TOPIC 1 Conservation Issues Facing the Sagebrush Steppe and Greater Sage-Grouse: SCIENCE

The Sagebrush Ecosystem

In 2010, concern over the loss of sagebrush habitats and the potential for listing the Greater Sage-Grouse under the Endangered Species Act (ESA) set in motion sweeping federal and state land management plan changes and proactive conservation actions to address threats within the realm of management control. In the fall of 2015, the U.S. Fish and Wildlife Service determined that the Greater Sage-Grouse did not warrant protection under the ESA due to on-going and successful efforts to address high-priority threats, but that the species status would be reevaluated in 2020 (USFWS 2015). These data from Garton et al. (2015), Figure 9, show a population reconstruction of the estimated decline in Greater Sage-Grouse across its range from the mid-1960’s to 2013 illustrating the timing and magnitude of the decline which triggered the management plan changes and conservation activity.

Figure 9 Click the image for a printable verison.

Nevada Department of Wildlife biologist Shawn Espinosa discusses sage-grouse declines in this video.

The Greater Sage-Grouse and other sagebrush-obligate animals are landscape-dependent species that require intact habitat and combinations of sagebrush and perennial herbaceous species to exist; restoration of landscapes for Greater Sage-Grouse also will benefit these other sagebrush-obligate species.

Subspecies of Big Sagebrush

The sagebrush ecosystem is dominated mostly by three subspecies of big sagebrush depending on gradients of soil temperature and moisture:

basin (Artemisia tridentata ssp. tridentata);
mountain (A. t. ssp. vaseyana); and
Wyoming (A. t. ssp. wyomingensis).

Big sagebrush subspecies do not re-sprout following disturbance such as fire. Rather, they rely on seed for reestablishment. Recovery periods range from shorter periods on productive sites (15 to 20 years for mountain big sagebrush) to much longer periods on harsher sites (50 to greater than 100 years for Wyoming big sagebrush).

The herbaceous component of sagebrush steppe ecosystems varies in the proportional amount of grasses to forbs with cool and moist sites having more forbs and more herbaceous vegetation.

Grasses in the northern Great Basin, Columbia Basin, Snake River Plain, and central and western Wyoming are mostly cool season plants (C₃ photosynthetic pathway). Ecosystems farther south (southern Great Basin and Colorado Plateau) and east (western Great Plains) tend to be dominated by warm season plants (C₄ photosynthetic pathway).

Wildlife

A small selection of the other forms of wildlife found in the sagebrush includes pygmy rabbit, pronghorn, sagebrush lizard, mule deer, elk, golden eagle, and many birds, including several obligate to the sagebrush. Click here for a list of 367 species of conservation concern associated with the sagebrush ecosystem.

Many of these species, especially the sagebrush obligate songbirds, have been shown to benefit from habitat conservation, restoration, and management activities that are targeted at the Greater Sage-Grouse (Donnelly et al. 2016, Holmes et al. 2016). For example, Donnelly et al. (2016), Figure 2, shows clearly the close alignment between the distribution of Greater Sage-Grouse and three species of songbirds most closely tied to sagebrush (Sage Thrasher [SATH], Sagebrush Sparrow [SAGS], Brewer’s Sparrow [BRSP]) in the sagebrush biome of the western U.S.

Photo credit: Jeremy R. Roberts, Conservation Media

Figure 2: Click the image for a printable verison.

Sagebrush steppe ecosystems in the United States currently occur on only about one-half of their historical land area because of changes in land use, urban growth, and degradation of land (see figure from USFWS). Changes from the vast sea of sagebrush described by early explorers include:

The total quantity of the landscape dominated by sagebrush has decreased.
At low elevations, an increasing variety of non-native plants, mostly annual grasses, have become dominant.
At higher elevations, trees have expanded downslope to dominate sagebrush communities.
Sagebrush lands have changed from a continuous sagebrush landscape containing small areas dominated by herbaceous plants or other shrubs to lands that are more fragmented with large patches of herbaceous plants, primarily non-native annual grasses, with smaller patches dominated by sagebrush.

USFWS Figure: Click the image for a printable verison.

THREATS TO THE GREATER SAGE-GROUSE AND THE SAGEBRUSH ECOSYSTEM

Begin by watching Pat Deibert discuss problems facing the sagebrush ecosystem and Steve Knick discuss threats to sage-grouse.

