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Humboldt County’s shoreline is changing faster than anywhere else on the West Coast, which leaves locals with the state’s smallest window to prepare for sea level rise. That is the central message of the North Coast Regional Report, part of California’s Fifth Climate Change Assessment.

The report’s coordinating lead authors, Rosemary Sherriff and Andrew Stubblefield, are both Cal Poly Humboldt professors. (They and co-author Jennifer Marlow were interviewed on a recent episode of “The EcoNews Report.”) Their report includes contributions from tribal, agency and community partners.

The 221-page document covers Humboldt, Mendocino, Del Norte, Lake, Siskiyou and Trinity counties, which have about 380,000 residents, all told. It features warnings about our region’s aging infrastructure as we look toward a future with rising seas, increased wildfire risk and more extreme weather.

“The Humboldt Bay region has become the ‘canary in the coal mine’ for SLR [sea level rise] in California,” it says. “Immediate action is required if the communities surrounding Humboldt Bay want to minimize the impacts from, or adapt and build resiliency against, SLR.”

While some old timers insist that local conditions haven’t changed a whit since they were kids, Humboldt Bay has seen about one foot of sea level rise since 1970, and the pace is accelerating. The main reason is geology: The land around the bay is sinking while the coast to the north is being pushed up. The tide gauge at the North Spit records the fastest relative sea level rise of any NOAA station on the West Coast. Since 2000, it has measured about 6.6 inches of rise. Crescent City, meanwhile, has seen less than an inch.

The report says other California communities still have decades to plan, but Humboldt does not.

Projections point to about 1.3 to 1.5 feet of rise by 2050. The stretch of Highway 101 between Arcata and Eureka already floods during king tides, and the report warns that low-lying areas such as King Salmon could face regular inundation in the near future.

Infrastructure at the water’s edge

The report lists weak points that have long been topics of local discussion among community leaders. For example, about 400 drainage pipes around Humboldt Bay depend on one-way tide gates. As seas rise and high tides last longer, those gates trap floodwater inland.

That phenomenon, in turn, impacts other infrastructure. The report quotes Cal Poly Humboldt Environmental Sciences Professor Craig Benson on risks to our region’s sewage treatment plants:

Built behind earthen levees with minimal safety margins, these facilities weren’t designed for projected SLR. Meanwhile, rising groundwater—pushed up by higher sea levels—is making it harder to maintain and repair underground utilities like sewer lines and power cables in low-lying areas. These are not future problems—they are happening now during king tides and will worsen as sea levels continue rising.

Groundwater pushed up by the sea is also complicating repairs to buried sewer lines and power cables. With about three feet of rise, groundwater could be pushed to the surface 160 to 425 feet from the shoreline. Already, some buildings mere blocks from the bay show structural distress.

“Interior valleys face the opposite problem,” the report says. “[D]rought causes expansive clay soils to shrink and crack, then swell when rains return, creating repeated cycles that stress foundations beyond their design limits.”

The report also warns that a Cascadia Subduction Zone quake could cause sudden coastal subsidence and permanent saltwater intrusion into water supplies around Eureka and Arcata.

As is often the case, King Salmon is singled out as one of the most at-risk communities in the state. One foot of additional rise would bring monthly flooding to many areas, and about three feet would mean daily inundation. Interviews with 17 residents and business operators found people deeply attached to the place but uncertain about its future.

‘Whiplash weather’

Annual rainfall in our region is not expected to change much, but it will arrive differently. Precipitation is projected to concentrate in intense winter storms, with drier springs and falls. Atmospheric rivers, which supply 30 to 40 percent of the region’s rainfall, are expected to grow 25 to 40 percent more intense by mid-century. In other words, expect Humboldt County’s rainiest day of each year to be significantly wetter.

The report points to recent examples. Honeydew recorded more than six inches of rain in early January 2023. In November 2024, an atmospheric river and high tides pushed the Eel River to 25.3 feet, well above its 23-foot major flood stage. The flooding mixed salt and fresh water across pastures near Ferndale and submerged parts of Cannibal Island Road. Two landowners in the tidal zone have since decided to sell portions of their land to the California Department of Fish and Wildlife, which the report cites as an example of managed retreat.

Sediment is making floods worse. Jacoby Creek has accumulated so much material that its bed now sits higher than the surrounding land, and the creek leaves its channel to flood nearby farms during high flows. The report notes that flood infrastructure was often designed for rivers that no longer behave as they once did.

Humboldt is also expected to see more “whiplash” years, in which a dry year is followed by a wet one, and vice versa.

