Climate Change on the 

Shoshone National Forest, Wyoming:

A Synthesis of Past Climate, Climate Projections, and 

Ecosystem Implications

Janine Rice, Andrew Tredennick, and Linda A. Joyce

United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-264

January 2012
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Rice, Janine; Tredennick, Andrew; Joyce, Linda A. 2012. Climate change on 

the Shoshone National Forest, Wyoming: a synthesis of past climate, climate 

projections, and ecosystem implications. Gen. Tech. Rep. RMRS-GTR-264. Fort 

Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain 

Research Station. 60 p.

Abstract

The Shoshone National Forest (Shoshone) covers 2.4 million acres of mountainous 

topography in northwest Wyoming and is a vital ecosystem that provides clean 

water, wildlife habitat, timber, grazing, recreational opportunities, and aesthetic 

value. The Shoshone has experienced and adapted to changes in climate for 

many millennia, and is currently experiencing a warming trend that is expected 

to accelerate in the next century. Climate change directly and indirectly affects 

the Shoshone’s high-elevation, mountainous terrain that supports unique and 

sometimes rare ecological components. Several vulnerable and very responsive 

resources and processes on the Shoshone could interact to produce unforeseeable 

or undesirable ecosystem changes, highlighting the need to identify potential 

resource vulnerabilities and develop adaptation pathways and flexibility in 

resource management options. The objective of this report is to synthesize the 

current understanding of the paleo and historical climate of the Shoshone as 

a reference point, determine what future climates may look like, and what the 

effects of future climate may be on natural resources. This information allows 

for the identification of vulnerabilities and information gaps, thereby aiding the 

development of adaptation tools and strategies.

Keywords: climate change, ecosystem services, vulnerability, resource 

management, Shoshone National Forest, Greater Yellowstone Ecosytem

Authors

Janine Rice is a Research Associate with the University of Colorado, Western 

Water Assessment and the U.S. Department of Agriculture Forest Service, Rocky 

Mountain Research Station, Fort Collins, Colorado.

Andrew Tredennick is a doctoral student at Colorado State University, Fort 

Collins, Colorado.

Linda A. Joyce is a Quantitative Ecologist with the Human Dimensions Research 

Program at the U.S. Department of Agriculture Forest Service, Rocky Mountain 

Research Station, Fort Collins, Colorado.

Acnowledgments

We acknowledge support for this project from the USDA Forest Service, Global 

Change Research Program, which funded the larger project “A Toolkit for Adapting 

to Climate Change on Western National Forests: Incorporating Climate into 

Resource Management and Planning.” We also thank several reviewers: Bryan 

Armel, Greg Bevenger, Ray Zubik, Kent Houston, Claudia Regan, Polly Hays, 

Cindy Swanson, Tom Olliff, and Virginia Kelly.
Contents

Introduction............................................................................................................................1

Climate of the Greater Yellowstone Ecosystem and Shoshone National Forest........................3

Current Climate of the Greater Yellowstone Ecosystem and Shoshone National Forest ....3

Greater Yellowstone Ecosystem Twentieth Century Precipitation Variability ...................11

Historic Climate of the Shoshone National Forest and Greater Yellowstone 

Ecosystem: 20,000 BP to the Twentieth Century ........................................................12

Future Climate on the Shoshone National Forest..................................................................14

Climate Projections.......................................................................................................14

Climate Projections Used in Existing Ecological Response Models................................16

Climate Change Effects on Ecosystems: Observed Trends and Future Projections.................20

Introduction..................................................................................................................20

Water and Aquatic Systems...........................................................................................20

Water Quality ...............................................................................................................23

Glaciers........................................................................................................................24

Snow ............................................................................................................................25

Wetlands ......................................................................................................................27

Vegetation.....................................................................................................................28

Invasive Species............................................................................................................33

Fire ...............................................................................................................................33

Insects and Pathogens ...................................................................................................35

Wildlife.........................................................................................................................37

Fish...............................................................................................................................39

Biochemical Cycling.....................................................................................................41

Economies....................................................................................................................42

Land Use ......................................................................................................................44

Knowledge and Data Gaps....................................................................................................48

Conclusion and Summary .....................................................................................................49

Literature Cited.....................................................................................................................50

Appendix Tables....................................................................................................................59

Shoshone National Forest
Figure 1. Shoshone National Forest boundary.
USDA Forest Service RMRS-GTR-264. 2012. 1

Introduction

Climate is defined as the average weather or, more rigorously, as the statistical description in terms of the mean and 

variability of relevant quantities (for example, temperature, 

precipitation, snow, and wind) over a period of time ranging 

from months to thousands or millions of years (IPCC 2007a). 

From the paleo (prehistoric) records, we know that climate is 

constantly changing and that these changes prompt ecosystems to adjust (Whitlock 1993; Lyford and others 2003). As 

a natural process, this reactive adjustment is the adaptation 

that species and ecosystems make in response to environmental changes. Within human systems, adaptation refers 

to management actions and decisions that help ecological, 

social, and economic systems accommodate the challenges 

imposed or seek opportunities that arise from variations in 

climate and other disturbances (Joyce and others 2008a).

The effects of climate change on ecosystem structure, 

function, and benefits humankind receives from natural 

ecosystem resources and processes (ecosystem services) 

are functions of the ecological sensitivity to variations in 

climate, the degree to which the climate changes, and the 

adaptability of plants and animals (Hassan and others 2005 

[Part II: Assessment of Ecosystem Services]; Brown and 

others 2006; Joyce and others 2008a). While knowledge 

of regional and local climates and their variations across 

the landscape is important for resource management decisions, even more important may be an understanding of the 

vulnerability and the adaptive capacity of plants, animals, 

and ecosystems facing a changing climate. The information 

provided in this report helps to identify potential adaptation 

pathways and flexibility in resource management options.

Climate change introduces a significant challenge for 

land managers and decision-makers in the western United 

States, as climate related changes of ecosystems behavior 

(e.g., glacier melt, snow cover, snowpack, beetle outbreaks, 

length of growing season, and wildfires) are already being 

documented (Ryan and others 2008; U.S. EPA 2010). The 

rapid accumulation of scientific information of the effects of 

climate change over the last 20 years has been challenging 

for resource managers to effectively incorporate into on-theground management. While much information is available, 

it is difficult to extrapolate research results from other environments to the landscape of interest to resource managers. 

Also, many existing paradigms (e.g., historic range of variation) and tools (e.g., planting guidelines) assume long-term 

climate stability, which may no longer be viable.

East of Yellowstone National Park (YNP) and west of 

small towns, ranches, irrigated agricultural lands, and the 

Wind River Indian Reservation, the Shoshone National Forest 

(Shoshone) in northwest Wyoming provides diverse habitats 

for plants and animals as well as a variety of ecosystem services (Figure 1). Covering 2.4 million acres (982,982 ha) 

and elevation gradients spanning from 4599 (1402 m) at 

Clarks Fork Canyon to 13,845 ft (4221 m) at Gannet Peak, 

Wyoming’s highest peak, the Shoshone is home to alpine 

meadows, conifer and aspen forests, grasslands, and sagebrush shrublands. Sensitive species such as the Yellowstone 

cutthroat trout (Oncorhynchus clarkii bouvieri) and lynx 

(Lynx canadensis) find habitat on the Shoshone. The diversity of ecosystem services includes domestic livestock 

grazing, mining, oil and gas leasing, and timber harvest, 

as well as recreation, tourism, and water for irrigation. The 

surrounding communities benefit economically from tourism and recreation activities within the Shoshone and the 

nearby YNP. Opportunities include the first designated Wild 

and Scenic River, the Clarks Fork of the Yellowstone River, 

the internationally recognized Continental Divide National 

Scenic Trail and Nez Perce National Historic Trail, as 

well as five wilderness areas—North Absaroka, AbsarokaBeartooth, Washakie, Fitzpatrick, and Popo Agie. Water 

runoff from the Shoshone contributes to hydropower generation at the Buffalo Bill and Shoshone dams, and to irrigation 

water for agricultural lands to the east. The Shoshone is 

home to a large concentration of glaciers that occupy high 

elevations in the Wind River and Absaroka mountain ranges 

(Krimmel 2002).

The Shoshone’s diverse ecosystems and services they 

provide may experience changes in climate that they may or 

may not be able to adapt to. Ecosystem services (benefits we 

receive from ecosystems) that may be vulnerable to climate 

change include: provisioning services such as water supply 

and food production, regulating services such as erosion or 

flood control and carbon (C) storage, cultural services such 

as recreational benefits, and supporting services such as 

nutrient cycling that maintain conditions for life on Earth 

(MEA 2005). The objective of this report is to synthesize the 

current understanding of the paleo and historical climate of 

the Shoshone as a reference point, determine what future climates may look like, and what the effects of future climate 

may be on natural resources. This information allows for the 

identification of vulnerabilities and information gaps, thereby aiding the development of adaptation tools and strategies. 

Current scientific information presented in this report draws 

on the referred and gray literature for studies done within the 

boundaries of the Shoshone and studies conducted in similar geographic areas, and at larger spatial scales. We draw 

on studies focusing on the Greater Yellowstone Ecosystem 

(GYE) (Figure 2) or on the western or entire United States, 

or on general studies when no Shoshone-specific information is available. However, many of these studies focus on 

YNP—the differences between the outlying areas and the 

Shoshone have not been studied in depth. Where existing 

paradigms and tools have been scrutinized in the light of 

a changing climate, we report the implications of climate 

change to these traditional management practices. Where 

little information is available, we identify needed research.
2 USDA Forest Service RMRS-GTR-264. 2012.

Figure 2. Climate station locations for (a) the Historical Climate Network on the Shoshone and GYE; (b) Climate 

Divisions 1, 4, and 9; and (c) Climate stations on or near the Shoshone National Forest.

(a)

(b) (c)
USDA Forest Service RMRS-GTR-264. 2012. 3

Climate of the Greater 

Yellowstone Ecosystem and 

Shoshone National Forest

Scientific research combined with management experience reflects an awareness of the variation in current climate 

and an understanding of the great variation of climate from 

20,000 years before present (BP) to present within the GYE. 

We summarize current climate and climate of the Twentieth 

Century for the GYE based on observations. Over this period, management direction within the GYE has evolved based 

on the experience of managers with climatic events such as 

droughts and fire. Research studies on climate in the western 

United States from the Last Glacial Maximum (20,000 BP) 

to the Twentieth Century has deepened the understanding of 

climate dynamics and the response of vegetation and ecosystems to changes in climate. We summarize this research 

where it focused on the GYE and the Shoshone. We compare 

the variation of the paleoclimate with the historical climate 

on which current management is based.

Current Climate of the Greater Yellowstone 

Ecosystem and Shoshone National Forest

Introduction

Although the State of Wyoming has many climate and 

hydrology networks collecting weather and water data 

(Curtis and Grimes 2004; Table 2.A), few with complete, 

long-term records are found within the Shoshone or at high 

elevations in the GYE. We draw on a variety of published 

sources and data to describe the current (1971 to 2000) 

and Twentieth Century historical climate of the GYE and 

Shoshone. To explore the spatial patterns of climate within 

the GYE, we use spatially interpolated climate data from the 

Parameter-Elevation Regressions and Independent Slopes 

Model (PRISM) at 2625-ft (800-m) grid resolution (Daly 

and others 2008). Two generalized precipitation regimes 

have been used to define seasonal precipitation patterns in 

the GYE (Despain 1987). We use the ratio between summer 

and winter precipitation to explore these patterns across the 

GYE.

To establish a basis for comparison of climate over 

time, we obtained climate data (see below for sources, also 

Appendix Tables 1 through 3) to compute 30-year averages 

over the Twentieth Century (1901-1930 to 1971-2000) and 

explore the variation in this metric over 100 years following Curtis and Grimes (2002). The temporal patterns of 

the Twentieth Century climate are explored at three different spatial scales: GYE, climate division within northwest 

Wyoming, and the Shoshone (Figure 2). To establish the recent historical climate of the GYE, data from 19 Historic 

Climate Network stations (http://cdiac.ornl.gov/epubs/ndp/

ushcn/access.html) located in northwest Wyoming, eastern 

Idaho, and southwest Montana were analyzed (Figure 2a). 

Three of the 10 climate divisions in the State of Wyoming 

fall on the Shoshone: the Yellowstone River Drainage 

(Division 1), the Big Horn River Drainage (Division 4), 

and the Wind River Drainage (Division 9) (NOAA 2010, 

http://www.esrl.noaa.gov/psd/data/timeseries/). Divisional 

data have been used to explore large scale anomalies such 

as droughts and cold winters (Guttman and Quayle 1996). 

Gray and others (2007) found that the climate records from 

Division 1 were closely related to the tree growth, as measured in long-term tree ring data in southwestern Montana 

and northwestern Wyoming (Figure 3). Temporal patterns 

are examined at the level of these three divisions to contrast 

with the climate of the GYE (Figure 2b). Finally, 6 climate 

stations (Western Regional Climate Center 2010; http://

www.wrcc.dri.edu/summary/Climsmwy.html) and 20 snowpack telemetry (SNOTEL) stations (NRCS 2010; http://

www.wcc.nrcs.usda.gov/snotel/Wyoming/wyoming.html) 

that fall within or near the Shoshone are used to identify 

finer spatial patterns (Figures 2a and 2c). The data available 

from the six climate stations varies in length from 10 years 

Figure 3. Approximate location for tree ring sites from 

Gray and others (2006), and pollen record sites from 

Whitlock and Bartlein (1993), Whitlock (1993), and 

Huerta and others (2009).
4 USDA Forest Service RMRS-GTR-264. 2012.

to nearly 100 years; whereas the SNOTEL sites have periods of record of about 30 years (1980s to 2009). Elevations 

of the climate stations range from 5390 to 8160 ft (1643 to 

2489 m), and for the SNOTEL sites from 7120 to 10,100 ft 

(2170 to 3078 m) (Appendix Table 3).

Spatial Climate Patterns

Spatial patterns of annual temperature and cumulative 

annual precipitation vary greatly across the GYE region 

(Figures 4 and 5). The coolest temperatures (<32 oF [0 oC]) 

were recorded mostly on the Shoshone in the Wind River 

Mountains, in the Absaroka Mountains, and just to the 

north of the Shoshone into southern Montana (see Figure 1 

for mountain range location and Figure 4 for temperature). 

Annual precipitation is greatest in the western parts of YNP 

and just south of this area (Figure 5). Valley bottoms and 

the high plains are the warmest and driest areas of the GYE, 

which have a growing season (sum of growing degree days 

greater than 2500) longer than five months, while upper elevations can have a growing season of two to three months 

(Hansen 2006). Based on the PRISM data (Daly and others 

2008), annual temperatures within the Shoshone range from 

47 oF (8 oC) in the lowest elevations to 10 °F (-12 °C) in the 

highest elevations (Figure 4). Annual precipitation for the 

Shoshone ranges from 10 inches/year (254 mm/year) in the 

lowest elevations to 60 inches/year (1525 mm/year) in the 

highest elevations—much less than the nearly 100 inches 

(2540 mm) received in other mountain ranges of the GYE 

(Figure 5). Precipitation in the valleys and plains to the east 

and south of the Shoshone can be less than 10 inches per 

year (254 mm/year) (Figure 5).

Figure 4. Average temperature (°F) (1971 to 2000).

Figure 5. Average precipitation (inches) (1971 to 2000).
USDA Forest Service RMRS-GTR-264. 2012. 5

Winter-wet and summer-wet precipitation regimes 

(Figure 6) are a result of the GYE being situated between 

a transition zone of two major continental air masses in the 

Southwest and Pacific Northwest that have remained stable 

for about 9000 years (Despain 1987; Mock 1996; Huerta and 

others 2009). The summer monsoon cycle from the Gulfs 

of California and Mexico influences the summer-wet areas 

of the GYE. Summer-wet areas can be seen in the northern 

and eastern areas of the GYE, especially at lower elevations 

(Figure 6, pink areas). The Pacific Northwest experiences 

high levels of winter precipitation and dry summers that influence the winter-wet areas of the GYE. Winter-wet areas 

can be seen to the west and south of the GYE, especially 

at high elevations (Figure 6, blue areas). Winter season is 

defined as December through February, and summer as June 

through August.

Shoshone summer-wet, low-elevation areas commonly 

receive twice as much precipitation during summer as opposed to winter. Some of these low-elevation areas can 

receive up to four times as much precipitation during summer as opposed to winter. Winter-wet areas can commonly 

receive twice as much precipitation during winter, and in the 

highest elevations of the Western Shoshone, up to four times 

as much precipitation during winter (Figure 6). Areas west 

of the Shoshone can receive as much as 4 to 10 times more 

precipitation during winter compared to summer (Figure 6).

Temporal Climate Patterns

The Greater Yellowstone Ecosystem

Temporal patterns of temperature and precipitation across 

the GYE show several months with an average temperature 

less than freezing and monthly precipitation of 1 to 2.5 

inches (25.4 to 63.5 mm) (Figure 7). According to data from 

19 Historical Climate Network stations within the GYE, 

annual precipitation averaged around 16 inches (406 mm) 

(Figure 7a), and annual temperature was just under 40 °F 

(4.4 °C) (moving average of 30-year periods from 1901 to 

2000) (Figure 7b).

The 30-year averages for annual precipitation increased 

from slightly above 15 inches (381 mm) from 1901 to 1930, 

to over 18 inches (457 mm) from 1971 to 2000 (Figure 7a). 

Monthly precipitation is greatest in May and June, and these 

months also show the greatest variation—nearly 1 inch 

(25 mm) across all of the 30-year averages. Other months, 

such as February showed little variation in the 30-year 

precipitation averages across the 100-year period; however, precipitation for all months except January, June, and 

December, increased in the second half of the century.

The 30-year averages for annual temperature increased 

nearly 1 °F (0.6 °C) across the 100-year period (Figure 7b). 

Monthly temperatures ranged from 17 °F (-8 °C) during 

January to 63 °F (17 °C) during July. As with precipitation, 

the monthly 30-year averages varied over the 100 years. 

The greatest variation (more than 2 °F [1.1 °C]) was seen in 

February and March. June through August 30-year averages 

varied less than 1 °F (0.6 °C). A decrease in fall temperatures 

was observed since mid-century.

Climate Divisions of Northwest Wyoming

The Twentieth Century increases in the 30-year precipitation averages that were observed at the scale of the GYE 

were not observed in the Divisional summaries (Drainages) 

(Figure 8); however, the increases in GYE annual temperatures were consistently observed in all three Drainages 

(Figure 9). The seasonal and temporal patterns of the summaries differ in magnitude and seasonality from the GYE 

summary, reflecting topography within the Drainages as 

well as their relationship to the summer-wet and winter-wet 

regimes. Elevations of the 19 stations used to describe the 

climate of the GYE ranged from 4744 to 7866 ft (1447 to 

2400 m), and averaged 5960 ft (1818 m); thus, the data may 

reflect limitations of climate stations at higher elevations 

and probably represent climate from lower GYE elevations. 

GYE elevations span approximately 4000 to 14,000 ft (1220 

to 4270 m).

In contrast to the patterns seen at the scale of the GYE, the 

30-year annual precipitation averages declined throughout 

the Twentieth Century for the Yellowstone River and Wind 

River Drainages (see Figure 8). The Yellowstone and Wind 

River monthly precipitation patterns were more similar to Figure 6. Summer/winter precipitation ratio (1971 to 

2000 average).
6 USDA Forest Service RMRS-GTR-264. 2012.

each other than the Big Horn patterns. For Yellowstone 

River and Wind River Drainages, the 30-year precipitation 

averages for most months tended to drop throughout the 

Twentieth Century, whereas the Big Horn monthly values 

exhibited much variability over time. The Yellowstone River 

Drainage had its largest monthly decreases of precipitation 

during winter and in May, the Big Horn River Drainage had 

its largest monthly decreases during late summer and in 

May, and the Wind River Drainage had its largest monthly 

decreases during early fall and late spring (Figure 8). The 

Big Horn River and Wind River Drainages generally fall on 

the east side of the GYE, which are influenced more by a 

summer-wet precipitation regime in contrast to the western 

parts of the GYE (Figure 6).

In addition to reflecting the increases in 30-year average temperatures observed at the scale of the GYE, all three 

Drainages also showed the decline in fall temperatures observed at the GYE since mid-century (Figure 9). Annual 

temperatures for each 30-year period have increased 1 to 

2 °F (0.6 to 1.1 °C) over the Twentieth Century, a much larger 

variation than at the GYE (Figure 7b). This difference may 

reflect the topographic variation within each division. The 

Yellowstone River Drainage encompasses northern portions 

of the Shoshone and YNP with few lower valley climate stations. While the Big Horn River and Wind River Drainages 

include climate stations from a larger number of lower valleys and towns, these Drainages also include the south and 

central Shoshone (Figure 2b). Monthly temperature averages have generally increased the most during winter (2 to 

4 °F [1.1 to 2.2 °C]) at all Drainages, exceeding the variation 

in the GYE (Figure 9). Monthly temperature averages have 

decreased the most during fall (1 to 3 °F [0.6 to 1.7 °C]) at all 

Drainages. The Yellowstone River Drainage had the highest 

winter and summer temperature increases compared to the 

Big Horn River and Wind River Drainage. The variations 

in mean monthly temperature were greatest in the winter 

months and least in the summer months (Figure 9).

Figure 7. Mean monthly and annual precipitation (inches) and temperatures (°F) of the GYE Historic Climate 

Network stations. (a) 30-year means (annual precipitation on right axis, monthly precipitation on left axis) 

and (b) 30-year means for monthly and annual temperature.

0	
  

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4	
  

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16	
  

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0	
  

0.5	
  

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2.5	
  

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Inches	
  

Inches	
  

1901-­‐1930	
  

1911-­‐1940	
  

1921-­‐1950	
  

1931-­‐1960	
  

1941-­‐1970	
  

1951-­‐1980	
  

1961-­‐1990	
  

1971-­‐2000	
  

a	
  

1901-­‐1930 1911-­‐1940 1921-­‐1950 1931-19611941-19701951-19801961-19901971-2000

Jan 16.80842 16.41912 15.82509 16.74491 17.00912 17.12281 17.53421 18.32

Feb 20.01632 19.74649 20.18018 20.20667 21.40912 21.95877 21.97263 22.31088

Mar 26.99421 26.85316 26.73825 26.33526 25.70263 26.16088 27.84807 29.51263

Apr 37.04211 37.09579 37.69018 37.69596 37.07596 36.48982 37.18719 37.89754

May 46.18193 47.02088 47.47421 47.57982 47.07982 46.94509 46.85807 47.13947

Jun 54.54263 55.5893 54.92965 54.87333 54.18807 55.03368 55.47579 55.67211

Jul 62.03961 62.94 63.04456 63.02351 62.50807 62.68211 62.63982 62.32912

Aug 60.21807 60.64579 60.93842 61.03667 60.7893 60.56667 60.75404 61.18088

Sep 50.83456 51.50228 51.76404 52.40544 51.67719 51.67807 51.27544 51.84509

Oct 40.86947 41.04368 42.13544 42.56175 42.14105 41.96702 41.64386 41.53421

Nov 29.69772 28.99982 29.16877 28.67737 29.01965 28.52965 28.77316 28.08807

Dec 19.09544 19.53772 20.47281 21.49965 20.78632 20.55842 19.2093 19.48246

Annual 38.69504 38.9495 39.1968 39.3867 39.11553 39.14108 39.2643 39.60937

10	
  

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60	
  

70	
  

Degree	
  F	
  

1901-­‐1930	
  

1911-­‐1940	
  

1921-­‐1950	
  

1931-­‐1961	
  

1941-­‐1970	
  

1951-­‐1980	
  

1961-­‐1990	
  

1971-­‐2000	
  

b	
  
USDA Forest Service RMRS-GTR-264. 2012. 7

Figure 8. Mean monthly and annual precipitation 30-year averages (a, b, and c) (annual 

precipitation on right axis, monthly precipitation on left axis) for Climate Divisions 1, 4, and 9.