Click the tabs below to view a summary of major threats to Greater Sage-Grouse, their respective contribution to the problem, and their area of occurrence across the range (RISCT 2012, USFWS 2013):

Primary Threat

The primary threat to the Greater Sage-Grouse and the sagebrush ecosystem is loss and fragmentation of habitat caused by numerous factors listed below. Note, threats shown in bold are fuels related and are covered in this and subsequent lessons:

Increases in wildfire size, frequency and intensity are a major threat, combined with an increase in invasive annual grasses (below). This is a dominant threat in the western (Great Basin) range and is discussed in this lesson.
Invasive annual grasses are another major threat, primarily in the western (Great Basin) range, particularly as a contributor to larger and more frequent wildfires (above); they will be discussed more fully in the Invasive Grasses lesson.
The encroachment and expansion of conifers, primarily several species of juniper, has affected many parts of the sagebrush ecosystem in both the western and eastern (Rocky Mountains) range; it will be discussed more fully in the Conifer Encroachment lesson.
Renewable and non-renewable energy development is a localized, but substantial, threat in many areas.
Conversion of sagebrush for agriculture is primarily a threat in the eastern (Rocky Mountains) range.
Mining is a threat of high severity where it occurs, but is relatively minor in impact range-wide.
Infrastructure (such as roads and transmission lines) is another threat that can be substantial where it occurs, but has relatively low impact across the range.
Poor grazing management can be a threat in some areas, but can also be a useful tool for fuels management and restoration in others.
Feral horses are a threat to the ecosystem, particularly in some parts of the western range.
Recreational activities are generally a minor threat to sage-grouse.
Urbanization and suburbanization has a localized moderate to severe impact on sagebrush, particularly in parts of the eastern range, but is not widespread enough to be considered a major threat.

Other Threats

Additional threats to sage-grouse include:

Parasites, although known to occur in sage-grouse, are not a significant issue for the species.
Infectious diseases (e.g., West Nile virus) may regulate sage-grouse populations in some places at some times, but currently are not felt to be a primary limiting factor.
Predation of adults, young, or eggs is not a significant contributing factor to current or historical declines of sage-grouse.
Weather events such as drought and late spring storms are known to cause fluctuations in sage-grouse populations.

To summarize, persistent ecosystem threats (fire, weeds/annual grasses, conifers) are ranked more highly in the western than eastern range, and fire and weeds/invasive annual grasses are ranked more highly than conifer expansion. In the eastern range, persistent and widespread threats are fire, weeds/annual grasses, and conifers and a variety of anthropogenic threats (Chambers et al. 2017). Issues specific to the eastern range will be discussed in the Eastern Range Lesson.

Climate Change

Climate change is a global threat that is impacting all ecosystems, including the sagebrush. In this video Steve Knick talks about the effects of climate change.

Climate change will undoubtedly affect the Greater Sage-Grouse and the sagebrush ecosystem, but the future effects are not yet predictable enough at a scale to plan for them. Bioclimate envelope models for big sagebrush and other sagebrush species project large decreases in southern latitudes and lower elevations, but relatively small increases in northern latitudes and higher elevations. For example, a 39% reduction in suitable climate for Wyoming big sagebrush, which occupies the warmest and driest portions of the range, is predicted by mid-century and would lead to a loss of 42 million ha of this habitat type (Still and Richardson 2015, Figure 1B).

Figure 1B Click on the image for a printable version.

Regions that may retain or gain climate suitability include higher elevations in the Cold Deserts and the entirety of the Northern Great Plains. Cheatgrass will likely spread upwards in elevation and red brome (B. rubens) might expand northward and/or increase its abundance in the Cold Deserts and Colorado Plateau. If average summer, plant available water declines, the land area susceptible to cheatgrass invasion may increase by up to 45%, particularly in mountain big sagebrush steppe in Montana and higher elevation areas of the Colorado Plateau (Chambers et al. 2017).

Some more detailed ideas on addressing climate change in the sagebrush ecosystem by building resistance, increasing resilience, and facilitating a response to changing environmental conditions are available in the Resistance and Resilience topic.

In this video, Jeanne Chambers shares some of her thoughts on management options and considerations for the sagebrush ecosystem in the future.

Wildfire

Begin by listening to Shawn Espinosa discuss the effects of fire on sage-grouse.

Large fires are an increasing threat to the sagebrush ecosystem and sage-grouse and are greatly exacerbated by a positive feedback cycle between invasive grass species and large, intense wildfires, as illustrated by the fire cycle graphic.

