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

Tribal communities in the Pacific Northwest of the United States of America (USA) have long-standing relationships to ancestral lands now managed by federal land management agencies. In recent decades, federal and state governments have increasingly recognized tribal rights to resources on public lands and to participate in their management. In support of a new planning initiative to promote sustainable land management, we reviewed scientific publications to examine relationships between tribal social-ecological systems and public lands in the region. We identified key ecocultural resources, impacts to those resources, and associated forest ecosystems, and strategies that have been piloted to redress those impacts. We found that many factors stemming from colonization by Euro-Americans have engendered social-ecological traps that have inhibited tribes from continuing traditional land stewardship activities that supported their well-being and maintained ecological integrity. These long-standing factors include legal and political constraints on tribal access and management; declining quality and abundance of forest resources due to inhibition of both natural disturbance and indigenous tending regimes; competition with nontribal users; species extirpations and introductions of invasive species; and erosion of tribal traditional ecological knowledge and relationships that are important for revitalizing resource use. As a consequence, both supply and demand for these forest resources have been reduced, as have the resilience and diversity of these ecosystems. Simply permitting resource harvest by tribal members does not sufficiently address the underlying constraints in ways that will promote tribal well-being. Escaping these traps will require addressing a gamut of ecological and social constraints through cooperative restoration efforts between land management agencies and tribes, several of which we highlight as examples. Because tribally focused restoration strategies generally align with broader strategies suggested to restore national forests in the region, they can foster both tribal well-being and ecological sustainability.

North American tribes have traditional knowledge about fire effects on ecosystems, habitats, and resources. For millennia, tribes have used fire to promote valued resources. Sharing our collective understanding of fire, derived from traditional and western knowledge systems, can benefit landscapes and people. We organized two workshops to investigate how traditional and western knowledge can be used to enhance wildland fire and fuels management and research. We engaged tribal members, managers, and researchers to formulate solutions regarding the main topics identified as important to tribal and other land managers: cross-jurisdictional work, fuels reduction strategies, and wildland fire management and research involving traditional knowledge. A key conclusion from the workshops is that successful management of wildland fire and fuels requires collaborative partnerships that share traditional and western fire knowledge through culturally sensitive consultation, coordination, and communication for building trust. We present a framework for developing these partnerships based on workshop discussions.

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

For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management are informed by historical baselines. This need is particularly acute in California, where 20th-century fire suppression, coupled with a warming climate, has caused forest densification and increasingly large wildfires that threaten forest ecosystem integrity and management of the forests as part of climate mitigation efforts. We examine climatic versus anthropogenic influence on forest conditions over 3 millennia in the western Klamath Mountains—the ancestral territories of the Karuk and Yurok Tribes—by combining paleoenvironmental data with Western and Indigenous knowledge. A fire regime consisting of tribal burning practices and lightning were associated with long-term stability of forest biomass. Before Euro-American colonization, the long-term median forest biomass was between 104 and 128 Mg/ha, compared to values over 250 Mg/ha today. Indigenous depopulation after AD 1800, coupled with 20th-century fire suppression, likely allowed biomass to increase, culminating in the current landscape: a closed Douglas fir–dominant forest unlike any seen in the preceding 3,000 y. These findings are consistent with precontact forest conditions being influenced by Indigenous land management and suggest large-scale interventions could be needed to return to historic forest biomass levels.

Climate change related impacts, such as increased frequency and intensity of wildfires, higher temperatures, extreme changes to ecosystem processes, forest conversion and habitat degradation are threatening tribal access to valued resources. Climate change is and will affect the quantity and quality of resources tribes depend upon to perpetuate their cultures and livelihoods. Climate impacts on forests are expected to directly affect culturally important fungi, plant and animal species, in turn affecting tribal sovereignty, culture, and economy. This article examines the climate impacts on forests and the resulting effects on tribal cultures and resources. To understand potential adaptive strategies to climate change, the article also explores traditional ecological knowledge and historical tribal adaptive approaches in resource management, and contemporary examples of research and tribal practices related to forestry, invasive species, traditional use of fire and tribal-federal coordination on resource management projects. The article concludes by summarizing tribal adaptive strategies to climate change and considerations for strengthening the federal-tribal relationship to address climate change impacts to forests and tribal valued resources.

Background Karuk and Yurok tribes in northwestern California, USA, are revitalizing the practice of cultural burning, which is the use of prescribed burns to enhance culturally important species. These cultural burns are critical to the livelihoods of indigenous peoples, and were widespread prior to the establishment of fire exclusion policies. One of the major objectives of cultural burning is to enhance California hazelnut ( Corylus cornuta Marsh var. californica ) basketry stem production for Karuk and Yurok basketweavers. To evaluate cultural burning as a form of human ecosystem engineering, we monitored hazelnut basketry stem production, qualities, and shrub density in 48 plots (400 m 2 ) within two prescribed and 19 cultural burn sites. Socio-ecological variables that were analyzed included burn frequency, burn season, overstory tree (≥10 cm diameter at breast height) basal area, ungulate browse, and aspect. We also observed basketry stem gathering to compare travel distances, gathering rates, and basketweaver preferences across sites with different fire histories and land tenure. Results Hazelnut shrubs, one growing season post burn, produced a 13-fold increase in basketry stems compared with shrubs growing at least three seasons post burn ( P < 0.0001). Basketry stem production and stem length displayed negative relationships with overstory tree basal area ( P < 0.01) and ungulate browse ( P < 0.0001). Plots burned at high frequency (at least three burn events from 1989 to 2019) had 1.86-fold greater hazelnut shrubs than plots experiencing less than three burn events ( P < 0.0001), and were all located on the Yurok Reservation where land tenure of indigenous people is comparatively stronger. Basketweavers travelled 3.8-fold greater distance to reach gathering sites burned by wildfires compared with those that were culturally burned ( P < 0.01). At cultural burn sites, wildfire sites, and fire-excluded sites, mean gathering rates were 4.9, 1.6, and 0.5 stems per minute per individual, respectively. Conclusions Karuk and Yurok cultural fire regimes with high burn frequencies ( e.g., three to five years) promote high densities of hazelnut shrubs and increase hazelnut basketry stem production. This improves gathering efficiency and lowers travel costs to support the revitalization of a vital cultural practice. Our findings provide evidence of positive human ecosystem engineering, and show that increasing tribal sovereignty over fire management improves socio-economic well-being while at the same time supports measures of ecosystem structure and function.

