Strangers in the Rangeland
A field biologist battles back-country plant invaders
Gilbert Gale ’69 was “pretty much bored to death” studying agricultural economics at the University of California, Davis, when someone told him that U.S. Forest Service (USFS) workers get paid to ride horses. “’You’ve got to be kidding,’” he recalls saying. But the tip was true, and the idea of swinging into a saddle and working outdoors every day lured Gale to work on the Western range.
These days Gale still keeps his own horses, mainly so his daughters can learn to ride, but he does a lot more hiking in his field work: directing the rangelands and invasive-plants program in the Bitterroot National Forest for the USFS. Often called one of the world’s last great places, this southwestern Montana forest includes two mountain ranges: the rock-ribbed Sapphires and the jagged-peaked Bitterroot expanse that divides Montana from Idaho. The lakes and streams teem with trout. Wildflowers bloom in late July above 10,000 feet. Elk, deer, bighorn sheep, black bears, grizzlies, moose, wolves, and mountain lions roam across 1.6 million acres, half of which is designated wilderness: roadless, primeval, and off-limits to motorized vehicles and timber-cutting. Such areas seem little changed since the days when the Lewis and Clark expedition passed through the nearby Bitterroot Valley. “You have these long views,” Gale says. “You can see for a hundred miles.”
For 15 years Gale lived in Wisdom, Montana, in the Big Hole Valley where, at 6,000 feet, it can snow in almost any month of the year and summer is a fleeting phenomenon. Now he and his wife, Debra, also a USFS forester, live near the Bitterroot Forest along with two horses, two dogs, two cats, two rabbits—and the two girls, ages six and nine (“one of them a budding ecologist”).
Gale’s job, like that of the USFS generally, is not to manage fish or game directly, but to govern the habitats where plants and animals live. National forests like the Bitterroot may appear to the untrained eye to be pristine sanctuaries, but in fact they are threatened by radical changes that could ruin the sustainability of native plant and animal communities and associations: the wildflowers, the trout, and the big-game animals that live there. It is not the hand of man that directly threatens this destruction, but those most quiet and apparently unobtrusive human co-conspirators, invasive species from the plant and animal kingdoms.
Plant invaders—foreign species that escape into an environment where they have neither natural predators nor pathogens to keep them in check—can rapidly displace native vegetation. They have made stunning advances across the West in recent years. Gale’s work to control them may partly explain why, during his time in Montana, his perceptions of the area have changed. The land “doesn’t seem as vast, or imposing, or as wild as when I got here,” he says. The plant invasions caused, often unwittingly, by humans may have contributed to “this awareness that, three or four drainages over, there is a town or a highway.”
Gale speaks slowly, even with a faint drawl. No one would guess that, until the first grade, he lived in the Bronx about eight blocks from Yankee Stadium. “I wasn’t a complete urban rube,” he explains. Later, living in New England, “I’d ridden horses a little bit and been exposed to the outdoors.” At Harvard, he concentrated in social relations, but afterwards didn’t know what direction to take. The prospect of work with the Agency for International Development appealed to him then, though he now says, “If I had understood more about natural resource areas, I would have gone into that right away.” He tells his daughters: “You need to find something that you like, that inspires you, and you have to be able to do high-quality work.”
Gale’s own job has two parts. About a third of his work involves managing the rangelands within the forest, where ranchers can graze their livestock for a fee. Because the cows compete for food with wild animals such as elk, he weighs “forage availability, type, quantity and location, as well as erosion potential, and the needs of communities of vegetation” in formulating a management plan. A program Gale runs aims to mitigate the impact of the roughly 1,500 cows on the ground by encouraging ranchers to adopt techniques that minimize effects on soil, water, vegetation, and wildlife. Resistance to best practices “can run the gamut from mild to intense,” he says. Though he’s had run-ins with rifle-toting ranchers in other national forests, up in Montana, “Things are more verbal than physical.”
His primary concern remains the impact of invasive plant species on both grazing lands and wilderness areas. One species that now dominates millions of acres in the West illustrates the surprising ways in which a small plant can alter the landscape.
Spotted knapweed entered North America from eastern Europe around 1900 as a contaminant in crop seed. Once established, populations of this thistle-like plant explode. “It puts out what’s called an allelopathic agent,” explains Gale, “a chemical compound exuded from the roots” that interferes with the growth of any other plant nearby. Knapweed prefers hot, dry, relatively open habitats, and drought-prone, xeric-type soils—“Just the sort of ground that supports our grasslands in this part of the West,” he notes. “You know the story of the tall grass prairie with rich, dark soil many feet deep turning under the plow,” says Gale. “That is the accumulation of eons.” Knapweed, a lanky plant that doesn’t produce much in the way of “litter” (organic matter), won’t make that kind of soil.
