from http://www.dfw.state.or.us/conservationstrategy/docs/document_pdf/b-eco_wv.pdf
Willamette Valley Ecoregion
Overview
The Willamette Valley ecoregion is both the fastest growing ecoregion in Oregon and the most densely populated, containing the states’ three largest urban centers (Portland, Salem, Eugene). The population projected for 2050 is approximately four million, nearly double today’s population. The ecoregion also provides about half of the state’s agricultural sales and includes six of the top 10 agricultural-producing counties. Also,16 of top 17 private sector employers (manufacturing, high technology, forest products, agriculture, and services) are located in this ecoregion.
Historical accounts indicate that prior to European settlement, much of the Willamette Valley was covered by native grasses and forbs. The Calapooia people regularly set fires to improve hunting and travel. The fires helped maintain the valley’s mosaic of grasslands, oak savannas, wet prairies and other open habitats.
Since the 1850’s, much of the Willamette Valley ecoregion has been altered by development (agricultural or urban), particularly affecting oak woodlands, oak savanna, grassland, riverine, and wetland habitats. The Willamette River has been disconnected from its floodplain, and much of the historic habitats have been fragmented. About 96 percent of the Willamette Valley ecoregion is privately owned, presenting challenges to conservation management. “Fine-filter” conservation strategies that focus on needs of individual at-risk species and key sites are particularly critical in this ecoregion.
The Willamette River
With a watershed of more than 11,200 square miles, the Willamette River is the longest river in Oregon and the primary waterway in the valley. From the junction of the Coast Fork and Middle Fork near Springfield, the Willamette meanders more than 185 miles north to its confluence with the Columbia. Along the way, the river swells with the waters of numerous tributaries flowing out of the Cascades and the Coast Range. Prior to European settlement, the Willamette River system dominated the landscape, occupying braided, shallow channels that moved constantly across a broad floodplain with numerous sloughs and extensive marshlands. The river’s flows varied with the seasons, rising slowly from late August through the winter, peaking during spring snowmelt in the Cascades, then falling sharply until the rains returned. During times of peak flow, the river frequently flooded large portions of the valley, at times attaining widths of two to six miles. Over the past 150 years, the river has been transformed into a deeper, straighter, and narrower channel, and flows have been regulated by a number of dams in the upper watersheds of the Willamette’s tributaries. These modifications resulted in a complex web of unintended secondary changes that have fundamentally altered the river system’s natural ecological processes and functions. Recently, there have been coordinated efforts to address concerns such as clean water, water quantity, and habitat loss.
Factor: Land use conversion and urbanization. Habitat continues to be lost through conversion to other uses.
Approach: Because 96 percent of the Willamette Valley ecoregion is privately-owned, voluntary cooperative approaches are the key to long-term conservation using tools such as financial incentives, Candidate Conservation Agreements with Assurances, and conservation easements. Careful land use planning also is essential. Work with agency partners to support and implement existing land use regulations to preserve farmland, open spaces, recreation areas, and natural habitats. Monitor changes in land uses across the landscape and in land use plans and policies.
Factor: Altered fire regimes. Maintenance of open-structured Strategy Habitats such as grasslands, oak savannas and wet prairies, are dependent in part on periodic burning. Fire exclusion has allowed succession to more forested habitats. Reintroduction of fire poses significant management problems in many areas of the Willamette Valley. These problems include conflicts with surrounding land use, smoke management and air quality, and safety.
Approach: Use multiple tools, including mowing and controlled grazing, to maintain open-structured habitats. Ensure that tools are site-appropriate and implemented to minimize impacts to native species. Re-introduce fire at locations where conflicts such as smoke and safety concerns can be minimized. Work with local communities to ensure that local concerns such as air quality are addressed.
Factor: Altered floodplain. The floodplain dynamics of the Willamette River have been significantly altered. Multiple braided channels dispersed floodwaters, deposited fertile soil, moderated water flow and temperatures, and provided a variety of slow-water habitats such as sloughs and oxbow lakes. The Willamette River has largely been confined to a single channel and disconnected from its floodplain.
