Fire in coastal fog belt forests
The coastal fog belt is a narrow environmental band that hugs Oregon’s coastline. It can extend about 20 miles inland and up to elevations of about 500 feet. In other areas, it may be only a few miles wide. Due to its proximity to the ocean, this ecoregion has a temperate climate. Winters are wet, and summers are often foggy.
Despite their generally cool, moist conditions, these forests produce a lot of fuel and can burn at high intensity when weather conditions feature low relative humidity, high temperatures, sustained wind speeds and an ignition source. Most fires burn under moderate conditions and are extinguished at less than 1 acre. Historically, the coastal fog belt forests burned infrequently — every 300–1,000 years — and at high-severity (stand-replacing crown fire). Well-documented large fires occurred in the late 1800s to mid-1900s. In addition to wildfire, windthrow, flooding, landslides, pests and diseases can also disturb these forests.
While the overall probability of a wildfire in the coastal fog belt is relatively low, extreme conditions, such as preceding drought and east wind events, dramatically heighten fire hazard and risk. Humans exacerbate the fire potential through unattended campfires or accidental ignitions, especially during high fire danger. Increased human population, especially in forest and wildland areas, and climate and land-use changes have increased the risks and potential impacts of wildfire on the coast. The 2020 Echo Mountain Fire Complex in Lincoln County and the Pike Road Fire in Tillamook County illustrate that coastal fog belt wildfires can spread quickly and have large impacts. For instance, the 2,500-acre Echo Mountain Fire Complex impacted over 360 structures.
The cessation of Indigenous cultural burning, fire suppression and broad land-use changes have allowed shrubs and trees to encroach on interspersed coastal grasslands, reducing them to about 5 percent of their precolonial extent. The Nature Conservancy at Cascade Head, the USDA Forest Service, and the U.S. Fish & Wildlife Service conduct prescribed burns on federal lands along the coast to maintain remaining habitat for grassland species, including early blue violet, an obligate host plant to the threatened Oregon Silverspot Butterfly.
Coastal fog belt forests
In this environment, moisture-dependent tree species, such as Sitka spruce and western hemlock, are most abundant and often referred to as “spruce-hemlock forests.” Western redcedar, red alder and Douglas-fir are also present with Oregon myrtle, tanoak and Port-Orford-cedar inhabiting the southern extent of the fog belt. Shore pine is found in boggy areas and sandy soils along the coast and tolerates moderately to poorly drained sites.
The mild climate, plentiful rainfall and fertile soil result in highly productive forests. However, the mild climate also creates favorable conditions for forest tree diseases, such as Swiss needle cast and laminated root rot in Douglas-fir and sudden oak death in tanoak in Curry County. During warmer winters, the invasive spruce aphid can have periodic outbreaks and cause heavy defoliation of Sitka spruce, especially in large trees near the coast. Whole-tree mortality is rare, but other confounding conditions, such as English ivy growing on the trunk, can further compromise and eventually kill trees.
Because forests are so productive, understory vegetation such as huckleberry, salal, rhododendron, salmonberry, thimbleberry, elderberry and vine maple can grow quickly and dominate a site after harvesting or removing trees or following disturbance. Invasive species such as scotch broom, gorse and Himalayan blackberry can also grow quickly and dominate, outcompeting the native vegetation for resources. In coastal forests near dunes, invasive annual American and European beachgrasses stabilize dunes but change vegetative communities and reduce open sandy habitats that are vital to native species. These beachgrass dunes can also harbor additional invasive species that threaten adjacent forests. Rapidly growing shrubs can increase the amount of fuel and provide ladder fuels up into the canopy, exposing tree crowns to potential fire spread. Some invasive plant species, such as gorse, are highly flammable and can contribute to rapid fire spread.
Monitoring forest health is important. The presence of invasive species can contribute to rapid fire spread and outcompete native vegetation. Pests and diseases alter canopy, surface, litter and duff fuel availability over time. On your forest land, consider: Are any pests or diseases contributing to tree mortality? Are these pests or diseases spreading to other trees nearby?
Fire resilience strategies for small woodland owners in this forest type
Recent fires remind us why we should manage coastal fog belt forests with fire in mind. Develop a management plan for your property. A management plan is a strategic plan to accomplish management objectives for your woodlands. It encompasses all the resources on your property, including water sources, roads and more. To improve your woodland’s resistance to wildfire and its ability to withstand negative impacts and recover from, consider applying these three principles in your management approach:
- Protect structures through home hardening and creating defensible space.
- Utilize strategic fuel breaks.
- Increase the patchiness and diversity of your woodlands.
Home hardening and defensible space within the Home Ignition Zone (HIZ)
There is a lot to consider when managing your coastal fog belt forest with fire in mind. These forests are productive, and vegetation grows fast. Strategic thinning and other treatments (for example, mechanical, chemical and biological) to reduce fuel build-up on your property can mitigate the risk of a fire moving from crown to crown, embers burning structures from outside and from within the home, and radiant heat from fire. The home ignition zone, or “HIZ,” is the structure itself and everything around it out to 100 feet or 200 feet on steeper slopes. Consider starting with the home structure and moving out to the edges of your property.
Protect structures by applying home-hardening techniques such as building or updating with fire-resistant materials like a metal roof. Within the area closest to the structure, there should be no vegetation touching or hanging over the structure. Minimize the structure ignition potential by modifying the arrangement and distribution of vegetation around and beyond the structure. When shrubs and trees are planted closely together, they form what’s called “ladder fuel,” and fire can easily climb from shrub to tree crowns and increase the likelihood of an ember igniting the structure.
