Evidence for widespread changes in the structure, composition, and fire regimes of western North American forests

Ecological Applications, Journal Year: 2021, Volume and Issue: 31(8)

Published: Aug. 2, 2021

Implementation of wildfire- and climate-adaptation strategies in seasonally dry forests western North America is impeded by numerous constraints uncertainties. After more than a century resource land use change, some question the need for proactive management, particularly given novel social, ecological, climatic conditions. To address this question, we first provide framework assessing changes landscape conditions fire regimes. Using framework, then evaluate evidence change contemporary relative to those maintained active regimes, i.e., uninterrupted or human-induced exclusion. The cumulative results research document persistent substantial deficit widespread alterations ecological structures functions. These are not necessarily apparent at all spatial scales dimensions regimes forest nonforest Nonetheless, loss once abundant influence low- moderate-severity fires suggests that even least fire-prone ecosystems may be affected alteration surrounding and, consequently, ecosystem Vegetation patterns fire-excluded forested landscapes no longer reflect heterogeneity interacting Live dead vegetation (surface canopy fuels) generally continuous before European colonization. As result, current vulnerable direct indirect effects seasonal episodic increases drought fire, especially under rapidly warming climate. Long-term exclusion contemporaneous social-ecological influences continue extensively modify landscapes. Management realigns adapts can moderate transitions as human communities adapt changing disturbance adaptation developed, evaluated, implemented, objective scientific evaluation ongoing monitoring aid differentiation warranted unwarranted

Language: Английский

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Adapting western North American forests to climate change and wildfires: 10 common questions

Ecological Applications, Journal Year: 2021, Volume and Issue: 31(8)

Published: Aug. 2, 2021

We review science-based adaptation strategies for western North American (wNA) forests that include restoring active fire regimes and fostering resilient structure composition of forested landscapes. As part the review, we address common questions associated with climate realignment treatments run counter to a broad consensus in literature. These following: (1) Are effects exclusion overstated? If so, are unwarranted even counterproductive? (2) Is forest thinning alone sufficient mitigate wildfire hazard? (3) Can prescribed burning solve problem? (4) Should management, including thinning, be concentrated wildland urban interface (WUI)? (5) wildfires on their own do work fuel treatments? (6) primary objective reduction assist future firefighting response containment? (7) Do under extreme weather? (8) scale problem too great? ever catch up? (9) Will planting more trees change wNA forests? And (10) is post-fire management needed or ecologically justified? Based our scientific evidence, range proactive actions justified necessary keep pace changing climatic declining heterogeneity after severe wildfires. Science-based options use managed wildfire, burning, coupled mechanical as consistent land allocations conditions. Although some current models averse short-term risks uncertainties, long-term environmental, social, cultural consequences primarily grounded suppression well documented, highlighting an urgency invest intentional restoration regimes.

Language: Английский

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Projected increases in western US forest fire despite growing fuel constraints

Communications Earth & Environment, Journal Year: 2021, Volume and Issue: 2(1)

Published: Nov. 2, 2021

Escalating burned area in western US forests punctuated by the 2020 fire season has heightened need to explore near-term macroscale forest-fire trajectories. As fires remove fuels for subsequent fires, feedbacks may impose constraints on otherwise climate-driven trend of increasing area. Here, we test how fire-fuel moderate (2021–2050) increases across US. Assuming constant fuels, climate–fire models project a doubling compared 1991–2020. Fire-fuel only modestly attenuate projected increase Even with strong interannual variability and more than two-fold likelihood years exceeding season. Fuel limitations from are unlikely strongly constrain profound broad-scale mid-21st century, highlighting proactive adaptation increased impacts. Reduced fuel availability will moderately diminish forest Western US, according model.