2.5

2

1.5

1

Inches

0.5

0

Jan

Feb

Mar

Apr

May

Jun

Jul

AugSep

Oct

NovDec

Annual

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16

WIND RIVER DRAINAGE

DIVISION 9

Inches

1901-1930

1911-1940

1921-1950

1931-1960

1941-1970

1951-1980

1961-1990

1971-2000

c

2.5

2

1.5

1

Inches

0.5

0

Jan

FebMar

Apr

May

Jun

Jul

AugSep

Oct

NovDec

Annual

18

14

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4

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10

8

6

16

BIG HORN DRAINAGE

DIVISION 4

Inches

1901-1930

1911-1940

1921-1950

1931-1960

1941-1970

1951-1980

1961-1990

1971-2000

b

2.5

2

1.5

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Inches

0.5

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Jan

Feb

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May

Jun

Jul

AugSep

Oct

NovDec

Annual

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YELLOWSTONE RIVER DRAINAGE

DIVISION 1

Inches

1901-1930

1911-1940

1921-1950

1931-1960

1941-1970

1951-1980

1961-1990

1971-2000

a

18

14

12

4

2

0

10

8

6

16
8 USDA Forest Service RMRS-GTR-264. 2012.

Figure 9. Monthly and annual temperature 30-year averages (a, b, and c) for Climate 

Divisions 1, 4, and 9.

Jan

Feb

Mar

Apr

May

Jun

Jul

AugSep

Oct

NovDec

Annual

1901-1930

1911-1940

1921-1950

1931-1960

1941-1970

1951-1980

1961-1990

1971-2000

a

80

70

40

30

Degree F

10

50

20

60

WIND RIVER DRAINAGE

DIVISION 9

BIG HORN DRAINAGE

DIVISION 4

YELLOWSTONE RIVER DRAINAGE

DIVISION 1

Jan

Feb

Mar

Apr

May

Jun

Jul

AugSep

Oct

NovDec

Annual

1901-1930

1911-1940

1921-1950

1931-1960

1941-1970

1951-1980

1961-1990

1971-2000

b

80

70

40

30

Degree F

10

50

20

60

Jan

Feb

Mar

Apr

May

Jun

Jul

AugSep

Oct

NovDec

Annual

1901-1930

1911-1940

1921-1950

1931-1960

1941-1970

1951-1980

1961-1990

1971-2000

c

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70

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30

Degree F

10

50

20

60
USDA Forest Service RMRS-GTR-264. 2012. 9

The Shoshone Climate and SNOTEL Stations

The small set of stations within or near the Shoshone 

show averages for monthly and annual temperature and 

precipitation that range above and below the GYE averages 

(Figures 10 and 11). The three mountain ranges—Beartooth, 

Absaroka, and Wind River—provide orographic (the effect 

associated with mountains) variation along the 180 miles 

(290 km) north to south of the Shoshone (Figure 1). This 

topography creates a general east-west precipitation gradient 

in conjunction with the regional weather patterns—more precipitation occurs at higher elevations and less occurs at lower 

elevations and on the lee side of mountain ranges, which is 

generally the case with these six stations (Figure 10).

Higher-elevation areas in the western Shoshone experience wetter winters (Figure 6) because they receive winter 

storms from the Pacific air mass that moves in from the west. 

Summers are drier because these higher-elevation areas do 

not receive as much precipitation or intercept summer monsoonal flow from the south and east (Hansen 2006). The 

station with the highest precipitation is also the station with 

the shortest record—Yellowstone NP East Entrance. This 

station exhibits a more winter-wet precipitation regime, 

receiving highest monthly precipitation during December. 

Situated at 6952 ft (2119 m) on the boundary between YNP 

and the Shoshone, this station had a mean annual precipitation of 23 inches (584 mm) from 2000 to 2009 (Figure 10). 

The stations that exhibit more summer-wet conditions, 

receiving highest monthly precipitation during May and 

June are: Darwin Ranch, at the highest elevation (8160 ft 

[2489 m]) with 16 inches (406 mm) (36-year record); 

Crandall Creek (6640 ft [2025 m]) with 16 inches (406 mm) 

(60-year record); South Pass at the second highest elevation 

(7840 ft [2391 m]) with 13 inches (330 mm) (110-year record); Buffalo Bill Dam (5160 ft [1574 m]) with 11 inches 

(279 mm) (104-year record); and Dubois (6955 ft [2121 m]) 

with 9 inches (229 mm) (104-year record) (Figure 11).

Darwin Ranch, at the highest elevation (8160 ft 

[2489 m]), has the lowest mean annual temperature of 31 °F 

(-0.6 °C) (1974 to 2009) (Figure 10). Located along the Gros 

Ventre River in a nearly flat 0.5 mile (0.8 km) wide valley 

with mountains on all sides rising 2000 to 3000 ft (610 to 

915 m), the record low temperature at Darwin Ranch is 

-62 °F (-52 °C) (recorded February 10, 1981). South Pass, 

slightly lower in elevation (7840 ft [2391 m]), has a slightly higher mean annual temperature of 35 °F (1.7 °C) and 

a much longer weather record (1900 to 2009) (Figure 11). 

Buffalo Bill Dam, at the lowest elevation (5390 ft [1643 m]) 

and east of the Shoshone along the Shoshone River, has the 

warmest mean annual temperature of 47 °F (8.3 °C) (1905 

to 2009). Dubois, also at lower elevation (6962 ft [2122 m]) 

and at the east boundary of the central Shoshone and northeast boundary of the Wind River Mountain Range, has the 

second warmest mean annual temperature of 40 °F (4.4 °C) 

(1905 to 2009) (Figures 10 and 11).

Crandall Creek is at 6600 ft (2013 m) in the northern part 

of the Shoshone with annual mean precipitation of 16 inches 

(406 mm), and a mean temperature of 38 °F (3.3 °C) (1948 

to 2008). Located in Division 1, Crandall Creek shows 

a similar seasonal pattern to the Divisional data, with the 

greatest amount of precipitation coming in January, May, 

and June, and monthly temperatures the highest at around 

60 °F (15.6 °C) in June. Monthly temperatures are the 

Figure 10. Mean monthly and annual precipitation (inches) for the period of record is shown for Crandall 

Creek (1948-2008), Buffalo Dam (1905-2009), Yellowstone National Park East Entrance (2000-2009), 

Dubois (1905-2009), Darwin Ranch (1974-2009), South Pass (1900-2009), and GYE Historical Climate 

Network station average (1901-2000) (from Western Regional Climate Center 2010; Historical Climate 

Network 2010) (annual precipitation is on right axis, monthly precipitation is on left axis).

COOP Stations Average Monthly Precipitation (Annual on Secondary Axis)

Jan

FebMar

Apr

May

Jun

Jul

Aug

Sep

Oct

NovDec

Annual

Crandall Creek

Buffalo Dam

Yellowstone NP

East Entrance

Dubois

Darwin Ranch

South Pass

4

3

1

Inches

0

2

10

15

5

0

20

25
10 USDA Forest Service RMRS-GTR-264. 2012.

highest at around 60 °F (15.6 °C) in July. However, January 

temperatures at Crandall Creek are warmer than the Division 

1 average (Figures 10 and 11).

Yellowstone NP East Entrance has a mean annual temperature of 36 °F (2.2 °C) (2000 to 2009). This station and 

the Buffalo Bill Dam station are located in Division 4, and 

the average temperatures of these two stations bracket the 

annual temperature of the Division (Figure 9). Precipitation 

at Buffalo Bill Dam is close to the Division average whereas 

Yellowstone NP East Entrance precipitation is nearly twice 

the Division average. These station/Division differences reflect variation that can occur within a climate Division in 

western Wyoming and in the GYE (Figures 10 and 11).

Twenty SNOTEL sites, mostly within the Shoshone 

(Figure 2a and Appendix Table 3), span elevations from 

7120 ft (2170 m) to 10,100 ft (3078 m), averaging 8986 ft 

(2739 m). Over the 30-year record, annual average temperature data of the combined SNOTEL sites (http://www.wcc.

nrcs.usda.gov/snotel/Wyoming/wyoming.html) show a statistically significant increasing trend (p<0.01) for minimum 

and maximum temperature (minimum temperature +2.6 °F/

decade [+1.4 °C/decade], and maximum temperature +1.3 °F 

/decade [+0.7 °C/decade]) (Figures 12 and 13). No statistically significant trend was found for snow water equivalent 

or precipitation. April average snow water equivalent averaged 2.7 inches (68.6 mm) and ranged from 0.6 to 7.9 inches 

(15.2 to 200.6 mm) (data not shown).

Entrance 16.95 17.6 25 34.45 43.15 50.85 60 56.1 47.8 36.35 26.9 16.9 36

Dubois 21.95 23.95 29.35 37.35 46 54.35 60.75 59.25 50.65 41.5 30.65 23.55 39.9

Darwin	
  Ranch 9.4 12.65 20.2 29.65 39.85 47.5 53.55 51.9 44.35 33.75 19.85 9.7 31

South	
  Pass 13.5 15.7 21.5 32.65 42.8 50.9 58.2 56.5 47.55 37.2 24.35 15.55 34.7

GYE 17.52091 21.08576 27.6407 37.50628 47.08329 55.06746 62.76971 60.93559 51.79454 41.63472 29.07851 20.03964 39.34643

0	
  

10	
  

20	
  

30	
  

40	
  

50	
  

60	
  

70	
  

80	
  

Degree	
  F	
  

COOP	
  Stations	
  Average	
  Monthly	
  Temperature	
  

Crandall	
  Creek	
  

Buffalo	
  Dam	
  

Yellowstone	
  NP	
  

East	
  Entrance	
  

Dubois	
  

Darwin	
  Ranch	
  

South	
  Pass	
  

Figure 11. Mean monthly and annual temperature (°F) for the period of record are shown for Crandall 

Creek (1948-2008), Buffalo Dam (1905-2009), Yellowstone National Park East Entrance (2000-2009), 

Dubois (1905-2009), Darwin Ranch (1974-2009), South Pass (1900-2009), and GYE Historical 

Climate Network station average (1901-2000) (from Western Regional Climate Center 2010; 

Historical Climate Network 2010).

Figure 12. Shoshone SNOTEL 

sites annual average maximum 

temperature 1986-2009.

35

37

39

41

43

45

47

49

Degree F

Annual Average Max Temperature

p < 0.01
USDA Forest Service RMRS-GTR-264. 2012. 11

Over the Twentieth Century, several studies in the GYE 

have shown increases in annual temperature (Naftz and others 2002; Wilmers and Getz 2005; Hansen 2006; McWethy 

and others 2010), similar to patterns reported here (Figures 

7b and 9). The GYE climate station average annual temperature for 1971 to 2000 is approximately 1 °F (0.6 °C) 

higher than the 1901 to 1930 annual average, reflecting 

similar increases seen in the Twentieth Century global mean 

temperature (IPCC 2007b). Using isotopic oxygen to reconstruct air temperatures from ice cores, Naftz and others 

(2002) found a 6.3 °F (3.5 °C) temperature increase from 

1960 to the 1990s at 13,120 ft (4000 m) in the Wind River 

Range. The reconstructed air temperatures are comparable 

to other alpine sites around the world (Naftz and others 

2002), however the recent rapid air temperature increase at 

this site in the Winter River Range may also reflect a shift in 

the proportion of snowfall from southerly storm tracks and 

moisture sources.

Wilmers and Getz (2005) found that the length of winter 

(defined by the number of days with snow on the ground) in 

the GYE has decreased since 1955. This decline is a function 

of both minimum and maximum temperatures increasing as 

well as days above 32 °F (0 °C) that caused a decline in 

snow depth since 1955 (Wilmers and Getz 2005). Increasing 

temperatures have led to earlier and longer growing seasons 

globally (Steltzer and Post 2009); growing seasons may 

have increased 15 to 20 days since 1970 (Penuelas and others 2009). Earlier and longer growing seasons have been 

noted in YNP (NPS 2009).

Greater Yellowstone Ecosystem Twentieth 

Century Precipitation Variability

Annual precipitation variability and drought conditions 

have intermittently existed over the last century in the GYE 

area (Gray and others 2007). Precipitation has varied on 

multi-decadal scales, with the worst drought periods occurring during the 1930s, 1950s, and 2000s (Balling and others 

1992; Curtis and Grimes 2004; Hansen 2006; Gray and others 2007). GYE tree ring reconstructions of precipitation 

by Gray and others (2007) found the wettest year of the 

Twentieth Century was 1916 (20.3 inches/year or 516 mm/

year precipitation) and the driest year was 1977 (11.6 inches/

year or 295 mm/year precipitation). These reconstructions 

are representative of the east and north GYE with elevations 

that span 6800 and 8500 ft (2100 to 2600 m) (two locations 

in the central Shoshone Absaroka Mountains, and two sites 

north of YNP) (Figure 2). These precipitation extremes were 

likely equaled or exceeded at least 30 times in the past 600 

years (Gray and others 2007).

Twentieth Century annual- and decadal-scale variability 

of GYE climate has been attributed to varied responses of El 

Niño Southern Oscillation (ENSO) events (Figure 14) and the 

Pacific Decadal Oscillation (PDO) (Figure 15) (Graumlich 

and others 2003; Gray and others 2007). Anomalously warm 

(El Niño) and cool (La Niña) sea surface temperatures in 

equatorial Pacific (El Niño Southern Oscillation [ENSO]) 

and north Pacific (Pacific Decadal Oscillation [PDO]) define 

warm and cool phases that inversely influence northwest and 

southwest United States climate and ecology (Rasmussen 

and Wallace 1983; Mantua and others 1997; Cayan and others 1999). The PDO has been observed to switch between a 

cool and warm phase every 10 to 30 years, while the ENSO 

switches phases every 3 to 7 years (Dettinger and others 

1998).

The GYE lies near the transition zone between the 

Southwest and Pacific Northwest response types to ENSO 

(Despain 1987; Whitlock and Bartlein 1993; Gray and 

others 2007). The Pacific Northwest and northern Rocky 

Mountains are generally drier than average during El Niño 

years and wetter than average during La Niña years (Hunter 

and others 2006; Gray and others 2007). The winter-wet 

regions of the GYE (Figure 6) exhibit Pacific Northwest responses (in other words, drier during El Niño), especially 

during the winter (Graumlich and others 2003). Conversely, 

the Southwest United States and summer-wet regions of the 

Figure 13. Shoshone SNOTEL 

sites annual average minimum 

temperature 1986-2009.

15

17

19

21

23

25

27

Degree F

Annual Average Minimum Temperature

p <0.01
12 USDA Forest Service RMRS-GTR-264. 2012.

GYE (Figure 6) typically demonstrate the opposite response 

(wetter during El Niño). The GYE may also show no significant response to ENSO at all, thus, the mean response of 

the GYE to an ENSO event likely depends upon the magnitude of sea surface temperature anomalies (Gray and others 

2007). However, there is some uncertainty regarding the 

overall strength of the ENSO effect in the GYE because of 

complications due to elevation effects and the relative dearth 

of meteorological data, especially from high-elevation sites 

(Hansen 2006).

Sea surface temperatures associated with the PDO also influence decadal variability in GYE precipitation (Graumlich 

and others 2003). In the northern Rocky Mountains, winters have more precipitation and are cooler during the cool 

PDO phase, while the warm phase is associated with drier 

winters (Mantua and others 1997). Graumlich and others 

(2003) found that winter precipitation in the south and central summer-dry region of the GYE closely follows the PDO 

on decadal time scales, while ENSO exerts more influence 

on annual time scales.

Historic Climate of the Shoshone National 

Forest and Greater Yellowstone Ecosystem: 

20,000 BP to the Twentieth Century

Historic climate of the Shoshone is inferred from climatological studies that are focused largely in YNP with 

fewer sites in the GYE (Figure 3). The Shoshone average 

elevation (9100 ft or 2773 m) is over 1000 ft higher than 

YNP (Lueneburg 2007), and more than 25 percent of the 

Shoshone (625,000 acres or 252,930 ha) is above tree line 

(USDA Forest Service 2009c). The Shoshone is more topographically complex than YNP, which is situated on the 

flatter Yellowstone Plateau (see Figure 1). The historic climate described for the GYE may be more characteristic 

of areas west of the Shoshone and should be considered 

in the context of the observation’s location and elevation. 

Although most descriptions of paleoclimates in the GYE focus on YNP, many of the long-term, large-scale trends (for 

example, temperature trends and shifting of jet stream) hold 

true for the Shoshone as well.

The climate of the GYE has varied over the last 20,000 

years (Figure 16), and the most important control of climate in the GYE on large time scales (103

 to 104 years) has 

been the tilt of the Earth’s axis and the timing of perihelion 

(the point of orbit at which the earth is closest to the sun) 

(Kutzbach and Guetter 1986; Whitlock 1993; Millspaugh 

and others 2000). During the last glacial maximum 20,000 

BP, temperatures in the region were ~5 to ~20 °F (~2.8 to 

~11.1 °C) colder than present with less precipitation (Brocoli 

and Manabe 1987; Whitlock 1993). The entire northern 

hemisphere warmed from 20,000 to 10,000 BP as the tilt 

of the Earth increased. Temperatures increased slightly by 

18,000 to 15,000 BP (approximately 13 °F [7.2 °C] cooler 

Figure 14. El Nino Southern Oscillation (ENSO) from 1950-2010. Source: NOAA http://www.esrl.

noaa.gov/psd/people/klaus.wolter/MEI/.

Figure 15. Pacific Decadal 

Oscillation (PDO) from 

1950-2010. Source: NOAA 

http://www.nwfsc.noaa.gov/

research/divisions/fed/oeip/

ca-pdo.cfm.
USDA Forest Service RMRS-GTR-264. 2012. 13

than present at mid-latitudes) due to the southern branch of 

the jet stream being shifted south by the continental ice sheet 

(Whitlock 1993). By 14,000 to 12,000 BP, temperatures increased to 4 to 9 °F (2 to 5 °C) cooler than present and the 

ice sheet was reduced to 50 percent of its full-glacial height 

(Whitlock 1993). Temperatures were only 1 to 4 °F (0.6 to 

2.2 °C) cooler than present at Yellowstone Lake by 11,550 ± 

350 BP (Baker 1970).

Approximately 10,000 BP, perihelion occurred in the 

summer, as opposed to today’s winter occurrence, creating 

the greatest contrast in winter and summer insolation (a measure of solar radiation) in the past 20,000 years (Kutzbach 

and Guetter 1986; Whitlock 1993; Millspaugh and others 

2000). Around 10,000 BP, insolation at GYE latitudes was 

8.5 percent greater than present in the summer, and 10 percent less than present in the winter (Berger 1978; Millspaugh 

and others 2000). Summer temperatures were 1 to 4 °F (0.6 

to 2.2 °C) warmer than present as a direct result of greater 

summer insolation, and moisture decreased (Fall and others 

1995; Bartlein and others 1998; Huerta and others 2009). 

Concurrently, seasonal amplification of solar radiation indirectly enhanced summer drought in the region by causing 

an expansion of the Pacific subtropical high-pressure system 

(Whitlock 1993; Whitlock and Bartlein 1993). Climate simulations also suggest moist air flowed into the GYE during 

the early Holocene (11,000 to 8000 BP) because of intensified monsoonal circulation, also a result of seasonal solar 

radiation amplification (Whitlock 1993; Bartlein and others 

1998; Millspaugh and others 2000; Huerta and others 2009). 

Thus, the northern GYE was likely wetter than present between 11,000 and 8000 BP (Figure 16).

Around 9500 BP, the climate of the GYE split between 

two distinct regions: north (summer-wet/winter-dry) and 

south (summer-dry/winter-wet) (Whitlock 1993; Whitlock 

and Bartlein 1993; Huerta and others 2009) (see Figure 6). 

Based on vegetation reconstructions of pollen records from 

lake sediment (locations in Figure 3), Whitlock and Bartlein 

(1993) and Huerta and others (2009) suggested the GYE 

northern (summer-wet/winter-dry) region exhibited wetterthan-present conditions between 9500 to 7000 BP and then 

became steadily more arid until 3000 BP, while the southern 

(summer-dry/winter-wet) region was drier at about 9000 BP 

and steadily became wetter until 3000 BP. Pollen records 

from ~9840 ft (~3001 m) in the Wind River Range showed 

that maximum warmth and aridity occurred around 5400 BP 

(Fall and others 1995). Cooler and moister conditions persisted in the region after 3000 BP until the Medieval Warm 

Period, about 1000 BP (Hansen 2006; Huerta and others 

2009). However, there is some evidence from high-elevation 

sites in the Wind River Range that summer temperatures 

were still warmer than today around 3000 BP (Fall and others 1995) (Figure 16).

The GYE also warmed during the Medieval Warm Period 

(about 1000 BP) and, as a whole, experienced drought conditions (Gray and others 2007). The end of the Little Ice Age 

(1860 to 1890) marked the coldest and wettest conditions in 

the GYE in the previous 700 years (Gray and others 2007). 

This was especially true at higher elevations, where ice core 

evidence from Fremont Glacier (13,120 ft [4002 m]) in the 

Wind River Range indicates that temperatures were approximately 9 °F (~5 °C) cooler than present during the Little 

Ice Age (Naftz and others 2002) (Figure 16). During the 

Twentieth Century, temperatures in the GYE have generally 

increased ~1 °F (~0.6 °C) and potentially from 4 to 6 °F (2.2 

to 3.3 °C) at higher elevations (see the “Temporal Climate 

Patterns” section).

Figure 16. Historic climate of the GYE.
14 USDA Forest Service RMRS-GTR-264. 2012.

Future Climate on the 

Shoshone National Forest

Climate Projections

Atmospheric science is continually improving the understanding of and the ability to model the processes that 

influence global climate. Analysis of the results of climate 

models from research centers around the world is reported in 

the IPCC (2007a), and the output from these global climate 

models is archived by the Coupled Model Intercomparison 

Project, Phase 3 (Meehl and others 2007). Climate simulations are included in this large data set that scientists around 

the world can access. This additional analysis provides insight 

into the strengths and weaknesses of these models.

Projecting future climate involves not only understanding the dynamics of the global climate but also developing a 

story line for how the world economy and population growth 

might affect the emissions of greenhouse gases, which alter 

the chemistry of the climate. Three greenhouse gas emission 

scenarios were developed in the Special Report on Emissions 

Scenarios and are called A1B, A2, and B1 to avoid judging the 

effects of these scenarios. For each scenario, the world economies and population growth into the future varies. These 

scenarios offer a range of potential future global average surface warming: B1 is +3.2 °F (+1.8 °C), A1B is +5 °F (+2.8 

°C), and A2 is +6.1 °F (+3.4 °C) for 2090 to 2100 relative to 

1980 to 1999 (IPCC 2007b).