Forest densification, wildfires, and disease can reduce the growth and survival of hardwood trees that are important for biological and cultural diversity within the Pacific Northwest of USA. Large, full-crowned hardwoods that produce fruit and that form large cavities used by wildlife were sustained by frequent, low-severity fires prior to Euro-American colonization. Shifts in fire regimes and other threats could be causing declines in, large hardwood trees. To better understand whether and where such declines might be occurring, we evaluated recent trends in Forest Inventory and Analysis (FIA) data from 1991–2016 in California and southern Oregon. We included plots that lay within areas of frequent fire regimes during pre-colonial times and potential forest habitats for fisher, a rare mammal that depends on large live hardwoods. We analyzed changes in basal area for eight hardwood species, both overall and within size classes, over three time periods within ecoregions, and in public and private land ownerships. We found the basal area to generally be stable or increasing for these species. However, data for California black oak suggested a slight decline in basal area overall, and among both very large trees and understory trees; that decline was associated with fire mortality on national forest lands. In addition, mature trees with full crowns appeared to sharply decline across all species. Many trends were not statistically significant due to high variation, especially since more precise data from remeasured trees were only available for the two most recent time periods. Continued analysis of these indicators using remeasured trees will help to evaluate whether conservation efforts are sustaining large, full-crowned trees and their associated benefits.

Historically, wildfire and tribal burning practices played important roles in shaping ecosystems throughout the Klamath Siskiyou Bioregion of northern California and southern Oregon. Over the past several decades, there has been increased interest in the application of fire for forest management through the implementation of prescribed fires within habitats that are used by a diversity of migrant and resident land birds. While many bird species may benefit from habitat enhancements associated with wildfires, cultural burning, and prescribed fire, individuals may face direct or indirect harm. In this study, we analyzed the timing of breeding and molting in 11 species of culturally significant land birds across five ecologically distinct regions of northern California and southern Oregon to explore the potential timeframes that these bird species may be vulnerable to wildland fires (wildfire, prescribed fire, or cultural burning). We estimated that these selected species adhered to a breeding season from April 21 to August 23 and a molting season from June 30 to October 7 based on bird capture data collected between 1992 and 2014. Within these date ranges, we found that breeding and molting seasons of resident and migratory bird species varied temporally and spatially throughout our study region. Given this variability, spring fires that occur prior to April 21 and fall fires that occur after October 7 may reduce the potential for direct and indirect negative impacts on these culturally significant birds across the region. This timing corresponds with some Indigenous ecocultural burning practices that are aligned with traditionally observed environmental cues relating to patterns of biological phenology, weather, and astronomy. We detail the timing of breeding and molting seasons more specific to regions and species, and estimate 75%, 50%, and 25% quartiles for each season to allow for greater flexibility in planning the timing of prescribed fires and cultural burning, or regarding the potential implications of wildfires. The results of our study may serve as an additional resource for tribal members and cultural practitioners (when examined within the context of Indigenous Traditional Ecological Knowledge) and forest and wildland fire managers to promote stable populations of culturally significant bird species within fire‐dependent forest systems.

The influence of Native American land-use practices on vegetation composition and structure has long been a subject of significant debate. This is particularly true in portions of the western United States where tribal hunter-gatherers did not use agriculture to meet subsistence and other cultural needs. Climate has been viewed as the dominant determinant of vegetation structure and composition change over time, but ethnographic and anthropological evidence suggests that Native American land-use practices (particularly through the use of fire) had significant landscape effects on vegetation. However, it is difficult to distinguish climatically driven vegetation change from human-caused vegetation change using traditional paleoecological methods. To address this problem, we use a multidisciplinary methodology that incorporates paleoecology with local ethnographic and archaeological information at two lake sites in northwestern California. We show that anthropogenic impacts can be distinguished at our Fish Lake site during the cool and wet ‘Little Ice Age’, when we have evidence for open-forest or shade-intolerant vegetation, fostered for subsistence and cultural purposes, rather than the closed-forest or shade-tolerant vegetation expected due to the climatic shift. We also see a strong anthropogenic influence on modern vegetation at both sites following European settlement, decline in tribal use, and subsequent fire exclusion. These results demonstrate that Native American influences on vegetation structure and composition can be distinguished using methods that take into account both physical and cultural aspects of the landscape. They also begin to determine the scale at which western forests were influenced by Native American land-use practices and how modern forests of northwestern California are not solely products of climate alone.