasslands and reduce sage-grouse 

(Centrocercus urophasianus) populations 

(Copeland et al. 2009). Biological invasions 

and habitat loss and fragmentation also pose 

major threats, and climate change will likely 

exacerbate their effects (Noss et al. 1995, 

Knick 2000, Knick et al. 2003, Aldridge et al. 

2008). 

There is evidence that warmer temperatures 

may promote the invasion of woodlands into 

grasslands, alter species composition and 

productivity, change herbivore pressure, and 

alter fire regimes. Pinyon-juniper woodland 

has increased an estimated 10-fold since the 

late 1800s (Miller and Tausch 2001), expanding into sagebrush and, to a lesser extent, 

other western grassland ecosystems (Miller 

et al. 2005). Climate change has been implicated in previous fluctuations in pinyonjuniper woodland extent (Soule et al. 2004). 

There is some evidence that woody species 

have also increased in subalpine grasslands, 

particularly in alpine-ecotones (e.g., Fagre 

2009) and montane meadows (Berlow et al. 

2002, Zier and Baker 2006). 

Experimental work suggests that warming, 

particularly when coupled with drier conditions, can decrease sagebrush and grassland 

productivity and alter species composition 

(Poore et al. 2009). However, productivity 

is influenced by species diversity and grazing intensity (De Valpine and Harte 2001). 

Warming experiments in a montane grassland enhanced the growth of sagebrush 

compared to herbaceous species (Perfors 

et al. 2003). However, grasslands do not appear to be as responsive to warming as other 

community types such as tundra and forests 

(Rustad et al. 2001). Because grasslands 

are primarily limited by water and nutrient 

availability, an alteration in precipitation 

and fertilization may have larger effects 

than does temperature change (Parton et al. 

1994). Changes in the frequency, duration, 

or quantity of precipitation can cause large 

changes in productivity, composition, and 

fire regimes (Knapp et al. 2002). Precipitation increases may favor invasive species. 

For example, increases in snow were shown 

to increase the invasion of forbs into mixed 

grass prairie (Blumenthal et al. 2008). The 

invasion of sagebrush steppe by cheatgrass 

has been shown to be strongly influenced by 

temperature and precipitation (Chambers et 
31

Communities

al. 2009). Climate variability has been shown 

to promote stability in grasslands by promoting the coexistence of different plant species 

(Adler et al. 2006). Increased atmospheric 

CO2 may promote species compositional 

changes (Smith et al. 2000). There has been 

much work suggesting that rising CO2 concentrations may differentially affect C3and 

C4 grasses. These two pathways that plants 

use to capture CO2 during photosynthesis 

correspond to other traits such as feed quality, production, and frost tolerance. Enrichment experiments in the shortgrass steppe 

have seen moderate increases in C3 grasses 

(Morgan et al. 2004) and a large increase in 

shrub biomass (Morgan et al. 2007). Weed 

invasion may also be driven by atmospheric 

CO2 in semiarid ecosystems (Smith et al. 

2000). 

Large grazers and insect herbivores play a 

major role in structuring grassland communities. For instance, grasslands that evolved 

with large grazers, such as those east of the 

Rockies, have proved to be more resistant 

to invasion and degradation from cattle and 

development than have other areas (Mack 

1986). Moreover, productivity is increased 

in grasslands where native grazers are present (Frank and McNaughton 1993). During 

a warming period 55.8 million years ago, 

insect damage to plants increased and was 

correlated with rising temperatures (Currano 

et al. 2008). A study in Yellowstone National 

Park found that drought caused a decline in 

belowground productivity and altered the 

effects of grazers (Frank 2007). 

The best demonstrated effect of climate on 

grassland and sagebrush ecosystems is an 

indirect effect of fire. Large grassland fires 

typically follow a normal or wetter than 

usual summer the previous year and are 

more likely where exotic annual grasses are 

present (Knapp 1998). There is a well-established feedback loop in which fire promotes 

invasive grasses such as cheatgrass which 

promote more frequent fires (D’Antonio and 

Vitousek 2003). The cheatgrass-fire cycle has 

been a major factor in the loss of ecological 

integrity of sagebrush steppe ecosystems 

and, as previously discussed, climate change 

is likely to exacerbate a shift toward cheatgrass-dominated rangelands in the northern 

portions of the ROCO region (Chambers et 

al. 2009, Bradley et al. 2009). 

4.5 Projected trends

Over the short-term, the greatest threats to 

grasslands and sagebrush ecosystems come 

from oil and gas development, increasing 

urban and agricultural development, and 

invasive species. However, wildfires are 

increasing and likely to intensify in a warmer 

future with drier soils, longer growing seasons, and more severe droughts (Field et al. 

2007), and these may cause large changes in 

grassland and sagebrush ecosystems (fig. 8). 

Direct impacts on big sagebrush, a keystone 

species throughout its range, may also be 

severe (Smith et al. 1997). The species is not 

fire tolerant and once removed from large 

disturbances, is very slow to recover (Smith 

et al. 1997). Weed invasion typically follows 

removal of sagebrush (Prevey et al. 2010), 

and this disturbance will likely be exacerbated by drought-induced stress on the species 

(e.g., Poore et al. 2009).

Modeling suggests that climate change will 

likely increase net primary production in 

grasslands and decrease soil carbon, but high 

annual variability in plant production makes 

these projections uncertain (Parton et al. 

2005). Nutrient cycling and plant production are expected to occur more rapidly in 

response to climate change than changes in 

community composition (Parton et al. 1994). 

Climate change is also expected to cause 

major changes in grassland and sagebrush 

distribution across the landscape (Bachelet 

et al. 2001). Range expansions of woody 

species are predicted to continue, particularly the expansion of pinyon-juniper into 

sagebrush steppe and grasslands (Rowland 

et al. 2008), resulting in a decrease in sagebrush and an increase in woodlands across 

the West. Changes in grassland cover are 

more subtle, but cover is generally predicted 

to decrease (Bachelet et al. 2001). Cremer et 

al. 1996, who used an earlier generation of 

downscaled global circulation models to predict the response of warming and reduced 

precipitation scenarios in eastern Washington, suggested that native sagebrush would 

decline and a less productive, invasive-an-
32

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

nual dominated grassland would persist or 

increase. Such a shift has major implications 

for sagebrush-obligate vertebrates such as 

certain bird species (Knick et al. 2005). Climatic suitability models suggest that by 2100 

sagebrush communities in Nevada, southern 

Idaho, Utah, Colorado, and eastern Wyoming may be at risk of loss due to climate 

change; regions in southwestern Wyoming 

will be at less risk (Bradley 2010). 

There are a number of uncertainties in 

projecting the response of grasslands and 

sagebrush to climate change. First, regional, 

elevational, and grassland type may strongly 

influence response. A recent estimate of the 

velocity of climate change across biomes 

found that temperature changes will occur 

much more quickly in xeric shrublands and 

flooded grasslands than in other biomes, and 

much more slowly in montane grasslands 

(Laorie et al. 2009). Second, the magnitude 

and velocity of changes caused by the strong 

link between invasive species, fire, and grasslands and sagebrush is difficult to estimate. 

Third, precipitation and drought rather 

than temperature will likely drive changes 

in grasslands, and they are more difficult to 

predict. Fourth, the future impact of grazers 

is difficult to estimate, particularly as grassland fragmentation increases. Finally, many 

grassland and sagebrush systems are actively 

managed through livestock grazing, invasive 

species control, and prescribed and suppressed fire. 

4.5.1  Summary

Other immediate threats to grasslands and 

sagebrush such as invasive species and land 

use change appear to have outweighed the 

effects of climate change, but this assessment is likely to be modified if accelerated 

climate change continues. Observed changes 

over the last century and manipulative 

experiments suggest that warming, altered 

precipitation, and enhanced CO2 can alter 

the productivity and diversity of grasslands. 

These effects are expected to continue, but 

the magnitude of changes may be small. 

Models project a large reduction in the distribution of sagebrush in the next century as 

it is converted to woodlands. Big sagebrush, 

the keystone species throughout much of 

the assessment area, is fire intolerant and appears to be vulnerable to both warming and 

drought, and is therefore likely to decrease 

Figure 8. Conceptual diagram 

describing projected 

changes to sagebrush and grassland 

ecosystems.
33

Communities

throughout its range under climate change 

scenarios. However, the largest changes in 

sagebrush and grasslands are likely to occur 

where warmer temperatures and changing 

precipitation promote invasive species and 

altered fire regimes. 

35

Aquatic Systems Chapter 5: Aquatic Systems

The ROCO region contains an abundance of 

glaciers, snowfields, lakes, streams, wetlands, 

rivers, and managed reservoirs that provide 

critical water resources to human and wildlife populations and support sensitive plant 

communities. High-elevation and snow-driven ecosystems such as those in the ROCO 

region are particularly sensitive to climate 

change and have seen a decline in freshwater resources (Field et al. 2007). Snowpack, 

which varies across the ROCO region but is 

typically greatest in high-elevation forests, 

peaks in early April and melts off during the 

summer, contributing an estimated 75% of 

the water in streams. High-elevation areas 

feed lower elevations through a network 

of lakes, streams, groundwater, and wetlands. Water levels and peaks in streamflow, 

which follow predictably from the pattern of 

snowmelt, are typically greatest in the spring 

and lowest in the fall. However, dams and 

reservoirs are common throughout the West 

and have significantly altered natural flow 

regimes. 

Glaciers are common on the highest peaks of 

the ROCO region (Fountain 2006). Wyoming 

has the largest total area of glaciers (73.3 

km2) in the region and the most glaciers 

(1,475), most of which lie within the Teton 

and Wind River Ranges. Montana has 1,158 

glaciers covering 68.6 km2; Idaho has 208 

(2.6 km2), and Colorado has 141 (4.8 km2) 

(Fountain 2006). 

The ROCO region includes 26 stretches of 

river designated as “wild and scenic,” most 

of them in Idaho (NWSR 2010). The numerous reservoirs and natural lakes managed 

for public water supplies and recreation vary 

from small alpine tarns to Flathead Lake 

in Montana, the largest natural freshwater 

lake in the West. Moving north through the 

ROCO region, the extent and volume of 

surface waters generally increases, following 

the prevailing precipitation gradient (fig. 1). 

These streams, lakes, and rivers are fundamental components of the western landscape and their ecology is intimately linked 

to the watersheds that they drain. Numerous species are dependent on these aquatic 

resources for part (e.g., aquatic invertebrates 

and amphibians), or all of their life cycle 

(e.g., freshwater fishes and aquatic plants). 

In addition, they provide a broad spectrum 

of ecological services, including nutrient 

processing, hydrologic cycling, and multiple 

socioeconomic functions for humans (e.g., 

water sources, fisheries, recreation, and 

irrigation). 

Although they comprise less than 5% of the 

land area in the ROCO region (OTA 1993), 

wetlands are an integral component of its 

aquatic resources. They provide numerous 

important ecological functions by supporting biodiversity, increasing water and carbon 

storage, improving water quality, and providing wildlife habitat (Mitsch and Gosselink 

2007). The most prevalent wetlands in the 

Rocky Mountains are associated with seepage slopes, river floodplains, surficial depressions, or the landforms associated with 

glacial retreat (Hauer et al. 1997).

There is much literature on how climate 

change may alter freshwater resources in 

the West (e.g., Ray et al. 2008, Williams et al. 

2009, CIG 2010, Pederson et al. 2010); fig. 

9). Here, we briefly summarize the observed 

and predicted changes in hydrology, surface 

water ecology, and wetlands. The effects of 

climate change on aquatic invertebrates, 

amphibians, and fish are discussed further in 

the wildlife section. 

5.5.1  Observed trends

Changes to the hydrology in the West over 

the past 50 years due to climate change 

are well documented (Barnett et al. 2008), 

although land use, invasive species, agriculture, and increasing human demands have 

played a large role in determining trends 

in aquatic resources. In the northern and 

central Rockies, streamflows have shifted 

toward earlier peak runoff, which has been 

attributed to more precipitation falling as 

rain rather than snow and earlier snowmelt 

(Knowles et al. 2006, Hamlet et al. 2005; 

Mote 2005). Warmer and more variable 

winter and spring air temperatures (Sheppard et al. 2002, Abatzoglou and Redmond 

2007) have accelerated melt and caused an 

overall decline in spring snowpack, particu-
36

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

larly at lower elevations, despite increases in 

winter precipitation in many places (Mote et 

al. 2005, Field et al. 2007, Mote et al. 2008a, 

Ray et al. 2008). Reduced snowpacks have 

melted earlier and have advanced the timing of peak runoff by several days to weeks 

across much of the region (Stewart et al. 

2005; Barnett et al. 2008). The most dramatic 

change in the past 50 years has been the 

decline of glaciers throughout the region. In 

1993 the largest glaciers in Glacier National 

Park were measured at 72% of their 1850 

areal extent and many small glaciers had 

vanished (Hall and Fagre 2003; Pederson et 

al. 2004). Although the distribution of lakes 

changed dramatically as the balance among 

precipitation, evapotranspiration, and runoff 

shifted during previous periods of climate 

change (Street and Grove 1979), a more recent change in lake distribution has not been 

reported for the region.

Changes in hydrological regimes have 

impacted the ecology of western aquatic 

resources (Barnett et al. 2008). For instance, 

warming temperatures may be contributing 

to the spread of the diatom Didymosphenia 

geminate, with more extensive nuisance 

growths becoming common in the region 

(Kumar et al. 2009). Another study documented that mayflies and other aquatic 

insects on which trout feed are emerging 

earlier and at smaller sizes in Rocky Mountain streams because of warmer streamflows 

and earlier peak runoff (Harper and Peckarsky 2006). Higher stream temperatures 

also affect fish access, survival, and spawning 

(Morrison et al. 2002; Keleher and Rahel 

1996; Rieman et al. 2007; Williams et al. 

2009). Increased wildfire activity has caused 

more debris flow events in streams with the 

potential to alter stream structure and function (Westerling et al. 2006; Morgan et al. 

2008). 

5.5.2  Projected trends

Climate change will significantly impact 

ROCO aquatic resources and will likely make 

it more difficult to achieve water quality standards nationwide (Field et al. 2007). While 

there are likely to be regional variations, 

projected effects across the West include 

loss of glaciers, less snow, earlier peak flows, 

less streamflow, warmer water temperatures, 

more frequent droughts, and more intense 

storms (fig. 9). 

At the current rate of melting, it has been 

suggested that the Glacier National Park’s 

remnant glaciers will be gone in the next 

25 to 30 years (Hall and Fagre 2003) due to 

increases in summer temperatures and a 

reduction in winter snowpack. Streamflow 

may increase during this initial period of 

melt, but flows will decline when the glaciers disappear (Morris and Walls 2009). 

Total winter precipitation may increase but 

overall snowpack is projected to decline 

throughout the West. For example, with a 

4oC (7°F) temperature increase and doubling 

of atmospheric CO2 in Loch Vale Watershed 

at Rocky Mountain National Park, models 

predict a 50% reduction in snowpack and 

4–5 week earlier increases in soil moisture 

and runoff compared to mean onset of 

spring conditions from 1984 to 1998 (Baron 

et al. 2000b)

The loss of winter snowpack will greatly 

reduce the major source of groundwater 

recharge and summer runoff, resulting in 

a potentially significant lowering of water 

levels in streams, rivers, lakes, and wetlands 

during the growing season (Mote et al. 2005; 

Barnett et al. 2008). With warmer temperatures and increasing droughts, municipal and 

agricultural demands for water are likely to 

increase, drawing down freshwater resources even further (National Assessment Synthesis Team 2001). Lower summer base flows 

reduce the amount of instream habitat for 

invertebrates and fish and cause a reduction 

in stream-side groundwater tables which are 

important for sustaining riparian vegetation 

communities (Stromberg et al. 1996; Scott 

et al. 1999). Reduced water depths may also 

increase the vulnerability of sensitive species (e.g., amphibians) to harmful ultraviolet 

radiation (Kiesecker et al. 2001). 

In addition to the shift in the quantity of water, climate change may reduce water quality due to increased erosion and decreased 

dilution of pollutants. Decreases in snow 

cover and more winter rain on bare soil are 

likely to lengthen the erosion season (Walker 

2001), which could lead to average phosphorus concentrations in streams increasing 25 

to 35% (Walker 2001). Predicted increases in 
37

Aquatic Systems

the severity and frequency of floods may also 

contribute to increases in erosion, as well as 

affect ecological processes that are sensitive 

to changes in the probability distributions 

of high flow events such as habitat stability, 

biodiversity, and trophic structure (Konrad 

and Booth 2005, Hamlet and Lettenmaier 

2007). Degradation of water quality will 

likely lead to a reduction in or loss of sensitive stream species (Waters 1995). 

Warming air temperatures and a reduction 

in glacial inputs will lead to warmer water 

temperatures across the West. Surface and 

bottom water temperatures of lakes, reservoirs, rivers, and estuaries are projected 

to increase from 2 to 7°C (4–13°F) (Fang 

and Stefan 1998, 1999; Hostetler and Small 

1999; Gooseff et al. 2005). Warmer waters 

may lead to oxygen depletion, a change in 

fish distribution, an increase in algae and 

zooplankton in coldwater lakes, and a loss 

of some species. Species that are isolated 

in habitats near thermal tolerance limits or 

that occupy rare and vulnerable habitats like 

alpine wetlands may become extinct (Williams et al. 2007), and fish such as trout that 

are dependent on cool waters will likely 

decline (Williams et al. 2009; Pederson et al. 

2010). In contrast, many fish species that prefer warmer water, such as largemouth bass 

and carp, may expand their ranges if surface 

waters warm (Battin et al. 2007). Warmer 

waters may also cause aquatic diseases and 

parasites to become more widespread (Hari 

et al. 2006). 

5.1 Wetlands

Wetlands are among the most significantly 

altered ecosystems in North America due to 

stressors such as changes in hydrology from 

flow regulation, ground water pumping, fill 

placement, overgrazing by domestic and native ungulates, atmospheric deposition, and 

biological invasion (Patten 1998, Zedler and 

Kercher 2005). Over the last 200 years, wetland areas have declined approximately 56% 

in Idaho, 50% in Colorado, 38% in Wyoming, and 27% in Montana (OTA 1993). Like 

other freshwater ecosystems, wetlands are 

considered extremely vulnerable to climate 

change, which is projected to diminish their 

number and extent and cause a decline in 

associated flora and fauna (Field et al. 2007). 

Wetlands are already facing widespread 

Figure 9. Projected 

climate changes 

to the hydrological 

cycle in the Rocky 

Mountains and 

Upper Columbia 

Basin.
38

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

degradation so that even small reductions in 

precipitation could exacerbate wetland loss. 

A few of the wetland types considered at 

greatest risk globally are found in the ROCO 

region, including riparian wetlands in arid 

zones, peatlands, and alpine wet meadows 

(OTA 1993, Burkett and Kusler 2000). But 

despite the recognition of the increasing 

role of climate change in altering wetland 

functions (e.g., Baron et al. 2000b), there 

is a paucity of studies in the ROCO region 

that document climate-driven declines in 

wetland function or extent. One exception is a recent article describing changes in 

hydrology leading to wetland desiccation in 

Yellowstone National Park (McMenamin et 

al. 2008). Currently, the biggest losses are in 

the marshes on Yellowstone’s northern range 

(Colorado State University, David Cooper, 

Research Scientist, email, May 2010). It is 

expected that loss of wetlands will result in a 

corresponding loss in biodiversity and critical functions such as carbon storage in peat 

and water storage (OTA 1993). 

Warmer temperatures will affect the growth 

and reproduction of wetland species by 

increasing decomposition rates and evaporation from wetlands and their water supplies, 

reducing peat accumulation, and thawing upper layers of permafrost in alpine 

wetlands (Burkett and Kusler 2000, OTA 

1993). Where warmer temperatures lead to 

increased fire severity and extent, peat bodies, particularly those in a matrix of forest, 

will be at risk. Where warmer temperatures 

cause an increase in wetland decomposition 

rates and reduce peat accumulation, carbon 

storage will be reduced.