Approach: While restoration of multiple channels may be neither practical nor desirable, cooperative efforts are needed to restore floodplain function and critical off-channel habitats. Approaches are discussed in Restoring a River of Life, Willamette Restoration Initiative (2001).
Factor: Habitat fragmentation. Habitats for at-risk native plant and
animal species are largely confined to small and often isolated
fragments such as roadsides and sloughs. Opportunities for largescale
protection or restoration of native landscapes are limited.
Barriers to large-scale ecosystem restoration include: existing development,
growth pressures, high land costs, and the fragmented
nature of ownerships and remaining native vegetation types.
Approach: Broad-scale conservation strategies will need to focus on
restoring and maintaining more natural ecosystem processes and
functions within a landscape that is managed primarily for other
values. This may include an emphasis on more “conservationfriendly”
management techniques for existing land uses and restoration
of some key ecosystem components such as river-floodplain
connections and wetland and riparian habitats. “Fine-filter”
conservation strategies that focus on needs of individual Strategy
Species and key sites are particularly critical in this ecoregion.
Factor: Invasive species. Invasive plants and animals disrupt native
plant and animal communities and impact populations of at-risk
native species.
Approach: Emphasize prevention, risk assessment, early detection
and quick control to prevent new invasives from becoming fully
established. Use multiple-site appropriate tools (mechanical,
chemical and biological) to control the most damaging non-native
species. Prioritize efforts that focus on key invasive species
in high priority areas, particularly where Strategy Habitats and
Species occur. Work with the Oregon Invasive Species Council and
other partners to educate people about invasive species issues
and to prevent introductions of potentially high-impact species
such as zebra mussel. Provide technical and financial assistance
to landowners interested in controlling invasive species on their
properties. Promote the use of native “local” stock for restoration
and revegetation.
Conservation Success Story: Fescue farm supports wetlands
restoration in the Willamette Valley
Located several miles west of Salem off Route 22 are 400 acres of
restored wetlands owned by landowners Mark and Debora Knaupp,
second generation Oregonians whose voluntary decision to convert a
portion of his farmland to wetland is producing ecological, recreational
and financial benefits.
The Knaupps are commercial grass seed growers who, with technical
assistance from ODFW and others, have nurtured back to life a mosaic
of shallow seasonal marshes and wet prairies. As a result, wildlife, waterfowl
and rare plants along Mud Slough in Polk County have returned
in full splendor. Knaupps’ wetlands also help purify local drinking water
by removing pollutants that might otherwise percolate into the local
watershed of Rickreall.
In 1996, the Knaupps retired 320 acres of grass seed production by
enrolling this land in U.S. Department of Agriculture Department’s Wetlands
Reserve Program (WRP). Under this program, private landowners
agree to take agricultural land out of production and place those acres
into a conservation easement. In exchange they are paid the agricultural
value of their land, which in the Willamette Valley has increased to
$2,500 per acre since 1999. Landowners maintain complete ownership
of the land enrolled in WRP and the right to pursue undeveloped recreational
uses such as hunting and fishing. Indeed, the Knaupps operates
a duck-hunting club to take advantage of plentiful waterfowl drawn to
their wetland.
The Knaupps have found another way for the wetland to pay for itself
and diversify his business. They created a 57-acre mitigation bank that
offers wetland credits to area landowners who develop their property
but must offset any loss of wetlands under federal law. Purchasing
credits from the Knaupps’ Mud Slough Mitigation Bank enables landowners
to meet wetland regulatory requirements without developing a
detailed mitigation plan or paying for new wetlands construction.
For Mark and Debora Knaupp, restoring marginal farmland to a
healthy, fully functional wetland was as much a personal desire as it
was a business decision. After all, Mark Knaupp says “supporting wildlife
conservation by participating in USDA’s Wetland Reserve Program
and selling mitigation credits has resulted in economic benefits for our
business and brought our family tremendous personal satisfaction.”