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Can fuel-reduction treatments really increase forest carbon storage in the western US by reducing future fire emissions?

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It has been suggested that thinning trees and other fuel-reduction practices aimed at reducing the probability of high-severity forest fire are consistent with efforts to keep carbon (C) sequestered in terrestrial pools, and that such practices should therefore be rewarded rather than penalized in C-accounting schemes. By evaluating how fuel treatments, wildfire, and their interactions affect forest stocks across a wide range of spatial and temporal scales, we conclude that this is extremely unlikely. Our review reveals high losses associated with fuel treatment, only modest differences in the combustive losses associated with high-severity fire and the low-severity fire that fuel treatment is meant to encourage, and a low likelihood that treated forests will be exposed to fire. Although fuel-reduction treatments may be necessary to restore historical functionality to firesuppressed ecosystems, we found little credible evidence that such efforts have the added benefit of increasing terrestrial stocks.
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... Typically fuel treatments increase carbon emissions in the short term but are likely to reduce long-term carbon emissions when wildfires are considered. Some recent research (e.g. , Campbell et al. 2011) shows that fuel treatments may not result in net carbon gains when the rarity of high-severity wildfire is considered. ...
... Various methods for fuel modification, collectively termed "fuel treatments," include mastication or removal of sub-merchantable timber and understory biomass, pre-commercial and commercial timber harvest, and prescribed fire. While the effectiveness of these treatments in reducing potential fire severity are well documented (Moghaddas and Craggs 2007, Moghaddas et al. 2010, Safford et al. 2012, Stephens et al. 2009a, the implications for the effects that both treated and untreated areas have on forest carbon balances and GHG emissions are less understood (Campbell et al. 2011, Hurteau and North 2008, Hurteau and North 2010, North et al. 2009, Stephens et al. 2009b). ...
... On the other hand, larger trees exhibit higher susceptibility to mortality from non-fire causes such as insects and disease (North et al. 2009). Campbell et al. (2011) point out that fire exclusion does not necessarily reduce stand carbon levels. ...
Technical Report
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We summarized key studies from the published literature describing forest carbon storage and the effects of wildfires and fuel treatments on stored carbon with a focus on California mixed conifer forests. We also compiled results from the published literature quantifying carbon released by wildfires in treated and untreated forests. We analyzed three sets of California field measurements for patterns relating wildfire severity, fuel consumption, and wildfire emissions and then produced a regression equation relating wildfire severity and fuel consumption. Finally, we used this result to estimate fuel consumption and wildfire emissions during the 2014 King Fire. Our King Fire consumption and emissions estimates seem reasonable when compared with studies of similar fires. This approach can be applied virtually anywhere to retroactively estimate wildfire consumption and emissions using LANDFIRE fuels and vegetation mapping products as long as spatial wildfire severity information is available. In addition, this approach could be applied predictively to project consumption and emissions from modeled fire severity.
... It is difficult to determine on relatively small scales how this resiliency translates into management practices that optimize ecological integrity and carbon storage. In the western United States, drought and decades of fire suppression have increased the occurrence and severity of wildfires, a major source of carbon emissions, but the net carbon balance of forest management practices associated with wildfire risk reduction are a subject of debate (McKinley et al. 2011;North and Hurteau 2011;Campbell et al. 2012). A better appreciation of these complexities is necessary to optimize land carbon in public and private forests, especially in the West, where wildfire management is a high priority. ...
... Long-run carbon storage may increase as the risk of catastrophic wildfire lessens (North and Hurteau 2011), but some research suggests that repeated interventions are necessary to maintain the benefits yielded by the initial fuels reduction activity (Agee and Skinner 2005;Collins et al. 2011) and that situation-specific factors can influence the response of treated areas to future fires (Rhodes and Baker 2008). Still others argue that the net carbon implications of fuels treatment may be negligible (Mitchell 2015) and that even with the bioenergy benefits stemming from removed material, an increase in maximum stand carbon storage is necessary to yield net GHG improvements through fuels treatment (Hudiburg et al. 2011;Campbell et al. 2012). ...
Technical Report
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The vegetation and soils found in landscapes across the United States serve as carbon sinks, removing an estimated 850 million metric tons of CO2e from the atmosphere each year and offsetting 16 percent of annual industrial emissions. There is significant uncertainty about the future and scale of this sink. Failure to stabilize the current sink and preserve U.S. land carbon mitigation capacity could jeopardize the effectiveness of U.S. climate change policy and the nation’s ability to meet future emissions reduction targets. To address this challenge, a consortium of organizations and experts came together to launch the Land Carbon Policy Roadmap (LCPR) initiative to develop and implement policy recommendations that ensure U.S. lands continue to significantly reduce economy-wide emissions through 2050 and to provide robust agricultural, silvicultural, and ecosystem services. This report is the first step toward developing that roadmap.