When knapweed takes over an area, the ground is laid bare; exposed to the elements, soils erode and native plants die away. And because knapweed has a taproot, rather than the fibrous network of roots characteristic of a grass, there is nothing to hold together the loose, coarse-grained, granitic soils common to the area. “Put a high-intensity thunderstorm over that,” says Gale, “and you are going to get a lot of sediment moving downhill pretty fast.”
Without the thick grass mats to “intercept the force of the rain” coming down the region’s steep mountainous slopes, triple the amount of soil washes into nearby streams. This not only degrades the quality of surface water that in some areas is used for drinking, it also threatens the spawning habitat of trout, the dominant fish in mountain streams. Trout lay their eggs in gravel streambeds, but sediments fill the spaces between the pebbles where the eggs would normally lie, in some cases wiping out the fish altogether.
Knapweed also facilitates a 50 to 90 percent loss of certain key soil nutrients that native plants need. Some are taken up by knapweed itself, while knapweed-induced erosion takes the very soil, and the nutrients with it. “It’s a one-two punch,” says Gale. The loss of prairie grass affects animals and insects alike. In some cases, host-specific bugs have co-evolved with the native plants and can’t survive without them. Herds of wild animals rely on native grasses, which hold their forage value into winter. Knapweed, on the other hand, “has a very poor forage quality,” particularly later in the season when the plant is coarse and stemmy. Cattle won’t eat it.
Another destructive invader uses fire to establish vast monocultures. Cheatgrass, native to Eurasia, dries early in the summer, advancing the seasonal fire cycle in parts of the West. Unlike native grasses, cheatgrass also seeds early. Thus, if fires do come, native plants burn before their seed has matured, leaving only cheatgrass to revegetate the freshly fertilized ground.
These and other invasives are so well established that they’ll never be eradicated entirely, Gale says: their seeds can remain viable in the soil for a decade or more. Instead, “the objective is to minimize their presence on the landscape in order to prevent further erosion of native plant communities and native plant genetic diversity.” In the growing season, Gale directs eradication expeditions into the forest. Access is not always easy. “It’s a six-day hitch into the Frank Church” wilderness, he notes, and requires the coordinated efforts of boats, to ferry in supplies via the Salmon River, and pack animals, to transport water to treatment sites that crown steep slopes rising up 2,000 feet from the river’s edge in less than a mile.
The work may seem Sisyphean, but prescribed burns, herbicide applications, reseeding with certain native plants that hold their own against invasives, and releases of biological controls (generally root- and seed-feeding insects) have all proven effective. Though not without controversy, the last strategy offers the most promising long-term hope for restoring balance to disrupted ecosystems, Gale believes. In its native Romania, for example, knapweed is scarce. “The plant evolved with other, equally competitive plant species as well as predators and pathogens that hold it in check and keep it from taking too big a slice of the habitat pie,” he explains. In the Bitterroot Valley, he adds, knapweed has virtually disappeared in areas treated with a quartet of biocontrols: two gallflies, a root moth, and “a root-mining weevil with a snout like Jimmy Durante” (see opposite).
Though they have been carefully tested in European laboratories for years before being approved for use in the United States, such biocontrols have some critics worried that they might jump to feed on another species. The risk is small, Gale emphasizes. For him, what tips the scale in favor of controlling invaders is not only what he has learned on the ground, but also a more subtle concern related to genetic diversity. “There have been lots of examples of climate change in the geologic history of the earth,” he notes. “Ecosystems have the highest resilience to change when they have the largest gene pool available to respond.” Biotic invasions have the opposite effect; they tend to homogenize life and shrink the gene pool. “Humans triggered this pauperization,” he notes. Faced with large-scale disturbances to life on the planet, such as those caused by climate change, “Do we just say, ‘Okay, we started this chain of events but we’re not going to worry about it?’ Is that the responsible course to take? I don’t think so.”
Other opponents object to any human intervention in wilderness areas on philosophical grounds, preferring to let nature take its course: survival of the fittest. But Gale disagrees with this tack as well. “It is true that plant and animal invasions are a natural process and that they have always occurred as long as there has been life on this planet,” he says. “But the current rate and intensity of biotic invasions is strictly human-caused. There is no comparison between natural rates of invasion and current rates of invasion. Some people don’t understand what we stand to lose by doing nothing.”
In the West, plant invaders have become a potent issue that people respond to, Gale says. “I tell people, ‘You can make a significant contribution by training yourself to recognize plants and doing something about it on your own piece of ground. If you don’t do something about it, you can become the infection source for all your neighbors and the ground around you.’” The solution is not high-tech, he says. “The solution is involvement.”