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Photo credit: Alex Pajunas.
Why they’re important:
Since the 1850s, much of the Willamette Valley has seen a significant reduction in important wildlife habitat.
This is due to development of urban communities and agricultural lands. The majority of remaining habitat is located on private lands, making landowners important participants in wildlife conservation.
The Oregon Conservation Strategy (OCS) outlines methods for conserving and restoring fish and wildlife habitat across the state.
OCS identifies 11 “strategy” habitats statewide that are threatened or endangered. Five of these strategy habitats are found in Washington County, including oak woodlands, prairies, wetlands, riparian areas, and mixed conifer forests.
Oak woodlandsOak Woodlands A mix of oak trees and shrubs. and prairies:
Oak woodlands and prairies are among the most endangered habitat types in the Pacific Northwest.
These lands provide a unique ecosystem used by roughly 200 species of wildlife, including birds, mammals, amphibians, and reptiles – some of which rely solely on oak habitat to survive. Many species make use of acorns for food, tree cavities for nesting, and specifically require a lack of shrubs and sparse tree density found in oak savanna.
The characteristic oak species in this habitat is the mighty Oregon white oak (Quercus garryana):
These important trees, along with their associated prairie habitat, were once common throughout the region but have become increasingly rare.
- Fun fact:
Mature Oregon white oaks can become enormous trees, ranging from 50 to 90 feet tall and 2 to 4 feet around. They can even live up to 500 years!
For thousands of years, Native Americans strategically burned oak prairiesOak Prairies Sparse oak trees spread across a grass-dominated prairie. and oak woodlands.
These burns helped maintain the open habitat for hunting and produced acorns and camas bulbs – important staples in their diet . The low-intensity fires kept other tree species from competing with the more fire-resistant oaks and allowed the prairie species to flourish. A common threat to existing oak woodlands comes from competition by Douglas fir, grand fir, cherry, and big leaf maple trees. Oak has only a moderate tolerance to shade, and once shaded out by taller trees, it will eventually die.
Prior to European settlement, there were about 400,000 acres of oak-dominated habitat in the Willamette Valley .
Extensive development, wildfire suppression, and the introduction of non-native species have threatened these habitats.
- Not-so-fun fact:
Only 1 to 5% of oak habitat exists today. Remnant “legacy” oaks dot the landscape as iconic landmarks and shade trees on our farmlands.
Landowners can protect mature oak trees and plant new oaks in open areas.
Over 80% of remaining oak habitat in the Pacific Northwest is on private lands, which offer some of the best opportunities for oak conservation.
Wetlands are home to an astounding number of plants, birds, amphibians, reptiles, fish, mammals, and insects.
Over one-third of the species considered threatened or endangered in the United States depend on wetland habitats for survival .
- Fun fact:
Wetlands are some of the most productive ecosystems in the world, producing vegetation (food!) at a fast rate and supporting a lot of animal species. The saturated soils in a wetland create a nutrient-rich environment, allowing plants and wildlife to flourish.
Wetlands provide many benefits for humans, too:
Depending on the time of year, it might be hard to tell that an area is even a wetland!
Some wetlands are covered with water year-round while others are only seasonally wet. Some wetland types you may see in Washington County include wet prairiesWet Prairies Areas dominated by grasses that are wet most of the year but dry out in the summer., marshes, and off-channel habitat.
Learn more about these wetland types and functions on the Environmental Protection Agency website.
Wetland habitats face numerous threats:
Careful management, protection, and restoration of wetlands is a priority for supporting watershed health.
Interested in visiting a wetland?
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Important: Earth-moving activity in wetlands is regulated by the Oregon Department of State Lands, the Army Corps of Engineers, and the Environmental Protection Agency. Review regulations and obtain necessary permits before initiating any activity in a wetland area.
Riparian areasRiparian Areas Areas of land that occur along the edges of rivers, streams, lakes, and other bodies of water.:
Riparian – or streamside – areas are the link between land and water habitats.
Waterways and their associated riparian areas are essential components of nutrient cyclesNutrient Cycles The movement of a chemical through a system.. They also provide important pathways for animals traveling from one part of a landscape to another. This often means there is higher diversity of wildlife species using these areas.
Streamside-area plants like willows, alders, maple trees, and others provide:
A healthy stream is one that can meander through a landscape and naturally spill water onto its floodplainFloodplain Low-lying land adjacent to a body of water that is susceptible to flooding or prolonged wetness. in times of high flow.
Channelization and development within floodplains restrict streams’ ability to meander, which limits the creation of new habitat and can cause flood damage when streams are unable to handle large flows. And while there is a huge network of creeks, streams, and rivers in our region, many of these habitats have been degraded and disconnected over time.
If you have a property with a streamside area, check out our replanting programs.
Mixed conifer (upland) forests are a mixture of broadleafBroadleaf A plant with large, flat leaves instead of needles. and conifer trees, shade-tolerant understoryUnderstory The layer of plants that exists closer to the ground under large trees. vegetation, and dead wood like snagsSnags Dead or dying trees that remain standing. and nurse logsNurse Logs A fallen tree that supports plant seedlings and provides food and habitat for wildlife..
In Washington County, our upland forests are located mostly near the Tualatin River’s headwaters, and are dominated by Douglas fir, Western red cedar, salmonberry, sword fern, and a high density of mosses and lichens.
Conifer forests benefit watershed health by:
Public land management agencies regulate most mature mixed conifer forests, but they are often fragmented by very young forests being managed on a short rotation to generate timber products.
While these younger forests maintain their capacity to become mature forests, the fragmented patches do not provide the same ecological benefits and cannot support the wide array of wildlife species as mature upland forests.
1. USFWS Willamette Valley Conservation Study: https://www.fws.gov/yourwillamettevalley/Conservation_Study/WVCS_Study.pdf
2. Oregon Conservation Strategy: https://www.oregonconservationstrategy.org/strategy-habitat/oak-woodlands/
3. National Park Service: https://www.nps.gov/subjects/wetlands/why.htm