Mastication harms native plant and bird habitat and
increases flammable invasive plants
Written by:
Suzie Savoie
For many Applegate residents, the wildflowers, birds, butterflies, and wildlife that inhabit their land bring joy to their lives. There are many ways to reduce fuel for fire safety near homes and communities, but some fuel-reduction methods have more negative impacts on native plants and wildlife than others do. Some fuel-reduction methods can enhance native plant communities, while others can do irreparable harm, like mastication.
Masticators come in various sizes, from attachments on excavators or skid steers to smaller remote-controlled units. They drive through forests or chaparral and grind, shred, or flail trees and shrubs into mulch. The machinery doesn't remove fuels; it just reorganizes vertical fuels into horizontal fuels on the ground. Masticators save money because they can work faster than hand crews, but the impacts and results are not the same as those from hand crews on foot with chainsaws.
Mastication of forests and shrub communities with machines can be detrimental to native plant habitats, especially understory wildflowers and grasses. The tread of masticators, even with rubber tread, churns up and often compacts the soil and damages or kills plants. As the machines drive over and churn up the soil, they kill ground-nesting bees, including bumble bees, or pupae of butterflies buried under the soil surface, along with many other species that live within the soil biome.
Mastication can alter plant composition and set the stage for a conversion of native plants to nonnative plants in a way that can often never be undone, affecting many species that once relied on that habitat.
In a study titled Decade-Long Plant Community Responses to Shrubland Fuel Hazard Reduction, the authors found that “The number of non-native plants, including non-native annual grasses, was higher after mastication treatments compared to fire treatments after 10 years.” The authors of the study found that the native plant community that existed prior to mastication was damaged by the machine work and that an explosion of nonnative plants colonized the disturbed soil after mastication.
The increase of nonnative grasses, like cheatgrass, following mastication can actually counteract any gains in fire safety that might be achieved from removing trees and shrubs because nonnative annual grasses are highly flammable and are fueling fast-moving fires across the West. The study's authors explained, “Non-native annual grasses increase fuel continuity between natural areas and homes, increase how quickly fire spreads, and lengthen the fire season by drying earlier than native species. Thus, non-native annual grass invasion and persistence in chaparral is detrimental to people and biodiversity in the WUI [Wildland Urban Interface].”
The conversion of native plant communities, they argue, is actually increasing fire frequency due to highly flammable and abundant nonnative annual grasses. This is a concern across the West right now as cheatgrass and ripgut brome are spreading quickly, especially in areas that have experienced soil disturbance.
The authors also concluded that mastication increased buckbrush populations ten years after treatment compared to control areas because of the solar heat intensified by sparse shrub cover, which favors buckbrush seed germination.
Another study, Understory Vegetation Response to Mechanical Mastication and Other Fuels Treatments in a Ponderosa Pine Forest, reached similar conclusions: “Some potential drawbacks to this treatment include an increase of non-native species and stimulation of shrub seed germination, which could alter ecosystem functions and compromise fire hazard reduction in the long-term.”
Naturalists joke when you're in Nevada, “Don't look down,” because the native plants have been overrun by noxious weeds from livestock grazing, and it's best to just look up at the scenic mountains instead of looking down at unsightly weeds. Increasingly, the same can also be true in the Applegate in areas where masticators have been. You don't want to look down and see cheatgrass, medusahead, or ripgut brome where shooting stars, fawn lilies, and paintbrush once grew.
Mastication negatively affects birds, too. A study titled Chaparral Bird Community Responses to Prescribed Fire and Shrub Removal in Three Management Seasons found that although bird species diversity and abundance rebounded after one-time use of prescribed fires, most birds never returned to masticated sites. Mastication reduced the number of bird species by about 50 percent and reduced the total number of birds by about 60 percent.
Better noncommercial fuel-reduction methods exist that don't have the same negative ecological impacts. Prescribed fire and hand crews do a better job than machines.
Suzie Savoie
Photo 1: Remote-controlled masticator tread tracks damage soils and chaparral bird habitat on private land in the Little Applegate in fall 2025. All native vegetation was masticated and turned into wood chips in the bare area in the photo. Photo: Marion Hadden.
