How to build a highway in the age of climate change
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- Caltrans and the Metropolitan Transportation Commission are pursuing a $500 million, five-year remake of California State Route 37: replacing one of five bridges with a span 5 feet taller, raising two one-mile sections by up to 8 inches, adding carpool and bus lanes in each direction, and restoring tidal marsh habitat.
- Critics including TransForm CA's Zack Deutsch-Gross argue that's too modest; they back a $10 billion, 20-year alternative that would raise nearly the entire 21-mile roadway, add a cyclist and pedestrian lane, and possibly include rail tracks, warning that 'highway expansion does not solve congestion and will worsen climate change.'
- Fraser Shilling of UC Davis's Road Ecology Center calls the berm-based approach 'the least resilient' option and favors relocating the highway as much as 5 miles inland, noting the route 'goes through the marshes' in a way that 'you would never ever get permission to build that today.'
- The Metropolitan Transportation Commission has secured $270 million to replace the Novato Creek Bridge as the first phase, which spokesperson John Goodwin said is designed to accommodate sea-level rise and storm surges on SR-37 until 2130 while the agency works to fund the long-term plan.
- California's projected sea-level rise — an average 10 inches by 2050 and 1.6 to 3.1 feet by 2100 — puts portions of SR-37 at risk of permanent inundation without adaptation, while bolstering U.S. bridges alone could cost $170 billion by 2050.
- Comparable causeways illustrate the stakes: Hurricane Ian flooded Sanibel Causeway in 2022 (reopened in 15 days), and Tybee Island's 11-mile causeway to Georgia closed four times in 2024, stranding residents for as long as five hours.
- Nature-based and equity concerns are surfacing: Tybee Island added three rain gardens via National Fish and Wildlife Foundation funding, and Stetson University's Jason Evans warned that using tax revenue to elevate causeways 'so the millionaires and billionaires can get to their beach house' diverts money from projects serving broader communities.
Why it matters: California alone faces $170 billion in bridge-hardening costs by 2050, and the SR-37 decision will set the template for whether states adapt in place, retreat inland, or invest in nature-based defenses — each path locking in different cost, equity, and ecological tradeoffs for the millions of commuters and freight routes on coastal roads.