The global climate models simulate climate at a coarse 

spatial scale—large grid cells exceed 124 miles (200 km) 

on a side. To explore the finer scale of climate, these global 

projections are downscaled using a variety of techniques. For 

the Rapid-Response Climate Assessment for the Fish and 

Wildlife Service, Ray and others (2010) downscaled global 

projections for the western United States to a 2.4-mile (4-km) 

spatial scale using the delta method. Using the same information, McWethy and others (2010) summarized the projections 

for the Rocky Mountains and Upper Columbia Basin.

The global models show warming for large parts of the 

world, including North America (IPCC 2007b). Focusing on 

the results from an ensemble of 22 climate models used in the 

Fourth Assessment Report of the Intergovernmental Panel on 

Climate Change (IPCC 2007a), McWethy and others (2010) 

described changes by 2050 for the GYE as ranging from +3 

°F (+1.7 °C) for annual temperature, to +4 °F (+2.2 °C) for 

winter temperature, to +5 °F (+2.8 °C) for summer temperatures, relative to the 1950 to 1999 period. Precipitation was 

described as increasing between 0 and 10 percent annually 

and in the winter, whereas summer precipitation was modeled 

to decline about 10 percent. However, McWethy and others 

(2010) noted that changes in the amount and spatial distribution of precipitation were still poorly understood and difficult 

to project.

Statistically downscaled projections of summer temperatures show a shift in temperature zones northward and upward 

in elevation across the western Pacific Northwest, including 

the GYE (McWethy and others 2010; Ray and others 2010). 

Ray and others (2010) concluded that by 2050, the warming 

signal may be clearly seen throughout the western United 

States. To further explore the potential changes in temperature 

at locations that represent pika habitats, Ray and others (2010) 

downscaled climate projections to 22 specific grid cells that 

either were locations of known pika habitats or a local summit chosen as a representative. No locations in the Shoshone 

were included in Ray and others’ (2010) analysis; however 

locations in the nearby National Forests of the Bighorn, Wind 

River/Bridger Teton, and Gallatin were represented (Table 1). 

At these three locations, the 2050 summer temperature projections are consistently higher than the 1950 to 1999 PRISM 

mean temperatures, and the projected temperature exceeds 

the 90th percentile of the 1950 to 1999 summer temperatures 

(Table 1). For example, the 1950 to 1999 average temperature 

for the Gallatin National Forest grid was 50.7 °F (10.4 °C), 

and the projected temperature for 2050 is 56.2 °F (13.44 °C). 

For the grids within these three National Forests, the lowest 

summer projection is higher than the 90th percent of the 1950 

to 1999 period, suggesting that the coolest summers of the 

mid-Twenty-First Century will be warmer than the warmest summers of the last 50 years in the Twentieth Century 

(Table 1).

To interpret potential future climate change, we summarize 

observed Twentieth Century climate, and projections for the 

Twenty-First Century in Table 2. McWethy and others (2010) 

stressed that natural variations in climate and the accompanying ecological response occur at multiple temporal and spatial 

scales.

Studies across the western United States have described 

observed changes in climate: warmer annual temperature, 

winter warming more than summer, nighttime temperature 

warming more than daytime, increased intensity of rainfall 

events, more rain versus snow within the winter season, earlier peak runoff, and changes in fire regimes. While a number 

of studies have explored these data, climate stations within 

northwest Wyoming are not often included in these studies. 

For example, Knowles and others (2006: Figure 1a) documented the shift of winter snowfall to rainfall across the United 

States; however, no station data were available for northwest 

Wyoming. Similarly, data quality limitations eliminated 

nearly all northwest Wyoming climate stations in Kunkel and 

others’ (2003) analysis of temporal variations of extreme precipitation events. Further, assessing climate patterns within 

the GYE is complicated because of the topographic variability 

as well as the location of the GYE in a transition area between 

northwestern and southwestern circulation patterns. McWethy 

and others (2010) noted that variations in the climate dynamics that influence these circulations patterns often result in 

opposite trends in climatic conditions at sites within the same 

region (see also Gray and others 2007).

Projections for future climatic conditions in the GYE 

include increasing temperatures annually and potentially 

increased but highly variable precipitation. The projected 

increase in temperatures suggests that more extreme temperature episodes will occur; the coolest of the future summer 

projections was warmer than most summers in the historical 

period.
USDA Forest Service RMRS-GTR-264. 2012. 15

Table 1. Mid-Century average temperature projections and extremes compared with historical climate data for summer seasons at single locations within 

three National Forests in Wyoming. This analysis was developed as part of the Rapid-Response Climate Assessment for the Fish and Wildlife Service on 

pika (Ray and others 2010). Historical climate information is based on PRISM. Summer season is June-July-August (JJA).

Single location 

within each 

National Forest 

(NF)

Gridbox 

latitude, 

longitude

Mean 

gridbox

elevation 

ft (m)

Pika site 

elevation 

(ft)

JJA 10th

percentile 

(1950-

1999)

°F (°C)

JJA Mean 

(1950-1999) 

°F (°C)

JJA

90th

percentile 

(1950-1999) 

°F (°C)

Low model 

(10th

percentile 

A1B [2040-

2060] °F (°C)

JJA CMIP 

projection 

mean (2040-

2060) °F 

(°C)

High model 

(90th

percentile 

A1B [2040-

2060] °F (°C)

Gallatin NF 45.44,

-110.94

9167.4

(2778)

9180 48.7 (9.27) 50.7 (10.39) 52.5 (11.38) 54.1 (12.25) 56.2 (13.44) 58.7 (14.84)

Wind 

River/BridgerTeton

43.19,

-109.69

 12153.9

(3683)

* 40.7 (4.81) 43.3 (6.3) 46.3 (7.97) 47.1 (8.39) 49.2 (9.55) 51.7 (10.96)

 Bighorn NF 44.44,

-107.19

12048.3

(3651)

* 43.3 (6.25) 44.9 (7.19) 46.5 (8.04) 48.2 (8.99) 50.3 (10.17) 52.6 (11.44)

*No information

Table 2. Observed 20th Century and future climate projections of temperature and precipitation for the GYE and 

Shoshone.

Observed 20th Century Climate projections

GYE • Annual temperature increases range from 

2 to 4 °F (1 to 2 °C) with greatest increases 

in the second half of the 20th Century

• Temperature increases more pronounced in 

winter and spring

• April soil water equivalent from snow 

courses over 1960 to 2002 show declines in 

most basins in northwest Wyoming

• Precipitation highly variable, with the 1930s 

and 1950s significantly drier than average, 

although prolonged droughts in the last 

millennia rival these 20th Century droughts 

in duration and magnitude

• Annual temperature increases projected to be 3 °F 

(1.7 °C) by 2050

• Ranges for increases in annual temperature by 

2100 are from 2 to 10 °F (1.1 to 5.5 °C)

• Winter temperatures are projected to increase 4 °F 

(2.2 °C) relative to 1950 to 1999

• Summer temperatures are projected to increase 

5 °F (2.7 °C) relative to 1950 to 1999

• Annual precipitation is projected to increase by 10 

percent. Winter precipitation increases of 10 percent 

and summer precipitation decreases of 10 percent. 

(Precipitation projections are more uncertain as 

about half of the Global Circulation Model 

projections agree.)

Shoshone • Topography creates an east-west 

precipitation gradient with more precipitation 

occurring at western higher elevations and 

less at eastern lower elevations

• Western higher elevations experience 

wetter winters—the result of winter storms 

from the Pacific air masses—and have 

summer-dry climate. Eastern and lower 

elevations lie in a rain shadow where 

moisture from Pacific flow is intercepted by 

mountains to the west. However, these 

areas have a summer-wet climate, receiving 

summer monsoonal flow.

• Annual temperature increases projected to be 3 °F 

(1.7 °C) by 2050

• Ranges for increases in annual temperature by 

2100 are from 2 to 10 °F (1.1 to 5.5 °C)

• Winter temperatures are projected to increase 4 °F 

(2.2 °C) relative to 1950 to 1999

• Summer temperatures are projected to increase 

5 °F (2.7 °C) relative to 1950 to 1999

• Annual precipitation is projected to increase by 

10 percent. Winter precipitation increases of 

10 percent and summer precipitation decreases 

of 10 percent. (Precipitation projections are more 

uncertain as about half of the Global Circulation 

Model projections agree.)
16 USDA Forest Service RMRS-GTR-264. 2012.

Climate Projections Used in Existing 

Ecological Response Models

Eighteen modeling studies associated with the Shoshone 

and outlying areas use climate projections to analyze the effects on ecosystems for scales that range from global and 

western hemisphere, to the western or entire United States, 

to the GYE and YNP regions (Table 3). Given that the first 

study was published in 1991, vintage of climate model and 

projection differs across these studies. The ability of climate 

models to quantify processes that include global climate, such 

as atmosphere interaction with oceans, has improved over the 

last 20 years. In this section, we describe these climate projections that have been used in ecological response models in 

light of recent studies exploring the future impact of climate 

in the Shoshone and GYE region.

Types of climate models are: Atmosphere-Ocean Global 

Circulation Models (AOGCMs), Global Circulation Models 

(GCMs), and Regional Circulation Models (RegCM). The ecological models that quantify the ecosystem response include 

Dynamic Global Vegetation Models (DGVMs), Bioclimate 

Envelope Models, Equilibrium Vegetation Models, and a variety of regression and qualitative techniques. These climate 

models and projections have also been useful in assessing the 

historical relationships between past climate and fire regimes, 

glacier changes, or lake dynamics as well as future effects 

of climate change (Table 3). The temperature and precipitation projections used in these response models vary over time 

as some studies use earlier versions of climate models. One 

study by Romme and Turner (1991) used qualitative methods to infer ecosystem responses under a warmer-wetter and 

warmer-drier situation.

Interpretation of the results of these studies for management 

use must consider what climate future was explored, how that 

climate future compares to other studies exploring the same 

natural resource, and how that climate future compares to 

what is now thought to be the future climate for the Shoshone 

and the GYE. For example, Bartlein and others (1997) incorporated a very wet future—100 percent change in winter 

precipitation—into their analysis and described the modern 

climate analogue to this projection as occurring in northwestern Montana and northern Idaho. In contrast, Diffenbaugh and 

others (2003) assumed no change to a decline in annual precipitation in their study. Comparing temperature projections 

across studies, Bachelet and others (2001) used temperature 

projections that span a range of 7 °F (4 °C) in contrast to the 

2.7 °F (1.5 °C) range used by Shafer and others (2001). Many 

of these studies used projections that describe a future with 

increased precipitation; McWethy and others (2010) characterized the increases in future precipitation as less certain.

Future Temperature

The modeling studies in Table 3 used several scenarios that 

project temperatures that range from 2 to 18 °F (1 to 10 °C) 

to capture a range of potential future temperature conditions. 

The GCM projections used as input for environmental response models by Bartlein and others (1997) and Smithwick 

and others (2009) had the highest temperature increases and 

assumed a doubling of CO2 (Table 3). Bartlein and others 

(1997) used GCM-projected temperature increases of approximately 9 to 18 °F (5 to 10 °C), and Smithwick and others 

(2009) used a temperature increase that ranged from 5 to 

16.4 °F (2.8 to 9.1 °C). The other modeling studies in Table 3 

utilized more modest temperature increases that ranged from 

2 to 12 °F (1 to 6.7 °C). The most extensive projections were 

from Christensen and others (2007) who used a multi-model 

ensemble of 21 GCMs and Lawler and others (2009) who 

used an ensemble of 10 AOGCMs. Both used several scenarios of temperature increases ranging from 2 to 10 °F (1.1 to 

5.5 °C). Study resolutions spanned from 0.6 to 37 miles (1 km 

to 60 km).

Future Precipitation

Projections of precipitation are more variable and uncertain than temperature projections (IPCC 2007b). The A1B 

simulations used by Christensen and others (2007) include an 

ensemble of several AOGCMs and project a modest increase 

in precipitation during winter (~10 percent more annual precipitation) for most of North America, including the Shoshone 

(Table 3). Yellowstone regionally based (regional and downscaled GCM) projections for annual precipitation range from 

no increase to a 50 percent increase (Table 3). Winter precipitation is projected to increase, and summer precipitation 

has a projected small decrease to no change (Bartlein and 

others 1997; Diffenbaugh and others 2003; Hall and Farge 

2003; Whitlock and others 2003; Schrag and others 2008; 

Smithwick and others 2008). Bartlein and others (1997) indicated winter precipitation may increase on the Shoshone but 

not as much as projected for YNP (Bartlein and others 1997: 

Figure 2). Most of the climate projections used as input for 

response models in Table 3 project an increase in winter precipitation, while summer precipitation is expected to remain 

the same or decrease. Understanding how the precipitation 

projections and corresponding temperature projections interact is important; McWethy and others (2010) suggested that 

increased precipitation is unlikely to offset increased evapotranspiration associated with even a modest warming of 0.6 to 

1.1 oF (1 to 2 oC).

Future Temperature and Precipitation Changes Used 

in Ecological Impact Models

The projected range of annual temperature changes for 

the GYE is 2 to 10 oF (1.1 to 18 oC), and the projected range 

of precipitation change is no change to a 10 percent increase 

(McWethy and others 2010). When these ranges are compared 

to the range of future changes used in the current impacts literature, one can see that many of the impact models explored 

a greater range of possible futures (Figure 17). These differences reflect the nature of the scenarios (IPCC or a simple 

twice the ambient carbon dioxide [CO2]concentration) and 

which climate models were used. While these studies offer 

much information, the results must be compared in light of 

climate projections since the climate ranges differ greatly 

among these studies.
USDA Forest Service RMRS-GTR-264. 2012. 17 Table 3. Climate scenarios and projections used in modeling studies exploring the ecological responses to climate change effects on the GYE or larger geographic areas. Study (region) GCM model Response models Resolution Future scenario Ending CO2 (ppm) Temperature change oF (oC) Precipitation change (%) By year Bachelet and others (2001) (U.S.) HADCM2GH, HADCM2SU, CGCM1, UKMO, GISS, GFDL- R30, OSU MAPPS, MC1 (Vegetation) 10 km IPCC First Assessment Report, 2 x CO2 712 +4 to +12 (+2.2 to +6.6) +2 to +30 2099 Bachelet and others (2003) (U.S.) HADCM2SUL, CGCM1 MC1, LPJ (Vegetation) 10 km IPCC First Assessment Report, 2 x CO2 712 +4 to +10 (+2.2 to +5.5) +23 2100 Bartlein and others (1997) (GYE) CCC Equilibrium (Vegetation) 25 km 2 x CO2 724 +9 to +18 (+5 to +10) +100 in winter, almost no summer change 2100 Bradley and others (2009) (West U.S.) 10 AOGCMs Bioclimate Envelope Model (Invasive Vegetation) 4.5 km IPCC Fourth Assessment Report, A1B 700 +3 to +8 (+1.7 to +4.4) -47 to +72 2100 Christensen and others (2007) (Global) Multi-model ensemble of several types of climate models (PCMDI) Global Various IPCC Fourth Assessment Report, All Scenarios 500 to 1000 +2 to +10 (+1.1 to +5.5) -20 to +20 2100 Diffenbaugh and others (2003) (West U.S.) RegCM2.5, CCM3.6.6 BIOME4 (Vegetation) 40 km 2 x CO2 560 +4 to +11 (+2.2 to +6 ) 0 to -10 * Gray and McCabe (2010) Multi-model average Water Balance Model * IPCC Fourth Assessment Report, A1B Average 715 +1.5 (+0.88) +3 (+1.7) +6.1 (+3.4) Based on historic tree ring records 2025,205 0,2100 Hall and Fagre (2003) (Glacier National Park) GISS, GFDL, OSU GLACier Prediction * IPCC First Assessment Report, 2 x CO2 704 +5.4 (+3.3) +5 to +10 2100 Hostetler and Giorgi (1995) (Pyramid and Yellowstone Lakes) MM4 RegCM nested in GENESIS GCM Lake Model 60 km 2 x CO2 718 +5.5 to +6 (+3 to +3.4) +17 to +22 2100
18 USDA Forest Service RMRS-GTR-264. 2012. Study (region) GCM model Response models Resolution Future scenario Ending CO2 (ppm) Temperature change oF (oC) Precipitatio n change (%) By year Lawler and others (2009) (Western Hemisphere) 10 AOGCMs Bioclimate Envelope (Vegetation) 50 km IPCC Fourth Assessment Report B1, A1B, A2 500 to 1200 +2 to +10 (+1.1 to +5.5) -20 to +20 2100 Rehfeldt and others (2009) (Western U.S.) CGCM3, GFDLCM2.1, HADCM3 Climate Envelope (Vegetation) 1 km IPCC Fourth Assessment Report B1, B2, A2 500 to 1200 +2 to +9 (+1 to +5) -10 to +6 2100 Romme and Turner (1991) (GYE) Qualitative Qualitative Qualitative Warm-dry, Warm- wet * * * * Schlaepfer and others (2011) Composite of 16 Sagebrush Bioclimate 10 km IPCC Fourth Assessment Report B1 and A2 500- 1200 +2 to +9 (+1 to +5) * 2100 Schrag and others (2008) (Yellowstone and Grand Teton National Parks) Based on Bartlein and others (1997) Random Forest (Tree-line prediction) * Based on Bartlein and others (1997) * 0 and +8 (0 and +4.5) 0 and +35 * Shafer and others (2001) (North America) HADCM2, CGCM1, and CSIRO Regression of bioclimate variables (vegetation) 25 km Annual 1% compound increase in GHG (IPCC IS92a) 700 +2.7 (+1.5) Not available 2100 HADCM2 CENTURY Climate Envelope (vegetation) ~55 km grid cell centered at Old Faithful * 708 Min / Max +5 / +11 (+2.8 / +4.7) +22 2100 Smithwick and others (2009) (Yellowstone National Park) CCC 1 708 +7.7 / +16.4 (+4.3 / +9.1) +12 2100 Stonefeldt and others (2000) Wind River, Wyoming Nested RCM (NCAR/Penn State) Soil Water Assessment Tool (SWAT) * 2 x CO2 660 +4 (+2.2) -10 to +10 2100 Whitlock and others (2003) (GYE) HADCM2 HCGSa Regression * Annual 1% compound increase in CO2 940 * * 2059 *Information not available Abbreviations: AOGCM = Atmospheric-Ocean Global Circulation Model; CO2 = Carbon dioxide concentration; CCC, CCC1 = Canadian Climate Centre; CGCM1 = Canadian Global Coupled Model; CSIRO = Commonwealth Science and Industrial Research Organisation, Australia; GISS = Goddard Institute for Space Studies (NASA) model; GFDL, GFDL-R30 = Geophysical Fluid Dynamics Laboratory; GHG = greenhouse gases; HADCM, HADCM2GH, HADCM2SU = Hadley Centre Climate Model; HCGSa = Hadley Center Greenhouse Gas Sulfate Aerosol; LPJ = Lund, Potsdam, Jena Dynamic Global Vegetation Model; MAPPS = Mapped Atmosphere-Plant-Soil System Vegetation Model; MC1 = MAPPS – CENTURY Dynamic Global Vegetation Model; MM4 RegCM = Mesoscale model Regional Climate Model (NCAR); NCAR = National Center for Atmospheric Research, Boulder, Colorado; Nested RCM = Nested Regional Climate Model; OSU = Oregon State University model; PCMDI = Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, California; UKMO = United Kingdom Meterological Office Model. Table 3. Continued.
USDA Forest Service RMRS-GTR-264. 2012. 19

Figure 17. Future temperature and precipitation range changes used in ecological impact models.
20 USDA Forest Service RMRS-GTR-264. 2012.

Climate Change Effects on 

Ecosystems: Observed Trends 

and Future Projections

Introduction

At the national scale, U.S. temperatures have warmed 

about 1.5 oF (0.8 oC) over the last 100 years (Karl and others 2009); studies focused on the western United States and 

the GYE suggest that similar increases in temperature have 

been documented, with some effects also noted in the physical and ecological characteristics of the GYE and western 

United States ecosystems (Naftz and others 2002; Wilmers 

and Getz 2005; Hansen 2006; McWethy and others 2010). 

The projected changes in climate, particularly the increasing temperatures, suggest that these observed changes will 

continue and diversify as climate continues to change on 

the Shoshone and within the GYE. The effects of climate 

change on ecosystems, economies, and land use are likely to 

be complex and involve interacting factors that directly and 

indirectly affect both the physical and ecological processes.

The vulnerability of Shoshone landscapes to climate 

change is a function of the sensitivity of those landscapes 

to changes in climate, the extent to which climate changes, 

and the adaptive capacity of those landscapes. An example 

of vulnerability to climate is the relationship between fish 

and stream temperatures (Reiman and Isaak 2010). When 

temperatures exceed a certain range, the quality of habitat 

degrades; the greater the temperature increase, the greater 

the impact on salmonids. How fast and how much stream 

temperatures increase directly influences the impact of climate change that salmonids are exposed to. Streams that 

are shaded by vegetation, which helps cool stream temperatures, would have a higher adaptive capacity than unshaded 

streams.

Ecological responses to future climate change are challenging to quantify, especially when the changes are 

spatially and temporally variable with several interacting 

factors and stressors defining behavior. Large gradients in 

topography, climate, and soils (and consequently in vegetation) are found within the Shoshone. Shoshone geology 

varies greatly with precambrian granitic rock, Paleozoic 

and Mesozoic limestone, sandstone, shale, and andesite 

lava overlain by rhyolites diversifying soil development 

(Hansen 2006). Temperature varies with elevation, and 

seasonal precipitation varies from summer-wet regimes to 

winter-wet regimes. Early European settlement around the 

Shoshone brought mining, tie hacking and timber harvesting, and livestock grazing activities. Only 4 percent of the 

Shoshone has been harvested for timber; a contrast to the 

more widespread impacts of livestock grazing at the turn of 

the Twentieth Century (USDA Forest Service 2009c). The 

legacies of these historical disturbances affect the current 

condition of these landscapes (USDA Forest Service 2011a) 

and may influence their adaptive capacity to future climate 

change. In addition, human communities surrounding the 

Shoshone today depend upon economic activities related to 

tourism and recreation and upon ecosystem benefits such as 

water for urban and agricultural uses, thus linking the adaptive capacity of these human communities to the potential 

changes on the Shoshone.

In the following section, we synthesize current resource 

conditions and the latest scientific information about how 

future climate change may affect natural resources on the 

Shoshone and GYE. Species and ecological responses to 

previous and current climate change are typified by variable thresholds with nonlinear dynamics (Burkett and others 

2005). Many studies have examined complex ecological behavior and project climate change effects. We synthesize the 

studies related to resources and natural or human influenced 

processes that may be vulnerable to climate change—specifically, water, vegetation, fish and wildlife, fire or insect 

disturbance, biochemical cycling, economic activities, and 

land use.

Water and Aquatic Systems

Current Conditions

The watersheds of the Shoshone provide vital water supplies for agriculture, human use, natural vegetation, and 

wildlife that extend outside the State of Wyoming (USDA 

Forest Service 2009c). The Shoshone has about 3850 miles 

(6200 km) of perennial streams, ~1492 miles (2401 km) of 

which support fish, and 310 lakes covering 10,050 acres 

(4067 ha) (USDA Forest Service 2008a) (Table 4). These 

streams and lakes provide fishery and recreation value, 

and are crucial for managing Yellowstone cutthroat trout, 

which is listed as a sensitive species in the Forest Service 

Rocky Mountain Region (USDA Forest Service 2009c). 