Greater changes in wetlands are expected 

to result from altered precipitation as it affects soil and vegetation conditions (Winter 

2000). Many models project wetter winters 

in the ROCO region, but any positive effect 

of increased winter flows for wetlands is 

expected to be outweighed by drier summers 

and warmer temperatures. It is predicted 

that wetlands response will first become evident in water table changes and alterations 

in the formation and duration of soil anoxic 

conditions. Alterations in the composition of 

short-lived and then longer-lived perennial 

plants will follow. Soils may be altered after 

many decades unless fire occurs. Alterations of plant cover and soil permeability 

may act in a feedback loop to further modify 

the hydrological cycle. Some wetlands, such 

as forest wetlands and wet meadows, are 

particularly sensitive to hydrological changes 

and a reduction in the water table of a few 

inches could convert wetlands to upland 

habitats (Kusler 2006). 

Reduced ground water flow due to lower 

snowpack, earlier melt dates, or reduced 

summer precipitation could result in lower 

water tables in wetlands dependant on 

ground water inputs (Poff et al. 2002). Riparian wetlands will be sensitive to precipitation 

because changes in the timing and magnitude of flooding will affect the flux of water, 

nutrients, sediment, and biota between main 

river channels and riparian wetlands (Hauer 

et al. 1997). 

5.1.1  Summary

Climate change is a significant threat to the 

structure and function of US aquatic ecosystems. Changes in precipitation and warmer 

temperatures will have negative impacts on 

western water resources and there is high 

confidence that climate change will make 

it more difficult to maintain existing water 

quality due to warmer water temperatures 

and increasing erosion (Field et al. 2007). 

Warmer temperatures and earlier runoff will 

likely result in less available water for summer irrigation needs (Barnett et al. 2009, 

Knowles et al. 2006). Although rare, wetlands are hotspots of biodiversity and critical 

components of hydrological and biogeochemical cycles in the ROCO region. Wetlands have been reduced dramatically in the 

last century due to agriculture, development, 

and water management practices. It has only 

recently been recognized that climate change 

may also play a role in the loss of wetlands. 

Alpine wetlands, peatlands, and riparian 

corridors in arid regions may be particularly 

vulnerable.

While there is high confidence that climate 

change will alter freshwater ecosystems, 

numerous uncertainties exist. Many of the 

projected changes are based on precipitation 

changes, which are inherently more difficult 

to model than temperature. Moreover, the 
39

Aquatic Systems

magnitude and frequency of extreme events 

such as droughts and floods are unpredictable, and these will have large impacts on 

water resources. The interacting effects of 

other stressors such as pollution, ultraviolet 

light, diseases, and environmental toxins 

with climate change are unknown. Moreover, the ramification of changes in food web 

structure and dynamics caused by the loss 

of some species and the expansion of others 

is unclear. Finally, and perhaps most importantly, the threat to water resources posed 

by increasing human demand is difficult to 

quantify. 

41

Wildlife Chapter 6: Wildlife

The ROCO region is a diverse landscape 

with habitats ranging from alpine tundra to 

arid plains. Sparse settlement has left much 

of the habitat relatively intact and it is one 

of the last places in the continental United 

States with an intact assemblage of carnivores including gray wolves, grizzly bears, 

wolverine (Gulo gulo), and Canada lynx 

(Lynx canadensis). Within Colorado, Wyoming, Idaho, and Montana are 34 animal 

species listed as threatened or endangered, 

including gray wolves, Canada lynx, and 

grizzly bears, bull trout (Salvelinus confluentus), and black-footed ferrets (Mustela nigripes), and each of the four states has identified 200–300 species (about 10–20% of the 

fauna) as being of special management concern (CODoW 2009, IDFG 2009, MTNHP 

2009, WGFD 2009). The taxa at the greatest 

current risk proportionally are freshwater 

fish and amphibians (IDFG 2009). 

6.1.1  Observed trends

The abundance and diversity of wildlife in 

the West has declined due to severe hunting 

and trapping pressure in the past and landuse changes in more recent years. While 

hunting pressure has decreased since the 

early 1900s, development has accelerated. 

Increases in disturbance, fragmentation, and 

invasive species resulting from human development are a severe and immediate threat 

to wildlife in the ROCO region. Changes in 

climate, however, are already altering animal 

populations at global scales (Parmesan and 

Yohe 2003). There is evidence that warmer 

temperatures and changes in precipitation 

have caused range shifts, changes in population size, altered phenology, increases in 

disease prevalence, and altered migration 

patterns (Walther et al. 2002, Root et al. 

2003). Moreover, climate change has indirectly affected animal populations through 

its effects on disturbance regimes, such as 

fire frequency, and the abundance and distribution of exotic species (Logan et al. 2003). 

Some of the best documented effects of 

climate change on wildlife are from its effects on range size, population growth, and 

phenology. Range shifts have been well 

documented in a variety of species, including 

birds (see references in Parmesan 2006), butterflies (Crozier 2003, 2004, Forister 2010, 

Parmesan 1996), Odonata (dragonflies and 

damselflies) (Hickling et al. 2005), and small 

mammals (Moritz et al. 2008). Several of 

these species have moved their range upward 

in elevation as a result of warmer temperatures (Parmesan 1996, Parmesan and Yohe 

2003). Concurrently, high elevations species such as pika have seen substantial range 

contractions (Moritz et al. 2008). Reduced 

precipitation, especially less snow, has created more favorable conditions for elk population growth in Montana (Creel and Creel 

2009) and is predicted to improve conditions 

for elk in Colorado (Wang et al. 2002). Bats, 

which are difficult to study and generally 

under-represented in climate change assessments, are strongly controlled by environmental constraints on their physiology and 

tight energy budget (Humphries et al. 2002). 

Warming and altered precipitation under 

accelerated climate change are predicted to 

cause species range shifts and population 

declines, but no studies have documented 

recent shifts (Humphries et al. 2002, Adams and Hayes 2008). Changes in phenology and migration may cause asynchronies 

between wildlife populations and food 

sources, resulting in population declines, 

as has been seen for flycatchers (Ficedula 

hypoleuca) (Both et al. 2006). Asynchronies 

have developed for marmots and their food 

plants in the Rocky Mountains (Inouye et al. 

2000), but there is no evidence of population declines. While there are many reports 

documenting the effects of climate change 

on wildlife in the ROCO region, they may 

not reflect the true effects of climate change 

because monitoring and research efforts are 

geographically and taxonomically biased 

(Joyce et al 2008). For instance, it appears 

from the literature that range expansions in 

birds may be the most common ecological 

consequence of climate change in the region 

(fig. 10), but other taxa are also presumably 

responding to climate change.

6.1.2  Projected trends

The IPCC predicts that climate change will 

continue to pressure species to shift their 

ranges northward and upward, causing a 
42

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

fundamental rearrangement of North American ecosystems (Field et al. 2007). While 

past warming was gradual, future change is 

expected to be more rapid and outpace wildlife’s ability to adapt to new environments 

(Bradshaw and Holzapfel 2006). The magnitude and direction of species response to climate change will be highly variable and may 

differ among populations or regions (Parmesan 2006). For instance, small mammals in 

the West are more adapted to experiencing 

temperature variability in the southern parts 

of their range than in the northern parts, and 

this may buffer the effects of climate change 

in southern populations (Guralnick 2006). 

An analysis of potential climate change 

impacts on US national parks indicates that 

on average about 8% of current mammalian 

species diversity may be lost (Burns et al. 

2003). The greatest losses are predicted to 

occur in rodent species (44%), bats (22%), 

and carnivores (19%) (Burns et al. 2003).

Although wildlife responses are expected to 

be complex and species-specific, several patterns can be projected based on life-history 

characteristics. First, highly mobile species 

with large geographic ranges, wide physiological tolerances, faster generation times, 

and generalist diets are more likely to adapt 

to a changing climate, while endemic specialists are projected to decline. For example, 

global change is generally predicted to increase the spread of invasive species (Dukes 

and Mooney 1999), and generalists such as 

coyotes (Canis latrans) are expected to expand their range further north. Threatened 

and endangered species, particularly those 

with low genetic diversity, small population 

sizes, and narrow ranges, will be increasingly threatened by climate change. As an 

example, bull trout, which are dependent 

on cool water temperatures, are expected to 

continue to decline and populations will be 

restricted to high elevations (Rieman et al. 

2007). Bats are considered susceptible to climate change because of their slow reproduction rate, sensitivity to roost temperatures 

and water availability close to their roosts, 

and dependency on the availability of large 

insect populations (e.g., Adams and Hayes 

2008).

Second, species that are currently limited 

by temperature or precipitation are likely to 

respond more quickly to climate change than 

are other species. While disease and invasive 

species are driving a decline in the abundance and diversity of freshwater fish and 

amphibians in the ROCO region, these species’ sensitivity to warming temperatures is a 

contributing factor. Snow-dependent species 

such as wolverine, lynx, and snowshoe hare 

(Lepus americanus) are considered particularly vulnerable to climate change. For example, modeling of potential future climate and 

subsequent changes in vegetation and snow 

cover indicates that potential lynx habitat 

may decrease significantly by 2100 (Gonzales 

et al. 2007). Wolverines are dependent on 

Figure 10. Documented terrestrial 

wildlife response to 

observed changes 

in climate, based on 

189 studies within 

the United States; 

none included Hawaii. From Joyce et 

al. 2008. 
43

Wildlife

persistent spring snow cover for successful 

denning and, as climate warms, fewer sites 

will be suitable, connectivity among sites will 

decrease, and there may be substantial loss in 

the wolverine’s range (Copeland et al. 2010). 

Third, climate change is expected to alter the 

distribution of vegetation, which will alter 

the availability of wildlife habitat. Several 

community types are likely to greatly decrease in area, including alpine, subalpine 

spruce-fir, and sagebrush (fig. 5; Lenihan 

et al. 2008; evidence from sagebrush bird 

declines supports this contention (Knick et 

al. 2003, Aldridge et al. 2008). Climate-driven 

losses of high-elevation habitat are expected 

to contribute to declines of many mammals including grizzly bears, bighorn sheep, 

pikas, mountain goats, and wolverines (GAO 

2007). Similarly, movement patterns of deer, 

bighorn sheep, and elk may be affected temporally as snowpack patterns shift (Janetos 

et al. 2008). A projected 60–90% loss of 

suitable bird habitat is predicted to decrease 

neotropical migratory bird species richness 

30–57% during the next century (Price and 

Root 2005).

Above, we have described in general terms 

the recent and predicted trends of wildlife 

responses to climate change in the ROCO 

region. We now highlight select species or 

taxa that are of particular concern to land 

managers or may be especially good indicators of the broader effects of climate change. 

These case studies include fish, amphibians, 

birds, pika, invertebrates, ungulates, and 

grizzly bears.

6.1 Fish 

Of the roughly 800 native freshwater fishes in 

the United States, only about 21% are found 

in the West. However, the ROCO region contains many threatened or endangered fish, 

including greenback cutthroat (Oncorhynchus clarki stomias), bull trout, pike minnow (Ptychocheilus lucius), several species 

of salmon, and white sturgeon (Acipenser 

transmontanus) (CODoW 2009, IDFG 2009, 

MTNHP 2009, WGFD 2009). 

Warmer stream and lake temperatures and 

changing streamflow will affect fish access, 

survival, and spawning (Morrison et al. 

2002). While climate change is expected to 

have a large impact on all native fish, trout 

and salmon will likely fare worse than many 

because of their dependency on cool, clear 

water and because they have narrow thermal 

tolerances (Williams et al. 2007). Salmonids 

may provide an early indicator of climate 

change in the ROCO region (Pederson et al. 

2010), where warming is projected to cause 

a loss of up to 42% of current trout and 

salmon habitat by the end of the century and 

losses of western trout populations may exceed 60% (Keleher and Rahel 1996). Losses 

of migratory bull trout may be as high as 

90% (Rieman et al. 2007). In addition to the 

direct effect of warmer water temperatures, 

fish populations will be indirectly affected by 

warmer waters promoting the expansion of 

aquatic invasive or nuisance species such as 

Didymosphenia geminate (Kumar et al. 2009) 

and invasive aquatic plants which can alter 

food web dynamics and oxygen availability. 

Aquatic invertebrates, which are the primary food source for trout and fish, will be 

affected where climate causes earlier emergence, species loss, or smaller size (Harper 

and Peckarsky 2006). Changes in streamflow 

and fire regimes will also likely contribute to 

habitat loss (Pederson et al. 2010).

6.2 Amphibians

Amphibians are likely to be highly sensitive to climate change (Blaustein et al. 2001; 

Carey and Alexander 2003; Corn 2005; 

Lawler et al. 2010b) and have been identified as one of the taxonomic groups showing 

early responses to it (McCarty 2001; Walther 

et al. 2002). Within the Western hemisphere, 

amphibians are predicted to experience 

more range shifts than either birds or mammals (Lawler et al. 2009). Climate change is 

expected to have large effects on amphibians because as ectotherms, all aspects of 

their physiology and life history are strongly 

influenced by their physical environment. 

Direct effects of climate change on amphibians include changes in movements, phenology, and physiological stress. Indirect effects 

include changes in predators, competitors, 

food supply and habitat (Donnelly and 

Crump 1998), and invasive species, e.g., bullfrogs (Ficetola et al. 2007). The documented 

and anticipated impacts of climate change on 
44

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

amphibians vary according to species-specific life history traits and although generally 

considered detrimental, may in limited cases 

by beneficial (McCarty 2001; Werner et al. 

2009). Region-specific empirical data are 

limited, but below we briefly review some of 

the general concepts of how climate change 

may affect amphibians in the ROCO region.

Precipitation has a strong influence on amphibian abundance, activity and migration. 

Populations of several species have declined 

dramatically in years of drought (Stewart 1995; Pounds and Crump 1994). Low 

precipitation or drought can decrease the 

amount of available wetland breeding habitat, reduce water depth thereby exposing 

amphibian embryos to more extreme water 

temperatures, and increasing the potential 

for pond drying before metamorphosis occurs. Climate change also has the potential 

to fragment amphibian habitat and result in 

dry open areas that are barriers to dispersal 

(Dodd and Smith 2003). Gibbons and Bennett (1974) reported that activity patterns 

among 16 frog species were positively correlated with the incidence of precipitation, 

and it is generally thought that precipitation 

increases the ability of amphibians to move 

across the landscape. Species associated with 

ephemeral waters, including shallow ponds 

and intermittent streams, may be particularly 

vulnerable to altered precipitation patterns. 

Amphibian monitoring in Grand Teton and 

Yellowstone national parks showed that in 

2007 and 2008 the majority of amphibian 

breeding sites were in temporary or seasonally flooded wetlands and the minority were 

in saturated or semi-permanent wetlands 

(Patla et al. 2009). McMenamin et al. (2008) 

documented an increase in the number of 

permanently dry ponds in Yellowstone’s 

Lamar Valley over a 16-year period and a 

concomitant reduction in the number of 

remaining wetlands that were occupied by 

amphibians (but see Patla et al. 2009). However, the documented and anticipated effects 

of climate change on amphibians are not all 

detrimental. Werner et al. (2009) found that 

drought greatly reduced pond hydroperiods 

and caused a corresponding decrease in 

predator densities, which lead to increased 

colonization probability and decreased extinction probability for chorus frogs (Pseudacris triseriata).

Temperature also exerts a strong influence 

on amphibian survival and reproduction. 

Environmental temperature affects growth 

rates, time to reach metamorphosis, mechanisms of gas exchange, and rates of energy 

metabolism (Ultsch et al. 1999). Amphibians 

use behavioral and physiological mechanisms for thermoregulation but are limited 

by their need for water (Hutchison and 

Dupre 1992). The temperature tolerance of 

anuran larvae is a key factor in determining the species’ range limits. Kiesecker et al. 

(2001) found that ENSO events in the Pacific 

Northwest resulted in low winter precipitation, and in the spring following an ENSO 

event, boreal toad (Bufo boreas) embryos developed in shallower water and had greater 

mortality than in wetter years when embryos 

developed in deeper water. In years with low 

precipitation, infection of toad embryos by 

the pathogenic fungus Saprolegnia ferax was 

>50% at water depths <20cm. Furthermore, 

Kiesecker and Blaustein (1995) documented 

that boreal toad embryos are only susceptible to S. ferax in the presence of UV-B 

radiation. However, in a related study, Corn 

and Muths (2002) found that earlier breeding during dry years minimized exposure 

to UV-B due to shallow water depths; they 

proposed extreme water temperatures as an 

alternative or additional plausible hypothesis 

to explain the high mortality of boreal toads 

observed by Kiesecker et al (2001). Still, 

these studies suggest that climate change has 

the potential to increase the prevalence of 

infectious disease.

Chytridiomycosis is a potentially lethal disease caused by the amphibian chytrid fungus 

(Batrachochytrium dendrobatidis) that has 

been implicated in population declines of 

several amphibian species throughout the 

world (Daszak et al. 1999; Carey 2000; Muths 

et al. 2008). Several studies suggest that 

climate change may enable the fungus to expand its range due to warmer temperatures 

and moisture at higher elevations (Bosch et 

al. 2007; Pounds et al. 2006). Boreal toads 

appear to have experienced a population 

decline across the Rocky Mountains from 

north to south, a pattern potentially associated with the distribution of chytrid fungus. 

Muths et al. (2008) found that the fungus is 

widespread in the Rocky Mountains from 

northern Montana to southern Colorado. 
45

Wildlife

The fungus was found at a higher proportion 

of low-elevation boreal toad breeding sites, 

and results from this study suggested that 

the distribution of chytrid fungus is limited 

by temperature, which is moderated in the 

higher elevations. Increased temperatures 

associated with climate change are likely to 

allow the expansion of chytrid fungus into 

high elevation areas.

Climate change has been associated with 

phenological changes in several amphibian 

species. Beebee (1995) documented earlier 

breeding correlated with increasing temperatures since the 1970s for two species of frogs 

and four salamanders in Britain. However, in 

montane habitats winter snow accumulation 

is more important than temperature in predicting the behavior of amphibians (Inouye 

et al. 2000; Corn and Muths 2002). Corn 

(2003) found a strong correlation between 

timing of breeding and both snow water 

equivalent and air temperature for amphibians in the Pacific Northwest. Although some 

studies have not found significant changes 

in amphibian breeding phenology, Beebee 

(2002) suggested that interspecies differences 

in reproductive biology might explain differing responses to warming temperatures. In 

Britain, the “explosive” breeders that spawn 

early in the year have shown minimal signs 

of response to climate change, whereas the 

later and more protracted breeders, which 

include urodeles or salamanders, have bred 

progressively earlier over the past 20 to 30 

years (Beebee 2002). 

In summary, the effects of climate change on 

amphibians are expected to be multi-faceted 

and include direct physiological impacts as 

well as indirect impacts to the species’ habitat, competitors, predators, and pathogens.

6.3 Invertebrates

The population size and range of numerous 

species of mollusks, amphipods, butterflies, 

and aquatic invertebrates have declined in 

the last century, and invertebrates now make 

up roughly half of the species of special 

concern in Colorado, Idaho, Wyoming, and 

Montana despite being one of the least wellstudied taxa (CODoW 2009, IDFG 2009, 

MTNHP 2009, WGFD 2009). Invertebrate 

declines are attributed to a variety of causes, 

including land use, invasive species, changing food web dynamics, and climate change. 

However, some invertebrates are increasing their geographic range and population 

size in response to climate change, as has 

been seen for disease vectors like ticks and 

mosquitoes (Field et al. 2007). This is not 

surprising because invertebrates, which are 

ecotherms, are generally expected to increase activity and reproduction in warmer 

temperatures. Their short generation times 

also increase the capacity of invertebrates 

to adapt to changing conditions (Parmesan 

2006). For many species of invertebrates, 

however, drought and changing biotic interactions have outweighed any positive effects 

of warmer temperatures, and evolutionary 

responses to climate change are not occurring rapidly enough to prevent extinctions 

(Parmesan 2006).

