Background
In Portland, approximately 20% of the city's acreage is urban greenspace, including natural areas, stream corridors, parks, and open spaces. Those features contribute to quality of life for people and animals who live, work, play, or visit the area. They do this by providing wildlife habitat, clean air and water, scenery, recreation trails, and other ecosystem functions.
In addition to the benefits they provide, the wild spaces within our urban area also present challenges. Decades of human suppression of naturally occurring wildfire on these landscapes has caused a build-up in material that can be potential fuel for wildfires. As commercial and residential development expands to the boundaries of our urban natural areas, the risk of significant property loss due to wildfires is increasing. This is because the likelihood of human-caused fires increases where people live, and because wildfires in these areas pose a greater risk to lives and homes and are more difficult to fight. In addition, with more homes close to natural areas, letting natural fires burn becomes increasingly dangerous. Recent significant wildfires in close proximity to communities in the Columbia River Gorge, Oregon Cascades, and throughout California have shown the growing importance of wildfire risk management.
Incorporating Wildfire Risk Reduction into Land Management
In 2006, with the help of grant funding from the Federal Emergency Management Agency (FEMA), Portland Parks & Recreation (PP&R), Portland Fire & Rescue (PFR), the Bureau of Environmental Services (BES), and the Portland Bureau of Emergency Management (PBEM) began incorporating wildfire risk reduction into land management practices, including the use of prescribed burns to improve the safety and ecological health of our urban greenspaces.
The initial FEMA-funded project, Urban Fuel Load Reduction in Portland, Oregon, allowed crews to conduct specific wildfire risk reduction actions within the Willamette Bluffs (including Oaks Bottom), Forest Park, and Powell Butte. Grant funding of $940,000 lasted for three years (2006-2008). Thirty percent of this funding was used for wildfire risk and vegetation management planning, while seventy percent was used for on-the-ground wildfire risk reduction work. Some key accomplishments included:
- Ladder fuel reduction;
- Creation of defensible space;
- Diversification of native forest vegetation to increase resilience;
- Increased monitoring and control of invasive plant species that increase wildfire risk in the wildland-urban interface;
- Long-term vegetation management plans and wildfire fuel reduction plans developed for the focus areas; and
- Materials produced to enhance public awareness and communication around wildfire risk reduction on public and private property.
Ladder Fuel Reduction
Woody debris, vegetation, or other flammable material that can carry a fire burning in low-growing vegetation to taller vegetation is called ladder fuel. In areas prone to wildfire, creating a separation in vegetation by removing ladder fuels is an important task.
Creation of Defensible Space
Defensible space is the buffer between a structure such as a house, fence, or outbuilding and the surrounding area. Adequate defensible space acts as a barrier to slow or halt the progress of fire that would otherwise engulf these structures. Good defensible space allows firefighters to protect and save buildings or structures safely without facing unacceptable risk to their lives. Creation of defensible space through vegetation management usually means reducing the amount of fuel around the building or structure, providing separation between fuels, and or reshaping retained fuels by trimming.
Diversification of Forest Vegetation
Forests with many different tree species (conifer, deciduous, mixed-species) and development stages (young, mid-age, mature/old-growth) are more resilient to disturbances such as wildfire and have greater capacity to maintain and recover ecological functions following disturbance.
Control of Invasive Plant Species
The interaction between invasive species, particularly invasive plants, and wildfire presents increased risks to the integrity of natural systems, human safety, and rural economies throughout the United States. Invasive plants are responsible for changing the patterns of fire activity in many ecosystems including leading to hotter and more frequent fires and reducing fire frequency and fire intensity.
Portland Parks & Recreation has continued to leverage that initial FEMA funding investment by incorporating these same actions throughout parks and natural areas stewarded by the City. Each year, ecologists work closely with staff, contractors, and community volunteers to remove invasive plants that could spread fire into tree canopies or to nearby structures (such as fences and houses), and to diversify tree and shrub species.
For the last several years, an average of about 870 acres have been treated annually for invasive plant removal, and about 37,600 native plants have been planted across the 8,000 acres of natural areas stewarded by PP&R.
Initial Areas of Focus
Portland Fire & Rescue, with the assistance of the Oregon Department of Forestry, identified and mapped the Willamette Bluffs, Forest Park, and Powell Butte as significant fire prone areas because of the buildup of flammable natural materials at these sites, and because of their proximity to neighborhoods and commercial areas.
Since 1940, over 3,600 acres have burned in Forest Park and Powell Butte, and along the Willamette Bluffs. Today, over 8,000 homes and businesses worth more than $2.5 billion lie within the fire prone area documented on the City’s Wildfire Hazard Zone Map.
Willamette Escarpment (also known as Willamette Bluffs)
Rising steeply on the east bank of the Willamette River, the Willamette Bluffs are a unique geologic artifact of the Lake Missoula floods from 15,000 years ago. The well-drained, gravelly soils of the south- and west-facing escarpment landscapes were once covered with Oregon white oak, Pacific madrone, and native grassland habitats.
People have lived along the Willamette’s banks for approximately 10,000 years. Historically, Native Americans used fire as a tool to favor Oregon white oak and native grassland plant species by igniting grass fires that would kill conifer and shrub seedlings, keeping them from overtaking oak habitats. These burns enhanced acorn crops, grasses, and other useful plants and kept the landscape fuels low and easily manageable. In the mid-1800s, European settlers began logging, clearing and converting land, and suppressing fire regularly, resulting in large-scale degradation of the landscape. In many areas, after the last trees were cut, non-native trees seeded in, along with clematis, Scot's broom, and non-native blackberry. Soon, impenetrable thickets began to envelop the landscape and the remaining native oaks and other indigenous plants were smothered, resulting in a condition prone to serious wildfire. Highly flammable vines and shrubs act as ladder fuels which create a pathway for fire to quickly spread into the tree canopy. Once in the canopy, the fire can easily become catastrophic.
