Global and Regional Trends and Drivers of Fire Under Climate Change

Reviews of Geophysics, Journal Year: 2022, Volume and Issue: 60(3)

Published: April 11, 2022

Abstract Recent wildfire outbreaks around the world have prompted concern that climate change is increasing fire incidence, threatening human livelihood and biodiversity, perpetuating change. Here, we review current understanding of impacts on weather (weather conditions conducive to ignition spread wildfires) consequences for regional activity as mediated by a range other bioclimatic factors (including vegetation biogeography, productivity lightning) ignition, suppression, land use). Through supplemental analyses, present stocktake trends in burned area (BA) during recent decades, examine how relates its drivers. Fire controls annual timing fires most regions also drives inter‐annual variability BA Mediterranean, Pacific US high latitude forests. Increases frequency extremity been globally pervasive due 1979–2019, meaning landscapes are primed burn more frequently. Correspondingly, increases ∼50% or higher seen some extratropical forest ecoregions including high‐latitude forests 2001–2019, though interannual remains large these regions. Nonetheless, can override relationship between weather. For example, savannahs strongly patterns fuel production fragmentation naturally fire‐prone agriculture. Similarly, tropical relate deforestation rates degradation than changing Overall, has reduced 27% past two part decline African savannahs. According models, prevalence already emerged beyond pre‐industrial Mediterranean change, emergence will become increasingly widespread at additional levels warming. Moreover, several major wildfires experienced years, Australian bushfires 2019/2020, occurred amidst were considerably likely Current models incompletely reproduce observed spatial based their existing representations relationships controls, historical vary across models. Advances observation controlling supporting addition optimization processes exerting upwards pressure intensity weather, this escalate with each increment global Improvements better interactions climate, extremes, humans required predict future mitigate against consequences.

Language: Английский

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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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Mechanisms of forest resilience

Forest Ecology and Management, Journal Year: 2022, Volume and Issue: 512, P. 120129 - 120129

Published: March 25, 2022

Language: Английский

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Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States

Proceedings of the National Academy of Sciences, Journal Year: 2023, Volume and Issue: 120(11)

Published: March 6, 2023

Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, relative importance of interactions between these drivers forest change remain unresolved, particularly over upcoming decades. Here, we assess how interactive impacts changing climate wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset from 10,230 field plots. Our findings highlight declining capacity across West past four decades for eight dominant species studied. Postfire is sensitive high-severity fire, which limits seed availability, climate, influences seedling establishment. In near-term, projected differences recruitment probability low- scenarios were larger than most species, suggesting that reductions severity, resultant on could partially offset expected climate-driven declines regeneration. Across 40 42% study area, project be likely following low-severity but not under future (2031 2050). However, increasingly warm, dry eventually outweigh influence availability. The percent area considered unlikely experience regeneration, regardless increased 5% 1981 2000 26 31% by mid-century, highlighting limited time window management actions reduce may effectively support

Language: Английский

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Wildfire, Smoke Exposure, Human Health, and Environmental Justice Need to be Integrated into Forest Restoration and Management

Current Environmental Health Reports, Journal Year: 2022, Volume and Issue: 9(3), P. 366 - 385

Published: May 7, 2022

Increasing wildfire size and severity across the western United States has created an environmental social crisis that must be approached from a transdisciplinary perspective. Climate change more than century of fire exclusion suppression have led to contemporary wildfires with severe impacts human smoke exposure. Wildfires increase exposure for broad swaths US population, though outdoor workers socially disadvantaged groups limited adaptive capacity can disproportionally exposed. Exposure is associated range health in children adults, including exacerbation existing respiratory diseases such as asthma chronic obstructive pulmonary disease, worse birth outcomes, cardiovascular events. Seasonally dry forests Washington, Oregon, California benefit ecological restoration way adapt climate reduce on affected communities.

Language: Английский

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Operational resilience in western US frequent-fire forests

Forest Ecology and Management, Journal Year: 2022, Volume and Issue: 507, P. 120004 - 120004

Published: Jan. 18, 2022

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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