Groundwater supply is provided to water users through 

more than 600 groundwater wells covering the north, central, and southern tip of the Shoshone (Wyoming State 

Engineers Office 2010, http://wygl.wygisc.org/wygeolib/

catalog/browse/browse.page). Surface water is supplied to 

users via more than 50 points of diversions that are mostly 

in the valleys of the northern Shoshone (Water Resource 

Data System points of diversion 2007, GIS data http://

waterplan.state.wy.us/plan/statewide/gis/gis.html). Many 

Shoshone watersheds are headwater basins that channel 

water from snow melt, rain, and glaciers primarily into the 

Yellowstone River and a smaller portion to the Platte River, 

both of which are within the Missouri Basin. Watersheds 

of the GYE have undergone extreme drought and wet periods over the last 700 years; wetter periods have occurred 

in the last century during the 1910s, 1960s, and 1970s, 

and drought periods occurred during the 1930s and 1950s 

(Graumlich and others 2003; Gray and others 2007; Kalra 

and others 2008). Tree ring records in the western United 

States and Wind River Range headwaters suggest that the 

Twentieth Century has been relatively wet compared to the 

previous 1200 years (Cook and others 2004; Watson and 

others 2009) (Table 4).
USDA Forest Service RMRS-GTR-264. 2012. 21

Stream gages on or near the Shoshone have not shown 

any statistically significant trend (USGS NWIS 2010, unpublished data, http://waterdata.usgs.gov/wy/nwis/rt). However, 

in western Wyoming, western Montana, and Idaho, an approximately 25 percent decrease in stream flow has been 

observed and the timing of runoff has shifted 12 days earlier since 1967 (Clark 2010) (Table 4). River basins behave 

similarly in that the volume of runoff is most sensitive to 

precipitation changes that affect snow accumulation during 

winter, while the timing of runoff is most affected by temperature that leads to earlier spring runoff and lower summer 

flows (Barnett and others 2005). Temperature increases over 

the latter half of the Twentieth Century have already caused 

stream flow timing to be one to four weeks earlier in western 

North America (Stewart and others 2005) (Table 4).

Almost all of the Shoshone watersheds are currently classified as in good to excellent condition (Brown and Froemke 

2010; USDA Forest Service 2011a). Those watersheds in 

Table 4. Summary of water quantity and timing of annual flow conditions for the 20th Century, projections for 

the 21st Century, and potential consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature increase 

of 2 to 4 °F (1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Water 

quantity 

• Up to a 25 percent 

decrease in annual 

flows has been 

observed in ID, 

western WY and MT 

since 1967.

• Stream flows are 

largely unmeasured 

on much of the 

Shoshone, and gages 

show no statistically 

significant trends.

• Peak flow increase 40 to 154 

percent with 4 oF (2.2 oC) 

temperature increase

• Summer flows decrease 30 to 

62 percent with 4 oF (2.2 oC) 

temperature increase

• Annual flows decrease 5 to 

24 percent with 1 oF (0.6 oC) to 

6 oF (3.4 oC) temperature 

increase 

• Drought period annual flow 

decrease 41 to 55 percent with 

1 oF (0.6 oC) to 6 oF (3.4 oC) 

temperature increase and 

associated precipitation 

decreases

• Potential increase in 

flood magnitude with 

degradation of aquatic 

habitat

• Potential loss of habitat 

for aquatic species from 

reduced streamflow

• Potential reduction of 5 

to 25 percent of the 

annual water supply for 

water storage

• Potential reduction of up 

to half the annual water 

supply for human and 

agricultural use and 

recreation opportunities 

during drought

• Potential increase in the 

use of groundwater

Timing of 

annual 

flows

• Timing ~11 days 

earlier in western WY, 

ID, and western MT 

since 1967

• Timing 1 to 4 weeks 

earlier than mid 

century in western U.S.

• Timing 4 to 5 weeks earlier 

than present with 3.6 to 7.2 oF 

(2 to 4 oC) temperature 

increase

• Altered timing of water 

availability for storage

• Altered peak flows 

shifting or hindering 

salmonid spawning 

activity 

• Altered timing of 

recreational 

opportunities—

potentially earlier and 

shorter for fishing, 

rafting, and kayaking
22 USDA Forest Service RMRS-GTR-264. 2012.

excellent condition are primarily in wilderness areas. The 

condition of these watersheds reflects to varying degrees 

past and present land use (USDA Forest Service 2011a). 

Generally, most are on an improving trend, and watershed 

concerns relate to historical uses such as heavy grazing or 

roading associated with motorized recreation and timber 

harvest. Best management practices have been put into place 

to address these concerns as well as concerns about wildfire 

activities, debris flows, and road sediment (USDA Forest 

Service 2008a, 2011a) (Table 4).

One additional disturbance that has recently affected 

many forests on the Shoshone and large areas in the western United States is bark beetle outbreaks. Bark beetle 

outbreaks have been observed to have variable effects on 

the timing and quantity of stream flow. Basin-scale changes 

of stream flow and timing have not been found to be consistently associated with beetle tree mortality (Lukas and 

Gordon 2010). However, smaller-scale observations of tree 

mortality from beetle outbreaks and subsequent reductions 

in transpiration have been observed to increase stream flow 

(Love 1955; Bethlahmy 1974; Potts 1984; Helie and others 2005). Stream flow was found to increase for 20 years 

after a beetle epidemic in Colorado (Bethlahmy 1974). Potts 

(1984) found a 15 percent increase in annual water yield (as 

did Love [1955] in Colorado), a two to three week advance 

in the peak hydrograph, a 10 percent increase in low flows, 

and little change in peak flows for the Jack Creek watershed in southwestern Montana. Troendle and Nankervis 

(2000) modeled the effect of spruce beetle kill on 30 and 

50 percent of the spruce-fir stands in the North Platte River 

Basin of Colorado and Wyoming, and projected a 14 percent 

increase in water yield after 10 years. The authors hypothesized that the water increase would decay as vegetation 

grew back, but could last for 50 to 60 years. In Canada, 

the modeled hydrologic function of watersheds that have 

been infested by beetles (for example, earlier spring runoff 

and increased stream flow) have been projected to behave 

similar to clear cut areas for 40 to 60 years post-infestation 

(Lewis and Huggard 2010). However, these modeled effects of increased stream flow are not always consistent with 

observations. In the Rocky Mountains, if precipitation is 

below 20 inches (508 mm) per year, no changes in stream 

flow have been observed (MacDonald and Stednick 2003; 

Stednick and Jensen 2007). The potential water gains from 

less interception and transpiration from trees may be offset 

by increases in soil evaporation and increased evapotranspiration from the understory or residual trees. Additionally, the 

individual effects on stream flow from mountain pine beetle 

outbreaks that occur during precipitation and temperature 

variations are difficult to differentiate (Lukas and Gordon 

2010). Changes to stream flow and timing due to beetle kill 

are not well understood at this point.

Climate Change Effects on Water Quantity and the 

Timing of Runoff

Globally, in snow-dominated regions, climate change 

is expected to reduce stream flow, ground water recharge, 

and reservoir storage through reduced snowpack, increased 

evaporation, and earlier spring runoffs with longer summers (Danielopol and others 2003; Barnett and others 2005). 

Temperature increases of 2 to 10 oF (1.1 to 5.5 oC) or higher 

are predicted to occur this century (Table 2). The timing of 

runoff is expected to be most dependent on winter and spring 

temperatures, and runoff may occur four to five weeks earlier under a 3.6 to 7.2 oF (2 to 4 oC) temperature increase in 

the Colorado Rocky Mountains and western United States 

(Baron and others 2000b; Stewart and others 2004). These 

timing shifts could potentially alter water availability for 

storage and shift salmonid spawning activity and recreational opportunities such as fishing, rafting, and kayaking 

(Table 4).

Several modeling studies have projected considerably reduced surface water supplies due to the effects of increasing 

temperatures and resulting increased evaporation, as well as 

precipitation reductions and extended drought. Stonefelt and 

others’ (2000) modeling of the Upper Wind River Basin of 

Wyoming projected that by 2100, there could be a 100 to 

154 percent increase in January to April surface runoff and 

a 30 to 47 percent decrease in June to August runoff with a 

4 oF (2.2 oC) temperature increase and a 10 percent increase 

in annual precipitation. Inputting a 4 oF (2.2 oC) temperature increase and a 10 percent decrease in precipitation into 

the model resulted in a 40 to 75 percent January to April 

runoff increase, and a 50 to 62 percent decrease in June to 

August runoff. Gray and McCabe’s (2010) modeling study 

for the Upper Yellowstone River of Wyoming projected that 

a 1 oF (0.6 oC) temperature increase by 2025 can reduce 

annual runoff by 11 percent below baseline levels, a 3 oF 

(1.7 oC) temperature increase by 2050 could reduce runoff 

by 15 percent, and a 4 oF (2.2 oC) temperature increase by 

2100 could reduce annual runoff by 24 percent. Baseline 

levels were based on runoff estimates generated using tree 

ring precipitation and PRISM temperatures over the period 1911 to 1995. Gray and McCabe’s (2010) projections 

for worst case scenarios of extended drought (as observed 

in historical records) with expected temperature increases 

up to 6.3 oF (3.5 oC) by 2100 resulted in 10th percentile driest annual runoff reductions of 41 percent, 45 percent, and 

55 percent for 2025, 2050, and 2100, respectively, in the 

central Rocky Mountain region. In other words, the driest runoff levels (10th percentile) in the future may be less 

than half of the driest runoff levels of the historical record. 

Although groundwater on the Shoshone is not as well studied, globally, it is expected that high-elevation bogs (many 

of which occur on the northern Shoshone) may be particularly vulnerable to drying and decreased groundwater recharge 

(Finlayson and others 2005). The potential consequences to 

ecosystem services may be a degradation of aquatic habitat 

and a reduction of up to half of the current water supply for 

human and agricultural use, recreational opportunities, and 

aquatic wildlife (Table 4).

The projections for stream flow have large ranges that 

vary from 40 to 150 percent peak flow increases, 30 to 

62 percent decreases in summer flow, and up to 55 percent 
USDA Forest Service RMRS-GTR-264. 2012. 23

annual flow reductions by 2100 (Table 4). Similarly, runoff 

projections for the Colorado River, though well studied, also 

have a wide range of runoff reductions (-5 to -45 percent by 

the 2050s) (Barnett and Pierce 2009). When the large differences for the Colorado River were examined more closely, 

scientists identified sources of variability, such as the spatial scale at which hydrology is modeled, the data available 

(or not) to calibrate the hydrological models, and the climate models used to project future climate change and the 

models’ assumptions (Hoerling and others 2009). However, 

some agreements in a cross-model analysis were identified. 

Hoerling and others (2009) noted that the models show similar sensitivity of stream flow to precipitation changes, with 

a 2:1 ratio of percent change in flow to percent change in 

precipitation using historic data. For the Upper Colorado 

River, model sensitivity suggested that a 10 percent reduction in precipitation would result in a 20 percent decline in 

runoff. In contrast, runoff sensitivity to temperature was not 

as consistent across the models. Further studies are needed, particularly in areas that are not as well studied as the 

Colorado River.

Severe flooding events on or near the Shoshone occurred 

in 1918, 1923, 1963, and 1986 during June and were likely 

caused by snowmelt combined with severe thunderstorm activity (USGS 1989). Recent heavy precipitation and flooding 

events in the western United States, especially the West Coast, 

have been associated to atmospheric rivers. Atmospheric 

rivers are narrow bands of enhanced water vapor and strong 

atmospheric flow that originate from tropical regions of the 

Pacific and Atlantic oceans. These events bring extremely 

heavy precipitation and warmer temperatures as they make 

landfall in the western United States, and sometimes extend 

to the GYE. The water carrying capacity of atmospheric rivers is expected to increase as temperatures rise under climate 

change (Leung and Qian 2009). The western United States 

may experience rain-on-snow events that produce large runoff and flooding associated with these atmospheric rivers 

(Leung and Qian 2009). At the time of this report, no further 

specific published information was found about the effects 

of climate change on the magnitude and frequency of flooding in the Shoshone.

Water Quality

Current Conditions

The majority of watersheds on the Shoshone are in 

Wilderness Areas, and although they are largely unmeasured 

for water quality, the majority are classified in good condition (USDA Forest Service 2011a) (Table 5). Problems 

with sediments, nutrients, and toxins have been ranked very 

low for Shoshone watersheds (Brown and Froemke 2010). 

Water quality in a few watersheds is of concern due to 

mining activity and these watersheds are targeted for mitigation through watershed improvement plans (USDA Forest 

Service 2011a).

Climate Change Effects

Climate change effects could play a role in water quality degradation in several ways: (1) warmer temperatures 

and increased atmospheric CO2 could affect the rates of 

biogeochemical processes that determine water quality (for 

example, algae); (2) changes in flow volumes could alter 

Table 5. Summary of water quality conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature increase 

of 2 to 4 °F (1 to 2 °C)

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Water 

quality 

The majority of 

Shoshone watersheds 

are in good condition

• Altered biogeochemical cycles

• Decreased flows may increase 

chemical loading.

• Increased disturbance may 

increase sedimentation.

• Potential reduction of 

water quality

• Higher stream 

temperatures could 

potentially reduce the 

quality of aquatic habitat.

• Potential increase of 

algae 

• Potential increased cost 

of water treatment
24 USDA Forest Service RMRS-GTR-264. 2012.

residence times and chemical loading to streams, thereby 

altering water quality (Arnell 1998; Murdock and others 

2000); and (3) shifts in disturbance regimes (for example, 

increased fire) caused by a warmer, drier climate may alter water quality indirectly by increasing sediment loads 

(Meyer and others 1992). Flanagan and others (2003) compared temperature and lakes occupying latitudes ranging 

from 40 to 80o, and suggested that the warmer temperatures 

at lower latitudes could cause increased algal productivity. The effects from increased atmospheric CO2

 have 

been observed to alter algae and plant dynamics in global 

oceans (Feely and others 2004). Increased temperatures 

have also been found to increase algae growth and, therefore, the need for water treatment (Koschel 2010). Algae 

causes problems in the drinking water supply in reservoirs 

such as toxicity, water deoxygenation, odor, and clogged 

systems (Koschel 2010). Several algae types have already 

been found in Colorado reservoirs, most commonly in 

the reservoirs that allow motorized watercraft, and could 

cause a public health hazard under a climate with warmer temperatures and increased drought (Koschel 2010). A 

longer growing season, glacial retreat, and warmer water temperatures are expected to increase sediment fluxes 

and concentrations, affecting the chemical, mineral, and 

nutrient status of streams and lakes and having deleterious effects on the food chain of western North America 

(Moore and others 2009). Nitrate increases in Colorado 

high-elevation streams has occurred and is thought to be 

largely due to increased glacial melt water flushing microbially rich sediments (Baron and others 2009). Water 

quality degradation may exceed thresholds of ecosystem 

tolerance during extreme events such as storms, drought, 

or extended periods of elevated temperatures and increased 

fire (Murdoch and others 2000). At the time of this report, 

no studies on the Shoshone have been found that link future climate change with water quality changes. However, 

the potential consequences to water quality may be higher 

temperatures that reduce the quality of aquatic habitat and 

increase the potential for higher amounts of algae, as well 

as the projected increase in disturbance that would cause 

more sedimentation to occur more frequently (Table 5).

Glaciers

Current Condition

Glacial retreat and advance for the Pinedale and Bull 

Lake glaciers in YNP and Teton National Park (TNP) has 

been highly variable spatially and temporally from about 

150,000 to 12,000 years ago (Liciardi and Pierce 2008). 

Since the Little Ice Age (1300 to 1850), glaciers in western North America have retreated in response to general 

warming trends (Moore and others 2009). Wyoming contributes approximately 6 percent of total glacial area in 

the conterminous United States (http://www.glaciers.pdx.

edu/), a large fraction of which is found on the Shoshone in 

the Wind River Range (Cheesebrough 2009) (Figure 18). 

The Wind River Range contains 7 of the 10 largest glaciers 

in the U.S. Rocky Mountains (Oswald and Wohl 2008). 

Recent glacial mass reductions of 25 percent have been 

observed since 1985 (Cheesbrough and others 2009), and 

there was a loss of 0.53 mi3 (0.86 km3) of glacial ice volume 

from 1966 to 2001 (Bell 2009). Pochop and others (1990) 

reported evidence that the two largest glaciers in the Wind 

Rivers have receded in the past 50 years and are continuing 

to do so. More recently, a jökulhlaup (a type of outburst 

flood that originates from melt water ponded by glacial ice) 

that burst from the Grasshopper Glacier provides indirect 

evidence of glacial melt (Oswald and Wohl 2008).

Glacier retreat can temporarily mitigate reductions in 

runoff volume. Cheesebrough and others (2009) found that 

the 25 percent reduction of glacial mass that has occurred 

since 1985 has been contributing 4 to 10 percent of July to 

October stream flow in the Wind River Range (Table 6). 

And the 0.53 mi3 (0.86 km3) loss of glacial ice that occurred 

from 1966 to 2001 may have contributed +6 to +25 percent 

to annual stream flow and 35 to 40 percent of late summer 

flow (Table 6). However, changes in stream flow may also 

be attributed to precipitation changes (Graumlich and others 2003), making it difficult to discern precise stream flow 

increases from glacial melt.

Figure 18. Glacier distribution, 2005. Source: http://

glaciers.us/Downloads.
USDA Forest Service RMRS-GTR-264. 2012. 25

Climate Change Effects on Glaciers

The response of glaciers to future climate change is a complex interaction among temperature, precipitation, and solar 

radiation (Hall and Fagre 2003). Increased winter precipitation (as projected for the Shoshone during winter) would 

result in greater accumulation but only if winter temperatures are low enough to create snow (Hall and Fagre 2003). 

Summer temperature has been found to explain 92 percent of 

glacier change in Glacier National Park (GNP), mostly by its 

direct effect on ablation (the erosive process of melting and 

evaporation by which a glacier is reduced) and the associated 

increase in solar radiation (Hall and Fagre 2003). However, 

Hall and Fagre (2003) modeled glacial loss in GNP under a 

doubling of CO2 and found that winter precipitation did not 

buffer glacial loss. On the contrary, the modeled summer 

temperature increase of 4.5 °F (2.5 °C) by 2050 resulted in 

the complete loss of glaciers by 2030 (Hall and Fagre 2003).

The local effect of climate change on glaciers on the 

Shoshone will vary according to glacier elevation, size, 

shape, slope/aspect position, and local monthly temperature and precipitation (Hall and Fagre 2003; Granshaw and 

Fountain 2006). The elevation of a glacier plays a role in the 

location of its equilibrium line (the point at which on either 

side the accumulation and ablation zones are equal in area) 

(Granshaw and Fountain 2006). Larger glaciers are less susceptible to loss in the near-term, and the shape of the glacier 

influences the dynamics between the ablation and accumulation zones.

Table 6. Summary of glacier conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature increase 

of 2 to 4 °F (1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Glaciers • Large reduction 

(~25 percent) since mid 

century in Wind River 

Range

• Glacial melt may 

contribute 4 to 

25 percent of annual 

flows and 35 to 

40 percent of late 

summer flow in the 

Wind River Range

• Potential for complete glacier 

loss before mid century with 

4.5 °F (2.5 °C) annual 

temperature increase 

• Reductions in streamflow with 

eventual loss of glaciers

• Potential increase of stream 

temperatures as glaciers 

disappear

• Existing glaciers may 

help mitigate reductions 

in water supply during 

summer

• Potential reductions in 

summer streamflow as 

glaciers disappear

• Potential loss of microsite terrestrial habitat 

adjacent to glaciers 

• Potential shift in 

suitability of aquatic 

thermal habitat

Overall, there is consensus that western U.S. glaciers 

will continue to retreat in the next 100 years (Hall and Fagre 

2003; Christensen and others 2007; Moore and others 2009). 

Even though glacial loss affects a relatively small portion 

of the landscape, the effects are far reaching: downstream 

aquatic habitats and water quality may be degraded by increased stream temperatures and sediment; and summer 

stream flow may be reduced, thereby altering the reliability 

of water resources for human communities (Burkett and others 2005; Moore and others 2009). However, future stream 

flow reductions could be partially mitigated by glacier melt 

(while glaciers are present). The potential consequences to 

ecosystem services may be a temporary increase in summer 

stream flow followed by a reduction as glaciers disappear, 

terrestrial habitat that is near glaciers could be lost, and the 

suitability of aquatic thermal habitat near glaciers will likely 

shift as glaciers disappear (Table 6).

Snow

Current Conditions

Most of the western United States has already experienced declines in snowpack that may be associated with 

warming, earlier snowmelt, and more precipitation falling 

as rain instead of snow (Naftz and others 2002; Regonda 

and others 2004; Mote and others 2005; Stewart and others 

2005; Knowles and others 2006). Since the 1940s, a moderate warming trend has shifted snowmelt 10 to 28 days 
26 USDA Forest Service RMRS-GTR-264. 2012.

earlier in western North America (Regonda and others 2004; 

Stewart and others 2005) (Table 7).

Windstorm events in Arizona, Utah, and western 

Colorado have recently been observed to deposit a layer of 

dust on snowpack in Colorado and southern Wyoming that 

change hydrologic function (Rhoades and others 2010). The 

dust increases solar radiation absorption, accelerating snow 

melt, causing an earlier runoff, and altering water chemistry (Painter and others 2007, 2010; Neff and others 2008; 

Steltzer and others 2009; Rhoades and others 2010). Duston-snow events have largely impacted the Colorado Rocky 

Mountains, but at this time, no information has been found 

about dust-on-snow events of this magnitude in the GYE.

Climate Change Effects on Snow

In the near-term, increased winter precipitation could 

increase snowpack in the northwestern United States 

(Whitlock and others 2003)1. While this has been simulated 

up to 2059, if temperatures continue to increase, a threshold 

will eventually be crossed where most winter precipitation 

will fall as rain instead of snow (Whitlock and others 2003). 

Baron and others (2000a) simulated a doubling of CO2 with 

a concurrent 7 °F (4 °C) temperature increase at a high-altitude watershed (9800 to 13,000 ft [2990 to 3965 m]) in 

Rocky Mountain National Park, Colorado. Under those conditions, simulated snowpack was reduced by 50 percent and 

runoff began four to five weeks earlier (Baron and others 

2000a). Under future climate projections for the Shoshone, 

snowfall will likely shift to rainfall at progressively higher 

elevations, and snowmelt will continually start earlier in the 

year as temperatures warm (Ray and others 2008). A modeling study for the Colorado River Basin showed that areas 

above 8200 ft (2500 m) elevation had less snow loss compared to areas below 8200 ft (2500 m) by the year 2050 (Ray 

and others 2008). A 30 to 50 percent reduction in snowpack 

was projected at elevations above 8200 ft (2500 m) with a 

9 °F (5 °C) temperature increase by the year 2100 (Ray and 

others 2008). The highest elevations of the Shoshone may 

be buffered from snowpack loss if results from the Colorado 

study can be extended to Wyoming. However, the overall 

consequences to ecosystem services may be: a reduced annual water supply being stored as snow, an earlier release 

of stream flow for water storage, a loss of winter habitat for 

snow-dependent wildlife, and reduced snow recreation opportunities, especially at lower elevations (Table 7).

Table 7. Summary of snow conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature increase 

of 2 to 4 °F (1 to 2 °C)

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Snow • Declining snowpack

in the western U.S. 

