Fact Sheet / Brief
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Land managers and fire professionals use predictions of wildfire behavior and probability to prepare for
the fire season.
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It’s no secret that wildland fires kill trees, but are more trees killed by fire when they are already stressed from drought? New research from the U.S. Department of Agriculture, Forest Service indicates that prefire drought can increase tree mortality after fire, even with the same level of tree damage.
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To understand trends in fire severity and area burned, researchers analyzed satellite images taken before and after each fire in western US forests from 1985 to 2022. They classified areas as high severity when at least 95% of the tree canopy was lost according to a satellite-derived fire severity metric called the Composite Burn Index. To understand climate’s role, they combined three key indicators during the summer fire season (vapor pressure deficit, maximum temperature, and climate water deficit) into a single metric called fire season aridity to capture how hot and dry each fire season was. This same method was used to model future fire conditions, projecting changes in total and high-severity burn areas through the mid-21st century under a 2°C warming scenario.
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Data-driven decision support can help guide sustainable grazing management by providing an accurate estimate of grazing capacity, in coproduction with managers. Here, we described the development of a decision support model to estimate grazing capacity and illustrated its application on two sites in the western United States. For the Montgomery PassWild Horse Territory in California and Nevada, the upper limit estimated in the capacity assessment was 398 horses and the current population was 654 horses. For the Eagle Creek watershed of the Apache-Sitgreaves National Forest of eastern Arizona, the lower end of capacity was estimated at 1560 cattle annually, compared to the current average of 1090 cattle annually. In addition to being spatio-temporally comprehensive, the model provides a repeatable, cost-effective, and transparent process for establishing and adjusting capacity estimates and associated grazing plans that are supported by scientific information, in order to support livestock numbers at levels that are sustainable over time, including levels that are below average forage production during drought conditions. This modeling process acts as a decision support tool because it enables different assumptions to be used and explored to accommodate multiple viewpoints during the planning process.
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Fire retardants have known toxicological outcomes on aquatic organisms when introduced into flowing freshwater systems and have been evaluated in USFS Environmental Impact Statements; however, affects on still-water aquatic environments such as ponds and wetlands are poorly understood. This fact sheet reviews the impacts of a commonly-used fire retardant on aquatic macroinvertebrates.
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To reduce the risk of wildfire, it’s important to understand where fuel treatments are most likely to succeed. Recent research by Rocky Mountain Research Station (RMRS) scientists and their collaborators provides insights for prioritizing fuel treatments in sagebrush country. The group first developed four spatial layers to characterize sagebrush and pinyon-juniper landscapes: (1) indicators of ecological resilience to disturbance and resistance to invasion, (2) sagebrush associations, (3) persistent pinyon-juniper woodlands, and (4) pinyon-juniper expansion phases. The new indicators of resilience and resistance are dynamic because they are based on climate and soil moisture availability and allow assessment of potential treatment effects in a rapidly changing environment.
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Ventenata and medusahead are winter annuals that emerge in late fall, winter, and spring. These grasses mature early in the summer providing fine fuels for wildfires.Ventenata and medusahead are frequently found together where conditions allow. These invasive annual grasses increase wildfire danger in shrublands and woodlands of the American West.
- Fine, highly flammable fuel loads facilitate larger and more frequent fires.
- Relatively high silica content make these grasses less palatable for grazing (unlike cheatgrass which is palatable in its green phase), and creates a build-up of litter on the soil surface.
- These species can spread throughout areas that once acted as natural fire breaks.
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Fire is an ecosystem process managed in the contemporary western U.S. at great expense, but with mixed results— yet it is one that can be re-worked to positive effect by melding ancient burning practices with contemporary scientific findings.
The “natural infrastructure” elements of stone and wood are components of ecosystem processes whose contemporary application, when guided by ancient practices and recent research, can mitigate some of the negative effects of contemporary fire regimes.
The following fact sheet is a summary of our 2025 working paper which considers how scientific research and creative on-the-ground applications that merge ancient and contemporary approaches and techniques can improve both pre-event resilience, and post-event recovery outcomes.
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In mountain big sagebrush associations, simulations of prescribed burn fuel treatments indicated that treatments were economically efficient in ecosystems dominated by sagebrush or in the early to mid-phases of pinyon-juniper expansion when compared to expected suppression costs. For low sagebrush, mechanical fuel treatments were not economically efficient, mainly due to higher associated costs. For black sagebrush, mechanical fuel treatments led to increased suppression costs in three of six potential treatment settings largely due to increases in surface fuels and fire behavior.
While wildfire suppression cost savings were the primary benefit, economic benefits included enhanced wildlife habitat, water availability, livestock grazing, and recreational opportunities. This research suggests that if land managers consider treatment costs along with specific sagebrush associations and their resilience and resistance levels, they can plan more effective and efficient fuel treatments.
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• Tree invasion of sagebrush habitat in southwest Montana has caused a 30% decline in the population of Brewer’s sparrows since 1954.
• If nothing is done to prevent tree encroachment, Brewer’s sparrows will decline by 60% in the next 30 years.
• Defending core sagebrush habitat through conifer removal can maintain populations of Brewer’s sparrows into the future