Wildfires in North Central Washington

Large wildfires have become frequent visitors to North Central Washington over the last several decades, with major impacts to communities, forests, rangelands, and air quality. This StoryMap documents 36 years of wildfires in our region — from 1985 to 2021 — through maps, photos, and figures that examine where fires burned, where they overlapped, and their severity. 

North Central Washington has been host to some of the largest recorded wildfires in Washington state history, including the 2020 Cold Springs Fire, the 2015 North Star Fire, and the 2014 Carlton Complex Fire. It is also a region experiencing rapid change, in part due to these large and often severe wildfires events and in part due to effects from climate change.

Continue scrolling to explore the geography and impacts of recent fires in our region.

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The total area burned by wildfires has markedly increased over the past 20 years within North Central Washington, with especially large fires in 2014, 2015, 2020, and 2021. Over half of the area burned in the last four decades has been in predominantly forests (green bars), with the remaining area burned occurring in predominantly shrub-steppe and grasslands (yellow bars).

The following fire perimeter maps show how fires have mostly burned new areas with very little overlap between each progressive wildfire year from 2000 to 2021. Keep scrolling to see how wildfires have mostly fit together like puzzle pieces, but in recent years have started reburning (represented by hatched lines) through past burns.

The following section explores trends in how severely wildfires have burned within North Central Washington state. We include an overview of how burn severity is calculated and how to interpret this data for the region.

Broadly, burn severity is a measurement of the magnitude of effects of fire on elements of the landscape, such as vegetation or soil. Often, burn severity is categorized into more interpretable classes of fire severity such as unburned/very low, low, moderate, and high. For more information about burn severity,  click here .

When we consider all fires throughout the region, much of the area within fire perimeters was either unburned or experienced very low to low severity effects. However, many of these wildfires burned in grasslands and shrublands (non-forest) where burn severity is more difficult to define. We expand on this in the sections below.

The next set of maps explore spatial patterns of fire severity across the region, ranging from unburned to high-severity impacts in both forested and non-forested fires that burned between 1985 and 2021. Forested areas are more common west of the Okanogan River and have experienced high tree mortality, associated with large areas of high and moderate severity fire (red and orange).

There are many different ways to calculate burn severity. Here, burn severity is determined using  modeled Composite Burn Index (CBI) values . CBI is a field-based measurement of fire effects to vegetation and soil. For more information on how CBI is determined in the field,  click here .

To model CBI values across broad regions over time, satellite imagery (Landsat TM) taken one year before and one year after a fire is used. We measure the relative difference in reflectance (light reflected from the Earth's surface) between these images and model those values with climate variables and field-validated burn severity data to obtain values that can then be categorized into unburned/very low, low, medium, and high severity classes. Specifically, we use imagery taken one year after the fire (rather than immediately after) to ensure we capture any delayed tree death that may occur in the months following fire. However, because of rapid revegetation in non-forest ecosystems, assessing what burn severity means a year after fire in grasslands and shrublands is a challenge.

Because burn severity in non-forested areas — such as shrub-steppe or grasslands — is often impossible to accurately measure with one-year post-fire imagery, the approach used here is most appropriate to interpret wildfire impacts to forested ecosystems. Burn severity classifications are generally most accurate at very low severity (like in unburned areas) and at very high severity (full tree crown consumption).

Unburned / Very Low Severity Within any given fire, areas of unburned vegetation or vegetation that burned very minimally may exist. These patches may result from a variety of factors and occur in a variety of locations, such as in moist riparian areas, moist subalpine meadows, or on barren soils with sparse vegetation cover. Depending on the timing and existing vegetation cover, areas recently burned in previous fires may be complete barriers or burn at very low severity in subsequent fires.

Low Severity Forested areas that burn at low severity experience minimal effects to soils and overstory trees. In low elevation forests, historically frequent fires were dominated by low and moderate severity effects. Large, resilient trees may be scarred in low severity fire, but tree mortality is generally less than 25 percent and typically concentrated on small- to medium-sized trees.