• Western U.S.

snowmelt 10 to 28

days earlier since mid 

20th Century

• 30 to 50 percent annual

snowpack loss with 9 °F (5 °C) 

temperature increase in the 

Colorado River Basin

• Potentially less annual 

water supply stored as 

snow and earlier release 

of stream flows for 

storage

• Potential loss of winter 

habitat for snowdependent wildlife

• Potential reductions of

snow recreation 

opportunities for skiing, 

snow shoeing, and snow 

mobiling, especially at 

lower elevations

1

 Whitlock and others (2003) used climate data from HADCM2 

HCGSa for the period 2050-2059, as found in Mitchell and 

Johns (1997).
USDA Forest Service RMRS-GTR-264. 2012. 27

Wetlands

Current Condition

Wetlands occupy a small percentage of the Shoshone 

but serve important ecological functions such as increasing biodiversity, providing important spawning grounds, 

supporting a wide variety of biota, serving as natural flood 

control, cleansing and replenishing groundwater, cleansing 

agricultural and urban runoff, and offering recreation and 

aesthetic value (Copeland and others 2010). The wetlands 

in the Beartooth Mountains of the northern Shoshone have 

high botanical significance, representing the widest known 

array of wetland fen2 types in Wyoming, and are among the 

highest known concentrations of fen sites and rare plant species in Wyoming (Heidel and Rodemaker 2008). In 1961, a 

permanently frozen peat deposit in the Northern Shoshone 

Beartooth Mountains was reported as a very rare occurrence of permafrost at that latitude, indicating that climate 

conditions and insulating cover were sufficient to support 

permafrost at that time (Pierce 1961).

Some Shoshone wetlands were affected by tie hacking 

(especially at high elevations), water diversions (at low elevations), and grazing (especially at lower elevations) at 

the turn of the Twentieth Century. These effects may have 

decreased the abundance of some willow communities 

and favored succession to conifers within riparian areas 

(Table 8). Analysis of aerial photos (1937 to 1997) has 

documented changes to some riparian areas from livestock 

grazing, and encroachment by conifers that has caused the 

decline of deciduous aspen (Populus tremuloides) and willow vegetation (USDA Forest Service 2009b).

Climate Change Effects on Wetlands

Globally, wetlands are expected to decline in area over 

the next century as they are extremely vulnerable to climate change (IPCC 2007b). Warmer temperatures will 

increase evaporation, leading to an increased chance of 

wetland desiccation, as well as altering wetland species 

communities and nutrient cycling, increasing decomposition, and potentially creating a C source (Burkett and Kusler 

2000). Lower-elevation wetlands of Wyoming outside the 

Shoshone have been found to be the most affected by land 

use, are classified in the poorest condition, and are most 

vulnerable to future changes (Copeland and others 2010). 

Wetlands are very sensitive to changes in precipitation, especially if precipitation is the major source of water as opposed 

to groundwater (Winter 2000). At the time of this report, no 

published information was found on groundwater and climate change on the Shoshone. However, earlier snow melt, 

reduced summer precipitation, and longer growing seasons 

will likely cause reduced water inputs and lowering of water tables in wetlands, especially during late summer (Erwin 

2009). The potential consequences to the Shoshone wetlands 

Table 8. Summary of wetland conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 4 °F 

(1 to 2 °C)

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Wetlands • Willow communities 

on the Shoshone 

have experienced an 

increase in conifer 

encroachment

• Increased potential for wetland 

desiccation globally

• Potential reduction or 

loss of wetlands

• Potential loss of habitat 

for many species using 

or dependent on 

wetlands

• Potential alteration in 

local hydrology because 

of changes to, or 

disappearance of, 

wetlands

2

 Fens are peat forming wetlands that receive their nutrients 

from sources other than precipitation. Fens are less acidic and 

have high nutrient contents that can support diverse plant and 

animal communities.
28 USDA Forest Service RMRS-GTR-264. 2012.

that will likely face higher temperatures may be a reduction 

or loss of these habitats and the associated species dependent 

upon them, as well as altered hydrology if these habitats disappear (Table 8).

Vegetation

Paleo-Historic and Current Vegetation

Plant species distributions and compositions on the 

Shoshone and the GYE have varied greatly for thousands 

of years (Table 9). Paleo-ecological studies for the GYE 

show that individual species respond to climate change 

predominately by shifting ranges (Whitlock and Bartlein 

1993). Pollen records for the Wind River Range, Grand 

Teton National Forest and YNP (study site locations in 

Figure 2) show that cooler conditions between ~14,000 BP 

and ~11,500 BP caused the upper tree line of birch (Betula 

spp.) and juniper (Juniperus spp.) species to be about 1000 ft 

(305 m) lower than present (below 9200 ft [2800 m] elevation). Warmer temperatures and wetter conditions from 

~11,500 BP to ~10,500 BP allowed the presence of spruce 

(Picea spp.), fir (Abies spp.), and whitebark pine (Pinus albicaulis) in the northern and southern Yellowstone regions and 

in the Wind River Range. Lodgepole pine (Pinus contorta) 

appeared and persisted around 10,500 BP as temperatures 

continued to increase. Douglas-fir (Pseudotseuga menziesii) 

and poplar (Populus spp.) were present in lodgepole pinedominated forests in the southern Yellowstone region from 

~9500 to ~5000 BP under warmer and drier conditions. 

Mixed forests of spruce, fir, and pine have been present 

for the last ~5000 years, and the modern tree-line position 

occupied by whitebark pine at around 10,500 ft (3200 m) 

Table 9. Paleo-historic vegetation of the Wind River Range and YNP (Fall and others 2005; Whitlock 1993).

14,000 to 

11,500 BP

11,500 to 

10,500 BP

10,500 to 

9500 BP

9500 to 

5000 BP

5000 to 

3000 BP

3000 BP to 

present

YNP area

6500 to 9200 

ft (2000 to 

2800 m) 

elevation

Alpine 

meadow, 

shrub

(grass, 

herb, birch, 

juniper)

Spruce 

parkland 

(Englemann 

spruce, fir, 

whitebark 

pine)

Spruce-firpine forestLodgepole 

pine forest 

with 

Douglas-fir, 

aspen

Lodgepole pine forest, 

increasing spruce, fir, 

grass; decreasing Douglasfir

Wind River 

Range

9800 ft (3000 

m) elevation

Alpine 

tundra

(juniper)

Mixed conifer forest

(pine, fir, spruce)

Whitebark 

pine 

parkland

Figure 19. Shoshone tree 

species elevation ranges.
USDA Forest Service RMRS-GTR-264. 2012. 29

elevation was established ~ 3000 years ago (Whitlock 1993; 

Fall and others 1995) (Table 9).

The current vegetation of the Shoshone varies widely 

due to variations in elevation, aspect, latitude, climate, site 

conditions, and past disturbances (Figure 19) (USDA Forest 

Service 2009b). The Shoshone lies in the Yellowstone 

Highlands section of the Southern Rocky Mountain SteppeOpen Woodland-Coniferous Forest-Alpine Meadow 

Province (McNab and others 2005). This landscape includes 

rugged mountains with glacially formed cirques, broad valleys, and rounded ridges with rocks of volcanic origin. About 

60 percent of the Shoshone’s rugged landscape is covered by 

trees, about 30 percent is dominated by grasses and forbs, 

and about 10 percent is rock and ice at the highest elevations. 

Tree cover in the montane and subalpine zones is between 

about 6000 ft (1829 m) and about 10,500 ft (3200 m) elevation and comprises about 57 million tons (63 million metric 

tons) of live biomass (Menlove 2008).

Climate Change Effects on Vegetation

Climate has influenced the patterns of vegetation distributions and their fluctuation in the GYE over long time periods. 

The ongoing and rapid rates of climate change that are expected in the next 100 years will likely outpace post-glacial 

rates since 20,000 BP and will likely have far reaching effects 

on future biogeography (Whitlock and others 2003). Some 

species may benefit from warmer temperatures and longer 

growing seasons, other species may adapt to new conditions 

or migrate to a more suitable environment, and some may go 

extinct (Aitkin 2008). Although it is difficult to predict how 

plant communities will develop and interact under climate 

change, the future dynamics of vegetation communities will 

likely be complex and determined by species dispersal rates, 

individual species response to environmental conditions, 

availability of suitable recruitment sites (for example, suitable 

soil depth or available habitat), disturbance regime (for example, fire, wind, or insects), nutrient availability, microclimate, 

and precipitation and temperature (Whitlock and Bartlein 

1993; Bartlein and others 1998; Shafer and others 2001).

Alpine Zone Vegetation

Current Conditions

Alpine areas comprise 25 percent (625,000 acres or 

252,930 ha) of the Shoshone (Table 10). These are highbiodiversity areas with short growing seasons and rugged or 

rocky topography that host shrubs, grass, and forb species. 

Over 400 of the worldwide 8000 to 10,000 species of alpine 

flora occur on the Beartooth Plateau that extends into the 

northern Shoshone (Kripps and Eddington 2005). Several of 

these 400 species are considered rare taxa (for example, the 

insectivorious English sundew [drosera anglica], Alpine arnica [Arnica angustifolia ssp. Tomentosa], and White arctic 

whitlow-grass [Draba fladnizensis var. pattersonii]).

It is uncertain whether other environmental factors limit 

tree line migration into alpine areas on the Shoshone (Table 

10). On the northern Shoshone Beartooth Plateau, no evidence was found of whitebark pine invasions into alpine 

meadows above its current ecotone (Mellman-Brown 2002). 

However, alpine vegetation has been observed to shift upward 

in elevation (Swiss Alps, Walther and others 2005; Italian 

Alps, Cannone and others 2007). Rocky Mountain studies 

have found a 60-ft (20-m) advance in tree line since 1938 

on the west side of Pikes Peak in Colorado (Freiden 2010), 

episodic tree line advancement during the 1950s and 1960s 

in Rocky Mountain National Park (Hessl and Baker 1997), 

and no tree line advance but increased tree line density and 

fragmentation in Glacier National Park (Klasner and Fagre 

2002) (fragmentation is defined here as the disconnection 

of areas from one another within a landscape or ecosystem 

[Hobbs and others 2008]). The inconsistency of tree line 

advance in these areas may be due to inertia (slow tree establishment, growth, and reproduction rates), disturbance, 

drought, and nutrient or soil limitations (Mellman-Brown 

2002; Dullinger and others 2004; Malanson and others 2007; 

Smith and others 2009).

Climate Change Effects on Alpine Zone Vegetation

Alpine areas are expected to undergo the greatest amount 

of warming (Christensen and others 2007) and are sensitive to climate change (Christensen and others 2007). While 

Christensen and others (2007) reported that high elevations 

are expected to undergo the greatest amount of warming, 

Pepin and Lundquist (2008) reported that, based on observed Twentieth Century temperature trends, there has been 

no simplistic elevational increase in warming rates globally. 

Pepin and Lundquist (2008) documented the most rapid temperature trends at the annual 0 °C isotherm (the line where 

mean annual temperature is 32 oF) due to snow-ice feedback; 

and they suggested that ecosystems near the isotherm in the 

mid latitudes beyond the tropics are at increased risk from 

accelerated warming. The dynamics of tree line change will 

be influenced by the nature of the spatial changes in temperature across the higher elevations.

Globally, alpine vegetation extent is expected to decrease 

and fragment because temperatures may warm at higher 

rates than at lower elevations (Christensen and others 2007). 

Alpine areas are projected to be reduced or eliminated by 

the advancement of the tree line (Romme and Turner 1991; 

Bachelet and others 2001; Ashton 2010) (Table 10). The potential consequences to ecosystem services include a decline 

in alpine habitat with a potential for high-elevation refugia 

to develop dynamic and novel plant communities (Table 10). 

Grace and others (2002) suggested that tree line could be 

expected to advance vertically by 2100 ft (640 m) by the 

year 2100 with a future temperature increase of 7.2 to 9 oF 

(4 to 5 oC) in the alpine areas of northern Europe. Given the 

potentially large magnitude of temperature increase and the 

rapid rate of potential upslope migration, rare species, those 

with low dispersal rates, and those with narrow bioclimatic 

niches may be affected negatively (Shafer and others 2001). 

However, adaptable species may survive in refugia sites that 

develop as climate changes (Noss 2001; Ashcroft 2010). 

Within YNP and Grand Teton National Park, Schrag and 

others (2008) found a complex response of tree-line conifer 
30 USDA Forest Service RMRS-GTR-264. 2012.

Table 10. Summary of vegetation conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 

20th Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 

4 °F (1 to 2 °C) 

(especially in 

winter and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Vegetation • Alpine areas 

comprise 25 

percent or 625,000 

acres (252,930 ha) 

of the Shoshone

• Episodic tree line 

advance in 

southern Rocky 

Mountains

• Tree line dynamics 

largely unknown on 

Shoshone

• Whitebark pine 

decline in GYE

• Aspen decline in 

early 2000s in parts 

of North America, 

with aspen 

expansion in some 

areas of Rocky 

Mountains

• Montane lowerelevation species 

expanding to lower 

elevations on 

Shohone

• Grass and 

sagebrush 

experiencing 

conifer 

encroachment on 

Shoshone

• Decreased alpine vegetation 

area extent and increased 

fragmentation

• Tree line advance to higher 

elevations of Shoshone that is 

affected by moisture availability

• Whitebark pine retreats from 

lower-elevation range and 

either marginally exists at 

highest elevations of the 

Shoshone or is extirpated

• Aspen suitable climate moves 

upward in elevation on 

Shoshone 

• Douglas-fir, lodgepole pine 

expand range up in elevation 

and vacate lower elevations

• Expansion of grass and 

sagebrush upward in elevation

• Potential decline or 

extirpation of alpine 

habitat

• Potential for higherelevation refugia for 

dynamic and novel 

combinations of plant 

species 

• Potential reduction in or 

loss of the keystone 

species whitebark pine 

that is used by wildlife

• Potential loss of lowelevation habitat 

associated with aspen

• Potential reduction or 

loss of low-elevation 

habitat associated with 

Douglas-fir and lodgepole 

pine, but increase in 

higher-elevation 

associated habitat

• Potential increased 

grazing opportunities as 

grasslands expand 

upward in elevation
USDA Forest Service RMRS-GTR-264. 2012. 31

species to modeled changes in future temperature and precipitation. Under a scenario with a temperature increase 

and a scenario with temperature and precipitation increases, 

areas occupied by each tree species (whitebark pine, subalpine fire, and Engelmann spruce) decreased. Changes in the 

spatial distribution of tree line conifers were coupled with 

relative moisture, which identified the importance of moisture availability to tree line composition and structure.

Subalpine Zone Vegetation

Current Conditions

The subalpine zone (above 9000 to 10,500 ft or 2743 to 

3200 m) on the Shoshone hosts whitebark pine at the upper 

edges of tree line and mixes with subalpine fir, Engelmann 

spruce, and lodgepole pine at lower elevations, with minor 

occurrences of aspen and willow on moister sites (USDA 

Forest Service 2009b).

Whitebark pine is a keystone species of the subalpine 

zone of the Rocky Mountains of Wyoming, Montana, 

Idaho, and Alberta (Canada) that enhances biodiversity, 

regulates watershed function, and is an important ecosystem 

component involving Clark’s nutcracker (Nucifraga columbiana), red squirrel (Tamiasciurus hudsonicus), black bear 

(Ursus americanus), and grizzly bear (Ursus arctos horriblis) (Ellison and others 2005; Tomback and Resler 2007). 

Whitebark pine population decrease has been observed 

over the last 40 years (Kendall and Keane 2001), and is 

thought to be due to the spread of white pine blister rust 

(Cronartium ribicola), fire suppression, and mountain pine 

beetle (Dendroctonus ponderosae) outbreaks (Keane and 

Arno 1993; Koteen 2002; Gibson 2006) (Table 10). The decline of whitebark pine may be beyond historic observations 

of beetle outbreaks during the 1930s and 1970s in the GYE 

(Logan and others 2010) (Table 10). The rate of whitebark 

pine regeneration has recently been increasing in Montana, 

Idaho, and Oregon, especially where widespread mortality 

from mountain pine beetle infestations provided suitable 

conditions for regeneration (Larson and Kipfmueller 2010). 

However, restoration projects in central-eastern Idaho and 

western Montana have not produced significant whitebark 

pine regeneration due to white pine blister rust mortality of 

seed sources (Keane and Parsons 2010).

Climate Change Effects on Subalpine Zone Vegetation

The effect of climate change on whitebark pine may not 

be clear in the short term due to inertia and the likely involvement of complex interacting factors. Warmer temperatures 

may limit the available habitat, especially at lower elevations, and it is projected that whitebark pine populations will 

continue to decline (Romme and Turner 1991; Bartlein and 

others 1997; Schrag and others 2008) (Table 10). Growth 

and regeneration could be enhanced by longer and warmer 

growing seasons, increased precipitation, and higher atmospheric CO2

, but it could inhibited by drought and heat stress, 

species competition, increased spread of white pine blister 

rust, and mountain pine beetle infestations under warmer 

temperatures and wetter winters (Romme and Turner 1991; 

Bartlein and others 1997; Koteen 2002; Schrag and others 

2008). Climate envelope modeling by the USDA Forest 

Service (http://forest.moscowfsl.wsu.edu/climate/species/) 

using the A2 scenario projects that by 2090, a temperature 

increase of 9.1 °F (5.1 °C) would cause whitebark pine suitable climate to contract to the highest elevation areas in the 

northern Shoshone and GYE or be extirpated (Table 10). 

Loehman and others’ (2010) modeling study indicated that 

climate changes may significantly impact whitebark pines in 

Glacier National Park through the indirect mechanisms of 

altered distributions of competing tree species and increased 

fire frequency and fire size.

Montane Zone Vegetation

Current Conditions

Lower-elevation forest (6000 to 9000 ft [1829 to 2743 

m]) montane zone species are characterized by Douglas-fir, 

lodgepole pine, and limber pine (Pinus flexilis) (Steele and 

others 1981) with minor occurrences of aspen in wetter areas 

(USDA Forest Service 2009b) (Figure 19). Subalpine species (whitebark pine, subalpine fir, aspen, and Englemann 

spruce) can extend down into the montane zone, occuring in 

both the montane and subalpine zones. Dominant montane 

understory forest plant species vary greatly with environmental conditions. Among the species used to distinguish 

the habitat types are snowberry (Symphoricarpos albus), 

common juniper (Juniperus communis), hollyleaved barberry (Mahonia aquifolium), russet buffaloberry (Shepherdia 

canadensis), dwarf huckleberry (Gaylusssacia dumosa), 

heartleaf arnica (Arnica cordifolia), and graminoids Idaho 

fescue (Festuca idahoensis) and Ross’ sedge (Carex rossii) 

(USDA Forest Service 2009b).

Climate Change Effects on Montane Zone Vegetation

The montane lower-elevation species composition may 

be altered by future climate change (Romme and Turner 

1991; Bartlein and others 1997; Shafer and others 2001). 

Species such as Douglas-fir and lodgepole pine may expand 

in range, dominating not only their current range but also 

higher elevations (Bartlein and others 1998) (Table 10). 

Lower tree line may move downslope in response to greater 

winter precipitation (Romme and Turner 1991) but could 

eventually retreat to higher elevations when temperature increases prohibit tree establishment and growth (Shafer and 

others 2001). Upper-elevation species occupying the lower 

end of their environmental tolerance are predicted to abandon lower elevations, causing a shift in community structure 

and function (Romme and Turner 1991; Bachelet and others 

2003; Rehfeldt and others 2009).

Aspen

Current Conditions

Aspen on the Shoshone occupy about 22,000 acres (8903 

ha) or 0.9 percent, spanning elevations from about 7000 to 

10,000 ft elevation (2135 to 3050 m). The species is most 

prevalent on the south end of the Shoshone (USDA Forest 

Service 2009b), which is thought to be due to the presence of 
32 USDA Forest Service RMRS-GTR-264. 2012.

clay soils and areas of moisture collection in the Wind River 

Mountains (K. Houston, personal communication, 2011). 

Aspen in the western United States are valued for their high 

biodiversity, forage production, water yield regulation, nutrient cycling, and aesthetic value (McCool 2001; LaMalfa 

and Ryel 2008; Morelli and Carr 2011). Some aspen communities throughout North America have been declining 

in the latter half of the Twentieth Century, primarily due to 

fire suppression, conifer encroachment, excessive ungulate 

grazing, insects, fungal pathogens, and drought (Romme and 

others 1995; Chong and others 2001; Hogg and others 2002, 

2008; Krishnan and others 2006; Hollenbeck and Ripple 

2007; Rehfeldt and others 2009; Durham and Marlow 2010; 

Morelli and Carr 2011) (Table 10). Until recently, some 

areas of the Rocky Mountains have experienced an expansion in aspen regeneration and coverage extent at a local 

scale (western Colorado, Manier and Laven 2002; western 

Wyoming, Hessl and Graumlich 2002). Recent aspen mortality episodes from 2000 to 2003 in North America have 

been attributed to drought (Hogg and others 2008; Rehfeldt 

and others 2009). Aspen growth has been shown to have 

variable sensitivity to temperature and precipitation in YNP 

(Jules and others 2010). Factors that can contribute to aspen 

success in the United States are:

• precipitation between 15 and 40 inches (381 to 1018 mm);

• mild winters and warm, wet summers (Brown and others 

2006);

• fine, well-drained soils that are high in organic matter 

derived from igneous rock with water tables 2 to 8 ft (0.6 

to 2.5 m) deep (Perala 1990);

• lack of conifer competition;

• enhanced water use efficiency and photosynthesis from 

higher atmospheric CO2 levels (Lindroth and others 

1993);

• less browsing pressure by elk due to wolf predation in 

YNP (Halofsky and Ripple 2008); and

• reductions in elk browsing from hunting or feeding of elk 

in the YNP area (Hessl and Graumlich 2002).

Climate Change Effects on Aspen

One bioclimate modeling study has projected that aspen 

populations are likely to decline in the future under expected changes in climate (Rehfeldt and others 2009). Rehfeldt 

and others (2009) projected that future reduction of potential aspen distributions would largely be due to dryness and 

temperature warming. However, the bioclimate model did 

not take into account increasing atmospheric CO2 concentrations, which have been experimentally shown to increase 

aspen growth in Wisconsin (Isebrands and others 2001), or 

other factors that may influence aspen distribution such as 

soils, disturbance regime, or species competition. However, 

Rehfeldt and others’ (2009) projections that considered 

future temperature and precipitation showed an upslope 

migration of aspen and a reduction in potentially suitable 

habitat at higher elevation on the Shoshone. By 2100, the 

upper elevation of the mid and southern Shoshone was one 

of the few potential climatically suitable aspen refugia left 

in the western United States as aspen migrated up to 3280 ft 

(1000 m) upslope and vacated up to 50 percent of its current 

distribution in the western United States (Rehfeldt and others 2009) (Table 10).

Grass and Sagebrush

Current Conditions

Grasslands on the Shoshone cover over 700,000 acres 

(283,279 ha), much of which occurs below ~6500 ft (1982 

m) elevation, but also includes forest openings and alpine 

areas of higher elevations (USDA Forest Service 2009b). 

These grasslands are dominated by Idaho fescue (Festuca 

idahoensis), bluebunch wheatgrass (Pseudoroegneria spicata), sandberg bluegrass (Poa secunda), and june grass 

(Koelaria spp.). Grasses are sometimes mixed with sagebrush below the montane zone in the foothills. Sagebrush 

occupies over 30,000 acres (1240 ha) of the Shoshone, with 

Artemesia spp. dominating most of these areas that occur 

on deeper more developed soils (Tweit and Houston 1980). 

