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Fog Forests
Introduction
In the redwood forests of coastal California, the soupy white fog that often blankets the trees is as distinctive and memorable as the trees themselves. But according to a recent study, the fog does more than just sit there and look pretty. It may provide essential resources for the entire forest.
Podcast
Fog Forests
Transcript
How fog can feed a forest. I'm Bob Hirshon and this is Science Update.
If you walk through a redwood forest on a foggy day, you might end up drenched. That's because the dense, needled foliage can trap fog droplets, and shed them on the ground below.
Now, there's evidence that this so-called fog drip is essential to the forest's survival. It comes from Cornell University ecologist Todd Dawson.
Dawson:
If we look at it on an annual basis, about a third of the moisture that is coming into the forest over the course of the year is actually coming from fog drip off the trees.
And that benefits not only the trees, but also the plants that live underneath. In fact, during the dry season, those plants can get about two thirds of their water from fog—twice as much as the redwoods themselves.
The data came from water samples, taken from a California redwood forest over a three-year period. Dr. Dawson says fogwater and rainwater have distinctive chemical fingerprints. And that makes it possible to trace the water's origin.
His team also looked at a clearcut forest nearby. They found that without the redwoods, less than half as much fogwater is going into the environment. That's worrisome because the redwoods are vanishing quickly.
Dawson:
Only about 4% of the original redwood forests in coastal California are actually left.
And as the big trees go, they could be leaving other plants and animals without an essential source of water.
For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
Every summer, high pressure areas over the Gulf of Alaska interact with very cold upwellings from deep within the ocean, causing fog to form off the coast of California. The fog moves on shore into California's coastal plant communities, where it is intercepted by the foliage of the redwoods. Once trapped in the tall old growth, the fog drips off the foliage and onto the forest understory. Researchers are working to determine the amount of fogwater that is used by the forest's vegetation and to learn how it contributes to the other cyles that go on in this rare and endangered ecosystem.
This Science Update investigates the remarkably important role that fog plays in nurturing forest growth. The accompanying websites explore different ways that humans have engineered methods for harvesting fog to increase local water supplies.
Now try and answer these questions: - What does the fog do for the plants?
- What percentage of the water in the forest comes from the fog collected on the needles of the redwoods?
- What might threaten this water supply?
- What about the structure of redwood trees makes them ideal fog catchers? Based on this information, can you predict other trees that might be good fog collectors as well?
- If the trees were to diminish, is there an engineering solution that could be put in place to maintain the water collection? What materials would you choose and why?
Going Further
To learn more about how fog is formed, try the Exploratorium activity entitled Fog Chamber. (Suitable for younger grades.)
Go to the FogQuest site to learn more about sustainable water solutions. Here, you can print out PDF versions of the monthly Fog Newsletter, which profiles global fog and dew-related projects. These newsletters include descriptions and illustrations of fog catchers currently used around the world.
Visit Canada's Biosphere Ecowatch Center, to read more about the challenges related to water supply and collection, and to look at other low-cost technologies employed in developing countries.
For additional resources related to this topic, see Content Section(s): III. The Nature of Technology; V. The Living Environment; VIII. The Designed World.
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