Aquatic insect assemblages are thought to 

be particularly vulnerable to climate change, 

and experiments support the expectation 

that the structure and function of these communities will be altered (Hogg and Williams 

1996). For example, as alpine stream temperatures rise and flow regimes change, rare, 

cold-water-obligate, aquatic invertebrate 

species may be driven to extinction (Hauer 

et al. 1997). Higher water temperatures can 

increase the rate of microbial activity and decomposition of organic material, which may 

result in less food being available for invertebrates (Meyer and Edwards 1990). Moreover, warmer temperatures will allow many 

lower-elevation invertebrates to colonize 

alpine streams and lakes, causing changes in 

food-web dynamics (Hauer et al. 1997).

Terrestrial invertebrates are also likely to 

be responsive to climate change. Endemic 

insects that have limited home ranges, 

such as the Great Sand Dunes tiger beetle 

(Cicindela theatina), may be sensitive to loss 

of habitat in a warmer, drier climate. Pollinators such as bees may be at risk where 

plant composition and phenology changes; 

asynchronies between insects, pollinators, 

and flowering plants have been documented 

(Visser and Both 2005). The best evidence of 

the ecological response of invertebrates to 

climate change comes from butterflies. Many 

populations of Edith’s checkerspot butterfly 
46

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

(Euphydryas editha) in the western United 

States, Canada, and Mexico have gone 

extinct in the last century and extinction 

rates were significantly lower at high elevations and high latitudes (Parmesan 1996). 

Alpine butterflies are particularly vulnerable 

to changes in climate because their brief life 

cycle is highly correlated with the melting of 

snow and increasing summer temperatures 

(McLaughlin et al. 2002). For the alpine 

butterfly, encroaching forests into meadows 

may reduce dispersal and gene flow among 

populations (Roland and Matter 2007). During the last 35 years there has been a general 

trend for butterfly species richness to decline 

and an upward migration of butterfly ranges 

in California (Forister et al. 2010). 

At this point, it is difficult to distinguish 

among the effects of climate change, landuse change, and other stressors on invertebrate populations. However, despite relatively fast generation times, it is clear that 

many invertebrates are sensitive to climate 

and species with isolated or rare populations 

may be particularly vulnerable. 

6.4 Birds

Birds have been suggested as ideal early 

indicators of climate change (Berthold et 

al. 2004; Fiedler 2009; Niven et al. 2009) 

because they are sensitive to weather and 

climate and are generally easy to detect, 

identify, and count, and much knowledge 

base exists regarding their life history and 

population trends. Because they are wellstudied and include both widespread and 

geographically restricted species, they are 

considered an ideal class of organisms with 

which to investigate and test the current and 

predicted impacts of climate change.

More is known about the responses of birds 

to climate change than any other group of 

animals (Wormworth and Mallon 2008) 

and the evidence that recent climate change 

has already begun to affect birds is compelling. Almost all aspects in the life cycle of 

birds that have been studied so far show 

recent changes that can be linked to climate 

change, including the declining size of North 

American birds (Van Buskirk et al. 2010). 

Avian responses to climate change can be 

broadly categorized as changes in range 

and distribution, phenology, behavior, and 

morphology (Fiedler 2009; Van Buskirk et al. 

2010). Weather conditions are known to affect avian metabolic rates (e.g., cold weather 

increases the energy expenditure necessary 

for body maintenance), the abundance and 

distribution of their prey, and their ability 

to forage, migrate, and carry out courtship 

behaviors. Extreme weather events such as 

prolonged freezes or droughts can have catastrophic effects on juvenile and adult birds 

(Schreiber and Schreiber 1984; Stenseth et 

al. 2002). Climate change is anticipated to 

affect the staging, stopover ecology, and fuelling of migratory birds (DEFRA 2005).

Documentation of range shifts was employed early on to detect the ecological 

effects of climate change (Vitousek 1992). 

Documented changes in bird ranges and 

distribution are numerous and include both 

altitudinal (Pounds et al. 1999) and latitudinal shifts in breeding ranges (Hitch and Leberg 2007) and wintering ranges (La Sorte and 

Thompson 2007; Sekerciouglu et al. 2008). 

Niven and colleagues (2009), who analyzed 

Christmas bird count data (1966–67 through 

2005–06) to estimate population trends for 

North American bird species, found a significant northern shift in the latitudinal center 

of abundance in 177 of 305 species (overall 

mean shift = 56 km, 35 mi) coincident with 

a positive increase in monthly temperature 

over the 40-year period. Among the four 

habitat-based guilds they investigated, woodland birds, shrubland birds, and generalists 

showed significant shifts, while grassland 

birds did not. Further evidence that climate 

change is likely to be the cause of these range 

shifts is provided by Root (1988), who found 

that the entire length of the northern range 

limits of 62 species wintering in the conterminous United States and southern Canada 

was tightly associated with a particular average minimum January temperature isotherm. 

Substantial empirical evidence of range shifts 

occurring in the late 20th century (citations 

above and Walther et al. 2002; Parmesan 

and Yohe 2003; Root et al. 2003; Parmesan 

2006) confirms that a widespread ecological response to climate change is underway. 

Consequently, researchers are transitioning 

from documenting range shifts to attempt-
47

Wildlife

ing to forecast them (La Sorte and Jetz 2010). 

There is also a focus on improving predictions of extinction risk related to climate 

change (Shoo et al. 2005). Sekerciouglu et 

al. (2008) found that elevational limitation 

of range size explained 97% of the variation 

in the probability of 8,459 species of Western Hemisphere landbirds being in a World 

Conservation Union category of extinction 

risk. Many highland taxa will likely experience population decreases as climate change 

forces them to move to higher elevations 

(Pounds et al. 1999; Shoo et al. 2005). To improve the precision of estimates of climateinduced extinction risk, high-resolution (<1 

km, 0.6 mi) data on elevational limit shifts 

(Sekerciouglu et al. 2008) and spatial patterns of abundance within a species distribution are needed (Shoo et al. 2005). 

Phenological responses of birds to climate 

change are well documented, including 

earlier migration (Inouye et al. 2000; Sparks 

et al. 2005), development of partial migration (only part of a bird population migrates; 

Fiedler 2003), and earlier breeding (Crick et 

al. 1997; Dunn and Winkler 1999). Climate 

warming can cause negative impacts migration and breeding are no longer synchronized with the timing of peak resources. 

According to the phenology mismatch 

hypothesis, migrant birds that experience 

a greater rate of warming in their breeding 

grounds than their wintering grounds are 

likely to experience population declines 

because their migration will occur later and 

they may miss the beginning of the breeding 

season. Population trends are also expected 

to be negatively associated with migration 

distance because the potential for phenology mismatch increases with the number 

of staging sites. Jones and Cresswell (2010), 

who examined population and temperature 

trends in the wintering and breeding areas 

for 193 spatially separate migrant bird populations, found that phenology mismatch was 

correlated with population declines in the 

Nearctic, whereas migratory distance was 

more important in explaining population 

declines in the Paleaeartic. These results suggest that differential global climate change 

may already be contributing to the decline 

of some species, and the effect may be more 

important in the Nearctic. Furthermore, 

climate change is generally expected to be a 

greater threat to long-distance migrants than 

to resident species, and to species breeding 

in more strongly seasonal habitat (Winkler et 

al. 2002). 

In association with earlier breeding (Crick 

et al. 1997), clutch sizes have increased and 

nesting success has declined for some species (Both et al 2006). While earlier arrival at 

breeding sites and earlier onset of egg laying 

could lead to larger clutch sizes for some 

species, reduced survival of post-fledging 

birds may prevent these populations from 

increasing (Fiedler 2009). For example, Both 

et al. (2006) showed that populations of a 

small passerine had reduced nesting success 

and declined because the phenology of their 

main food supply during breeding had advanced faster than the birds’ breeding date. 

Almost all aspects in the life cycle of birds 

that have been studied so far show recent 

changes that can be linked to climate change. 

While relatively few studies have been conducted within the ROCO region, the responses of birds to climate change there are 

expected to be similar to those documented 

elsewhere. Generally speaking, birds with 

restricted ranges or bounded distributions 

(e.g., mountain-top species), poor dispersal 

ability, and small population size are most at 

risk of extinction. Species within the ROCO 

region that are known to be at heightened 

risk of extinction due to climate change 

are alpine birds such as rosy finches and 

ptarmigan. 

Because they are easy to detect, identify and 

count, are well-studied and include both 

widespread and geographically restricted 

species, birds have been suggested as ideal 

early indicators of climate change (Berthold 

et al. 2004; Fiedler 2009; Niven et al. 2009). 

6.5 Pika

The American pika is a small mammal related to rabbits and hares (Order Lagomorpha) 

that lives in montane rocky environments of 

western North America from British Columbia to the southern Great Basin (Smith and 

Weston 1990). In the ROCO region, pika can 

be found in lava flows at low elevations and 

in talus slopes of high alpine environments 
48

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

(Smith and Weston 1990). Over the last 

century, local populations in the Great Basin 

have disappeared coincident with warming 

temperatures (Beever et al. 2003, Beever et 

al. 2010), and their range in California has 

contracted and moved to higher elevations 

(Moritz et al. 2008). 

Pikas are suspected of being particularly 

vulnerable to climate change for a number of 

reasons. First, they are physiologically unable 

to survive high temperatures without access 

to cooler microclimates such as talus fields, 

which offer sub-surface temperatures several 

degrees cooler than shaded locations at the 

surface (MacArthur and Wang 1974, Millar 

and Westfall 2010) and high temperatures 

can limit foraging. Second, some populations 

of pika are snow-dependent because snowpack serves as insulation in winter months 

for active pikas in alpine regions (Morrison 

and Hik 2007). Where snowpack is reduced, 

pikas may die of exposure to low temperatures, and evidence for snowpack-demographic correlations has been described 

(Kreuzer and Huntly 2003, Morrison and 

Hik 2007, Beever et al. 2010). Finally, pika 

populations are restricted to isolated talus 

or lava flows and it is thought that they have 

low dispersal capacity (Hafner and Sullivan 

1995). 

Recent models predict that high-elevation 

pika habitats will see significant warming 

(Ray et al. 2010). Genetic evidence shows 

a very strong climate signal for Holocene 

range contractions (Galbreath et al. 2009). A 

recent study in Craters of the Moon showed 

that the species was restricted to the park’s 

highest elevation lava flows (Rodhouse et al. 

2010), suggesting that range shifts may occur 

along an elevational gradient, reflecting the 

direct impacts of temperature and precipitation. The US Fish and Wildlife Service, 

however, concluded that the best available 

scientific information indicates that pikas 

will be able to survive despite higher temperatures and will have enough suitable high 

elevation habitats to prevent them from becoming threatened or endangered (USFWS 

2010). Recent evidence suggests that many 

populations in the western Great Basin and 

Sierra Nevada are thriving (Millar and Westfall 2010), although the same study found the 

species to be elevationally restricted in other 

portions of the Great Basin. In summary, pikas are vulnerable to climate change but the 

magnitude of climate effects varies regionally 

and more research is needed to understand 

the future of pika populations in a warmer 

climate. 

6.6 Ungulates

The ecology of ungulates in the ROCO region is strongly influenced by climate. Summer precipitation, winter snow pack, and the 

timing of spring green-up affect their physiology, demography, diet, habitat selection, 

and predator-prey interactions. Ungulate 

body size and mortality have been shown to 

follow patterns of climate variability (Post 

and Stenseth 1999). For instance, moose 

survival has been linked to temperature and, 

in the southern areas of its range, warmer 

temperatures combined with high humidity 

may cause populations to decline (Lenarz 

et al. 2009). It is unclear whether the large 

increases in moose population in Colorado 

since its reintroduction in 1978 (Vieira 2006) 

is due to climate. The degree of response 

to climate change from species such as elk, 

moose, mule deer, and white-tail deer, and 

pronghorn antelope is uncertain. Some species such as pronghorn are threatened most 

by land-use change.

Ungulates dependent on high-elevation 

habitats, such as mountain goats and bighorn 

sheep, are expected to decline in response to 

warmer temperatures and habitat loss (GAO 

2007). Glacier National Park has lost about 

4% of its alpine zones to trees because of a 

warming climate, and this threatens mountain goat populations by reducing forage, 

providing shelter for predators, and fragmenting habitat (Fagre 2009). Bighorn sheep 

populations are inversely correlated with elk 

population size and are particularly sensitive 

to reductions in precipitation (Picton 1984). 

One of the key issues for ungulate management is wildlife disease, the spread and virulence of which is likely to be exacerbated by 

climate change (Harvell et al. 2002). Species 

such as bighorn sheep that are particularly 

sensitive to disease may be threatened. 

While some ungulates populations will 

decrease in a warmer climate, others that are 
49

Wildlife

currently limited by winter mortality may 

increase as winter snowpack declines. As 

discussed earlier, elk populations in Montana and Colorado are expected to increase 

as winters become less severe and forage 

plants increase in productivity (Wang et al. 

2002, Creel and Creel 2009). 

6.7 Grizzly bears 

The grizzly bear (Ursus arctos horribilis) is a 

subspecies of brown bear that once roamed 

the mountains and prairies of the West. Between 1800 and when the species was listed 

as threatened in 1975, grizzly populations 

south of Canada plummeted from 50,000 

animals to fewer than 1,000 (Tomback and 

Kendall 2002). Today, the grizzly bear remains in a few isolated locations in the lower 

48 states, including the Greater Yellowstone 

Area and parts of northern Montana and 

Idaho, where active recovery management 

has increased populations during the last 

two decades (Schwartz et al. 2006, Kendall 

et al. 2009). Current mortalities are primarily caused by human activity and population 

densities are generally inversely related to 

human population (Schwartz et al. 2006, 

Kendall et al. 2008, Ciarniello et al. 2009). 

Bear populations may decline as winter 

ungulate mortality decreases as a result of 

warmer temperatures and shorter winters 

(Schwartz et al. 2006) and because of projected declines in the availability of whitebark pine seeds (Kendall and Keane 2001). 

In the Greater Yellowstone Area, the frequency of captures of problem grizzly bears 

increases sixfold and bear mortality rates are 

two to three times higher during years of low 

whitebark pine seed production (Mattson 

and Reinhart 1997). Reductions in other 

important food sources such as native trout, 

army cutworm moth, and huckleberries as 

a result of warmer, drier conditions may 

contribute to grizzly decline. In a warmer 

climate, grizzly bears may increasingly rely 

on exotic species that are considered less 

nutritious than native food sources (Reinhart 

et al. 2001). In the Greater Yellowstone Area, 

males bears have shown later den entrance 

dates (Haroldson et al. 2002), and denning 

times are expected to be shorter as temperatures rise. Interactions with humans are 

expected to increase with land use changes, 

decreased denning, and declining food 

sources. 

It is unclear how climate change will affect 

grizzly bear populations. Through its effects 

on fire, insect outbreaks, and plant disease, 

climate will indirectly affect the food sources 

of bears and their potential for interacting 

with humans, and this could threaten their 

future. However, grizzly bears are highly 

mobile and generalist omnivores, two characteristics that suggest they will not be as 

sensitive to climate change as other wildlife. 

They may adapt to changing conditions, 

move to new areas and new food sources, 

and maintain their population sizes under a 

warmer climate.

6.7.1  Summary

There are numerous uncertainties involved 

in predicting wildlife responses to climate 

change, the largest being that associated 

with vegetation change. Shifts in vegetation 

and habitat availability, whether caused by 

climate or land use change, will have strong 

impacts on wildlife populations. Another 

uncertainty results from the lack of the basic 

life-history data needed to estimate vulnerability. How biotic interactions will be altered 

and to what degree this will affect populations remains unknown. Phenotypic plasticity and behavior adaptations may allow 

species to respond to change in unpredictable ways. The responses of wildlife to nonclimate stressors such as fire, disease, and 

invasive species may dampen or strengthen 

responses to climate change. 

There is evidence that warmer temperatures 

and changes in precipitation have caused 

range shifts, asynchronies, altered migration and hibernation patterns, increases in 

disease prevalence, and ultimately a reduction in the population size of many species (Walther et al. 2002, Root et al. 2003). 

Moreover, climate change can strongly affect 

animal populations through its effects on 

disturbance regimes, disease, land use, and 

invasive species. The predicted responses of 

wildlife to climate change are that: 

● Many species’ ranges will move northward 

and upward in elevation.
50

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

● Species will respond differentially, creating 

non-analog communities and asynchronies among interacting species.

● In most cases, climate changes will be 

more rapid than evolutionary adaptations.

● Species that are mobile, genetically diverse, show wide physiological tolerances, 

and have generalist diets will respond the 

most positively.

● Temperature-limited and snow-adapted 

species are at particular risk to a changing 

climate.

● Wildlife associated with habitat types and 

communities such as spruce-fir, alpine and 

sagebrush that are expected to decline are 

at greater risk.
51

Conclusions Chapter 7: Conclusions

Climate change is having significant effects 

on organisms and ecosystems throughout 

the ROCO region. Although uncertainties 

remain, for many processes and resources 

there is published evidence of observed 

responses to climate change within the last 

century and well-developed hypotheses and 

models that project a continued response 

during the next decade. This report provides a synthesis of information available as 

of March 2010, but because of the diversity 

of topics addressed and rapid progress in 

climate change science, we are sure to have 

missed some relevant literature.

We found that surface waters, glaciers, alpine 

communities, wetlands, fire regimes, wildlife and plant disease, narrowly endemic 

species, and freshwater fish are particularly 

responsive or vulnerable to climate change 

and may be useful indicators for the ROCO 

region. For many other ecological properties 

and processes, communities, and species, 

non-climate stressors such as pollution and 

habitat loss, are anticipated to drive changes 

over the next century. For instance, grasslands and sagebrush are extremely vulnerable to changes in fire regimes and biological 

invasions. Still, other systems and resources 

may respond to climate change by increasing 

population size and range. In many cases, 

we lack published evidence that link recent 

trends in a resource to climate change, but 

well-developed hypotheses suggest that the 

resource may be vulnerable in the future. For 

example, it is projected that bats and mounTable 2. Inventory, monitoring, and research needed to better understand ecological responses to 

climate change in the Rocky Mountains and Upper Columbia Basin.

Inventory, Monitoring, and Research Needs 

Climate and Air Quality 

Inventory & Monitoring 

• Increase climate monitoring at high elevations.

• Create baseline climate records that are appropriately QA/QC’ed for long-term trends and variability analyses. 

• Increase geographic coverage of air quality and visibility monitoring in remote areas.

• Monitor sensitive ecosystems for air pollution effects (e.g., species composition changes due to N 

deposition, ozone injury to plants in riparian or sagebrush areas).

Research 

• Downscale global and regional climate models to local and watershed scales.

• Conduct research on how N deposition and its ecological effects will change in a warming climate.

• Incorporate information on fire emissions, particulate matter concentrations, and visibility effects 

into fire management plans and models of fire effects.

• Examine the effects of energy development on ground-level ozone concentrations

• Improve region-wide atmospheric and ecosystem modeling to predict the effect of climate change 

on air quality and the resources sensitive to it.

Ecological Processes

Inventory & Monitoring

• Monitor key taxa or communities that are considered to be at risk of extinction.

• Monitor forest and grassland productivity across precipitation gradients. 

• Compile, analyze, and report on historical phenological records in the western United States. 

• Develop a phenology monitoring program and identify key taxa to monitor from the National Phenology Network or based on availability of historical data, projected response to climate change, or 

ease of measurement 

Research

• Research wildlife migration and dispersal, habitat-use, and metapopulation dynamics to aid in 

prioritizing management actions and documenting climate-driven changes. 

