Mechanical alteration to the landscape can include mowing, weed-whacking, haying, raking and plowing. Mechanical methods, especially in grasses, can often be more effective at smaller scales and may not be very applicable to alter fire behavior in spatial scales needed to reduce landscape-scale fire. For smaller scale treatments, such as those in residential areas adjacent to grass fuels, it is recommended to maintain grasses in Zone 2 (5-30 ft from a structure) at a height of 4 inches or less, especially before and during periods of increased fire risk. For Zone 1 (0-5 ft from a structure), it is recommended to not have any grasses (see Low Flammability Landscape Plants) (Live Wildfire Ready, 2024). In Zone 3 (30-100 ft from a structure), grass should be considered ladder fuels and treated as such. Equipment such as weed whackers or mowers can be used in green vegetation but should be used with caution in dry conditions where fine fuels like grasses can easily ignite. When used in dry conditions equipment should be free from faults and mechanical defects that could cause a spark and ignite a fire (Country Fire Authority, 2023).

Mowing, raking and other methods of fuel break construction that overturn soil can create erosion and facilitate the establishment of non-native and invasive species, which can alter fire behavior (Country Fire Authority, 2023). Additionally, excessive mowing in grass-dominated landscapes is not recommended. Over-mowing can alter vegetation in the short term but can result in detrimental impacts to ecological integrity for the treatment site and can exacerbate future fire behavior by facilitating woody encroachment and the introduction of other non-native plants, potentially leading to increased fire intensity and behavior (C. Julian, personal communication, May 30, 2024).

It is essential to develop strategies that are adapted to local growing conditions, as factors such as timing, frequency and other conditions may vary across landscapes. For example, regions characterized by tall-grasses may find it beneficial to remove cut or mowed grasses after treatment to mitigate vegetative fuel accumulation on treatment sites, whereas regions with mixed- or short-grass may not have the same necessity. As a result, a thorough understanding of local site conditions is critical for devising effective strategies.

Herbicides can be used to complement vegetative fuel treatments in wildfire-prone areas. Herbicide treatment can target specific vegetation types, like non-native species, which contribute to vegetative fuel loads while ideally minimizing impact on non-target species, which can help to effectively reduce fuel continuity and decrease the intensity and spread of wildfires.

When combined with mechanical treatments or prescribed burns, herbicide use can assist in achieving more effective fuel reduction treatments. They can be used initially to reduce vegetation density and are then followed by mechanical treatments to further modify fuel characteristics and structure. Herbicide can be an option in areas where prescribed burning or mechanical treatments are difficult or unlikely, and can offer an alternative approach to managing vegetation fuels that address both immediate and long-term wildfire risk.

For further insights into effective application methods, potential environmental impacts, and strategies for integrating herbicide use into comprehensive fuels treatments, consider consulting with local land management agencies and conservation districts to provide specific guidelines and best practices.

Grass-dominated landscapes have historically been influenced by grazing and have played a key role in their evolutionary history (Blair et al., 2014). However, human activities in North America have greatly increased livestock herbivore dominance and nearly eliminated the role of fire. These disruptions include the decline of wild herbivores, livestock expansion and altered fire regimes. These human-driven changes have resulted in major ecological impacts, threatening biodiversity in these landscapes as both fire and herbivores have historically shaped ecological niches (Wendt et al., 2023). These factors, along with a changing climate and alterations in land use, further complicate landscape responses to large herbivores that have historically grazed these landscapes (Engle et al., 2001).

In rangelands, fire behavior can vary based on factors such as grazing history, weather patterns, fire frequency, topography, vegetative composition, and soil conditions (Engle et al., 2001). Wildfire can pose risks to livestock and also disrupt management practices by consuming forage and damaging structures (Middlemis-Brown, 2015). Conversely, grazing can decrease the overall flame length through reducing fuel loads and height through consuming and trampling vegetation. Wild or feral grazers can contribute to the reduction of grass fuel loads; however, effective mitigation requires intentional management of grazing areas at adequate stocking rates to strategically reduce fuels (Trauernicht et al, 2021).

