Limiting Factor: Habitat Loss
A high percentage of low-elevation and valley bottom wetlands have been lost or degraded through diking and draining, particularly in the Klamath Mountains and Coast Range ecoregions. In other areas, overgrazing has led to soil compaction, changes in plant species composition, and spread of invasive plants. Due to short growing seasons and other factors, degraded wet meadows can be slow to recover if overgrazed. Saltmarshes have experienced substantial losses over historical condition from diking, installation of tide gates, draining, and filling of tidally influenced marshes. Wetlands provide vital habitat for migrating shorebirds and waterfowl. Loss or degradation of wetland habitat in the Pacific Flyway could potentially have large impacts on bird populations while early season haying in wetland habitats can result in poor reproduction of ground-nesting birds due to destruction of nests and direct mortality of young.
Many wetlands are lost through urbanization, which involves filling or draining the wetland for development. Unfortunately, this removes wetlands from locations where the functions they provide might have the most value for SGCN. Maintaining wetland and adjacent habitats provides social benefits, such as storage of flood water and treatment of contaminants before reaching streams and ground water.
Recommended Approach
Protect and conserve priority wetland habitat that provides vital breeding habitat for SGCN and stopover sites for migrating species (KCI: Barriers to Animal Movement). Identify wetlands that have been altered or lost and determine their potential for restoration. Build upon current cooperative efforts to maintain and restore wetlands in partnership with private and public landowners. Cooperative voluntary approaches are important for wetland conservation on private lands. Continue to provide incentives to protect, maintain, or restore wetlands, such as the Wetland Reserve Enhancement Partnership (WREP) offered through the Natural Resources Conservation Service and private mitigation banking. Prioritizing development of wetland mitigation banks to support SGCN also provides a strategic landscape approach to addressing wetland loss.
Develop and implement grazing regimes that are compatible with wet meadow conservation objectives. Use cooperative efforts and incentive programs to establish semi-permanent livestock exclusion zones in priority areas. In partnership with landowners, implement later haying dates in critical bird nesting areas (see The Willamette Valley Landowner’s Guide to Creating Habitat for Grassland Birds). Manage beaver populations to contribute to wetland creation and maintenance, when compatible with existing land uses.
Promote outreach and education programs to educate individuals, communities, city and county planners, agricultural groups, and forest industries about the function and services provided by wetlands. Work with the local planning process and the Oregon Department of State Lands to promote the value of maintaining wetlands and habitat corridors, especially along floodways, where they can best function to protect structures, infrastructure, and water quality.
Limiting Factor: Drought
Drought affects the quality and extent of wetlands across the state. Drought has resulted in less precipitation, interception, infiltration, and percolation of water into the soil, falling water tables, increased evaporation, decreased transpiration, decreased plant and animal diversity and distribution, and the acidification, cracking, and compaction of wetland soils. These changes in hydrology and soils affect plant and animal diversity, connectivity with other aquatic resources and upland habitats, the proportion of invasive plant species in the wetland, and wetland functions. Climate change patterns are expected to exacerbate and or extend drought periods resulting in wetland loss of acreage and functional changes.
Recommended Approach
Educate the public and water users to conserve water. Look for opportunities to restore and enhance wetlands (i.e. Barnes and Agency Wetland Restoration- Upper Klamath National Wildlife Refuge), reuse water for multi-benefit solutions, and improve wetland habitat through water use efficiencies (i.e. Lower Klamath and Tule Lake National Wildlife Refuges). Coordinate with ODFW Fish Passage and District Fish Biologist staff on appropriate approvals for instream, beaver-mimicry (e.g., beaver dam analogs, small and/or large wood structures) and/or coexistence (e.g., pond levelers, culvert exclusion devices) structures to raise the water table, restore wetland and waterway connections, and improve habitat conditions (i.e. Sprague Watershed).
Limiting Factor: Water Quantity
Water is extremely limited in much of the Blue Mountains, East Cascades, and Northern Basin and Range ecoregions. As a result of limited water availability, there is competition for water resources, particularly in late summer. Lowered water tables affect wetland habitats. Competition for water harms both ecological and economic goals. Water diversions for other uses change the seasonality of flooding, slow habitat recovery, and increase invasion of non-native grasses. Drought years intensify water shortages.
Recommended Approach
Use cooperative efforts and incentive programs, such as financial incentives, for wetland restoration, water right acquisition, and wetland mitigation banking, to enhance management of water allocation and improve wetland habitats. Implement water conservation actions, where possible, to increase availability (quantity, timing, and duration).
Limiting Factor: Degraded Water Quality
Although wetlands have a role in purifying water, water quality is poor in some wetland systems. High temperatures affect water quality in some areas. Non-point source runoff from agricultural and residential areas contains pollutants that can affect water quality and nutrient levels, and these levels may increase as water evaporates throughout the season. High nutrient loads can contribute to toxic algal blooms.
Recommended Approach
Provide incentives to decrease and manage the release of potential contaminants, such as fertilizers or pesticides, by controlling the timing of application. Use incentives to promote substitutes that are less toxic to wildlife and break down quickly in the environment. Promote the creation of stormwater treatment projects, fencing of aquatic habitats to exclude livestock, and restoration of riparian buffers and additional wetlands to increase filtering capacity. Support irrigation systems that conserve, re-collect, and re-use water more effectively, use gray water, and provide shaded treatment areas that can provide cooling and habitat. In the Willamette Valley, adopt critical actions recommended by the Willamette Restoration Initiative on Clean Water, such as: reduce the levels of toxins and other pollutants in the Willamette Basin, provide incentives to decrease water pollution, and promote education and outreach programs for landowners.
Limiting Factor: Invasive Species
Invasive species, such as reed canary grass, purple loosestrife, Ludwigia spp. and Japanese knotweed, invade and degrade wetlands, thereby displacing native plants, reducing plant community diversity, reducing sources of food for wildlife, and altering water flow and storage function. Invasions of non-native grasses, such as reed canary grass, can also create conditions more prone to wildfires.
Invasive, non-native carp can impact wetlands by consuming important plants and by increasing turbidity, disturbing sediments, and altering biological dynamics for sediment-associated plants and animals. Turbidity also contributes to higher water temperatures and lower levels of dissolved oxygen. Non-native bullfrogs have had a devastating impact on native amphibians and reptiles, leading to the extirpation of Oregon spotted frog and leopard frogs from much of their historic range. Emerald ash borer is now present in the Willamette Valley and threatens to cause extensive losses to ash trees, which are a critical component of off-channel wetland habitats.
Native trees and shrubs can become invasive due to the exclusion of fire from wetlands. Without fires from natural ignitions and Indigenous peoples cultural burning practices, encroachment by native vegetation can overwhelm wetlands and out compete wetland grasses and flowers by reducing water availability, shading, and changing soil chemistry.
Recommended Approach
Emphasize prevention, risk assessment, early detection, and quick control to prevent new invasive species from becoming fully established. Control key invasive plants using site-appropriate tools, such as flooding (reed canary grass), biological control (purple loosestrife), and mechanical treatment including mowing. Use chemical treatment carefully and where compatible with water quality concerns, focusing on spot treatment during the dry season. Consider screening or adjusting water levels to control carp. Use revegetation and other means to establish and maintain native plant communities that are relatively resistant to invasion and that also meet other land use objectives.