• Focus on the differential effects of climate change on interacting species to identify asynchronies 

and mismatches. 

• Conduct vulnerability assessments on communities and taxa (or groups of taxa such as tropical 

migrants) of concern.

• Identify opportunities to maintain and/or increase connectivity across the landscape.
52

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Table 2. (continued)

Disturbance Regimes

Inventory & Monitoring

• Improve early detection of native and non-native invasive species and other exotic species.

• Improve region-wide assessment, maps, and spatial data on invasive presence and cover.

• Monitor sensitive habitats for invasive spread (e.g., high elevations, wetlands, and areas containing 

species of conservation concern).

• Monitor visitor use and other vectors of invasive spread (e.g., fishing and boating activity).

• Collect baseline monitoring information on native and non-native organisms. 

• Increase collaboration and partnerships among federal, state, and private landowners to monitor 

disturbance and invasion across the West

Research

• Create bioclimatic models to predict the effect of climate change on invasive species ranges.

• Conduct research to discriminate between multiple climate variables’ effects on disease.

• Develop forecast models for epidemics. 

• Evaluate and understand the role of evolution in disease dynamics.

Alpine and Subalpine 

Inventory & Monitoring

• Monitor long-term changes in alpine vegetation.

• Monitor native and exotic plant and animal migration upslope.

Research 

• Research and monitor to document historical and future tree line movement in the mid- and southern Rockies through repeat photography and seedling establishment.

• Link changes in floras with fauna (e.g., plant community changes and pika/ptarmigan abundance).

tain ungulates will be sensitive to climate 

change, but there is little evidence that their 

recent population trends are climate-driven. 

As temperatures and precipitation patterns 

change over the coming decades, a better 

understanding of how climate change affects 

resources will become critical to effective 

mitigation and management. Climate change 

will interact with multiple stressors, such as 

land-use change, atmospheric pollution, and 

invasive species, many of which are more 

proximate than climate change, making it difficult to predict changes. The only certainty 

is that ecosystem properties, processes, and 

resources will continue to change over the 

next century. Species will be lost, others will 

be gained, and disturbances will increase and 

alter the structure and function of ecosystems. Future management, monitoring, and 

research efforts will need to embrace these 

changing conditions. 

Finally, through the synthesis process we 

were able to identify inventory, monitoring, 

and research needs that can lead to a better understanding of ecological responses 

to climate change in the Rocky Mountains 

and Upper Columbia Basin (Table 2). While 

these represent only a portion of the needs, 

our goal is to begin to guide future research 

directions and prioritization for the ROCO 

region. 
53

Conclusions

Table 2. (continued)

Forests and Woodlands

Inventory & Monitoring 

• Monitor aspen recruitment and growth following disturbance such as beetle-kill and fire.

• Monitor landscape-level changes in the character and distribution of forests through repeat photography and remote sensing. 

• Develop better vegetation maps.

• Monitor the status and trends in forest growth and health. 

Research

• Link local climate to vegetation. 

• Research the feedbacks between insect, fire, and climate.

• Research and monitor forest recovery and wildlife use following widespread die-offs caused by 

insect infestations, blister rust, and fire. 

• Understand the climate triggers for disturbance.

• Research the effects of climate change on mycorrhizae and their relationships with forest trees and 

other species with known fungal associations.

• Research the effects of microclimate on resistance of plant assemblages to climate change.

Sagebrush & Grasslands

Inventory & Monitoring

• Improve early invasive/exotic detection.

• Monitor the status and trends of invasive species.

• Monitor soil stability.

• Monitor status and trends of native and non-native vegetation.

• Monitor status and trends of important wildlife species such as sage grouse.

Research

• Examine the trends, causes, and consequences of woody encroachment.

• Research the multiple effects of grazing, climate, and fire on grasslands. 

Aquatic Resources

Inventory & Monitoring

• Monitor the status and trends of wetlands. 

• Continuously monitor streamflows and lake levels.

• Monitor status and trends in water quality. 

• Monitor the status and trends of glaciers. 

• Conduct wetlands inventories and vulnerability assessments.

Research

• Research changes in snowpack across elevational gradients.

• Research how warmer water temperatures and changing flows will affect aquatic organisms.

• Research high-elevation aquatic food webs and how they will be affected by climate change.

• Research the relationship between hydrology and wetland species composition and function.

Wildlife

Inventory & Monitoring 

• Monitor status and trends in populations of at-risk species.

• Monitor status and trends in wildlife diseases and develop research linking disease outbreaks to 

climate change.

Research

• Research asynchronies in life history characters among interdependent species and the plasticity of 

species to adapt to disruptions.

• Research and monitor snow-dependent species.

• Research the effectiveness of different adaptation strategies for species of concern (e.g., nest 

boxes, food augmentation).

• Complete vulnerability assessments at large geographic scales and for land management units.

• Research the primary driver (e.g., temperature tolerances, precipitation changes vs. habitat/productivity response) of a species’ response to climate change.

55

Literature Cited Chapter 8: Literature Cited

Abatzoglou, J. T., and K. T. Redmond. 2007. Asymmetry between trends in spring and autumn 

temperature and circulation regimes over western North America. Geophysical Research 

Letters 34:L18808.

Adams, R. A., and M. A. Hayes. 2008. Water availability and successful lactation by bats as related 

to climate change in arid regions of western North America. Journal of Animal Ecology 

77:1115–1121.

Adler, P. B., J. HilleRisLambers, P. C. Kyriakidis, Q. Guan, and J. M. Levine. 2006. Climate variability has a stabilizing effect on the coexistence of prairie grasses. Proceedings of the 

National Academy of Sciences of the United States of America 103:12,793–12,798.

Aldridge, C. L., S. E. Nielsen, H. L. Beyer, M. S. Boyce, J. W. Connelly, S. T. Knick, and M. A. 

Schroeder. 2008. Range-wide patterns of greater sage-grouse persistence. Diversity and 

Distributions 14:983-994.

Allen, J. A., C. S. Brown, and T. J. Stohlgren. 2009. Non-native plant invasions of United States 

national parks. Biological Invasions 11:2195–2207.

Allen, C. D., A. K. Macalady, H. Chenchouni, D. Bachelet, N. McDowell, M. Vennetier, T. Kitzberger, A. Rigling, D. D. Breshears, E. H. Hogg, and others. 2010. A global overview of 

drought and heat-induced tree mortality reveals emerging climate change risks for forests. 

Forest Ecology and Management 259:660–684.

Anderson, L., C. E. Carlson, and R. H. Wakimoto. 1987. Forest fire frequency and western spruce 

budworm outbreaks in western Montana. Forest Ecology and Management 22:251–260.

Arno, S. F., and R. P. Hammerly. 1984. Timberline: Mountain and arctic forest frontiers. The 

Mountaineers, Seattle, Washington, USA.

Arno, S. F., and R. J. Hoff. 1990. Whitebark pine Pinus albicaulis Engelm. Pages 268–279 in R. M. 

Burns and B. H. Honkala, editors. Silvics of North America, Vol. 1, Conifers. USDA Forest 

Service, Agriculture Handbook. 654, Washington, D.C., USA.

Aw, J., and M. J. Kleeman. 2003. Evaluating the first-order effect of intraannual temperature variability on urban air pollution. Journal of Geophysical Research 108 (D12) Art. No. 4365.

Bachelet, D., J. Lenihan, R. Drapek, and R. Neilson. 2008. VEMAP vs VINCERA: A DGVM sensitivity to differences in climate scenarios. Global and Planetary Change 64:38–48.

Bachelet, D., R. P. Neilson, J. M. Lenihan, and R. J. Drapek. 2001. Climate change effects on vegetation distribution and carbon budget in the United States. Ecosystems 4:164–185.

Barnett, T. P., and D. W. Pierce. 2009. Sustainable water deliveries from the Colorado River in a 

changing climate. Proceedings of the National Academy of Sciences of the United States of 

America 106:7334-7338.

Barnett, T. P., D. W. Pierce, H. G. Hidalgo, C. Bonfils, B. D. Santer, T. Das, G. Bala, A. W. Wood, T. 

Nozawa, A. A. Mirin, D. R. Cayan, and M. D. Dettinger. 2008. Human-induced changes in 

the hydrology of the western United States. Science 319:1080–1083.

Baron, J. S. 2006. Hindcasting nitrogen deposition to determine an ecological critical load. Ecological Applications 16:433–439.
56

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Baron, J. S., C. D. Allen, E. Fleishman, L. Gunderson, D. McKenzie, L. Meyerson, J. Oropeza, 

and N. Stephenson. 2008b. National Parks. Pages 4-1 to 4-68 in S. H. Julius and J. M. West, 

editors. Preliminary review of adaptation options for climate-sensitive ecosystems and 

resources. A Report by the US Climate Change Science Program and the Subcommittee on 

Global Change Research. US Environmental Protection Agency, Washington, D.C., USA.

Baron, J. S., M. D. Hartman, L. E. Band, and R. B. Lammers. 2000b. Sensitivity of a high-elevation 

rocky mountain watershed to altered climate and CO2. Water Resources Research 36:89–99.

Baron, J. S., S. H. Julius, J. M. West, L. A. Joyce, G. M. Blate, C. H. Peterson, M. Palmer, B. D. 

Keller, P. Karieva, J. M. Scott, and B. Griffith. 2008a. Some guidelines for helping natural 

resources adapt to climate change. IHDP Update 2:46–52.

Baron, J. S., K. R. Nydick, H. M. Rueth, B. M.,Lafrancois, and A. P. Wolfe. 2003. High elevation 

ecosystem responses to atmospheric deposition of nitrogen in the Colorado Rocky Mountains, USA. Pages 429-436 in U. M. Huber, H. K. Bugmann, and M. A. Reasoner, editors. 

Global change and mountain regions: A state of knowledge overview. Kluwer Academic 

Publishers, Dordrecht, The Netherlands. 

Baron, J. S., D. S. Ojima, E. A. Holland, and W. J. Parton. 1994. Analysis of nitrogen saturation 

potential in Rocky-Mountain tundra and forest—implications for aquatic systems. Biogeochemistry 27:61–82.

Baron, J. S., H. M. Rueth, A. M. Wolfe, K. R. Nydick, E. J. Allstott, J. T. Minear, and B. Moraska. 

2000a. Ecosystem responses to nitrogen deposition in the Colorado Front Range. Ecosystems 3:352–368.

Baron, J. S., T. M. Schmidt, and M. D. Hartman. 2009. Climate-induced changes in high elevation 

stream nitrate dynamics. Global Change Biology 15:1777–1789.

Bartos, D. L. 2001. Landscape dynamics of aspen and conifer forests. USDA Forest Service Proceedings RMRS-P-18, Fort Collins, Colorado, USA.

Battin, J., M. W. Wiley, M. H. Ruckelshaus, R. N. Palmer, E. Korb, K. K. Bartz, and H. Imaki. 2007. 

Projected impacts of climate change on salmon habitat restoration. Proceedings of the National Academy of Sciences of the United States of America 104:6720–6725.

Beebee, T. J. C. 1995. Amphibian breeding and climate. Nature 374:219–220.

Beebee, T. J. C. 2002. Amphibian phenology and climate change. Conservation Biology 

16:1454–1454.

Beever, E. A., P. F. Brussard, and J. Berger. 2003. Patterns of apparent extirpation among isolated populations of pikas (Ochotona princeps) in the Great Basin. Journal of Mammalogy 

84:37–54.

Beever, E. A., C. Ray, P. W. Mote, and J. L. Wilkening. 2010. Testing alternative models of climatemediated extirpations. Ecological Applications 20:164–178.

Bentz, B. 2008. Western US Bark Beetles and Climate Change. Available at http://www.fs.fed.us/

ccrc/topics/bark-beetles.shtml. USDA Forest Service, Climate Change Resource Center.

Berger, J. 2004. The last mile: How to sustain long-distance migration in mammals. Conservation 

Biology 18:320–331.

Berger, J., S. L. Cain, and K. M. Berger. 2006. Connecting the dots: An invariant migration corridor links the Holocene to the present. Biology Letters 2:528-531.
57

Literature Cited Literature Cited

Berlow, E. L., C. M. D’Antonio, and S. A. Reynolds. 2002. Shrub expansion in montane meadows: The interaction of local-scale disturbance and site aridity. Ecological Applications 

12:1103–1118.

Bernard, S. M., J. M. Samet, A. Grambsch, K. L. Ebi, and I. Romieu. 2001. The potential impacts 

of climate variability and change on air pollution-related health effects in the United States. 

Environmental Health Perspectives 109:199–209.

Berthold P., Møller A.P. & Fiedler W. 2004. Page vii (Preface) in A. Møller, P. Berthold, and W. 

Fiedler, editors. Birds and climate change. Advances in Ecological Research 35. Elsevier 

Academic Press.

Binkley, D. 2008. Age distribution of aspen in Rocky Mountain National Park, USA. Forest Ecology and Management 255:797–802.

Birdnature. 1998. North American migration flyways. http://www.birdnature.com/flyways.html.

Blaustein, A.R., L.K. Belden, D. H. Olson, D.M. Green, T.L. Toot and J. M. Kiesecker. 2001. Amphibian breeding and climate change. Conservation Biology 15:1804–1809.

Blehert, D. S., A. C. Hicks, M. Behr, C. U. Meteyer, B. M. Berlowski-Zier, E. L. Buckles, J. T. H. 

Coleman, S. R. Darling, A. Gargas, R. Niver, J. C. Okoniewski, R. J. Rudd, and W. B. Stone. 

2009. Bat white-nose syndrome: An emerging fungal pathogen? Science 323:227–227.

Blumenthal, D., R. A. Chimner, J. M. Welker, and J. A. Morgan. 2008. Increased snow facilitates 

plant invasion in mixedgrass prairie. New Phytologist 179:440–448.

Boisvenue, C., and S. W. Running. 2006. Impacts of climate change on natural forest productivity—evidence since the middle of the 20th century. Global Change Biology 12:862–882.

Bonfils, C., B. D. Santer, D. W. Pierce, H. G. Hidalgo, G. Bala, T. Das, T. P. Barnett, D. R. Cayan, 

C. Doutriaux, A. W. Wood, A. Mirin, and T. Nozawa. 2008. Detection and attribution 

of temperature changes in the mountainous western United States. Journal of Climate 

21:6404-6424.

Bosch, J., L. M. Carrascal, L. Duran, S. Walker, and M. C. Fisher. 2007. Climate change and outbreaks of amphibian chytridiomycosis in a montane area of central Spain: Is there a link? 

Proceedings of the Royal Society B-Biological Sciences 274:253–260.

Both, C., S. Bouwhuis, C. M. Lessells, and M. E. Visser. 2006. Climate change and population 

declines in a long-distance migratory bird. Nature 441:81–83.

Bowman, W. D. 2000. Biotic controls over ecosystem response to environmental change in alpine 

tundra of the Rocky Mountains. Ambio 29:396–400.

Bowman, W. D. 2001. Introduction: Historical perspective and significance of alpine ecosystem 

studies. Pages 3–12 in W. D. Bowman and T. Seastedt, editors. Structure and function of an 

alpine ecosystem. Niwot Ridge, Colorado. Oxford University Press, New York, New York, 

USA.

Bowman, W. D., D. M. Cairns, J. S. Baron, and T. Seastedt. 2002. Islands in the sky: Alpine and 

treeline ecosystems of the Rockies. Pages 183–202 in J. S. Baron, editor. Rocky Mountain 

futures: An ecological perspective. Island Press, Washington, D.C., USA.

Bowman, W., J. Larson, K. Holland, M. Wiedermann, and J. Nieves. 2006. Nitrogen critical loads 

for alpine vegetation and terrestrial ecosystem response—Are we there yet? Ecological Applications 16:1183–1193. 
58

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Bradley, B. A. 2010. Assessing ecosystem threats from global and regional change: Hierarchical 

modeling of risk to sagebrush ecosystems from climate change, land use and invasive species in Nevada, USA. Ecography 33:198–208.

Bradley, B. A., M. Oppenheimer, and D. S. Wilcove. 2009. Climate change and plant invasions: 

Restoration opportunities ahead? Global Change Biology 15:1511–1521.

Bradshaw, W. E., and C. M. Holzapfel. 2006. Evolutionary response to rapid climate change. Science 312:1477–1478.

Brazda, A. R. 1953. Elk migration patterns, and some of the factors affecting movements in the 

Gallatin River drainage, Montana. Journal of Wildlife Management 17:9–23.

Breshears, D. D., N. S. Cobb, P. M. Rich, K. P. Price, C. D. Allen, R. G. Balice, W. H. Romme, J. 

H. Kastens, M. L. Floyd, J. Belnap, J. J. Anderson, O. B. Myers, and C. W. Meyer. 2005. 

Regional vegetation die-off in response to global-change-type drought. Proceedings of the 

National Academy of Sciences of the United States of America 102:15,144-15,148.

Britten, M., E. W. Schweiger, B. Frakes, D. Manier, and D. Pillmore. 2007. Rocky Mountain Network vital signs monitoring plan. Natural Resource Report NPS/ROMN/ NRR-2007/010.

Brown, T. J., B. L. Hall, and A. L. Westerling. 2004. The impact of twenty-first century climate 

change on wildland fire danger in the western United States: An applications perspective. . 

Climatic Change 62:365–388.

Bunting, S. C., J. L. Kingery, M. A. Hemstrom, M. A. Schroeder, R. A. Gravenmier, and W. J. Hann. 

2002. Altered rangeland ecosystems in the Interior Columbia Basin. General Technical Report PNW-GTR-553. USDA Forest Service, Pacific Northwest Research Station, Portland, 

Oregon, USA.

Burkett, V., and J. Kusler. 2000. Climate change: Potential impacts and interactions in wetlands of 

the United States. Journal of the American Water Resources Association 36:313–320.

Burns, C. E., K. M. Johnston, and O. J. Schmitz. 2003. Global climate change and mammalian species diversity in US national parks. Proceedings of the National Academy of Sciences of the 

United States of America 100:11474–11477.

Butler, D. R., G. P. Malanson, and D. M. Cairns. 1994. Stability of alpine treeline in northern 

Montana, USA. Phytocoenologia 22:485–500.

Carey, C. 2000. Infectious disease and worldwide declines of amphibiain populations, with comments on emerging diseases in coral reef organisms and in humans. Environmental Health 

Perspectives, Supplement 108(1):143–150.

Carey, C., and M. A. Alexander. 2003. Climate change and amphibian declines: Is there a link? 

Diversity and Distributions 9:111–121.

Cayan, D. R., S. A. Kammerdiener, M. D. Dettinger, J. Caprio, and D. H. Peterson. 2001. Changes 

in the onset of spring in the western United States. Bulletin of the American Meteorological 

Society 82:399–415.

Chambers, J. C., B. A. Roundy, R. R. Blank, S. E. Meyer, and A. Whittaker. 2007. What makes 

Great Basin sagebrush ecosystems invasible by Bromus tectorum? Ecological Monographs 

77:117–145.

Chambers, J. C., and M. J. Wisdom. 2009. Priority research and management issues for the imperiled Great Basin of the western United States. Restoration Ecology 17:707–714.
59

Literature Cited Literature Cited

Ciarniello, L. M., M. S. Boyce, D. R. Seip, and D. C. Heard. 2009. Comparison of grizzly bear 

Ursus arctos demographics in wilderness mountains versus a plateau with resource development. Wildlife Biology 15:247–265.

CIG [Climate Impacts Group]. 2010. http://cses.washington.edu/cig/. University of Washington, 

Seattle, Washington, USA.

Civerolo, K. L., C. Hogrefe, B. Lynn, C. Rosenzweig, R. Goldberg, J. Rosenthal, K. Knowlton, and 

P. L. Kinney. 2008. Simulated effects of climate change on summertime nitrogen deposition 

in the eastern US. Atmospheric Environment 42:2074–2082.

