Weather and Climate: the Redwoods, Sequoia, and Death Valley
Take a tour of the Redwoods
Weather and Climate in the Redwoods
licensed under CC BY-NC-SA 4.0
First, as usual, here is some background material on national parks you might want to visit. This background also raises some questions that we find fascinating, about why there are such huge differences in climate between nearby national parks. After we raise these questions, we start to answer them with Why the Wind Blows, below.
Redwood National Park has the feel of a soaring, gothic cathedral—only more so. One of the great Sequoia sempervirens trees may live for over two thousand years, but when it falls, new trees will grow from the fallen trunk. (This growth of new trees from a fallen giant gave us the scientific name, which means “ever-living sequoia” in Latin.) The redwoods are the tallest trees on Earth, commonly more than 200 feet (60 meters) and with the very tallest soaring above 380 feet (more than 115 meters). If such a tree grew on the goal line of a US football field and then fell over, it would knock down the goalposts on the other end, and the top branches would extend into the stands. Ferns growing beneath the redwoods may be shoulder-high on a person, yet appear lost and inconsequential. Reports from early loggers included trees even taller than any known today.
The redwoods lie in the southern part of the great, coastal, temperate rainforest that extends north from near San Francisco along the Pacific coast to southeastern Alaska and includes Olympic National Park, which we visited earlier. The redwoods grow in soils that came from rocks much like those of the Olympic.
Redwoods are mostly restricted to a narrow band along the coast with 50-100 inches (1.25-2.5 meters) of rain per year, and with frequent to continuous fogs that help the trees avoid drying out. The trees, in turn, help maintain the fog. Cutting the trees may decrease the fog, making it difficult or impossible for the redwoods to re-grow.
The wood of redwood trees is highly resistant to fire and rot, and so is greatly sought after. Logging of old-growth redwoods thus is a contentious issue. An estimated 96% of the old-growth forest has been cut already. Those trees typically were 500-700 years old, with some about 2000 years old, so a new "old-growth" forest cannot return soon. Some people still want to cut the remaining 4% or so of the original old-growth redwood forest.
Fossil evidence shows that redwoods once were much more widespread. U.S. parks that preserve fossilized redwood logs include the Petrified Forest, Yellowstone, and the Florissant Fossil Beds.
A bit farther south and higher on the slopes of the Sierra, but still in a zone that gets plenty of rain and snow, are the great sequoias of Yosemite, Kings Canyon, and Sequoia National Parks. The Sequoiadendron gigantea are close relatives of the redwoods. Although not as tall (“only” up to 311 feet, or about 95 meters), the great sequoias are more massive. The General Sherman tree, at 275 feet tall and 102.6 feet around, is generally considered to be the largest single-trunk tree on Earth (and much larger than the largest whales). Sequoias can live for 3500 years.
The great sequoias are extremely fire-resistant and require fire to clear out competing trees and trigger the sprouting of sequoia seeds. Fire suppression instituted after the parks were established led to a period with few or no new sequoias sprouting. Dead wood, leaves, sticks, and other debris that can burn accumulated during this time of fire suppression and can make wildfires (which are being made worse by human-caused climate change) hot enough to endanger the sequoias. Carefully planned burns started by experts, and procedures that allow some natural fires to burn, are being used to help return the forest to a more natural state.