Fire Cycle Graphic. Click on the image for a printable version.

Some sage-grouse can be killed by fire and others will seek out unburned islands within or near the fire perimeter. However, the effects of fire on sage-grouse are often not seen until after a time lag of up to three years due to the high site-fidelity of individual birds.

Recent datasets mapping the burn probability (also called “wildland fire potential”) across the west illustrates that the Great Basin is dominated by high burn probability, as modeled from past fire frequency, current fuel type, and probable fire spread patterns (see Burn Probability map).

Burn probability map. Click on the image for a printable version.

WHAT IS THE SCIENCE OF WILDFIRE TELLING US?

Peter Coates begins by discussing burn-rates.

Although the relative frequency of historic fire in the sagebrush ecosystem is up for debate, it is important to acknowledge that fire has always played a role as a disturbance factor. Generally speaking, lower elevations experienced much less frequent fires than upper elevation sagebrush communities. A century of fire suppression has greatly altered those historic fire regimes across all sagebrush systems. Today, we are left with a management paradox of both too much fire and too little fire. Too little fire at upper elevations, characterized by mountain big sagebrush, has allowed conifer expansion into sagebrush communities on a massive scale. Too much fire at lower elevations, characterized by Wyoming big sagebrush, is resulting in wholesale habitat conversion to exotic annual grasslands (Murphy et al. 2013).

USGS FIRE PATTERNS STUDY

The USGS fire patterns study (Brooks et al. 2015) revealed the following:

Fires were generally larger in the western (Great Basin) region than in the eastern (Rocky Mountain) region (Brooks et al. 2015, Figure 7).

Figure 7 Click on the image for a printable version.

Even within the western region, the distributions of fire area differed among the four management zones (Brooks et al. 2015, Figure 6). Fire sizes were largest for the Northern Great Basin management zone, followed by the Snake River Plain management zone and the Southern Great Basin management zone. Fire sizes in the Columbia Basin management zone were smaller; the very largest fires in Columbia Basin did not exceed about 30,000 ha whereas in the other three management zones they exceeded 100,000 ha. The Northern Great Basin has experienced 3 fires which were at least 500,000 acres in the last decade.

Figure 6 Click on the image for a printable version.

To summarize, the Brooks et al. (2015) fire threats assessment indicates that threats are higher in the four western management zones than in the three eastern management zones; among the four western zones, the Snake River Plain and the Columbia Basin ranked somewhat higher than the Southern Great Basin and Northern Great Basin.

USGS WILDFIRE EFFECTS STUDY

The USGS study of wildfire effects on sage-grouse (Coates et al. 2015) revealed the following (more detailed information on this topic is contained within the lesson on Systems Invaded by Annual Grasses):

Burned areas near leks nullify population growth that normally follows years with relatively high precipitation.
Increased suppression effectiveness could reduce cumulative burned area if potentially large wildfires (mega-wildfires) are suppressed before they grow to unmanageable sizes.
Predicted outcomes of increasing sage-grouse populations with reductions of cumulative wildfire in core areas under high precipitation conditions will likely be most effective in northern areas where Resistance and Resilience is relatively high and conditions generally are colder and wetter; reductions may be less effective in southern areas of the Great Basin.

THE BASICS OF FUELS MANAGEMENT TO CONSERVE SAGE-GROUSE
AND SAGEBRUSH ECOSYSTEMS

Vegetation and fuels management projects are important for the conservation, maintenance, and restoration of sagebrush landscapes. Resilience and Resistance concepts (see the lesson on Resilience and Resistance) provide a science-based background that can inform strategic placement of fuels treatments, augment effective fire operations, and inform allocation of scarce assets during periods of heightened fire activity across the Interior West. Collectively, fuels management includes vegetation projects that mitigate wildfire risk, improve resilience to disturbance, and restore habitat, as well as habitat protection projects (actions intended to protect intact sage-grouse habitat; Chambers et al. 2017).

Resilience and Resistance concepts are especially relevant for evaluating tradeoffs related to current ecological conditions, rates of recovery, and possible ecological consequences of different fire management activities. For example, prioritizing initial attack efforts based on ecological types and their resilience and resistance at fire locations is one application. In another, fire prevention efforts can be focused on intact, high quality habitats with inherently low resilience and resistance where human ignitions have commonly occurred.