Cleland, E. E., N. R. Chiariello, S. R. Loarie, H. A. Mooney, and C. B. Field. 2006. Diverse responses of phenology to global changes in a grassland ecosystem. Proceedings of the National Academy of Sciences of the United States of America 103:13740–13744.

CoDoW [Colorado Department of Wildlife ]. 2009. Threatened and Endangered List. Online. 

http://wildlife.state.co.us/WildlifeSpecies/SpeciesOfConcern/ThreatenedEndangeredList/

ListOfThreatenedAndEndangeredSpecies.htm. Accessed 10 June 2010.

Collins, B., J. Miller, A. Thode, M. Kelly, J. van Wagtendonk, and S. Stephens. 2009. Interactions 

among wildland fires in a long-established Sierra Nevada natural fire area. ecosystems 

12:114–128.

Cook, E. R., R. Seager, M. A. Cane, and D. W. Stahle. 2007. North American drought: Reconstructions, causes, and consequences. Earth Science Reviews 81:93–134.

Cook, E. R., C. A. Woodhouse, C. M. Eakin, D. M. Meko, and D. W. Stahle. 2004. Long-term aridity changes in the western United States. Science 306:1015–1018.

Copeland, H. E., K. E. Doherty, D. E. Naugle, A. Pocewicz, and J. M. Kiesecker. 2009. Mapping 

oil and gas development potential in the US intermountain west and estimating impacts to 

species. PLoS ONE 4(10):e7400.

Copeland, J. P., K. S. McKelvey, K. B. Aubry, A. Landa, J. Persson, R. M. Inman, J. Krebs, E. Lofroth, H. Golden, J. R. Squires, A. Magoun, M. K. Schwartz, J. Wilmot, C. L. Copeland, R. 

E. Yates, I. Kojola, and R. May. 2010. The bioclimatic envelope of the wolverine (Gulo gulo): 

Do climatic constraints limits its geographic distribution? Canadian Journal of Zoology 

88:233–246.

Corn, P. S. 2003. Amphibian breeding and climate change: Importance of snow in the mountains. 

Conservation Biology 17:622–625.

Corn, P. S. 2005. Climate change and amphibians. Animal biodiversity and conservation 28:59-67.

Corn, P. S., and E. Muths. 2002. Variable breeding phenology affects the exposure of amphibian 

embryos to ultraviolet radiation. Ecology 83:2958–2963.

Cox, G. 1999. Alien species in North America and Hawaii: Impacts on natural ecosystems. Island 

Press, Washington D.C., USA.

Crozier, L. 2003. Winter warming facilitates range expansion: Cold tolerance of the butterfly Atalopedes campestris. Oecologia 135:648–656.

Crozier, L. 2004. Warmer winters drive butterfly range expansion by increasing survivorship. 

Ecology 85:231–241.

Cryan, P. M. 2003. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in 

North America. Journal of Mammalogy 84:579–593.
60

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Cryan, P. M., M. A. Bogan, and J. S. Altenbach. 2000. Effect of elevation on distribution of female 

bats in the Black Hills, South Dakota. Journal of Mammalogy 81:719–725.

Cryan, P. M., and A. C. Brown. 2007. Migration of bats past a remote island offers clues toward 

the problem of bat fatalities at wind turbines. Biological Conservation 139:1–11.

Creel, S., and M. Creel. 2009. Density-dependence and climate effects in Rocky Mountain elk: 

An application of regression with instrumental variables for population time series with 

sampling error. Journal of Animal Ecology 78:1291–1297.

Crick, H. Q. P., C. Dudley, D. E. Glue, and D. L. Thomson. 1997. UK birds are laying their eggs 

earlier. Nature 388:526

Cross, P. C., E. K. Cole, A. P. Dobson, W. H. Edwards, K. L. Hamlin, G. Luikart, A. D. Middleton, 

B. M. Scurlock, and P. J. White. 2010. Probable causes of increasing brucellosis in free-ranging elk of the Greater Yellowstone Ecosystem. Ecological Applications 20:278–288.

Cross, M. S., J. A. Hilty, G. M. Tabor, J. J. Lawler, L. J. Graumlich, and J. Berger. From connect-thedots to dynamic networks: Maintaining and enhancing connectivity as a strategy to address 

climate change impacts on wildlife. In J. Brodie, E. Post, and D. Doak, editors. Wildlife conservation in a changing climate. Chicago University Press, Chicago, Illinois, USA, in press. 

Crutzen, P. J., and J. G. Goldhammer, editors. 1993. Fire in the environment: The ecological, atmospheric, and climatic importance of vegetation fires. Wiley, New York, New York, USA.

Currano, E. D., P. Wilf, S. L. Wing, C. C. Labandeira, E. C. Lovelock, and D. L. Royer. 2008. 

Sharply increased insect herbivory during the Paleocene–Eocene Thermal Maximum. 

Proceedings of the National Academy of Sciences of the United States of America 

105:1960–1964.

Dale, V. H., L. A. Joyce, S. McNulty, R. P. Neilson, M. P. Ayres, M. D. Flannigan, P. J. Hanson, L. C. 

Irland, A. E. Lugo, C. J. Peterson, D. Simberloff, F. J. Swanson, B. J. Stocks, and B. M. Wotton. 2001. Climate change and forest disturbances. BioScience 51:723–734.

D’Antonio, C. M., and P. M. Vitousek. 2003. Biological invasions by exotic grasses, the grass/fire 

cycle, and global change. Annual Review of Ecology and Systematics 23:63–87.

Daszak, P. L. Berger, A. Cunningham, A. Hyatt, D. Green, and R. Speare. 1999. Emerging infectious diseases and amphibian population declines. Emerging Infectious Diseases 5:735–748.

De Valpine, P., and J. Harte. 2001. Plant responses to experimental warming in a montane meadow. Ecology 82:637–648.

DeByle, N. V., and R. P. Winokur. 1985. Aspen: Ecology and management in the western United 

States. General Technical Report RM-119. USDA Forest Service, Rocky Mountain Forest 

and Range Experiment Station, Fort Collins, Colorado, USA.

DEFRA [Department of Environment, Food and Rural Affairs]. 2005. Climate change and migratory species. A report by the British Trust for Ornithology. http://www.defra.gov.uk/wildlife-countryside/resprog/findings/climatechange-migratory/index.htm.

Diaz, H. F., and J. K. Eischeid. 2007. Disappearing “alpine tundra” Köppen climatic type in the 

western United States. Geophysical Research Letters 34:L18707.

Dobkin, D. S., R. D. Gettinger, and M. G. Gerdes. 1995. Springtime movements, roost use, and 

foraging activity of Townsend big-eared bat (Plecotis townsendii) in central Oregon. Great 

Basin Naturalist 55:315–321.
61

Literature Cited Literature Cited

Dodd, C.K., Jr., and L. L. Smith. 2003. Habitat destruction and alteration. Historical trends and 

future prospects for amphibians. Pages 94–112 in R.D. Semlitsch, editor. Amphibian Conservation. Smithsonian Institution Press, Washington, D.C., USA.

Donnelly, M.A., and M.L. Crump. 1998. Potential effects of climate change on two neotropical 

amphibian assemblages. Climate Change 39:541–561.

Dukes, J. S., and H. A. Mooney. 1999. Does global change increase the success of biological invaders? Trends in Ecology & Evolution 14:135–139.

Dunn, P.O., and D.W.Winkler. 1999. Climate change has affected the breeding date of tree 

swallows throughout North America. Proceedings of the Royal Society of London 

266:2487–2490.

Ehrenfeld, J. G. 2003. Effects of exotic plant invasions on soil nutrient cycling processes. Ecosystems 6:503–523.

Elliott, G. P., and W. L. Baker. 2004. Quaking aspen (Populus tremuloides Michx.) at treeline: A 

century of change in the San Juan Mountains, Colorado, USA. Journal of Biogeography 

31:733–745.

Fagre, D. B. 2009. Introduction: Understanding the importance of alpine treeline ecotones in 

mountain ecosystems. Pages 1–10 in D. R. Butler, G. P. Malanson, S. J. Walsh, and D. B. 

Fagre, editors. The changing alpine treeline. Elsevier, Netherlands.

Fahrig L. 2002. Effect of habitat fragmentation on the extinction threshold: A synthesis. Ecological Applications 12:346–353.

Fang, X., and H. G. Stefan. 1998. Potential climate warming effects on ice covers of small lakes in 

the contiguous US Cold Regions Science and Technology 27:119–140.

Fang, X., and H. G. Stefan. 1999. Projections of climate change effects on water temperature characteristics of small lakes in the contiguous US. Climatic Change 42:377–412.

Fausch, K. D., Y. Taniguchi, S. Nakano, G. D. Grossman, and C. R. Townsend. 2001. Flood disturbance regimes influence rainbow trout invasion success among five holartic regions. 

Ecological Applications 11:1438–1455.

Fenn, M. E., J. S. Baron, E. B. Allen, H. M. Rueth, K. R. Nydick, L. Geiser, W. D. Bowman, J. O. 

Sickman, T. Meixner, D. W. Johnson, and P. Neitlich. 2003. Ecological effects of nitrogen 

deposition in the western United States. BioScience 53:404–420.

Ficetola, G. F., W. Thuiller, and C. Miaud. 2007. Prediction and validation of the potential global 

distribution of a problematic alien invasive species - the American bullfrog. Diversity and 

Distributions 13:476-485.

Fiedler, W. 2003. Recent changes in migratory behavior of birds: A compilation of field observations and ringing data. Pages 21-38 in P. Berthold, E. Gwinner, and E. Sonnenschein, editors. Avian migration. Springer Verlag, Berlin.

Fiedler, W. 2009. Bird ecology as an indicator of climate and global change. Pages 181-196 in T. M. 

Letcher, editor. Climate change: Observed impacts on planet Earth. Elsevier, Amsterdam.

Field, C. B., L. D. Mortsch, M. Brklacich, D. L. Forbes, P. Kovacs, J. A. Patz, S. W. Running, and M. 

J. Scott. 2007. North America: Contribution of working group II to the fourth assessment 

report of the Intergovernmental Panel on Climate Change. Pages 617–652 in M. L. Parry, O. 

F. Canziani, J. P. Palutikof, P. J. van der Linden, and C. E. Hanson, editors. Climate change 

2007: Impacts, adaptation and vulnerability. Cambridge University Press, Cambridge, UK.
62

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Flannigan, M., B. Amiro, K. Logan, B. Stocks, and B. Wotton. 2006. Forest fires and climate 

change in the 21st Century. Mitigation and Adaptation Strategies for Global Change 

11:847–859.

Forister, M. L., A. C. McCall, N. J. Sanders, J. A. Fordyce, J. H. Thorne, J. O’Brien, D. P. Waetjen, 

and A. M. Shapiro. 2010. Compounded effects of climate change and habitat alteration 

shift patterns of butterfly diversity. Proceedings of the National Academy of Sciences of the 

United States of America 107:2088–2092.

Fountain, A. 2006. Glaciers of the American West. Available at http://glaciers.research.pdx.edu/

states.php. Portland State University, Portland, Washington, USA.

Frank, D. A. 2007. Drought effects on above- and belowground production of a grazed temperate 

grassland ecosystem. Oecologia 152:131–139.

Frank, D. A., and S. J. McNaughton. 1993. Evidence for the promotion of aboveground grassland 

production by native large herbivores in Yellowstone National Park. Oecologia 96:157–161.

Frankel, S. J. 2008. Forest plant disease and climate change. Available at http://www.fs.fed.us/ccrc/

topics/plant-diseases.shtml. USDA Forest Service, Climate Change Resource Center.

Galatowitsch, S., L. Frelich, and L. Phillips-Mao. 2009. Regional climate change adaptation strategies for biodiversity conservation in a midcontinental region of North America. Biological 

Conservation 142:2012–2022.

Galbreath, K. E., D. J. Hafner, and K. R. Zamudio. 2009. When cold is better: Climate-driven 

elevation shifts yield complex patterns of diversification and demography in an alpine specialist (American pika, Ochotona princeps). Evolution 63:2848–2863.

Galloway, J. N., J. D. Aber, J. W. Erisman, S. P. Seitzinger, R. W. Howarth, E. B. Cowling, and B. J. 

Cosby. 2003. The nitrogen cascade. Bioscience 53:341–356.

GAO [Government Accountability Office]. 2007. Climate change: Agencies should develop guidance for addressing the effects on federal land and water resources. GAO-07-863. Washington. D.C., USA. 

Garrett, L. K., T. J. Rodhouse, G. H. Dicus, C. C. Caudill, and M. R. Shardlow. 2007. Upper Columbia Basin Network vital signs monitoring plan.. Natural Resource Report NPS/UCBN/

NRR-2007/002. National Park Service, Fort Collins, Colorado, USA.

Gibbons, J. W.and D. H. Bennett. 1974. Determination of anuran terrestrial activity patterns by a 

drift fence method. Copeia 1974:236–243.

Gonzales, P., R.P. Neilson, K.S. McKelvey, J.M. Lenihan, and R.J. Drapek. 2007. Potential impacts 

of climate change on habitat and conservation priority areas for Lynx canadensis (Canada 

lynx). Report to the Forest Service, US Department of Agriculture, Washington D.C., and 

NatureServe, Arlington, Virginia, USA.

Gooseff, M. N., K. Strzepek, and S. C. Chapra. 2005. Modeling the potential effects of climate 

change on water temperature downstream of a shallow reservoir, Lower Madison River, 

MT. Climatic Change 68:331–353.

Gough, L., C. W. Osenberg, K. L. Gross, and S. L. Collins. 2000. Fertilization effects on species 

density and primary productivity in herbaceous plant communities. Oikos 89:428–439.

Grabherr, G., M. Gottfried, and H. Pauli. 1994. Climate effects on mountain plants. Nature 

369:448–448.
63

Literature Cited Literature Cited

Graumlich, L. J., L. A. Waggoner, and A. G. Bunn. 2005. Detecting global change at alpine treeline: 

Coupling paleoecology with contemporary studies. Pages 501–508 in U. M. Huber, H. Bugmann, and M. A. Reasoner, editors. Global change and mountain regions: An overview of 

current knowledge. Springer, Netherlands.

Gray, D. 2008. The relationship between climate and outbreak characteristics of the spruce budworm in eastern Canada. Climatic Change 87:361–383.

Groot, C., and L. Margolis. 1991. Pacific salmon life histories. UBC Press, Vancouver, British 

Columbia, Canada.

Guenther, A. 2002. The contribution of reactive carbon emissions from vegetation to the carbon 

balance of terrestrial ecosystems. Chemosphere 49:837–844.

Guralnick, R. 2006. The legacy of past climate and landscape change on species’ current experienced climate and elevation ranges across latitude: A multispecies study utilizing mammals 

in western North America. Global Ecology and Biogeography 15:505–518.

Gurevitch, J., and D. K. Padilla. 2004. Are invasive species a major cause of extinctions? Trends in 

Ecology & Evolution 19:470–474.

Hafner, D. J., and R. M. Sullivan. 1995. Historical and ecological biogeography of nearctic pikas 

(Lagomorpha, Ochotonidae). Journal of Mammalogy 76:302–321.

Hall, M. H. P., and D. B. Fagre. 2003. Modeled climate-induced glacier change in Glacier National 

Park, 1850–2100. BioScience 53:131–140.

Hamlet, A. F., and D. P. Lettenmaier. 2007. Effects of 20th century warming and climate variability 

on flood risk in the western US Water Resources. Research 43:W06427.

Hamlet, A. F., P. W. Mote, M. P. Clark, and D. P. Lettenmaier. 2005. Effects of temperature and 

precipitation variability on snowpack trends in the western United States. Journal of Climate 18:4545-4561.

Hamlet, A. F., P. W. Mote, M. P. Clark, and D. P. Lettenmaier. 2007. Twentieth-century trends 

in runoff, evapotranspiration, and soil moisture in the western United States. Journal of 

Climate 20:1468–1486.

Hamrick, J. L. 2004. Response of forest trees to global environmental changes. Forest Ecology and 

Management 197:323–335.

Hansen, A. J., R. A. Y. Rasker, B. Maxwell, J. J. Rotella, J. D. Johnson, A. W. Parmenter, U. T. E. 

Langner, W. B. Cohen, R. L. Lawrence, and M. P. V. Kraska. 2009. Ecological causes and 

consequences of demographic change in the new west. BioScience 52:151–162.

Hari, R. E., D. M. Livingstone, R. Siber, P. Burkhardt-Holm, and H. Guttinger. 2006. Consequences of climatic change for water temperature and brown trout populations in Alpine rivers 

and streams. Global Change Biology 12:10–26.

Haroldson, M. A., M. Ternent, K. A. Gunther, and C. C. Schwartz. 2002. Grizzly bear denning 

chronology and movements in the Greater Yellowstone Ecosystem. Ursus 13:29–37.

Harper, M. P., and B. L. Peckarsky. 2006. Emergence cues of a mayfly in a high-altitude stream 

ecosystem: Potential response to climate change. Ecological Applications 16:612–621.

Hart, J. H., and D. L. Hart. 2001. Interaction among cervids, fungi, and aspen in northwest Wyoming. Pages 197–205 in W. Sheppard, D. D. Binkley, D. L. Bartos, T. J. Stohlgren, L. G. Eskew, compilers. Proceedings RMRS-P-18. USDA Forest Service, Rocky Mountain Research 

Station, Fort Collins, Colorado, USA..
64

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Harte, J., and R. Shaw. 1995. Shifting dominance within a montane vegetation community: Results 

of a climate-warming experiment. Science 267:876–880.

Harvell, C. D., C. E. Mitchell, J. R. Ward, S. Altizer, A. P. Dobson, R. S. Ostfeld, and M. D. 

Samuel. 2002. Climate warming and disease risks for terrestrial and marine biota. Science 

296:2158–2162.

Harvey, A. E., J. W. Byler, G. I. McDonald, L. F. Neuenschwander, and J. R. Tonn. 2008. Death of 

an ecosystem: Perspectives on western white pine ecosystems of North America at the end 

of the twentieth century. General Technical Report RMRS-GTR-208. USDA Forest Service, 

Rocky Mountain Research Station, Fort Collins, Colorado, USA.

Hauer, F. R., J. S. Baron, D. Campbell, K. D. Fausch, S. Hostetler, W., G. H. Leavesley, P. R. Leavitt, 

D. McKnight, and J. A. Stanford. 1997. Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada. Hydrological Processes 11:903–924.

Hayes, M. P., and M. R. Jennings. 1986. Decline of ranid frog species in western North America—

Are bullfrogs (Rana catesbeiana) responsible? Journal of Herpetology 20:490–509.

Hellmann, J. J., J. E. Byers, B. G. Bierwagen, and J. S. Dukes. 2008. Five potential consequences of 

climate change for invasive species. Conservation Biology 22:534–543.

Hessl, A. 2002. Aspen, elk, and fire: The effects of human institutions on ecosystem processes. 

BioScience 52:1011–1022.

Hessl, A. E., and W. L. Baker. 1997. Spruce and fir regeneration and climate in the forest-tundra 

ecotone of Rocky Mountain National Park, Colorado USA. Arctic and Alpine Research 

29:173–183.

Hessl, A. E., D. McKenzie, and R. Schellhaas. 2004. Drought and Pacific Decadl Oscillation linked 

to fire occurrence in the inland Pacific northwest. Ecological Applications 14:425–442.

Hickling, R., D. B. Roy, J. K. Hill, and C. D. Thomas. 2005. A northward shift of range margins in 

British Odonata. Global Change Biology 11:502–506.

Higgins, P. A. T., and J. Harte. 2006. Biophysical and Biogeochemical Responses to Climate 

Change Depend on Dispersal and Migration. BioScience 56:407-417.

Higgins, S. I., and Richardson D. M. 1999. Predicting plant migration rates in a changing world: 

The role of long-distance dispersal.American Naturalist 153:464–475.

