文献阅读 260511-Wildfire damages and the cost-effective role of forest fuel treatments

Wildfire damages and the cost-effective role of forest fuel treatments

来自 <https://www.science.org/doi/10.1126/science.aea6463>

## Abstract:

1. Gave the core question:

Wildfires are among the most pressing environmental challenges of the 21st century,intensified by the accumulation of forest fuels after a century of fire suppression policies.

1. Gap-evaluate the economic value of fuel reduction

Although fuel-reduction treatments (“fuel treatments”) are a primary tool for reducing wildfire risk, they remain underutilized, partly owing to limited evidence of their economic value.

1. What this paper did:

In this study, we integrated high-resolution data on wildfires, fuel treatments, suppression effort, and damages across the Western United States to assess their cost-effectiveness. Usinga quasi-experimental design, we found that fuel treatments reduced wildfire spread and severity, avoiding an estimated $2.8 billion in damages by limiting structure loss, cutting carbon dioxide emissions, and lowering fine particulate matter (PM2.5) exposure. Each dollar invested yielded $3.73 in expected benefits.

1. The importance of this paper

Our findings demonstrate the value of fuel treatment investments and offer guidance for maximizing their effectiveness.

## Intro:

# Para1: fire threat:

Wildfire activity has intensified drastically in recent decades, leading to widespread economic, environmental, climate, and public health damages (1). In the United States alone, total annual wildfire-related damages are estimated at $394 billion to $893 billion, equivalent to 2 to 4% of the gross domestic product (2).

These costs stem from property loss, fire suppression, adverse health outcomes, labor disruptions, and degraded ecosystem services (3–8). Recent estimates suggest that health damages from wildfire-induced fine particulate matter (PM2.5) exposure alone may exceed all other climate-related damages in the United States (9).

Gap1: Lack rigorous evaluation at scale while wildfire risk↑

Globally, wildfire risk is projected to increase as a result of climate change, expanding development in the wildland-urban interface, and decades of fire suppression (10–12). Yet despite mounting damages, key mitigation strategies, such as fuel treatments, remain underutilized and lack rigorous evaluation at scale.

# Para2: fuel loads

The accumulation of combustible material in forests, known as fuel loads, isa primary driver of increasing wildfire severity in many semiarid and pine-dominated systems(13). Historically, frequent, low-severity fires helped regulate these loads. In California, for example, an estimated 5 to 12% of the landscape burned annually before 1800, much of it through Indigenous cultural burning practices (14). However, long-standing wildfire suppression policies have disrupted these fire cycles, allowing fuels to accumulate well beyond historical levels, threatening the functionality of forest ecosystems(15, 16).

# Para3: fuel treatments

Fuel-reduction treatments (“fuel treatments”), such as prescribed burns and mechanical biomass removals, have become central to wildfire risk strategies. These treatmentsaim to reduce the density and continuity of fuel loads, maintain open-canopy forest structures, and remove fire-intolerant species, thereby mimicking natural fire processes(17). The US Forest Service (USFS) has pledged to treat >50 million acres—an area roughly the size of Utah—over the next decade through its Wildfire Crisis Strategy, reflecting a shift in federal wildfire policy toward more proactive risk reduction (18).

# Gap2

Despite commitments to accelerate the pace and scale of fuel treatments, these treatments remain underutilized (19), in part becausepublic pressure and risk aversion skew wildfire management resources toward fire suppression rather than prevention(20). Suppression effort offers immediate and visible results, whereas the benefits of fuel treatments are delayed, uncertain, and difficult to observe. As a result, the value of fuel treatments is often underappreciated by the public and policy-makers, leading to persistent barriers in their broader implementation, including regulatory, funding, and capacity constraints. These dynamics reflect a classic public goods problem: Despite their broad societal benefits, there are insufficient incentives to invest in prevention measures without clear, credible evidence of their benefits.