The coast will stay cooler than the interior, and the report suggests a thin strip along the Humboldt and Del Norte coastline may be largely spared the worst heat through 2100. (The region has long been cited as a “climate refuge.”) Inland areas, including Southern Humboldt, could see 20 to 30 days a year averaging above 100 degrees by mid-century.

Offshore, the report cites marine heat waves that have wiped out 230 miles of kelp beds and led to the closure of a $44 million abalone fishery, a loss with deep cultural and economic consequences.

As fog declines and heat waves lengthen, the report warns of increased health risks, especially for older residents and people in mobile homes or poorly insulated buildings. (The report is cautious about climate change’s impacts on local fog. It cites “some limited evidence” of a decline in fog in recent decades but says more research is needed.)

On wildfire, the report finds the North Coast has few contractors trained in fire-hardening and little access to retrofit support. The state’s California Wildfire Mitigation Program has piloted in Lake, Shasta and Siskiyou counties but has not reached Humboldt. Wildfire risk is expected to spread from the interior toward the coast over time.

Adaptation examples

If you were to scan the report for good news, this might fit the bill: It highlights a few local projects as models for adapting to climate change.

For example, salt marsh restoration along the bay, including the organized removal of spartina (aka European beachgrass), has improved wave protection and habitat. Hundreds of acres of former tidelands have been reclaimed (inadvertently, in most cases) through dike breaching. McKinleyville’s eight-acre constructed wetland, which treats stormwater, controls floods and provides trails. And, looking forward, a proposal to use dredged material to build up berms and marshes between Arcata and Eureka would reduce wave threats to Highway 101, the report says.

More broadly, the report credits tribal leadership and Indigenous stewardship, including cultural burning, as models for the state. It calls for expanded prescribed fire permitting for tribes. It also points to the removal of Klamath River dams. The Karuk Tribe has secured $10 million from the state’s Proposition 4 climate bond for a resiliency center, though the report notes that is roughly one-third of what is ultimately needed.

The authors argue that rural areas like Humboldt are poorly served by policies and funding formulas designed for cities. As such, they call for community-led planning while noting that our region’s poverty rate is 17 percent, compared with 12 percent statewide.

The authors stress that these are projections shaped by choices still to be made, but that the Humboldt Bay area’s timeline is already running. 

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On Monday, Cal Poly Humboldt issued the following press release:

Climate change presents significant challenges for California’s North Coast, where Humboldt Bay is experiencing the state’s highest rate of sea-level rise. A new report brings together the latest climate science with local and Tribal knowledge to help communities prepare and develop solutions.

The North Coast Regional Report—released this October as part of California’s Fifth Climate Change Assessment—covers Humboldt, Mendocino, Del Norte, Lake, Siskiyou, and Trinity counties.

Conducted by the Governor’s Office of Land Use & Climate Innovation, the Climate Change Assessment examines impacts and projections in nine regions across the state, highlighting each region’s unique vulnerabilities and opportunities.

Regions include: the North Coast, Sacramento Valley, San Joaquin Valley, San Francisco Bay Area, Central Coast, Sierra Nevada, Los Angeles, Inland Deserts, and San Diego. Each focuses on the unique climate vulnerabilities and opportunities specific regions face.

The North Coast report emphasizes the region’s dependence on infrastructure that lacks redundancies. When these systems fail, the impacts cascade through every aspect of community life, from basic services to economic stability. The report also highlights Tribal leadership and local strategies that offer more promising pathways than conventional infrastructure approaches.

“Our climate has changed and will continue to change at accelerating rates, bringing coastal flooding, heatwaves, fire, drought, and flooding. By highlighting the unique strengths and challenges of our region, this report will be an important resource to help communities prepare,” says Andrew Stubblefield, co-author of the report and Forestry, Fire & Rangeland Management professor at Cal Poly Humboldt. “Preparing for climate change requires understanding the science as well as working with researchers, Tribes, and local communities to develop regional priorities and approaches that work.”

“We face some significant challenges, from increasing wildfire risk to reliance on roads with limited alternatives,” says the report’s co-author Rosemary Sherriff, Cal Poly Humboldt Geography, Environment & Spatial Analysis. “But we also have important strengths to build on, including Indigenous stewardship and Tribal knowledge, restoration and climate resilience efforts, and examples of community resilience models.”

“Regional knowledge matters,” she adds. “Understanding both the risks we face here and the work already underway can help communities prepare for what’s ahead.”

The North Coast Regional Report and other regional reports included in California’s Fifth Climate Change Assessment is available at https://climateassessment.ca.gov.