Science & Nature


The coastal area west of the park at Cape Mendocino is one of the most seismically active in the San Andreas Fault system. Cape Mendocino is the site of the Mendocino Triple Plate Junction, where the North American continental plate joins the Gorda and the Pacific plates.

Redwood Forest

California’s coast redwoods follow the fog and thrive at elevations below 2,000 feet with heavy winter rains and moderate year-round temperatures. Trees can grow to 350 feet or more, with a base diameter of about 20 feet. Their root systems are broad and shallow, from only a few inches to 6 feet underground. They resist insects, fire, and rot. Their vigor in sprouting back when cut or badly burned is an important factor in their longevity.  The oldest known tree has been around for more than 2,500 years

Redwoods  are named for the color of their bark and heartwood. The high tannin content of the wood gives the trees remarkable resistance to fungus diseases and insect infestations. The thick, fibrous bark has an even higher tannin content, and protects them from periodic fires.

These immense trees have delicate foliage. Narrow, sharp-pointed needles only one-half to three-quarters of an inch long grow flat along their stems, forming feathery sprays. Redwood cones are about an inch long. Each cone contains 14 to 24 tiny seeds; a pound of redwood seeds would number more than 100,000. Redwood seedlings grow rapidly, more than a foot per year in good conditions. Young trees also sprout from their parents' roots, taking advantage of the established root system.

Coast Redwoods form almost pure stands in some areas, especially on flat, silt-covered river and creek plains such as the Bull Creek Flats area and the Rockefeller Forest. Coast Redwoods are also found in mixed evergreen forest with the majestic Douglas-fir, as well as western hemlock, grand fir, and Sitka spruce. On drier slopes tanoak, madrone, maple, and California bay laurel grow along with the evergreens. Rhododendrons and a variety of ferns are the most common understory plants. Other plants under the trees include poison oak, huckleberry, hazel, and many flowering herbs. Among the most spectacular are pink redwood lilies (also called chaparral lilies) and purple calypso orchids.

It is generally believed that the last Ice Age limited the coast redwoods to their present range, a narrow 450-mile strip along the Pacific Ocean from central California to southern Oregon. The climate these trees require seems to have been far more common in earlier eras. Paleobotanists have discovered fossil redwoods throughout what is now the western United States and Canada, and along the coasts of Europe and Asia. Some of these fossils are as much as 160 million years old. Redwoods are relatively recent arrivals in their current region, however; the earliest fossil record in California is found in rocks less than 20 million years old.

For more information about plants in coast redwood forests, go to this National Park Service website.


Mammals found in the redwood forest include raccoons, skunks, black bears, Roosevelt elk, deer, squirrels, bobcats, porcupines, weasels, mink, and the rare ringtail cats.

There’s also a common mollusk, the gooey-looking banana slug (Ariolimax columbianus). Ranging from California’s redwood forests to coastal British Columbia, the slug’s color can range from bright yellow to greenish or brownish, depending on what it is eating, where it lives, and how healthy it is. Some banana slugs even have dark brown spots that help them hide on the forest floor. Up to eight inches long, banana slugs are the largest slugs in North America and the second largest slugs in the world. The hole at the back of a slug’s head is its lung or “pulmonata.”

The Eel River has salmon and steelhead trout. Despite the river’s name, it does not have eels. But it does have the look-alike Pacific lamprey, a jawless fish that spawns in the river each spring.

Among Humboldt Redwoods’ birds are the marbled murrelet (Brachyramphus marmoratus), which nests almost exclusively in old-growth redwood and Douglas-fir forests. The murrelet is known for its long commute. After spending the day fishing at sea, this chunky little auk returns, sometimes many miles inland, to nest in old-growth forests. Murrelets once numbered 60,000 along the California coast. Today less than 6,000 remain. You can learn how to safeguard their remaining habitat by watching the Crumb Clean video on the park's home page.
For more on wildlife in coast redwood forests, click here.

Visitors are required to watch this short video about the impact human food has on park wildlife.

Scientists studying the effects of rising global temperatures have found that the size and longevity of redwoods helps them store more climate-altering carbon dioxide than other plants. Even old redwoods continue to grow, each year adding more carbon-filled wood than smaller, younger trees. After redwoods die, their rot-resistant wood holds onto that carbon for a long time.

Redwoods cannot solve our climate problems all by themselves. People can do their share too, partly by protecting redwoods and other forests.

Research in the Park

With the help of Save the Redwoods League and other funding partners, Humboldt Redwoods State Park has become a living laboratory for scientists. Some recent findings include:

• The best way to move toward old-growth characteristics in a forest recovering from logging is with judicious thinning of young trees.
• In 2001 Pacific fishers and Humboldt martens didn’t show up in the Corridor from the Redwoods to the Sea (which includes part of Humboldt Redwoods State Park).  Motion cameras and track-box stations provided evidence of other carnivores, however, such as ringtails, gray foxes, and black bears.

To find out more about recent research in California's redwood parks, go to this Save the Redwoods League link.