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ACTION ALERT: Urge Mendocino National Forest to Say No to Toxic Herbicides

Updated: Oct 19, 2023

Mendocino National Forest.
Mendocino National Forest. Photo by U.S. Forest Service (Public Domain).

Take action! The U.S. Forest Service is proposing a project to reduce the extent and spread of invasive plants across the Mendocino National Forest that includes the application of toxic herbicides. There are approximately 1,900 known infestations of invasives on about 10,600 acres of the forest, the majority of which were likely spread by fire suppression efforts and other ground-disturbing activities during and following recent wildfires.

Methods proposed by the Mendocino Invasive Plant Treatment (IPT) Project include manual and mechanical removal, biological control, prescribed fire, and grazing, as well as herbicides.The proposed inclusion of numerous non-toxic alternative treatments to herbicides is encouraging, but the proposed application of toxic chemicals (including aminopyralid, chlorsulfuron, fluazifop, glyphosate, imazapyr, and triclopyr) on up to 200 acres of forest annually is concerning.

Removing invasive plants is a crucial part of conserving the health of our native ecosystems because non-native, invasive species aggressively displace and outcompete native species that provide us with countless ecosystem services and contribute to the balance of our natural ecosystems. The methods we choose to treat invasive species, however, are equally important as the efforts themselves.

Herbicides are well-known to be dangerous for human health, wildlife, and the environment. Even when herbicides are carefully applied, the potential remains for harm to native species through off-target drift, surface runoff, and/or leaching. Spraying herbicides around planted trees is unnecessary for sapling survival. As for treating invasive plant species, non-toxic alternatives must be prioritized.

Herbicide spraying.
Herbicide spraying. Photo by U.S. Forest Service (Public Domain).

Disregarding large-scale and long-term ecological impacts, environmental analysis for this type of project often justify herbicide use with reasons including reduced cost, seedling survival (due to less competition), faster tree growth, reduced longevity of treatment, and decreased applicability of prescribed fire without the prior use of herbicides. They fail, however, to adequately consider the benefits that are achieved through the use of non-toxic alternatives to herbicides. Around the world, forest managers have recently started to realize and embrace that herbicide use does more harm than good for our forests and watersheds, and therefore implement non-toxic alternatives such as biological controls and manual and mechanical removal.

Scotch broom, non-native and invasive in Northwest California.
Scotch broom (Cytisus scoparius), non-native and invasive in Northwest California. Photo by National Park Service (Public Domain).

Biological controls include three insects that attack non-native, invasive brooms (Cytisus spp., Genista spp., Spartium spp.) — the Scotch broom seed beetle (Bruchidius villosus), the Scotch broom seed weevil (Apion fuscirostre), and the Scotch broom twig miner moth (Leucoptera spartifoliella). Salal (Gaultheria shallon) and other plants in the Ericaceae family, as well as native perennial grasses, have also been reported to retard broom regeneration.Incorporating native plants and grasses to shade and out-compete invasive species may help to diminish and control the invaders long-term and would relieve maintenance needs. Non-toxic biopesticides derived from natural materials, such as vinegar, soap and sodium chloride (salt) and Pyrethrum, have additionally been used successfully to treat invasive plants.

2018 vs 2022, before and after manually removing roadside Scotch broom in Shasta-Trinity National Forest.
2018 vs 2022, before and after manually removing roadside Scotch broom in Shasta-Trinity National Forest. Photo by EPIC.

Manual and mechanical treatments include hand-pulling, mulching, tarping, burning, and cutting invasive plants and allowing them to dry on site, followed by burning. Scotch broom may be trimmed back by tractor-mounted mowers on even ground or by scythes on rough or stony ground. With all methods, timing is important, so it is imperative that project managers analyze the life cycles of target species and determine the best time of year to treat them. Manual and mechanical treatments have been shown to be as equally and perhaps more effective and safer than toxic chemical applications. For instance, EPIC has volunteered for seven years on the Shasta-Trinity National Forest to pull Scotch broom. After the first year, only tiny seedlings came back that were easy to hand pull or remove with a hoe. So far, manual removal has been more effective than the herbicide use.

Salal (Gaultheria shallon), a native plant in Northwest California.
Salal (Gaultheria shallon), a native plant in Northwest California. Photo by National Park Service (Public Domain).

GGiven the large scale of the invasive plant infestations in Mendocino National Forest, we also suggest that project planners consider using the Bradley Method, which consists of weeding small areas in a specific sequence, starting with the best stands of native vegetation (those with the least extent of invasive plant infestation) and working towards the stands with the worst invasive plant infestations. As the native plant populations stabilize in each cleared area, work deeper into the center of the densest invasive plant patches. This method has great promise on nature reserves with sensitive plant populations and low budgets.

No single control method is proven to be optimal for all situations, and successful, affordable long-term control may best be achieved by combining approaches. Whether you pull, cut, burn, etc., persistence and perseverance will be required to prevent new seed production and exhaust the seed banks in areas infested with broom and other invasive plants.

We strongly urge the U.S. Forest Service to implement an Integrated Pest Management Plan that utilizes a variety of non-toxic alternatives to treat the invasive plant infestations in Mendocino National Forest, and abstain from the use of toxic herbicides that have long-term, widespread, adverse environmental and human health effects. Please click here to take action!


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