MTPR

'That Wild And Purple Wilderness' Depends On The Ancient, Tenacious Sagebrush

Aug 21, 2017

I’ve always been impressed by survivors, especially here in the arid, unforgiving West. No species better demonstrates this survival instinct for me than does the lowly Artemisia tridentata, better known as big sagebrush. And few other species come as close to communicating such a significant part of the nature of the landscape.

When I’m out driving Montana’s highways or tramping around the backcountry, my eyes tend to slide right past the sage – maybe because it seems to be everywhere. Yet its characteristic scrubby sprawl captures some essence of the American West – and not just for me. Nevada claims it as its state flower, and Zane Grey, in his classic cowboy novel, "Riders of the Purple Sage," refers to it as “that wild and purple wilderness.” It elicits a response that’s more emotional than scientific. But in a practical sense, how does this common plant’s existence impact its ecosystem?

Several species of Artemisia exist, but big sagebrush is the most widespread, the most common, and the most ecologically important. It’s also an American native: pollen records indicate that it existed here over 35,000 years ago. Big sagebrush can be identified by its grayish color; silvery, toothed leaves; and astringent, characteristic aroma. Individual plants tend to be large and robust and can reach heights of eight feet. By late summer or early fall, it flowers, producing numerous small, yellow blossoms in long, narrow clusters along its branches. It also relies on the wind to pollinate its blooms, exacerbating allergies and hay fever.

Sagebrush leaves.
Credit BLM Idaho (CC-BY-2.0)

The availability of water is the major limiting factor in the growth and reproduction of this survivor. But Artemisia has developed sophisticated forms of drought avoidance. If you rub a branch of the plant between your fingers, you’ll feel a waxy coating on the stems and leaves that protects them from the blazing sun. You’ll also feel a fine, dense hair that reduces evaporation and reflects sunlight, helping the inner, succulent tissue retain water. It has even found a way to discourage herbaceous interlopers: its decaying fallen leaves release a kind of natural weed killer into the ground. This toxic substance frustrates the ambitions of species that compete with sage for its habitats’ limited resources.

Yet this ancient plant has not adapted as efficiently to two more recent competitors: humans and non-native species. Human settlement brought with it farming, mining, roads, and cattle – and cattle ranching, in particular, poses an unprecedented threat to its survival. Traditionally, ranchers would clear their lands of as much sagebrush as possible to facilitate grazing and, with its removal, in moved exotic, non-native plants. These exotics form great fuel for wildfires. Fires on some big sagebrush habitats have increased in frequency from every 30 to 70 years to every five and a half years. Frequent fires do not allow immature plants time to establish their root systems and reach adulthood.

We might be tempted to dismiss the fate of the lowly Artemisia. After all, it’s just a homely, insignificant shrub. But many weaker, more vulnerable species depend on it. The sage grouse takes refuge under its curving branches. The pygmy rabbit tunnels among its roots for shelter. The sagebrush lizard scuttles up its trunk and feeds on the insects that dwell on its leaves. Big sagebrush defines its ecosystem and consequently defines the lives of the creatures that rely on it.

Sagebrush.
Credit Flickr user Julie Falk (CC-BY-NC-2.0)

The loss of sagebrush from our region equals the loss of its heart, both literally and figuratively. Our habitat would be irretrievably altered, and some part of our spirit would suffer, too. How would we feel about our own, human contribution to our region if, one day, we looked out on a landscape void of the ancient, tenacious Artemisia tridentata?

"Field Notes" is produced by the Montana Natural History Center.

("Fieldnotes," Broadcast: 9/25/16 and 9/30/16. You can listen on the radio Sundays at 12:55 p.m., Tuesdays at 4:54 p.m., and Fridays at 4:54 p.m., or listen via podcast.)