Sagebrush is sometimes mixed with grass in forest openings 

at lower elevations and in areas of limited moisture, disturbance, or harsh environmental conditions (USDA Forest 

Service 2009b). Grasslands and sagebrush are largely constrained by water availability, temperature, nutrients, soil, 

and disturbance (Parton and others 1994; Polley and others 

1997). Grass and sagebrush dominate Shoshone elevations 

below 6500 ft (1982 m) but also occur at higher elevation 

where trees are precluded due to moisture limitation, thin 

soils, wind, and/or disturbance (Tweit and Houston 1980; 

USDA Forest Service 2009b). Areas of grass and sagebrush 

have been impacted by Euro-American settlement, land use, 

grazing, fire suppression, and invasive species, especially 

at lower elevations (Meyer and others 2006; USDA Forest 

Service 2009b).

Recently, conifer invasion into sagebrush and grasslands 

has been increasing on the Shoshone (USDA Forest Service 

2009c) (Table 10). Powell and Hansen (2007) reported conifer cover increase in transects that were recently burned 

or logged over the 1971 to 1999 period, suggesting that the 

structure and composition of conifer-grass ecotones in the 

GYE are rapidly changing. A 10-fold juniper expansion into 

sagebrush has been observed in eastern Oregon (Rowland 

and others 2008), which has experienced a climate regime 

similar to low elevations on the Shoshone. The explicit 

cause for this conifer increase and any potential interaction 

with the current bark beetle outbreak remains to be studied.

Climate Change Effects on Grasslands and Sagebrush

Information about the effects of climate change on grasslands and sagebrush on the Shoshone is limited. However, 

the effects of increased CO2 have been shown to particularly favor sagebrush increase over grass in the Great 

Plains (Polley 1997; Morgan and others 2007). Improved 

water use efficiency from higher atmospheric CO2 concentrations available for trees may also facilitate the expansion 

of conifers (Powell and Hansen 2007). Tree invasion may 
USDA Forest Service RMRS-GTR-264. 2012. 33

continue or increase on the Shoshone (Bachelet and others 2001, 2003) in the short term, while water availability 

is adequate to support conifers. But conifer expansion into 

grass and sagebrush at lower elevations could eventually be reversed when temperature increases and moisture 

limitations at the forest-grassland ecotone prohibit tree establishment and growth (Shafer and others 2001), allowing 

grass and sagebrush to expand upward in elevation (Table 

10). Big sagebrush (Artemisia tridentada) distribution in the 

western United States is projected to decrease in the southern portion of its range (New Mexico, Arizona, Colorado, 

Utah, and Nevada), and increase in the northern portion of 

its range (Montana) by the end of the Twenty-First Century 

(Schlaepfer and others 2011). Projections for big sagebrush 

in the lower elevations of the GYE and Shoshone indicated 

that a contraction may occur, while higher elevations could 

see some expansion (Schlaepfer and others 2011) (Table 10). 

A potential consequence to ecosystem services, if moisture 

limitations are a factor in the future, may be the eventual 

expansion of grasslands to higher elevations that could increase the area available for grazing (Table 10).

Invasive Species

Invasives are introduced species to ecosystems that harm 

the environment, economy, or human health (NISIC 2010). 

Invasive species can destroy or degrade ecosystem health 

by reducing native species richness, biodiversity, and productivity (DiTomaso 2000), and they can degrade forage 

for wildlife and livestock grazing (USDA Forest Service 

2011a). Millions of acres of U.S. land and water have been 

affected by thousands of invasive plants, aquatic organisms, 

pests, and pathogens that have caused major disruptions to 

ecosystem function (NISIC 2010).

Current Conditions

Statewide, Wyoming’s forests, rangelands, and aquatic 

systems are threatened by the expansion of 30 invasive plant 

species (USDA 2010), 3 mollusk species (USGS 2010), 9 

fish species (USGS 2010; Wyoming Game and Fish 2010), 

and 3 pathogens.

On the Shoshone, 5000 to 6000 acres (2023 to 2428 ha) 

have been impacted by invasive populations of knapweeds 

(Centaurea), thistles (Cirsium), leafy spurge (Euphorbia 

esula), oxeye daisy (Leucanthemum vulgare), whitetop 

(Lepidium draba), houndstongue (Cynoglossum officinale), 

common tansy (Tanacetum vulgare), cheatgrass (Bromustectorum), and toadflax (Linaria vulgaris) (USDA Forest Service 

2011a) (Table 11). White pine blister rust (Cronartium ribicola) affects white and limber pine trees on the Shoshone. 

Aquatic nuisances—whirling disease (Myxobolus cerebralis), New Zealand mudsnails (Potamopyrgus antipodarum), 

Eurasian watermilfoil (Myriophyllum spicatum L.), and didymo (Didymosphenia geminata [Lyngb.] M. Schmidt)—also 

threaten Shoshone aquatic habitats (USDA Forest Service 

2009c). Non-native fish species (for example, brown trout 

[Salmo trutta] and rainbow trout [Oncorhynchus mykiss]) 

threaten native Yellowstone cutthroat trout populations 

by competition and hybridization (USDA Forest Service 

2009c) (Table 11). The pathogen brucellosis affects elk and 

cattle (Cross and others 2010).

Climate Change Effects on Invasives

Globally, the effects of climate change on invasive species are expected to exacerbate the spread of some species 

directly by increasing suitable habitat and indirectly by increased disturbance such as fire (Dukes and Mooney 1999; 

Dietz and Edwards 2006). Yet some invasive species may be 

reduced or eliminated in the western United States (Bradley 

and others 2009, 2010). Bradley and others (2009) used a 

bioclimate model for the western United States to show 

that precipitation was a large factor in predicting the future 

range of suitable area for invasive plant species. In northwest Wyoming, the projected climate conditions by 2100 

contributed to for the increased spread of yellow starthistle 

(Centaurea solstitialis), cheatgrass (Bromus tectorum), and 

spotted knapweed (Centaurea maculosa); however, white 

leafy spurge (Euphorbia esula) was projected to contract 

in southwestern Montana. Tamarisk (Tamarix spp.) was not 

projected to have a large change in distribution but had a low 

possibility of retreat from north-central Wyoming (Bradley 

and others 2009). The potential consequences to ecosystem 

services include reduced grazing quality and habitat function 

impairment and decreased aesthetic value on the landscape 

(Table 11).

The current expansion of aquatic invasive species 

throughout the United States (for example, the New Zealand 

mudsnail currently found on the Shoshone) is expected 

to continue, and future dynamics are expected to involve 

complex interactions for multiple factors (Rahel and Olden 

2008). Warmer future temperatures are expected to increase 

the range of suitable habitat for temperature-tolerant invading species, while increased rainfall or flooding would 

increase their spread and drought would be expected to hinder their spread (U.S. EPA 2008). Warmer temperatures have 

been found to shorten the duration of ice cover and to increase water temperatures, thereby enhancing conditions for 

non-native warm water species and stressing native cold water species in Canada (Sharma and others 2007). Increased 

demand for water resources may lead to more construction 

of reservoirs in the United States that can be hotspots for 

invasive species (Rahel and Olden 2008). Another potential 

consequence to ecosystem services is an enhanced competitive ability for warm water, non-native aquatic species that 

could hold a competitive advantage over native cold water 

species (Table 11).

Fire

Paleo-Historic and Recent Fire History

Historic fire behavior since 17,000 BP in the GYE has 

been largely influenced by climate, with major fires tending to occur during relatively dry or hot periods (Millspaugh 

and others 2000; Whitlock and others 2003; Higuera and 
34 USDA Forest Service RMRS-GTR-264. 2012.

others 2010). The spatial variability of fire has been influenced by elevation, forest structure, and rugged topography 

(Millspaugh and others 2000; Whitlock and others 2003; 

Higuera and others 2010). Although insufficient data exist 

to precisely quantify historic fire behavior on the Shoshone, 

it is likely that high-elevation forests—where most of the 

Shoshone occurs—have experienced less frequent, larger, 

stand replacing fires (Turner and Romme 1994) that were 

most likely caused by lightning. High-elevation forests of 

the Shoshone may have a historical mean fire interval (MFI) 

ranging from 150 to 700 years for high intensity, stand replacing fires and 10 to 300 years for all fire events (Meyer 

and others 2006). Lower-elevation forests of the Shoshone 

may have been more affected than higher-elevation forest 

by Native American burning prior to Euro-American settlement (Barrett and Arno 1982; Schoennagel and others 2004) 

and post Euro-American settlement fire suppression since 

the late 1800s. Human influences on fire in these lowerelevation forests have likely caused lower intensity fires 

with MFI from 20 to 200 years, which may be outside the 

historic range of variability (Meyer and others 2006). Since 

1971, Shoshone high-elevation forests have experienced 

high intensity crown fires but a lower numbers of fire starts 

(29 starts/247,105 acres [100,000 ha]/year) compared to 

lower-elevation forests (USDA Forest Service, Shoshone 

Fire and RIS databases 1970 to 2000) (Table 12). Almost all 

of these fires were in whitebark pine stands (27 of the total 

29) (USDA Forest Service, Shoshone Fire and RIS databases 1970 to 2000). Lower-elevation forests of the Shoshone 

have experienced lower intensity fires and a higher numbers 

of fire starts (120 starts/247,105 acres [100,000 ha]/year) 

than higher elevations (USDA Forest Service, Shoshone Fire 

and RIS databases 1970 to 2000) (Table 12). In the last 5 

years, ~115,000 acres (46,538 ha) have burned; and in the 

last 10 years, ~161,500 acres (65,356 ha) have burned on the 

Shoshone (USDA Forest Service 2011a).

Climate Change Impacts on Fire

The majority of research focuses on fire history, and projections for future fire on the Shoshone are limited (Flannigan 

and others 2000; Whitlock and others 2003; Smithwick and 

others 2009) or inferred from historic fire behavior under given climatic conditions (Romme and Turner 1991). 

Certainly, increased temperatures without precipitation increases can result in drier fuels and increased fire occurrence. 

Whitlock and others (2003) simulated potential changes in 

summer soil moisture for the western United States under 

warmer temperatures. Their simulations suggested that the 

mid Twenty-First Century will exhibit drier-than-present 

conditions similar to those of 6000 BP—a period of high 

fire occurrence (Whitlock and others 2003). Generally, increased temperatures can also lead to earlier and longer fire 

seasons that burn more area and younger forests with decreased C storage, thereby increasing forest fragmentation 

(Flannigan and others 2000). Earlier snowmelt at high elevations could bring more area into a longer fire season (Miller 

2006). Drier conditions are expected to cause fires to be larger and may spread more often from wilderness areas (Miller 

2006). An increase in fire occurrence will also create younger stands and decrease the amount of mature forest in the 

GYE (Romme and Turner 1991; Whitlock and others 2003). 

However, a fire model projects that future warming and increased atmospheric CO2

 concentrations would increase the 

productivity of lodgepole pine forests in YNP, resulting in a 

Table 11. Summary of invasive conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 4 °F 

(1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Invasives • Invasive plant species 

include knapweed, 

toadflax, cheatgrass, 

musk thistle, and 

oxeye daisy

• Non-native fish 

species compete and 

hybridize with native 

Yellowstone cutthroat 

trout

• Increased spread of yellow 

starthistle, spotted knapweed, 

and cheatgrass 

• Potential contraction of white 

leafy spurge in GYE

• Enhanced habitat for nonnative, warm water species

• Potential reduction in 

habitat function and 

grazing quality

• Potential decrease in 

aesthetic value of 

landscape

• Potential increased 

competitive advantage 

for non-native fish over 

native species
USDA Forest Service RMRS-GTR-264. 2012. 35

reduction of the time needed to recover C stocks to pre-fire 

levels (Smithwick and others 2009).

The indirect effects of future climate warming may also 

influence future fire regimes on the Shoshone. Increased 

temperature, winter precipitation, and atmospheric CO2 concentration may enhance primary productivity of re-growth 

following fire in western forests (Powell and Hansen 2007), 

increasing fuel loads and contributing to more severe fires 

than present (Whitlock and others 2003). Warmer and earlier springs have been associated with an increase in large, 

western United States wildfire activity since the mid 1980s, 

especially in the mid elevations of the northern Rockies 

(Westerling and others 2006). Likewise, increased fires 

would enhance the expansion of fire adapted species, such 

as lodgepole pine, and create environmental conditions suitable for invasion by non-native plants (Bartlein and others 

1997). Overall, fires are expected to increase in frequency 

and severity under future climate change, but it is uncertain what role interacting human factors, such as human 

caused fire ignitions and fire suppression efforts, will play. 

The effects of other future disturbance, such as bark beetle 

epidemics, are also uncertain as bark beetle outbreaks have 

been found to both increase and decrease fire occurrence and 

severity (see the “Insect and Pathogen” section) (Table 12). 

The potential consequence to ecosystem services from the 

projected changes in the fire regime may be an increase in 

post-fire area affected by short-term terrestrial and aquatic 

habitat degradation. Also, the C sequestration potential of 

the landscape may be reduced and may vary spatially and 

temporally (Table 12).

Insects and Pathogens

Current Conditions

Native insects, such as bark beetles (Dendroctonus spp.,

including Mountain Pine beetle [Dendroctonus pondersae], 

Spruce beetle [Dendroctonus rufipennis], and Douglas-fir 

beetle [Dendroctonus pseudotsugae]) are endemic species of western U.S. forests and are important ecological 

regulators that aid in the sustained regeneration of forests 

(Logan and Powell 2001). Beetle population dynamics are 

influenced by stand conditions (Amman 1977), host availability and susceptibility (Breshears and others 2005), land 

management (Keane and others 2002), climate (Logan and 

Powell 2001), disturbance history, and predation. Epidemic 

outbreaks occur periodically, resulting in large tracts of dead 

stands (Logan and Powell 2001; Kurz and others 2008) that 

reduce the ability of land managers to meet short-term desired conditions and management objectives (USDA Forest 

Service 2009b).

The Shoshone hosts endemic bark beetles that have been 

at epidemic proportions within the last 10 years, resulting 

in substantial mortality, especially of larger diameter trees 

(USDA Forest Service 2009c). By 2010, the Douglas-fir 

beetle has caused mortality over roughly 203,000 acres 

(82,151 ha) of the total 373,000 acres (150,948 ha) of 

Table 12. Summary of fire conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 4 °F 

(1 to 2 °C)

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 5.5 

oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers (-

10%) (more uncertain)

Fire • More fires at lower 

elevations of 

Shoshone than at 

higher elevations

• Higher intensity fires 

at higher elevations of 

Shoshone

• Increased fire activity, 

especially at mid 

elevations of Rocky 

Mountains

• Earlier, longer fire seasons

• More burned area

• More fragmentation

• Younger, more fire resistant 

forest species 

• Less C storage

• Uncertain role of human 

interactions (ignitions and fire 

suppression) and bark beetle 

outbreaks in the future fire 

regime

• Increased fire occurrence 

may cause more post-fire

areas to be affected by 

short-term degradation of 

terrestrial and aquatic 

habitat 

• Potential spatial and 

temporal variability and 

reduction of C 

sequestration ability 
36 USDA Forest Service RMRS-GTR-264. 2012.

Douglas-fir stands (USDA Forest Service 2011b) (Table 13). 

The spruce beetle has also caused mortality on about 278,000 

acres (112,502 ha) of the total 348,000 acres (140,830 ha) of 

spruce forest. The number of Douglas-fir and spruce beetle affected acres has increased since 2009 (USDA Forest 

Service 2011b) (Table 13). Lodgepole pine and threatened 

five-needle pines (whitebark pine and bristlecone pine) are 

affected by the mountain pine beetle in the Rocky Mountains 

(Koteen 2002; Tomback and Resler 2007). Prior to 2010, 

mountain pine beetle activity on the Shoshone has increased and has affected 605,000 acres (244,835 ha) of 

lodgepole, ponderosa, and five-needle pine forests since 

1996 (USDA Forest Service 2011b) (Table 13).

Over 100,000 acres (40,469 ha) of the Shoshone have 

been affected by both the mountain pine beetle and the white 

pine blister rust (USDA Forest Service 2009c) (Table 13), 

which can reduce tree resistance to beetle attacks (Parker 

and others 2006). Comandra blister rust (Cronartium 

comandrae Pk.) and the parasitic plant dwarf mistletoe 

(Arceuthobium sp.) are widespread on the southern part of 

the Forest. Comandra blister rust and dwarf mistletoe serve 

as suppression agents that leave the hosts more vulnerable to 

stressors, such as drought and insect attacks (USDA Forest 

Service 2009a, 2009c). Blister rust and mountain pine beetle 

have been observed to attack whitebark pine simultaneously, 

creating different spatial patterns of tree mortality (Hatala 

and others 2009). Spatially clustered patches of mortality 

with infilling dominated in blister rust-infected areas at two 

sites just north of the Shoshone, while more spatially contiguous mountain pine beetle mortality patterns dominated a 

site near the northwestern border of YNP (Hatala and others 

2009).

The interactions between beetles and fire are well documented in the literature (McCullough and others 1998; 

Logan and Powell 2001; Kulakowski and others 2003; Lynch 

and others 2006); however, these interactions are not well 

Table 13. Summary of insect and pathogen Conditions for the 20th Century, projections for the 21st Century, 

and potential consequences to ecosystem services.

Current trend or 

condition over the 

20th Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 

4 °F (1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Insects and 

pathogens

• Bark beetle 

outbreaks in 

lodgepole pine, 

ponderosa pine,

five-needle pine, 

Douglas-fir, and 

spruce forests since 

1996 causing 

moderate to high 

tree mortality on 

~1,086,000 acres 

(439,438 ha) of the 

Shoshone’s 1.4 

million forested 

acres (566,599 ha) 

by 2010

• Over 100,000 acres 

(40,468 ha) affected 

by both white pine 

blister rust and pine 

beetle

• The number of acres 

affected by bark 

beetles and blister 

rust has been 

increasing since 

2000.

• Moderate probability of 

increased number of bark 

beetle outbreaks on 

Shoshone and GYE, shifting 

to higher elevation and 

northward

• High temporal and spatial 

variability of bark beetle 

outbreaks

• Little is known about future 

pathogen dynamics under 

climate change

• Reduced aesthetic and 

timber value

• Potential increase in the 

variability and possibility 

of forested areas at 

higher elevations on the 

Shoshone turning into 

carbon sources after 

beetle outbreaks
USDA Forest Service RMRS-GTR-264. 2012. 37

understood (Bentz 2005). Retrospective studies have shown 

both increases and decreases of fire intensity, extent, and severity in post-beetle outbreak areas of the Rocky Mountains. 

The longer-term influence of mountain pine beetle outbreaks 

has been found to slightly increase the severity and probability of fire occurrence and to increase fuel loads in the Rocky 

Mountains of northern Colorado and YNP (Turner and others 1999; Bigler and others 2005; Lynch and others 2006). 

However, stand structure was found to be a better predictor of fire severity (Bigler and others 2005). Simard (2010) 

found that for GYE lodgepole pine forests, the probability 

of active crown fire was decreased for 35 years after beetle 

outbreak, but the probability of passive crown fire increased 

when understory growth provided vertical continuity between the forest floor and tree crowns. A decrease in, or no 

impact to, fire occurrence, extent, and severity has been observed in subalpine areas of mountain pine beetle and spruce 

beetle outbreak areas in Colorado and the GYE (Bebi and 

others 2003; Kulakowski and others 2003; Kulakowski and 

Veblen 2007; Simard and others 2008). Surface fire intensity 

was predicted to increase for Douglas-fir, spruce, and pine 

stands with beetle outbreaks 0 to 5 years after an outbreak, 

but crown fire intensity was predicted to decrease 5 to 60 

years after a beetle outbreak (Jenkins and others 2008). Fuel 

characteristics are altered over the course of the bark beetle 

epidemic, potentially resulting in increased or decreased fire 

intensity and severity (Jenkins and others 2008). Beetle outbreak occurrence may also be dependent on the availability 

of suitable hosts. Paleoecologic evidence shows that mountain pine beetle outbreaks occurred 8000 BP during a cooler 

and wetter period with low fire occurrence, when there was 

a prevalence of susceptible whitebark pine hosts in Idaho 

and Montana (Brunelle and others 2008) that likely were not 

exposed to blister rust.

Increased bark beetle outbreaks may also alter the C cycle 

in ecosystems. Kurz and others (2008) found the cumulative effects of large-scale, unprecedented beetle outbreaks 

to convert lodgepole pine forests to large net C sources, as 

opposed to the net sinks that occurred in British Columbia, 

Canada3. This could effectively negate any potential C sink 

enhancement effects; such has longer growing seasons, 

expanded range, and CO2 and nitrogen (N) fertilization 

(Hansen and others 2001; Kurz and others 2008; Smithwick 

and others 2009).

Climate Change Effects on Insects and Pathogens

Climate change may be altering the dynamics between 

bark beetles and forests. Increased temperatures may be 

one factor that results in higher rates of insect outbreaks 

when suitable hosts are available (Logan and Powell 2001; 

Romme and others 2006). Under a warmer climate, many 

forest insects will experience greater survival, reproduction, 

and development rates (Bentz 2005; Hicke and others 2006). 

Range expansions are possible as more habitat becomes 

suitable for host establishment (Bale and others 2002; Ryan 

and others 2008). Likewise, increased drought stress and 

warmer temperatures may cause some plant species to exhibit a decline in their capacity to resist insect attack (Ayres 

and Lombardero 2000). Bentz and others’ (2010) modeling 

study projected a large increase in the probability of spruce 

beetle outbreaks and a moderate increase in the probability 

of mountain pine beetle outbreaks over the next century on 

the Shoshone and GYE. Future beetle outbreaks may shift 

northward and upward in elevation, be highly variable spatially and temporally, and result in forest ecosystem regime 

shifts beyond historical bounds (Bentz and others 2010). 

These outbreaks also leave behind dead and decaying trees 

that have decreased wood product value (Lowell and others 

2010).

Bark beetles will likely follow the range of hosts as they 

track changes in climate, abandoning areas where the climate becomes too warm (Bentz 2005). Concurrently, bark 

beetles are capable of responding to climate changes faster 

than tree species (Bentz 2005). Evidence of this expansion 

has already occurred in British Columbia, Canada, where 

an increased area of mature pine stands in recent decades 

has resulted in unprecedented outbreaks of mountain pine 

beetle (Kurz and others 2008). Thus, elevated temperatures 

at higher altitudes could allow for mountain pine beetles to 

attack five-needle pines—suitable hosts that, to date, have 

been buffered from attack by harsh climate (Logan and 

Powell 2001). Carroll and others (2006) found an increase 

in mountain pine beetle presence in formerly unsuitable 

habitat in Canada that “can only be explained by changes in 

climate.” Overall, the potential consequences to ecosystem 

services include reduced aesthetic and commercial timber 

value on the landscape and an increase in the variability and 

number of forested areas turning into C sources after beetle 

outbreaks at higher elevations on the Shoshone (Table 13).

Wildlife

Current Conditions

The Shoshone supports a variety of mammal, bird, amphibian, and invertebrates, of which 25 species of are special 

management interest and concern (USDA Forest Service 

2009c). Some species have limited ranges, and other species such as bighorn sheep (Ovis canadensis), elk (Cervus 

elaphus), mule deer (Odocoileus hemionus), bald eagle 

(Haliaeetus leucocephalus), coyotes (Canis latrans), and 

gray wolves (Canis lupus) can move long distances between 

summer and winter ranges. The large extent of roadless and 

wilderness areas on the Shoshone provides crucial connected habitat for these wide ranging species. Riparian areas are 

also an important a source of water, forage, prey, and cover. 

