In the Hawai‘i Highways Climate Adaptation Action Plan, the state Department of Transportation (DOT) points out that while there’s uncertainty about the scale of future threats to roads here, what’s certain is that it no longer makes sense to approach maintenance and upgrades based on the assumption that environmental conditions will remain largely unchanged.

The newly released action plan notes that in some recent cases of extreme weather events, heavy damage and disruption has caught DOT “unaware” — in part because the impacts to highways were “much greater than had been expected when the road was designed.”

Nearly 60% of Hawaii’s roads and slightly more than 75% of its bridges are now exposed to potential climate stresses such as landslides, coastal erosion, sea level rise, storm surges, tsunamis, wildfires or other natural hazards, according to the report, which identifies vulnerable areas in the state’s portion of the National Highways System and recommends strategies to make them more resilient to climate-related wallops.

There’s really no time to waste. In an alarming report issued this week by the Intergovernmental Panel on Climate Change, its authors — a group of scientists convened by the United Nations — warned that while there’s still opportunity to fend off dangerous environmental “tipping points,” such as glacial meltdown, there’s now no stopping global warming from intensifying in the next three decades.

Hawaii’s highway network is particularly vulnerable to accelerating climate change, because many of the roads wind along low-lying coastal areas, as steep mountain ranges limit the number of cross-island routes. Since 1960, sea level has risen between 2 inches and 8 inches relative to Hawaii’s shoreline, and climate scientists project at least 3 feet of sea level rise in the islands by the year 2100.

Implementing effective long-range resiliency for Hawaii will be a heavy lift for the state, requiring collaborative effort among government agencies and community buy-in. But in the absence of a concerted push, the state is expected to face devastating losses. Among the projections tied to foot-dragging or inaction: With 3 feet of sea level rise on Oahu, 18 miles of coastal roads will become impassable and 13,000 residents will be displaced.

What’s more, aside from climate change risks, a majority of the state’s infrastructure framework — roads, bridges, dams, drinking water apparatus and other systems — have been operating beyond their useful life, with some components more than 100 years old, according to a 2019 report card issued by the American Society of Civil Engineers’ Hawaii Section, in which the state earned an overall grade of D+.

Substantial and sustained investments are needed to avoid wasteful spending on Band-Aid patches. To that end, it’s encouraging that the Biden administration’s $1 trillion infrastructure investment plan, which passed the U.S. Senate on Tuesday, could help Hawaii swiftly move forward with long-lasting fixes. The Infrastructure Investment and Jobs Act would give the state $225 million for bridge replacement and repairs over five years, as well as $1.2 billion for highways.

The DOT’s Highways Division is responsible for conditions along 971 miles of state-owned highways and 303 bridges as well as scores of culverts and a half dozen tunnels. The agency’s action plan serves as a necessary step toward tackling a growing roster of challenges. Among the next steps: a risk prioritization and capital investment plan, drafting of statewide multi-agency resilience plans, and establishing a project funding program.

For the sake of future generations that will surely continue to wrestle with climate change, and pay the heavy infrastructure bills, Hawaii must to move forward with a sharply focused adaptation plan — before the weather changes too much.