Northern California coastal forests
The Northern California coastal forests ecoregion consists of two disjunctive geographic units in Northern California: (1) a smaller unit in the Santa Cruz and Montara Mountains and (2) the larger unit from Marin County, California to the Oregon border. These forests are classified as an element of the Temperate Coniferous Forests biome. There is moderate faunal diversity as exemplified by occurrence of 347 vertebrate taxa.
The Northern California coastal forests are largely defined by two features, the persistent moist environments provided by winter Pacific storms and coastal fog in the summer, and the distribution of the Coast Redwood (Sequoia sempervirens). Redwoods range from central California to the Oregon border, and are typically found within 65 kilometers 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.
North Coast grasslands, often called bald hills, as well as coastal scrub can be found close to the Pacific Ocean in some areas, particularly on coastal terraces below Coast Redwood stands. 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.
Location and general depiction
The southern disjunctive portion of the ecoregion lies in the upper elevations of Santa Cruz and San Mateo Counties within the Santa Cruz and Montara Mountain Ranges. The major catchment basin within the Santa Cruz Mountains is the San Lorenzo River system. For the Montara Mountains there is no dominant drainage, but a series of smaller watersheds that discharge to the Pacific Ocean or San Francisco Bay.
The larger northern disjunctive element of the ecoregion stretches from the coastal forests of Marin County to slightly beyond the Oregon border. These forests span a number of coastal watersheds including the Russian River, Eel River and Navarro River, as well as a number of smaller coastal catchment basins. The total areal extent of the ecoregion is approximately 5100 square miles. The California coastal forests ecoregion is denoted by the WWF code NA0519.
The coastal forests of Northern California can be regarded as an extension of the temperate rainforests that hug the coasts in Washington and Oregon, except that the California coastal forests have Coast Redwoods and Douglas-fir–Tanoak forests as dominant in lowland areas. These ancient and spectacular conifers are among the largest, tallest and oldest trees on Earth, often exceeding sixty meters (m) (more than 112 m in some individuals) in height, 4.6 m in diameter, and around 2200 years old. Redwood groves have the greatest plant biomass accumulation known for any terrestrial ecosystem.
They are globally distinctive forests, and few other forests on Earth exhibiting a similar assemblage and structure of ancient, giant conifers, e.g., Giant Sequoia groves of the Sierra Nevada Range, Sitka spruce and Douglas-fir forests of the Pacific Northwest, and Alerce forests of southern Chile. The Coast redwood distribution is patchy, but this species is generally found in the fog belt ranging from five to thirty-five miles wide along the coast and from 30 to 610 m in elevation. Coast redwood dominated forests tend to occur in valley bottoms or steep parts of drainages, where there is abundant fog drip, alluvial soils, and periodic floods occur approximately every thirty to sixty years. Many of the coastal forests in northern Sonoma County are dominated by Bishop pine (Pinus muricata) with understory shrubs such as Salal, Ceanothus spp. and numerous ferns.
On the uplands where fire was a reoccurring disturbance, a more diverse assemblage of trees occur with Coast redwoods, including Douglas-fir, Grand fir (Abies grandis), western hemlock, Sitka spruce, western red cedar, Tanbark oak, Bigleaf maple, California bay, and Port Orford cedar. Without periodic disturbances, some ecologists expect that Coast redwood groves could be eventually be substantially displaced by Western hemlock.
The more arid slopes within this ecoregion support many other tree species including Douglas-fir and tanoak. Principal co-dominant trees in a Douglas-fir–tanoak forest are: Pacific madrone, Oregon oak (Quercus garryana), Black oak (Quercus kelloggii), interior live oak, and Coast live oak (Quercus agrifolia). Eight conifer taxa are endemic to the ecoregion. A rich understory of herbs, shrubs, treelets, ferns, and fungi is found under the massive Coast redwood and other conifers.
Redwood forests hold a diversity of fauna including the American Black Bear (Ursus americanus), Fisher (Martes pennanti), Brush Rabbit (Sylvilagus bachmani), American Shrew Mole (Neurotrichus gibbsii) and North American Marten (Martes americana).
Numerous warblers are found in the ecoregion, as well as other avian species such as the Black Rail (Laterallus jamaicensis NT) and the endangered Marbled Murrelet (Brachyramphus marmoratus EN), the latter taxon which nests in mature forest canopies. The Burrowing Owl (Athene cunicularia) is a raptor occuring within the California coastal forests ecoregion.
A number of amphibians live herein the California coastal forests, including the Speckled Black Salamander (Aneides flavipunctatus NT), California Giant Salamander (Dicamptodon ensatus NT), one of the most massive North American salamanders and one of the few salamanders capable of vocalizing. (Hogan. 2008) Also found in the ecoregion are Red-bellied Newt (Taricha rivularis), Roughskin Newt (Taricha granulosa), Olympic Salamander (Rhyacotriton olympicus VU), California Slender Salamander (Batrachoseps attenuatus), Del Norte Salamander (Plethodon elongatus NT), Arboreal Salamander (Aneides lugubris), Clouded Salamander (Aneides ferreus NT), Foothill Yellow-legged Frog (Rana boylii NT), Northern Red-legged Frog (Rana aurora), Pacific Treefrog (Pseudacris regilla), Coastal Tailed Frog (Ascaphus truei), Western Toad (Anaxyrus boreas) and Monterey Ensatina (Ensatina eschscholtzii).