Language: Английский

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Wildfire and climate change adaptation of western North American forests: a case for intentional management

Ecological Applications, Journal Year: 2021, Volume and Issue: 31(8)

Published: Aug. 2, 2021

Forest landscapes across western North America (wNA) have experienced extensive changes over the last two centuries, while climatic warming has become a global reality four decades. Resulting interactions between historical increases in forested area and density recent rapid warming, increasing insect mortality, wildfire burned areas, are now leading to substantial abrupt landscape alterations. These outcomes forcing forest planners managers identify strategies that can modify future ecologically and/or socially undesirable. Past management, including widespread harvest of fire- climate-tolerant large old trees forests, fire exclusion (both Indigenous lightning ignitions), highly effective suppression contributed current state wNA forests. practices were successful at meeting short-term demands, but they match poorly modern realities. Hagmann et al. review century observations multi-scale, multi-proxy, research evidence details regimes since influx European colonists. Over preceding 10 millennia, areas already settled proactively managed with intentional burning by tribes. Prichard then on management historically applied tribes currently some intentionally manage forests for resilient conditions. They address questions surrounding application relevance these practices. Here, we highlight main findings both papers offer recommendations management. We discuss progress paralysis often occurs strict adherence precautionary principle; insights dealing common problem irreducible uncertainty suggestions reframing policy direction; key knowledge gaps needs.

Language: Английский

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Mass fire behavior created by extensive tree mortality and high tree density not predicted by operational fire behavior models in the southern Sierra Nevada

Forest Ecology and Management, Journal Year: 2022, Volume and Issue: 518, P. 120258 - 120258

Published: May 16, 2022

Large, severe wildfires continue to burn in frequent-fire adapted forests but the mechanisms that contribute them and their predictability are important questions. Using a combination of ground based remotely sensed data we analyzed behavior patterns 2020 Creek Fire where drought bark beetles had previously created substantial levels tree mortality southern Sierra Nevada. We found dead biomass live densities were most variables predicting fire severity; high severity encompassed 41% area largest patch (19,592 ha) comprised 13% total burned. Areas with highest amounts also positively related size indicating larger, more homogenous conditions this forest characteristic resulted adverse, landscape-scale effects. The first two days abnormally hot dry weather during greatest growth was largely within normal range variation for time year one day lower windspeeds. From September 5 8th burned almost 50% its entire intensity inferred from brightness-temperature typical except on 6th when heat increased towards interior fire. Not only concentrated away perimeter, significant amount still being generated perimeter previous day. This is classic pattern mass along critical factors developing behavior. Operational models not able predict because they do include post-frontal combustion fire-atmosphere interactions. An question regarding if event preceded it could have been avoided or reduced natural these forests? episode outside historical analogs exacerbated by past management decisions. shows us how vulnerable our current suffering offering fuel capable generating fires which future recovery questionable type conversion probable reoccurring

Language: Английский

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Mega‐disturbances cause rapid decline of mature conifer forest habitat in California

Ecological Applications, Journal Year: 2022, Volume and Issue: 33(2)

Published: Oct. 20, 2022

Abstract Mature forests provide important wildlife habitat and support critical ecosystem functions globally. Within the dry conifer of western United States, past management fire exclusion have contributed to forest conditions that are susceptible increasingly severe wildfire drought. We evaluated declines in cover southern Sierra Nevada California during a decade record disturbance by using spatially comprehensive structure estimates, perimeter data, eDaRT tracking algorithm. Primarily due combination wildfires, drought, drought‐associated beetle epidemics, 30% region's extent transitioned nonforest vegetation 2011–2020. In total, 50% mature 85% high density either lower or types. spotted owl protected activity centers (PAC) experienced greater canopy decline (49% 2011 cover) than non‐PAC areas (42% decline). Areas with initial without tall trees were most vulnerable declines, likely explaining disproportionate within PACs. Drought attack caused cumulative where drought mortality overlapped, both types natural far outpaced attributable mechanical activities. disproportionately affects large conifers is particularly problematic specialist species reliant on trees. However, patches degraded perimeters larger core area those outside burned areas, remnant habitats more fragmented affected alone. The percentage survived potentially benefited from severity increased over time as total declined. These some opportunity for improved resilience future disturbances, but strategic interventions also necessary mitigate worsening mega‐disturbances. Remaining may be complete loss coming decades rapid transition conservation paradigm attempts maintain static one manages sustainable dynamics.