Fuels management projects are often applied on a landscape scale to:

Constrain or minimize fire spread
Alter species composition
Modify fire intensity, severity, or effects
Create fuel breaks or anchor points that augment fire management efforts
Improve wildlife habitat
Create resilient landscapes
Restore habitats or vegetation conditions

These activities are selectively used based on the projected ecosystem response, anticipated fire patterns, and probability of success. For example, in areas that are difficult to restore due to low to moderate resilience, fuel treatments can be placed to minimize fire spread and conserve sagebrush habitat. In areas with moderate to high resilience and resistance, mechanical or prescribed fire treatments may be appropriate to prevent conifer expansion and dominance.

Given projected climate change and longer fire seasons across the western U.S., fuels management represents a proactive approach for modifying large fire trends and maintaining desired vegetation patterns. Fire operations and fuels management programs contribute to a strategic, landscape approach when coupled with data that illustrate the likelihood of fire occurrence, potential fire behavior, and risk assessments. In tandem with resilience and resistance concepts, these data can further inform fire operations and fuels management decisions.

Proactive fuels management practices differ in the eastern vs. western portion of the sagebrush biome. For example, roadside linear fuel breaks are seldom used in the east, but are more commonly used in the west. Also, while conifer expansion in the western range is largely pinyon and juniper species, expanding conifers in the eastern range include limber pine (Pinus flexilus), Douglas-fir (Pseudotsuga menziesii), and ponderosa pine (Pinus ponderosa). These differences are more fully explained in the Eastern Range lesson.

Management Units and Priority Areas:
Subdividing the Sage-Grouse Range

The current range of the sage-grouse has been divided into seven Management Zones by the Western Association of Fish and Wildlife Agencies (WAFWA; Stiver et al. 2006) that encompass the major populations of these birds. The Management Zones are shown in this map (from Knick and Connelly 2001, Figure I.3) and described further in the table from Doherty et al. (2016).

Figure I.3 Click on the image for a printable version.

Management Zone	Ecological Description
Northern Great Plains (MZ 1)	Includes the northeastern portions of sage-grouse range. This MZ experiences the most precipitation, thus it contains larger portions of the landscape dominated by grasslands, smaller patches of sagebrush, and contains more silver sagebrush than other MZs. MZ I also has the highest amount of land in private ownership and the highest amount of cropland.
Wyoming Basin (MZ II)	Characterized by large expanses of Wyoming big sagebrush with little fragmentation. It experiences the greatest amount of oil and gas development. Most of the precipitation comes in the form of winter snowfall. MZ II contains the highest densities of sage-grouse across their range.
Southern Great Basin (MZ III)	Includes the southern- and western-most populations of sage-grouse. MZ III is the most arid of all the MZs and includes a mix of Wyoming big sagebrush, mountain big sagebrush, low sagebrush, and black sagebrush. Topography is rugged with sagebrush on many of the valley floors transitioning to arid coniferous forests at higher elevations on the mountain slopes.
Snake River Plain (MZ IV)	Encompasses the north-central populations of sage-grouse. Like MZs III and V, it is characterized by salt deserts in the lower elevations and conifer forests at higher elevations. Wyoming and basin big sagebrush are dominant, with mountain big sagebrush at higher elevations. MZ IV contains the second highest density of sage-grouse across the range. This MZ also experiences dense cropland areas, although clustered at lower elevations.
Northern Great Basin (MZ V)	Similar to MZ III, but less arid with precipitation occurring primarily in the winter and spring. Similar to MZ’s III and IV, lower elevations are dominated by salt deserts and higher elevations are dominated by conifer forest.
Columbia Basin (MZ VI)	This MZ is isolated from the rest of the range and is contained entirely within Washington state. Wyoming big sagebrush and basin big sagebrush are the predominant species. MZ VI contains the lowest elevation sagebrush across the range and experiences high amounts of cropland in comparison to all other MZs with the exception of MZ I.
Colorado Plateau (MZ VII)	The southeastern-most MZ and contains a small fraction of sage-grouse populations. It is similar to MZ III, but receives more precipitation. Soil types within this MZ greatly restrict sagebrush distribution.

PRIORITY AREAS FOR CONSERVATION (PACs)

Within the Management Zones, Priority Areas for Conservation (PACs) were identified by state wildlife agencies as being crucial to ensure the representation, redundancy, and resilience for the conservation of populations. These PACs tend to closely follow remaining landscapes of large and intact cover of sagebrush (figure from USFWS).

