Fire Regimes
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This study estimates how fire regimes have changed in the major Great Basin vegetation types over the past 60 years with comparisons to historical (pre-1900) fire regimes. We explore potential drivers of fire regime changes using existing spatial data and analysis. Across vegetation types, wildfires were larger and more frequent in the contemporary period (1991–2020) than in the recent past (1961–1990). Contemporary fires were more frequent than historical in two of three ecoregions for the most widespread vegetation type, basin and Wyoming big sagebrush. Increases in fire frequency also occurred in saltbush, greasewood, and blackbrush shrublands, although current fire return intervals remain on the order of centuries. Persistent juniper and pinyon pine woodlands burned more frequently in contemporary times than in historical times. Fire frequency was relatively unchanged in mixed dwarf sagebrush shrublands, suggesting they remain fuel-limited. Results suggest that quaking aspen woodlands may be burning less frequently now than historically, but more frequently in the contemporary period than in the recent past. We found that increased fire occurrence in the Great Basin is associated with increased abundance and extent of nonnative annual grasses and areas with high concentrations of anthropogenic ignitions. Findings support the need for continuing efforts to reduce fire occurrences in Great Basin plant communities experiencing excess fire and to implement treatments in communities experiencing fire deficits. Results underscore the importance of anthropogenic ignitions and discuss more targeted education and prevention efforts. Knowledge about signals of fire regime changes across the region can support effective deployment of resources to protect or restore plant communities and human values.
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The most destructive and deadly wildfires in US history were also fast. Using satellite data, we analyzed the daily growth rates of more than 60,000 fires from 2001 to 2020 across the contiguous US. Nearly half of the ecoregions experienced destructive fast fires that grew more than 1620 hectares in 1 day. These fires accounted for 78% of structures destroyed and 61% of suppression costs($18.9 billion). From 2001 to 2020, the average peak daily growth rate for these fires more than doubled (+249% relative to 2001) in the Western US. Nearly 3 million structures were within 4 kilometers of a fast fire during this period across the US. Given recent devastating wildfires, understanding fast fires is crucial for improving firefighting strategies and community preparedness
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February 9-13, 2025
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Fire is an integral component of many Southwest ecosystems; however, fire regimes across the region have been affected by climate change, creating conditions to which these ecosystems have not adapted. Since 1980, fire frequency, size and severity have increased in many ecosystems in the western US due to changes in climate combined with a history of fire suppression and other forest management practices, such as grazing and logging…
…The goal of this synthesis is to provide a summary of the literature, published in 2023, on fire and fire-related topics
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Climate change is altering fire regimes and post-fire conditions, contributing to relatively rapid transformation of landscapes across the western US. Studies are increasingly documenting post-fire vegetation transitions, particularly from forest to non-forest conditions or from sagebrush to invasive annual grasses. The prevalence of climate-driven, post-fire vegetation transitions is likely to increase in the future with major impacts on social–ecological systems. However, research and management communities have only recently focused attention on this emerging climate risk, and many knowledge gaps remain. We identify three key needs for advancing the management of post-fire vegetation transitions, including centering Indigenous communities in collaborative management of fire-prone ecosystems, developing decision-relevant science to inform pre-and post-fire management, and supporting adaptive management through improved monitoring and information-sharing across geographic and organizational boundaries. We highlight promising examples that are helping to transform the perception and management of post-fire vegetation transitions.
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We conducted a natural range of variation (NRV) assessment of montane conifer forests in the Transverse and Peninsular Mountain Ranges of southern California. Using current and historical literature and data, we present a quantitative analysis of forest function, structure, composition, and ecological processes prior to Euro-American settlement and compare those elements to the forests of today. We highlight how grazing, logging and fire suppression have altered natural fire regimes and examine how departure from NRV conditions may inform forest management in the era of climate change.
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Frequent and catastrophic wildfires are an increasing threat to the ecological and economic stability of Great Basin rangelands, specifically sagebrush rangelands at risk of exotic annual grass invasion (Crist et al. this issue). Historically, fires were a periodic disturbance in these communities that shifted dominance from woody vegetation to herbaceous vegetation (Wright and Bailey 1982; Miller and Rose 1999) and likely promoted diversity (Davies and Bates 2020). Alterations in fuel characteristics with exotic plant invasions and increased anthropogenic ignitions have greatly elevated the likelihood of wildfires in many of these rangelands (Balch et al. 2013; Fusco et al. 2022). However, other rangelands are experiencing decreased fire frequency, largely caused by reduced fine fuels from anthropogenic-induced alterations to plant community composition or land use. Though longer fire return intervals can also be problematic because they cause undesirable plant community compositional shifts and decreased heterogeneity in some rangelands, this special issue is focused on the problem of more frequent and catastrophic wildfires as this is a more pressing concern in terms of the rate of undesirable ecosystem change and risk to property and life.
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Increases in fire activity and changes in fire regimes have been documented in recent decades across the western United States. Climate change is expected to continue to exacerbate impacts to forested ecosystems by increasing the frequency, size, and severity of wildfires across the western United States (US). Warming temperatures and shifting precipitation patterns are altering western landscapes and making them more susceptible to high-severity fire. Increases in large patches of high-severity fire can result in significant impacts to landscape processes and ecosystem function and changes to vegetation structure and composition. In this synthesis, we examine the predicted climatic influence on fire regimes and discuss the impacts on fire severity, vegetation dynamics, and the interactions between fire, vegetation, and climate. We describe predicted changes, impacts, and risks related to fire with climate change and discuss how management options may mitigate some impacts of predicted fire severity, and moderate some impacts to forests, carbon, and vegetation changes post fire.
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Pyrodiversity may affect biodiversity by diversifying available ecological niches, stabilizing community networks and/or supporting diverse species pools available for post-fire colonization. Further, pyrodiversity’s effects on biodiversity vary across different spatial, temporal and organismal scales depending on the mobility and other life history traits of the organisms in question and
may be mediated by regional eco-evolutionary factors such as historical fire regimes. Developing a generalizable understanding of pyrodiversity effects on biodiversity has been challenging, in part because pyrodiversity can be quantified in various ways.