Language: Английский

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Anthropogenic climate change impacts exacerbate summer forest fires in California

Proceedings of the National Academy of Sciences, Journal Year: 2023, Volume and Issue: 120(25)

Published: June 12, 2023

Record-breaking summer forest fires have become a regular occurrence in California. Observations indicate fivefold increase burned area (BA) forests northern and central California during 1996 to 2021 relative 1971 1995. While the higher temperature increased dryness been suggested be leading causes of BA, extent which BA changes are due natural variability or anthropogenic climate change remains unresolved. Here, we develop climate-driven model evolution combine it with natural-only historical simulations assess importance on BA. Our results that nearly all observed is as accounting for forcing yield 172% (range 84 310%) more than only. We detect signal combined emerging 2001 no detectable influence alone. In addition, even when considering fuel limitations from fire-fuel feedbacks, 3 52% last decades expected next (2031 2050), highlighting need proactive adaptations.

Language: Английский

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Reimagine fire science for the anthropocene

PNAS Nexus, Journal Year: 2022, Volume and Issue: 1(3)

Published: July 1, 2022

Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are fundamental cause consequence global change, impacting people the biophysical systems on which they depend. As part newly emerging Anthropocene, marked by human-caused climate change radical changes to ecosystems, danger increasing, fires having increasingly devastating impacts human health, infrastructure, ecosystem services. Increasing vexing problem requires deep transdisciplinary, trans-sector, inclusive partnerships address. Here, we outline barriers opportunities in next generation science provide guidance investment future research. We synthesize insights needed better address long-standing challenges innovation across disciplines (i) promote coordinated research efforts; (ii) embrace different ways knowing knowledge generation; (iii) exploration science; (iv) capitalize "firehose" data societal benefit; (v) integrate natural into models multiple scales. thus at critical transitional moment. need shift from observation modeled representations varying components climate, people, vegetation, more integrative predictive approaches support pathways toward mitigating adapting our flammable world, including utilization safety benefit. Only through overcoming institutional silos accessing diverse communities can effectively undertake improves outcomes fiery future.

Language: Английский

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Vegetation type conversion in the US Southwest: frontline observations and management responses

Fire Ecology, Journal Year: 2022, Volume and Issue: 18(1)

Published: May 19, 2022

Abstract Background Forest and nonforest ecosystems of the western United States are experiencing major transformations in response to land-use change, climate warming, their interactive effects with wildland fire. Some transitioning persistent alternative types, hereafter called “vegetation type conversion” (VTC). VTC is one most pressing management issues southwestern US, yet current strategies intervene address change often use trial-and-error approaches devised after fact. To better understand how manage VTC, we gathered managers, scientists, practitioners from across US collect experiences challenges, responses, outcomes. Results Participants two workshops provided 11 descriptive case studies 61 examples own field observations. These demonstrate extent complexity ecological reorganization region. High-severity fire was predominant driver semi-arid coniferous forests. By a large margin, these forests converted shrubland, fewer conversions native or non-native herbaceous communities. Chaparral sagebrush areas nearly always grasses through interactions among land use, climate, Management interventions attempted reverse changes, although found that efforts cover only small portion high-severity burn undergoing VTC. incurred long (>10 years) observational periods prior initiating interventions. Efforts facilitate were rare, but could spatial areas. Conclusions Our findings underscore conversion common outcome US. Ecosystem managers frontline observers far-reaching potentially making valuable further developing intervention research agendas. As its drivers increase appears increasingly likely many contexts may require paradigms transition as well. Approaches include new models desired conditions, experimentation by broader implementation adaptive strategies. Continuing support develop science-manager partnerships peer learning groups will help shape our ongoing rapid transformations.

Language: Английский

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Have western USA fire suppression and megafire active management approaches become a contemporary Sisyphus?

Biological Conservation, Journal Year: 2022, Volume and Issue: 268, P. 109499 - 109499

Published: March 3, 2022

Language: Английский

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