Climate

How The ‘Black Fingers Of Death’ Can Help Defeat Climate Change

CREDIT: Tom Kenworthy

U.S. Forest Service research ecologist Susan Meyer examining cheatgrass seeds for signs of Black Fingers of Death pathogen near West Mountain south of Provo, Utah.

PROVO, UTAH — This small city on the Wasatch Front south of Salt Lake City seems an unlikely locale for what could turn out to be an important battle against climate change. But here, in a modest building housing the U.S. Forest Service’s Shrub Sciences Laboratory, research ecologist Susan Meyer and her colleagues are working laboriously to defeat a tenacious alien plant, cheatgrass, once dubbed the “invader that won the West.”

If they succeed and a broad effort is launched to restore millions of acres of degraded western land that have been profoundly altered by the invader, they may also be able to suck an enormous amount of carbon out of the atmosphere and store it below ground. There is “immense potential for increasing carbon sequestration through restoration of these degraded systems,” Meyer concluded in a 2012 research paper.

It is a quiet, but epic, undertaking. And it features a couple of nature’s own weapon systems, pathogens with vividly descriptive names: the Black Fingers of Death and Bleach Blonde Syndrome.

At the heart of this struggle is cheatgrass, an annual grass that arrived, likely hitchhiking among edible grains, in the U.S. from Europe and central Asia beginning in the 1800s. It has basically taken over vast landscapes in the West, particularly in the Great Basin, a cold desert region between the Sierra Nevada and Rocky Mountain ranges that includes parts of Nevada, Utah, Idaho, Oregon and California.

In the Great Basin, cheatgrass has invaded more than 25 million acres of rangelands managed by the federal Bureau of Land Management. Over vast areas of the West, cheatgrass has out-competed and dominated areas where native shrubs and grasses once ruled, setting up shop easily in places where livestock grazing — particularly the unregulated grazing that prevailed prior to the 1930s — and other disturbances have altered the natural order of things.

Black fingers of death

Black fingers of death

CREDIT: Julie Beckstead

One of those disturbances is fire, something that has always occurred in the Great Basin, but which has greatly accelerated as cheatgrass has spread. Between 1990 and 2007, more than 16 million acres burned in the Great Basin, including 1.9 million acres in the disastrous year of 1999 that prompted calls for a broad ecosystem restoration effort in the region.

Cheatgrass and fire work together, in a kind of symbiotic disaster. Wildfires kill native perennials like sagebrush and pave the way for invasive plants like cheatgrass to thrive. Cheatgrass, which matures and dries out early in the growing season, in turn provides abundant fuels for fire. “As the exotic annual grasses become more abundant, the potential for fire increases, resulting in a positive feedback loop,” said the BLM’s Mike Pellant in testimony to Congress in 2007.

A study published in 2012 found that areas in the Great Basin dominated by cheatgrass were four times more likely to burn during the period from 2000 to 2009 than lands with native vegetation and that they fueled the largest fires, 39 of the 50 largest during that period.

As cheatgrass has steadily advanced, it has “changed the structure and function of ecosystems,” according to Stan Kitchen, a research botanist at the Shrub Sciences Laboratory. Once the native sagebrush is removed, Kitchen said, the land is “quickly converted to a cheatgrass monoculture or near monoculture.”

Cheatgrass is so tenacious in part because it is a prolific seed producer, sending out 15,000 or more seeds per square meter in some studies. That can produce densities of more than 10,000 plants per square meter. Those plants, germinating in the fall and maturing in the spring before natives do, hog the sparse moisture in the Great Basin, giving the invader another huge advantage. And the seed bank — surviving viable seeds left in the soil — lasts for two or three years, making chemical treatments less effective.

Among other things, cheatgrass’ advantages over native plants has dire implications for wildlife, in particular the sage grouse, a chicken-like bird that is dependent on sagebrush. Sage grouse population has declined to less than half a million from as many as 16 million a century ago due to loss of habitat. The bird is now being considered for protection under the Endangered Species Act, a listing that could have profound economic consequences throughout the West, potentially restricting oil and gas development and ranching.

Cheatgrass dominance also has implications for the fight against climate change. Cheatgrass, notes Meyer, “is the worst” in terms of carbon sequestration. “It burns all the time and it doesn’t have a very good root system,” so far less carbon is stored in underground root systems than is true for native perennials like sagebrush.

In 2006, researchers found that the invasion of cheatgrass in the West had turned some areas from carbon sinks to a net source of carbon — in fact, the invasion has released up to nearly nine million tons of carbon into the atmosphere and will likely release as much as another 55 million tons in the next few decades.

In a 2012 paper published by the Forest Service’s Rocky Mountain Research Station, Meyer wrote that “cold desert shrublands are a particularly good choice for management for increased carbon sequestration.” That potential, her paper explained, stems from sagebrush having deep root systems and a high ratio of roots to above ground foliage. ”

And, she mused during a recent interview, if the U.S. ever establishes a carbon market, then restoration of the Great Basin could become economically attractive if enough carbon credits could be generated and sold.

But first, how to kill the cheatgrass?

Herbicides can kill cheatgrass, but they tend to be broad spectrum chemical controls and “if you try to seed in perennials after it kills them. It’s expensive and environmentally dubious,” Meyer said.

Enter the black fingers of death. It’s a fungal seed pathogen (pyrenophora semeniperda) that gets its name because it looks like black fingers sticking out of cheatgrass seeds. The fungus kills the seeds before they germinate, when they are dormant. Meyer and her colleagues discovered the fungus when examining cheatgrass seed banks in their study plots in Utah’s Skull Valley.

While promising, the black fingers of death isn’t a silver bullet. It can be used in combination with herbicides, but it doesn’t kill all the dormant seeds in an area. “I think the black fingers of death will never be more than a tool in the tool box,” Meyer said. “It can’t eliminate cheatgrass all by itself. All it can do is reduce the seed bank.”

Enter the bleach blonde syndrome, caused by another fungal pathogen that appears to be a factor in natural die-offs of cheatgrass stands. Bleach blonde attacks the head of cheatgrass plants, turning it a bleach blonde color, stunting its growth, making it fall over and often preventing the production of viable seed. The fallen-over plants form a litter on the ground that when wet stimulates another fungus that kills germinating seeds.

Meyer believes that further study may show that using black fingers of death in combination with bleach blonde syndrome may be the ticket, allowing for attacks not just on dormant seeds, but germinating ones as well.

“Were trying to find out if we can make it happen, create die-offs,” she said. “If you could just manipulate the environment and wake up the pathogens that are there and cause die-offs, you could seed [native perennials] into that.”

Other promising research is being conducted by scientists with the federal Agricultural Research Service in Pullman, Washington. There, soil scientist Ann Kennedy has found that a strain of soil bacteria can stunt the growth of cheatgrass and cut seed production — enough to give natives a competitive shot.

Meyer believes that with continued research “we can develop the scientific knowledge and technology to restore the Great Basin.” But, she adds, “it would be a major investment to do it on any scale.”

And she has her doubts whether taxpayers would want to make the investment. “I’m not sure society is ready to invest in ugly,” Meyer said. “When people drive from Salt Lake City to San Francisco they just endure the Great Basin. They think it’s nothing. As climate change worsens, we’ll probably be more worried about how to keep growing corn in the Midwest.”