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Northern California coastal forests

The Northern California Coastal Forests are largely defined by two features, the largely persistent moist environments provided by Pacific storms in the winter and coastal fogs in the summer, and the distribution of the redwood (Sequoia sempervirens). Redwoods range from central California to the Oregon border, and are typically found within 65 km (40 miles) of the coast. Redwood groves are patchily distributed among a variety of natural communities found within this coastal belt, including Douglas-fir-tanoak forests, oak woodlands, closed-cone pine forests, bogs, and coastal grasslands (Sawyer 1996)

  • Scientific Code
    (NA0519)
  • Ecoregion Category
    Nearctic
  • Size
    5,100 square miles
  • Status
    Critical/Endangered
  • Habitats

Description
Biological Distinctiveness
The coastal forests of Northern California are in many ways an extension of the temperate rainforests that hug the coasts in Washington and Oregon, except that, in California, redwoods and Douglas-fir - tanoak forests dominate many lowland areas. These ancient and spectacular conifers are among the biggest, tallest, and oldest trees in the world, often exceeding 200 ft (more than 369 ft in some individuals) in height, 15 ft in diameter, and 2,200 years old. Redwood groves have the greatest biomass accumulation known for any terrestrial ecosystem. They are globally unique forests, and only a few other forests in the world have a similar assemblage and structure of ancient, giant conifers, e.g., Giant Sequoia groves of the Sierra Nevada, Sitka spruce and Douglas-fir forests of the Pacific Northwest, and Alerce forests of southern Chile. Redwood distribution is patchy, but they generally occur in the fog belt ranging from five to thirty-five miles wide along the coast and from 100 to 2,000 ft in elevation (Barbour et al. 1993). Redwood dominated forests tend to occur in valley bottoms, where there is abundant fog drip,alluvial soils, and periodic floods about every thirty to sixty years. On the uplands where fire was a reoccurring disturbance, a more diverse assemblage of trees occur with redwoods, including Douglas-fir, grand fir, western hemlock, Sitka spruce, western red cedar, tanoak, bigleaf maple, California bay, and Port Orford cedar. Without periodic disturbances, some ecologists suspect that redwood groves may be eventually be replaced by western hemlock (Zinke 1995, but see Viers 1982).

Drier slopes within this ecoregion support many other trees including Douglas-fir and tanoak are the most extensive tree species in the ecoregion. They equally dominate in a "Douglas-fir - tanoak forest" madrone, Garry oak, black oak, interior live oak, and coast live oak. Eight conifer species are endemic to the ecoregion. A rich understory of herbs, shrubs, treelets, ferns, and fungi is found under the towering redwood and other conifers.

Redwood forests harbored a diversity of animal life including bears (Ursus spp.), fishers (Martes pennanti), pine martens (Martes americana), numerous warblers, and the endangered marbled murrelet (Brachyramphus marmoratus) which nests in mature forest canopies. A number of amphibians live here including the Pacific giant salamanders (Dicamptodon ensatus), red-bellied newts (Taricha rivularis), and tailed frogs (Ascaphus truei). Silver salmon and steelhead trout breed in coastal rivers and streams. Also found in this ecoregions is the extraordinary bright yellow-orange banana slug (Ariolimax columbianus), a mature forest specialist and a candidate for California’s state invertebrate. A number of other invertebrate species, including beetles, harvestman, spiders, millipedes, and freshwater mussels are specialists on habitats modified by old Redwood and other conifer forests and maintain very local distributions (Frest and Johannes 1991, Olson 1991). Given the propensity of species in these invertebrate groups for very restricted ranges and the virtual elimination of mature forests in this ecoregion, the probability that numerous species extinctions have already occurred is high (Olson 1991).

North Coast grasslands, often called "bald hills and coastal scrubs can be found close to the sea in some areas, particulary on coastal terraces below redwoods. Grasses, spring wildflowers, and shrubs dominate these habitats, which have now been largely converted to farmland and pasture. Unusual closed-cone pine forests, sphagnum bogs, and pygmy forests also occur on coastal terraces, often above the redwood belt in some areas.

Conservation Status
"Redwoods rank among the most resilient trees on Earth. Adapted to naturally occurring floods and fires and able to resprout, they can turn a burned or cut over. Hillsides into a green forest within a century. But during that century, the plants and animals dependent on the shade, soil moisture, shelter, and interrelated life of the old growth ecosystem, have died and vanished. And the Second-growth forest replacement cannot begin to compare with the primeval beauty, the ambience, and the biodiversity of the 1,000+ -year-old forest gem long gone." (Johnston 1994, p.27).

Habitat Loss
Less than 4 percent of the original extent of virgin redwood forests remain, and only 2.5 percent of this is protected. Unfortunately, protected lower elevation groves can be threatened by severe flooding and sedimentation caused by logging in surrounding watersheds. Several large groves of old growth redwoods on the Eel, Klamath, and Van Duzen Rivers were lost due to severe floods in the 1950's exacerbated by extensive and ecologically-damaging logging in surrounding watersheds. Most of the coastal grasslands have been converted to agriculture or rangelands. All vegetation types have been reduced due to urbanization.

