Between 1990 and 2000, the incidence of leafy spurge—a particularly pernicious weed that sends roots as deep as 25 feet below the surface of the earth and makes lesser weeds “look like Bambi,” in the words of one forester—increased by 433 percent in the Bitterroot National Forest.
And that’s only one weed among more than a dozen that have infested 270,000 scattered acres, or nearly 17 percent of the BNF’s 1.6 million acres, in mere decades—the blink of an eye in geologic time.
There are plenty of folks in the Bitterroot Valley with a good working knowledge of the damage weeds inflict on any environment: farmers and ranchers, of course, and more recently, local foresters, who last month issued a record of decision on a first-ever plan to contain the spread of invasive species across the BNF, eradicate them where possible, and prevent their spread into the adjacent and largely weed-free Big Hole Valley.
The nutshell version of the program, officially called the Noxious Weed Treatment Project, is a seven- to 10-year effort beginning this summer that relies on aerial and spot herbicide application in selected areas, release of “biocontrol agents” or weed-eating moths, flies and weevils—most of which are collected from native habitats in Eurasia and bred at MSU’s Western Agricultural Research Center in Corvallis—some hand-pulling and grazing, and public education.
The latter may be one of the more difficult components of the program, says Gil Gale, a Sula Ranger District-based range manager charged with carrying out the plan. Many people, particularly suburbanites, are simply unaware of the havoc weeds wreak on the highly evolved and complex forest ecosystem.
“Farmers and ranchers understand the threat,” says Gale. “But if you’re not in agriculture, weeds to a lot of people mean dandelions in your lawn.”
The spread of invasive species is actually a global problem fostered by ease of movement of people around the world. As easily and quickly as Severe Acute Respiratory Syndrome, or SARS, spread from Beijing to Toronto, so invasive species spread—often via horse traffic—from one corner of the world to other, utterly unconnected ecosystems.
Knapweed, that ubiquitous demon and scourge of the west, is a good example of global connectedness, but a better analogy might be drawn to HIV. Like the virus that causes AIDS, knapweed, too, spreads rather easily and has a long incubation period. In 1920, decades before anyone knew how threatening to agriculture and native plants knapweed would become, it was confined to Ravalli County. Twenty years later, it had infected another three or four western Montana counties. By 1980 it could be found in half the counties of the state, and a mere two years later, when a sincere and coordinated effort to contain it might have been successfully launched, it simply exploded across the Montana landscape and spread to all 56 counties.
Weeds—or invasive species, as Gale prefers—damage the environment literally from the ground up. At the soil level, they reduce vital nutrients like potassium, nitrogen and phosphorous by as much as 90 percent, thereby starving native plants of the food they need to survive and thrive. Knapweed in particular puts out a nasty toxin around its rosettes that prevents native seedlings from establishing themselves anywhere nearby. That cuts down on the organic ground litter that helps hold water in the soil. In a typical rainstorm, then, a knapweedy hillside will send two to three times the normal sediment load down the mountain and into the streams.
“You lose the native plant component,” Gale says, “and possibly some microorganisms we’re not even aware of.”
The megafauna—elk, moose, deer—tend to be displaced by weeds and go off in search of edible food, which in the Bitterroot often means some ranchers’ winter hay supply.
The entire weedification process, says Stu Lovejoy, acting Sula District Ranger, results in a significant loss of biodiversity and simplifies an inherently complex ecological process. Lovejoy also suspects that the spread of invasive species may create unknown, and unhealthy, synergistic relationships between insects and plants. “Undoubtedly,” he says, “there are some changes there we don’t have a good understanding of.”
In short, Gale and Lovejoy say, invasive species have disrupted probably 10,000 years of highly complex evolutionary relationships in the geologic equivalent of a millisecond.
Can the Bitterroot National Forest be saved from such a relentless march of weeds? Both men believe so, even if the project seems too little, too late. Of the 270,000 weed-infested acres, the BNF proposes to treat a maximum of 35,445 acres over a decade. Why so scaled-down? Gale rubs his thumb and forefinger together. In a word, money.
Still, it’s a start, and it represents the first-ever comprehensive effort by the Bitterroot National Forest to tackle a problem that, if left unchecked, could well leave the forest a monocultural wasteland, devoid of the values the present generation holds dear.
The most controversial aspect of the program is the decision to aerially spray herbicides over up to 1,000 acres in the project’s first year, as a test. Even so, the project’s draft environmental impact statement drew only 64 comments. Gale maintains that foresters are taking a “restrained approach” to herbicide spraying. “We don’t propose to go out and drench the landscape in herbicide,” he says.
Ignoring the problem is simply unacceptable in light of the threat weeds pose to a wide range of values—from economic to recreational—and particularly since U.S. Forest Service Chief Dale Bosworth recently identified weed spread as the number one threat to the national forests.
“That’s a significant change in awareness of the problem,” says Gale.
“We’re at a dynamic point,” he adds. “We’re right in the middle of an invasive process. This is not a minor irritation. This is a major threat to the ecosystem.”
If the project is carried out successfully, what will the forest look like in 100 years? Lovejoy considers the question. Knapweed will never be completely eradicated, he says, but “with biocontrol we’ll reach some level of equilibrium. But that will take decades, if not centuries.”
Gale, who last summer wrapped up a 16-year Forest Service range management stint in the Big Hole Valley, adds, “If we’re successful, we’ll have no new invasive species in major habitats. All the uninfested areas will be weed-free, and we’ll have protected the Big Hole.”