At this location, which includes Oaks Bottom Wildlife Refuge, wildfire risk reduction work has focused on reducing hazardous wildfire fuels and eventually restoring the bluffs to Oregon oak woodland, which is much less susceptible to serious wildfire. Without the "ladder fuels" present today, a wildfire would be less likely to reach the tree canopy and escalate.
Forest Park
Despite Forest Park’s reputation as an urban “wilderness,” the park has seen widespread human influence over many generations, beginning with use by indigenous peoples and most recently in the form of logging, roadbuilding, and other development. Currently, it interfaces extensively with residential and urban development at its borders. These factors have led to the spread of invasive weed species such as ivy, clematis, and non-native blackberry in about half of the park. As in the Willamette Bluffs, these invasive plants increase wildfire risk in Forest Park because they out-compete native species and impact the health of the forest, making it less resilient to wildfire. They can also serve as “ladder fuels” that can carry a fire burning in low-growing vegetation to taller vegetation, resulting in more intense wildfire. Recent years of drought and changing climate, resulting in warmer and drier than average weather, is also elevating wildfire risk in the park.
PP&R is working to reduce wildfire risk in Forest Park by removing invasive plants and fuels in the park near communities and in high-risk areas. Portland Fire & Rescue, Forest Park Conservancy, and PP&R collaborate to help neighboring residents enhance the wildfire resiliency of homes and communities as well. These activities reduce the risk of a catastrophic wildfire within the park. They also protect neighboring homes and communities, as well as critical utility lines, transportation corridors, and other public resources in and around the park.
Learn more about Wildfire Risk Reduction in Forest Park.
Powell Butte
Along with our partners at the Portland Water Bureau, PP&R has worked to reduce wildfire risk at Powell Butte by removing invasive plants and fuels in the park. These activities reduce the risk of a catastrophic wildfire within the park. They also protect neighboring homes and communities, as well as critical utility lines, transportation corridors, and other public resources in and around the park.
For initial project work, contracts for professional services were secured through a competitive process and fuel reduction treatments (control of invasive species by mechanical cutting and spraying of herbicide) commenced on 303 acres of public lands in early May 2007. Treatments targeted the removal of non-native trees (English hawthorn), the shrub layer (non-native blackberry and Scots broom), and tall non-native grasses.
Three prescribed fires on a total of 103 acres were conducted by Portland Fire & Rescue at Powell Butte (September 2007, September 2008, and September 2009). Prescribed fire was used to reduce flashy fuels, control flammable non-native weeds, and raise public awareness about the role of prescribed fire as a natural process.
Expanding Wildfire Risk Reduction Activities Across the Landscape
Work begun in 2006 has continued in and also expanded beyond the initial focus areas to include most other natural areas throughout the City of Portland. Ecologists incorporate the same activities: ladder fuel reduction, creation of defensible space, diversifying native forest vegetation to increase resilience, and increasing monitoring and control of invasive species into management best practices and natural area restoration projects. With the help of community member volunteers and contracted restoration crews, these actions are implemented daily.
Protect the Best
The Protect the Best Invasive Plant Management Program (PTB) is designed to treat and prevent invasive infestations in Portland Parks & Recreation’s natural areas by identifying and treating ecologically healthy habitat and then creating relatively invasive-free “buffer habitat” surrounding it. PTB staff removes targeted invasive species including ivy, holly, non-native blackberry, and garlic mustard. Treatments are tracked in an ArcGIS database. The PTB program is expected to reduce total invasive vegetation on a greater number of acres, at lower cost, and using less herbicide, as compared with other invasive vegetation management approaches. Read more about Protect the Best.
Prescribed Burning
Additionally, a strong partnership between Portland Parks & Recreation and Portland Fire & Rescue has resulted in the planning of several new prescribed burns at Oaks Bottom Wildlife Refuge, Baltimore Woods Natural Area, and Whitaker Ponds. Read more about prescribed fire within natural areas stewarded by Portland Parks & Recreation.
Prescribed burns have been used in Oaks Bottom Wildlife Refuge by the City of Portland since the mid-1990s as a management tool to reduce fuels, kill invasive plant seed banks, and return nutrients to the soil. Funded by the 2006-2009 FEMA wildfire risk reduction grant, the City of Portland conducted prescribed burns in Oaks Bottom Wildlife Refuge in September 2006, August 2007, and August 2008. The 2006 burn was conducted on an 8-acre grassland area in the south end of Oaks Bottom Wildlife Refuge. The 2007 burn was conducted in the north end of the refuge. The north end was burned again in 2008. Since these burns, staff and volunteers have planted thousands of native trees, shrubs and ground cover plants. Additional burns are being planned for these same areas in the coming years.
The Baltimore Woods meadows were burned in 2012 in an effort to reduce invasive pasture grass growth and remove years of dead and dried vegetation. Since that original burn, thousands of native wildflowers and shrubs have been planted throughout the meadows and PP&R is planning to use additional prescribed burns to maintain this ecologically sensitive habitat.
Related Links
- Portland Wildfire Readiness Assessment 2009
- City of Portland Hazard Mitigation Action Plan (2021)
- Portland Fire & Rescue: reducing the risk of wildfire
- Multnomah County Community Wildfire Protection Plan (CWPP)
- Portland Parks & Recreation natural areas volunteer stewardship
- Portland Parks and Recreation Nature and Land Stewardship
- Information about local Firewise communities