Last week I walked through a grove of coast redwoods. The sun shone with nary a cloud in the sky. But I become depressed. What was wrong with this picture? Simple, it was January but felt like September. The forest floor was brittle, not soft, the moss dry and compressed, there were few mushrooms, and I was in a t-shirt. This was not California's winter weather. The blue sky and bright sun were actually ominous.
But I realized that these redwoods were at least 600 years old and had seen many winters like this one. So I should not give up on the rains quite yet.
California has two trees for their state tree -- the giant sequoia and the coast redwood. Both are biological wonders. The General Sherman tree, a giant sequoia, is the largest tree in the world. And a coast redwood named Hyperion is the tallest tree at 380 feet.
140 million years ago when the worldwide climate was much wetter and warmer, redwoods covered the entire northern hemisphere and were a dominant conifer. As the climate changed, redwoods become more restricted until now they exist in a narrow band from Big Sur to just over the Oregon border; and inland no more than 45 miles. The largest specimens thrive in deep valleys with abundant rain and fog where the soil is moist all year.
But the key to distribution is coastal fog. In August and September, the winter rains are a distant memory and hot, dry east winds desiccate the trees, creating intense water stress. But fog rolling in from the ocean is literally a lifesaver. As the moist air hits the redwood foliage the water condenses out and drops to the floor. The giant trees have tiny, ubiquitous root hairs that take up the precious commodity. Scientists estimate that fog contributes about 20 percent of the water needed by redwoods.