Treatments that involve grazing can effectively reduce fuel loads and continuity while altering the structure of vegetative fuels (Blair et al., 2014). However, trade-offs can exist between fire risk reduction and long-term forage quality and production. Grazing can effectively reduce fire risk, but if not managed properly, overgrazing may lead to increased erosion and contribute to the conversion of woody vegetation over the long-term. This can result not only in increased fire behavior but can also prohibit future grazing due to unpalatable vegetation. Similar outcomes can occur with overuse of mechanical methods (Trauernicht et al, 2021).

While herbivore grazing can help support grass-dominated landscapes conducive to low-intensity fires and reduce fire frequency (even light grazing and browsing can mitigate fire intensity) intensive grazing may have the opposite effect by diminishing grassy vegetation cover and promoting the growth of highly combustible woody vegetation. In some instances, grazing management practices have been linked to an increase in fire ignitions and frequency. However, there are also circumstances in which grazing only reduces fire frequency under certain conditions, such as specific times of the year, under specific management practices or specific vegetation types. In other instances, grazing leads to more frequent but lower-intensity fires, thereby decreasing the likelihood of extreme wildfires. Ultimately, the effectiveness of herbivores in reducing fire frequency is influenced by factors such as the season, grazing intensity and landscape type (Rouet-Leduc et al., 2021).

In a 2021 review of 74 studies on the impacts of grazing on wildfire, 21 studies specifically examined the effects of herbivores on fire frequency. Thirteen of these studies found that grazing reduces wildfire frequency. The remaining studies indicated that grazing only reduces fire frequency under certain conditions, such as specific times of the year or different vegetation types. In some instances, the presence of herbivores leads to more frequent but lower-intensity fires, thereby decreasing the likelihood of extreme wildfires (Rouet-Leduc et al. 2021). The effectiveness of grazing in reducing fire frequency is influenced by factors such as the season, grazing intensity and landscape type. For effective land management, it is crucial to understand the conditions in which grazing supports the preservation of grass-dominated landscapes that facilitate low-intensity fires and reduce fire frequency. Conversely, recognizing situations where intensive grazing reduces grassy vegetation cover and promotes the proliferation of woody vegetation is equally important. Achieving this understanding may require local knowledge and experimental approaches (Rouet-Leduc et al., 2021). Reduced grazing and fire suppression in rangelands adjacent to urban and WUI areas may have extended fire regime intervals in these regions, leading to an increase of less palatable woody vegetation, which is considered one of the largest threats to rangelands, and can result in increased fire behavior (Fogarty et al, 2023; Scasta, 2019). These changes, particularly in low to mid elevations, can result in more frequent and larger wildfires (Texas A&M, accessed 2023). In these circumstances, emerging technologies, such as virtual fencing, can offer additional solutions for grazing fences and enhance the effectiveness of certain treatments in areas where prescribed fire may not be an option, with the goal of improving the overall resilience to disturbances of rangelands, especially in areas where impacts from altered fire regimes and land conversion may increase the amount and continuity of fine fuels like grasses (Middlemiss-Brown, 2015; Schachtschneider, 2016; Trauernicht et al., 2021).

Prescribed fire can be a relatively low-cost and effective management method used to reduce fuels at scale and wildfire risk, while potentially supporting other management goals, including the restoration of keystone ecological processes, where frequent low intensity prescribed fires may be a key piece to restoring and maintaining certain landscapes (Donovan et al., 2023; Addington et al., 2020; Vogl, 1979). Fire plays a critical role in grass-dominated landscapes and while management practices, including mechanical, grazing and herbicides, can yield comparable outcomes, they do not substitute for the unique ecological functions of fire (Ellensworth et al., 2022; Vermeire et al., 2020). However, despite the many benefits, prescribed fire is often challenging to implement due to a host of factors, including high-risk fuel loads, proximity to HVRAs (such as homes, utilities and other assets), susceptibility to weather conditions, smoke management and air quality regulations, agency resource capacity and public perception (Ellensworth et al., 2022).

Prescribed fire, also referred to as burning, can be a beneficial tool for rangeland management, offering ecological and economic advantages that can lead to more effective outcomes. Burning has been shown to improve livestock performance, forage quality and palatability. Studies show that burning also provides benefits to wildlife habitat without adversely impacting livestock (Weir et al., 2009). Additionally, because grazers (both domestic and wild) are drawn to the fresh growth that emerges after a fire, this technique can help to move grazers from one area to another, which can reduce the need for fencing (The Nature Conservancy, accessed 2023).

