Heartiest congratulations to Muir Woods National Monument, which is celebrating its 101st anniversary today. President Theodore Roosevelt used authority granted him by the Antiquities Act of 1906 to establish the park by proclamation on January 9, 1908. In doing so he honored John Muir, the “Father of the National Park System," and created the country’s tenth National Monument.
Muir Woods was the first National Monument created from land donated by private individuals (William and Elizabeth Kent), the first created to preserve a living species (the Coast redwood), and the first created in an “urban setting.” Administered by Golden Gate National Recreation Area, one of the world’s largest urban parks, the park is situated just 12 miles north of San Francisco where it is easily accessible by Bay Area residents and hordes of tourists. It drew 811,000 visitors in 2007. Given that it is the only remaining stand of old-growth Coast redwoods situated within a metropolitan day-tripper zone, it’s a wonder that the park doesn’t draw even more.
People all over the world know about Muir Woods, and on any given day the park’s six-mile trail system, which features some of the best, most accessible loop walks in the Park System, swarm with internationals. The visitor guide distributed at the park entrance is available in Spanish, Chinese, Japanese, Russian, German, and French.
When people think of Muir Woods, they usually think of the giant redwoods. What else should we expect? The Coast redwood (Sequoia sempervirens) is the tallest tree species in the world, and those in the park average 600 to 800 years old. Some of the park’s redwoods are over 1,000 years old and as tall as a 25-story building. Sure, there are older and taller redwoods further up the California coast, but these will certainly do.
Muir Woods is not just a place to gaze in awe at giant redwoods. Visitors who aren’t completely mesmerized by the forest giants can look more carefully and see that Muir Woods is populated by hundreds of other interesting species. Not all of these species are trees, either. In fact, some aren’t even plants.
That is not to say that this compact park (less than one square mile) doesn’t have lots of interesting plants. The inventory of flora includes tanoak, bigleaf maple, California bay laurel, Douglas fir, redwood sorrel, various mosses, 13 species of ferns, over 200 species of mushrooms and other fungi, numerous wildflowers, and a very long list of other species -- including a few nasties like poison oak and stinging nettle.
The faunal complement embraces a wide range of species too, including black-tailed deer, raccoons, Sonoma chipmunks, western gray squirrels, American shrew moles, bats (11 species), Steller’s jays, winter wrens, spotted owls, western garter snakes, banana slugs, giant salamanders, butterflies, and ladybugs, to name just a few. Though black bears don't live in the park, a wandering bruin was recently seen passing through.
If you're a birder, don’t expect to expand your lifelist much. Redwood forests don’t have a lot of birds because the tannin in the trees repels insects, greatly reducing food for birds. That said, Muir Woods is visited by migrants in season, and the park's bird species count is around 50.
When you browse lists like these you become more mindful of the fact that Muir Woods is not just a batch of really old, really big trees. It is a diverse ecosystem – a community of living things interacting with each other and their nonliving environment.
When you visit Muir Woods, by all means go ahead and admire those big old redwoods. Stand there, gaze up and up and up, and feel drawfed by them. Pause to reflect on the fact that the typical redwood you see was already a century or more old when European explorers first set foot on the continent. But also be sure to notice the profusion of life that surrounds those big trees, interacts with them, and participates with them in the intricate processes of energy flow and matter recycling that sustain the ecosystem.
Recall too, that some of the most vital components of this ecosystem are things that you cannot see at all. Take away the decomposers in the soil – the bacteria and fungi that feed on dead and decaying organic matter – and the whole ecosystem will collapse.
Take time to notice the elongated riparian ecosystem that nearly bisects the park. Redwood Creek, which rises on the slopes of nearby Mount Tamalpais, hosts a variety of aquatic and semi-aquatic creatures (fish, salamanders, insects) and provides vital water for the trees and animals of Muir Woods.
Redwood Creek runs year round, but not always with the same vigor. Late summer finds it scarcely more than trickling, with much of the aquatic life sheltering in the deeper pools. But winter is the wet season (most of the annual precipitation of about 40 inches falls then), and the big rains dump enough water to turn the creek into a torrent. Three miles away at Muir Beach, the creek’s rushing waters breach the sandbar at the river’s mouth each winter and open the way for the anadromous fish (Coho and steelhead salmon) that spend part of their life cycle at sea and return to the creek to spawn.
It’s actually a bit more complicated than that. The Coho salmon is also called silver salmon because spawning adults (most likely to be seen in December and January) have silver sides and dark blue backs. Although “steelhead trout” is the term traditionally used to denote the other anadromous fish species in Redwood Creek, the fish is actually a salmon that scientists at the park now refer to as the ”steelhead salmon (formerly steelhead trout)”. The true steelhead trout, as you may know, is actually the anadromous form of the rainbow trout, an altogether different fish.
If you’re confused, just remember that Cohos die immediately after they spawn (thus beginning and ending their lives in the creek), whereas the steelheads return to the sea after spawning. And there aren’t any steelhead trout, rainbow trout, or any other kind of trout in Redwood Creek, even if some of the relevant literature doesn’t make that clear.
Scientists with electrofishing gear are studying the Coho population to better understand the smolt, juvenile, and adult phases of this interesting fish’s life. You can see a neat podcast on this research project at this site. Spawning data are available via a link on the same page.
Like the canary in the coal mine, the creek’s state of health provides vital clues to the overall health of the ecosystem. Redwood is a very healthy creek, at least so far, and for that we are very grateful. Sad to say, the salmon species in Redwood Creek are endangered, and this creek is one of the last streams in all of California that still has its native stock of salmon. For that we can thank the healthy, largely undisturbed forest through which it flows.
Studying the interrelationship of the redwoods and the creek (which is the sort of thing ecologists do) makes one profoundly aware that Muir Woods abounds in symbiotic relationships. The creek provides the trees with most of their water. In turn, the trees shade the water (helping it to stay cool), provide nutrients when they die and decay, create pools behind deadfalls, and anchor the humus-rich soil with their roots. The latter function is particularly vital, since excessive sediment would clog the stream, eliminate the pools, bury the gravel in the salmon spawning beds, and wreak general havoc on the stream’s aquatic life.