To manage your forest with fire in mind, account for the topography of your land and changing weather conditions (daily and seasonally). For example, you might not thin vegetation on steep slopes for safety or environmental concerns. Consider on-shore and off-shore winds. Recreational beach fires have caused wildfires when on-shore winds push flames upslope into forest vegetation. Some coastal landowners clear out or thin more fuels to the east and north of their properties to buffer the impacts of wind-driven wildfire.
Under extreme fire weather conditions, focus on life and safety. Practice evacuation with your neighbors. If you are given an evacuation order or feel unsafe, leave without delay. Given limited firefighting personnel and resources, manage expectations about the ability of firefighters to protect your home property.
Fuel breaks
Think about potential threats to your forested property, such as lightning (even though rare in this region), a downed powerline, a public trail, highway, or even your neighbors. Buffer for those threats by taking advantage of natural fuel breaks —a paved or gravel driveway, trails or creek — on your property. Creating additional fuel breaks can increase forest resilience along the narrow-treated areas. Thinning to separate tree crowns, reduce fuel continuity and remove ladder fuels contributes to reducing fire exposure in high-risk or high-value areas and creates a safer, more accessible area for fire control operations. Thinning will create gaps and openings for understory growth, so maintain understory vegetation in strategic fuel breaks.
Patchiness and diversity
Managing for a diversity of stand densities and tree species may promote fire resilient woodlands. Areas of low density can create gaps in the canopy cover and reduce the probability of crown fire spread. Develop low- to high-density patches across your woodland in a strategic manner.
Be thoughtful of how you balance your objectives with fuel reduction. For example, consider creating or maintaining wildlife habitat (for example, unthinned areas, unburned slash piles) beyond the HIZ, instead of within the HIZ, to reduce the risk to your home and any outbuildings. Adding or maintaining a hardwood component to your woodlands can be helpful with fire resistance, with the added benefit of enhancing wildlife habitat. Alder, big-leaf maple, cascara and madrone are all important hardwoods of the coastal fog belt. Hardwood foliage has higher moisture and lower resin content compared to conifers and is less susceptible to ignition. It requires a lot of energy generated from fires to burn hardwood forests. Encouraging the growth of hardwoods amongst stands of conifer can decrease the chance of a crown fire spreading by breaking up the canopy of conifer trees. However, hardwoods can create ladder fuels into the conifer canopy, and there may be increased risk in late summer and fall when leaves die and become dry and can carry fire through the forest. Moss on trees can also carry fire.
When selecting species, consider the diversity of species in your woodlands, the species’ fire ecologies, fire resistance and resilience characteristics, and climate change projections. Coastal Douglas-fir is more fire resistant than many of its associated species (Sitka spruce, western redcedar, western hemlock and bigleaf maple, for example) and can survive moderately intense fires. Thick, corky bark on the lower bole and roots protects the living cambium from heat damage. Douglas-fir likely accounted for a larger proportion of trees in certain areas of the coastal fog belt than found today. Once Douglas-fir reaches maturity, the tree becomes “more” fire-resistant. Under multiple climate change scenarios, Douglas-fir and white pine are projected to expand westward towards the Coast, with a reduction in the extent of Sitka spruce.
Related publications
We are still learning
Since the early 1910s, land managers have actively suppressed wildfire. Declining summer wetting rain (July-August precipitation) and increasing summer temperatures have increased wildfire risk during wildfire season. With a changing climate, we are adjusting management guidance to address the increased need to manage westside forests for wildfire resilience. This is in addition to the other forest management objectives that landowners may have. It is important to recognize tradeoffs, caveats and unknowns when managing coastal fog belt forests in western Oregon for wildfire.
Use of broadcast burning in this forest type has declined since the 1970s and 1980s. The role of fire in site preparation for reforestation should be revisited to understand benefits, costs and constraints. Indigenous burning prior to Euro-American settlement in this forest type and historical fire regimes as a whole require further study. For instance, prescribed fire (and cultural burning by Tribes) in coastal grasslands habitat may be necessary for species conservation (to arrest succession from grassland to closed canopy forest), so we need to learn more. More research using effective and appropriate study methods across a greater extent of this forest type will help us gain greater understanding of historical fire regimes.
When using a shaded fuel break technique, you can thin to a wide-enough spacing to create gaps between tree crowns. This can reduce crown fire spreading, but the trade-off is that an open canopy invites increased growth of understory vegetation (fuel), including invasive species. Finding the density of thinning to create a shaded fuel break that moderates fire behavior while also allowing for moisture retention and minimizing understory growth requires further research.
For more information
Bailey, J.D. 2024. A walk with wildland fire. Waveland Press, Inc. Long Grove, Illinois.
Bennett, M, S. Fitzgerald, A. Christiansen and K. Baylog. 2017. Keeping your home and property safe from wildfire: A defensible space and fuel reduction guide for homeowners and landowners (EM 9184). Oregon State University Extension Catalog.
Detweiler, A.J., S. Fitzgerald, A. Cowan, N. Bell and T. Stokely. 2023. Fire-resistant plants for home landscapes: Reduce wildfire risk with proper plant selection and placement. (PNW 590). Oregon State University Extension Catalog.
Prescribed fire basics, a collection of 11 modules that provide introductory-level information.