California Native Plant Society

Forestry Program

Herbicide Use on National Forest Lands in California

Herbicides are used in silvicultural practices on federal forest lands in California, including national forests, as well as on private forest lands, primarily to remove vegetation that competes with the growth of commercially valuable timber. Statewide, 264,539 pounds of pesticides were applied to the forests of the state in 2002—an astonishing quantity of chemicals that are essentially unregulated and unmonitored as to their effects on native plants and wildlife.

Under the implementing regulations of the National Forest Management Act, the Forest Service must restock timberlands that have been clearcut or logged after wildfire (termed salvage logging), by replanting within five years after harvest. Planted units, known as plantations, are managed by the silvicultural division of each forest and ranger district. The mission to grow trees as quickly as possible has led to a reliance on the use of chemicals to remove competing vegetation that grows up quickly after wildfire or clearcutting, including native vegetation.

Many native plant species are fire dependent, and require multiple years of vigorous growth after wildfire in order to replenish seed banks that may lay dormant for hundreds of years, awaiting the next stand replacing wildfire. The vigorous young growth of many native shrubs produce nutritious food, shelter, and nesting materials for neotropical migratory bird species, for small mammals, and for deer and bear. Many of our native wildflowers appear and bloom prolifically after fire, producing abundant food in the form of seeds, pollen, and nectar for a variety of small animals and insects. Thus, the use of chemicals to enhance tree farm-type management of national forest lands is a practice that does not mesh well with a commitment to ecology-based management of national forest lands.

In 1984, in response to several court rulings, the USFS in California placed a moratorium on the use of herbicides for forestry application in the state. After the development of a new analysis (Region 5 Final Environmental Impact Statement for Vegetation Management for Reforestation, USDA Forest Service, 1988) the moratorium was lifted in 1988, and herbicide use resumed in 1992. The most hazardous of chemicals, such as atrazine and 2,4-D, used prior to 1984 were essentially dropped, although the USFS did not completely ban their use.

Over the last two years, on average the USFS has applied pesticides to 24,050 national forest acres in California per year; the majority of these applications were herbicides. In 2003, the USFS reported using 41,076 pounds of herbicides (active ingredient) on national forests in the state (link “USFS reported” to PUR R5 2003.pdf). Only 181 pounds, or less than 1% of this total was used for “noxious weed” control—the rest was used for "conifer release," forestry jargon for killing the native species that normally grow along with the commercial trees.

Of the 18 national forests in California, several do not use any herbicides at all, and most use very little. The Shasta-Trinity, Six Rivers, Modoc, and Plumas National Forests produce large amounts of timber for the agency but use no herbicides in their silviculture programs. These forests have demonstrated that trees can be grown perfectly well without the use of toxic chemicals. In contrast, the Stanislaus National Forest led the way with use of over 25,277 pounds of herbicides in 2003. Today the Stanislaus National Forest is proposing an aerial spraying project close to Yosemite National Park that will kill thousands of acres of beautiful and diverse native black oak and other hardwood and understory species.

Out of the 108 different herbicide products registered for forestry use in California, the USFS uses primarily four: glyphosate, hexazinone, triclopyr, and clopyralid. While glyphosate is widely considered to be one of the most environmentally benign of the herbicides used today, it is mixed with surfactants known to adversely impact amphibians and other aquatic organisms. The volume of its use globally is also considered by many to contribute to cumulative impacts of concern for human health and for wildlife. Aerial applications of herbicides over many thousands of acres is of particular concern to CNPS due to the broad destruction of all native plant species that occur in the targeted area.

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