Why restoration matters….to aquatic habitat

Posted by Renee Magyar on October 18, 2016

Planning Team takes integrated look at effects of vegetation management on important aquatic species, like bull trout

Bull trout. Photo by US Fish and Wildlife Service

The Blue Mountains provide important habitat for a diverse range of aquatic species, including various fish and wildlife, and large high-severity wildfires can have adverse effects on this habitat. Topography, forest conditions, climate change, and past management all impact fire behavior and affect how we are able to manage fire as part of a complex system. Understanding the role of fire and its effects on aquatic and wildlife habitat is an important part of efforts to reduce the risk of large uncharacteristic wildfires.

The mission of the Forest Service is to “sustain the health, diversity and productivity of the Nation’s forests and grasslands to meet the needs of present and future generations.” One way of accomplishing this is by managing vegetation to restore ecological processes and functions, benefiting the aquatic and wildlife species that depend on these ecosystems. 

Photo by US Forest Service
Photo by US Forest Service

What kind of habitat do aquatic species need? Fish, for example, need to access many different parts of a stream network to find cold water, particularly during the summer, to ensure adequate growth. Large and severe wildfires can influence hill-slope erosion, stream sedimentation and transport, potential stream shade, and large woody debris inputs to streams. Uncharacteristic wildfires can also cook the soil, removing organic matter and beneficial soil microorganisms. This loss in soil productivity can greatly slow the regeneration of shrubs and grasses that prevent soil erosion and provide shade. All of these factors influence aquatic species’ abilities to grow, reproduce, and even survive in the freshwater environment. Climate change has been linked to declining snow packs, retreating glaciers, and changing patterns of precipitation and runoff, all of which affect the natural processes that create and maintain aquatic habitat. 

The Forest Resiliency Project is being designed to set up our forests to be resilient against natural disturbances in the face of a changing climate. By reducing stand density across large landscapes (thinning the number of trees on an acre), adjusting species composition (altering the species of trees and other vegetation growing on a site), and creating mosaic forest patterns, we can create a more resilient forest ecosystem. Doing so will reduce the risk from uncharacteristic wildfires, and allow fire to play its natural role. 

An important consideration we must make when proposing land management activities is the impacts these activities could have on species listed under the Endangered Species Act, which directs all federal agencies to assist in conserving species “listed” as threatened or endangered. The Blue Mountains are home to various federally-listed salmon, steelhead, and trout species. For example, bull trout are listed as threatened under the Endangered Species Act. Bull trout were once found in about 60 percent of the Columbia River Basin, but today they occur in less than half of their historic range, with scattered populations in portions of Oregon, Washington, Nevada, Idaho and Montana. Bull trout require colder water temperature than most salmon and trout. They also require the cleanest streams for spawning and rearing. They need complex habitats, including streams with riffles and deep pools, undercut banks and lots of large logs. They also rely on river habitats that connect to headwater streams for annual spawning and feeding migrations. 

Resident bull trout spawning Cliff Creek. Photo by Devin Olsen
Resident bull trout spawning in Cliff Creek. Photo by Devin Olsen

The Forest Resiliency Project will protect streamside vegetation, by prescribing buffers along the streams where thinning would only be allowed on trees smaller than nine inches in diameter. The planning team is also proposing prescribed fire treatments in these areas. These protections will maintain stream shading, limit the amount of sediment in fish bearing streams, and provide future recruitment of large wood to streams, where standing trees could eventually fall into the stream and provide habitat, sediment storage, or bank stability for the stream channel. All of these elements are critical to maintaining healthy bull trout populations into the future as well as meeting the requirements for conservation of the species under the Endangered Species Act. 

Bull trout are also a species that could be highly impacted by climate change. The planning team is using climate change modeling to predict where forest vegetation will change at a watershed scale. The extent of this change could impact vegetation available for bull trout, and potentially affect stream flow and stream temperature. The Forest Resiliency project will look for potential refugia -- areas protected from the effects of climate change -- and determine how forest management can protect these areas and reduce the impacts on bull trout. Suitable refugia are portions of watersheds that currently support bull trout and are predicted to support them in the future taking into consideration climate change and its effects on bull trout habitat.

We may not be able to precisely predict the extent, location, or timing of climate change impacts, but we can recognize ecosystem changes and respond with flexible and adaptive watershed management strategies. These strategies will help minimize impacts to the highly sensitive bull trout and help conserve bull trout populations.

Do you want to know what others are saying about this project? Find out more by visiting the public reading room. Additionally, you can find notes from recent public engagement sessions on the project public engagement website.

This is the tenth of twelve issues of Features from the Blue Mountains Restoration Strategy brought to you by Sustainable Northwest and the U.S. Forest Service Blue Mountains Restoration Strategy Team. This monthly series highlights the environmental and economic challenges and opportunities present in the Blue Mountains region, and includes updates from the Blue Mountains Forest Resiliency Project.