Drab Appearance Masks Complexity of Imperiled Sagebrush Ecosystems
Compared to the rich diversity of forests, sagebrush shrublands contain relatively few species. Yet, these shrublands in the western United States have incredibly complex dynamics that present major challenges for conservation. They are also one of the most imperiled habitats in North America, primarily due to invasive plant species. Non-native cheatgrass promotes more frequent and larger wildfires, preventing sagebrush re-establishment. USGS ecologist Steve Knick provides an overview of sagebrush ecosystems and discusses research priorities, birds and their habitats, and indicators of change over a broad landscape.
[Intro Music: Scott Pemberton Trio, Little Bobby Cobalt]
[Segment #1: Introduction to Sagebrush Ecosystems]
[Damon Runberg] Hello and welcome to the Oregon Science Podcast. I am Damon Runberg.
Today we’ll hear an interview recorded last month with USGS Forest and Rangeland Ecosystem Science Center Research Ecologist Steve Knick. I traveled to Boise, Idaho to visit Steve at the Snake River Field Station.
Steve joined me to speak about his current research on sage birds, including the Greater Sage-Grouse, and the changing sagebrush ecosystems of the western United States.
[Midtro Music #1: Scott Pemberton Trio, Little Bobby Cobalt]
[Segment #2: Interview with Steve Knick, USGS Ecologist]
[Damon Runberg] Thanks for joining us today Steve.
[Steve Knick] You’re welcome.
[Damon Runberg] Can you tell us a little bit about what the sagebrush ecosystem is?
[Steve Knick] The sagebrush ecosystem is shrubland, which is one of the largest systems in western North America. Its dominant plant species is sagebrush. What people see as they drive across miles and miles of these flat, open spaces in the Western United States is sagebrush shrublands. It looks very boring to them because they usually drive through in the middle of the day while the sun is overhead. All they see is this drab, olive-green plant that’s no higher than two or three feet and extends for miles and miles.
[Damon Runberg] How large is this ecosystem, and what area does it encompass in the U.S.?
[Steve Knick] It’s primarily distributed through the western portion of the U.S. The Great Plains are primarily grassland, and as you move west, you begin to grade into a mixed grassland/ shrubland community. Then you have the Rocky Mountains where the higher elevations are forested. But again, these low-lying valleys and basins throughout western North America are covered by sagebrush or were once dominated by sagebrush.
[Damon Runberg] So you said earlier that to the casual viewer that drives through these sagebrush ecosystems that they just seem bland and desolate. But, what is it that is so fascinating about these ecosystems?
[Steve Knick] Compared to forests and other kinds of plant communities, they have relatively few numbers of species. They are simple systems, but the dynamics in these systems are so incredibly complex and often play out over centuries. Trying to unravel how these ecosystems function, how the birds interact in these systems, how the plants dictate future dynamics of the communities, and how to manage these systems is an incredible challenge. It’s not like you can go out and apply a simple treatment and produce predictable results. It’s not an orderly progression of plant communities in a succession the way a forester may think of it. There are any number of endpoints for these communities, and trying to understand how these communities are going to respond to different things, such as land-use or treatments, is so challenging that we really haven’t figured out how to do it yet.
[Damon Runberg] It seems like there has been greater attention directed towards the loss of sagebrush habitat. Is this happening, and what are the causes of this loss?
[Steve Knick] Sagebrush is one of the most imperiled habitats in western North America. Many expanses of sagebrush have been lost completely, fragmented, or converted to a different habitat type. The primary cause of this loss of sagebrush is invasive plant species; cheatgrass is the most common, and in combination with fire, starts a nasty cycle of burning off the sagebrush. Then the cheatgrass will come in and replace what was there in the sagebrush. Cheatgrass has different characteristics from the native grasses in that it promotes fire - much more frequently and much larger fires. As a result, the sagebrush never gets a chance to recover.
[Damon Runberg] What does this loss of habitat in sagebrush ecosystems mean for biodiversity? Specifically, are plants and animals in these ecosystems affected by the loss of sagebrush habitat?
[Steve Knick] Yes, particularly birds that depend on sagebrush, as well as birds that depend on grassland habitats. These general shrubland communities are experiencing some of the most rapid declines of any group of birds in North America, largely because of this loss of habitat.
[Damon Runberg] Looking into the future of research needs for shrubland or sagebrush ecosystems, what are some of the research areas that scientists need to be focusing on in the future to help land managers with this loss of habitat?