Hitch, A. T., and P. L Leberg. 2007. Breeding distributions of North American birds species moving north as a result of climate change. Conservation Biology 21:534–539.

Hogg, I. D., and D. D. Williams. 1996. Response of stream invertebrates to a global-warming thermal regime: An ecosystem-level manipulation. ecology 77:395–407.

Hoskinson, R. L., and J. R. Tester. 1980. Migration behavior of pronghorn in southeastern Idaho. 

Journal of Wildlife Management 44:132–144.

Hostetler, S. W., and E. E. Small. 1999. Response of North American freshwater lakes to simulated 

future climates. Journal of the American Water Resources Association 35:1625–1637.

Humphries, M. M., D. W. Thomas, and J. R. Speakman. 2002. Climate-mediated energetic constraints on the distribution of hibernating mammals. Nature 418:313–316.

Hutchison, V. H, and R. K. Dupré. 1992. Thermoregulation. Pages 206–249 in M. E. Feder, W. 

W. Burggren, editors. Environmental physiology of the amphibians. University of Chicago 

Press, Chicago, Illinois, USA.
65

Literature Cited Literature Cited

IDFG [Idaho Department of Fish and Game]. 2009. Idaho comprehensive wildlife conservation 

strategy. Online. http://fishandgame.idaho.gov/cdc/cwcs_table_of_contents.cfm. Accessed 

10 June 2010. 

Ingersoll, G. P., M. A. Mast, D. H. Campbell, D. W. Clow, L. Nanus, and J. T. Turk. 2008. Trends in 

snowpack chemistry and comparison to National Atmospheric Deposition Program results 

for the Rocky Mountains, US, 1993–2004. Atmospheric Environment 42:6098–6113.

Inkley, D. B., M. G. Anderson, A. R. Blaustein, V. R. Burkett, B. Felzer, B. Griffith, J. Price, and T. L. 

Root. 2004. Global climate change and wildlife in North America. Wildlife Society Technical Review 04–2. The Wildlife Society, Bethesda, Maryland, USA.

Inouye, D. W. 2008. Effects of climate change on phenology, frost damage, and floral abundance 

of montane wildflowers. Ecology 89:353–362.

Inouye, D. W., B. Barr, K. B. Armitage, and B. D. Inouye. 2000. Climate change is affecting altitudinal migrants and hibernating species. Proceedings of the National Academy of Sciences of 

the United States of America 97:1630–1633.

Izaurralde, R. C., A. M. Thomson, N. J. Rosenberg, and R. A. Brown. 2005. Climate change 

impacts for the conterminous USA: An integrated assessment. Part 6. Distribution and 

productivity of unmanaged ecosystems. Climatic Change 69:107–126.

Jacob, D. J., and D. A. Winner. 2009. Effect of climate change on air quality. Atmospheric Environment 43:51–63.

Jacques, C. N., J. A. Jenks, and R. W. Klaver. 2009. Seasonal movements and home-range use by 

female pronghorns in sagebrush-steppe communities of western South Dakota. Journal of 

Mammalogy 90:433-441.

Janetos, A., L. Hansen, D. Inouye, B .P. Kelly, L. Meyerson, B. Peterson, and R. Shaw. 2008. Biodiversity. Chapter 5 in The Effects of Climate Change on Agriculture, Land Resources, Water 

Resources, and Biodiversity in the United States. US Climate Change Science Program, 

Washington, D.C., USA.. 

Jean, C., A. Schrag, R. Bennetts, R. Daley, E. Crowe, and S. O’Ney. 2005. Vital signs monitoring 

plan for the Greater Yellowstone Network. . National Park Service, Greater Yellowstone 

Network, Bozeman, Montana, USA.

Jones, T., and W. Cresswell. 2010. The phenology mismatch hypothesis: Are declines of migrant 

birds linked to uneven global climate change? Journal of Animal Ecology 79:98–108.

Joyce, L. A., G. M. Blate, S. G. McNulty, C. I. Millar, S. Moser, R. P. Neilson, and D. L. Peterson. 

2009. Managing for multiple resources under climate change: National forests. Environmental Management 44:1022–1032.

Joyce, L. A., C. H. Flather, and M. Koopman. 2008. Analysis of potential impacts of climate 

change on wildlife habitats in the US 10-31-08 Final Report, Wildlife Habitat Policy Research Program. USDA Forest Service. Rocky Mountain Research Station, Fort Collins, 

Colorado, USA.

Karl, T., J. Melillo, and T. Peterson, editors. 2009. Global climate change impacts in the United 

States. Cambridge University Press, Cambridge, England.

Karnosky, D. F., K. S. Pregitzer, D. R. Zak, M. E. Kubiske, G. R. Hendrey, D. Weinstein, M. Nosal, 

and K. E. Percy. 2005. Scaling ozone responses of forest trees to the ecosystem level in a 

changing climate. Plant Cell and Environment 28:965–981.
66

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Kashian, D. M., W. H. Romme, and C. M. Regan. 2007. Reconciling divergent interpretations of 

quaking aspen decline on the northern Colorado Front Range. Ecological Applications 

17:1296–1311.

Kaye, M. W., D. Binkley, and T. J. Stohlgren. 2005. Effects of conifers and elk browsing on quaking 

aspen forests in the central Rocky Mountains, USA. Ecological Applications 15:1284–1295.

Keane, R. E., and S. F. Arno. 1993. Rapid decline of whitebark pine in western Montana: Evidence 

from 20-year remeasurements. Western Journal of Applied Forestry 8:44–47.

Keane, R. E., K. C. Ryan, T. T. Veblen, C. D. Allen, J. Logan, and B. Hawkes. 2002. The cascading 

effects of fire exclusion in Rocky Mountain ecosystems. Pages 133–152 in J. S. Baron, editor. 

Rocky Mountain futures: An ecological perspective. Island Press, Washington, D.C., USA.

Keleher, C. J., and F. J. Rahel. 1996. Thermal limits to salmonid distributions in the rocky mountain region and potential habitat loss due to global warming: A geographic information 

system (GIS) approach. Transactions of the American Fisheries Society 125:1-13.

Kelsey, R. G., and G. Joseph. 2003. Ethanol in ponderosa pine as an indicator of physiological 

injury from fire and its relationship to secondary beetles. Canadian Journal Of Forest Research 33:870–884.

Kendall, K.C. 2010. Whitebark pine communities. http://www.nrmsc.usgs.gov/research/whitebar.

htm. Accessed 10 June 2010. 

Kendall, K. C., D. Ayers, and D. Schirokauer. 1996. Limber pine status from Alberta to Wyoming. 

Nutcracker Notes 7:23–24.

Kendall, K. C., and R. E. Keane. 2001. Whitebark pine decline: Infection, mortality, and population trends. Pages 221–242 in D. F. Tomback, S. F. Arno, and R. E. Keane, editors. Whitebark pine communities: Ecology and restoration. Island Press, Washington, D.C., USA.

Kendall, K. C., J. B. Stetz, J. Boulanger, A. C. Macleod, D. Paetkau, and G. C. White. 2009. Demography and genetic structure of a recovering grizzly bear population. Journal of Wildlife 

Management 73:3–17.

Kendall, K. C., J. B. Stetz, D. A. Roon, L. P. Waits, J. B. Boulanger, and D. Paetkau. 2008. Grizzly bear density in Glacier National Park, Montana. Journal of Wildlife Management 

72:1693–1705.

Kiesecker, J. M., and A. R. Blaustein. 1995. Synergism between UV-B radiation and a pathogen 

magnifies amphibian embryo mortality in nature. Proceedings of the National Academy of 

Sciences of the United States of America 92:11049–11052.

Kiesecker, J. M., A. R. Blaustein, and L. K. Belden. 2001. Complex causes of amphibian population declines. Nature 410:681–684.

Kitzberger,T., P.M. Brown, E.K. Heyerdahl, T.W. Swetnam, and T.T. Veblen (2007). Contingent 

Pacific-Atlantic Ocean influence on multi-century wildfire synchrony over western North 

America. Proceedings of the National Academy of Sciences of the United States of America 

104:543-548.

Kittel, T. G. F., P. E. Thornton, A. Royle, and T. N. Chase. 2002. Climates of the Rocky Mountains: 

Historical and future patterns. Pages 59–82 in J. S. Baron, editor. Rocky Mountain futures: 

An ecological perspective. Island Press, Washington, D.C., USA.

Klasner, F. L., and D. B. Fagre. 2002. A half century of change in alpine treeline patterns at Glacier 

National Park, Montana, USA. Arctic Antarctic and Alpine Research 34:49–56.
67

Literature Cited Literature Cited

Knapp, P. A. 1998. Spatio-temporal patterns of large grassland fires in the Intermountain West, 

USA. Global Ecology and Biogeography Letters 7:259–272.

Knapp, A. K., P. A. Fay, J. M. Blair, S. L. Collins, M. D. Smith, J. D. Carlisle, C. W. Harper, B. T. 

Danner, M. S. Lett, and J. K. McCarron. 2002. Rainfall variability, carbon cycling, and plant 

species diversity in a mesic grassland. Science 298:2202–2205.

Knick, S. T., D. S. Dobkin, J. T. Rotenberry, M. A. Schroeder, W. M. Vander Haegen, and C. van 

Riper. 2003. Teetering on the edge or too late? Conservation and research issues for avifauna of sagebrush habitats. Condor 105:611–634.

Knick, S. T., A. L. Holmes and R. F. Miller. 2005. The role of fire in structuring sagebrush habitats 

and bird communities. Studies in Avian Biology 30:63–75.

Knick, S. T., and J. T. Rotenberry. 2000. Ghosts of habitats past: Contribution of landscape change 

to current habitats used by shrubland birds. Ecology 81:220-227.

Knowles, N., M. D. Dettinger, and D. R. Cayan. 2006. Trends in snowfall versus rainfall in the 

western United States. Journal of Climate 18:4,545–544,559.

Konrad, C. P., and D. B. Booth. 2005. Ecological significance of hydrologic changes in

urban streams. Pages 157–177 in L. R. Brown, R. H. Gray, R. M. Hughes, and M. R. 

Meador, editors. Effects of urbanization on stream ecosystems. American Fisheries 

Society, Symposium 47, Bethesda, Maryland, USA.

Koteen L. 1999. Climate change, whitebark pine, and grizzly bears in the Greater Yellowstone 

Ecosystem. M.S. Thesis. School of Forestry and Environmental Studies, Yale University, 

New Haven, Connecticut.

Kreuzer, M. P., and N. J. Huntly. 2003. Habitat-specific demography: Evidence for source-sink 

population structure in a mammal, the pika. Oecologia 134:343–349.

Kruse, C. G., W. Hurbert, and F. J. Rahel. 1997. Geomorphic influences on the distribution of 

Yellowstone cutthroat trout in the Absaroka Mountains, Wyoming. Transactions of the 

American Fisheries Society 126:418–427.

Kulakowski, D., T. T. Veblen, and B. P. Kurzel. 2006. Influences of infrequent fire, elevation and 

pre-fire vegetation on the persistence of quaking aspen (Populus tremuloides Michx.) in the 

Flat Tops area, Colorado, USA. Journal of Biogeography 33:1397–1413.

Kumar, S., S. A. Spaulding, T. J. Stohlgren, K. A. Hermann, T. S. Schmidt, and L. L. Bahls. 2009. 

Potential habitat distribution for the freshwater diatom Didymosphenia geminata in the 

continental US. Frontiers in Ecology and the Environment 7:415–420.

Kusler, J. 2006. Common questions: Wetlands, climate change, and carbon sequestering. . Association of State Wetland Managers, Berne, New York, USA.

La Sorte, F. A., and W. Jetz. 2010. Avian distributions under climate change: Towards improved 

projections. Journal of Experimental Biology 213:862–869.

La Sorte, F. A., and F. R. Thompson. 2007. Poleward shifts in winter ranges of North American 

birds. Ecology 88:1803–812.
68

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Landers, D. H., S. L. Simonich, D. A. Jaffe, L. H. Geiser, D. H. Campbell, A. R. Schwindt, C. B. 

Schreck, M. L. Kent, W. D. Hafner, H. E. Taylor, K. J. Hageman, S. Usenko, L. K., Ackerman, 

J. E. Schrlau, N. . Rose, T. F. Blett, and M. M. Erway. 2008. The fate, transport, and ecological impacts of airborne contaminants in western national parks (USA). EPA/600/R-07/138. 

US Environmental Protection Agency, Office of Research and Development, NHEERL, 

Western Ecology Division, Corvallis, Oregon, USA.

Landhausser, S. M., D. Deshaies, and V. J. Lieffers. 2010. Disturbance facilitates rapid range expansion of aspen into higher elevations of the Rocky Mountains under a warming climate. 

Journal of Biogeography 37:68–76.

Lawler, J. J., S. I. Shafer, B. A. Bancroft and A.R. Blaustein. 2009. Projected climate impacts for 

amphibians of the Western Hemisphere. Conservation Biology 24:38–50.

Lawler, J.J., S.I. Shafer, D. White, P. Kareiva, E. P. Maurer, A. R. Blaustein, and P. J. Bartlein. 2010b. 

Projected climate-induced faunal change in the Western Hemisphere. Ecology 90:588-597.

Leatherman, D. A., I. Aguayo, and T. M. Mehall. 2009a. Mountain pine beetle. Available at 

http://www.ext.colostate.edu/pubs/insect/05528.html. Colorado State University, Fort Collins, Colorado, USA.

Lawler, J. J., T. H. Tear, C. Pyke, M. R. Shaw, P. Gonzalez, P. Kareiva, L. Hansen, L. Hannah, K. 

Klausmeyer, A. Aldous, C. Bienz, and S. Pearsall. 2010a. Resource management in a changing and uncertain climate. Frontiers in Ecology and the Environment 8:35–43.

Leatherman, D. A., J. W. Brewer, and R. E. Stevens. 2009b. Western spruce budworms. Available 

at http://www.ext.colostate.edu/pubs/insect/05543.html. Colorado State University, Fort 

Collins, Colorado, USA.

Lenarz, M. S., M. E. Nelson, M. W. Schrage, and A. J. Edwards. 2009. Temperature Mediated 

Moose Survival in Northeastern Minnesota. Journal of Wildlife Management 73:503–510.

Lenihan, J. M., D. Bachelet, R. P. Neilson, and R. Drapek. 2008. Simulated response of conterminous United States ecosystems to climate change at different levels of fire suppression, CO2

emission rate, and growth response to CO2. Global and Planetary Change 64:16–25.

Lesica, P., and B. McCune. 2004. Decline of arctic-alpine plants at the southern margin of their 

range following a decade of climatic warming. Journal of Vegetation Science 15:679–690.

Littell, J. S., D. McKenzie, D. L. Peterson, and A. L. Westerling. 2009. Climate and wildfire area 

burned in western U. S. ecoprovinces, 1916–2003. Ecological Applications 19:1003–1021.

Lindroth, R. L., K. K. Kinney, and C. L. Platz. 1993. Responses of deciduous trees to elevated 

atmospheric CO2: Productivity, phytochemistry, and insect performance. Ecology 

74:763–777.

Little, E. L. 1971. Atlas of United States trees. Volume 1, Conifers and important hardwoods. 

USDA Forest Service, Miscellaneous Publications 1146. Washington , D. C., USA.

Loarie, S. R., P. B. Duffy, H. Hamilton, G. P. Asner, C. B. Field, and D. D. Ackerly. 2009. The velocity of climate change. Nature 462:1052-1055.

Logan, J. A., J. Regniere, and J. A. Powell. 2003. Assessing the impacts of global warming on forest 

pest dynamics. Frontiers in Ecology and the Environment 1:130–137.

Loreau, M., S. Naeem, P. Inchausti, J. Bengtsson, J. P. Grime, A. Hector, D. U. Hooper, M. A. Huston, D. Raffaelli, B. Schmid, D. Tilman, and D. A. Wardle. 2001. Ecology—Biodiversity and 

ecosystem functioning: Current knowledge and future challenges. Science 294:804–808.
69

Literature Cited Literature Cited

Lowe, P. N., W. K. Lauenroth, and I. C. Burke. 2003. Effects of nitrogen availability on competition between Bromus tectorum and Bouteloua gracilis. Plant Ecology 167:247–254.

Luckman, B., and T. Kavanagh. 2000. Impact of climate fluctuations on mountain environments 

in the Canadian Rockies. AMBIO: A Journal of the Human Environment 29:371–380.

MacArthur, R. H., and L. C. Wang. 1974. Behavioral thermoregulation in the pika Ochotona princeps: A field study using radiotelemetry. Canadian Journal of Zoology 52:353–358.

MacArthur, R. H., and E. O. Wilson. 1967. The theory of island biogeography. Princeton University Press, Princeton, New Jersey, USA. 

Mack, R. N. 1986. Alien plant invasion into the Intermountain West: A case history. Pages 

192–213 in H. A. Mooney and J. Drake, editors. Ecology of biological invasions of North 

America and Hawaii. Springer-Verlag, New York, New York, USA.

Malanson, G. P., D. R. Butler, and D. B. Fagre. 2007a. Alpine ecosystem dynamics and change: A 

view from the heights. Pages 85–101 in T. Prato and D. B. Fagre, editors. Sustaining Rocky 

Mountain landscapes: Science, policy, and management of the Crown of the Continent 

Ecosystem. Resources for the Future, Washington, D.C., USA.

Malanson, G. P., D. R. Butler, D. B. Fagre, S. J. Walsh, D. F. Tomback, L. D. Daniels, L. M. Resler, W. K. Smith, D. J. Weiss, D. L. Peterson, A. G. Bunn, C. A. Hiemstra, D. Liptzin, P. S. 

Bourgeron, Z. Shen, and C. I. Millar. 2007b. Alpine treeline of Western North America: 

Linking organism-to-landscape dynamics. Physical Geography 28:378–396.

Mattson, D. J., and D. P. Reinhart. 1997. Excavation of red squirrel middens by grizzly bears in the 

whitebark pine zone. Journal of Applied Ecology 34:926–940.

Mawdsley, J. R., R. O’Malley, and D. S. Ojima. 2009. A review of climate-change adaptation 

strategies for wildlife management and biodiversity conservation. Conservation Biology 

23:1080–1089.

McCarty, J. P. 2001. Ecological consequences of recent climate change. Conservation Biology 

15:320–331.

McKenzie, D., Z. Gedalof, D. L. Peterson, and P. Mote. 2004. Climatic change, wildfire, and conservation. Conservation Biology 18:890–902.

McLaughlin, J. F., J. J. Hellmann, C. L. Boggs, and P. R. Ehrlich. 2002. Climate change hastens 

population extinctions. Proceedings of the National Academy of Sciences of the United 

States of America 99:6070–6074.

McMenamin, S. K., E. A. Hadly, and C. K. Wright. 2008. Climatic change and wetland desiccation 

cause amphibian decline in Yellowstone National Park. Proceedings of the National Academy of Sciences of the United States of America 105:16988–16993.

McWethy, D. (in press). Observed and projected trends in climate and associated ecosystem effects: A synthesis of the best available science. NPS Natural Resources Report, Fort Collins, 

CO. 

Meko, D. M., C. A. Woodhouse, C. A. Baisan, T. Knight, J. J. Lukas, M. K. Hughes, and M. W. 

Salzer. 2007. Medieval drought in the upper Colorado River Basin. Geophysical Research 

Letters 34.

Meyer, J. L., and R. T. Edwards. 1990. Ecosystem metabolism and turnover of organic carbon 

along a Blackwater River continuum. Ecology 71:668–677.
70

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Millar, C. I., N. L. Stephenson, and S. L. Stephens. 2007. Climate change and forests of the future: 

Managing in the face of uncertainty. Ecological Applications 17:2145–2151.

Millar, C. I., and R. Westfall. 2010. Distribution and climatic relationships of the American pika 

(Ochotona princeps) in the Sierra Nevada and Western Great Basin, USA; Periglacial landforms as refugia in warming climates. Arctic, Antarctic, and Alpine Research 42:76–88.