Fire-adapted landscapes rely on fire to maintain their functionality and biodiversity. Fire is essential for the health and sustainability of grass-dominated landscapes, which host native plants and animals that depend on periodic fires for survival. Since European settlement, fire suppression in North American grasslands has led to ecological and economic degradation (The Nature Conservancy, 2022). Many landscapes across North America, particularly in the western continental U.S., have historically been influenced by natural fires, including those ignited by lightning, and human-introduced fires used for purposes like land clearing and fuels reduction.

Increasing human development has resulted in the need for fire suppression in many of these regions. Estimates suggest that in the conterminous US, burning in the late 20th-century was 7-12 times less prevalent than during pre-industrial times. The consequence of these suppressed and altered fire regimes have led to a reduction or loss of ecosystem services and drastically altered fuels and potential future fire behavior. Without the disturbance of periodic fire, woody plant density increases and landscape structure becomes more homogeneous (Ryan et al., 2013). In almost all regions of North America, the application of fire falls short of its historical prevalence and has not kept pace with historical levels. The combined effects of fire suppression and reduced prescribed burning have significantly altered fire regimes across much of North America. This shift led to a marked decline in fire occurrence in the western U.S., where the total area burned decreased sharply, often due to fire suppression efforts. Consequently, the area being burned today across much of North America is significantly less than what burned historically (USDA, 2023). To preserve these landscapes, the US Forest Service and other agencies and organizations have developed prescribed fire programs. As part of the Wildfire Crisis Strategy, the US Forest Service has identified landscapes that urgently need work to mitigate wildfire risks, in which a major component of this strategy is the reduction of hazardous fuels, with prescribed fire playing a key role in this effort. These programs introduce fire under controlled conditions to achieve specific management objectives (USDA, 2023).

Agricultural land encompasses croplands, rangelands, pastures and other lands used for crop or livestock production. Historically, fire has been an essential tool in agricultural management, a practice that continues in modern agriculture where burning remains a cost-effective method for managing crop residue. Agricultural burning can include practices such as rangeland and crop residue burning, land clearance and ditch lines (USDA, 2023; AAQTF,1999).

Common reasons for burning include reducing pre- and post-harvest vegetation that interferes with harvest, tillage and seedbed preparation, or for pest and weed control, which subsequently reduces the need for herbicides and pesticides. Additionally, certain crops require burning to stimulate growth and increase yield, burning supports nutrient cycling and soil health. Periodic burning is also utilized to reduce fire hazards and for clearing irrigation canals for maintenance of water conveyance structures related to agricultural operations and can be a cost-effective method for managing agricultural lands (USDA, 2023; AAQTF,1999).

For more information on agricultural burning in Colorado, see the Code of Colorado Regulations https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=1085

Irrigation ditches can contribute to fire spread due to the abundance of vegetative fuels. Ditches that are dry or inadequately maintained can act as pathways for fire spread, especially when there is an accumulation of woody fuels. Under certain wind and topographical conditions, these features can facilitate the movement of fire along corridors, potentially extending into nearby communities. Risks can be compounded by ember production from woody fuels in the ditch and the connectivity of available fuels. Conversely, ditches that are well-maintained or adequately hydrated can act as effective barriers, preventing the spread of fire (Scasta et al., 2019).

Ditch management can include mowing, dredging, herbicide use and burning (Scasta et al., 2019). Treatments that employ mowing or herbicide only reduce risk if accumulated vegetation is removed, and dredging physically impacts the soil which can increase the risk of erosion, a concern in ditch management. The practice of burning ditches presents both advantages and disadvantages. It effectively reduces fuel loads and can improve water management efficiency by removing vegetation that accumulates along ditches, drains and fence lines. While burning can be more efficient and cost-effective for vegetation removal compared to alternative methods, it can also negatively impact water quality, biodiversity, and soil health (US Dept. of Interior, 2017). Therefore, identifying risks and hazards, potential outcomes, goals and objectives, and other considerations in advance can help to guide the most effective treatment.

In Colorado, ditches are generally owned and maintain by private companies. Contact a local company regarding vegetation management in irrigation ditches.

For more information on agricultural burning in Colorado, see the Code of Colorado Regulations: https://extension.colostate.edu/topic-areas/natural-resources/irrigation-ditches-and-their-operation-6-701/