Moderate Severity Moderate severity captures a broad range of post-fire effects in forests, from around 25 to 75 percent tree morality in a given area with moderate impacts on soils. When it occurs in patches across the landscape, moderate severity fire is often considered an effective tool for restoring lower elevation forests that have experienced long fire-free periods and a buildup of fuels. Moderate severity is typically more difficult to accurately measure with satellite imagery, unlike high severity or unburned areas.

High Severity Areas of forest that burn at high severity experience widespread to total tree mortality and consumption of understory vegetation. Whether or not these areas regenerate with new trees is dependent on a variety of factors, including distance to live seed sources, management decisions, and post-fire climate. In lower elevation, dry forest types that historically burned frequently, patches of high severity occurred but occupied a relatively small portion of the post-fire landscape. In higher elevation forests that experienced less frequent fire, larger proportions of high severity effects were common.

As described in the previous section, severity of fires that burn non-forested areas, such as grass or shrubland, can be difficult to interpret.

In the next set of figures, we explore trends in severity for only forest fires: fires that burned over a majority (at least 50%) conifer forest.

Although area burned in forest fires has increased markedly over the past 20 years, wildfires in North Central Washington still contain a large percentage (39%) of unburned and low severity effects. Within unburned areas and low severity burns, wildfires may be accomplishing some restoration goals by thinning forests and reducing understory fuels that can burn in subsequent fires.

Since 1985, high severity effects tend to be concentrated in large patches greater than 1,000 acres. By contrast, unburned areas and areas burned at very low severity tend to be dispersed as many smaller patches (less than 100 acres) across the landscape. Unburned/very low severity only accounts for 10% of forested area burned in our study area, and a decline in this important category means that fewer and smaller patches of unburned forests are left following wildfire events. These areas of refugia serve important roles in the post-fire landscape: the trees within these patches provide seed sources to promote regeneration in nearby burnt forests, they act as habitat and food source for wildlife following fire, and they contribute to the overall structural diversity of the broader landscape.

How do forests recover from high severity fire? One of the key considerations is how large burn patches are and if any living trees remain nearby to provide seed sources for regeneration. An additional concern is that hotter, drier summers make it more difficult for new trees to grow. Since 1985, nearly 225,000 acres have burned in large patches of high severity far from nearby seed sources, called 'core area'. These core areas will be important to monitor in years to come to determine how sites are recovering following high severity fire events.

Over 40% of North Central Washington has burned in wildfire events since 1985. In forest fires, a total of 2,428,750 acres have burned with 29% of this area burned at high severity, 31% at moderate severity, 30% at low severity, and 10% at unburned or very low severity. Areas burned at high and moderate severity (60% of burned forests) represent major changes for forest structure and future fuel accumulations from dead and dying trees.

The past 20 years of wildfires in our region have shattered records for Washington state. However — perhaps surprisingly — the total area burned within these two decades is much more typical of historical fire regimes than the total area burned between 1950 and 2000. Historically, cultural burning by Indigenous peoples and dry lightning ignitions maintained frequent fires throughout the region. These fires were typically dominated by low- and moderate-severity fire effects, which in turn maintained forest conditions resilient to drought, broad-scale insect outbreaks, and subsequent fire.

As we adapt to climate change, we can expect wildfires to continue to be regular visitors to our region and even become more common. More than total area burned, it will be critical to evaluate the full range of wildfire impacts on forests, including where high severity fire has threatened tree regeneration, and where low or moderate severity fire has bolstered forest resilience.

To learn more about climate and wildfire adaptation strategies, read the related paper  "Adapting western North American forests to climate change and wildfires: 10 common questions" .

For more information about fire research in this area, please visit our North Central WA Wildfires site at:  https://depts.washington.edu/nwfire/ncw/ 

To view burn severity data by individual fires highlighted in this report,  click here .