USFWS. Click the image for a printable version.

PRIORITY HABITAT MANAGEMENT AREAS (PHMA)

Priority Habitat Management Areas (PHMAs) are highly valued habitats which are managed for their role in maintaining sustainable Greater Sage-Grouse populations. In these areas, development and other disturbance types are limited. All of the Sagebrush Focal Areas are incorporated within PHMA.

An example of PHMA (and GHMA, discussed below) from Nevada is shown.

Example of PHMA. Click the image for a printable version.

GENERAL HABITAT MANAGEMENT AREAS (GHMA)

General Habitat Management Areas (GHMA) are lesser quality habitat than PGMA, and may be occupied seasonally or year-round outside of PHMA. Because they are a lower quality habitat than PHMA, greater flexibility exists for land use activities in GHMA. Mitigation and required design features ensure that impacts from development are avoided, minimized and mitigated in GHMA. The BLM and USFS use the PHMA and GHMA naming conventions in their recently completed land use plans.

SAGEBRUSH FOCAL AREAS (SFAs)

Sagebrush Focal Areas (SFAs) are landscapes with highest breeding population densities of sage-grouse, high-quality sagebrush habitat, and as such, have high conservation value. Occurring only on Federal lands, SFAs are essential for species persistence range-wide, and contain a preponderance of federal ownership or protected areas that serve to anchor the conservation value of the landscape. These areas were identified in the final land-use plan amendments to address threats to the Greater Sage-Grouse by BLM and USFS, based on recommendations from the U.S. Fish & Wildlife Service. The SFAs are prioritized for habitat improvement and vegetation management efforts.

As an example, the SFAs identified in Idaho are shown.

Idaho SFAs. Click the image for a printable version.

Landscape-Level Influences on Sage-Grouse

The landscape context of any given site has a strong influence on its suitability for sage-grouse and their long-term persistence at that site. Begin by watching Steve Knick discuss sagebrush cover thresholds.

Numerous analyses have shown clearly that landscape variables have strong influences on the probability of sage-grouse occurrence and persistence. Two extremely important variables in the surrounding landscape are sagebrush cover and amount of human disturbance.

Landscape Cover of Sagebrush

Two breakpoints have been identified in the amount of sagebrush cover in the landscape that pertain to habitat management and restoration (Chambers et al. 2014, Figure 8; Pyke et al. 2015, Figure 9). There is a low probability of maintaining sage‑grouse leks (and local extirpation of sage-grouse is likely) when landscape cover of sagebrush is less than approximately 25 percent. However, when landscape cover of sagebrush exceeds approximately 65 percent, the probability of sustaining active leks and population persistence is high. Between about 25 and 65 percent landscape sagebrush cover, increases in landscape cover of sagebrush have a constant positive relationship with the probability of persistence of sage-grouse at a site.

Figure 8. Click the image for a printable version.

Human Disturbance

The amount of different kinds of human disturbance on the landscape is strongly negatively related to sage-grouse occurrence and persistence. This is true for a variety of different types of anthropogenic disturbance:

Agriculture. In the western portion of the sage-grouse range, < 2% of leks were in areas surrounded by > 25% agriculture within a 5-km radius, and 93% by < 10% agriculture (Knick et al. 2013, Figure 5B).
Human development. Ninety-nine percent of active leks were in landscapes with < 3% developed; all lands surrounding leks were < 14% developed (Knick et al. 2013, Figure 5C).
Road density. High lek habitat similarity was associated with large-scale densities of < 1.0 km/km² of secondary roads, 0.05 km/km² of highways, and 0.01 km/km² of interstate highways; 93% of active leks fell below this threshold for interstate highways (Knick et al. 2013, Figure 5D).

Figure 5B.

Figure 5C.

Figure 5D.

Power line and communication tower density. Habitat suitability was highest at power line densities < 0.06 km/km² and pipeline and communication tower densities < 0.01 km/km². Leks were absent from areas where power line densities exceeded 0.20 km/km², pipeline densities exceeded 0.47 km/km², or communication towers exceeded 0.08 km/km² (Knick et al. 2013).

Leks were absent from areas with even relatively low levels of anthropogenic development and infrastructure. Minimum thresholds defining lek presence provide a basis from which to determine effects of projected or proposed levels of land use and anthropogenic development in areas that currently support active leks or to identify areas suitable for restoration of future sage-grouse habitat (Knick et al. 2013).

Sublette County, WY

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