Demonstrating the benefits of fuel treatments, however, has proven difficult because of data limitations and the complexity of attributing reductions in wildfire spread, severity, and damages to fuel treatments.Until recently, comprehensive records on fuel treatment locations, wildfire perimeters, suppression effort, and damages were scarce or fragmented. Furthermore, wildfire behavior is shaped by the interaction of fuels, weather, topography, and suppression effort, making causal identification challenging. Consequently, prior studies rely on model-based fire simulations or localized case studies that are difficult to generalize and often assess hypothetical treatment scenarios rather than real-world implementations (21–23). As a result, they offer limited insights into whether current treatments are cost-effective or under which conditions they deliver the greatest benefits.

# What this paper did:

We present large-scale empirical evidence on the effectiveness of fuel treatments in mitigating wildfire spread, severity, and damages. Focusing on the Western United States—where wildfire risk is high and spatial data are uniquely rich—we compiled high-resolution data on 285 wildfires that intersected with USFS fuel treatments across 11 states between 2017 and 2023(Fig. 1). These data include wildfire perimeters, treatment locations, suppression effort, fire simulation outputs, and key determinants of fire behavior and damages.We focus on three primary sources of wildfire damages—structure loss, CO2 emissions, and PM2.5 exposure—which together account for an estimated $185 billion to $540 billion in annual losses (2). We first estimatedhow fuel treatments affect fire spread and severity, exploring heterogeneity by treatment type, size, timing, and proximity to suppression effort. We thensimulated counterfactual wildfire behavior in the absence of treatment to quantify avoided damages. By monetizing these avoided damages, we assessed the cost-effectiveness of current fuel treatments and identified the conditions under which they are most beneficial, providing evidence to guide wildfire mitigation policy and investment decisions.

## METHODS:

Estimating the effect of fuel treatments on wildfires

The methods:

Interpreting an empirical relationship between fuel treatments and wildfire behavior as causal is challenging owing to thenonrandom allocation of treatments and suppression effort, creating the potential for selection bias. Both fuel treatments and fire suppression resources are allocated to protect areas of elevated wildfire risk, where fires are more likely to spread or threaten valuable assets (4, 24–27). Moreover, suppression resources are often deployed in ways that respond to the presence of nearby fuel treatments (28). As a result, simple comparisons of wildfire behavior between treated and untreated areas are likely to be confounded by systematic differences in underlying fire risk and fire management.

# how they solve these questions

We addressed these challengesusing a spatial difference-in-differences researchdesign thatexploits the quasi-random nature of wildfire ignition and directional spread[see (29) for details]. The precise location of ignition points is largely unpredictable, meaning that the direction and distance at which a fire encounters a fuel treatment is likely to be independent of factors that also influence fire behavior. For each fire, we compared changes in fire behavior in directions that encounter treatments to those that do not, before and after the fire reaches a treatment, controlling for predictable fire spread patterns from fire simulation outputs, weather, and suppression effort (Fig. 2).

Fuel treatments reduce fire spread and severity

The determinants of fuel treatment effectiveness

来自 <https://www.science.org/doi/10.1126/science.aea6463#supplementary-materials>

The mechanism:

There is considerable heterogeneity in the effectiveness of fuel treatments in halting wildfire spread (fig. S2). Weexamined four factors that may explain this heterogeneity:

• treatment type,
• time since treatment implementation,
• treatment size,
• and proximity to suppression resources.

Previous research in fire ecology has shown that treatments are most effective when recently completed and when mechanical thinning is combined with prescribed burning (33, 34). Our results reinforce the importance of treatment type: Treatments that include prescribed fire—either alone or alongside mechanical thinning—are significantly more effective than mechanical-only treatments (Fig. 5C). These effects are especially pronounced immediately after encountering a fuel treatment, indicating that prescribed fire enhances the short-term effectiveness of treatments in halting fire spread. We also find that larger treatments lead to greater reductions in fire spread and burn severity (Fig. 5B and fig. S4), which is likely due to their having more interior area relative to their boundary, thereby reducing exposure to surrounding fuels and making them more effective at disrupting fuel continuity and slowing fire progression (35–37). In contrast, we find limited evidence that time since treatment significantly affects fire spread within a 10-year window (Fig. 5D), although it does influence conditional burn severity (fig. S5).