... www.nature.com/natrevearthenviron is combined with mechanical thinning. This latter approach has the potential to increase resilience in US coniferous forests where fire has been excluded for up to a century, with the possible benefit of reduced carbon emissions from subsequent wildfires [145][146][147] . However, prescribed burning has significant constraints, particularly owing to the potential for shrinking safe weather windows due to climate change 148 , and the effectiveness of prescribed burning in altering wildfire behaviour sharply declines under extreme fire weather 149 . ...
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Vegetation fires are an essential component of the Earth system but can also cause substantial economic losses, severe air pollution, human mortality and environmental damage. Contemporary fire regimes are increasingly impacted by human activities and climate change, but, owing to the complex fire–human–climate interactions and incomplete historical or long-term datasets, it is difficult to detect and project fire-regime trajectories. In this Review, we describe recent global and regional trends in fire activity and examine projections for fire regimes in the near future. Although there are large uncertainties, it is likely that the economic and environmental impacts of vegetation fires will worsen as a result of anthropogenic climate change. These effects will be particularly prominent in flammable forests in populated temperate zones, the sparsely inhabited flammable boreal zone and fire-sensitive tropical rainforests, and will contribute to greenhouse gas emissions. The impacts of increased fire activity can be mitigated through effective stewardship of fire regimes, which should be achieved through evidence-based fire management that incorporates indigenous and local knowledge, combined with planning and design of natural and urban landscapes. Increasing transdisciplinary research is needed to fully understand how Anthropocene fire regimes are changing and how humans must adapt.
... For example, a recently proposed commercial thinning in Willamette National Forest was designed to increase forest heterogeneity and early successional habitat, decrease long-term fire risk, and create jobs in local communities (USFS 2018). However, past research shows thinning reduced total carbon storage in western Oregon forests (Burton et al. 2013), a loss that is not necessarily offset by reduced future fire severity (Campbell et al. 2012). Although the management agency "acknowledge[d] the trade-off," they also pointed out that "the intent of the project is not maximizing carbon, but to promote biodiversity by increasing landscape diversity" (USFS 2018:422). ...
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Should conservationists use lethal management to control introduced wildlife populations? Should they kill individual animals to protect endangered species? Are trade-offs that prioritize some values at the expense of others morally appropriate? These sorts of ethical questions are common in conservation. In debating such questions, conservationists often seem to presume 1 of 2 possible answers: the act in question is right or it is wrong. But morality in conservation is considerably more complex than this simple binary suggests. A robust conservation ethic requires a vocabulary that gives voice to the uncertainty and unease that arise when what seems to be the best available course of action also seems to involve a measure of wrongdoing. The philosophical literature on moral residue and moral dilemmas supplies this vocabulary. Moral dilemmas arise when one must neglect certain moral requirements to fulfill others. Under such circumstances, even the best possible decision leaves a moral residue, which is experienced emotionally as some form of grief. Examples of conservation scenarios that leave a moral residue include management of introduced rabbits in Australia, trophy hunting in Africa, and forest management trade-offs in the Pacific Northwest. Moral residue is integral to the moral experience of conservationists today, and grief is an appropriate response to many decisions conservationists must make. Article impact statement: Defensible conservation decisions may neglect moral requirements, leaving a moral residue; conservationists should respond with grief. © 2020 Society for Conservation Biology.
... While the management of beetle-killed stands is currently an acute concern in Rocky Mountain forests, the research questions identified here are also relevant to the broader issues of biomass removal for fuels reduction treatments in forests with short fire return intervals, and forest ecological restoration more generally. The degree to which targeted biomass removals can support landscape-scale increases in ecosystem carbon storage is widely debated (Campbell et al., 2012). Similarly, the extent to which woodbased bioenergy systems can contribute to net mitigation has also been controversial (Schlesinger 2018;DeCicco & Schlesinger 2018). ...
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Carbon accounting at the nexus of forest management and bioenergy production has long been complex and controversial, particularly regarding whether woody feedstocks can be sustainably sourced without counter-productive reductions in forest ecosystem carbon storage. In the western U.S., recent bark beetle outbreaks have caused widespread tree mortality across more than 40 million acres of pine and spruce forests, slowing or even reversing their near-term carbon sink value. Often there is ‘push’ from land managers to remove beetle-killed trees in the interest of extracting timber value, reducing fuels, and protecting critical infrastructure. While such treatments can be cost-prohibitive, the use of non-merchantable wood fractions for bioenergy production might potentially add market ‘pull’ and enable treatment of larger areas of beetle-kill forest. The Bioenergy Alliance Network of the Rockies has been assessing the economic, environmental, and social sustainability of such a potential new regional bioenergy industry. In this presentation we describe our preliminary efforts to estimate the climate impacts of beetle-kill harvest for bioenergy production at the regional scale in northern Colorado and southern Wyoming. Specifically, we consider whether and over what time-scales the potential climate mitigation benefits of biofuel and biochar co-production might outweigh the ecosystem carbon losses of harvesting those dead trees. We have extensively calibrated and validated the Forest Vegetation Simulator (FVS) model to better represent post-disturbance dynamics in local lodgepole pine and aspen stands. Coupling Forest Inventory and Analysis program plot data, FVS modeling, and machine learning techniques enables estimation and spatial interpolation of the ecosystem ‘carbon debt’ of beetle-kill harvests over time, as compared to a no-harvest status quo. We then couple these results with a simple mass balance for a local industry partner’s thermochemical conversion process producing gasoline blend-stock and a biochar co-product. We will present our preliminary regional-scale climate mitigation assessment results, and quantify the sensitivity to various ecosystem and technology factors.