There are a number of reptilian taxa found in the ecoregion: Pacific pond turtle (Emys marmorata VU); Western rattlesnake (Crotalus viridis); Northern Pacific rattlesnake (Crotalus oreganus); Western gopher snake (Pituophis catenifer); Ringneck snake (Diadophis punctatus); Sharp-tailed snake (Contia tenuis); Couch's garter snake (Thamnophis couchii); Western terrestrial garter snake (Thamnophis elegans); Common garter snake (Thamnophis sirtalis); Northwestern garter snake (Thamnophis ordinoides); Yellow-bellied racer (Coluber constrictor); California striped racer (Masticophis lateralis); Rubber boa (Charina bottae); California legless lizard (Anniella pulchra); Northern alligator lizard (Elgaria coerulea); Southern alligator lizard (Elgaria multicarinata); Western fence lizard (Sceloporus occidentalis) and Sagebrush lizard (Sceloporus graciosus).
Silver salmon and Steelhead trout are found in many of the coastal watersheds. Conservation efforts are underway to remove impoundments and restore native vegetation to these riparian areas, in order to enhance populations of these anadromous species.
Also found in this ecoregion 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 Coast Redwood and other conifer forests and maintain highly localized distributions. 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.
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 ambiance, and the biodiversity of the 1000+ year-old forest gem long gone." (Johnston. 1994)The California coastal forests is classified as Critical and Endangered as an ecoregion, based upon the extent of pristine habitat already destroyed and the significance of biota contained in this region. Johnston has noted that Coast Redwood is an extremely resilient species, in its adaptation to naturally occurring wildfires and flood events. Moreover, they are able to resprout from the base after fire, and are able to regenerate a closed forest cover within the span of one hundred years. However, according to Johnston: "during that century, the plants and animals dependent on the shade,
Less than four percent of the original extent of virgin redwood forests remain, and only about 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 agricultural land conversion and urbanization.
Remaining blocks of intact habitat
One large remaining block of intact Coast 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.
Most remaining blocks of Coast Redwoods may be too small in area to sustain viable Coast Redwood ecosystems into the future. However, for a low elevation forest type, Coast Redwood forest has more acreage than any other coastal forest type in California, Oregon, or Washington. Moreover, the larger patches of coastal grassland occur in:
- Mendocino County
- Marin County
- Point Reyes National Seashore
- Bodega Bay area northward to Jenner, Sonoma County
In addition, there are large areas of old growth Coast Redwood forest in:
- Jedediah Smith Redwood State Park
- Prairie Creek watershed
- 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 termed mixed evergreen forest). Only a few acres of this forest association exist in this ecoregion as old growth. Most of this forest type was cut in the 1950’s and 60’s before ecologists even recognized this specific type of forest.
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 harvested.
Ecological threat profile
The last major Coast Redwood groves on private land, mostly in the Headwater Forest area near the Van Duzen River, a tributary of the Eel River, are under threat of harvesting for commercial use. Compromising agreements between State and Federal agencies and the private landowner leave in doubt the survival of these last remnants. It is unfathomable with the knowledge and resources present 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.
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 Coast Redwoods. Local conditions of rainfall and understory moisture can be changed due to landscape-level deforestation. Selective logging in Coast Redwood forests has significant impacts on native invertebrate biodiversity, even after fifteen years, and may be responsible for outright extinction of some taxa. 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 Mountains. due to the loss of its host plant (Dicentra spp.) from fire and timber management practices. The lotis blue butterfly, a local endemic of a coastal sphagnum bog in Mendocino County, was lost in 1983 as forest cover replaced the wetland, perhaps due to changes in disturbance regimes and 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 one of the highest percentages (34%) of introduced plant species for any ecoregion in the continental USA 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 actions to enhance ecological conservation
- Remaining patches of Coast Redwood forest warrant unequivocal protection for their trees, understory and entirety of their surrounding watersheds.
- Long-term management plans should be implemented to ensure that appropriate natural disturbances occur to facilitate long-term regeneration and ecological viability.
- Restoration of degraded Coast Redwood habitat is desirable, particularly in areas adjacent to undisturbed patches.
- Surveys and conservation analyses of terrestrial and aquatic invertebrates are urgently needed. Conservation is recommended for remaining coastal prairies, scrubs, and pygmy forests on coastal terraces.
Some of the principal conservation entities active in the ecoregion are:
- California Native Plant Society
- U.S. Department of Interior, National Park Service
- Humboldt State University
- Mattole River Coalition
- Sonoma Land Trust
- U.S. Army
- 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 Coast Redwoods. There is approximate congruence with Bailey’s Northern California Coast Section (263A), which is broader towards the north and does not include the Coast 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.
- California interior chaparral and woodlands, at the south and southeast
- Klamath-Siskiyou forests, to the northeast
- Central Pacific coastal forests, at the northern tip
- Michael G. Barbour, Todd Keeler-Wolf, Allan A. Schoenherr. 2007. Terrestrial vegetation of California. University of California Press. 712 pages
- C. Michael Hogan. 2008. California Giant Salamander: Dicamptodon ensatus. iGoTerra. com. Nicklas Stromberg (ed.)
- Willis Linn Jepson. 1909. The Trees of California, published by Cunningham, Curtis & Welch, 228 pages
- Verna R. Johnston. 1994. California Forests and Woodlands: A Natural History. University of California Press, Berkeley, California
- Gerry Moore, Bruce Kershner; Craig Tufts; Daniel Mathews; Gil Nelson; Spellenberg, Richard; Thieret, John W.; Terry Purinton; Block, Andrew (2008). National Wildlife Federation Field Guide to Trees of North America. New York: Sterling. p. 90. ISBN 1-4027-3875-7
- Philip Alexander Munz, David D. Keck. 1973. A California flora. University of California Press. 1905 pages
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