Review of Public Broadcasting Nature film The Sagebrush Sea

This past week, Public Broadcasting’s Nature film series featured the Sagebrush Sea.  The film’s main focus was on the Greater Sage Grouse which is the emblematic creature found in this vast landscape that covers the bulk of many western states including substantial parts of New Mexico Wyoming, Colorado, Utah, Nevada, Oregon, California, Montana and Idaho.

The movie followed the sage grouse through the year as it tries to survive in what many might suggest is a harsh environment dominated by freezing winters, and blazing hot summers. One of the themes of the film is that this ecosystem is under appreciated.  What may appear at first impression to be a land devoid of life is really teeming with wildlife from the sage grouse to eagles, jackrabbits, pronghorn and mule deer.

The second theme is that this vast ecosystem is in jeopardy from a host of threats including oil and gas development, urbanization, and changes in fire regimes and the fate of the sage grouse as well as many other species is linked to the future survival of this landscape.

While the movie did a fine job of introducing people to the variety of life and beauty of the sagebrush ecosystem, it missed an opportunity to provide a more in-depth analysis of how and why the ecosystem as well as the sage grouse is threatened. No doubt it was an omission done on purpose to avoid controversy.

While the movie’s producers did mention fragmentation of habitat resulting from oil and gas development as one major threat, it failed to articulate the greatest threat coming from livestock production. Like everyone from Secretary of Interior Sally Jewell on down to some conservation organizations, there is a disconnect between the proximate causes of sage grouse decline and the ultimate cause.

For example, the movie did mention cheatgrass wildfires as a threat to the grouse. Cheatgrass is an annual grass that dries out early and becomes highly flammable fuel for fires.  While sage brush ecosystems are adapted to fire, the historic fire regime burned these landscapes at intervals of decades to hundreds of years. This gave sage brush plenty of time to recover from any fire. However, with the advent of cheatgrass fires, the interval has shortened dramatically with some Sagebrush Sea sites burning every few years so that the only plant that can survive on cheatgrass infested sites is cheatgrass.

Where the film failed, however, is making the connection between livestock grazing and the spread of cheatgrass. Cheatgrass does not magically appear. Its spread is exacerbated by livestock production.

The natural sage brush grassland is dominated by perennial bunchgrasses that are widely spaced with the intervening soil covered by lichens, mosses, and algae collectively called “biocrusts”. These biocrusts serve many purposes. By capping the soil, they prevent wind and water erosion. They capture atmospheric nitrogen and transfer it to the soil, enriching the site for all plants.

However, what might be the most important factor in the health of the Sagebrush Sea ecosystem is these biocrusts hinder the establishment and germination of cheatgrass seeds. So when the biocrust is intact and healthy, cheatgrass has a difficult time becoming established and competing with the native grasses on the site.

Livestock hooves, however, trample and break up the soil biocrusts giving cheatgrass the added advantage it needs to colonize the landscape. Cattle further tip the balance in favor of cheatgrass by selectively grazing the native perennial grasses. Heavy grazing can reduce the production of seeds by such natives, and reduce their vigor. Over time the loss of perennial grasses favors even greater colonization by cheatgrass.

It must be mentioned that historically over most of the Sagebrush Sea ecosystem bison or other large herding herbivores were absent. The dominant hoofed animals were highly migratory bands of pronghorn and deer so the soils of these sagebrush ecosystems are not adapted to concentrated heavy trampling by native wildlife.

Finally if the annual cheatgrass burns, its seeds, buried in the soil, quickly germinate, and outcompete the native perennial grasses which tend to produce successful seed crops and germination at irregular and long intervals.

Livestock production also harms sage grouse in many other ways. For instance, sage grouse depend on tall grass to disguise nests, and provide hiding cover from predators.  Grazing by livestock reduces this cover making sage grouse more vulnerable to predators. Again, the movie while documenting how various predators from coyotes to ravens to golden eagles can prey upon sage grouse, failed to make the connection that the vulnerability of grouse to these predators is a consequence of livestock’s removal of grass cover.

Livestock production also requires fencing. Sage grouse are poor fliers and regularly fly into barbed wire fences with surprising frequency. In some studies up to 30% of all mortality comes from collisions with fences.

Despite their name, sage grouse do depend on other plants and animals (insects) for their survival. Chicks in particular feed almost exclusively on insects and forbs (flowers) during the first couple of months of their lives. The most important feeding sites for sage grouse chicks early in life are moist meadows and riparian areas; those green lines of vegetation along streams.

However, another way that livestock degrade sage grouse habitat, is by compacting soils, breaking down the banks of streams, and reducing the vegetative cover thereby exposing sage grouse to greater predator losses. Cattle in particular gravitate towards these riparian areas and other moist green sites and degrade this habitat component for the grouse.

Because so much of the Sagebrush Sea is arid, ranchers often install watering troughs and develop springs to provide cattle with water. Yet these water developments are often breeding habitat for breeding mosquitoes that carry West Nile Virus, a disease that has been shown to cause high mortality in some sage grouse populations.

In short, livestock production negatively impacts sage grouse at every stage of its lifecycle. Yet this connection between the sage grouse’s decline, and the ecological degradation of the Sagebrush Sea was not mentioned in the movie, nor have top leaders in our government effectively made this connection either. Over and over we hear from ranchers and other livestock advocates how ranching can “save” the sage grouse. But in reality there is simply no way to have an economically viable livestock operation in this ecosystem without diminishing the ecosystem. Trying to raise a water-loving, largely sedentary animal in an arid landscape is fool hardy and not only is the grouse paying the ultimate price for this by being put at risk of extinction, but the entire ecosystem is in jeopardized across its historic range.  In the end there is no right way to do the wrong thing.

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