Endangered species such as Canada lynx (Lynx canadensis) are rare in the GYE, and black footed ferrets (Mustela 

3

 The cumulative impact of beetle outbreaks is the combined 

effect of beetle kill, fire, and harvesting on productivity. Carbon balance and forest productivity were modeled from 2000 

to 2020 using the Carbon Budget Model of the Canadian Forest 

Sector (CMB-CFS3). Climate was not explicitly modeled.
38 USDA Forest Service RMRS-GTR-264. 2012.

nigripes) are not known to occur on the Shoshone but 

have been reintroduced in southern Wyoming. Populations 

of moose (Alces alces) have recently declined, which is 

thought to be due to drought (USDA Forest Service 2011a). 

Amphibian populations may also be declining in the GYE 

(Corn 2007; McMenamin and others 2008). Brucellosis infections of elk have been increasing (Xie 2008), although 

the infection’s effect on elk populations is statistically undetectable (Cross and others 2010). Shoshone large-scale 

population trends for gray wolf, grizzly bear, bald eagle, 

elk, and big horn sheep have been stable or increasing over 

the last decade, but population trends vary at the local scale 

(Wyoming Game and Fish 2008; USDA Forest Service 

2009c; Jimenez and others 2010) (Table 14).

Climate Change Effects on Wildlife

Globally, climate change effects on wildlife have already 

been noted to cause shifts in species populations, distribution, and phenology (Root and Schneider 2002; Parmesan 

2006, 2007). Throughout the western hemisphere, climate 

change is expected to effect the largest shifts in faunal change 

in the coming century, with the greatest effects occurring at 

high elevations and high latitudes (Lawler and others 2009). 

Generally, species that are range restricted (for example, 

those that are on mountaintops or are endemics), are located 

at the margins of climate tolerance, have slow reproduction 

rates, or have narrow environmental tolerances (for example, 

amphibians, lynx, and wolverines [Gulo gulo]) are projected 

to be the most sensitive to climate change and experience 

the largest range contractions, population reductions, and 

extinctions (Parmesan 2006; Ohlemuller and others 2008). 

Species that have larger habitat ranges (for example, elk and 

deer), tolerate a wider range of environment and diet (for 

example, coyote), and reproduce more quickly (for example, 

insects or birds) are expected to be less affected by climate 

change. For example, bird species have been expanding their 

range in Wyoming (Joyce and others 2008b). Also, the presence of certain species may function to buffer the effects 

of climate change. Modeling results for Wilmers and Getz 

(2005) and Wilmers and Post (2006) projected a warmer 

climate to reduce late winter carrion for scavenger species, 

such as grizzly bear, but these reductions were buffered by 

the presence of gray wolf within YNP increasing the availability of carrion.

Vegetation distribution changes or reductions of food 

sources may ultimately determine the future dynamics of 

Table 14. Summary of wildlife conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 20th

Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 4 °F 

(1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Wildlife • Big game, eagle, and 

wolf populations are 

stable or increasing 

but are spatially 

variable on the 

Shoshone.

• Amphibian 

populations may be 

declining in YNP.

• Increased spatial variability, 

phenology changes, and 

population changes of wildlife 

associated with changes in 

food source locations and 

vegetation distribution

• Higher adaptability potential 

by species with large habitat 

ranges, wider diet and 

environment tolerance, and 

higher reproductive rates (for 

example, birds, coyote, and 

grizzly bear)

• Lower adaptability potential 

by species that are located at 

the margins of climate 

tolerance, have slow 

reproduction rates, or have 

narrow environmental 

tolerances (for example, 

amphibians, lynx, and 

wolverines)

• Potential high-elevation 

refugia for species 

seeking cooler habitats

• Potential reduction of 

suitable habitat and 

species that are unable 

to adapt
USDA Forest Service RMRS-GTR-264. 2012. 39

wildlife populations. Although climate change effects on 

wildlife biodiversity have not been specifically studied on 

the Shoshone, GYE studies may apply. High-elevation habitat of the GYE is predicted to fragment and shrink (Romme 

and Turner 1991; Schrag and others 2008), and may contribute to the relocation or reduction of many mammals (for 

example, grizzly bear, mountain goat, pika, and lynx). For 

example, grizzly bear habitat in the subalpine may be linked 

to whitebark pine (Koteen 2002). Whitebark pine seeds are 

larger and more nutritious than other conifer seeds, offering 

grizzly bears an important food resource at higher elevations 

(7500 to 9000 ft or 2288 to 2745 m) (Koteen 2002). In subalpine forests of the GYE, whitebark pine is considered a 

keystone species that has been declining due to white pine 

blister rust, mountain pine beetle outbreaks, and fire suppression (Koteen 2002; Schrag and others 2008). Continued 

decline of whitebark pine could cause grizzly bears to shift 

to lower elevations where other food sources exist, potentially moving the bears closer to humans and outside of 

Federal protected areas (Mattson and others 1992; Schwartz 

and others 2010). Grizzly bears have been observed to move 

to lower elevations during years when whitebark pine seed 

crops are poor (Mattson and others 1992). Additionally, grizzly bear populations have been relatively stable within YNP 

but are expanding outside of the park (Schwartz and others 

2006). Elk migrations have been found to be related to the 

severity and duration of the previous winter, and elk populations have also been expanding north outside of YNP (White 

and others 2010). The elk expansion could influence wolf 

populations to expand concurrently (White and others 2010).

Potential consequences to ecosystem services are that 

the Shoshone may serve as high-elevation refugia for species seeking cooler habitats, while some habitats and species 

may be reduced and/or redistributed, especially at lower elevations (Table 14).

Fish

Current Conditions

The Shoshone has approximately 3850 miles (6200 km) 

of perennial streams, of which about 1492 miles (2401 km) 

are occupied by Yellowstone cutthroat trout, and 395 miles 

(636 km) are occupied by non-hybridized Yellowstone cutthroat trout (Figure 20) (Table 15). Stream slope has been 

found to be a strong predictor (model accuracy of 83 percent) of the presence of Yellowstone cutthroat trout in the 

Absaroka Mountains on the Shoshone (Kruse and others 

1999). The trout generally do not occur on slopes steeper 

than 10 percent, and populations linearly increase as slope 

decreases (Kruse and others 1999).Yellowstone cutthroat 

trout are native to the GYE and have been partially displaced 

or hybridized with the introduction of non-native trout species (DeRito and others 2010). Hybridization of Yellowstone 

cutthroat trout has been found to occur in the Yellowstone 

River due to the spatial and temporal overlap of spawning periods for Yellowstone cutthroat trout (beginning during June 

and July) and rainbow trout and hybrids (beginning during 

April and May) (DeRito and others 2010). The separation of 

the majority of spawning periods has helped preserve some 

of the native Yellowstone cutthroat trout populations; however, competition from other non-native species, especially 

at young stages, has been shown in models to eventually displace and threaten the extinction of Yellowstone cutthroat 

trout (Van Kirk and others 2009).

Climate Change Effects on Fish

Flows are a primary control for fish that are highly sensitive to climate change (Rieman and Isaac 2010) as salmonid 

habitat availability can be limited by stream flow. Low flows 

can reduce habitat, forcing a migration to more suitable habitat (Gregory and others (2009). Gregory and others (2009) 

found that Yellowstone cutthroat trout move as much as 

25 miles (40 km) up or downstream prior to spawning in the 

East Fork Wind River. Future Wind River stream flows have 

been projected to be reduced overall, with further decreases in late summer and increases during peak spring runoff 

(Stonefeldt and others 2000). Peak flows have been projected 

to occur four to five weeks earlier under climate change in the 

western United States (Stewart and others 2004). Stream flow 

may become more dominated by rain instead of snow melt, 

Figure 20. Distribution of non-hybridized Yellowstone 

cutthroat trout and other fish present (other fish can 

include hybridized Yellowstone cutthroat trout).
40 USDA Forest Service RMRS-GTR-264. 2012.

especially at lower elevation, with earlier peak flows and lower summer flows (San Francisco basin, Knowles and Cayan 

2004; Washington, Elsner and others 2010). Lower summer 

flows may limit salmonid habitat availability, and peak flows 

or flooding can hinder spawning activity (Gregory and others 

2009).

In addition to stream flow, stream temperature is another 

control that can limit salmonid habitat. Stream temperatures 

have been found to have a strong relationship with air temperatures (Webb and Noblis 2007; Kaushal and others 2010). 

Keleher and Rahel (1996) found the distribution of Rocky 

Mountain salmonids to be limited by temperature—salmonids 

were restricted to areas where average July air temperatures 

do not exceed 72 °F (22 °C).

Cold-adapted fish species ranges are projected to generally 

shift upward in elevation due to downstream temperature increases, and to become increasingly fragmented and disjointed 

from larger streams that naturally hold source populations 

(Keleher and Rahel 1996). Future air temperature increases 

for the high-elevation areas of the Shoshone are predicted to 

range from 6 to 18 °F (3.3 to 10 °C) by 2100. In the State of 

Wyoming, using an air temperature increase projection of 6 

°F (3.3 °C), salmonid habitat could be reduced ~38 percent 

(Keleher and Rahel 1996). An air temperature increase of 9 

°F (5 °C) could result in approximately a 68 percent reduction of the current area suitable for salmonids (Keleher and 

Rahel 1996). However, increased temperatures may improve 

habitat for native cutthroat trout at higher elevations, and 

isolated headwater streams may provide protection from nonnative invasive trout (Cook and others 2010). But the smaller 

tributaries and lower populations supported at these higher elevations have been projected to experience decreased genetic 

variability and probability of native trout survival (Cook and 

others 2010).

Stream temperature increases may also indirectly affect cutthroat trout populations by altering inter-species competition. 

Jenkins and Keeley’s (2010) bioenergetic modeling study in 

the Yellowstone River found that increasing temperatures can 

extend the growing season, benefiting larger fish if suitable 

habitat exists; but higher temperatures consistently had a negative effect on smaller sizes of fish with higher metabolisms. 

(Bioenergetic models estimate the net energy intake rates to 

estimate the profitability of stream habitat by calculating the 

energetic costs and benefits of foraging locations.)

Table 15. Summary of fish conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 

20th Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate 

trend

• Temperature increase 

of 2 to 4 °F (1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature increase 

range of 2 to 10 oF (1.1 to 

5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Fish • The Shoshone has 

~3850 miles (6196 km) 

of perennial streams

• Yellowstone cutthroat 

trout (including 

hybridized) and other 

fish species occupy 

~1492 stream miles 

(2401 km), largely in 

the central and 

northern Shoshone

• Non-hybridized 

Yellowstone cutthroat 

trout occupy about 

361 stream miles 

(581 km).

• Cold temperature may 

be limiting fish habitat.

• Reduced summer stream 

flow, increased spring runoff, 

and earlier peak runoffs may 

further limit salmonid habitat 

and could hinder spawning 

activity.

• Higher temperatures may 

hinder or reduce salmonid 

habitat, especially at lower 

elevations.

• Higher-elevation salmonid 

habitat may improve as 

stream temperatures 

increase; however, higher 

numbers of smaller tributaries 

and more fragmented habitat 

at higher elevations.

• Warmer temperatures may 

shift the competitive 

advantage to non-native and 

larger trout.

• Potential shifts or 

reductions in suitable 

salmonid habitat and 

associated fish species

• Potential reduction or 

loss of recreational 

opportunities for fishing 

native cold water species 

with the reduction in 

habitat quality and area

• Potential decrease in 

recreational fishing 

opportunities

• Potential high-elevation 

refugia for fish seeking 

cooler habitats
USDA Forest Service RMRS-GTR-264. 2012. 41

Non-native brook trout have been shown to behaviorally dominate cutthroat trout and gather more food at higher 

temperatures, further tipping the competitive balance to nonnative trout (Hauer and others 1997). Thus, increased water 

temperature reduces salmonid habitat (especially at lower elevations), improves stream habitat for native trout at higher 

elevations where there is a higher number of smaller tributaries and more fragmented habitat, and can shift the competitive 

advantage to non-native and larger trout (Table 15).

Glacial loss, reduced stream flow (especially in late summer), and increased water temperatures have been found to 

negatively affect aquatic organisms in the Rocky Mountains 

(Hauer and others 1997). Fish populations in the streams of 

the Rocky Mountains are dominated by salmonids, whose 

habitat could be highly susceptible to climate warming 

(Hauer and others 1997). Potential consequences to ecosystem services include shifted or reduced salmonid habitat and 

associated species, and reduced recreational fishing opportunities for native cold water fish if salmonid habitat is reduced 

or degraded. Also, the Shoshone may serve as a high-elevation refugium for salmonid populations (Table 15).

Biochemical Cycling

Current Conditions

Here, we focus on C and N cycling, because the former 

helps to offset atmospheric CO2 from fossil fuel emissions 

(MEA 2005; Ryan and others 2008), and the latter can limit 

forest productivity and C sequestration potential (Fahey 

and others 1985; Luo and others 2004; Smithwick and others 2009). Several interacting factors can influence C and 

N-cycling in forests directly or indirectly. The factors that 

are likely to affect the Shoshone include: increased nitrogen 

oxide (NOx) emissions in surrounding areas; fire and insect 

disturbance that alter forest structure and soil properties; and 

changes in forest productivity from climate (for example, 

precipitation and temperature) or atmospheric CO2 increase 

and N deposition. Forests on the Shoshone currently sequesters roughly 22 to 33 million tons (20 to 30 million metric 

tons) of C and are thought to be N limited (Fahey and others 1985; Turner and others 2007; Romme and others 2009), 

although N deposition may be occurring from upwind agricultural and oil and gas development (USDA Forest Service 

2009c) (Table 16). Future activities could lead to more NOx

emissions (Story and others 2005). Glacial melt water has 

recently had increased N concentrations in high-elevation 

streams in the Colorado Front Range (Baron and others 

2009). The increase in N may not only be caused by increased atmospheric N deposition, but also may be the result 

of flushing microbially active, N enriched sediment from 

glacial melt water that may already be N enriched (Baron 

and others 2009).

Climate Change Effects on Biochemical Cycling

Climate change will likely have both direct (increased productivity) and indirect (shifted disturbance regimes) effects 

on biochemical cycling on the Shoshone. Several interacting factors under climate change can influence C cycling: 

(1) disturbance such as fire, insect outbreaks, windthrow, and 

ice storms, (2) increased productivity of forests due to higher 

temperatures and precipitation in areas where temperature or 

precipitation limits growth, (3) higher atmospheric CO2 and 

Table 16. Summary of biochemical cycling conditions for the 20th Century, projections for the 21st Century, and 

potential consequences to ecosystem services.

Current trend or 

condition over the 

20th Century

Anticipated ecological 

response over 21st Century

Potential consequences 

to ecosystem services

Climate trend • Temperature 

increase of 2 to 

4 °F (1 to 2 °C) 

(especially in 

winter and spring)

• Precipitation and 

snowpack decline

• Annual temperature 

increase range of 2 to 10 oF 

(1.1 to 5.5 oC) by 2100

• Annual precipitation 10% 

increase with wetter winters 

(+10%) and drier summers 

(-10%) (more uncertain)

Biochemical 

cycling

• C storage is 

roughly 22 to 

33 million tons 

(20 to 30 million 

metric tons) on the 

Shoshone.

• The Shoshone 

forests are N 

limited.

• Increased fire or insect 

disturbance could result in 

forests shifting C balance.

• N availability may be 

increased with warmer 

temperatures and increased 

decomposition rates, thereby 

increasing productivity, but 

future frequent fire activity 

(<95-year return) may cause 

N loss.

• Potential for less C 

sequestration with 

younger forests

• Potential shift to C source 

instead of C sink in areas 

of disturbance

• Potential increase in 

forest productivity from 

higher N. This may be 

offset by increased fire 

frequency.
42 USDA Forest Service RMRS-GTR-264. 2012.

increased N deposition, and (4) decreased forest productivity 

from drought or nutrient limitation. C storage generally decreases after a disturbance and then increases as trees grow 

larger (Kashian and others 2006). More frequent fires or insect outbreaks could result in younger stands that assimilate 

less C than intermediate and old-growth stands (Romme and 

Turner 1991; Kashian and others 2006). Increased forest productivity associated with elevated atmospheric CO2

 could 

directly result in increased C uptake from the atmosphere 

(Powell and Hansen 2007). Faster-than-present post-fire 

productivity responses to fire have been simulated in lodgepole pine forests at YNP (Smithwick and others 2009). Also, 

at higher elevations where trees grow near the temperature 

limit, increased temperature with sufficient precipitation 

may directly result in greater productivity (Ryan and others 2008). Forest productivity and C sequestration potential 

could increase from higher atmospheric CO2 concentrations 

in young, nutrient rich, non-water limited forests (FACE experiment by Norby and others 2005); however, the evidence 

is not consistent (Ryan and others 2008) as higher productivity may be limited by water or N availability (Luo 2004), 

and transient responses have been shown in older trees and 

different species (Korner and others 2005). Increased fire or 

insect outbreak activity has the capacity to offset any C gains 

from climate induced increases in temperature, precipitation, atmospheric CO2

 or N fertilization (Kashian and others 

2006; Kurz and others 2008). However, Kashian and others 

(2006) suggested that the fire return interval would have to 

decrease to 80 years before any noticeable shift in the total C 

balance of the GYE would occur.

The coniferous N limited forests on the Shoshone (Fahey 

and others 1985; Turner and others 2007; Romme and others 2009) could experience an increase in productivity if 

an increase in N availability occurs. Warmer temperatures 

and increased precipitation could accelerate decomposition 

rates and directly increase N turnover. Smithwick and others (2005) simulated N dynamics for lodgepole pine under 

future climate scenarios (using the Canadian Climate Center 

and Hadley GCMs) and found that net N mineralization did 

not increase, but available N did increase as a function of 

precipitation and increased rates of decomposition. Thus, 

under future climate, more N may be readily available for 

plant uptake due to increased rates of decomposition, which 

would increase productivity. However, climate change may 

influence N-cycling in the Shoshone by altering the fire regime (Romme and Turner 1991; Turner and others 2007; 

Romme and others 2009; Smithwick and others 2009). There 

is an increased potential for N losses via nitrate leaching 

with more frequent fires (Hansen 2007; Turner and others 

2007). Turner and others (2007) found that immobilization 

rates of ammonium increased after the Yellowstone fires, 

prohibiting nitrate buildup. However, a longer-term simulation study by Smithwick and others (2009) indicated that fire 

return intervals would have to decrease to about 95 years 

to affect long-term N storage in lodgepole pine ecosystems. 

Overall, a possible consequence to ecosystem services is decreased C sequestration potential, with areas of disturbance 

becoming C sources as opposed to C sinks. Also, forests 

on the Shoshone may become more productive if N is increased; however, increased disturbance may offset these 

productivity gains (Table 16).

Economies

Current Conditions

Recreation and tourism are major economic activities in 

the GYE and Shoshone (Power 1991; Rasker and Hansen 

2000; USDA Forest Service 2009c). The tourism and recreation economy in the three-county area of the Shoshone 

was more than $350 million in 2006 (Table 17). During 

2002 and 2003, the five top recreation activities on the 

Shoshone were: (1) viewing natural features (60 percent), 

(2) viewing wildlife (55 percent), (3) relaxing (48 percent), 

(4) hiking/walking (38 percent), and (5) driving for pleasure 

(33 percent), followed by picnicking (16 percent), fishing 

(14 percent), nature study (13 percent), visiting historical 

sites (10 percent), and hunting (10 percent) (Taylor and others 2008). (Individuals surveyed may have indicated more 

than one activity.)

Agriculture is also an important economic activity that 

grossed about $170 million in the three-county area in 2005 

(USDA Forest Service 2009c). Snowmelt is the major source 

of water for agriculture in the western United States (Baron 

and others 2000b), and it is also used for hydropower energy generation at the Buffalo Bill (40 to 110 GWt/year) and 

Shoshone dams (15 to 23 GWt/year) (USBR 2007a, 2007b) 

(Table 17).

Domestic livestock grazing is an important activity on the 

Shoshone that supported over 62,500 animal unit months in 

2007, resulting in $2.6 million of production, $5.4 million of 

total economic activity, $1.7 million in labor earnings, and 

52 jobs in the region’s economy (Taylor and others 2008) 

(Table 17).

Climate Change Effects on the Economies

Few specific studies have been focused on the economy 

of the area surrounding the Shoshone. We draw from economic studies in the United States and GYE and extend the 

potential ecological impacts to the economic sectors surrounding the Shoshone.

Nature based recreation and tourism are lucrative economic activities in Montana that are increasing and are expected 

to continue to increase as the population grows (Swanson 

2008). Climate change may directly (weather related) and 

indirectly (resource related) affect recreation (Richardson 

and Loomis 2004), with variable effects depending on the 

individual preference of the recreator and the magnitude of 

climate change. For example, if climate change caused less 

water to be available in reservoirs and streams, fewer recreational opportunities would exist though the demand would 

be increasing. On the other hand, increased flooding under 

climate change may pose new risks to recreators using riparian areas.
USDA Forest Service RMRS-GTR-264. 2012. 43

Potential consequences to ecosystem services are increased summer recreation and tourism activity and fewer 

winter recreation opportunities (Table 17). An analysis of 

climate change effects on visitation in Rocky Mountain 

National Park indicated the net effect would be slightly positive for tourism (Richardson and Loomis 2004). Richardson 

and Loomis’ (2004) survey respondents said their visitation 

behavior would change in response to hypothetical climate 

scenarios, a majority of which stated that driving Trail Ridge 

Road is a major attraction to the park. Recent warmer temperatures have allowed Trail Ridge Road to be open longer, 

thus the potential for increased tourism. Visitors to the 

Shoshone in 2003 cited viewing natural features, viewing 

wildlife, and driving for pleasure as their main recreational 

activities (Taylor and others 2008), which could portend 

similar results to those from the Rocky Mountain National 

Park study. Warmer temperatures, earlier springs, and longer 

summers are expected to increase the demand for outdoor 

recreation activities that could shift to higher latitudes and altitudes in North America (Morris and Walls 2009). However, 

climate change may have a negative impact on winter recreation activities such as alpine skiing (Joyce and others 

2001). Loomis and Crespi (1999) estimated that a 4.5 °F 

(2.5 °C) temperature increase and a 7 percent precipitation 

increase could reduce downhill and cross country skiing by 

52 percent in the United States. However, reductions in these 

winter recreation activities and associated economic losses 

were projected to be offset by an increase in reservoir, beach, 

golf, and stream recreational activities (Loomis and Crespi 

1999). Fishing and hunting activities, though not claiming 

the highest percentage of visits on the Shoshone (10 and 14 

percent, respectively; Taylor and others 2008) are increasing 

in neighboring Montana (Swanson 2008).

Climate change could reduce Shoshone water supplies 

for hydropower generation and agriculturalists and urban 

areas to the east (Table 17). Water sources could become 

unreliable during summer months if snowmelt shifted earlier in the season (Stonefelt and others 2000; Gray and 

McCabe 2010), potentially causing water shortages during critical summer months (Christensen and others 2004) 

and leaving less water available during summer months in 

the western United States (Adams and Peck 2009) . Model 

simulations at the U.S. farm level indicated decreased 

profits with more frequent drought conditions (Adams 

and Peck 2009). Adams and Peck’s (2009) simulation also 

projected that planters were better able to adapt to more 

frequent but less severe drought than they were to less frequent but more severe drought, both of which are projected 

to occur under climate change. Losses could be mitigated by not planting low value crops, not planting on low 

value land, or not planting crops that require water during critical late summer months (Adams and Peck 2009). 

