Report summary on Cascades to Olympics Connectivity

Report summary on Cascades to Olympics Connectivity

Conservation Northwest / Feb 25, 2020 / Cascades to Olympics, Connecting Habitat, Restoring Wildlife

Cascades to Olympics program bolstered by new findings and conclusions from research on habitat connectivity in the Chehalis Basin.


Conservation Northwest’s new Cascades to Olympics program works to restore habitat and improve wildlife connectivity between Washington’s Cascades Range and Olympic Peninsula.

The program geography stretches from Mount Rainier to the southern end of the Cascades in Washington at the Columbia River Gorge, west across I-5 and the Willapa Hills to Willapa Bay and then north past Grays Harbor to the Olympic National Forest, and east around the south Puget Sound back to the Cascades.

An existing structure under I-5 at Newaukum River. Our Cascades to Olympics program seeks to enhance structures like these to better serve as wildlife crossings. Photo: Brian Stewart

A land of classic Pacific Northwest rainforests, gentle mountains, and river valleys featuring wide floodplains, the region is home to a remarkable diversity of wildlife. Native species include the marbled murrelet, Roosevelt elk, fisher, northern spotted owl, cougar, black-tailed deer, and many more. Moreover, it’s home to Chinook, coho and chum salmon, steelhead, bull trout and other fish as well as semiaquatic species.

However, development, habitat fragmentation, poor forest and land management, accelerated resource extraction, and other human activities have had a lasting negative impact on habitat and wildlife in this region. Climate change will likely exacerbate these pressures.

As the Cascades to Olympics Connectivity Contractor, I’ve been conducting research for Conservation Northwest and other partners on migration corridors and potential locations for wildlife crossings across Interstate 5 (I-5). Based out of Onalaska in the Chehalis Basin, I’m also engaging with local stakeholders on the Chehalis Basin Strategy—a basin-wide plan to address extreme flooding and habitat degradation on the Chehalis River.

The results of this research are now available. View our full Cascades to Olympics Connectivity Report (2019). Or read on for a summary.

Map of our Cascades to Olympics program. Click for a larger version!

Wildlife Crossings on I-5

One of the major contributors to past habitat loss and the region’s current state of fragmentation are state highways and federal freeways, including the largest and most traveled road in Washington: I-5. Using habitat connectivity maps produced by the Washington Wildlife Habitat Connectivity Working Group and “naturalness” linkage maps from their current project in partnership with the Cascades to Coast Landscape Collaborative, we’ve been able to identify important habitat linkages that cross state highways.

In addition, my recent thesis research and connectivity report Conservation Northwest used wildlife-vehicle collision data, land use data, and habitat connectivity maps to identify existing structures (underpasses/viaducts) that would be suitable for enhancements for more effective wildlife crossings. These structures, located at the Newaukum River, Skookumchuck River to Prairie Creek, and Owl Creek, are priority areas for fencing and habitat restoration projects to allow safe passage. Furthermore, the area north of the Toutle River is a location where a wildlife bridge is needed and may be viable.

This research suggests that large structures on I-5 that lack  accompanying wildlife infrastructure (i.e. fencing, barriers, passable substrates) may be associated with higher rates of wildlife-vehicle collisions. Those areas tend to be where wildlife are already present, so if the animals are surprised by the sudden appearance of people or loud noises from vehicles on the freeway, they may jump out onto I-5. This emphasizes the importance of upgrading and enhancing large structures that wildlife may be already using to move through the landscape.

Our Cascades to Olympics program goals also include wildlife crossings on Highway 12 between Olympia and Aberdeen. Unfortunately, there is a lack of detailed data for this highway, and more needs to be done to better understand the limitations and opportunities presented by this road and its associated underpasses and culverts. Conservation Northwest will continue to advocate for needed wildlife infrastructure on busy roads and facilitate the collection of more data through the Cascades to Olympics program.

The Chehalis River near Pel Ell, Washington. Through our Cascades to Olympics program, we’re working closely with agency, community and nonprofit partners focused on habitat restoration and conservation in the Chehalis Basin. Photo: WA Department of Ecology

The Chehalis Basin

The Chehalis Basin is an important part of the coastal landscape—home to more amphibian species than anywhere else in Washington, it’s the second-largest river basin in the state. Through our Cascades to Olympics program, we’re working closely with agency, community and nonprofit partners focused on habitat restoration and conservation in the Chehalis Basin.

The Chehalis Basin is one of the last strongholds of wild steelhead, Washington’s State Fish and a threatened species across much of their range. This large wild steelhead was caught and released in the Chehalis Basin. Photo: Chase Gunnell

This area has vibrant but economically-challenged communities still recovering from historic dependence on the timber and fishing industries, as well as the homelands of the Quinault, Chehalis and other Indigenous peoples. And areas such as Centralia are seeing explosive growth along the I-5 corridor, putting future connectivity in jeopardy without growth management.

Historic floods, which can be so severe that portions of I-5 must be closed for several days, have also brought these issues to prominence. Another important element of the Cascades to Olympics program is the implementation of the Aquatic Species Restoration Plan (ASRP), a plan initiated by the Governor’s Office of Chehalis Basin (and being conducted by the Department of Ecology, Department of Fish and Wildlife, Quinault Nation and Chehalis Tribe) that seeks to conserve and restore hundreds of miles of riparian habitat in the Chehalis Basin as part of the overall Chehalis Basin Strategy.

Check out this trailer for an upcoming documentary film about the Chehalis Basin!

Many of the ASRP target areas and goals overlap with the needs of terrestrial and semiaquatic habitat connectivity in the region. In fact, evaluated structures on I-5 with the two highest rates of wildlife-vehicle collisions between the Oregon-Washington border and Tumwater, just south of Olympia, are both in the Chehalis Basin.

A fisher being released in the Olympic Peninsula. The Chehalis Basin is important habitat for fishers and other species. Photo: Paul Bannick

To communicate the need for integrating habitat connectivity in the ASRP, I gave a presentation to the ASRP Scientific Review Team explaining how terrestrial connectivity helps maintain healthy ecosystems and should be a part of building basin-wide climate resiliency. Additionally, we recently submitted public organizational comments for the first phase of the ASRP, advocating for more consideration of connectivity for terrestrial and semiaquatic species, specifically around high speed, high volume highways.

In parallel with the ASRP is a flood retention proposal, including a massive proposed dam on private timberlands in the upper Chehalis River, south of the town Pe Ell. This is controversial, yet the status quo in this landscape is not tenable, and restoration alone may not be enough to reduce flood impacts. We previously did comments and action alerts on this, and will continue to be engaged during the next round this spring.

We’re looking forward to improving wildlife conservation and connectivity in this landscape through our Cascades to Olympics program, and working with partners and stakeholders to help make this landscape more resilient for wildlife and rural communities. Including permanent habitat, watershed and wildlands protections through the Wild Olympics proposal. Stay tuned for more program updates, including maps showing priority areas and habitat connectivity from the South Cascades to the Olympic Peninsula!

Our Cascades to Olympics program works to restore habitat and improve wildlife connectivity between Washington’s Cascades Range and Olympic Peninsula. Photo: Eric Foltz