Remaining Blocks of Intact Habitat
One large remaining block of Redwood forest occurs at Redwood Creek within the National Park. Redwood National Park is largely surrounded by plantations and its core habitat area is thus influenced by pronounced edge effects.

It is possible that all remaining blocks of Redwoods are too small to maintain viable Redwood ecosystems into the future. However, for a low elevation forest type, redwood forest has more acreage than any other coastal forest tpye in CA, OR, or WA. The larger patches of coastal grassland occur in:

•Mendocino County
•Marin County
•Point Reyes National Seashore
•Bodega Bay area
In addition, there are large areas of old growth redwood forest in:

•Jedediath Smith
•Prairie Creek
•Humboldt State Parks
A far more critical kind of forest for the ecoregion, which was once quite extensive, is the Douglas-fir-tanoak forest (often called "mixed evergreen forest"). All but a few acres exist in this ecoregion as old growth. Most was cut in the 1950’s and 60’s before ecologists even recognized this specific type of forest (Sawyer. 1996).

Degree of Fragmentation
Redwood forests were naturally patchy to some degree, but wholesale logging has greatly isolated remaining patches and caused much fragmentation.

Degree of Protection
Redwood National Park is the only hope for survival of functioning redwood ecosystems, yet even this is questionable given their size and surrounding land use. Jedediah Smith and Del Norte Redwood State Parks are two smaller reserves. Muir Woods and Big Basin towards the south are too small for realistic prospects of long-term conservation of this unique community.

King’s Range Conservation Area, considered at one point for National Park status, lacks the better known redwood, but does contain remnants of the Douglas-fir - tanoak forest, although this has been mostly cut.

Types and Severity of Threats
The last Redwood groves on private land, mostly in the Headwater Forest area near the van Duzan River, are under imminent threat of cutting by Pacific Lumber. Compromising agreements between State and Federal agencies and this company leave in doubt the survival of these last remnants. It is unfathomable with the knowledge and resources we have today that there would be any question of total protection of the last remaining groves of these globally unique ecosystems, and unconscionable that the government and citizens of this country have let the destruction continue to this point.

Many remaining groves, both protected and unprotected, are threatened by significant alteration of surrounding watersheds from development and logging which can increase the frequency and severity of floods, fires, and sedimentation. Fire suppression can lead to hot fires that kill many individual trees and other species or allow other tree species to eventually out-compete young redwoods. Local conditions of rainfall and understory moisture can be changed due to landscape-level deforestation. Selective logging in redwood forests has significant impacts on native invertebrate biodiversity, even after 15 years, and may be responsible for whole extinctions of some taxa (Hoekstra et al. 1995). Marbled murrelets and other old growth specialist species continue to be threatened through deforestation and subsequent ecological changes in remaining habitats.

Ecological change from other human activities has also contributed to the loss of species. Strobeen’s parnassian butterfly , a redwood subspecies of Parnassius clodius, disappeared 33 years ago from former redwood habitats of the Santa Cruz Mts. due to the loss of its host plant (Dicentra spp.) from fire and timber management practices (Murphy 1993). The lotis blue butterfly, a local endemic of a coastal sphagnum bog in Mendocino, was lost in 1983 as forest cover replaced the wetland, perhaps due to changes in disturbance regimes or the loss of alternate habitats. Salmon migrations have been severely compromised through stream destruction from logging and mining as well as overfishing. The native flora competes with the highest percentage (34%) of introduced plant species for any ecoregion in the continental U.S. and Canada.

Urbanization is also a major threat to this ecoregion, due to the spread of urban areas between Monterey and San Francisco and the area north of San Francisco.

Suite of Priority Activities to Enhance Biodiversity Conservation

•All remaining patches of redwood forest require strict and unequivocal protection for their groves and surrounding watersheds.
•Long-term management plans need to be implemented to ensure that appropriate disturbances occur to facilitate long-term regeneration and ecological viability.
•Restoration of degraded redwood habitat is needed, particularly in areas adjacent to undisturbed patches.
•Surveys and conservation analyses of terrestrial and aquatic invertebrates are urgently needed. Conservation of remaining coastal prairies, scrubs, and pygmy forests on coastal terraces is needed.
Conservation Partners

•The California Native Plant Society
•The Department of Interior, National Park Service
•Humboldt State University
•Mattole River Coalition
•The Sierra Club
•The U.S. Army
•The Wildlands Project
Relationship to other classification schemes
This ecoregion is based on the southern section of Omernik’s Coast Range ecoregion (1). The northern boundary was determined by the northernmost extent of Redwoods. There is approximate congruence with Bailey’s Northern California Coast Section (263A), which is broader towards the north and does not include the Redwood areas south of San Francisco Bay. The ecoregion generally corresponds to Küchler’s vegetation classes, Redwood Forest, Mixed Evergreen Forest with Rhododendron, and Coastal Prairie and Coastal Scrub.

Prepared by: D. Olson and John Sawyer

 

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