Miller, R. F., J. D. Bates, T. J. Svejcar, F. Pierson, and L. Eddleman. 2005. Biology, ecology, and 

management of western juniper. Tech. Bull. 152. Oregon State University, Agricultural Experiment Station, Corvallis, Oregon, USA.

Miller, R. F., and R. J. Tausch. 2001. The role of fire in juniper and pinyon woodlands: A descriptive analysis. Pages 15–30 in K.E.M. Galley and T.P. Wilson, editors. Proceedings of the invasive species workshop: The role of fire in the control and spread of invasive species. Fire 

conference 2000: First National Congress on Fire Ecology, Prevention, and Management. 

Miscellaneous publication No. 11, Tall Timbers Research Station Tallahassee, Florida, USA.

Mitsch, W. J., and J. G. Gosselink. 2007. Wetlands. 4th edition. Wiley & Sons, Inc., Hoboken, New 

Jersey, USA.

Mitton, J. B., and M. C. Grant. 1996. Genetic variation and the natural history of quaking aspen. 

BioScience 46:25–31.

Mohseni, O., H. G. Stefan, and J. G. Eaton. 2003. Global warming and potential changes in fish 

habitat in US Streams. Climatic Change 59:389–409.

Monaco, T. A., D. A. Johnson, J. M. Norton, T. A. Jones, K. J. Connors, J. B. Norton, and M. B. 

Redinbaugh. 2003. Contrasting responses of intermountain west grasses to soil nitrogen. 

Journal of Range Management 56:282–290.

Morgan, P., E. K. Heyerdahl, and C. E. Gibson. 2008. Multi-season climate synchronized forest 

fires throughout the 20th century, Northern Rockies, USA. Ecology 89:717-728.

Morgan, J. A., D. R. Lecain, A. R. Mosier, and D. G. Milchunas. 2001. Elevated CO2 enhances 

water relations and productivity and affects gas exchange in C3 and C4 grasses of the Colorado shortgrass steppe. Global Change Biology 7:451–466.

Morgan, J. A., D. G. Milchunas, D. R. LeCain, M. West, and A. R. Mosier. 2007. Carbon dioxide 

enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe. Proceedings of the National Academy of Sciences of the United States of 

America 104:14724–14729.

Morgan, J. A., A. R. Mosier, D. G. Milchunas, D. R. LeCain, J. A. Nelson, and W. J. Parton. 2004. 

CO2 enhances productivity, alters species composition, and reduces digestibility of shortgrass steppe vegetation. Ecological Applications 14:208–219.

Moritz, C., J. L. Patton, C. J. Conroy, J. L. Parra, G. C. White, and S. R. Beissinger. 2008. Impact 

of a century of climate change on small-mammal communities in Yosemite National Park, 

USA. Science 322:261–264.

Morrison, J. Climate change in the Kootenai, in prep.

Morrison, J., M. C. Quick, and M. G. G. Foreman. 2002. Climate change in the Fraser River watershed: Flow and temperature projections. Journal of Hydrology 263:230–244.

Morrison, S. F., and D. S. Hik. 2007. Demographic analysis of a declining pika Ochotona collaris

population: Linking survival to broad-scale climate patterns via spring snowmelt patterns. 

Journal of Animal Ecology 76:899–907.
71

Literature Cited Literature Cited

Mote, P. W. 2003. Trends in snow water equivalent in the Pacific Northwest and their climatic 

causes. Geophysical Research Letters 30:1601.

Mote, P. W., A. F. Hamlet, M. P. Clark, and D. P. Lettenmaier. 2005. Declining mountain snowpack in western North America. Bulletin of the American Meteorological Society 86:39–49.

MTNHP [Montana Natural Heritage Program]. 2009. Montana animal species of concern. Montana Natural Heritage Program and Montana Fish, Wildlife, and Parks. http://fwp.mt.gov/

wildthings/concern/

Muths, E., D. S. Pilliod, and L. J. Livo. 2008. Distribution and environmental limitations of an amphibian pathogen in the Rocky Mountains, USA. Biological Conservation 141:1484–1492.

National Assessment Synthesis Team. 2001. Climate change impacts on the United States: The 

potential consequences of climate variability and change. Report for the US Global Change 

Research Program, Cambridge University Press, Cambridge, UK.

Neff, J. C., A. P. Ballantyne, G. L. Farmer, N. M. Mahowald, J. L. Conroy, C. C. Landry, J. T. Overpeck, T. H. Painter, C. R. Lawrence, and R. L. Reynolds. 2008. Increasing eolian dust deposition in the western United States linked to human activity. Nature Geoscience 1:189–195.

Negron, J. F., B. J. Bentz, C. J. Fettig, N. Gillette, E. M. Hansen, J. L. Hays, R. G. Kelsey, J. E. 

Lundquist, A. M. Lynch, R. A. Progar, and S. J. Seybold. 2008. USDA Forest Service bark 

beetle research in the western United States: Looking toward the future. Journal of Forestry 

106:325–331.

Neilson, R. P., L. F. Pitelka, A. M. Solomon, R. A. N. Nathan, G. F. Midgley, J. M. V. Fragoso, H. 

Lischke, and K. E. N. Thompson. 2005. Forecasting regional to global plant migration in 

response to climate change. BioScience 55:749–759.

Neuenschwander, L. F., J. W. Byler, A. E. Harvey, G. I. McDonald, D. S. Ortiz, H. L. Osborne, G. C. 

Snyder, and A. C. Zack. 1999. White pine in the American west: A vanishing species—Can 

we save it? General Technical Report RMRS-GTR-35. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, Colorado, USA.

NICC [National Interagency Coordination Center]. 2010. Fire Information—Wildland Fire Statistics. Available at http://www.nifc.gov/fire_info/ytd_state_2009.htm.

NISIC [National Invasive Species Information Center]. 2010. What is an invasive species? Available at http://www.invasivespeciesinfo.gov/whatis.shtml.

Niven, D. K., G. S. Butcher, G. T. Bancroft, W. B. Monahan, and G. Langham. 2009. Birds and climate change: Ecological disruption in motion. http://www.audubon.org/news/pressroom/

bacc/pdfs/Birds%20and%20Climate%20Report.pdf. Audubon Society, New York, New 

York, USA.

Noss, RF, E.T. LaRoe, J.M. Scott. 1995. Endangered ecosystems of the United States: A preliminary assessment of loss and degradation. Biological Report. US Fish and Wildlife Service.

NPS [National Park Service]. 2008. Yellowstone Superintendent’s Report. Yellowstone National 

Park, Wyoming, USA.

NWHC [National Wildlife Health Center, USGS]. 2010. White-nose syndrome. Available at 

http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/.

NWSR [National Wild and Scenic Rivers]. 2010. Designated wild and scenic rivers. Available at 

http://www.rivers.gov/wildriverslist.html..
72

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Ogden, N. H., A. Maarouf, I. K. Barker, M. Bigras-Poulin, L. R. Lindsay, M. G. Morshed, C. J. 

O’Callaghan, F. Ramay, D. Waltner-Toews, and D. F. Charron. 2006. Climate change and 

the potential for range expansion of the Lyme disease vector Ixodes scapularis in Canada. 

International Journal for Parasitology 36:63–70.

Opdam, P., and D. Wascher. 2004. Climate change meets habitat fragmentation: Linking landscape and biogeographical scale levels in research and conservation. Biological Conservation 117:285–297.

OTA [Office of Technology Assessment]. 1993. Wetlands. Preparing for an uncertain climate, Vol. 

II OTA-O-568. US Congress, Washington, D.C., USA.

Parmesan, C. 1996. Climate and species range. Nature 382:765–766.

Parmesan, C. 2006. Ecological and evolutionary responses to recent climate change. Annual Review of Ecology, Evolution, and Systematics 37:637–669.

Parmesan, C., and G. Yohe. 2003. A globally coherent fingerprint of climate change impacts across 

natural systems. Nature 421:37–42.

Parton, W. J., M. P. Gutmann, S. A. Williams, M. Easter, and D. Ojima. 2005. Ecological impact of 

historical land-use patterns in the great plains: A methodological assessment. Ecological 

Applications 15:1915-1928.

Parton, W. J., D. S. Ojima, and D. S. Schimel. 1994. Environmental change in grasslands: Assessment using models. Climatic Change 28:111–141

Patla, D. A., C. R. Peterson, and P. S. Corn. 2009. Amphibian decline in Yellowstone National 

Park. Proceedings of the National Academy of Sciences 106:E22–E22.

Patten, D. T. 1998. Riparian ecosystems of semi-arid North America: Diversity and human impacts. Wetlands 18:498–512.

Patz, J. A., T. K. Graczyk, N. Geller, and A. Y. Vittor. 2000. Effects of environmental change on 

emerging parasitic diseases. International Journal for Parasitology 30:1395–1405.

Pauchard, A., C. Kueffer, H. Dietz, C. C. Daehler, J. Alexander, P. J. Edwards, J. R. Arevalo, L. A. 

Cavieres, A. Guisan, S. Haider, G. Jakobs, K. McDougall, C. I. Millar, B. J. Naylor, C. G. 

Parks, L. J. Rew, and T. Seipel. 2009. Ain’t no mountain high enough: Plant invasions reaching new elevations. Frontiers in Ecology and the Environment 7:479–486.

Pederson, G. T., D. B. Fagre, S. T. Gray, and L. J. Graumlich. 2004. Decadal-scale climate drivers 

for glacial dynamics in Glacier National Park, Montana, USA. Geophysical Research Letters 31:L12203.

Pederson, G. T., L. J. Graumlich, D. B. Fagre, T. Kipfer, and C. C. Muhlfeld. 2010. A century of 

climate and ecosystem change in western Montana: What do temperature trends portend? 

Climatic Change 98:133–154.

Pederson, G., C. Whitlock, E. Watson, B. Luckman, and L. J. Graumlich. 2007. Paleoperspectives 

on climate and ecosystem change. Pages 151–170 in T. Prato and D. B. Fagre, editors. Sustaining Rocky Mountain landscapes: Science, policy, and management of the Crown of the 

Continent Ecosystem. Resources for the Future, Washington, D.C., USA.

Perfors, T., J. Harte, and S. E. Alter. 2003. Enhanced growth of sagebrush (Artemisia tridentata) in 

response to manipulated ecosystem warming. Global Change Biology 9:736–742.

Perry, D. A. 1994. Forest ecosystems. Johns Hopkins University Press, Baltimore, Maryland, USA.
73

Literature Cited Literature Cited

Peterson, D. L., and D. McKenzie. 2008. Wildland fire and climate change. Available at http://

www.fs.fed.us/ccrc/topics/wildland-fire.shtml. USDA Forest Service, Climate Change Resource Center.

Peterson, D. P., K. D. Fausch, J. Watmough, and R. A. Cunjak. 2008. When eradication is not an 

option: Modeling strategies for electrofishing suppression of nonnative brook trout to 

foster persistence of sympatric native cutthroat trout in small streams. North American 

Journal of Fisheries Management 28:1847–1867.

Petersen, J. H., and J. F. Kitchell. 2001. Climate regimes and water temperature changes in the Columbia River: Bioenergetic implications for predators of juvenile salmon. Canadian Journal 

of Fisheries and Aquatic Sciences 58:1831–1841.

Picton, H. D. 1984. Climate and the prediction of reproduction of three ungulate species. Journal 

of Applied Ecology 21:869–879.

Pitelka, L. F. 1997. Plant migration and climate change. American Scientist 85:464.

Poff, N. L., M. M. Brinson, and J. W. Day. 2002. Aquatic ecosystems and global climate change. 

Pew Center on Global Climate Change, Arlington, Virginia, USA.

Poore, R. E., C. A. Lamanna, J. J. Ebersole, and B. J. Enquist. 2009. Controls on radial growth of 

mountain big sagebrush and implications for climatic change. Western North American 

Naturalist 69:556–562.

Post, E., and N. C. Stenseth. 1999. Climatic variability, plant phenology, and northern ungulates. 

Ecology 80:1322–1339.

Pounds, J. A., M. R. Bustamante, L. A. Coloma, J. A. Consuegra, M. P. L. Fogden, P. N. Foster, E. 

La Marca, K. L. Masters, A. Merino-Viteri, R. Puschendorf, S. R. Ron, G. A. Sanchez-Azofeifa, C. J. Still, and B. E. Young. 2006. Widespread amphibian extinctions from epidemic 

disease driven by global warming. Nature 439:161–167.

Pounds, J. A., and M. L. Crump. 1994. Amphibian declines and climate disturbance: The case of 

the golden toad and the harlequin frog. Conservation Biology 8:72–85.

Pounds, J. A., M. P. Fogden, and J. H. Campbell. 1999. Biological response to climate change on a 

tropical mountain. Nature 398:611–615.

Prevey, J. S., M. J. Germino, N. J. Huntly, and R. S. Inouye. 2010. Exotic plants increase and native plants decrease with loss of foundation species in sagebrush steppe. Plant Ecology 

207:39–51.

Price, J. T., and T. L. Root. 2005. Potential impacts of climate change on neotropical migrants: 

Management implications. Pages 1123-1128 in C.J. Ralph and T.D. Rich, editors. Bird conservation implementation and integration in the Americas: Proceedings of the Third International Partners in Flight Conference, Pacific Southwest Research Station, PSW-GTR-191.

Raffa, K. F., B. H. Aukema, B. J. Bentz, C. A.L., J. A. Hicke, M. G. Turner, and W. H. Romme. 2008. 

Cross-scale drivers of natural disturbances prone to anthropogenic amplification: Dynamics of biome-wide bark beetle eruptions. BioScience 58:501–517.

Rahel, F. J., and J. D. Olden. 2008. Assessing the effects of climate change on aquatic invasive species. Conservation Biology 22:521–533.

Ray, A. J., J. J. Barsugli, and K. B. Averyt. 2008. Climate change in Colorado: A synthesis to support 

water resources management and adaptation. A report by the Western Water Assessment 

for the Colorado Water Conservation Board. CU–NOAA Western Water Assessment, Boulder, Colorado, USA.
74

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Ray, A. J., J. J. Barsugli, K. Wolter, and J. K. Eischeid. 2010. Rapid-response climate assessment to 

support the FWS status review of the American pika. NOAA Earth Systems Research Laboratory, Boulder, Colorado, USA.

Rehfeldt, G. E., D. E. Ferguson, and N. L. Crookston. 2009. Aspen, climate, and sudden decline in 

western USA. Forest Ecology and Management 258:2353–2364.

Rehfeldt, G., W. Wykoff, and C. Ying. 2001. Physiologic plasticity, evolution, and impacts of a 

changing climate on Pinus Contorta. Climatic Change 50:355–376.

Reinhart, D. P., M. A. Haroldson, D. J. Mattson, and K. A. Gunther. 2001. Effects of exotic species 

on Yellowstone’s grizzly bears. Western North American Naturalist 61:277–288.

Reisen, W. K., Y. Fang, and V. M. Martinez. 2009. Effects of temperature on the transmission 

of West Nile virus by Culex tarsalis (Diptera: Culicidae). Journal of Medical Entomology 

43:309–317.

Rice, A. V., and D. W. Langor. 2009. Mountain pine beetle-associated blue-stain fungi in 

lodgepole–jack pine hybrids near Grande Prairie, Alberta (Canada). Forest Pathology 

39:323–334.

Rieman, B. E., D. Isaak, S. Adams, D. Horan, D. Nagel, C. Luce, and D. Myers. 2007. Anticipated 

climate warming effects on bull trout habitats and populations across the interior Columbia 

River basin. Transactions of the American Fisheries Society 136:1552–1565.

Ripple, W. J., and R. L. Beschta. 2004. Wolves and the ecology of fear: Can predation risk structure ecosystems? BioScience 54:755–766.

Rodhouse, T. J., E.A. Beever, L.K. Garrett, K.M. Irvine, M. Munts, C. Ray, and M. R. Shardlow. 

2010. Distribution of American pikas in a low-elevation lava landscape: Conservation implications from the range periphery. Journal of Mammalogy 91(5): in press.

Roland, J., and S. F. Matter. 2007. Encroaching forests decouple alpine butterfly population dynamics. Proceedings of the National Academy of Sciences of the United States of America 

104:13702–13704.

Romme, W. H., J. Clement, J. Hicke, D. Kulakowski, L. H. MacDonald, T. Schoennagel, and T. Veblen. 2006. Recent forest insect outbreaks and fire risk in Colorado forests: A brief synthesis 

of relevant research. Colorado Forest Restoration Institute, Fort Collins, Colorado, USA.

Romme, W. H., D. H. Knight, and J. B. Yavitt. 1986. Mountain pine beetle outbreaks in the Rocky 

Mountains: Regulators of primary productivity? The American Naturalist 127:484–494.

Romme, W. H., M. G. Turner, G. A. Tuskan, and R. A. Reed. 2005. Establishment, persistence, and 

growth of aspen (Populus tremuloides) seedlings in Yellowstone National Park. Ecology 

86:404–418.

Root, T. L., J. T. Price, K. R. Hall, S. H. Schneider, C. Rosenzweig, and J. A. Pounds. 2003. Fingerprints of global warming on wild animals and plants. Nature 421:57–60.

Rowland, M. M., L. H. Suring, R. J. Tausch, S. Geer, and M. J. Wisdom. 2008. Characteristics of 

western juniper encroachment into sagebrush communities in central Oregon. USDA Forest Service Forestry and Range Sciences Laboratory, La Grande, Oregon, USA. 

Rowland, M. M., M. J. Wisdom, L. H. Suring, and C. W. Meinke. 2006. Greater sage-grouse 

as an umbrella species for sagebrush-associated vertebrates. Biological Conservation 

129:323–335.
75

Literature Cited Literature Cited

Running, S. W. 2009. Impacts of climate change on forests of the northern Rocky 

Mountains. Available at http://www.bipartisanpolicy.org/library/research/

impacts-climate-change-forests-northern-rocky-mountains.

Rustad, L. E., J. L. Campbell, G. M. Marion, R. J. Norby, M. J. Mitchell, A. E. Hartley, J. H. C. 

Cornelissen, J. Gurevitch, and N. Gcte. 2001. A meta-analysis of the response of soil respiration, net nitrogen mineralization, and aboveground plant growth to experimental ecosystem warming. Oecologia 126:543–562.

Ryan, M. G., S. R. Archer, R. Birdsey, C. Dahm, L. Heath, J. Hicke, D. Hollinger, T. Huxman, G. 

Okin, R. Oren, J. Randerson, and Schlesinger, W. H. 2008. Land resources: Forests and Arid 

Lands. Pages 75–120 in P. Backlund, A. Janetos, D. Schimel, M. Walsh, editors. The effects 

of climate change on agriculture, land resources, water resources, and biodiversity in the 

United States. A Report by the US Climate Change Science Program and the Subcommittee 

on Global Change Research. US Department of Agriculture, Washington, D.C., USA.

Sage, R., and D. Kubien. 2003. Quo vadis C4? An ecophysiological perspective on global change 

and the future of C4 plants. Photosynthesis Research 77:209–225.

Salzer, M. W., M. K. Hughes, A. G. Bunn, and K. F. Kipfmueller. 2009. Recent unprecedented 

tree-ring growth in bristlecone pine at the highest elevations and possible causes. Proceedings of the National Academy of Sciences of the United States of America 106:20348–20353.

Sawyer, H., F. Lindzey, and D. McWhirter. 2005. Mule deer and pronghorn migration in western 

Wyoming. Wildlife Society Bulletin 33:1266–1273.

SCBD [Secretariat of the Convention on Biological Diversity]. 2003. Interlinkages between 

biological diversity and climate change. Advice on the integration of biodiversity considerations into the implementation of the United Nations Framework Convention on Climate 

Change and its Kyoto protocol., Montreal, Canada.

