Amphibians in northwest Portland have a big problem, and it’s called U.S. Route 30. Twice a year, frogs and salamanders must cross the busy four-lane roadway that separates their upland forest habitat from their wetland breeding grounds. Many of them don’t make it.
A recent effort led by the Columbia River Estuary Study Taskforce (CREST) and supported by Metro took one big step — or maybe we should say “hop” — toward solving this problem.
In December, construction was completed on a new wildlife underpass that allows amphibians and other small animals to safely travel between the breeding ponds of the Oregon Department of Fish and Wildlife-managed Palensky Wildlife Area and the forests of Metro’s Burlington Creek Forest Natural Area.
Constructed in 2024 over the course of about six months, the project was the result of years of conversation and design work involving engineers, wildlife biologists and road experts. To help make the project happen, Metro contributed just under $500,000 of the $3.4 million budget, with most funding coming from the Bonneville Power Administration and the Oregon Department of Fish and Wildlife, along with grants from the Oregon Watershed Enhancement Board and Oregon Wildlife Foundation. Metro’s contribution came from the voter-approved 2019 parks and nature bond.
The tunnel might look like just another storm culvert to passersby. But closer inspection reveals some differences. At more than 4 feet in diameter, it’s large enough to allow small mammals to pass through it. The bottom is lined with dirt and sticks to duplicate the kind of terrain amphibians are used to traveling across. And the tunnel includes gentle lighting and grates that function like skylights, as many amphibians avoid dark caves and tunnels.
The opening is flanked by “wing walls,” barriers that direct wildlife to the underpass. Trail cameras can monitor which species are using the tunnel, and how often. This, in turn, will help inform future projects like this. The tunnel is Oregon’s first wildlife crossing designed specifically for amphibians, so there’s a lot to learn.
The goal is to help protect species like the northern red-legged frog, which is designated a sensitive species in Oregon. A significant population of these frogs live in the forests of the Tualatin Mountains, which include Portland’s Forest Park as well as more than 1,400 acres of natural areas protected by Metro.
Every winter, these frogs wait for wet evenings to move from the forests to their breeding ponds, and then later, move back to their terrestrial habitat for the remainder of the year. So twice a year, they are forced to cross U.S. Highway 30, which separates a 7-mile stretch of wetlands and floodplain along Multnomah Channel from the Tualatin forests.
For years, volunteers have collected frogs in buckets near the Portland General Electric-owned Harborton Wetlands, a few miles south of the new underpass. But that solution is far from ideal: It depends on a large group of volunteers working at night near the highway, and wildlife can often find even gentle handling by humans traumatizing and harmful.
A safe crossing that animals can use without assistance is a much better option. The information gathered from the Palensky underpass could eventually help find a solution for the Harborton frogs. It could also help inform plans to improve the current crossing to the Metro-owned North Multnomah Channel Marsh, which is a few miles to the north of the new underpass.
Just like humans, wildlife needs connection to thrive — though in the case of wildlife, those connections are often literal ones between habitat areas. Even modest connectivity between habitat patches creates more robust populations, better able to find high-quality habitat, withstand wildfire or disease outbreaks, and adapt to a changing climate. Our community has made remarkable investments in conserving nature close to home in the greater Portland area, but human infrastructure (the roads, homes and businesses we rely on for modern life) often isolates otherwise high-quality habitat, limiting its value.
A regional habitat connectivity working group is helping to tackle the issue across the region. Metro is one participant. The group is exploring not just projects like the Palensky underpass, but also ideas like acquiring land that connects large natural areas owned by different agencies, re-foresting currently paved areas, and improving regional transportation projects to minimize conflict between humans and wildlife.
Projects like this require significant funding from public agencies and nonprofits, as well as coordination between multiple organizations. That’s only possible when voters agree to invest in nature stewardship. So the next time you hear frogs chorusing in the evening, listen closely: Maybe you’ll hear a “thanks, everyone!” in their call.
This story was written by Jonathan Soll, Metro Parks and Nature’s science manager, and by Katy Weil, senior natural resource scientist.