Marin climate change risks assessed in ‘biosphere’ report

Coastal redwood forests like Muir Woods are at heightened risk of water stress, mortality and overall poor health if climate change remains unchecked, according to a new report.

The finding is one of many in the report produced by the Golden Gate Biosphere Network, a collaboration of state and federal park managers, environmental researchers and preservation groups. The organization covers 28,000 square miles from San Mateo to Mendocino counties.

The report, done in partnership with the climate-focused organization EcoAdapt, assesses 21 key species and habitats within the region.

One of the first actions recommended in the report is to bring back prescribed burns in Muir Woods, said Alison Forrestel, a natural resource management and science official for the Golden Gate National Recreation Area.

“There hasn’t been fire in Muir Woods since the late 1990s,” said Forrestel, a lead author of the report.

Historic timber harvesting and fire suppression have altered forest structure and composition and increased vulnerability to large, intense fires, the report says. Reintroducing prescribed burns would help increase forest resilience to drought, wildfire and disease, the report says.

“For us to be able to use this as a tool, this climate change vulnerability assessment, to really highlight what are the most vulnerable resources — where do we need to take action? — I think that’s really the power of it,” Forrestel said.

The assessment measures how vulnerable habitats and species are to climate change, in order to understand how to fight back, Forrestel said.

“Vulnerability is really the sum of three different factors,” Forrestel said. “One is exposure, another is sensitivity and the third is adaptive capacity.”

As an example, coastal dunes of the Point Reyes National Seashore have been identified as having a high vulnerability to climate change, Forrestel said.

She said coastal dunes might have a high level of exposure to climate change stressors because of rising seas, increasing wave runup and more intense storms hitting the dunes. Dunes might be quite sensitive to climate change because with increased frequency and intensity of wave impact, there could be a lot of erosion, Forrestel said.

When it comes to a dune’s adaptive capacity, in some instances dunes are able to migrate away from the ocean and up in elevation. In other cases, there might be infrastructure behind the dune, hemming its adaptability, Forrestel said.

The report provides a summary of sites with descriptions of what animal and plant species live there, as well as details of the climate change stressors that are a detriment to their health. The report also recommends actions that parkland managers can take to offset the damage, as well as combat and adapt to threats.

“It’s critically important for us to have this kind of analysis because it helps us prioritize where we’re taking our restoration actions,” Forrestel said.

Other habitats at high risk include freshwater and tidal marshes and riparian forests and woodlands throughout Marin County.

As for species, coho salmon and steelhead trout, which run through Lagunitas Creek tributaries, are also at high risk, suffering from heat stress of warming waters, habitat loss from severity and length of drought and other impacts.

Restoration efforts to repair or recreate natural creek flows are underway, with the largest project led by the Marin Municipal Water District, one of the partner agencies in the biosphere network.

Danny Franco, a project manager at the Golden Gate National Parks Conservancy, said one of the goals of the assessment was to better understand climate projections. The reporting looked at different climate modeling scenarios to help inform the analysis.

The modeling scenarios “generally agree that a hotter future for the Golden Gate Biosphere region is what we’re looking at,” Franco said. That is paired with dramatic shifts in the amount of precipitation, he said.

“We’re already seeing this manifest in the biosphere region,” Franco said.

For example, the droughts from 2012 to 2016 and from 2020 to 2022 were followed by record water years in 2017 and 2023, Franco said. Total precipitation is being compressed into shorter windows, and there are more potent “atmospheric river” events, Franco said.

Additionally, six of the warmest years on record have all happened since 2014, Franco said.

Researchers are also teaming with the Greater Farallones National Marine Sanctuary and the Cordell Bank National Marine Sanctuary, which recently updated their marine-focused climate vulnerability assessment that covers eight habitats, 31 species and five ecosystems.

Combining the projects was made easier because they were both led by EcoAdapt using the same methodology, and they have similar objectives.

“From massive blue whales to dime-size mission blue butterflies, we can now look at the species and ecosystems that are most at risk from climate change across the whole, interconnected system in ways that better reflect how the natural world really works, as opposed to how we have drawn our agency boundaries,” said Maria Brown, superintendent of the marine sanctuaries.

The reports are available for review at goldengatebiosphere.org/ccva.