Anyone who has been to Northern California in July or August knows that the fog is part of the landscape. Photographers call it atmosphere, it has been a back-drop to many movies and adds a certain romance and mood. The only thing that can be seen for miles around in San Francisco would be the two lights on top of the Golden Gate Bridge. The very fog that made this particular area very dangerous for shipping a few decades ago also plays an important role in climate control. Without fog there would be no redwoods and no salmon.
This fact was reinforced when I visited the woods a few weeks ago and a park ranger was generous enough with her time to explain to me the dependence of the ecosystem on fog. To anyone who has been to Muir Woods, the thought of no redwoods would send them into a mild panic. Muir Woods is a natural haven north of Sausalito and named after Sierra Club founder and famous environmentalist - John Muir. Walking through the groves of redwoods of indescribable proportions opens your senses to the over-whelming silence and that fresh forest smell. Quiet simply beautiful.
Before I get carried away, I was talking about fog. The formation of summer fog in a rather unique phenomenon influenced by the difference in temperatures between Central Valley and the coast. There are several factors responsible for the fog every summer and now with global warming, the fog is changing as well. Fog enables all life in California acting as a natural air-conditioner.
The redwood trees in Muir Woods and elsewhere require a cloud cover in order not to become desiccated. During the summer months, the trees absorb moisture from the air in order to survive as ground water levels are too low. The trees themselves are rather inefficient reservoirs of water and because of their size lose more water than they can hold. Reduction in summer fog can dry out the forest so much that it becomes vulnerable to forest fires. Fog also influence Coho salmon spawning and the survival of amphibians like salamanders. It is also one of the essential components for wine-making in Napa and Sonoma Valleys.
Current climate predictions are not sophisticated enough to accurately say whether the rising temperatures will result in an increase or decrease of fog. We do know that fog in addition to adding a certain beauty to the coast, also acts a vital thermostat. In The Sea Wolf, native San Franciscan Jack London compared the fog to "the gray shadow of infinite mystery, brooding over the whirling speck of earth". Since the beginning of the century when London wrote that line, we know a lot about how fog behaves and what causes it. However we do not understand everything and it remains a gray shadow of infinite mystery - as perplexing now as it ever was.
Photo: Muir Woods. Akhila Vijayaraghavan ©