Schade, C. B., and S. A. Bonar. 2005. Distribution and abundance of nonnative fishes in 

streams of the western United States. North American Journal of Fisheries Management 

25:1386–1394.

Schmitz, O. J., E. Post, C. E. Burns, and K. M. Johnston. 2003. Ecosystem responses to global 

climate change: Moving beyond color mapping. BioScience 53:1199-1205.

Schoennagel, T., T. T. Veblen, W. H. Romme, J. S. Sibold, and E. R. Cook. 2005. ENSO and PDO 

variability affect drought-induced fire occurance in Rocky Mountain subalpine forests. 

Ecological Applications 15:2000–2014.

Schrag, A. M., A. G. Bunn, and L. J. Graumlich. 2008. Influence of bioclimatic variables on treeline conifer distribution in the Greater Yellowstone Ecosystem: Implications for species of 

conservation concern. Journal of Biogeography 35:698–710.

Schreiber, R. W., and E.A. Schreiber 1984. Central pacific seabirds and the El Nino-Southern 

Oscillation: 1982–1983 perspectives. Science 225:713–716.

Schwartz, C. C., M. A. Haroldson, G. C. White, R. B. Harris, S. Cherry, K. A. Keating, D. Moody, 

and C. Servheen. 2006. Temporal, spatial, and environmental influences on the demographics of grizzly bears in the Greater Yellowstone Ecosystem. Wildlife Monographs:1–68.

Scott, M. L., J. M. Friedman, and G. T. Auble. 1996. Fluvial process and the establishment of bottomland trees. Geomorphology 14:327-339.

Scott, M. L., P. B. Shafroth, and G. T. Auble. 1999. Responses of riparian cottonwoods to alluvial 

water table declines. Environmental Management 23:347-358.
76

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Seastedt, T. 2002. Base camps of the Rockies: The intermountain grasslands. Pages 219–236 in J. S. 

Baron, editor. Rocky Mountain futures: An ecological perspective. Island Press, Washington, D.C., USA.

Seastedt, T. R., W. D. Bowman, T. N. Caine, D. McKnight, A. Townsend, and M. W. Williams. 

2004. The landscape continuum: A model for high-elevation ecosystems. BioScience 

54:111–121.

Sekercioglu, C. H., S. H. Schneider, J. P. Fay, and S. R. Loarie. 2008. Climate change, elevational 

range shifts, and bird extinctions. Conservation Biology 22:140–150.

Shaw, J. D., B. E. Steed, and L. T. DeBlander. 2005. Forest inventory and analysis (FIA) annual 

inventory answers the question: What is happening to pinyon-juniper woodlands? Journal 

of Forestry 103:280–285.

Sheppard, P. R., A. C. Comrie, G. D. Packin, K. Angersbach, and M. K. Hughes. 2002. The climate 

of the US Southwest. Climate Research 21:219-238.

Shepperd, W. D., D. L. Bartos, and S. A. Mata. 2001a. Above- and below-ground effects of aspen 

clonal regeneration and succession to conifers. Canadian Journal Of Forest Research-Revue Canadienne De Recherche Forestiere 31:739–745.

Shepperd, W. D., D. Binkley, D. L. Bartos, T. J. Stohlgren, and L. G. Eskew. 2001b. Sustaining 

aspen in western landscapes, symposium proceedings, 13-15 June 2000,; Grand Junction, 

Colorado. Proceedings RMRS-P-18. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, Colorado, USA.

Sherriff, R. L., and T. T. Veblen. 2008. Variability in fire-climate relationships in ponderosa pine 

forests in the Colorado front range. International Journal of Wildland Fire 17:50-59.

Shoo, L. P., S. E. Williams, and J. M. Hero. 2005. Potential decoupling of trends in distribution area and population size of species with climate change. Global Change Biology 

11:1469–1476.

Sibold, J. S., and T. T. Veblen. 2006. Relationships of subalpine forest fires in the Colorado front 

range to interannual and multi-decadal scale climatic variation. Journal of Biogeography 

33:833–842.

Sibold, J. S., T. T. Veblen and M. E. Gonzalez. 2006. Spatial and temporal variation in historic fire 

regimes in subalpine forests across the Colorado front range in Rocky Mountain National 

Park. Journal of Biogeography 32:631–647. 

Smith, A. T., and M. L. Weston. 1990. Ochotona princeps. Mammalian Species:1–8.

Smith, S. D., R. K. Monson, and J.E. Anderson. 1997. Physiological ecology of North American 

desert plants. Springer-Verlag, Berlin. 

Smith, S. D., T. E. Huxman, S. F. Zitzer, T. N. Charlet, D. C. Housman, J. S. Coleman, L. K. Fenstermaker, J. R. Seemann, and R. S. Nowak. 2000. Elevated CO2

 increases productivity and 

invasive species success in an arid ecosystem. Nature 408:79–82.

Smith, W. B., J. S. Vissage, D. R. Darr, and R. M. Sheffield. 2001. Forest resources of the United 

States, 1997. General Technical Report NC-219. USDA Forest Service, North Central Research Station, St. Paul, Minnesota, USA.

Soule, P. T., P. A. Knapp, and H. D. Grissino-Mayer. 2004. Human agency, environmental drivers, and western juniper establishment during the late holocene. Ecological Applications 

14:96–112.
77

Literature Cited Literature Cited

Sparks, T. H., F. Bairlein, J. G. Bojarinova, O. Huppop, E. A. Lehikoinen, K. Rainio, L. V. Sokolov, 

and D. Walker. 2005. Examining the total arrival distribution of migratory birds. Global 

Change Biology 11:22–30.

Steltzer, H., C. Landry, T. H. Painter, J. Anderson, and E. Ayres. 2009. Biological consequences 

of earlier snowmelt from desert dust deposition in alpine landscapes. Proceedings of the 

National Academy of Sciences of the United States of America 106:11629–11634.

Steltzer, H., and E. Post. 2009. Seasons and life cycles. Science 324:886–887.

Stenseth, M. C., A. Mysterud, G. Ottersen, J. W. Hurrell, K.S. Chan, and M. Lima. 2002. Ecological effects of climate fluctuations. Science 297:1292–1296.

Stewart, I. T., D. R. Cayan, and M. D. Dettinger. 2005. Changes toward earlier streamflow timing 

across western North America. Journal of Climate 18:1136–1155.

Stewart, M. M. 1995. Climate driven population fluctuations in rain forest frogs. Journal of Herpetology 29:437-466.

Stohlgren, T. J., T. T. Veblen, K. C. Kendall, W. L. Baker, C. D. Allen, J. A. Logan, and K. C. Ryan. 

2002. The heart of the Rockies: Montane and subalpine ecosystems. Pages 203–218 in J. S. 

Baron, editor. Rocky Mountain futures: An ecological perspective. Island Press, Washington, D.C., USA.

Strand, E. K., S. C. Bunting, R. K. Steinhorst, L. K. Garrett, and G. H. Dicus. 2009. Upper Columbia Basin Network aspen monitoring protocol. Natural Resource Report NPS/UCBN/

NRR-2009/147. National Park Service, Fort Collins, Colorado, USA.

Street, F. A., and A. T. Grove. 1979. Global maps of lake-level fluctuations since 30,000 yr BP. Quaternary Research 12:83–118.

Stromberg, J. C., R. Tiller, and B. Richter. 1996. Effects of groundwater decline on riparian vegetation of semiarid regions: The San Pedro, Arizona. Ecological Applications 6:113–131.

Sturm, M., C. Racine, and K. Tape. 2001. Climate change: Increasing shrub abundance in the 

Arctic. Nature 411:546–547.

Swetnam, T. W., and A. M. Lynch. 1993. Multicentury, regional-scale patterns of western spruce 

budworm outbreaks. Ecological Monographs 63:399–424.

Tagaris, E., K.-J. Liao, K. Manomaiphiboon, J.-H. Woo, S. He, P. Amar, and A. G. Russell. 

2008. Impacts of future climate change and emissions reductions on nitrogen and 

sulfur deposition over the United States, Geophysical Research Letters 35, L08811, 

doi:10.1029/2008GL033477.

Taylor, P. D., L. Fahrig, K. Henein, and G. Merriam. 1993. Connectivity is a vital element of landscape structure. Oikos 68:571-573.

TNC [The Nature Conservancy]. 2009. Montana’s Northern Prairies. [Available online?] 

Helena,Montana, USA.

Tomback, D. F., and K. C. Kendall. 2002. Rocky road in the Rockies: Challenges to biodiversity. 

Pages 153–180 in J. S. Baron, editor. Rocky Mountain futures: An ecological perspective. 

Island Press, Washington.

Ultsch, G. R., D. F. Bradford, and J. Freda. 1999. Physiology: Coping with the environment. Pages 

189–214 in R. W. McDiarmid and R. Altig, editors, Tadpoles: The biology of anuran larvae. 

University of Chicago Press, Chicago, Illinois, USA.
78

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

USDA [US Department of Agriculture]. 2008a. Colorado forest heath highlights 2008. Available 

at http://www.fs.fed.us/foresthealth/fhm/fhh/fhh_08/co_fhh_08.pdf. USDA Forest Service, 

Fort Collins, Colorado, USA.

USDA [US Department of Agriculture]. 2008b. Wyoming forest heath highlights 2008. Available 

at http://www.fs.fed.us/foresthealth/fhm/fhh/fhh_08/wy_fhh_08.pdf. USDA Forest Service, 

Cheyenne, Wyoming, USA.

USEPA [US Environmental Protection Agency]. 1998. National air quality and emissions trends 

report,1997. Office of Air Quality Planning and Standards, Washington, D.C., USA.

USEPA [US Environmental Protection Agency]. 2008a. Key elements of the Clean Air Act. Available at http://www.epa.gov/air/peg/elements.html. Washington, D. C.

USEPA [US Environmental Protection Agency]. 2008b. National air quality status and trends 

through 2007. Office of Air Quality Planning and Standards, Washington, D.C., USA.

USFWS [US Fish and Wildlife Service]. 2010. Endangered and threatened wildlife and plants; 

12-month finding on a petition to list the American pika as threatened or endangered. 50 

CFR Part 17. Available online at http://www.fws.gov/mountain-prairie/species/mammals/

americanpika/02052010FRTemp.pdf

USGS [US Geological Survey]. 2010. Nonindigenous aquatic species. Available at http://nas.

er.usgs.gov/taxgroup/mollusks/zebramussel/. Department of the Interior.

Van Arsdel, E. P, B. W. Geils, and P. J. Zambino. 2006. Epidemiology for hazard rating of white 

pine blister rust. Pages 49-61 in J. Guyon, compiler. Proceedings of the 53rdWestern International Forest Disease Work Conference; 26–29 August 2005; Jackson, Wyoming. USDA 

Forest Service, Intermountain Region, Ogden, Utah, USA. 

Van Buskirk, J. R. S. Mulvihill, and R. C. Leberman. 2010. Declining body sizes in North American birds associated with climate change. Oikos 000:001-009.

Van Mantgem, P. J., and N. L. Stephenson. 2007. Apparent climatically induced increase of tree 

mortality rates in a temperate forest. Ecology Letters 10:909–916.

Van Ruijven, J., and F. Berendse. 2005. Diversity–productivity relationships: Initial effects, longterm patterns, and underlying mechanisms. Proceedings of the National Academy of Sciences of the United States of America 102:695–700.

Veblen, T. T., T. Kitzberger, and J. Donnegan. 2000. Climatic and human influences on fire 

regims in ponderosa pine forests in the Colorado front range. Ecological Applications 

10:1178–1195.

Vieira, M. 2006. Moose management plan: Data analysis unit M-2 Laramie River herd. Colorado 

Division of Wildlife, Fort Collins, Colorado, USA.

Vingarzan, R. 2004. A review of surface ozone background levels and trends. Atmospheric Environment 38:3431–3442.

Visser, M. E., and C. Both. 2005. Shifts in phenology due to global climate change: The need for a 

yardstick. Proceedings of the Royal Society of London, Series B 272:2561–2569.

Vitousek, P. M. 1992. Global environmental change: An introduction. Annual Review of Ecology 

and Systematics 23:1–14.

Vitousek, P. M., H. A. Mooney, J. Lubchenco, and J. M. Melillo. 1997. Human domination of 

Earth’s ecosystems. Science 277:494–499.
79

Literature Cited Literature Cited

Volney, W. J. A., and R. A. Fleming. 2000. Climate change and impacts of boreal forest insects. 

Agriculture, Ecosystems & Environment 82:283–294.

Vose, R. S., D. Wuertz, T. C. Peterson, and P. D. Jones. 2005. An intercomparison of trends in 

surface air temperature analyses at the global, hemispheric, and grid-box scale. Geophysical 

Research Letters 32.

Walker, M. D., C. H. Wahren, R. D. Hollister, G. H. R. Henry, L. E. Ahlquist, J. M. Alatalo, M. S. 

Bret-Harte, M. P. Calef, T. V. Callaghan, A. B. Carroll, and others. 2006. Plant community 

responses to experimental warming across the tundra biome. Proceedings of the National 

Academy of Sciences of the United States of America 103:1342–1346.

Walker, M. D., D. A. Walker, T. A. Theodose, and P. J. Webber. 2001. The vegetation: Hierarchial 

species-environment relationships. Pages 99–127 in W. D. Bowman and T. Seastedt, editors. Structure and function of an alpine ecosystem. Oxford University Press, Niwot Ridge, 

Colorado, USA.

Walther, G. R., S. Beißner, C. A. Burga, and P. S. White. 2005. Trends in the upward shift of alpine 

plants. Journal of Vegetation Science 16:541–548.

Walther, G. R., S. Beißner, C. A. Burga, and P. S. White. 2005. Trends in the upward shift of alpine 

plants. Journal of Vegetation Science 16:541–548.

Walther, G. R., E. Post, P. Convey, A. Menzel, C. Parmesan, T. J. C. Beebee, J. M. Fromentin, O. 

Hoegh-Guldberg, and F. Bairlein. 2002. Ecological responses to recent climate change. 

Nature 416:389–395.

Wang, G., N. Thompson Hobbs, F. J. Singer, D. S. Ojima, and B. C. Lubow. 2002. Impacts of Climate Changes on Elk Population Dynamics in Rocky Mountain National Park, Colorado, 

USA. Climatic Change 54:205–223.

Wang, H., S. Schubert, M. Suarez, J. Chen, M. Hoerling, A. Kumar, and P. Pegion. 2008. Attribution of the seasonality and regionality in climate trends over the United States during 

1950–2000. Journal of Climate 22:2571–2590.

Waters, T. F. 1995. Sediment in streams: Sources, biological effects, and control. American Fisheries Society Monograph 7.

Werner, E. E., R. A. Relyea, K. L. Yurewicz, D. K. Skelly, and C. J. Davis. 2009. Comparative landscape dynamics of two anuran species: Climate-driven interaction of local and regional 

processes. Ecological Monographs 79:503–521.

West, N. E., and J. A. Young. 2000. Intermountain valleys and lower mountain slopes. Pages 

255–284 in M. G. Barbour and W. D. Billings, editors. North American terrestrial vegetation. Cambridge University Press, Cambridge, UK.

Westerling, A., and B. Bryant. 2008. Climate change and wildfire in California. Climatic Change 

87:231–249.

Westerling, A. L., H. G. Hidalgo, D. R. Cayan, and T. W. Swetnam. 2006. Warming and earlier 

spring increase western US forest wildfire activity. Science 313:940–943.

WGFD [Wyoming Game and Fish Department]. 2005. Wyoming’s species of greatest conservation need. http://gf.state.wy.us/wildlife/CompConvStrategy/CWCSSpeciesList050505.pdf.

http://gf.state.wy.us/wildlife/CompConvStrategy/CWCSSpeciesList050505.pdf

Whitlock, C., and P. J. Bartlein. 1993. Spatial variations of holocene climatic change in the Yellowstone region. Quaternary research 39:231–238.
80

Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin

Whitlock, C., J. Marlon, C. Briles, A. Brunelle, C. Long, and P. Bartlein. 2008. Long-term relations 

among fire, fuel, and climate in the northwestern US based on lake-sediment studies. International Journal of Wildland Fire 17:72–83.

Whitlock, C., M. A. Reasoner, and C. H. Key. 2002. Paleoenvironmental history of the rocky 

mountain region during the past 20,000 years. Pages 41–57 in J. S. Baron, editor. Rocky 

Mountain futures: An ecological perspective. Island Press, Washington, D.C., USA.

Whitlock, C., S. L. Shafer, and J. Marlon. 2003. The role of climate and vegetation change in shaping past and future fire regimes in the northwestern US and the implications for ecosystem 

management. Forest Ecology and Management 178:5–21.

Wickham, J. D., T. G. Wade, K. B. Jones, K. H. Riitters, and R. V. O’Neill. 1995. Diversity of ecological communities of the United States. Vegetatio 119:91–100.

Williams, J. E., N. G. Gillespie, H. M. Nelville, and W. T. Colyer. 2007. Healing troubled waters: 

Preparing trout and salmon habitat for a changing climate. Trout Unlimited, Arlington, 

Virginia, USA.

Williams, J. E., A. L. Haak, H. M. Neville, and W. T. Colyer. 2009. Potential consequences of 

climate change to persistence of cutthroat trout populations. North American Journal of 

Fisheries Management 29:533–548.

Williams, M. W., and N. Caine. 2001. Hydrology and hydrochemistry. Pages 75–96 in W. D. 

Bowman and T. Seastedt, editors. Structure and function of an alpine ecosystem. Oxford 

University Press, Niwot Ridge, Colorado, USA.

Williams, M. W., and K. A. Tonnessen. 2000. Critical loads for inorganic nitrogen deposition in the 

Colorado front range, USA. Ecological Applications 10:1648–1665.

Williamson, M., and A. Fitter. 1996. The varying success of invaders. Ecology 77:1661–1666.

Winder, M., and D. E. Schindler. 2004. Climatic effects on the phenology of lake processes. 

Global Change Biology 10:1844–1856.

Winkler, D. W., P. O. Dunn, and C. E. McCulloch. 2002. Predicting the effects of climate change 

on avian life-histories. Proceedings of the National Academy of Science of the United States 

99:13,595–13,599.

Winter, T. C. 2000. The vulnerability of wetlands to climate change: A hydrologic landscape perspective. Journal of the American Water Resources Association 36:305–311.

Wormworth, J., and K. Mallon. 2008. Bird species and climate change. The global status report: A 

synthesis of current scientific understanding of anthropogenic climate change impacts on 

global bird species now and projected future effects. Climate Risk Pty Limited, Fairlight, 

NSW.

Worrall, J. J., R. A. Mask, T. Eager, L. Egeland, and W. D. Shepperd. 2008. Sudden aspen decline in 

southwest Colorado. Phytopathology 98:S173–S173.

WSF [Wild Sheep Foundation]. 2010. Bighorn sheep continue to succumb to pneumonia. Available at http://www.wildsheepfoundation.org/Page.php/News/131. Cody, Wyoming, USA.

Young, P. J., A. Arneth, G. Schurgers, G. Zeng, and J. A. Pyle. 2009. The CO2 inhibition of terrestrial isoprene emission significantly affects future ozone projections. Atmospheric Chemistry 

and Physics 9:2793–2803.
81

Literature Cited Literature Cited

Zedler, J. B., and S. Kercher. 2005. Wetland resources: Status, trends, ecosystem services, and 

restorability. Annual Review of Environment and Resources 30:39–74.

Zier, J. L., and W. L. Baker. 2006. A century of vegetation change in the San Juan Mountains, 

Colorado: An analysis using repeat photography. Forest Ecology and Management 

228:251–262.

The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and 

other information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated 

Island Communities.

NPS 960/104295, June 2010 
National Park Service

U.S. Department of the Interior

Natural Resource Program Center 

1201 Oak Ridge Drive, Suite 150 

Fort Collins, Colorado 80525

www.nature.nps.gov

EXPERIENCE YOUR AMERICATM