[Steve Knick] One of the basic questions is just simple biology. What is it that Sage-Grouse require or Brewer Sparrows require in terms of amount of habitat that they need? We really don’t have a good handle on some of these things because we are learning that the quality of the habitat (that is how much sagebrush is in a given area) is just as important as the size of the habitat patch that you have. It’s not just a matter of managing for an area that is a single size, but the landscape in which that area is embedded. For instance, you can take a square mile of sagebrush, and if that square mile is in the middle of a total agricultural landscape and it’s totally inhospitable outside of that square mile, then that is not going to be nearly as attractive as if it were in a larger mosaic of shrubland systems. We often tend to think too small for what birds require and focus on an immediate home range. In reality, the reason that bird is there is because of a much larger context that allows it to put its home range in that place.
[Damon Runberg] What is the range of many of these shrubland birds?
[Steve Knick] An individual home range might be about the size of an acre for some of the smaller birds, such as Brewer or Sage Sparrows. Sage Thrashers, which are a larger bird about the size of a Robin, would use an area about two to three acres in size. The real challenging bird is Sage-Grouse, which will expand over an area within their annual range of a little over 2,500 square kilometers. I know that you are going to ask me to convert that into square miles, but I am geographically challenged.
[Damon Runberg] It’s a pretty large area though?
[Steve Knick] It’s an area that’s larger than Rhode Island. That’s where the real challenge comes because you are trying to manage habitat over that large an area. Within that area there may be a wide variety of conditions, as well as land ownerships. Some of that land may be managed by federal agencies, and some of that land may be owned by private interests. You have different management objectives for different parcels of that area within the entire range of Sage-Grouse. You may focus on one area to do your management or treatment to conserve sagebrush, but in reality, the part that may be affecting the population may be fifty miles away and experiencing an entirely different set of circumstances.
[Damon Runberg] This is more of a research question, but how do you go about finding these birds in such as vast and oftentimes harsh landscape?
[Steve Knick] Most of the surveys for birds are focused on the breeding period. In that time males are attracting females with singing, so you hear their songs. Most of the surveys are based on how many of these songs you detect in a given area. Sage-Grouse do this elaborate display in the spring on a small breeding area called the “lek.” The males get out and strut and make popping noises while inflating their air sacs, which is really quite a dramatic display. For many birds, these leks are traditional, in that birds will show up at these same locations for literally centuries.
[Damon Runberg] So you know where to show up then?
[Steve Knick] The biologists know where to show up to count the Sage-Grouse. They will do this display, and it is through these counts that we get an idea of population trend as well as the number of birds in different areas.
[Damon Runberg] Are these shrubland birds intricately tied to the landscape, and if so, what changes can have the biggest effect on the sage bird populations?
[Steve Knick] Many of these species are dependent on sagebrush itself, the plant, either for nesting or cover. Sage-Grouse depend on sagebrush for much of their food requirements. In the winter time sagebrush leaves can form up to one-hundred percent of their diet. So, they are totally dependent on sagebrush, the plant.
[Damon Runberg] Why has the Sage-Grouse received so much attention recently?
[Steve Knick] It’s important right now because of its representation of what is happening in the sagebrush system. As such, it is an icon for sagebrush systems throughout the western United States. Losses of Sage-Grouse populations reflect the changes that are happening in the sagebrush ecosystem. This is sort of the “canary in the coal mine,” in terms of telling us what is happening within the system.
[Damon Runberg] It sounds like you have your work cut out for you.
[Steve Knick] I think I and many other people do.
[Damon Runberg] Well, thanks for joining us today.
[Steve Knick] You’re welcome.
[Midtro Music #2: Scott Pemberton Trio, Little Bobby Cobalt]
[Damon Runberg] That’s all the time we have for today’s episode. Make sure to check out our transcripts for links to more information on the research going on at USGS FRESC. For those who subscribe through iTunes, you can access the transcripts at our website: or.usgs.gov/podcasts. If you have any questions or comments about the USGS Oregon Science Podcast, email us at email@example.com. As always, thank you all for listening. If you want to hear more about other research the USGS is doing around the country, please check out the other USGS podcasts at usgs.gov/podcasts.
Until next time, I’m Damon Runberg.
This podcast is a product of the U.S. Geological Survey, Department of the Interior.
[Outro Music: Scott Pemberton Trio, Little Bobby Cobalt]