Currently, drought is estimated to cost $6 to $8 billion annually in the United States due to crop failure, municipal 

Table 17. Summary of economic conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 

20th Century

Anticipated ecological 

response over 21st

Century

Potential consequences to 

ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 4°F 

(1 to 2 °C) 

(especially in winter 

and spring)

• Precipitation and 

snowpack decline

• Annual temperature 

increase range of 2 to 

10 oF (1.1 to 5.5 oC) by 

2100

• Annual precipitation 

+10% increase with 

wetter winters (+10%) 

and drier summers 

(-10%) (more uncertain)

Economies • $350 million in 

tourist activity

• $170 million in 

agricultural activity

• $5.4 million in 

livestock grazing 

total economic 

activity

• Hydropower 

generation (40 to 

100 GWt/year at 

Buffalo Bill Dam and 

15 to 23 GWt/year at 

Shoshone Dam)

• Longer tourist seasons

• Reduced and unreliable 

water resources for 

agriculture and 

hydropower 

• Potential increase in summer 

recreation and tourism 

opportunities but decreased 

winter recreation opportunities

• Potential decrease in 

agricultural production and 

hydropower generation with 

reduced water supply

• Potential short-term reduction of 

grazing area by conifer 

encroachment, followed by 

eventual increase in grazing 

area as future climate causes 

grasslands to expand
44 USDA Forest Service RMRS-GTR-264. 2012.

water shortages, wildfires, fish and wildlife mortality, and 

reduced hydropower generation. Mitigation planning is required to reduce the economic cost of drought (Adams and 

Peck 2009).

The expansion of forest into grass and shrublands that 

has been observed on the Shoshone (USDA Forest Service 

2009c) could continue to contract suitable habitat for grazing in the short term. Some studies have noted a decrease 

in forage for native ungulates under future climate change 

(Romme and Turner 1991), which in the short term, may 

also imply a reduction in domestic grazing opportunities 

that utilize similar habitat. However, many factors (for example, sufficient precipitation and increased tree water use 

efficiency from increased CO2) must coalesce to create this 

effect (Romme and Turner 1991). A potential consequence 

to ecosystem services may be the eventual expansion of 

grasslands and reduction of sagebrush (Schlaepfer and others 2011) and conifers (Bachelet and others 2003) that may 

eventually increase the area available for grazing (Table 

17).

Land Use

Current Conditions

The area surrounding the Shoshone includes lands managed by the private sector, Wind River Indian Reservation, 

other National Forests, the Bureau of Land Management, the 

State of Wyoming, National Park Service, and The Nature 

Conservancy (Figure 21). Among the fastest growing counties in the United States (Figure 22; United States Census 

2010) are those surrounding Yellowstone National Park, 

directly west of the Shoshone (Rasker and Hansen 2000) 

(Table 18). Expansion of urban areas, commercial development, and industrial development are increasing across the 

GYE as populations grow, and this trend is projected to continue (Gude and others 2006; Hansen 2006). Protected areas, 

such as designated wilderness in the Shoshone, do not function in isolation and are, in fact, parts of larger ecosystems 

that comprise unprotected segments vulnerable to land use 

change (Hansen and DeFries 2007). While the core land use 

of wilderness areas within the Shoshone (as protected areas) 

Figure 21. Wyoming land ownership.
USDA Forest Service RMRS-GTR-264. 2012. 45

may not change, the surrounding land uses in the GYE likely 

will change in the future (Gude and others 2006). Private 

lands comprise about 25 percent of the GYE area, mostly 

along the low lying riparian corridors, and are primarily used 

for agricultural production (Gosnell and others 2006). In the 

GYE, these lands are experiencing a transition in ownership 

from traditional ranchers to more amenity or investment 

owners that may manage their properties with more explicit 

conservation goals like enhancing and protecting wildlife 

habitat and aesthetic value (Gosnell and others 2006). In 

Montana, although there has been population growth and an 

increase in development of some rural lands, the loss of agricultural land on a regional scale has been minimal (Johnson 

2008). Rural home sites have mostly been in shrublands or 

forested areas at higher elevations, while agricultural lands 

are mostly in riparian bottomlands and are projected to remain in agricultural production even though there is a shift 

in the use of these lands to more amenity purposes (Johnson 

2008).

Land use change bordering protected areas can have 

multiple effects on ecosystem function (Hansen and others 

2002). It can effectively shrink the size of the ecosystem; 

alter biogeochemical flows; disrupt source-sink dynamics 

by fragmenting corridors and/or eliminating important habitats; and create negative edge effects (Hansen and DeFries 

2007). The growth rates of available housing within 31 miles 

(50 km) of wilderness areas in northwest Wyoming have increased over 200 percent since 1940, and in some cases, over 

400 percent (Radeloff and others 2010). When coupled with 

a changing climate, these land use effects can be compounded (Dale 1997).

Land use change directly influences climate (for example, 

changes in albedo [a measure of how much a surface reflects 

sunlight, which determines its visual brightness and affects 

the temperature] and C-cycling) and can also intensify climate change related effects on the ecosystem (Dale 1997). 

Several studies show increased human presence and influence bordering the GYE (Rasker and Hansen 2000; Hansen 

and others 2002; Parmenter and others 2003; Story and others 2005; Gude and others 2006, 2007; Hansen and DeFries 

2007). The type, location, and rate of land use change will 

likely interact with climate change in differing ways, as will 

policy decisions made by future stakeholders.

Exurban development is not the only new and increasing 

human pressure on the Shoshone. Oil and gas development 

in the Green River Basin, directly upwind of the Wind River 

Range, is also rapidly expanding (Story and others 2005). 

As noted by Story and others (2005), increased emissions 

are inextricably linked to energy development, and of greatest concern are NOx

 emissions. In fact, NOx emissions near 

Pinedale, Wyoming, have already reached levels six to eight 

times greater than originally proposed by energy projects 

(Story and others 2005) (Table 18). The Shoshone is currently experiencing increases in nitrate storage at the inlets of 

lakes, most likely from the upwind agricultural and oil and 

gas development (USDA Forest Service 2009c) (Table 18).

Figure 22. Wyoming population change 

by county, 2000-2010. Source: U.S. 

Census 2010.
46 USDA Forest Service RMRS-GTR-264. 2012.

Climate Change Effects on Land Use

Gude and others (2007) estimated exurban growth in the 

GYE by 2020 to be at least 28 percent under a low growth 

scenario and as high as 234 percent under a “boom” scenario. Most of the private lands available for this growth in 

the GYE are low-elevation, fertile valleys, which are important habitats for large animals during parts of the year 

and are considered “hot spots for avian biodiversity” (Gude 

and others 2007). Pressure on public lands and wilderness 

area on the Shoshone and GYE is currently moderate but 

is projected to increase to moderately heavy by 2020 due 

to non-agricultural economic development (Cordell and 

Overdevest 2001). Grizzly bear mortality has recently decreased in areas with secure habitat (such as Federal lands) 

and higher elevation, but it has increased when the density of roads, homes, developed sites, and ungulate hunting 

have increased in the GYE (Schwartz and others 2010). 

The potential consequences to ecosystem services include 

increased fragmentation and habitat degradation with more 

demand for recreational opportunities in the GYE if population growth continues (Table 18).

Along with low-elevation settlements, more development 

is occurring at the wild land interface directly bordering 

Federal lands in the GYE (Gude and others 2006; Radeloff 

and others 2010). Gude and others (2006) suggested that 

wildlife management and fire policies will certainly be influenced by these new stake-holders. Although it is likely 

that a greater human presence will result in greater fire suppression efforts, warmer climate has been historically linked 

to fire increase, even with fire suppression (Flannigan and 

others 2000), and more fire activity is predicted in the future 

in the western United States (Whitlock and others 2003; 

Westerling and others 2006). The future net effect of land 

use and climate on fire frequency, severity, and magnitude 

on the Shoshone is uncertain and depends on future policy 

as well as climatic conditions. Nonetheless, the uncertain 

future of the Shoshone fire regime may alter almost every 

aspect of ecosystem functioning (such as C and N cycling, 

mountain pine beetle influence, and hydrology) and highlights the important role that land use change will play.

In the past, atmospheric N deposition on the Shoshone 

has been negligible but has recently been increasing from 

upwind agricultural and oil and gas development (Turner 

and others 2007; USDA Forest Service 2009c). N deposition 

may continue to increase with warmer temperatures, potential increases in winter precipitation due to climate change, 

and increased NOx emissions due to land use change. Since 

the Shoshone is generally a N limited system, the projected 

increase could have dramatic effects on biogeochemical 

cycling. Smithwick and others’ (2009) simulations of a 

lodgepole pine forest in the YNP included increased atmospheric N deposition, which was shown to bolster the direct 

effects of a warmer climate on forest productivity, and which 

could possibly enhance any potential C sink effect (Vitousek 

and others 1997). However, increased N deposition in 

aquatic systems leads to acidification and, if sufficient phosphorous exists, eutrophication4

 (Vitousek and others 1997; 

Table 18. Summary of land use conditions for the 20th Century, projections for the 21st Century, and potential 

consequences to ecosystem services.

Current trend or 

condition over the 

20th Century

Anticipated ecological 

response over 21st

Century

Potential consequences to 

ecosystem services

Climate 

trend

• Temperature 

increase of 2 to 

4°F (1 to 2 °C) 

(especially in 

winter and spring)

• Precipitation and 

snowpack decline

• Annual temperature 

increase range of 2 to 

10 oF (1.1 to 5.5 oC) by 

2100

• Annual precipitation 

+10% increase with 

wetter winters (+10%) 

and drier summers 

(-10%) (more uncertain)

Land use • Population increase, 

especially west of 

the Shoshone

• Increased NOx

emissions

• Increased urbanization 

bordering Federal lands 

in the GYE

• Potential increase of 

NOx emissions

• Increased landscape 

fragmentation and potential 

wildlife habitat degradation in 

the GYE

• Increased demand for 

recreation, hunting, and fishing 

opportunities with fewer 

opportunities

• N deposition increases potential 

for aquatic system acidification

4

 Eutrophication is a process that occurs in a body of water 

where dissolved oxygen is depleated by the stimulation of 

aquatic plant life from an enrichment of dissolved nutrients 

(phosphates).
USDA Forest Service RMRS-GTR-264. 2012. 47

Baron and others 2000b). Thus, the pristine alpine lakes of 

the Shoshone, and the fish populations they sustain, could be 

more vulnerable to eutrophication (Table 18).

Landscape fragmentation poses a great threat to biodiversity in the GYE and the Shoshone (Gude and others 2007; 

Radeloff and others 2010). As previously discussed, human 

development will directly displace some important habitat. 

Just as important are the isolation of remaining habitat and 

the disruption of species’ movement. Land use change will 

inevitably produce barriers to traditional seasonal migrations of large animals (Gude and others 2007) and to new 

migrations as species track shifts in climate (Hansen and 

others 2001).

Migration corridors will become even more important 

as the landscape becomes fragmented and habitats become increasingly isolated. Gude and others (2007) found 

simulations of future exurban growth (by 2020) occurred 

disproportionately on potential mammal migration corridors. 

On a large scale, the genetic diversity of grizzly bears in the 

GYE is the lowest in continental North America (Miller and 

Waits 2003), owing mostly to the relative isolation of the 

population. Although grizzly bears have been increasing in 

numbers and expanding their range, natural immigration between the GYE and the Northern Continental Divide System 

(NCDS) in northwest Montana has not been found to occur (Haroldson and others 2010). As a result, the reduced 

gene flow among these isolated populations is a concern for 

the long-term genetic health of the grizzly bear (Haroldson 

and others 2010). Increased human development in linkage 

zones between the GYE and NCDS may decrease the likelihood of natural immigration of the grizzly bear (Haroldson 

and others 2010).
48 USDA Forest Service RMRS-GTR-264. 2012.

Knowledge and Data Gaps

In this synthesis, we have drawn on general literature 

when no information was available specific to the Shoshone. 

Many studies synthesized here focused on larger areas, such 

as the western United States or GYE, and study sites outside of the Shoshone, especially at YNP (for example, paleo 

and fire studies). Therefore, local conditions, elevation and 

topographic effects, and variability and extremes of climate 

effects may not be specifically representative of processes 

acting in Shoshone ecosystems.

There is a paucity of climatic, ecologic, and hydrologic 

data, as well as fine-scale modeling projections that capture 

topographic and elevation gradients that affect Shoshone climate and ecosystem processes, especially at high elevations. 

This lack of information produces knowledge gaps about 

the spatial and temporal variability of climate and affected 

ecosystem processes, disturbance regimes, hydrology, and 

human impacts.

Climate and vegetation information is sparse, especially 

at higher elevations. No long-term climate stations with records greater than 50 years exist above 7866 ft (2400 m) 

elevation in the GYE, and no climate stations with records 

longer than 30 years exist above 8160 ft (2490 m) within 

in the Shoshone. Two longer-term climate stations (early 

1900s), and nine climate stations with shorter or incomplete 

records are on or near the Shoshone. Additionally, COOP, 

SNOTEL, and RAWS sites on or near the Shoshone have 

a limited distribution, which may or may not contribute to 

uncertainty in PRISM climate estimates (Figures 4, 5, and 

6) at high elevations. Additionally, information is limited on 

current Shoshone vegetation, especially endemics and plant 

communities at high elevation and tree lines. Vegetation 

modeling for the Shoshone has been done at a 0.6-mile 

(1-km) scale, which may or may not capture topographic 

variability effects. Few studies of climate change effects on 

vegetation or other ecosystem functions in the GYE or the 

Shoshone have used the most recent GCM climate change 

projections from the Fourth Assessment of the IPCC (IPCC 

2007b).

Specific hydrologic data and future model projects for the 

Shoshone are limited. Currently, there are no active gages 

continuously measuring stream flow on the Shoshone, and 

the historic gage records on or near the Shoshone (upstream 

of diversions) have temporal and spatial gaps. The specific 

magnitudes of projected variability of water quantity, timing 

of runoff, and evapotranspiration are not specifically known 

for the Shoshone. The effect of insect outbreaks on Shoshone 

hydrology has not been examined. Additionally, no specific 

published information has been found about climate effect 

on groundwater or water quality in the Shoshone.

Disturbance of existing ecosystems, such as insect outbreaks, fire, invasives, and their interactions with climate 

change have not been well studied on the Shoshone. Fire 

studies are more focused on YNP and the historic fire regimes on the east side of the GYE where the Shoshone 

lies are not well defined. Information is lacking about how 

human impacts, such as recreational use and management 

activities, on Shoshone ecosystems may affect and interact 

with climate change.

Although knowledge gaps exist and new information may 

be available in the future, we found that several resources 

and processes on the Shoshone may be vulnerable to climate 

change. The previously described gaps lead to uncertainties about how complex environmental factors interact (for 

example, topography-precipitation, or higher temperaturesmore drought-more fire-more invasive species). While it 

is challenging to precisely project ecosystem responses to 

climate change at the local level on the Shoshone, the published records of observed trends along with well-supported 

hypotheses and model projections provide indications of 

Shoshone ecosystem vulnerabilities and responses to climate change.
USDA Forest Service RMRS-GTR-264. 2012. 49

Conclusion and Summary

The Shoshone has undergone and adapted to large changes in climate that have spanned thousands of years. Twentieth 

Century warming of 1.8 to 3.6 °F (1 to 2 °C) is expected to 

continue and accelerate in the next century. The expected 

changes in climate leave many questions as to how these 

ecosystems will adapt. Shoshone ecosystems are dynamic 

and unique components of the GYE whose higher elevations, cooler temperatures, and drier precipitation regime 

causes ecosystems to function differently than surrounding 

areas, such as YNP. Micro-climate conditions in the high 

elevations of the Shoshone have, and will likely continue 

to provide refugia for unique and sometimes rare ecologic 

components. These high elevations and environmental variability will likely offer opportunities for climate adaptation 

for some resources or species, while others may be vulnerable to undesirable effects from climate change.

In this synthesis, we identified several vulnerable and 

very responsive resources and processes on the Shoshone. 

Water resources are particularly vulnerable as warmer 

temperatures are projected to reduce snowpacks, increase 

evaporation, lengthen summer seasons, and start spring runoff earlier. Warmer temperatures are likely to lead to reduced 

stream flows, which are critical to habitat and reservoir storage for agricultural and human uses. However, the potential 

effects of warmer temperatures may be mitigated or exacerbated by future changes in precipitation, which are more 

uncertain. Annual precipitation has recently increased at the 

scale of the GYE but has decreased at finer scales around 

the Shoshone. Winter precipitation is projected to increase 

10 percent in the GYE and may help offset evaporative 

losses from higher temperatures and longer summers, but 

projected temperatures may negate any gains in precipitation. Summer precipitation trends remain uncertain, and 

future reductions (as projected for the Pacific Northwest) 

would intensify water shortages at a critical time. Shoshone 

glaciers are highly vulnerable to climate change, and are projected to disappear early to mid-century, reducing summer 

flow to glacial fed streams, increasing sediment and stream 

temperatures. Shoshone landscapes may be more vulnerable to increased fire occurrence, magnitude, and severity 

as warmer temperatures cause drier conditions and longer 

fire seasons. Shoshone habitats and wildlife that are particularly vulnerable to climate change are alpine ecosystems, 

wetlands, and species that are stressed, with lower adaptive 

ability to higher temperatures, or existing at the edge of an 

environmental tolerance (for example, cold water salmonid 

Yellowstone cutthroat trout, lynx, pika, aspen, and whitebark pine). The genetic adaptive capacity of these and other 

species on the Shoshone remains an area of limited information. Grass and sagebrush on the Shoshone may continue to 

be vulnerable to conifer encroachment in the short term until 

increased temperatures and moisture limitations inhibit conifer establishment, especially at lower elevations. Hosts of 

insect infestations are likely to remain vulnerable to future 

outbreaks under warmer temperatures. Shoshone terrestrial 

and aquatic habitats are expected to remain vulnerable to 

the spread of some invasive species. Local economic sectors such as agriculture may be vulnerable to the effects of 

reduced water supply. Warmer temperatures and longer summers could increase summer tourism but could hinder winter 

tourism activities. Human activities will likely have a large 

influence on how Shoshone ecosystems respond in the future, especially regarding fire (fire suppression), N cycling 

(increase from oil and gas development), and land use (increasing fragmentation).

The interaction of Shoshone ecosystem processes with 

future climate change could produce unforeseeable or undesirable ecosystem changes, highlighting the need to identify 

potential resource vulnerabilities, and use this information to 

help develop adaptation strategies.
50 USDA Forest Service RMRS-GTR-264. 2012.

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Table 1. Historic Climate Network Stations used in this report (from http://cdiac.ornl.gov/epubs/ndp/ushcn/ushcn.html).

Station name ID number Elevation Period of record Latitude Longitude

Ashton, Idaho 100470 5364 1895-Present 44.0425 -111.2739

Bern, Idaho 100803 5961 1895-Present 42.3353 -111.3850

Grace, Idaho 103732 5548 1895-Present 42.5900 -111.7497

Lifton Pumping Station, Idaho 105275 5925 1895-Present 42.1231 111.3139 

Bozeman, Montana 241044 4911 1895-Present 45.6622 111.0453 

Ennis, Montana 242793 4951 1895-Present 45.3394 111.7111 

Hebgen Dam, Montana 244038 6485 1895-Present 44.8667 111.3392 

Livingston 12 S, Montana 245080 4869 1895-Present 45.4836 110.5689 

Norris Madison P H, Montana 246157 4745 1895-Present 45.4856 111.6325 

Red Lodge 2 N, Montana 246918 5498 1895-Present 45.2131 109.2375 

Virginia City, Montana 248597 5770 1895-Present 45.2925 111.9481 

West Yellowstone, Montana 248857 6656 1895-Present 44.6500 111.1000 

Alta 1 NNW, Wyoming 480140 6426 1895-Present 43.7728 111.0339 

Cody, Wyoming 481840 5088 1895-Present 44.5219 109.0633 

Dubois, Wyoming 482715 6957 1895-Present 43.5397 109.6553 

Lake Yellowstone, Wyoming 485345 7865 1895-Present 44.5619 110.3986 

Moran 5 WNW, Wyoming 486440 6797 1895-Present 43.8567 110.5889 

Pinedale, Wyoming 487260 7174 1895-Present 42.8797 109.8642 

Yellowstone Mammoth, Wyoming 489905 6226 1895-Present 44.9772 110.6953 

Appendix Tables.

Table 2. Wyoming climate stations from the Coop Network used in this report (from http://www.wrcc.dri.edu/coopmap/).

Station name ID number Elevation (ft) Period of record Latitude Longitude Climate Division

Crandall Creek 482135 6509 8/1/1948 - present 44.87 -109.64 1

Yellowstone NP 

East Entrance

489902 6952 11/1/1999 - present 44.49 -110.00 4

Buffalo Bill Dam 481175 5160 1/ 1/1905 - present 44.30 -109.11 4

Darwin Ranch 482375 8160 8/1/1974 - present 43.42 -110.15 2

Dubois 472715 6955 8/1/1948 - present 43.53 -110.6 9

South Pass 488385 7840 8/1/1948 - present 42.47 -108.80 9
60 USDA Forest Service RMRS-GTR-264. 2012.

Table 3. Wyoming SNOTEL Stations used in this report (from http://www.wcc.nrcs.usda.gov/snotel/Wyoming/wyoming.html).

Station name Station ID Elevation Period of record Latitude Longitude Basin

Beartooth Lake 326 9360 10/1/1979 - present 44.94 -109.57 Clarks Fork Yellowstone

Blackwater 350 9780 10/1/1979 - present 44.38 -109.79 North Fork Shoshone

Burroughs Creek 379 8750 10/1/1978 - present 43.7 -109.67 Upper Wind

Cold Springs 405 9630 10/1/1988 - present 43.28 -109.45 Upper Wind

Deer Park 923 9700 8/14/1997 - present 42.59 -108.9 Popo Agie

Evening Star 472 9200 10/1/1979 - present 44.65 -109.78 Clarks Fork Yellowstone

Gunsight Pass 944 9820 9/3/1998 - present 43.38 -109.88 Gros Ventre

Hobbs Park 525 10100 10/1/1978 - present 42.87 -109.09 Little Wind

Kirwin 560 9550 10/1/1979 - present 43.86 -109.32 Greybull

Little Warm 585 9370 10/1/1978 - present 43.5 -109.75 Upper Wind

Marquette 616 8760 10/1/1979 - present 44.3 -109.24 North Fork Shoshone

Owl Creek 676 8975 10/1/1979 - present 43.66 -109.01 Upper Bighorn

Parker Peak 683 9400 10/1/1979 - present 44.73 -109.91 Yellowstone Headwaters

South Pass 775 9040 10/1/1984 - present 42.57 -108.84 Popo Agie

St. Lawrence Alt 786 8620 10/1/1983 - present 43.03 -109.17 Little Wind

Sylvan Road 807 7120 10/1/1986 - present 44.48 -110.04 North Fork Shoshone

Timber Creek 819 7950 10/1/1986 - present 44.03 -109.18 Greybull

Townsend Creek 826 8700 10/1/1979 - present 42.7 -108.9 Popo Agie

Wolverine 875 7650 10/1/1979 - present 44.8 -109.66 Clarks Fork Yellowstone

Younts Peak 878 8350 10/1/1979 - present 43.93 -109.82 South Fork Shoshone

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