... However, drought-induced mortality of species far less resistant to decay overwhelmed live tree biomass increments in three plots, including two (CBT, FC) where A. lowiana had the highest rate of productivity (Fig. 12). Fires sufficiently intense to stimulate Sequoiadendron regeneration in these forests would have high carbon emissions as drought-killed trees and accumulated debris are consumed, but this immediate cost may be exceeded by long-term benefits such as decreased emissions from decomposition and increasing growth of fireresistant trees (Hurteau and North, 2008;North and Hurteau, 2011;Campbell et al., 2012). ...
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The largest tree species, Sequoiadendron giganteum has a small native range restricted to California’s Sierra Nevada. Awe-inspiring stature contributed to its protection from logging, but anthropogenic climate change—particularly hotter drought—and over a century of fire suppression are possible threats. We measured 60 trees in seven forests to improve allometric equations for the species and installed five 1-ha plots to quantify biomass of Sequoiadendron and associated vegetation. Plots were re-measured after 5 yr to compute biomass increments and examine effects of management history as well as impacts of recent drought. Forests held up to 2683 Mg ha⁻¹ aboveground biomass (1373 Mg C ha⁻¹) and had leaf area index (LAI) up to 14.5 with Sequoiadendron accounting for the bulk of biomass but not LAI. Live trees of other species contributed up to 10.6 LAI and had biomass increments up to 6.1 Mg ha⁻¹ yr⁻¹, but drought contributed to tree mortality in three plots, where live biomass declined by 6.2–10.3 Mg ha⁻¹ yr⁻¹. Two plots had very little tree mortality and gained 5.5–7.9 Mg ha⁻¹ yr⁻¹. Sequoiadendron productivity was strongly correlated with tree-level photosynthetic capacity, but at the height of the drought, relative growth—expressed as the ratio of biomass produced during the driest and wettest recent years—correlated positively with site productivity and negatively with both vertical distance to water and presumed competition from neighboring trees. Prescribed fire in one plot caused a growth release in trees whose lower trunks were burnt and small neighboring Abies lowiana were killed. Effects of 21st century drought on Sequoiadendron productivity were greater in northern than southern locations but of lesser magnitude than many past events. No Sequoiadendron recruitment was observed. Planting can overcome the species’ dependence on fire for regeneration, and Sequoiadendron has great potential for carbon sequestration in a variety of settings, including commercial forestry.
... ctivity and biomass (Hudiberg et al. 2009). Several recent studies have investigated the seemingly competing values of carbon sequestration and fuel treatment, examining whether and to what extent reduced carbon sequestration from treatment is mitigated by avoided emissions , Stephens et al. . 2009b, Ager et al. . 2010, Reinhardt and Holsinger 2010, Campbell et al. . 2011. Improving the accuracy and usefulness of assessments of fuel treatment wildfire trade-offs for C storage, requires understanding the long-term effects of multiple management and disturbance scenarios, including post wildfire treatments (salvage, reforestation) over time (Loehman et al. 2014;Restaino and Peterson 2013). ...
Technical Report
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We quantified the effects and efficacy of fuel reduction treatments in the Sierra Nevada as measured by expected fire behavior and carbon life cycle pathways. The analysis integrated forecasted forest growth and GHG sequestration, expected changes in wildfire behavior following fuel reduction treatments (efficacy), expected changes in wildfire emissions following fuel reduction treatments, and a life cycle analysis (LCA) of the fate of GHGs in wood removals over a forty year period post‐treatment. The LCA tracked the fate of carbon from wood removals stored in durable wood products, woody material used for bioenergy and biofuels, forest harvest residues and waste, operational emissions. There was a net GHG liability (carbon loss) incurred by the one‐time treatment of the landscape between 2003 and 2008, under a 1% annual probability of fire occurrence. The treatments only remained effective at reducing fire size through 2025 (17‐22 years after treatment) after which simulated fires were actually larger on the project landscape. Benefits that were slowly accumulating from avoided direct stock loss and improved growth rates on the treated landscape (by 2045) were erased by this outcome. Performing two maintenance prescribed fires on the treated landscape resulted in additional carbon deficit of in‐forest C stock, but kept fire sizes smaller. Although under a 1% annual probability of fire a benefit was not realized by 2050, the liability was decreasing from 2025 onward, suggesting that a benefit was forthcoming. With a higher assumed probability of fire (2% annual), a benefit was realized by 2045. A sensitivity analysis of growth rates used in modeling suggests that if rates in the untreated stands are overestimated then recovery of carbon in the treated landscape may occur more rapidly compared to the baseline, which would result in a much quicker achievement of greenhouse gas emissions benefits.
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