Thousands of people visit Muir Woods National Monument every year to take in its grand redwood trees, but climate change could dissipate the cooling, wet fog that enables those trees to grow to towering heights.
And it's not only Muir Woods that's in the dangerous path of climate change. Researchers warn the phenomenon could bring peril to many of Marin's natural wonders in the coming years as weather conditions change.
"It's trees at Muir Woods. It's a concern about sea level rise at Fort Baker. It's many things," said Alex Picavet, spokeswoman for the Golden Gate National Recreation Area, part of the National Park Service. "But it's not only local. We are grappling with this across the country."
It could have no greater visible effect than in Muir Woods, where redwoods about 500 to 800 years old climb more than 200 feet toward the sky, providing a serene setting for visitors from Marin and around the world.
A report recently issued by the nonprofit National Parks Conservation Association concludes climate change could affect the formation and presence of fog along the entire Pacific Coast, and that in turn could stunt the giant redwoods.
"It's a concern that has been floating around the park service: How do you deal with the fog issue?" said Neal Desai, associate director of the National Parks Conservation Association Pacific Region. "The redwoods at Muir Woods are the iconic trees, and the fog is their lifeblood."
Another recent report issued by the Rocky Mountain Climate Organization in Colorado looking at the impact on state parks comes to the same conclusion -- and says it's already happening.
It's fog that rolls over the trees and provides moisture -- nature's drip irrigation system -- that allows the redwoods to grow even in the driest of months. Branches covered with fine needles catch the fog's water particles, which then condense and fall to the forest floor below where their roots can absorb the water.
Coast redwoods are limited to a few hundred miles in Northern California, where a confluence of location, climate and elevation provides the only place they can be found. The fog created by the Pacific Ocean and atmospheric conditions keep the trees continually damp, even during summer droughts. The summertime fog provides about 40 percent of their annual water supply, according to the Rocky Mountain report.
Scientists have found that during the past century the amount of fog has dropped by about one-third, leading them to believe that the trees will have trouble growing to the dizzying heights they do now.
The average temperature in Muir Woods could increase by more than 5 degrees by 2070, making it as hot as San Diego has been historically, according to the report.
It wouldn't only be Muir Woods heating up. The Point Reyes National Seashore could also see a 6-degree temperature rise, making it as warm as Santa Barbara has been.
"What could happen if temperatures rise and sea level rises?" said John Dell'Osso, chief of interpretation at the seashore. "Might we lose species of plants, 60 of which at Point Reyes are found nowhere else in Marin County? Will beaches become less accessible? We don't know, but we can all do something about this. I don't want to be too doom and gloom, but there are challenges."
Wetlands would be at risk too, including the wildlife-rich estuaries of Abbotts Lagoon and Drakes Estero, home to many of the seashore's harbor seals and shorebirds and endangered species from peregrine falcons and marbled murrelets to several species of fish.
Also at Point Reyes, harbor seals could lose rocky tidal areas where they give birth, molt and rest. These areas are critical for sustaining the 7,000 harbor seals at the seashore, which make up 20 percent of the mainland population of the species in the state.
Point Reyes has a wide diversity of bird life with nearly 490 species recorded -- 45 percent of all bird species in North America. But with widespread changes expected to occur at Point Reyes, changes in the bird species present at the seashore are likely.
Beyond environmental impacts of climate change, there could be financial impacts to the local economy if people no longer have reason to visit local parks.
Muir Woods has more than 800,000 visitors annually, generates $100 million locally and creates almost 1,000 jobs. Point Reyes has 2.5 million visitors, generates $175 million and creates 1,600 jobs. The Golden Gate National Recreation Area has 14.5 million visitors, generates $365 million and 2,000 jobs.
"To really protect these special places, we need to get serious about sharply cutting heat-trapping pollution, and doing it now," researcher Saunders said. "The good news is that the actions that protect the climate also save energy costs and create clean-energy jobs."