Window on Nature
By Lowell & Kaye Christie, F47246
November 2002
Some years back, we lived in an area that claimed to be the foggiest place in the United States. Old-timers said the location had been used during World War II to test the ability of pilots to land their planes under extremely foggy conditions, and the airport in the northern California town of Arcata had some of the most consistent fog anywhere.
More recently, we checked some weather maps and found that the area along the northern California coast still is as foggy as we remembered — more than 60 days a year the visibility drops to less than a quarter-mile. There are only a few other areas in the United States with similar conditions: the coastal portions of Washington and Oregon; large areas of Maine and New Hampshire; and a relatively narrow band that follows the Great Smoky Mountains from Pennsylvania to Georgia.
Our primary interest in Arcata’s weather conditions is the effect the fog has on the surrounding countryside. This is redwood country. Our backyard had a huge redwood stump in the middle of it, and younger and smaller redwoods grew less than a block away. They wouldn’t have been able to survive and thrive were it not for the frequent (and much complained about) fog that rolls in from nearby Humboldt Bay.
Fog is made of the same water vapor as clouds: tiny water particles almost too small to fall, and so light that even minute air currents keep them aloft. But it is fog’s proximity to the ground that makes us look at it in slightly different ways. Walking though a foggy forest gives all your senses a workout. Sounds are subdued, absorbed by the thick underbrush that could not exist without the additional moisture that fog provides. Colors take on a deeper hue, making the reds of coast red elderberries and the yellow petals of sourgrass stand out against the green background. Somehow even the air smells different from the normal fresh scent following a rain. Speaking of rain, if you plan to stroll through a redwood forest on a foggy day, take a raincoat. When forest fog is thick, one can become seriously soaked from what’s called “fog drip.”
California’s redwoods grow where they do because of the fog that rolls in from the Pacific Ocean much of the year. According to University of California at Berkeley ecologist Todd Dawson, as much as half of the moisture coming into the forest each year is from fog moisture dripping from the redwood needles until it reaches the ground. During the dry season, many plants get as much as two-thirds of their moisture from fog. Scientists also found that they can actually trace the origin of water collected in the redwood forest. This is possible because fog water and rainwater have a slightly different chemical composition.
With only about 4 percent of the original redwood forests of coastal California remaining, the relationship between fog and forest may be in jeopardy. When Redwood National Park was first created, we toured some heavily logged areas in the new park. According to the interpreter, there was some question of how much redwood regrowth would occur since the local climate had actually been changed by the logging. Before the trees were taken down, they trapped the fog, which increased the humidity. But with the big trees gone, fog passes right through the area, lowering the humidity below what is necessary for a successful redwood forest. Time will tell whether the redwood forests can regenerate themselves.
The fact that fog drip increases the amount of water available in the forest has been used by humans to supplement their natural water sources for thousands of years. Pliny the Elder wrote of Canary Islands natives gathering water from fog trapped by the trees. In more recent times, fog farms in various places in the world collect fog water for local use.
The town of Chungungo, Chile, is located in one of the driest parts of the world. Before 1992 the local inhabitants subsisted on water that was trucked in from other areas. Working with polypropylene mesh screening stretched between poles, Chilean and Canadian scientists developed fogcatchers to provide enough water for the entire town. Simply put, they placed a vertical surface in the path of moving fog and strained the water from the air.
Once again the world looks to nature for solutions. In fact, in 1998 the first International Conference on Fog and Fog Collection was held in Vancouver, British Columbia; the second was held in 2001 in St. Johns, Canada. There are many dry regions in the world that experience fog for at least part of the year. As their water supplies dwindle, it is hoped that fog can become part of the solution.
For motorhomers, fog is a normal part of traveling. It can be anything from a slight annoyance to a serious danger for travelers. However, once you park the motorhome, get out your raincoats and take a walk in the fog. You’ll find you’ve entered a completely different world.