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n forestry, herbicides serve two purposes. One involves the control of invasive plants like Scotch broom and Himalayan blackberry that can quickly replace native plant species. Even herbicide skeptics accept this targeted use. The other, far more widely used purpose is to eliminate any vegetation that, post-clearcut, might compete with replanted conifer seedlings. Here begins the polemic of herbicide use in Oregon’s forests. Some of the most popular herbicides used on Oregon’s forests include familiar names and usual suspects. Glyphosate, the active ingredient in Roundup, is considered a “probable” carcinogen by the International Agency for Research on Cancer. Another standard forestry herbicide, atrazine, is banned in the European Union. The herbicide 2,4-D is listed as a “possible” carcinogen by the IARC, and was one of two key components in Agent Orange—the other component, 2,4,5-T, triggered enough controversy in Oregon’s woods in the 1970s that it isn’t used here anymore. Because the state’s arid east side doesn’t grow a raucous understory of plants, herbicide use affects forests in Western Oregon. The total amount used each year remains unknown
because spray application records are not routinely reported to any governmental agency. But a study by Oregon State University researchers found that chemical applications cover “potentially 1 million acres of Oregon forest land annually, with the vast majority of these herbicides being applied to harvested units.” How herbicides are applied, or not applied at all, matters. Controlling competitive vegetation is only necessary after replanting a clearcut, a disturbance that opens the land up to the plants, including invasives, that emerge to re-establish the natural order. Spraying herbicides is the norm across most of Western Oregon’s industrial and state-owned timberlands, which account for nearly three-quarters of the timber harvest here, and where clearcutting remains king. A dose—or two, or three, or maybe four—of herbicides arrests competition in the first few years of post-clearcut regeneration. Ground-based applications, often with backpack sprayers, offer a somewhat precise method for applying herbicides. But on rugged terrain, all too common in Western Oregon, aerial spraying takes over. Like a crop duster, a plane or helicopter covers the clearcut, leaving wind drift as a serious, contentious issue because the toxic spray can travel far from its intended target, into waterways and onto communities. In 2017, Lincoln County voted to ban aerial herbicide spraying, the first county in the nation to do so. But a judge overturned the ban because Oregon state law preempts county rules on pesticide use. Competitive vegetation and invasives can be controlled without herbicides—mechanically, with chainsaws and bulldozers—but this requires extra time, labor and expense. The Forest Service and the Bureau of Land Management prove it’s possible, but they don’t manage their lands exclusively for timber, and they don’t clearcut in Western Oregon anymore. Heavy logging and spraying led to a federal court injunction in 1984 that prohibits those agencies from using herbicides, with exceptions for invasives. Jim Furnish, who served as the Siuslaw National Forest supervisor in the 1990s and later as deputy chief of the Forest Service, admitted that herbicide-free forestry wasn’t easy. “It was more costly, more labor intensive,” he once told a reporter. “But forestry in Oregon is profitable under many different scenarios. The Forest Service just saddled itself to a different horse and rode off into the future.”
W Tall grass cloaks a determined young Sitka spruce.
62 1859 OREGON’S MAGAZINE JANUARY | FEBRUARY 2025
hen droplets of herbicide hit the earth, certain, or all, plants soon die. With them goes biodiversity, the backbone of a healthy forest. Like a symphony, biodiversity relies on a wide range of contributors. The variety of early-successional plants that sprout after a disturbance, like wildfire or a clearcut, work hard to renew life below and above ground, offering habitat to the many species of fauna that make a forest ecosystem complete.
